xref: /linux/Documentation/admin-guide/kernel-parameters.txt (revision 9591fdb0611dccdeeeeacb99d89f0098737d209b)
1	accept_memory=  [MM]
2			Format: { eager | lazy }
3			default: lazy
4			By default, unaccepted memory is accepted lazily to
5			avoid prolonged boot times. The lazy option will add
6			some runtime overhead until all memory is eventually
7			accepted. In most cases the overhead is negligible.
8			For some workloads or for debugging purposes
9			accept_memory=eager can be used to accept all memory
10			at once during boot.
11
12	acpi=		[HW,ACPI,X86,ARM64,RISCV64,EARLY]
13			Advanced Configuration and Power Interface
14			Format: { force | on | off | strict | noirq | rsdt |
15				  copy_dsdt | nospcr }
16			force -- enable ACPI if default was off
17			on -- enable ACPI but allow fallback to DT [arm64,riscv64]
18			off -- disable ACPI if default was on
19			noirq -- do not use ACPI for IRQ routing
20			strict -- Be less tolerant of platforms that are not
21				strictly ACPI specification compliant.
22			rsdt -- prefer RSDT over (default) XSDT
23			copy_dsdt -- copy DSDT to memory
24			nocmcff -- Disable firmware first mode for corrected
25			errors. This disables parsing the HEST CMC error
26			source to check if firmware has set the FF flag. This
27			may result in duplicate corrected error reports.
28			nospcr -- disable console in ACPI SPCR table as
29				default _serial_ console on ARM64
30			For ARM64, ONLY "acpi=off", "acpi=on", "acpi=force" or
31			"acpi=nospcr" are available
32			For RISCV64, ONLY "acpi=off", "acpi=on" or "acpi=force"
33			are available
34
35			See also Documentation/power/runtime_pm.rst, pci=noacpi
36
37	acpi_apic_instance=	[ACPI,IOAPIC,EARLY]
38			Format: <int>
39			2: use 2nd APIC table, if available
40			1,0: use 1st APIC table
41			default: 0
42
43	acpi_backlight=	[HW,ACPI]
44			{ vendor | video | native | none }
45			If set to vendor, prefer vendor-specific driver
46			(e.g. thinkpad_acpi, sony_acpi, etc.) instead
47			of the ACPI video.ko driver.
48			If set to video, use the ACPI video.ko driver.
49			If set to native, use the device's native backlight mode.
50			If set to none, disable the ACPI backlight interface.
51
52	acpi_force_32bit_fadt_addr [ACPI,EARLY]
53			force FADT to use 32 bit addresses rather than the
54			64 bit X_* addresses. Some firmware have broken 64
55			bit addresses for force ACPI ignore these and use
56			the older legacy 32 bit addresses.
57
58	acpica_no_return_repair [HW, ACPI]
59			Disable AML predefined validation mechanism
60			This mechanism can repair the evaluation result to make
61			the return objects more ACPI specification compliant.
62			This option is useful for developers to identify the
63			root cause of an AML interpreter issue when the issue
64			has something to do with the repair mechanism.
65
66	acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
67	acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
68			Format: <int>
69			CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
70			debug output.  Bits in debug_layer correspond to a
71			_COMPONENT in an ACPI source file, e.g.,
72			    #define _COMPONENT ACPI_EVENTS
73			Bits in debug_level correspond to a level in
74			ACPI_DEBUG_PRINT statements, e.g.,
75			    ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
76			The debug_level mask defaults to "info".  See
77			Documentation/firmware-guide/acpi/debug.rst for more information about
78			debug layers and levels.
79
80			Enable processor driver info messages:
81			    acpi.debug_layer=0x20000000
82			Enable AML "Debug" output, i.e., stores to the Debug
83			object while interpreting AML:
84			    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
85			Enable all messages related to ACPI hardware:
86			    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
87
88			Some values produce so much output that the system is
89			unusable.  The "log_buf_len" parameter may be useful
90			if you need to capture more output.
91
92	acpi_enforce_resources=	[ACPI]
93			{ strict | lax | no }
94			Check for resource conflicts between native drivers
95			and ACPI OperationRegions (SystemIO and SystemMemory
96			only). IO ports and memory declared in ACPI might be
97			used by the ACPI subsystem in arbitrary AML code and
98			can interfere with legacy drivers.
99			strict (default): access to resources claimed by ACPI
100			is denied; legacy drivers trying to access reserved
101			resources will fail to bind to device using them.
102			lax: access to resources claimed by ACPI is allowed;
103			legacy drivers trying to access reserved resources
104			will bind successfully but a warning message is logged.
105			no: ACPI OperationRegions are not marked as reserved,
106			no further checks are performed.
107
108	acpi_force_table_verification	[HW,ACPI,EARLY]
109			Enable table checksum verification during early stage.
110			By default, this is disabled due to x86 early mapping
111			size limitation.
112
113	acpi_irq_balance [HW,ACPI]
114			ACPI will balance active IRQs
115			default in APIC mode
116
117	acpi_irq_nobalance [HW,ACPI]
118			ACPI will not move active IRQs (default)
119			default in PIC mode
120
121	acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
122			Format: <irq>,<irq>...
123
124	acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
125			use by PCI
126			Format: <irq>,<irq>...
127
128	acpi_mask_gpe=	[HW,ACPI]
129			Due to the existence of _Lxx/_Exx, some GPEs triggered
130			by unsupported hardware/firmware features can result in
131			GPE floodings that cannot be automatically disabled by
132			the GPE dispatcher.
133			This facility can be used to prevent such uncontrolled
134			GPE floodings.
135			Format: <byte> or <bitmap-list>
136
137	acpi_no_auto_serialize	[HW,ACPI]
138			Disable auto-serialization of AML methods
139			AML control methods that contain the opcodes to create
140			named objects will be marked as "Serialized" by the
141			auto-serialization feature.
142			This feature is enabled by default.
143			This option allows to turn off the feature.
144
145	acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
146			   kernels.
147
148	acpi_no_static_ssdt	[HW,ACPI,EARLY]
149			Disable installation of static SSDTs at early boot time
150			By default, SSDTs contained in the RSDT/XSDT will be
151			installed automatically and they will appear under
152			/sys/firmware/acpi/tables.
153			This option turns off this feature.
154			Note that specifying this option does not affect
155			dynamic table installation which will install SSDT
156			tables to /sys/firmware/acpi/tables/dynamic.
157
158	acpi_no_watchdog	[HW,ACPI,WDT]
159			Ignore the ACPI-based watchdog interface (WDAT) and let
160			a native driver control the watchdog device instead.
161
162	acpi_rsdp=	[ACPI,EFI,KEXEC,EARLY]
163			Pass the RSDP address to the kernel, mostly used
164			on machines running EFI runtime service to boot the
165			second kernel for kdump.
166
167	acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
168			Format: To spoof as Windows 98: ="Microsoft Windows"
169
170	acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
171			of 2 which is mandated by ACPI 6) as the supported ACPI
172			specification revision (when using this switch, it may
173			be necessary to carry out a cold reboot _twice_ in a
174			row to make it take effect on the platform firmware).
175
176	acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
177			acpi_osi="string1"	# add string1
178			acpi_osi="!string2"	# remove string2
179			acpi_osi=!*		# remove all strings
180			acpi_osi=!		# disable all built-in OS vendor
181						  strings
182			acpi_osi=!!		# enable all built-in OS vendor
183						  strings
184			acpi_osi=		# disable all strings
185
186			'acpi_osi=!' can be used in combination with single or
187			multiple 'acpi_osi="string1"' to support specific OS
188			vendor string(s).  Note that such command can only
189			affect the default state of the OS vendor strings, thus
190			it cannot affect the default state of the feature group
191			strings and the current state of the OS vendor strings,
192			specifying it multiple times through kernel command line
193			is meaningless.  This command is useful when one do not
194			care about the state of the feature group strings which
195			should be controlled by the OSPM.
196			Examples:
197			  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
198			     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
199			     can make '_OSI("Windows 2000")' TRUE.
200
201			'acpi_osi=' cannot be used in combination with other
202			'acpi_osi=' command lines, the _OSI method will not
203			exist in the ACPI namespace.  NOTE that such command can
204			only affect the _OSI support state, thus specifying it
205			multiple times through kernel command line is also
206			meaningless.
207			Examples:
208			  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
209			     FALSE.
210
211			'acpi_osi=!*' can be used in combination with single or
212			multiple 'acpi_osi="string1"' to support specific
213			string(s).  Note that such command can affect the
214			current state of both the OS vendor strings and the
215			feature group strings, thus specifying it multiple times
216			through kernel command line is meaningful.  But it may
217			still not able to affect the final state of a string if
218			there are quirks related to this string.  This command
219			is useful when one want to control the state of the
220			feature group strings to debug BIOS issues related to
221			the OSPM features.
222			Examples:
223			  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
224			     '_OSI("Module Device")' FALSE.
225			  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
226			     '_OSI("Module Device")' TRUE.
227			  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
228			     equivalent to
229			     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
230			     and
231			     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
232			     they all will make '_OSI("Windows 2000")' TRUE.
233
234	acpi_pm_good	[X86]
235			Override the pmtimer bug detection: force the kernel
236			to assume that this machine's pmtimer latches its value
237			and always returns good values.
238
239	acpi_sci=	[HW,ACPI,EARLY] ACPI System Control Interrupt trigger mode
240			Format: { level | edge | high | low }
241
242	acpi_skip_timer_override [HW,ACPI,EARLY]
243			Recognize and ignore IRQ0/pin2 Interrupt Override.
244			For broken nForce2 BIOS resulting in XT-PIC timer.
245
246	acpi_sleep=	[HW,ACPI] Sleep options
247			Format: { s3_bios, s3_mode, s3_beep, s4_hwsig,
248				  s4_nohwsig, old_ordering, nonvs,
249				  sci_force_enable, nobl }
250			See Documentation/power/video.rst for information on
251			s3_bios and s3_mode.
252			s3_beep is for debugging; it makes the PC's speaker beep
253			as soon as the kernel's real-mode entry point is called.
254			s4_hwsig causes the kernel to check the ACPI hardware
255			signature during resume from hibernation, and gracefully
256			refuse to resume if it has changed. This complies with
257			the ACPI specification but not with reality, since
258			Windows does not do this and many laptops do change it
259			on docking. So the default behaviour is to allow resume
260			and simply warn when the signature changes, unless the
261			s4_hwsig option is enabled.
262			s4_nohwsig prevents ACPI hardware signature from being
263			used (or even warned about) during resume.
264			old_ordering causes the ACPI 1.0 ordering of the _PTS
265			control method, with respect to putting devices into
266			low power states, to be enforced (the ACPI 2.0 ordering
267			of _PTS is used by default).
268			nonvs prevents the kernel from saving/restoring the
269			ACPI NVS memory during suspend/hibernation and resume.
270			sci_force_enable causes the kernel to set SCI_EN directly
271			on resume from S1/S3 (which is against the ACPI spec,
272			but some broken systems don't work without it).
273			nobl causes the internal blacklist of systems known to
274			behave incorrectly in some ways with respect to system
275			suspend and resume to be ignored (use wisely).
276
277	acpi_use_timer_override [HW,ACPI,EARLY]
278			Use timer override. For some broken Nvidia NF5 boards
279			that require a timer override, but don't have HPET
280
281	add_efi_memmap	[EFI,X86,EARLY] Include EFI memory map in
282			kernel's map of available physical RAM.
283
284	agp=		[AGP]
285			{ off | try_unsupported }
286			off: disable AGP support
287			try_unsupported: try to drive unsupported chipsets
288				(may crash computer or cause data corruption)
289
290	ALSA		[HW,ALSA]
291			See Documentation/sound/alsa-configuration.rst
292
293	alignment=	[KNL,ARM]
294			Allow the default userspace alignment fault handler
295			behaviour to be specified.  Bit 0 enables warnings,
296			bit 1 enables fixups, and bit 2 sends a segfault.
297
298	align_va_addr=	[X86-64]
299			Align virtual addresses by clearing slice [14:12] when
300			allocating a VMA at process creation time. This option
301			gives you up to 3% performance improvement on AMD F15h
302			machines (where it is enabled by default) for a
303			CPU-intensive style benchmark, and it can vary highly in
304			a microbenchmark depending on workload and compiler.
305
306			32: only for 32-bit processes
307			64: only for 64-bit processes
308			on: enable for both 32- and 64-bit processes
309			off: disable for both 32- and 64-bit processes
310
311	alloc_snapshot	[FTRACE]
312			Allocate the ftrace snapshot buffer on boot up when the
313			main buffer is allocated. This is handy if debugging
314			and you need to use tracing_snapshot() on boot up, and
315			do not want to use tracing_snapshot_alloc() as it needs
316			to be done where GFP_KERNEL allocations are allowed.
317
318	allow_mismatched_32bit_el0 [ARM64,EARLY]
319			Allow execve() of 32-bit applications and setting of the
320			PER_LINUX32 personality on systems where only a strict
321			subset of the CPUs support 32-bit EL0. When this
322			parameter is present, the set of CPUs supporting 32-bit
323			EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
324			and hot-unplug operations may be restricted.
325
326			See Documentation/arch/arm64/asymmetric-32bit.rst for more
327			information.
328
329	amd_iommu=	[HW,X86-64]
330			Pass parameters to the AMD IOMMU driver in the system.
331			Possible values are:
332			fullflush - Deprecated, equivalent to iommu.strict=1
333			off	  - do not initialize any AMD IOMMU found in
334				    the system
335			force_isolation - Force device isolation for all
336					  devices. The IOMMU driver is not
337					  allowed anymore to lift isolation
338					  requirements as needed. This option
339					  does not override iommu=pt
340			force_enable    - Force enable the IOMMU on platforms known
341				          to be buggy with IOMMU enabled. Use this
342				          option with care.
343			pgtbl_v1        - Use v1 page table for DMA-API (Default).
344			pgtbl_v2        - Use v2 page table for DMA-API.
345			irtcachedis     - Disable Interrupt Remapping Table (IRT) caching.
346			nohugepages     - Limit page-sizes used for v1 page-tables
347				          to 4 KiB.
348			v2_pgsizes_only - Limit page-sizes used for v1 page-tables
349				          to 4KiB/2Mib/1GiB.
350
351
352	amd_iommu_dump=	[HW,X86-64]
353			Enable AMD IOMMU driver option to dump the ACPI table
354			for AMD IOMMU. With this option enabled, AMD IOMMU
355			driver will print ACPI tables for AMD IOMMU during
356			IOMMU initialization.
357
358	amd_iommu_intr=	[HW,X86-64]
359			Specifies one of the following AMD IOMMU interrupt
360			remapping modes:
361			legacy     - Use legacy interrupt remapping mode.
362			vapic      - Use virtual APIC mode, which allows IOMMU
363			             to inject interrupts directly into guest.
364			             This mode requires kvm-amd.avic=1.
365			             (Default when IOMMU HW support is present.)
366
367	amd_pstate=	[X86,EARLY]
368			disable
369			  Do not enable amd_pstate as the default
370			  scaling driver for the supported processors
371			passive
372			  Use amd_pstate with passive mode as a scaling driver.
373			  In this mode autonomous selection is disabled.
374			  Driver requests a desired performance level and platform
375			  tries to match the same performance level if it is
376			  satisfied by guaranteed performance level.
377			active
378			  Use amd_pstate_epp driver instance as the scaling driver,
379			  driver provides a hint to the hardware if software wants
380			  to bias toward performance (0x0) or energy efficiency (0xff)
381			  to the CPPC firmware. then CPPC power algorithm will
382			  calculate the runtime workload and adjust the realtime cores
383			  frequency.
384			guided
385			  Activate guided autonomous mode. Driver requests minimum and
386			  maximum performance level and the platform autonomously
387			  selects a performance level in this range and appropriate
388			  to the current workload.
389
390	amd_prefcore=
391			[X86]
392			disable
393			  Disable amd-pstate preferred core.
394
395	amijoy.map=	[HW,JOY] Amiga joystick support
396			Map of devices attached to JOY0DAT and JOY1DAT
397			Format: <a>,<b>
398			See also Documentation/input/joydev/joystick.rst
399
400	analog.map=	[HW,JOY] Analog joystick and gamepad support
401			Specifies type or capabilities of an analog joystick
402			connected to one of 16 gameports
403			Format: <type1>,<type2>,..<type16>
404
405	apc=		[HW,SPARC]
406			Power management functions (SPARCstation-4/5 + deriv.)
407			Format: noidle
408			Disable APC CPU standby support. SPARCstation-Fox does
409			not play well with APC CPU idle - disable it if you have
410			APC and your system crashes randomly.
411
412	apic		[APIC,X86-64] Use IO-APIC. Default.
413
414	apic=		[APIC,X86,EARLY] Advanced Programmable Interrupt Controller
415			Change the output verbosity while booting
416			Format: { quiet (default) | verbose | debug }
417			Change the amount of debugging information output
418			when initialising the APIC and IO-APIC components.
419
420	apic_extnmi=	[APIC,X86,EARLY] External NMI delivery setting
421			Format: { bsp (default) | all | none }
422			bsp:  External NMI is delivered only to CPU 0
423			all:  External NMIs are broadcast to all CPUs as a
424			      backup of CPU 0
425			none: External NMI is masked for all CPUs. This is
426			      useful so that a dump capture kernel won't be
427			      shot down by NMI
428
429	apicpmtimer	Do APIC timer calibration using the pmtimer. Implies
430			apicmaintimer. Useful when your PIT timer is totally
431			broken.
432
433	autoconf=	[IPV6]
434			See Documentation/networking/ipv6.rst.
435
436	apm=		[APM] Advanced Power Management
437			See header of arch/x86/kernel/apm_32.c.
438
439	apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
440			Format: { "0" | "1" }
441			See security/apparmor/Kconfig help text
442			0 -- disable.
443			1 -- enable.
444			Default value is set via kernel config option.
445
446	arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
447			Format: <io>,<irq>,<nodeID>
448
449	arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
450			32 bit applications.
451
452	arm64.nobti	[ARM64] Unconditionally disable Branch Target
453			Identification support
454
455	arm64.nogcs	[ARM64] Unconditionally disable Guarded Control Stack
456			support
457
458	arm64.nomops	[ARM64] Unconditionally disable Memory Copy and Memory
459			Set instructions support
460
461	arm64.nompam	[ARM64] Unconditionally disable Memory Partitioning And
462			Monitoring support
463
464	arm64.nomte	[ARM64] Unconditionally disable Memory Tagging Extension
465			support
466
467	arm64.nopauth	[ARM64] Unconditionally disable Pointer Authentication
468			support
469
470	arm64.nosme	[ARM64] Unconditionally disable Scalable Matrix
471			Extension support
472
473	arm64.nosve	[ARM64] Unconditionally disable Scalable Vector
474			Extension support
475
476	ataflop=	[HW,M68k]
477
478	atarimouse=	[HW,MOUSE] Atari Mouse
479
480	atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
481			EzKey and similar keyboards
482
483	atkbd.reset=	[HW] Reset keyboard during initialization
484
485	atkbd.set=	[HW] Select keyboard code set
486			Format: <int> (2 = AT (default), 3 = PS/2)
487
488	atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
489			keyboards
490
491	atkbd.softraw=	[HW] Choose between synthetic and real raw mode
492			Format: <bool> (0 = real, 1 = synthetic (default))
493
494	atkbd.softrepeat= [HW]
495			Use software keyboard repeat
496
497	audit=		[KNL] Enable the audit sub-system
498			Format: { "0" | "1" | "off" | "on" }
499			0 | off - kernel audit is disabled and can not be
500			    enabled until the next reboot
501			unset - kernel audit is initialized but disabled and
502			    will be fully enabled by the userspace auditd.
503			1 | on - kernel audit is initialized and partially
504			    enabled, storing at most audit_backlog_limit
505			    messages in RAM until it is fully enabled by the
506			    userspace auditd.
507			Default: unset
508
509	audit_backlog_limit= [KNL] Set the audit queue size limit.
510			Format: <int> (must be >=0)
511			Default: 64
512
513	bau=		[X86_UV] Enable the BAU on SGI UV.  The default
514			behavior is to disable the BAU (i.e. bau=0).
515			Format: { "0" | "1" }
516			0 - Disable the BAU.
517			1 - Enable the BAU.
518			unset - Disable the BAU.
519
520	baycom_epp=	[HW,AX25]
521			Format: <io>,<mode>
522
523	baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
524			Format: <io>,<mode>
525			See header of drivers/net/hamradio/baycom_par.c.
526
527	baycom_ser_fdx=	[HW,AX25]
528			BayCom Serial Port AX.25 Modem (Full Duplex Mode)
529			Format: <io>,<irq>,<mode>[,<baud>]
530			See header of drivers/net/hamradio/baycom_ser_fdx.c.
531
532	baycom_ser_hdx=	[HW,AX25]
533			BayCom Serial Port AX.25 Modem (Half Duplex Mode)
534			Format: <io>,<irq>,<mode>
535			See header of drivers/net/hamradio/baycom_ser_hdx.c.
536
537	bdev_allow_write_mounted=
538			Format: <bool>
539			Control the ability to open a mounted block device
540			for writing, i.e., allow / disallow writes that bypass
541			the FS. This was implemented as a means to prevent
542			fuzzers from crashing the kernel by overwriting the
543			metadata underneath a mounted FS without its awareness.
544			This also prevents destructive formatting of mounted
545			filesystems by naive storage tooling that don't use
546			O_EXCL. Default is Y and can be changed through the
547			Kconfig option CONFIG_BLK_DEV_WRITE_MOUNTED.
548
549	bert_disable	[ACPI]
550			Disable BERT OS support on buggy BIOSes.
551
552	bgrt_disable	[ACPI,X86,EARLY]
553			Disable BGRT to avoid flickering OEM logo.
554
555	blkdevparts=	Manual partition parsing of block device(s) for
556			embedded devices based on command line input.
557			See Documentation/block/cmdline-partition.rst
558
559	boot_delay=	[KNL,EARLY]
560			Milliseconds to delay each printk during boot.
561			Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
562			and you may also have to specify "lpj=".  Boot_delay
563			values larger than 10 seconds (10000) are assumed
564			erroneous and ignored.
565			Format: integer
566
567	bootconfig	[KNL,EARLY]
568			Extended command line options can be added to an initrd
569			and this will cause the kernel to look for it.
570
571			See Documentation/admin-guide/bootconfig.rst
572
573	bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
574	bttv.radio=	Most important insmod options are available as
575			kernel args too.
576	bttv.pll=	See Documentation/admin-guide/media/bttv.rst
577	bttv.tuner=
578
579	bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
580			firmware feature for flushing multiple hpte entries
581			at a time.
582
583	c101=		[NET] Moxa C101 synchronous serial card
584
585	cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
586			Sometimes CPU hardware bugs make them report the cache
587			size incorrectly. The kernel will attempt work arounds
588			to fix known problems, but for some CPUs it is not
589			possible to determine what the correct size should be.
590			This option provides an override for these situations.
591
592	carrier_timeout=
593			[NET] Specifies amount of time (in seconds) that
594			the kernel should wait for a network carrier. By default
595			it waits 120 seconds.
596
597	ca_keys=	[KEYS] This parameter identifies a specific key(s) on
598			the system trusted keyring to be used for certificate
599			trust validation.
600			format: { id:<keyid> | builtin }
601
602	cca=		[MIPS,EARLY] Override the kernel pages' cache coherency
603			algorithm.  Accepted values range from 0 to 7
604			inclusive. See arch/mips/include/asm/pgtable-bits.h
605			for platform specific values (SB1, Loongson3 and
606			others).
607
608	ccw_timeout_log	[S390]
609			See Documentation/arch/s390/common_io.rst for details.
610
611	cfi=		[X86-64] Set Control Flow Integrity checking features
612			when CONFIG_FINEIBT is enabled.
613			Format: feature[,feature...]
614			Default: auto
615
616			auto:	  Use FineIBT if IBT available, otherwise kCFI.
617				  Under FineIBT, enable "paranoid" mode when
618				  FRED is not available.
619			off:	  Turn off CFI checking.
620			kcfi:	  Use kCFI (disable FineIBT).
621			fineibt:  Use FineIBT (even if IBT not available).
622			norand:   Do not re-randomize CFI hashes.
623			paranoid: Add caller hash checking under FineIBT.
624			bhi:	  Enable register poisoning to stop speculation
625				  across FineIBT. (Disabled by default.)
626			warn:	  Do not enforce CFI checking: warn only.
627			debug:    Report CFI initialization details.
628
629	cgroup_disable=	[KNL] Disable a particular controller or optional feature
630			Format: {name of the controller(s) or feature(s) to disable}
631			The effects of cgroup_disable=foo are:
632			- foo isn't auto-mounted if you mount all cgroups in
633			  a single hierarchy
634			- foo isn't visible as an individually mountable
635			  subsystem
636			- if foo is an optional feature then the feature is
637			  disabled and corresponding cgroup files are not
638			  created
639			{Currently only "memory" controller deal with this and
640			cut the overhead, others just disable the usage. So
641			only cgroup_disable=memory is actually worthy}
642			Specifying "pressure" disables per-cgroup pressure
643			stall information accounting feature
644
645	cgroup_no_v1=	[KNL] Disable cgroup controllers and named hierarchies in v1
646			Format: { { controller | "all" | "named" }
647			          [,{ controller | "all" | "named" }...] }
648			Like cgroup_disable, but only applies to cgroup v1;
649			the blacklisted controllers remain available in cgroup2.
650			"all" blacklists all controllers and "named" disables
651			named mounts. Specifying both "all" and "named" disables
652			all v1 hierarchies.
653
654	cgroup_v1_proc=	[KNL] Show also missing controllers in /proc/cgroups
655			Format: { "true" | "false" }
656			/proc/cgroups lists only v1 controllers by default.
657			This compatibility option enables listing also v2
658			controllers (whose v1 code is not compiled!), so that
659			semi-legacy software can check this file to decide
660			about usage of v2 (sic) controllers.
661
662	cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
663			Format: { "true" | "false" }
664			Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.
665
666	cgroup.memory=	[KNL] Pass options to the cgroup memory controller.
667			Format: <string>
668			nosocket -- Disable socket memory accounting.
669			nokmem -- Disable kernel memory accounting.
670			nobpf -- Disable BPF memory accounting.
671
672	checkreqprot=	[SELINUX] Set initial checkreqprot flag value.
673			Format: { "0" | "1" }
674			See security/selinux/Kconfig help text.
675			0 -- check protection applied by kernel (includes
676				any implied execute protection).
677			1 -- check protection requested by application.
678			Default value is set via a kernel config option.
679			Value can be changed at runtime via
680				/sys/fs/selinux/checkreqprot.
681			Setting checkreqprot to 1 is deprecated.
682
683	cio_ignore=	[S390]
684			See Documentation/arch/s390/common_io.rst for details.
685
686	clearcpuid=X[,X...] [X86]
687			Disable CPUID feature X for the kernel. See
688			arch/x86/include/asm/cpufeatures.h for the valid bit
689			numbers X. Note the Linux-specific bits are not necessarily
690			stable over kernel options, but the vendor-specific
691			ones should be.
692			X can also be a string as appearing in the flags: line
693			in /proc/cpuinfo which does not have the above
694			instability issue. However, not all features have names
695			in /proc/cpuinfo.
696			Note that using this option will taint your kernel.
697			Also note that user programs calling CPUID directly
698			or using the feature without checking anything
699			will still see it. This just prevents it from
700			being used by the kernel or shown in /proc/cpuinfo.
701			Also note the kernel might malfunction if you disable
702			some critical bits.
703
704	clk_ignore_unused
705			[CLK]
706			Prevents the clock framework from automatically gating
707			clocks that have not been explicitly enabled by a Linux
708			device driver but are enabled in hardware at reset or
709			by the bootloader/firmware. Note that this does not
710			force such clocks to be always-on nor does it reserve
711			those clocks in any way. This parameter is useful for
712			debug and development, but should not be needed on a
713			platform with proper driver support.  For more
714			information, see Documentation/driver-api/clk.rst.
715
716	clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
717			[Deprecated]
718			Forces specified clocksource (if available) to be used
719			when calculating gettimeofday(). If specified
720			clocksource is not available, it defaults to PIT.
721			Format: { pit | tsc | cyclone | pmtmr }
722
723	clocksource=	Override the default clocksource
724			Format: <string>
725			Override the default clocksource and use the clocksource
726			with the name specified.
727			Some clocksource names to choose from, depending on
728			the platform:
729			[all] jiffies (this is the base, fallback clocksource)
730			[ACPI] acpi_pm
731			[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
732				pxa_timer,timer3,32k_counter,timer0_1
733			[X86-32] pit,hpet,tsc;
734				scx200_hrt on Geode; cyclone on IBM x440
735			[MIPS] MIPS
736			[PARISC] cr16
737			[S390] tod
738			[SH] SuperH
739			[SPARC64] tick
740			[X86-64] hpet,tsc
741
742	clocksource.arm_arch_timer.evtstrm=
743			[ARM,ARM64,EARLY]
744			Format: <bool>
745			Enable/disable the eventstream feature of the ARM
746			architected timer so that code using WFE-based polling
747			loops can be debugged more effectively on production
748			systems.
749
750	clocksource.verify_n_cpus= [KNL]
751			Limit the number of CPUs checked for clocksources
752			marked with CLOCK_SOURCE_VERIFY_PERCPU that
753			are marked unstable due to excessive skew.
754			A negative value says to check all CPUs, while
755			zero says not to check any.  Values larger than
756			nr_cpu_ids are silently truncated to nr_cpu_ids.
757			The actual CPUs are chosen randomly, with
758			no replacement if the same CPU is chosen twice.
759
760	clocksource-wdtest.holdoff= [KNL]
761			Set the time in seconds that the clocksource
762			watchdog test waits before commencing its tests.
763			Defaults to zero when built as a module and to
764			10 seconds when built into the kernel.
765
766	cma=nn[MG]@[start[MG][-end[MG]]]
767			[KNL,CMA,EARLY]
768			Sets the size of kernel global memory area for
769			contiguous memory allocations and optionally the
770			placement constraint by the physical address range of
771			memory allocations. A value of 0 disables CMA
772			altogether. For more information, see
773			kernel/dma/contiguous.c
774
775	cma_pernuma=nn[MG]
776			[KNL,CMA,EARLY]
777			Sets the size of kernel per-numa memory area for
778			contiguous memory allocations. A value of 0 disables
779			per-numa CMA altogether. And If this option is not
780			specified, the default value is 0.
781			With per-numa CMA enabled, DMA users on node nid will
782			first try to allocate buffer from the pernuma area
783			which is located in node nid, if the allocation fails,
784			they will fallback to the global default memory area.
785
786	numa_cma=<node>:nn[MG][,<node>:nn[MG]]
787			[KNL,CMA,EARLY]
788			Sets the size of kernel numa memory area for
789			contiguous memory allocations. It will reserve CMA
790			area for the specified node.
791
792			With numa CMA enabled, DMA users on node nid will
793			first try to allocate buffer from the numa area
794			which is located in node nid, if the allocation fails,
795			they will fallback to the global default memory area.
796
797	cmo_free_hint=	[PPC] Format: { yes | no }
798			Specify whether pages are marked as being inactive
799			when they are freed.  This is used in CMO environments
800			to determine OS memory pressure for page stealing by
801			a hypervisor.
802			Default: yes
803
804	coherent_pool=nn[KMG]	[ARM,KNL,EARLY]
805			Sets the size of memory pool for coherent, atomic dma
806			allocations, by default set to 256K.
807
808	com20020=	[HW,NET] ARCnet - COM20020 chipset
809			Format:
810			<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
811
812	com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
813			Format: <io>[,<irq>]
814
815	com90xx=	[HW,NET]
816			ARCnet - COM90xx chipset (memory-mapped buffers)
817			Format: <io>[,<irq>[,<memstart>]]
818
819	condev=		[HW,S390] console device
820	conmode=
821
822	con3215_drop=	[S390,EARLY] 3215 console drop mode.
823			Format: y|n|Y|N|1|0
824			When set to true, drop data on the 3215 console when
825			the console buffer is full. In this case the
826			operator using a 3270 terminal emulator (for example
827			x3270) does not have to enter the clear key for the
828			console output to advance and the kernel to continue.
829			This leads to a much faster boot time when a 3270
830			terminal emulator is active. If no 3270 terminal
831			emulator is used, this parameter has no effect.
832
833	console=	[KNL] Output console device and options.
834
835		tty<n>	Use the virtual console device <n>.
836
837		ttyS<n>[,options]
838		ttyUSB0[,options]
839			Use the specified serial port.  The options are of
840			the form "bbbbpnf", where "bbbb" is the baud rate,
841			"p" is parity ("n", "o", or "e"), "n" is number of
842			bits, and "f" is flow control ("r" for RTS or
843			omit it).  Default is "9600n8".
844
845			See Documentation/admin-guide/serial-console.rst for more
846			information.  See
847			Documentation/networking/netconsole.rst for an
848			alternative.
849
850		<DEVNAME>:<n>.<n>[,options]
851			Use the specified serial port on the serial core bus.
852			The addressing uses DEVNAME of the physical serial port
853			device, followed by the serial core controller instance,
854			and the serial port instance. The options are the same
855			as documented for the ttyS addressing above.
856
857			The mapping of the serial ports to the tty instances
858			can be viewed with:
859
860			$ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
861			/sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
862
863			In the above example, the console can be addressed with
864			console=00:04:0.0. Note that a console addressed this
865			way will only get added when the related device driver
866			is ready. The use of an earlycon parameter in addition to
867			the console may be desired for console output early on.
868
869		uart[8250],io,<addr>[,options]
870		uart[8250],mmio,<addr>[,options]
871		uart[8250],mmio16,<addr>[,options]
872		uart[8250],mmio32,<addr>[,options]
873		uart[8250],0x<addr>[,options]
874			Start an early, polled-mode console on the 8250/16550
875			UART at the specified I/O port or MMIO address,
876			switching to the matching ttyS device later.
877			MMIO inter-register address stride is either 8-bit
878			(mmio), 16-bit (mmio16), or 32-bit (mmio32).
879			If none of [io|mmio|mmio16|mmio32], <addr> is assumed
880			to be equivalent to 'mmio'. 'options' are specified in
881			the same format described for ttyS above; if unspecified,
882			the h/w is not re-initialized.
883
884		hvc<n>	Use the hypervisor console device <n>. This is for
885			both Xen and PowerPC hypervisors.
886
887		{ null | "" }
888			Use to disable console output, i.e., to have kernel
889			console messages discarded.
890			This must be the only console= parameter used on the
891			kernel command line.
892
893		If the device connected to the port is not a TTY but a braille
894		device, prepend "brl," before the device type, for instance
895			console=brl,ttyS0
896		For now, only VisioBraille is supported.
897
898	console_msg_format=
899			[KNL] Change console messages format
900		default
901			By default we print messages on consoles in
902			"[time stamp] text\n" format (time stamp may not be
903			printed, depending on CONFIG_PRINTK_TIME or
904			`printk_time' param).
905		syslog
906			Switch to syslog format: "<%u>[time stamp] text\n"
907			IOW, each message will have a facility and loglevel
908			prefix. The format is similar to one used by syslog()
909			syscall, or to executing "dmesg -S --raw" or to reading
910			from /proc/kmsg.
911
912	consoleblank=	[KNL] The console blank (screen saver) timeout in
913			seconds. A value of 0 disables the blank timer.
914			Defaults to 0.
915
916	coredump_filter=
917			[KNL] Change the default value for
918			/proc/<pid>/coredump_filter.
919			See also Documentation/filesystems/proc.rst.
920
921	coresight_cpu_debug.enable
922			[ARM,ARM64]
923			Format: <bool>
924			Enable/disable the CPU sampling based debugging.
925			0: default value, disable debugging
926			1: enable debugging at boot time
927
928	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
929			Format:
930			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
931
932	cpuidle.off=1	[CPU_IDLE]
933			disable the cpuidle sub-system
934
935	cpuidle.governor=
936			[CPU_IDLE] Name of the cpuidle governor to use.
937
938	cpufreq.off=1	[CPU_FREQ]
939			disable the cpufreq sub-system
940
941	cpufreq.default_governor=
942			[CPU_FREQ] Name of the default cpufreq governor or
943			policy to use. This governor must be registered in the
944			kernel before the cpufreq driver probes.
945
946	cpu_init_udelay=N
947			[X86,EARLY] Delay for N microsec between assert and de-assert
948			of APIC INIT to start processors.  This delay occurs
949			on every CPU online, such as boot, and resume from suspend.
950			Default: 10000
951
952	cpuhp.parallel=
953			[SMP] Enable/disable parallel bringup of secondary CPUs
954			Format: <bool>
955			Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
956			the parameter has no effect.
957
958	crash_kexec_post_notifiers
959			Only jump to kdump kernel after running the panic
960			notifiers and dumping kmsg. This option increases
961			the risks of a kdump failure, since some panic
962			notifiers can make the crashed kernel more unstable.
963			In configurations where kdump may not be reliable,
964			running the panic notifiers could allow collecting
965			more data on dmesg, like stack traces from other CPUS
966			or extra data dumped by panic_print. Note that some
967			configurations enable this option unconditionally,
968			like Hyper-V, PowerPC (fadump) and AMD SEV-SNP.
969
970	crashkernel=size[KMG][@offset[KMG]]
971			[KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'
972			upon panic. This parameter reserves the physical
973			memory region [offset, offset + size] for that kernel
974			image. If '@offset' is omitted, then a suitable offset
975			is selected automatically.
976			[KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
977			under 4G first, and fall back to reserve region above
978			4G when '@offset' hasn't been specified.
979			See Documentation/admin-guide/kdump/kdump.rst for further details.
980
981	crashkernel=range1:size1[,range2:size2,...][@offset]
982			[KNL] Same as above, but depends on the memory
983			in the running system. The syntax of range is
984			start-[end] where start and end are both
985			a memory unit (amount[KMG]). See also
986			Documentation/admin-guide/kdump/kdump.rst for an example.
987
988	crashkernel=size[KMG],high
989			[KNL, X86-64, ARM64, RISCV, LoongArch] range could be
990			above 4G.
991			Allow kernel to allocate physical memory region from top,
992			so could be above 4G if system have more than 4G ram
993			installed. Otherwise memory region will be allocated
994			below 4G, if available.
995			It will be ignored if crashkernel=X is specified.
996	crashkernel=size[KMG],low
997			[KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
998			When crashkernel=X,high is passed, kernel could allocate
999			physical memory region above 4G, that cause second kernel
1000			crash on system that require some amount of low memory,
1001			e.g. swiotlb requires at least 64M+32K low memory, also
1002			enough extra low memory is needed to make sure DMA buffers
1003			for 32-bit devices won't run out. Kernel would try to allocate
1004			default	size of memory below 4G automatically. The default
1005			size is	platform dependent.
1006			  --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
1007			  --> arm64: 128MiB
1008			  --> riscv: 128MiB
1009			  --> loongarch: 128MiB
1010			This one lets the user specify own low range under 4G
1011			for second kernel instead.
1012			0: to disable low allocation.
1013			It will be ignored when crashkernel=X,high is not used
1014			or memory reserved is below 4G.
1015	crashkernel=size[KMG],cma
1016			[KNL, X86] Reserve additional crash kernel memory from
1017			CMA. This reservation is usable by the first system's
1018			userspace memory and kernel movable allocations (memory
1019			balloon, zswap). Pages allocated from this memory range
1020			will not be included in the vmcore so this should not
1021			be used if dumping of userspace memory is intended and
1022			it has to be expected that some movable kernel pages
1023			may be missing from the dump.
1024
1025			A standard crashkernel reservation, as described above,
1026			is still needed to hold the crash kernel and initrd.
1027
1028			This option increases the risk of a kdump failure: DMA
1029			transfers configured by the first kernel may end up
1030			corrupting the second kernel's memory.
1031
1032			This reservation method is intended for systems that
1033			can't afford to sacrifice enough memory for standard
1034			crashkernel reservation and where less reliable and
1035			possibly incomplete kdump is preferable to no kdump at
1036			all.
1037
1038	cryptomgr.notests
1039			[KNL] Disable crypto self-tests
1040
1041	cs89x0_dma=	[HW,NET]
1042			Format: <dma>
1043
1044	cs89x0_media=	[HW,NET]
1045			Format: { rj45 | aui | bnc }
1046
1047	csdlock_debug=	[KNL] Enable or disable debug add-ons of cross-CPU
1048			function call handling. When switched on,
1049			additional debug data is printed to the console
1050			in case a hanging CPU is detected, and that
1051			CPU is pinged again in order to try to resolve
1052			the hang situation.  The default value of this
1053			option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
1054			Kconfig option.
1055
1056	dasd=		[HW,NET]
1057			See header of drivers/s390/block/dasd_devmap.c.
1058
1059	db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
1060			(one device per port)
1061			Format: <port#>,<type>
1062			See also Documentation/input/devices/joystick-parport.rst
1063
1064	debug		[KNL,EARLY] Enable kernel debugging (events log level).
1065
1066	debug_boot_weak_hash
1067			[KNL,EARLY] Enable printing [hashed] pointers early in the
1068			boot sequence.  If enabled, we use a weak hash instead
1069			of siphash to hash pointers.  Use this option if you are
1070			seeing instances of '(___ptrval___)') and need to see a
1071			value (hashed pointer) instead. Cryptographically
1072			insecure, please do not use on production kernels.
1073
1074	debug_locks_verbose=
1075			[KNL] verbose locking self-tests
1076			Format: <int>
1077			Print debugging info while doing the locking API
1078			self-tests.
1079			Bitmask for the various LOCKTYPE_ tests. Defaults to 0
1080			(no extra messages), setting it to -1 (all bits set)
1081			will print _a_lot_ more information - normally only
1082			useful to lockdep developers.
1083
1084	debug_objects	[KNL,EARLY] Enable object debugging
1085
1086	debug_guardpage_minorder=
1087			[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this
1088			parameter allows control of the order of pages that will
1089			be intentionally kept free (and hence protected) by the
1090			buddy allocator. Bigger value increase the probability
1091			of catching random memory corruption, but reduce the
1092			amount of memory for normal system use. The maximum
1093			possible value is MAX_PAGE_ORDER/2.  Setting this
1094			parameter to 1 or 2 should be enough to identify most
1095			random memory corruption problems caused by bugs in
1096			kernel or driver code when a CPU writes to (or reads
1097			from) a random memory location. Note that there exists
1098			a class of memory corruptions problems caused by buggy
1099			H/W or F/W or by drivers badly programming DMA
1100			(basically when memory is written at bus level and the
1101			CPU MMU is bypassed) which are not detectable by
1102			CONFIG_DEBUG_PAGEALLOC, hence this option will not
1103			help tracking down these problems.
1104
1105	debug_pagealloc=
1106			[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1107			enables the feature at boot time. By default, it is
1108			disabled and the system will work mostly the same as a
1109			kernel built without CONFIG_DEBUG_PAGEALLOC.
1110			Note: to get most of debug_pagealloc error reports, it's
1111			useful to also enable the page_owner functionality.
1112			on: enable the feature
1113
1114	debugfs=    	[KNL,EARLY] This parameter enables what is exposed to
1115			userspace and debugfs internal clients.
1116			Format: { on, no-mount, off }
1117			on: 	All functions are enabled.
1118			no-mount:
1119				Filesystem is not registered but kernel clients can
1120			        access APIs and a crashkernel can be used to read
1121				its content. There is nothing to mount.
1122			off: 	Filesystem is not registered and clients
1123			        get a -EPERM as result when trying to register files
1124				or directories within debugfs.
1125				This is equivalent of the runtime functionality if
1126				debugfs was not enabled in the kernel at all.
1127			Default value is set in build-time with a kernel configuration.
1128
1129	debugpat	[X86] Enable PAT debugging
1130
1131	default_hugepagesz=
1132			[HW] The size of the default HugeTLB page. This is
1133			the size represented by the legacy /proc/ hugepages
1134			APIs.  In addition, this is the default hugetlb size
1135			used for shmget(), mmap() and mounting hugetlbfs
1136			filesystems.  If not specified, defaults to the
1137			architecture's default huge page size.  Huge page
1138			sizes are architecture dependent.  See also
1139			Documentation/admin-guide/mm/hugetlbpage.rst.
1140			Format: size[KMG]
1141
1142	deferred_probe_timeout=
1143			[KNL] Debugging option to set a timeout in seconds for
1144			deferred probe to give up waiting on dependencies to
1145			probe. Only specific dependencies (subsystems or
1146			drivers) that have opted in will be ignored. A timeout
1147			of 0 will timeout at the end of initcalls. If the time
1148			out hasn't expired, it'll be restarted by each
1149			successful driver registration. This option will also
1150			dump out devices still on the deferred probe list after
1151			retrying.
1152
1153	delayacct	[KNL] Enable per-task delay accounting
1154
1155	dell_smm_hwmon.ignore_dmi=
1156			[HW] Continue probing hardware even if DMI data
1157			indicates that the driver is running on unsupported
1158			hardware.
1159
1160	dell_smm_hwmon.force=
1161			[HW] Activate driver even if SMM BIOS signature does
1162			not match list of supported models and enable otherwise
1163			blacklisted features.
1164
1165	dell_smm_hwmon.power_status=
1166			[HW] Report power status in /proc/i8k
1167			(disabled by default).
1168
1169	dell_smm_hwmon.restricted=
1170			[HW] Allow controlling fans only if SYS_ADMIN
1171			capability is set.
1172
1173	dell_smm_hwmon.fan_mult=
1174			[HW] Factor to multiply fan speed with.
1175
1176	dell_smm_hwmon.fan_max=
1177			[HW] Maximum configurable fan speed.
1178
1179	dfltcc=		[HW,S390]
1180			Format: { on | off | def_only | inf_only | always }
1181			on:       s390 zlib hardware support for compression on
1182			          level 1 and decompression (default)
1183			off:      No s390 zlib hardware support
1184			def_only: s390 zlib hardware support for deflate
1185			          only (compression on level 1)
1186			inf_only: s390 zlib hardware support for inflate
1187			          only (decompression)
1188			always:   Same as 'on' but ignores the selected compression
1189			          level always using hardware support (used for debugging)
1190
1191	dhash_entries=	[KNL]
1192			Set number of hash buckets for dentry cache.
1193
1194	disable_1tb_segments [PPC,EARLY]
1195			Disables the use of 1TB hash page table segments. This
1196			causes the kernel to fall back to 256MB segments which
1197			can be useful when debugging issues that require an SLB
1198			miss to occur.
1199
1200	disable=	[IPV6]
1201			See Documentation/networking/ipv6.rst.
1202
1203	disable_radix	[PPC,EARLY]
1204			Disable RADIX MMU mode on POWER9
1205
1206	disable_tlbie	[PPC]
1207			Disable TLBIE instruction. Currently does not work
1208			with KVM, with HASH MMU, or with coherent accelerators.
1209
1210	disable_ddw	[PPC/PSERIES,EARLY]
1211			Disable Dynamic DMA Window support. Use this
1212			to workaround buggy firmware.
1213
1214	disable_ipv6=	[IPV6]
1215			See Documentation/networking/ipv6.rst.
1216
1217	disable_mtrr_cleanup [X86,EARLY]
1218			The kernel tries to adjust MTRR layout from continuous
1219			to discrete, to make X server driver able to add WB
1220			entry later. This parameter disables that.
1221
1222	disable_mtrr_trim [X86, Intel and AMD only,EARLY]
1223			By default the kernel will trim any uncacheable
1224			memory out of your available memory pool based on
1225			MTRR settings.  This parameter disables that behavior,
1226			possibly causing your machine to run very slowly.
1227
1228	disable_timer_pin_1 [X86,EARLY]
1229			Disable PIN 1 of APIC timer
1230			Can be useful to work around chipset bugs.
1231
1232	dis_ucode_ldr	[X86] Disable the microcode loader.
1233
1234	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
1235			this option disables the debugging code at boot.
1236
1237	dma_debug_entries=<number>
1238			This option allows to tune the number of preallocated
1239			entries for DMA-API debugging code. One entry is
1240			required per DMA-API allocation. Use this if the
1241			DMA-API debugging code disables itself because the
1242			architectural default is too low.
1243
1244	dma_debug_driver=<driver_name>
1245			With this option the DMA-API debugging driver
1246			filter feature can be enabled at boot time. Just
1247			pass the driver to filter for as the parameter.
1248			The filter can be disabled or changed to another
1249			driver later using sysfs.
1250
1251	reg_file_data_sampling=
1252			[X86] Controls mitigation for Register File Data
1253			Sampling (RFDS) vulnerability. RFDS is a CPU
1254			vulnerability which may allow userspace to infer
1255			kernel data values previously stored in floating point
1256			registers, vector registers, or integer registers.
1257			RFDS only affects Intel Atom processors.
1258
1259			on:	Turns ON the mitigation.
1260			off:	Turns OFF the mitigation.
1261
1262			This parameter overrides the compile time default set
1263			by CONFIG_MITIGATION_RFDS. Mitigation cannot be
1264			disabled when other VERW based mitigations (like MDS)
1265			are enabled. In order to disable RFDS mitigation all
1266			VERW based mitigations need to be disabled.
1267
1268			For details see:
1269			Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1270
1271	driver_async_probe=  [KNL]
1272			List of driver names to be probed asynchronously. *
1273			matches with all driver names. If * is specified, the
1274			rest of the listed driver names are those that will NOT
1275			match the *.
1276			Format: <driver_name1>,<driver_name2>...
1277
1278	drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1279			Broken monitors, graphic adapters, KVMs and EDIDless
1280			panels may send no or incorrect EDID data sets.
1281			This parameter allows to specify an EDID data sets
1282			in the /lib/firmware directory that are used instead.
1283			An EDID data set will only be used for a particular
1284			connector, if its name and a colon are prepended to
1285			the EDID name. Each connector may use a unique EDID
1286			data set by separating the files with a comma. An EDID
1287			data set with no connector name will be used for
1288			any connectors not explicitly specified.
1289
1290	dscc4.setup=	[NET]
1291
1292	dt_cpu_ftrs=	[PPC,EARLY]
1293			Format: {"off" | "known"}
1294			Control how the dt_cpu_ftrs device-tree binding is
1295			used for CPU feature discovery and setup (if it
1296			exists).
1297			off: Do not use it, fall back to legacy cpu table.
1298			known: Do not pass through unknown features to guests
1299			or userspace, only those that the kernel is aware of.
1300
1301	dump_apple_properties	[X86]
1302			Dump name and content of EFI device properties on
1303			x86 Macs.  Useful for driver authors to determine
1304			what data is available or for reverse-engineering.
1305
1306	dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
1307	<module>.dyndbg[="val"]
1308			Enable debug messages at boot time.  See
1309			Documentation/admin-guide/dynamic-debug-howto.rst
1310			for details.
1311
1312	early_ioremap_debug [KNL,EARLY]
1313			Enable debug messages in early_ioremap support. This
1314			is useful for tracking down temporary early mappings
1315			which are not unmapped.
1316
1317	earlycon=	[KNL,EARLY] Output early console device and options.
1318
1319			When used with no options, the early console is
1320			determined by stdout-path property in device tree's
1321			chosen node or the ACPI SPCR table if supported by
1322			the platform.
1323
1324		cdns,<addr>[,options]
1325			Start an early, polled-mode console on a Cadence
1326			(xuartps) serial port at the specified address. Only
1327			supported option is baud rate. If baud rate is not
1328			specified, the serial port must already be setup and
1329			configured.
1330
1331		uart[8250],io,<addr>[,options[,uartclk]]
1332		uart[8250],mmio,<addr>[,options[,uartclk]]
1333		uart[8250],mmio32,<addr>[,options[,uartclk]]
1334		uart[8250],mmio32be,<addr>[,options[,uartclk]]
1335		uart[8250],0x<addr>[,options]
1336			Start an early, polled-mode console on the 8250/16550
1337			UART at the specified I/O port or MMIO address.
1338			MMIO inter-register address stride is either 8-bit
1339			(mmio) or 32-bit (mmio32 or mmio32be).
1340			If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1341			to be equivalent to 'mmio'. 'options' are specified
1342			in the same format described for "console=ttyS<n>"; if
1343			unspecified, the h/w is not initialized. 'uartclk' is
1344			the uart clock frequency; if unspecified, it is set
1345			to 'BASE_BAUD' * 16.
1346
1347		pl011,<addr>
1348		pl011,mmio32,<addr>
1349			Start an early, polled-mode console on a pl011 serial
1350			port at the specified address. The pl011 serial port
1351			must already be setup and configured. Options are not
1352			yet supported.  If 'mmio32' is specified, then only
1353			the driver will use only 32-bit accessors to read/write
1354			the device registers.
1355
1356		liteuart,<addr>
1357			Start an early console on a litex serial port at the
1358			specified address. The serial port must already be
1359			setup and configured. Options are not yet supported.
1360
1361		meson,<addr>
1362			Start an early, polled-mode console on a meson serial
1363			port at the specified address. The serial port must
1364			already be setup and configured. Options are not yet
1365			supported.
1366
1367		msm_serial,<addr>
1368			Start an early, polled-mode console on an msm serial
1369			port at the specified address. The serial port
1370			must already be setup and configured. Options are not
1371			yet supported.
1372
1373		msm_serial_dm,<addr>
1374			Start an early, polled-mode console on an msm serial
1375			dm port at the specified address. The serial port
1376			must already be setup and configured. Options are not
1377			yet supported.
1378
1379		owl,<addr>
1380			Start an early, polled-mode console on a serial port
1381			of an Actions Semi SoC, such as S500 or S900, at the
1382			specified address. The serial port must already be
1383			setup and configured. Options are not yet supported.
1384
1385		rda,<addr>
1386			Start an early, polled-mode console on a serial port
1387			of an RDA Micro SoC, such as RDA8810PL, at the
1388			specified address. The serial port must already be
1389			setup and configured. Options are not yet supported.
1390
1391		sbi
1392			Use RISC-V SBI (Supervisor Binary Interface) for early
1393			console.
1394
1395		smh	Use ARM semihosting calls for early console.
1396
1397		s3c2410,<addr>
1398		s3c2412,<addr>
1399		s3c2440,<addr>
1400		s3c6400,<addr>
1401		s5pv210,<addr>
1402		exynos4210,<addr>
1403			Use early console provided by serial driver available
1404			on Samsung SoCs, requires selecting proper type and
1405			a correct base address of the selected UART port. The
1406			serial port must already be setup and configured.
1407			Options are not yet supported.
1408
1409		lantiq,<addr>
1410			Start an early, polled-mode console on a lantiq serial
1411			(lqasc) port at the specified address. The serial port
1412			must already be setup and configured. Options are not
1413			yet supported.
1414
1415		lpuart,<addr>
1416		lpuart32,<addr>
1417			Use early console provided by Freescale LP UART driver
1418			found on Freescale Vybrid and QorIQ LS1021A processors.
1419			A valid base address must be provided, and the serial
1420			port must already be setup and configured.
1421
1422		ec_imx21,<addr>
1423		ec_imx6q,<addr>
1424			Start an early, polled-mode, output-only console on the
1425			Freescale i.MX UART at the specified address. The UART
1426			must already be setup and configured.
1427
1428		ar3700_uart,<addr>
1429			Start an early, polled-mode console on the
1430			Armada 3700 serial port at the specified
1431			address. The serial port must already be setup
1432			and configured. Options are not yet supported.
1433
1434		qcom_geni,<addr>
1435			Start an early, polled-mode console on a Qualcomm
1436			Generic Interface (GENI) based serial port at the
1437			specified address. The serial port must already be
1438			setup and configured. Options are not yet supported.
1439
1440		efifb,[options]
1441			Start an early, unaccelerated console on the EFI
1442			memory mapped framebuffer (if available). On cache
1443			coherent non-x86 systems that use system memory for
1444			the framebuffer, pass the 'ram' option so that it is
1445			mapped with the correct attributes.
1446
1447		linflex,<addr>
1448			Use early console provided by Freescale LINFlexD UART
1449			serial driver for NXP S32V234 SoCs. A valid base
1450			address must be provided, and the serial port must
1451			already be setup and configured.
1452
1453	earlyprintk=	[X86,SH,ARM,M68k,S390,UM,EARLY]
1454			earlyprintk=vga
1455			earlyprintk=sclp
1456			earlyprintk=xen
1457			earlyprintk=serial[,ttySn[,baudrate]]
1458			earlyprintk=serial[,0x...[,baudrate]]
1459			earlyprintk=ttySn[,baudrate]
1460			earlyprintk=dbgp[debugController#]
1461			earlyprintk=mmio32,membase[,{nocfg|baudrate}]
1462			earlyprintk=pciserial[,force],bus:device.function[,{nocfg|baudrate}]
1463			earlyprintk=xdbc[xhciController#]
1464			earlyprintk=bios
1465
1466			earlyprintk is useful when the kernel crashes before
1467			the normal console is initialized. It is not enabled by
1468			default because it has some cosmetic problems.
1469
1470			Use "nocfg" to skip UART configuration, assume
1471			BIOS/firmware has configured UART correctly.
1472
1473			Append ",keep" to not disable it when the real console
1474			takes over.
1475
1476			Only one of vga, serial, or usb debug port can
1477			be used at a time.
1478
1479			Currently only ttyS0 and ttyS1 may be specified by
1480			name.  Other I/O ports may be explicitly specified
1481			on some architectures (x86 and arm at least) by
1482			replacing ttySn with an I/O port address, like this:
1483				earlyprintk=serial,0x1008,115200
1484			You can find the port for a given device in
1485			/proc/tty/driver/serial:
1486				2: uart:ST16650V2 port:00001008 irq:18 ...
1487
1488			Interaction with the standard serial driver is not
1489			very good.
1490
1491			The VGA output is eventually overwritten by
1492			the real console.
1493
1494			The xen option can only be used in Xen domains.
1495
1496			The sclp output can only be used on s390.
1497
1498			The bios output can only be used on SuperH.
1499
1500			The optional "force" to "pciserial" enables use of a
1501			PCI device even when its classcode is not of the
1502			UART class.
1503
1504	edac_report=	[HW,EDAC] Control how to report EDAC event
1505			Format: {"on" | "off" | "force"}
1506			on: enable EDAC to report H/W event. May be overridden
1507			by other higher priority error reporting module.
1508			off: disable H/W event reporting through EDAC.
1509			force: enforce the use of EDAC to report H/W event.
1510			default: on.
1511
1512	edd=		[EDD]
1513			Format: {"off" | "on" | "skip[mbr]"}
1514
1515	efi=		[EFI,EARLY]
1516			Format: { "debug", "disable_early_pci_dma",
1517				  "nochunk", "noruntime", "nosoftreserve",
1518				  "novamap", "no_disable_early_pci_dma" }
1519			debug: enable misc debug output.
1520			disable_early_pci_dma: disable the busmaster bit on all
1521			PCI bridges while in the EFI boot stub.
1522			nochunk: disable reading files in "chunks" in the EFI
1523			boot stub, as chunking can cause problems with some
1524			firmware implementations.
1525			noruntime : disable EFI runtime services support
1526			nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1527			attribute may cause the kernel to reserve the
1528			memory range for a memory mapping driver to
1529			claim. Specify efi=nosoftreserve to disable this
1530			reservation and treat the memory by its base type
1531			(i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1532			novamap: do not call SetVirtualAddressMap().
1533			no_disable_early_pci_dma: Leave the busmaster bit set
1534			on all PCI bridges while in the EFI boot stub
1535
1536	efi_no_storage_paranoia [EFI,X86,EARLY]
1537			Using this parameter you can use more than 50% of
1538			your efi variable storage. Use this parameter only if
1539			you are really sure that your UEFI does sane gc and
1540			fulfills the spec otherwise your board may brick.
1541
1542	efivar_ssdt=	[EFI; X86] Name of an EFI variable that contains an SSDT
1543			that is to be dynamically loaded by Linux. If there are
1544			multiple variables with the same name but with different
1545			vendor GUIDs, all of them will be loaded. See
1546			Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1547
1548
1549	eisa_irq_edge=	[PARISC,HW]
1550			See header of drivers/parisc/eisa.c.
1551
1552	ekgdboc=	[X86,KGDB,EARLY] Allow early kernel console debugging
1553			Format: ekgdboc=kbd
1554
1555			This is designed to be used in conjunction with
1556			the boot argument: earlyprintk=vga
1557
1558			This parameter works in place of the kgdboc parameter
1559			but can only be used if the backing tty is available
1560			very early in the boot process. For early debugging
1561			via a serial port see kgdboc_earlycon instead.
1562
1563	elanfreq=	[X86-32]
1564			See comment before function elanfreq_setup() in
1565			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1566
1567	elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390,EARLY]
1568			Specifies physical address of start of kernel core
1569			image elf header and optionally the size. Generally
1570			kexec loader will pass this option to capture kernel.
1571			See Documentation/admin-guide/kdump/kdump.rst for details.
1572
1573	enable_mtrr_cleanup [X86,EARLY]
1574			The kernel tries to adjust MTRR layout from continuous
1575			to discrete, to make X server driver able to add WB
1576			entry later. This parameter enables that.
1577
1578	enable_timer_pin_1 [X86]
1579			Enable PIN 1 of APIC timer
1580			Can be useful to work around chipset bugs
1581			(in particular on some ATI chipsets).
1582			The kernel tries to set a reasonable default.
1583
1584	enforcing=	[SELINUX] Set initial enforcing status.
1585			Format: {"0" | "1"}
1586			See security/selinux/Kconfig help text.
1587			0 -- permissive (log only, no denials).
1588			1 -- enforcing (deny and log).
1589			Default value is 0.
1590			Value can be changed at runtime via
1591			/sys/fs/selinux/enforce.
1592
1593	erst_disable	[ACPI]
1594			Disable Error Record Serialization Table (ERST)
1595			support.
1596
1597	ether=		[HW,NET] Ethernet cards parameters
1598			This option is obsoleted by the "netdev=" option, which
1599			has equivalent usage. See its documentation for details.
1600
1601	evm=		[EVM]
1602			Format: { "fix" }
1603			Permit 'security.evm' to be updated regardless of
1604			current integrity status.
1605
1606	early_page_ext [KNL,EARLY] Enforces page_ext initialization to earlier
1607			stages so cover more early boot allocations.
1608			Please note that as side effect some optimizations
1609			might be disabled to achieve that (e.g. parallelized
1610			memory initialization is disabled) so the boot process
1611			might take longer, especially on systems with a lot of
1612			memory. Available with CONFIG_PAGE_EXTENSION=y.
1613
1614	failslab=
1615	fail_usercopy=
1616	fail_page_alloc=
1617	fail_skb_realloc=
1618	fail_make_request=[KNL]
1619			General fault injection mechanism.
1620			Format: <interval>,<probability>,<space>,<times>
1621			See also Documentation/fault-injection/.
1622
1623	fb_tunnels=	[NET]
1624			Format: { initns | none }
1625			See Documentation/admin-guide/sysctl/net.rst for
1626			fb_tunnels_only_for_init_ns
1627
1628	floppy=		[HW]
1629			See Documentation/admin-guide/blockdev/floppy.rst.
1630
1631	forcepae	[X86-32]
1632			Forcefully enable Physical Address Extension (PAE).
1633			Many Pentium M systems disable PAE but may have a
1634			functionally usable PAE implementation.
1635			Warning: use of this parameter will taint the kernel
1636			and may cause unknown problems.
1637
1638	fred=		[X86-64]
1639			Enable/disable Flexible Return and Event Delivery.
1640			Format: { on | off }
1641			on: enable FRED when it's present.
1642			off: disable FRED, the default setting.
1643
1644	ftrace=[tracer]
1645			[FTRACE] will set and start the specified tracer
1646			as early as possible in order to facilitate early
1647			boot debugging.
1648
1649	ftrace_boot_snapshot
1650			[FTRACE] On boot up, a snapshot will be taken of the
1651			ftrace ring buffer that can be read at:
1652			/sys/kernel/tracing/snapshot.
1653			This is useful if you need tracing information from kernel
1654			boot up that is likely to be overridden by user space
1655			start up functionality.
1656
1657			Optionally, the snapshot can also be defined for a tracing
1658			instance that was created by the trace_instance= command
1659			line parameter.
1660
1661			trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
1662
1663			The above will cause the "foo" tracing instance to trigger
1664			a snapshot at the end of boot up.
1665
1666	ftrace_dump_on_oops[=2(orig_cpu) | =<instance>][,<instance> |
1667			  ,<instance>=2(orig_cpu)]
1668			[FTRACE] will dump the trace buffers on oops.
1669			If no parameter is passed, ftrace will dump global
1670			buffers of all CPUs, if you pass 2 or orig_cpu, it
1671			will dump only the buffer of the CPU that triggered
1672			the oops, or the specific instance will be dumped if
1673			its name is passed. Multiple instance dump is also
1674			supported, and instances are separated by commas. Each
1675			instance supports only dump on CPU that triggered the
1676			oops by passing 2 or orig_cpu to it.
1677
1678			ftrace_dump_on_oops=foo=orig_cpu
1679
1680			The above will dump only the buffer of "foo" instance
1681			on CPU that triggered the oops.
1682
1683			ftrace_dump_on_oops,foo,bar=orig_cpu
1684
1685			The above will dump global buffer on all CPUs, the
1686			buffer of "foo" instance on all CPUs and the buffer
1687			of "bar" instance on CPU that triggered the oops.
1688
1689	ftrace_filter=[function-list]
1690			[FTRACE] Limit the functions traced by the function
1691			tracer at boot up. function-list is a comma-separated
1692			list of functions. This list can be changed at run
1693			time by the set_ftrace_filter file in the debugfs
1694			tracing directory.
1695
1696	ftrace_notrace=[function-list]
1697			[FTRACE] Do not trace the functions specified in
1698			function-list. This list can be changed at run time
1699			by the set_ftrace_notrace file in the debugfs
1700			tracing directory.
1701
1702	ftrace_graph_filter=[function-list]
1703			[FTRACE] Limit the top level callers functions traced
1704			by the function graph tracer at boot up.
1705			function-list is a comma-separated list of functions
1706			that can be changed at run time by the
1707			set_graph_function file in the debugfs tracing directory.
1708
1709	ftrace_graph_notrace=[function-list]
1710			[FTRACE] Do not trace from the functions specified in
1711			function-list.  This list is a comma-separated list of
1712			functions that can be changed at run time by the
1713			set_graph_notrace file in the debugfs tracing directory.
1714
1715	ftrace_graph_max_depth=<uint>
1716			[FTRACE] Used with the function graph tracer. This is
1717			the max depth it will trace into a function. This value
1718			can be changed at run time by the max_graph_depth file
1719			in the tracefs tracing directory. default: 0 (no limit)
1720
1721	fw_devlink=	[KNL,EARLY] Create device links between consumer and supplier
1722			devices by scanning the firmware to infer the
1723			consumer/supplier relationships. This feature is
1724			especially useful when drivers are loaded as modules as
1725			it ensures proper ordering of tasks like device probing
1726			(suppliers first, then consumers), supplier boot state
1727			clean up (only after all consumers have probed),
1728			suspend/resume & runtime PM (consumers first, then
1729			suppliers).
1730			Format: { off | permissive | on | rpm }
1731			off --	Don't create device links from firmware info.
1732			permissive -- Create device links from firmware info
1733				but use it only for ordering boot state clean
1734				up (sync_state() calls).
1735			on -- 	Create device links from firmware info and use it
1736				to enforce probe and suspend/resume ordering.
1737			rpm --	Like "on", but also use to order runtime PM.
1738
1739	fw_devlink.strict=<bool>
1740			[KNL,EARLY] Treat all inferred dependencies as mandatory
1741			dependencies. This only applies for fw_devlink=on|rpm.
1742			Format: <bool>
1743
1744	fw_devlink.sync_state =
1745			[KNL,EARLY] When all devices that could probe have finished
1746			probing, this parameter controls what to do with
1747			devices that haven't yet received their sync_state()
1748			calls.
1749			Format: { strict | timeout }
1750			strict -- Default. Continue waiting on consumers to
1751				probe successfully.
1752			timeout -- Give up waiting on consumers and call
1753				sync_state() on any devices that haven't yet
1754				received their sync_state() calls after
1755				deferred_probe_timeout has expired or by
1756				late_initcall() if !CONFIG_MODULES.
1757
1758	gamecon.map[2|3]=
1759			[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1760			support via parallel port (up to 5 devices per port)
1761			Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1762			See also Documentation/input/devices/joystick-parport.rst
1763
1764	gamma=		[HW,DRM]
1765
1766	gart_fix_e820=	[X86-64,EARLY] disable the fix e820 for K8 GART
1767			Format: off | on
1768			default: on
1769
1770	gather_data_sampling=
1771			[X86,INTEL,EARLY] Control the Gather Data Sampling (GDS)
1772			mitigation.
1773
1774			Gather Data Sampling is a hardware vulnerability which
1775			allows unprivileged speculative access to data which was
1776			previously stored in vector registers.
1777
1778			This issue is mitigated by default in updated microcode.
1779			The mitigation may have a performance impact but can be
1780			disabled. On systems without the microcode mitigation
1781			disabling AVX serves as a mitigation.
1782
1783			force:	Disable AVX to mitigate systems without
1784				microcode mitigation. No effect if the microcode
1785				mitigation is present. Known to cause crashes in
1786				userspace with buggy AVX enumeration.
1787
1788			off:	Disable GDS mitigation.
1789
1790	gbpages		[X86] Use GB pages for kernel direct mappings.
1791
1792	gcov_persist=	[GCOV] When non-zero (default), profiling data for
1793			kernel modules is saved and remains accessible via
1794			debugfs, even when the module is unloaded/reloaded.
1795			When zero, profiling data is discarded and associated
1796			debugfs files are removed at module unload time.
1797
1798	goldfish	[X86] Enable the goldfish android emulator platform.
1799			Don't use this when you are not running on the
1800			android emulator
1801
1802	gpio-mockup.gpio_mockup_ranges
1803			[HW] Sets the ranges of gpiochip of for this device.
1804			Format: <start1>,<end1>,<start2>,<end2>...
1805	gpio-mockup.gpio_mockup_named_lines
1806			[HW] Let the driver know GPIO lines should be named.
1807
1808	gpt		[EFI] Forces disk with valid GPT signature but
1809			invalid Protective MBR to be treated as GPT. If the
1810			primary GPT is corrupted, it enables the backup/alternate
1811			GPT to be used instead.
1812
1813	grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1814			the "Enable 0" bit of the configuration register.
1815			Format: 0 | 1
1816			Default: 0
1817	grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1818			the "Enable 0" bit of the configuration register.
1819			Format: 0 | 1
1820			Default: 0
1821	grcan.select=	[HW] Select which physical interface to use.
1822			Format: 0 | 1
1823			Default: 0
1824	grcan.txsize=	[HW] Sets the size of the tx buffer.
1825			Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1826			Default: 1024
1827	grcan.rxsize=	[HW] Sets the size of the rx buffer.
1828			Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1829			Default: 1024
1830
1831	hardened_usercopy=
1832			[KNL] Under CONFIG_HARDENED_USERCOPY, whether
1833			hardening is enabled for this boot. Hardened
1834			usercopy checking is used to protect the kernel
1835			from reading or writing beyond known memory
1836			allocation boundaries as a proactive defense
1837			against bounds-checking flaws in the kernel's
1838			copy_to_user()/copy_from_user() interface.
1839			The default is determined by
1840			CONFIG_HARDENED_USERCOPY_DEFAULT_ON.
1841		on	Perform hardened usercopy checks.
1842		off	Disable hardened usercopy checks.
1843
1844	hardlockup_all_cpu_backtrace=
1845			[KNL] Should the hard-lockup detector generate
1846			backtraces on all cpus.
1847			Format: 0 | 1
1848
1849	hash_pointers=
1850			[KNL,EARLY]
1851			By default, when pointers are printed to the console
1852			or buffers via the %p format string, that pointer is
1853			"hashed", i.e. obscured by hashing the pointer value.
1854			This is a security feature that hides actual kernel
1855			addresses from unprivileged users, but it also makes
1856			debugging the kernel more difficult since unequal
1857			pointers can no longer be compared. The choices are:
1858			Format: { auto | always | never }
1859			Default: auto
1860
1861			auto   - Hash pointers unless slab_debug is enabled.
1862			always - Always hash pointers (even if slab_debug is
1863				 enabled).
1864			never  - Never hash pointers. This option should only
1865				 be specified when debugging the kernel. Do
1866				 not use on production kernels. The boot
1867				 param "no_hash_pointers" is an alias for
1868				 this mode.
1869
1870	hashdist=	[KNL,NUMA] Large hashes allocated during boot
1871			are distributed across NUMA nodes.  Defaults on
1872			for 64-bit NUMA, off otherwise.
1873			Format: 0 | 1 (for off | on)
1874
1875	hd=		[EIDE] (E)IDE hard drive subsystem geometry
1876			Format: <cyl>,<head>,<sect>
1877
1878	hest_disable	[ACPI]
1879			Disable Hardware Error Source Table (HEST) support;
1880			corresponding firmware-first mode error processing
1881			logic will be disabled.
1882
1883	hibernate=	[HIBERNATION]
1884		noresume	Don't check if there's a hibernation image
1885				present during boot.
1886		nocompress	Don't compress/decompress hibernation images.
1887		no		Disable hibernation and resume.
1888		protect_image	Turn on image protection during restoration
1889				(that will set all pages holding image data
1890				during restoration read-only).
1891
1892	hibernate.compressor= 	[HIBERNATION] Compression algorithm to be
1893				used with hibernation.
1894				Format: { lzo | lz4 }
1895				Default: lzo
1896
1897				lzo: Select LZO compression algorithm to
1898				compress/decompress hibernation image.
1899
1900				lz4: Select LZ4 compression algorithm to
1901				compress/decompress hibernation image.
1902
1903	hibernate.pm_test_delay=
1904			[HIBERNATION]
1905			Sets the number of seconds to remain in a hibernation test
1906			mode before resuming the system (see
1907			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
1908			is set. Default value is 5.
1909
1910	highmem=nn[KMG]	[KNL,BOOT,EARLY] forces the highmem zone to have an exact
1911			size of <nn>. This works even on boxes that have no
1912			highmem otherwise. This also works to reduce highmem
1913			size on bigger boxes.
1914
1915	highres=	[KNL] Enable/disable high resolution timer mode.
1916			Valid parameters: "on", "off"
1917			Default: "on"
1918
1919	hlt		[BUGS=ARM,SH]
1920
1921	hostname=	[KNL,EARLY] Set the hostname (aka UTS nodename).
1922			Format: <string>
1923			This allows setting the system's hostname during early
1924			startup. This sets the name returned by gethostname.
1925			Using this parameter to set the hostname makes it
1926			possible to ensure the hostname is correctly set before
1927			any userspace processes run, avoiding the possibility
1928			that a process may call gethostname before the hostname
1929			has been explicitly set, resulting in the calling
1930			process getting an incorrect result. The string must
1931			not exceed the maximum allowed hostname length (usually
1932			64 characters) and will be truncated otherwise.
1933
1934	hpet=		[X86-32,HPET] option to control HPET usage
1935			Format: { enable (default) | disable | force |
1936				verbose }
1937			disable: disable HPET and use PIT instead
1938			force: allow force enabled of undocumented chips (ICH4,
1939				VIA, nVidia)
1940			verbose: show contents of HPET registers during setup
1941
1942	hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1943			registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1944
1945	hugepages=	[HW,EARLY] Number of HugeTLB pages to allocate at boot.
1946			If this follows hugepagesz (below), it specifies
1947			the number of pages of hugepagesz to be allocated.
1948			If this is the first HugeTLB parameter on the command
1949			line, it specifies the number of pages to allocate for
1950			the default huge page size. If using node format, the
1951			number of pages to allocate per-node can be specified.
1952			See also Documentation/admin-guide/mm/hugetlbpage.rst.
1953			Format: <integer> or (node format)
1954				<node>:<integer>[,<node>:<integer>]
1955
1956	hugepagesz=
1957			[HW,EARLY] The size of the HugeTLB pages.  This is
1958			used in conjunction with hugepages (above) to
1959			allocate huge pages of a specific size at boot. The
1960			pair hugepagesz=X hugepages=Y can be specified once
1961			for each supported huge page size. Huge page sizes
1962			are architecture dependent. See also
1963			Documentation/admin-guide/mm/hugetlbpage.rst.
1964			Format: size[KMG]
1965
1966	hugepage_alloc_threads=
1967			[HW] The number of threads that should be used to
1968			allocate hugepages during boot. This option can be
1969			used to improve system bootup time when allocating
1970			a large amount of huge pages.
1971			The default value is 25% of the available hardware threads.
1972
1973			Note that this parameter only applies to non-gigantic huge pages.
1974
1975	hugetlb_cma=	[HW,CMA,EARLY] The size of a CMA area used for allocation
1976			of gigantic hugepages. Or using node format, the size
1977			of a CMA area per node can be specified.
1978			Format: nn[KMGTPE] or (node format)
1979				<node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1980
1981			Reserve a CMA area of given size and allocate gigantic
1982			hugepages using the CMA allocator. If enabled, the
1983			boot-time allocation of gigantic hugepages is skipped.
1984
1985	hugetlb_cma_only=
1986			[HW,CMA,EARLY] When allocating new HugeTLB pages, only
1987			try to allocate from the CMA areas.
1988
1989			This option does nothing if hugetlb_cma= is not also
1990			specified.
1991
1992	hugetlb_free_vmemmap=
1993			[KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1994			enabled.
1995			Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1996			Allows heavy hugetlb users to free up some more
1997			memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1998			Format: { on | off (default) }
1999
2000			on: enable HVO
2001			off: disable HVO
2002
2003			Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
2004			the default is on.
2005
2006			Note that the vmemmap pages may be allocated from the added
2007			memory block itself when memory_hotplug.memmap_on_memory is
2008			enabled, those vmemmap pages cannot be optimized even if this
2009			feature is enabled.  Other vmemmap pages not allocated from
2010			the added memory block itself do not be affected.
2011
2012	hung_task_panic=
2013			[KNL] Should the hung task detector generate panics.
2014			Format: 0 | 1
2015
2016			A value of 1 instructs the kernel to panic when a
2017			hung task is detected. The default value is controlled
2018			by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
2019			option. The value selected by this boot parameter can
2020			be changed later by the kernel.hung_task_panic sysctl.
2021
2022	hvc_iucv=	[S390]	Number of z/VM IUCV hypervisor console (HVC)
2023				terminal devices. Valid values: 0..8
2024	hvc_iucv_allow=	[S390]	Comma-separated list of z/VM user IDs.
2025				If specified, z/VM IUCV HVC accepts connections
2026				from listed z/VM user IDs only.
2027
2028	hv_nopvspin	[X86,HYPER_V,EARLY]
2029			Disables the paravirt spinlock optimizations
2030			which allow the hypervisor to 'idle' the guest
2031			on lock contention.
2032
2033	hw_protection=	[HW]
2034			Format: reboot | shutdown
2035
2036			Hardware protection action taken on critical events like
2037			overtemperature or imminent voltage loss.
2038
2039	i2c_bus=	[HW]	Override the default board specific I2C bus speed
2040				or register an additional I2C bus that is not
2041				registered from board initialization code.
2042				Format:
2043				<bus_id>,<clkrate>
2044
2045	i2c_touchscreen_props= [HW,ACPI,X86]
2046			Set device-properties for ACPI-enumerated I2C-attached
2047			touchscreen, to e.g. fix coordinates of upside-down
2048			mounted touchscreens. If you need this option please
2049			submit a drivers/platform/x86/touchscreen_dmi.c patch
2050			adding a DMI quirk for this.
2051
2052			Format:
2053			<ACPI_HW_ID>:<prop_name>=<val>[:prop_name=val][:...]
2054			Where <val> is one of:
2055			Omit "=<val>" entirely	Set a boolean device-property
2056			Unsigned number		Set a u32 device-property
2057			Anything else		Set a string device-property
2058
2059			Examples (split over multiple lines):
2060			i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x:
2061			touchscreen-inverted-y
2062
2063			i2c_touchscreen_props=MSSL1680:touchscreen-size-x=1920:
2064			touchscreen-size-y=1080:touchscreen-inverted-y:
2065			firmware-name=gsl1680-vendor-model.fw:silead,home-button
2066
2067	i8042.debug	[HW] Toggle i8042 debug mode
2068	i8042.unmask_kbd_data
2069			[HW] Enable printing of interrupt data from the KBD port
2070			     (disabled by default, and as a pre-condition
2071			     requires that i8042.debug=1 be enabled)
2072	i8042.direct	[HW] Put keyboard port into non-translated mode
2073	i8042.dumbkbd	[HW] Pretend that controller can only read data from
2074			     keyboard and cannot control its state
2075			     (Don't attempt to blink the leds)
2076	i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
2077	i8042.nokbd	[HW] Don't check/create keyboard port
2078	i8042.noloop	[HW] Disable the AUX Loopback command while probing
2079			     for the AUX port
2080	i8042.nomux	[HW] Don't check presence of an active multiplexing
2081			     controller
2082	i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
2083			     controllers
2084	i8042.notimeout	[HW] Ignore timeout condition signalled by controller
2085	i8042.reset	[HW] Reset the controller during init, cleanup and
2086			     suspend-to-ram transitions, only during s2r
2087			     transitions, or never reset
2088			Format: { 1 | Y | y | 0 | N | n }
2089			1, Y, y: always reset controller
2090			0, N, n: don't ever reset controller
2091			Default: only on s2r transitions on x86; most other
2092			architectures force reset to be always executed
2093	i8042.unlock	[HW] Unlock (ignore) the keylock
2094	i8042.kbdreset	[HW] Reset device connected to KBD port
2095	i8042.probe_defer
2096			[HW] Allow deferred probing upon i8042 probe errors
2097
2098	i810=		[HW,DRM]
2099
2100	i915.invert_brightness=
2101			[DRM] Invert the sense of the variable that is used to
2102			set the brightness of the panel backlight. Normally a
2103			brightness value of 0 indicates backlight switched off,
2104			and the maximum of the brightness value sets the backlight
2105			to maximum brightness. If this parameter is set to 0
2106			(default) and the machine requires it, or this parameter
2107			is set to 1, a brightness value of 0 sets the backlight
2108			to maximum brightness, and the maximum of the brightness
2109			value switches the backlight off.
2110			-1 -- never invert brightness
2111			 0 -- machine default
2112			 1 -- force brightness inversion
2113
2114	ia32_emulation=	[X86-64]
2115			Format: <bool>
2116			When true, allows loading 32-bit programs and executing 32-bit
2117			syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at
2118			boot time. When false, unconditionally disables IA32 emulation.
2119
2120	icn=		[HW,ISDN]
2121			Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
2122
2123
2124	idle=		[X86,EARLY]
2125			Format: idle=poll, idle=halt, idle=nomwait
2126
2127			idle=poll:  Don't do power saving in the idle loop
2128			using HLT, but poll for rescheduling event. This will
2129			make the CPUs eat a lot more power, but may be useful
2130			to get slightly better performance in multiprocessor
2131			benchmarks. It also makes some profiling using
2132			performance counters more accurate.  Please note that
2133			on systems with MONITOR/MWAIT support (like Intel
2134			EM64T CPUs) this option has no performance advantage
2135			over the normal idle loop.  It may also interact badly
2136			with hyperthreading.
2137
2138			idle=halt: Halt is forced to be used for CPU idle.
2139			In such case C2/C3 won't be used again.
2140
2141			idle=nomwait: Disable mwait for CPU C-states
2142
2143	idxd.sva=	[HW]
2144			Format: <bool>
2145			Allow force disabling of Shared Virtual Memory (SVA)
2146			support for the idxd driver. By default it is set to
2147			true (1).
2148
2149	idxd.tc_override= [HW]
2150			Format: <bool>
2151			Allow override of default traffic class configuration
2152			for the device. By default it is set to false (0).
2153
2154	ieee754=	[MIPS] Select IEEE Std 754 conformance mode
2155			Format: { strict | legacy | 2008 | relaxed | emulated }
2156			Default: strict
2157
2158			Choose which programs will be accepted for execution
2159			based on the IEEE 754 NaN encoding(s) supported by
2160			the FPU and the NaN encoding requested with the value
2161			of an ELF file header flag individually set by each
2162			binary.  Hardware implementations are permitted to
2163			support either or both of the legacy and the 2008 NaN
2164			encoding mode.
2165
2166			Available settings are as follows:
2167			strict	accept binaries that request a NaN encoding
2168				supported by the FPU
2169			legacy	only accept legacy-NaN binaries, if supported
2170				by the FPU
2171			2008	only accept 2008-NaN binaries, if supported
2172				by the FPU
2173			relaxed	accept any binaries regardless of whether
2174				supported by the FPU
2175			emulated accept any binaries but enable FPU emulator
2176				if binary mode is unsupported by the FPU.
2177
2178			The FPU emulator is always able to support both NaN
2179			encodings, so if no FPU hardware is present or it has
2180			been disabled with 'nofpu', then the settings of
2181			'legacy' and '2008' strap the emulator accordingly,
2182			'relaxed' straps the emulator for both legacy-NaN and
2183			2008-NaN, whereas 'strict' enables legacy-NaN only on
2184			legacy processors and both NaN encodings on MIPS32 or
2185			MIPS64 CPUs.
2186
2187			The setting for ABS.fmt/NEG.fmt instruction execution
2188			mode generally follows that for the NaN encoding,
2189			except where unsupported by hardware.
2190
2191	ignore_loglevel	[KNL,EARLY]
2192			Ignore loglevel setting - this will print /all/
2193			kernel messages to the console. Useful for debugging.
2194			We also add it as printk module parameter, so users
2195			could change it dynamically, usually by
2196			/sys/module/printk/parameters/ignore_loglevel.
2197
2198	ignore_rlimit_data
2199			Ignore RLIMIT_DATA setting for data mappings,
2200			print warning at first misuse.  Can be changed via
2201			/sys/module/kernel/parameters/ignore_rlimit_data.
2202
2203	ihash_entries=	[KNL]
2204			Set number of hash buckets for inode cache.
2205
2206	ima_appraise=	[IMA] appraise integrity measurements
2207			Format: { "off" | "enforce" | "fix" | "log" }
2208			default: "enforce"
2209
2210	ima_appraise_tcb [IMA] Deprecated.  Use ima_policy= instead.
2211			The builtin appraise policy appraises all files
2212			owned by uid=0.
2213
2214	ima_canonical_fmt [IMA]
2215			Use the canonical format for the binary runtime
2216			measurements, instead of host native format.
2217
2218	ima_hash=	[IMA]
2219			Format: { md5 | sha1 | rmd160 | sha256 | sha384
2220				   | sha512 | ... }
2221			default: "sha1"
2222
2223			The list of supported hash algorithms is defined
2224			in crypto/hash_info.h.
2225
2226	ima_policy=	[IMA]
2227			The builtin policies to load during IMA setup.
2228			Format: "tcb | appraise_tcb | secure_boot |
2229				 fail_securely | critical_data"
2230
2231			The "tcb" policy measures all programs exec'd, files
2232			mmap'd for exec, and all files opened with the read
2233			mode bit set by either the effective uid (euid=0) or
2234			uid=0.
2235
2236			The "appraise_tcb" policy appraises the integrity of
2237			all files owned by root.
2238
2239			The "secure_boot" policy appraises the integrity
2240			of files (eg. kexec kernel image, kernel modules,
2241			firmware, policy, etc) based on file signatures.
2242
2243			The "fail_securely" policy forces file signature
2244			verification failure also on privileged mounted
2245			filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2246			flag.
2247
2248			The "critical_data" policy measures kernel integrity
2249			critical data.
2250
2251	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
2252			Load a policy which meets the needs of the Trusted
2253			Computing Base.  This means IMA will measure all
2254			programs exec'd, files mmap'd for exec, and all files
2255			opened for read by uid=0.
2256
2257	ima_template=	[IMA]
2258			Select one of defined IMA measurements template formats.
2259			Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2260				   "ima-sigv2" }
2261			Default: "ima-ng"
2262
2263	ima_template_fmt=
2264			[IMA] Define a custom template format.
2265			Format: { "field1|...|fieldN" }
2266
2267	ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2268			Format: <min_file_size>
2269			Set the minimal file size for using asynchronous hash.
2270			If left unspecified, ahash usage is disabled.
2271
2272			ahash performance varies for different data sizes on
2273			different crypto accelerators. This option can be used
2274			to achieve the best performance for a particular HW.
2275
2276	ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2277			Format: <bufsize>
2278			Set hashing buffer size. Default: 4k.
2279
2280			ahash performance varies for different chunk sizes on
2281			different crypto accelerators. This option can be used
2282			to achieve best performance for particular HW.
2283
2284	ima=		[IMA] Enable or disable IMA
2285			Format: { "off" | "on" }
2286			Default: "on"
2287			Note that disabling IMA is limited to kdump kernel.
2288
2289	indirect_target_selection= [X86,Intel] Mitigation control for Indirect
2290			Target Selection(ITS) bug in Intel CPUs. Updated
2291			microcode is also required for a fix in IBPB.
2292
2293			on:     Enable mitigation (default).
2294			off:    Disable mitigation.
2295			force:	Force the ITS bug and deploy default
2296				mitigation.
2297			vmexit: Only deploy mitigation if CPU is affected by
2298				guest/host isolation part of ITS.
2299			stuff:	Deploy RSB-fill mitigation when retpoline is
2300				also deployed. Otherwise, deploy the default
2301				mitigation.
2302
2303			For details see:
2304			Documentation/admin-guide/hw-vuln/indirect-target-selection.rst
2305
2306	init=		[KNL]
2307			Format: <full_path>
2308			Run specified binary instead of /sbin/init as init
2309			process.
2310
2311	initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
2312			for working out where the kernel is dying during
2313			startup.
2314
2315	initcall_blacklist=  [KNL] Do not execute a comma-separated list of
2316			initcall functions.  Useful for debugging built-in
2317			modules and initcalls.
2318
2319	initramfs_async= [KNL]
2320			Format: <bool>
2321			Default: 1
2322			This parameter controls whether the initramfs
2323			image is unpacked asynchronously, concurrently
2324			with devices being probed and
2325			initialized. This should normally just work,
2326			but as a debugging aid, one can get the
2327			historical behaviour of the initramfs
2328			unpacking being completed before device_ and
2329			late_ initcalls.
2330
2331	initrd=		[BOOT,EARLY] Specify the location of the initial ramdisk
2332
2333	initrdmem=	[KNL,EARLY] Specify a physical address and size from which to
2334			load the initrd. If an initrd is compiled in or
2335			specified in the bootparams, it takes priority over this
2336			setting.
2337			Format: ss[KMG],nn[KMG]
2338			Default is 0, 0
2339
2340	init_on_alloc=	[MM,EARLY] Fill newly allocated pages and heap objects with
2341			zeroes.
2342			Format: 0 | 1
2343			Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2344
2345	init_on_free=	[MM,EARLY] Fill freed pages and heap objects with zeroes.
2346			Format: 0 | 1
2347			Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2348
2349	init_pkru=	[X86] Specify the default memory protection keys rights
2350			register contents for all processes.  0x55555554 by
2351			default (disallow access to all but pkey 0).  Can
2352			override in debugfs after boot.
2353
2354	inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
2355			Format: <irq>
2356
2357	int_pln_enable	[X86] Enable power limit notification interrupt
2358
2359	integrity_audit=[IMA]
2360			Format: { "0" | "1" }
2361			0 -- basic integrity auditing messages. (Default)
2362			1 -- additional integrity auditing messages.
2363
2364	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
2365		on
2366			Enable intel iommu driver.
2367		off
2368			Disable intel iommu driver.
2369		igfx_off [Default Off]
2370			By default, gfx is mapped as normal device. If a gfx
2371			device has a dedicated DMAR unit, the DMAR unit is
2372			bypassed by not enabling DMAR with this option. In
2373			this case, gfx device will use physical address for
2374			DMA.
2375		strict [Default Off]
2376			Deprecated, equivalent to iommu.strict=1.
2377		sp_off [Default Off]
2378			By default, super page will be supported if Intel IOMMU
2379			has the capability. With this option, super page will
2380			not be supported.
2381		sm_on
2382			Enable the Intel IOMMU scalable mode if the hardware
2383			advertises that it has support for the scalable mode
2384			translation.
2385		sm_off
2386			Disallow use of the Intel IOMMU scalable mode.
2387		tboot_noforce [Default Off]
2388			Do not force the Intel IOMMU enabled under tboot.
2389			By default, tboot will force Intel IOMMU on, which
2390			could harm performance of some high-throughput
2391			devices like 40GBit network cards, even if identity
2392			mapping is enabled.
2393			Note that using this option lowers the security
2394			provided by tboot because it makes the system
2395			vulnerable to DMA attacks.
2396
2397	intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
2398			0	disables intel_idle and fall back on acpi_idle.
2399			1 to 9	specify maximum depth of C-state.
2400
2401	intel_pstate=	[X86,EARLY]
2402			disable
2403			  Do not enable intel_pstate as the default
2404			  scaling driver for the supported processors
2405                        active
2406                          Use intel_pstate driver to bypass the scaling
2407                          governors layer of cpufreq and provides it own
2408                          algorithms for p-state selection. There are two
2409                          P-state selection algorithms provided by
2410                          intel_pstate in the active mode: powersave and
2411                          performance.  The way they both operate depends
2412                          on whether or not the hardware managed P-states
2413                          (HWP) feature has been enabled in the processor
2414                          and possibly on the processor model.
2415			passive
2416			  Use intel_pstate as a scaling driver, but configure it
2417			  to work with generic cpufreq governors (instead of
2418			  enabling its internal governor).  This mode cannot be
2419			  used along with the hardware-managed P-states (HWP)
2420			  feature.
2421			force
2422			  Enable intel_pstate on systems that prohibit it by default
2423			  in favor of acpi-cpufreq. Forcing the intel_pstate driver
2424			  instead of acpi-cpufreq may disable platform features, such
2425			  as thermal controls and power capping, that rely on ACPI
2426			  P-States information being indicated to OSPM and therefore
2427			  should be used with caution. This option does not work with
2428			  processors that aren't supported by the intel_pstate driver
2429			  or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2430			no_hwp
2431			  Do not enable hardware P state control (HWP)
2432			  if available.
2433			hwp_only
2434			  Only load intel_pstate on systems which support
2435			  hardware P state control (HWP) if available.
2436			support_acpi_ppc
2437			  Enforce ACPI _PPC performance limits. If the Fixed ACPI
2438			  Description Table, specifies preferred power management
2439			  profile as "Enterprise Server" or "Performance Server",
2440			  then this feature is turned on by default.
2441			per_cpu_perf_limits
2442			  Allow per-logical-CPU P-State performance control limits using
2443			  cpufreq sysfs interface
2444			no_cas
2445			  Do not enable capacity-aware scheduling (CAS) on
2446			  hybrid systems
2447
2448	intremap=	[X86-64,Intel-IOMMU,EARLY]
2449			on	enable Interrupt Remapping (default)
2450			off	disable Interrupt Remapping
2451			nosid	disable Source ID checking
2452			no_x2apic_optout
2453				BIOS x2APIC opt-out request will be ignored
2454			nopost	disable Interrupt Posting
2455			posted_msi
2456				enable MSIs delivered as posted interrupts
2457
2458	iomem=		Disable strict checking of access to MMIO memory
2459		strict	regions from userspace.
2460		relaxed
2461
2462	iommu=		[X86,EARLY]
2463
2464		off
2465			Don't initialize and use any kind of IOMMU.
2466
2467		force
2468			Force the use of the hardware IOMMU even when
2469			it is not actually needed (e.g. because < 3 GB
2470			memory).
2471
2472		noforce
2473			Don't force hardware IOMMU usage when it is not
2474			needed. (default).
2475
2476		biomerge
2477		panic
2478		nopanic
2479		merge
2480		nomerge
2481
2482		soft
2483			Use software bounce buffering (SWIOTLB) (default for
2484			Intel machines). This can be used to prevent the usage
2485			of an available hardware IOMMU.
2486
2487			[X86]
2488		pt
2489			[X86]
2490		nopt
2491			[PPC/POWERNV]
2492		nobypass
2493			Disable IOMMU bypass, using IOMMU for PCI devices.
2494
2495		[X86]
2496		AMD Gart HW IOMMU-specific options:
2497
2498		<size>
2499			Set the size of the remapping area in bytes.
2500
2501		allowed
2502			Overwrite iommu off workarounds for specific chipsets
2503
2504		fullflush
2505			Flush IOMMU on each allocation (default).
2506
2507		nofullflush
2508			Don't use IOMMU fullflush.
2509
2510		memaper[=<order>]
2511			Allocate an own aperture over RAM with size
2512			32MB<<order.  (default: order=1, i.e. 64MB)
2513
2514		merge
2515			Do scatter-gather (SG) merging. Implies "force"
2516			(experimental).
2517
2518		nomerge
2519			Don't do scatter-gather (SG) merging.
2520
2521		noaperture
2522			Ask the IOMMU not to touch the aperture for AGP.
2523
2524		noagp
2525			Don't initialize the AGP driver and use full aperture.
2526
2527		panic
2528			Always panic when IOMMU overflows.
2529
2530	iommu.forcedac=	[ARM64,X86,EARLY] Control IOVA allocation for PCI devices.
2531			Format: { "0" | "1" }
2532			0 - Try to allocate a 32-bit DMA address first, before
2533			  falling back to the full range if needed.
2534			1 - Allocate directly from the full usable range,
2535			  forcing Dual Address Cycle for PCI cards supporting
2536			  greater than 32-bit addressing.
2537
2538	iommu.strict=	[ARM64,X86,S390,EARLY] Configure TLB invalidation behaviour
2539			Format: { "0" | "1" }
2540			0 - Lazy mode.
2541			  Request that DMA unmap operations use deferred
2542			  invalidation of hardware TLBs, for increased
2543			  throughput at the cost of reduced device isolation.
2544			  Will fall back to strict mode if not supported by
2545			  the relevant IOMMU driver.
2546			1 - Strict mode.
2547			  DMA unmap operations invalidate IOMMU hardware TLBs
2548			  synchronously.
2549			unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2550			Note: on x86, strict mode specified via one of the
2551			legacy driver-specific options takes precedence.
2552
2553	iommu.passthrough=
2554			[ARM64,X86,EARLY] Configure DMA to bypass the IOMMU by default.
2555			Format: { "0" | "1" }
2556			0 - Use IOMMU translation for DMA.
2557			1 - Bypass the IOMMU for DMA.
2558			unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2559
2560	io7=		[HW] IO7 for Marvel-based Alpha systems
2561			See comment before marvel_specify_io7 in
2562			arch/alpha/kernel/core_marvel.c.
2563
2564	io_delay=	[X86,EARLY] I/O delay method
2565		0x80
2566			Standard port 0x80 based delay
2567		0xed
2568			Alternate port 0xed based delay (needed on some systems)
2569		udelay
2570			Simple two microseconds delay
2571		none
2572			No delay
2573
2574	ip=		[IP_PNP]
2575			See Documentation/admin-guide/nfs/nfsroot.rst.
2576
2577	ipcmni_extend	[KNL,EARLY] Extend the maximum number of unique System V
2578			IPC identifiers from 32,768 to 16,777,216.
2579
2580	ipe.enforce=	[IPE]
2581			Format: <bool>
2582			Determine whether IPE starts in permissive (0) or
2583			enforce (1) mode. The default is enforce.
2584
2585	ipe.success_audit=
2586			[IPE]
2587			Format: <bool>
2588			Start IPE with success auditing enabled, emitting
2589			an audit event when a binary is allowed. The default
2590			is 0.
2591
2592	irqaffinity=	[SMP] Set the default irq affinity mask
2593			The argument is a cpu list, as described above.
2594
2595	irqchip.gicv2_force_probe=
2596			[ARM,ARM64,EARLY]
2597			Format: <bool>
2598			Force the kernel to look for the second 4kB page
2599			of a GICv2 controller even if the memory range
2600			exposed by the device tree is too small.
2601
2602	irqchip.gicv3_nolpi=
2603			[ARM,ARM64,EARLY]
2604			Force the kernel to ignore the availability of
2605			LPIs (and by consequence ITSs). Intended for system
2606			that use the kernel as a bootloader, and thus want
2607			to let secondary kernels in charge of setting up
2608			LPIs.
2609
2610	irqchip.gicv3_pseudo_nmi= [ARM64,EARLY]
2611			Enables support for pseudo-NMIs in the kernel. This
2612			requires the kernel to be built with
2613			CONFIG_ARM64_PSEUDO_NMI.
2614
2615	irqchip.riscv_imsic_noipi
2616			[RISC-V,EARLY]
2617			Force the kernel to not use IMSIC software injected MSIs
2618			as IPIs. Intended for system where IMSIC is trap-n-emulated,
2619			and thus want to reduce MMIO traps when triggering IPIs
2620			to multiple harts.
2621
2622	irqfixup	[HW]
2623			When an interrupt is not handled search all handlers
2624			for it. Intended to get systems with badly broken
2625			firmware running.
2626
2627	irqhandler.duration_warn_us= [KNL]
2628			Warn if an IRQ handler exceeds the specified duration
2629			threshold in microseconds. Useful for identifying
2630			long-running IRQs in the system.
2631
2632	irqpoll		[HW]
2633			When an interrupt is not handled search all handlers
2634			for it. Also check all handlers each timer
2635			interrupt. Intended to get systems with badly broken
2636			firmware running.
2637
2638	isapnp=		[ISAPNP]
2639			Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2640
2641	isolcpus=	[KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2642			[Deprecated - use cpusets instead]
2643			Format: [flag-list,]<cpu-list>
2644
2645			Specify one or more CPUs to isolate from disturbances
2646			specified in the flag list (default: domain):
2647
2648			nohz
2649			  Disable the tick when a single task runs as well as
2650			  disabling other kernel noises like having RCU callbacks
2651			  offloaded. This is equivalent to the nohz_full parameter.
2652
2653			  A residual 1Hz tick is offloaded to workqueues, which you
2654			  need to affine to housekeeping through the global
2655			  workqueue's affinity configured via the
2656			  /sys/devices/virtual/workqueue/cpumask sysfs file, or
2657			  by using the 'domain' flag described below.
2658
2659			  NOTE: by default the global workqueue runs on all CPUs,
2660			  so to protect individual CPUs the 'cpumask' file has to
2661			  be configured manually after bootup.
2662
2663			domain
2664			  Isolate from the general SMP balancing and scheduling
2665			  algorithms. Note that performing domain isolation this way
2666			  is irreversible: it's not possible to bring back a CPU to
2667			  the domains once isolated through isolcpus. It's strongly
2668			  advised to use cpusets instead to disable scheduler load
2669			  balancing through the "cpuset.sched_load_balance" file.
2670			  It offers a much more flexible interface where CPUs can
2671			  move in and out of an isolated set anytime.
2672
2673			  You can move a process onto or off an "isolated" CPU via
2674			  the CPU affinity syscalls or cpuset.
2675			  <cpu number> begins at 0 and the maximum value is
2676			  "number of CPUs in system - 1".
2677
2678			managed_irq
2679
2680			  Isolate from being targeted by managed interrupts
2681			  which have an interrupt mask containing isolated
2682			  CPUs. The affinity of managed interrupts is
2683			  handled by the kernel and cannot be changed via
2684			  the /proc/irq/* interfaces.
2685
2686			  This isolation is best effort and only effective
2687			  if the automatically assigned interrupt mask of a
2688			  device queue contains isolated and housekeeping
2689			  CPUs. If housekeeping CPUs are online then such
2690			  interrupts are directed to the housekeeping CPU
2691			  so that IO submitted on the housekeeping CPU
2692			  cannot disturb the isolated CPU.
2693
2694			  If a queue's affinity mask contains only isolated
2695			  CPUs then this parameter has no effect on the
2696			  interrupt routing decision, though interrupts are
2697			  only delivered when tasks running on those
2698			  isolated CPUs submit IO. IO submitted on
2699			  housekeeping CPUs has no influence on those
2700			  queues.
2701
2702			The format of <cpu-list> is described above.
2703
2704	iucv=		[HW,NET]
2705
2706	ivrs_ioapic	[HW,X86-64]
2707			Provide an override to the IOAPIC-ID<->DEVICE-ID
2708			mapping provided in the IVRS ACPI table.
2709			By default, PCI segment is 0, and can be omitted.
2710
2711			For example, to map IOAPIC-ID decimal 10 to
2712			PCI segment 0x1 and PCI device 00:14.0,
2713			write the parameter as:
2714				ivrs_ioapic=10@0001:00:14.0
2715
2716			Deprecated formats:
2717			* To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2718			  write the parameter as:
2719				ivrs_ioapic[10]=00:14.0
2720			* To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2721			  PCI device 00:14.0 write the parameter as:
2722				ivrs_ioapic[10]=0001:00:14.0
2723
2724	ivrs_hpet	[HW,X86-64]
2725			Provide an override to the HPET-ID<->DEVICE-ID
2726			mapping provided in the IVRS ACPI table.
2727			By default, PCI segment is 0, and can be omitted.
2728
2729			For example, to map HPET-ID decimal 10 to
2730			PCI segment 0x1 and PCI device 00:14.0,
2731			write the parameter as:
2732				ivrs_hpet=10@0001:00:14.0
2733
2734			Deprecated formats:
2735			* To map HPET-ID decimal 0 to PCI device 00:14.0
2736			  write the parameter as:
2737				ivrs_hpet[0]=00:14.0
2738			* To map HPET-ID decimal 10 to PCI segment 0x1 and
2739			  PCI device 00:14.0 write the parameter as:
2740				ivrs_ioapic[10]=0001:00:14.0
2741
2742	ivrs_acpihid	[HW,X86-64]
2743			Provide an override to the ACPI-HID:UID<->DEVICE-ID
2744			mapping provided in the IVRS ACPI table.
2745			By default, PCI segment is 0, and can be omitted.
2746
2747			For example, to map UART-HID:UID AMD0020:0 to
2748			PCI segment 0x1 and PCI device ID 00:14.5,
2749			write the parameter as:
2750				ivrs_acpihid=AMD0020:0@0001:00:14.5
2751
2752			Deprecated formats:
2753			* To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2754			  PCI device ID 00:14.5, write the parameter as:
2755				ivrs_acpihid[00:14.5]=AMD0020:0
2756			* To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2757			  PCI device ID 00:14.5, write the parameter as:
2758				ivrs_acpihid[0001:00:14.5]=AMD0020:0
2759
2760	js=		[HW,JOY] Analog joystick
2761			See Documentation/input/joydev/joystick.rst.
2762
2763	kasan_multi_shot
2764			[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2765			report on every invalid memory access. Without this
2766			parameter KASAN will print report only for the first
2767			invalid access.
2768
2769	keep_bootcon	[KNL,EARLY]
2770			Do not unregister boot console at start. This is only
2771			useful for debugging when something happens in the window
2772			between unregistering the boot console and initializing
2773			the real console.
2774
2775	keepinitrd	[HW,ARM] See retain_initrd.
2776
2777	kernelcore=	[KNL,X86,PPC,EARLY]
2778			Format: nn[KMGTPE] | nn% | "mirror"
2779			This parameter specifies the amount of memory usable by
2780			the kernel for non-movable allocations.  The requested
2781			amount is spread evenly throughout all nodes in the
2782			system as ZONE_NORMAL.  The remaining memory is used for
2783			movable memory in its own zone, ZONE_MOVABLE.  In the
2784			event, a node is too small to have both ZONE_NORMAL and
2785			ZONE_MOVABLE, kernelcore memory will take priority and
2786			other nodes will have a larger ZONE_MOVABLE.
2787
2788			ZONE_MOVABLE is used for the allocation of pages that
2789			may be reclaimed or moved by the page migration
2790			subsystem.  Note that allocations like PTEs-from-HighMem
2791			still use the HighMem zone if it exists, and the Normal
2792			zone if it does not.
2793
2794			It is possible to specify the exact amount of memory in
2795			the form of "nn[KMGTPE]", a percentage of total system
2796			memory in the form of "nn%", or "mirror".  If "mirror"
2797			option is specified, mirrored (reliable) memory is used
2798			for non-movable allocations and remaining memory is used
2799			for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
2800			are exclusive, so you cannot specify multiple forms.
2801
2802	kgdbdbgp=	[KGDB,HW,EARLY] kgdb over EHCI usb debug port.
2803			Format: <Controller#>[,poll interval]
2804			The controller # is the number of the ehci usb debug
2805			port as it is probed via PCI.  The poll interval is
2806			optional and is the number seconds in between
2807			each poll cycle to the debug port in case you need
2808			the functionality for interrupting the kernel with
2809			gdb or control-c on the dbgp connection.  When
2810			not using this parameter you use sysrq-g to break into
2811			the kernel debugger.
2812
2813	kgdboc=		[KGDB,HW] kgdb over consoles.
2814			Requires a tty driver that supports console polling,
2815			or a supported polling keyboard driver (non-usb).
2816			 Serial only format: <serial_device>[,baud]
2817			 keyboard only format: kbd
2818			 keyboard and serial format: kbd,<serial_device>[,baud]
2819			Optional Kernel mode setting:
2820			 kms, kbd format: kms,kbd
2821			 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2822
2823	kgdboc_earlycon=	[KGDB,HW,EARLY]
2824			If the boot console provides the ability to read
2825			characters and can work in polling mode, you can use
2826			this parameter to tell kgdb to use it as a backend
2827			until the normal console is registered. Intended to
2828			be used together with the kgdboc parameter which
2829			specifies the normal console to transition to.
2830
2831			The name of the early console should be specified
2832			as the value of this parameter. Note that the name of
2833			the early console might be different than the tty
2834			name passed to kgdboc. It's OK to leave the value
2835			blank and the first boot console that implements
2836			read() will be picked.
2837
2838	kgdbwait	[KGDB,EARLY] Stop kernel execution and enter the
2839			kernel debugger at the earliest opportunity.
2840
2841	kho=		[KEXEC,EARLY]
2842			Format: { "0" | "1" | "off" | "on" | "y" | "n" }
2843			Enables or disables Kexec HandOver.
2844			"0" | "off" | "n" - kexec handover is disabled
2845			"1" | "on" | "y" - kexec handover is enabled
2846
2847	kho_scratch=	[KEXEC,EARLY]
2848			Format: ll[KMG],mm[KMG],nn[KMG] | nn%
2849			Defines the size of the KHO scratch region. The KHO
2850			scratch regions are physically contiguous memory
2851			ranges that can only be used for non-kernel
2852			allocations. That way, even when memory is heavily
2853			fragmented with handed over memory, the kexeced
2854			kernel will always have enough contiguous ranges to
2855			bootstrap itself.
2856
2857			It is possible to specify the exact amount of
2858			memory in the form of "ll[KMG],mm[KMG],nn[KMG]"
2859			where the first parameter defines the size of a low
2860			memory scratch area, the second parameter defines
2861			the size of a global scratch area and the third
2862			parameter defines the size of additional per-node
2863			scratch areas.  The form "nn%" defines scale factor
2864			(in percents) of memory that was used during boot.
2865
2866	kmac=		[MIPS] Korina ethernet MAC address.
2867			Configure the RouterBoard 532 series on-chip
2868			Ethernet adapter MAC address.
2869
2870	kmemleak=	[KNL,EARLY] Boot-time kmemleak enable/disable
2871			Valid arguments: on, off
2872			Default: on
2873			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2874			the default is off.
2875
2876	kprobe_event=[probe-list]
2877			[FTRACE] Add kprobe events and enable at boot time.
2878			The probe-list is a semicolon delimited list of probe
2879			definitions. Each definition is same as kprobe_events
2880			interface, but the parameters are comma delimited.
2881			For example, to add a kprobe event on vfs_read with
2882			arg1 and arg2, add to the command line;
2883
2884			      kprobe_event=p,vfs_read,$arg1,$arg2
2885
2886			See also Documentation/trace/kprobetrace.rst "Kernel
2887			Boot Parameter" section.
2888
2889	kpti=		[ARM64,EARLY] Control page table isolation of
2890			user and kernel address spaces.
2891			Default: enabled on cores which need mitigation.
2892			0: force disabled
2893			1: force enabled
2894
2895	kunit.enable=	[KUNIT] Enable executing KUnit tests. Requires
2896			CONFIG_KUNIT to be set to be fully enabled. The
2897			default value can be overridden via
2898			KUNIT_DEFAULT_ENABLED.
2899			Default is 1 (enabled)
2900
2901	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2902			Default is 0 (don't ignore, but inject #GP)
2903
2904	kvm.eager_page_split=
2905			[KVM,X86] Controls whether or not KVM will try to
2906			proactively split all huge pages during dirty logging.
2907			Eager page splitting reduces interruptions to vCPU
2908			execution by eliminating the write-protection faults
2909			and MMU lock contention that would otherwise be
2910			required to split huge pages lazily.
2911
2912			VM workloads that rarely perform writes or that write
2913			only to a small region of VM memory may benefit from
2914			disabling eager page splitting to allow huge pages to
2915			still be used for reads.
2916
2917			The behavior of eager page splitting depends on whether
2918			KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2919			disabled, all huge pages in a memslot will be eagerly
2920			split when dirty logging is enabled on that memslot. If
2921			enabled, eager page splitting will be performed during
2922			the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2923			cleared.
2924
2925			Eager page splitting is only supported when kvm.tdp_mmu=Y.
2926
2927			Default is Y (on).
2928
2929	kvm.enable_virt_at_load=[KVM,ARM64,LOONGARCH,MIPS,RISCV,X86]
2930			If enabled, KVM will enable virtualization in hardware
2931			when KVM is loaded, and disable virtualization when KVM
2932			is unloaded (if KVM is built as a module).
2933
2934			If disabled, KVM will dynamically enable and disable
2935			virtualization on-demand when creating and destroying
2936			VMs, i.e. on the 0=>1 and 1=>0 transitions of the
2937			number of VMs.
2938
2939			Enabling virtualization at module load avoids potential
2940			latency for creation of the 0=>1 VM, as KVM serializes
2941			virtualization enabling across all online CPUs.  The
2942			"cost" of enabling virtualization when KVM is loaded,
2943			is that doing so may interfere with using out-of-tree
2944			hypervisors that want to "own" virtualization hardware.
2945
2946	kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2947				   Default is false (don't support).
2948
2949	kvm.nx_huge_pages=
2950			[KVM] Controls the software workaround for the
2951			X86_BUG_ITLB_MULTIHIT bug.
2952			force	: Always deploy workaround.
2953			off	: Never deploy workaround.
2954			auto    : Deploy workaround based on the presence of
2955				  X86_BUG_ITLB_MULTIHIT.
2956
2957			Default is 'auto'.
2958
2959			If the software workaround is enabled for the host,
2960			guests do need not to enable it for nested guests.
2961
2962	kvm.nx_huge_pages_recovery_ratio=
2963			[KVM] Controls how many 4KiB pages are periodically zapped
2964			back to huge pages.  0 disables the recovery, otherwise if
2965			the value is N KVM will zap 1/Nth of the 4KiB pages every
2966			period (see below).  The default is 60.
2967
2968	kvm.nx_huge_pages_recovery_period_ms=
2969			[KVM] Controls the time period at which KVM zaps 4KiB pages
2970			back to huge pages. If the value is a non-zero N, KVM will
2971			zap a portion (see ratio above) of the pages every N msecs.
2972			If the value is 0 (the default), KVM will pick a period based
2973			on the ratio, such that a page is zapped after 1 hour on average.
2974
2975	kvm-amd.nested=	[KVM,AMD] Control nested virtualization feature in
2976			KVM/SVM. Default is 1 (enabled).
2977
2978	kvm-amd.npt=	[KVM,AMD] Control KVM's use of Nested Page Tables,
2979			a.k.a. Two-Dimensional Page Tables. Default is 1
2980			(enabled). Disable by KVM if hardware lacks support
2981			for NPT.
2982
2983	kvm-amd.ciphertext_hiding_asids=
2984			[KVM,AMD] Ciphertext hiding prevents disallowed accesses
2985			to SNP private memory from reading ciphertext.  Instead,
2986			reads will see constant default values (0xff).
2987
2988			If ciphertext hiding is enabled, the joint SEV-ES and
2989			SEV-SNP ASID space is partitioned into separate SEV-ES
2990			and SEV-SNP ASID ranges, with the SEV-SNP range being
2991			[1..max_snp_asid] and the SEV-ES range being
2992			(max_snp_asid..min_sev_asid), where min_sev_asid is
2993			enumerated by CPUID.0x.8000_001F[EDX].
2994
2995			A non-zero value enables SEV-SNP ciphertext hiding and
2996			adjusts the ASID ranges for SEV-ES and SEV-SNP guests.
2997			KVM caps the number of SEV-SNP ASIDs at the maximum
2998			possible value, e.g. specifying -1u will assign all
2999			joint SEV-ES and SEV-SNP ASIDs to SEV-SNP.  Note,
3000			assigning all joint ASIDs to SEV-SNP, i.e. configuring
3001			max_snp_asid == min_sev_asid-1, will effectively make
3002			SEV-ES unusable.
3003
3004	kvm-arm.mode=
3005			[KVM,ARM,EARLY] Select one of KVM/arm64's modes of
3006			operation.
3007
3008			none: Forcefully disable KVM.
3009
3010			nvhe: Standard nVHE-based mode, without support for
3011			      protected guests.
3012
3013			protected: Mode with support for guests whose state is
3014				   kept private from the host, using VHE or
3015				   nVHE depending on HW support.
3016
3017			nested: VHE-based mode with support for nested
3018				virtualization. Requires at least ARMv8.4
3019				hardware (with FEAT_NV2).
3020
3021			Defaults to VHE/nVHE based on hardware support. Setting
3022			mode to "protected" will disable kexec and hibernation
3023			for the host. To force nVHE on VHE hardware, add
3024			"arm64_sw.hvhe=0 id_aa64mmfr1.vh=0" to the
3025			command-line.
3026			"nested" is experimental and should be used with
3027			extreme caution.
3028
3029	kvm-arm.vgic_v3_group0_trap=
3030			[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0
3031			system registers
3032
3033	kvm-arm.vgic_v3_group1_trap=
3034			[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1
3035			system registers
3036
3037	kvm-arm.vgic_v3_common_trap=
3038			[KVM,ARM,EARLY] Trap guest accesses to GICv3 common
3039			system registers
3040
3041	kvm-arm.vgic_v4_enable=
3042			[KVM,ARM,EARLY] Allow use of GICv4 for direct
3043			injection of LPIs.
3044
3045	kvm-arm.wfe_trap_policy=
3046			[KVM,ARM] Control when to set WFE instruction trap for
3047			KVM VMs. Traps are allowed but not guaranteed by the
3048			CPU architecture.
3049
3050			trap: set WFE instruction trap
3051
3052			notrap: clear WFE instruction trap
3053
3054	kvm-arm.wfi_trap_policy=
3055			[KVM,ARM] Control when to set WFI instruction trap for
3056			KVM VMs. Traps are allowed but not guaranteed by the
3057			CPU architecture.
3058
3059			trap: set WFI instruction trap
3060
3061			notrap: clear WFI instruction trap
3062
3063	kvm_cma_resv_ratio=n [PPC,EARLY]
3064			Reserves given percentage from system memory area for
3065			contiguous memory allocation for KVM hash pagetable
3066			allocation.
3067			By default it reserves 5% of total system memory.
3068			Format: <integer>
3069			Default: 5
3070
3071	kvm-intel.ept=	[KVM,Intel] Control KVM's use of Extended Page Tables,
3072			a.k.a. Two-Dimensional Page Tables.  Default is 1
3073			(enabled). Disable by KVM if hardware lacks support
3074			for EPT.
3075
3076	kvm-intel.emulate_invalid_guest_state=
3077			[KVM,Intel] Control whether to emulate invalid guest
3078			state. Ignored if kvm-intel.enable_unrestricted_guest=1,
3079			as guest state is never invalid for unrestricted
3080			guests. This param doesn't apply to nested guests (L2),
3081			as KVM never emulates invalid L2 guest state.
3082			Default is 1 (enabled).
3083
3084	kvm-intel.flexpriority=
3085			[KVM,Intel] Control KVM's use of FlexPriority feature
3086			(TPR shadow). Default is 1 (enabled). Disable by KVM if
3087			hardware lacks support for it.
3088
3089	kvm-intel.nested=
3090			[KVM,Intel] Control nested virtualization feature in
3091			KVM/VMX. Default is 1 (enabled).
3092
3093	kvm-intel.unrestricted_guest=
3094			[KVM,Intel] Control KVM's use of unrestricted guest
3095			feature (virtualized real and unpaged mode). Default
3096			is 1 (enabled). Disable by KVM if EPT is disabled or
3097			hardware lacks support for it.
3098
3099	kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
3100			CVE-2018-3620.
3101
3102			Valid arguments: never, cond, always
3103
3104			always: L1D cache flush on every VMENTER.
3105			cond:	Flush L1D on VMENTER only when the code between
3106				VMEXIT and VMENTER can leak host memory.
3107			never:	Disables the mitigation
3108
3109			Default is cond (do L1 cache flush in specific instances)
3110
3111	kvm-intel.vpid=	[KVM,Intel] Control KVM's use of Virtual Processor
3112			Identification feature (tagged TLBs). Default is 1
3113			(enabled). Disable by KVM if hardware lacks support
3114			for it.
3115
3116	l1d_flush=	[X86,INTEL,EARLY]
3117			Control mitigation for L1D based snooping vulnerability.
3118
3119			Certain CPUs are vulnerable to an exploit against CPU
3120			internal buffers which can forward information to a
3121			disclosure gadget under certain conditions.
3122
3123			In vulnerable processors, the speculatively
3124			forwarded data can be used in a cache side channel
3125			attack, to access data to which the attacker does
3126			not have direct access.
3127
3128			This parameter controls the mitigation. The
3129			options are:
3130
3131			on         - enable the interface for the mitigation
3132
3133	l1tf=           [X86,EARLY] Control mitigation of the L1TF vulnerability on
3134			      affected CPUs
3135
3136			The kernel PTE inversion protection is unconditionally
3137			enabled and cannot be disabled.
3138
3139			full
3140				Provides all available mitigations for the
3141				L1TF vulnerability. Disables SMT and
3142				enables all mitigations in the
3143				hypervisors, i.e. unconditional L1D flush.
3144
3145				SMT control and L1D flush control via the
3146				sysfs interface is still possible after
3147				boot.  Hypervisors will issue a warning
3148				when the first VM is started in a
3149				potentially insecure configuration,
3150				i.e. SMT enabled or L1D flush disabled.
3151
3152			full,force
3153				Same as 'full', but disables SMT and L1D
3154				flush runtime control. Implies the
3155				'nosmt=force' command line option.
3156				(i.e. sysfs control of SMT is disabled.)
3157
3158			flush
3159				Leaves SMT enabled and enables the default
3160				hypervisor mitigation, i.e. conditional
3161				L1D flush.
3162
3163				SMT control and L1D flush control via the
3164				sysfs interface is still possible after
3165				boot.  Hypervisors will issue a warning
3166				when the first VM is started in a
3167				potentially insecure configuration,
3168				i.e. SMT enabled or L1D flush disabled.
3169
3170			flush,nosmt
3171
3172				Disables SMT and enables the default
3173				hypervisor mitigation.
3174
3175				SMT control and L1D flush control via the
3176				sysfs interface is still possible after
3177				boot.  Hypervisors will issue a warning
3178				when the first VM is started in a
3179				potentially insecure configuration,
3180				i.e. SMT enabled or L1D flush disabled.
3181
3182			flush,nowarn
3183				Same as 'flush', but hypervisors will not
3184				warn when a VM is started in a potentially
3185				insecure configuration.
3186
3187			off
3188				Disables hypervisor mitigations and doesn't
3189				emit any warnings.
3190				It also drops the swap size and available
3191				RAM limit restriction on both hypervisor and
3192				bare metal.
3193
3194			Default is 'flush'.
3195
3196			For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
3197
3198	l2cr=		[PPC]
3199
3200	l3cr=		[PPC]
3201
3202	lapic		[X86-32,APIC,EARLY] Enable the local APIC even if BIOS
3203			disabled it.
3204
3205	lapic=		[X86,APIC] Do not use TSC deadline
3206			value for LAPIC timer one-shot implementation. Default
3207			back to the programmable timer unit in the LAPIC.
3208			Format: notscdeadline
3209
3210	lapic_timer_c2_ok	[X86,APIC,EARLY] trust the local apic timer
3211			in C2 power state.
3212
3213	libata.dma=	[LIBATA] DMA control
3214			libata.dma=0	  Disable all PATA and SATA DMA
3215			libata.dma=1	  PATA and SATA Disk DMA only
3216			libata.dma=2	  ATAPI (CDROM) DMA only
3217			libata.dma=4	  Compact Flash DMA only
3218			Combinations also work, so libata.dma=3 enables DMA
3219			for disks and CDROMs, but not CFs.
3220
3221	libata.ignore_hpa=	[LIBATA] Ignore HPA limit
3222			libata.ignore_hpa=0	  keep BIOS limits (default)
3223			libata.ignore_hpa=1	  ignore limits, using full disk
3224
3225	libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
3226			when set.
3227			Format: <int>
3228
3229	libata.force=	[LIBATA] Force configurations.  The format is a comma-
3230			separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
3231			PORT and DEVICE are decimal numbers matching port, link
3232			or device.  Basically, it matches the ATA ID string
3233			printed on console by libata.  If the whole ID part is
3234			omitted, the last PORT and DEVICE values are used.  If
3235			ID hasn't been specified yet, the configuration applies
3236			to all ports, links and devices.
3237
3238			If only DEVICE is omitted, the parameter applies to
3239			the port and all links and devices behind it.  DEVICE
3240			number of 0 either selects the first device or the
3241			first fan-out link behind PMP device.  It does not
3242			select the host link.  DEVICE number of 15 selects the
3243			host link and device attached to it.
3244
3245			The VAL specifies the configuration to force.  As long
3246			as there is no ambiguity, shortcut notation is allowed.
3247			For example, both 1.5 and 1.5G would work for 1.5Gbps.
3248			The following configurations can be forced.
3249
3250			* Cable type: 40c, 80c, short40c, unk, ign or sata.
3251			  Any ID with matching PORT is used.
3252
3253			* SATA link speed limit: 1.5Gbps or 3.0Gbps.
3254
3255			* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
3256			  udma[/][16,25,33,44,66,100,133] notation is also
3257			  allowed.
3258
3259			* nohrst, nosrst, norst: suppress hard, soft and both
3260			  resets.
3261
3262			* rstonce: only attempt one reset during hot-unplug
3263			  link recovery.
3264
3265			* [no]dbdelay: Enable or disable the extra 200ms delay
3266			  before debouncing a link PHY and device presence
3267			  detection.
3268
3269			* [no]ncq: Turn on or off NCQ.
3270
3271			* [no]ncqtrim: Enable or disable queued DSM TRIM.
3272
3273			* [no]ncqati: Enable or disable NCQ trim on ATI chipset.
3274
3275			* [no]trim: Enable or disable (unqueued) TRIM.
3276
3277			* trim_zero: Indicate that TRIM command zeroes data.
3278
3279			* max_trim_128m: Set 128M maximum trim size limit.
3280
3281			* [no]dma: Turn on or off DMA transfers.
3282
3283			* atapi_dmadir: Enable ATAPI DMADIR bridge support.
3284
3285			* atapi_mod16_dma: Enable the use of ATAPI DMA for
3286			  commands that are not a multiple of 16 bytes.
3287
3288			* [no]dmalog: Enable or disable the use of the
3289			  READ LOG DMA EXT command to access logs.
3290
3291			* [no]iddevlog: Enable or disable access to the
3292			  identify device data log.
3293
3294			* [no]logdir: Enable or disable access to the general
3295			  purpose log directory.
3296
3297			* max_sec_128: Set transfer size limit to 128 sectors.
3298
3299			* max_sec_1024: Set or clear transfer size limit to
3300			  1024 sectors.
3301
3302			* max_sec_lba48: Set or clear transfer size limit to
3303			  65535 sectors.
3304
3305			* external: Mark port as external (hotplug-capable).
3306
3307			* [no]lpm: Enable or disable link power management.
3308
3309			* [no]setxfer: Indicate if transfer speed mode setting
3310			  should be skipped.
3311
3312			* [no]fua: Disable or enable FUA (Force Unit Access)
3313			  support for devices supporting this feature.
3314
3315			* dump_id: Dump IDENTIFY data.
3316
3317			* disable: Disable this device.
3318
3319			If there are multiple matching configurations changing
3320			the same attribute, the last one is used.
3321
3322	load_ramdisk=	[RAM] [Deprecated]
3323
3324	lockd.nlm_grace_period=P  [NFS] Assign grace period.
3325			Format: <integer>
3326
3327	lockd.nlm_tcpport=N	[NFS] Assign TCP port.
3328			Format: <integer>
3329
3330	lockd.nlm_timeout=T	[NFS] Assign timeout value.
3331			Format: <integer>
3332
3333	lockd.nlm_udpport=M	[NFS] Assign UDP port.
3334			Format: <integer>
3335
3336	lockdown=	[SECURITY,EARLY]
3337			{ integrity | confidentiality }
3338			Enable the kernel lockdown feature. If set to
3339			integrity, kernel features that allow userland to
3340			modify the running kernel are disabled. If set to
3341			confidentiality, kernel features that allow userland
3342			to extract confidential information from the kernel
3343			are also disabled.
3344
3345	locktorture.acq_writer_lim= [KNL]
3346			Set the time limit in jiffies for a lock
3347			acquisition.  Acquisitions exceeding this limit
3348			will result in a splat once they do complete.
3349
3350	locktorture.bind_readers= [KNL]
3351			Specify the list of CPUs to which the readers are
3352			to be bound.
3353
3354	locktorture.bind_writers= [KNL]
3355			Specify the list of CPUs to which the writers are
3356			to be bound.
3357
3358	locktorture.call_rcu_chains= [KNL]
3359			Specify the number of self-propagating call_rcu()
3360			chains to set up.  These are used to ensure that
3361			there is a high probability of an RCU grace period
3362			in progress at any given time.	Defaults to 0,
3363			which disables these call_rcu() chains.
3364
3365	locktorture.long_hold= [KNL]
3366			Specify the duration in milliseconds for the
3367			occasional long-duration lock hold time.  Defaults
3368			to 100 milliseconds.  Select 0 to disable.
3369
3370	locktorture.nested_locks= [KNL]
3371			Specify the maximum lock nesting depth that
3372			locktorture is to exercise, up to a limit of 8
3373			(MAX_NESTED_LOCKS).  Specify zero to disable.
3374			Note that this parameter is ineffective on types
3375			of locks that do not support nested acquisition.
3376
3377	locktorture.nreaders_stress= [KNL]
3378			Set the number of locking read-acquisition kthreads.
3379			Defaults to being automatically set based on the
3380			number of online CPUs.
3381
3382	locktorture.nwriters_stress= [KNL]
3383			Set the number of locking write-acquisition kthreads.
3384
3385	locktorture.onoff_holdoff= [KNL]
3386			Set time (s) after boot for CPU-hotplug testing.
3387
3388	locktorture.onoff_interval= [KNL]
3389			Set time (s) between CPU-hotplug operations, or
3390			zero to disable CPU-hotplug testing.
3391
3392	locktorture.rt_boost= [KNL]
3393			Do periodic testing of real-time lock priority
3394			boosting.  Select 0 to disable, 1 to boost
3395			only rt_mutex, and 2 to boost unconditionally.
3396			Defaults to 2, which might seem to be an
3397			odd choice, but which should be harmless for
3398			non-real-time spinlocks, due to their disabling
3399			of preemption.	Note that non-realtime mutexes
3400			disable boosting.
3401
3402	locktorture.rt_boost_factor= [KNL]
3403			Number that determines how often and for how
3404			long priority boosting is exercised.  This is
3405			scaled down by the number of writers, so that the
3406			number of boosts per unit time remains roughly
3407			constant as the number of writers increases.
3408			On the other hand, the duration of each boost
3409			increases with the number of writers.
3410
3411	locktorture.shuffle_interval= [KNL]
3412			Set task-shuffle interval (jiffies).  Shuffling
3413			tasks allows some CPUs to go into dyntick-idle
3414			mode during the locktorture test.
3415
3416	locktorture.shutdown_secs= [KNL]
3417			Set time (s) after boot system shutdown.  This
3418			is useful for hands-off automated testing.
3419
3420	locktorture.stat_interval= [KNL]
3421			Time (s) between statistics printk()s.
3422
3423	locktorture.stutter= [KNL]
3424			Time (s) to stutter testing, for example,
3425			specifying five seconds causes the test to run for
3426			five seconds, wait for five seconds, and so on.
3427			This tests the locking primitive's ability to
3428			transition abruptly to and from idle.
3429
3430	locktorture.torture_type= [KNL]
3431			Specify the locking implementation to test.
3432
3433	locktorture.verbose= [KNL]
3434			Enable additional printk() statements.
3435
3436	locktorture.writer_fifo= [KNL]
3437			Run the write-side locktorture kthreads at
3438			sched_set_fifo() real-time priority.
3439
3440	logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
3441			Format: <irq>
3442
3443	loglevel=	[KNL,EARLY]
3444			All Kernel Messages with a loglevel smaller than the
3445			console loglevel will be printed to the console. It can
3446			also be changed with klogd or other programs. The
3447			loglevels are defined as follows:
3448
3449			0 (KERN_EMERG)		system is unusable
3450			1 (KERN_ALERT)		action must be taken immediately
3451			2 (KERN_CRIT)		critical conditions
3452			3 (KERN_ERR)		error conditions
3453			4 (KERN_WARNING)	warning conditions
3454			5 (KERN_NOTICE)		normal but significant condition
3455			6 (KERN_INFO)		informational
3456			7 (KERN_DEBUG)		debug-level messages
3457
3458	log_buf_len=n[KMG] [KNL,EARLY]
3459			Sets the size of the printk ring buffer, in bytes.
3460			n must be a power of two and greater than the
3461			minimal size. The minimal size is defined by
3462			LOG_BUF_SHIFT kernel config parameter. There
3463			is also CONFIG_LOG_CPU_MAX_BUF_SHIFT config
3464			parameter that allows to increase the default size
3465			depending on the number of CPUs. See init/Kconfig
3466			for more details.
3467
3468	logo.nologo	[FB] Disables display of the built-in Linux logo.
3469			This may be used to provide more screen space for
3470			kernel log messages and is useful when debugging
3471			kernel boot problems.
3472
3473	lp=0		[LP]	Specify parallel ports to use, e.g,
3474	lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
3475	lp=reset		first parallel port). 'lp=0' disables the
3476	lp=auto			printer driver. 'lp=reset' (which can be
3477				specified in addition to the ports) causes
3478				attached printers to be reset. Using
3479				lp=port1,port2,... specifies the parallel ports
3480				to associate lp devices with, starting with
3481				lp0. A port specification may be 'none' to skip
3482				that lp device, or a parport name such as
3483				'parport0'. Specifying 'lp=auto' instead of a
3484				port specification list means that device IDs
3485				from each port should be examined, to see if
3486				an IEEE 1284-compliant printer is attached; if
3487				so, the driver will manage that printer.
3488				See also header of drivers/char/lp.c.
3489
3490	lpj=n		[KNL]
3491			Sets loops_per_jiffy to given constant, thus avoiding
3492			time-consuming boot-time autodetection (up to 250 ms per
3493			CPU). 0 enables autodetection (default). To determine
3494			the correct value for your kernel, boot with normal
3495			autodetection and see what value is printed. Note that
3496			on SMP systems the preset will be applied to all CPUs,
3497			which is likely to cause problems if your CPUs need
3498			significantly divergent settings. An incorrect value
3499			will cause delays in the kernel to be wrong, leading to
3500			unpredictable I/O errors and other breakage. Although
3501			unlikely, in the extreme case this might damage your
3502			hardware.
3503
3504	lsm.debug	[SECURITY] Enable LSM initialization debugging output.
3505
3506	lsm=lsm1,...,lsmN
3507			[SECURITY] Choose order of LSM initialization. This
3508			overrides CONFIG_LSM, and the "security=" parameter.
3509
3510	machtype=	[Loongson] Share the same kernel image file between
3511			different yeeloong laptops.
3512			Example: machtype=lemote-yeeloong-2f-7inch
3513
3514	maxcpus=	[SMP,EARLY] Maximum number of processors that an SMP kernel
3515			will bring up during bootup.  maxcpus=n : n >= 0 limits
3516			the kernel to bring up 'n' processors. Surely after
3517			bootup you can bring up the other plugged cpu by executing
3518			"echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3519			only takes effect during system bootup.
3520			While n=0 is a special case, it is equivalent to "nosmp",
3521			which also disables the IO APIC.
3522
3523	max_loop=	[LOOP] The number of loop block devices that get
3524	(loop.max_loop)	unconditionally pre-created at init time. The default
3525			number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3526			of statically allocating a predefined number, loop
3527			devices can be requested on-demand with the
3528			/dev/loop-control interface.
3529
3530	mce=		[X86-{32,64}]
3531
3532			Please see Documentation/arch/x86/x86_64/machinecheck.rst for sysfs runtime tunables.
3533
3534		off
3535			disable machine check
3536
3537		no_cmci
3538			disable CMCI(Corrected Machine Check Interrupt) that
3539			Intel processor supports.  Usually this disablement is
3540			not recommended, but it might be handy if your
3541			hardware is misbehaving.
3542
3543			Note that you'll get more problems without CMCI than
3544			with due to the shared banks, i.e. you might get
3545			duplicated error logs.
3546
3547		dont_log_ce
3548			don't make logs for corrected errors.  All events
3549			reported as corrected are silently cleared by OS. This
3550			option will be useful if you have no interest in any
3551			of corrected errors.
3552
3553		ignore_ce
3554			disable features for corrected errors, e.g.
3555			polling timer and CMCI.  All events reported as
3556			corrected are not cleared by OS and remained in its
3557			error banks.
3558
3559			Usually this disablement is not recommended, however
3560			if there is an agent checking/clearing corrected
3561			errors (e.g. BIOS or hardware monitoring
3562			applications), conflicting with OS's error handling,
3563			and you cannot deactivate the agent, then this option
3564			will be a help.
3565
3566		no_lmce
3567			do not opt-in to Local MCE delivery. Use legacy method
3568			to broadcast MCEs.
3569
3570		bootlog
3571			enable logging of machine checks left over from
3572			booting. Disabled by default on AMD Fam10h and older
3573			because some BIOS leave bogus ones.
3574
3575			If your BIOS doesn't do that it's a good idea to
3576			enable though to make sure you log even machine check
3577			events that result in a reboot. On Intel systems it is
3578			enabled by default.
3579
3580		nobootlog
3581			disable boot machine check logging.
3582
3583		monarchtimeout (number)
3584			sets the time in us to wait for other CPUs on machine
3585			checks. 0 to disable.
3586
3587		bios_cmci_threshold
3588			don't overwrite the bios-set CMCI threshold. This boot
3589			option prevents Linux from overwriting the CMCI
3590			threshold set by the bios.  Without this option, Linux
3591			always sets the CMCI threshold to 1. Enabling this may
3592			make memory predictive failure analysis less effective
3593			if the bios sets thresholds for memory errors since we
3594			will not see details for all errors.
3595
3596		recovery
3597			force-enable recoverable machine check code paths
3598
3599			Everything else is in sysfs now.
3600
3601
3602	md=		[HW] RAID subsystems devices and level
3603			See Documentation/admin-guide/md.rst.
3604
3605	mdacon=		[MDA]
3606			Format: <first>,<last>
3607			Specifies range of consoles to be captured by the MDA.
3608
3609	mds=		[X86,INTEL,EARLY]
3610			Control mitigation for the Micro-architectural Data
3611			Sampling (MDS) vulnerability.
3612
3613			Certain CPUs are vulnerable to an exploit against CPU
3614			internal buffers which can forward information to a
3615			disclosure gadget under certain conditions.
3616
3617			In vulnerable processors, the speculatively
3618			forwarded data can be used in a cache side channel
3619			attack, to access data to which the attacker does
3620			not have direct access.
3621
3622			This parameter controls the MDS mitigation. The
3623			options are:
3624
3625			full       - Enable MDS mitigation on vulnerable CPUs
3626			full,nosmt - Enable MDS mitigation and disable
3627				     SMT on vulnerable CPUs
3628			off        - Unconditionally disable MDS mitigation
3629
3630			On TAA-affected machines, mds=off can be prevented by
3631			an active TAA mitigation as both vulnerabilities are
3632			mitigated with the same mechanism so in order to disable
3633			this mitigation, you need to specify tsx_async_abort=off
3634			too.
3635
3636			Not specifying this option is equivalent to
3637			mds=full.
3638
3639			For details see: Documentation/admin-guide/hw-vuln/mds.rst
3640
3641	mem=nn[KMG]	[HEXAGON,EARLY] Set the memory size.
3642			Must be specified, otherwise memory size will be 0.
3643
3644	mem=nn[KMG]	[KNL,BOOT,EARLY] Force usage of a specific amount
3645			of memory Amount of memory to be used in cases
3646			as follows:
3647
3648			1 for test;
3649			2 when the kernel is not able to see the whole system memory;
3650			3 memory that lies after 'mem=' boundary is excluded from
3651			 the hypervisor, then assigned to KVM guests.
3652			4 to limit the memory available for kdump kernel.
3653
3654			[ARC,MICROBLAZE] - the limit applies only to low memory,
3655			high memory is not affected.
3656
3657			[ARM64] - only limits memory covered by the linear
3658			mapping. The NOMAP regions are not affected.
3659
3660			[X86] Work as limiting max address. Use together
3661			with memmap= to avoid physical address space collisions.
3662			Without memmap= PCI devices could be placed at addresses
3663			belonging to unused RAM.
3664
3665			Note that this only takes effects during boot time since
3666			in above case 3, memory may need be hot added after boot
3667			if system memory of hypervisor is not sufficient.
3668
3669	mem=nn[KMG]@ss[KMG]
3670			[ARM,MIPS,EARLY] - override the memory layout
3671			reported by firmware.
3672			Define a memory region of size nn[KMG] starting at
3673			ss[KMG].
3674			Multiple different regions can be specified with
3675			multiple mem= parameters on the command line.
3676
3677	mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
3678			memory.
3679
3680	memblock=debug	[KNL,EARLY] Enable memblock debug messages.
3681
3682	memchunk=nn[KMG]
3683			[KNL,SH] Allow user to override the default size for
3684			per-device physically contiguous DMA buffers.
3685
3686	memhp_default_state=online/offline/online_kernel/online_movable
3687			[KNL] Set the initial state for the memory hotplug
3688			onlining policy. If not specified, the default value is
3689			set according to the
3690			CONFIG_MHP_DEFAULT_ONLINE_TYPE kernel config
3691			options.
3692			See Documentation/admin-guide/mm/memory-hotplug.rst.
3693
3694	memmap=exactmap	[KNL,X86,EARLY] Enable setting of an exact
3695			E820 memory map, as specified by the user.
3696			Such memmap=exactmap lines can be constructed based on
3697			BIOS output or other requirements. See the memmap=nn@ss
3698			option description.
3699
3700	memmap=nn[KMG]@ss[KMG]
3701			[KNL, X86,MIPS,XTENSA,EARLY] Force usage of a specific region of memory.
3702			Region of memory to be used is from ss to ss+nn.
3703			If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3704			which limits max address to nn[KMG].
3705			Multiple different regions can be specified,
3706			comma delimited.
3707			Example:
3708				memmap=100M@2G,100M#3G,1G!1024G
3709
3710	memmap=nn[KMG]#ss[KMG]
3711			[KNL,ACPI,EARLY] Mark specific memory as ACPI data.
3712			Region of memory to be marked is from ss to ss+nn.
3713
3714	memmap=nn[KMG]$ss[KMG]
3715			[KNL,ACPI,EARLY] Mark specific memory as reserved.
3716			Region of memory to be reserved is from ss to ss+nn.
3717			Example: Exclude memory from 0x18690000-0x1869ffff
3718			         memmap=64K$0x18690000
3719			         or
3720			         memmap=0x10000$0x18690000
3721			Some bootloaders may need an escape character before '$',
3722			like Grub2, otherwise '$' and the following number
3723			will be eaten.
3724
3725	memmap=nn[KMG]!ss[KMG,EARLY]
3726			[KNL,X86] Mark specific memory as protected.
3727			Region of memory to be used, from ss to ss+nn.
3728			The memory region may be marked as e820 type 12 (0xc)
3729			and is NVDIMM or ADR memory.
3730
3731	memmap=<size>%<offset>-<oldtype>+<newtype>
3732			[KNL,ACPI,EARLY] Convert memory within the specified region
3733			from <oldtype> to <newtype>. If "-<oldtype>" is left
3734			out, the whole region will be marked as <newtype>,
3735			even if previously unavailable. If "+<newtype>" is left
3736			out, matching memory will be removed. Types are
3737			specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3738			3 = ACPI, 12 = PRAM.
3739
3740	memory_corruption_check=0/1 [X86,EARLY]
3741			Some BIOSes seem to corrupt the first 64k of
3742			memory when doing things like suspend/resume.
3743			Setting this option will scan the memory
3744			looking for corruption.  Enabling this will
3745			both detect corruption and prevent the kernel
3746			from using the memory being corrupted.
3747			However, it's intended as a diagnostic tool; if
3748			repeatable BIOS-originated corruption always
3749			affects the same memory, you can use memmap=
3750			to prevent the kernel from using that memory.
3751
3752	memory_corruption_check_size=size [X86,EARLY]
3753			By default it checks for corruption in the low
3754			64k, making this memory unavailable for normal
3755			use.  Use this parameter to scan for
3756			corruption in more or less memory.
3757
3758	memory_corruption_check_period=seconds [X86,EARLY]
3759			By default it checks for corruption every 60
3760			seconds.  Use this parameter to check at some
3761			other rate.  0 disables periodic checking.
3762
3763	memory_hotplug.memmap_on_memory
3764			[KNL,X86,ARM] Boolean flag to enable this feature.
3765			Format: {on | off (default)}
3766			When enabled, runtime hotplugged memory will
3767			allocate its internal metadata (struct pages,
3768			those vmemmap pages cannot be optimized even
3769			if hugetlb_free_vmemmap is enabled) from the
3770			hotadded memory which will allow to hotadd a
3771			lot of memory without requiring additional
3772			memory to do so.
3773			This feature is disabled by default because it
3774			has some implication on large (e.g. GB)
3775			allocations in some configurations (e.g. small
3776			memory blocks).
3777			The state of the flag can be read in
3778			/sys/module/memory_hotplug/parameters/memmap_on_memory.
3779			Note that even when enabled, there are a few cases where
3780			the feature is not effective.
3781
3782	memtest=	[KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest
3783			Format: <integer>
3784			default : 0 <disable>
3785			Specifies the number of memtest passes to be
3786			performed. Each pass selects another test
3787			pattern from a given set of patterns. Memtest
3788			fills the memory with this pattern, validates
3789			memory contents and reserves bad memory
3790			regions that are detected.
3791
3792	mem_encrypt=	[X86-64] AMD Secure Memory Encryption (SME) control
3793			Valid arguments: on, off
3794			Default: off
3795			mem_encrypt=on:		Activate SME
3796			mem_encrypt=off:	Do not activate SME
3797
3798			Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3799			for details on when memory encryption can be activated.
3800
3801	mem_sleep_default=	[SUSPEND] Default system suspend mode:
3802			s2idle  - Suspend-To-Idle
3803			shallow - Power-On Suspend or equivalent (if supported)
3804			deep    - Suspend-To-RAM or equivalent (if supported)
3805			See Documentation/admin-guide/pm/sleep-states.rst.
3806
3807	mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
3808			the BIOS has incorrectly applied a workaround. TinyBIOS
3809			version 0.98 is known to be affected, 0.99 fixes the
3810			problem by letting the user disable the workaround.
3811
3812	mga=		[HW,DRM]
3813
3814	microcode=      [X86] Control the behavior of the microcode loader.
3815	                Available options, comma separated:
3816
3817			base_rev=X - with <X> with format: <u32>
3818			Set the base microcode revision of each thread when in
3819			debug mode.
3820
3821			dis_ucode_ldr: disable the microcode loader
3822
3823			force_minrev:
3824			Enable or disable the microcode minimal revision
3825			enforcement for the runtime microcode loader.
3826
3827	mini2440=	[ARM,HW,KNL]
3828			Format:[0..2][b][c][t]
3829			Default: "0tb"
3830			MINI2440 configuration specification:
3831			0 - The attached screen is the 3.5" TFT
3832			1 - The attached screen is the 7" TFT
3833			2 - The VGA Shield is attached (1024x768)
3834			Leaving out the screen size parameter will not load
3835			the TFT driver, and the framebuffer will be left
3836			unconfigured.
3837			b - Enable backlight. The TFT backlight pin will be
3838			linked to the kernel VESA blanking code and a GPIO
3839			LED. This parameter is not necessary when using the
3840			VGA shield.
3841			c - Enable the s3c camera interface.
3842			t - Reserved for enabling touchscreen support. The
3843			touchscreen support is not enabled in the mainstream
3844			kernel as of 2.6.30, a preliminary port can be found
3845			in the "bleeding edge" mini2440 support kernel at
3846			https://repo.or.cz/w/linux-2.6/mini2440.git
3847
3848	mitigations=
3849			[X86,PPC,S390,ARM64,EARLY] Control optional mitigations for
3850			CPU vulnerabilities.  This is a set of curated,
3851			arch-independent options, each of which is an
3852			aggregation of existing arch-specific options.
3853
3854			Note, "mitigations" is supported if and only if the
3855			kernel was built with CPU_MITIGATIONS=y.
3856
3857			off
3858				Disable all optional CPU mitigations.  This
3859				improves system performance, but it may also
3860				expose users to several CPU vulnerabilities.
3861				Equivalent to: if nokaslr then kpti=0 [ARM64]
3862					       gather_data_sampling=off [X86]
3863					       indirect_target_selection=off [X86]
3864					       kvm.nx_huge_pages=off [X86]
3865					       l1tf=off [X86]
3866					       mds=off [X86]
3867					       mmio_stale_data=off [X86]
3868					       no_entry_flush [PPC]
3869					       no_uaccess_flush [PPC]
3870					       nobp=0 [S390]
3871					       nopti [X86,PPC]
3872					       nospectre_bhb [ARM64]
3873					       nospectre_v1 [X86,PPC]
3874					       nospectre_v2 [X86,PPC,S390,ARM64]
3875					       reg_file_data_sampling=off [X86]
3876					       retbleed=off [X86]
3877					       spec_rstack_overflow=off [X86]
3878					       spec_store_bypass_disable=off [X86,PPC]
3879					       spectre_bhi=off [X86]
3880					       spectre_v2_user=off [X86]
3881					       srbds=off [X86,INTEL]
3882					       ssbd=force-off [ARM64]
3883					       tsx_async_abort=off [X86]
3884					       vmscape=off [X86]
3885
3886				Exceptions:
3887					       This does not have any effect on
3888					       kvm.nx_huge_pages when
3889					       kvm.nx_huge_pages=force.
3890
3891			auto (default)
3892				Mitigate all CPU vulnerabilities, but leave SMT
3893				enabled, even if it's vulnerable.  This is for
3894				users who don't want to be surprised by SMT
3895				getting disabled across kernel upgrades, or who
3896				have other ways of avoiding SMT-based attacks.
3897				Equivalent to: (default behavior)
3898
3899			auto,nosmt
3900				Mitigate all CPU vulnerabilities, disabling SMT
3901				if needed.  This is for users who always want to
3902				be fully mitigated, even if it means losing SMT.
3903				Equivalent to: l1tf=flush,nosmt [X86]
3904					       mds=full,nosmt [X86]
3905					       tsx_async_abort=full,nosmt [X86]
3906					       mmio_stale_data=full,nosmt [X86]
3907					       retbleed=auto,nosmt [X86]
3908
3909			[X86] After one of the above options, additionally
3910			supports attack-vector based controls as documented in
3911			Documentation/admin-guide/hw-vuln/attack_vector_controls.rst
3912
3913	mminit_loglevel=
3914			[KNL,EARLY] When CONFIG_DEBUG_MEMORY_INIT is set, this
3915			parameter allows control of the logging verbosity for
3916			the additional memory initialisation checks. A value
3917			of 0 disables mminit logging and a level of 4 will
3918			log everything. Information is printed at KERN_DEBUG
3919			so loglevel=8 may also need to be specified.
3920
3921	mmio_stale_data=
3922			[X86,INTEL,EARLY] Control mitigation for the Processor
3923			MMIO Stale Data vulnerabilities.
3924
3925			Processor MMIO Stale Data is a class of
3926			vulnerabilities that may expose data after an MMIO
3927			operation. Exposed data could originate or end in
3928			the same CPU buffers as affected by MDS and TAA.
3929			Therefore, similar to MDS and TAA, the mitigation
3930			is to clear the affected CPU buffers.
3931
3932			This parameter controls the mitigation. The
3933			options are:
3934
3935			full       - Enable mitigation on vulnerable CPUs
3936
3937			full,nosmt - Enable mitigation and disable SMT on
3938				     vulnerable CPUs.
3939
3940			off        - Unconditionally disable mitigation
3941
3942			On MDS or TAA affected machines,
3943			mmio_stale_data=off can be prevented by an active
3944			MDS or TAA mitigation as these vulnerabilities are
3945			mitigated with the same mechanism so in order to
3946			disable this mitigation, you need to specify
3947			mds=off and tsx_async_abort=off too.
3948
3949			Not specifying this option is equivalent to
3950			mmio_stale_data=full.
3951
3952			For details see:
3953			Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3954
3955	<module>.async_probe[=<bool>] [KNL]
3956			If no <bool> value is specified or if the value
3957			specified is not a valid <bool>, enable asynchronous
3958			probe on this module.  Otherwise, enable/disable
3959			asynchronous probe on this module as indicated by the
3960			<bool> value. See also: module.async_probe
3961
3962	module.async_probe=<bool>
3963			[KNL] When set to true, modules will use async probing
3964			by default. To enable/disable async probing for a
3965			specific module, use the module specific control that
3966			is documented under <module>.async_probe. When both
3967			module.async_probe and <module>.async_probe are
3968			specified, <module>.async_probe takes precedence for
3969			the specific module.
3970
3971	module.enable_dups_trace
3972			[KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
3973			this means that duplicate request_module() calls will
3974			trigger a WARN_ON() instead of a pr_warn(). Note that
3975			if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
3976			will always be issued and this option does nothing.
3977	module.sig_enforce
3978			[KNL] When CONFIG_MODULE_SIG is set, this means that
3979			modules without (valid) signatures will fail to load.
3980			Note that if CONFIG_MODULE_SIG_FORCE is set, that
3981			is always true, so this option does nothing.
3982
3983	module_blacklist=  [KNL] Do not load a comma-separated list of
3984			modules.  Useful for debugging problem modules.
3985
3986	mousedev.tap_time=
3987			[MOUSE] Maximum time between finger touching and
3988			leaving touchpad surface for touch to be considered
3989			a tap and be reported as a left button click (for
3990			touchpads working in absolute mode only).
3991			Format: <msecs>
3992	mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
3993			reporting absolute coordinates, such as tablets
3994	mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
3995			reporting absolute coordinates, such as tablets
3996
3997	movablecore=	[KNL,X86,PPC,EARLY]
3998			Format: nn[KMGTPE] | nn%
3999			This parameter is the complement to kernelcore=, it
4000			specifies the amount of memory used for migratable
4001			allocations.  If both kernelcore and movablecore is
4002			specified, then kernelcore will be at *least* the
4003			specified value but may be more.  If movablecore on its
4004			own is specified, the administrator must be careful
4005			that the amount of memory usable for all allocations
4006			is not too small.
4007
4008	movable_node	[KNL,EARLY] Boot-time switch to make hotplugable memory
4009			NUMA nodes to be movable. This means that the memory
4010			of such nodes will be usable only for movable
4011			allocations which rules out almost all kernel
4012			allocations. Use with caution!
4013
4014	MTD_Partition=	[MTD]
4015			Format: <name>,<region-number>,<size>,<offset>
4016
4017	MTD_Region=	[MTD] Format:
4018			<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
4019
4020	mtdparts=	[MTD]
4021			See drivers/mtd/parsers/cmdlinepart.c
4022
4023	mtouchusb.raw_coordinates=
4024			[HW] Make the MicroTouch USB driver use raw coordinates
4025			('y', default) or cooked coordinates ('n')
4026
4027	mtrr=debug	[X86,EARLY]
4028			Enable printing debug information related to MTRR
4029			registers at boot time.
4030
4031	mtrr_chunk_size=nn[KMG,X86,EARLY]
4032			used for mtrr cleanup. It is largest continuous chunk
4033			that could hold holes aka. UC entries.
4034
4035	mtrr_gran_size=nn[KMG,X86,EARLY]
4036			Used for mtrr cleanup. It is granularity of mtrr block.
4037			Default is 1.
4038			Large value could prevent small alignment from
4039			using up MTRRs.
4040
4041	mtrr_spare_reg_nr=n [X86,EARLY]
4042			Format: <integer>
4043			Range: 0,7 : spare reg number
4044			Default : 1
4045			Used for mtrr cleanup. It is spare mtrr entries number.
4046			Set to 2 or more if your graphical card needs more.
4047
4048	multitce=off	[PPC]  This parameter disables the use of the pSeries
4049			firmware feature for updating multiple TCE entries
4050			at a time.
4051
4052	n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
4053
4054	netdev=		[NET] Network devices parameters
4055			Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
4056			Note that mem_start is often overloaded to mean
4057			something different and driver-specific.
4058			This usage is only documented in each driver source
4059			file if at all.
4060
4061	netpoll.carrier_timeout=
4062			[NET] Specifies amount of time (in seconds) that
4063			netpoll should wait for a carrier. By default netpoll
4064			waits 4 seconds.
4065
4066	nf_conntrack.acct=
4067			[NETFILTER] Enable connection tracking flow accounting
4068			0 to disable accounting
4069			1 to enable accounting
4070			Default value is 0.
4071
4072	nfs.cache_getent=
4073			[NFS] sets the pathname to the program which is used
4074			to update the NFS client cache entries.
4075
4076	nfs.cache_getent_timeout=
4077			[NFS] sets the timeout after which an attempt to
4078			update a cache entry is deemed to have failed.
4079
4080	nfs.callback_nr_threads=
4081			[NFSv4] set the total number of threads that the
4082			NFS client will assign to service NFSv4 callback
4083			requests.
4084
4085	nfs.callback_tcpport=
4086			[NFS] set the TCP port on which the NFSv4 callback
4087			channel should listen.
4088
4089	nfs.delay_retrans=
4090			[NFS] specifies the number of times the NFSv4 client
4091			retries the request before returning an EAGAIN error,
4092			after a reply of NFS4ERR_DELAY from the server.
4093			Only applies if the softerr mount option is enabled,
4094			and the specified value is >= 0.
4095
4096	nfs.enable_ino64=
4097			[NFS] enable 64-bit inode numbers.
4098			If zero, the NFS client will fake up a 32-bit inode
4099			number for the readdir() and stat() syscalls instead
4100			of returning the full 64-bit number.
4101			The default is to return 64-bit inode numbers.
4102
4103	nfs.idmap_cache_timeout=
4104			[NFS] set the maximum lifetime for idmapper cache
4105			entries.
4106
4107	nfs.max_session_cb_slots=
4108			[NFSv4.1] Sets the maximum number of session
4109			slots the client will assign to the callback
4110			channel. This determines the maximum number of
4111			callbacks the client will process in parallel for
4112			a particular server.
4113
4114	nfs.max_session_slots=
4115			[NFSv4.1] Sets the maximum number of session slots
4116			the client will attempt to negotiate with the server.
4117			This limits the number of simultaneous RPC requests
4118			that the client can send to the NFSv4.1 server.
4119			Note that there is little point in setting this
4120			value higher than the max_tcp_slot_table_limit.
4121
4122	nfs.nfs4_disable_idmapping=
4123			[NFSv4] When set to the default of '1', this option
4124			ensures that both the RPC level authentication
4125			scheme and the NFS level operations agree to use
4126			numeric uids/gids if the mount is using the
4127			'sec=sys' security flavour. In effect it is
4128			disabling idmapping, which can make migration from
4129			legacy NFSv2/v3 systems to NFSv4 easier.
4130			Servers that do not support this mode of operation
4131			will be autodetected by the client, and it will fall
4132			back to using the idmapper.
4133			To turn off this behaviour, set the value to '0'.
4134
4135	nfs.nfs4_unique_id=
4136			[NFS4] Specify an additional fixed unique ident-
4137			ification string that NFSv4 clients can insert into
4138			their nfs_client_id4 string.  This is typically a
4139			UUID that is generated at system install time.
4140
4141	nfs.recover_lost_locks=
4142			[NFSv4] Attempt to recover locks that were lost due
4143			to a lease timeout on the server. Please note that
4144			doing this risks data corruption, since there are
4145			no guarantees that the file will remain unchanged
4146			after the locks are lost.
4147			If you want to enable the kernel legacy behaviour of
4148			attempting to recover these locks, then set this
4149			parameter to '1'.
4150			The default parameter value of '0' causes the kernel
4151			not to attempt recovery of lost locks.
4152
4153	nfs.send_implementation_id=
4154			[NFSv4.1] Send client implementation identification
4155			information in exchange_id requests.
4156			If zero, no implementation identification information
4157			will be sent.
4158			The default is to send the implementation identification
4159			information.
4160
4161	nfs4.layoutstats_timer=
4162			[NFSv4.2] Change the rate at which the kernel sends
4163			layoutstats to the pNFS metadata server.
4164
4165			Setting this to value to 0 causes the kernel to use
4166			whatever value is the default set by the layout
4167			driver. A non-zero value sets the minimum interval
4168			in seconds between layoutstats transmissions.
4169
4170	nfsd.inter_copy_offload_enable=
4171			[NFSv4.2] When set to 1, the server will support
4172			server-to-server copies for which this server is
4173			the destination of the copy.
4174
4175	nfsd.nfs4_disable_idmapping=
4176			[NFSv4] When set to the default of '1', the NFSv4
4177			server will return only numeric uids and gids to
4178			clients using auth_sys, and will accept numeric uids
4179			and gids from such clients.  This is intended to ease
4180			migration from NFSv2/v3.
4181
4182	nfsd.nfsd4_ssc_umount_timeout=
4183			[NFSv4.2] When used as the destination of a
4184			server-to-server copy, knfsd temporarily mounts
4185			the source server.  It caches the mount in case
4186			it will be needed again, and discards it if not
4187			used for the number of milliseconds specified by
4188			this parameter.
4189
4190	nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
4191			See Documentation/admin-guide/nfs/nfsroot.rst.
4192
4193	nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
4194			See Documentation/admin-guide/nfs/nfsroot.rst.
4195
4196	nfsrootdebug	[NFS] enable nfsroot debugging messages.
4197			See Documentation/admin-guide/nfs/nfsroot.rst.
4198
4199	nmi_backtrace.backtrace_idle [KNL]
4200			Dump stacks even of idle CPUs in response to an
4201			NMI stack-backtrace request.
4202
4203	nmi_debug=	[KNL,SH] Specify one or more actions to take
4204			when a NMI is triggered.
4205			Format: [state][,regs][,debounce][,die]
4206
4207	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
4208			Format: [panic,][nopanic,][rNNN,][num]
4209			Valid num: 0 or 1
4210			0 - turn hardlockup detector in nmi_watchdog off
4211			1 - turn hardlockup detector in nmi_watchdog on
4212			rNNN - configure the watchdog with raw perf event 0xNNN
4213
4214			When panic is specified, panic when an NMI watchdog
4215			timeout occurs (or 'nopanic' to not panic on an NMI
4216			watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
4217			To disable both hard and soft lockup detectors,
4218			please see 'nowatchdog'.
4219			This is useful when you use a panic=... timeout and
4220			need the box quickly up again.
4221
4222			These settings can be accessed at runtime via
4223			the nmi_watchdog and hardlockup_panic sysctls.
4224
4225	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
4226			emulation library even if a 387 maths coprocessor
4227			is present.
4228
4229	no4lvl		[RISCV,EARLY] Disable 4-level and 5-level paging modes.
4230			Forces kernel to use 3-level paging instead.
4231
4232	no5lvl		[X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces
4233			kernel to use 4-level paging instead.
4234
4235	noalign		[KNL,ARM]
4236
4237	noapic		[SMP,APIC,EARLY] Tells the kernel to not make use of any
4238			IOAPICs that may be present in the system.
4239
4240	noapictimer	[APIC,X86] Don't set up the APIC timer
4241
4242	noautogroup	Disable scheduler automatic task group creation.
4243
4244	nocache		[ARM,EARLY]
4245
4246	no_console_suspend
4247			[HW] Never suspend the console
4248			Disable suspending of consoles during suspend and
4249			hibernate operations.  Once disabled, debugging
4250			messages can reach various consoles while the rest
4251			of the system is being put to sleep (ie, while
4252			debugging driver suspend/resume hooks).  This may
4253			not work reliably with all consoles, but is known
4254			to work with serial and VGA consoles.
4255			To facilitate more flexible debugging, we also add
4256			console_suspend, a printk module parameter to control
4257			it. Users could use console_suspend (usually
4258			/sys/module/printk/parameters/console_suspend) to
4259			turn on/off it dynamically.
4260
4261	no_debug_objects
4262			[KNL,EARLY] Disable object debugging
4263
4264	nodsp		[SH] Disable hardware DSP at boot time.
4265
4266	noefi		[EFI,EARLY] Disable EFI runtime services support.
4267
4268	no_entry_flush  [PPC,EARLY] Don't flush the L1-D cache when entering the kernel.
4269
4270	noexec32	[X86-64]
4271			This affects only 32-bit executables.
4272			noexec32=on: enable non-executable mappings (default)
4273				read doesn't imply executable mappings
4274			noexec32=off: disable non-executable mappings
4275				read implies executable mappings
4276
4277	no_file_caps	Tells the kernel not to honor file capabilities.  The
4278			only way then for a file to be executed with privilege
4279			is to be setuid root or executed by root.
4280
4281	nofpu		[MIPS,SH] Disable hardware FPU at boot time.
4282
4283	nofsgsbase	[X86] Disables FSGSBASE instructions.
4284
4285	nofxsr		[BUGS=X86-32] Disables x86 floating point extended
4286			register save and restore. The kernel will only save
4287			legacy floating-point registers on task switch.
4288
4289	nogbpages	[X86] Do not use GB pages for kernel direct mappings.
4290
4291	no_hash_pointers
4292			[KNL,EARLY]
4293			Alias for "hash_pointers=never".
4294
4295	nohibernate	[HIBERNATION] Disable hibernation and resume.
4296
4297	nohlt		[ARM,ARM64,MICROBLAZE,MIPS,PPC,RISCV,SH] Forces the kernel to
4298			busy wait in do_idle() and not use the arch_cpu_idle()
4299			implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
4300			to be effective. This is useful on platforms where the
4301			sleep(SH) or wfi(ARM,ARM64) instructions do not work
4302			correctly or when doing power measurements to evaluate
4303			the impact of the sleep instructions. This is also
4304			useful when using JTAG debugger.
4305
4306	nohpet		[X86] Don't use the HPET timer.
4307
4308	nohugeiomap	[KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings.
4309
4310	nohugevmalloc	[KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings.
4311
4312	nohz=		[KNL] Boottime enable/disable dynamic ticks
4313			Valid arguments: on, off
4314			Default: on
4315
4316	nohz_full=	[KNL,BOOT,SMP,ISOL]
4317			The argument is a cpu list, as described above.
4318			In kernels built with CONFIG_NO_HZ_FULL=y, set
4319			the specified list of CPUs whose tick will be stopped
4320			whenever possible. The boot CPU will be forced outside
4321			the range to maintain the timekeeping.  Any CPUs
4322			in this list will have their RCU callbacks offloaded,
4323			just as if they had also been called out in the
4324			rcu_nocbs= boot parameter.
4325
4326			Note that this argument takes precedence over
4327			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4328
4329	noinitrd	[RAM] Tells the kernel not to load any configured
4330			initial RAM disk.
4331
4332	nointremap	[X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
4333			remapping.
4334			[Deprecated - use intremap=off]
4335
4336	noinvpcid	[X86,EARLY] Disable the INVPCID cpu feature.
4337
4338	noiotrap	[SH] Disables trapped I/O port accesses.
4339
4340	noirqdebug	[X86-32] Disables the code which attempts to detect and
4341			disable unhandled interrupt sources.
4342
4343	noisapnp	[ISAPNP] Disables ISA PnP code.
4344
4345	nokaslr		[KNL,EARLY]
4346			When CONFIG_RANDOMIZE_BASE is set, this disables
4347			kernel and module base offset ASLR (Address Space
4348			Layout Randomization).
4349
4350	no-kvmapf	[X86,KVM,EARLY] Disable paravirtualized asynchronous page
4351			fault handling.
4352
4353	no-kvmclock	[X86,KVM,EARLY] Disable paravirtualized KVM clock driver
4354
4355	nolapic		[X86-32,APIC,EARLY] Do not enable or use the local APIC.
4356
4357	nolapic_timer	[X86-32,APIC,EARLY] Do not use the local APIC timer.
4358
4359	nomce		[X86-32] Disable Machine Check Exception
4360
4361	nomfgpt		[X86-32] Disable Multi-Function General Purpose
4362			Timer usage (for AMD Geode machines).
4363
4364	nomodeset	Disable kernel modesetting. Most systems' firmware
4365			sets up a display mode and provides framebuffer memory
4366			for output. With nomodeset, DRM and fbdev drivers will
4367			not load if they could possibly displace the pre-
4368			initialized output. Only the system framebuffer will
4369			be available for use. The respective drivers will not
4370			perform display-mode changes or accelerated rendering.
4371
4372			Useful as error fallback, or for testing and debugging.
4373
4374	nomodule	Disable module load
4375
4376	nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
4377			shutdown the other cpus.  Instead use the REBOOT_VECTOR
4378			irq.
4379
4380	nopat		[X86,EARLY] Disable PAT (page attribute table extension of
4381			pagetables) support.
4382
4383	nopcid		[X86-64,EARLY] Disable the PCID cpu feature.
4384
4385	nopku		[X86] Disable Memory Protection Keys CPU feature found
4386			in some Intel CPUs.
4387
4388	nopti		[X86-64,EARLY]
4389			Equivalent to pti=off
4390
4391	nopv=		[X86,XEN,KVM,HYPER_V,VMWARE,EARLY]
4392			Disables the PV optimizations forcing the guest to run
4393			as generic guest with no PV drivers. Currently support
4394			XEN HVM, KVM, HYPER_V and VMWARE guest.
4395
4396	nopvspin	[X86,XEN,KVM,EARLY]
4397			Disables the qspinlock slow path using PV optimizations
4398			which allow the hypervisor to 'idle' the guest on lock
4399			contention.
4400
4401	norandmaps	Don't use address space randomization.  Equivalent to
4402			echo 0 > /proc/sys/kernel/randomize_va_space
4403
4404	noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
4405			with UP alternatives
4406
4407	noresume	[SWSUSP] Disables resume and restores original swap
4408			space.
4409
4410	no-scroll	[VGA] Disables scrollback.
4411			This is required for the Braillex ib80-piezo Braille
4412			reader made by F.H. Papenmeier (Germany).
4413
4414	nosgx		[X86-64,SGX,EARLY] Disables Intel SGX kernel support.
4415
4416	nosmap		[PPC,EARLY]
4417			Disable SMAP (Supervisor Mode Access Prevention)
4418			even if it is supported by processor.
4419
4420	nosmep		[PPC64s,EARLY]
4421			Disable SMEP (Supervisor Mode Execution Prevention)
4422			even if it is supported by processor.
4423
4424	nosmp		[SMP,EARLY] Tells an SMP kernel to act as a UP kernel,
4425			and disable the IO APIC.  legacy for "maxcpus=0".
4426
4427	nosmt		[KNL,MIPS,PPC,EARLY] Disable symmetric multithreading (SMT).
4428			Equivalent to smt=1.
4429
4430			[KNL,X86,PPC,S390] Disable symmetric multithreading (SMT).
4431			nosmt=force: Force disable SMT, cannot be undone
4432				     via the sysfs control file.
4433
4434	nosoftlockup	[KNL] Disable the soft-lockup detector.
4435
4436	nospec_store_bypass_disable
4437			[HW,EARLY] Disable all mitigations for the Speculative
4438			Store Bypass vulnerability
4439
4440	nospectre_bhb	[ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch
4441			history injection) vulnerability. System may allow data leaks
4442			with this option.
4443
4444	nospectre_v1	[X86,PPC,EARLY] Disable mitigations for Spectre Variant 1
4445			(bounds check bypass). With this option data leaks are
4446			possible in the system.
4447
4448	nospectre_v2	[X86,PPC_E500,ARM64,EARLY] Disable all mitigations
4449			for the Spectre variant 2 (indirect branch
4450			prediction) vulnerability. System may allow data
4451			leaks with this option.
4452
4453	no-steal-acc	[X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY]
4454			Disable paravirtualized steal time accounting. steal time
4455			is computed, but won't influence scheduler behaviour
4456
4457	nosync		[HW,M68K] Disables sync negotiation for all devices.
4458
4459	no_timer_check	[X86,APIC] Disables the code which tests for broken
4460			timer IRQ sources, i.e., the IO-APIC timer. This can
4461			work around problems with incorrect timer
4462			initialization on some boards.
4463
4464	no_uaccess_flush
4465	                [PPC,EARLY] Don't flush the L1-D cache after accessing user data.
4466
4467	novmcoredd	[KNL,KDUMP]
4468			Disable device dump. Device dump allows drivers to
4469			append dump data to vmcore so you can collect driver
4470			specified debug info.  Drivers can append the data
4471			without any limit and this data is stored in memory,
4472			so this may cause significant memory stress.  Disabling
4473			device dump can help save memory but the driver debug
4474			data will be no longer available.  This parameter
4475			is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
4476			is set.
4477
4478	no-vmw-sched-clock
4479			[X86,PV_OPS,EARLY] Disable paravirtualized VMware
4480			scheduler clock and use the default one.
4481
4482	nowatchdog	[KNL] Disable both lockup detectors, i.e.
4483			soft-lockup and NMI watchdog (hard-lockup).
4484
4485	nowb		[ARM,EARLY]
4486
4487	nox2apic	[X86-64,APIC,EARLY] Do not enable x2APIC mode.
4488
4489			NOTE: this parameter will be ignored on systems with the
4490			LEGACY_XAPIC_DISABLED bit set in the
4491			IA32_XAPIC_DISABLE_STATUS MSR.
4492
4493	noxsave		[BUGS=X86] Disables x86 extended register state save
4494			and restore using xsave. The kernel will fallback to
4495			enabling legacy floating-point and sse state.
4496
4497	noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
4498			register states. The kernel will fall back to use
4499			xsave to save the states. By using this parameter,
4500			performance of saving the states is degraded because
4501			xsave doesn't support modified optimization while
4502			xsaveopt supports it on xsaveopt enabled systems.
4503
4504	noxsaves	[X86] Disables xsaves and xrstors used in saving and
4505			restoring x86 extended register state in compacted
4506			form of xsave area. The kernel will fall back to use
4507			xsaveopt and xrstor to save and restore the states
4508			in standard form of xsave area. By using this
4509			parameter, xsave area per process might occupy more
4510			memory on xsaves enabled systems.
4511
4512	nr_cpus=	[SMP,EARLY] Maximum number of processors that an SMP kernel
4513			could support.  nr_cpus=n : n >= 1 limits the kernel to
4514			support 'n' processors. It could be larger than the
4515			number of already plugged CPU during bootup, later in
4516			runtime you can physically add extra cpu until it reaches
4517			n. So during boot up some boot time memory for per-cpu
4518			variables need be pre-allocated for later physical cpu
4519			hot plugging.
4520
4521	nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
4522
4523	numa=off 	[KNL, ARM64, PPC, RISCV, SPARC, X86, EARLY]
4524			Disable NUMA, Only set up a single NUMA node
4525			spanning all memory.
4526
4527	numa=fake=<size>[MG]
4528			[KNL, ARM64, RISCV, X86, EARLY]
4529			If given as a memory unit, fills all system RAM with
4530			nodes of size interleaved over physical nodes.
4531
4532	numa=fake=<N>
4533			[KNL, ARM64, RISCV, X86, EARLY]
4534			If given as an integer, fills all system RAM with N
4535			fake nodes interleaved over physical nodes.
4536
4537	numa=fake=<N>U
4538			[KNL, ARM64, RISCV, X86, EARLY]
4539			If given as an integer followed by 'U', it will
4540			divide each physical node into N emulated nodes.
4541
4542	numa=noacpi	[X86] Don't parse the SRAT table for NUMA setup
4543
4544	numa=nohmat	[X86] Don't parse the HMAT table for NUMA setup, or
4545			soft-reserved memory partitioning.
4546
4547	numa_balancing=	[KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4548			NUMA balancing.
4549			Allowed values are enable and disable
4550
4551	numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4552			'node', 'default' can be specified
4553			This can be set from sysctl after boot.
4554			See Documentation/admin-guide/sysctl/vm.rst for details.
4555
4556	ohci1394_dma=early	[HW,EARLY] enable debugging via the ohci1394 driver.
4557			See Documentation/core-api/debugging-via-ohci1394.rst for more
4558			info.
4559
4560	olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4561			Rather than timing out after 20 ms if an EC
4562			command is not properly ACKed, override the length
4563			of the timeout.  We have interrupts disabled while
4564			waiting for the ACK, so if this is set too high
4565			interrupts *may* be lost!
4566
4567	omap_mux=	[OMAP] Override bootloader pin multiplexing.
4568			Format: <mux_mode0.mode_name=value>...
4569			For example, to override I2C bus2:
4570			omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4571
4572	onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
4573
4574			Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4575
4576			boundary - index of last SLC block on Flex-OneNAND.
4577				   The remaining blocks are configured as MLC blocks.
4578			lock	 - Configure if Flex-OneNAND boundary should be locked.
4579				   Once locked, the boundary cannot be changed.
4580				   1 indicates lock status, 0 indicates unlock status.
4581
4582	oops=panic	[KNL,EARLY]
4583			Always panic on oopses. Default is to just kill the
4584			process, but there is a small probability of
4585			deadlocking the machine.
4586			This will also cause panics on machine check exceptions.
4587			Useful together with panic=30 to trigger a reboot.
4588
4589	page_alloc.shuffle=
4590			[KNL] Boolean flag to control whether the page allocator
4591			should randomize its free lists. This parameter can be
4592			used to enable/disable page randomization. The state of
4593			the flag can be read from sysfs at:
4594			/sys/module/page_alloc/parameters/shuffle.
4595			This parameter is only available if CONFIG_SHUFFLE_PAGE_ALLOCATOR=y.
4596
4597	page_owner=	[KNL,EARLY] Boot-time page_owner enabling option.
4598			Storage of the information about who allocated
4599			each page is disabled in default. With this switch,
4600			we can turn it on.
4601			on: enable the feature
4602
4603	page_poison=	[KNL,EARLY] Boot-time parameter changing the state of
4604			poisoning on the buddy allocator, available with
4605			CONFIG_PAGE_POISONING=y.
4606			off: turn off poisoning (default)
4607			on: turn on poisoning
4608
4609	page_reporting.page_reporting_order=
4610			[KNL] Minimal page reporting order
4611			Format: <integer>
4612			Adjust the minimal page reporting order. The page
4613			reporting is disabled when it exceeds MAX_PAGE_ORDER.
4614
4615	panic=		[KNL] Kernel behaviour on panic: delay <timeout>
4616			timeout > 0: seconds before rebooting
4617			timeout = 0: wait forever
4618			timeout < 0: reboot immediately
4619			Format: <timeout>
4620
4621	panic_on_taint=	[KNL,EARLY]
4622			Bitmask for conditionally calling panic() in add_taint()
4623			Format: <hex>[,nousertaint]
4624			Hexadecimal bitmask representing the set of TAINT flags
4625			that will cause the kernel to panic when add_taint() is
4626			called with any of the flags in this set.
4627			The optional switch "nousertaint" can be utilized to
4628			prevent userspace forced crashes by writing to sysctl
4629			/proc/sys/kernel/tainted any flagset matching with the
4630			bitmask set on panic_on_taint.
4631			See Documentation/admin-guide/tainted-kernels.rst for
4632			extra details on the taint flags that users can pick
4633			to compose the bitmask to assign to panic_on_taint.
4634
4635	panic_on_warn=1	panic() instead of WARN().  Useful to cause kdump
4636			on a WARN().
4637
4638	panic_print=	Bitmask for printing system info when panic happens.
4639			User can chose combination of the following bits:
4640			bit 0: print all tasks info
4641			bit 1: print system memory info
4642			bit 2: print timer info
4643			bit 3: print locks info if CONFIG_LOCKDEP is on
4644			bit 4: print ftrace buffer
4645			bit 5: replay all kernel messages on consoles at the end of panic
4646			bit 6: print all CPUs backtrace (if available in the arch)
4647			bit 7: print only tasks in uninterruptible (blocked) state
4648			*Be aware* that this option may print a _lot_ of lines,
4649			so there are risks of losing older messages in the log.
4650			Use this option carefully, maybe worth to setup a
4651			bigger log buffer with "log_buf_len" along with this.
4652
4653	panic_sys_info= A comma separated list of extra information to be dumped
4654                        on panic.
4655                        Format: val[,val...]
4656                        Where @val can be any of the following:
4657
4658                        tasks:          print all tasks info
4659                        mem:            print system memory info
4660			timers:         print timers info
4661                        locks:          print locks info if CONFIG_LOCKDEP is on
4662                        ftrace:         print ftrace buffer
4663                        all_bt:         print all CPUs backtrace (if available in the arch)
4664                        blocked_tasks:  print only tasks in uninterruptible (blocked) state
4665
4666                        This is a human readable alternative to the 'panic_print' option.
4667
4668	panic_console_replay
4669			When panic happens, replay all kernel messages on
4670			consoles at the end of panic.
4671
4672	parkbd.port=	[HW] Parallel port number the keyboard adapter is
4673			connected to, default is 0.
4674			Format: <parport#>
4675	parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
4676			0 for XT, 1 for AT (default is AT).
4677			Format: <mode>
4678
4679	parport=	[HW,PPT] Specify parallel ports. 0 disables.
4680			Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4681			Use 'auto' to force the driver to use any
4682			IRQ/DMA settings detected (the default is to
4683			ignore detected IRQ/DMA settings because of
4684			possible conflicts). You can specify the base
4685			address, IRQ, and DMA settings; IRQ and DMA
4686			should be numbers, or 'auto' (for using detected
4687			settings on that particular port), or 'nofifo'
4688			(to avoid using a FIFO even if it is detected).
4689			Parallel ports are assigned in the order they
4690			are specified on the command line, starting
4691			with parport0.
4692
4693	parport_init_mode=	[HW,PPT]
4694			Configure VIA parallel port to operate in
4695			a specific mode. This is necessary on Pegasos
4696			computer where firmware has no options for setting
4697			up parallel port mode and sets it to spp.
4698			Currently this function knows 686a and 8231 chips.
4699			Format: [spp|ps2|epp|ecp|ecpepp]
4700
4701	pata_legacy.all=	[HW,LIBATA]
4702			Format: <int>
4703			Set to non-zero to probe primary and secondary ISA
4704			port ranges on PCI systems where no PCI PATA device
4705			has been found at either range.  Disabled by default.
4706
4707	pata_legacy.autospeed=	[HW,LIBATA]
4708			Format: <int>
4709			Set to non-zero if a chip is present that snoops speed
4710			changes.  Disabled by default.
4711
4712	pata_legacy.ht6560a=	[HW,LIBATA]
4713			Format: <int>
4714			Set to 1, 2, or 3 for HT 6560A on the primary channel,
4715			the secondary channel, or both channels respectively.
4716			Disabled by default.
4717
4718	pata_legacy.ht6560b=	[HW,LIBATA]
4719			Format: <int>
4720			Set to 1, 2, or 3 for HT 6560B on the primary channel,
4721			the secondary channel, or both channels respectively.
4722			Disabled by default.
4723
4724	pata_legacy.iordy_mask=	[HW,LIBATA]
4725			Format: <int>
4726			IORDY enable mask.  Set individual bits to allow IORDY
4727			for the respective channel.  Bit 0 is for the first
4728			legacy channel handled by this driver, bit 1 is for
4729			the second channel, and so on.  The sequence will often
4730			correspond to the primary legacy channel, the secondary
4731			legacy channel, and so on, but the handling of a PCI
4732			bus and the use of other driver options may interfere
4733			with the sequence.  By default IORDY is allowed across
4734			all channels.
4735
4736	pata_legacy.opti82c46x=	[HW,LIBATA]
4737			Format: <int>
4738			Set to 1, 2, or 3 for Opti 82c611A on the primary
4739			channel, the secondary channel, or both channels
4740			respectively.  Disabled by default.
4741
4742	pata_legacy.opti82c611a=	[HW,LIBATA]
4743			Format: <int>
4744			Set to 1, 2, or 3 for Opti 82c465MV on the primary
4745			channel, the secondary channel, or both channels
4746			respectively.  Disabled by default.
4747
4748	pata_legacy.pio_mask=	[HW,LIBATA]
4749			Format: <int>
4750			PIO mode mask for autospeed devices.  Set individual
4751			bits to allow the use of the respective PIO modes.
4752			Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4753			All modes allowed by default.
4754
4755	pata_legacy.probe_all=	[HW,LIBATA]
4756			Format: <int>
4757			Set to non-zero to probe tertiary and further ISA
4758			port ranges on PCI systems.  Disabled by default.
4759
4760	pata_legacy.probe_mask=	[HW,LIBATA]
4761			Format: <int>
4762			Probe mask for legacy ISA PATA ports.  Depending on
4763			platform configuration and the use of other driver
4764			options up to 6 legacy ports are supported: 0x1f0,
4765			0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4766			of individual ports can be disabled by setting the
4767			corresponding bits in the mask to 1.  Bit 0 is for
4768			the first port in the list above (0x1f0), and so on.
4769			By default all supported ports are probed.
4770
4771	pata_legacy.qdi=	[HW,LIBATA]
4772			Format: <int>
4773			Set to non-zero to probe QDI controllers.  By default
4774			set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4775
4776	pata_legacy.winbond=	[HW,LIBATA]
4777			Format: <int>
4778			Set to non-zero to probe Winbond controllers.  Use
4779			the standard I/O port (0x130) if 1, otherwise the
4780			value given is the I/O port to use (typically 0x1b0).
4781			By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4782			0 otherwise.
4783
4784	pata_platform.pio_mask=	[HW,LIBATA]
4785			Format: <int>
4786			Supported PIO mode mask.  Set individual bits to allow
4787			the use of the respective PIO modes.  Bit 0 is for
4788			mode 0, bit 1 is for mode 1, and so on.  Mode 0 only
4789			allowed by default.
4790
4791	pause_on_oops=<int>
4792			Halt all CPUs after the first oops has been printed for
4793			the specified number of seconds.  This is to be used if
4794			your oopses keep scrolling off the screen.
4795
4796	pcbit=		[HW,ISDN]
4797
4798	pci=option[,option...]	[PCI,EARLY] various PCI subsystem options.
4799
4800				Some options herein operate on a specific device
4801				or a set of devices (<pci_dev>). These are
4802				specified in one of the following formats:
4803
4804				[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4805				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4806
4807				Note: the first format specifies a PCI
4808				bus/device/function address which may change
4809				if new hardware is inserted, if motherboard
4810				firmware changes, or due to changes caused
4811				by other kernel parameters. If the
4812				domain is left unspecified, it is
4813				taken to be zero. Optionally, a path
4814				to a device through multiple device/function
4815				addresses can be specified after the base
4816				address (this is more robust against
4817				renumbering issues).  The second format
4818				selects devices using IDs from the
4819				configuration space which may match multiple
4820				devices in the system.
4821
4822		earlydump	dump PCI config space before the kernel
4823				changes anything
4824		off		[X86] don't probe for the PCI bus
4825		bios		[X86-32] force use of PCI BIOS, don't access
4826				the hardware directly. Use this if your machine
4827				has a non-standard PCI host bridge.
4828		nobios		[X86-32] disallow use of PCI BIOS, only direct
4829				hardware access methods are allowed. Use this
4830				if you experience crashes upon bootup and you
4831				suspect they are caused by the BIOS.
4832		conf1		[X86] Force use of PCI Configuration Access
4833				Mechanism 1 (config address in IO port 0xCF8,
4834				data in IO port 0xCFC, both 32-bit).
4835		conf2		[X86] Force use of PCI Configuration Access
4836				Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4837				the function, IO port 0xCFA, also 8-bit, sets
4838				bus number. The config space is then accessed
4839				through ports 0xC000-0xCFFF).
4840				See http://wiki.osdev.org/PCI for more info
4841				on the configuration access mechanisms.
4842		noaer		[PCIE] If the PCIEAER kernel config parameter is
4843				enabled, this kernel boot option can be used to
4844				disable the use of PCIE advanced error reporting.
4845		nodomains	[PCI] Disable support for multiple PCI
4846				root domains (aka PCI segments, in ACPI-speak).
4847		nommconf	[X86] Disable use of MMCONFIG for PCI
4848				Configuration
4849		check_enable_amd_mmconf [X86] check for and enable
4850				properly configured MMIO access to PCI
4851				config space on AMD family 10h CPU
4852		nomsi		[MSI] If the PCI_MSI kernel config parameter is
4853				enabled, this kernel boot option can be used to
4854				disable the use of MSI interrupts system-wide.
4855		noioapicquirk	[APIC] Disable all boot interrupt quirks.
4856				Safety option to keep boot IRQs enabled. This
4857				should never be necessary.
4858		ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
4859				primary IO-APIC for bridges that cannot disable
4860				boot IRQs. This fixes a source of spurious IRQs
4861				when the system masks IRQs.
4862		noioapicreroute	[APIC] Disable workaround that uses the
4863				boot IRQ equivalent of an IRQ that connects to
4864				a chipset where boot IRQs cannot be disabled.
4865				The opposite of ioapicreroute.
4866		biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
4867				routing table. These calls are known to be buggy
4868				on several machines and they hang the machine
4869				when used, but on other computers it's the only
4870				way to get the interrupt routing table. Try
4871				this option if the kernel is unable to allocate
4872				IRQs or discover secondary PCI buses on your
4873				motherboard.
4874		rom		[X86] Assign address space to expansion ROMs.
4875				Use with caution as certain devices share
4876				address decoders between ROMs and other
4877				resources.
4878		norom		[X86] Do not assign address space to
4879				expansion ROMs that do not already have
4880				BIOS assigned address ranges.
4881		nobar		[X86] Do not assign address space to the
4882				BARs that weren't assigned by the BIOS.
4883		irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
4884				assigned automatically to PCI devices. You can
4885				make the kernel exclude IRQs of your ISA cards
4886				this way.
4887		pirqaddr=0xAAAAA	[X86] Specify the physical address
4888				of the PIRQ table (normally generated
4889				by the BIOS) if it is outside the
4890				F0000h-100000h range.
4891		lastbus=N	[X86] Scan all buses thru bus #N. Can be
4892				useful if the kernel is unable to find your
4893				secondary buses and you want to tell it
4894				explicitly which ones they are.
4895		assign-busses	[X86] Always assign all PCI bus
4896				numbers ourselves, overriding
4897				whatever the firmware may have done.
4898		usepirqmask	[X86] Honor the possible IRQ mask stored
4899				in the BIOS $PIR table. This is needed on
4900				some systems with broken BIOSes, notably
4901				some HP Pavilion N5400 and Omnibook XE3
4902				notebooks. This will have no effect if ACPI
4903				IRQ routing is enabled.
4904		noacpi		[X86] Do not use ACPI for IRQ routing
4905				or for PCI scanning.
4906		use_crs		[X86] Use PCI host bridge window information
4907				from ACPI.  On BIOSes from 2008 or later, this
4908				is enabled by default.  If you need to use this,
4909				please report a bug.
4910		nocrs		[X86] Ignore PCI host bridge windows from ACPI.
4911				If you need to use this, please report a bug.
4912		use_e820	[X86] Use E820 reservations to exclude parts of
4913				PCI host bridge windows. This is a workaround
4914				for BIOS defects in host bridge _CRS methods.
4915				If you need to use this, please report a bug to
4916				<linux-pci@vger.kernel.org>.
4917		no_e820		[X86] Ignore E820 reservations for PCI host
4918				bridge windows. This is the default on modern
4919				hardware. If you need to use this, please report
4920				a bug to <linux-pci@vger.kernel.org>.
4921		routeirq	Do IRQ routing for all PCI devices.
4922				This is normally done in pci_enable_device(),
4923				so this option is a temporary workaround
4924				for broken drivers that don't call it.
4925		skip_isa_align	[X86] do not align io start addr, so can
4926				handle more pci cards
4927		noearly		[X86] Don't do any early type 1 scanning.
4928				This might help on some broken boards which
4929				machine check when some devices' config space
4930				is read. But various workarounds are disabled
4931				and some IOMMU drivers will not work.
4932		bfsort		Sort PCI devices into breadth-first order.
4933				This sorting is done to get a device
4934				order compatible with older (<= 2.4) kernels.
4935		nobfsort	Don't sort PCI devices into breadth-first order.
4936		pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
4937				tuning and use the BIOS-configured MPS defaults.
4938		pcie_bus_safe	Set every device's MPS to the largest value
4939				supported by all devices below the root complex.
4940		pcie_bus_perf	Set device MPS to the largest allowable MPS
4941				based on its parent bus. Also set MRRS (Max
4942				Read Request Size) to the largest supported
4943				value (no larger than the MPS that the device
4944				or bus can support) for best performance.
4945		pcie_bus_peer2peer	Set every device's MPS to 128B, which
4946				every device is guaranteed to support. This
4947				configuration allows peer-to-peer DMA between
4948				any pair of devices, possibly at the cost of
4949				reduced performance.  This also guarantees
4950				that hot-added devices will work.
4951		cbiosize=nn[KMG]	The fixed amount of bus space which is
4952				reserved for the CardBus bridge's IO window.
4953				The default value is 256 bytes.
4954		cbmemsize=nn[KMG]	The fixed amount of bus space which is
4955				reserved for the CardBus bridge's memory
4956				window. The default value is 64 megabytes.
4957		resource_alignment=
4958				Format:
4959				[<order of align>@]<pci_dev>[; ...]
4960				Specifies alignment and device to reassign
4961				aligned memory resources. How to
4962				specify the device is described above.
4963				If <order of align> is not specified,
4964				PAGE_SIZE is used as alignment.
4965				A PCI-PCI bridge can be specified if resource
4966				windows need to be expanded.
4967				To specify the alignment for several
4968				instances of a device, the PCI vendor,
4969				device, subvendor, and subdevice may be
4970				specified, e.g., 12@pci:8086:9c22:103c:198f
4971				for 4096-byte alignment.
4972		ecrc=		Enable/disable PCIe ECRC (transaction layer
4973				end-to-end CRC checking). Only effective if
4974				OS has native AER control (either granted by
4975				ACPI _OSC or forced via "pcie_ports=native")
4976				bios: Use BIOS/firmware settings. This is the
4977				the default.
4978				off: Turn ECRC off
4979				on: Turn ECRC on.
4980		hpiosize=nn[KMG]	The fixed amount of bus space which is
4981				reserved for hotplug bridge's IO window.
4982				Default size is 256 bytes.
4983		hpmmiosize=nn[KMG]	The fixed amount of bus space which is
4984				reserved for hotplug bridge's MMIO window.
4985				Default size is 2 megabytes.
4986		hpmmioprefsize=nn[KMG]	The fixed amount of bus space which is
4987				reserved for hotplug bridge's MMIO_PREF window.
4988				Default size is 2 megabytes.
4989		hpmemsize=nn[KMG]	The fixed amount of bus space which is
4990				reserved for hotplug bridge's MMIO and
4991				MMIO_PREF window.
4992				Default size is 2 megabytes.
4993		hpbussize=nn	The minimum amount of additional bus numbers
4994				reserved for buses below a hotplug bridge.
4995				Default is 1.
4996		realloc=	Enable/disable reallocating PCI bridge resources
4997				if allocations done by BIOS are too small to
4998				accommodate resources required by all child
4999				devices.
5000				off: Turn realloc off
5001				on: Turn realloc on
5002		realloc		same as realloc=on
5003		noari		do not use PCIe ARI.
5004		noats		[PCIE, Intel-IOMMU, AMD-IOMMU]
5005				do not use PCIe ATS (and IOMMU device IOTLB).
5006		pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
5007				only look for one device below a PCIe downstream
5008				port.
5009		big_root_window	Try to add a big 64bit memory window to the PCIe
5010				root complex on AMD CPUs. Some GFX hardware
5011				can resize a BAR to allow access to all VRAM.
5012				Adding the window is slightly risky (it may
5013				conflict with unreported devices), so this
5014				taints the kernel.
5015		disable_acs_redir=<pci_dev>[; ...]
5016				Specify one or more PCI devices (in the format
5017				specified above) separated by semicolons.
5018				Each device specified will have the PCI ACS
5019				redirect capabilities forced off which will
5020				allow P2P traffic between devices through
5021				bridges without forcing it upstream. Note:
5022				this removes isolation between devices and
5023				may put more devices in an IOMMU group.
5024		config_acs=
5025				Format:
5026				<ACS flags>@<pci_dev>[; ...]
5027				Specify one or more PCI devices (in the format
5028				specified above) optionally prepended with flags
5029				and separated by semicolons. The respective
5030				capabilities will be enabled, disabled or
5031				unchanged based on what is specified in
5032				flags.
5033
5034				ACS Flags is defined as follows:
5035				  bit-0 : ACS Source Validation
5036				  bit-1 : ACS Translation Blocking
5037				  bit-2 : ACS P2P Request Redirect
5038				  bit-3 : ACS P2P Completion Redirect
5039				  bit-4 : ACS Upstream Forwarding
5040				  bit-5 : ACS P2P Egress Control
5041				  bit-6 : ACS Direct Translated P2P
5042				Each bit can be marked as:
5043				  '0' – force disabled
5044				  '1' – force enabled
5045				  'x' – unchanged
5046				For example,
5047				  pci=config_acs=10x@pci:0:0
5048				would configure all devices that support
5049				ACS to enable P2P Request Redirect, disable
5050				Translation Blocking, and leave Source
5051				Validation unchanged from whatever power-up
5052				or firmware set it to.
5053
5054				Note: this may remove isolation between devices
5055				and may put more devices in an IOMMU group.
5056		force_floating	[S390] Force usage of floating interrupts.
5057		nomio		[S390] Do not use MIO instructions.
5058		norid		[S390] ignore the RID field and force use of
5059				one PCI domain per PCI function
5060		notph		[PCIE] If the PCIE_TPH kernel config parameter
5061				is enabled, this kernel boot option can be used
5062				to disable PCIe TLP Processing Hints support
5063				system-wide.
5064
5065	pcie_aspm=	[PCIE] Forcibly enable or ignore PCIe Active State Power
5066			Management.
5067		off	Don't touch ASPM configuration at all.  Leave any
5068			configuration done by firmware unchanged.
5069		force	Enable ASPM even on devices that claim not to support it.
5070			WARNING: Forcing ASPM on may cause system lockups.
5071
5072	pcie_ports=	[PCIE] PCIe port services handling:
5073		native	Use native PCIe services (PME, AER, DPC, PCIe hotplug)
5074			even if the platform doesn't give the OS permission to
5075			use them.  This may cause conflicts if the platform
5076			also tries to use these services.
5077		dpc-native	Use native PCIe service for DPC only.  May
5078				cause conflicts if firmware uses AER or DPC.
5079		compat	Disable native PCIe services (PME, AER, DPC, PCIe
5080			hotplug).
5081
5082	pcie_port_pm=	[PCIE] PCIe port power management handling:
5083		off	Disable power management of all PCIe ports
5084		force	Forcibly enable power management of all PCIe ports
5085
5086	pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
5087		nomsi	Do not use MSI for native PCIe PME signaling (this makes
5088			all PCIe root ports use INTx for all services).
5089
5090	pcmv=		[HW,PCMCIA] BadgePAD 4
5091
5092	pd_ignore_unused
5093			[PM]
5094			Keep all power-domains already enabled by bootloader on,
5095			even if no driver has claimed them. This is useful
5096			for debug and development, but should not be
5097			needed on a platform with proper driver support.
5098
5099	pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
5100			boot time.
5101			Format: { 0 | 1 }
5102			See arch/parisc/kernel/pdc_chassis.c
5103
5104	percpu_alloc=	[MM,EARLY]
5105			Select which percpu first chunk allocator to use.
5106			Currently supported values are "embed" and "page".
5107			Archs may support subset or none of the	selections.
5108			See comments in mm/percpu.c for details on each
5109			allocator.  This parameter is primarily	for debugging
5110			and performance comparison.
5111
5112	pirq=		[SMP,APIC] Manual mp-table setup
5113			See Documentation/arch/x86/i386/IO-APIC.rst.
5114
5115	plip=		[PPT,NET] Parallel port network link
5116			Format: { parport<nr> | timid | 0 }
5117			See also Documentation/admin-guide/parport.rst.
5118
5119	pmtmr=		[X86] Manual setup of pmtmr I/O Port.
5120			Override pmtimer IOPort with a hex value.
5121			e.g. pmtmr=0x508
5122
5123	pmu_override=	[PPC] Override the PMU.
5124			This option takes over the PMU facility, so it is no
5125			longer usable by perf. Setting this option starts the
5126			PMU counters by setting MMCR0 to 0 (the FC bit is
5127			cleared). If a number is given, then MMCR1 is set to
5128			that number, otherwise (e.g., 'pmu_override=on'), MMCR1
5129			remains 0.
5130
5131	pm_async=	[PM]
5132			Format: off
5133			This parameter sets the initial value of the
5134			/sys/power/pm_async sysfs knob at boot time.
5135			If set to "off", disables asynchronous suspend and
5136			resume of devices during system-wide power transitions.
5137			This can be useful on platforms where device
5138			dependencies are not well-defined, or for debugging
5139			power management issues. Asynchronous operations are
5140			enabled by default.
5141
5142
5143	pm_debug_messages	[SUSPEND,KNL]
5144			Enable suspend/resume debug messages during boot up.
5145
5146	pnp.debug=1	[PNP]
5147			Enable PNP debug messages (depends on the
5148			CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
5149			via /sys/module/pnp/parameters/debug.  We always show
5150			current resource usage; turning this on also shows
5151			possible settings and some assignment information.
5152
5153	pnpacpi=	[ACPI]
5154			{ off }
5155
5156	pnpbios=	[ISAPNP]
5157			{ on | off | curr | res | no-curr | no-res }
5158
5159	pnp_reserve_irq=
5160			[ISAPNP] Exclude IRQs for the autoconfiguration
5161
5162	pnp_reserve_dma=
5163			[ISAPNP] Exclude DMAs for the autoconfiguration
5164
5165	pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
5166			Ranges are in pairs (I/O port base and size).
5167
5168	pnp_reserve_mem=
5169			[ISAPNP] Exclude memory regions for the
5170			autoconfiguration.
5171			Ranges are in pairs (memory base and size).
5172
5173	ports=		[IP_VS_FTP] IPVS ftp helper module
5174			Default is 21.
5175			Up to 8 (IP_VS_APP_MAX_PORTS) ports
5176			may be specified.
5177			Format: <port>,<port>....
5178
5179	possible_cpus=  [SMP,S390,X86]
5180			Format: <unsigned int>
5181			Set the number of possible CPUs, overriding the
5182			regular discovery mechanisms (such as ACPI/FW, etc).
5183
5184	powersave=off	[PPC] This option disables power saving features.
5185			It specifically disables cpuidle and sets the
5186			platform machine description specific power_save
5187			function to NULL. On Idle the CPU just reduces
5188			execution priority.
5189
5190	ppc_strict_facility_enable
5191			[PPC,ENABLE] This option catches any kernel floating point,
5192			Altivec, VSX and SPE outside of regions specifically
5193			allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
5194			There is some performance impact when enabling this.
5195
5196	ppc_tm=		[PPC,EARLY]
5197			Format: {"off"}
5198			Disable Hardware Transactional Memory
5199
5200	preempt=	[KNL]
5201			Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
5202			none - Limited to cond_resched() calls
5203			voluntary - Limited to cond_resched() and might_sleep() calls
5204			full - Any section that isn't explicitly preempt disabled
5205			       can be preempted anytime.  Tasks will also yield
5206			       contended spinlocks (if the critical section isn't
5207			       explicitly preempt disabled beyond the lock itself).
5208			lazy - Scheduler controlled. Similar to full but instead
5209			       of preempting the task immediately, the task gets
5210			       one HZ tick time to yield itself before the
5211			       preemption will be forced. One preemption is when the
5212			       task returns to user space.
5213
5214	print-fatal-signals=
5215			[KNL] debug: print fatal signals
5216
5217			If enabled, warn about various signal handling
5218			related application anomalies: too many signals,
5219			too many POSIX.1 timers, fatal signals causing a
5220			coredump - etc.
5221
5222			If you hit the warning due to signal overflow,
5223			you might want to try "ulimit -i unlimited".
5224
5225			default: off.
5226
5227	printk.always_kmsg_dump=
5228			Trigger kmsg_dump for cases other than kernel oops or
5229			panics
5230			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
5231			default: disabled
5232
5233	printk.console_no_auto_verbose=
5234			Disable console loglevel raise on oops, panic
5235			or lockdep-detected issues (only if lock debug is on).
5236			With an exception to setups with low baudrate on
5237			serial console, keeping this 0 is a good choice
5238			in order to provide more debug information.
5239			Format: <bool>
5240			default: 0 (auto_verbose is enabled)
5241
5242	printk.debug_non_panic_cpus=
5243			Allows storing messages from non-panic CPUs into
5244			the printk log buffer during panic(). They are
5245			flushed to consoles by the panic-CPU on
5246			a best-effort basis.
5247			Format: <bool> (1/Y/y=enable, 0/N/n=disable)
5248			Default: disabled
5249
5250	printk.devkmsg={on,off,ratelimit}
5251			Control writing to /dev/kmsg.
5252			on - unlimited logging to /dev/kmsg from userspace
5253			off - logging to /dev/kmsg disabled
5254			ratelimit - ratelimit the logging
5255			Default: ratelimit
5256
5257	printk.time=	Show timing data prefixed to each printk message line
5258			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
5259
5260	proc_mem.force_override= [KNL]
5261			Format: {always | ptrace | never}
5262			Traditionally /proc/pid/mem allows memory permissions to be
5263			overridden without restrictions. This option may be set to
5264			restrict that. Can be one of:
5265			- 'always': traditional behavior always allows mem overrides.
5266			- 'ptrace': only allow mem overrides for active ptracers.
5267			- 'never':  never allow mem overrides.
5268			If not specified, default is the CONFIG_PROC_MEM_* choice.
5269
5270	processor.max_cstate=	[HW,ACPI]
5271			Limit processor to maximum C-state
5272			max_cstate=9 overrides any DMI blacklist limit.
5273
5274	processor.nocst	[HW,ACPI]
5275			Ignore the _CST method to determine C-states,
5276			instead using the legacy FADT method
5277
5278	profile=	[KNL] Enable kernel profiling via /proc/profile
5279			Format: [<profiletype>,]<number>
5280			Param: <profiletype>: "schedule" or "kvm"
5281				[defaults to kernel profiling]
5282			Param: "schedule" - profile schedule points.
5283			Param: "kvm" - profile VM exits.
5284			Param: <number> - step/bucket size as a power of 2 for
5285				statistical time based profiling.
5286
5287	prompt_ramdisk=	[RAM] [Deprecated]
5288
5289	prot_virt=	[S390] enable hosting protected virtual machines
5290			isolated from the hypervisor (if hardware supports
5291			that). If enabled, the default kernel base address
5292			might be overridden even when Kernel Address Space
5293			Layout Randomization is disabled.
5294			Format: <bool>
5295
5296	psi=		[KNL] Enable or disable pressure stall information
5297			tracking.
5298			Format: <bool>
5299
5300	psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
5301			probe for; one of (bare|imps|exps|lifebook|any).
5302	psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
5303			per second.
5304	psmouse.resetafter=	[HW,MOUSE]
5305			Try to reset the device after so many bad packets
5306			(0 = never).
5307	psmouse.resolution=
5308			[HW,MOUSE] Set desired mouse resolution, in dpi.
5309	psmouse.smartscroll=
5310			[HW,MOUSE] Controls Logitech smartscroll autorepeat.
5311			0 = disabled, 1 = enabled (default).
5312
5313	pstore.backend=	Specify the name of the pstore backend to use
5314
5315	pti=		[X86-64] Control Page Table Isolation of user and
5316			kernel address spaces.  Disabling this feature
5317			removes hardening, but improves performance of
5318			system calls and interrupts.
5319
5320			on   - unconditionally enable
5321			off  - unconditionally disable
5322			auto - kernel detects whether your CPU model is
5323			       vulnerable to issues that PTI mitigates
5324
5325			Not specifying this option is equivalent to pti=auto.
5326
5327	pty.legacy_count=
5328			[KNL] Number of legacy pty's. Overwrites compiled-in
5329			default number.
5330
5331	quiet		[KNL,EARLY] Disable most log messages
5332
5333	r128=		[HW,DRM]
5334
5335	radix_hcall_invalidate=on  [PPC/PSERIES]
5336			Disable RADIX GTSE feature and use hcall for TLB
5337			invalidate.
5338
5339	raid=		[HW,RAID]
5340			See Documentation/admin-guide/md.rst.
5341
5342	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
5343			See Documentation/admin-guide/blockdev/ramdisk.rst.
5344
5345	ramdisk_start=	[RAM] RAM disk image start address
5346
5347	random.trust_cpu=off
5348			[KNL,EARLY] Disable trusting the use of the CPU's
5349			random number generator (if available) to
5350			initialize the kernel's RNG.
5351
5352	random.trust_bootloader=off
5353			[KNL,EARLY] Disable trusting the use of the a seed
5354			passed by the bootloader (if available) to
5355			initialize the kernel's RNG.
5356
5357	randomize_kstack_offset=
5358			[KNL,EARLY] Enable or disable kernel stack offset
5359			randomization, which provides roughly 5 bits of
5360			entropy, frustrating memory corruption attacks
5361			that depend on stack address determinism or
5362			cross-syscall address exposures. This is only
5363			available on architectures that have defined
5364			CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
5365			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
5366			Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
5367
5368	ras=option[,option,...]	[KNL] RAS-specific options
5369
5370		cec_disable	[X86]
5371				Disable the Correctable Errors Collector,
5372				see CONFIG_RAS_CEC help text.
5373
5374	rcu_nocbs[=cpu-list]
5375			[KNL] The optional argument is a cpu list,
5376			as described above.
5377
5378			In kernels built with CONFIG_RCU_NOCB_CPU=y,
5379			enable the no-callback CPU mode, which prevents
5380			such CPUs' callbacks from being invoked in
5381			softirq context.  Invocation of such CPUs' RCU
5382			callbacks will instead be offloaded to "rcuox/N"
5383			kthreads created for that purpose, where "x" is
5384			"p" for RCU-preempt, "s" for RCU-sched, and "g"
5385			for the kthreads that mediate grace periods; and
5386			"N" is the CPU number. This reduces OS jitter on
5387			the offloaded CPUs, which can be useful for HPC
5388			and real-time workloads.  It can also improve
5389			energy efficiency for asymmetric multiprocessors.
5390
5391			If a cpulist is passed as an argument, the specified
5392			list of	CPUs is set to no-callback mode from boot.
5393
5394			Otherwise, if the '=' sign and the cpulist
5395			arguments are omitted, no CPU will be set to
5396			no-callback mode from boot but the mode may be
5397			toggled at runtime via cpusets.
5398
5399			Note that this argument takes precedence over
5400			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
5401
5402	rcu_nocb_poll	[KNL]
5403			Rather than requiring that offloaded CPUs
5404			(specified by rcu_nocbs= above) explicitly
5405			awaken the corresponding "rcuoN" kthreads,
5406			make these kthreads poll for callbacks.
5407			This improves the real-time response for the
5408			offloaded CPUs by relieving them of the need to
5409			wake up the corresponding kthread, but degrades
5410			energy efficiency by requiring that the kthreads
5411			periodically wake up to do the polling.
5412
5413	rcutree.blimit=	[KNL]
5414			Set maximum number of finished RCU callbacks to
5415			process in one batch.
5416
5417	rcutree.csd_lock_suppress_rcu_stall=	[KNL]
5418			Do only a one-line RCU CPU stall warning when
5419			there is an ongoing too-long CSD-lock wait.
5420
5421	rcutree.do_rcu_barrier=	[KNL]
5422			Request a call to rcu_barrier().  This is
5423			throttled so that userspace tests can safely
5424			hammer on the sysfs variable if they so choose.
5425			If triggered before the RCU grace-period machinery
5426			is fully active, this will error out with EAGAIN.
5427
5428	rcutree.dump_tree=	[KNL]
5429			Dump the structure of the rcu_node combining tree
5430			out at early boot.  This is used for diagnostic
5431			purposes, to verify correct tree setup.
5432
5433	rcutree.gp_cleanup_delay=	[KNL]
5434			Set the number of jiffies to delay each step of
5435			RCU grace-period cleanup.
5436
5437	rcutree.gp_init_delay=	[KNL]
5438			Set the number of jiffies to delay each step of
5439			RCU grace-period initialization.
5440
5441	rcutree.gp_preinit_delay=	[KNL]
5442			Set the number of jiffies to delay each step of
5443			RCU grace-period pre-initialization, that is,
5444			the propagation of recent CPU-hotplug changes up
5445			the rcu_node combining tree.
5446
5447	rcutree.jiffies_till_first_fqs= [KNL]
5448			Set delay from grace-period initialization to
5449			first attempt to force quiescent states.
5450			Units are jiffies, minimum value is zero,
5451			and maximum value is HZ.
5452
5453	rcutree.jiffies_till_next_fqs= [KNL]
5454			Set delay between subsequent attempts to force
5455			quiescent states.  Units are jiffies, minimum
5456			value is one, and maximum value is HZ.
5457
5458	rcutree.jiffies_till_sched_qs= [KNL]
5459			Set required age in jiffies for a
5460			given grace period before RCU starts
5461			soliciting quiescent-state help from
5462			rcu_note_context_switch() and cond_resched().
5463			If not specified, the kernel will calculate
5464			a value based on the most recent settings
5465			of rcutree.jiffies_till_first_fqs
5466			and rcutree.jiffies_till_next_fqs.
5467			This calculated value may be viewed in
5468			rcutree.jiffies_to_sched_qs.  Any attempt to set
5469			rcutree.jiffies_to_sched_qs will be cheerfully
5470			overwritten.
5471
5472	rcutree.kthread_prio= 	 [KNL,BOOT]
5473			Set the SCHED_FIFO priority of the RCU per-CPU
5474			kthreads (rcuc/N). This value is also used for
5475			the priority of the RCU boost threads (rcub/N)
5476			and for the RCU grace-period kthreads (rcu_bh,
5477			rcu_preempt, and rcu_sched). If RCU_BOOST is
5478			set, valid values are 1-99 and the default is 1
5479			(the least-favored priority).  Otherwise, when
5480			RCU_BOOST is not set, valid values are 0-99 and
5481			the default is zero (non-realtime operation).
5482			When RCU_NOCB_CPU is set, also adjust the
5483			priority of NOCB callback kthreads.
5484
5485	rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5486			On callback-offloaded (rcu_nocbs) CPUs,
5487			RCU reduces the lock contention that would
5488			otherwise be caused by callback floods through
5489			use of the ->nocb_bypass list.	However, in the
5490			common non-flooded case, RCU queues directly to
5491			the main ->cblist in order to avoid the extra
5492			overhead of the ->nocb_bypass list and its lock.
5493			But if there are too many callbacks queued during
5494			a single jiffy, RCU pre-queues the callbacks into
5495			the ->nocb_bypass queue.  The definition of "too
5496			many" is supplied by this kernel boot parameter.
5497
5498	rcutree.nohz_full_patience_delay= [KNL]
5499			On callback-offloaded (rcu_nocbs) CPUs, avoid
5500			disturbing RCU unless the grace period has
5501			reached the specified age in milliseconds.
5502			Defaults to zero.  Large values will be capped
5503			at five seconds.  All values will be rounded down
5504			to the nearest value representable by jiffies.
5505
5506	rcutree.qhimark= [KNL]
5507			Set threshold of queued RCU callbacks beyond which
5508			batch limiting is disabled.
5509
5510	rcutree.qlowmark= [KNL]
5511			Set threshold of queued RCU callbacks below which
5512			batch limiting is re-enabled.
5513
5514	rcutree.qovld= [KNL]
5515			Set threshold of queued RCU callbacks beyond which
5516			RCU's force-quiescent-state scan will aggressively
5517			enlist help from cond_resched() and sched IPIs to
5518			help CPUs more quickly reach quiescent states.
5519			Set to less than zero to make this be set based
5520			on rcutree.qhimark at boot time and to zero to
5521			disable more aggressive help enlistment.
5522
5523	rcutree.rcu_delay_page_cache_fill_msec= [KNL]
5524			Set the page-cache refill delay (in milliseconds)
5525			in response to low-memory conditions.  The range
5526			of permitted values is in the range 0:100000.
5527
5528	rcutree.rcu_divisor= [KNL]
5529			Set the shift-right count to use to compute
5530			the callback-invocation batch limit bl from
5531			the number of callbacks queued on this CPU.
5532			The result will be bounded below by the value of
5533			the rcutree.blimit kernel parameter.  Every bl
5534			callbacks, the softirq handler will exit in
5535			order to allow the CPU to do other work.
5536
5537			Please note that this callback-invocation batch
5538			limit applies only to non-offloaded callback
5539			invocation.  Offloaded callbacks are instead
5540			invoked in the context of an rcuoc kthread, which
5541			scheduler will preempt as it does any other task.
5542
5543	rcutree.rcu_fanout_exact= [KNL]
5544			Disable autobalancing of the rcu_node combining
5545			tree.  This is used by rcutorture, and might
5546			possibly be useful for architectures having high
5547			cache-to-cache transfer latencies.
5548
5549	rcutree.rcu_fanout_leaf= [KNL]
5550			Change the number of CPUs assigned to each
5551			leaf rcu_node structure.  Useful for very
5552			large systems, which will choose the value 64,
5553			and for NUMA systems with large remote-access
5554			latencies, which will choose a value aligned
5555			with the appropriate hardware boundaries.
5556
5557	rcutree.rcu_min_cached_objs= [KNL]
5558			Minimum number of objects which are cached and
5559			maintained per one CPU. Object size is equal
5560			to PAGE_SIZE. The cache allows to reduce the
5561			pressure to page allocator, also it makes the
5562			whole algorithm to behave better in low memory
5563			condition.
5564
5565	rcutree.rcu_nocb_gp_stride= [KNL]
5566			Set the number of NOCB callback kthreads in
5567			each group, which defaults to the square root
5568			of the number of CPUs.	Larger numbers reduce
5569			the wakeup overhead on the global grace-period
5570			kthread, but increases that same overhead on
5571			each group's NOCB grace-period kthread.
5572
5573	rcutree.rcu_kick_kthreads= [KNL]
5574			Cause the grace-period kthread to get an extra
5575			wake_up() if it sleeps three times longer than
5576			it should at force-quiescent-state time.
5577			This wake_up() will be accompanied by a
5578			WARN_ONCE() splat and an ftrace_dump().
5579
5580	rcutree.rcu_resched_ns= [KNL]
5581			Limit the time spend invoking a batch of RCU
5582			callbacks to the specified number of nanoseconds.
5583			By default, this limit is checked only once
5584			every 32 callbacks in order to limit the pain
5585			inflicted by local_clock() overhead.
5586
5587	rcutree.rcu_unlock_delay= [KNL]
5588			In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5589			this specifies an rcu_read_unlock()-time delay
5590			in microseconds.  This defaults to zero.
5591			Larger delays increase the probability of
5592			catching RCU pointer leaks, that is, buggy use
5593			of RCU-protected pointers after the relevant
5594			rcu_read_unlock() has completed.
5595
5596	rcutree.sysrq_rcu= [KNL]
5597			Commandeer a sysrq key to dump out Tree RCU's
5598			rcu_node tree with an eye towards determining
5599			why a new grace period has not yet started.
5600
5601	rcutree.use_softirq=	[KNL]
5602			If set to zero, move all RCU_SOFTIRQ processing to
5603			per-CPU rcuc kthreads.  Defaults to a non-zero
5604			value, meaning that RCU_SOFTIRQ is used by default.
5605			Specify rcutree.use_softirq=0 to use rcuc kthreads.
5606
5607			But note that CONFIG_PREEMPT_RT=y kernels disable
5608			this kernel boot parameter, forcibly setting it
5609			to zero.
5610
5611	rcutree.enable_rcu_lazy= [KNL]
5612			To save power, batch RCU callbacks and flush after
5613			delay, memory pressure or callback list growing too
5614			big.
5615
5616	rcutree.rcu_normal_wake_from_gp= [KNL]
5617			Reduces a latency of synchronize_rcu() call. This approach
5618			maintains its own track of synchronize_rcu() callers, so it
5619			does not interact with regular callbacks because it does not
5620			use a call_rcu[_hurry]() path. Please note, this is for a
5621			normal grace period.
5622
5623			How to enable it:
5624
5625			echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp
5626			or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1"
5627
5628			Default is 1 if num_possible_cpus() <= 16 and it is not explicitly
5629			disabled by the boot parameter passing 0.
5630
5631	rcuscale.gp_async= [KNL]
5632			Measure performance of asynchronous
5633			grace-period primitives such as call_rcu().
5634
5635	rcuscale.gp_async_max= [KNL]
5636			Specify the maximum number of outstanding
5637			callbacks per writer thread.  When a writer
5638			thread exceeds this limit, it invokes the
5639			corresponding flavor of rcu_barrier() to allow
5640			previously posted callbacks to drain.
5641
5642	rcuscale.gp_exp= [KNL]
5643			Measure performance of expedited synchronous
5644			grace-period primitives.
5645
5646	rcuscale.holdoff= [KNL]
5647			Set test-start holdoff period.  The purpose of
5648			this parameter is to delay the start of the
5649			test until boot completes in order to avoid
5650			interference.
5651
5652	rcuscale.kfree_by_call_rcu= [KNL]
5653			In kernels built with CONFIG_RCU_LAZY=y, test
5654			call_rcu() instead of kfree_rcu().
5655
5656	rcuscale.kfree_mult= [KNL]
5657			Instead of allocating an object of size kfree_obj,
5658			allocate one of kfree_mult * sizeof(kfree_obj).
5659			Defaults to 1.
5660
5661	rcuscale.kfree_rcu_test= [KNL]
5662			Set to measure performance of kfree_rcu() flooding.
5663
5664	rcuscale.kfree_rcu_test_double= [KNL]
5665			Test the double-argument variant of kfree_rcu().
5666			If this parameter has the same value as
5667			rcuscale.kfree_rcu_test_single, both the single-
5668			and double-argument variants are tested.
5669
5670	rcuscale.kfree_rcu_test_single= [KNL]
5671			Test the single-argument variant of kfree_rcu().
5672			If this parameter has the same value as
5673			rcuscale.kfree_rcu_test_double, both the single-
5674			and double-argument variants are tested.
5675
5676	rcuscale.kfree_nthreads= [KNL]
5677			The number of threads running loops of kfree_rcu().
5678
5679	rcuscale.kfree_alloc_num= [KNL]
5680			Number of allocations and frees done in an iteration.
5681
5682	rcuscale.kfree_loops= [KNL]
5683			Number of loops doing rcuscale.kfree_alloc_num number
5684			of allocations and frees.
5685
5686	rcuscale.minruntime= [KNL]
5687			Set the minimum test run time in seconds.  This
5688			does not affect the data-collection interval,
5689			but instead allows better measurement of things
5690			like CPU consumption.
5691
5692	rcuscale.nreaders= [KNL]
5693			Set number of RCU readers.  The value -1 selects
5694			N, where N is the number of CPUs.  A value
5695			"n" less than -1 selects N-n+1, where N is again
5696			the number of CPUs.  For example, -2 selects N
5697			(the number of CPUs), -3 selects N+1, and so on.
5698			A value of "n" less than or equal to -N selects
5699			a single reader.
5700
5701	rcuscale.nwriters= [KNL]
5702			Set number of RCU writers.  The values operate
5703			the same as for rcuscale.nreaders.
5704			N, where N is the number of CPUs
5705
5706	rcuscale.scale_type= [KNL]
5707			Specify the RCU implementation to test.
5708
5709	rcuscale.shutdown= [KNL]
5710			Shut the system down after performance tests
5711			complete.  This is useful for hands-off automated
5712			testing.
5713
5714	rcuscale.verbose= [KNL]
5715			Enable additional printk() statements.
5716
5717	rcuscale.writer_holdoff= [KNL]
5718			Write-side holdoff between grace periods,
5719			in microseconds.  The default of zero says
5720			no holdoff.
5721
5722	rcuscale.writer_holdoff_jiffies= [KNL]
5723			Additional write-side holdoff between grace
5724			periods, but in jiffies.  The default of zero
5725			says no holdoff.
5726
5727	rcutorture.fqs_duration= [KNL]
5728			Set duration of force_quiescent_state bursts
5729			in microseconds.
5730
5731	rcutorture.fqs_holdoff= [KNL]
5732			Set holdoff time within force_quiescent_state bursts
5733			in microseconds.
5734
5735	rcutorture.fqs_stutter= [KNL]
5736			Set wait time between force_quiescent_state bursts
5737			in seconds.
5738
5739	rcutorture.fwd_progress= [KNL]
5740			Specifies the number of kthreads to be used
5741			for  RCU grace-period forward-progress testing
5742			for the types of RCU supporting this notion.
5743			Defaults to 1 kthread, values less than zero or
5744			greater than the number of CPUs cause the number
5745			of CPUs to be used.
5746
5747	rcutorture.fwd_progress_div= [KNL]
5748			Specify the fraction of a CPU-stall-warning
5749			period to do tight-loop forward-progress testing.
5750
5751	rcutorture.fwd_progress_holdoff= [KNL]
5752			Number of seconds to wait between successive
5753			forward-progress tests.
5754
5755	rcutorture.fwd_progress_need_resched= [KNL]
5756			Enclose cond_resched() calls within checks for
5757			need_resched() during tight-loop forward-progress
5758			testing.
5759
5760	rcutorture.gp_cond= [KNL]
5761			Use conditional/asynchronous update-side
5762			normal-grace-period primitives, if available.
5763
5764	rcutorture.gp_cond_exp= [KNL]
5765			Use conditional/asynchronous update-side
5766			expedited-grace-period primitives, if available.
5767
5768	rcutorture.gp_cond_full= [KNL]
5769			Use conditional/asynchronous update-side
5770			normal-grace-period primitives that also take
5771			concurrent expedited grace periods into account,
5772			if available.
5773
5774	rcutorture.gp_cond_exp_full= [KNL]
5775			Use conditional/asynchronous update-side
5776			expedited-grace-period primitives that also take
5777			concurrent normal grace periods into account,
5778			if available.
5779
5780	rcutorture.gp_cond_wi= [KNL]
5781			Nominal wait interval for normal conditional
5782			grace periods (specified by rcutorture's
5783			gp_cond and gp_cond_full module parameters),
5784			in microseconds.  The actual wait interval will
5785			be randomly selected to nanosecond granularity up
5786			to this wait interval.	Defaults to 16 jiffies,
5787			for example, 16,000 microseconds on a system
5788			with HZ=1000.
5789
5790	rcutorture.gp_cond_wi_exp= [KNL]
5791			Nominal wait interval for expedited conditional
5792			grace periods (specified by rcutorture's
5793			gp_cond_exp and gp_cond_exp_full module
5794			parameters), in microseconds.  The actual wait
5795			interval will be randomly selected to nanosecond
5796			granularity up to this wait interval.  Defaults to
5797			128 microseconds.
5798
5799	rcutorture.gp_exp= [KNL]
5800			Use expedited update-side primitives, if available.
5801
5802	rcutorture.gp_normal= [KNL]
5803			Use normal (non-expedited) asynchronous
5804			update-side primitives, if available.
5805
5806	rcutorture.gp_poll= [KNL]
5807			Use polled update-side normal-grace-period
5808			primitives, if available.
5809
5810	rcutorture.gp_poll_exp= [KNL]
5811			Use polled update-side expedited-grace-period
5812			primitives, if available.
5813
5814	rcutorture.gp_poll_full= [KNL]
5815			Use polled update-side normal-grace-period
5816			primitives that also take concurrent expedited
5817			grace periods into account, if available.
5818
5819	rcutorture.gp_poll_exp_full= [KNL]
5820			Use polled update-side expedited-grace-period
5821			primitives that also take concurrent normal
5822			grace periods into account, if available.
5823
5824	rcutorture.gp_poll_wi= [KNL]
5825			Nominal wait interval for normal conditional
5826			grace periods (specified by rcutorture's
5827			gp_poll and gp_poll_full module parameters),
5828			in microseconds.  The actual wait interval will
5829			be randomly selected to nanosecond granularity up
5830			to this wait interval.	Defaults to 16 jiffies,
5831			for example, 16,000 microseconds on a system
5832			with HZ=1000.
5833
5834	rcutorture.gp_poll_wi_exp= [KNL]
5835			Nominal wait interval for expedited conditional
5836			grace periods (specified by rcutorture's
5837			gp_poll_exp and gp_poll_exp_full module
5838			parameters), in microseconds.  The actual wait
5839			interval will be randomly selected to nanosecond
5840			granularity up to this wait interval.  Defaults to
5841			128 microseconds.
5842
5843	rcutorture.gp_sync= [KNL]
5844			Use normal (non-expedited) synchronous
5845			update-side primitives, if available.  If all
5846			of rcutorture.gp_cond=, rcutorture.gp_exp=,
5847			rcutorture.gp_normal=, and rcutorture.gp_sync=
5848			are zero, rcutorture acts as if is interpreted
5849			they are all non-zero.
5850
5851	rcutorture.gpwrap_lag= [KNL]
5852			Enable grace-period wrap lag testing. Setting
5853			to false prevents the gpwrap lag test from
5854			running. Default is true.
5855
5856	rcutorture.gpwrap_lag_gps= [KNL]
5857			Set the value for grace-period wrap lag during
5858			active lag testing periods. This controls how many
5859			grace periods differences we tolerate between
5860			rdp and rnp's gp_seq before setting overflow flag.
5861			The default is always set to 8.
5862
5863	rcutorture.gpwrap_lag_cycle_mins= [KNL]
5864			Set the total cycle duration for gpwrap lag
5865			testing in minutes. This is the total time for
5866			one complete cycle of active and inactive
5867			testing periods. Default is 30 minutes.
5868
5869	rcutorture.gpwrap_lag_active_mins= [KNL]
5870			Set the duration for which gpwrap lag is active
5871			within each cycle, in minutes. During this time,
5872			the grace-period wrap lag will be set to the
5873			value specified by gpwrap_lag_gps. Default is
5874			5 minutes.
5875
5876	rcutorture.irqreader= [KNL]
5877			Run RCU readers from irq handlers, or, more
5878			accurately, from a timer handler.  Not all RCU
5879			flavors take kindly to this sort of thing.
5880
5881	rcutorture.leakpointer= [KNL]
5882			Leak an RCU-protected pointer out of the reader.
5883			This can of course result in splats, and is
5884			intended to test the ability of things like
5885			CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5886			such leaks.
5887
5888	rcutorture.n_barrier_cbs= [KNL]
5889			Set callbacks/threads for rcu_barrier() testing.
5890
5891	rcutorture.nfakewriters= [KNL]
5892			Set number of concurrent RCU writers.  These just
5893			stress RCU, they don't participate in the actual
5894			test, hence the "fake".
5895
5896	rcutorture.nocbs_nthreads= [KNL]
5897			Set number of RCU callback-offload togglers.
5898			Zero (the default) disables toggling.
5899
5900	rcutorture.nocbs_toggle= [KNL]
5901			Set the delay in milliseconds between successive
5902			callback-offload toggling attempts.
5903
5904	rcutorture.nreaders= [KNL]
5905			Set number of RCU readers.  The value -1 selects
5906			N-1, where N is the number of CPUs.  A value
5907			"n" less than -1 selects N-n-2, where N is again
5908			the number of CPUs.  For example, -2 selects N
5909			(the number of CPUs), -3 selects N+1, and so on.
5910
5911	rcutorture.object_debug= [KNL]
5912			Enable debug-object double-call_rcu() testing.
5913
5914	rcutorture.onoff_holdoff= [KNL]
5915			Set time (s) after boot for CPU-hotplug testing.
5916
5917	rcutorture.onoff_interval= [KNL]
5918			Set time (jiffies) between CPU-hotplug operations,
5919			or zero to disable CPU-hotplug testing.
5920
5921	rcutorture.preempt_duration= [KNL]
5922			Set duration (in milliseconds) of preemptions
5923			by a high-priority FIFO real-time task.  Set to
5924			zero (the default) to disable.	The CPUs to
5925			preempt are selected randomly from the set that
5926			are online at a given point in time.  Races with
5927			CPUs going offline are ignored, with that attempt
5928			at preemption skipped.
5929
5930	rcutorture.preempt_interval= [KNL]
5931			Set interval (in milliseconds, defaulting to one
5932			second) between preemptions by a high-priority
5933			FIFO real-time task.  This delay is mediated
5934			by an hrtimer and is further fuzzed to avoid
5935			inadvertent synchronizations.
5936
5937	rcutorture.read_exit_burst= [KNL]
5938			The number of times in a given read-then-exit
5939			episode that a set of read-then-exit kthreads
5940			is spawned.
5941
5942	rcutorture.read_exit_delay= [KNL]
5943			The delay, in seconds, between successive
5944			read-then-exit testing episodes.
5945
5946	rcutorture.reader_flavor= [KNL]
5947			A bit mask indicating which readers to use.
5948			If there is more than one bit set, the readers
5949			are entered from low-order bit up, and are
5950			exited in the opposite order.  For SRCU, the
5951			0x1 bit is normal readers, 0x2 NMI-safe readers,
5952			and 0x4 light-weight readers.
5953
5954	rcutorture.shuffle_interval= [KNL]
5955			Set task-shuffle interval (s).  Shuffling tasks
5956			allows some CPUs to go into dyntick-idle mode
5957			during the rcutorture test.
5958
5959	rcutorture.shutdown_secs= [KNL]
5960			Set time (s) after boot system shutdown.  This
5961			is useful for hands-off automated testing.
5962
5963	rcutorture.stall_cpu= [KNL]
5964			Duration of CPU stall (s) to test RCU CPU stall
5965			warnings, zero to disable.
5966
5967	rcutorture.stall_cpu_block= [KNL]
5968			Sleep while stalling if set.  This will result
5969			in warnings from preemptible RCU in addition to
5970			any other stall-related activity.  Note that
5971			in kernels built with CONFIG_PREEMPTION=n and
5972			CONFIG_PREEMPT_COUNT=y, this parameter will
5973			cause the CPU to pass through a quiescent state.
5974			Given CONFIG_PREEMPTION=n, this will suppress
5975			RCU CPU stall warnings, but will instead result
5976			in scheduling-while-atomic splats.
5977
5978			Use of this module parameter results in splats.
5979
5980
5981	rcutorture.stall_cpu_holdoff= [KNL]
5982			Time to wait (s) after boot before inducing stall.
5983
5984	rcutorture.stall_cpu_irqsoff= [KNL]
5985			Disable interrupts while stalling if set, but only
5986			on the first stall in the set.
5987
5988	rcutorture.stall_cpu_repeat= [KNL]
5989			Number of times to repeat the stall sequence,
5990			so that rcutorture.stall_cpu_repeat=3 will result
5991			in four stall sequences.
5992
5993	rcutorture.stall_gp_kthread= [KNL]
5994			Duration (s) of forced sleep within RCU
5995			grace-period kthread to test RCU CPU stall
5996			warnings, zero to disable.  If both stall_cpu
5997			and stall_gp_kthread are specified, the
5998			kthread is starved first, then the CPU.
5999
6000	rcutorture.stat_interval= [KNL]
6001			Time (s) between statistics printk()s.
6002
6003	rcutorture.stutter= [KNL]
6004			Time (s) to stutter testing, for example, specifying
6005			five seconds causes the test to run for five seconds,
6006			wait for five seconds, and so on.  This tests RCU's
6007			ability to transition abruptly to and from idle.
6008
6009	rcutorture.test_boost= [KNL]
6010			Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
6011			"Maybe" means test if the RCU implementation
6012			under test support RCU priority boosting.
6013
6014	rcutorture.test_boost_duration= [KNL]
6015			Duration (s) of each individual boost test.
6016
6017	rcutorture.test_boost_holdoff= [KNL]
6018			Holdoff time (s) from start of test to the start
6019			of RCU priority-boost testing.	Defaults to zero,
6020			that is, no holdoff.
6021
6022	rcutorture.test_boost_interval= [KNL]
6023			Interval (s) between each boost test.
6024
6025	rcutorture.test_no_idle_hz= [KNL]
6026			Test RCU's dyntick-idle handling.  See also the
6027			rcutorture.shuffle_interval parameter.
6028
6029	rcutorture.torture_type= [KNL]
6030			Specify the RCU implementation to test.
6031
6032	rcutorture.verbose= [KNL]
6033			Enable additional printk() statements.
6034
6035	rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
6036			Dump ftrace buffer after reporting RCU CPU
6037			stall warning.
6038
6039	rcupdate.rcu_cpu_stall_notifiers= [KNL]
6040			Provide RCU CPU stall notifiers, but see the
6041			warnings in the RCU_CPU_STALL_NOTIFIER Kconfig
6042			option's help text.  TL;DR:  You almost certainly
6043			do not want rcupdate.rcu_cpu_stall_notifiers.
6044
6045	rcupdate.rcu_cpu_stall_suppress= [KNL]
6046			Suppress RCU CPU stall warning messages.
6047
6048	rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
6049			Suppress RCU CPU stall warning messages and
6050			rcutorture writer stall warnings that occur
6051			during early boot, that is, during the time
6052			before the init task is spawned.
6053
6054	rcupdate.rcu_cpu_stall_timeout= [KNL]
6055			Set timeout for RCU CPU stall warning messages.
6056			The value is in seconds and the maximum allowed
6057			value is 300 seconds.
6058
6059	rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
6060			Set timeout for expedited RCU CPU stall warning
6061			messages.  The value is in milliseconds
6062			and the maximum allowed value is 21000
6063			milliseconds. Please note that this value is
6064			adjusted to an arch timer tick resolution.
6065			Setting this to zero causes the value from
6066			rcupdate.rcu_cpu_stall_timeout to be used (after
6067			conversion from seconds to milliseconds).
6068
6069	rcupdate.rcu_cpu_stall_cputime= [KNL]
6070			Provide statistics on the cputime and count of
6071			interrupts and tasks during the sampling period. For
6072			multiple continuous RCU stalls, all sampling periods
6073			begin at half of the first RCU stall timeout.
6074
6075	rcupdate.rcu_exp_stall_task_details= [KNL]
6076			Print stack dumps of any tasks blocking the
6077			current expedited RCU grace period during an
6078			expedited RCU CPU stall warning.
6079
6080	rcupdate.rcu_expedited= [KNL]
6081			Use expedited grace-period primitives, for
6082			example, synchronize_rcu_expedited() instead
6083			of synchronize_rcu().  This reduces latency,
6084			but can increase CPU utilization, degrade
6085			real-time latency, and degrade energy efficiency.
6086			No effect on CONFIG_TINY_RCU kernels.
6087
6088	rcupdate.rcu_normal= [KNL]
6089			Use only normal grace-period primitives,
6090			for example, synchronize_rcu() instead of
6091			synchronize_rcu_expedited().  This improves
6092			real-time latency, CPU utilization, and
6093			energy efficiency, but can expose users to
6094			increased grace-period latency.  This parameter
6095			overrides rcupdate.rcu_expedited.  No effect on
6096			CONFIG_TINY_RCU kernels.
6097
6098	rcupdate.rcu_normal_after_boot= [KNL]
6099			Once boot has completed (that is, after
6100			rcu_end_inkernel_boot() has been invoked), use
6101			only normal grace-period primitives.  No effect
6102			on CONFIG_TINY_RCU kernels.
6103
6104			But note that CONFIG_PREEMPT_RT=y kernels enables
6105			this kernel boot parameter, forcibly setting
6106			it to the value one, that is, converting any
6107			post-boot attempt at an expedited RCU grace
6108			period to instead use normal non-expedited
6109			grace-period processing.
6110
6111	rcupdate.rcu_task_collapse_lim= [KNL]
6112			Set the maximum number of callbacks present
6113			at the beginning of a grace period that allows
6114			the RCU Tasks flavors to collapse back to using
6115			a single callback queue.  This switching only
6116			occurs when rcupdate.rcu_task_enqueue_lim is
6117			set to the default value of -1.
6118
6119	rcupdate.rcu_task_contend_lim= [KNL]
6120			Set the minimum number of callback-queuing-time
6121			lock-contention events per jiffy required to
6122			cause the RCU Tasks flavors to switch to per-CPU
6123			callback queuing.  This switching only occurs
6124			when rcupdate.rcu_task_enqueue_lim is set to
6125			the default value of -1.
6126
6127	rcupdate.rcu_task_enqueue_lim= [KNL]
6128			Set the number of callback queues to use for the
6129			RCU Tasks family of RCU flavors.  The default
6130			of -1 allows this to be automatically (and
6131			dynamically) adjusted.	This parameter is intended
6132			for use in testing.
6133
6134	rcupdate.rcu_task_ipi_delay= [KNL]
6135			Set time in jiffies during which RCU tasks will
6136			avoid sending IPIs, starting with the beginning
6137			of a given grace period.  Setting a large
6138			number avoids disturbing real-time workloads,
6139			but lengthens grace periods.
6140
6141	rcupdate.rcu_task_lazy_lim= [KNL]
6142			Number of callbacks on a given CPU that will
6143			cancel laziness on that CPU.  Use -1 to disable
6144			cancellation of laziness, but be advised that
6145			doing so increases the danger of OOM due to
6146			callback flooding.
6147
6148	rcupdate.rcu_task_stall_info= [KNL]
6149			Set initial timeout in jiffies for RCU task stall
6150			informational messages, which give some indication
6151			of the problem for those not patient enough to
6152			wait for ten minutes.  Informational messages are
6153			only printed prior to the stall-warning message
6154			for a given grace period. Disable with a value
6155			less than or equal to zero.  Defaults to ten
6156			seconds.  A change in value does not take effect
6157			until the beginning of the next grace period.
6158
6159	rcupdate.rcu_task_stall_info_mult= [KNL]
6160			Multiplier for time interval between successive
6161			RCU task stall informational messages for a given
6162			RCU tasks grace period.  This value is clamped
6163			to one through ten, inclusive.	It defaults to
6164			the value three, so that the first informational
6165			message is printed 10 seconds into the grace
6166			period, the second at 40 seconds, the third at
6167			160 seconds, and then the stall warning at 600
6168			seconds would prevent a fourth at 640 seconds.
6169
6170	rcupdate.rcu_task_stall_timeout= [KNL]
6171			Set timeout in jiffies for RCU task stall
6172			warning messages.  Disable with a value less
6173			than or equal to zero.	Defaults to ten minutes.
6174			A change in value does not take effect until
6175			the beginning of the next grace period.
6176
6177	rcupdate.rcu_tasks_lazy_ms= [KNL]
6178			Set timeout in milliseconds RCU Tasks asynchronous
6179			callback batching for call_rcu_tasks().
6180			A negative value will take the default.  A value
6181			of zero will disable batching.	Batching is
6182			always disabled for synchronize_rcu_tasks().
6183
6184	rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
6185			Set timeout in milliseconds RCU Tasks
6186			Trace asynchronous callback batching for
6187			call_rcu_tasks_trace().  A negative value
6188			will take the default.	A value of zero will
6189			disable batching.  Batching is always disabled
6190			for synchronize_rcu_tasks_trace().
6191
6192	rcupdate.rcu_self_test= [KNL]
6193			Run the RCU early boot self tests
6194
6195	rdinit=		[KNL]
6196			Format: <full_path>
6197			Run specified binary instead of /init from the ramdisk,
6198			used for early userspace startup. See initrd.
6199
6200	rdrand=		[X86,EARLY]
6201			force - Override the decision by the kernel to hide the
6202				advertisement of RDRAND support (this affects
6203				certain AMD processors because of buggy BIOS
6204				support, specifically around the suspend/resume
6205				path).
6206
6207	rdt=		[HW,X86,RDT]
6208			Turn on/off individual RDT features. List is:
6209			cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
6210			mba, smba, bmec, abmc.
6211			E.g. to turn on cmt and turn off mba use:
6212				rdt=cmt,!mba
6213
6214	reboot=		[KNL]
6215			Format (x86 or x86_64):
6216				[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
6217				[[,]s[mp]#### \
6218				[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
6219				[[,]f[orce]
6220			Where reboot_mode is one of warm (soft) or cold (hard) or gpio
6221					(prefix with 'panic_' to set mode for panic
6222					reboot only),
6223			      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
6224			      reboot_force is either force or not specified,
6225			      reboot_cpu is s[mp]#### with #### being the processor
6226					to be used for rebooting.
6227
6228		acpi
6229			Use the ACPI RESET_REG in the FADT. If ACPI is not
6230			configured or the ACPI reset does not work, the reboot
6231			path attempts the reset using the keyboard controller.
6232
6233		bios
6234			Use the CPU reboot vector for warm reset
6235
6236		cold
6237			Set the cold reboot flag
6238
6239		default
6240			There are some built-in platform specific "quirks"
6241			- you may see: "reboot: <name> series board detected.
6242			Selecting <type> for reboots." In the case where you
6243			think the quirk is in error (e.g. you have newer BIOS,
6244			or newer board) using this option will ignore the
6245			built-in quirk table, and use the generic default
6246			reboot actions.
6247
6248		efi
6249			Use efi reset_system runtime service. If EFI is not
6250			configured or the EFI reset does not work, the reboot
6251			path attempts the reset using the keyboard controller.
6252
6253		force
6254			Don't stop other CPUs on reboot. This can make reboot
6255			more reliable in some cases.
6256
6257		kbd
6258			Use the keyboard controller. cold reset (default)
6259
6260		pci
6261			Use a write to the PCI config space register 0xcf9 to
6262			trigger reboot.
6263
6264		triple
6265			Force a triple fault (init)
6266
6267		warm
6268			Don't set the cold reboot flag
6269
6270			Using warm reset will be much faster especially on big
6271			memory systems because the BIOS will not go through
6272			the memory check.  Disadvantage is that not all
6273			hardware will be completely reinitialized on reboot so
6274			there may be boot problems on some systems.
6275
6276
6277	refscale.holdoff= [KNL]
6278			Set test-start holdoff period.  The purpose of
6279			this parameter is to delay the start of the
6280			test until boot completes in order to avoid
6281			interference.
6282
6283	refscale.lookup_instances= [KNL]
6284			Number of data elements to use for the forms of
6285			SLAB_TYPESAFE_BY_RCU testing.  A negative number
6286			is negated and multiplied by nr_cpu_ids, while
6287			zero specifies nr_cpu_ids.
6288
6289	refscale.loops= [KNL]
6290			Set the number of loops over the synchronization
6291			primitive under test.  Increasing this number
6292			reduces noise due to loop start/end overhead,
6293			but the default has already reduced the per-pass
6294			noise to a handful of picoseconds on ca. 2020
6295			x86 laptops.
6296
6297	refscale.nreaders= [KNL]
6298			Set number of readers.  The default value of -1
6299			selects N, where N is roughly 75% of the number
6300			of CPUs.  A value of zero is an interesting choice.
6301
6302	refscale.nruns= [KNL]
6303			Set number of runs, each of which is dumped onto
6304			the console log.
6305
6306	refscale.readdelay= [KNL]
6307			Set the read-side critical-section duration,
6308			measured in microseconds.
6309
6310	refscale.scale_type= [KNL]
6311			Specify the read-protection implementation to test.
6312
6313	refscale.shutdown= [KNL]
6314			Shut down the system at the end of the performance
6315			test.  This defaults to 1 (shut it down) when
6316			refscale is built into the kernel and to 0 (leave
6317			it running) when refscale is built as a module.
6318
6319	refscale.verbose= [KNL]
6320			Enable additional printk() statements.
6321
6322	refscale.verbose_batched= [KNL]
6323			Batch the additional printk() statements.  If zero
6324			(the default) or negative, print everything.  Otherwise,
6325			print every Nth verbose statement, where N is the value
6326			specified.
6327
6328	regulator_ignore_unused
6329			[REGULATOR]
6330			Prevents regulator framework from disabling regulators
6331			that are unused, due no driver claiming them. This may
6332			be useful for debug and development, but should not be
6333			needed on a platform with proper driver support.
6334
6335	relax_domain_level=
6336			[KNL, SMP] Set scheduler's default relax_domain_level.
6337			See Documentation/admin-guide/cgroup-v1/cpusets.rst.
6338
6339	reserve=	[KNL,BUGS] Force kernel to ignore I/O ports or memory
6340			Format: <base1>,<size1>[,<base2>,<size2>,...]
6341			Reserve I/O ports or memory so the kernel won't use
6342			them.  If <base> is less than 0x10000, the region
6343			is assumed to be I/O ports; otherwise it is memory.
6344
6345	reserve_mem=	[RAM]
6346			Format: nn[KMG]:<align>:<label>
6347			Reserve physical memory and label it with a name that
6348			other subsystems can use to access it. This is typically
6349			used for systems that do not wipe the RAM, and this command
6350			line will try to reserve the same physical memory on
6351			soft reboots. Note, it is not guaranteed to be the same
6352			location. For example, if anything about the system changes
6353			or if booting a different kernel. It can also fail if KASLR
6354			places the kernel at the location of where the RAM reservation
6355			was from a previous boot, the new reservation will be at a
6356			different location.
6357			Any subsystem using this feature must add a way to verify
6358			that the contents of the physical memory is from a previous
6359			boot, as there may be cases where the memory will not be
6360			located at the same location.
6361
6362			The format is size:align:label for example, to request
6363			12 megabytes of 4096 alignment for ramoops:
6364
6365			reserve_mem=12M:4096:oops ramoops.mem_name=oops
6366
6367	reservetop=	[X86-32,EARLY]
6368			Format: nn[KMG]
6369			Reserves a hole at the top of the kernel virtual
6370			address space.
6371
6372	reset_devices	[KNL] Force drivers to reset the underlying device
6373			during initialization.
6374
6375	resume=		[SWSUSP]
6376			Specify the partition device for software suspend
6377			Format:
6378			{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
6379
6380	resume_offset=	[SWSUSP]
6381			Specify the offset from the beginning of the partition
6382			given by "resume=" at which the swap header is located,
6383			in <PAGE_SIZE> units (needed only for swap files).
6384			See  Documentation/power/swsusp-and-swap-files.rst
6385
6386	resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
6387			read the resume files
6388
6389	resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
6390			Useful for devices that are detected asynchronously
6391			(e.g. USB and MMC devices).
6392
6393	retain_initrd	[RAM] Keep initrd memory after extraction. After boot, it will
6394			be accessible via /sys/firmware/initrd.
6395
6396	retbleed=	[X86] Control mitigation of RETBleed (Arbitrary
6397			Speculative Code Execution with Return Instructions)
6398			vulnerability.
6399
6400			AMD-based UNRET and IBPB mitigations alone do not stop
6401			sibling threads from influencing the predictions of other
6402			sibling threads. For that reason, STIBP is used on pro-
6403			cessors that support it, and mitigate SMT on processors
6404			that don't.
6405
6406			off          - no mitigation
6407			auto         - automatically select a migitation
6408			auto,nosmt   - automatically select a mitigation,
6409				       disabling SMT if necessary for
6410				       the full mitigation (only on Zen1
6411				       and older without STIBP).
6412			ibpb         - On AMD, mitigate short speculation
6413				       windows on basic block boundaries too.
6414				       Safe, highest perf impact. It also
6415				       enables STIBP if present. Not suitable
6416				       on Intel.
6417			ibpb,nosmt   - Like "ibpb" above but will disable SMT
6418				       when STIBP is not available. This is
6419				       the alternative for systems which do not
6420				       have STIBP.
6421			unret        - Force enable untrained return thunks,
6422				       only effective on AMD f15h-f17h based
6423				       systems.
6424			unret,nosmt  - Like unret, but will disable SMT when STIBP
6425				       is not available. This is the alternative for
6426				       systems which do not have STIBP.
6427
6428			Selecting 'auto' will choose a mitigation method at run
6429			time according to the CPU.
6430
6431			Not specifying this option is equivalent to retbleed=auto.
6432
6433	rfkill.default_state=
6434		0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
6435			etc. communication is blocked by default.
6436		1	Unblocked.
6437
6438	rfkill.master_switch_mode=
6439		0	The "airplane mode" button does nothing.
6440		1	The "airplane mode" button toggles between everything
6441			blocked and the previous configuration.
6442		2	The "airplane mode" button toggles between everything
6443			blocked and everything unblocked.
6444
6445	ring3mwait=disable
6446			[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
6447			CPUs.
6448
6449	riscv_isa_fallback [RISCV,EARLY]
6450			When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
6451			falling back to detecting extension support by parsing
6452			"riscv,isa" property on devicetree systems when the
6453			replacement properties are not found. See the Kconfig
6454			entry for RISCV_ISA_FALLBACK.
6455
6456	ro		[KNL] Mount root device read-only on boot
6457
6458	rodata=		[KNL,EARLY]
6459		on	Mark read-only kernel memory as read-only (default).
6460		off	Leave read-only kernel memory writable for debugging.
6461		noalias	Mark read-only kernel memory as read-only but retain
6462			writable aliases in the direct map for regions outside
6463			of the kernel image. [arm64]
6464
6465	rockchip.usb_uart
6466			[EARLY]
6467			Enable the uart passthrough on the designated usb port
6468			on Rockchip SoCs. When active, the signals of the
6469			debug-uart get routed to the D+ and D- pins of the usb
6470			port and the regular usb controller gets disabled.
6471
6472	root=		[KNL] Root filesystem
6473			Usually this is a block device specifier of some kind,
6474			see the early_lookup_bdev comment in
6475			block/early-lookup.c for details.
6476			Alternatively this can be "ram" for the legacy initial
6477			ramdisk, "nfs" and "cifs" for root on a network file
6478			system, or "mtd" and "ubi" for mounting from raw flash.
6479
6480	rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
6481			mount the root filesystem
6482
6483	rootflags=	[KNL] Set root filesystem mount option string
6484
6485	initramfs_options= [KNL]
6486                        Specify mount options for for the initramfs mount.
6487
6488	rootfstype=	[KNL] Set root filesystem type
6489
6490	rootwait	[KNL] Wait (indefinitely) for root device to show up.
6491			Useful for devices that are detected asynchronously
6492			(e.g. USB and MMC devices).
6493
6494	rootwait=	[KNL] Maximum time (in seconds) to wait for root device
6495			to show up before attempting to mount the root
6496			filesystem.
6497
6498	rproc_mem=nn[KMG][@address]
6499			[KNL,ARM,CMA] Remoteproc physical memory block.
6500			Memory area to be used by remote processor image,
6501			managed by CMA.
6502
6503	rt_group_sched=	[KNL] Enable or disable SCHED_RR/FIFO group scheduling
6504			when CONFIG_RT_GROUP_SCHED=y. Defaults to
6505			!CONFIG_RT_GROUP_SCHED_DEFAULT_DISABLED.
6506			Format: <bool>
6507
6508	rw		[KNL] Mount root device read-write on boot
6509
6510	S		[KNL] Run init in single mode
6511
6512	s390_iommu=	[HW,S390]
6513			Set s390 IOTLB flushing mode
6514		strict
6515			With strict flushing every unmap operation will result
6516			in an IOTLB flush. Default is lazy flushing before
6517			reuse, which is faster. Deprecated, equivalent to
6518			iommu.strict=1.
6519
6520	s390_iommu_aperture=	[KNL,S390]
6521			Specifies the size of the per device DMA address space
6522			accessible through the DMA and IOMMU APIs as a decimal
6523			factor of the size of main memory.
6524			The default is 1 meaning that one can concurrently use
6525			as many DMA addresses as physical memory is installed,
6526			if supported by hardware, and thus map all of memory
6527			once. With a value of 2 one can map all of memory twice
6528			and so on. As a special case a factor of 0 imposes no
6529			restrictions other than those given by hardware at the
6530			cost of significant additional memory use for tables.
6531
6532	sa1100ir	[NET]
6533			See drivers/net/irda/sa1100_ir.c.
6534
6535	sched_proxy_exec= [KNL]
6536			Enables or disables "proxy execution" style
6537			solution to mutex-based priority inversion.
6538			Format: <bool>
6539
6540	sched_verbose	[KNL,EARLY] Enables verbose scheduler debug messages.
6541
6542	schedstats=	[KNL,X86] Enable or disable scheduled statistics.
6543			Allowed values are enable and disable. This feature
6544			incurs a small amount of overhead in the scheduler
6545			but is useful for debugging and performance tuning.
6546
6547	sched_thermal_decay_shift=
6548			[Deprecated]
6549			[KNL, SMP] Set a decay shift for scheduler thermal
6550			pressure signal. Thermal pressure signal follows the
6551			default decay period of other scheduler pelt
6552			signals(usually 32 ms but configurable). Setting
6553			sched_thermal_decay_shift will left shift the decay
6554			period for the thermal pressure signal by the shift
6555			value.
6556			i.e. with the default pelt decay period of 32 ms
6557			sched_thermal_decay_shift   thermal pressure decay pr
6558				1			64 ms
6559				2			128 ms
6560			and so on.
6561			Format: integer between 0 and 10
6562			Default is 0.
6563
6564	scftorture.holdoff= [KNL]
6565			Number of seconds to hold off before starting
6566			test.  Defaults to zero for module insertion and
6567			to 10 seconds for built-in smp_call_function()
6568			tests.
6569
6570	scftorture.longwait= [KNL]
6571			Request ridiculously long waits randomly selected
6572			up to the chosen limit in seconds.  Zero (the
6573			default) disables this feature.  Please note
6574			that requesting even small non-zero numbers of
6575			seconds can result in RCU CPU stall warnings,
6576			softlockup complaints, and so on.
6577
6578	scftorture.nthreads= [KNL]
6579			Number of kthreads to spawn to invoke the
6580			smp_call_function() family of functions.
6581			The default of -1 specifies a number of kthreads
6582			equal to the number of CPUs.
6583
6584	scftorture.onoff_holdoff= [KNL]
6585			Number seconds to wait after the start of the
6586			test before initiating CPU-hotplug operations.
6587
6588	scftorture.onoff_interval= [KNL]
6589			Number seconds to wait between successive
6590			CPU-hotplug operations.  Specifying zero (which
6591			is the default) disables CPU-hotplug operations.
6592
6593	scftorture.shutdown_secs= [KNL]
6594			The number of seconds following the start of the
6595			test after which to shut down the system.  The
6596			default of zero avoids shutting down the system.
6597			Non-zero values are useful for automated tests.
6598
6599	scftorture.stat_interval= [KNL]
6600			The number of seconds between outputting the
6601			current test statistics to the console.  A value
6602			of zero disables statistics output.
6603
6604	scftorture.stutter_cpus= [KNL]
6605			The number of jiffies to wait between each change
6606			to the set of CPUs under test.
6607
6608	scftorture.use_cpus_read_lock= [KNL]
6609			Use use_cpus_read_lock() instead of the default
6610			preempt_disable() to disable CPU hotplug
6611			while invoking one of the smp_call_function*()
6612			functions.
6613
6614	scftorture.verbose= [KNL]
6615			Enable additional printk() statements.
6616
6617	scftorture.weight_single= [KNL]
6618			The probability weighting to use for the
6619			smp_call_function_single() function with a zero
6620			"wait" parameter.  A value of -1 selects the
6621			default if all other weights are -1.  However,
6622			if at least one weight has some other value, a
6623			value of -1 will instead select a weight of zero.
6624
6625	scftorture.weight_single_wait= [KNL]
6626			The probability weighting to use for the
6627			smp_call_function_single() function with a
6628			non-zero "wait" parameter.  See weight_single.
6629
6630	scftorture.weight_many= [KNL]
6631			The probability weighting to use for the
6632			smp_call_function_many() function with a zero
6633			"wait" parameter.  See weight_single.
6634			Note well that setting a high probability for
6635			this weighting can place serious IPI load
6636			on the system.
6637
6638	scftorture.weight_many_wait= [KNL]
6639			The probability weighting to use for the
6640			smp_call_function_many() function with a
6641			non-zero "wait" parameter.  See weight_single
6642			and weight_many.
6643
6644	scftorture.weight_all= [KNL]
6645			The probability weighting to use for the
6646			smp_call_function_all() function with a zero
6647			"wait" parameter.  See weight_single and
6648			weight_many.
6649
6650	scftorture.weight_all_wait= [KNL]
6651			The probability weighting to use for the
6652			smp_call_function_all() function with a
6653			non-zero "wait" parameter.  See weight_single
6654			and weight_many.
6655
6656	sdw_mclk_divider=[SDW]
6657			Specify the MCLK divider for Intel SoundWire buses in
6658			case the BIOS does not provide the clock rate properly.
6659
6660	skew_tick=	[KNL,EARLY] Offset the periodic timer tick per cpu to mitigate
6661			xtime_lock contention on larger systems, and/or RCU lock
6662			contention on all systems with CONFIG_MAXSMP set.
6663			Format: { "0" | "1" }
6664			0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6665			1 -- enable.
6666			Note: increases power consumption, thus should only be
6667			enabled if running jitter sensitive (HPC/RT) workloads.
6668
6669	security=	[SECURITY] Choose a legacy "major" security module to
6670			enable at boot. This has been deprecated by the
6671			"lsm=" parameter.
6672
6673	selinux=	[SELINUX] Disable or enable SELinux at boot time.
6674			Format: { "0" | "1" }
6675			See security/selinux/Kconfig help text.
6676			0 -- disable.
6677			1 -- enable.
6678			Default value is 1.
6679
6680	serialnumber	[BUGS=X86-32]
6681
6682	sev=option[,option...] [X86-64]
6683
6684		debug
6685			Enable debug messages.
6686
6687		nosnp
6688			Do not enable SEV-SNP (applies to host/hypervisor
6689			only). Setting 'nosnp' avoids the RMP check overhead
6690			in memory accesses when users do not want to run
6691			SEV-SNP guests.
6692
6693	shapers=	[NET]
6694			Maximal number of shapers.
6695
6696	show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
6697			Limit apic dumping. The parameter defines the maximal
6698			number of local apics being dumped. Also it is possible
6699			to set it to "all" by meaning -- no limit here.
6700			Format: { 1 (default) | 2 | ... | all }.
6701			The parameter valid if only apic=debug or
6702			apic=verbose is specified.
6703			Example: apic=debug show_lapic=all
6704
6705	slab_debug[=options[,slabs][;[options[,slabs]]...]	[MM]
6706			Enabling slab_debug allows one to determine the
6707			culprit if slab objects become corrupted. Enabling
6708			slab_debug can create guard zones around objects and
6709			may poison objects when not in use. Also tracks the
6710			last alloc / free. For more information see
6711			Documentation/admin-guide/mm/slab.rst.
6712			(slub_debug legacy name also accepted for now)
6713
6714			Using this option implies the "no_hash_pointers"
6715			option which can be undone by adding the
6716			"hash_pointers=always" option.
6717
6718	slab_max_order= [MM]
6719			Determines the maximum allowed order for slabs.
6720			A high setting may cause OOMs due to memory
6721			fragmentation. For more information see
6722			Documentation/admin-guide/mm/slab.rst.
6723			(slub_max_order legacy name also accepted for now)
6724
6725	slab_merge	[MM]
6726			Enable merging of slabs with similar size when the
6727			kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
6728			(slub_merge legacy name also accepted for now)
6729
6730	slab_min_objects=	[MM]
6731			The minimum number of objects per slab. SLUB will
6732			increase the slab order up to slab_max_order to
6733			generate a sufficiently large slab able to contain
6734			the number of objects indicated. The higher the number
6735			of objects the smaller the overhead of tracking slabs
6736			and the less frequently locks need to be acquired.
6737			For more information see
6738			Documentation/admin-guide/mm/slab.rst.
6739			(slub_min_objects legacy name also accepted for now)
6740
6741	slab_min_order=	[MM]
6742			Determines the minimum page order for slabs. Must be
6743			lower or equal to slab_max_order. For more information see
6744			Documentation/admin-guide/mm/slab.rst.
6745			(slub_min_order legacy name also accepted for now)
6746
6747	slab_nomerge	[MM]
6748			Disable merging of slabs with similar size. May be
6749			necessary if there is some reason to distinguish
6750			allocs to different slabs, especially in hardened
6751			environments where the risk of heap overflows and
6752			layout control by attackers can usually be
6753			frustrated by disabling merging. This will reduce
6754			most of the exposure of a heap attack to a single
6755			cache (risks via metadata attacks are mostly
6756			unchanged). Debug options disable merging on their
6757			own.
6758			For more information see
6759			Documentation/admin-guide/mm/slab.rst.
6760			(slub_nomerge legacy name also accepted for now)
6761
6762	slab_strict_numa	[MM]
6763			Support memory policies on a per object level
6764			in the slab allocator. The default is for memory
6765			policies to be applied at the folio level when
6766			a new folio is needed or a partial folio is
6767			retrieved from the lists. Increases overhead
6768			in the slab fastpaths but gains more accurate
6769			NUMA kernel object placement which helps with slow
6770			interconnects in NUMA systems.
6771
6772	slram=		[HW,MTD]
6773
6774	smart2=		[HW]
6775			Format: <io1>[,<io2>[,...,<io8>]]
6776
6777	smp.csd_lock_timeout= [KNL]
6778			Specify the period of time in milliseconds
6779			that smp_call_function() and friends will wait
6780			for a CPU to release the CSD lock.  This is
6781			useful when diagnosing bugs involving CPUs
6782			disabling interrupts for extended periods
6783			of time.  Defaults to 5,000 milliseconds, and
6784			setting a value of zero disables this feature.
6785			This feature may be more efficiently disabled
6786			using the csdlock_debug- kernel parameter.
6787
6788	smp.panic_on_ipistall= [KNL]
6789			If a csd_lock_timeout extends for more than
6790			the specified number of milliseconds, panic the
6791			system.  By default, let CSD-lock acquisition
6792			take as long as they take.  Specifying 300,000
6793			for this value provides a 5-minute timeout.
6794
6795	smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
6796	smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
6797	smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
6798	smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
6799	smsc-ircc2.ircc_irq=	[HW] IRQ line
6800	smsc-ircc2.ircc_dma=	[HW] DMA channel
6801	smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6802				0: Toshiba Satellite 1800 (GP data pin select)
6803				1: Fast pin select (default)
6804				2: ATC IRMode
6805
6806	smt=		[KNL,MIPS,S390,EARLY] Set the maximum number of threads
6807			(logical CPUs) to use per physical CPU on systems
6808			capable of symmetric multithreading (SMT). Will
6809			be capped to the actual hardware limit.
6810			Format: <integer>
6811			Default: -1 (no limit)
6812
6813	softlockup_panic=
6814			[KNL] Should the soft-lockup detector generate panics.
6815			Format: 0 | 1
6816
6817			A value of 1 instructs the soft-lockup detector
6818			to panic the machine when a soft-lockup occurs. It is
6819			also controlled by the kernel.softlockup_panic sysctl
6820			and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6821			respective build-time switch to that functionality.
6822
6823	softlockup_all_cpu_backtrace=
6824			[KNL] Should the soft-lockup detector generate
6825			backtraces on all cpus.
6826			Format: 0 | 1
6827
6828	sonypi.*=	[HW] Sony Programmable I/O Control Device driver
6829			See Documentation/admin-guide/laptops/sonypi.rst
6830
6831	spectre_bhi=	[X86] Control mitigation of Branch History Injection
6832			(BHI) vulnerability.  This setting affects the
6833			deployment of the HW BHI control and the SW BHB
6834			clearing sequence.
6835
6836			on     - (default) Enable the HW or SW mitigation as
6837				 needed.  This protects the kernel from
6838				 both syscalls and VMs.
6839			vmexit - On systems which don't have the HW mitigation
6840				 available, enable the SW mitigation on vmexit
6841				 ONLY.  On such systems, the host kernel is
6842				 protected from VM-originated BHI attacks, but
6843				 may still be vulnerable to syscall attacks.
6844			off    - Disable the mitigation.
6845
6846	spectre_v2=	[X86,EARLY] Control mitigation of Spectre variant 2
6847			(indirect branch speculation) vulnerability.
6848			The default operation protects the kernel from
6849			user space attacks.
6850
6851			on   - unconditionally enable, implies
6852			       spectre_v2_user=on
6853			off  - unconditionally disable, implies
6854			       spectre_v2_user=off
6855			auto - kernel detects whether your CPU model is
6856			       vulnerable
6857
6858			Selecting 'on' will, and 'auto' may, choose a
6859			mitigation method at run time according to the
6860			CPU, the available microcode, the setting of the
6861			CONFIG_MITIGATION_RETPOLINE configuration option,
6862			and the compiler with which the kernel was built.
6863
6864			Selecting 'on' will also enable the mitigation
6865			against user space to user space task attacks.
6866			Selecting specific mitigation does not force enable
6867			user mitigations.
6868
6869			Selecting 'off' will disable both the kernel and
6870			the user space protections.
6871
6872			Specific mitigations can also be selected manually:
6873
6874			retpoline	  - replace indirect branches
6875			retpoline,generic - Retpolines
6876			retpoline,lfence  - LFENCE; indirect branch
6877			retpoline,amd     - alias for retpoline,lfence
6878			eibrs		  - Enhanced/Auto IBRS
6879			eibrs,retpoline   - Enhanced/Auto IBRS + Retpolines
6880			eibrs,lfence      - Enhanced/Auto IBRS + LFENCE
6881			ibrs		  - use IBRS to protect kernel
6882
6883			Not specifying this option is equivalent to
6884			spectre_v2=auto.
6885
6886	spectre_v2_user=
6887			[X86] Control mitigation of Spectre variant 2
6888		        (indirect branch speculation) vulnerability between
6889		        user space tasks
6890
6891			on	- Unconditionally enable mitigations. Is
6892				  enforced by spectre_v2=on
6893
6894			off     - Unconditionally disable mitigations. Is
6895				  enforced by spectre_v2=off
6896
6897			prctl   - Indirect branch speculation is enabled,
6898				  but mitigation can be enabled via prctl
6899				  per thread.  The mitigation control state
6900				  is inherited on fork.
6901
6902			prctl,ibpb
6903				- Like "prctl" above, but only STIBP is
6904				  controlled per thread. IBPB is issued
6905				  always when switching between different user
6906				  space processes.
6907
6908			seccomp
6909				- Same as "prctl" above, but all seccomp
6910				  threads will enable the mitigation unless
6911				  they explicitly opt out.
6912
6913			seccomp,ibpb
6914				- Like "seccomp" above, but only STIBP is
6915				  controlled per thread. IBPB is issued
6916				  always when switching between different
6917				  user space processes.
6918
6919			auto    - Kernel selects the mitigation depending on
6920				  the available CPU features and vulnerability.
6921
6922			Default mitigation: "prctl"
6923
6924			Not specifying this option is equivalent to
6925			spectre_v2_user=auto.
6926
6927	spec_rstack_overflow=
6928			[X86,EARLY] Control RAS overflow mitigation on AMD Zen CPUs
6929
6930			off		- Disable mitigation
6931			microcode	- Enable microcode mitigation only
6932			safe-ret	- Enable sw-only safe RET mitigation (default)
6933			ibpb		- Enable mitigation by issuing IBPB on
6934					  kernel entry
6935			ibpb-vmexit	- Issue IBPB only on VMEXIT
6936					  (cloud-specific mitigation)
6937
6938	spec_store_bypass_disable=
6939			[HW,EARLY] Control Speculative Store Bypass (SSB) Disable mitigation
6940			(Speculative Store Bypass vulnerability)
6941
6942			Certain CPUs are vulnerable to an exploit against a
6943			a common industry wide performance optimization known
6944			as "Speculative Store Bypass" in which recent stores
6945			to the same memory location may not be observed by
6946			later loads during speculative execution. The idea
6947			is that such stores are unlikely and that they can
6948			be detected prior to instruction retirement at the
6949			end of a particular speculation execution window.
6950
6951			In vulnerable processors, the speculatively forwarded
6952			store can be used in a cache side channel attack, for
6953			example to read memory to which the attacker does not
6954			directly have access (e.g. inside sandboxed code).
6955
6956			This parameter controls whether the Speculative Store
6957			Bypass optimization is used.
6958
6959			On x86 the options are:
6960
6961			on      - Unconditionally disable Speculative Store Bypass
6962			off     - Unconditionally enable Speculative Store Bypass
6963			auto    - Kernel detects whether the CPU model contains an
6964				  implementation of Speculative Store Bypass and
6965				  picks the most appropriate mitigation. If the
6966				  CPU is not vulnerable, "off" is selected. If the
6967				  CPU is vulnerable the default mitigation is
6968				  architecture and Kconfig dependent. See below.
6969			prctl   - Control Speculative Store Bypass per thread
6970				  via prctl. Speculative Store Bypass is enabled
6971				  for a process by default. The state of the control
6972				  is inherited on fork.
6973			seccomp - Same as "prctl" above, but all seccomp threads
6974				  will disable SSB unless they explicitly opt out.
6975
6976			Default mitigations:
6977			X86:	"prctl"
6978
6979			On powerpc the options are:
6980
6981			on,auto - On Power8 and Power9 insert a store-forwarding
6982				  barrier on kernel entry and exit. On Power7
6983				  perform a software flush on kernel entry and
6984				  exit.
6985			off	- No action.
6986
6987			Not specifying this option is equivalent to
6988			spec_store_bypass_disable=auto.
6989
6990	split_lock_detect=
6991			[X86] Enable split lock detection or bus lock detection
6992
6993			When enabled (and if hardware support is present), atomic
6994			instructions that access data across cache line
6995			boundaries will result in an alignment check exception
6996			for split lock detection or a debug exception for
6997			bus lock detection.
6998
6999			off	- not enabled
7000
7001			warn	- the kernel will emit rate-limited warnings
7002				  about applications triggering the #AC
7003				  exception or the #DB exception. This mode is
7004				  the default on CPUs that support split lock
7005				  detection or bus lock detection. Default
7006				  behavior is by #AC if both features are
7007				  enabled in hardware.
7008
7009			fatal	- the kernel will send SIGBUS to applications
7010				  that trigger the #AC exception or the #DB
7011				  exception. Default behavior is by #AC if
7012				  both features are enabled in hardware.
7013
7014			ratelimit:N -
7015				  Set system wide rate limit to N bus locks
7016				  per second for bus lock detection.
7017				  0 < N <= 1000.
7018
7019				  N/A for split lock detection.
7020
7021
7022			If an #AC exception is hit in the kernel or in
7023			firmware (i.e. not while executing in user mode)
7024			the kernel will oops in either "warn" or "fatal"
7025			mode.
7026
7027			#DB exception for bus lock is triggered only when
7028			CPL > 0.
7029
7030	srbds=		[X86,INTEL,EARLY]
7031			Control the Special Register Buffer Data Sampling
7032			(SRBDS) mitigation.
7033
7034			Certain CPUs are vulnerable to an MDS-like
7035			exploit which can leak bits from the random
7036			number generator.
7037
7038			By default, this issue is mitigated by
7039			microcode.  However, the microcode fix can cause
7040			the RDRAND and RDSEED instructions to become
7041			much slower.  Among other effects, this will
7042			result in reduced throughput from /dev/urandom.
7043
7044			The microcode mitigation can be disabled with
7045			the following option:
7046
7047			off:    Disable mitigation and remove
7048				performance impact to RDRAND and RDSEED
7049
7050	srcutree.big_cpu_lim [KNL]
7051			Specifies the number of CPUs constituting a
7052			large system, such that srcu_struct structures
7053			should immediately allocate an srcu_node array.
7054			This kernel-boot parameter defaults to 128,
7055			but takes effect only when the low-order four
7056			bits of srcutree.convert_to_big is equal to 3
7057			(decide at boot).
7058
7059	srcutree.convert_to_big [KNL]
7060			Specifies under what conditions an SRCU tree
7061			srcu_struct structure will be converted to big
7062			form, that is, with an rcu_node tree:
7063
7064				   0:  Never.
7065				   1:  At init_srcu_struct() time.
7066				   2:  When rcutorture decides to.
7067				   3:  Decide at boot time (default).
7068				0x1X:  Above plus if high contention.
7069
7070			Either way, the srcu_node tree will be sized based
7071			on the actual runtime number of CPUs (nr_cpu_ids)
7072			instead of the compile-time CONFIG_NR_CPUS.
7073
7074	srcutree.counter_wrap_check [KNL]
7075			Specifies how frequently to check for
7076			grace-period sequence counter wrap for the
7077			srcu_data structure's ->srcu_gp_seq_needed field.
7078			The greater the number of bits set in this kernel
7079			parameter, the less frequently counter wrap will
7080			be checked for.  Note that the bottom two bits
7081			are ignored.
7082
7083	srcutree.exp_holdoff [KNL]
7084			Specifies how many nanoseconds must elapse
7085			since the end of the last SRCU grace period for
7086			a given srcu_struct until the next normal SRCU
7087			grace period will be considered for automatic
7088			expediting.  Set to zero to disable automatic
7089			expediting.
7090
7091	srcutree.srcu_max_nodelay [KNL]
7092			Specifies the number of no-delay instances
7093			per jiffy for which the SRCU grace period
7094			worker thread will be rescheduled with zero
7095			delay. Beyond this limit, worker thread will
7096			be rescheduled with a sleep delay of one jiffy.
7097
7098	srcutree.srcu_max_nodelay_phase [KNL]
7099			Specifies the per-grace-period phase, number of
7100			non-sleeping polls of readers. Beyond this limit,
7101			grace period worker thread will be rescheduled
7102			with a sleep delay of one jiffy, between each
7103			rescan of the readers, for a grace period phase.
7104
7105	srcutree.srcu_retry_check_delay [KNL]
7106			Specifies number of microseconds of non-sleeping
7107			delay between each non-sleeping poll of readers.
7108
7109	srcutree.small_contention_lim [KNL]
7110			Specifies the number of update-side contention
7111			events per jiffy will be tolerated before
7112			initiating a conversion of an srcu_struct
7113			structure to big form.	Note that the value of
7114			srcutree.convert_to_big must have the 0x10 bit
7115			set for contention-based conversions to occur.
7116
7117	ssbd=		[ARM64,HW,EARLY]
7118			Speculative Store Bypass Disable control
7119
7120			On CPUs that are vulnerable to the Speculative
7121			Store Bypass vulnerability and offer a
7122			firmware based mitigation, this parameter
7123			indicates how the mitigation should be used:
7124
7125			force-on:  Unconditionally enable mitigation for
7126				   for both kernel and userspace
7127			force-off: Unconditionally disable mitigation for
7128				   for both kernel and userspace
7129			kernel:    Always enable mitigation in the
7130				   kernel, and offer a prctl interface
7131				   to allow userspace to register its
7132				   interest in being mitigated too.
7133
7134	stack_guard_gap=	[MM]
7135			override the default stack gap protection. The value
7136			is in page units and it defines how many pages prior
7137			to (for stacks growing down) resp. after (for stacks
7138			growing up) the main stack are reserved for no other
7139			mapping. Default value is 256 pages.
7140
7141	stack_depot_disable= [KNL,EARLY]
7142			Setting this to true through kernel command line will
7143			disable the stack depot thereby saving the static memory
7144			consumed by the stack hash table. By default this is set
7145			to false.
7146
7147	stack_depot_max_pools= [KNL,EARLY]
7148			Specify the maximum number of pools to use for storing
7149			stack traces. Pools are allocated on-demand up to this
7150			limit. Default value is 8191 pools.
7151
7152	stacktrace	[FTRACE]
7153			Enabled the stack tracer on boot up.
7154
7155	stacktrace_filter=[function-list]
7156			[FTRACE] Limit the functions that the stack tracer
7157			will trace at boot up. function-list is a comma-separated
7158			list of functions. This list can be changed at run
7159			time by the stack_trace_filter file in the debugfs
7160			tracing directory. Note, this enables stack tracing
7161			and the stacktrace above is not needed.
7162
7163	sti=		[PARISC,HW]
7164			Format: <num>
7165			Set the STI (builtin display/keyboard on the HP-PARISC
7166			machines) console (graphic card) which should be used
7167			as the initial boot-console.
7168			See also comment in drivers/video/console/sticore.c.
7169
7170	sti_font=	[HW]
7171			See comment in drivers/video/console/sticore.c.
7172
7173	stifb=		[HW]
7174			Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
7175
7176        strict_sas_size=
7177			[X86]
7178			Format: <bool>
7179			Enable or disable strict sigaltstack size checks
7180			against the required signal frame size which
7181			depends on the supported FPU features. This can
7182			be used to filter out binaries which have
7183			not yet been made aware of AT_MINSIGSTKSZ.
7184
7185	stress_hpt	[PPC,EARLY]
7186			Limits the number of kernel HPT entries in the hash
7187			page table to increase the rate of hash page table
7188			faults on kernel addresses.
7189
7190	stress_slb	[PPC,EARLY]
7191			Limits the number of kernel SLB entries, and flushes
7192			them frequently to increase the rate of SLB faults
7193			on kernel addresses.
7194
7195	sunrpc.min_resvport=
7196	sunrpc.max_resvport=
7197			[NFS,SUNRPC]
7198			SunRPC servers often require that client requests
7199			originate from a privileged port (i.e. a port in the
7200			range 0 < portnr < 1024).
7201			An administrator who wishes to reserve some of these
7202			ports for other uses may adjust the range that the
7203			kernel's sunrpc client considers to be privileged
7204			using these two parameters to set the minimum and
7205			maximum port values.
7206
7207	sunrpc.svc_rpc_per_connection_limit=
7208			[NFS,SUNRPC]
7209			Limit the number of requests that the server will
7210			process in parallel from a single connection.
7211			The default value is 0 (no limit).
7212
7213	sunrpc.pool_mode=
7214			[NFS]
7215			Control how the NFS server code allocates CPUs to
7216			service thread pools.  Depending on how many NICs
7217			you have and where their interrupts are bound, this
7218			option will affect which CPUs will do NFS serving.
7219			Note: this parameter cannot be changed while the
7220			NFS server is running.
7221
7222			auto	    the server chooses an appropriate mode
7223				    automatically using heuristics
7224			global	    a single global pool contains all CPUs
7225			percpu	    one pool for each CPU
7226			pernode	    one pool for each NUMA node (equivalent
7227				    to global on non-NUMA machines)
7228
7229	sunrpc.tcp_slot_table_entries=
7230	sunrpc.udp_slot_table_entries=
7231			[NFS,SUNRPC]
7232			Sets the upper limit on the number of simultaneous
7233			RPC calls that can be sent from the client to a
7234			server. Increasing these values may allow you to
7235			improve throughput, but will also increase the
7236			amount of memory reserved for use by the client.
7237
7238	suspend.pm_test_delay=
7239			[SUSPEND]
7240			Sets the number of seconds to remain in a suspend test
7241			mode before resuming the system (see
7242			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
7243			is set. Default value is 5.
7244
7245	svm=		[PPC]
7246			Format: { on | off | y | n | 1 | 0 }
7247			This parameter controls use of the Protected
7248			Execution Facility on pSeries.
7249
7250	swiotlb=	[ARM,PPC,MIPS,X86,S390,EARLY]
7251			Format: { <int> [,<int>] | force | noforce }
7252			<int> -- Number of I/O TLB slabs
7253			<int> -- Second integer after comma. Number of swiotlb
7254				 areas with their own lock. Will be rounded up
7255				 to a power of 2.
7256			force -- force using of bounce buffers even if they
7257			         wouldn't be automatically used by the kernel
7258			noforce -- Never use bounce buffers (for debugging)
7259
7260	switches=	[HW,M68k,EARLY]
7261
7262	sysctl.*=	[KNL]
7263			Set a sysctl parameter, right before loading the init
7264			process, as if the value was written to the respective
7265			/proc/sys/... file. Both '.' and '/' are recognized as
7266			separators. Unrecognized parameters and invalid values
7267			are reported in the kernel log. Sysctls registered
7268			later by a loaded module cannot be set this way.
7269			Example: sysctl.vm.swappiness=40
7270
7271	sysrq_always_enabled
7272			[KNL]
7273			Ignore sysrq setting - this boot parameter will
7274			neutralize any effect of /proc/sys/kernel/sysrq.
7275			Useful for debugging.
7276
7277	tcpmhash_entries= [KNL,NET]
7278			Set the number of tcp_metrics_hash slots.
7279			Default value is 8192 or 16384 depending on total
7280			ram pages. This is used to specify the TCP metrics
7281			cache size. See Documentation/networking/ip-sysctl.rst
7282			"tcp_no_metrics_save" section for more details.
7283
7284	tdfx=		[HW,DRM]
7285
7286	test_suspend=	[SUSPEND]
7287			Format: { "mem" | "standby" | "freeze" }[,N]
7288			Specify "mem" (for Suspend-to-RAM) or "standby" (for
7289			standby suspend) or "freeze" (for suspend type freeze)
7290			as the system sleep state during system startup with
7291			the optional capability to repeat N number of times.
7292			The system is woken from this state using a
7293			wakeup-capable RTC alarm.
7294
7295	thash_entries=	[KNL,NET]
7296			Set number of hash buckets for TCP connection
7297
7298	thermal.act=	[HW,ACPI]
7299			-1: disable all active trip points in all thermal zones
7300			<degrees C>: override all lowest active trip points
7301
7302	thermal.crt=	[HW,ACPI]
7303			-1: disable all critical trip points in all thermal zones
7304			<degrees C>: override all critical trip points
7305
7306	thermal.off=	[HW,ACPI]
7307			1: disable ACPI thermal control
7308
7309	thermal.psv=	[HW,ACPI]
7310			-1: disable all passive trip points
7311			<degrees C>: override all passive trip points to this
7312			value
7313
7314	thermal.tzp=	[HW,ACPI]
7315			Specify global default ACPI thermal zone polling rate
7316			<deci-seconds>: poll all this frequency
7317			0: no polling (default)
7318
7319	thp_anon=	[KNL]
7320			Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
7321			state is one of "always", "madvise", "never" or "inherit".
7322			Control the default behavior of the system with respect
7323			to anonymous transparent hugepages.
7324			Can be used multiple times for multiple anon THP sizes.
7325			See Documentation/admin-guide/mm/transhuge.rst for more
7326			details.
7327
7328	threadirqs	[KNL,EARLY]
7329			Force threading of all interrupt handlers except those
7330			marked explicitly IRQF_NO_THREAD.
7331
7332	thp_shmem=	[KNL]
7333			Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
7334			Control the default policy of each hugepage size for the
7335			internal shmem mount. <policy> is one of policies available
7336			for the shmem mount ("always", "inherit", "never", "within_size",
7337			and "advise").
7338			It can be used multiple times for multiple shmem THP sizes.
7339			See Documentation/admin-guide/mm/transhuge.rst for more
7340			details.
7341
7342	topology=	[S390,EARLY]
7343			Format: {off | on}
7344			Specify if the kernel should make use of the cpu
7345			topology information if the hardware supports this.
7346			The scheduler will make use of this information and
7347			e.g. base its process migration decisions on it.
7348			Default is on.
7349
7350	torture.disable_onoff_at_boot= [KNL]
7351			Prevent the CPU-hotplug component of torturing
7352			until after init has spawned.
7353
7354	torture.ftrace_dump_at_shutdown= [KNL]
7355			Dump the ftrace buffer at torture-test shutdown,
7356			even if there were no errors.  This can be a
7357			very costly operation when many torture tests
7358			are running concurrently, especially on systems
7359			with rotating-rust storage.
7360
7361	torture.verbose_sleep_frequency= [KNL]
7362			Specifies how many verbose printk()s should be
7363			emitted between each sleep.  The default of zero
7364			disables verbose-printk() sleeping.
7365
7366	torture.verbose_sleep_duration= [KNL]
7367			Duration of each verbose-printk() sleep in jiffies.
7368
7369	tpm.disable_pcr_integrity= [HW,TPM]
7370			Do not protect PCR registers from unintended physical
7371			access, or interposers in the bus by the means of
7372			having an integrity protected session wrapped around
7373			TPM2_PCR_Extend command. Consider this in a situation
7374			where TPM is heavily utilized by IMA, thus protection
7375			causing a major performance hit, and the space where
7376			machines are deployed is by other means guarded.
7377
7378	tpm_crb_ffa.busy_timeout_ms= [ARM64,TPM]
7379			Maximum time in milliseconds to retry sending a message
7380			to the TPM service before giving up. This parameter controls
7381			how long the system will continue retrying when the TPM
7382			service is busy.
7383			Format: <unsigned int>
7384			Default: 2000 (2 seconds)
7385
7386	tpm_suspend_pcr=[HW,TPM]
7387			Format: integer pcr id
7388			Specify that at suspend time, the tpm driver
7389			should extend the specified pcr with zeros,
7390			as a workaround for some chips which fail to
7391			flush the last written pcr on TPM_SaveState.
7392			This will guarantee that all the other pcrs
7393			are saved.
7394
7395	tpm_tis.interrupts= [HW,TPM]
7396			Enable interrupts for the MMIO based physical layer
7397			for the FIFO interface. By default it is set to false
7398			(0). For more information about TPM hardware interfaces
7399			defined by Trusted Computing Group (TCG) see
7400			https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
7401
7402	tp_printk	[FTRACE]
7403			Have the tracepoints sent to printk as well as the
7404			tracing ring buffer. This is useful for early boot up
7405			where the system hangs or reboots and does not give the
7406			option for reading the tracing buffer or performing a
7407			ftrace_dump_on_oops.
7408
7409			To turn off having tracepoints sent to printk,
7410			 echo 0 > /proc/sys/kernel/tracepoint_printk
7411			Note, echoing 1 into this file without the
7412			tp_printk kernel cmdline option has no effect.
7413
7414			The tp_printk_stop_on_boot (see below) can also be used
7415			to stop the printing of events to console at
7416			late_initcall_sync.
7417
7418			** CAUTION **
7419
7420			Having tracepoints sent to printk() and activating high
7421			frequency tracepoints such as irq or sched, can cause
7422			the system to live lock.
7423
7424	tp_printk_stop_on_boot [FTRACE]
7425			When tp_printk (above) is set, it can cause a lot of noise
7426			on the console. It may be useful to only include the
7427			printing of events during boot up, as user space may
7428			make the system inoperable.
7429
7430			This command line option will stop the printing of events
7431			to console at the late_initcall_sync() time frame.
7432
7433	trace_buf_size=nn[KMG]
7434			[FTRACE] will set tracing buffer size on each cpu.
7435
7436	trace_clock=	[FTRACE] Set the clock used for tracing events
7437			at boot up.
7438			local - Use the per CPU time stamp counter
7439				(converted into nanoseconds). Fast, but
7440				depending on the architecture, may not be
7441				in sync between CPUs.
7442			global - Event time stamps are synchronized across
7443				CPUs. May be slower than the local clock,
7444				but better for some race conditions.
7445			counter - Simple counting of events (1, 2, ..)
7446				note, some counts may be skipped due to the
7447				infrastructure grabbing the clock more than
7448				once per event.
7449			uptime - Use jiffies as the time stamp.
7450			perf - Use the same clock that perf uses.
7451			mono - Use ktime_get_mono_fast_ns() for time stamps.
7452			mono_raw - Use ktime_get_raw_fast_ns() for time
7453				stamps.
7454			boot - Use ktime_get_boot_fast_ns() for time stamps.
7455			Architectures may add more clocks. See
7456			Documentation/trace/ftrace.rst for more details.
7457
7458	trace_event=[event-list]
7459			[FTRACE] Set and start specified trace events in order
7460			to facilitate early boot debugging. The event-list is a
7461			comma-separated list of trace events to enable. See
7462			also Documentation/trace/events.rst
7463
7464			To enable modules, use :mod: keyword:
7465
7466			trace_event=:mod:<module>
7467
7468			The value before :mod: will only enable specific events
7469			that are part of the module. See the above mentioned
7470			document for more information.
7471
7472	trace_instance=[instance-info]
7473			[FTRACE] Create a ring buffer instance early in boot up.
7474			This will be listed in:
7475
7476				/sys/kernel/tracing/instances
7477
7478			Events can be enabled at the time the instance is created
7479			via:
7480
7481				trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
7482
7483			Note, the "<system*>:" portion is optional if the event is
7484			unique.
7485
7486				trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
7487
7488			will enable the "sched_switch" event (note, the "sched:" is optional, and
7489			the same thing would happen if it was left off). The irq_handler_entry
7490			event, and all events under the "initcall" system.
7491
7492			Flags can be added to the instance to modify its behavior when it is
7493			created. The flags are separated by '^'.
7494
7495			The available flags are:
7496
7497			    traceoff	- Have the tracing instance tracing disabled after it is created.
7498			    traceprintk	- Have trace_printk() write into this trace instance
7499					  (note, "printk" and "trace_printk" can also be used)
7500
7501				trace_instance=foo^traceoff^traceprintk,sched,irq
7502
7503			The flags must come before the defined events.
7504
7505			If memory has been reserved (see memmap for x86), the instance
7506			can use that memory:
7507
7508				memmap=12M$0x284500000 trace_instance=boot_map@0x284500000:12M
7509
7510			The above will create a "boot_map" instance that uses the physical
7511			memory at 0x284500000 that is 12Megs. The per CPU buffers of that
7512			instance will be split up accordingly.
7513
7514			Alternatively, the memory can be reserved by the reserve_mem option:
7515
7516				reserve_mem=12M:4096:trace trace_instance=boot_map@trace
7517
7518			This will reserve 12 megabytes at boot up with a 4096 byte alignment
7519			and place the ring buffer in this memory. Note that due to KASLR, the
7520			memory may not be the same location each time, which will not preserve
7521			the buffer content.
7522
7523			Also note that the layout of the ring buffer data may change between
7524			kernel versions where the validator will fail and reset the ring buffer
7525			if the layout is not the same as the previous kernel.
7526
7527			If the ring buffer is used for persistent bootups and has events enabled,
7528			it is recommend to disable tracing so that events from a previous boot do not
7529			mix with events of the current boot (unless you are debugging a random crash
7530			at boot up).
7531
7532				reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq
7533
7534			Note, saving the trace buffer across reboots does require that the system
7535			is set up to not wipe memory. For instance, CONFIG_RESET_ATTACK_MITIGATION
7536			can force a memory reset on boot which will clear any trace that was stored.
7537			This is just one of many ways that can clear memory. Make sure your system
7538			keeps the content of memory across reboots before relying on this option.
7539
7540			NB: Both the mapped address and size must be page aligned for the architecture.
7541
7542			See also Documentation/trace/debugging.rst
7543
7544
7545	trace_options=[option-list]
7546			[FTRACE] Enable or disable tracer options at boot.
7547			The option-list is a comma delimited list of options
7548			that can be enabled or disabled just as if you were
7549			to echo the option name into
7550
7551			    /sys/kernel/tracing/trace_options
7552
7553			For example, to enable stacktrace option (to dump the
7554			stack trace of each event), add to the command line:
7555
7556			      trace_options=stacktrace
7557
7558			See also Documentation/trace/ftrace.rst "trace options"
7559			section.
7560
7561	trace_trigger=[trigger-list]
7562			[FTRACE] Add an event trigger on specific events.
7563			Set a trigger on top of a specific event, with an optional
7564			filter.
7565
7566			The format is "trace_trigger=<event>.<trigger>[ if <filter>],..."
7567			Where more than one trigger may be specified that are comma delimited.
7568
7569			For example:
7570
7571			  trace_trigger="sched_switch.stacktrace if prev_state == 2"
7572
7573			The above will enable the "stacktrace" trigger on the "sched_switch"
7574			event but only trigger it if the "prev_state" of the "sched_switch"
7575			event is "2" (TASK_UNINTERRUPTIBLE).
7576
7577			See also "Event triggers" in Documentation/trace/events.rst
7578
7579
7580	traceoff_after_boot
7581			[FTRACE] Sometimes tracing is used to debug issues
7582			during the boot process. Since the trace buffer has a
7583			limited amount of storage, it may be prudent to
7584			disable tracing after the boot is finished, otherwise
7585			the critical information may be overwritten.  With this
7586			option, the main tracing buffer will be turned off at
7587			the end of the boot process.
7588
7589	traceoff_on_warning
7590			[FTRACE] enable this option to disable tracing when a
7591			warning is hit. This turns off "tracing_on". Tracing can
7592			be enabled again by echoing '1' into the "tracing_on"
7593			file located in /sys/kernel/tracing/
7594
7595			This option is useful, as it disables the trace before
7596			the WARNING dump is called, which prevents the trace to
7597			be filled with content caused by the warning output.
7598
7599			This option can also be set at run time via the sysctl
7600			option:  kernel/traceoff_on_warning
7601
7602	transparent_hugepage=
7603			[KNL]
7604			Format: [always|madvise|never]
7605			Can be used to control the default behavior of the system
7606			with respect to transparent hugepages.
7607			See Documentation/admin-guide/mm/transhuge.rst
7608			for more details.
7609
7610	transparent_hugepage_shmem= [KNL]
7611			Format: [always|within_size|advise|never|deny|force]
7612			Can be used to control the hugepage allocation policy for
7613			the internal shmem mount.
7614			See Documentation/admin-guide/mm/transhuge.rst
7615			for more details.
7616
7617	transparent_hugepage_tmpfs= [KNL]
7618			Format: [always|within_size|advise|never]
7619			Can be used to control the default hugepage allocation policy
7620			for the tmpfs mount.
7621			See Documentation/admin-guide/mm/transhuge.rst
7622			for more details.
7623
7624	trusted.source=	[KEYS]
7625			Format: <string>
7626			This parameter identifies the trust source as a backend
7627			for trusted keys implementation. Supported trust
7628			sources:
7629			- "tpm"
7630			- "tee"
7631			- "caam"
7632			- "dcp"
7633			If not specified then it defaults to iterating through
7634			the trust source list starting with TPM and assigns the
7635			first trust source as a backend which is initialized
7636			successfully during iteration.
7637
7638	trusted.rng=	[KEYS]
7639			Format: <string>
7640			The RNG used to generate key material for trusted keys.
7641			Can be one of:
7642			- "kernel"
7643			- the same value as trusted.source: "tpm" or "tee"
7644			- "default"
7645			If not specified, "default" is used. In this case,
7646			the RNG's choice is left to each individual trust source.
7647
7648	trusted.dcp_use_otp_key
7649			This is intended to be used in combination with
7650			trusted.source=dcp and will select the DCP OTP key
7651			instead of the DCP UNIQUE key blob encryption.
7652
7653	trusted.dcp_skip_zk_test
7654			This is intended to be used in combination with
7655			trusted.source=dcp and will disable the check if the
7656			blob key is all zeros. This is helpful for situations where
7657			having this key zero'ed is acceptable. E.g. in testing
7658			scenarios.
7659
7660	tsa=		[X86] Control mitigation for Transient Scheduler
7661			Attacks on AMD CPUs. Search the following in your
7662			favourite search engine for more details:
7663
7664			"Technical guidance for mitigating transient scheduler
7665			attacks".
7666
7667			off		- disable the mitigation
7668			on		- enable the mitigation (default)
7669			user		- mitigate only user/kernel transitions
7670			vm		- mitigate only guest/host transitions
7671
7672
7673	tsc=		Disable clocksource stability checks for TSC.
7674			Format: <string>
7675			[x86] reliable: mark tsc clocksource as reliable, this
7676			disables clocksource verification at runtime, as well
7677			as the stability checks done at bootup.	Used to enable
7678			high-resolution timer mode on older hardware, and in
7679			virtualized environment.
7680			[x86] noirqtime: Do not use TSC to do irq accounting.
7681			Used to run time disable IRQ_TIME_ACCOUNTING on any
7682			platforms where RDTSC is slow and this accounting
7683			can add overhead.
7684			[x86] unstable: mark the TSC clocksource as unstable, this
7685			marks the TSC unconditionally unstable at bootup and
7686			avoids any further wobbles once the TSC watchdog notices.
7687			[x86] nowatchdog: disable clocksource watchdog. Used
7688			in situations with strict latency requirements (where
7689			interruptions from clocksource watchdog are not
7690			acceptable).
7691			[x86] recalibrate: force recalibration against a HW timer
7692			(HPET or PM timer) on systems whose TSC frequency was
7693			obtained from HW or FW using either an MSR or CPUID(0x15).
7694			Warn if the difference is more than 500 ppm.
7695			[x86] watchdog: Use TSC as the watchdog clocksource with
7696			which to check other HW timers (HPET or PM timer), but
7697			only on systems where TSC has been deemed trustworthy.
7698			This will be suppressed by an earlier tsc=nowatchdog and
7699			can be overridden by a later tsc=nowatchdog.  A console
7700			message will flag any such suppression or overriding.
7701
7702	tsc_early_khz=  [X86,EARLY] Skip early TSC calibration and use the given
7703			value instead. Useful when the early TSC frequency discovery
7704			procedure is not reliable, such as on overclocked systems
7705			with CPUID.16h support and partial CPUID.15h support.
7706			Format: <unsigned int>
7707
7708	tsx=		[X86] Control Transactional Synchronization
7709			Extensions (TSX) feature in Intel processors that
7710			support TSX control.
7711
7712			This parameter controls the TSX feature. The options are:
7713
7714			on	- Enable TSX on the system. Although there are
7715				mitigations for all known security vulnerabilities,
7716				TSX has been known to be an accelerator for
7717				several previous speculation-related CVEs, and
7718				so there may be unknown	security risks associated
7719				with leaving it enabled.
7720
7721			off	- Disable TSX on the system. (Note that this
7722				option takes effect only on newer CPUs which are
7723				not vulnerable to MDS, i.e., have
7724				MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
7725				the new IA32_TSX_CTRL MSR through a microcode
7726				update. This new MSR allows for the reliable
7727				deactivation of the TSX functionality.)
7728
7729			auto	- Disable TSX if X86_BUG_TAA is present,
7730				  otherwise enable TSX on the system.
7731
7732			Not specifying this option is equivalent to tsx=off.
7733
7734			See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7735			for more details.
7736
7737	tsx_async_abort= [X86,INTEL,EARLY] Control mitigation for the TSX Async
7738			Abort (TAA) vulnerability.
7739
7740			Similar to Micro-architectural Data Sampling (MDS)
7741			certain CPUs that support Transactional
7742			Synchronization Extensions (TSX) are vulnerable to an
7743			exploit against CPU internal buffers which can forward
7744			information to a disclosure gadget under certain
7745			conditions.
7746
7747			In vulnerable processors, the speculatively forwarded
7748			data can be used in a cache side channel attack, to
7749			access data to which the attacker does not have direct
7750			access.
7751
7752			This parameter controls the TAA mitigation.  The
7753			options are:
7754
7755			full       - Enable TAA mitigation on vulnerable CPUs
7756				     if TSX is enabled.
7757
7758			full,nosmt - Enable TAA mitigation and disable SMT on
7759				     vulnerable CPUs. If TSX is disabled, SMT
7760				     is not disabled because CPU is not
7761				     vulnerable to cross-thread TAA attacks.
7762			off        - Unconditionally disable TAA mitigation
7763
7764			On MDS-affected machines, tsx_async_abort=off can be
7765			prevented by an active MDS mitigation as both vulnerabilities
7766			are mitigated with the same mechanism so in order to disable
7767			this mitigation, you need to specify mds=off too.
7768
7769			Not specifying this option is equivalent to
7770			tsx_async_abort=full.  On CPUs which are MDS affected
7771			and deploy MDS mitigation, TAA mitigation is not
7772			required and doesn't provide any additional
7773			mitigation.
7774
7775			For details see:
7776			Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7777
7778	turbografx.map[2|3]=	[HW,JOY]
7779			TurboGraFX parallel port interface
7780			Format:
7781			<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
7782			See also Documentation/input/devices/joystick-parport.rst
7783
7784	udbg-immortal	[PPC] When debugging early kernel crashes that
7785			happen after console_init() and before a proper
7786			console driver takes over, this boot options might
7787			help "seeing" what's going on.
7788
7789	uhash_entries=	[KNL,NET]
7790			Set number of hash buckets for UDP/UDP-Lite connections
7791
7792	uhci-hcd.ignore_oc=
7793			[USB] Ignore overcurrent events (default N).
7794			Some badly-designed motherboards generate lots of
7795			bogus events, for ports that aren't wired to
7796			anything.  Set this parameter to avoid log spamming.
7797			Note that genuine overcurrent events won't be
7798			reported either.
7799
7800	unaligned_scalar_speed=
7801			[RISCV]
7802			Format: {slow | fast | unsupported}
7803			Allow skipping scalar unaligned access speed tests. This
7804			is useful for testing alternative code paths and to skip
7805			the tests in environments where they run too slowly. All
7806			CPUs must have the same scalar unaligned access speed.
7807
7808	unaligned_vector_speed=
7809			[RISCV]
7810			Format: {slow | fast | unsupported}
7811			Allow skipping vector unaligned access speed tests. This
7812			is useful for testing alternative code paths and to skip
7813			the tests in environments where they run too slowly. All
7814			CPUs must have the same vector unaligned access speed.
7815
7816	unknown_nmi_panic
7817			[X86] Cause panic on unknown NMI.
7818
7819	unwind_debug	[X86-64,EARLY]
7820			Enable unwinder debug output.  This can be
7821			useful for debugging certain unwinder error
7822			conditions, including corrupt stacks and
7823			bad/missing unwinder metadata.
7824
7825	usbcore.authorized_default=
7826			[USB] Default USB device authorization:
7827			(default -1 = authorized (same as 1),
7828			0 = not authorized, 1 = authorized, 2 = authorized
7829			if device connected to internal port)
7830
7831	usbcore.autosuspend=
7832			[USB] The autosuspend time delay (in seconds) used
7833			for newly-detected USB devices (default 2).  This
7834			is the time required before an idle device will be
7835			autosuspended.  Devices for which the delay is set
7836			to a negative value won't be autosuspended at all.
7837
7838	usbcore.usbfs_snoop=
7839			[USB] Set to log all usbfs traffic (default 0 = off).
7840
7841	usbcore.usbfs_snoop_max=
7842			[USB] Maximum number of bytes to snoop in each URB
7843			(default = 65536).
7844
7845	usbcore.blinkenlights=
7846			[USB] Set to cycle leds on hubs (default 0 = off).
7847
7848	usbcore.old_scheme_first=
7849			[USB] Start with the old device initialization
7850			scheme (default 0 = off).
7851
7852	usbcore.usbfs_memory_mb=
7853			[USB] Memory limit (in MB) for buffers allocated by
7854			usbfs (default = 16, 0 = max = 2047).
7855
7856	usbcore.use_both_schemes=
7857			[USB] Try the other device initialization scheme
7858			if the first one fails (default 1 = enabled).
7859
7860	usbcore.initial_descriptor_timeout=
7861			[USB] Specifies timeout for the initial 64-byte
7862			USB_REQ_GET_DESCRIPTOR request in milliseconds
7863			(default 5000 = 5.0 seconds).
7864
7865	usbcore.nousb	[USB] Disable the USB subsystem
7866
7867	usbcore.quirks=
7868			[USB] A list of quirk entries to augment the built-in
7869			usb core quirk list. List entries are separated by
7870			commas. Each entry has the form
7871			VendorID:ProductID:Flags. The IDs are 4-digit hex
7872			numbers and Flags is a set of letters. Each letter
7873			will change the built-in quirk; setting it if it is
7874			clear and clearing it if it is set. The letters have
7875			the following meanings:
7876				a = USB_QUIRK_STRING_FETCH_255 (string
7877					descriptors must not be fetched using
7878					a 255-byte read);
7879				b = USB_QUIRK_RESET_RESUME (device can't resume
7880					correctly so reset it instead);
7881				c = USB_QUIRK_NO_SET_INTF (device can't handle
7882					Set-Interface requests);
7883				d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7884					handle its Configuration or Interface
7885					strings);
7886				e = USB_QUIRK_RESET (device can't be reset
7887					(e.g morph devices), don't use reset);
7888				f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7889					more interface descriptions than the
7890					bNumInterfaces count, and can't handle
7891					talking to these interfaces);
7892				g = USB_QUIRK_DELAY_INIT (device needs a pause
7893					during initialization, after we read
7894					the device descriptor);
7895				h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7896					high speed and super speed interrupt
7897					endpoints, the USB 2.0 and USB 3.0 spec
7898					require the interval in microframes (1
7899					microframe = 125 microseconds) to be
7900					calculated as interval = 2 ^
7901					(bInterval-1).
7902					Devices with this quirk report their
7903					bInterval as the result of this
7904					calculation instead of the exponent
7905					variable used in the calculation);
7906				i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7907					handle device_qualifier descriptor
7908					requests);
7909				j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7910					generates spurious wakeup, ignore
7911					remote wakeup capability);
7912				k = USB_QUIRK_NO_LPM (device can't handle Link
7913					Power Management);
7914				l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7915					(Device reports its bInterval as linear
7916					frames instead of the USB 2.0
7917					calculation);
7918				m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7919					to be disconnected before suspend to
7920					prevent spurious wakeup);
7921				n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7922					pause after every control message);
7923				o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7924					delay after resetting its port);
7925				p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT
7926					(Reduce timeout of the SET_ADDRESS
7927					request from 5000 ms to 500 ms);
7928			Example: quirks=0781:5580:bk,0a5c:5834:gij
7929
7930	usbhid.mousepoll=
7931			[USBHID] The interval which mice are to be polled at.
7932
7933	usbhid.jspoll=
7934			[USBHID] The interval which joysticks are to be polled at.
7935
7936	usbhid.kbpoll=
7937			[USBHID] The interval which keyboards are to be polled at.
7938
7939	usb-storage.delay_use=
7940			[UMS] The delay in seconds before a new device is
7941			scanned for Logical Units (default 1).
7942			Optionally the delay in milliseconds if the value has
7943			suffix with "ms".
7944			Example: delay_use=2567ms
7945
7946	usb-storage.quirks=
7947			[UMS] A list of quirks entries to supplement or
7948			override the built-in unusual_devs list.  List
7949			entries are separated by commas.  Each entry has
7950			the form VID:PID:Flags where VID and PID are Vendor
7951			and Product ID values (4-digit hex numbers) and
7952			Flags is a set of characters, each corresponding
7953			to a common usb-storage quirk flag as follows:
7954				a = SANE_SENSE (collect more than 18 bytes
7955					of sense data, not on uas);
7956				b = BAD_SENSE (don't collect more than 18
7957					bytes of sense data, not on uas);
7958				c = FIX_CAPACITY (decrease the reported
7959					device capacity by one sector);
7960				d = NO_READ_DISC_INFO (don't use
7961					READ_DISC_INFO command, not on uas);
7962				e = NO_READ_CAPACITY_16 (don't use
7963					READ_CAPACITY_16 command);
7964				f = NO_REPORT_OPCODES (don't use report opcodes
7965					command, uas only);
7966				g = MAX_SECTORS_240 (don't transfer more than
7967					240 sectors at a time, uas only);
7968				h = CAPACITY_HEURISTICS (decrease the
7969					reported device capacity by one
7970					sector if the number is odd);
7971				i = IGNORE_DEVICE (don't bind to this
7972					device);
7973				j = NO_REPORT_LUNS (don't use report luns
7974					command, uas only);
7975				k = NO_SAME (do not use WRITE_SAME, uas only)
7976				l = NOT_LOCKABLE (don't try to lock and
7977					unlock ejectable media, not on uas);
7978				m = MAX_SECTORS_64 (don't transfer more
7979					than 64 sectors = 32 KB at a time,
7980					not on uas);
7981				n = INITIAL_READ10 (force a retry of the
7982					initial READ(10) command, not on uas);
7983				o = CAPACITY_OK (accept the capacity
7984					reported by the device, not on uas);
7985				p = WRITE_CACHE (the device cache is ON
7986					by default, not on uas);
7987				r = IGNORE_RESIDUE (the device reports
7988					bogus residue values, not on uas);
7989				s = SINGLE_LUN (the device has only one
7990					Logical Unit);
7991				t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7992					commands, uas only);
7993				u = IGNORE_UAS (don't bind to the uas driver);
7994				w = NO_WP_DETECT (don't test whether the
7995					medium is write-protected).
7996				y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7997					even if the device claims no cache,
7998					not on uas)
7999			Example: quirks=0419:aaf5:rl,0421:0433:rc
8000
8001	user_debug=	[KNL,ARM]
8002			Format: <int>
8003			See arch/arm/Kconfig.debug help text.
8004				 1 - undefined instruction events
8005				 2 - system calls
8006				 4 - invalid data aborts
8007				 8 - SIGSEGV faults
8008				16 - SIGBUS faults
8009			Example: user_debug=31
8010
8011	vdso=		[X86,SH,SPARC]
8012			On X86_32, this is an alias for vdso32=.  Otherwise:
8013
8014			vdso=1: enable VDSO (the default)
8015			vdso=0: disable VDSO mapping
8016
8017	vdso32=		[X86] Control the 32-bit vDSO
8018			vdso32=1: enable 32-bit VDSO
8019			vdso32=0 or vdso32=2: disable 32-bit VDSO
8020
8021			See the help text for CONFIG_COMPAT_VDSO for more
8022			details.  If CONFIG_COMPAT_VDSO is set, the default is
8023			vdso32=0; otherwise, the default is vdso32=1.
8024
8025			For compatibility with older kernels, vdso32=2 is an
8026			alias for vdso32=0.
8027
8028			Try vdso32=0 if you encounter an error that says:
8029			dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
8030
8031	video=		[FB,EARLY] Frame buffer configuration
8032			See Documentation/fb/modedb.rst.
8033
8034	video.brightness_switch_enabled= [ACPI]
8035			Format: [0|1]
8036			If set to 1, on receiving an ACPI notify event
8037			generated by hotkey, video driver will adjust brightness
8038			level and then send out the event to user space through
8039			the allocated input device. If set to 0, video driver
8040			will only send out the event without touching backlight
8041			brightness level.
8042			default: 1
8043
8044	virtio_mmio.device=
8045			[VMMIO] Memory mapped virtio (platform) device.
8046
8047				<size>@<baseaddr>:<irq>[:<id>]
8048			where:
8049				<size>     := size (can use standard suffixes
8050						like K, M and G)
8051				<baseaddr> := physical base address
8052				<irq>      := interrupt number (as passed to
8053						request_irq())
8054				<id>       := (optional) platform device id
8055			example:
8056				virtio_mmio.device=1K@0x100b0000:48:7
8057
8058			Can be used multiple times for multiple devices.
8059
8060	vga=		[BOOT,X86-32] Select a particular video mode
8061			See Documentation/arch/x86/boot.rst and
8062			Documentation/admin-guide/svga.rst.
8063			Use vga=ask for menu.
8064			This is actually a boot loader parameter; the value is
8065			passed to the kernel using a special protocol.
8066
8067	vm_debug[=options]	[KNL] Available with CONFIG_DEBUG_VM=y.
8068			May slow down system boot speed, especially when
8069			enabled on systems with a large amount of memory.
8070			All options are enabled by default, and this
8071			interface is meant to allow for selectively
8072			enabling or disabling specific virtual memory
8073			debugging features.
8074
8075			Available options are:
8076			  P	Enable page structure init time poisoning
8077			  -	Disable all of the above options
8078
8079	vmalloc=nn[KMG]	[KNL,BOOT,EARLY] Forces the vmalloc area to have an
8080			exact size of <nn>. This can be used to increase
8081			the minimum size (128MB on x86, arm32 platforms).
8082			It can also be used to decrease the size and leave more room
8083			for directly mapped kernel RAM. Note that this parameter does
8084			not exist on many other platforms (including arm64, alpha,
8085			loongarch, arc, csky, hexagon, microblaze, mips, nios2, openrisc,
8086			parisc, m64k, powerpc, riscv, sh, um, xtensa, s390, sparc).
8087
8088	vmcp_cma=nn[MG]	[KNL,S390,EARLY]
8089			Sets the memory size reserved for contiguous memory
8090			allocations for the vmcp device driver.
8091
8092	vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
8093			Format: <command>
8094
8095	vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
8096			Format: <command>
8097
8098	vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
8099			Format: <command>
8100
8101	vmscape=	[X86] Controls mitigation for VMscape attacks.
8102			VMscape attacks can leak information from a userspace
8103			hypervisor to a guest via speculative side-channels.
8104
8105			off		- disable the mitigation
8106			ibpb		- use Indirect Branch Prediction Barrier
8107					  (IBPB) mitigation (default)
8108			force		- force vulnerability detection even on
8109					  unaffected processors
8110
8111	vsyscall=	[X86-64,EARLY]
8112			Controls the behavior of vsyscalls (i.e. calls to
8113			fixed addresses of 0xffffffffff600x00 from legacy
8114			code).  Most statically-linked binaries and older
8115			versions of glibc use these calls.  Because these
8116			functions are at fixed addresses, they make nice
8117			targets for exploits that can control RIP.
8118
8119			emulate     Vsyscalls turn into traps and are emulated
8120			            reasonably safely.  The vsyscall page is
8121				    readable.
8122
8123			xonly       [default] Vsyscalls turn into traps and are
8124			            emulated reasonably safely.  The vsyscall
8125				    page is not readable.
8126
8127			none        Vsyscalls don't work at all.  This makes
8128			            them quite hard to use for exploits but
8129			            might break your system.
8130
8131	vt.color=	[VT] Default text color.
8132			Format: 0xYX, X = foreground, Y = background.
8133			Default: 0x07 = light gray on black.
8134
8135	vt.cur_default=	[VT] Default cursor shape.
8136			Format: 0xCCBBAA, where AA, BB, and CC are the same as
8137			the parameters of the <Esc>[?A;B;Cc escape sequence;
8138			see vga-softcursor.rst. Default: 2 = underline.
8139
8140	vt.default_blu=	[VT]
8141			Format: <blue0>,<blue1>,<blue2>,...,<blue15>
8142			Change the default blue palette of the console.
8143			This is a 16-member array composed of values
8144			ranging from 0-255.
8145
8146	vt.default_grn=	[VT]
8147			Format: <green0>,<green1>,<green2>,...,<green15>
8148			Change the default green palette of the console.
8149			This is a 16-member array composed of values
8150			ranging from 0-255.
8151
8152	vt.default_red=	[VT]
8153			Format: <red0>,<red1>,<red2>,...,<red15>
8154			Change the default red palette of the console.
8155			This is a 16-member array composed of values
8156			ranging from 0-255.
8157
8158	vt.default_utf8=
8159			[VT]
8160			Format=<0|1>
8161			Set system-wide default UTF-8 mode for all tty's.
8162			Default is 1, i.e. UTF-8 mode is enabled for all
8163			newly opened terminals.
8164
8165	vt.global_cursor_default=
8166			[VT]
8167			Format=<-1|0|1>
8168			Set system-wide default for whether a cursor
8169			is shown on new VTs. Default is -1,
8170			i.e. cursors will be created by default unless
8171			overridden by individual drivers. 0 will hide
8172			cursors, 1 will display them.
8173
8174	vt.italic=	[VT] Default color for italic text; 0-15.
8175			Default: 2 = green.
8176
8177	vt.underline=	[VT] Default color for underlined text; 0-15.
8178			Default: 3 = cyan.
8179
8180	watchdog timers	[HW,WDT] For information on watchdog timers,
8181			see Documentation/watchdog/watchdog-parameters.rst
8182			or other driver-specific files in the
8183			Documentation/watchdog/ directory.
8184
8185	watchdog_thresh=
8186			[KNL]
8187			Set the hard lockup detector stall duration
8188			threshold in seconds. The soft lockup detector
8189			threshold is set to twice the value. A value of 0
8190			disables both lockup detectors. Default is 10
8191			seconds.
8192
8193	workqueue.unbound_cpus=
8194			[KNL,SMP] Specify to constrain one or some CPUs
8195			to use in unbound workqueues.
8196			Format: <cpu-list>
8197			By default, all online CPUs are available for
8198			unbound workqueues.
8199
8200	workqueue.watchdog_thresh=
8201			If CONFIG_WQ_WATCHDOG is configured, workqueue can
8202			warn stall conditions and dump internal state to
8203			help debugging.  0 disables workqueue stall
8204			detection; otherwise, it's the stall threshold
8205			duration in seconds.  The default value is 30 and
8206			it can be updated at runtime by writing to the
8207			corresponding sysfs file.
8208
8209	workqueue.panic_on_stall=<uint>
8210			Panic when workqueue stall is detected by
8211			CONFIG_WQ_WATCHDOG. It sets the number times of the
8212			stall to trigger panic.
8213
8214			The default is 0, which disables the panic on stall.
8215
8216	workqueue.cpu_intensive_thresh_us=
8217			Per-cpu work items which run for longer than this
8218			threshold are automatically considered CPU intensive
8219			and excluded from concurrency management to prevent
8220			them from noticeably delaying other per-cpu work
8221			items. Default is 10000 (10ms).
8222
8223			If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
8224			will report the work functions which violate this
8225			threshold repeatedly. They are likely good
8226			candidates for using WQ_UNBOUND workqueues instead.
8227
8228	workqueue.cpu_intensive_warning_thresh=<uint>
8229			If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
8230			will report the work functions which violate the
8231			intensive_threshold_us repeatedly. In order to prevent
8232			spurious warnings, start printing only after a work
8233			function has violated this threshold number of times.
8234
8235			The default is 4 times. 0 disables the warning.
8236
8237	workqueue.power_efficient
8238			Per-cpu workqueues are generally preferred because
8239			they show better performance thanks to cache
8240			locality; unfortunately, per-cpu workqueues tend to
8241			be more power hungry than unbound workqueues.
8242
8243			Enabling this makes the per-cpu workqueues which
8244			were observed to contribute significantly to power
8245			consumption unbound, leading to measurably lower
8246			power usage at the cost of small performance
8247			overhead.
8248
8249			The default value of this parameter is determined by
8250			the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
8251
8252        workqueue.default_affinity_scope=
8253			Select the default affinity scope to use for unbound
8254			workqueues. Can be one of "cpu", "smt", "cache",
8255			"numa" and "system". Default is "cache". For more
8256			information, see the Affinity Scopes section in
8257			Documentation/core-api/workqueue.rst.
8258
8259			This can be changed after boot by writing to the
8260			matching /sys/module/workqueue/parameters file. All
8261			workqueues with the "default" affinity scope will be
8262			updated accordingly.
8263
8264	workqueue.debug_force_rr_cpu
8265			Workqueue used to implicitly guarantee that work
8266			items queued without explicit CPU specified are put
8267			on the local CPU.  This guarantee is no longer true
8268			and while local CPU is still preferred work items
8269			may be put on foreign CPUs.  This debug option
8270			forces round-robin CPU selection to flush out
8271			usages which depend on the now broken guarantee.
8272			When enabled, memory and cache locality will be
8273			impacted.
8274
8275	writecombine=	[LOONGARCH,EARLY] Control the MAT (Memory Access
8276			Type) of ioremap_wc().
8277
8278			on   - Enable writecombine, use WUC for ioremap_wc()
8279			off  - Disable writecombine, use SUC for ioremap_wc()
8280
8281	x2apic_phys	[X86-64,APIC,EARLY] Use x2apic physical mode instead of
8282			default x2apic cluster mode on platforms
8283			supporting x2apic.
8284
8285	xen_512gb_limit		[KNL,X86-64,XEN]
8286			Restricts the kernel running paravirtualized under Xen
8287			to use only up to 512 GB of RAM. The reason to do so is
8288			crash analysis tools and Xen tools for doing domain
8289			save/restore/migration must be enabled to handle larger
8290			domains.
8291
8292	xen_emul_unplug=		[HW,X86,XEN,EARLY]
8293			Unplug Xen emulated devices
8294			Format: [unplug0,][unplug1]
8295			ide-disks -- unplug primary master IDE devices
8296			aux-ide-disks -- unplug non-primary-master IDE devices
8297			nics -- unplug network devices
8298			all -- unplug all emulated devices (NICs and IDE disks)
8299			unnecessary -- unplugging emulated devices is
8300				unnecessary even if the host did not respond to
8301				the unplug protocol
8302			never -- do not unplug even if version check succeeds
8303
8304	xen_legacy_crash	[X86,XEN,EARLY]
8305			Crash from Xen panic notifier, without executing late
8306			panic() code such as dumping handler.
8307
8308	xen_mc_debug	[X86,XEN,EARLY]
8309			Enable multicall debugging when running as a Xen PV guest.
8310			Enabling this feature will reduce performance a little
8311			bit, so it should only be enabled for obtaining extended
8312			debug data in case of multicall errors.
8313
8314	xen_msr_safe=	[X86,XEN,EARLY]
8315			Format: <bool>
8316			Select whether to always use non-faulting (safe) MSR
8317			access functions when running as Xen PV guest. The
8318			default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
8319
8320	xen_nopv	[X86]
8321			Disables the PV optimizations forcing the HVM guest to
8322			run as generic HVM guest with no PV drivers.
8323			This option is obsoleted by the "nopv" option, which
8324			has equivalent effect for XEN platform.
8325
8326	xen_no_vector_callback
8327			[KNL,X86,XEN,EARLY] Disable the vector callback for Xen
8328			event channel interrupts.
8329
8330	xen_scrub_pages=	[XEN]
8331			Boolean option to control scrubbing pages before giving them back
8332			to Xen, for use by other domains. Can be also changed at runtime
8333			with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
8334			Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
8335
8336	xen_timer_slop=	[X86-64,XEN,EARLY]
8337			Set the timer slop (in nanoseconds) for the virtual Xen
8338			timers (default is 100000). This adjusts the minimum
8339			delta of virtualized Xen timers, where lower values
8340			improve timer resolution at the expense of processing
8341			more timer interrupts.
8342
8343	xen.balloon_boot_timeout= [XEN]
8344			The time (in seconds) to wait before giving up to boot
8345			in case initial ballooning fails to free enough memory.
8346			Applies only when running as HVM or PVH guest and
8347			started with less memory configured than allowed at
8348			max. Default is 180.
8349
8350	xen.event_eoi_delay=	[XEN]
8351			How long to delay EOI handling in case of event
8352			storms (jiffies). Default is 10.
8353
8354	xen.event_loop_timeout=	[XEN]
8355			After which time (jiffies) the event handling loop
8356			should start to delay EOI handling. Default is 2.
8357
8358	xen.fifo_events=	[XEN]
8359			Boolean parameter to disable using fifo event handling
8360			even if available. Normally fifo event handling is
8361			preferred over the 2-level event handling, as it is
8362			fairer and the number of possible event channels is
8363			much higher. Default is on (use fifo events).
8364
8365	xirc2ps_cs=	[NET,PCMCIA]
8366			Format:
8367			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
8368
8369	xive=		[PPC]
8370			By default on POWER9 and above, the kernel will
8371			natively use the XIVE interrupt controller. This option
8372			allows the fallback firmware mode to be used:
8373
8374			off       Fallback to firmware control of XIVE interrupt
8375				  controller on both pseries and powernv
8376				  platforms. Only useful on POWER9 and above.
8377
8378	xive.store-eoi=off	[PPC]
8379			By default on POWER10 and above, the kernel will use
8380			stores for EOI handling when the XIVE interrupt mode
8381			is active. This option allows the XIVE driver to use
8382			loads instead, as on POWER9.
8383
8384	xhci-hcd.quirks		[USB,KNL]
8385			A hex value specifying bitmask with supplemental xhci
8386			host controller quirks. Meaning of each bit can be
8387			consulted in header drivers/usb/host/xhci.h.
8388
8389	xmon		[PPC,EARLY]
8390			Format: { early | on | rw | ro | off }
8391			Controls if xmon debugger is enabled. Default is off.
8392			Passing only "xmon" is equivalent to "xmon=early".
8393			early	Call xmon as early as possible on boot; xmon
8394				debugger is called from setup_arch().
8395			on	xmon debugger hooks will be installed so xmon
8396				is only called on a kernel crash. Default mode,
8397				i.e. either "ro" or "rw" mode, is controlled
8398				with CONFIG_XMON_DEFAULT_RO_MODE.
8399			rw	xmon debugger hooks will be installed so xmon
8400				is called only on a kernel crash, mode is write,
8401				meaning SPR registers, memory and, other data
8402				can be written using xmon commands.
8403			ro 	same as "rw" option above but SPR registers,
8404				memory, and other data can't be written using
8405				xmon commands.
8406			off	xmon is disabled.
8407