xref: /linux/Documentation/admin-guide/kernel-parameters.txt (revision 2c1ed907520c50326b8f604907a8478b27881a2e)
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			For X86-32, this can also be used to specify an APIC
420			driver name.
421			Format: apic=driver_name
422			Examples: apic=bigsmp
423
424	apic_extnmi=	[APIC,X86,EARLY] External NMI delivery setting
425			Format: { bsp (default) | all | none }
426			bsp:  External NMI is delivered only to CPU 0
427			all:  External NMIs are broadcast to all CPUs as a
428			      backup of CPU 0
429			none: External NMI is masked for all CPUs. This is
430			      useful so that a dump capture kernel won't be
431			      shot down by NMI
432
433	apicpmtimer	Do APIC timer calibration using the pmtimer. Implies
434			apicmaintimer. Useful when your PIT timer is totally
435			broken.
436
437	autoconf=	[IPV6]
438			See Documentation/networking/ipv6.rst.
439
440	apm=		[APM] Advanced Power Management
441			See header of arch/x86/kernel/apm_32.c.
442
443	apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
444			Format: { "0" | "1" }
445			See security/apparmor/Kconfig help text
446			0 -- disable.
447			1 -- enable.
448			Default value is set via kernel config option.
449
450	arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
451			Format: <io>,<irq>,<nodeID>
452
453	arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
454			32 bit applications.
455
456	arm64.nobti	[ARM64] Unconditionally disable Branch Target
457			Identification support
458
459	arm64.nogcs	[ARM64] Unconditionally disable Guarded Control Stack
460			support
461
462	arm64.nomops	[ARM64] Unconditionally disable Memory Copy and Memory
463			Set instructions support
464
465	arm64.nomte	[ARM64] Unconditionally disable Memory Tagging Extension
466			support
467
468	arm64.nopauth	[ARM64] Unconditionally disable Pointer Authentication
469			support
470
471	arm64.nosme	[ARM64] Unconditionally disable Scalable Matrix
472			Extension support
473
474	arm64.nosve	[ARM64] Unconditionally disable Scalable Vector
475			Extension support
476
477	ataflop=	[HW,M68k]
478
479	atarimouse=	[HW,MOUSE] Atari Mouse
480
481	atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
482			EzKey and similar keyboards
483
484	atkbd.reset=	[HW] Reset keyboard during initialization
485
486	atkbd.set=	[HW] Select keyboard code set
487			Format: <int> (2 = AT (default), 3 = PS/2)
488
489	atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
490			keyboards
491
492	atkbd.softraw=	[HW] Choose between synthetic and real raw mode
493			Format: <bool> (0 = real, 1 = synthetic (default))
494
495	atkbd.softrepeat= [HW]
496			Use software keyboard repeat
497
498	audit=		[KNL] Enable the audit sub-system
499			Format: { "0" | "1" | "off" | "on" }
500			0 | off - kernel audit is disabled and can not be
501			    enabled until the next reboot
502			unset - kernel audit is initialized but disabled and
503			    will be fully enabled by the userspace auditd.
504			1 | on - kernel audit is initialized and partially
505			    enabled, storing at most audit_backlog_limit
506			    messages in RAM until it is fully enabled by the
507			    userspace auditd.
508			Default: unset
509
510	audit_backlog_limit= [KNL] Set the audit queue size limit.
511			Format: <int> (must be >=0)
512			Default: 64
513
514	bau=		[X86_UV] Enable the BAU on SGI UV.  The default
515			behavior is to disable the BAU (i.e. bau=0).
516			Format: { "0" | "1" }
517			0 - Disable the BAU.
518			1 - Enable the BAU.
519			unset - Disable the BAU.
520
521	baycom_epp=	[HW,AX25]
522			Format: <io>,<mode>
523
524	baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
525			Format: <io>,<mode>
526			See header of drivers/net/hamradio/baycom_par.c.
527
528	baycom_ser_fdx=	[HW,AX25]
529			BayCom Serial Port AX.25 Modem (Full Duplex Mode)
530			Format: <io>,<irq>,<mode>[,<baud>]
531			See header of drivers/net/hamradio/baycom_ser_fdx.c.
532
533	baycom_ser_hdx=	[HW,AX25]
534			BayCom Serial Port AX.25 Modem (Half Duplex Mode)
535			Format: <io>,<irq>,<mode>
536			See header of drivers/net/hamradio/baycom_ser_hdx.c.
537
538	bdev_allow_write_mounted=
539			Format: <bool>
540			Control the ability to open a mounted block device
541			for writing, i.e., allow / disallow writes that bypass
542			the FS. This was implemented as a means to prevent
543			fuzzers from crashing the kernel by overwriting the
544			metadata underneath a mounted FS without its awareness.
545			This also prevents destructive formatting of mounted
546			filesystems by naive storage tooling that don't use
547			O_EXCL. Default is Y and can be changed through the
548			Kconfig option CONFIG_BLK_DEV_WRITE_MOUNTED.
549
550	bert_disable	[ACPI]
551			Disable BERT OS support on buggy BIOSes.
552
553	bgrt_disable	[ACPI,X86,EARLY]
554			Disable BGRT to avoid flickering OEM logo.
555
556	blkdevparts=	Manual partition parsing of block device(s) for
557			embedded devices based on command line input.
558			See Documentation/block/cmdline-partition.rst
559
560	boot_delay=	[KNL,EARLY]
561			Milliseconds to delay each printk during boot.
562			Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
563			and you may also have to specify "lpj=".  Boot_delay
564			values larger than 10 seconds (10000) are assumed
565			erroneous and ignored.
566			Format: integer
567
568	bootconfig	[KNL,EARLY]
569			Extended command line options can be added to an initrd
570			and this will cause the kernel to look for it.
571
572			See Documentation/admin-guide/bootconfig.rst
573
574	bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
575	bttv.radio=	Most important insmod options are available as
576			kernel args too.
577	bttv.pll=	See Documentation/admin-guide/media/bttv.rst
578	bttv.tuner=
579
580	bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
581			firmware feature for flushing multiple hpte entries
582			at a time.
583
584	c101=		[NET] Moxa C101 synchronous serial card
585
586	cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
587			Sometimes CPU hardware bugs make them report the cache
588			size incorrectly. The kernel will attempt work arounds
589			to fix known problems, but for some CPUs it is not
590			possible to determine what the correct size should be.
591			This option provides an override for these situations.
592
593	carrier_timeout=
594			[NET] Specifies amount of time (in seconds) that
595			the kernel should wait for a network carrier. By default
596			it waits 120 seconds.
597
598	ca_keys=	[KEYS] This parameter identifies a specific key(s) on
599			the system trusted keyring to be used for certificate
600			trust validation.
601			format: { id:<keyid> | builtin }
602
603	cca=		[MIPS,EARLY] Override the kernel pages' cache coherency
604			algorithm.  Accepted values range from 0 to 7
605			inclusive. See arch/mips/include/asm/pgtable-bits.h
606			for platform specific values (SB1, Loongson3 and
607			others).
608
609	ccw_timeout_log	[S390]
610			See Documentation/arch/s390/common_io.rst for details.
611
612	cgroup_disable=	[KNL] Disable a particular controller or optional feature
613			Format: {name of the controller(s) or feature(s) to disable}
614			The effects of cgroup_disable=foo are:
615			- foo isn't auto-mounted if you mount all cgroups in
616			  a single hierarchy
617			- foo isn't visible as an individually mountable
618			  subsystem
619			- if foo is an optional feature then the feature is
620			  disabled and corresponding cgroup files are not
621			  created
622			{Currently only "memory" controller deal with this and
623			cut the overhead, others just disable the usage. So
624			only cgroup_disable=memory is actually worthy}
625			Specifying "pressure" disables per-cgroup pressure
626			stall information accounting feature
627
628	cgroup_no_v1=	[KNL] Disable cgroup controllers and named hierarchies in v1
629			Format: { { controller | "all" | "named" }
630			          [,{ controller | "all" | "named" }...] }
631			Like cgroup_disable, but only applies to cgroup v1;
632			the blacklisted controllers remain available in cgroup2.
633			"all" blacklists all controllers and "named" disables
634			named mounts. Specifying both "all" and "named" disables
635			all v1 hierarchies.
636
637	cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
638			Format: { "true" | "false" }
639			Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.
640
641	cgroup.memory=	[KNL] Pass options to the cgroup memory controller.
642			Format: <string>
643			nosocket -- Disable socket memory accounting.
644			nokmem -- Disable kernel memory accounting.
645			nobpf -- Disable BPF memory accounting.
646
647	checkreqprot=	[SELINUX] Set initial checkreqprot flag value.
648			Format: { "0" | "1" }
649			See security/selinux/Kconfig help text.
650			0 -- check protection applied by kernel (includes
651				any implied execute protection).
652			1 -- check protection requested by application.
653			Default value is set via a kernel config option.
654			Value can be changed at runtime via
655				/sys/fs/selinux/checkreqprot.
656			Setting checkreqprot to 1 is deprecated.
657
658	cio_ignore=	[S390]
659			See Documentation/arch/s390/common_io.rst for details.
660
661	clearcpuid=X[,X...] [X86]
662			Disable CPUID feature X for the kernel. See
663			arch/x86/include/asm/cpufeatures.h for the valid bit
664			numbers X. Note the Linux-specific bits are not necessarily
665			stable over kernel options, but the vendor-specific
666			ones should be.
667			X can also be a string as appearing in the flags: line
668			in /proc/cpuinfo which does not have the above
669			instability issue. However, not all features have names
670			in /proc/cpuinfo.
671			Note that using this option will taint your kernel.
672			Also note that user programs calling CPUID directly
673			or using the feature without checking anything
674			will still see it. This just prevents it from
675			being used by the kernel or shown in /proc/cpuinfo.
676			Also note the kernel might malfunction if you disable
677			some critical bits.
678
679	clk_ignore_unused
680			[CLK]
681			Prevents the clock framework from automatically gating
682			clocks that have not been explicitly enabled by a Linux
683			device driver but are enabled in hardware at reset or
684			by the bootloader/firmware. Note that this does not
685			force such clocks to be always-on nor does it reserve
686			those clocks in any way. This parameter is useful for
687			debug and development, but should not be needed on a
688			platform with proper driver support.  For more
689			information, see Documentation/driver-api/clk.rst.
690
691	clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
692			[Deprecated]
693			Forces specified clocksource (if available) to be used
694			when calculating gettimeofday(). If specified
695			clocksource is not available, it defaults to PIT.
696			Format: { pit | tsc | cyclone | pmtmr }
697
698	clocksource=	Override the default clocksource
699			Format: <string>
700			Override the default clocksource and use the clocksource
701			with the name specified.
702			Some clocksource names to choose from, depending on
703			the platform:
704			[all] jiffies (this is the base, fallback clocksource)
705			[ACPI] acpi_pm
706			[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
707				pxa_timer,timer3,32k_counter,timer0_1
708			[X86-32] pit,hpet,tsc;
709				scx200_hrt on Geode; cyclone on IBM x440
710			[MIPS] MIPS
711			[PARISC] cr16
712			[S390] tod
713			[SH] SuperH
714			[SPARC64] tick
715			[X86-64] hpet,tsc
716
717	clocksource.arm_arch_timer.evtstrm=
718			[ARM,ARM64,EARLY]
719			Format: <bool>
720			Enable/disable the eventstream feature of the ARM
721			architected timer so that code using WFE-based polling
722			loops can be debugged more effectively on production
723			systems.
724
725	clocksource.verify_n_cpus= [KNL]
726			Limit the number of CPUs checked for clocksources
727			marked with CLOCK_SOURCE_VERIFY_PERCPU that
728			are marked unstable due to excessive skew.
729			A negative value says to check all CPUs, while
730			zero says not to check any.  Values larger than
731			nr_cpu_ids are silently truncated to nr_cpu_ids.
732			The actual CPUs are chosen randomly, with
733			no replacement if the same CPU is chosen twice.
734
735	clocksource-wdtest.holdoff= [KNL]
736			Set the time in seconds that the clocksource
737			watchdog test waits before commencing its tests.
738			Defaults to zero when built as a module and to
739			10 seconds when built into the kernel.
740
741	cma=nn[MG]@[start[MG][-end[MG]]]
742			[KNL,CMA,EARLY]
743			Sets the size of kernel global memory area for
744			contiguous memory allocations and optionally the
745			placement constraint by the physical address range of
746			memory allocations. A value of 0 disables CMA
747			altogether. For more information, see
748			kernel/dma/contiguous.c
749
750	cma_pernuma=nn[MG]
751			[KNL,CMA,EARLY]
752			Sets the size of kernel per-numa memory area for
753			contiguous memory allocations. A value of 0 disables
754			per-numa CMA altogether. And If this option is not
755			specified, the default value is 0.
756			With per-numa CMA enabled, DMA users on node nid will
757			first try to allocate buffer from the pernuma area
758			which is located in node nid, if the allocation fails,
759			they will fallback to the global default memory area.
760
761	numa_cma=<node>:nn[MG][,<node>:nn[MG]]
762			[KNL,CMA,EARLY]
763			Sets the size of kernel numa memory area for
764			contiguous memory allocations. It will reserve CMA
765			area for the specified node.
766
767			With numa CMA enabled, DMA users on node nid will
768			first try to allocate buffer from the numa area
769			which is located in node nid, if the allocation fails,
770			they will fallback to the global default memory area.
771
772	cmo_free_hint=	[PPC] Format: { yes | no }
773			Specify whether pages are marked as being inactive
774			when they are freed.  This is used in CMO environments
775			to determine OS memory pressure for page stealing by
776			a hypervisor.
777			Default: yes
778
779	coherent_pool=nn[KMG]	[ARM,KNL,EARLY]
780			Sets the size of memory pool for coherent, atomic dma
781			allocations, by default set to 256K.
782
783	com20020=	[HW,NET] ARCnet - COM20020 chipset
784			Format:
785			<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
786
787	com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
788			Format: <io>[,<irq>]
789
790	com90xx=	[HW,NET]
791			ARCnet - COM90xx chipset (memory-mapped buffers)
792			Format: <io>[,<irq>[,<memstart>]]
793
794	condev=		[HW,S390] console device
795	conmode=
796
797	con3215_drop=	[S390,EARLY] 3215 console drop mode.
798			Format: y|n|Y|N|1|0
799			When set to true, drop data on the 3215 console when
800			the console buffer is full. In this case the
801			operator using a 3270 terminal emulator (for example
802			x3270) does not have to enter the clear key for the
803			console output to advance and the kernel to continue.
804			This leads to a much faster boot time when a 3270
805			terminal emulator is active. If no 3270 terminal
806			emulator is used, this parameter has no effect.
807
808	console=	[KNL] Output console device and options.
809
810		tty<n>	Use the virtual console device <n>.
811
812		ttyS<n>[,options]
813		ttyUSB0[,options]
814			Use the specified serial port.  The options are of
815			the form "bbbbpnf", where "bbbb" is the baud rate,
816			"p" is parity ("n", "o", or "e"), "n" is number of
817			bits, and "f" is flow control ("r" for RTS or
818			omit it).  Default is "9600n8".
819
820			See Documentation/admin-guide/serial-console.rst for more
821			information.  See
822			Documentation/networking/netconsole.rst for an
823			alternative.
824
825		<DEVNAME>:<n>.<n>[,options]
826			Use the specified serial port on the serial core bus.
827			The addressing uses DEVNAME of the physical serial port
828			device, followed by the serial core controller instance,
829			and the serial port instance. The options are the same
830			as documented for the ttyS addressing above.
831
832			The mapping of the serial ports to the tty instances
833			can be viewed with:
834
835			$ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
836			/sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
837
838			In the above example, the console can be addressed with
839			console=00:04:0.0. Note that a console addressed this
840			way will only get added when the related device driver
841			is ready. The use of an earlycon parameter in addition to
842			the console may be desired for console output early on.
843
844		uart[8250],io,<addr>[,options]
845		uart[8250],mmio,<addr>[,options]
846		uart[8250],mmio16,<addr>[,options]
847		uart[8250],mmio32,<addr>[,options]
848		uart[8250],0x<addr>[,options]
849			Start an early, polled-mode console on the 8250/16550
850			UART at the specified I/O port or MMIO address,
851			switching to the matching ttyS device later.
852			MMIO inter-register address stride is either 8-bit
853			(mmio), 16-bit (mmio16), or 32-bit (mmio32).
854			If none of [io|mmio|mmio16|mmio32], <addr> is assumed
855			to be equivalent to 'mmio'. 'options' are specified in
856			the same format described for ttyS above; if unspecified,
857			the h/w is not re-initialized.
858
859		hvc<n>	Use the hypervisor console device <n>. This is for
860			both Xen and PowerPC hypervisors.
861
862		{ null | "" }
863			Use to disable console output, i.e., to have kernel
864			console messages discarded.
865			This must be the only console= parameter used on the
866			kernel command line.
867
868		If the device connected to the port is not a TTY but a braille
869		device, prepend "brl," before the device type, for instance
870			console=brl,ttyS0
871		For now, only VisioBraille is supported.
872
873	console_msg_format=
874			[KNL] Change console messages format
875		default
876			By default we print messages on consoles in
877			"[time stamp] text\n" format (time stamp may not be
878			printed, depending on CONFIG_PRINTK_TIME or
879			`printk_time' param).
880		syslog
881			Switch to syslog format: "<%u>[time stamp] text\n"
882			IOW, each message will have a facility and loglevel
883			prefix. The format is similar to one used by syslog()
884			syscall, or to executing "dmesg -S --raw" or to reading
885			from /proc/kmsg.
886
887	consoleblank=	[KNL] The console blank (screen saver) timeout in
888			seconds. A value of 0 disables the blank timer.
889			Defaults to 0.
890
891	coredump_filter=
892			[KNL] Change the default value for
893			/proc/<pid>/coredump_filter.
894			See also Documentation/filesystems/proc.rst.
895
896	coresight_cpu_debug.enable
897			[ARM,ARM64]
898			Format: <bool>
899			Enable/disable the CPU sampling based debugging.
900			0: default value, disable debugging
901			1: enable debugging at boot time
902
903	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
904			Format:
905			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
906
907	cpuidle.off=1	[CPU_IDLE]
908			disable the cpuidle sub-system
909
910	cpuidle.governor=
911			[CPU_IDLE] Name of the cpuidle governor to use.
912
913	cpufreq.off=1	[CPU_FREQ]
914			disable the cpufreq sub-system
915
916	cpufreq.default_governor=
917			[CPU_FREQ] Name of the default cpufreq governor or
918			policy to use. This governor must be registered in the
919			kernel before the cpufreq driver probes.
920
921	cpu_init_udelay=N
922			[X86,EARLY] Delay for N microsec between assert and de-assert
923			of APIC INIT to start processors.  This delay occurs
924			on every CPU online, such as boot, and resume from suspend.
925			Default: 10000
926
927	cpuhp.parallel=
928			[SMP] Enable/disable parallel bringup of secondary CPUs
929			Format: <bool>
930			Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
931			the parameter has no effect.
932
933	crash_kexec_post_notifiers
934			Only jump to kdump kernel after running the panic
935			notifiers and dumping kmsg. This option increases
936			the risks of a kdump failure, since some panic
937			notifiers can make the crashed kernel more unstable.
938			In configurations where kdump may not be reliable,
939			running the panic notifiers could allow collecting
940			more data on dmesg, like stack traces from other CPUS
941			or extra data dumped by panic_print. Note that some
942			configurations enable this option unconditionally,
943			like Hyper-V, PowerPC (fadump) and AMD SEV-SNP.
944
945	crashkernel=size[KMG][@offset[KMG]]
946			[KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'
947			upon panic. This parameter reserves the physical
948			memory region [offset, offset + size] for that kernel
949			image. If '@offset' is omitted, then a suitable offset
950			is selected automatically.
951			[KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
952			under 4G first, and fall back to reserve region above
953			4G when '@offset' hasn't been specified.
954			See Documentation/admin-guide/kdump/kdump.rst for further details.
955
956	crashkernel=range1:size1[,range2:size2,...][@offset]
957			[KNL] Same as above, but depends on the memory
958			in the running system. The syntax of range is
959			start-[end] where start and end are both
960			a memory unit (amount[KMG]). See also
961			Documentation/admin-guide/kdump/kdump.rst for an example.
962
963	crashkernel=size[KMG],high
964			[KNL, X86-64, ARM64, RISCV, LoongArch] range could be
965			above 4G.
966			Allow kernel to allocate physical memory region from top,
967			so could be above 4G if system have more than 4G ram
968			installed. Otherwise memory region will be allocated
969			below 4G, if available.
970			It will be ignored if crashkernel=X is specified.
971	crashkernel=size[KMG],low
972			[KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
973			When crashkernel=X,high is passed, kernel could allocate
974			physical memory region above 4G, that cause second kernel
975			crash on system that require some amount of low memory,
976			e.g. swiotlb requires at least 64M+32K low memory, also
977			enough extra low memory is needed to make sure DMA buffers
978			for 32-bit devices won't run out. Kernel would try to allocate
979			default	size of memory below 4G automatically. The default
980			size is	platform dependent.
981			  --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
982			  --> arm64: 128MiB
983			  --> riscv: 128MiB
984			  --> loongarch: 128MiB
985			This one lets the user specify own low range under 4G
986			for second kernel instead.
987			0: to disable low allocation.
988			It will be ignored when crashkernel=X,high is not used
989			or memory reserved is below 4G.
990
991	cryptomgr.notests
992			[KNL] Disable crypto self-tests
993
994	cs89x0_dma=	[HW,NET]
995			Format: <dma>
996
997	cs89x0_media=	[HW,NET]
998			Format: { rj45 | aui | bnc }
999
1000	csdlock_debug=	[KNL] Enable or disable debug add-ons of cross-CPU
1001			function call handling. When switched on,
1002			additional debug data is printed to the console
1003			in case a hanging CPU is detected, and that
1004			CPU is pinged again in order to try to resolve
1005			the hang situation.  The default value of this
1006			option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
1007			Kconfig option.
1008
1009	dasd=		[HW,NET]
1010			See header of drivers/s390/block/dasd_devmap.c.
1011
1012	db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
1013			(one device per port)
1014			Format: <port#>,<type>
1015			See also Documentation/input/devices/joystick-parport.rst
1016
1017	debug		[KNL,EARLY] Enable kernel debugging (events log level).
1018
1019	debug_boot_weak_hash
1020			[KNL,EARLY] Enable printing [hashed] pointers early in the
1021			boot sequence.  If enabled, we use a weak hash instead
1022			of siphash to hash pointers.  Use this option if you are
1023			seeing instances of '(___ptrval___)') and need to see a
1024			value (hashed pointer) instead. Cryptographically
1025			insecure, please do not use on production kernels.
1026
1027	debug_locks_verbose=
1028			[KNL] verbose locking self-tests
1029			Format: <int>
1030			Print debugging info while doing the locking API
1031			self-tests.
1032			Bitmask for the various LOCKTYPE_ tests. Defaults to 0
1033			(no extra messages), setting it to -1 (all bits set)
1034			will print _a_lot_ more information - normally only
1035			useful to lockdep developers.
1036
1037	debug_objects	[KNL,EARLY] Enable object debugging
1038
1039	debug_guardpage_minorder=
1040			[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this
1041			parameter allows control of the order of pages that will
1042			be intentionally kept free (and hence protected) by the
1043			buddy allocator. Bigger value increase the probability
1044			of catching random memory corruption, but reduce the
1045			amount of memory for normal system use. The maximum
1046			possible value is MAX_PAGE_ORDER/2.  Setting this
1047			parameter to 1 or 2 should be enough to identify most
1048			random memory corruption problems caused by bugs in
1049			kernel or driver code when a CPU writes to (or reads
1050			from) a random memory location. Note that there exists
1051			a class of memory corruptions problems caused by buggy
1052			H/W or F/W or by drivers badly programming DMA
1053			(basically when memory is written at bus level and the
1054			CPU MMU is bypassed) which are not detectable by
1055			CONFIG_DEBUG_PAGEALLOC, hence this option will not
1056			help tracking down these problems.
1057
1058	debug_pagealloc=
1059			[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1060			enables the feature at boot time. By default, it is
1061			disabled and the system will work mostly the same as a
1062			kernel built without CONFIG_DEBUG_PAGEALLOC.
1063			Note: to get most of debug_pagealloc error reports, it's
1064			useful to also enable the page_owner functionality.
1065			on: enable the feature
1066
1067	debugfs=    	[KNL,EARLY] This parameter enables what is exposed to
1068			userspace and debugfs internal clients.
1069			Format: { on, no-mount, off }
1070			on: 	All functions are enabled.
1071			no-mount:
1072				Filesystem is not registered but kernel clients can
1073			        access APIs and a crashkernel can be used to read
1074				its content. There is nothing to mount.
1075			off: 	Filesystem is not registered and clients
1076			        get a -EPERM as result when trying to register files
1077				or directories within debugfs.
1078				This is equivalent of the runtime functionality if
1079				debugfs was not enabled in the kernel at all.
1080			Default value is set in build-time with a kernel configuration.
1081
1082	debugpat	[X86] Enable PAT debugging
1083
1084	default_hugepagesz=
1085			[HW] The size of the default HugeTLB page. This is
1086			the size represented by the legacy /proc/ hugepages
1087			APIs.  In addition, this is the default hugetlb size
1088			used for shmget(), mmap() and mounting hugetlbfs
1089			filesystems.  If not specified, defaults to the
1090			architecture's default huge page size.  Huge page
1091			sizes are architecture dependent.  See also
1092			Documentation/admin-guide/mm/hugetlbpage.rst.
1093			Format: size[KMG]
1094
1095	deferred_probe_timeout=
1096			[KNL] Debugging option to set a timeout in seconds for
1097			deferred probe to give up waiting on dependencies to
1098			probe. Only specific dependencies (subsystems or
1099			drivers) that have opted in will be ignored. A timeout
1100			of 0 will timeout at the end of initcalls. If the time
1101			out hasn't expired, it'll be restarted by each
1102			successful driver registration. This option will also
1103			dump out devices still on the deferred probe list after
1104			retrying.
1105
1106	delayacct	[KNL] Enable per-task delay accounting
1107
1108	dell_smm_hwmon.ignore_dmi=
1109			[HW] Continue probing hardware even if DMI data
1110			indicates that the driver is running on unsupported
1111			hardware.
1112
1113	dell_smm_hwmon.force=
1114			[HW] Activate driver even if SMM BIOS signature does
1115			not match list of supported models and enable otherwise
1116			blacklisted features.
1117
1118	dell_smm_hwmon.power_status=
1119			[HW] Report power status in /proc/i8k
1120			(disabled by default).
1121
1122	dell_smm_hwmon.restricted=
1123			[HW] Allow controlling fans only if SYS_ADMIN
1124			capability is set.
1125
1126	dell_smm_hwmon.fan_mult=
1127			[HW] Factor to multiply fan speed with.
1128
1129	dell_smm_hwmon.fan_max=
1130			[HW] Maximum configurable fan speed.
1131
1132	dfltcc=		[HW,S390]
1133			Format: { on | off | def_only | inf_only | always }
1134			on:       s390 zlib hardware support for compression on
1135			          level 1 and decompression (default)
1136			off:      No s390 zlib hardware support
1137			def_only: s390 zlib hardware support for deflate
1138			          only (compression on level 1)
1139			inf_only: s390 zlib hardware support for inflate
1140			          only (decompression)
1141			always:   Same as 'on' but ignores the selected compression
1142			          level always using hardware support (used for debugging)
1143
1144	dhash_entries=	[KNL]
1145			Set number of hash buckets for dentry cache.
1146
1147	disable_1tb_segments [PPC,EARLY]
1148			Disables the use of 1TB hash page table segments. This
1149			causes the kernel to fall back to 256MB segments which
1150			can be useful when debugging issues that require an SLB
1151			miss to occur.
1152
1153	disable=	[IPV6]
1154			See Documentation/networking/ipv6.rst.
1155
1156	disable_radix	[PPC,EARLY]
1157			Disable RADIX MMU mode on POWER9
1158
1159	disable_tlbie	[PPC]
1160			Disable TLBIE instruction. Currently does not work
1161			with KVM, with HASH MMU, or with coherent accelerators.
1162
1163	disable_ddw	[PPC/PSERIES,EARLY]
1164			Disable Dynamic DMA Window support. Use this
1165			to workaround buggy firmware.
1166
1167	disable_ipv6=	[IPV6]
1168			See Documentation/networking/ipv6.rst.
1169
1170	disable_mtrr_cleanup [X86,EARLY]
1171			The kernel tries to adjust MTRR layout from continuous
1172			to discrete, to make X server driver able to add WB
1173			entry later. This parameter disables that.
1174
1175	disable_mtrr_trim [X86, Intel and AMD only,EARLY]
1176			By default the kernel will trim any uncacheable
1177			memory out of your available memory pool based on
1178			MTRR settings.  This parameter disables that behavior,
1179			possibly causing your machine to run very slowly.
1180
1181	disable_timer_pin_1 [X86,EARLY]
1182			Disable PIN 1 of APIC timer
1183			Can be useful to work around chipset bugs.
1184
1185	dis_ucode_ldr	[X86] Disable the microcode loader.
1186
1187	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
1188			this option disables the debugging code at boot.
1189
1190	dma_debug_entries=<number>
1191			This option allows to tune the number of preallocated
1192			entries for DMA-API debugging code. One entry is
1193			required per DMA-API allocation. Use this if the
1194			DMA-API debugging code disables itself because the
1195			architectural default is too low.
1196
1197	dma_debug_driver=<driver_name>
1198			With this option the DMA-API debugging driver
1199			filter feature can be enabled at boot time. Just
1200			pass the driver to filter for as the parameter.
1201			The filter can be disabled or changed to another
1202			driver later using sysfs.
1203
1204	reg_file_data_sampling=
1205			[X86] Controls mitigation for Register File Data
1206			Sampling (RFDS) vulnerability. RFDS is a CPU
1207			vulnerability which may allow userspace to infer
1208			kernel data values previously stored in floating point
1209			registers, vector registers, or integer registers.
1210			RFDS only affects Intel Atom processors.
1211
1212			on:	Turns ON the mitigation.
1213			off:	Turns OFF the mitigation.
1214
1215			This parameter overrides the compile time default set
1216			by CONFIG_MITIGATION_RFDS. Mitigation cannot be
1217			disabled when other VERW based mitigations (like MDS)
1218			are enabled. In order to disable RFDS mitigation all
1219			VERW based mitigations need to be disabled.
1220
1221			For details see:
1222			Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1223
1224	driver_async_probe=  [KNL]
1225			List of driver names to be probed asynchronously. *
1226			matches with all driver names. If * is specified, the
1227			rest of the listed driver names are those that will NOT
1228			match the *.
1229			Format: <driver_name1>,<driver_name2>...
1230
1231	drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1232			Broken monitors, graphic adapters, KVMs and EDIDless
1233			panels may send no or incorrect EDID data sets.
1234			This parameter allows to specify an EDID data sets
1235			in the /lib/firmware directory that are used instead.
1236			An EDID data set will only be used for a particular
1237			connector, if its name and a colon are prepended to
1238			the EDID name. Each connector may use a unique EDID
1239			data set by separating the files with a comma. An EDID
1240			data set with no connector name will be used for
1241			any connectors not explicitly specified.
1242
1243	dscc4.setup=	[NET]
1244
1245	dt_cpu_ftrs=	[PPC,EARLY]
1246			Format: {"off" | "known"}
1247			Control how the dt_cpu_ftrs device-tree binding is
1248			used for CPU feature discovery and setup (if it
1249			exists).
1250			off: Do not use it, fall back to legacy cpu table.
1251			known: Do not pass through unknown features to guests
1252			or userspace, only those that the kernel is aware of.
1253
1254	dump_apple_properties	[X86]
1255			Dump name and content of EFI device properties on
1256			x86 Macs.  Useful for driver authors to determine
1257			what data is available or for reverse-engineering.
1258
1259	dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
1260	<module>.dyndbg[="val"]
1261			Enable debug messages at boot time.  See
1262			Documentation/admin-guide/dynamic-debug-howto.rst
1263			for details.
1264
1265	early_ioremap_debug [KNL,EARLY]
1266			Enable debug messages in early_ioremap support. This
1267			is useful for tracking down temporary early mappings
1268			which are not unmapped.
1269
1270	earlycon=	[KNL,EARLY] Output early console device and options.
1271
1272			When used with no options, the early console is
1273			determined by stdout-path property in device tree's
1274			chosen node or the ACPI SPCR table if supported by
1275			the platform.
1276
1277		cdns,<addr>[,options]
1278			Start an early, polled-mode console on a Cadence
1279			(xuartps) serial port at the specified address. Only
1280			supported option is baud rate. If baud rate is not
1281			specified, the serial port must already be setup and
1282			configured.
1283
1284		uart[8250],io,<addr>[,options[,uartclk]]
1285		uart[8250],mmio,<addr>[,options[,uartclk]]
1286		uart[8250],mmio32,<addr>[,options[,uartclk]]
1287		uart[8250],mmio32be,<addr>[,options[,uartclk]]
1288		uart[8250],0x<addr>[,options]
1289			Start an early, polled-mode console on the 8250/16550
1290			UART at the specified I/O port or MMIO address.
1291			MMIO inter-register address stride is either 8-bit
1292			(mmio) or 32-bit (mmio32 or mmio32be).
1293			If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1294			to be equivalent to 'mmio'. 'options' are specified
1295			in the same format described for "console=ttyS<n>"; if
1296			unspecified, the h/w is not initialized. 'uartclk' is
1297			the uart clock frequency; if unspecified, it is set
1298			to 'BASE_BAUD' * 16.
1299
1300		pl011,<addr>
1301		pl011,mmio32,<addr>
1302			Start an early, polled-mode console on a pl011 serial
1303			port at the specified address. The pl011 serial port
1304			must already be setup and configured. Options are not
1305			yet supported.  If 'mmio32' is specified, then only
1306			the driver will use only 32-bit accessors to read/write
1307			the device registers.
1308
1309		liteuart,<addr>
1310			Start an early console on a litex serial port at the
1311			specified address. The serial port must already be
1312			setup and configured. Options are not yet supported.
1313
1314		meson,<addr>
1315			Start an early, polled-mode console on a meson serial
1316			port at the specified address. The serial port must
1317			already be setup and configured. Options are not yet
1318			supported.
1319
1320		msm_serial,<addr>
1321			Start an early, polled-mode console on an msm serial
1322			port at the specified address. The serial port
1323			must already be setup and configured. Options are not
1324			yet supported.
1325
1326		msm_serial_dm,<addr>
1327			Start an early, polled-mode console on an msm serial
1328			dm port at the specified address. The serial port
1329			must already be setup and configured. Options are not
1330			yet supported.
1331
1332		owl,<addr>
1333			Start an early, polled-mode console on a serial port
1334			of an Actions Semi SoC, such as S500 or S900, at the
1335			specified address. The serial port must already be
1336			setup and configured. Options are not yet supported.
1337
1338		rda,<addr>
1339			Start an early, polled-mode console on a serial port
1340			of an RDA Micro SoC, such as RDA8810PL, at the
1341			specified address. The serial port must already be
1342			setup and configured. Options are not yet supported.
1343
1344		sbi
1345			Use RISC-V SBI (Supervisor Binary Interface) for early
1346			console.
1347
1348		smh	Use ARM semihosting calls for early console.
1349
1350		s3c2410,<addr>
1351		s3c2412,<addr>
1352		s3c2440,<addr>
1353		s3c6400,<addr>
1354		s5pv210,<addr>
1355		exynos4210,<addr>
1356			Use early console provided by serial driver available
1357			on Samsung SoCs, requires selecting proper type and
1358			a correct base address of the selected UART port. The
1359			serial port must already be setup and configured.
1360			Options are not yet supported.
1361
1362		lantiq,<addr>
1363			Start an early, polled-mode console on a lantiq serial
1364			(lqasc) port at the specified address. The serial port
1365			must already be setup and configured. Options are not
1366			yet supported.
1367
1368		lpuart,<addr>
1369		lpuart32,<addr>
1370			Use early console provided by Freescale LP UART driver
1371			found on Freescale Vybrid and QorIQ LS1021A processors.
1372			A valid base address must be provided, and the serial
1373			port must already be setup and configured.
1374
1375		ec_imx21,<addr>
1376		ec_imx6q,<addr>
1377			Start an early, polled-mode, output-only console on the
1378			Freescale i.MX UART at the specified address. The UART
1379			must already be setup and configured.
1380
1381		ar3700_uart,<addr>
1382			Start an early, polled-mode console on the
1383			Armada 3700 serial port at the specified
1384			address. The serial port must already be setup
1385			and configured. Options are not yet supported.
1386
1387		qcom_geni,<addr>
1388			Start an early, polled-mode console on a Qualcomm
1389			Generic Interface (GENI) based serial port at the
1390			specified address. The serial port must already be
1391			setup and configured. Options are not yet supported.
1392
1393		efifb,[options]
1394			Start an early, unaccelerated console on the EFI
1395			memory mapped framebuffer (if available). On cache
1396			coherent non-x86 systems that use system memory for
1397			the framebuffer, pass the 'ram' option so that it is
1398			mapped with the correct attributes.
1399
1400		linflex,<addr>
1401			Use early console provided by Freescale LINFlexD UART
1402			serial driver for NXP S32V234 SoCs. A valid base
1403			address must be provided, and the serial port must
1404			already be setup and configured.
1405
1406	earlyprintk=	[X86,SH,ARM,M68k,S390,UM,EARLY]
1407			earlyprintk=vga
1408			earlyprintk=sclp
1409			earlyprintk=xen
1410			earlyprintk=serial[,ttySn[,baudrate]]
1411			earlyprintk=serial[,0x...[,baudrate]]
1412			earlyprintk=ttySn[,baudrate]
1413			earlyprintk=dbgp[debugController#]
1414			earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1415			earlyprintk=xdbc[xhciController#]
1416			earlyprintk=bios
1417
1418			earlyprintk is useful when the kernel crashes before
1419			the normal console is initialized. It is not enabled by
1420			default because it has some cosmetic problems.
1421
1422			Append ",keep" to not disable it when the real console
1423			takes over.
1424
1425			Only one of vga, serial, or usb debug port can
1426			be used at a time.
1427
1428			Currently only ttyS0 and ttyS1 may be specified by
1429			name.  Other I/O ports may be explicitly specified
1430			on some architectures (x86 and arm at least) by
1431			replacing ttySn with an I/O port address, like this:
1432				earlyprintk=serial,0x1008,115200
1433			You can find the port for a given device in
1434			/proc/tty/driver/serial:
1435				2: uart:ST16650V2 port:00001008 irq:18 ...
1436
1437			Interaction with the standard serial driver is not
1438			very good.
1439
1440			The VGA output is eventually overwritten by
1441			the real console.
1442
1443			The xen option can only be used in Xen domains.
1444
1445			The sclp output can only be used on s390.
1446
1447			The bios output can only be used on SuperH.
1448
1449			The optional "force" to "pciserial" enables use of a
1450			PCI device even when its classcode is not of the
1451			UART class.
1452
1453	edac_report=	[HW,EDAC] Control how to report EDAC event
1454			Format: {"on" | "off" | "force"}
1455			on: enable EDAC to report H/W event. May be overridden
1456			by other higher priority error reporting module.
1457			off: disable H/W event reporting through EDAC.
1458			force: enforce the use of EDAC to report H/W event.
1459			default: on.
1460
1461	edd=		[EDD]
1462			Format: {"off" | "on" | "skip[mbr]"}
1463
1464	efi=		[EFI,EARLY]
1465			Format: { "debug", "disable_early_pci_dma",
1466				  "nochunk", "noruntime", "nosoftreserve",
1467				  "novamap", "no_disable_early_pci_dma" }
1468			debug: enable misc debug output.
1469			disable_early_pci_dma: disable the busmaster bit on all
1470			PCI bridges while in the EFI boot stub.
1471			nochunk: disable reading files in "chunks" in the EFI
1472			boot stub, as chunking can cause problems with some
1473			firmware implementations.
1474			noruntime : disable EFI runtime services support
1475			nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1476			attribute may cause the kernel to reserve the
1477			memory range for a memory mapping driver to
1478			claim. Specify efi=nosoftreserve to disable this
1479			reservation and treat the memory by its base type
1480			(i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1481			novamap: do not call SetVirtualAddressMap().
1482			no_disable_early_pci_dma: Leave the busmaster bit set
1483			on all PCI bridges while in the EFI boot stub
1484
1485	efi_no_storage_paranoia [EFI,X86,EARLY]
1486			Using this parameter you can use more than 50% of
1487			your efi variable storage. Use this parameter only if
1488			you are really sure that your UEFI does sane gc and
1489			fulfills the spec otherwise your board may brick.
1490
1491	efivar_ssdt=	[EFI; X86] Name of an EFI variable that contains an SSDT
1492			that is to be dynamically loaded by Linux. If there are
1493			multiple variables with the same name but with different
1494			vendor GUIDs, all of them will be loaded. See
1495			Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1496
1497
1498	eisa_irq_edge=	[PARISC,HW]
1499			See header of drivers/parisc/eisa.c.
1500
1501	ekgdboc=	[X86,KGDB,EARLY] Allow early kernel console debugging
1502			Format: ekgdboc=kbd
1503
1504			This is designed to be used in conjunction with
1505			the boot argument: earlyprintk=vga
1506
1507			This parameter works in place of the kgdboc parameter
1508			but can only be used if the backing tty is available
1509			very early in the boot process. For early debugging
1510			via a serial port see kgdboc_earlycon instead.
1511
1512	elanfreq=	[X86-32]
1513			See comment before function elanfreq_setup() in
1514			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1515
1516	elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390,EARLY]
1517			Specifies physical address of start of kernel core
1518			image elf header and optionally the size. Generally
1519			kexec loader will pass this option to capture kernel.
1520			See Documentation/admin-guide/kdump/kdump.rst for details.
1521
1522	enable_mtrr_cleanup [X86,EARLY]
1523			The kernel tries to adjust MTRR layout from continuous
1524			to discrete, to make X server driver able to add WB
1525			entry later. This parameter enables that.
1526
1527	enable_timer_pin_1 [X86]
1528			Enable PIN 1 of APIC timer
1529			Can be useful to work around chipset bugs
1530			(in particular on some ATI chipsets).
1531			The kernel tries to set a reasonable default.
1532
1533	enforcing=	[SELINUX] Set initial enforcing status.
1534			Format: {"0" | "1"}
1535			See security/selinux/Kconfig help text.
1536			0 -- permissive (log only, no denials).
1537			1 -- enforcing (deny and log).
1538			Default value is 0.
1539			Value can be changed at runtime via
1540			/sys/fs/selinux/enforce.
1541
1542	erst_disable	[ACPI]
1543			Disable Error Record Serialization Table (ERST)
1544			support.
1545
1546	ether=		[HW,NET] Ethernet cards parameters
1547			This option is obsoleted by the "netdev=" option, which
1548			has equivalent usage. See its documentation for details.
1549
1550	evm=		[EVM]
1551			Format: { "fix" }
1552			Permit 'security.evm' to be updated regardless of
1553			current integrity status.
1554
1555	early_page_ext [KNL,EARLY] Enforces page_ext initialization to earlier
1556			stages so cover more early boot allocations.
1557			Please note that as side effect some optimizations
1558			might be disabled to achieve that (e.g. parallelized
1559			memory initialization is disabled) so the boot process
1560			might take longer, especially on systems with a lot of
1561			memory. Available with CONFIG_PAGE_EXTENSION=y.
1562
1563	failslab=
1564	fail_usercopy=
1565	fail_page_alloc=
1566	fail_skb_realloc=
1567	fail_make_request=[KNL]
1568			General fault injection mechanism.
1569			Format: <interval>,<probability>,<space>,<times>
1570			See also Documentation/fault-injection/.
1571
1572	fb_tunnels=	[NET]
1573			Format: { initns | none }
1574			See Documentation/admin-guide/sysctl/net.rst for
1575			fb_tunnels_only_for_init_ns
1576
1577	floppy=		[HW]
1578			See Documentation/admin-guide/blockdev/floppy.rst.
1579
1580	forcepae	[X86-32]
1581			Forcefully enable Physical Address Extension (PAE).
1582			Many Pentium M systems disable PAE but may have a
1583			functionally usable PAE implementation.
1584			Warning: use of this parameter will taint the kernel
1585			and may cause unknown problems.
1586
1587	fred=		[X86-64]
1588			Enable/disable Flexible Return and Event Delivery.
1589			Format: { on | off }
1590			on: enable FRED when it's present.
1591			off: disable FRED, the default setting.
1592
1593	ftrace=[tracer]
1594			[FTRACE] will set and start the specified tracer
1595			as early as possible in order to facilitate early
1596			boot debugging.
1597
1598	ftrace_boot_snapshot
1599			[FTRACE] On boot up, a snapshot will be taken of the
1600			ftrace ring buffer that can be read at:
1601			/sys/kernel/tracing/snapshot.
1602			This is useful if you need tracing information from kernel
1603			boot up that is likely to be overridden by user space
1604			start up functionality.
1605
1606			Optionally, the snapshot can also be defined for a tracing
1607			instance that was created by the trace_instance= command
1608			line parameter.
1609
1610			trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
1611
1612			The above will cause the "foo" tracing instance to trigger
1613			a snapshot at the end of boot up.
1614
1615	ftrace_dump_on_oops[=2(orig_cpu) | =<instance>][,<instance> |
1616			  ,<instance>=2(orig_cpu)]
1617			[FTRACE] will dump the trace buffers on oops.
1618			If no parameter is passed, ftrace will dump global
1619			buffers of all CPUs, if you pass 2 or orig_cpu, it
1620			will dump only the buffer of the CPU that triggered
1621			the oops, or the specific instance will be dumped if
1622			its name is passed. Multiple instance dump is also
1623			supported, and instances are separated by commas. Each
1624			instance supports only dump on CPU that triggered the
1625			oops by passing 2 or orig_cpu to it.
1626
1627			ftrace_dump_on_oops=foo=orig_cpu
1628
1629			The above will dump only the buffer of "foo" instance
1630			on CPU that triggered the oops.
1631
1632			ftrace_dump_on_oops,foo,bar=orig_cpu
1633
1634			The above will dump global buffer on all CPUs, the
1635			buffer of "foo" instance on all CPUs and the buffer
1636			of "bar" instance on CPU that triggered the oops.
1637
1638	ftrace_filter=[function-list]
1639			[FTRACE] Limit the functions traced by the function
1640			tracer at boot up. function-list is a comma-separated
1641			list of functions. This list can be changed at run
1642			time by the set_ftrace_filter file in the debugfs
1643			tracing directory.
1644
1645	ftrace_notrace=[function-list]
1646			[FTRACE] Do not trace the functions specified in
1647			function-list. This list can be changed at run time
1648			by the set_ftrace_notrace file in the debugfs
1649			tracing directory.
1650
1651	ftrace_graph_filter=[function-list]
1652			[FTRACE] Limit the top level callers functions traced
1653			by the function graph tracer at boot up.
1654			function-list is a comma-separated list of functions
1655			that can be changed at run time by the
1656			set_graph_function file in the debugfs tracing directory.
1657
1658	ftrace_graph_notrace=[function-list]
1659			[FTRACE] Do not trace from the functions specified in
1660			function-list.  This list is a comma-separated list of
1661			functions that can be changed at run time by the
1662			set_graph_notrace file in the debugfs tracing directory.
1663
1664	ftrace_graph_max_depth=<uint>
1665			[FTRACE] Used with the function graph tracer. This is
1666			the max depth it will trace into a function. This value
1667			can be changed at run time by the max_graph_depth file
1668			in the tracefs tracing directory. default: 0 (no limit)
1669
1670	fw_devlink=	[KNL,EARLY] Create device links between consumer and supplier
1671			devices by scanning the firmware to infer the
1672			consumer/supplier relationships. This feature is
1673			especially useful when drivers are loaded as modules as
1674			it ensures proper ordering of tasks like device probing
1675			(suppliers first, then consumers), supplier boot state
1676			clean up (only after all consumers have probed),
1677			suspend/resume & runtime PM (consumers first, then
1678			suppliers).
1679			Format: { off | permissive | on | rpm }
1680			off --	Don't create device links from firmware info.
1681			permissive -- Create device links from firmware info
1682				but use it only for ordering boot state clean
1683				up (sync_state() calls).
1684			on -- 	Create device links from firmware info and use it
1685				to enforce probe and suspend/resume ordering.
1686			rpm --	Like "on", but also use to order runtime PM.
1687
1688	fw_devlink.strict=<bool>
1689			[KNL,EARLY] Treat all inferred dependencies as mandatory
1690			dependencies. This only applies for fw_devlink=on|rpm.
1691			Format: <bool>
1692
1693	fw_devlink.sync_state =
1694			[KNL,EARLY] When all devices that could probe have finished
1695			probing, this parameter controls what to do with
1696			devices that haven't yet received their sync_state()
1697			calls.
1698			Format: { strict | timeout }
1699			strict -- Default. Continue waiting on consumers to
1700				probe successfully.
1701			timeout -- Give up waiting on consumers and call
1702				sync_state() on any devices that haven't yet
1703				received their sync_state() calls after
1704				deferred_probe_timeout has expired or by
1705				late_initcall() if !CONFIG_MODULES.
1706
1707	gamecon.map[2|3]=
1708			[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1709			support via parallel port (up to 5 devices per port)
1710			Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1711			See also Documentation/input/devices/joystick-parport.rst
1712
1713	gamma=		[HW,DRM]
1714
1715	gart_fix_e820=	[X86-64,EARLY] disable the fix e820 for K8 GART
1716			Format: off | on
1717			default: on
1718
1719	gather_data_sampling=
1720			[X86,INTEL,EARLY] Control the Gather Data Sampling (GDS)
1721			mitigation.
1722
1723			Gather Data Sampling is a hardware vulnerability which
1724			allows unprivileged speculative access to data which was
1725			previously stored in vector registers.
1726
1727			This issue is mitigated by default in updated microcode.
1728			The mitigation may have a performance impact but can be
1729			disabled. On systems without the microcode mitigation
1730			disabling AVX serves as a mitigation.
1731
1732			force:	Disable AVX to mitigate systems without
1733				microcode mitigation. No effect if the microcode
1734				mitigation is present. Known to cause crashes in
1735				userspace with buggy AVX enumeration.
1736
1737			off:	Disable GDS mitigation.
1738
1739	gbpages		[X86] Use GB pages for kernel direct mappings.
1740
1741	gcov_persist=	[GCOV] When non-zero (default), profiling data for
1742			kernel modules is saved and remains accessible via
1743			debugfs, even when the module is unloaded/reloaded.
1744			When zero, profiling data is discarded and associated
1745			debugfs files are removed at module unload time.
1746
1747	goldfish	[X86] Enable the goldfish android emulator platform.
1748			Don't use this when you are not running on the
1749			android emulator
1750
1751	gpio-mockup.gpio_mockup_ranges
1752			[HW] Sets the ranges of gpiochip of for this device.
1753			Format: <start1>,<end1>,<start2>,<end2>...
1754	gpio-mockup.gpio_mockup_named_lines
1755			[HW] Let the driver know GPIO lines should be named.
1756
1757	gpt		[EFI] Forces disk with valid GPT signature but
1758			invalid Protective MBR to be treated as GPT. If the
1759			primary GPT is corrupted, it enables the backup/alternate
1760			GPT to be used instead.
1761
1762	grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1763			the "Enable 0" bit of the configuration register.
1764			Format: 0 | 1
1765			Default: 0
1766	grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1767			the "Enable 0" bit of the configuration register.
1768			Format: 0 | 1
1769			Default: 0
1770	grcan.select=	[HW] Select which physical interface to use.
1771			Format: 0 | 1
1772			Default: 0
1773	grcan.txsize=	[HW] Sets the size of the tx buffer.
1774			Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1775			Default: 1024
1776	grcan.rxsize=	[HW] Sets the size of the rx buffer.
1777			Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1778			Default: 1024
1779
1780	hardened_usercopy=
1781			[KNL] Under CONFIG_HARDENED_USERCOPY, whether
1782			hardening is enabled for this boot. Hardened
1783			usercopy checking is used to protect the kernel
1784			from reading or writing beyond known memory
1785			allocation boundaries as a proactive defense
1786			against bounds-checking flaws in the kernel's
1787			copy_to_user()/copy_from_user() interface.
1788		on	Perform hardened usercopy checks (default).
1789		off	Disable hardened usercopy checks.
1790
1791	hardlockup_all_cpu_backtrace=
1792			[KNL] Should the hard-lockup detector generate
1793			backtraces on all cpus.
1794			Format: 0 | 1
1795
1796	hashdist=	[KNL,NUMA] Large hashes allocated during boot
1797			are distributed across NUMA nodes.  Defaults on
1798			for 64-bit NUMA, off otherwise.
1799			Format: 0 | 1 (for off | on)
1800
1801	hd=		[EIDE] (E)IDE hard drive subsystem geometry
1802			Format: <cyl>,<head>,<sect>
1803
1804	hest_disable	[ACPI]
1805			Disable Hardware Error Source Table (HEST) support;
1806			corresponding firmware-first mode error processing
1807			logic will be disabled.
1808
1809	hibernate=	[HIBERNATION]
1810		noresume	Don't check if there's a hibernation image
1811				present during boot.
1812		nocompress	Don't compress/decompress hibernation images.
1813		no		Disable hibernation and resume.
1814		protect_image	Turn on image protection during restoration
1815				(that will set all pages holding image data
1816				during restoration read-only).
1817
1818	hibernate.compressor= 	[HIBERNATION] Compression algorithm to be
1819				used with hibernation.
1820				Format: { lzo | lz4 }
1821				Default: lzo
1822
1823				lzo: Select LZO compression algorithm to
1824				compress/decompress hibernation image.
1825
1826				lz4: Select LZ4 compression algorithm to
1827				compress/decompress hibernation image.
1828
1829	highmem=nn[KMG]	[KNL,BOOT,EARLY] forces the highmem zone to have an exact
1830			size of <nn>. This works even on boxes that have no
1831			highmem otherwise. This also works to reduce highmem
1832			size on bigger boxes.
1833
1834	highres=	[KNL] Enable/disable high resolution timer mode.
1835			Valid parameters: "on", "off"
1836			Default: "on"
1837
1838	hlt		[BUGS=ARM,SH]
1839
1840	hostname=	[KNL,EARLY] Set the hostname (aka UTS nodename).
1841			Format: <string>
1842			This allows setting the system's hostname during early
1843			startup. This sets the name returned by gethostname.
1844			Using this parameter to set the hostname makes it
1845			possible to ensure the hostname is correctly set before
1846			any userspace processes run, avoiding the possibility
1847			that a process may call gethostname before the hostname
1848			has been explicitly set, resulting in the calling
1849			process getting an incorrect result. The string must
1850			not exceed the maximum allowed hostname length (usually
1851			64 characters) and will be truncated otherwise.
1852
1853	hpet=		[X86-32,HPET] option to control HPET usage
1854			Format: { enable (default) | disable | force |
1855				verbose }
1856			disable: disable HPET and use PIT instead
1857			force: allow force enabled of undocumented chips (ICH4,
1858				VIA, nVidia)
1859			verbose: show contents of HPET registers during setup
1860
1861	hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1862			registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1863
1864	hugepages=	[HW] Number of HugeTLB pages to allocate at boot.
1865			If this follows hugepagesz (below), it specifies
1866			the number of pages of hugepagesz to be allocated.
1867			If this is the first HugeTLB parameter on the command
1868			line, it specifies the number of pages to allocate for
1869			the default huge page size. If using node format, the
1870			number of pages to allocate per-node can be specified.
1871			See also Documentation/admin-guide/mm/hugetlbpage.rst.
1872			Format: <integer> or (node format)
1873				<node>:<integer>[,<node>:<integer>]
1874
1875	hugepagesz=
1876			[HW] The size of the HugeTLB pages.  This is used in
1877			conjunction with hugepages (above) to allocate huge
1878			pages of a specific size at boot.  The pair
1879			hugepagesz=X hugepages=Y can be specified once for
1880			each supported huge page size. Huge page sizes are
1881			architecture dependent.  See also
1882			Documentation/admin-guide/mm/hugetlbpage.rst.
1883			Format: size[KMG]
1884
1885	hugetlb_cma=	[HW,CMA,EARLY] The size of a CMA area used for allocation
1886			of gigantic hugepages. Or using node format, the size
1887			of a CMA area per node can be specified.
1888			Format: nn[KMGTPE] or (node format)
1889				<node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1890
1891			Reserve a CMA area of given size and allocate gigantic
1892			hugepages using the CMA allocator. If enabled, the
1893			boot-time allocation of gigantic hugepages is skipped.
1894
1895	hugetlb_free_vmemmap=
1896			[KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1897			enabled.
1898			Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1899			Allows heavy hugetlb users to free up some more
1900			memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1901			Format: { on | off (default) }
1902
1903			on: enable HVO
1904			off: disable HVO
1905
1906			Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1907			the default is on.
1908
1909			Note that the vmemmap pages may be allocated from the added
1910			memory block itself when memory_hotplug.memmap_on_memory is
1911			enabled, those vmemmap pages cannot be optimized even if this
1912			feature is enabled.  Other vmemmap pages not allocated from
1913			the added memory block itself do not be affected.
1914
1915	hung_task_panic=
1916			[KNL] Should the hung task detector generate panics.
1917			Format: 0 | 1
1918
1919			A value of 1 instructs the kernel to panic when a
1920			hung task is detected. The default value is controlled
1921			by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1922			option. The value selected by this boot parameter can
1923			be changed later by the kernel.hung_task_panic sysctl.
1924
1925	hvc_iucv=	[S390]	Number of z/VM IUCV hypervisor console (HVC)
1926				terminal devices. Valid values: 0..8
1927	hvc_iucv_allow=	[S390]	Comma-separated list of z/VM user IDs.
1928				If specified, z/VM IUCV HVC accepts connections
1929				from listed z/VM user IDs only.
1930
1931	hv_nopvspin	[X86,HYPER_V,EARLY]
1932			Disables the paravirt spinlock optimizations
1933			which allow the hypervisor to 'idle' the guest
1934			on lock contention.
1935
1936	i2c_bus=	[HW]	Override the default board specific I2C bus speed
1937				or register an additional I2C bus that is not
1938				registered from board initialization code.
1939				Format:
1940				<bus_id>,<clkrate>
1941
1942	i2c_touchscreen_props= [HW,ACPI,X86]
1943			Set device-properties for ACPI-enumerated I2C-attached
1944			touchscreen, to e.g. fix coordinates of upside-down
1945			mounted touchscreens. If you need this option please
1946			submit a drivers/platform/x86/touchscreen_dmi.c patch
1947			adding a DMI quirk for this.
1948
1949			Format:
1950			<ACPI_HW_ID>:<prop_name>=<val>[:prop_name=val][:...]
1951			Where <val> is one of:
1952			Omit "=<val>" entirely	Set a boolean device-property
1953			Unsigned number		Set a u32 device-property
1954			Anything else		Set a string device-property
1955
1956			Examples (split over multiple lines):
1957			i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x:
1958			touchscreen-inverted-y
1959
1960			i2c_touchscreen_props=MSSL1680:touchscreen-size-x=1920:
1961			touchscreen-size-y=1080:touchscreen-inverted-y:
1962			firmware-name=gsl1680-vendor-model.fw:silead,home-button
1963
1964	i8042.debug	[HW] Toggle i8042 debug mode
1965	i8042.unmask_kbd_data
1966			[HW] Enable printing of interrupt data from the KBD port
1967			     (disabled by default, and as a pre-condition
1968			     requires that i8042.debug=1 be enabled)
1969	i8042.direct	[HW] Put keyboard port into non-translated mode
1970	i8042.dumbkbd	[HW] Pretend that controller can only read data from
1971			     keyboard and cannot control its state
1972			     (Don't attempt to blink the leds)
1973	i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1974	i8042.nokbd	[HW] Don't check/create keyboard port
1975	i8042.noloop	[HW] Disable the AUX Loopback command while probing
1976			     for the AUX port
1977	i8042.nomux	[HW] Don't check presence of an active multiplexing
1978			     controller
1979	i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1980			     controllers
1981	i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1982	i8042.reset	[HW] Reset the controller during init, cleanup and
1983			     suspend-to-ram transitions, only during s2r
1984			     transitions, or never reset
1985			Format: { 1 | Y | y | 0 | N | n }
1986			1, Y, y: always reset controller
1987			0, N, n: don't ever reset controller
1988			Default: only on s2r transitions on x86; most other
1989			architectures force reset to be always executed
1990	i8042.unlock	[HW] Unlock (ignore) the keylock
1991	i8042.kbdreset	[HW] Reset device connected to KBD port
1992	i8042.probe_defer
1993			[HW] Allow deferred probing upon i8042 probe errors
1994
1995	i810=		[HW,DRM]
1996
1997	i915.invert_brightness=
1998			[DRM] Invert the sense of the variable that is used to
1999			set the brightness of the panel backlight. Normally a
2000			brightness value of 0 indicates backlight switched off,
2001			and the maximum of the brightness value sets the backlight
2002			to maximum brightness. If this parameter is set to 0
2003			(default) and the machine requires it, or this parameter
2004			is set to 1, a brightness value of 0 sets the backlight
2005			to maximum brightness, and the maximum of the brightness
2006			value switches the backlight off.
2007			-1 -- never invert brightness
2008			 0 -- machine default
2009			 1 -- force brightness inversion
2010
2011	ia32_emulation=	[X86-64]
2012			Format: <bool>
2013			When true, allows loading 32-bit programs and executing 32-bit
2014			syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at
2015			boot time. When false, unconditionally disables IA32 emulation.
2016
2017	icn=		[HW,ISDN]
2018			Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
2019
2020
2021	idle=		[X86,EARLY]
2022			Format: idle=poll, idle=halt, idle=nomwait
2023
2024			idle=poll:  Don't do power saving in the idle loop
2025			using HLT, but poll for rescheduling event. This will
2026			make the CPUs eat a lot more power, but may be useful
2027			to get slightly better performance in multiprocessor
2028			benchmarks. It also makes some profiling using
2029			performance counters more accurate.  Please note that
2030			on systems with MONITOR/MWAIT support (like Intel
2031			EM64T CPUs) this option has no performance advantage
2032			over the normal idle loop.  It may also interact badly
2033			with hyperthreading.
2034
2035			idle=halt: Halt is forced to be used for CPU idle.
2036			In such case C2/C3 won't be used again.
2037
2038			idle=nomwait: Disable mwait for CPU C-states
2039
2040	idxd.sva=	[HW]
2041			Format: <bool>
2042			Allow force disabling of Shared Virtual Memory (SVA)
2043			support for the idxd driver. By default it is set to
2044			true (1).
2045
2046	idxd.tc_override= [HW]
2047			Format: <bool>
2048			Allow override of default traffic class configuration
2049			for the device. By default it is set to false (0).
2050
2051	ieee754=	[MIPS] Select IEEE Std 754 conformance mode
2052			Format: { strict | legacy | 2008 | relaxed | emulated }
2053			Default: strict
2054
2055			Choose which programs will be accepted for execution
2056			based on the IEEE 754 NaN encoding(s) supported by
2057			the FPU and the NaN encoding requested with the value
2058			of an ELF file header flag individually set by each
2059			binary.  Hardware implementations are permitted to
2060			support either or both of the legacy and the 2008 NaN
2061			encoding mode.
2062
2063			Available settings are as follows:
2064			strict	accept binaries that request a NaN encoding
2065				supported by the FPU
2066			legacy	only accept legacy-NaN binaries, if supported
2067				by the FPU
2068			2008	only accept 2008-NaN binaries, if supported
2069				by the FPU
2070			relaxed	accept any binaries regardless of whether
2071				supported by the FPU
2072			emulated accept any binaries but enable FPU emulator
2073				if binary mode is unsupported by the FPU.
2074
2075			The FPU emulator is always able to support both NaN
2076			encodings, so if no FPU hardware is present or it has
2077			been disabled with 'nofpu', then the settings of
2078			'legacy' and '2008' strap the emulator accordingly,
2079			'relaxed' straps the emulator for both legacy-NaN and
2080			2008-NaN, whereas 'strict' enables legacy-NaN only on
2081			legacy processors and both NaN encodings on MIPS32 or
2082			MIPS64 CPUs.
2083
2084			The setting for ABS.fmt/NEG.fmt instruction execution
2085			mode generally follows that for the NaN encoding,
2086			except where unsupported by hardware.
2087
2088	ignore_loglevel	[KNL,EARLY]
2089			Ignore loglevel setting - this will print /all/
2090			kernel messages to the console. Useful for debugging.
2091			We also add it as printk module parameter, so users
2092			could change it dynamically, usually by
2093			/sys/module/printk/parameters/ignore_loglevel.
2094
2095	ignore_rlimit_data
2096			Ignore RLIMIT_DATA setting for data mappings,
2097			print warning at first misuse.  Can be changed via
2098			/sys/module/kernel/parameters/ignore_rlimit_data.
2099
2100	ihash_entries=	[KNL]
2101			Set number of hash buckets for inode cache.
2102
2103	ima_appraise=	[IMA] appraise integrity measurements
2104			Format: { "off" | "enforce" | "fix" | "log" }
2105			default: "enforce"
2106
2107	ima_appraise_tcb [IMA] Deprecated.  Use ima_policy= instead.
2108			The builtin appraise policy appraises all files
2109			owned by uid=0.
2110
2111	ima_canonical_fmt [IMA]
2112			Use the canonical format for the binary runtime
2113			measurements, instead of host native format.
2114
2115	ima_hash=	[IMA]
2116			Format: { md5 | sha1 | rmd160 | sha256 | sha384
2117				   | sha512 | ... }
2118			default: "sha1"
2119
2120			The list of supported hash algorithms is defined
2121			in crypto/hash_info.h.
2122
2123	ima_policy=	[IMA]
2124			The builtin policies to load during IMA setup.
2125			Format: "tcb | appraise_tcb | secure_boot |
2126				 fail_securely | critical_data"
2127
2128			The "tcb" policy measures all programs exec'd, files
2129			mmap'd for exec, and all files opened with the read
2130			mode bit set by either the effective uid (euid=0) or
2131			uid=0.
2132
2133			The "appraise_tcb" policy appraises the integrity of
2134			all files owned by root.
2135
2136			The "secure_boot" policy appraises the integrity
2137			of files (eg. kexec kernel image, kernel modules,
2138			firmware, policy, etc) based on file signatures.
2139
2140			The "fail_securely" policy forces file signature
2141			verification failure also on privileged mounted
2142			filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2143			flag.
2144
2145			The "critical_data" policy measures kernel integrity
2146			critical data.
2147
2148	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
2149			Load a policy which meets the needs of the Trusted
2150			Computing Base.  This means IMA will measure all
2151			programs exec'd, files mmap'd for exec, and all files
2152			opened for read by uid=0.
2153
2154	ima_template=	[IMA]
2155			Select one of defined IMA measurements template formats.
2156			Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2157				   "ima-sigv2" }
2158			Default: "ima-ng"
2159
2160	ima_template_fmt=
2161			[IMA] Define a custom template format.
2162			Format: { "field1|...|fieldN" }
2163
2164	ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2165			Format: <min_file_size>
2166			Set the minimal file size for using asynchronous hash.
2167			If left unspecified, ahash usage is disabled.
2168
2169			ahash performance varies for different data sizes on
2170			different crypto accelerators. This option can be used
2171			to achieve the best performance for a particular HW.
2172
2173	ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2174			Format: <bufsize>
2175			Set hashing buffer size. Default: 4k.
2176
2177			ahash performance varies for different chunk sizes on
2178			different crypto accelerators. This option can be used
2179			to achieve best performance for particular HW.
2180
2181	init=		[KNL]
2182			Format: <full_path>
2183			Run specified binary instead of /sbin/init as init
2184			process.
2185
2186	initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
2187			for working out where the kernel is dying during
2188			startup.
2189
2190	initcall_blacklist=  [KNL] Do not execute a comma-separated list of
2191			initcall functions.  Useful for debugging built-in
2192			modules and initcalls.
2193
2194	initramfs_async= [KNL]
2195			Format: <bool>
2196			Default: 1
2197			This parameter controls whether the initramfs
2198			image is unpacked asynchronously, concurrently
2199			with devices being probed and
2200			initialized. This should normally just work,
2201			but as a debugging aid, one can get the
2202			historical behaviour of the initramfs
2203			unpacking being completed before device_ and
2204			late_ initcalls.
2205
2206	initrd=		[BOOT,EARLY] Specify the location of the initial ramdisk
2207
2208	initrdmem=	[KNL,EARLY] Specify a physical address and size from which to
2209			load the initrd. If an initrd is compiled in or
2210			specified in the bootparams, it takes priority over this
2211			setting.
2212			Format: ss[KMG],nn[KMG]
2213			Default is 0, 0
2214
2215	init_on_alloc=	[MM,EARLY] Fill newly allocated pages and heap objects with
2216			zeroes.
2217			Format: 0 | 1
2218			Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2219
2220	init_on_free=	[MM,EARLY] Fill freed pages and heap objects with zeroes.
2221			Format: 0 | 1
2222			Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2223
2224	init_pkru=	[X86] Specify the default memory protection keys rights
2225			register contents for all processes.  0x55555554 by
2226			default (disallow access to all but pkey 0).  Can
2227			override in debugfs after boot.
2228
2229	inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
2230			Format: <irq>
2231
2232	int_pln_enable	[X86] Enable power limit notification interrupt
2233
2234	integrity_audit=[IMA]
2235			Format: { "0" | "1" }
2236			0 -- basic integrity auditing messages. (Default)
2237			1 -- additional integrity auditing messages.
2238
2239	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
2240		on
2241			Enable intel iommu driver.
2242		off
2243			Disable intel iommu driver.
2244		igfx_off [Default Off]
2245			By default, gfx is mapped as normal device. If a gfx
2246			device has a dedicated DMAR unit, the DMAR unit is
2247			bypassed by not enabling DMAR with this option. In
2248			this case, gfx device will use physical address for
2249			DMA.
2250		strict [Default Off]
2251			Deprecated, equivalent to iommu.strict=1.
2252		sp_off [Default Off]
2253			By default, super page will be supported if Intel IOMMU
2254			has the capability. With this option, super page will
2255			not be supported.
2256		sm_on
2257			Enable the Intel IOMMU scalable mode if the hardware
2258			advertises that it has support for the scalable mode
2259			translation.
2260		sm_off
2261			Disallow use of the Intel IOMMU scalable mode.
2262		tboot_noforce [Default Off]
2263			Do not force the Intel IOMMU enabled under tboot.
2264			By default, tboot will force Intel IOMMU on, which
2265			could harm performance of some high-throughput
2266			devices like 40GBit network cards, even if identity
2267			mapping is enabled.
2268			Note that using this option lowers the security
2269			provided by tboot because it makes the system
2270			vulnerable to DMA attacks.
2271
2272	intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
2273			0	disables intel_idle and fall back on acpi_idle.
2274			1 to 9	specify maximum depth of C-state.
2275
2276	intel_pstate=	[X86,EARLY]
2277			disable
2278			  Do not enable intel_pstate as the default
2279			  scaling driver for the supported processors
2280                        active
2281                          Use intel_pstate driver to bypass the scaling
2282                          governors layer of cpufreq and provides it own
2283                          algorithms for p-state selection. There are two
2284                          P-state selection algorithms provided by
2285                          intel_pstate in the active mode: powersave and
2286                          performance.  The way they both operate depends
2287                          on whether or not the hardware managed P-states
2288                          (HWP) feature has been enabled in the processor
2289                          and possibly on the processor model.
2290			passive
2291			  Use intel_pstate as a scaling driver, but configure it
2292			  to work with generic cpufreq governors (instead of
2293			  enabling its internal governor).  This mode cannot be
2294			  used along with the hardware-managed P-states (HWP)
2295			  feature.
2296			force
2297			  Enable intel_pstate on systems that prohibit it by default
2298			  in favor of acpi-cpufreq. Forcing the intel_pstate driver
2299			  instead of acpi-cpufreq may disable platform features, such
2300			  as thermal controls and power capping, that rely on ACPI
2301			  P-States information being indicated to OSPM and therefore
2302			  should be used with caution. This option does not work with
2303			  processors that aren't supported by the intel_pstate driver
2304			  or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2305			no_hwp
2306			  Do not enable hardware P state control (HWP)
2307			  if available.
2308			hwp_only
2309			  Only load intel_pstate on systems which support
2310			  hardware P state control (HWP) if available.
2311			support_acpi_ppc
2312			  Enforce ACPI _PPC performance limits. If the Fixed ACPI
2313			  Description Table, specifies preferred power management
2314			  profile as "Enterprise Server" or "Performance Server",
2315			  then this feature is turned on by default.
2316			per_cpu_perf_limits
2317			  Allow per-logical-CPU P-State performance control limits using
2318			  cpufreq sysfs interface
2319
2320	intremap=	[X86-64,Intel-IOMMU,EARLY]
2321			on	enable Interrupt Remapping (default)
2322			off	disable Interrupt Remapping
2323			nosid	disable Source ID checking
2324			no_x2apic_optout
2325				BIOS x2APIC opt-out request will be ignored
2326			nopost	disable Interrupt Posting
2327			posted_msi
2328				enable MSIs delivered as posted interrupts
2329
2330	iomem=		Disable strict checking of access to MMIO memory
2331		strict	regions from userspace.
2332		relaxed
2333
2334	iommu=		[X86,EARLY]
2335
2336		off
2337			Don't initialize and use any kind of IOMMU.
2338
2339		force
2340			Force the use of the hardware IOMMU even when
2341			it is not actually needed (e.g. because < 3 GB
2342			memory).
2343
2344		noforce
2345			Don't force hardware IOMMU usage when it is not
2346			needed. (default).
2347
2348		biomerge
2349		panic
2350		nopanic
2351		merge
2352		nomerge
2353
2354		soft
2355			Use software bounce buffering (SWIOTLB) (default for
2356			Intel machines). This can be used to prevent the usage
2357			of an available hardware IOMMU.
2358
2359			[X86]
2360		pt
2361			[X86]
2362		nopt
2363			[PPC/POWERNV]
2364		nobypass
2365			Disable IOMMU bypass, using IOMMU for PCI devices.
2366
2367		[X86]
2368		AMD Gart HW IOMMU-specific options:
2369
2370		<size>
2371			Set the size of the remapping area in bytes.
2372
2373		allowed
2374			Overwrite iommu off workarounds for specific chipsets
2375
2376		fullflush
2377			Flush IOMMU on each allocation (default).
2378
2379		nofullflush
2380			Don't use IOMMU fullflush.
2381
2382		memaper[=<order>]
2383			Allocate an own aperture over RAM with size
2384			32MB<<order.  (default: order=1, i.e. 64MB)
2385
2386		merge
2387			Do scatter-gather (SG) merging. Implies "force"
2388			(experimental).
2389
2390		nomerge
2391			Don't do scatter-gather (SG) merging.
2392
2393		noaperture
2394			Ask the IOMMU not to touch the aperture for AGP.
2395
2396		noagp
2397			Don't initialize the AGP driver and use full aperture.
2398
2399		panic
2400			Always panic when IOMMU overflows.
2401
2402	iommu.forcedac=	[ARM64,X86,EARLY] Control IOVA allocation for PCI devices.
2403			Format: { "0" | "1" }
2404			0 - Try to allocate a 32-bit DMA address first, before
2405			  falling back to the full range if needed.
2406			1 - Allocate directly from the full usable range,
2407			  forcing Dual Address Cycle for PCI cards supporting
2408			  greater than 32-bit addressing.
2409
2410	iommu.strict=	[ARM64,X86,S390,EARLY] Configure TLB invalidation behaviour
2411			Format: { "0" | "1" }
2412			0 - Lazy mode.
2413			  Request that DMA unmap operations use deferred
2414			  invalidation of hardware TLBs, for increased
2415			  throughput at the cost of reduced device isolation.
2416			  Will fall back to strict mode if not supported by
2417			  the relevant IOMMU driver.
2418			1 - Strict mode.
2419			  DMA unmap operations invalidate IOMMU hardware TLBs
2420			  synchronously.
2421			unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2422			Note: on x86, strict mode specified via one of the
2423			legacy driver-specific options takes precedence.
2424
2425	iommu.passthrough=
2426			[ARM64,X86,EARLY] Configure DMA to bypass the IOMMU by default.
2427			Format: { "0" | "1" }
2428			0 - Use IOMMU translation for DMA.
2429			1 - Bypass the IOMMU for DMA.
2430			unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2431
2432	io7=		[HW] IO7 for Marvel-based Alpha systems
2433			See comment before marvel_specify_io7 in
2434			arch/alpha/kernel/core_marvel.c.
2435
2436	io_delay=	[X86,EARLY] I/O delay method
2437		0x80
2438			Standard port 0x80 based delay
2439		0xed
2440			Alternate port 0xed based delay (needed on some systems)
2441		udelay
2442			Simple two microseconds delay
2443		none
2444			No delay
2445
2446	ip=		[IP_PNP]
2447			See Documentation/admin-guide/nfs/nfsroot.rst.
2448
2449	ipcmni_extend	[KNL,EARLY] Extend the maximum number of unique System V
2450			IPC identifiers from 32,768 to 16,777,216.
2451
2452	ipe.enforce=	[IPE]
2453			Format: <bool>
2454			Determine whether IPE starts in permissive (0) or
2455			enforce (1) mode. The default is enforce.
2456
2457	ipe.success_audit=
2458			[IPE]
2459			Format: <bool>
2460			Start IPE with success auditing enabled, emitting
2461			an audit event when a binary is allowed. The default
2462			is 0.
2463
2464	irqaffinity=	[SMP] Set the default irq affinity mask
2465			The argument is a cpu list, as described above.
2466
2467	irqchip.gicv2_force_probe=
2468			[ARM,ARM64,EARLY]
2469			Format: <bool>
2470			Force the kernel to look for the second 4kB page
2471			of a GICv2 controller even if the memory range
2472			exposed by the device tree is too small.
2473
2474	irqchip.gicv3_nolpi=
2475			[ARM,ARM64,EARLY]
2476			Force the kernel to ignore the availability of
2477			LPIs (and by consequence ITSs). Intended for system
2478			that use the kernel as a bootloader, and thus want
2479			to let secondary kernels in charge of setting up
2480			LPIs.
2481
2482	irqchip.gicv3_pseudo_nmi= [ARM64,EARLY]
2483			Enables support for pseudo-NMIs in the kernel. This
2484			requires the kernel to be built with
2485			CONFIG_ARM64_PSEUDO_NMI.
2486
2487	irqfixup	[HW]
2488			When an interrupt is not handled search all handlers
2489			for it. Intended to get systems with badly broken
2490			firmware running.
2491
2492	irqpoll		[HW]
2493			When an interrupt is not handled search all handlers
2494			for it. Also check all handlers each timer
2495			interrupt. Intended to get systems with badly broken
2496			firmware running.
2497
2498	isapnp=		[ISAPNP]
2499			Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2500
2501	isolcpus=	[KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2502			[Deprecated - use cpusets instead]
2503			Format: [flag-list,]<cpu-list>
2504
2505			Specify one or more CPUs to isolate from disturbances
2506			specified in the flag list (default: domain):
2507
2508			nohz
2509			  Disable the tick when a single task runs as well as
2510			  disabling other kernel noises like having RCU callbacks
2511			  offloaded. This is equivalent to the nohz_full parameter.
2512
2513			  A residual 1Hz tick is offloaded to workqueues, which you
2514			  need to affine to housekeeping through the global
2515			  workqueue's affinity configured via the
2516			  /sys/devices/virtual/workqueue/cpumask sysfs file, or
2517			  by using the 'domain' flag described below.
2518
2519			  NOTE: by default the global workqueue runs on all CPUs,
2520			  so to protect individual CPUs the 'cpumask' file has to
2521			  be configured manually after bootup.
2522
2523			domain
2524			  Isolate from the general SMP balancing and scheduling
2525			  algorithms. Note that performing domain isolation this way
2526			  is irreversible: it's not possible to bring back a CPU to
2527			  the domains once isolated through isolcpus. It's strongly
2528			  advised to use cpusets instead to disable scheduler load
2529			  balancing through the "cpuset.sched_load_balance" file.
2530			  It offers a much more flexible interface where CPUs can
2531			  move in and out of an isolated set anytime.
2532
2533			  You can move a process onto or off an "isolated" CPU via
2534			  the CPU affinity syscalls or cpuset.
2535			  <cpu number> begins at 0 and the maximum value is
2536			  "number of CPUs in system - 1".
2537
2538			managed_irq
2539
2540			  Isolate from being targeted by managed interrupts
2541			  which have an interrupt mask containing isolated
2542			  CPUs. The affinity of managed interrupts is
2543			  handled by the kernel and cannot be changed via
2544			  the /proc/irq/* interfaces.
2545
2546			  This isolation is best effort and only effective
2547			  if the automatically assigned interrupt mask of a
2548			  device queue contains isolated and housekeeping
2549			  CPUs. If housekeeping CPUs are online then such
2550			  interrupts are directed to the housekeeping CPU
2551			  so that IO submitted on the housekeeping CPU
2552			  cannot disturb the isolated CPU.
2553
2554			  If a queue's affinity mask contains only isolated
2555			  CPUs then this parameter has no effect on the
2556			  interrupt routing decision, though interrupts are
2557			  only delivered when tasks running on those
2558			  isolated CPUs submit IO. IO submitted on
2559			  housekeeping CPUs has no influence on those
2560			  queues.
2561
2562			The format of <cpu-list> is described above.
2563
2564	iucv=		[HW,NET]
2565
2566	ivrs_ioapic	[HW,X86-64]
2567			Provide an override to the IOAPIC-ID<->DEVICE-ID
2568			mapping provided in the IVRS ACPI table.
2569			By default, PCI segment is 0, and can be omitted.
2570
2571			For example, to map IOAPIC-ID decimal 10 to
2572			PCI segment 0x1 and PCI device 00:14.0,
2573			write the parameter as:
2574				ivrs_ioapic=10@0001:00:14.0
2575
2576			Deprecated formats:
2577			* To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2578			  write the parameter as:
2579				ivrs_ioapic[10]=00:14.0
2580			* To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2581			  PCI device 00:14.0 write the parameter as:
2582				ivrs_ioapic[10]=0001:00:14.0
2583
2584	ivrs_hpet	[HW,X86-64]
2585			Provide an override to the HPET-ID<->DEVICE-ID
2586			mapping provided in the IVRS ACPI table.
2587			By default, PCI segment is 0, and can be omitted.
2588
2589			For example, to map HPET-ID decimal 10 to
2590			PCI segment 0x1 and PCI device 00:14.0,
2591			write the parameter as:
2592				ivrs_hpet=10@0001:00:14.0
2593
2594			Deprecated formats:
2595			* To map HPET-ID decimal 0 to PCI device 00:14.0
2596			  write the parameter as:
2597				ivrs_hpet[0]=00:14.0
2598			* To map HPET-ID decimal 10 to PCI segment 0x1 and
2599			  PCI device 00:14.0 write the parameter as:
2600				ivrs_ioapic[10]=0001:00:14.0
2601
2602	ivrs_acpihid	[HW,X86-64]
2603			Provide an override to the ACPI-HID:UID<->DEVICE-ID
2604			mapping provided in the IVRS ACPI table.
2605			By default, PCI segment is 0, and can be omitted.
2606
2607			For example, to map UART-HID:UID AMD0020:0 to
2608			PCI segment 0x1 and PCI device ID 00:14.5,
2609			write the parameter as:
2610				ivrs_acpihid=AMD0020:0@0001:00:14.5
2611
2612			Deprecated formats:
2613			* To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2614			  PCI device ID 00:14.5, write the parameter as:
2615				ivrs_acpihid[00:14.5]=AMD0020:0
2616			* To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2617			  PCI device ID 00:14.5, write the parameter as:
2618				ivrs_acpihid[0001:00:14.5]=AMD0020:0
2619
2620	js=		[HW,JOY] Analog joystick
2621			See Documentation/input/joydev/joystick.rst.
2622
2623	kasan_multi_shot
2624			[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2625			report on every invalid memory access. Without this
2626			parameter KASAN will print report only for the first
2627			invalid access.
2628
2629	keep_bootcon	[KNL,EARLY]
2630			Do not unregister boot console at start. This is only
2631			useful for debugging when something happens in the window
2632			between unregistering the boot console and initializing
2633			the real console.
2634
2635	keepinitrd	[HW,ARM] See retain_initrd.
2636
2637	kernelcore=	[KNL,X86,PPC,EARLY]
2638			Format: nn[KMGTPE] | nn% | "mirror"
2639			This parameter specifies the amount of memory usable by
2640			the kernel for non-movable allocations.  The requested
2641			amount is spread evenly throughout all nodes in the
2642			system as ZONE_NORMAL.  The remaining memory is used for
2643			movable memory in its own zone, ZONE_MOVABLE.  In the
2644			event, a node is too small to have both ZONE_NORMAL and
2645			ZONE_MOVABLE, kernelcore memory will take priority and
2646			other nodes will have a larger ZONE_MOVABLE.
2647
2648			ZONE_MOVABLE is used for the allocation of pages that
2649			may be reclaimed or moved by the page migration
2650			subsystem.  Note that allocations like PTEs-from-HighMem
2651			still use the HighMem zone if it exists, and the Normal
2652			zone if it does not.
2653
2654			It is possible to specify the exact amount of memory in
2655			the form of "nn[KMGTPE]", a percentage of total system
2656			memory in the form of "nn%", or "mirror".  If "mirror"
2657			option is specified, mirrored (reliable) memory is used
2658			for non-movable allocations and remaining memory is used
2659			for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
2660			are exclusive, so you cannot specify multiple forms.
2661
2662	kgdbdbgp=	[KGDB,HW,EARLY] kgdb over EHCI usb debug port.
2663			Format: <Controller#>[,poll interval]
2664			The controller # is the number of the ehci usb debug
2665			port as it is probed via PCI.  The poll interval is
2666			optional and is the number seconds in between
2667			each poll cycle to the debug port in case you need
2668			the functionality for interrupting the kernel with
2669			gdb or control-c on the dbgp connection.  When
2670			not using this parameter you use sysrq-g to break into
2671			the kernel debugger.
2672
2673	kgdboc=		[KGDB,HW] kgdb over consoles.
2674			Requires a tty driver that supports console polling,
2675			or a supported polling keyboard driver (non-usb).
2676			 Serial only format: <serial_device>[,baud]
2677			 keyboard only format: kbd
2678			 keyboard and serial format: kbd,<serial_device>[,baud]
2679			Optional Kernel mode setting:
2680			 kms, kbd format: kms,kbd
2681			 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2682
2683	kgdboc_earlycon=	[KGDB,HW,EARLY]
2684			If the boot console provides the ability to read
2685			characters and can work in polling mode, you can use
2686			this parameter to tell kgdb to use it as a backend
2687			until the normal console is registered. Intended to
2688			be used together with the kgdboc parameter which
2689			specifies the normal console to transition to.
2690
2691			The name of the early console should be specified
2692			as the value of this parameter. Note that the name of
2693			the early console might be different than the tty
2694			name passed to kgdboc. It's OK to leave the value
2695			blank and the first boot console that implements
2696			read() will be picked.
2697
2698	kgdbwait	[KGDB,EARLY] Stop kernel execution and enter the
2699			kernel debugger at the earliest opportunity.
2700
2701	kmac=		[MIPS] Korina ethernet MAC address.
2702			Configure the RouterBoard 532 series on-chip
2703			Ethernet adapter MAC address.
2704
2705	kmemleak=	[KNL,EARLY] Boot-time kmemleak enable/disable
2706			Valid arguments: on, off
2707			Default: on
2708			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2709			the default is off.
2710
2711	kprobe_event=[probe-list]
2712			[FTRACE] Add kprobe events and enable at boot time.
2713			The probe-list is a semicolon delimited list of probe
2714			definitions. Each definition is same as kprobe_events
2715			interface, but the parameters are comma delimited.
2716			For example, to add a kprobe event on vfs_read with
2717			arg1 and arg2, add to the command line;
2718
2719			      kprobe_event=p,vfs_read,$arg1,$arg2
2720
2721			See also Documentation/trace/kprobetrace.rst "Kernel
2722			Boot Parameter" section.
2723
2724	kpti=		[ARM64,EARLY] Control page table isolation of
2725			user and kernel address spaces.
2726			Default: enabled on cores which need mitigation.
2727			0: force disabled
2728			1: force enabled
2729
2730	kunit.enable=	[KUNIT] Enable executing KUnit tests. Requires
2731			CONFIG_KUNIT to be set to be fully enabled. The
2732			default value can be overridden via
2733			KUNIT_DEFAULT_ENABLED.
2734			Default is 1 (enabled)
2735
2736	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2737			Default is 0 (don't ignore, but inject #GP)
2738
2739	kvm.eager_page_split=
2740			[KVM,X86] Controls whether or not KVM will try to
2741			proactively split all huge pages during dirty logging.
2742			Eager page splitting reduces interruptions to vCPU
2743			execution by eliminating the write-protection faults
2744			and MMU lock contention that would otherwise be
2745			required to split huge pages lazily.
2746
2747			VM workloads that rarely perform writes or that write
2748			only to a small region of VM memory may benefit from
2749			disabling eager page splitting to allow huge pages to
2750			still be used for reads.
2751
2752			The behavior of eager page splitting depends on whether
2753			KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2754			disabled, all huge pages in a memslot will be eagerly
2755			split when dirty logging is enabled on that memslot. If
2756			enabled, eager page splitting will be performed during
2757			the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2758			cleared.
2759
2760			Eager page splitting is only supported when kvm.tdp_mmu=Y.
2761
2762			Default is Y (on).
2763
2764	kvm.enable_virt_at_load=[KVM,ARM64,LOONGARCH,MIPS,RISCV,X86]
2765			If enabled, KVM will enable virtualization in hardware
2766			when KVM is loaded, and disable virtualization when KVM
2767			is unloaded (if KVM is built as a module).
2768
2769			If disabled, KVM will dynamically enable and disable
2770			virtualization on-demand when creating and destroying
2771			VMs, i.e. on the 0=>1 and 1=>0 transitions of the
2772			number of VMs.
2773
2774			Enabling virtualization at module load avoids potential
2775			latency for creation of the 0=>1 VM, as KVM serializes
2776			virtualization enabling across all online CPUs.  The
2777			"cost" of enabling virtualization when KVM is loaded,
2778			is that doing so may interfere with using out-of-tree
2779			hypervisors that want to "own" virtualization hardware.
2780
2781	kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2782				   Default is false (don't support).
2783
2784	kvm.nx_huge_pages=
2785			[KVM] Controls the software workaround for the
2786			X86_BUG_ITLB_MULTIHIT bug.
2787			force	: Always deploy workaround.
2788			off	: Never deploy workaround.
2789			auto    : Deploy workaround based on the presence of
2790				  X86_BUG_ITLB_MULTIHIT.
2791
2792			Default is 'auto'.
2793
2794			If the software workaround is enabled for the host,
2795			guests do need not to enable it for nested guests.
2796
2797	kvm.nx_huge_pages_recovery_ratio=
2798			[KVM] Controls how many 4KiB pages are periodically zapped
2799			back to huge pages.  0 disables the recovery, otherwise if
2800			the value is N KVM will zap 1/Nth of the 4KiB pages every
2801			period (see below).  The default is 60.
2802
2803	kvm.nx_huge_pages_recovery_period_ms=
2804			[KVM] Controls the time period at which KVM zaps 4KiB pages
2805			back to huge pages. If the value is a non-zero N, KVM will
2806			zap a portion (see ratio above) of the pages every N msecs.
2807			If the value is 0 (the default), KVM will pick a period based
2808			on the ratio, such that a page is zapped after 1 hour on average.
2809
2810	kvm-amd.nested=	[KVM,AMD] Control nested virtualization feature in
2811			KVM/SVM. Default is 1 (enabled).
2812
2813	kvm-amd.npt=	[KVM,AMD] Control KVM's use of Nested Page Tables,
2814			a.k.a. Two-Dimensional Page Tables. Default is 1
2815			(enabled). Disable by KVM if hardware lacks support
2816			for NPT.
2817
2818	kvm-arm.mode=
2819			[KVM,ARM,EARLY] Select one of KVM/arm64's modes of
2820			operation.
2821
2822			none: Forcefully disable KVM.
2823
2824			nvhe: Standard nVHE-based mode, without support for
2825			      protected guests.
2826
2827			protected: Mode with support for guests whose state is
2828				   kept private from the host, using VHE or
2829				   nVHE depending on HW support.
2830
2831			nested: VHE-based mode with support for nested
2832				virtualization. Requires at least ARMv8.4
2833				hardware (with FEAT_NV2).
2834
2835			Defaults to VHE/nVHE based on hardware support. Setting
2836			mode to "protected" will disable kexec and hibernation
2837			for the host. To force nVHE on VHE hardware, add
2838			"arm64_sw.hvhe=0 id_aa64mmfr1.vh=0" to the
2839			command-line.
2840			"nested" is experimental and should be used with
2841			extreme caution.
2842
2843	kvm-arm.vgic_v3_group0_trap=
2844			[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0
2845			system registers
2846
2847	kvm-arm.vgic_v3_group1_trap=
2848			[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1
2849			system registers
2850
2851	kvm-arm.vgic_v3_common_trap=
2852			[KVM,ARM,EARLY] Trap guest accesses to GICv3 common
2853			system registers
2854
2855	kvm-arm.vgic_v4_enable=
2856			[KVM,ARM,EARLY] Allow use of GICv4 for direct
2857			injection of LPIs.
2858
2859	kvm-arm.wfe_trap_policy=
2860			[KVM,ARM] Control when to set WFE instruction trap for
2861			KVM VMs. Traps are allowed but not guaranteed by the
2862			CPU architecture.
2863
2864			trap: set WFE instruction trap
2865
2866			notrap: clear WFE instruction trap
2867
2868	kvm-arm.wfi_trap_policy=
2869			[KVM,ARM] Control when to set WFI instruction trap for
2870			KVM VMs. Traps are allowed but not guaranteed by the
2871			CPU architecture.
2872
2873			trap: set WFI instruction trap
2874
2875			notrap: clear WFI instruction trap
2876
2877	kvm_cma_resv_ratio=n [PPC,EARLY]
2878			Reserves given percentage from system memory area for
2879			contiguous memory allocation for KVM hash pagetable
2880			allocation.
2881			By default it reserves 5% of total system memory.
2882			Format: <integer>
2883			Default: 5
2884
2885	kvm-intel.ept=	[KVM,Intel] Control KVM's use of Extended Page Tables,
2886			a.k.a. Two-Dimensional Page Tables.  Default is 1
2887			(enabled). Disable by KVM if hardware lacks support
2888			for EPT.
2889
2890	kvm-intel.emulate_invalid_guest_state=
2891			[KVM,Intel] Control whether to emulate invalid guest
2892			state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2893			as guest state is never invalid for unrestricted
2894			guests. This param doesn't apply to nested guests (L2),
2895			as KVM never emulates invalid L2 guest state.
2896			Default is 1 (enabled).
2897
2898	kvm-intel.flexpriority=
2899			[KVM,Intel] Control KVM's use of FlexPriority feature
2900			(TPR shadow). Default is 1 (enabled). Disable by KVM if
2901			hardware lacks support for it.
2902
2903	kvm-intel.nested=
2904			[KVM,Intel] Control nested virtualization feature in
2905			KVM/VMX. Default is 1 (enabled).
2906
2907	kvm-intel.unrestricted_guest=
2908			[KVM,Intel] Control KVM's use of unrestricted guest
2909			feature (virtualized real and unpaged mode). Default
2910			is 1 (enabled). Disable by KVM if EPT is disabled or
2911			hardware lacks support for it.
2912
2913	kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2914			CVE-2018-3620.
2915
2916			Valid arguments: never, cond, always
2917
2918			always: L1D cache flush on every VMENTER.
2919			cond:	Flush L1D on VMENTER only when the code between
2920				VMEXIT and VMENTER can leak host memory.
2921			never:	Disables the mitigation
2922
2923			Default is cond (do L1 cache flush in specific instances)
2924
2925	kvm-intel.vpid=	[KVM,Intel] Control KVM's use of Virtual Processor
2926			Identification feature (tagged TLBs). Default is 1
2927			(enabled). Disable by KVM if hardware lacks support
2928			for it.
2929
2930	l1d_flush=	[X86,INTEL,EARLY]
2931			Control mitigation for L1D based snooping vulnerability.
2932
2933			Certain CPUs are vulnerable to an exploit against CPU
2934			internal buffers which can forward information to a
2935			disclosure gadget under certain conditions.
2936
2937			In vulnerable processors, the speculatively
2938			forwarded data can be used in a cache side channel
2939			attack, to access data to which the attacker does
2940			not have direct access.
2941
2942			This parameter controls the mitigation. The
2943			options are:
2944
2945			on         - enable the interface for the mitigation
2946
2947	l1tf=           [X86,EARLY] Control mitigation of the L1TF vulnerability on
2948			      affected CPUs
2949
2950			The kernel PTE inversion protection is unconditionally
2951			enabled and cannot be disabled.
2952
2953			full
2954				Provides all available mitigations for the
2955				L1TF vulnerability. Disables SMT and
2956				enables all mitigations in the
2957				hypervisors, i.e. unconditional L1D flush.
2958
2959				SMT control and L1D flush control via the
2960				sysfs interface is still possible after
2961				boot.  Hypervisors will issue a warning
2962				when the first VM is started in a
2963				potentially insecure configuration,
2964				i.e. SMT enabled or L1D flush disabled.
2965
2966			full,force
2967				Same as 'full', but disables SMT and L1D
2968				flush runtime control. Implies the
2969				'nosmt=force' command line option.
2970				(i.e. sysfs control of SMT is disabled.)
2971
2972			flush
2973				Leaves SMT enabled and enables the default
2974				hypervisor mitigation, i.e. conditional
2975				L1D flush.
2976
2977				SMT control and L1D flush control via the
2978				sysfs interface is still possible after
2979				boot.  Hypervisors will issue a warning
2980				when the first VM is started in a
2981				potentially insecure configuration,
2982				i.e. SMT enabled or L1D flush disabled.
2983
2984			flush,nosmt
2985
2986				Disables SMT and enables the default
2987				hypervisor mitigation.
2988
2989				SMT control and L1D flush control via the
2990				sysfs interface is still possible after
2991				boot.  Hypervisors will issue a warning
2992				when the first VM is started in a
2993				potentially insecure configuration,
2994				i.e. SMT enabled or L1D flush disabled.
2995
2996			flush,nowarn
2997				Same as 'flush', but hypervisors will not
2998				warn when a VM is started in a potentially
2999				insecure configuration.
3000
3001			off
3002				Disables hypervisor mitigations and doesn't
3003				emit any warnings.
3004				It also drops the swap size and available
3005				RAM limit restriction on both hypervisor and
3006				bare metal.
3007
3008			Default is 'flush'.
3009
3010			For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
3011
3012	l2cr=		[PPC]
3013
3014	l3cr=		[PPC]
3015
3016	lapic		[X86-32,APIC,EARLY] Enable the local APIC even if BIOS
3017			disabled it.
3018
3019	lapic=		[X86,APIC] Do not use TSC deadline
3020			value for LAPIC timer one-shot implementation. Default
3021			back to the programmable timer unit in the LAPIC.
3022			Format: notscdeadline
3023
3024	lapic_timer_c2_ok	[X86,APIC,EARLY] trust the local apic timer
3025			in C2 power state.
3026
3027	libata.dma=	[LIBATA] DMA control
3028			libata.dma=0	  Disable all PATA and SATA DMA
3029			libata.dma=1	  PATA and SATA Disk DMA only
3030			libata.dma=2	  ATAPI (CDROM) DMA only
3031			libata.dma=4	  Compact Flash DMA only
3032			Combinations also work, so libata.dma=3 enables DMA
3033			for disks and CDROMs, but not CFs.
3034
3035	libata.ignore_hpa=	[LIBATA] Ignore HPA limit
3036			libata.ignore_hpa=0	  keep BIOS limits (default)
3037			libata.ignore_hpa=1	  ignore limits, using full disk
3038
3039	libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
3040			when set.
3041			Format: <int>
3042
3043	libata.force=	[LIBATA] Force configurations.  The format is a comma-
3044			separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
3045			PORT and DEVICE are decimal numbers matching port, link
3046			or device.  Basically, it matches the ATA ID string
3047			printed on console by libata.  If the whole ID part is
3048			omitted, the last PORT and DEVICE values are used.  If
3049			ID hasn't been specified yet, the configuration applies
3050			to all ports, links and devices.
3051
3052			If only DEVICE is omitted, the parameter applies to
3053			the port and all links and devices behind it.  DEVICE
3054			number of 0 either selects the first device or the
3055			first fan-out link behind PMP device.  It does not
3056			select the host link.  DEVICE number of 15 selects the
3057			host link and device attached to it.
3058
3059			The VAL specifies the configuration to force.  As long
3060			as there is no ambiguity, shortcut notation is allowed.
3061			For example, both 1.5 and 1.5G would work for 1.5Gbps.
3062			The following configurations can be forced.
3063
3064			* Cable type: 40c, 80c, short40c, unk, ign or sata.
3065			  Any ID with matching PORT is used.
3066
3067			* SATA link speed limit: 1.5Gbps or 3.0Gbps.
3068
3069			* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
3070			  udma[/][16,25,33,44,66,100,133] notation is also
3071			  allowed.
3072
3073			* nohrst, nosrst, norst: suppress hard, soft and both
3074			  resets.
3075
3076			* rstonce: only attempt one reset during hot-unplug
3077			  link recovery.
3078
3079			* [no]dbdelay: Enable or disable the extra 200ms delay
3080			  before debouncing a link PHY and device presence
3081			  detection.
3082
3083			* [no]ncq: Turn on or off NCQ.
3084
3085			* [no]ncqtrim: Enable or disable queued DSM TRIM.
3086
3087			* [no]ncqati: Enable or disable NCQ trim on ATI chipset.
3088
3089			* [no]trim: Enable or disable (unqueued) TRIM.
3090
3091			* trim_zero: Indicate that TRIM command zeroes data.
3092
3093			* max_trim_128m: Set 128M maximum trim size limit.
3094
3095			* [no]dma: Turn on or off DMA transfers.
3096
3097			* atapi_dmadir: Enable ATAPI DMADIR bridge support.
3098
3099			* atapi_mod16_dma: Enable the use of ATAPI DMA for
3100			  commands that are not a multiple of 16 bytes.
3101
3102			* [no]dmalog: Enable or disable the use of the
3103			  READ LOG DMA EXT command to access logs.
3104
3105			* [no]iddevlog: Enable or disable access to the
3106			  identify device data log.
3107
3108			* [no]logdir: Enable or disable access to the general
3109			  purpose log directory.
3110
3111			* max_sec_128: Set transfer size limit to 128 sectors.
3112
3113			* max_sec_1024: Set or clear transfer size limit to
3114			  1024 sectors.
3115
3116			* max_sec_lba48: Set or clear transfer size limit to
3117			  65535 sectors.
3118
3119			* [no]lpm: Enable or disable link power management.
3120
3121			* [no]setxfer: Indicate if transfer speed mode setting
3122			  should be skipped.
3123
3124			* [no]fua: Disable or enable FUA (Force Unit Access)
3125			  support for devices supporting this feature.
3126
3127			* dump_id: Dump IDENTIFY data.
3128
3129			* disable: Disable this device.
3130
3131			If there are multiple matching configurations changing
3132			the same attribute, the last one is used.
3133
3134	load_ramdisk=	[RAM] [Deprecated]
3135
3136	lockd.nlm_grace_period=P  [NFS] Assign grace period.
3137			Format: <integer>
3138
3139	lockd.nlm_tcpport=N	[NFS] Assign TCP port.
3140			Format: <integer>
3141
3142	lockd.nlm_timeout=T	[NFS] Assign timeout value.
3143			Format: <integer>
3144
3145	lockd.nlm_udpport=M	[NFS] Assign UDP port.
3146			Format: <integer>
3147
3148	lockdown=	[SECURITY,EARLY]
3149			{ integrity | confidentiality }
3150			Enable the kernel lockdown feature. If set to
3151			integrity, kernel features that allow userland to
3152			modify the running kernel are disabled. If set to
3153			confidentiality, kernel features that allow userland
3154			to extract confidential information from the kernel
3155			are also disabled.
3156
3157	locktorture.acq_writer_lim= [KNL]
3158			Set the time limit in jiffies for a lock
3159			acquisition.  Acquisitions exceeding this limit
3160			will result in a splat once they do complete.
3161
3162	locktorture.bind_readers= [KNL]
3163			Specify the list of CPUs to which the readers are
3164			to be bound.
3165
3166	locktorture.bind_writers= [KNL]
3167			Specify the list of CPUs to which the writers are
3168			to be bound.
3169
3170	locktorture.call_rcu_chains= [KNL]
3171			Specify the number of self-propagating call_rcu()
3172			chains to set up.  These are used to ensure that
3173			there is a high probability of an RCU grace period
3174			in progress at any given time.	Defaults to 0,
3175			which disables these call_rcu() chains.
3176
3177	locktorture.long_hold= [KNL]
3178			Specify the duration in milliseconds for the
3179			occasional long-duration lock hold time.  Defaults
3180			to 100 milliseconds.  Select 0 to disable.
3181
3182	locktorture.nested_locks= [KNL]
3183			Specify the maximum lock nesting depth that
3184			locktorture is to exercise, up to a limit of 8
3185			(MAX_NESTED_LOCKS).  Specify zero to disable.
3186			Note that this parameter is ineffective on types
3187			of locks that do not support nested acquisition.
3188
3189	locktorture.nreaders_stress= [KNL]
3190			Set the number of locking read-acquisition kthreads.
3191			Defaults to being automatically set based on the
3192			number of online CPUs.
3193
3194	locktorture.nwriters_stress= [KNL]
3195			Set the number of locking write-acquisition kthreads.
3196
3197	locktorture.onoff_holdoff= [KNL]
3198			Set time (s) after boot for CPU-hotplug testing.
3199
3200	locktorture.onoff_interval= [KNL]
3201			Set time (s) between CPU-hotplug operations, or
3202			zero to disable CPU-hotplug testing.
3203
3204	locktorture.rt_boost= [KNL]
3205			Do periodic testing of real-time lock priority
3206			boosting.  Select 0 to disable, 1 to boost
3207			only rt_mutex, and 2 to boost unconditionally.
3208			Defaults to 2, which might seem to be an
3209			odd choice, but which should be harmless for
3210			non-real-time spinlocks, due to their disabling
3211			of preemption.	Note that non-realtime mutexes
3212			disable boosting.
3213
3214	locktorture.rt_boost_factor= [KNL]
3215			Number that determines how often and for how
3216			long priority boosting is exercised.  This is
3217			scaled down by the number of writers, so that the
3218			number of boosts per unit time remains roughly
3219			constant as the number of writers increases.
3220			On the other hand, the duration of each boost
3221			increases with the number of writers.
3222
3223	locktorture.shuffle_interval= [KNL]
3224			Set task-shuffle interval (jiffies).  Shuffling
3225			tasks allows some CPUs to go into dyntick-idle
3226			mode during the locktorture test.
3227
3228	locktorture.shutdown_secs= [KNL]
3229			Set time (s) after boot system shutdown.  This
3230			is useful for hands-off automated testing.
3231
3232	locktorture.stat_interval= [KNL]
3233			Time (s) between statistics printk()s.
3234
3235	locktorture.stutter= [KNL]
3236			Time (s) to stutter testing, for example,
3237			specifying five seconds causes the test to run for
3238			five seconds, wait for five seconds, and so on.
3239			This tests the locking primitive's ability to
3240			transition abruptly to and from idle.
3241
3242	locktorture.torture_type= [KNL]
3243			Specify the locking implementation to test.
3244
3245	locktorture.verbose= [KNL]
3246			Enable additional printk() statements.
3247
3248	locktorture.writer_fifo= [KNL]
3249			Run the write-side locktorture kthreads at
3250			sched_set_fifo() real-time priority.
3251
3252	logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
3253			Format: <irq>
3254
3255	loglevel=	[KNL,EARLY]
3256			All Kernel Messages with a loglevel smaller than the
3257			console loglevel will be printed to the console. It can
3258			also be changed with klogd or other programs. The
3259			loglevels are defined as follows:
3260
3261			0 (KERN_EMERG)		system is unusable
3262			1 (KERN_ALERT)		action must be taken immediately
3263			2 (KERN_CRIT)		critical conditions
3264			3 (KERN_ERR)		error conditions
3265			4 (KERN_WARNING)	warning conditions
3266			5 (KERN_NOTICE)		normal but significant condition
3267			6 (KERN_INFO)		informational
3268			7 (KERN_DEBUG)		debug-level messages
3269
3270	log_buf_len=n[KMG] [KNL,EARLY]
3271			Sets the size of the printk ring buffer, in bytes.
3272			n must be a power of two and greater than the
3273			minimal size. The minimal size is defined by
3274			LOG_BUF_SHIFT kernel config parameter. There
3275			is also CONFIG_LOG_CPU_MAX_BUF_SHIFT config
3276			parameter that allows to increase the default size
3277			depending on the number of CPUs. See init/Kconfig
3278			for more details.
3279
3280	logo.nologo	[FB] Disables display of the built-in Linux logo.
3281			This may be used to provide more screen space for
3282			kernel log messages and is useful when debugging
3283			kernel boot problems.
3284
3285	lp=0		[LP]	Specify parallel ports to use, e.g,
3286	lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
3287	lp=reset		first parallel port). 'lp=0' disables the
3288	lp=auto			printer driver. 'lp=reset' (which can be
3289				specified in addition to the ports) causes
3290				attached printers to be reset. Using
3291				lp=port1,port2,... specifies the parallel ports
3292				to associate lp devices with, starting with
3293				lp0. A port specification may be 'none' to skip
3294				that lp device, or a parport name such as
3295				'parport0'. Specifying 'lp=auto' instead of a
3296				port specification list means that device IDs
3297				from each port should be examined, to see if
3298				an IEEE 1284-compliant printer is attached; if
3299				so, the driver will manage that printer.
3300				See also header of drivers/char/lp.c.
3301
3302	lpj=n		[KNL]
3303			Sets loops_per_jiffy to given constant, thus avoiding
3304			time-consuming boot-time autodetection (up to 250 ms per
3305			CPU). 0 enables autodetection (default). To determine
3306			the correct value for your kernel, boot with normal
3307			autodetection and see what value is printed. Note that
3308			on SMP systems the preset will be applied to all CPUs,
3309			which is likely to cause problems if your CPUs need
3310			significantly divergent settings. An incorrect value
3311			will cause delays in the kernel to be wrong, leading to
3312			unpredictable I/O errors and other breakage. Although
3313			unlikely, in the extreme case this might damage your
3314			hardware.
3315
3316	lsm.debug	[SECURITY] Enable LSM initialization debugging output.
3317
3318	lsm=lsm1,...,lsmN
3319			[SECURITY] Choose order of LSM initialization. This
3320			overrides CONFIG_LSM, and the "security=" parameter.
3321
3322	machtype=	[Loongson] Share the same kernel image file between
3323			different yeeloong laptops.
3324			Example: machtype=lemote-yeeloong-2f-7inch
3325
3326	maxcpus=	[SMP,EARLY] Maximum number of processors that an SMP kernel
3327			will bring up during bootup.  maxcpus=n : n >= 0 limits
3328			the kernel to bring up 'n' processors. Surely after
3329			bootup you can bring up the other plugged cpu by executing
3330			"echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3331			only takes effect during system bootup.
3332			While n=0 is a special case, it is equivalent to "nosmp",
3333			which also disables the IO APIC.
3334
3335	max_loop=	[LOOP] The number of loop block devices that get
3336	(loop.max_loop)	unconditionally pre-created at init time. The default
3337			number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3338			of statically allocating a predefined number, loop
3339			devices can be requested on-demand with the
3340			/dev/loop-control interface.
3341
3342	mce=		[X86-{32,64}]
3343
3344			Please see Documentation/arch/x86/x86_64/machinecheck.rst for sysfs runtime tunables.
3345
3346		off
3347			disable machine check
3348
3349		no_cmci
3350			disable CMCI(Corrected Machine Check Interrupt) that
3351			Intel processor supports.  Usually this disablement is
3352			not recommended, but it might be handy if your
3353			hardware is misbehaving.
3354
3355			Note that you'll get more problems without CMCI than
3356			with due to the shared banks, i.e. you might get
3357			duplicated error logs.
3358
3359		dont_log_ce
3360			don't make logs for corrected errors.  All events
3361			reported as corrected are silently cleared by OS. This
3362			option will be useful if you have no interest in any
3363			of corrected errors.
3364
3365		ignore_ce
3366			disable features for corrected errors, e.g.
3367			polling timer and CMCI.  All events reported as
3368			corrected are not cleared by OS and remained in its
3369			error banks.
3370
3371			Usually this disablement is not recommended, however
3372			if there is an agent checking/clearing corrected
3373			errors (e.g. BIOS or hardware monitoring
3374			applications), conflicting with OS's error handling,
3375			and you cannot deactivate the agent, then this option
3376			will be a help.
3377
3378		no_lmce
3379			do not opt-in to Local MCE delivery. Use legacy method
3380			to broadcast MCEs.
3381
3382		bootlog
3383			enable logging of machine checks left over from
3384			booting. Disabled by default on AMD Fam10h and older
3385			because some BIOS leave bogus ones.
3386
3387			If your BIOS doesn't do that it's a good idea to
3388			enable though to make sure you log even machine check
3389			events that result in a reboot. On Intel systems it is
3390			enabled by default.
3391
3392		nobootlog
3393			disable boot machine check logging.
3394
3395		monarchtimeout (number)
3396			sets the time in us to wait for other CPUs on machine
3397			checks. 0 to disable.
3398
3399		bios_cmci_threshold
3400			don't overwrite the bios-set CMCI threshold. This boot
3401			option prevents Linux from overwriting the CMCI
3402			threshold set by the bios.  Without this option, Linux
3403			always sets the CMCI threshold to 1. Enabling this may
3404			make memory predictive failure analysis less effective
3405			if the bios sets thresholds for memory errors since we
3406			will not see details for all errors.
3407
3408		recovery
3409			force-enable recoverable machine check code paths
3410
3411			Everything else is in sysfs now.
3412
3413
3414	md=		[HW] RAID subsystems devices and level
3415			See Documentation/admin-guide/md.rst.
3416
3417	mdacon=		[MDA]
3418			Format: <first>,<last>
3419			Specifies range of consoles to be captured by the MDA.
3420
3421	mds=		[X86,INTEL,EARLY]
3422			Control mitigation for the Micro-architectural Data
3423			Sampling (MDS) vulnerability.
3424
3425			Certain CPUs are vulnerable to an exploit against CPU
3426			internal buffers which can forward information to a
3427			disclosure gadget under certain conditions.
3428
3429			In vulnerable processors, the speculatively
3430			forwarded data can be used in a cache side channel
3431			attack, to access data to which the attacker does
3432			not have direct access.
3433
3434			This parameter controls the MDS mitigation. The
3435			options are:
3436
3437			full       - Enable MDS mitigation on vulnerable CPUs
3438			full,nosmt - Enable MDS mitigation and disable
3439				     SMT on vulnerable CPUs
3440			off        - Unconditionally disable MDS mitigation
3441
3442			On TAA-affected machines, mds=off can be prevented by
3443			an active TAA mitigation as both vulnerabilities are
3444			mitigated with the same mechanism so in order to disable
3445			this mitigation, you need to specify tsx_async_abort=off
3446			too.
3447
3448			Not specifying this option is equivalent to
3449			mds=full.
3450
3451			For details see: Documentation/admin-guide/hw-vuln/mds.rst
3452
3453	mem=nn[KMG]	[HEXAGON,EARLY] Set the memory size.
3454			Must be specified, otherwise memory size will be 0.
3455
3456	mem=nn[KMG]	[KNL,BOOT,EARLY] Force usage of a specific amount
3457			of memory Amount of memory to be used in cases
3458			as follows:
3459
3460			1 for test;
3461			2 when the kernel is not able to see the whole system memory;
3462			3 memory that lies after 'mem=' boundary is excluded from
3463			 the hypervisor, then assigned to KVM guests.
3464			4 to limit the memory available for kdump kernel.
3465
3466			[ARC,MICROBLAZE] - the limit applies only to low memory,
3467			high memory is not affected.
3468
3469			[ARM64] - only limits memory covered by the linear
3470			mapping. The NOMAP regions are not affected.
3471
3472			[X86] Work as limiting max address. Use together
3473			with memmap= to avoid physical address space collisions.
3474			Without memmap= PCI devices could be placed at addresses
3475			belonging to unused RAM.
3476
3477			Note that this only takes effects during boot time since
3478			in above case 3, memory may need be hot added after boot
3479			if system memory of hypervisor is not sufficient.
3480
3481	mem=nn[KMG]@ss[KMG]
3482			[ARM,MIPS,EARLY] - override the memory layout
3483			reported by firmware.
3484			Define a memory region of size nn[KMG] starting at
3485			ss[KMG].
3486			Multiple different regions can be specified with
3487			multiple mem= parameters on the command line.
3488
3489	mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
3490			memory.
3491
3492	memblock=debug	[KNL,EARLY] Enable memblock debug messages.
3493
3494	memchunk=nn[KMG]
3495			[KNL,SH] Allow user to override the default size for
3496			per-device physically contiguous DMA buffers.
3497
3498	memhp_default_state=online/offline/online_kernel/online_movable
3499			[KNL] Set the initial state for the memory hotplug
3500			onlining policy. If not specified, the default value is
3501			set according to the
3502			CONFIG_MHP_DEFAULT_ONLINE_TYPE kernel config
3503			options.
3504			See Documentation/admin-guide/mm/memory-hotplug.rst.
3505
3506	memmap=exactmap	[KNL,X86,EARLY] Enable setting of an exact
3507			E820 memory map, as specified by the user.
3508			Such memmap=exactmap lines can be constructed based on
3509			BIOS output or other requirements. See the memmap=nn@ss
3510			option description.
3511
3512	memmap=nn[KMG]@ss[KMG]
3513			[KNL, X86,MIPS,XTENSA,EARLY] Force usage of a specific region of memory.
3514			Region of memory to be used is from ss to ss+nn.
3515			If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3516			which limits max address to nn[KMG].
3517			Multiple different regions can be specified,
3518			comma delimited.
3519			Example:
3520				memmap=100M@2G,100M#3G,1G!1024G
3521
3522	memmap=nn[KMG]#ss[KMG]
3523			[KNL,ACPI,EARLY] Mark specific memory as ACPI data.
3524			Region of memory to be marked is from ss to ss+nn.
3525
3526	memmap=nn[KMG]$ss[KMG]
3527			[KNL,ACPI,EARLY] Mark specific memory as reserved.
3528			Region of memory to be reserved is from ss to ss+nn.
3529			Example: Exclude memory from 0x18690000-0x1869ffff
3530			         memmap=64K$0x18690000
3531			         or
3532			         memmap=0x10000$0x18690000
3533			Some bootloaders may need an escape character before '$',
3534			like Grub2, otherwise '$' and the following number
3535			will be eaten.
3536
3537	memmap=nn[KMG]!ss[KMG,EARLY]
3538			[KNL,X86] Mark specific memory as protected.
3539			Region of memory to be used, from ss to ss+nn.
3540			The memory region may be marked as e820 type 12 (0xc)
3541			and is NVDIMM or ADR memory.
3542
3543	memmap=<size>%<offset>-<oldtype>+<newtype>
3544			[KNL,ACPI,EARLY] Convert memory within the specified region
3545			from <oldtype> to <newtype>. If "-<oldtype>" is left
3546			out, the whole region will be marked as <newtype>,
3547			even if previously unavailable. If "+<newtype>" is left
3548			out, matching memory will be removed. Types are
3549			specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3550			3 = ACPI, 12 = PRAM.
3551
3552	memory_corruption_check=0/1 [X86,EARLY]
3553			Some BIOSes seem to corrupt the first 64k of
3554			memory when doing things like suspend/resume.
3555			Setting this option will scan the memory
3556			looking for corruption.  Enabling this will
3557			both detect corruption and prevent the kernel
3558			from using the memory being corrupted.
3559			However, its intended as a diagnostic tool; if
3560			repeatable BIOS-originated corruption always
3561			affects the same memory, you can use memmap=
3562			to prevent the kernel from using that memory.
3563
3564	memory_corruption_check_size=size [X86,EARLY]
3565			By default it checks for corruption in the low
3566			64k, making this memory unavailable for normal
3567			use.  Use this parameter to scan for
3568			corruption in more or less memory.
3569
3570	memory_corruption_check_period=seconds [X86,EARLY]
3571			By default it checks for corruption every 60
3572			seconds.  Use this parameter to check at some
3573			other rate.  0 disables periodic checking.
3574
3575	memory_hotplug.memmap_on_memory
3576			[KNL,X86,ARM] Boolean flag to enable this feature.
3577			Format: {on | off (default)}
3578			When enabled, runtime hotplugged memory will
3579			allocate its internal metadata (struct pages,
3580			those vmemmap pages cannot be optimized even
3581			if hugetlb_free_vmemmap is enabled) from the
3582			hotadded memory which will allow to hotadd a
3583			lot of memory without requiring additional
3584			memory to do so.
3585			This feature is disabled by default because it
3586			has some implication on large (e.g. GB)
3587			allocations in some configurations (e.g. small
3588			memory blocks).
3589			The state of the flag can be read in
3590			/sys/module/memory_hotplug/parameters/memmap_on_memory.
3591			Note that even when enabled, there are a few cases where
3592			the feature is not effective.
3593
3594	memtest=	[KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest
3595			Format: <integer>
3596			default : 0 <disable>
3597			Specifies the number of memtest passes to be
3598			performed. Each pass selects another test
3599			pattern from a given set of patterns. Memtest
3600			fills the memory with this pattern, validates
3601			memory contents and reserves bad memory
3602			regions that are detected.
3603
3604	mem_encrypt=	[X86-64] AMD Secure Memory Encryption (SME) control
3605			Valid arguments: on, off
3606			Default: off
3607			mem_encrypt=on:		Activate SME
3608			mem_encrypt=off:	Do not activate SME
3609
3610			Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3611			for details on when memory encryption can be activated.
3612
3613	mem_sleep_default=	[SUSPEND] Default system suspend mode:
3614			s2idle  - Suspend-To-Idle
3615			shallow - Power-On Suspend or equivalent (if supported)
3616			deep    - Suspend-To-RAM or equivalent (if supported)
3617			See Documentation/admin-guide/pm/sleep-states.rst.
3618
3619	mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
3620			the BIOS has incorrectly applied a workaround. TinyBIOS
3621			version 0.98 is known to be affected, 0.99 fixes the
3622			problem by letting the user disable the workaround.
3623
3624	mga=		[HW,DRM]
3625
3626	microcode.force_minrev=	[X86]
3627			Format: <bool>
3628			Enable or disable the microcode minimal revision
3629			enforcement for the runtime microcode loader.
3630
3631	mini2440=	[ARM,HW,KNL]
3632			Format:[0..2][b][c][t]
3633			Default: "0tb"
3634			MINI2440 configuration specification:
3635			0 - The attached screen is the 3.5" TFT
3636			1 - The attached screen is the 7" TFT
3637			2 - The VGA Shield is attached (1024x768)
3638			Leaving out the screen size parameter will not load
3639			the TFT driver, and the framebuffer will be left
3640			unconfigured.
3641			b - Enable backlight. The TFT backlight pin will be
3642			linked to the kernel VESA blanking code and a GPIO
3643			LED. This parameter is not necessary when using the
3644			VGA shield.
3645			c - Enable the s3c camera interface.
3646			t - Reserved for enabling touchscreen support. The
3647			touchscreen support is not enabled in the mainstream
3648			kernel as of 2.6.30, a preliminary port can be found
3649			in the "bleeding edge" mini2440 support kernel at
3650			https://repo.or.cz/w/linux-2.6/mini2440.git
3651
3652	mitigations=
3653			[X86,PPC,S390,ARM64,EARLY] Control optional mitigations for
3654			CPU vulnerabilities.  This is a set of curated,
3655			arch-independent options, each of which is an
3656			aggregation of existing arch-specific options.
3657
3658			Note, "mitigations" is supported if and only if the
3659			kernel was built with CPU_MITIGATIONS=y.
3660
3661			off
3662				Disable all optional CPU mitigations.  This
3663				improves system performance, but it may also
3664				expose users to several CPU vulnerabilities.
3665				Equivalent to: if nokaslr then kpti=0 [ARM64]
3666					       gather_data_sampling=off [X86]
3667					       kvm.nx_huge_pages=off [X86]
3668					       l1tf=off [X86]
3669					       mds=off [X86]
3670					       mmio_stale_data=off [X86]
3671					       no_entry_flush [PPC]
3672					       no_uaccess_flush [PPC]
3673					       nobp=0 [S390]
3674					       nopti [X86,PPC]
3675					       nospectre_bhb [ARM64]
3676					       nospectre_v1 [X86,PPC]
3677					       nospectre_v2 [X86,PPC,S390,ARM64]
3678					       reg_file_data_sampling=off [X86]
3679					       retbleed=off [X86]
3680					       spec_rstack_overflow=off [X86]
3681					       spec_store_bypass_disable=off [X86,PPC]
3682					       spectre_bhi=off [X86]
3683					       spectre_v2_user=off [X86]
3684					       srbds=off [X86,INTEL]
3685					       ssbd=force-off [ARM64]
3686					       tsx_async_abort=off [X86]
3687
3688				Exceptions:
3689					       This does not have any effect on
3690					       kvm.nx_huge_pages when
3691					       kvm.nx_huge_pages=force.
3692
3693			auto (default)
3694				Mitigate all CPU vulnerabilities, but leave SMT
3695				enabled, even if it's vulnerable.  This is for
3696				users who don't want to be surprised by SMT
3697				getting disabled across kernel upgrades, or who
3698				have other ways of avoiding SMT-based attacks.
3699				Equivalent to: (default behavior)
3700
3701			auto,nosmt
3702				Mitigate all CPU vulnerabilities, disabling SMT
3703				if needed.  This is for users who always want to
3704				be fully mitigated, even if it means losing SMT.
3705				Equivalent to: l1tf=flush,nosmt [X86]
3706					       mds=full,nosmt [X86]
3707					       tsx_async_abort=full,nosmt [X86]
3708					       mmio_stale_data=full,nosmt [X86]
3709					       retbleed=auto,nosmt [X86]
3710
3711	mminit_loglevel=
3712			[KNL,EARLY] When CONFIG_DEBUG_MEMORY_INIT is set, this
3713			parameter allows control of the logging verbosity for
3714			the additional memory initialisation checks. A value
3715			of 0 disables mminit logging and a level of 4 will
3716			log everything. Information is printed at KERN_DEBUG
3717			so loglevel=8 may also need to be specified.
3718
3719	mmio_stale_data=
3720			[X86,INTEL,EARLY] Control mitigation for the Processor
3721			MMIO Stale Data vulnerabilities.
3722
3723			Processor MMIO Stale Data is a class of
3724			vulnerabilities that may expose data after an MMIO
3725			operation. Exposed data could originate or end in
3726			the same CPU buffers as affected by MDS and TAA.
3727			Therefore, similar to MDS and TAA, the mitigation
3728			is to clear the affected CPU buffers.
3729
3730			This parameter controls the mitigation. The
3731			options are:
3732
3733			full       - Enable mitigation on vulnerable CPUs
3734
3735			full,nosmt - Enable mitigation and disable SMT on
3736				     vulnerable CPUs.
3737
3738			off        - Unconditionally disable mitigation
3739
3740			On MDS or TAA affected machines,
3741			mmio_stale_data=off can be prevented by an active
3742			MDS or TAA mitigation as these vulnerabilities are
3743			mitigated with the same mechanism so in order to
3744			disable this mitigation, you need to specify
3745			mds=off and tsx_async_abort=off too.
3746
3747			Not specifying this option is equivalent to
3748			mmio_stale_data=full.
3749
3750			For details see:
3751			Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3752
3753	<module>.async_probe[=<bool>] [KNL]
3754			If no <bool> value is specified or if the value
3755			specified is not a valid <bool>, enable asynchronous
3756			probe on this module.  Otherwise, enable/disable
3757			asynchronous probe on this module as indicated by the
3758			<bool> value. See also: module.async_probe
3759
3760	module.async_probe=<bool>
3761			[KNL] When set to true, modules will use async probing
3762			by default. To enable/disable async probing for a
3763			specific module, use the module specific control that
3764			is documented under <module>.async_probe. When both
3765			module.async_probe and <module>.async_probe are
3766			specified, <module>.async_probe takes precedence for
3767			the specific module.
3768
3769	module.enable_dups_trace
3770			[KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
3771			this means that duplicate request_module() calls will
3772			trigger a WARN_ON() instead of a pr_warn(). Note that
3773			if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
3774			will always be issued and this option does nothing.
3775	module.sig_enforce
3776			[KNL] When CONFIG_MODULE_SIG is set, this means that
3777			modules without (valid) signatures will fail to load.
3778			Note that if CONFIG_MODULE_SIG_FORCE is set, that
3779			is always true, so this option does nothing.
3780
3781	module_blacklist=  [KNL] Do not load a comma-separated list of
3782			modules.  Useful for debugging problem modules.
3783
3784	mousedev.tap_time=
3785			[MOUSE] Maximum time between finger touching and
3786			leaving touchpad surface for touch to be considered
3787			a tap and be reported as a left button click (for
3788			touchpads working in absolute mode only).
3789			Format: <msecs>
3790	mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
3791			reporting absolute coordinates, such as tablets
3792	mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
3793			reporting absolute coordinates, such as tablets
3794
3795	movablecore=	[KNL,X86,PPC,EARLY]
3796			Format: nn[KMGTPE] | nn%
3797			This parameter is the complement to kernelcore=, it
3798			specifies the amount of memory used for migratable
3799			allocations.  If both kernelcore and movablecore is
3800			specified, then kernelcore will be at *least* the
3801			specified value but may be more.  If movablecore on its
3802			own is specified, the administrator must be careful
3803			that the amount of memory usable for all allocations
3804			is not too small.
3805
3806	movable_node	[KNL,EARLY] Boot-time switch to make hotplugable memory
3807			NUMA nodes to be movable. This means that the memory
3808			of such nodes will be usable only for movable
3809			allocations which rules out almost all kernel
3810			allocations. Use with caution!
3811
3812	MTD_Partition=	[MTD]
3813			Format: <name>,<region-number>,<size>,<offset>
3814
3815	MTD_Region=	[MTD] Format:
3816			<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3817
3818	mtdparts=	[MTD]
3819			See drivers/mtd/parsers/cmdlinepart.c
3820
3821	mtouchusb.raw_coordinates=
3822			[HW] Make the MicroTouch USB driver use raw coordinates
3823			('y', default) or cooked coordinates ('n')
3824
3825	mtrr=debug	[X86,EARLY]
3826			Enable printing debug information related to MTRR
3827			registers at boot time.
3828
3829	mtrr_chunk_size=nn[KMG,X86,EARLY]
3830			used for mtrr cleanup. It is largest continuous chunk
3831			that could hold holes aka. UC entries.
3832
3833	mtrr_gran_size=nn[KMG,X86,EARLY]
3834			Used for mtrr cleanup. It is granularity of mtrr block.
3835			Default is 1.
3836			Large value could prevent small alignment from
3837			using up MTRRs.
3838
3839	mtrr_spare_reg_nr=n [X86,EARLY]
3840			Format: <integer>
3841			Range: 0,7 : spare reg number
3842			Default : 1
3843			Used for mtrr cleanup. It is spare mtrr entries number.
3844			Set to 2 or more if your graphical card needs more.
3845
3846	multitce=off	[PPC]  This parameter disables the use of the pSeries
3847			firmware feature for updating multiple TCE entries
3848			at a time.
3849
3850	n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
3851
3852	netdev=		[NET] Network devices parameters
3853			Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3854			Note that mem_start is often overloaded to mean
3855			something different and driver-specific.
3856			This usage is only documented in each driver source
3857			file if at all.
3858
3859	netpoll.carrier_timeout=
3860			[NET] Specifies amount of time (in seconds) that
3861			netpoll should wait for a carrier. By default netpoll
3862			waits 4 seconds.
3863
3864	nf_conntrack.acct=
3865			[NETFILTER] Enable connection tracking flow accounting
3866			0 to disable accounting
3867			1 to enable accounting
3868			Default value is 0.
3869
3870	nfs.cache_getent=
3871			[NFS] sets the pathname to the program which is used
3872			to update the NFS client cache entries.
3873
3874	nfs.cache_getent_timeout=
3875			[NFS] sets the timeout after which an attempt to
3876			update a cache entry is deemed to have failed.
3877
3878	nfs.callback_nr_threads=
3879			[NFSv4] set the total number of threads that the
3880			NFS client will assign to service NFSv4 callback
3881			requests.
3882
3883	nfs.callback_tcpport=
3884			[NFS] set the TCP port on which the NFSv4 callback
3885			channel should listen.
3886
3887	nfs.delay_retrans=
3888			[NFS] specifies the number of times the NFSv4 client
3889			retries the request before returning an EAGAIN error,
3890			after a reply of NFS4ERR_DELAY from the server.
3891			Only applies if the softerr mount option is enabled,
3892			and the specified value is >= 0.
3893
3894	nfs.enable_ino64=
3895			[NFS] enable 64-bit inode numbers.
3896			If zero, the NFS client will fake up a 32-bit inode
3897			number for the readdir() and stat() syscalls instead
3898			of returning the full 64-bit number.
3899			The default is to return 64-bit inode numbers.
3900
3901	nfs.idmap_cache_timeout=
3902			[NFS] set the maximum lifetime for idmapper cache
3903			entries.
3904
3905	nfs.max_session_cb_slots=
3906			[NFSv4.1] Sets the maximum number of session
3907			slots the client will assign to the callback
3908			channel. This determines the maximum number of
3909			callbacks the client will process in parallel for
3910			a particular server.
3911
3912	nfs.max_session_slots=
3913			[NFSv4.1] Sets the maximum number of session slots
3914			the client will attempt to negotiate with the server.
3915			This limits the number of simultaneous RPC requests
3916			that the client can send to the NFSv4.1 server.
3917			Note that there is little point in setting this
3918			value higher than the max_tcp_slot_table_limit.
3919
3920	nfs.nfs4_disable_idmapping=
3921			[NFSv4] When set to the default of '1', this option
3922			ensures that both the RPC level authentication
3923			scheme and the NFS level operations agree to use
3924			numeric uids/gids if the mount is using the
3925			'sec=sys' security flavour. In effect it is
3926			disabling idmapping, which can make migration from
3927			legacy NFSv2/v3 systems to NFSv4 easier.
3928			Servers that do not support this mode of operation
3929			will be autodetected by the client, and it will fall
3930			back to using the idmapper.
3931			To turn off this behaviour, set the value to '0'.
3932
3933	nfs.nfs4_unique_id=
3934			[NFS4] Specify an additional fixed unique ident-
3935			ification string that NFSv4 clients can insert into
3936			their nfs_client_id4 string.  This is typically a
3937			UUID that is generated at system install time.
3938
3939	nfs.recover_lost_locks=
3940			[NFSv4] Attempt to recover locks that were lost due
3941			to a lease timeout on the server. Please note that
3942			doing this risks data corruption, since there are
3943			no guarantees that the file will remain unchanged
3944			after the locks are lost.
3945			If you want to enable the kernel legacy behaviour of
3946			attempting to recover these locks, then set this
3947			parameter to '1'.
3948			The default parameter value of '0' causes the kernel
3949			not to attempt recovery of lost locks.
3950
3951	nfs.send_implementation_id=
3952			[NFSv4.1] Send client implementation identification
3953			information in exchange_id requests.
3954			If zero, no implementation identification information
3955			will be sent.
3956			The default is to send the implementation identification
3957			information.
3958
3959	nfs4.layoutstats_timer=
3960			[NFSv4.2] Change the rate at which the kernel sends
3961			layoutstats to the pNFS metadata server.
3962
3963			Setting this to value to 0 causes the kernel to use
3964			whatever value is the default set by the layout
3965			driver. A non-zero value sets the minimum interval
3966			in seconds between layoutstats transmissions.
3967
3968	nfsd.inter_copy_offload_enable=
3969			[NFSv4.2] When set to 1, the server will support
3970			server-to-server copies for which this server is
3971			the destination of the copy.
3972
3973	nfsd.nfs4_disable_idmapping=
3974			[NFSv4] When set to the default of '1', the NFSv4
3975			server will return only numeric uids and gids to
3976			clients using auth_sys, and will accept numeric uids
3977			and gids from such clients.  This is intended to ease
3978			migration from NFSv2/v3.
3979
3980	nfsd.nfsd4_ssc_umount_timeout=
3981			[NFSv4.2] When used as the destination of a
3982			server-to-server copy, knfsd temporarily mounts
3983			the source server.  It caches the mount in case
3984			it will be needed again, and discards it if not
3985			used for the number of milliseconds specified by
3986			this parameter.
3987
3988	nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
3989			See Documentation/admin-guide/nfs/nfsroot.rst.
3990
3991	nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
3992			See Documentation/admin-guide/nfs/nfsroot.rst.
3993
3994	nfsrootdebug	[NFS] enable nfsroot debugging messages.
3995			See Documentation/admin-guide/nfs/nfsroot.rst.
3996
3997	nmi_backtrace.backtrace_idle [KNL]
3998			Dump stacks even of idle CPUs in response to an
3999			NMI stack-backtrace request.
4000
4001	nmi_debug=	[KNL,SH] Specify one or more actions to take
4002			when a NMI is triggered.
4003			Format: [state][,regs][,debounce][,die]
4004
4005	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
4006			Format: [panic,][nopanic,][rNNN,][num]
4007			Valid num: 0 or 1
4008			0 - turn hardlockup detector in nmi_watchdog off
4009			1 - turn hardlockup detector in nmi_watchdog on
4010			rNNN - configure the watchdog with raw perf event 0xNNN
4011
4012			When panic is specified, panic when an NMI watchdog
4013			timeout occurs (or 'nopanic' to not panic on an NMI
4014			watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
4015			To disable both hard and soft lockup detectors,
4016			please see 'nowatchdog'.
4017			This is useful when you use a panic=... timeout and
4018			need the box quickly up again.
4019
4020			These settings can be accessed at runtime via
4021			the nmi_watchdog and hardlockup_panic sysctls.
4022
4023	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
4024			emulation library even if a 387 maths coprocessor
4025			is present.
4026
4027	no4lvl		[RISCV,EARLY] Disable 4-level and 5-level paging modes.
4028			Forces kernel to use 3-level paging instead.
4029
4030	no5lvl		[X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces
4031			kernel to use 4-level paging instead.
4032
4033	noalign		[KNL,ARM]
4034
4035	noapic		[SMP,APIC,EARLY] Tells the kernel to not make use of any
4036			IOAPICs that may be present in the system.
4037
4038	noapictimer	[APIC,X86] Don't set up the APIC timer
4039
4040	noautogroup	Disable scheduler automatic task group creation.
4041
4042	nocache		[ARM,EARLY]
4043
4044	no_console_suspend
4045			[HW] Never suspend the console
4046			Disable suspending of consoles during suspend and
4047			hibernate operations.  Once disabled, debugging
4048			messages can reach various consoles while the rest
4049			of the system is being put to sleep (ie, while
4050			debugging driver suspend/resume hooks).  This may
4051			not work reliably with all consoles, but is known
4052			to work with serial and VGA consoles.
4053			To facilitate more flexible debugging, we also add
4054			console_suspend, a printk module parameter to control
4055			it. Users could use console_suspend (usually
4056			/sys/module/printk/parameters/console_suspend) to
4057			turn on/off it dynamically.
4058
4059	no_debug_objects
4060			[KNL,EARLY] Disable object debugging
4061
4062	nodsp		[SH] Disable hardware DSP at boot time.
4063
4064	noefi		[EFI,EARLY] Disable EFI runtime services support.
4065
4066	no_entry_flush  [PPC,EARLY] Don't flush the L1-D cache when entering the kernel.
4067
4068	noexec32	[X86-64]
4069			This affects only 32-bit executables.
4070			noexec32=on: enable non-executable mappings (default)
4071				read doesn't imply executable mappings
4072			noexec32=off: disable non-executable mappings
4073				read implies executable mappings
4074
4075	no_file_caps	Tells the kernel not to honor file capabilities.  The
4076			only way then for a file to be executed with privilege
4077			is to be setuid root or executed by root.
4078
4079	nofpu		[MIPS,SH] Disable hardware FPU at boot time.
4080
4081	nofsgsbase	[X86] Disables FSGSBASE instructions.
4082
4083	nofxsr		[BUGS=X86-32] Disables x86 floating point extended
4084			register save and restore. The kernel will only save
4085			legacy floating-point registers on task switch.
4086
4087	nogbpages	[X86] Do not use GB pages for kernel direct mappings.
4088
4089	no_hash_pointers
4090			[KNL,EARLY]
4091			Force pointers printed to the console or buffers to be
4092			unhashed.  By default, when a pointer is printed via %p
4093			format string, that pointer is "hashed", i.e. obscured
4094			by hashing the pointer value.  This is a security feature
4095			that hides actual kernel addresses from unprivileged
4096			users, but it also makes debugging the kernel more
4097			difficult since unequal pointers can no longer be
4098			compared.  However, if this command-line option is
4099			specified, then all normal pointers will have their true
4100			value printed. This option should only be specified when
4101			debugging the kernel.  Please do not use on production
4102			kernels.
4103
4104	nohibernate	[HIBERNATION] Disable hibernation and resume.
4105
4106	nohlt		[ARM,ARM64,MICROBLAZE,MIPS,PPC,RISCV,SH] Forces the kernel to
4107			busy wait in do_idle() and not use the arch_cpu_idle()
4108			implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
4109			to be effective. This is useful on platforms where the
4110			sleep(SH) or wfi(ARM,ARM64) instructions do not work
4111			correctly or when doing power measurements to evaluate
4112			the impact of the sleep instructions. This is also
4113			useful when using JTAG debugger.
4114
4115	nohpet		[X86] Don't use the HPET timer.
4116
4117	nohugeiomap	[KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings.
4118
4119	nohugevmalloc	[KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings.
4120
4121	nohz=		[KNL] Boottime enable/disable dynamic ticks
4122			Valid arguments: on, off
4123			Default: on
4124
4125	nohz_full=	[KNL,BOOT,SMP,ISOL]
4126			The argument is a cpu list, as described above.
4127			In kernels built with CONFIG_NO_HZ_FULL=y, set
4128			the specified list of CPUs whose tick will be stopped
4129			whenever possible. The boot CPU will be forced outside
4130			the range to maintain the timekeeping.  Any CPUs
4131			in this list will have their RCU callbacks offloaded,
4132			just as if they had also been called out in the
4133			rcu_nocbs= boot parameter.
4134
4135			Note that this argument takes precedence over
4136			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4137
4138	noinitrd	[RAM] Tells the kernel not to load any configured
4139			initial RAM disk.
4140
4141	nointremap	[X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
4142			remapping.
4143			[Deprecated - use intremap=off]
4144
4145	noinvpcid	[X86,EARLY] Disable the INVPCID cpu feature.
4146
4147	noiotrap	[SH] Disables trapped I/O port accesses.
4148
4149	noirqdebug	[X86-32] Disables the code which attempts to detect and
4150			disable unhandled interrupt sources.
4151
4152	noisapnp	[ISAPNP] Disables ISA PnP code.
4153
4154	nokaslr		[KNL,EARLY]
4155			When CONFIG_RANDOMIZE_BASE is set, this disables
4156			kernel and module base offset ASLR (Address Space
4157			Layout Randomization).
4158
4159	no-kvmapf	[X86,KVM,EARLY] Disable paravirtualized asynchronous page
4160			fault handling.
4161
4162	no-kvmclock	[X86,KVM,EARLY] Disable paravirtualized KVM clock driver
4163
4164	nolapic		[X86-32,APIC,EARLY] Do not enable or use the local APIC.
4165
4166	nolapic_timer	[X86-32,APIC,EARLY] Do not use the local APIC timer.
4167
4168	nomce		[X86-32] Disable Machine Check Exception
4169
4170	nomfgpt		[X86-32] Disable Multi-Function General Purpose
4171			Timer usage (for AMD Geode machines).
4172
4173	nomodeset	Disable kernel modesetting. Most systems' firmware
4174			sets up a display mode and provides framebuffer memory
4175			for output. With nomodeset, DRM and fbdev drivers will
4176			not load if they could possibly displace the pre-
4177			initialized output. Only the system framebuffer will
4178			be available for use. The respective drivers will not
4179			perform display-mode changes or accelerated rendering.
4180
4181			Useful as error fallback, or for testing and debugging.
4182
4183	nomodule	Disable module load
4184
4185	nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
4186			shutdown the other cpus.  Instead use the REBOOT_VECTOR
4187			irq.
4188
4189	nopat		[X86,EARLY] Disable PAT (page attribute table extension of
4190			pagetables) support.
4191
4192	nopcid		[X86-64,EARLY] Disable the PCID cpu feature.
4193
4194	nopku		[X86] Disable Memory Protection Keys CPU feature found
4195			in some Intel CPUs.
4196
4197	nopti		[X86-64,EARLY]
4198			Equivalent to pti=off
4199
4200	nopv=		[X86,XEN,KVM,HYPER_V,VMWARE,EARLY]
4201			Disables the PV optimizations forcing the guest to run
4202			as generic guest with no PV drivers. Currently support
4203			XEN HVM, KVM, HYPER_V and VMWARE guest.
4204
4205	nopvspin	[X86,XEN,KVM,EARLY]
4206			Disables the qspinlock slow path using PV optimizations
4207			which allow the hypervisor to 'idle' the guest on lock
4208			contention.
4209
4210	norandmaps	Don't use address space randomization.  Equivalent to
4211			echo 0 > /proc/sys/kernel/randomize_va_space
4212
4213	noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
4214			with UP alternatives
4215
4216	noresume	[SWSUSP] Disables resume and restores original swap
4217			space.
4218
4219	no-scroll	[VGA] Disables scrollback.
4220			This is required for the Braillex ib80-piezo Braille
4221			reader made by F.H. Papenmeier (Germany).
4222
4223	nosgx		[X86-64,SGX,EARLY] Disables Intel SGX kernel support.
4224
4225	nosmap		[PPC,EARLY]
4226			Disable SMAP (Supervisor Mode Access Prevention)
4227			even if it is supported by processor.
4228
4229	nosmep		[PPC64s,EARLY]
4230			Disable SMEP (Supervisor Mode Execution Prevention)
4231			even if it is supported by processor.
4232
4233	nosmp		[SMP,EARLY] Tells an SMP kernel to act as a UP kernel,
4234			and disable the IO APIC.  legacy for "maxcpus=0".
4235
4236	nosmt		[KNL,MIPS,PPC,S390,EARLY] Disable symmetric multithreading (SMT).
4237			Equivalent to smt=1.
4238
4239			[KNL,X86,PPC] Disable symmetric multithreading (SMT).
4240			nosmt=force: Force disable SMT, cannot be undone
4241				     via the sysfs control file.
4242
4243	nosoftlockup	[KNL] Disable the soft-lockup detector.
4244
4245	nospec_store_bypass_disable
4246			[HW,EARLY] Disable all mitigations for the Speculative
4247			Store Bypass vulnerability
4248
4249	nospectre_bhb	[ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch
4250			history injection) vulnerability. System may allow data leaks
4251			with this option.
4252
4253	nospectre_v1	[X86,PPC,EARLY] Disable mitigations for Spectre Variant 1
4254			(bounds check bypass). With this option data leaks are
4255			possible in the system.
4256
4257	nospectre_v2	[X86,PPC_E500,ARM64,EARLY] Disable all mitigations
4258			for the Spectre variant 2 (indirect branch
4259			prediction) vulnerability. System may allow data
4260			leaks with this option.
4261
4262	no-steal-acc	[X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY]
4263			Disable paravirtualized steal time accounting. steal time
4264			is computed, but won't influence scheduler behaviour
4265
4266	nosync		[HW,M68K] Disables sync negotiation for all devices.
4267
4268	no_timer_check	[X86,APIC] Disables the code which tests for broken
4269			timer IRQ sources, i.e., the IO-APIC timer. This can
4270			work around problems with incorrect timer
4271			initialization on some boards.
4272
4273	no_uaccess_flush
4274	                [PPC,EARLY] Don't flush the L1-D cache after accessing user data.
4275
4276	novmcoredd	[KNL,KDUMP]
4277			Disable device dump. Device dump allows drivers to
4278			append dump data to vmcore so you can collect driver
4279			specified debug info.  Drivers can append the data
4280			without any limit and this data is stored in memory,
4281			so this may cause significant memory stress.  Disabling
4282			device dump can help save memory but the driver debug
4283			data will be no longer available.  This parameter
4284			is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
4285			is set.
4286
4287	no-vmw-sched-clock
4288			[X86,PV_OPS,EARLY] Disable paravirtualized VMware
4289			scheduler clock and use the default one.
4290
4291	nowatchdog	[KNL] Disable both lockup detectors, i.e.
4292			soft-lockup and NMI watchdog (hard-lockup).
4293
4294	nowb		[ARM,EARLY]
4295
4296	nox2apic	[X86-64,APIC,EARLY] Do not enable x2APIC mode.
4297
4298			NOTE: this parameter will be ignored on systems with the
4299			LEGACY_XAPIC_DISABLED bit set in the
4300			IA32_XAPIC_DISABLE_STATUS MSR.
4301
4302	noxsave		[BUGS=X86] Disables x86 extended register state save
4303			and restore using xsave. The kernel will fallback to
4304			enabling legacy floating-point and sse state.
4305
4306	noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
4307			register states. The kernel will fall back to use
4308			xsave to save the states. By using this parameter,
4309			performance of saving the states is degraded because
4310			xsave doesn't support modified optimization while
4311			xsaveopt supports it on xsaveopt enabled systems.
4312
4313	noxsaves	[X86] Disables xsaves and xrstors used in saving and
4314			restoring x86 extended register state in compacted
4315			form of xsave area. The kernel will fall back to use
4316			xsaveopt and xrstor to save and restore the states
4317			in standard form of xsave area. By using this
4318			parameter, xsave area per process might occupy more
4319			memory on xsaves enabled systems.
4320
4321	nr_cpus=	[SMP,EARLY] Maximum number of processors that an SMP kernel
4322			could support.  nr_cpus=n : n >= 1 limits the kernel to
4323			support 'n' processors. It could be larger than the
4324			number of already plugged CPU during bootup, later in
4325			runtime you can physically add extra cpu until it reaches
4326			n. So during boot up some boot time memory for per-cpu
4327			variables need be pre-allocated for later physical cpu
4328			hot plugging.
4329
4330	nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
4331
4332	numa=off 	[KNL, ARM64, PPC, RISCV, SPARC, X86, EARLY]
4333			Disable NUMA, Only set up a single NUMA node
4334			spanning all memory.
4335
4336	numa=fake=<size>[MG]
4337			[KNL, ARM64, RISCV, X86, EARLY]
4338			If given as a memory unit, fills all system RAM with
4339			nodes of size interleaved over physical nodes.
4340
4341	numa=fake=<N>
4342			[KNL, ARM64, RISCV, X86, EARLY]
4343			If given as an integer, fills all system RAM with N
4344			fake nodes interleaved over physical nodes.
4345
4346	numa=fake=<N>U
4347			[KNL, ARM64, RISCV, X86, EARLY]
4348			If given as an integer followed by 'U', it will
4349			divide each physical node into N emulated nodes.
4350
4351	numa=noacpi	[X86] Don't parse the SRAT table for NUMA setup
4352
4353	numa=nohmat	[X86] Don't parse the HMAT table for NUMA setup, or
4354			soft-reserved memory partitioning.
4355
4356	numa_balancing=	[KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4357			NUMA balancing.
4358			Allowed values are enable and disable
4359
4360	numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4361			'node', 'default' can be specified
4362			This can be set from sysctl after boot.
4363			See Documentation/admin-guide/sysctl/vm.rst for details.
4364
4365	ohci1394_dma=early	[HW,EARLY] enable debugging via the ohci1394 driver.
4366			See Documentation/core-api/debugging-via-ohci1394.rst for more
4367			info.
4368
4369	olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4370			Rather than timing out after 20 ms if an EC
4371			command is not properly ACKed, override the length
4372			of the timeout.  We have interrupts disabled while
4373			waiting for the ACK, so if this is set too high
4374			interrupts *may* be lost!
4375
4376	omap_mux=	[OMAP] Override bootloader pin multiplexing.
4377			Format: <mux_mode0.mode_name=value>...
4378			For example, to override I2C bus2:
4379			omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4380
4381	onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
4382
4383			Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4384
4385			boundary - index of last SLC block on Flex-OneNAND.
4386				   The remaining blocks are configured as MLC blocks.
4387			lock	 - Configure if Flex-OneNAND boundary should be locked.
4388				   Once locked, the boundary cannot be changed.
4389				   1 indicates lock status, 0 indicates unlock status.
4390
4391	oops=panic	[KNL,EARLY]
4392			Always panic on oopses. Default is to just kill the
4393			process, but there is a small probability of
4394			deadlocking the machine.
4395			This will also cause panics on machine check exceptions.
4396			Useful together with panic=30 to trigger a reboot.
4397
4398	page_alloc.shuffle=
4399			[KNL] Boolean flag to control whether the page allocator
4400			should randomize its free lists. This parameter can be
4401			used to enable/disable page randomization. The state of
4402			the flag can be read from sysfs at:
4403			/sys/module/page_alloc/parameters/shuffle.
4404			This parameter is only available if CONFIG_SHUFFLE_PAGE_ALLOCATOR=y.
4405
4406	page_owner=	[KNL,EARLY] Boot-time page_owner enabling option.
4407			Storage of the information about who allocated
4408			each page is disabled in default. With this switch,
4409			we can turn it on.
4410			on: enable the feature
4411
4412	page_poison=	[KNL,EARLY] Boot-time parameter changing the state of
4413			poisoning on the buddy allocator, available with
4414			CONFIG_PAGE_POISONING=y.
4415			off: turn off poisoning (default)
4416			on: turn on poisoning
4417
4418	page_reporting.page_reporting_order=
4419			[KNL] Minimal page reporting order
4420			Format: <integer>
4421			Adjust the minimal page reporting order. The page
4422			reporting is disabled when it exceeds MAX_PAGE_ORDER.
4423
4424	panic=		[KNL] Kernel behaviour on panic: delay <timeout>
4425			timeout > 0: seconds before rebooting
4426			timeout = 0: wait forever
4427			timeout < 0: reboot immediately
4428			Format: <timeout>
4429
4430	panic_on_taint=	[KNL,EARLY]
4431			Bitmask for conditionally calling panic() in add_taint()
4432			Format: <hex>[,nousertaint]
4433			Hexadecimal bitmask representing the set of TAINT flags
4434			that will cause the kernel to panic when add_taint() is
4435			called with any of the flags in this set.
4436			The optional switch "nousertaint" can be utilized to
4437			prevent userspace forced crashes by writing to sysctl
4438			/proc/sys/kernel/tainted any flagset matching with the
4439			bitmask set on panic_on_taint.
4440			See Documentation/admin-guide/tainted-kernels.rst for
4441			extra details on the taint flags that users can pick
4442			to compose the bitmask to assign to panic_on_taint.
4443
4444	panic_on_warn=1	panic() instead of WARN().  Useful to cause kdump
4445			on a WARN().
4446
4447	panic_print=	Bitmask for printing system info when panic happens.
4448			User can chose combination of the following bits:
4449			bit 0: print all tasks info
4450			bit 1: print system memory info
4451			bit 2: print timer info
4452			bit 3: print locks info if CONFIG_LOCKDEP is on
4453			bit 4: print ftrace buffer
4454			bit 5: print all printk messages in buffer
4455			bit 6: print all CPUs backtrace (if available in the arch)
4456			bit 7: print only tasks in uninterruptible (blocked) state
4457			*Be aware* that this option may print a _lot_ of lines,
4458			so there are risks of losing older messages in the log.
4459			Use this option carefully, maybe worth to setup a
4460			bigger log buffer with "log_buf_len" along with this.
4461
4462	parkbd.port=	[HW] Parallel port number the keyboard adapter is
4463			connected to, default is 0.
4464			Format: <parport#>
4465	parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
4466			0 for XT, 1 for AT (default is AT).
4467			Format: <mode>
4468
4469	parport=	[HW,PPT] Specify parallel ports. 0 disables.
4470			Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4471			Use 'auto' to force the driver to use any
4472			IRQ/DMA settings detected (the default is to
4473			ignore detected IRQ/DMA settings because of
4474			possible conflicts). You can specify the base
4475			address, IRQ, and DMA settings; IRQ and DMA
4476			should be numbers, or 'auto' (for using detected
4477			settings on that particular port), or 'nofifo'
4478			(to avoid using a FIFO even if it is detected).
4479			Parallel ports are assigned in the order they
4480			are specified on the command line, starting
4481			with parport0.
4482
4483	parport_init_mode=	[HW,PPT]
4484			Configure VIA parallel port to operate in
4485			a specific mode. This is necessary on Pegasos
4486			computer where firmware has no options for setting
4487			up parallel port mode and sets it to spp.
4488			Currently this function knows 686a and 8231 chips.
4489			Format: [spp|ps2|epp|ecp|ecpepp]
4490
4491	pata_legacy.all=	[HW,LIBATA]
4492			Format: <int>
4493			Set to non-zero to probe primary and secondary ISA
4494			port ranges on PCI systems where no PCI PATA device
4495			has been found at either range.  Disabled by default.
4496
4497	pata_legacy.autospeed=	[HW,LIBATA]
4498			Format: <int>
4499			Set to non-zero if a chip is present that snoops speed
4500			changes.  Disabled by default.
4501
4502	pata_legacy.ht6560a=	[HW,LIBATA]
4503			Format: <int>
4504			Set to 1, 2, or 3 for HT 6560A on the primary channel,
4505			the secondary channel, or both channels respectively.
4506			Disabled by default.
4507
4508	pata_legacy.ht6560b=	[HW,LIBATA]
4509			Format: <int>
4510			Set to 1, 2, or 3 for HT 6560B on the primary channel,
4511			the secondary channel, or both channels respectively.
4512			Disabled by default.
4513
4514	pata_legacy.iordy_mask=	[HW,LIBATA]
4515			Format: <int>
4516			IORDY enable mask.  Set individual bits to allow IORDY
4517			for the respective channel.  Bit 0 is for the first
4518			legacy channel handled by this driver, bit 1 is for
4519			the second channel, and so on.  The sequence will often
4520			correspond to the primary legacy channel, the secondary
4521			legacy channel, and so on, but the handling of a PCI
4522			bus and the use of other driver options may interfere
4523			with the sequence.  By default IORDY is allowed across
4524			all channels.
4525
4526	pata_legacy.opti82c46x=	[HW,LIBATA]
4527			Format: <int>
4528			Set to 1, 2, or 3 for Opti 82c611A on the primary
4529			channel, the secondary channel, or both channels
4530			respectively.  Disabled by default.
4531
4532	pata_legacy.opti82c611a=	[HW,LIBATA]
4533			Format: <int>
4534			Set to 1, 2, or 3 for Opti 82c465MV on the primary
4535			channel, the secondary channel, or both channels
4536			respectively.  Disabled by default.
4537
4538	pata_legacy.pio_mask=	[HW,LIBATA]
4539			Format: <int>
4540			PIO mode mask for autospeed devices.  Set individual
4541			bits to allow the use of the respective PIO modes.
4542			Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4543			All modes allowed by default.
4544
4545	pata_legacy.probe_all=	[HW,LIBATA]
4546			Format: <int>
4547			Set to non-zero to probe tertiary and further ISA
4548			port ranges on PCI systems.  Disabled by default.
4549
4550	pata_legacy.probe_mask=	[HW,LIBATA]
4551			Format: <int>
4552			Probe mask for legacy ISA PATA ports.  Depending on
4553			platform configuration and the use of other driver
4554			options up to 6 legacy ports are supported: 0x1f0,
4555			0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4556			of individual ports can be disabled by setting the
4557			corresponding bits in the mask to 1.  Bit 0 is for
4558			the first port in the list above (0x1f0), and so on.
4559			By default all supported ports are probed.
4560
4561	pata_legacy.qdi=	[HW,LIBATA]
4562			Format: <int>
4563			Set to non-zero to probe QDI controllers.  By default
4564			set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4565
4566	pata_legacy.winbond=	[HW,LIBATA]
4567			Format: <int>
4568			Set to non-zero to probe Winbond controllers.  Use
4569			the standard I/O port (0x130) if 1, otherwise the
4570			value given is the I/O port to use (typically 0x1b0).
4571			By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4572			0 otherwise.
4573
4574	pata_platform.pio_mask=	[HW,LIBATA]
4575			Format: <int>
4576			Supported PIO mode mask.  Set individual bits to allow
4577			the use of the respective PIO modes.  Bit 0 is for
4578			mode 0, bit 1 is for mode 1, and so on.  Mode 0 only
4579			allowed by default.
4580
4581	pause_on_oops=<int>
4582			Halt all CPUs after the first oops has been printed for
4583			the specified number of seconds.  This is to be used if
4584			your oopses keep scrolling off the screen.
4585
4586	pcbit=		[HW,ISDN]
4587
4588	pci=option[,option...]	[PCI,EARLY] various PCI subsystem options.
4589
4590				Some options herein operate on a specific device
4591				or a set of devices (<pci_dev>). These are
4592				specified in one of the following formats:
4593
4594				[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4595				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4596
4597				Note: the first format specifies a PCI
4598				bus/device/function address which may change
4599				if new hardware is inserted, if motherboard
4600				firmware changes, or due to changes caused
4601				by other kernel parameters. If the
4602				domain is left unspecified, it is
4603				taken to be zero. Optionally, a path
4604				to a device through multiple device/function
4605				addresses can be specified after the base
4606				address (this is more robust against
4607				renumbering issues).  The second format
4608				selects devices using IDs from the
4609				configuration space which may match multiple
4610				devices in the system.
4611
4612		earlydump	dump PCI config space before the kernel
4613				changes anything
4614		off		[X86] don't probe for the PCI bus
4615		bios		[X86-32] force use of PCI BIOS, don't access
4616				the hardware directly. Use this if your machine
4617				has a non-standard PCI host bridge.
4618		nobios		[X86-32] disallow use of PCI BIOS, only direct
4619				hardware access methods are allowed. Use this
4620				if you experience crashes upon bootup and you
4621				suspect they are caused by the BIOS.
4622		conf1		[X86] Force use of PCI Configuration Access
4623				Mechanism 1 (config address in IO port 0xCF8,
4624				data in IO port 0xCFC, both 32-bit).
4625		conf2		[X86] Force use of PCI Configuration Access
4626				Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4627				the function, IO port 0xCFA, also 8-bit, sets
4628				bus number. The config space is then accessed
4629				through ports 0xC000-0xCFFF).
4630				See http://wiki.osdev.org/PCI for more info
4631				on the configuration access mechanisms.
4632		noaer		[PCIE] If the PCIEAER kernel config parameter is
4633				enabled, this kernel boot option can be used to
4634				disable the use of PCIE advanced error reporting.
4635		nodomains	[PCI] Disable support for multiple PCI
4636				root domains (aka PCI segments, in ACPI-speak).
4637		nommconf	[X86] Disable use of MMCONFIG for PCI
4638				Configuration
4639		check_enable_amd_mmconf [X86] check for and enable
4640				properly configured MMIO access to PCI
4641				config space on AMD family 10h CPU
4642		nomsi		[MSI] If the PCI_MSI kernel config parameter is
4643				enabled, this kernel boot option can be used to
4644				disable the use of MSI interrupts system-wide.
4645		noioapicquirk	[APIC] Disable all boot interrupt quirks.
4646				Safety option to keep boot IRQs enabled. This
4647				should never be necessary.
4648		ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
4649				primary IO-APIC for bridges that cannot disable
4650				boot IRQs. This fixes a source of spurious IRQs
4651				when the system masks IRQs.
4652		noioapicreroute	[APIC] Disable workaround that uses the
4653				boot IRQ equivalent of an IRQ that connects to
4654				a chipset where boot IRQs cannot be disabled.
4655				The opposite of ioapicreroute.
4656		biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
4657				routing table. These calls are known to be buggy
4658				on several machines and they hang the machine
4659				when used, but on other computers it's the only
4660				way to get the interrupt routing table. Try
4661				this option if the kernel is unable to allocate
4662				IRQs or discover secondary PCI buses on your
4663				motherboard.
4664		rom		[X86] Assign address space to expansion ROMs.
4665				Use with caution as certain devices share
4666				address decoders between ROMs and other
4667				resources.
4668		norom		[X86] Do not assign address space to
4669				expansion ROMs that do not already have
4670				BIOS assigned address ranges.
4671		nobar		[X86] Do not assign address space to the
4672				BARs that weren't assigned by the BIOS.
4673		irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
4674				assigned automatically to PCI devices. You can
4675				make the kernel exclude IRQs of your ISA cards
4676				this way.
4677		pirqaddr=0xAAAAA	[X86] Specify the physical address
4678				of the PIRQ table (normally generated
4679				by the BIOS) if it is outside the
4680				F0000h-100000h range.
4681		lastbus=N	[X86] Scan all buses thru bus #N. Can be
4682				useful if the kernel is unable to find your
4683				secondary buses and you want to tell it
4684				explicitly which ones they are.
4685		assign-busses	[X86] Always assign all PCI bus
4686				numbers ourselves, overriding
4687				whatever the firmware may have done.
4688		usepirqmask	[X86] Honor the possible IRQ mask stored
4689				in the BIOS $PIR table. This is needed on
4690				some systems with broken BIOSes, notably
4691				some HP Pavilion N5400 and Omnibook XE3
4692				notebooks. This will have no effect if ACPI
4693				IRQ routing is enabled.
4694		noacpi		[X86] Do not use ACPI for IRQ routing
4695				or for PCI scanning.
4696		use_crs		[X86] Use PCI host bridge window information
4697				from ACPI.  On BIOSes from 2008 or later, this
4698				is enabled by default.  If you need to use this,
4699				please report a bug.
4700		nocrs		[X86] Ignore PCI host bridge windows from ACPI.
4701				If you need to use this, please report a bug.
4702		use_e820	[X86] Use E820 reservations to exclude parts of
4703				PCI host bridge windows. This is a workaround
4704				for BIOS defects in host bridge _CRS methods.
4705				If you need to use this, please report a bug to
4706				<linux-pci@vger.kernel.org>.
4707		no_e820		[X86] Ignore E820 reservations for PCI host
4708				bridge windows. This is the default on modern
4709				hardware. If you need to use this, please report
4710				a bug to <linux-pci@vger.kernel.org>.
4711		routeirq	Do IRQ routing for all PCI devices.
4712				This is normally done in pci_enable_device(),
4713				so this option is a temporary workaround
4714				for broken drivers that don't call it.
4715		skip_isa_align	[X86] do not align io start addr, so can
4716				handle more pci cards
4717		noearly		[X86] Don't do any early type 1 scanning.
4718				This might help on some broken boards which
4719				machine check when some devices' config space
4720				is read. But various workarounds are disabled
4721				and some IOMMU drivers will not work.
4722		bfsort		Sort PCI devices into breadth-first order.
4723				This sorting is done to get a device
4724				order compatible with older (<= 2.4) kernels.
4725		nobfsort	Don't sort PCI devices into breadth-first order.
4726		pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
4727				tuning and use the BIOS-configured MPS defaults.
4728		pcie_bus_safe	Set every device's MPS to the largest value
4729				supported by all devices below the root complex.
4730		pcie_bus_perf	Set device MPS to the largest allowable MPS
4731				based on its parent bus. Also set MRRS (Max
4732				Read Request Size) to the largest supported
4733				value (no larger than the MPS that the device
4734				or bus can support) for best performance.
4735		pcie_bus_peer2peer	Set every device's MPS to 128B, which
4736				every device is guaranteed to support. This
4737				configuration allows peer-to-peer DMA between
4738				any pair of devices, possibly at the cost of
4739				reduced performance.  This also guarantees
4740				that hot-added devices will work.
4741		cbiosize=nn[KMG]	The fixed amount of bus space which is
4742				reserved for the CardBus bridge's IO window.
4743				The default value is 256 bytes.
4744		cbmemsize=nn[KMG]	The fixed amount of bus space which is
4745				reserved for the CardBus bridge's memory
4746				window. The default value is 64 megabytes.
4747		resource_alignment=
4748				Format:
4749				[<order of align>@]<pci_dev>[; ...]
4750				Specifies alignment and device to reassign
4751				aligned memory resources. How to
4752				specify the device is described above.
4753				If <order of align> is not specified,
4754				PAGE_SIZE is used as alignment.
4755				A PCI-PCI bridge can be specified if resource
4756				windows need to be expanded.
4757				To specify the alignment for several
4758				instances of a device, the PCI vendor,
4759				device, subvendor, and subdevice may be
4760				specified, e.g., 12@pci:8086:9c22:103c:198f
4761				for 4096-byte alignment.
4762		ecrc=		Enable/disable PCIe ECRC (transaction layer
4763				end-to-end CRC checking). Only effective if
4764				OS has native AER control (either granted by
4765				ACPI _OSC or forced via "pcie_ports=native")
4766				bios: Use BIOS/firmware settings. This is the
4767				the default.
4768				off: Turn ECRC off
4769				on: Turn ECRC on.
4770		hpiosize=nn[KMG]	The fixed amount of bus space which is
4771				reserved for hotplug bridge's IO window.
4772				Default size is 256 bytes.
4773		hpmmiosize=nn[KMG]	The fixed amount of bus space which is
4774				reserved for hotplug bridge's MMIO window.
4775				Default size is 2 megabytes.
4776		hpmmioprefsize=nn[KMG]	The fixed amount of bus space which is
4777				reserved for hotplug bridge's MMIO_PREF window.
4778				Default size is 2 megabytes.
4779		hpmemsize=nn[KMG]	The fixed amount of bus space which is
4780				reserved for hotplug bridge's MMIO and
4781				MMIO_PREF window.
4782				Default size is 2 megabytes.
4783		hpbussize=nn	The minimum amount of additional bus numbers
4784				reserved for buses below a hotplug bridge.
4785				Default is 1.
4786		realloc=	Enable/disable reallocating PCI bridge resources
4787				if allocations done by BIOS are too small to
4788				accommodate resources required by all child
4789				devices.
4790				off: Turn realloc off
4791				on: Turn realloc on
4792		realloc		same as realloc=on
4793		noari		do not use PCIe ARI.
4794		noats		[PCIE, Intel-IOMMU, AMD-IOMMU]
4795				do not use PCIe ATS (and IOMMU device IOTLB).
4796		pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
4797				only look for one device below a PCIe downstream
4798				port.
4799		big_root_window	Try to add a big 64bit memory window to the PCIe
4800				root complex on AMD CPUs. Some GFX hardware
4801				can resize a BAR to allow access to all VRAM.
4802				Adding the window is slightly risky (it may
4803				conflict with unreported devices), so this
4804				taints the kernel.
4805		disable_acs_redir=<pci_dev>[; ...]
4806				Specify one or more PCI devices (in the format
4807				specified above) separated by semicolons.
4808				Each device specified will have the PCI ACS
4809				redirect capabilities forced off which will
4810				allow P2P traffic between devices through
4811				bridges without forcing it upstream. Note:
4812				this removes isolation between devices and
4813				may put more devices in an IOMMU group.
4814		config_acs=
4815				Format:
4816				<ACS flags>@<pci_dev>[; ...]
4817				Specify one or more PCI devices (in the format
4818				specified above) optionally prepended with flags
4819				and separated by semicolons. The respective
4820				capabilities will be enabled, disabled or
4821				unchanged based on what is specified in
4822				flags.
4823
4824				ACS Flags is defined as follows:
4825				  bit-0 : ACS Source Validation
4826				  bit-1 : ACS Translation Blocking
4827				  bit-2 : ACS P2P Request Redirect
4828				  bit-3 : ACS P2P Completion Redirect
4829				  bit-4 : ACS Upstream Forwarding
4830				  bit-5 : ACS P2P Egress Control
4831				  bit-6 : ACS Direct Translated P2P
4832				Each bit can be marked as:
4833				  '0' – force disabled
4834				  '1' – force enabled
4835				  'x' – unchanged
4836				For example,
4837				  pci=config_acs=10x@pci:0:0
4838				would configure all devices that support
4839				ACS to enable P2P Request Redirect, disable
4840				Translation Blocking, and leave Source
4841				Validation unchanged from whatever power-up
4842				or firmware set it to.
4843
4844				Note: this may remove isolation between devices
4845				and may put more devices in an IOMMU group.
4846		force_floating	[S390] Force usage of floating interrupts.
4847		nomio		[S390] Do not use MIO instructions.
4848		norid		[S390] ignore the RID field and force use of
4849				one PCI domain per PCI function
4850		notph		[PCIE] If the PCIE_TPH kernel config parameter
4851				is enabled, this kernel boot option can be used
4852				to disable PCIe TLP Processing Hints support
4853				system-wide.
4854
4855	pcie_aspm=	[PCIE] Forcibly enable or ignore PCIe Active State Power
4856			Management.
4857		off	Don't touch ASPM configuration at all.  Leave any
4858			configuration done by firmware unchanged.
4859		force	Enable ASPM even on devices that claim not to support it.
4860			WARNING: Forcing ASPM on may cause system lockups.
4861
4862	pcie_ports=	[PCIE] PCIe port services handling:
4863		native	Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4864			even if the platform doesn't give the OS permission to
4865			use them.  This may cause conflicts if the platform
4866			also tries to use these services.
4867		dpc-native	Use native PCIe service for DPC only.  May
4868				cause conflicts if firmware uses AER or DPC.
4869		compat	Disable native PCIe services (PME, AER, DPC, PCIe
4870			hotplug).
4871
4872	pcie_port_pm=	[PCIE] PCIe port power management handling:
4873		off	Disable power management of all PCIe ports
4874		force	Forcibly enable power management of all PCIe ports
4875
4876	pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
4877		nomsi	Do not use MSI for native PCIe PME signaling (this makes
4878			all PCIe root ports use INTx for all services).
4879
4880	pcmv=		[HW,PCMCIA] BadgePAD 4
4881
4882	pd_ignore_unused
4883			[PM]
4884			Keep all power-domains already enabled by bootloader on,
4885			even if no driver has claimed them. This is useful
4886			for debug and development, but should not be
4887			needed on a platform with proper driver support.
4888
4889	pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
4890			boot time.
4891			Format: { 0 | 1 }
4892			See arch/parisc/kernel/pdc_chassis.c
4893
4894	percpu_alloc=	[MM,EARLY]
4895			Select which percpu first chunk allocator to use.
4896			Currently supported values are "embed" and "page".
4897			Archs may support subset or none of the	selections.
4898			See comments in mm/percpu.c for details on each
4899			allocator.  This parameter is primarily	for debugging
4900			and performance comparison.
4901
4902	pirq=		[SMP,APIC] Manual mp-table setup
4903			See Documentation/arch/x86/i386/IO-APIC.rst.
4904
4905	plip=		[PPT,NET] Parallel port network link
4906			Format: { parport<nr> | timid | 0 }
4907			See also Documentation/admin-guide/parport.rst.
4908
4909	pmtmr=		[X86] Manual setup of pmtmr I/O Port.
4910			Override pmtimer IOPort with a hex value.
4911			e.g. pmtmr=0x508
4912
4913	pmu_override=	[PPC] Override the PMU.
4914			This option takes over the PMU facility, so it is no
4915			longer usable by perf. Setting this option starts the
4916			PMU counters by setting MMCR0 to 0 (the FC bit is
4917			cleared). If a number is given, then MMCR1 is set to
4918			that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4919			remains 0.
4920
4921	pm_debug_messages	[SUSPEND,KNL]
4922			Enable suspend/resume debug messages during boot up.
4923
4924	pnp.debug=1	[PNP]
4925			Enable PNP debug messages (depends on the
4926			CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
4927			via /sys/module/pnp/parameters/debug.  We always show
4928			current resource usage; turning this on also shows
4929			possible settings and some assignment information.
4930
4931	pnpacpi=	[ACPI]
4932			{ off }
4933
4934	pnpbios=	[ISAPNP]
4935			{ on | off | curr | res | no-curr | no-res }
4936
4937	pnp_reserve_irq=
4938			[ISAPNP] Exclude IRQs for the autoconfiguration
4939
4940	pnp_reserve_dma=
4941			[ISAPNP] Exclude DMAs for the autoconfiguration
4942
4943	pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
4944			Ranges are in pairs (I/O port base and size).
4945
4946	pnp_reserve_mem=
4947			[ISAPNP] Exclude memory regions for the
4948			autoconfiguration.
4949			Ranges are in pairs (memory base and size).
4950
4951	ports=		[IP_VS_FTP] IPVS ftp helper module
4952			Default is 21.
4953			Up to 8 (IP_VS_APP_MAX_PORTS) ports
4954			may be specified.
4955			Format: <port>,<port>....
4956
4957	possible_cpus=  [SMP,S390,X86]
4958			Format: <unsigned int>
4959			Set the number of possible CPUs, overriding the
4960			regular discovery mechanisms (such as ACPI/FW, etc).
4961
4962	powersave=off	[PPC] This option disables power saving features.
4963			It specifically disables cpuidle and sets the
4964			platform machine description specific power_save
4965			function to NULL. On Idle the CPU just reduces
4966			execution priority.
4967
4968	ppc_strict_facility_enable
4969			[PPC,ENABLE] This option catches any kernel floating point,
4970			Altivec, VSX and SPE outside of regions specifically
4971			allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4972			There is some performance impact when enabling this.
4973
4974	ppc_tm=		[PPC,EARLY]
4975			Format: {"off"}
4976			Disable Hardware Transactional Memory
4977
4978	preempt=	[KNL]
4979			Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4980			none - Limited to cond_resched() calls
4981			voluntary - Limited to cond_resched() and might_sleep() calls
4982			full - Any section that isn't explicitly preempt disabled
4983			       can be preempted anytime.  Tasks will also yield
4984			       contended spinlocks (if the critical section isn't
4985			       explicitly preempt disabled beyond the lock itself).
4986			lazy - Scheduler controlled. Similar to full but instead
4987			       of preempting the task immediately, the task gets
4988			       one HZ tick time to yield itself before the
4989			       preemption will be forced. One preemption is when the
4990			       task returns to user space.
4991
4992	print-fatal-signals=
4993			[KNL] debug: print fatal signals
4994
4995			If enabled, warn about various signal handling
4996			related application anomalies: too many signals,
4997			too many POSIX.1 timers, fatal signals causing a
4998			coredump - etc.
4999
5000			If you hit the warning due to signal overflow,
5001			you might want to try "ulimit -i unlimited".
5002
5003			default: off.
5004
5005	printk.always_kmsg_dump=
5006			Trigger kmsg_dump for cases other than kernel oops or
5007			panics
5008			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
5009			default: disabled
5010
5011	printk.console_no_auto_verbose=
5012			Disable console loglevel raise on oops, panic
5013			or lockdep-detected issues (only if lock debug is on).
5014			With an exception to setups with low baudrate on
5015			serial console, keeping this 0 is a good choice
5016			in order to provide more debug information.
5017			Format: <bool>
5018			default: 0 (auto_verbose is enabled)
5019
5020	printk.devkmsg={on,off,ratelimit}
5021			Control writing to /dev/kmsg.
5022			on - unlimited logging to /dev/kmsg from userspace
5023			off - logging to /dev/kmsg disabled
5024			ratelimit - ratelimit the logging
5025			Default: ratelimit
5026
5027	printk.time=	Show timing data prefixed to each printk message line
5028			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
5029
5030	proc_mem.force_override= [KNL]
5031			Format: {always | ptrace | never}
5032			Traditionally /proc/pid/mem allows memory permissions to be
5033			overridden without restrictions. This option may be set to
5034			restrict that. Can be one of:
5035			- 'always': traditional behavior always allows mem overrides.
5036			- 'ptrace': only allow mem overrides for active ptracers.
5037			- 'never':  never allow mem overrides.
5038			If not specified, default is the CONFIG_PROC_MEM_* choice.
5039
5040	processor.max_cstate=	[HW,ACPI]
5041			Limit processor to maximum C-state
5042			max_cstate=9 overrides any DMI blacklist limit.
5043
5044	processor.nocst	[HW,ACPI]
5045			Ignore the _CST method to determine C-states,
5046			instead using the legacy FADT method
5047
5048	profile=	[KNL] Enable kernel profiling via /proc/profile
5049			Format: [<profiletype>,]<number>
5050			Param: <profiletype>: "schedule" or "kvm"
5051				[defaults to kernel profiling]
5052			Param: "schedule" - profile schedule points.
5053			Param: "kvm" - profile VM exits.
5054			Param: <number> - step/bucket size as a power of 2 for
5055				statistical time based profiling.
5056
5057	prompt_ramdisk=	[RAM] [Deprecated]
5058
5059	prot_virt=	[S390] enable hosting protected virtual machines
5060			isolated from the hypervisor (if hardware supports
5061			that). If enabled, the default kernel base address
5062			might be overridden even when Kernel Address Space
5063			Layout Randomization is disabled.
5064			Format: <bool>
5065
5066	psi=		[KNL] Enable or disable pressure stall information
5067			tracking.
5068			Format: <bool>
5069
5070	psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
5071			probe for; one of (bare|imps|exps|lifebook|any).
5072	psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
5073			per second.
5074	psmouse.resetafter=	[HW,MOUSE]
5075			Try to reset the device after so many bad packets
5076			(0 = never).
5077	psmouse.resolution=
5078			[HW,MOUSE] Set desired mouse resolution, in dpi.
5079	psmouse.smartscroll=
5080			[HW,MOUSE] Controls Logitech smartscroll autorepeat.
5081			0 = disabled, 1 = enabled (default).
5082
5083	pstore.backend=	Specify the name of the pstore backend to use
5084
5085	pti=		[X86-64] Control Page Table Isolation of user and
5086			kernel address spaces.  Disabling this feature
5087			removes hardening, but improves performance of
5088			system calls and interrupts.
5089
5090			on   - unconditionally enable
5091			off  - unconditionally disable
5092			auto - kernel detects whether your CPU model is
5093			       vulnerable to issues that PTI mitigates
5094
5095			Not specifying this option is equivalent to pti=auto.
5096
5097	pty.legacy_count=
5098			[KNL] Number of legacy pty's. Overwrites compiled-in
5099			default number.
5100
5101	quiet		[KNL,EARLY] Disable most log messages
5102
5103	r128=		[HW,DRM]
5104
5105	radix_hcall_invalidate=on  [PPC/PSERIES]
5106			Disable RADIX GTSE feature and use hcall for TLB
5107			invalidate.
5108
5109	raid=		[HW,RAID]
5110			See Documentation/admin-guide/md.rst.
5111
5112	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
5113			See Documentation/admin-guide/blockdev/ramdisk.rst.
5114
5115	ramdisk_start=	[RAM] RAM disk image start address
5116
5117	random.trust_cpu=off
5118			[KNL,EARLY] Disable trusting the use of the CPU's
5119			random number generator (if available) to
5120			initialize the kernel's RNG.
5121
5122	random.trust_bootloader=off
5123			[KNL,EARLY] Disable trusting the use of the a seed
5124			passed by the bootloader (if available) to
5125			initialize the kernel's RNG.
5126
5127	randomize_kstack_offset=
5128			[KNL,EARLY] Enable or disable kernel stack offset
5129			randomization, which provides roughly 5 bits of
5130			entropy, frustrating memory corruption attacks
5131			that depend on stack address determinism or
5132			cross-syscall address exposures. This is only
5133			available on architectures that have defined
5134			CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
5135			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
5136			Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
5137
5138	ras=option[,option,...]	[KNL] RAS-specific options
5139
5140		cec_disable	[X86]
5141				Disable the Correctable Errors Collector,
5142				see CONFIG_RAS_CEC help text.
5143
5144	rcu_nocbs[=cpu-list]
5145			[KNL] The optional argument is a cpu list,
5146			as described above.
5147
5148			In kernels built with CONFIG_RCU_NOCB_CPU=y,
5149			enable the no-callback CPU mode, which prevents
5150			such CPUs' callbacks from being invoked in
5151			softirq context.  Invocation of such CPUs' RCU
5152			callbacks will instead be offloaded to "rcuox/N"
5153			kthreads created for that purpose, where "x" is
5154			"p" for RCU-preempt, "s" for RCU-sched, and "g"
5155			for the kthreads that mediate grace periods; and
5156			"N" is the CPU number. This reduces OS jitter on
5157			the offloaded CPUs, which can be useful for HPC
5158			and real-time workloads.  It can also improve
5159			energy efficiency for asymmetric multiprocessors.
5160
5161			If a cpulist is passed as an argument, the specified
5162			list of	CPUs is set to no-callback mode from boot.
5163
5164			Otherwise, if the '=' sign and the cpulist
5165			arguments are omitted, no CPU will be set to
5166			no-callback mode from boot but the mode may be
5167			toggled at runtime via cpusets.
5168
5169			Note that this argument takes precedence over
5170			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
5171
5172	rcu_nocb_poll	[KNL]
5173			Rather than requiring that offloaded CPUs
5174			(specified by rcu_nocbs= above) explicitly
5175			awaken the corresponding "rcuoN" kthreads,
5176			make these kthreads poll for callbacks.
5177			This improves the real-time response for the
5178			offloaded CPUs by relieving them of the need to
5179			wake up the corresponding kthread, but degrades
5180			energy efficiency by requiring that the kthreads
5181			periodically wake up to do the polling.
5182
5183	rcutree.blimit=	[KNL]
5184			Set maximum number of finished RCU callbacks to
5185			process in one batch.
5186
5187	rcutree.csd_lock_suppress_rcu_stall=	[KNL]
5188			Do only a one-line RCU CPU stall warning when
5189			there is an ongoing too-long CSD-lock wait.
5190
5191	rcutree.do_rcu_barrier=	[KNL]
5192			Request a call to rcu_barrier().  This is
5193			throttled so that userspace tests can safely
5194			hammer on the sysfs variable if they so choose.
5195			If triggered before the RCU grace-period machinery
5196			is fully active, this will error out with EAGAIN.
5197
5198	rcutree.dump_tree=	[KNL]
5199			Dump the structure of the rcu_node combining tree
5200			out at early boot.  This is used for diagnostic
5201			purposes, to verify correct tree setup.
5202
5203	rcutree.gp_cleanup_delay=	[KNL]
5204			Set the number of jiffies to delay each step of
5205			RCU grace-period cleanup.
5206
5207	rcutree.gp_init_delay=	[KNL]
5208			Set the number of jiffies to delay each step of
5209			RCU grace-period initialization.
5210
5211	rcutree.gp_preinit_delay=	[KNL]
5212			Set the number of jiffies to delay each step of
5213			RCU grace-period pre-initialization, that is,
5214			the propagation of recent CPU-hotplug changes up
5215			the rcu_node combining tree.
5216
5217	rcutree.jiffies_till_first_fqs= [KNL]
5218			Set delay from grace-period initialization to
5219			first attempt to force quiescent states.
5220			Units are jiffies, minimum value is zero,
5221			and maximum value is HZ.
5222
5223	rcutree.jiffies_till_next_fqs= [KNL]
5224			Set delay between subsequent attempts to force
5225			quiescent states.  Units are jiffies, minimum
5226			value is one, and maximum value is HZ.
5227
5228	rcutree.jiffies_till_sched_qs= [KNL]
5229			Set required age in jiffies for a
5230			given grace period before RCU starts
5231			soliciting quiescent-state help from
5232			rcu_note_context_switch() and cond_resched().
5233			If not specified, the kernel will calculate
5234			a value based on the most recent settings
5235			of rcutree.jiffies_till_first_fqs
5236			and rcutree.jiffies_till_next_fqs.
5237			This calculated value may be viewed in
5238			rcutree.jiffies_to_sched_qs.  Any attempt to set
5239			rcutree.jiffies_to_sched_qs will be cheerfully
5240			overwritten.
5241
5242	rcutree.kthread_prio= 	 [KNL,BOOT]
5243			Set the SCHED_FIFO priority of the RCU per-CPU
5244			kthreads (rcuc/N). This value is also used for
5245			the priority of the RCU boost threads (rcub/N)
5246			and for the RCU grace-period kthreads (rcu_bh,
5247			rcu_preempt, and rcu_sched). If RCU_BOOST is
5248			set, valid values are 1-99 and the default is 1
5249			(the least-favored priority).  Otherwise, when
5250			RCU_BOOST is not set, valid values are 0-99 and
5251			the default is zero (non-realtime operation).
5252			When RCU_NOCB_CPU is set, also adjust the
5253			priority of NOCB callback kthreads.
5254
5255	rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5256			On callback-offloaded (rcu_nocbs) CPUs,
5257			RCU reduces the lock contention that would
5258			otherwise be caused by callback floods through
5259			use of the ->nocb_bypass list.	However, in the
5260			common non-flooded case, RCU queues directly to
5261			the main ->cblist in order to avoid the extra
5262			overhead of the ->nocb_bypass list and its lock.
5263			But if there are too many callbacks queued during
5264			a single jiffy, RCU pre-queues the callbacks into
5265			the ->nocb_bypass queue.  The definition of "too
5266			many" is supplied by this kernel boot parameter.
5267
5268	rcutree.nohz_full_patience_delay= [KNL]
5269			On callback-offloaded (rcu_nocbs) CPUs, avoid
5270			disturbing RCU unless the grace period has
5271			reached the specified age in milliseconds.
5272			Defaults to zero.  Large values will be capped
5273			at five seconds.  All values will be rounded down
5274			to the nearest value representable by jiffies.
5275
5276	rcutree.qhimark= [KNL]
5277			Set threshold of queued RCU callbacks beyond which
5278			batch limiting is disabled.
5279
5280	rcutree.qlowmark= [KNL]
5281			Set threshold of queued RCU callbacks below which
5282			batch limiting is re-enabled.
5283
5284	rcutree.qovld= [KNL]
5285			Set threshold of queued RCU callbacks beyond which
5286			RCU's force-quiescent-state scan will aggressively
5287			enlist help from cond_resched() and sched IPIs to
5288			help CPUs more quickly reach quiescent states.
5289			Set to less than zero to make this be set based
5290			on rcutree.qhimark at boot time and to zero to
5291			disable more aggressive help enlistment.
5292
5293	rcutree.rcu_delay_page_cache_fill_msec= [KNL]
5294			Set the page-cache refill delay (in milliseconds)
5295			in response to low-memory conditions.  The range
5296			of permitted values is in the range 0:100000.
5297
5298	rcutree.rcu_divisor= [KNL]
5299			Set the shift-right count to use to compute
5300			the callback-invocation batch limit bl from
5301			the number of callbacks queued on this CPU.
5302			The result will be bounded below by the value of
5303			the rcutree.blimit kernel parameter.  Every bl
5304			callbacks, the softirq handler will exit in
5305			order to allow the CPU to do other work.
5306
5307			Please note that this callback-invocation batch
5308			limit applies only to non-offloaded callback
5309			invocation.  Offloaded callbacks are instead
5310			invoked in the context of an rcuoc kthread, which
5311			scheduler will preempt as it does any other task.
5312
5313	rcutree.rcu_fanout_exact= [KNL]
5314			Disable autobalancing of the rcu_node combining
5315			tree.  This is used by rcutorture, and might
5316			possibly be useful for architectures having high
5317			cache-to-cache transfer latencies.
5318
5319	rcutree.rcu_fanout_leaf= [KNL]
5320			Change the number of CPUs assigned to each
5321			leaf rcu_node structure.  Useful for very
5322			large systems, which will choose the value 64,
5323			and for NUMA systems with large remote-access
5324			latencies, which will choose a value aligned
5325			with the appropriate hardware boundaries.
5326
5327	rcutree.rcu_min_cached_objs= [KNL]
5328			Minimum number of objects which are cached and
5329			maintained per one CPU. Object size is equal
5330			to PAGE_SIZE. The cache allows to reduce the
5331			pressure to page allocator, also it makes the
5332			whole algorithm to behave better in low memory
5333			condition.
5334
5335	rcutree.rcu_nocb_gp_stride= [KNL]
5336			Set the number of NOCB callback kthreads in
5337			each group, which defaults to the square root
5338			of the number of CPUs.	Larger numbers reduce
5339			the wakeup overhead on the global grace-period
5340			kthread, but increases that same overhead on
5341			each group's NOCB grace-period kthread.
5342
5343	rcutree.rcu_kick_kthreads= [KNL]
5344			Cause the grace-period kthread to get an extra
5345			wake_up() if it sleeps three times longer than
5346			it should at force-quiescent-state time.
5347			This wake_up() will be accompanied by a
5348			WARN_ONCE() splat and an ftrace_dump().
5349
5350	rcutree.rcu_resched_ns= [KNL]
5351			Limit the time spend invoking a batch of RCU
5352			callbacks to the specified number of nanoseconds.
5353			By default, this limit is checked only once
5354			every 32 callbacks in order to limit the pain
5355			inflicted by local_clock() overhead.
5356
5357	rcutree.rcu_unlock_delay= [KNL]
5358			In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5359			this specifies an rcu_read_unlock()-time delay
5360			in microseconds.  This defaults to zero.
5361			Larger delays increase the probability of
5362			catching RCU pointer leaks, that is, buggy use
5363			of RCU-protected pointers after the relevant
5364			rcu_read_unlock() has completed.
5365
5366	rcutree.sysrq_rcu= [KNL]
5367			Commandeer a sysrq key to dump out Tree RCU's
5368			rcu_node tree with an eye towards determining
5369			why a new grace period has not yet started.
5370
5371	rcutree.use_softirq=	[KNL]
5372			If set to zero, move all RCU_SOFTIRQ processing to
5373			per-CPU rcuc kthreads.  Defaults to a non-zero
5374			value, meaning that RCU_SOFTIRQ is used by default.
5375			Specify rcutree.use_softirq=0 to use rcuc kthreads.
5376
5377			But note that CONFIG_PREEMPT_RT=y kernels disable
5378			this kernel boot parameter, forcibly setting it
5379			to zero.
5380
5381	rcutree.enable_rcu_lazy= [KNL]
5382			To save power, batch RCU callbacks and flush after
5383			delay, memory pressure or callback list growing too
5384			big.
5385
5386	rcutree.rcu_normal_wake_from_gp= [KNL]
5387			Reduces a latency of synchronize_rcu() call. This approach
5388			maintains its own track of synchronize_rcu() callers, so it
5389			does not interact with regular callbacks because it does not
5390			use a call_rcu[_hurry]() path. Please note, this is for a
5391			normal grace period.
5392
5393			How to enable it:
5394
5395			echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp
5396			or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1"
5397
5398			Default is 0.
5399
5400	rcuscale.gp_async= [KNL]
5401			Measure performance of asynchronous
5402			grace-period primitives such as call_rcu().
5403
5404	rcuscale.gp_async_max= [KNL]
5405			Specify the maximum number of outstanding
5406			callbacks per writer thread.  When a writer
5407			thread exceeds this limit, it invokes the
5408			corresponding flavor of rcu_barrier() to allow
5409			previously posted callbacks to drain.
5410
5411	rcuscale.gp_exp= [KNL]
5412			Measure performance of expedited synchronous
5413			grace-period primitives.
5414
5415	rcuscale.holdoff= [KNL]
5416			Set test-start holdoff period.  The purpose of
5417			this parameter is to delay the start of the
5418			test until boot completes in order to avoid
5419			interference.
5420
5421	rcuscale.kfree_by_call_rcu= [KNL]
5422			In kernels built with CONFIG_RCU_LAZY=y, test
5423			call_rcu() instead of kfree_rcu().
5424
5425	rcuscale.kfree_mult= [KNL]
5426			Instead of allocating an object of size kfree_obj,
5427			allocate one of kfree_mult * sizeof(kfree_obj).
5428			Defaults to 1.
5429
5430	rcuscale.kfree_rcu_test= [KNL]
5431			Set to measure performance of kfree_rcu() flooding.
5432
5433	rcuscale.kfree_rcu_test_double= [KNL]
5434			Test the double-argument variant of kfree_rcu().
5435			If this parameter has the same value as
5436			rcuscale.kfree_rcu_test_single, both the single-
5437			and double-argument variants are tested.
5438
5439	rcuscale.kfree_rcu_test_single= [KNL]
5440			Test the single-argument variant of kfree_rcu().
5441			If this parameter has the same value as
5442			rcuscale.kfree_rcu_test_double, both the single-
5443			and double-argument variants are tested.
5444
5445	rcuscale.kfree_nthreads= [KNL]
5446			The number of threads running loops of kfree_rcu().
5447
5448	rcuscale.kfree_alloc_num= [KNL]
5449			Number of allocations and frees done in an iteration.
5450
5451	rcuscale.kfree_loops= [KNL]
5452			Number of loops doing rcuscale.kfree_alloc_num number
5453			of allocations and frees.
5454
5455	rcuscale.minruntime= [KNL]
5456			Set the minimum test run time in seconds.  This
5457			does not affect the data-collection interval,
5458			but instead allows better measurement of things
5459			like CPU consumption.
5460
5461	rcuscale.nreaders= [KNL]
5462			Set number of RCU readers.  The value -1 selects
5463			N, where N is the number of CPUs.  A value
5464			"n" less than -1 selects N-n+1, where N is again
5465			the number of CPUs.  For example, -2 selects N
5466			(the number of CPUs), -3 selects N+1, and so on.
5467			A value of "n" less than or equal to -N selects
5468			a single reader.
5469
5470	rcuscale.nwriters= [KNL]
5471			Set number of RCU writers.  The values operate
5472			the same as for rcuscale.nreaders.
5473			N, where N is the number of CPUs
5474
5475	rcuscale.scale_type= [KNL]
5476			Specify the RCU implementation to test.
5477
5478	rcuscale.shutdown= [KNL]
5479			Shut the system down after performance tests
5480			complete.  This is useful for hands-off automated
5481			testing.
5482
5483	rcuscale.verbose= [KNL]
5484			Enable additional printk() statements.
5485
5486	rcuscale.writer_holdoff= [KNL]
5487			Write-side holdoff between grace periods,
5488			in microseconds.  The default of zero says
5489			no holdoff.
5490
5491	rcuscale.writer_holdoff_jiffies= [KNL]
5492			Additional write-side holdoff between grace
5493			periods, but in jiffies.  The default of zero
5494			says no holdoff.
5495
5496	rcutorture.fqs_duration= [KNL]
5497			Set duration of force_quiescent_state bursts
5498			in microseconds.
5499
5500	rcutorture.fqs_holdoff= [KNL]
5501			Set holdoff time within force_quiescent_state bursts
5502			in microseconds.
5503
5504	rcutorture.fqs_stutter= [KNL]
5505			Set wait time between force_quiescent_state bursts
5506			in seconds.
5507
5508	rcutorture.fwd_progress= [KNL]
5509			Specifies the number of kthreads to be used
5510			for  RCU grace-period forward-progress testing
5511			for the types of RCU supporting this notion.
5512			Defaults to 1 kthread, values less than zero or
5513			greater than the number of CPUs cause the number
5514			of CPUs to be used.
5515
5516	rcutorture.fwd_progress_div= [KNL]
5517			Specify the fraction of a CPU-stall-warning
5518			period to do tight-loop forward-progress testing.
5519
5520	rcutorture.fwd_progress_holdoff= [KNL]
5521			Number of seconds to wait between successive
5522			forward-progress tests.
5523
5524	rcutorture.fwd_progress_need_resched= [KNL]
5525			Enclose cond_resched() calls within checks for
5526			need_resched() during tight-loop forward-progress
5527			testing.
5528
5529	rcutorture.gp_cond= [KNL]
5530			Use conditional/asynchronous update-side
5531			normal-grace-period primitives, if available.
5532
5533	rcutorture.gp_cond_exp= [KNL]
5534			Use conditional/asynchronous update-side
5535			expedited-grace-period primitives, if available.
5536
5537	rcutorture.gp_cond_full= [KNL]
5538			Use conditional/asynchronous update-side
5539			normal-grace-period primitives that also take
5540			concurrent expedited grace periods into account,
5541			if available.
5542
5543	rcutorture.gp_cond_exp_full= [KNL]
5544			Use conditional/asynchronous update-side
5545			expedited-grace-period primitives that also take
5546			concurrent normal grace periods into account,
5547			if available.
5548
5549	rcutorture.gp_cond_wi= [KNL]
5550			Nominal wait interval for normal conditional
5551			grace periods (specified by rcutorture's
5552			gp_cond and gp_cond_full module parameters),
5553			in microseconds.  The actual wait interval will
5554			be randomly selected to nanosecond granularity up
5555			to this wait interval.	Defaults to 16 jiffies,
5556			for example, 16,000 microseconds on a system
5557			with HZ=1000.
5558
5559	rcutorture.gp_cond_wi_exp= [KNL]
5560			Nominal wait interval for expedited conditional
5561			grace periods (specified by rcutorture's
5562			gp_cond_exp and gp_cond_exp_full module
5563			parameters), in microseconds.  The actual wait
5564			interval will be randomly selected to nanosecond
5565			granularity up to this wait interval.  Defaults to
5566			128 microseconds.
5567
5568	rcutorture.gp_exp= [KNL]
5569			Use expedited update-side primitives, if available.
5570
5571	rcutorture.gp_normal= [KNL]
5572			Use normal (non-expedited) asynchronous
5573			update-side primitives, if available.
5574
5575	rcutorture.gp_poll= [KNL]
5576			Use polled update-side normal-grace-period
5577			primitives, if available.
5578
5579	rcutorture.gp_poll_exp= [KNL]
5580			Use polled update-side expedited-grace-period
5581			primitives, if available.
5582
5583	rcutorture.gp_poll_full= [KNL]
5584			Use polled update-side normal-grace-period
5585			primitives that also take concurrent expedited
5586			grace periods into account, if available.
5587
5588	rcutorture.gp_poll_exp_full= [KNL]
5589			Use polled update-side expedited-grace-period
5590			primitives that also take concurrent normal
5591			grace periods into account, if available.
5592
5593	rcutorture.gp_poll_wi= [KNL]
5594			Nominal wait interval for normal conditional
5595			grace periods (specified by rcutorture's
5596			gp_poll and gp_poll_full module parameters),
5597			in microseconds.  The actual wait interval will
5598			be randomly selected to nanosecond granularity up
5599			to this wait interval.	Defaults to 16 jiffies,
5600			for example, 16,000 microseconds on a system
5601			with HZ=1000.
5602
5603	rcutorture.gp_poll_wi_exp= [KNL]
5604			Nominal wait interval for expedited conditional
5605			grace periods (specified by rcutorture's
5606			gp_poll_exp and gp_poll_exp_full module
5607			parameters), in microseconds.  The actual wait
5608			interval will be randomly selected to nanosecond
5609			granularity up to this wait interval.  Defaults to
5610			128 microseconds.
5611
5612	rcutorture.gp_sync= [KNL]
5613			Use normal (non-expedited) synchronous
5614			update-side primitives, if available.  If all
5615			of rcutorture.gp_cond=, rcutorture.gp_exp=,
5616			rcutorture.gp_normal=, and rcutorture.gp_sync=
5617			are zero, rcutorture acts as if is interpreted
5618			they are all non-zero.
5619
5620	rcutorture.irqreader= [KNL]
5621			Run RCU readers from irq handlers, or, more
5622			accurately, from a timer handler.  Not all RCU
5623			flavors take kindly to this sort of thing.
5624
5625	rcutorture.leakpointer= [KNL]
5626			Leak an RCU-protected pointer out of the reader.
5627			This can of course result in splats, and is
5628			intended to test the ability of things like
5629			CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5630			such leaks.
5631
5632	rcutorture.n_barrier_cbs= [KNL]
5633			Set callbacks/threads for rcu_barrier() testing.
5634
5635	rcutorture.nfakewriters= [KNL]
5636			Set number of concurrent RCU writers.  These just
5637			stress RCU, they don't participate in the actual
5638			test, hence the "fake".
5639
5640	rcutorture.nocbs_nthreads= [KNL]
5641			Set number of RCU callback-offload togglers.
5642			Zero (the default) disables toggling.
5643
5644	rcutorture.nocbs_toggle= [KNL]
5645			Set the delay in milliseconds between successive
5646			callback-offload toggling attempts.
5647
5648	rcutorture.nreaders= [KNL]
5649			Set number of RCU readers.  The value -1 selects
5650			N-1, where N is the number of CPUs.  A value
5651			"n" less than -1 selects N-n-2, where N is again
5652			the number of CPUs.  For example, -2 selects N
5653			(the number of CPUs), -3 selects N+1, and so on.
5654
5655	rcutorture.object_debug= [KNL]
5656			Enable debug-object double-call_rcu() testing.
5657
5658	rcutorture.onoff_holdoff= [KNL]
5659			Set time (s) after boot for CPU-hotplug testing.
5660
5661	rcutorture.onoff_interval= [KNL]
5662			Set time (jiffies) between CPU-hotplug operations,
5663			or zero to disable CPU-hotplug testing.
5664
5665	rcutorture.preempt_duration= [KNL]
5666			Set duration (in milliseconds) of preemptions
5667			by a high-priority FIFO real-time task.  Set to
5668			zero (the default) to disable.	The CPUs to
5669			preempt are selected randomly from the set that
5670			are online at a given point in time.  Races with
5671			CPUs going offline are ignored, with that attempt
5672			at preemption skipped.
5673
5674	rcutorture.preempt_interval= [KNL]
5675			Set interval (in milliseconds, defaulting to one
5676			second) between preemptions by a high-priority
5677			FIFO real-time task.  This delay is mediated
5678			by an hrtimer and is further fuzzed to avoid
5679			inadvertent synchronizations.
5680
5681	rcutorture.read_exit_burst= [KNL]
5682			The number of times in a given read-then-exit
5683			episode that a set of read-then-exit kthreads
5684			is spawned.
5685
5686	rcutorture.read_exit_delay= [KNL]
5687			The delay, in seconds, between successive
5688			read-then-exit testing episodes.
5689
5690	rcutorture.reader_flavor= [KNL]
5691			A bit mask indicating which readers to use.
5692			If there is more than one bit set, the readers
5693			are entered from low-order bit up, and are
5694			exited in the opposite order.  For SRCU, the
5695			0x1 bit is normal readers, 0x2 NMI-safe readers,
5696			and 0x4 light-weight readers.
5697
5698	rcutorture.shuffle_interval= [KNL]
5699			Set task-shuffle interval (s).  Shuffling tasks
5700			allows some CPUs to go into dyntick-idle mode
5701			during the rcutorture test.
5702
5703	rcutorture.shutdown_secs= [KNL]
5704			Set time (s) after boot system shutdown.  This
5705			is useful for hands-off automated testing.
5706
5707	rcutorture.stall_cpu= [KNL]
5708			Duration of CPU stall (s) to test RCU CPU stall
5709			warnings, zero to disable.
5710
5711	rcutorture.stall_cpu_block= [KNL]
5712			Sleep while stalling if set.  This will result
5713			in warnings from preemptible RCU in addition to
5714			any other stall-related activity.  Note that
5715			in kernels built with CONFIG_PREEMPTION=n and
5716			CONFIG_PREEMPT_COUNT=y, this parameter will
5717			cause the CPU to pass through a quiescent state.
5718			Given CONFIG_PREEMPTION=n, this will suppress
5719			RCU CPU stall warnings, but will instead result
5720			in scheduling-while-atomic splats.
5721
5722			Use of this module parameter results in splats.
5723
5724
5725	rcutorture.stall_cpu_holdoff= [KNL]
5726			Time to wait (s) after boot before inducing stall.
5727
5728	rcutorture.stall_cpu_irqsoff= [KNL]
5729			Disable interrupts while stalling if set, but only
5730			on the first stall in the set.
5731
5732	rcutorture.stall_cpu_repeat= [KNL]
5733			Number of times to repeat the stall sequence,
5734			so that rcutorture.stall_cpu_repeat=3 will result
5735			in four stall sequences.
5736
5737	rcutorture.stall_gp_kthread= [KNL]
5738			Duration (s) of forced sleep within RCU
5739			grace-period kthread to test RCU CPU stall
5740			warnings, zero to disable.  If both stall_cpu
5741			and stall_gp_kthread are specified, the
5742			kthread is starved first, then the CPU.
5743
5744	rcutorture.stat_interval= [KNL]
5745			Time (s) between statistics printk()s.
5746
5747	rcutorture.stutter= [KNL]
5748			Time (s) to stutter testing, for example, specifying
5749			five seconds causes the test to run for five seconds,
5750			wait for five seconds, and so on.  This tests RCU's
5751			ability to transition abruptly to and from idle.
5752
5753	rcutorture.test_boost= [KNL]
5754			Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
5755			"Maybe" means test if the RCU implementation
5756			under test support RCU priority boosting.
5757
5758	rcutorture.test_boost_duration= [KNL]
5759			Duration (s) of each individual boost test.
5760
5761	rcutorture.test_boost_interval= [KNL]
5762			Interval (s) between each boost test.
5763
5764	rcutorture.test_no_idle_hz= [KNL]
5765			Test RCU's dyntick-idle handling.  See also the
5766			rcutorture.shuffle_interval parameter.
5767
5768	rcutorture.torture_type= [KNL]
5769			Specify the RCU implementation to test.
5770
5771	rcutorture.verbose= [KNL]
5772			Enable additional printk() statements.
5773
5774	rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5775			Dump ftrace buffer after reporting RCU CPU
5776			stall warning.
5777
5778	rcupdate.rcu_cpu_stall_notifiers= [KNL]
5779			Provide RCU CPU stall notifiers, but see the
5780			warnings in the RCU_CPU_STALL_NOTIFIER Kconfig
5781			option's help text.  TL;DR:  You almost certainly
5782			do not want rcupdate.rcu_cpu_stall_notifiers.
5783
5784	rcupdate.rcu_cpu_stall_suppress= [KNL]
5785			Suppress RCU CPU stall warning messages.
5786
5787	rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5788			Suppress RCU CPU stall warning messages and
5789			rcutorture writer stall warnings that occur
5790			during early boot, that is, during the time
5791			before the init task is spawned.
5792
5793	rcupdate.rcu_cpu_stall_timeout= [KNL]
5794			Set timeout for RCU CPU stall warning messages.
5795			The value is in seconds and the maximum allowed
5796			value is 300 seconds.
5797
5798	rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5799			Set timeout for expedited RCU CPU stall warning
5800			messages.  The value is in milliseconds
5801			and the maximum allowed value is 21000
5802			milliseconds. Please note that this value is
5803			adjusted to an arch timer tick resolution.
5804			Setting this to zero causes the value from
5805			rcupdate.rcu_cpu_stall_timeout to be used (after
5806			conversion from seconds to milliseconds).
5807
5808	rcupdate.rcu_cpu_stall_cputime= [KNL]
5809			Provide statistics on the cputime and count of
5810			interrupts and tasks during the sampling period. For
5811			multiple continuous RCU stalls, all sampling periods
5812			begin at half of the first RCU stall timeout.
5813
5814	rcupdate.rcu_exp_stall_task_details= [KNL]
5815			Print stack dumps of any tasks blocking the
5816			current expedited RCU grace period during an
5817			expedited RCU CPU stall warning.
5818
5819	rcupdate.rcu_expedited= [KNL]
5820			Use expedited grace-period primitives, for
5821			example, synchronize_rcu_expedited() instead
5822			of synchronize_rcu().  This reduces latency,
5823			but can increase CPU utilization, degrade
5824			real-time latency, and degrade energy efficiency.
5825			No effect on CONFIG_TINY_RCU kernels.
5826
5827	rcupdate.rcu_normal= [KNL]
5828			Use only normal grace-period primitives,
5829			for example, synchronize_rcu() instead of
5830			synchronize_rcu_expedited().  This improves
5831			real-time latency, CPU utilization, and
5832			energy efficiency, but can expose users to
5833			increased grace-period latency.  This parameter
5834			overrides rcupdate.rcu_expedited.  No effect on
5835			CONFIG_TINY_RCU kernels.
5836
5837	rcupdate.rcu_normal_after_boot= [KNL]
5838			Once boot has completed (that is, after
5839			rcu_end_inkernel_boot() has been invoked), use
5840			only normal grace-period primitives.  No effect
5841			on CONFIG_TINY_RCU kernels.
5842
5843			But note that CONFIG_PREEMPT_RT=y kernels enables
5844			this kernel boot parameter, forcibly setting
5845			it to the value one, that is, converting any
5846			post-boot attempt at an expedited RCU grace
5847			period to instead use normal non-expedited
5848			grace-period processing.
5849
5850	rcupdate.rcu_task_collapse_lim= [KNL]
5851			Set the maximum number of callbacks present
5852			at the beginning of a grace period that allows
5853			the RCU Tasks flavors to collapse back to using
5854			a single callback queue.  This switching only
5855			occurs when rcupdate.rcu_task_enqueue_lim is
5856			set to the default value of -1.
5857
5858	rcupdate.rcu_task_contend_lim= [KNL]
5859			Set the minimum number of callback-queuing-time
5860			lock-contention events per jiffy required to
5861			cause the RCU Tasks flavors to switch to per-CPU
5862			callback queuing.  This switching only occurs
5863			when rcupdate.rcu_task_enqueue_lim is set to
5864			the default value of -1.
5865
5866	rcupdate.rcu_task_enqueue_lim= [KNL]
5867			Set the number of callback queues to use for the
5868			RCU Tasks family of RCU flavors.  The default
5869			of -1 allows this to be automatically (and
5870			dynamically) adjusted.	This parameter is intended
5871			for use in testing.
5872
5873	rcupdate.rcu_task_ipi_delay= [KNL]
5874			Set time in jiffies during which RCU tasks will
5875			avoid sending IPIs, starting with the beginning
5876			of a given grace period.  Setting a large
5877			number avoids disturbing real-time workloads,
5878			but lengthens grace periods.
5879
5880	rcupdate.rcu_task_lazy_lim= [KNL]
5881			Number of callbacks on a given CPU that will
5882			cancel laziness on that CPU.  Use -1 to disable
5883			cancellation of laziness, but be advised that
5884			doing so increases the danger of OOM due to
5885			callback flooding.
5886
5887	rcupdate.rcu_task_stall_info= [KNL]
5888			Set initial timeout in jiffies for RCU task stall
5889			informational messages, which give some indication
5890			of the problem for those not patient enough to
5891			wait for ten minutes.  Informational messages are
5892			only printed prior to the stall-warning message
5893			for a given grace period. Disable with a value
5894			less than or equal to zero.  Defaults to ten
5895			seconds.  A change in value does not take effect
5896			until the beginning of the next grace period.
5897
5898	rcupdate.rcu_task_stall_info_mult= [KNL]
5899			Multiplier for time interval between successive
5900			RCU task stall informational messages for a given
5901			RCU tasks grace period.  This value is clamped
5902			to one through ten, inclusive.	It defaults to
5903			the value three, so that the first informational
5904			message is printed 10 seconds into the grace
5905			period, the second at 40 seconds, the third at
5906			160 seconds, and then the stall warning at 600
5907			seconds would prevent a fourth at 640 seconds.
5908
5909	rcupdate.rcu_task_stall_timeout= [KNL]
5910			Set timeout in jiffies for RCU task stall
5911			warning messages.  Disable with a value less
5912			than or equal to zero.	Defaults to ten minutes.
5913			A change in value does not take effect until
5914			the beginning of the next grace period.
5915
5916	rcupdate.rcu_tasks_lazy_ms= [KNL]
5917			Set timeout in milliseconds RCU Tasks asynchronous
5918			callback batching for call_rcu_tasks().
5919			A negative value will take the default.  A value
5920			of zero will disable batching.	Batching is
5921			always disabled for synchronize_rcu_tasks().
5922
5923	rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
5924			Set timeout in milliseconds RCU Tasks
5925			Trace asynchronous callback batching for
5926			call_rcu_tasks_trace().  A negative value
5927			will take the default.	A value of zero will
5928			disable batching.  Batching is always disabled
5929			for synchronize_rcu_tasks_trace().
5930
5931	rcupdate.rcu_self_test= [KNL]
5932			Run the RCU early boot self tests
5933
5934	rdinit=		[KNL]
5935			Format: <full_path>
5936			Run specified binary instead of /init from the ramdisk,
5937			used for early userspace startup. See initrd.
5938
5939	rdrand=		[X86,EARLY]
5940			force - Override the decision by the kernel to hide the
5941				advertisement of RDRAND support (this affects
5942				certain AMD processors because of buggy BIOS
5943				support, specifically around the suspend/resume
5944				path).
5945
5946	rdt=		[HW,X86,RDT]
5947			Turn on/off individual RDT features. List is:
5948			cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5949			mba, smba, bmec.
5950			E.g. to turn on cmt and turn off mba use:
5951				rdt=cmt,!mba
5952
5953	reboot=		[KNL]
5954			Format (x86 or x86_64):
5955				[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
5956				[[,]s[mp]#### \
5957				[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5958				[[,]f[orce]
5959			Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5960					(prefix with 'panic_' to set mode for panic
5961					reboot only),
5962			      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5963			      reboot_force is either force or not specified,
5964			      reboot_cpu is s[mp]#### with #### being the processor
5965					to be used for rebooting.
5966
5967		acpi
5968			Use the ACPI RESET_REG in the FADT. If ACPI is not
5969			configured or the ACPI reset does not work, the reboot
5970			path attempts the reset using the keyboard controller.
5971
5972		bios
5973			Use the CPU reboot vector for warm reset
5974
5975		cold
5976			Set the cold reboot flag
5977
5978		default
5979			There are some built-in platform specific "quirks"
5980			- you may see: "reboot: <name> series board detected.
5981			Selecting <type> for reboots." In the case where you
5982			think the quirk is in error (e.g. you have newer BIOS,
5983			or newer board) using this option will ignore the
5984			built-in quirk table, and use the generic default
5985			reboot actions.
5986
5987		efi
5988			Use efi reset_system runtime service. If EFI is not
5989			configured or the EFI reset does not work, the reboot
5990			path attempts the reset using the keyboard controller.
5991
5992		force
5993			Don't stop other CPUs on reboot. This can make reboot
5994			more reliable in some cases.
5995
5996		kbd
5997			Use the keyboard controller. cold reset (default)
5998
5999		pci
6000			Use a write to the PCI config space register 0xcf9 to
6001			trigger reboot.
6002
6003		triple
6004			Force a triple fault (init)
6005
6006		warm
6007			Don't set the cold reboot flag
6008
6009			Using warm reset will be much faster especially on big
6010			memory systems because the BIOS will not go through
6011			the memory check.  Disadvantage is that not all
6012			hardware will be completely reinitialized on reboot so
6013			there may be boot problems on some systems.
6014
6015
6016	refscale.holdoff= [KNL]
6017			Set test-start holdoff period.  The purpose of
6018			this parameter is to delay the start of the
6019			test until boot completes in order to avoid
6020			interference.
6021
6022	refscale.lookup_instances= [KNL]
6023			Number of data elements to use for the forms of
6024			SLAB_TYPESAFE_BY_RCU testing.  A negative number
6025			is negated and multiplied by nr_cpu_ids, while
6026			zero specifies nr_cpu_ids.
6027
6028	refscale.loops= [KNL]
6029			Set the number of loops over the synchronization
6030			primitive under test.  Increasing this number
6031			reduces noise due to loop start/end overhead,
6032			but the default has already reduced the per-pass
6033			noise to a handful of picoseconds on ca. 2020
6034			x86 laptops.
6035
6036	refscale.nreaders= [KNL]
6037			Set number of readers.  The default value of -1
6038			selects N, where N is roughly 75% of the number
6039			of CPUs.  A value of zero is an interesting choice.
6040
6041	refscale.nruns= [KNL]
6042			Set number of runs, each of which is dumped onto
6043			the console log.
6044
6045	refscale.readdelay= [KNL]
6046			Set the read-side critical-section duration,
6047			measured in microseconds.
6048
6049	refscale.scale_type= [KNL]
6050			Specify the read-protection implementation to test.
6051
6052	refscale.shutdown= [KNL]
6053			Shut down the system at the end of the performance
6054			test.  This defaults to 1 (shut it down) when
6055			refscale is built into the kernel and to 0 (leave
6056			it running) when refscale is built as a module.
6057
6058	refscale.verbose= [KNL]
6059			Enable additional printk() statements.
6060
6061	refscale.verbose_batched= [KNL]
6062			Batch the additional printk() statements.  If zero
6063			(the default) or negative, print everything.  Otherwise,
6064			print every Nth verbose statement, where N is the value
6065			specified.
6066
6067	regulator_ignore_unused
6068			[REGULATOR]
6069			Prevents regulator framework from disabling regulators
6070			that are unused, due no driver claiming them. This may
6071			be useful for debug and development, but should not be
6072			needed on a platform with proper driver support.
6073
6074	relax_domain_level=
6075			[KNL, SMP] Set scheduler's default relax_domain_level.
6076			See Documentation/admin-guide/cgroup-v1/cpusets.rst.
6077
6078	reserve=	[KNL,BUGS] Force kernel to ignore I/O ports or memory
6079			Format: <base1>,<size1>[,<base2>,<size2>,...]
6080			Reserve I/O ports or memory so the kernel won't use
6081			them.  If <base> is less than 0x10000, the region
6082			is assumed to be I/O ports; otherwise it is memory.
6083
6084	reserve_mem=	[RAM]
6085			Format: nn[KNG]:<align>:<label>
6086			Reserve physical memory and label it with a name that
6087			other subsystems can use to access it. This is typically
6088			used for systems that do not wipe the RAM, and this command
6089			line will try to reserve the same physical memory on
6090			soft reboots. Note, it is not guaranteed to be the same
6091			location. For example, if anything about the system changes
6092			or if booting a different kernel. It can also fail if KASLR
6093			places the kernel at the location of where the RAM reservation
6094			was from a previous boot, the new reservation will be at a
6095			different location.
6096			Any subsystem using this feature must add a way to verify
6097			that the contents of the physical memory is from a previous
6098			boot, as there may be cases where the memory will not be
6099			located at the same location.
6100
6101			The format is size:align:label for example, to request
6102			12 megabytes of 4096 alignment for ramoops:
6103
6104			reserve_mem=12M:4096:oops ramoops.mem_name=oops
6105
6106	reservetop=	[X86-32,EARLY]
6107			Format: nn[KMG]
6108			Reserves a hole at the top of the kernel virtual
6109			address space.
6110
6111	reset_devices	[KNL] Force drivers to reset the underlying device
6112			during initialization.
6113
6114	resume=		[SWSUSP]
6115			Specify the partition device for software suspend
6116			Format:
6117			{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
6118
6119	resume_offset=	[SWSUSP]
6120			Specify the offset from the beginning of the partition
6121			given by "resume=" at which the swap header is located,
6122			in <PAGE_SIZE> units (needed only for swap files).
6123			See  Documentation/power/swsusp-and-swap-files.rst
6124
6125	resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
6126			read the resume files
6127
6128	resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
6129			Useful for devices that are detected asynchronously
6130			(e.g. USB and MMC devices).
6131
6132	retain_initrd	[RAM] Keep initrd memory after extraction. After boot, it will
6133			be accessible via /sys/firmware/initrd.
6134
6135	retbleed=	[X86] Control mitigation of RETBleed (Arbitrary
6136			Speculative Code Execution with Return Instructions)
6137			vulnerability.
6138
6139			AMD-based UNRET and IBPB mitigations alone do not stop
6140			sibling threads from influencing the predictions of other
6141			sibling threads. For that reason, STIBP is used on pro-
6142			cessors that support it, and mitigate SMT on processors
6143			that don't.
6144
6145			off          - no mitigation
6146			auto         - automatically select a migitation
6147			auto,nosmt   - automatically select a mitigation,
6148				       disabling SMT if necessary for
6149				       the full mitigation (only on Zen1
6150				       and older without STIBP).
6151			ibpb         - On AMD, mitigate short speculation
6152				       windows on basic block boundaries too.
6153				       Safe, highest perf impact. It also
6154				       enables STIBP if present. Not suitable
6155				       on Intel.
6156			ibpb,nosmt   - Like "ibpb" above but will disable SMT
6157				       when STIBP is not available. This is
6158				       the alternative for systems which do not
6159				       have STIBP.
6160			unret        - Force enable untrained return thunks,
6161				       only effective on AMD f15h-f17h based
6162				       systems.
6163			unret,nosmt  - Like unret, but will disable SMT when STIBP
6164				       is not available. This is the alternative for
6165				       systems which do not have STIBP.
6166
6167			Selecting 'auto' will choose a mitigation method at run
6168			time according to the CPU.
6169
6170			Not specifying this option is equivalent to retbleed=auto.
6171
6172	rfkill.default_state=
6173		0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
6174			etc. communication is blocked by default.
6175		1	Unblocked.
6176
6177	rfkill.master_switch_mode=
6178		0	The "airplane mode" button does nothing.
6179		1	The "airplane mode" button toggles between everything
6180			blocked and the previous configuration.
6181		2	The "airplane mode" button toggles between everything
6182			blocked and everything unblocked.
6183
6184	ring3mwait=disable
6185			[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
6186			CPUs.
6187
6188	riscv_isa_fallback [RISCV,EARLY]
6189			When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
6190			falling back to detecting extension support by parsing
6191			"riscv,isa" property on devicetree systems when the
6192			replacement properties are not found. See the Kconfig
6193			entry for RISCV_ISA_FALLBACK.
6194
6195	ro		[KNL] Mount root device read-only on boot
6196
6197	rodata=		[KNL,EARLY]
6198		on	Mark read-only kernel memory as read-only (default).
6199		off	Leave read-only kernel memory writable for debugging.
6200		full	Mark read-only kernel memory and aliases as read-only
6201		        [arm64]
6202
6203	rockchip.usb_uart
6204			[EARLY]
6205			Enable the uart passthrough on the designated usb port
6206			on Rockchip SoCs. When active, the signals of the
6207			debug-uart get routed to the D+ and D- pins of the usb
6208			port and the regular usb controller gets disabled.
6209
6210	root=		[KNL] Root filesystem
6211			Usually this a a block device specifier of some kind,
6212			see the early_lookup_bdev comment in
6213			block/early-lookup.c for details.
6214			Alternatively this can be "ram" for the legacy initial
6215			ramdisk, "nfs" and "cifs" for root on a network file
6216			system, or "mtd" and "ubi" for mounting from raw flash.
6217
6218	rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
6219			mount the root filesystem
6220
6221	rootflags=	[KNL] Set root filesystem mount option string
6222
6223	rootfstype=	[KNL] Set root filesystem type
6224
6225	rootwait	[KNL] Wait (indefinitely) for root device to show up.
6226			Useful for devices that are detected asynchronously
6227			(e.g. USB and MMC devices).
6228
6229	rootwait=	[KNL] Maximum time (in seconds) to wait for root device
6230			to show up before attempting to mount the root
6231			filesystem.
6232
6233	rproc_mem=nn[KMG][@address]
6234			[KNL,ARM,CMA] Remoteproc physical memory block.
6235			Memory area to be used by remote processor image,
6236			managed by CMA.
6237
6238	rw		[KNL] Mount root device read-write on boot
6239
6240	S		[KNL] Run init in single mode
6241
6242	s390_iommu=	[HW,S390]
6243			Set s390 IOTLB flushing mode
6244		strict
6245			With strict flushing every unmap operation will result
6246			in an IOTLB flush. Default is lazy flushing before
6247			reuse, which is faster. Deprecated, equivalent to
6248			iommu.strict=1.
6249
6250	s390_iommu_aperture=	[KNL,S390]
6251			Specifies the size of the per device DMA address space
6252			accessible through the DMA and IOMMU APIs as a decimal
6253			factor of the size of main memory.
6254			The default is 1 meaning that one can concurrently use
6255			as many DMA addresses as physical memory is installed,
6256			if supported by hardware, and thus map all of memory
6257			once. With a value of 2 one can map all of memory twice
6258			and so on. As a special case a factor of 0 imposes no
6259			restrictions other than those given by hardware at the
6260			cost of significant additional memory use for tables.
6261
6262	sa1100ir	[NET]
6263			See drivers/net/irda/sa1100_ir.c.
6264
6265	sched_verbose	[KNL,EARLY] Enables verbose scheduler debug messages.
6266
6267	schedstats=	[KNL,X86] Enable or disable scheduled statistics.
6268			Allowed values are enable and disable. This feature
6269			incurs a small amount of overhead in the scheduler
6270			but is useful for debugging and performance tuning.
6271
6272	sched_thermal_decay_shift=
6273			[Deprecated]
6274			[KNL, SMP] Set a decay shift for scheduler thermal
6275			pressure signal. Thermal pressure signal follows the
6276			default decay period of other scheduler pelt
6277			signals(usually 32 ms but configurable). Setting
6278			sched_thermal_decay_shift will left shift the decay
6279			period for the thermal pressure signal by the shift
6280			value.
6281			i.e. with the default pelt decay period of 32 ms
6282			sched_thermal_decay_shift   thermal pressure decay pr
6283				1			64 ms
6284				2			128 ms
6285			and so on.
6286			Format: integer between 0 and 10
6287			Default is 0.
6288
6289	scftorture.holdoff= [KNL]
6290			Number of seconds to hold off before starting
6291			test.  Defaults to zero for module insertion and
6292			to 10 seconds for built-in smp_call_function()
6293			tests.
6294
6295	scftorture.longwait= [KNL]
6296			Request ridiculously long waits randomly selected
6297			up to the chosen limit in seconds.  Zero (the
6298			default) disables this feature.  Please note
6299			that requesting even small non-zero numbers of
6300			seconds can result in RCU CPU stall warnings,
6301			softlockup complaints, and so on.
6302
6303	scftorture.nthreads= [KNL]
6304			Number of kthreads to spawn to invoke the
6305			smp_call_function() family of functions.
6306			The default of -1 specifies a number of kthreads
6307			equal to the number of CPUs.
6308
6309	scftorture.onoff_holdoff= [KNL]
6310			Number seconds to wait after the start of the
6311			test before initiating CPU-hotplug operations.
6312
6313	scftorture.onoff_interval= [KNL]
6314			Number seconds to wait between successive
6315			CPU-hotplug operations.  Specifying zero (which
6316			is the default) disables CPU-hotplug operations.
6317
6318	scftorture.shutdown_secs= [KNL]
6319			The number of seconds following the start of the
6320			test after which to shut down the system.  The
6321			default of zero avoids shutting down the system.
6322			Non-zero values are useful for automated tests.
6323
6324	scftorture.stat_interval= [KNL]
6325			The number of seconds between outputting the
6326			current test statistics to the console.  A value
6327			of zero disables statistics output.
6328
6329	scftorture.stutter_cpus= [KNL]
6330			The number of jiffies to wait between each change
6331			to the set of CPUs under test.
6332
6333	scftorture.use_cpus_read_lock= [KNL]
6334			Use use_cpus_read_lock() instead of the default
6335			preempt_disable() to disable CPU hotplug
6336			while invoking one of the smp_call_function*()
6337			functions.
6338
6339	scftorture.verbose= [KNL]
6340			Enable additional printk() statements.
6341
6342	scftorture.weight_single= [KNL]
6343			The probability weighting to use for the
6344			smp_call_function_single() function with a zero
6345			"wait" parameter.  A value of -1 selects the
6346			default if all other weights are -1.  However,
6347			if at least one weight has some other value, a
6348			value of -1 will instead select a weight of zero.
6349
6350	scftorture.weight_single_wait= [KNL]
6351			The probability weighting to use for the
6352			smp_call_function_single() function with a
6353			non-zero "wait" parameter.  See weight_single.
6354
6355	scftorture.weight_many= [KNL]
6356			The probability weighting to use for the
6357			smp_call_function_many() function with a zero
6358			"wait" parameter.  See weight_single.
6359			Note well that setting a high probability for
6360			this weighting can place serious IPI load
6361			on the system.
6362
6363	scftorture.weight_many_wait= [KNL]
6364			The probability weighting to use for the
6365			smp_call_function_many() function with a
6366			non-zero "wait" parameter.  See weight_single
6367			and weight_many.
6368
6369	scftorture.weight_all= [KNL]
6370			The probability weighting to use for the
6371			smp_call_function_all() function with a zero
6372			"wait" parameter.  See weight_single and
6373			weight_many.
6374
6375	scftorture.weight_all_wait= [KNL]
6376			The probability weighting to use for the
6377			smp_call_function_all() function with a
6378			non-zero "wait" parameter.  See weight_single
6379			and weight_many.
6380
6381	sdw_mclk_divider=[SDW]
6382			Specify the MCLK divider for Intel SoundWire buses in
6383			case the BIOS does not provide the clock rate properly.
6384
6385	skew_tick=	[KNL,EARLY] Offset the periodic timer tick per cpu to mitigate
6386			xtime_lock contention on larger systems, and/or RCU lock
6387			contention on all systems with CONFIG_MAXSMP set.
6388			Format: { "0" | "1" }
6389			0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6390			1 -- enable.
6391			Note: increases power consumption, thus should only be
6392			enabled if running jitter sensitive (HPC/RT) workloads.
6393
6394	security=	[SECURITY] Choose a legacy "major" security module to
6395			enable at boot. This has been deprecated by the
6396			"lsm=" parameter.
6397
6398	selinux=	[SELINUX] Disable or enable SELinux at boot time.
6399			Format: { "0" | "1" }
6400			See security/selinux/Kconfig help text.
6401			0 -- disable.
6402			1 -- enable.
6403			Default value is 1.
6404
6405	serialnumber	[BUGS=X86-32]
6406
6407	sev=option[,option...] [X86-64]
6408
6409		debug
6410			Enable debug messages.
6411
6412		nosnp
6413			Do not enable SEV-SNP (applies to host/hypervisor
6414			only). Setting 'nosnp' avoids the RMP check overhead
6415			in memory accesses when users do not want to run
6416			SEV-SNP guests.
6417
6418	shapers=	[NET]
6419			Maximal number of shapers.
6420
6421	show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
6422			Limit apic dumping. The parameter defines the maximal
6423			number of local apics being dumped. Also it is possible
6424			to set it to "all" by meaning -- no limit here.
6425			Format: { 1 (default) | 2 | ... | all }.
6426			The parameter valid if only apic=debug or
6427			apic=verbose is specified.
6428			Example: apic=debug show_lapic=all
6429
6430	slab_debug[=options[,slabs][;[options[,slabs]]...]	[MM]
6431			Enabling slab_debug allows one to determine the
6432			culprit if slab objects become corrupted. Enabling
6433			slab_debug can create guard zones around objects and
6434			may poison objects when not in use. Also tracks the
6435			last alloc / free. For more information see
6436			Documentation/mm/slub.rst.
6437			(slub_debug legacy name also accepted for now)
6438
6439	slab_max_order= [MM]
6440			Determines the maximum allowed order for slabs.
6441			A high setting may cause OOMs due to memory
6442			fragmentation. For more information see
6443			Documentation/mm/slub.rst.
6444			(slub_max_order legacy name also accepted for now)
6445
6446	slab_merge	[MM]
6447			Enable merging of slabs with similar size when the
6448			kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
6449			(slub_merge legacy name also accepted for now)
6450
6451	slab_min_objects=	[MM]
6452			The minimum number of objects per slab. SLUB will
6453			increase the slab order up to slab_max_order to
6454			generate a sufficiently large slab able to contain
6455			the number of objects indicated. The higher the number
6456			of objects the smaller the overhead of tracking slabs
6457			and the less frequently locks need to be acquired.
6458			For more information see Documentation/mm/slub.rst.
6459			(slub_min_objects legacy name also accepted for now)
6460
6461	slab_min_order=	[MM]
6462			Determines the minimum page order for slabs. Must be
6463			lower or equal to slab_max_order. For more information see
6464			Documentation/mm/slub.rst.
6465			(slub_min_order legacy name also accepted for now)
6466
6467	slab_nomerge	[MM]
6468			Disable merging of slabs with similar size. May be
6469			necessary if there is some reason to distinguish
6470			allocs to different slabs, especially in hardened
6471			environments where the risk of heap overflows and
6472			layout control by attackers can usually be
6473			frustrated by disabling merging. This will reduce
6474			most of the exposure of a heap attack to a single
6475			cache (risks via metadata attacks are mostly
6476			unchanged). Debug options disable merging on their
6477			own.
6478			For more information see Documentation/mm/slub.rst.
6479			(slub_nomerge legacy name also accepted for now)
6480
6481	slab_strict_numa	[MM]
6482			Support memory policies on a per object level
6483			in the slab allocator. The default is for memory
6484			policies to be applied at the folio level when
6485			a new folio is needed or a partial folio is
6486			retrieved from the lists. Increases overhead
6487			in the slab fastpaths but gains more accurate
6488			NUMA kernel object placement which helps with slow
6489			interconnects in NUMA systems.
6490
6491	slram=		[HW,MTD]
6492
6493	smart2=		[HW]
6494			Format: <io1>[,<io2>[,...,<io8>]]
6495
6496	smp.csd_lock_timeout= [KNL]
6497			Specify the period of time in milliseconds
6498			that smp_call_function() and friends will wait
6499			for a CPU to release the CSD lock.  This is
6500			useful when diagnosing bugs involving CPUs
6501			disabling interrupts for extended periods
6502			of time.  Defaults to 5,000 milliseconds, and
6503			setting a value of zero disables this feature.
6504			This feature may be more efficiently disabled
6505			using the csdlock_debug- kernel parameter.
6506
6507	smp.panic_on_ipistall= [KNL]
6508			If a csd_lock_timeout extends for more than
6509			the specified number of milliseconds, panic the
6510			system.  By default, let CSD-lock acquisition
6511			take as long as they take.  Specifying 300,000
6512			for this value provides a 5-minute timeout.
6513
6514	smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
6515	smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
6516	smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
6517	smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
6518	smsc-ircc2.ircc_irq=	[HW] IRQ line
6519	smsc-ircc2.ircc_dma=	[HW] DMA channel
6520	smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6521				0: Toshiba Satellite 1800 (GP data pin select)
6522				1: Fast pin select (default)
6523				2: ATC IRMode
6524
6525	smt=		[KNL,MIPS,S390,EARLY] Set the maximum number of threads
6526			(logical CPUs) to use per physical CPU on systems
6527			capable of symmetric multithreading (SMT). Will
6528			be capped to the actual hardware limit.
6529			Format: <integer>
6530			Default: -1 (no limit)
6531
6532	softlockup_panic=
6533			[KNL] Should the soft-lockup detector generate panics.
6534			Format: 0 | 1
6535
6536			A value of 1 instructs the soft-lockup detector
6537			to panic the machine when a soft-lockup occurs. It is
6538			also controlled by the kernel.softlockup_panic sysctl
6539			and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6540			respective build-time switch to that functionality.
6541
6542	softlockup_all_cpu_backtrace=
6543			[KNL] Should the soft-lockup detector generate
6544			backtraces on all cpus.
6545			Format: 0 | 1
6546
6547	sonypi.*=	[HW] Sony Programmable I/O Control Device driver
6548			See Documentation/admin-guide/laptops/sonypi.rst
6549
6550	spectre_bhi=	[X86] Control mitigation of Branch History Injection
6551			(BHI) vulnerability.  This setting affects the
6552			deployment of the HW BHI control and the SW BHB
6553			clearing sequence.
6554
6555			on     - (default) Enable the HW or SW mitigation as
6556				 needed.  This protects the kernel from
6557				 both syscalls and VMs.
6558			vmexit - On systems which don't have the HW mitigation
6559				 available, enable the SW mitigation on vmexit
6560				 ONLY.  On such systems, the host kernel is
6561				 protected from VM-originated BHI attacks, but
6562				 may still be vulnerable to syscall attacks.
6563			off    - Disable the mitigation.
6564
6565	spectre_v2=	[X86,EARLY] Control mitigation of Spectre variant 2
6566			(indirect branch speculation) vulnerability.
6567			The default operation protects the kernel from
6568			user space attacks.
6569
6570			on   - unconditionally enable, implies
6571			       spectre_v2_user=on
6572			off  - unconditionally disable, implies
6573			       spectre_v2_user=off
6574			auto - kernel detects whether your CPU model is
6575			       vulnerable
6576
6577			Selecting 'on' will, and 'auto' may, choose a
6578			mitigation method at run time according to the
6579			CPU, the available microcode, the setting of the
6580			CONFIG_MITIGATION_RETPOLINE configuration option,
6581			and the compiler with which the kernel was built.
6582
6583			Selecting 'on' will also enable the mitigation
6584			against user space to user space task attacks.
6585
6586			Selecting 'off' will disable both the kernel and
6587			the user space protections.
6588
6589			Specific mitigations can also be selected manually:
6590
6591			retpoline	  - replace indirect branches
6592			retpoline,generic - Retpolines
6593			retpoline,lfence  - LFENCE; indirect branch
6594			retpoline,amd     - alias for retpoline,lfence
6595			eibrs		  - Enhanced/Auto IBRS
6596			eibrs,retpoline   - Enhanced/Auto IBRS + Retpolines
6597			eibrs,lfence      - Enhanced/Auto IBRS + LFENCE
6598			ibrs		  - use IBRS to protect kernel
6599
6600			Not specifying this option is equivalent to
6601			spectre_v2=auto.
6602
6603	spectre_v2_user=
6604			[X86] Control mitigation of Spectre variant 2
6605		        (indirect branch speculation) vulnerability between
6606		        user space tasks
6607
6608			on	- Unconditionally enable mitigations. Is
6609				  enforced by spectre_v2=on
6610
6611			off     - Unconditionally disable mitigations. Is
6612				  enforced by spectre_v2=off
6613
6614			prctl   - Indirect branch speculation is enabled,
6615				  but mitigation can be enabled via prctl
6616				  per thread.  The mitigation control state
6617				  is inherited on fork.
6618
6619			prctl,ibpb
6620				- Like "prctl" above, but only STIBP is
6621				  controlled per thread. IBPB is issued
6622				  always when switching between different user
6623				  space processes.
6624
6625			seccomp
6626				- Same as "prctl" above, but all seccomp
6627				  threads will enable the mitigation unless
6628				  they explicitly opt out.
6629
6630			seccomp,ibpb
6631				- Like "seccomp" above, but only STIBP is
6632				  controlled per thread. IBPB is issued
6633				  always when switching between different
6634				  user space processes.
6635
6636			auto    - Kernel selects the mitigation depending on
6637				  the available CPU features and vulnerability.
6638
6639			Default mitigation: "prctl"
6640
6641			Not specifying this option is equivalent to
6642			spectre_v2_user=auto.
6643
6644	spec_rstack_overflow=
6645			[X86,EARLY] Control RAS overflow mitigation on AMD Zen CPUs
6646
6647			off		- Disable mitigation
6648			microcode	- Enable microcode mitigation only
6649			safe-ret	- Enable sw-only safe RET mitigation (default)
6650			ibpb		- Enable mitigation by issuing IBPB on
6651					  kernel entry
6652			ibpb-vmexit	- Issue IBPB only on VMEXIT
6653					  (cloud-specific mitigation)
6654
6655	spec_store_bypass_disable=
6656			[HW,EARLY] Control Speculative Store Bypass (SSB) Disable mitigation
6657			(Speculative Store Bypass vulnerability)
6658
6659			Certain CPUs are vulnerable to an exploit against a
6660			a common industry wide performance optimization known
6661			as "Speculative Store Bypass" in which recent stores
6662			to the same memory location may not be observed by
6663			later loads during speculative execution. The idea
6664			is that such stores are unlikely and that they can
6665			be detected prior to instruction retirement at the
6666			end of a particular speculation execution window.
6667
6668			In vulnerable processors, the speculatively forwarded
6669			store can be used in a cache side channel attack, for
6670			example to read memory to which the attacker does not
6671			directly have access (e.g. inside sandboxed code).
6672
6673			This parameter controls whether the Speculative Store
6674			Bypass optimization is used.
6675
6676			On x86 the options are:
6677
6678			on      - Unconditionally disable Speculative Store Bypass
6679			off     - Unconditionally enable Speculative Store Bypass
6680			auto    - Kernel detects whether the CPU model contains an
6681				  implementation of Speculative Store Bypass and
6682				  picks the most appropriate mitigation. If the
6683				  CPU is not vulnerable, "off" is selected. If the
6684				  CPU is vulnerable the default mitigation is
6685				  architecture and Kconfig dependent. See below.
6686			prctl   - Control Speculative Store Bypass per thread
6687				  via prctl. Speculative Store Bypass is enabled
6688				  for a process by default. The state of the control
6689				  is inherited on fork.
6690			seccomp - Same as "prctl" above, but all seccomp threads
6691				  will disable SSB unless they explicitly opt out.
6692
6693			Default mitigations:
6694			X86:	"prctl"
6695
6696			On powerpc the options are:
6697
6698			on,auto - On Power8 and Power9 insert a store-forwarding
6699				  barrier on kernel entry and exit. On Power7
6700				  perform a software flush on kernel entry and
6701				  exit.
6702			off	- No action.
6703
6704			Not specifying this option is equivalent to
6705			spec_store_bypass_disable=auto.
6706
6707	split_lock_detect=
6708			[X86] Enable split lock detection or bus lock detection
6709
6710			When enabled (and if hardware support is present), atomic
6711			instructions that access data across cache line
6712			boundaries will result in an alignment check exception
6713			for split lock detection or a debug exception for
6714			bus lock detection.
6715
6716			off	- not enabled
6717
6718			warn	- the kernel will emit rate-limited warnings
6719				  about applications triggering the #AC
6720				  exception or the #DB exception. This mode is
6721				  the default on CPUs that support split lock
6722				  detection or bus lock detection. Default
6723				  behavior is by #AC if both features are
6724				  enabled in hardware.
6725
6726			fatal	- the kernel will send SIGBUS to applications
6727				  that trigger the #AC exception or the #DB
6728				  exception. Default behavior is by #AC if
6729				  both features are enabled in hardware.
6730
6731			ratelimit:N -
6732				  Set system wide rate limit to N bus locks
6733				  per second for bus lock detection.
6734				  0 < N <= 1000.
6735
6736				  N/A for split lock detection.
6737
6738
6739			If an #AC exception is hit in the kernel or in
6740			firmware (i.e. not while executing in user mode)
6741			the kernel will oops in either "warn" or "fatal"
6742			mode.
6743
6744			#DB exception for bus lock is triggered only when
6745			CPL > 0.
6746
6747	srbds=		[X86,INTEL,EARLY]
6748			Control the Special Register Buffer Data Sampling
6749			(SRBDS) mitigation.
6750
6751			Certain CPUs are vulnerable to an MDS-like
6752			exploit which can leak bits from the random
6753			number generator.
6754
6755			By default, this issue is mitigated by
6756			microcode.  However, the microcode fix can cause
6757			the RDRAND and RDSEED instructions to become
6758			much slower.  Among other effects, this will
6759			result in reduced throughput from /dev/urandom.
6760
6761			The microcode mitigation can be disabled with
6762			the following option:
6763
6764			off:    Disable mitigation and remove
6765				performance impact to RDRAND and RDSEED
6766
6767	srcutree.big_cpu_lim [KNL]
6768			Specifies the number of CPUs constituting a
6769			large system, such that srcu_struct structures
6770			should immediately allocate an srcu_node array.
6771			This kernel-boot parameter defaults to 128,
6772			but takes effect only when the low-order four
6773			bits of srcutree.convert_to_big is equal to 3
6774			(decide at boot).
6775
6776	srcutree.convert_to_big [KNL]
6777			Specifies under what conditions an SRCU tree
6778			srcu_struct structure will be converted to big
6779			form, that is, with an rcu_node tree:
6780
6781				   0:  Never.
6782				   1:  At init_srcu_struct() time.
6783				   2:  When rcutorture decides to.
6784				   3:  Decide at boot time (default).
6785				0x1X:  Above plus if high contention.
6786
6787			Either way, the srcu_node tree will be sized based
6788			on the actual runtime number of CPUs (nr_cpu_ids)
6789			instead of the compile-time CONFIG_NR_CPUS.
6790
6791	srcutree.counter_wrap_check [KNL]
6792			Specifies how frequently to check for
6793			grace-period sequence counter wrap for the
6794			srcu_data structure's ->srcu_gp_seq_needed field.
6795			The greater the number of bits set in this kernel
6796			parameter, the less frequently counter wrap will
6797			be checked for.  Note that the bottom two bits
6798			are ignored.
6799
6800	srcutree.exp_holdoff [KNL]
6801			Specifies how many nanoseconds must elapse
6802			since the end of the last SRCU grace period for
6803			a given srcu_struct until the next normal SRCU
6804			grace period will be considered for automatic
6805			expediting.  Set to zero to disable automatic
6806			expediting.
6807
6808	srcutree.srcu_max_nodelay [KNL]
6809			Specifies the number of no-delay instances
6810			per jiffy for which the SRCU grace period
6811			worker thread will be rescheduled with zero
6812			delay. Beyond this limit, worker thread will
6813			be rescheduled with a sleep delay of one jiffy.
6814
6815	srcutree.srcu_max_nodelay_phase [KNL]
6816			Specifies the per-grace-period phase, number of
6817			non-sleeping polls of readers. Beyond this limit,
6818			grace period worker thread will be rescheduled
6819			with a sleep delay of one jiffy, between each
6820			rescan of the readers, for a grace period phase.
6821
6822	srcutree.srcu_retry_check_delay [KNL]
6823			Specifies number of microseconds of non-sleeping
6824			delay between each non-sleeping poll of readers.
6825
6826	srcutree.small_contention_lim [KNL]
6827			Specifies the number of update-side contention
6828			events per jiffy will be tolerated before
6829			initiating a conversion of an srcu_struct
6830			structure to big form.	Note that the value of
6831			srcutree.convert_to_big must have the 0x10 bit
6832			set for contention-based conversions to occur.
6833
6834	ssbd=		[ARM64,HW,EARLY]
6835			Speculative Store Bypass Disable control
6836
6837			On CPUs that are vulnerable to the Speculative
6838			Store Bypass vulnerability and offer a
6839			firmware based mitigation, this parameter
6840			indicates how the mitigation should be used:
6841
6842			force-on:  Unconditionally enable mitigation for
6843				   for both kernel and userspace
6844			force-off: Unconditionally disable mitigation for
6845				   for both kernel and userspace
6846			kernel:    Always enable mitigation in the
6847				   kernel, and offer a prctl interface
6848				   to allow userspace to register its
6849				   interest in being mitigated too.
6850
6851	stack_guard_gap=	[MM]
6852			override the default stack gap protection. The value
6853			is in page units and it defines how many pages prior
6854			to (for stacks growing down) resp. after (for stacks
6855			growing up) the main stack are reserved for no other
6856			mapping. Default value is 256 pages.
6857
6858	stack_depot_disable= [KNL,EARLY]
6859			Setting this to true through kernel command line will
6860			disable the stack depot thereby saving the static memory
6861			consumed by the stack hash table. By default this is set
6862			to false.
6863
6864	stacktrace	[FTRACE]
6865			Enabled the stack tracer on boot up.
6866
6867	stacktrace_filter=[function-list]
6868			[FTRACE] Limit the functions that the stack tracer
6869			will trace at boot up. function-list is a comma-separated
6870			list of functions. This list can be changed at run
6871			time by the stack_trace_filter file in the debugfs
6872			tracing directory. Note, this enables stack tracing
6873			and the stacktrace above is not needed.
6874
6875	sti=		[PARISC,HW]
6876			Format: <num>
6877			Set the STI (builtin display/keyboard on the HP-PARISC
6878			machines) console (graphic card) which should be used
6879			as the initial boot-console.
6880			See also comment in drivers/video/console/sticore.c.
6881
6882	sti_font=	[HW]
6883			See comment in drivers/video/console/sticore.c.
6884
6885	stifb=		[HW]
6886			Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6887
6888        strict_sas_size=
6889			[X86]
6890			Format: <bool>
6891			Enable or disable strict sigaltstack size checks
6892			against the required signal frame size which
6893			depends on the supported FPU features. This can
6894			be used to filter out binaries which have
6895			not yet been made aware of AT_MINSIGSTKSZ.
6896
6897	stress_hpt	[PPC,EARLY]
6898			Limits the number of kernel HPT entries in the hash
6899			page table to increase the rate of hash page table
6900			faults on kernel addresses.
6901
6902	stress_slb	[PPC,EARLY]
6903			Limits the number of kernel SLB entries, and flushes
6904			them frequently to increase the rate of SLB faults
6905			on kernel addresses.
6906
6907	sunrpc.min_resvport=
6908	sunrpc.max_resvport=
6909			[NFS,SUNRPC]
6910			SunRPC servers often require that client requests
6911			originate from a privileged port (i.e. a port in the
6912			range 0 < portnr < 1024).
6913			An administrator who wishes to reserve some of these
6914			ports for other uses may adjust the range that the
6915			kernel's sunrpc client considers to be privileged
6916			using these two parameters to set the minimum and
6917			maximum port values.
6918
6919	sunrpc.svc_rpc_per_connection_limit=
6920			[NFS,SUNRPC]
6921			Limit the number of requests that the server will
6922			process in parallel from a single connection.
6923			The default value is 0 (no limit).
6924
6925	sunrpc.pool_mode=
6926			[NFS]
6927			Control how the NFS server code allocates CPUs to
6928			service thread pools.  Depending on how many NICs
6929			you have and where their interrupts are bound, this
6930			option will affect which CPUs will do NFS serving.
6931			Note: this parameter cannot be changed while the
6932			NFS server is running.
6933
6934			auto	    the server chooses an appropriate mode
6935				    automatically using heuristics
6936			global	    a single global pool contains all CPUs
6937			percpu	    one pool for each CPU
6938			pernode	    one pool for each NUMA node (equivalent
6939				    to global on non-NUMA machines)
6940
6941	sunrpc.tcp_slot_table_entries=
6942	sunrpc.udp_slot_table_entries=
6943			[NFS,SUNRPC]
6944			Sets the upper limit on the number of simultaneous
6945			RPC calls that can be sent from the client to a
6946			server. Increasing these values may allow you to
6947			improve throughput, but will also increase the
6948			amount of memory reserved for use by the client.
6949
6950	suspend.pm_test_delay=
6951			[SUSPEND]
6952			Sets the number of seconds to remain in a suspend test
6953			mode before resuming the system (see
6954			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6955			is set. Default value is 5.
6956
6957	svm=		[PPC]
6958			Format: { on | off | y | n | 1 | 0 }
6959			This parameter controls use of the Protected
6960			Execution Facility on pSeries.
6961
6962	swiotlb=	[ARM,PPC,MIPS,X86,S390,EARLY]
6963			Format: { <int> [,<int>] | force | noforce }
6964			<int> -- Number of I/O TLB slabs
6965			<int> -- Second integer after comma. Number of swiotlb
6966				 areas with their own lock. Will be rounded up
6967				 to a power of 2.
6968			force -- force using of bounce buffers even if they
6969			         wouldn't be automatically used by the kernel
6970			noforce -- Never use bounce buffers (for debugging)
6971
6972	switches=	[HW,M68k,EARLY]
6973
6974	sysctl.*=	[KNL]
6975			Set a sysctl parameter, right before loading the init
6976			process, as if the value was written to the respective
6977			/proc/sys/... file. Both '.' and '/' are recognized as
6978			separators. Unrecognized parameters and invalid values
6979			are reported in the kernel log. Sysctls registered
6980			later by a loaded module cannot be set this way.
6981			Example: sysctl.vm.swappiness=40
6982
6983	sysrq_always_enabled
6984			[KNL]
6985			Ignore sysrq setting - this boot parameter will
6986			neutralize any effect of /proc/sys/kernel/sysrq.
6987			Useful for debugging.
6988
6989	tcpmhash_entries= [KNL,NET]
6990			Set the number of tcp_metrics_hash slots.
6991			Default value is 8192 or 16384 depending on total
6992			ram pages. This is used to specify the TCP metrics
6993			cache size. See Documentation/networking/ip-sysctl.rst
6994			"tcp_no_metrics_save" section for more details.
6995
6996	tdfx=		[HW,DRM]
6997
6998	test_suspend=	[SUSPEND]
6999			Format: { "mem" | "standby" | "freeze" }[,N]
7000			Specify "mem" (for Suspend-to-RAM) or "standby" (for
7001			standby suspend) or "freeze" (for suspend type freeze)
7002			as the system sleep state during system startup with
7003			the optional capability to repeat N number of times.
7004			The system is woken from this state using a
7005			wakeup-capable RTC alarm.
7006
7007	thash_entries=	[KNL,NET]
7008			Set number of hash buckets for TCP connection
7009
7010	thermal.act=	[HW,ACPI]
7011			-1: disable all active trip points in all thermal zones
7012			<degrees C>: override all lowest active trip points
7013
7014	thermal.crt=	[HW,ACPI]
7015			-1: disable all critical trip points in all thermal zones
7016			<degrees C>: override all critical trip points
7017
7018	thermal.off=	[HW,ACPI]
7019			1: disable ACPI thermal control
7020
7021	thermal.psv=	[HW,ACPI]
7022			-1: disable all passive trip points
7023			<degrees C>: override all passive trip points to this
7024			value
7025
7026	thermal.tzp=	[HW,ACPI]
7027			Specify global default ACPI thermal zone polling rate
7028			<deci-seconds>: poll all this frequency
7029			0: no polling (default)
7030
7031	thp_anon=	[KNL]
7032			Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
7033			state is one of "always", "madvise", "never" or "inherit".
7034			Control the default behavior of the system with respect
7035			to anonymous transparent hugepages.
7036			Can be used multiple times for multiple anon THP sizes.
7037			See Documentation/admin-guide/mm/transhuge.rst for more
7038			details.
7039
7040	threadirqs	[KNL,EARLY]
7041			Force threading of all interrupt handlers except those
7042			marked explicitly IRQF_NO_THREAD.
7043
7044	thp_shmem=	[KNL]
7045			Format: <size>[KMG],<size>[KMG]:<policy>;<size>[KMG]-<size>[KMG]:<policy>
7046			Control the default policy of each hugepage size for the
7047			internal shmem mount. <policy> is one of policies available
7048			for the shmem mount ("always", "inherit", "never", "within_size",
7049			and "advise").
7050			It can be used multiple times for multiple shmem THP sizes.
7051			See Documentation/admin-guide/mm/transhuge.rst for more
7052			details.
7053
7054	topology=	[S390,EARLY]
7055			Format: {off | on}
7056			Specify if the kernel should make use of the cpu
7057			topology information if the hardware supports this.
7058			The scheduler will make use of this information and
7059			e.g. base its process migration decisions on it.
7060			Default is on.
7061
7062	torture.disable_onoff_at_boot= [KNL]
7063			Prevent the CPU-hotplug component of torturing
7064			until after init has spawned.
7065
7066	torture.ftrace_dump_at_shutdown= [KNL]
7067			Dump the ftrace buffer at torture-test shutdown,
7068			even if there were no errors.  This can be a
7069			very costly operation when many torture tests
7070			are running concurrently, especially on systems
7071			with rotating-rust storage.
7072
7073	torture.verbose_sleep_frequency= [KNL]
7074			Specifies how many verbose printk()s should be
7075			emitted between each sleep.  The default of zero
7076			disables verbose-printk() sleeping.
7077
7078	torture.verbose_sleep_duration= [KNL]
7079			Duration of each verbose-printk() sleep in jiffies.
7080
7081	tpm.disable_pcr_integrity= [HW,TPM]
7082			Do not protect PCR registers from unintended physical
7083			access, or interposers in the bus by the means of
7084			having an integrity protected session wrapped around
7085			TPM2_PCR_Extend command. Consider this in a situation
7086			where TPM is heavily utilized by IMA, thus protection
7087			causing a major performance hit, and the space where
7088			machines are deployed is by other means guarded.
7089
7090	tpm_suspend_pcr=[HW,TPM]
7091			Format: integer pcr id
7092			Specify that at suspend time, the tpm driver
7093			should extend the specified pcr with zeros,
7094			as a workaround for some chips which fail to
7095			flush the last written pcr on TPM_SaveState.
7096			This will guarantee that all the other pcrs
7097			are saved.
7098
7099	tpm_tis.interrupts= [HW,TPM]
7100			Enable interrupts for the MMIO based physical layer
7101			for the FIFO interface. By default it is set to false
7102			(0). For more information about TPM hardware interfaces
7103			defined by Trusted Computing Group (TCG) see
7104			https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
7105
7106	tp_printk	[FTRACE]
7107			Have the tracepoints sent to printk as well as the
7108			tracing ring buffer. This is useful for early boot up
7109			where the system hangs or reboots and does not give the
7110			option for reading the tracing buffer or performing a
7111			ftrace_dump_on_oops.
7112
7113			To turn off having tracepoints sent to printk,
7114			 echo 0 > /proc/sys/kernel/tracepoint_printk
7115			Note, echoing 1 into this file without the
7116			tp_printk kernel cmdline option has no effect.
7117
7118			The tp_printk_stop_on_boot (see below) can also be used
7119			to stop the printing of events to console at
7120			late_initcall_sync.
7121
7122			** CAUTION **
7123
7124			Having tracepoints sent to printk() and activating high
7125			frequency tracepoints such as irq or sched, can cause
7126			the system to live lock.
7127
7128	tp_printk_stop_on_boot [FTRACE]
7129			When tp_printk (above) is set, it can cause a lot of noise
7130			on the console. It may be useful to only include the
7131			printing of events during boot up, as user space may
7132			make the system inoperable.
7133
7134			This command line option will stop the printing of events
7135			to console at the late_initcall_sync() time frame.
7136
7137	trace_buf_size=nn[KMG]
7138			[FTRACE] will set tracing buffer size on each cpu.
7139
7140	trace_clock=	[FTRACE] Set the clock used for tracing events
7141			at boot up.
7142			local - Use the per CPU time stamp counter
7143				(converted into nanoseconds). Fast, but
7144				depending on the architecture, may not be
7145				in sync between CPUs.
7146			global - Event time stamps are synchronize across
7147				CPUs. May be slower than the local clock,
7148				but better for some race conditions.
7149			counter - Simple counting of events (1, 2, ..)
7150				note, some counts may be skipped due to the
7151				infrastructure grabbing the clock more than
7152				once per event.
7153			uptime - Use jiffies as the time stamp.
7154			perf - Use the same clock that perf uses.
7155			mono - Use ktime_get_mono_fast_ns() for time stamps.
7156			mono_raw - Use ktime_get_raw_fast_ns() for time
7157				stamps.
7158			boot - Use ktime_get_boot_fast_ns() for time stamps.
7159			Architectures may add more clocks. See
7160			Documentation/trace/ftrace.rst for more details.
7161
7162	trace_event=[event-list]
7163			[FTRACE] Set and start specified trace events in order
7164			to facilitate early boot debugging. The event-list is a
7165			comma-separated list of trace events to enable. See
7166			also Documentation/trace/events.rst
7167
7168			To enable modules, use :mod: keyword:
7169
7170			trace_event=:mod:<module>
7171
7172			The value before :mod: will only enable specific events
7173			that are part of the module. See the above mentioned
7174			document for more information.
7175
7176	trace_instance=[instance-info]
7177			[FTRACE] Create a ring buffer instance early in boot up.
7178			This will be listed in:
7179
7180				/sys/kernel/tracing/instances
7181
7182			Events can be enabled at the time the instance is created
7183			via:
7184
7185				trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
7186
7187			Note, the "<system*>:" portion is optional if the event is
7188			unique.
7189
7190				trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
7191
7192			will enable the "sched_switch" event (note, the "sched:" is optional, and
7193			the same thing would happen if it was left off). The irq_handler_entry
7194			event, and all events under the "initcall" system.
7195
7196			Flags can be added to the instance to modify its behavior when it is
7197			created. The flags are separated by '^'.
7198
7199			The available flags are:
7200
7201			    traceoff	- Have the tracing instance tracing disabled after it is created.
7202			    traceprintk	- Have trace_printk() write into this trace instance
7203					  (note, "printk" and "trace_printk" can also be used)
7204
7205				trace_instance=foo^traceoff^traceprintk,sched,irq
7206
7207			The flags must come before the defined events.
7208
7209			If memory has been reserved (see memmap for x86), the instance
7210			can use that memory:
7211
7212				memmap=12M$0x284500000 trace_instance=boot_map@0x284500000:12M
7213
7214			The above will create a "boot_map" instance that uses the physical
7215			memory at 0x284500000 that is 12Megs. The per CPU buffers of that
7216			instance will be split up accordingly.
7217
7218			Alternatively, the memory can be reserved by the reserve_mem option:
7219
7220				reserve_mem=12M:4096:trace trace_instance=boot_map@trace
7221
7222			This will reserve 12 megabytes at boot up with a 4096 byte alignment
7223			and place the ring buffer in this memory. Note that due to KASLR, the
7224			memory may not be the same location each time, which will not preserve
7225			the buffer content.
7226
7227			Also note that the layout of the ring buffer data may change between
7228			kernel versions where the validator will fail and reset the ring buffer
7229			if the layout is not the same as the previous kernel.
7230
7231			If the ring buffer is used for persistent bootups and has events enabled,
7232			it is recommend to disable tracing so that events from a previous boot do not
7233			mix with events of the current boot (unless you are debugging a random crash
7234			at boot up).
7235
7236				reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq
7237
7238			Note, saving the trace buffer across reboots does require that the system
7239			is set up to not wipe memory. For instance, CONFIG_RESET_ATTACK_MITIGATION
7240			can force a memory reset on boot which will clear any trace that was stored.
7241			This is just one of many ways that can clear memory. Make sure your system
7242			keeps the content of memory across reboots before relying on this option.
7243
7244			See also Documentation/trace/debugging.rst
7245
7246
7247	trace_options=[option-list]
7248			[FTRACE] Enable or disable tracer options at boot.
7249			The option-list is a comma delimited list of options
7250			that can be enabled or disabled just as if you were
7251			to echo the option name into
7252
7253			    /sys/kernel/tracing/trace_options
7254
7255			For example, to enable stacktrace option (to dump the
7256			stack trace of each event), add to the command line:
7257
7258			      trace_options=stacktrace
7259
7260			See also Documentation/trace/ftrace.rst "trace options"
7261			section.
7262
7263	trace_trigger=[trigger-list]
7264			[FTRACE] Add a event trigger on specific events.
7265			Set a trigger on top of a specific event, with an optional
7266			filter.
7267
7268			The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
7269			Where more than one trigger may be specified that are comma deliminated.
7270
7271			For example:
7272
7273			  trace_trigger="sched_switch.stacktrace if prev_state == 2"
7274
7275			The above will enable the "stacktrace" trigger on the "sched_switch"
7276			event but only trigger it if the "prev_state" of the "sched_switch"
7277			event is "2" (TASK_UNINTERUPTIBLE).
7278
7279			See also "Event triggers" in Documentation/trace/events.rst
7280
7281
7282	traceoff_on_warning
7283			[FTRACE] enable this option to disable tracing when a
7284			warning is hit. This turns off "tracing_on". Tracing can
7285			be enabled again by echoing '1' into the "tracing_on"
7286			file located in /sys/kernel/tracing/
7287
7288			This option is useful, as it disables the trace before
7289			the WARNING dump is called, which prevents the trace to
7290			be filled with content caused by the warning output.
7291
7292			This option can also be set at run time via the sysctl
7293			option:  kernel/traceoff_on_warning
7294
7295	transparent_hugepage=
7296			[KNL]
7297			Format: [always|madvise|never]
7298			Can be used to control the default behavior of the system
7299			with respect to transparent hugepages.
7300			See Documentation/admin-guide/mm/transhuge.rst
7301			for more details.
7302
7303	transparent_hugepage_shmem= [KNL]
7304			Format: [always|within_size|advise|never|deny|force]
7305			Can be used to control the hugepage allocation policy for
7306			the internal shmem mount.
7307			See Documentation/admin-guide/mm/transhuge.rst
7308			for more details.
7309
7310	transparent_hugepage_tmpfs= [KNL]
7311			Format: [always|within_size|advise|never]
7312			Can be used to control the default hugepage allocation policy
7313			for the tmpfs mount.
7314			See Documentation/admin-guide/mm/transhuge.rst
7315			for more details.
7316
7317	trusted.source=	[KEYS]
7318			Format: <string>
7319			This parameter identifies the trust source as a backend
7320			for trusted keys implementation. Supported trust
7321			sources:
7322			- "tpm"
7323			- "tee"
7324			- "caam"
7325			- "dcp"
7326			If not specified then it defaults to iterating through
7327			the trust source list starting with TPM and assigns the
7328			first trust source as a backend which is initialized
7329			successfully during iteration.
7330
7331	trusted.rng=	[KEYS]
7332			Format: <string>
7333			The RNG used to generate key material for trusted keys.
7334			Can be one of:
7335			- "kernel"
7336			- the same value as trusted.source: "tpm" or "tee"
7337			- "default"
7338			If not specified, "default" is used. In this case,
7339			the RNG's choice is left to each individual trust source.
7340
7341	trusted.dcp_use_otp_key
7342			This is intended to be used in combination with
7343			trusted.source=dcp and will select the DCP OTP key
7344			instead of the DCP UNIQUE key blob encryption.
7345
7346	trusted.dcp_skip_zk_test
7347			This is intended to be used in combination with
7348			trusted.source=dcp and will disable the check if the
7349			blob key is all zeros. This is helpful for situations where
7350			having this key zero'ed is acceptable. E.g. in testing
7351			scenarios.
7352
7353	tsc=		Disable clocksource stability checks for TSC.
7354			Format: <string>
7355			[x86] reliable: mark tsc clocksource as reliable, this
7356			disables clocksource verification at runtime, as well
7357			as the stability checks done at bootup.	Used to enable
7358			high-resolution timer mode on older hardware, and in
7359			virtualized environment.
7360			[x86] noirqtime: Do not use TSC to do irq accounting.
7361			Used to run time disable IRQ_TIME_ACCOUNTING on any
7362			platforms where RDTSC is slow and this accounting
7363			can add overhead.
7364			[x86] unstable: mark the TSC clocksource as unstable, this
7365			marks the TSC unconditionally unstable at bootup and
7366			avoids any further wobbles once the TSC watchdog notices.
7367			[x86] nowatchdog: disable clocksource watchdog. Used
7368			in situations with strict latency requirements (where
7369			interruptions from clocksource watchdog are not
7370			acceptable).
7371			[x86] recalibrate: force recalibration against a HW timer
7372			(HPET or PM timer) on systems whose TSC frequency was
7373			obtained from HW or FW using either an MSR or CPUID(0x15).
7374			Warn if the difference is more than 500 ppm.
7375			[x86] watchdog: Use TSC as the watchdog clocksource with
7376			which to check other HW timers (HPET or PM timer), but
7377			only on systems where TSC has been deemed trustworthy.
7378			This will be suppressed by an earlier tsc=nowatchdog and
7379			can be overridden by a later tsc=nowatchdog.  A console
7380			message will flag any such suppression or overriding.
7381
7382	tsc_early_khz=  [X86,EARLY] Skip early TSC calibration and use the given
7383			value instead. Useful when the early TSC frequency discovery
7384			procedure is not reliable, such as on overclocked systems
7385			with CPUID.16h support and partial CPUID.15h support.
7386			Format: <unsigned int>
7387
7388	tsx=		[X86] Control Transactional Synchronization
7389			Extensions (TSX) feature in Intel processors that
7390			support TSX control.
7391
7392			This parameter controls the TSX feature. The options are:
7393
7394			on	- Enable TSX on the system. Although there are
7395				mitigations for all known security vulnerabilities,
7396				TSX has been known to be an accelerator for
7397				several previous speculation-related CVEs, and
7398				so there may be unknown	security risks associated
7399				with leaving it enabled.
7400
7401			off	- Disable TSX on the system. (Note that this
7402				option takes effect only on newer CPUs which are
7403				not vulnerable to MDS, i.e., have
7404				MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
7405				the new IA32_TSX_CTRL MSR through a microcode
7406				update. This new MSR allows for the reliable
7407				deactivation of the TSX functionality.)
7408
7409			auto	- Disable TSX if X86_BUG_TAA is present,
7410				  otherwise enable TSX on the system.
7411
7412			Not specifying this option is equivalent to tsx=off.
7413
7414			See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7415			for more details.
7416
7417	tsx_async_abort= [X86,INTEL,EARLY] Control mitigation for the TSX Async
7418			Abort (TAA) vulnerability.
7419
7420			Similar to Micro-architectural Data Sampling (MDS)
7421			certain CPUs that support Transactional
7422			Synchronization Extensions (TSX) are vulnerable to an
7423			exploit against CPU internal buffers which can forward
7424			information to a disclosure gadget under certain
7425			conditions.
7426
7427			In vulnerable processors, the speculatively forwarded
7428			data can be used in a cache side channel attack, to
7429			access data to which the attacker does not have direct
7430			access.
7431
7432			This parameter controls the TAA mitigation.  The
7433			options are:
7434
7435			full       - Enable TAA mitigation on vulnerable CPUs
7436				     if TSX is enabled.
7437
7438			full,nosmt - Enable TAA mitigation and disable SMT on
7439				     vulnerable CPUs. If TSX is disabled, SMT
7440				     is not disabled because CPU is not
7441				     vulnerable to cross-thread TAA attacks.
7442			off        - Unconditionally disable TAA mitigation
7443
7444			On MDS-affected machines, tsx_async_abort=off can be
7445			prevented by an active MDS mitigation as both vulnerabilities
7446			are mitigated with the same mechanism so in order to disable
7447			this mitigation, you need to specify mds=off too.
7448
7449			Not specifying this option is equivalent to
7450			tsx_async_abort=full.  On CPUs which are MDS affected
7451			and deploy MDS mitigation, TAA mitigation is not
7452			required and doesn't provide any additional
7453			mitigation.
7454
7455			For details see:
7456			Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7457
7458	turbografx.map[2|3]=	[HW,JOY]
7459			TurboGraFX parallel port interface
7460			Format:
7461			<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
7462			See also Documentation/input/devices/joystick-parport.rst
7463
7464	udbg-immortal	[PPC] When debugging early kernel crashes that
7465			happen after console_init() and before a proper
7466			console driver takes over, this boot options might
7467			help "seeing" what's going on.
7468
7469	uhash_entries=	[KNL,NET]
7470			Set number of hash buckets for UDP/UDP-Lite connections
7471
7472	uhci-hcd.ignore_oc=
7473			[USB] Ignore overcurrent events (default N).
7474			Some badly-designed motherboards generate lots of
7475			bogus events, for ports that aren't wired to
7476			anything.  Set this parameter to avoid log spamming.
7477			Note that genuine overcurrent events won't be
7478			reported either.
7479
7480	unknown_nmi_panic
7481			[X86] Cause panic on unknown NMI.
7482
7483	unwind_debug	[X86-64,EARLY]
7484			Enable unwinder debug output.  This can be
7485			useful for debugging certain unwinder error
7486			conditions, including corrupt stacks and
7487			bad/missing unwinder metadata.
7488
7489	usbcore.authorized_default=
7490			[USB] Default USB device authorization:
7491			(default -1 = authorized (same as 1),
7492			0 = not authorized, 1 = authorized, 2 = authorized
7493			if device connected to internal port)
7494
7495	usbcore.autosuspend=
7496			[USB] The autosuspend time delay (in seconds) used
7497			for newly-detected USB devices (default 2).  This
7498			is the time required before an idle device will be
7499			autosuspended.  Devices for which the delay is set
7500			to a negative value won't be autosuspended at all.
7501
7502	usbcore.usbfs_snoop=
7503			[USB] Set to log all usbfs traffic (default 0 = off).
7504
7505	usbcore.usbfs_snoop_max=
7506			[USB] Maximum number of bytes to snoop in each URB
7507			(default = 65536).
7508
7509	usbcore.blinkenlights=
7510			[USB] Set to cycle leds on hubs (default 0 = off).
7511
7512	usbcore.old_scheme_first=
7513			[USB] Start with the old device initialization
7514			scheme (default 0 = off).
7515
7516	usbcore.usbfs_memory_mb=
7517			[USB] Memory limit (in MB) for buffers allocated by
7518			usbfs (default = 16, 0 = max = 2047).
7519
7520	usbcore.use_both_schemes=
7521			[USB] Try the other device initialization scheme
7522			if the first one fails (default 1 = enabled).
7523
7524	usbcore.initial_descriptor_timeout=
7525			[USB] Specifies timeout for the initial 64-byte
7526			USB_REQ_GET_DESCRIPTOR request in milliseconds
7527			(default 5000 = 5.0 seconds).
7528
7529	usbcore.nousb	[USB] Disable the USB subsystem
7530
7531	usbcore.quirks=
7532			[USB] A list of quirk entries to augment the built-in
7533			usb core quirk list. List entries are separated by
7534			commas. Each entry has the form
7535			VendorID:ProductID:Flags. The IDs are 4-digit hex
7536			numbers and Flags is a set of letters. Each letter
7537			will change the built-in quirk; setting it if it is
7538			clear and clearing it if it is set. The letters have
7539			the following meanings:
7540				a = USB_QUIRK_STRING_FETCH_255 (string
7541					descriptors must not be fetched using
7542					a 255-byte read);
7543				b = USB_QUIRK_RESET_RESUME (device can't resume
7544					correctly so reset it instead);
7545				c = USB_QUIRK_NO_SET_INTF (device can't handle
7546					Set-Interface requests);
7547				d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7548					handle its Configuration or Interface
7549					strings);
7550				e = USB_QUIRK_RESET (device can't be reset
7551					(e.g morph devices), don't use reset);
7552				f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7553					more interface descriptions than the
7554					bNumInterfaces count, and can't handle
7555					talking to these interfaces);
7556				g = USB_QUIRK_DELAY_INIT (device needs a pause
7557					during initialization, after we read
7558					the device descriptor);
7559				h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7560					high speed and super speed interrupt
7561					endpoints, the USB 2.0 and USB 3.0 spec
7562					require the interval in microframes (1
7563					microframe = 125 microseconds) to be
7564					calculated as interval = 2 ^
7565					(bInterval-1).
7566					Devices with this quirk report their
7567					bInterval as the result of this
7568					calculation instead of the exponent
7569					variable used in the calculation);
7570				i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7571					handle device_qualifier descriptor
7572					requests);
7573				j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7574					generates spurious wakeup, ignore
7575					remote wakeup capability);
7576				k = USB_QUIRK_NO_LPM (device can't handle Link
7577					Power Management);
7578				l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7579					(Device reports its bInterval as linear
7580					frames instead of the USB 2.0
7581					calculation);
7582				m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7583					to be disconnected before suspend to
7584					prevent spurious wakeup);
7585				n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7586					pause after every control message);
7587				o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7588					delay after resetting its port);
7589				p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT
7590					(Reduce timeout of the SET_ADDRESS
7591					request from 5000 ms to 500 ms);
7592			Example: quirks=0781:5580:bk,0a5c:5834:gij
7593
7594	usbhid.mousepoll=
7595			[USBHID] The interval which mice are to be polled at.
7596
7597	usbhid.jspoll=
7598			[USBHID] The interval which joysticks are to be polled at.
7599
7600	usbhid.kbpoll=
7601			[USBHID] The interval which keyboards are to be polled at.
7602
7603	usb-storage.delay_use=
7604			[UMS] The delay in seconds before a new device is
7605			scanned for Logical Units (default 1).
7606			Optionally the delay in milliseconds if the value has
7607			suffix with "ms".
7608			Example: delay_use=2567ms
7609
7610	usb-storage.quirks=
7611			[UMS] A list of quirks entries to supplement or
7612			override the built-in unusual_devs list.  List
7613			entries are separated by commas.  Each entry has
7614			the form VID:PID:Flags where VID and PID are Vendor
7615			and Product ID values (4-digit hex numbers) and
7616			Flags is a set of characters, each corresponding
7617			to a common usb-storage quirk flag as follows:
7618				a = SANE_SENSE (collect more than 18 bytes
7619					of sense data, not on uas);
7620				b = BAD_SENSE (don't collect more than 18
7621					bytes of sense data, not on uas);
7622				c = FIX_CAPACITY (decrease the reported
7623					device capacity by one sector);
7624				d = NO_READ_DISC_INFO (don't use
7625					READ_DISC_INFO command, not on uas);
7626				e = NO_READ_CAPACITY_16 (don't use
7627					READ_CAPACITY_16 command);
7628				f = NO_REPORT_OPCODES (don't use report opcodes
7629					command, uas only);
7630				g = MAX_SECTORS_240 (don't transfer more than
7631					240 sectors at a time, uas only);
7632				h = CAPACITY_HEURISTICS (decrease the
7633					reported device capacity by one
7634					sector if the number is odd);
7635				i = IGNORE_DEVICE (don't bind to this
7636					device);
7637				j = NO_REPORT_LUNS (don't use report luns
7638					command, uas only);
7639				k = NO_SAME (do not use WRITE_SAME, uas only)
7640				l = NOT_LOCKABLE (don't try to lock and
7641					unlock ejectable media, not on uas);
7642				m = MAX_SECTORS_64 (don't transfer more
7643					than 64 sectors = 32 KB at a time,
7644					not on uas);
7645				n = INITIAL_READ10 (force a retry of the
7646					initial READ(10) command, not on uas);
7647				o = CAPACITY_OK (accept the capacity
7648					reported by the device, not on uas);
7649				p = WRITE_CACHE (the device cache is ON
7650					by default, not on uas);
7651				r = IGNORE_RESIDUE (the device reports
7652					bogus residue values, not on uas);
7653				s = SINGLE_LUN (the device has only one
7654					Logical Unit);
7655				t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7656					commands, uas only);
7657				u = IGNORE_UAS (don't bind to the uas driver);
7658				w = NO_WP_DETECT (don't test whether the
7659					medium is write-protected).
7660				y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7661					even if the device claims no cache,
7662					not on uas)
7663			Example: quirks=0419:aaf5:rl,0421:0433:rc
7664
7665	user_debug=	[KNL,ARM]
7666			Format: <int>
7667			See arch/arm/Kconfig.debug help text.
7668				 1 - undefined instruction events
7669				 2 - system calls
7670				 4 - invalid data aborts
7671				 8 - SIGSEGV faults
7672				16 - SIGBUS faults
7673			Example: user_debug=31
7674
7675	userpte=
7676			[X86,EARLY] Flags controlling user PTE allocations.
7677
7678				nohigh = do not allocate PTE pages in
7679					HIGHMEM regardless of setting
7680					of CONFIG_HIGHPTE.
7681
7682	vdso=		[X86,SH,SPARC]
7683			On X86_32, this is an alias for vdso32=.  Otherwise:
7684
7685			vdso=1: enable VDSO (the default)
7686			vdso=0: disable VDSO mapping
7687
7688	vdso32=		[X86] Control the 32-bit vDSO
7689			vdso32=1: enable 32-bit VDSO
7690			vdso32=0 or vdso32=2: disable 32-bit VDSO
7691
7692			See the help text for CONFIG_COMPAT_VDSO for more
7693			details.  If CONFIG_COMPAT_VDSO is set, the default is
7694			vdso32=0; otherwise, the default is vdso32=1.
7695
7696			For compatibility with older kernels, vdso32=2 is an
7697			alias for vdso32=0.
7698
7699			Try vdso32=0 if you encounter an error that says:
7700			dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7701
7702	video=		[FB,EARLY] Frame buffer configuration
7703			See Documentation/fb/modedb.rst.
7704
7705	video.brightness_switch_enabled= [ACPI]
7706			Format: [0|1]
7707			If set to 1, on receiving an ACPI notify event
7708			generated by hotkey, video driver will adjust brightness
7709			level and then send out the event to user space through
7710			the allocated input device. If set to 0, video driver
7711			will only send out the event without touching backlight
7712			brightness level.
7713			default: 1
7714
7715	virtio_mmio.device=
7716			[VMMIO] Memory mapped virtio (platform) device.
7717
7718				<size>@<baseaddr>:<irq>[:<id>]
7719			where:
7720				<size>     := size (can use standard suffixes
7721						like K, M and G)
7722				<baseaddr> := physical base address
7723				<irq>      := interrupt number (as passed to
7724						request_irq())
7725				<id>       := (optional) platform device id
7726			example:
7727				virtio_mmio.device=1K@0x100b0000:48:7
7728
7729			Can be used multiple times for multiple devices.
7730
7731	vga=		[BOOT,X86-32] Select a particular video mode
7732			See Documentation/arch/x86/boot.rst and
7733			Documentation/admin-guide/svga.rst.
7734			Use vga=ask for menu.
7735			This is actually a boot loader parameter; the value is
7736			passed to the kernel using a special protocol.
7737
7738	vm_debug[=options]	[KNL] Available with CONFIG_DEBUG_VM=y.
7739			May slow down system boot speed, especially when
7740			enabled on systems with a large amount of memory.
7741			All options are enabled by default, and this
7742			interface is meant to allow for selectively
7743			enabling or disabling specific virtual memory
7744			debugging features.
7745
7746			Available options are:
7747			  P	Enable page structure init time poisoning
7748			  -	Disable all of the above options
7749
7750	vmalloc=nn[KMG]	[KNL,BOOT,EARLY] Forces the vmalloc area to have an
7751			exact size of <nn>. This can be used to increase
7752			the minimum size (128MB on x86, arm32 platforms).
7753			It can also be used to decrease the size and leave more room
7754			for directly mapped kernel RAM. Note that this parameter does
7755			not exist on many other platforms (including arm64, alpha,
7756			loongarch, arc, csky, hexagon, microblaze, mips, nios2, openrisc,
7757			parisc, m64k, powerpc, riscv, sh, um, xtensa, s390, sparc).
7758
7759	vmcp_cma=nn[MG]	[KNL,S390,EARLY]
7760			Sets the memory size reserved for contiguous memory
7761			allocations for the vmcp device driver.
7762
7763	vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
7764			Format: <command>
7765
7766	vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
7767			Format: <command>
7768
7769	vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
7770			Format: <command>
7771
7772	vsyscall=	[X86-64,EARLY]
7773			Controls the behavior of vsyscalls (i.e. calls to
7774			fixed addresses of 0xffffffffff600x00 from legacy
7775			code).  Most statically-linked binaries and older
7776			versions of glibc use these calls.  Because these
7777			functions are at fixed addresses, they make nice
7778			targets for exploits that can control RIP.
7779
7780			emulate     Vsyscalls turn into traps and are emulated
7781			            reasonably safely.  The vsyscall page is
7782				    readable.
7783
7784			xonly       [default] Vsyscalls turn into traps and are
7785			            emulated reasonably safely.  The vsyscall
7786				    page is not readable.
7787
7788			none        Vsyscalls don't work at all.  This makes
7789			            them quite hard to use for exploits but
7790			            might break your system.
7791
7792	vt.color=	[VT] Default text color.
7793			Format: 0xYX, X = foreground, Y = background.
7794			Default: 0x07 = light gray on black.
7795
7796	vt.cur_default=	[VT] Default cursor shape.
7797			Format: 0xCCBBAA, where AA, BB, and CC are the same as
7798			the parameters of the <Esc>[?A;B;Cc escape sequence;
7799			see vga-softcursor.rst. Default: 2 = underline.
7800
7801	vt.default_blu=	[VT]
7802			Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7803			Change the default blue palette of the console.
7804			This is a 16-member array composed of values
7805			ranging from 0-255.
7806
7807	vt.default_grn=	[VT]
7808			Format: <green0>,<green1>,<green2>,...,<green15>
7809			Change the default green palette of the console.
7810			This is a 16-member array composed of values
7811			ranging from 0-255.
7812
7813	vt.default_red=	[VT]
7814			Format: <red0>,<red1>,<red2>,...,<red15>
7815			Change the default red palette of the console.
7816			This is a 16-member array composed of values
7817			ranging from 0-255.
7818
7819	vt.default_utf8=
7820			[VT]
7821			Format=<0|1>
7822			Set system-wide default UTF-8 mode for all tty's.
7823			Default is 1, i.e. UTF-8 mode is enabled for all
7824			newly opened terminals.
7825
7826	vt.global_cursor_default=
7827			[VT]
7828			Format=<-1|0|1>
7829			Set system-wide default for whether a cursor
7830			is shown on new VTs. Default is -1,
7831			i.e. cursors will be created by default unless
7832			overridden by individual drivers. 0 will hide
7833			cursors, 1 will display them.
7834
7835	vt.italic=	[VT] Default color for italic text; 0-15.
7836			Default: 2 = green.
7837
7838	vt.underline=	[VT] Default color for underlined text; 0-15.
7839			Default: 3 = cyan.
7840
7841	watchdog timers	[HW,WDT] For information on watchdog timers,
7842			see Documentation/watchdog/watchdog-parameters.rst
7843			or other driver-specific files in the
7844			Documentation/watchdog/ directory.
7845
7846	watchdog_thresh=
7847			[KNL]
7848			Set the hard lockup detector stall duration
7849			threshold in seconds. The soft lockup detector
7850			threshold is set to twice the value. A value of 0
7851			disables both lockup detectors. Default is 10
7852			seconds.
7853
7854	workqueue.unbound_cpus=
7855			[KNL,SMP] Specify to constrain one or some CPUs
7856			to use in unbound workqueues.
7857			Format: <cpu-list>
7858			By default, all online CPUs are available for
7859			unbound workqueues.
7860
7861	workqueue.watchdog_thresh=
7862			If CONFIG_WQ_WATCHDOG is configured, workqueue can
7863			warn stall conditions and dump internal state to
7864			help debugging.  0 disables workqueue stall
7865			detection; otherwise, it's the stall threshold
7866			duration in seconds.  The default value is 30 and
7867			it can be updated at runtime by writing to the
7868			corresponding sysfs file.
7869
7870	workqueue.panic_on_stall=<uint>
7871			Panic when workqueue stall is detected by
7872			CONFIG_WQ_WATCHDOG. It sets the number times of the
7873			stall to trigger panic.
7874
7875			The default is 0, which disables the panic on stall.
7876
7877	workqueue.cpu_intensive_thresh_us=
7878			Per-cpu work items which run for longer than this
7879			threshold are automatically considered CPU intensive
7880			and excluded from concurrency management to prevent
7881			them from noticeably delaying other per-cpu work
7882			items. Default is 10000 (10ms).
7883
7884			If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
7885			will report the work functions which violate this
7886			threshold repeatedly. They are likely good
7887			candidates for using WQ_UNBOUND workqueues instead.
7888
7889	workqueue.cpu_intensive_warning_thresh=<uint>
7890			If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
7891			will report the work functions which violate the
7892			intensive_threshold_us repeatedly. In order to prevent
7893			spurious warnings, start printing only after a work
7894			function has violated this threshold number of times.
7895
7896			The default is 4 times. 0 disables the warning.
7897
7898	workqueue.power_efficient
7899			Per-cpu workqueues are generally preferred because
7900			they show better performance thanks to cache
7901			locality; unfortunately, per-cpu workqueues tend to
7902			be more power hungry than unbound workqueues.
7903
7904			Enabling this makes the per-cpu workqueues which
7905			were observed to contribute significantly to power
7906			consumption unbound, leading to measurably lower
7907			power usage at the cost of small performance
7908			overhead.
7909
7910			The default value of this parameter is determined by
7911			the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7912
7913        workqueue.default_affinity_scope=
7914			Select the default affinity scope to use for unbound
7915			workqueues. Can be one of "cpu", "smt", "cache",
7916			"numa" and "system". Default is "cache". For more
7917			information, see the Affinity Scopes section in
7918			Documentation/core-api/workqueue.rst.
7919
7920			This can be changed after boot by writing to the
7921			matching /sys/module/workqueue/parameters file. All
7922			workqueues with the "default" affinity scope will be
7923			updated accordingly.
7924
7925	workqueue.debug_force_rr_cpu
7926			Workqueue used to implicitly guarantee that work
7927			items queued without explicit CPU specified are put
7928			on the local CPU.  This guarantee is no longer true
7929			and while local CPU is still preferred work items
7930			may be put on foreign CPUs.  This debug option
7931			forces round-robin CPU selection to flush out
7932			usages which depend on the now broken guarantee.
7933			When enabled, memory and cache locality will be
7934			impacted.
7935
7936	writecombine=	[LOONGARCH,EARLY] Control the MAT (Memory Access
7937			Type) of ioremap_wc().
7938
7939			on   - Enable writecombine, use WUC for ioremap_wc()
7940			off  - Disable writecombine, use SUC for ioremap_wc()
7941
7942	x2apic_phys	[X86-64,APIC,EARLY] Use x2apic physical mode instead of
7943			default x2apic cluster mode on platforms
7944			supporting x2apic.
7945
7946	xen_512gb_limit		[KNL,X86-64,XEN]
7947			Restricts the kernel running paravirtualized under Xen
7948			to use only up to 512 GB of RAM. The reason to do so is
7949			crash analysis tools and Xen tools for doing domain
7950			save/restore/migration must be enabled to handle larger
7951			domains.
7952
7953	xen_emul_unplug=		[HW,X86,XEN,EARLY]
7954			Unplug Xen emulated devices
7955			Format: [unplug0,][unplug1]
7956			ide-disks -- unplug primary master IDE devices
7957			aux-ide-disks -- unplug non-primary-master IDE devices
7958			nics -- unplug network devices
7959			all -- unplug all emulated devices (NICs and IDE disks)
7960			unnecessary -- unplugging emulated devices is
7961				unnecessary even if the host did not respond to
7962				the unplug protocol
7963			never -- do not unplug even if version check succeeds
7964
7965	xen_legacy_crash	[X86,XEN,EARLY]
7966			Crash from Xen panic notifier, without executing late
7967			panic() code such as dumping handler.
7968
7969	xen_mc_debug	[X86,XEN,EARLY]
7970			Enable multicall debugging when running as a Xen PV guest.
7971			Enabling this feature will reduce performance a little
7972			bit, so it should only be enabled for obtaining extended
7973			debug data in case of multicall errors.
7974
7975	xen_msr_safe=	[X86,XEN,EARLY]
7976			Format: <bool>
7977			Select whether to always use non-faulting (safe) MSR
7978			access functions when running as Xen PV guest. The
7979			default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
7980
7981	xen_nopv	[X86]
7982			Disables the PV optimizations forcing the HVM guest to
7983			run as generic HVM guest with no PV drivers.
7984			This option is obsoleted by the "nopv" option, which
7985			has equivalent effect for XEN platform.
7986
7987	xen_no_vector_callback
7988			[KNL,X86,XEN,EARLY] Disable the vector callback for Xen
7989			event channel interrupts.
7990
7991	xen_scrub_pages=	[XEN]
7992			Boolean option to control scrubbing pages before giving them back
7993			to Xen, for use by other domains. Can be also changed at runtime
7994			with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7995			Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7996
7997	xen_timer_slop=	[X86-64,XEN,EARLY]
7998			Set the timer slop (in nanoseconds) for the virtual Xen
7999			timers (default is 100000). This adjusts the minimum
8000			delta of virtualized Xen timers, where lower values
8001			improve timer resolution at the expense of processing
8002			more timer interrupts.
8003
8004	xen.balloon_boot_timeout= [XEN]
8005			The time (in seconds) to wait before giving up to boot
8006			in case initial ballooning fails to free enough memory.
8007			Applies only when running as HVM or PVH guest and
8008			started with less memory configured than allowed at
8009			max. Default is 180.
8010
8011	xen.event_eoi_delay=	[XEN]
8012			How long to delay EOI handling in case of event
8013			storms (jiffies). Default is 10.
8014
8015	xen.event_loop_timeout=	[XEN]
8016			After which time (jiffies) the event handling loop
8017			should start to delay EOI handling. Default is 2.
8018
8019	xen.fifo_events=	[XEN]
8020			Boolean parameter to disable using fifo event handling
8021			even if available. Normally fifo event handling is
8022			preferred over the 2-level event handling, as it is
8023			fairer and the number of possible event channels is
8024			much higher. Default is on (use fifo events).
8025
8026	xirc2ps_cs=	[NET,PCMCIA]
8027			Format:
8028			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
8029
8030	xive=		[PPC]
8031			By default on POWER9 and above, the kernel will
8032			natively use the XIVE interrupt controller. This option
8033			allows the fallback firmware mode to be used:
8034
8035			off       Fallback to firmware control of XIVE interrupt
8036				  controller on both pseries and powernv
8037				  platforms. Only useful on POWER9 and above.
8038
8039	xive.store-eoi=off	[PPC]
8040			By default on POWER10 and above, the kernel will use
8041			stores for EOI handling when the XIVE interrupt mode
8042			is active. This option allows the XIVE driver to use
8043			loads instead, as on POWER9.
8044
8045	xhci-hcd.quirks		[USB,KNL]
8046			A hex value specifying bitmask with supplemental xhci
8047			host controller quirks. Meaning of each bit can be
8048			consulted in header drivers/usb/host/xhci.h.
8049
8050	xmon		[PPC,EARLY]
8051			Format: { early | on | rw | ro | off }
8052			Controls if xmon debugger is enabled. Default is off.
8053			Passing only "xmon" is equivalent to "xmon=early".
8054			early	Call xmon as early as possible on boot; xmon
8055				debugger is called from setup_arch().
8056			on	xmon debugger hooks will be installed so xmon
8057				is only called on a kernel crash. Default mode,
8058				i.e. either "ro" or "rw" mode, is controlled
8059				with CONFIG_XMON_DEFAULT_RO_MODE.
8060			rw	xmon debugger hooks will be installed so xmon
8061				is called only on a kernel crash, mode is write,
8062				meaning SPR registers, memory and, other data
8063				can be written using xmon commands.
8064			ro 	same as "rw" option above but SPR registers,
8065				memory, and other data can't be written using
8066				xmon commands.
8067			off	xmon is disabled.
8068