xref: /linux/Documentation/admin-guide/kernel-parameters.txt (revision c532de5a67a70f8533d495f8f2aaa9a0491c3ad0)
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			nospcr -- disable console in ACPI SPCR table as
25				default _serial_ console on ARM64
26			For ARM64, ONLY "acpi=off", "acpi=on", "acpi=force" or
27			"acpi=nospcr" are available
28			For RISCV64, ONLY "acpi=off", "acpi=on" or "acpi=force"
29			are available
30
31			See also Documentation/power/runtime_pm.rst, pci=noacpi
32
33	acpi_apic_instance=	[ACPI,IOAPIC,EARLY]
34			Format: <int>
35			2: use 2nd APIC table, if available
36			1,0: use 1st APIC table
37			default: 0
38
39	acpi_backlight=	[HW,ACPI]
40			{ vendor | video | native | none }
41			If set to vendor, prefer vendor-specific driver
42			(e.g. thinkpad_acpi, sony_acpi, etc.) instead
43			of the ACPI video.ko driver.
44			If set to video, use the ACPI video.ko driver.
45			If set to native, use the device's native backlight mode.
46			If set to none, disable the ACPI backlight interface.
47
48	acpi_force_32bit_fadt_addr [ACPI,EARLY]
49			force FADT to use 32 bit addresses rather than the
50			64 bit X_* addresses. Some firmware have broken 64
51			bit addresses for force ACPI ignore these and use
52			the older legacy 32 bit addresses.
53
54	acpica_no_return_repair [HW, ACPI]
55			Disable AML predefined validation mechanism
56			This mechanism can repair the evaluation result to make
57			the return objects more ACPI specification compliant.
58			This option is useful for developers to identify the
59			root cause of an AML interpreter issue when the issue
60			has something to do with the repair mechanism.
61
62	acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
63	acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
64			Format: <int>
65			CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
66			debug output.  Bits in debug_layer correspond to a
67			_COMPONENT in an ACPI source file, e.g.,
68			    #define _COMPONENT ACPI_EVENTS
69			Bits in debug_level correspond to a level in
70			ACPI_DEBUG_PRINT statements, e.g.,
71			    ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
72			The debug_level mask defaults to "info".  See
73			Documentation/firmware-guide/acpi/debug.rst for more information about
74			debug layers and levels.
75
76			Enable processor driver info messages:
77			    acpi.debug_layer=0x20000000
78			Enable AML "Debug" output, i.e., stores to the Debug
79			object while interpreting AML:
80			    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
81			Enable all messages related to ACPI hardware:
82			    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
83
84			Some values produce so much output that the system is
85			unusable.  The "log_buf_len" parameter may be useful
86			if you need to capture more output.
87
88	acpi_enforce_resources=	[ACPI]
89			{ strict | lax | no }
90			Check for resource conflicts between native drivers
91			and ACPI OperationRegions (SystemIO and SystemMemory
92			only). IO ports and memory declared in ACPI might be
93			used by the ACPI subsystem in arbitrary AML code and
94			can interfere with legacy drivers.
95			strict (default): access to resources claimed by ACPI
96			is denied; legacy drivers trying to access reserved
97			resources will fail to bind to device using them.
98			lax: access to resources claimed by ACPI is allowed;
99			legacy drivers trying to access reserved resources
100			will bind successfully but a warning message is logged.
101			no: ACPI OperationRegions are not marked as reserved,
102			no further checks are performed.
103
104	acpi_force_table_verification	[HW,ACPI,EARLY]
105			Enable table checksum verification during early stage.
106			By default, this is disabled due to x86 early mapping
107			size limitation.
108
109	acpi_irq_balance [HW,ACPI]
110			ACPI will balance active IRQs
111			default in APIC mode
112
113	acpi_irq_nobalance [HW,ACPI]
114			ACPI will not move active IRQs (default)
115			default in PIC mode
116
117	acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
118			Format: <irq>,<irq>...
119
120	acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
121			use by PCI
122			Format: <irq>,<irq>...
123
124	acpi_mask_gpe=	[HW,ACPI]
125			Due to the existence of _Lxx/_Exx, some GPEs triggered
126			by unsupported hardware/firmware features can result in
127			GPE floodings that cannot be automatically disabled by
128			the GPE dispatcher.
129			This facility can be used to prevent such uncontrolled
130			GPE floodings.
131			Format: <byte> or <bitmap-list>
132
133	acpi_no_auto_serialize	[HW,ACPI]
134			Disable auto-serialization of AML methods
135			AML control methods that contain the opcodes to create
136			named objects will be marked as "Serialized" by the
137			auto-serialization feature.
138			This feature is enabled by default.
139			This option allows to turn off the feature.
140
141	acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
142			   kernels.
143
144	acpi_no_static_ssdt	[HW,ACPI,EARLY]
145			Disable installation of static SSDTs at early boot time
146			By default, SSDTs contained in the RSDT/XSDT will be
147			installed automatically and they will appear under
148			/sys/firmware/acpi/tables.
149			This option turns off this feature.
150			Note that specifying this option does not affect
151			dynamic table installation which will install SSDT
152			tables to /sys/firmware/acpi/tables/dynamic.
153
154	acpi_no_watchdog	[HW,ACPI,WDT]
155			Ignore the ACPI-based watchdog interface (WDAT) and let
156			a native driver control the watchdog device instead.
157
158	acpi_rsdp=	[ACPI,EFI,KEXEC,EARLY]
159			Pass the RSDP address to the kernel, mostly used
160			on machines running EFI runtime service to boot the
161			second kernel for kdump.
162
163	acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
164			Format: To spoof as Windows 98: ="Microsoft Windows"
165
166	acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
167			of 2 which is mandated by ACPI 6) as the supported ACPI
168			specification revision (when using this switch, it may
169			be necessary to carry out a cold reboot _twice_ in a
170			row to make it take effect on the platform firmware).
171
172	acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
173			acpi_osi="string1"	# add string1
174			acpi_osi="!string2"	# remove string2
175			acpi_osi=!*		# remove all strings
176			acpi_osi=!		# disable all built-in OS vendor
177						  strings
178			acpi_osi=!!		# enable all built-in OS vendor
179						  strings
180			acpi_osi=		# disable all strings
181
182			'acpi_osi=!' can be used in combination with single or
183			multiple 'acpi_osi="string1"' to support specific OS
184			vendor string(s).  Note that such command can only
185			affect the default state of the OS vendor strings, thus
186			it cannot affect the default state of the feature group
187			strings and the current state of the OS vendor strings,
188			specifying it multiple times through kernel command line
189			is meaningless.  This command is useful when one do not
190			care about the state of the feature group strings which
191			should be controlled by the OSPM.
192			Examples:
193			  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
194			     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195			     can make '_OSI("Windows 2000")' TRUE.
196
197			'acpi_osi=' cannot be used in combination with other
198			'acpi_osi=' command lines, the _OSI method will not
199			exist in the ACPI namespace.  NOTE that such command can
200			only affect the _OSI support state, thus specifying it
201			multiple times through kernel command line is also
202			meaningless.
203			Examples:
204			  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
205			     FALSE.
206
207			'acpi_osi=!*' can be used in combination with single or
208			multiple 'acpi_osi="string1"' to support specific
209			string(s).  Note that such command can affect the
210			current state of both the OS vendor strings and the
211			feature group strings, thus specifying it multiple times
212			through kernel command line is meaningful.  But it may
213			still not able to affect the final state of a string if
214			there are quirks related to this string.  This command
215			is useful when one want to control the state of the
216			feature group strings to debug BIOS issues related to
217			the OSPM features.
218			Examples:
219			  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
220			     '_OSI("Module Device")' FALSE.
221			  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
222			     '_OSI("Module Device")' TRUE.
223			  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
224			     equivalent to
225			     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
226			     and
227			     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
228			     they all will make '_OSI("Windows 2000")' TRUE.
229
230	acpi_pm_good	[X86]
231			Override the pmtimer bug detection: force the kernel
232			to assume that this machine's pmtimer latches its value
233			and always returns good values.
234
235	acpi_sci=	[HW,ACPI,EARLY] ACPI System Control Interrupt trigger mode
236			Format: { level | edge | high | low }
237
238	acpi_skip_timer_override [HW,ACPI,EARLY]
239			Recognize and ignore IRQ0/pin2 Interrupt Override.
240			For broken nForce2 BIOS resulting in XT-PIC timer.
241
242	acpi_sleep=	[HW,ACPI] Sleep options
243			Format: { s3_bios, s3_mode, s3_beep, s4_hwsig,
244				  s4_nohwsig, old_ordering, nonvs,
245				  sci_force_enable, nobl }
246			See Documentation/power/video.rst for information on
247			s3_bios and s3_mode.
248			s3_beep is for debugging; it makes the PC's speaker beep
249			as soon as the kernel's real-mode entry point is called.
250			s4_hwsig causes the kernel to check the ACPI hardware
251			signature during resume from hibernation, and gracefully
252			refuse to resume if it has changed. This complies with
253			the ACPI specification but not with reality, since
254			Windows does not do this and many laptops do change it
255			on docking. So the default behaviour is to allow resume
256			and simply warn when the signature changes, unless the
257			s4_hwsig option is enabled.
258			s4_nohwsig prevents ACPI hardware signature from being
259			used (or even warned about) during resume.
260			old_ordering causes the ACPI 1.0 ordering of the _PTS
261			control method, with respect to putting devices into
262			low power states, to be enforced (the ACPI 2.0 ordering
263			of _PTS is used by default).
264			nonvs prevents the kernel from saving/restoring the
265			ACPI NVS memory during suspend/hibernation and resume.
266			sci_force_enable causes the kernel to set SCI_EN directly
267			on resume from S1/S3 (which is against the ACPI spec,
268			but some broken systems don't work without it).
269			nobl causes the internal blacklist of systems known to
270			behave incorrectly in some ways with respect to system
271			suspend and resume to be ignored (use wisely).
272
273	acpi_use_timer_override [HW,ACPI,EARLY]
274			Use timer override. For some broken Nvidia NF5 boards
275			that require a timer override, but don't have HPET
276
277	add_efi_memmap	[EFI,X86,EARLY] Include EFI memory map in
278			kernel's map of available physical RAM.
279
280	agp=		[AGP]
281			{ off | try_unsupported }
282			off: disable AGP support
283			try_unsupported: try to drive unsupported chipsets
284				(may crash computer or cause data corruption)
285
286	ALSA		[HW,ALSA]
287			See Documentation/sound/alsa-configuration.rst
288
289	alignment=	[KNL,ARM]
290			Allow the default userspace alignment fault handler
291			behaviour to be specified.  Bit 0 enables warnings,
292			bit 1 enables fixups, and bit 2 sends a segfault.
293
294	align_va_addr=	[X86-64]
295			Align virtual addresses by clearing slice [14:12] when
296			allocating a VMA at process creation time. This option
297			gives you up to 3% performance improvement on AMD F15h
298			machines (where it is enabled by default) for a
299			CPU-intensive style benchmark, and it can vary highly in
300			a microbenchmark depending on workload and compiler.
301
302			32: only for 32-bit processes
303			64: only for 64-bit processes
304			on: enable for both 32- and 64-bit processes
305			off: disable for both 32- and 64-bit processes
306
307	alloc_snapshot	[FTRACE]
308			Allocate the ftrace snapshot buffer on boot up when the
309			main buffer is allocated. This is handy if debugging
310			and you need to use tracing_snapshot() on boot up, and
311			do not want to use tracing_snapshot_alloc() as it needs
312			to be done where GFP_KERNEL allocations are allowed.
313
314	allow_mismatched_32bit_el0 [ARM64,EARLY]
315			Allow execve() of 32-bit applications and setting of the
316			PER_LINUX32 personality on systems where only a strict
317			subset of the CPUs support 32-bit EL0. When this
318			parameter is present, the set of CPUs supporting 32-bit
319			EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
320			and hot-unplug operations may be restricted.
321
322			See Documentation/arch/arm64/asymmetric-32bit.rst for more
323			information.
324
325	amd_iommu=	[HW,X86-64]
326			Pass parameters to the AMD IOMMU driver in the system.
327			Possible values are:
328			fullflush - Deprecated, equivalent to iommu.strict=1
329			off	  - do not initialize any AMD IOMMU found in
330				    the system
331			force_isolation - Force device isolation for all
332					  devices. The IOMMU driver is not
333					  allowed anymore to lift isolation
334					  requirements as needed. This option
335					  does not override iommu=pt
336			force_enable    - Force enable the IOMMU on platforms known
337				          to be buggy with IOMMU enabled. Use this
338				          option with care.
339			pgtbl_v1        - Use v1 page table for DMA-API (Default).
340			pgtbl_v2        - Use v2 page table for DMA-API.
341			irtcachedis     - Disable Interrupt Remapping Table (IRT) caching.
342			nohugepages     - Limit page-sizes used for v1 page-tables
343				          to 4 KiB.
344			v2_pgsizes_only - Limit page-sizes used for v1 page-tables
345				          to 4KiB/2Mib/1GiB.
346
347
348	amd_iommu_dump=	[HW,X86-64]
349			Enable AMD IOMMU driver option to dump the ACPI table
350			for AMD IOMMU. With this option enabled, AMD IOMMU
351			driver will print ACPI tables for AMD IOMMU during
352			IOMMU initialization.
353
354	amd_iommu_intr=	[HW,X86-64]
355			Specifies one of the following AMD IOMMU interrupt
356			remapping modes:
357			legacy     - Use legacy interrupt remapping mode.
358			vapic      - Use virtual APIC mode, which allows IOMMU
359			             to inject interrupts directly into guest.
360			             This mode requires kvm-amd.avic=1.
361			             (Default when IOMMU HW support is present.)
362
363	amd_pstate=	[X86,EARLY]
364			disable
365			  Do not enable amd_pstate as the default
366			  scaling driver for the supported processors
367			passive
368			  Use amd_pstate with passive mode as a scaling driver.
369			  In this mode autonomous selection is disabled.
370			  Driver requests a desired performance level and platform
371			  tries to match the same performance level if it is
372			  satisfied by guaranteed performance level.
373			active
374			  Use amd_pstate_epp driver instance as the scaling driver,
375			  driver provides a hint to the hardware if software wants
376			  to bias toward performance (0x0) or energy efficiency (0xff)
377			  to the CPPC firmware. then CPPC power algorithm will
378			  calculate the runtime workload and adjust the realtime cores
379			  frequency.
380			guided
381			  Activate guided autonomous mode. Driver requests minimum and
382			  maximum performance level and the platform autonomously
383			  selects a performance level in this range and appropriate
384			  to the current workload.
385
386	amd_prefcore=
387			[X86]
388			disable
389			  Disable amd-pstate preferred core.
390
391	amijoy.map=	[HW,JOY] Amiga joystick support
392			Map of devices attached to JOY0DAT and JOY1DAT
393			Format: <a>,<b>
394			See also Documentation/input/joydev/joystick.rst
395
396	analog.map=	[HW,JOY] Analog joystick and gamepad support
397			Specifies type or capabilities of an analog joystick
398			connected to one of 16 gameports
399			Format: <type1>,<type2>,..<type16>
400
401	apc=		[HW,SPARC]
402			Power management functions (SPARCstation-4/5 + deriv.)
403			Format: noidle
404			Disable APC CPU standby support. SPARCstation-Fox does
405			not play well with APC CPU idle - disable it if you have
406			APC and your system crashes randomly.
407
408	apic=		[APIC,X86,EARLY] Advanced Programmable Interrupt Controller
409			Change the output verbosity while booting
410			Format: { quiet (default) | verbose | debug }
411			Change the amount of debugging information output
412			when initialising the APIC and IO-APIC components.
413			For X86-32, this can also be used to specify an APIC
414			driver name.
415			Format: apic=driver_name
416			Examples: apic=bigsmp
417
418	apic_extnmi=	[APIC,X86,EARLY] External NMI delivery setting
419			Format: { bsp (default) | all | none }
420			bsp:  External NMI is delivered only to CPU 0
421			all:  External NMIs are broadcast to all CPUs as a
422			      backup of CPU 0
423			none: External NMI is masked for all CPUs. This is
424			      useful so that a dump capture kernel won't be
425			      shot down by NMI
426
427	autoconf=	[IPV6]
428			See Documentation/networking/ipv6.rst.
429
430	apm=		[APM] Advanced Power Management
431			See header of arch/x86/kernel/apm_32.c.
432
433	apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
434			Format: { "0" | "1" }
435			See security/apparmor/Kconfig help text
436			0 -- disable.
437			1 -- enable.
438			Default value is set via kernel config option.
439
440	arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
441			Format: <io>,<irq>,<nodeID>
442
443	arm64.no32bit_el0 [ARM64] Unconditionally disable the execution of
444			32 bit applications.
445
446	arm64.nobti	[ARM64] Unconditionally disable Branch Target
447			Identification support
448
449	arm64.nomops	[ARM64] Unconditionally disable Memory Copy and Memory
450			Set instructions support
451
452	arm64.nomte	[ARM64] Unconditionally disable Memory Tagging Extension
453			support
454
455	arm64.nopauth	[ARM64] Unconditionally disable Pointer Authentication
456			support
457
458	arm64.nosme	[ARM64] Unconditionally disable Scalable Matrix
459			Extension support
460
461	arm64.nosve	[ARM64] Unconditionally disable Scalable Vector
462			Extension support
463
464	ataflop=	[HW,M68k]
465
466	atarimouse=	[HW,MOUSE] Atari Mouse
467
468	atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
469			EzKey and similar keyboards
470
471	atkbd.reset=	[HW] Reset keyboard during initialization
472
473	atkbd.set=	[HW] Select keyboard code set
474			Format: <int> (2 = AT (default), 3 = PS/2)
475
476	atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
477			keyboards
478
479	atkbd.softraw=	[HW] Choose between synthetic and real raw mode
480			Format: <bool> (0 = real, 1 = synthetic (default))
481
482	atkbd.softrepeat= [HW]
483			Use software keyboard repeat
484
485	audit=		[KNL] Enable the audit sub-system
486			Format: { "0" | "1" | "off" | "on" }
487			0 | off - kernel audit is disabled and can not be
488			    enabled until the next reboot
489			unset - kernel audit is initialized but disabled and
490			    will be fully enabled by the userspace auditd.
491			1 | on - kernel audit is initialized and partially
492			    enabled, storing at most audit_backlog_limit
493			    messages in RAM until it is fully enabled by the
494			    userspace auditd.
495			Default: unset
496
497	audit_backlog_limit= [KNL] Set the audit queue size limit.
498			Format: <int> (must be >=0)
499			Default: 64
500
501	bau=		[X86_UV] Enable the BAU on SGI UV.  The default
502			behavior is to disable the BAU (i.e. bau=0).
503			Format: { "0" | "1" }
504			0 - Disable the BAU.
505			1 - Enable the BAU.
506			unset - Disable the BAU.
507
508	baycom_epp=	[HW,AX25]
509			Format: <io>,<mode>
510
511	baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
512			Format: <io>,<mode>
513			See header of drivers/net/hamradio/baycom_par.c.
514
515	baycom_ser_fdx=	[HW,AX25]
516			BayCom Serial Port AX.25 Modem (Full Duplex Mode)
517			Format: <io>,<irq>,<mode>[,<baud>]
518			See header of drivers/net/hamradio/baycom_ser_fdx.c.
519
520	baycom_ser_hdx=	[HW,AX25]
521			BayCom Serial Port AX.25 Modem (Half Duplex Mode)
522			Format: <io>,<irq>,<mode>
523			See header of drivers/net/hamradio/baycom_ser_hdx.c.
524
525	bdev_allow_write_mounted=
526			Format: <bool>
527			Control the ability to open a mounted block device
528			for writing, i.e., allow / disallow writes that bypass
529			the FS. This was implemented as a means to prevent
530			fuzzers from crashing the kernel by overwriting the
531			metadata underneath a mounted FS without its awareness.
532			This also prevents destructive formatting of mounted
533			filesystems by naive storage tooling that don't use
534			O_EXCL. Default is Y and can be changed through the
535			Kconfig option CONFIG_BLK_DEV_WRITE_MOUNTED.
536
537	bert_disable	[ACPI]
538			Disable BERT OS support on buggy BIOSes.
539
540	bgrt_disable	[ACPI,X86,EARLY]
541			Disable BGRT to avoid flickering OEM logo.
542
543	blkdevparts=	Manual partition parsing of block device(s) for
544			embedded devices based on command line input.
545			See Documentation/block/cmdline-partition.rst
546
547	boot_delay=	[KNL,EARLY]
548			Milliseconds to delay each printk during boot.
549			Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
550			and you may also have to specify "lpj=".  Boot_delay
551			values larger than 10 seconds (10000) are assumed
552			erroneous and ignored.
553			Format: integer
554
555	bootconfig	[KNL,EARLY]
556			Extended command line options can be added to an initrd
557			and this will cause the kernel to look for it.
558
559			See Documentation/admin-guide/bootconfig.rst
560
561	bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
562	bttv.radio=	Most important insmod options are available as
563			kernel args too.
564	bttv.pll=	See Documentation/admin-guide/media/bttv.rst
565	bttv.tuner=
566
567	bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
568			firmware feature for flushing multiple hpte entries
569			at a time.
570
571	c101=		[NET] Moxa C101 synchronous serial card
572
573	cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
574			Sometimes CPU hardware bugs make them report the cache
575			size incorrectly. The kernel will attempt work arounds
576			to fix known problems, but for some CPUs it is not
577			possible to determine what the correct size should be.
578			This option provides an override for these situations.
579
580	carrier_timeout=
581			[NET] Specifies amount of time (in seconds) that
582			the kernel should wait for a network carrier. By default
583			it waits 120 seconds.
584
585	ca_keys=	[KEYS] This parameter identifies a specific key(s) on
586			the system trusted keyring to be used for certificate
587			trust validation.
588			format: { id:<keyid> | builtin }
589
590	cca=		[MIPS,EARLY] Override the kernel pages' cache coherency
591			algorithm.  Accepted values range from 0 to 7
592			inclusive. See arch/mips/include/asm/pgtable-bits.h
593			for platform specific values (SB1, Loongson3 and
594			others).
595
596	ccw_timeout_log	[S390]
597			See Documentation/arch/s390/common_io.rst for details.
598
599	cgroup_disable=	[KNL] Disable a particular controller or optional feature
600			Format: {name of the controller(s) or feature(s) to disable}
601			The effects of cgroup_disable=foo are:
602			- foo isn't auto-mounted if you mount all cgroups in
603			  a single hierarchy
604			- foo isn't visible as an individually mountable
605			  subsystem
606			- if foo is an optional feature then the feature is
607			  disabled and corresponding cgroup files are not
608			  created
609			{Currently only "memory" controller deal with this and
610			cut the overhead, others just disable the usage. So
611			only cgroup_disable=memory is actually worthy}
612			Specifying "pressure" disables per-cgroup pressure
613			stall information accounting feature
614
615	cgroup_no_v1=	[KNL] Disable cgroup controllers and named hierarchies in v1
616			Format: { { controller | "all" | "named" }
617			          [,{ controller | "all" | "named" }...] }
618			Like cgroup_disable, but only applies to cgroup v1;
619			the blacklisted controllers remain available in cgroup2.
620			"all" blacklists all controllers and "named" disables
621			named mounts. Specifying both "all" and "named" disables
622			all v1 hierarchies.
623
624	cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
625			Format: { "true" | "false" }
626			Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.
627
628	cgroup.memory=	[KNL] Pass options to the cgroup memory controller.
629			Format: <string>
630			nosocket -- Disable socket memory accounting.
631			nokmem -- Disable kernel memory accounting.
632			nobpf -- Disable BPF memory accounting.
633
634	checkreqprot=	[SELINUX] Set initial checkreqprot flag value.
635			Format: { "0" | "1" }
636			See security/selinux/Kconfig help text.
637			0 -- check protection applied by kernel (includes
638				any implied execute protection).
639			1 -- check protection requested by application.
640			Default value is set via a kernel config option.
641			Value can be changed at runtime via
642				/sys/fs/selinux/checkreqprot.
643			Setting checkreqprot to 1 is deprecated.
644
645	cio_ignore=	[S390]
646			See Documentation/arch/s390/common_io.rst for details.
647
648	clearcpuid=X[,X...] [X86]
649			Disable CPUID feature X for the kernel. See
650			arch/x86/include/asm/cpufeatures.h for the valid bit
651			numbers X. Note the Linux-specific bits are not necessarily
652			stable over kernel options, but the vendor-specific
653			ones should be.
654			X can also be a string as appearing in the flags: line
655			in /proc/cpuinfo which does not have the above
656			instability issue. However, not all features have names
657			in /proc/cpuinfo.
658			Note that using this option will taint your kernel.
659			Also note that user programs calling CPUID directly
660			or using the feature without checking anything
661			will still see it. This just prevents it from
662			being used by the kernel or shown in /proc/cpuinfo.
663			Also note the kernel might malfunction if you disable
664			some critical bits.
665
666	clk_ignore_unused
667			[CLK]
668			Prevents the clock framework from automatically gating
669			clocks that have not been explicitly enabled by a Linux
670			device driver but are enabled in hardware at reset or
671			by the bootloader/firmware. Note that this does not
672			force such clocks to be always-on nor does it reserve
673			those clocks in any way. This parameter is useful for
674			debug and development, but should not be needed on a
675			platform with proper driver support.  For more
676			information, see Documentation/driver-api/clk.rst.
677
678	clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
679			[Deprecated]
680			Forces specified clocksource (if available) to be used
681			when calculating gettimeofday(). If specified
682			clocksource is not available, it defaults to PIT.
683			Format: { pit | tsc | cyclone | pmtmr }
684
685	clocksource=	Override the default clocksource
686			Format: <string>
687			Override the default clocksource and use the clocksource
688			with the name specified.
689			Some clocksource names to choose from, depending on
690			the platform:
691			[all] jiffies (this is the base, fallback clocksource)
692			[ACPI] acpi_pm
693			[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
694				pxa_timer,timer3,32k_counter,timer0_1
695			[X86-32] pit,hpet,tsc;
696				scx200_hrt on Geode; cyclone on IBM x440
697			[MIPS] MIPS
698			[PARISC] cr16
699			[S390] tod
700			[SH] SuperH
701			[SPARC64] tick
702			[X86-64] hpet,tsc
703
704	clocksource.arm_arch_timer.evtstrm=
705			[ARM,ARM64,EARLY]
706			Format: <bool>
707			Enable/disable the eventstream feature of the ARM
708			architected timer so that code using WFE-based polling
709			loops can be debugged more effectively on production
710			systems.
711
712	clocksource.verify_n_cpus= [KNL]
713			Limit the number of CPUs checked for clocksources
714			marked with CLOCK_SOURCE_VERIFY_PERCPU that
715			are marked unstable due to excessive skew.
716			A negative value says to check all CPUs, while
717			zero says not to check any.  Values larger than
718			nr_cpu_ids are silently truncated to nr_cpu_ids.
719			The actual CPUs are chosen randomly, with
720			no replacement if the same CPU is chosen twice.
721
722	clocksource-wdtest.holdoff= [KNL]
723			Set the time in seconds that the clocksource
724			watchdog test waits before commencing its tests.
725			Defaults to zero when built as a module and to
726			10 seconds when built into the kernel.
727
728	cma=nn[MG]@[start[MG][-end[MG]]]
729			[KNL,CMA,EARLY]
730			Sets the size of kernel global memory area for
731			contiguous memory allocations and optionally the
732			placement constraint by the physical address range of
733			memory allocations. A value of 0 disables CMA
734			altogether. For more information, see
735			kernel/dma/contiguous.c
736
737	cma_pernuma=nn[MG]
738			[KNL,CMA,EARLY]
739			Sets the size of kernel per-numa memory area for
740			contiguous memory allocations. A value of 0 disables
741			per-numa CMA altogether. And If this option is not
742			specified, the default value is 0.
743			With per-numa CMA enabled, DMA users on node nid will
744			first try to allocate buffer from the pernuma area
745			which is located in node nid, if the allocation fails,
746			they will fallback to the global default memory area.
747
748	numa_cma=<node>:nn[MG][,<node>:nn[MG]]
749			[KNL,CMA,EARLY]
750			Sets the size of kernel numa memory area for
751			contiguous memory allocations. It will reserve CMA
752			area for the specified node.
753
754			With numa CMA enabled, DMA users on node nid will
755			first try to allocate buffer from the numa area
756			which is located in node nid, if the allocation fails,
757			they will fallback to the global default memory area.
758
759	cmo_free_hint=	[PPC] Format: { yes | no }
760			Specify whether pages are marked as being inactive
761			when they are freed.  This is used in CMO environments
762			to determine OS memory pressure for page stealing by
763			a hypervisor.
764			Default: yes
765
766	coherent_pool=nn[KMG]	[ARM,KNL,EARLY]
767			Sets the size of memory pool for coherent, atomic dma
768			allocations, by default set to 256K.
769
770	com20020=	[HW,NET] ARCnet - COM20020 chipset
771			Format:
772			<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
773
774	com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
775			Format: <io>[,<irq>]
776
777	com90xx=	[HW,NET]
778			ARCnet - COM90xx chipset (memory-mapped buffers)
779			Format: <io>[,<irq>[,<memstart>]]
780
781	condev=		[HW,S390] console device
782	conmode=
783
784	con3215_drop=	[S390,EARLY] 3215 console drop mode.
785			Format: y|n|Y|N|1|0
786			When set to true, drop data on the 3215 console when
787			the console buffer is full. In this case the
788			operator using a 3270 terminal emulator (for example
789			x3270) does not have to enter the clear key for the
790			console output to advance and the kernel to continue.
791			This leads to a much faster boot time when a 3270
792			terminal emulator is active. If no 3270 terminal
793			emulator is used, this parameter has no effect.
794
795	console=	[KNL] Output console device and options.
796
797		tty<n>	Use the virtual console device <n>.
798
799		ttyS<n>[,options]
800		ttyUSB0[,options]
801			Use the specified serial port.  The options are of
802			the form "bbbbpnf", where "bbbb" is the baud rate,
803			"p" is parity ("n", "o", or "e"), "n" is number of
804			bits, and "f" is flow control ("r" for RTS or
805			omit it).  Default is "9600n8".
806
807			See Documentation/admin-guide/serial-console.rst for more
808			information.  See
809			Documentation/networking/netconsole.rst for an
810			alternative.
811
812		<DEVNAME>:<n>.<n>[,options]
813			Use the specified serial port on the serial core bus.
814			The addressing uses DEVNAME of the physical serial port
815			device, followed by the serial core controller instance,
816			and the serial port instance. The options are the same
817			as documented for the ttyS addressing above.
818
819			The mapping of the serial ports to the tty instances
820			can be viewed with:
821
822			$ ls -d /sys/bus/serial-base/devices/*:*.*/tty/*
823			/sys/bus/serial-base/devices/00:04:0.0/tty/ttyS0
824
825			In the above example, the console can be addressed with
826			console=00:04:0.0. Note that a console addressed this
827			way will only get added when the related device driver
828			is ready. The use of an earlycon parameter in addition to
829			the console may be desired for console output early on.
830
831		uart[8250],io,<addr>[,options]
832		uart[8250],mmio,<addr>[,options]
833		uart[8250],mmio16,<addr>[,options]
834		uart[8250],mmio32,<addr>[,options]
835		uart[8250],0x<addr>[,options]
836			Start an early, polled-mode console on the 8250/16550
837			UART at the specified I/O port or MMIO address,
838			switching to the matching ttyS device later.
839			MMIO inter-register address stride is either 8-bit
840			(mmio), 16-bit (mmio16), or 32-bit (mmio32).
841			If none of [io|mmio|mmio16|mmio32], <addr> is assumed
842			to be equivalent to 'mmio'. 'options' are specified in
843			the same format described for ttyS above; if unspecified,
844			the h/w is not re-initialized.
845
846		hvc<n>	Use the hypervisor console device <n>. This is for
847			both Xen and PowerPC hypervisors.
848
849		{ null | "" }
850			Use to disable console output, i.e., to have kernel
851			console messages discarded.
852			This must be the only console= parameter used on the
853			kernel command line.
854
855		If the device connected to the port is not a TTY but a braille
856		device, prepend "brl," before the device type, for instance
857			console=brl,ttyS0
858		For now, only VisioBraille is supported.
859
860	console_msg_format=
861			[KNL] Change console messages format
862		default
863			By default we print messages on consoles in
864			"[time stamp] text\n" format (time stamp may not be
865			printed, depending on CONFIG_PRINTK_TIME or
866			`printk_time' param).
867		syslog
868			Switch to syslog format: "<%u>[time stamp] text\n"
869			IOW, each message will have a facility and loglevel
870			prefix. The format is similar to one used by syslog()
871			syscall, or to executing "dmesg -S --raw" or to reading
872			from /proc/kmsg.
873
874	consoleblank=	[KNL] The console blank (screen saver) timeout in
875			seconds. A value of 0 disables the blank timer.
876			Defaults to 0.
877
878	coredump_filter=
879			[KNL] Change the default value for
880			/proc/<pid>/coredump_filter.
881			See also Documentation/filesystems/proc.rst.
882
883	coresight_cpu_debug.enable
884			[ARM,ARM64]
885			Format: <bool>
886			Enable/disable the CPU sampling based debugging.
887			0: default value, disable debugging
888			1: enable debugging at boot time
889
890	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
891			Format:
892			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
893
894	cpuidle.off=1	[CPU_IDLE]
895			disable the cpuidle sub-system
896
897	cpuidle.governor=
898			[CPU_IDLE] Name of the cpuidle governor to use.
899
900	cpufreq.off=1	[CPU_FREQ]
901			disable the cpufreq sub-system
902
903	cpufreq.default_governor=
904			[CPU_FREQ] Name of the default cpufreq governor or
905			policy to use. This governor must be registered in the
906			kernel before the cpufreq driver probes.
907
908	cpu_init_udelay=N
909			[X86,EARLY] Delay for N microsec between assert and de-assert
910			of APIC INIT to start processors.  This delay occurs
911			on every CPU online, such as boot, and resume from suspend.
912			Default: 10000
913
914	cpuhp.parallel=
915			[SMP] Enable/disable parallel bringup of secondary CPUs
916			Format: <bool>
917			Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
918			the parameter has no effect.
919
920	crash_kexec_post_notifiers
921			Run kdump after running panic-notifiers and dumping
922			kmsg. This only for the users who doubt kdump always
923			succeeds in any situation.
924			Note that this also increases risks of kdump failure,
925			because some panic notifiers can make the crashed
926			kernel more unstable.
927
928	crashkernel=size[KMG][@offset[KMG]]
929			[KNL,EARLY] Using kexec, Linux can switch to a 'crash kernel'
930			upon panic. This parameter reserves the physical
931			memory region [offset, offset + size] for that kernel
932			image. If '@offset' is omitted, then a suitable offset
933			is selected automatically.
934			[KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
935			under 4G first, and fall back to reserve region above
936			4G when '@offset' hasn't been specified.
937			See Documentation/admin-guide/kdump/kdump.rst for further details.
938
939	crashkernel=range1:size1[,range2:size2,...][@offset]
940			[KNL] Same as above, but depends on the memory
941			in the running system. The syntax of range is
942			start-[end] where start and end are both
943			a memory unit (amount[KMG]). See also
944			Documentation/admin-guide/kdump/kdump.rst for an example.
945
946	crashkernel=size[KMG],high
947			[KNL, X86-64, ARM64, RISCV, LoongArch] range could be
948			above 4G.
949			Allow kernel to allocate physical memory region from top,
950			so could be above 4G if system have more than 4G ram
951			installed. Otherwise memory region will be allocated
952			below 4G, if available.
953			It will be ignored if crashkernel=X is specified.
954	crashkernel=size[KMG],low
955			[KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
956			When crashkernel=X,high is passed, kernel could allocate
957			physical memory region above 4G, that cause second kernel
958			crash on system that require some amount of low memory,
959			e.g. swiotlb requires at least 64M+32K low memory, also
960			enough extra low memory is needed to make sure DMA buffers
961			for 32-bit devices won't run out. Kernel would try to allocate
962			default	size of memory below 4G automatically. The default
963			size is	platform dependent.
964			  --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
965			  --> arm64: 128MiB
966			  --> riscv: 128MiB
967			  --> loongarch: 128MiB
968			This one lets the user specify own low range under 4G
969			for second kernel instead.
970			0: to disable low allocation.
971			It will be ignored when crashkernel=X,high is not used
972			or memory reserved is below 4G.
973
974	cryptomgr.notests
975			[KNL] Disable crypto self-tests
976
977	cs89x0_dma=	[HW,NET]
978			Format: <dma>
979
980	cs89x0_media=	[HW,NET]
981			Format: { rj45 | aui | bnc }
982
983	csdlock_debug=	[KNL] Enable or disable debug add-ons of cross-CPU
984			function call handling. When switched on,
985			additional debug data is printed to the console
986			in case a hanging CPU is detected, and that
987			CPU is pinged again in order to try to resolve
988			the hang situation.  The default value of this
989			option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
990			Kconfig option.
991
992	dasd=		[HW,NET]
993			See header of drivers/s390/block/dasd_devmap.c.
994
995	db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
996			(one device per port)
997			Format: <port#>,<type>
998			See also Documentation/input/devices/joystick-parport.rst
999
1000	debug		[KNL,EARLY] Enable kernel debugging (events log level).
1001
1002	debug_boot_weak_hash
1003			[KNL,EARLY] Enable printing [hashed] pointers early in the
1004			boot sequence.  If enabled, we use a weak hash instead
1005			of siphash to hash pointers.  Use this option if you are
1006			seeing instances of '(___ptrval___)') and need to see a
1007			value (hashed pointer) instead. Cryptographically
1008			insecure, please do not use on production kernels.
1009
1010	debug_locks_verbose=
1011			[KNL] verbose locking self-tests
1012			Format: <int>
1013			Print debugging info while doing the locking API
1014			self-tests.
1015			Bitmask for the various LOCKTYPE_ tests. Defaults to 0
1016			(no extra messages), setting it to -1 (all bits set)
1017			will print _a_lot_ more information - normally only
1018			useful to lockdep developers.
1019
1020	debug_objects	[KNL,EARLY] Enable object debugging
1021
1022	debug_guardpage_minorder=
1023			[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this
1024			parameter allows control of the order of pages that will
1025			be intentionally kept free (and hence protected) by the
1026			buddy allocator. Bigger value increase the probability
1027			of catching random memory corruption, but reduce the
1028			amount of memory for normal system use. The maximum
1029			possible value is MAX_PAGE_ORDER/2.  Setting this
1030			parameter to 1 or 2 should be enough to identify most
1031			random memory corruption problems caused by bugs in
1032			kernel or driver code when a CPU writes to (or reads
1033			from) a random memory location. Note that there exists
1034			a class of memory corruptions problems caused by buggy
1035			H/W or F/W or by drivers badly programming DMA
1036			(basically when memory is written at bus level and the
1037			CPU MMU is bypassed) which are not detectable by
1038			CONFIG_DEBUG_PAGEALLOC, hence this option will not
1039			help tracking down these problems.
1040
1041	debug_pagealloc=
1042			[KNL,EARLY] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1043			enables the feature at boot time. By default, it is
1044			disabled and the system will work mostly the same as a
1045			kernel built without CONFIG_DEBUG_PAGEALLOC.
1046			Note: to get most of debug_pagealloc error reports, it's
1047			useful to also enable the page_owner functionality.
1048			on: enable the feature
1049
1050	debugfs=    	[KNL,EARLY] This parameter enables what is exposed to
1051			userspace and debugfs internal clients.
1052			Format: { on, no-mount, off }
1053			on: 	All functions are enabled.
1054			no-mount:
1055				Filesystem is not registered but kernel clients can
1056			        access APIs and a crashkernel can be used to read
1057				its content. There is nothing to mount.
1058			off: 	Filesystem is not registered and clients
1059			        get a -EPERM as result when trying to register files
1060				or directories within debugfs.
1061				This is equivalent of the runtime functionality if
1062				debugfs was not enabled in the kernel at all.
1063			Default value is set in build-time with a kernel configuration.
1064
1065	debugpat	[X86] Enable PAT debugging
1066
1067	default_hugepagesz=
1068			[HW] The size of the default HugeTLB page. This is
1069			the size represented by the legacy /proc/ hugepages
1070			APIs.  In addition, this is the default hugetlb size
1071			used for shmget(), mmap() and mounting hugetlbfs
1072			filesystems.  If not specified, defaults to the
1073			architecture's default huge page size.  Huge page
1074			sizes are architecture dependent.  See also
1075			Documentation/admin-guide/mm/hugetlbpage.rst.
1076			Format: size[KMG]
1077
1078	deferred_probe_timeout=
1079			[KNL] Debugging option to set a timeout in seconds for
1080			deferred probe to give up waiting on dependencies to
1081			probe. Only specific dependencies (subsystems or
1082			drivers) that have opted in will be ignored. A timeout
1083			of 0 will timeout at the end of initcalls. If the time
1084			out hasn't expired, it'll be restarted by each
1085			successful driver registration. This option will also
1086			dump out devices still on the deferred probe list after
1087			retrying.
1088
1089	delayacct	[KNL] Enable per-task delay accounting
1090
1091	dell_smm_hwmon.ignore_dmi=
1092			[HW] Continue probing hardware even if DMI data
1093			indicates that the driver is running on unsupported
1094			hardware.
1095
1096	dell_smm_hwmon.force=
1097			[HW] Activate driver even if SMM BIOS signature does
1098			not match list of supported models and enable otherwise
1099			blacklisted features.
1100
1101	dell_smm_hwmon.power_status=
1102			[HW] Report power status in /proc/i8k
1103			(disabled by default).
1104
1105	dell_smm_hwmon.restricted=
1106			[HW] Allow controlling fans only if SYS_ADMIN
1107			capability is set.
1108
1109	dell_smm_hwmon.fan_mult=
1110			[HW] Factor to multiply fan speed with.
1111
1112	dell_smm_hwmon.fan_max=
1113			[HW] Maximum configurable fan speed.
1114
1115	dfltcc=		[HW,S390]
1116			Format: { on | off | def_only | inf_only | always }
1117			on:       s390 zlib hardware support for compression on
1118			          level 1 and decompression (default)
1119			off:      No s390 zlib hardware support
1120			def_only: s390 zlib hardware support for deflate
1121			          only (compression on level 1)
1122			inf_only: s390 zlib hardware support for inflate
1123			          only (decompression)
1124			always:   Same as 'on' but ignores the selected compression
1125			          level always using hardware support (used for debugging)
1126
1127	dhash_entries=	[KNL]
1128			Set number of hash buckets for dentry cache.
1129
1130	disable_1tb_segments [PPC,EARLY]
1131			Disables the use of 1TB hash page table segments. This
1132			causes the kernel to fall back to 256MB segments which
1133			can be useful when debugging issues that require an SLB
1134			miss to occur.
1135
1136	disable=	[IPV6]
1137			See Documentation/networking/ipv6.rst.
1138
1139	disable_radix	[PPC,EARLY]
1140			Disable RADIX MMU mode on POWER9
1141
1142	disable_tlbie	[PPC]
1143			Disable TLBIE instruction. Currently does not work
1144			with KVM, with HASH MMU, or with coherent accelerators.
1145
1146	disable_ddw	[PPC/PSERIES,EARLY]
1147			Disable Dynamic DMA Window support. Use this
1148			to workaround buggy firmware.
1149
1150	disable_ipv6=	[IPV6]
1151			See Documentation/networking/ipv6.rst.
1152
1153	disable_mtrr_cleanup [X86,EARLY]
1154			The kernel tries to adjust MTRR layout from continuous
1155			to discrete, to make X server driver able to add WB
1156			entry later. This parameter disables that.
1157
1158	disable_mtrr_trim [X86, Intel and AMD only,EARLY]
1159			By default the kernel will trim any uncacheable
1160			memory out of your available memory pool based on
1161			MTRR settings.  This parameter disables that behavior,
1162			possibly causing your machine to run very slowly.
1163
1164	disable_timer_pin_1 [X86,EARLY]
1165			Disable PIN 1 of APIC timer
1166			Can be useful to work around chipset bugs.
1167
1168	dis_ucode_ldr	[X86] Disable the microcode loader.
1169
1170	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
1171			this option disables the debugging code at boot.
1172
1173	dma_debug_entries=<number>
1174			This option allows to tune the number of preallocated
1175			entries for DMA-API debugging code. One entry is
1176			required per DMA-API allocation. Use this if the
1177			DMA-API debugging code disables itself because the
1178			architectural default is too low.
1179
1180	dma_debug_driver=<driver_name>
1181			With this option the DMA-API debugging driver
1182			filter feature can be enabled at boot time. Just
1183			pass the driver to filter for as the parameter.
1184			The filter can be disabled or changed to another
1185			driver later using sysfs.
1186
1187	reg_file_data_sampling=
1188			[X86] Controls mitigation for Register File Data
1189			Sampling (RFDS) vulnerability. RFDS is a CPU
1190			vulnerability which may allow userspace to infer
1191			kernel data values previously stored in floating point
1192			registers, vector registers, or integer registers.
1193			RFDS only affects Intel Atom processors.
1194
1195			on:	Turns ON the mitigation.
1196			off:	Turns OFF the mitigation.
1197
1198			This parameter overrides the compile time default set
1199			by CONFIG_MITIGATION_RFDS. Mitigation cannot be
1200			disabled when other VERW based mitigations (like MDS)
1201			are enabled. In order to disable RFDS mitigation all
1202			VERW based mitigations need to be disabled.
1203
1204			For details see:
1205			Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1206
1207	driver_async_probe=  [KNL]
1208			List of driver names to be probed asynchronously. *
1209			matches with all driver names. If * is specified, the
1210			rest of the listed driver names are those that will NOT
1211			match the *.
1212			Format: <driver_name1>,<driver_name2>...
1213
1214	drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1215			Broken monitors, graphic adapters, KVMs and EDIDless
1216			panels may send no or incorrect EDID data sets.
1217			This parameter allows to specify an EDID data sets
1218			in the /lib/firmware directory that are used instead.
1219			An EDID data set will only be used for a particular
1220			connector, if its name and a colon are prepended to
1221			the EDID name. Each connector may use a unique EDID
1222			data set by separating the files with a comma. An EDID
1223			data set with no connector name will be used for
1224			any connectors not explicitly specified.
1225
1226	dscc4.setup=	[NET]
1227
1228	dt_cpu_ftrs=	[PPC,EARLY]
1229			Format: {"off" | "known"}
1230			Control how the dt_cpu_ftrs device-tree binding is
1231			used for CPU feature discovery and setup (if it
1232			exists).
1233			off: Do not use it, fall back to legacy cpu table.
1234			known: Do not pass through unknown features to guests
1235			or userspace, only those that the kernel is aware of.
1236
1237	dump_apple_properties	[X86]
1238			Dump name and content of EFI device properties on
1239			x86 Macs.  Useful for driver authors to determine
1240			what data is available or for reverse-engineering.
1241
1242	dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
1243	<module>.dyndbg[="val"]
1244			Enable debug messages at boot time.  See
1245			Documentation/admin-guide/dynamic-debug-howto.rst
1246			for details.
1247
1248	early_ioremap_debug [KNL,EARLY]
1249			Enable debug messages in early_ioremap support. This
1250			is useful for tracking down temporary early mappings
1251			which are not unmapped.
1252
1253	earlycon=	[KNL,EARLY] Output early console device and options.
1254
1255			When used with no options, the early console is
1256			determined by stdout-path property in device tree's
1257			chosen node or the ACPI SPCR table if supported by
1258			the platform.
1259
1260		cdns,<addr>[,options]
1261			Start an early, polled-mode console on a Cadence
1262			(xuartps) serial port at the specified address. Only
1263			supported option is baud rate. If baud rate is not
1264			specified, the serial port must already be setup and
1265			configured.
1266
1267		uart[8250],io,<addr>[,options[,uartclk]]
1268		uart[8250],mmio,<addr>[,options[,uartclk]]
1269		uart[8250],mmio32,<addr>[,options[,uartclk]]
1270		uart[8250],mmio32be,<addr>[,options[,uartclk]]
1271		uart[8250],0x<addr>[,options]
1272			Start an early, polled-mode console on the 8250/16550
1273			UART at the specified I/O port or MMIO address.
1274			MMIO inter-register address stride is either 8-bit
1275			(mmio) or 32-bit (mmio32 or mmio32be).
1276			If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1277			to be equivalent to 'mmio'. 'options' are specified
1278			in the same format described for "console=ttyS<n>"; if
1279			unspecified, the h/w is not initialized. 'uartclk' is
1280			the uart clock frequency; if unspecified, it is set
1281			to 'BASE_BAUD' * 16.
1282
1283		pl011,<addr>
1284		pl011,mmio32,<addr>
1285			Start an early, polled-mode console on a pl011 serial
1286			port at the specified address. The pl011 serial port
1287			must already be setup and configured. Options are not
1288			yet supported.  If 'mmio32' is specified, then only
1289			the driver will use only 32-bit accessors to read/write
1290			the device registers.
1291
1292		liteuart,<addr>
1293			Start an early console on a litex serial port at the
1294			specified address. The serial port must already be
1295			setup and configured. Options are not yet supported.
1296
1297		meson,<addr>
1298			Start an early, polled-mode console on a meson serial
1299			port at the specified address. The serial port must
1300			already be setup and configured. Options are not yet
1301			supported.
1302
1303		msm_serial,<addr>
1304			Start an early, polled-mode console on an msm serial
1305			port at the specified address. The serial port
1306			must already be setup and configured. Options are not
1307			yet supported.
1308
1309		msm_serial_dm,<addr>
1310			Start an early, polled-mode console on an msm serial
1311			dm port at the specified address. The serial port
1312			must already be setup and configured. Options are not
1313			yet supported.
1314
1315		owl,<addr>
1316			Start an early, polled-mode console on a serial port
1317			of an Actions Semi SoC, such as S500 or S900, at the
1318			specified address. The serial port must already be
1319			setup and configured. Options are not yet supported.
1320
1321		rda,<addr>
1322			Start an early, polled-mode console on a serial port
1323			of an RDA Micro SoC, such as RDA8810PL, at the
1324			specified address. The serial port must already be
1325			setup and configured. Options are not yet supported.
1326
1327		sbi
1328			Use RISC-V SBI (Supervisor Binary Interface) for early
1329			console.
1330
1331		smh	Use ARM semihosting calls for early console.
1332
1333		s3c2410,<addr>
1334		s3c2412,<addr>
1335		s3c2440,<addr>
1336		s3c6400,<addr>
1337		s5pv210,<addr>
1338		exynos4210,<addr>
1339			Use early console provided by serial driver available
1340			on Samsung SoCs, requires selecting proper type and
1341			a correct base address of the selected UART port. The
1342			serial port must already be setup and configured.
1343			Options are not yet supported.
1344
1345		lantiq,<addr>
1346			Start an early, polled-mode console on a lantiq serial
1347			(lqasc) port at the specified address. The serial port
1348			must already be setup and configured. Options are not
1349			yet supported.
1350
1351		lpuart,<addr>
1352		lpuart32,<addr>
1353			Use early console provided by Freescale LP UART driver
1354			found on Freescale Vybrid and QorIQ LS1021A processors.
1355			A valid base address must be provided, and the serial
1356			port must already be setup and configured.
1357
1358		ec_imx21,<addr>
1359		ec_imx6q,<addr>
1360			Start an early, polled-mode, output-only console on the
1361			Freescale i.MX UART at the specified address. The UART
1362			must already be setup and configured.
1363
1364		ar3700_uart,<addr>
1365			Start an early, polled-mode console on the
1366			Armada 3700 serial port at the specified
1367			address. The serial port must already be setup
1368			and configured. Options are not yet supported.
1369
1370		qcom_geni,<addr>
1371			Start an early, polled-mode console on a Qualcomm
1372			Generic Interface (GENI) based serial port at the
1373			specified address. The serial port must already be
1374			setup and configured. Options are not yet supported.
1375
1376		efifb,[options]
1377			Start an early, unaccelerated console on the EFI
1378			memory mapped framebuffer (if available). On cache
1379			coherent non-x86 systems that use system memory for
1380			the framebuffer, pass the 'ram' option so that it is
1381			mapped with the correct attributes.
1382
1383		linflex,<addr>
1384			Use early console provided by Freescale LINFlexD UART
1385			serial driver for NXP S32V234 SoCs. A valid base
1386			address must be provided, and the serial port must
1387			already be setup and configured.
1388
1389	earlyprintk=	[X86,SH,ARM,M68k,S390,UM,EARLY]
1390			earlyprintk=vga
1391			earlyprintk=sclp
1392			earlyprintk=xen
1393			earlyprintk=serial[,ttySn[,baudrate]]
1394			earlyprintk=serial[,0x...[,baudrate]]
1395			earlyprintk=ttySn[,baudrate]
1396			earlyprintk=dbgp[debugController#]
1397			earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1398			earlyprintk=xdbc[xhciController#]
1399			earlyprintk=bios
1400
1401			earlyprintk is useful when the kernel crashes before
1402			the normal console is initialized. It is not enabled by
1403			default because it has some cosmetic problems.
1404
1405			Append ",keep" to not disable it when the real console
1406			takes over.
1407
1408			Only one of vga, serial, or usb debug port can
1409			be used at a time.
1410
1411			Currently only ttyS0 and ttyS1 may be specified by
1412			name.  Other I/O ports may be explicitly specified
1413			on some architectures (x86 and arm at least) by
1414			replacing ttySn with an I/O port address, like this:
1415				earlyprintk=serial,0x1008,115200
1416			You can find the port for a given device in
1417			/proc/tty/driver/serial:
1418				2: uart:ST16650V2 port:00001008 irq:18 ...
1419
1420			Interaction with the standard serial driver is not
1421			very good.
1422
1423			The VGA output is eventually overwritten by
1424			the real console.
1425
1426			The xen option can only be used in Xen domains.
1427
1428			The sclp output can only be used on s390.
1429
1430			The bios output can only be used on SuperH.
1431
1432			The optional "force" to "pciserial" enables use of a
1433			PCI device even when its classcode is not of the
1434			UART class.
1435
1436	edac_report=	[HW,EDAC] Control how to report EDAC event
1437			Format: {"on" | "off" | "force"}
1438			on: enable EDAC to report H/W event. May be overridden
1439			by other higher priority error reporting module.
1440			off: disable H/W event reporting through EDAC.
1441			force: enforce the use of EDAC to report H/W event.
1442			default: on.
1443
1444	edd=		[EDD]
1445			Format: {"off" | "on" | "skip[mbr]"}
1446
1447	efi=		[EFI,EARLY]
1448			Format: { "debug", "disable_early_pci_dma",
1449				  "nochunk", "noruntime", "nosoftreserve",
1450				  "novamap", "no_disable_early_pci_dma" }
1451			debug: enable misc debug output.
1452			disable_early_pci_dma: disable the busmaster bit on all
1453			PCI bridges while in the EFI boot stub.
1454			nochunk: disable reading files in "chunks" in the EFI
1455			boot stub, as chunking can cause problems with some
1456			firmware implementations.
1457			noruntime : disable EFI runtime services support
1458			nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1459			attribute may cause the kernel to reserve the
1460			memory range for a memory mapping driver to
1461			claim. Specify efi=nosoftreserve to disable this
1462			reservation and treat the memory by its base type
1463			(i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1464			novamap: do not call SetVirtualAddressMap().
1465			no_disable_early_pci_dma: Leave the busmaster bit set
1466			on all PCI bridges while in the EFI boot stub
1467
1468	efi_no_storage_paranoia [EFI,X86,EARLY]
1469			Using this parameter you can use more than 50% of
1470			your efi variable storage. Use this parameter only if
1471			you are really sure that your UEFI does sane gc and
1472			fulfills the spec otherwise your board may brick.
1473
1474	efivar_ssdt=	[EFI; X86] Name of an EFI variable that contains an SSDT
1475			that is to be dynamically loaded by Linux. If there are
1476			multiple variables with the same name but with different
1477			vendor GUIDs, all of them will be loaded. See
1478			Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1479
1480
1481	eisa_irq_edge=	[PARISC,HW]
1482			See header of drivers/parisc/eisa.c.
1483
1484	ekgdboc=	[X86,KGDB,EARLY] Allow early kernel console debugging
1485			Format: ekgdboc=kbd
1486
1487			This is designed to be used in conjunction with
1488			the boot argument: earlyprintk=vga
1489
1490			This parameter works in place of the kgdboc parameter
1491			but can only be used if the backing tty is available
1492			very early in the boot process. For early debugging
1493			via a serial port see kgdboc_earlycon instead.
1494
1495	elanfreq=	[X86-32]
1496			See comment before function elanfreq_setup() in
1497			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1498
1499	elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390,EARLY]
1500			Specifies physical address of start of kernel core
1501			image elf header and optionally the size. Generally
1502			kexec loader will pass this option to capture kernel.
1503			See Documentation/admin-guide/kdump/kdump.rst for details.
1504
1505	enable_mtrr_cleanup [X86,EARLY]
1506			The kernel tries to adjust MTRR layout from continuous
1507			to discrete, to make X server driver able to add WB
1508			entry later. This parameter enables that.
1509
1510	enable_timer_pin_1 [X86]
1511			Enable PIN 1 of APIC timer
1512			Can be useful to work around chipset bugs
1513			(in particular on some ATI chipsets).
1514			The kernel tries to set a reasonable default.
1515
1516	enforcing=	[SELINUX] Set initial enforcing status.
1517			Format: {"0" | "1"}
1518			See security/selinux/Kconfig help text.
1519			0 -- permissive (log only, no denials).
1520			1 -- enforcing (deny and log).
1521			Default value is 0.
1522			Value can be changed at runtime via
1523			/sys/fs/selinux/enforce.
1524
1525	erst_disable	[ACPI]
1526			Disable Error Record Serialization Table (ERST)
1527			support.
1528
1529	ether=		[HW,NET] Ethernet cards parameters
1530			This option is obsoleted by the "netdev=" option, which
1531			has equivalent usage. See its documentation for details.
1532
1533	evm=		[EVM]
1534			Format: { "fix" }
1535			Permit 'security.evm' to be updated regardless of
1536			current integrity status.
1537
1538	early_page_ext [KNL,EARLY] Enforces page_ext initialization to earlier
1539			stages so cover more early boot allocations.
1540			Please note that as side effect some optimizations
1541			might be disabled to achieve that (e.g. parallelized
1542			memory initialization is disabled) so the boot process
1543			might take longer, especially on systems with a lot of
1544			memory. Available with CONFIG_PAGE_EXTENSION=y.
1545
1546	failslab=
1547	fail_usercopy=
1548	fail_page_alloc=
1549	fail_make_request=[KNL]
1550			General fault injection mechanism.
1551			Format: <interval>,<probability>,<space>,<times>
1552			See also Documentation/fault-injection/.
1553
1554	fb_tunnels=	[NET]
1555			Format: { initns | none }
1556			See Documentation/admin-guide/sysctl/net.rst for
1557			fb_tunnels_only_for_init_ns
1558
1559	floppy=		[HW]
1560			See Documentation/admin-guide/blockdev/floppy.rst.
1561
1562	forcepae	[X86-32]
1563			Forcefully enable Physical Address Extension (PAE).
1564			Many Pentium M systems disable PAE but may have a
1565			functionally usable PAE implementation.
1566			Warning: use of this parameter will taint the kernel
1567			and may cause unknown problems.
1568
1569	fred=		[X86-64]
1570			Enable/disable Flexible Return and Event Delivery.
1571			Format: { on | off }
1572			on: enable FRED when it's present.
1573			off: disable FRED, the default setting.
1574
1575	ftrace=[tracer]
1576			[FTRACE] will set and start the specified tracer
1577			as early as possible in order to facilitate early
1578			boot debugging.
1579
1580	ftrace_boot_snapshot
1581			[FTRACE] On boot up, a snapshot will be taken of the
1582			ftrace ring buffer that can be read at:
1583			/sys/kernel/tracing/snapshot.
1584			This is useful if you need tracing information from kernel
1585			boot up that is likely to be overridden by user space
1586			start up functionality.
1587
1588			Optionally, the snapshot can also be defined for a tracing
1589			instance that was created by the trace_instance= command
1590			line parameter.
1591
1592			trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
1593
1594			The above will cause the "foo" tracing instance to trigger
1595			a snapshot at the end of boot up.
1596
1597	ftrace_dump_on_oops[=2(orig_cpu) | =<instance>][,<instance> |
1598			  ,<instance>=2(orig_cpu)]
1599			[FTRACE] will dump the trace buffers on oops.
1600			If no parameter is passed, ftrace will dump global
1601			buffers of all CPUs, if you pass 2 or orig_cpu, it
1602			will dump only the buffer of the CPU that triggered
1603			the oops, or the specific instance will be dumped if
1604			its name is passed. Multiple instance dump is also
1605			supported, and instances are separated by commas. Each
1606			instance supports only dump on CPU that triggered the
1607			oops by passing 2 or orig_cpu to it.
1608
1609			ftrace_dump_on_oops=foo=orig_cpu
1610
1611			The above will dump only the buffer of "foo" instance
1612			on CPU that triggered the oops.
1613
1614			ftrace_dump_on_oops,foo,bar=orig_cpu
1615
1616			The above will dump global buffer on all CPUs, the
1617			buffer of "foo" instance on all CPUs and the buffer
1618			of "bar" instance on CPU that triggered the oops.
1619
1620	ftrace_filter=[function-list]
1621			[FTRACE] Limit the functions traced by the function
1622			tracer at boot up. function-list is a comma-separated
1623			list of functions. This list can be changed at run
1624			time by the set_ftrace_filter file in the debugfs
1625			tracing directory.
1626
1627	ftrace_notrace=[function-list]
1628			[FTRACE] Do not trace the functions specified in
1629			function-list. This list can be changed at run time
1630			by the set_ftrace_notrace file in the debugfs
1631			tracing directory.
1632
1633	ftrace_graph_filter=[function-list]
1634			[FTRACE] Limit the top level callers functions traced
1635			by the function graph tracer at boot up.
1636			function-list is a comma-separated list of functions
1637			that can be changed at run time by the
1638			set_graph_function file in the debugfs tracing directory.
1639
1640	ftrace_graph_notrace=[function-list]
1641			[FTRACE] Do not trace from the functions specified in
1642			function-list.  This list is a comma-separated list of
1643			functions that can be changed at run time by the
1644			set_graph_notrace file in the debugfs tracing directory.
1645
1646	ftrace_graph_max_depth=<uint>
1647			[FTRACE] Used with the function graph tracer. This is
1648			the max depth it will trace into a function. This value
1649			can be changed at run time by the max_graph_depth file
1650			in the tracefs tracing directory. default: 0 (no limit)
1651
1652	fw_devlink=	[KNL,EARLY] Create device links between consumer and supplier
1653			devices by scanning the firmware to infer the
1654			consumer/supplier relationships. This feature is
1655			especially useful when drivers are loaded as modules as
1656			it ensures proper ordering of tasks like device probing
1657			(suppliers first, then consumers), supplier boot state
1658			clean up (only after all consumers have probed),
1659			suspend/resume & runtime PM (consumers first, then
1660			suppliers).
1661			Format: { off | permissive | on | rpm }
1662			off --	Don't create device links from firmware info.
1663			permissive -- Create device links from firmware info
1664				but use it only for ordering boot state clean
1665				up (sync_state() calls).
1666			on -- 	Create device links from firmware info and use it
1667				to enforce probe and suspend/resume ordering.
1668			rpm --	Like "on", but also use to order runtime PM.
1669
1670	fw_devlink.strict=<bool>
1671			[KNL,EARLY] Treat all inferred dependencies as mandatory
1672			dependencies. This only applies for fw_devlink=on|rpm.
1673			Format: <bool>
1674
1675	fw_devlink.sync_state =
1676			[KNL,EARLY] When all devices that could probe have finished
1677			probing, this parameter controls what to do with
1678			devices that haven't yet received their sync_state()
1679			calls.
1680			Format: { strict | timeout }
1681			strict -- Default. Continue waiting on consumers to
1682				probe successfully.
1683			timeout -- Give up waiting on consumers and call
1684				sync_state() on any devices that haven't yet
1685				received their sync_state() calls after
1686				deferred_probe_timeout has expired or by
1687				late_initcall() if !CONFIG_MODULES.
1688
1689	gamecon.map[2|3]=
1690			[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1691			support via parallel port (up to 5 devices per port)
1692			Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1693			See also Documentation/input/devices/joystick-parport.rst
1694
1695	gamma=		[HW,DRM]
1696
1697	gart_fix_e820=	[X86-64,EARLY] disable the fix e820 for K8 GART
1698			Format: off | on
1699			default: on
1700
1701	gather_data_sampling=
1702			[X86,INTEL,EARLY] Control the Gather Data Sampling (GDS)
1703			mitigation.
1704
1705			Gather Data Sampling is a hardware vulnerability which
1706			allows unprivileged speculative access to data which was
1707			previously stored in vector registers.
1708
1709			This issue is mitigated by default in updated microcode.
1710			The mitigation may have a performance impact but can be
1711			disabled. On systems without the microcode mitigation
1712			disabling AVX serves as a mitigation.
1713
1714			force:	Disable AVX to mitigate systems without
1715				microcode mitigation. No effect if the microcode
1716				mitigation is present. Known to cause crashes in
1717				userspace with buggy AVX enumeration.
1718
1719			off:	Disable GDS mitigation.
1720
1721	gcov_persist=	[GCOV] When non-zero (default), profiling data for
1722			kernel modules is saved and remains accessible via
1723			debugfs, even when the module is unloaded/reloaded.
1724			When zero, profiling data is discarded and associated
1725			debugfs files are removed at module unload time.
1726
1727	goldfish	[X86] Enable the goldfish android emulator platform.
1728			Don't use this when you are not running on the
1729			android emulator
1730
1731	gpio-mockup.gpio_mockup_ranges
1732			[HW] Sets the ranges of gpiochip of for this device.
1733			Format: <start1>,<end1>,<start2>,<end2>...
1734	gpio-mockup.gpio_mockup_named_lines
1735			[HW] Let the driver know GPIO lines should be named.
1736
1737	gpt		[EFI] Forces disk with valid GPT signature but
1738			invalid Protective MBR to be treated as GPT. If the
1739			primary GPT is corrupted, it enables the backup/alternate
1740			GPT to be used instead.
1741
1742	grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1743			the "Enable 0" bit of the configuration register.
1744			Format: 0 | 1
1745			Default: 0
1746	grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1747			the "Enable 0" bit of the configuration register.
1748			Format: 0 | 1
1749			Default: 0
1750	grcan.select=	[HW] Select which physical interface to use.
1751			Format: 0 | 1
1752			Default: 0
1753	grcan.txsize=	[HW] Sets the size of the tx buffer.
1754			Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1755			Default: 1024
1756	grcan.rxsize=	[HW] Sets the size of the rx buffer.
1757			Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1758			Default: 1024
1759
1760	hardened_usercopy=
1761			[KNL] Under CONFIG_HARDENED_USERCOPY, whether
1762			hardening is enabled for this boot. Hardened
1763			usercopy checking is used to protect the kernel
1764			from reading or writing beyond known memory
1765			allocation boundaries as a proactive defense
1766			against bounds-checking flaws in the kernel's
1767			copy_to_user()/copy_from_user() interface.
1768		on	Perform hardened usercopy checks (default).
1769		off	Disable hardened usercopy checks.
1770
1771	hardlockup_all_cpu_backtrace=
1772			[KNL] Should the hard-lockup detector generate
1773			backtraces on all cpus.
1774			Format: 0 | 1
1775
1776	hashdist=	[KNL,NUMA] Large hashes allocated during boot
1777			are distributed across NUMA nodes.  Defaults on
1778			for 64-bit NUMA, off otherwise.
1779			Format: 0 | 1 (for off | on)
1780
1781	hd=		[EIDE] (E)IDE hard drive subsystem geometry
1782			Format: <cyl>,<head>,<sect>
1783
1784	hest_disable	[ACPI]
1785			Disable Hardware Error Source Table (HEST) support;
1786			corresponding firmware-first mode error processing
1787			logic will be disabled.
1788
1789	hibernate=	[HIBERNATION]
1790		noresume	Don't check if there's a hibernation image
1791				present during boot.
1792		nocompress	Don't compress/decompress hibernation images.
1793		no		Disable hibernation and resume.
1794		protect_image	Turn on image protection during restoration
1795				(that will set all pages holding image data
1796				during restoration read-only).
1797
1798	hibernate.compressor= 	[HIBERNATION] Compression algorithm to be
1799				used with hibernation.
1800				Format: { lzo | lz4 }
1801				Default: lzo
1802
1803				lzo: Select LZO compression algorithm to
1804				compress/decompress hibernation image.
1805
1806				lz4: Select LZ4 compression algorithm to
1807				compress/decompress hibernation image.
1808
1809	highmem=nn[KMG]	[KNL,BOOT,EARLY] forces the highmem zone to have an exact
1810			size of <nn>. This works even on boxes that have no
1811			highmem otherwise. This also works to reduce highmem
1812			size on bigger boxes.
1813
1814	highres=	[KNL] Enable/disable high resolution timer mode.
1815			Valid parameters: "on", "off"
1816			Default: "on"
1817
1818	hlt		[BUGS=ARM,SH]
1819
1820	hostname=	[KNL,EARLY] Set the hostname (aka UTS nodename).
1821			Format: <string>
1822			This allows setting the system's hostname during early
1823			startup. This sets the name returned by gethostname.
1824			Using this parameter to set the hostname makes it
1825			possible to ensure the hostname is correctly set before
1826			any userspace processes run, avoiding the possibility
1827			that a process may call gethostname before the hostname
1828			has been explicitly set, resulting in the calling
1829			process getting an incorrect result. The string must
1830			not exceed the maximum allowed hostname length (usually
1831			64 characters) and will be truncated otherwise.
1832
1833	hpet=		[X86-32,HPET] option to control HPET usage
1834			Format: { enable (default) | disable | force |
1835				verbose }
1836			disable: disable HPET and use PIT instead
1837			force: allow force enabled of undocumented chips (ICH4,
1838				VIA, nVidia)
1839			verbose: show contents of HPET registers during setup
1840
1841	hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1842			registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1843
1844	hugepages=	[HW] Number of HugeTLB pages to allocate at boot.
1845			If this follows hugepagesz (below), it specifies
1846			the number of pages of hugepagesz to be allocated.
1847			If this is the first HugeTLB parameter on the command
1848			line, it specifies the number of pages to allocate for
1849			the default huge page size. If using node format, the
1850			number of pages to allocate per-node can be specified.
1851			See also Documentation/admin-guide/mm/hugetlbpage.rst.
1852			Format: <integer> or (node format)
1853				<node>:<integer>[,<node>:<integer>]
1854
1855	hugepagesz=
1856			[HW] The size of the HugeTLB pages.  This is used in
1857			conjunction with hugepages (above) to allocate huge
1858			pages of a specific size at boot.  The pair
1859			hugepagesz=X hugepages=Y can be specified once for
1860			each supported huge page size. Huge page sizes are
1861			architecture dependent.  See also
1862			Documentation/admin-guide/mm/hugetlbpage.rst.
1863			Format: size[KMG]
1864
1865	hugetlb_cma=	[HW,CMA,EARLY] The size of a CMA area used for allocation
1866			of gigantic hugepages. Or using node format, the size
1867			of a CMA area per node can be specified.
1868			Format: nn[KMGTPE] or (node format)
1869				<node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1870
1871			Reserve a CMA area of given size and allocate gigantic
1872			hugepages using the CMA allocator. If enabled, the
1873			boot-time allocation of gigantic hugepages is skipped.
1874
1875	hugetlb_free_vmemmap=
1876			[KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1877			enabled.
1878			Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1879			Allows heavy hugetlb users to free up some more
1880			memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1881			Format: { on | off (default) }
1882
1883			on: enable HVO
1884			off: disable HVO
1885
1886			Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1887			the default is on.
1888
1889			Note that the vmemmap pages may be allocated from the added
1890			memory block itself when memory_hotplug.memmap_on_memory is
1891			enabled, those vmemmap pages cannot be optimized even if this
1892			feature is enabled.  Other vmemmap pages not allocated from
1893			the added memory block itself do not be affected.
1894
1895	hung_task_panic=
1896			[KNL] Should the hung task detector generate panics.
1897			Format: 0 | 1
1898
1899			A value of 1 instructs the kernel to panic when a
1900			hung task is detected. The default value is controlled
1901			by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1902			option. The value selected by this boot parameter can
1903			be changed later by the kernel.hung_task_panic sysctl.
1904
1905	hvc_iucv=	[S390]	Number of z/VM IUCV hypervisor console (HVC)
1906				terminal devices. Valid values: 0..8
1907	hvc_iucv_allow=	[S390]	Comma-separated list of z/VM user IDs.
1908				If specified, z/VM IUCV HVC accepts connections
1909				from listed z/VM user IDs only.
1910
1911	hv_nopvspin	[X86,HYPER_V,EARLY]
1912			Disables the paravirt spinlock optimizations
1913			which allow the hypervisor to 'idle' the guest
1914			on lock contention.
1915
1916	i2c_bus=	[HW]	Override the default board specific I2C bus speed
1917				or register an additional I2C bus that is not
1918				registered from board initialization code.
1919				Format:
1920				<bus_id>,<clkrate>
1921
1922	i2c_touchscreen_props= [HW,ACPI,X86]
1923			Set device-properties for ACPI-enumerated I2C-attached
1924			touchscreen, to e.g. fix coordinates of upside-down
1925			mounted touchscreens. If you need this option please
1926			submit a drivers/platform/x86/touchscreen_dmi.c patch
1927			adding a DMI quirk for this.
1928
1929			Format:
1930			<ACPI_HW_ID>:<prop_name>=<val>[:prop_name=val][:...]
1931			Where <val> is one of:
1932			Omit "=<val>" entirely	Set a boolean device-property
1933			Unsigned number		Set a u32 device-property
1934			Anything else		Set a string device-property
1935
1936			Examples (split over multiple lines):
1937			i2c_touchscreen_props=GDIX1001:touchscreen-inverted-x:
1938			touchscreen-inverted-y
1939
1940			i2c_touchscreen_props=MSSL1680:touchscreen-size-x=1920:
1941			touchscreen-size-y=1080:touchscreen-inverted-y:
1942			firmware-name=gsl1680-vendor-model.fw:silead,home-button
1943
1944	i8042.debug	[HW] Toggle i8042 debug mode
1945	i8042.unmask_kbd_data
1946			[HW] Enable printing of interrupt data from the KBD port
1947			     (disabled by default, and as a pre-condition
1948			     requires that i8042.debug=1 be enabled)
1949	i8042.direct	[HW] Put keyboard port into non-translated mode
1950	i8042.dumbkbd	[HW] Pretend that controller can only read data from
1951			     keyboard and cannot control its state
1952			     (Don't attempt to blink the leds)
1953	i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1954	i8042.nokbd	[HW] Don't check/create keyboard port
1955	i8042.noloop	[HW] Disable the AUX Loopback command while probing
1956			     for the AUX port
1957	i8042.nomux	[HW] Don't check presence of an active multiplexing
1958			     controller
1959	i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1960			     controllers
1961	i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1962	i8042.reset	[HW] Reset the controller during init, cleanup and
1963			     suspend-to-ram transitions, only during s2r
1964			     transitions, or never reset
1965			Format: { 1 | Y | y | 0 | N | n }
1966			1, Y, y: always reset controller
1967			0, N, n: don't ever reset controller
1968			Default: only on s2r transitions on x86; most other
1969			architectures force reset to be always executed
1970	i8042.unlock	[HW] Unlock (ignore) the keylock
1971	i8042.kbdreset	[HW] Reset device connected to KBD port
1972	i8042.probe_defer
1973			[HW] Allow deferred probing upon i8042 probe errors
1974
1975	i810=		[HW,DRM]
1976
1977	i915.invert_brightness=
1978			[DRM] Invert the sense of the variable that is used to
1979			set the brightness of the panel backlight. Normally a
1980			brightness value of 0 indicates backlight switched off,
1981			and the maximum of the brightness value sets the backlight
1982			to maximum brightness. If this parameter is set to 0
1983			(default) and the machine requires it, or this parameter
1984			is set to 1, a brightness value of 0 sets the backlight
1985			to maximum brightness, and the maximum of the brightness
1986			value switches the backlight off.
1987			-1 -- never invert brightness
1988			 0 -- machine default
1989			 1 -- force brightness inversion
1990
1991	ia32_emulation=	[X86-64]
1992			Format: <bool>
1993			When true, allows loading 32-bit programs and executing 32-bit
1994			syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at
1995			boot time. When false, unconditionally disables IA32 emulation.
1996
1997	icn=		[HW,ISDN]
1998			Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1999
2000
2001	idle=		[X86,EARLY]
2002			Format: idle=poll, idle=halt, idle=nomwait
2003			Poll forces a polling idle loop that can slightly
2004			improve the performance of waking up a idle CPU, but
2005			will use a lot of power and make the system run hot.
2006			Not recommended.
2007			idle=halt: Halt is forced to be used for CPU idle.
2008			In such case C2/C3 won't be used again.
2009			idle=nomwait: Disable mwait for CPU C-states
2010
2011	idxd.sva=	[HW]
2012			Format: <bool>
2013			Allow force disabling of Shared Virtual Memory (SVA)
2014			support for the idxd driver. By default it is set to
2015			true (1).
2016
2017	idxd.tc_override= [HW]
2018			Format: <bool>
2019			Allow override of default traffic class configuration
2020			for the device. By default it is set to false (0).
2021
2022	ieee754=	[MIPS] Select IEEE Std 754 conformance mode
2023			Format: { strict | legacy | 2008 | relaxed | emulated }
2024			Default: strict
2025
2026			Choose which programs will be accepted for execution
2027			based on the IEEE 754 NaN encoding(s) supported by
2028			the FPU and the NaN encoding requested with the value
2029			of an ELF file header flag individually set by each
2030			binary.  Hardware implementations are permitted to
2031			support either or both of the legacy and the 2008 NaN
2032			encoding mode.
2033
2034			Available settings are as follows:
2035			strict	accept binaries that request a NaN encoding
2036				supported by the FPU
2037			legacy	only accept legacy-NaN binaries, if supported
2038				by the FPU
2039			2008	only accept 2008-NaN binaries, if supported
2040				by the FPU
2041			relaxed	accept any binaries regardless of whether
2042				supported by the FPU
2043			emulated accept any binaries but enable FPU emulator
2044				if binary mode is unsupported by the FPU.
2045
2046			The FPU emulator is always able to support both NaN
2047			encodings, so if no FPU hardware is present or it has
2048			been disabled with 'nofpu', then the settings of
2049			'legacy' and '2008' strap the emulator accordingly,
2050			'relaxed' straps the emulator for both legacy-NaN and
2051			2008-NaN, whereas 'strict' enables legacy-NaN only on
2052			legacy processors and both NaN encodings on MIPS32 or
2053			MIPS64 CPUs.
2054
2055			The setting for ABS.fmt/NEG.fmt instruction execution
2056			mode generally follows that for the NaN encoding,
2057			except where unsupported by hardware.
2058
2059	ignore_loglevel	[KNL,EARLY]
2060			Ignore loglevel setting - this will print /all/
2061			kernel messages to the console. Useful for debugging.
2062			We also add it as printk module parameter, so users
2063			could change it dynamically, usually by
2064			/sys/module/printk/parameters/ignore_loglevel.
2065
2066	ignore_rlimit_data
2067			Ignore RLIMIT_DATA setting for data mappings,
2068			print warning at first misuse.  Can be changed via
2069			/sys/module/kernel/parameters/ignore_rlimit_data.
2070
2071	ihash_entries=	[KNL]
2072			Set number of hash buckets for inode cache.
2073
2074	ima_appraise=	[IMA] appraise integrity measurements
2075			Format: { "off" | "enforce" | "fix" | "log" }
2076			default: "enforce"
2077
2078	ima_appraise_tcb [IMA] Deprecated.  Use ima_policy= instead.
2079			The builtin appraise policy appraises all files
2080			owned by uid=0.
2081
2082	ima_canonical_fmt [IMA]
2083			Use the canonical format for the binary runtime
2084			measurements, instead of host native format.
2085
2086	ima_hash=	[IMA]
2087			Format: { md5 | sha1 | rmd160 | sha256 | sha384
2088				   | sha512 | ... }
2089			default: "sha1"
2090
2091			The list of supported hash algorithms is defined
2092			in crypto/hash_info.h.
2093
2094	ima_policy=	[IMA]
2095			The builtin policies to load during IMA setup.
2096			Format: "tcb | appraise_tcb | secure_boot |
2097				 fail_securely | critical_data"
2098
2099			The "tcb" policy measures all programs exec'd, files
2100			mmap'd for exec, and all files opened with the read
2101			mode bit set by either the effective uid (euid=0) or
2102			uid=0.
2103
2104			The "appraise_tcb" policy appraises the integrity of
2105			all files owned by root.
2106
2107			The "secure_boot" policy appraises the integrity
2108			of files (eg. kexec kernel image, kernel modules,
2109			firmware, policy, etc) based on file signatures.
2110
2111			The "fail_securely" policy forces file signature
2112			verification failure also on privileged mounted
2113			filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2114			flag.
2115
2116			The "critical_data" policy measures kernel integrity
2117			critical data.
2118
2119	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
2120			Load a policy which meets the needs of the Trusted
2121			Computing Base.  This means IMA will measure all
2122			programs exec'd, files mmap'd for exec, and all files
2123			opened for read by uid=0.
2124
2125	ima_template=	[IMA]
2126			Select one of defined IMA measurements template formats.
2127			Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2128				   "ima-sigv2" }
2129			Default: "ima-ng"
2130
2131	ima_template_fmt=
2132			[IMA] Define a custom template format.
2133			Format: { "field1|...|fieldN" }
2134
2135	ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2136			Format: <min_file_size>
2137			Set the minimal file size for using asynchronous hash.
2138			If left unspecified, ahash usage is disabled.
2139
2140			ahash performance varies for different data sizes on
2141			different crypto accelerators. This option can be used
2142			to achieve the best performance for a particular HW.
2143
2144	ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2145			Format: <bufsize>
2146			Set hashing buffer size. Default: 4k.
2147
2148			ahash performance varies for different chunk sizes on
2149			different crypto accelerators. This option can be used
2150			to achieve best performance for particular HW.
2151
2152	init=		[KNL]
2153			Format: <full_path>
2154			Run specified binary instead of /sbin/init as init
2155			process.
2156
2157	initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
2158			for working out where the kernel is dying during
2159			startup.
2160
2161	initcall_blacklist=  [KNL] Do not execute a comma-separated list of
2162			initcall functions.  Useful for debugging built-in
2163			modules and initcalls.
2164
2165	initramfs_async= [KNL]
2166			Format: <bool>
2167			Default: 1
2168			This parameter controls whether the initramfs
2169			image is unpacked asynchronously, concurrently
2170			with devices being probed and
2171			initialized. This should normally just work,
2172			but as a debugging aid, one can get the
2173			historical behaviour of the initramfs
2174			unpacking being completed before device_ and
2175			late_ initcalls.
2176
2177	initrd=		[BOOT,EARLY] Specify the location of the initial ramdisk
2178
2179	initrdmem=	[KNL,EARLY] Specify a physical address and size from which to
2180			load the initrd. If an initrd is compiled in or
2181			specified in the bootparams, it takes priority over this
2182			setting.
2183			Format: ss[KMG],nn[KMG]
2184			Default is 0, 0
2185
2186	init_on_alloc=	[MM,EARLY] Fill newly allocated pages and heap objects with
2187			zeroes.
2188			Format: 0 | 1
2189			Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2190
2191	init_on_free=	[MM,EARLY] Fill freed pages and heap objects with zeroes.
2192			Format: 0 | 1
2193			Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2194
2195	init_pkru=	[X86] Specify the default memory protection keys rights
2196			register contents for all processes.  0x55555554 by
2197			default (disallow access to all but pkey 0).  Can
2198			override in debugfs after boot.
2199
2200	inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
2201			Format: <irq>
2202
2203	int_pln_enable	[X86] Enable power limit notification interrupt
2204
2205	integrity_audit=[IMA]
2206			Format: { "0" | "1" }
2207			0 -- basic integrity auditing messages. (Default)
2208			1 -- additional integrity auditing messages.
2209
2210	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
2211		on
2212			Enable intel iommu driver.
2213		off
2214			Disable intel iommu driver.
2215		igfx_off [Default Off]
2216			By default, gfx is mapped as normal device. If a gfx
2217			device has a dedicated DMAR unit, the DMAR unit is
2218			bypassed by not enabling DMAR with this option. In
2219			this case, gfx device will use physical address for
2220			DMA.
2221		strict [Default Off]
2222			Deprecated, equivalent to iommu.strict=1.
2223		sp_off [Default Off]
2224			By default, super page will be supported if Intel IOMMU
2225			has the capability. With this option, super page will
2226			not be supported.
2227		sm_on
2228			Enable the Intel IOMMU scalable mode if the hardware
2229			advertises that it has support for the scalable mode
2230			translation.
2231		sm_off
2232			Disallow use of the Intel IOMMU scalable mode.
2233		tboot_noforce [Default Off]
2234			Do not force the Intel IOMMU enabled under tboot.
2235			By default, tboot will force Intel IOMMU on, which
2236			could harm performance of some high-throughput
2237			devices like 40GBit network cards, even if identity
2238			mapping is enabled.
2239			Note that using this option lowers the security
2240			provided by tboot because it makes the system
2241			vulnerable to DMA attacks.
2242
2243	intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
2244			0	disables intel_idle and fall back on acpi_idle.
2245			1 to 9	specify maximum depth of C-state.
2246
2247	intel_pstate=	[X86,EARLY]
2248			disable
2249			  Do not enable intel_pstate as the default
2250			  scaling driver for the supported processors
2251                        active
2252                          Use intel_pstate driver to bypass the scaling
2253                          governors layer of cpufreq and provides it own
2254                          algorithms for p-state selection. There are two
2255                          P-state selection algorithms provided by
2256                          intel_pstate in the active mode: powersave and
2257                          performance.  The way they both operate depends
2258                          on whether or not the hardware managed P-states
2259                          (HWP) feature has been enabled in the processor
2260                          and possibly on the processor model.
2261			passive
2262			  Use intel_pstate as a scaling driver, but configure it
2263			  to work with generic cpufreq governors (instead of
2264			  enabling its internal governor).  This mode cannot be
2265			  used along with the hardware-managed P-states (HWP)
2266			  feature.
2267			force
2268			  Enable intel_pstate on systems that prohibit it by default
2269			  in favor of acpi-cpufreq. Forcing the intel_pstate driver
2270			  instead of acpi-cpufreq may disable platform features, such
2271			  as thermal controls and power capping, that rely on ACPI
2272			  P-States information being indicated to OSPM and therefore
2273			  should be used with caution. This option does not work with
2274			  processors that aren't supported by the intel_pstate driver
2275			  or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2276			no_hwp
2277			  Do not enable hardware P state control (HWP)
2278			  if available.
2279			hwp_only
2280			  Only load intel_pstate on systems which support
2281			  hardware P state control (HWP) if available.
2282			support_acpi_ppc
2283			  Enforce ACPI _PPC performance limits. If the Fixed ACPI
2284			  Description Table, specifies preferred power management
2285			  profile as "Enterprise Server" or "Performance Server",
2286			  then this feature is turned on by default.
2287			per_cpu_perf_limits
2288			  Allow per-logical-CPU P-State performance control limits using
2289			  cpufreq sysfs interface
2290
2291	intremap=	[X86-64,Intel-IOMMU,EARLY]
2292			on	enable Interrupt Remapping (default)
2293			off	disable Interrupt Remapping
2294			nosid	disable Source ID checking
2295			no_x2apic_optout
2296				BIOS x2APIC opt-out request will be ignored
2297			nopost	disable Interrupt Posting
2298			posted_msi
2299				enable MSIs delivered as posted interrupts
2300
2301	iomem=		Disable strict checking of access to MMIO memory
2302		strict	regions from userspace.
2303		relaxed
2304
2305	iommu=		[X86,EARLY]
2306		off
2307		force
2308		noforce
2309		biomerge
2310		panic
2311		nopanic
2312		merge
2313		nomerge
2314		soft
2315		pt		[X86]
2316		nopt		[X86]
2317		nobypass	[PPC/POWERNV]
2318			Disable IOMMU bypass, using IOMMU for PCI devices.
2319
2320	iommu.forcedac=	[ARM64,X86,EARLY] Control IOVA allocation for PCI devices.
2321			Format: { "0" | "1" }
2322			0 - Try to allocate a 32-bit DMA address first, before
2323			  falling back to the full range if needed.
2324			1 - Allocate directly from the full usable range,
2325			  forcing Dual Address Cycle for PCI cards supporting
2326			  greater than 32-bit addressing.
2327
2328	iommu.strict=	[ARM64,X86,S390,EARLY] Configure TLB invalidation behaviour
2329			Format: { "0" | "1" }
2330			0 - Lazy mode.
2331			  Request that DMA unmap operations use deferred
2332			  invalidation of hardware TLBs, for increased
2333			  throughput at the cost of reduced device isolation.
2334			  Will fall back to strict mode if not supported by
2335			  the relevant IOMMU driver.
2336			1 - Strict mode.
2337			  DMA unmap operations invalidate IOMMU hardware TLBs
2338			  synchronously.
2339			unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2340			Note: on x86, strict mode specified via one of the
2341			legacy driver-specific options takes precedence.
2342
2343	iommu.passthrough=
2344			[ARM64,X86,EARLY] Configure DMA to bypass the IOMMU by default.
2345			Format: { "0" | "1" }
2346			0 - Use IOMMU translation for DMA.
2347			1 - Bypass the IOMMU for DMA.
2348			unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2349
2350	io7=		[HW] IO7 for Marvel-based Alpha systems
2351			See comment before marvel_specify_io7 in
2352			arch/alpha/kernel/core_marvel.c.
2353
2354	io_delay=	[X86,EARLY] I/O delay method
2355		0x80
2356			Standard port 0x80 based delay
2357		0xed
2358			Alternate port 0xed based delay (needed on some systems)
2359		udelay
2360			Simple two microseconds delay
2361		none
2362			No delay
2363
2364	ip=		[IP_PNP]
2365			See Documentation/admin-guide/nfs/nfsroot.rst.
2366
2367	ipcmni_extend	[KNL,EARLY] Extend the maximum number of unique System V
2368			IPC identifiers from 32,768 to 16,777,216.
2369
2370	ipe.enforce=	[IPE]
2371			Format: <bool>
2372			Determine whether IPE starts in permissive (0) or
2373			enforce (1) mode. The default is enforce.
2374
2375	ipe.success_audit=
2376			[IPE]
2377			Format: <bool>
2378			Start IPE with success auditing enabled, emitting
2379			an audit event when a binary is allowed. The default
2380			is 0.
2381
2382	irqaffinity=	[SMP] Set the default irq affinity mask
2383			The argument is a cpu list, as described above.
2384
2385	irqchip.gicv2_force_probe=
2386			[ARM,ARM64,EARLY]
2387			Format: <bool>
2388			Force the kernel to look for the second 4kB page
2389			of a GICv2 controller even if the memory range
2390			exposed by the device tree is too small.
2391
2392	irqchip.gicv3_nolpi=
2393			[ARM,ARM64,EARLY]
2394			Force the kernel to ignore the availability of
2395			LPIs (and by consequence ITSs). Intended for system
2396			that use the kernel as a bootloader, and thus want
2397			to let secondary kernels in charge of setting up
2398			LPIs.
2399
2400	irqchip.gicv3_pseudo_nmi= [ARM64,EARLY]
2401			Enables support for pseudo-NMIs in the kernel. This
2402			requires the kernel to be built with
2403			CONFIG_ARM64_PSEUDO_NMI.
2404
2405	irqfixup	[HW]
2406			When an interrupt is not handled search all handlers
2407			for it. Intended to get systems with badly broken
2408			firmware running.
2409
2410	irqpoll		[HW]
2411			When an interrupt is not handled search all handlers
2412			for it. Also check all handlers each timer
2413			interrupt. Intended to get systems with badly broken
2414			firmware running.
2415
2416	isapnp=		[ISAPNP]
2417			Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2418
2419	isolcpus=	[KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2420			[Deprecated - use cpusets instead]
2421			Format: [flag-list,]<cpu-list>
2422
2423			Specify one or more CPUs to isolate from disturbances
2424			specified in the flag list (default: domain):
2425
2426			nohz
2427			  Disable the tick when a single task runs.
2428
2429			  A residual 1Hz tick is offloaded to workqueues, which you
2430			  need to affine to housekeeping through the global
2431			  workqueue's affinity configured via the
2432			  /sys/devices/virtual/workqueue/cpumask sysfs file, or
2433			  by using the 'domain' flag described below.
2434
2435			  NOTE: by default the global workqueue runs on all CPUs,
2436			  so to protect individual CPUs the 'cpumask' file has to
2437			  be configured manually after bootup.
2438
2439			domain
2440			  Isolate from the general SMP balancing and scheduling
2441			  algorithms. Note that performing domain isolation this way
2442			  is irreversible: it's not possible to bring back a CPU to
2443			  the domains once isolated through isolcpus. It's strongly
2444			  advised to use cpusets instead to disable scheduler load
2445			  balancing through the "cpuset.sched_load_balance" file.
2446			  It offers a much more flexible interface where CPUs can
2447			  move in and out of an isolated set anytime.
2448
2449			  You can move a process onto or off an "isolated" CPU via
2450			  the CPU affinity syscalls or cpuset.
2451			  <cpu number> begins at 0 and the maximum value is
2452			  "number of CPUs in system - 1".
2453
2454			managed_irq
2455
2456			  Isolate from being targeted by managed interrupts
2457			  which have an interrupt mask containing isolated
2458			  CPUs. The affinity of managed interrupts is
2459			  handled by the kernel and cannot be changed via
2460			  the /proc/irq/* interfaces.
2461
2462			  This isolation is best effort and only effective
2463			  if the automatically assigned interrupt mask of a
2464			  device queue contains isolated and housekeeping
2465			  CPUs. If housekeeping CPUs are online then such
2466			  interrupts are directed to the housekeeping CPU
2467			  so that IO submitted on the housekeeping CPU
2468			  cannot disturb the isolated CPU.
2469
2470			  If a queue's affinity mask contains only isolated
2471			  CPUs then this parameter has no effect on the
2472			  interrupt routing decision, though interrupts are
2473			  only delivered when tasks running on those
2474			  isolated CPUs submit IO. IO submitted on
2475			  housekeeping CPUs has no influence on those
2476			  queues.
2477
2478			The format of <cpu-list> is described above.
2479
2480	iucv=		[HW,NET]
2481
2482	ivrs_ioapic	[HW,X86-64]
2483			Provide an override to the IOAPIC-ID<->DEVICE-ID
2484			mapping provided in the IVRS ACPI table.
2485			By default, PCI segment is 0, and can be omitted.
2486
2487			For example, to map IOAPIC-ID decimal 10 to
2488			PCI segment 0x1 and PCI device 00:14.0,
2489			write the parameter as:
2490				ivrs_ioapic=10@0001:00:14.0
2491
2492			Deprecated formats:
2493			* To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2494			  write the parameter as:
2495				ivrs_ioapic[10]=00:14.0
2496			* To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2497			  PCI device 00:14.0 write the parameter as:
2498				ivrs_ioapic[10]=0001:00:14.0
2499
2500	ivrs_hpet	[HW,X86-64]
2501			Provide an override to the HPET-ID<->DEVICE-ID
2502			mapping provided in the IVRS ACPI table.
2503			By default, PCI segment is 0, and can be omitted.
2504
2505			For example, to map HPET-ID decimal 10 to
2506			PCI segment 0x1 and PCI device 00:14.0,
2507			write the parameter as:
2508				ivrs_hpet=10@0001:00:14.0
2509
2510			Deprecated formats:
2511			* To map HPET-ID decimal 0 to PCI device 00:14.0
2512			  write the parameter as:
2513				ivrs_hpet[0]=00:14.0
2514			* To map HPET-ID decimal 10 to PCI segment 0x1 and
2515			  PCI device 00:14.0 write the parameter as:
2516				ivrs_ioapic[10]=0001:00:14.0
2517
2518	ivrs_acpihid	[HW,X86-64]
2519			Provide an override to the ACPI-HID:UID<->DEVICE-ID
2520			mapping provided in the IVRS ACPI table.
2521			By default, PCI segment is 0, and can be omitted.
2522
2523			For example, to map UART-HID:UID AMD0020:0 to
2524			PCI segment 0x1 and PCI device ID 00:14.5,
2525			write the parameter as:
2526				ivrs_acpihid=AMD0020:0@0001:00:14.5
2527
2528			Deprecated formats:
2529			* To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2530			  PCI device ID 00:14.5, write the parameter as:
2531				ivrs_acpihid[00:14.5]=AMD0020:0
2532			* To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2533			  PCI device ID 00:14.5, write the parameter as:
2534				ivrs_acpihid[0001:00:14.5]=AMD0020:0
2535
2536	js=		[HW,JOY] Analog joystick
2537			See Documentation/input/joydev/joystick.rst.
2538
2539	kasan_multi_shot
2540			[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2541			report on every invalid memory access. Without this
2542			parameter KASAN will print report only for the first
2543			invalid access.
2544
2545	keep_bootcon	[KNL,EARLY]
2546			Do not unregister boot console at start. This is only
2547			useful for debugging when something happens in the window
2548			between unregistering the boot console and initializing
2549			the real console.
2550
2551	keepinitrd	[HW,ARM] See retain_initrd.
2552
2553	kernelcore=	[KNL,X86,PPC,EARLY]
2554			Format: nn[KMGTPE] | nn% | "mirror"
2555			This parameter specifies the amount of memory usable by
2556			the kernel for non-movable allocations.  The requested
2557			amount is spread evenly throughout all nodes in the
2558			system as ZONE_NORMAL.  The remaining memory is used for
2559			movable memory in its own zone, ZONE_MOVABLE.  In the
2560			event, a node is too small to have both ZONE_NORMAL and
2561			ZONE_MOVABLE, kernelcore memory will take priority and
2562			other nodes will have a larger ZONE_MOVABLE.
2563
2564			ZONE_MOVABLE is used for the allocation of pages that
2565			may be reclaimed or moved by the page migration
2566			subsystem.  Note that allocations like PTEs-from-HighMem
2567			still use the HighMem zone if it exists, and the Normal
2568			zone if it does not.
2569
2570			It is possible to specify the exact amount of memory in
2571			the form of "nn[KMGTPE]", a percentage of total system
2572			memory in the form of "nn%", or "mirror".  If "mirror"
2573			option is specified, mirrored (reliable) memory is used
2574			for non-movable allocations and remaining memory is used
2575			for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
2576			are exclusive, so you cannot specify multiple forms.
2577
2578	kgdbdbgp=	[KGDB,HW,EARLY] kgdb over EHCI usb debug port.
2579			Format: <Controller#>[,poll interval]
2580			The controller # is the number of the ehci usb debug
2581			port as it is probed via PCI.  The poll interval is
2582			optional and is the number seconds in between
2583			each poll cycle to the debug port in case you need
2584			the functionality for interrupting the kernel with
2585			gdb or control-c on the dbgp connection.  When
2586			not using this parameter you use sysrq-g to break into
2587			the kernel debugger.
2588
2589	kgdboc=		[KGDB,HW] kgdb over consoles.
2590			Requires a tty driver that supports console polling,
2591			or a supported polling keyboard driver (non-usb).
2592			 Serial only format: <serial_device>[,baud]
2593			 keyboard only format: kbd
2594			 keyboard and serial format: kbd,<serial_device>[,baud]
2595			Optional Kernel mode setting:
2596			 kms, kbd format: kms,kbd
2597			 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2598
2599	kgdboc_earlycon=	[KGDB,HW,EARLY]
2600			If the boot console provides the ability to read
2601			characters and can work in polling mode, you can use
2602			this parameter to tell kgdb to use it as a backend
2603			until the normal console is registered. Intended to
2604			be used together with the kgdboc parameter which
2605			specifies the normal console to transition to.
2606
2607			The name of the early console should be specified
2608			as the value of this parameter. Note that the name of
2609			the early console might be different than the tty
2610			name passed to kgdboc. It's OK to leave the value
2611			blank and the first boot console that implements
2612			read() will be picked.
2613
2614	kgdbwait	[KGDB,EARLY] Stop kernel execution and enter the
2615			kernel debugger at the earliest opportunity.
2616
2617	kmac=		[MIPS] Korina ethernet MAC address.
2618			Configure the RouterBoard 532 series on-chip
2619			Ethernet adapter MAC address.
2620
2621	kmemleak=	[KNL,EARLY] Boot-time kmemleak enable/disable
2622			Valid arguments: on, off
2623			Default: on
2624			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2625			the default is off.
2626
2627	kprobe_event=[probe-list]
2628			[FTRACE] Add kprobe events and enable at boot time.
2629			The probe-list is a semicolon delimited list of probe
2630			definitions. Each definition is same as kprobe_events
2631			interface, but the parameters are comma delimited.
2632			For example, to add a kprobe event on vfs_read with
2633			arg1 and arg2, add to the command line;
2634
2635			      kprobe_event=p,vfs_read,$arg1,$arg2
2636
2637			See also Documentation/trace/kprobetrace.rst "Kernel
2638			Boot Parameter" section.
2639
2640	kpti=		[ARM64,EARLY] Control page table isolation of
2641			user and kernel address spaces.
2642			Default: enabled on cores which need mitigation.
2643			0: force disabled
2644			1: force enabled
2645
2646	kunit.enable=	[KUNIT] Enable executing KUnit tests. Requires
2647			CONFIG_KUNIT to be set to be fully enabled. The
2648			default value can be overridden via
2649			KUNIT_DEFAULT_ENABLED.
2650			Default is 1 (enabled)
2651
2652	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2653			Default is 0 (don't ignore, but inject #GP)
2654
2655	kvm.eager_page_split=
2656			[KVM,X86] Controls whether or not KVM will try to
2657			proactively split all huge pages during dirty logging.
2658			Eager page splitting reduces interruptions to vCPU
2659			execution by eliminating the write-protection faults
2660			and MMU lock contention that would otherwise be
2661			required to split huge pages lazily.
2662
2663			VM workloads that rarely perform writes or that write
2664			only to a small region of VM memory may benefit from
2665			disabling eager page splitting to allow huge pages to
2666			still be used for reads.
2667
2668			The behavior of eager page splitting depends on whether
2669			KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2670			disabled, all huge pages in a memslot will be eagerly
2671			split when dirty logging is enabled on that memslot. If
2672			enabled, eager page splitting will be performed during
2673			the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2674			cleared.
2675
2676			Eager page splitting is only supported when kvm.tdp_mmu=Y.
2677
2678			Default is Y (on).
2679
2680	kvm.enable_virt_at_load=[KVM,ARM64,LOONGARCH,MIPS,RISCV,X86]
2681			If enabled, KVM will enable virtualization in hardware
2682			when KVM is loaded, and disable virtualization when KVM
2683			is unloaded (if KVM is built as a module).
2684
2685			If disabled, KVM will dynamically enable and disable
2686			virtualization on-demand when creating and destroying
2687			VMs, i.e. on the 0=>1 and 1=>0 transitions of the
2688			number of VMs.
2689
2690			Enabling virtualization at module lode avoids potential
2691			latency for creation of the 0=>1 VM, as KVM serializes
2692			virtualization enabling across all online CPUs.  The
2693			"cost" of enabling virtualization when KVM is loaded,
2694			is that doing so may interfere with using out-of-tree
2695			hypervisors that want to "own" virtualization hardware.
2696
2697	kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2698				   Default is false (don't support).
2699
2700	kvm.nx_huge_pages=
2701			[KVM] Controls the software workaround for the
2702			X86_BUG_ITLB_MULTIHIT bug.
2703			force	: Always deploy workaround.
2704			off	: Never deploy workaround.
2705			auto    : Deploy workaround based on the presence of
2706				  X86_BUG_ITLB_MULTIHIT.
2707
2708			Default is 'auto'.
2709
2710			If the software workaround is enabled for the host,
2711			guests do need not to enable it for nested guests.
2712
2713	kvm.nx_huge_pages_recovery_ratio=
2714			[KVM] Controls how many 4KiB pages are periodically zapped
2715			back to huge pages.  0 disables the recovery, otherwise if
2716			the value is N KVM will zap 1/Nth of the 4KiB pages every
2717			period (see below).  The default is 60.
2718
2719	kvm.nx_huge_pages_recovery_period_ms=
2720			[KVM] Controls the time period at which KVM zaps 4KiB pages
2721			back to huge pages. If the value is a non-zero N, KVM will
2722			zap a portion (see ratio above) of the pages every N msecs.
2723			If the value is 0 (the default), KVM will pick a period based
2724			on the ratio, such that a page is zapped after 1 hour on average.
2725
2726	kvm-amd.nested=	[KVM,AMD] Control nested virtualization feature in
2727			KVM/SVM. Default is 1 (enabled).
2728
2729	kvm-amd.npt=	[KVM,AMD] Control KVM's use of Nested Page Tables,
2730			a.k.a. Two-Dimensional Page Tables. Default is 1
2731			(enabled). Disable by KVM if hardware lacks support
2732			for NPT.
2733
2734	kvm-arm.mode=
2735			[KVM,ARM,EARLY] Select one of KVM/arm64's modes of
2736			operation.
2737
2738			none: Forcefully disable KVM.
2739
2740			nvhe: Standard nVHE-based mode, without support for
2741			      protected guests.
2742
2743			protected: nVHE-based mode with support for guests whose
2744				   state is kept private from the host.
2745
2746			nested: VHE-based mode with support for nested
2747				virtualization. Requires at least ARMv8.3
2748				hardware.
2749
2750			Defaults to VHE/nVHE based on hardware support. Setting
2751			mode to "protected" will disable kexec and hibernation
2752			for the host. "nested" is experimental and should be
2753			used with extreme caution.
2754
2755	kvm-arm.vgic_v3_group0_trap=
2756			[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-0
2757			system registers
2758
2759	kvm-arm.vgic_v3_group1_trap=
2760			[KVM,ARM,EARLY] Trap guest accesses to GICv3 group-1
2761			system registers
2762
2763	kvm-arm.vgic_v3_common_trap=
2764			[KVM,ARM,EARLY] Trap guest accesses to GICv3 common
2765			system registers
2766
2767	kvm-arm.vgic_v4_enable=
2768			[KVM,ARM,EARLY] Allow use of GICv4 for direct
2769			injection of LPIs.
2770
2771	kvm-arm.wfe_trap_policy=
2772			[KVM,ARM] Control when to set WFE instruction trap for
2773			KVM VMs. Traps are allowed but not guaranteed by the
2774			CPU architecture.
2775
2776			trap: set WFE instruction trap
2777
2778			notrap: clear WFE instruction trap
2779
2780	kvm-arm.wfi_trap_policy=
2781			[KVM,ARM] Control when to set WFI instruction trap for
2782			KVM VMs. Traps are allowed but not guaranteed by the
2783			CPU architecture.
2784
2785			trap: set WFI instruction trap
2786
2787			notrap: clear WFI instruction trap
2788
2789	kvm_cma_resv_ratio=n [PPC,EARLY]
2790			Reserves given percentage from system memory area for
2791			contiguous memory allocation for KVM hash pagetable
2792			allocation.
2793			By default it reserves 5% of total system memory.
2794			Format: <integer>
2795			Default: 5
2796
2797	kvm-intel.ept=	[KVM,Intel] Control KVM's use of Extended Page Tables,
2798			a.k.a. Two-Dimensional Page Tables.  Default is 1
2799			(enabled). Disable by KVM if hardware lacks support
2800			for EPT.
2801
2802	kvm-intel.emulate_invalid_guest_state=
2803			[KVM,Intel] Control whether to emulate invalid guest
2804			state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2805			as guest state is never invalid for unrestricted
2806			guests. This param doesn't apply to nested guests (L2),
2807			as KVM never emulates invalid L2 guest state.
2808			Default is 1 (enabled).
2809
2810	kvm-intel.flexpriority=
2811			[KVM,Intel] Control KVM's use of FlexPriority feature
2812			(TPR shadow). Default is 1 (enabled). Disable by KVM if
2813			hardware lacks support for it.
2814
2815	kvm-intel.nested=
2816			[KVM,Intel] Control nested virtualization feature in
2817			KVM/VMX. Default is 1 (enabled).
2818
2819	kvm-intel.unrestricted_guest=
2820			[KVM,Intel] Control KVM's use of unrestricted guest
2821			feature (virtualized real and unpaged mode). Default
2822			is 1 (enabled). Disable by KVM if EPT is disabled or
2823			hardware lacks support for it.
2824
2825	kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2826			CVE-2018-3620.
2827
2828			Valid arguments: never, cond, always
2829
2830			always: L1D cache flush on every VMENTER.
2831			cond:	Flush L1D on VMENTER only when the code between
2832				VMEXIT and VMENTER can leak host memory.
2833			never:	Disables the mitigation
2834
2835			Default is cond (do L1 cache flush in specific instances)
2836
2837	kvm-intel.vpid=	[KVM,Intel] Control KVM's use of Virtual Processor
2838			Identification feature (tagged TLBs). Default is 1
2839			(enabled). Disable by KVM if hardware lacks support
2840			for it.
2841
2842	l1d_flush=	[X86,INTEL,EARLY]
2843			Control mitigation for L1D based snooping vulnerability.
2844
2845			Certain CPUs are vulnerable to an exploit against CPU
2846			internal buffers which can forward information to a
2847			disclosure gadget under certain conditions.
2848
2849			In vulnerable processors, the speculatively
2850			forwarded data can be used in a cache side channel
2851			attack, to access data to which the attacker does
2852			not have direct access.
2853
2854			This parameter controls the mitigation. The
2855			options are:
2856
2857			on         - enable the interface for the mitigation
2858
2859	l1tf=           [X86,EARLY] Control mitigation of the L1TF vulnerability on
2860			      affected CPUs
2861
2862			The kernel PTE inversion protection is unconditionally
2863			enabled and cannot be disabled.
2864
2865			full
2866				Provides all available mitigations for the
2867				L1TF vulnerability. Disables SMT and
2868				enables all mitigations in the
2869				hypervisors, i.e. unconditional L1D flush.
2870
2871				SMT control and L1D flush control via the
2872				sysfs interface is still possible after
2873				boot.  Hypervisors will issue a warning
2874				when the first VM is started in a
2875				potentially insecure configuration,
2876				i.e. SMT enabled or L1D flush disabled.
2877
2878			full,force
2879				Same as 'full', but disables SMT and L1D
2880				flush runtime control. Implies the
2881				'nosmt=force' command line option.
2882				(i.e. sysfs control of SMT is disabled.)
2883
2884			flush
2885				Leaves SMT enabled and enables the default
2886				hypervisor mitigation, i.e. conditional
2887				L1D flush.
2888
2889				SMT control and L1D flush control via the
2890				sysfs interface is still possible after
2891				boot.  Hypervisors will issue a warning
2892				when the first VM is started in a
2893				potentially insecure configuration,
2894				i.e. SMT enabled or L1D flush disabled.
2895
2896			flush,nosmt
2897
2898				Disables SMT and enables the default
2899				hypervisor mitigation.
2900
2901				SMT control and L1D flush control via the
2902				sysfs interface is still possible after
2903				boot.  Hypervisors will issue a warning
2904				when the first VM is started in a
2905				potentially insecure configuration,
2906				i.e. SMT enabled or L1D flush disabled.
2907
2908			flush,nowarn
2909				Same as 'flush', but hypervisors will not
2910				warn when a VM is started in a potentially
2911				insecure configuration.
2912
2913			off
2914				Disables hypervisor mitigations and doesn't
2915				emit any warnings.
2916				It also drops the swap size and available
2917				RAM limit restriction on both hypervisor and
2918				bare metal.
2919
2920			Default is 'flush'.
2921
2922			For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2923
2924	l2cr=		[PPC]
2925
2926	l3cr=		[PPC]
2927
2928	lapic		[X86-32,APIC,EARLY] Enable the local APIC even if BIOS
2929			disabled it.
2930
2931	lapic=		[X86,APIC] Do not use TSC deadline
2932			value for LAPIC timer one-shot implementation. Default
2933			back to the programmable timer unit in the LAPIC.
2934			Format: notscdeadline
2935
2936	lapic_timer_c2_ok	[X86,APIC,EARLY] trust the local apic timer
2937			in C2 power state.
2938
2939	libata.dma=	[LIBATA] DMA control
2940			libata.dma=0	  Disable all PATA and SATA DMA
2941			libata.dma=1	  PATA and SATA Disk DMA only
2942			libata.dma=2	  ATAPI (CDROM) DMA only
2943			libata.dma=4	  Compact Flash DMA only
2944			Combinations also work, so libata.dma=3 enables DMA
2945			for disks and CDROMs, but not CFs.
2946
2947	libata.ignore_hpa=	[LIBATA] Ignore HPA limit
2948			libata.ignore_hpa=0	  keep BIOS limits (default)
2949			libata.ignore_hpa=1	  ignore limits, using full disk
2950
2951	libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
2952			when set.
2953			Format: <int>
2954
2955	libata.force=	[LIBATA] Force configurations.  The format is a comma-
2956			separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
2957			PORT and DEVICE are decimal numbers matching port, link
2958			or device.  Basically, it matches the ATA ID string
2959			printed on console by libata.  If the whole ID part is
2960			omitted, the last PORT and DEVICE values are used.  If
2961			ID hasn't been specified yet, the configuration applies
2962			to all ports, links and devices.
2963
2964			If only DEVICE is omitted, the parameter applies to
2965			the port and all links and devices behind it.  DEVICE
2966			number of 0 either selects the first device or the
2967			first fan-out link behind PMP device.  It does not
2968			select the host link.  DEVICE number of 15 selects the
2969			host link and device attached to it.
2970
2971			The VAL specifies the configuration to force.  As long
2972			as there is no ambiguity, shortcut notation is allowed.
2973			For example, both 1.5 and 1.5G would work for 1.5Gbps.
2974			The following configurations can be forced.
2975
2976			* Cable type: 40c, 80c, short40c, unk, ign or sata.
2977			  Any ID with matching PORT is used.
2978
2979			* SATA link speed limit: 1.5Gbps or 3.0Gbps.
2980
2981			* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2982			  udma[/][16,25,33,44,66,100,133] notation is also
2983			  allowed.
2984
2985			* nohrst, nosrst, norst: suppress hard, soft and both
2986			  resets.
2987
2988			* rstonce: only attempt one reset during hot-unplug
2989			  link recovery.
2990
2991			* [no]dbdelay: Enable or disable the extra 200ms delay
2992			  before debouncing a link PHY and device presence
2993			  detection.
2994
2995			* [no]ncq: Turn on or off NCQ.
2996
2997			* [no]ncqtrim: Enable or disable queued DSM TRIM.
2998
2999			* [no]ncqati: Enable or disable NCQ trim on ATI chipset.
3000
3001			* [no]trim: Enable or disable (unqueued) TRIM.
3002
3003			* trim_zero: Indicate that TRIM command zeroes data.
3004
3005			* max_trim_128m: Set 128M maximum trim size limit.
3006
3007			* [no]dma: Turn on or off DMA transfers.
3008
3009			* atapi_dmadir: Enable ATAPI DMADIR bridge support.
3010
3011			* atapi_mod16_dma: Enable the use of ATAPI DMA for
3012			  commands that are not a multiple of 16 bytes.
3013
3014			* [no]dmalog: Enable or disable the use of the
3015			  READ LOG DMA EXT command to access logs.
3016
3017			* [no]iddevlog: Enable or disable access to the
3018			  identify device data log.
3019
3020			* [no]logdir: Enable or disable access to the general
3021			  purpose log directory.
3022
3023			* max_sec_128: Set transfer size limit to 128 sectors.
3024
3025			* max_sec_1024: Set or clear transfer size limit to
3026			  1024 sectors.
3027
3028			* max_sec_lba48: Set or clear transfer size limit to
3029			  65535 sectors.
3030
3031			* [no]lpm: Enable or disable link power management.
3032
3033			* [no]setxfer: Indicate if transfer speed mode setting
3034			  should be skipped.
3035
3036			* [no]fua: Disable or enable FUA (Force Unit Access)
3037			  support for devices supporting this feature.
3038
3039			* dump_id: Dump IDENTIFY data.
3040
3041			* disable: Disable this device.
3042
3043			If there are multiple matching configurations changing
3044			the same attribute, the last one is used.
3045
3046	load_ramdisk=	[RAM] [Deprecated]
3047
3048	lockd.nlm_grace_period=P  [NFS] Assign grace period.
3049			Format: <integer>
3050
3051	lockd.nlm_tcpport=N	[NFS] Assign TCP port.
3052			Format: <integer>
3053
3054	lockd.nlm_timeout=T	[NFS] Assign timeout value.
3055			Format: <integer>
3056
3057	lockd.nlm_udpport=M	[NFS] Assign UDP port.
3058			Format: <integer>
3059
3060	lockdown=	[SECURITY,EARLY]
3061			{ integrity | confidentiality }
3062			Enable the kernel lockdown feature. If set to
3063			integrity, kernel features that allow userland to
3064			modify the running kernel are disabled. If set to
3065			confidentiality, kernel features that allow userland
3066			to extract confidential information from the kernel
3067			are also disabled.
3068
3069	locktorture.acq_writer_lim= [KNL]
3070			Set the time limit in jiffies for a lock
3071			acquisition.  Acquisitions exceeding this limit
3072			will result in a splat once they do complete.
3073
3074	locktorture.bind_readers= [KNL]
3075			Specify the list of CPUs to which the readers are
3076			to be bound.
3077
3078	locktorture.bind_writers= [KNL]
3079			Specify the list of CPUs to which the writers are
3080			to be bound.
3081
3082	locktorture.call_rcu_chains= [KNL]
3083			Specify the number of self-propagating call_rcu()
3084			chains to set up.  These are used to ensure that
3085			there is a high probability of an RCU grace period
3086			in progress at any given time.	Defaults to 0,
3087			which disables these call_rcu() chains.
3088
3089	locktorture.long_hold= [KNL]
3090			Specify the duration in milliseconds for the
3091			occasional long-duration lock hold time.  Defaults
3092			to 100 milliseconds.  Select 0 to disable.
3093
3094	locktorture.nested_locks= [KNL]
3095			Specify the maximum lock nesting depth that
3096			locktorture is to exercise, up to a limit of 8
3097			(MAX_NESTED_LOCKS).  Specify zero to disable.
3098			Note that this parameter is ineffective on types
3099			of locks that do not support nested acquisition.
3100
3101	locktorture.nreaders_stress= [KNL]
3102			Set the number of locking read-acquisition kthreads.
3103			Defaults to being automatically set based on the
3104			number of online CPUs.
3105
3106	locktorture.nwriters_stress= [KNL]
3107			Set the number of locking write-acquisition kthreads.
3108
3109	locktorture.onoff_holdoff= [KNL]
3110			Set time (s) after boot for CPU-hotplug testing.
3111
3112	locktorture.onoff_interval= [KNL]
3113			Set time (s) between CPU-hotplug operations, or
3114			zero to disable CPU-hotplug testing.
3115
3116	locktorture.rt_boost= [KNL]
3117			Do periodic testing of real-time lock priority
3118			boosting.  Select 0 to disable, 1 to boost
3119			only rt_mutex, and 2 to boost unconditionally.
3120			Defaults to 2, which might seem to be an
3121			odd choice, but which should be harmless for
3122			non-real-time spinlocks, due to their disabling
3123			of preemption.	Note that non-realtime mutexes
3124			disable boosting.
3125
3126	locktorture.rt_boost_factor= [KNL]
3127			Number that determines how often and for how
3128			long priority boosting is exercised.  This is
3129			scaled down by the number of writers, so that the
3130			number of boosts per unit time remains roughly
3131			constant as the number of writers increases.
3132			On the other hand, the duration of each boost
3133			increases with the number of writers.
3134
3135	locktorture.shuffle_interval= [KNL]
3136			Set task-shuffle interval (jiffies).  Shuffling
3137			tasks allows some CPUs to go into dyntick-idle
3138			mode during the locktorture test.
3139
3140	locktorture.shutdown_secs= [KNL]
3141			Set time (s) after boot system shutdown.  This
3142			is useful for hands-off automated testing.
3143
3144	locktorture.stat_interval= [KNL]
3145			Time (s) between statistics printk()s.
3146
3147	locktorture.stutter= [KNL]
3148			Time (s) to stutter testing, for example,
3149			specifying five seconds causes the test to run for
3150			five seconds, wait for five seconds, and so on.
3151			This tests the locking primitive's ability to
3152			transition abruptly to and from idle.
3153
3154	locktorture.torture_type= [KNL]
3155			Specify the locking implementation to test.
3156
3157	locktorture.verbose= [KNL]
3158			Enable additional printk() statements.
3159
3160	locktorture.writer_fifo= [KNL]
3161			Run the write-side locktorture kthreads at
3162			sched_set_fifo() real-time priority.
3163
3164	logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
3165			Format: <irq>
3166
3167	loglevel=	[KNL,EARLY]
3168			All Kernel Messages with a loglevel smaller than the
3169			console loglevel will be printed to the console. It can
3170			also be changed with klogd or other programs. The
3171			loglevels are defined as follows:
3172
3173			0 (KERN_EMERG)		system is unusable
3174			1 (KERN_ALERT)		action must be taken immediately
3175			2 (KERN_CRIT)		critical conditions
3176			3 (KERN_ERR)		error conditions
3177			4 (KERN_WARNING)	warning conditions
3178			5 (KERN_NOTICE)		normal but significant condition
3179			6 (KERN_INFO)		informational
3180			7 (KERN_DEBUG)		debug-level messages
3181
3182	log_buf_len=n[KMG] [KNL,EARLY]
3183			Sets the size of the printk ring buffer, in bytes.
3184			n must be a power of two and greater than the
3185			minimal size. The minimal size is defined by
3186			LOG_BUF_SHIFT kernel config parameter. There
3187			is also CONFIG_LOG_CPU_MAX_BUF_SHIFT config
3188			parameter that allows to increase the default size
3189			depending on the number of CPUs. See init/Kconfig
3190			for more details.
3191
3192	logo.nologo	[FB] Disables display of the built-in Linux logo.
3193			This may be used to provide more screen space for
3194			kernel log messages and is useful when debugging
3195			kernel boot problems.
3196
3197	lp=0		[LP]	Specify parallel ports to use, e.g,
3198	lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
3199	lp=reset		first parallel port). 'lp=0' disables the
3200	lp=auto			printer driver. 'lp=reset' (which can be
3201				specified in addition to the ports) causes
3202				attached printers to be reset. Using
3203				lp=port1,port2,... specifies the parallel ports
3204				to associate lp devices with, starting with
3205				lp0. A port specification may be 'none' to skip
3206				that lp device, or a parport name such as
3207				'parport0'. Specifying 'lp=auto' instead of a
3208				port specification list means that device IDs
3209				from each port should be examined, to see if
3210				an IEEE 1284-compliant printer is attached; if
3211				so, the driver will manage that printer.
3212				See also header of drivers/char/lp.c.
3213
3214	lpj=n		[KNL]
3215			Sets loops_per_jiffy to given constant, thus avoiding
3216			time-consuming boot-time autodetection (up to 250 ms per
3217			CPU). 0 enables autodetection (default). To determine
3218			the correct value for your kernel, boot with normal
3219			autodetection and see what value is printed. Note that
3220			on SMP systems the preset will be applied to all CPUs,
3221			which is likely to cause problems if your CPUs need
3222			significantly divergent settings. An incorrect value
3223			will cause delays in the kernel to be wrong, leading to
3224			unpredictable I/O errors and other breakage. Although
3225			unlikely, in the extreme case this might damage your
3226			hardware.
3227
3228	lsm.debug	[SECURITY] Enable LSM initialization debugging output.
3229
3230	lsm=lsm1,...,lsmN
3231			[SECURITY] Choose order of LSM initialization. This
3232			overrides CONFIG_LSM, and the "security=" parameter.
3233
3234	machtype=	[Loongson] Share the same kernel image file between
3235			different yeeloong laptops.
3236			Example: machtype=lemote-yeeloong-2f-7inch
3237
3238	maxcpus=	[SMP,EARLY] Maximum number of processors that an SMP kernel
3239			will bring up during bootup.  maxcpus=n : n >= 0 limits
3240			the kernel to bring up 'n' processors. Surely after
3241			bootup you can bring up the other plugged cpu by executing
3242			"echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3243			only takes effect during system bootup.
3244			While n=0 is a special case, it is equivalent to "nosmp",
3245			which also disables the IO APIC.
3246
3247	max_loop=	[LOOP] The number of loop block devices that get
3248	(loop.max_loop)	unconditionally pre-created at init time. The default
3249			number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3250			of statically allocating a predefined number, loop
3251			devices can be requested on-demand with the
3252			/dev/loop-control interface.
3253
3254	mce		[X86-32] Machine Check Exception
3255
3256	mce=option	[X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
3257
3258	md=		[HW] RAID subsystems devices and level
3259			See Documentation/admin-guide/md.rst.
3260
3261	mdacon=		[MDA]
3262			Format: <first>,<last>
3263			Specifies range of consoles to be captured by the MDA.
3264
3265	mds=		[X86,INTEL,EARLY]
3266			Control mitigation for the Micro-architectural Data
3267			Sampling (MDS) vulnerability.
3268
3269			Certain CPUs are vulnerable to an exploit against CPU
3270			internal buffers which can forward information to a
3271			disclosure gadget under certain conditions.
3272
3273			In vulnerable processors, the speculatively
3274			forwarded data can be used in a cache side channel
3275			attack, to access data to which the attacker does
3276			not have direct access.
3277
3278			This parameter controls the MDS mitigation. The
3279			options are:
3280
3281			full       - Enable MDS mitigation on vulnerable CPUs
3282			full,nosmt - Enable MDS mitigation and disable
3283				     SMT on vulnerable CPUs
3284			off        - Unconditionally disable MDS mitigation
3285
3286			On TAA-affected machines, mds=off can be prevented by
3287			an active TAA mitigation as both vulnerabilities are
3288			mitigated with the same mechanism so in order to disable
3289			this mitigation, you need to specify tsx_async_abort=off
3290			too.
3291
3292			Not specifying this option is equivalent to
3293			mds=full.
3294
3295			For details see: Documentation/admin-guide/hw-vuln/mds.rst
3296
3297	mem=nn[KMG]	[HEXAGON,EARLY] Set the memory size.
3298			Must be specified, otherwise memory size will be 0.
3299
3300	mem=nn[KMG]	[KNL,BOOT,EARLY] Force usage of a specific amount
3301			of memory Amount of memory to be used in cases
3302			as follows:
3303
3304			1 for test;
3305			2 when the kernel is not able to see the whole system memory;
3306			3 memory that lies after 'mem=' boundary is excluded from
3307			 the hypervisor, then assigned to KVM guests.
3308			4 to limit the memory available for kdump kernel.
3309
3310			[ARC,MICROBLAZE] - the limit applies only to low memory,
3311			high memory is not affected.
3312
3313			[ARM64] - only limits memory covered by the linear
3314			mapping. The NOMAP regions are not affected.
3315
3316			[X86] Work as limiting max address. Use together
3317			with memmap= to avoid physical address space collisions.
3318			Without memmap= PCI devices could be placed at addresses
3319			belonging to unused RAM.
3320
3321			Note that this only takes effects during boot time since
3322			in above case 3, memory may need be hot added after boot
3323			if system memory of hypervisor is not sufficient.
3324
3325	mem=nn[KMG]@ss[KMG]
3326			[ARM,MIPS,EARLY] - override the memory layout
3327			reported by firmware.
3328			Define a memory region of size nn[KMG] starting at
3329			ss[KMG].
3330			Multiple different regions can be specified with
3331			multiple mem= parameters on the command line.
3332
3333	mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
3334			memory.
3335
3336	memblock=debug	[KNL,EARLY] Enable memblock debug messages.
3337
3338	memchunk=nn[KMG]
3339			[KNL,SH] Allow user to override the default size for
3340			per-device physically contiguous DMA buffers.
3341
3342	memhp_default_state=online/offline/online_kernel/online_movable
3343			[KNL] Set the initial state for the memory hotplug
3344			onlining policy. If not specified, the default value is
3345			set according to the
3346			CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3347			option.
3348			See Documentation/admin-guide/mm/memory-hotplug.rst.
3349
3350	memmap=exactmap	[KNL,X86,EARLY] Enable setting of an exact
3351			E820 memory map, as specified by the user.
3352			Such memmap=exactmap lines can be constructed based on
3353			BIOS output or other requirements. See the memmap=nn@ss
3354			option description.
3355
3356	memmap=nn[KMG]@ss[KMG]
3357			[KNL, X86,MIPS,XTENSA,EARLY] Force usage of a specific region of memory.
3358			Region of memory to be used is from ss to ss+nn.
3359			If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3360			which limits max address to nn[KMG].
3361			Multiple different regions can be specified,
3362			comma delimited.
3363			Example:
3364				memmap=100M@2G,100M#3G,1G!1024G
3365
3366	memmap=nn[KMG]#ss[KMG]
3367			[KNL,ACPI,EARLY] Mark specific memory as ACPI data.
3368			Region of memory to be marked is from ss to ss+nn.
3369
3370	memmap=nn[KMG]$ss[KMG]
3371			[KNL,ACPI,EARLY] Mark specific memory as reserved.
3372			Region of memory to be reserved is from ss to ss+nn.
3373			Example: Exclude memory from 0x18690000-0x1869ffff
3374			         memmap=64K$0x18690000
3375			         or
3376			         memmap=0x10000$0x18690000
3377			Some bootloaders may need an escape character before '$',
3378			like Grub2, otherwise '$' and the following number
3379			will be eaten.
3380
3381	memmap=nn[KMG]!ss[KMG,EARLY]
3382			[KNL,X86] Mark specific memory as protected.
3383			Region of memory to be used, from ss to ss+nn.
3384			The memory region may be marked as e820 type 12 (0xc)
3385			and is NVDIMM or ADR memory.
3386
3387	memmap=<size>%<offset>-<oldtype>+<newtype>
3388			[KNL,ACPI,EARLY] Convert memory within the specified region
3389			from <oldtype> to <newtype>. If "-<oldtype>" is left
3390			out, the whole region will be marked as <newtype>,
3391			even if previously unavailable. If "+<newtype>" is left
3392			out, matching memory will be removed. Types are
3393			specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3394			3 = ACPI, 12 = PRAM.
3395
3396	memory_corruption_check=0/1 [X86,EARLY]
3397			Some BIOSes seem to corrupt the first 64k of
3398			memory when doing things like suspend/resume.
3399			Setting this option will scan the memory
3400			looking for corruption.  Enabling this will
3401			both detect corruption and prevent the kernel
3402			from using the memory being corrupted.
3403			However, its intended as a diagnostic tool; if
3404			repeatable BIOS-originated corruption always
3405			affects the same memory, you can use memmap=
3406			to prevent the kernel from using that memory.
3407
3408	memory_corruption_check_size=size [X86,EARLY]
3409			By default it checks for corruption in the low
3410			64k, making this memory unavailable for normal
3411			use.  Use this parameter to scan for
3412			corruption in more or less memory.
3413
3414	memory_corruption_check_period=seconds [X86,EARLY]
3415			By default it checks for corruption every 60
3416			seconds.  Use this parameter to check at some
3417			other rate.  0 disables periodic checking.
3418
3419	memory_hotplug.memmap_on_memory
3420			[KNL,X86,ARM] Boolean flag to enable this feature.
3421			Format: {on | off (default)}
3422			When enabled, runtime hotplugged memory will
3423			allocate its internal metadata (struct pages,
3424			those vmemmap pages cannot be optimized even
3425			if hugetlb_free_vmemmap is enabled) from the
3426			hotadded memory which will allow to hotadd a
3427			lot of memory without requiring additional
3428			memory to do so.
3429			This feature is disabled by default because it
3430			has some implication on large (e.g. GB)
3431			allocations in some configurations (e.g. small
3432			memory blocks).
3433			The state of the flag can be read in
3434			/sys/module/memory_hotplug/parameters/memmap_on_memory.
3435			Note that even when enabled, there are a few cases where
3436			the feature is not effective.
3437
3438	memtest=	[KNL,X86,ARM,M68K,PPC,RISCV,EARLY] Enable memtest
3439			Format: <integer>
3440			default : 0 <disable>
3441			Specifies the number of memtest passes to be
3442			performed. Each pass selects another test
3443			pattern from a given set of patterns. Memtest
3444			fills the memory with this pattern, validates
3445			memory contents and reserves bad memory
3446			regions that are detected.
3447
3448	mem_encrypt=	[X86-64] AMD Secure Memory Encryption (SME) control
3449			Valid arguments: on, off
3450			Default: off
3451			mem_encrypt=on:		Activate SME
3452			mem_encrypt=off:	Do not activate SME
3453
3454			Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3455			for details on when memory encryption can be activated.
3456
3457	mem_sleep_default=	[SUSPEND] Default system suspend mode:
3458			s2idle  - Suspend-To-Idle
3459			shallow - Power-On Suspend or equivalent (if supported)
3460			deep    - Suspend-To-RAM or equivalent (if supported)
3461			See Documentation/admin-guide/pm/sleep-states.rst.
3462
3463	mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
3464			the BIOS has incorrectly applied a workaround. TinyBIOS
3465			version 0.98 is known to be affected, 0.99 fixes the
3466			problem by letting the user disable the workaround.
3467
3468	mga=		[HW,DRM]
3469
3470	microcode.force_minrev=	[X86]
3471			Format: <bool>
3472			Enable or disable the microcode minimal revision
3473			enforcement for the runtime microcode loader.
3474
3475	mini2440=	[ARM,HW,KNL]
3476			Format:[0..2][b][c][t]
3477			Default: "0tb"
3478			MINI2440 configuration specification:
3479			0 - The attached screen is the 3.5" TFT
3480			1 - The attached screen is the 7" TFT
3481			2 - The VGA Shield is attached (1024x768)
3482			Leaving out the screen size parameter will not load
3483			the TFT driver, and the framebuffer will be left
3484			unconfigured.
3485			b - Enable backlight. The TFT backlight pin will be
3486			linked to the kernel VESA blanking code and a GPIO
3487			LED. This parameter is not necessary when using the
3488			VGA shield.
3489			c - Enable the s3c camera interface.
3490			t - Reserved for enabling touchscreen support. The
3491			touchscreen support is not enabled in the mainstream
3492			kernel as of 2.6.30, a preliminary port can be found
3493			in the "bleeding edge" mini2440 support kernel at
3494			https://repo.or.cz/w/linux-2.6/mini2440.git
3495
3496	mitigations=
3497			[X86,PPC,S390,ARM64,EARLY] Control optional mitigations for
3498			CPU vulnerabilities.  This is a set of curated,
3499			arch-independent options, each of which is an
3500			aggregation of existing arch-specific options.
3501
3502			Note, "mitigations" is supported if and only if the
3503			kernel was built with CPU_MITIGATIONS=y.
3504
3505			off
3506				Disable all optional CPU mitigations.  This
3507				improves system performance, but it may also
3508				expose users to several CPU vulnerabilities.
3509				Equivalent to: if nokaslr then kpti=0 [ARM64]
3510					       gather_data_sampling=off [X86]
3511					       kvm.nx_huge_pages=off [X86]
3512					       l1tf=off [X86]
3513					       mds=off [X86]
3514					       mmio_stale_data=off [X86]
3515					       no_entry_flush [PPC]
3516					       no_uaccess_flush [PPC]
3517					       nobp=0 [S390]
3518					       nopti [X86,PPC]
3519					       nospectre_bhb [ARM64]
3520					       nospectre_v1 [X86,PPC]
3521					       nospectre_v2 [X86,PPC,S390,ARM64]
3522					       reg_file_data_sampling=off [X86]
3523					       retbleed=off [X86]
3524					       spec_rstack_overflow=off [X86]
3525					       spec_store_bypass_disable=off [X86,PPC]
3526					       spectre_bhi=off [X86]
3527					       spectre_v2_user=off [X86]
3528					       srbds=off [X86,INTEL]
3529					       ssbd=force-off [ARM64]
3530					       tsx_async_abort=off [X86]
3531
3532				Exceptions:
3533					       This does not have any effect on
3534					       kvm.nx_huge_pages when
3535					       kvm.nx_huge_pages=force.
3536
3537			auto (default)
3538				Mitigate all CPU vulnerabilities, but leave SMT
3539				enabled, even if it's vulnerable.  This is for
3540				users who don't want to be surprised by SMT
3541				getting disabled across kernel upgrades, or who
3542				have other ways of avoiding SMT-based attacks.
3543				Equivalent to: (default behavior)
3544
3545			auto,nosmt
3546				Mitigate all CPU vulnerabilities, disabling SMT
3547				if needed.  This is for users who always want to
3548				be fully mitigated, even if it means losing SMT.
3549				Equivalent to: l1tf=flush,nosmt [X86]
3550					       mds=full,nosmt [X86]
3551					       tsx_async_abort=full,nosmt [X86]
3552					       mmio_stale_data=full,nosmt [X86]
3553					       retbleed=auto,nosmt [X86]
3554
3555	mminit_loglevel=
3556			[KNL,EARLY] When CONFIG_DEBUG_MEMORY_INIT is set, this
3557			parameter allows control of the logging verbosity for
3558			the additional memory initialisation checks. A value
3559			of 0 disables mminit logging and a level of 4 will
3560			log everything. Information is printed at KERN_DEBUG
3561			so loglevel=8 may also need to be specified.
3562
3563	mmio_stale_data=
3564			[X86,INTEL,EARLY] Control mitigation for the Processor
3565			MMIO Stale Data vulnerabilities.
3566
3567			Processor MMIO Stale Data is a class of
3568			vulnerabilities that may expose data after an MMIO
3569			operation. Exposed data could originate or end in
3570			the same CPU buffers as affected by MDS and TAA.
3571			Therefore, similar to MDS and TAA, the mitigation
3572			is to clear the affected CPU buffers.
3573
3574			This parameter controls the mitigation. The
3575			options are:
3576
3577			full       - Enable mitigation on vulnerable CPUs
3578
3579			full,nosmt - Enable mitigation and disable SMT on
3580				     vulnerable CPUs.
3581
3582			off        - Unconditionally disable mitigation
3583
3584			On MDS or TAA affected machines,
3585			mmio_stale_data=off can be prevented by an active
3586			MDS or TAA mitigation as these vulnerabilities are
3587			mitigated with the same mechanism so in order to
3588			disable this mitigation, you need to specify
3589			mds=off and tsx_async_abort=off too.
3590
3591			Not specifying this option is equivalent to
3592			mmio_stale_data=full.
3593
3594			For details see:
3595			Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3596
3597	<module>.async_probe[=<bool>] [KNL]
3598			If no <bool> value is specified or if the value
3599			specified is not a valid <bool>, enable asynchronous
3600			probe on this module.  Otherwise, enable/disable
3601			asynchronous probe on this module as indicated by the
3602			<bool> value. See also: module.async_probe
3603
3604	module.async_probe=<bool>
3605			[KNL] When set to true, modules will use async probing
3606			by default. To enable/disable async probing for a
3607			specific module, use the module specific control that
3608			is documented under <module>.async_probe. When both
3609			module.async_probe and <module>.async_probe are
3610			specified, <module>.async_probe takes precedence for
3611			the specific module.
3612
3613	module.enable_dups_trace
3614			[KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
3615			this means that duplicate request_module() calls will
3616			trigger a WARN_ON() instead of a pr_warn(). Note that
3617			if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
3618			will always be issued and this option does nothing.
3619	module.sig_enforce
3620			[KNL] When CONFIG_MODULE_SIG is set, this means that
3621			modules without (valid) signatures will fail to load.
3622			Note that if CONFIG_MODULE_SIG_FORCE is set, that
3623			is always true, so this option does nothing.
3624
3625	module_blacklist=  [KNL] Do not load a comma-separated list of
3626			modules.  Useful for debugging problem modules.
3627
3628	mousedev.tap_time=
3629			[MOUSE] Maximum time between finger touching and
3630			leaving touchpad surface for touch to be considered
3631			a tap and be reported as a left button click (for
3632			touchpads working in absolute mode only).
3633			Format: <msecs>
3634	mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
3635			reporting absolute coordinates, such as tablets
3636	mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
3637			reporting absolute coordinates, such as tablets
3638
3639	movablecore=	[KNL,X86,PPC,EARLY]
3640			Format: nn[KMGTPE] | nn%
3641			This parameter is the complement to kernelcore=, it
3642			specifies the amount of memory used for migratable
3643			allocations.  If both kernelcore and movablecore is
3644			specified, then kernelcore will be at *least* the
3645			specified value but may be more.  If movablecore on its
3646			own is specified, the administrator must be careful
3647			that the amount of memory usable for all allocations
3648			is not too small.
3649
3650	movable_node	[KNL,EARLY] Boot-time switch to make hotplugable memory
3651			NUMA nodes to be movable. This means that the memory
3652			of such nodes will be usable only for movable
3653			allocations which rules out almost all kernel
3654			allocations. Use with caution!
3655
3656	MTD_Partition=	[MTD]
3657			Format: <name>,<region-number>,<size>,<offset>
3658
3659	MTD_Region=	[MTD] Format:
3660			<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3661
3662	mtdparts=	[MTD]
3663			See drivers/mtd/parsers/cmdlinepart.c
3664
3665	mtouchusb.raw_coordinates=
3666			[HW] Make the MicroTouch USB driver use raw coordinates
3667			('y', default) or cooked coordinates ('n')
3668
3669	mtrr=debug	[X86,EARLY]
3670			Enable printing debug information related to MTRR
3671			registers at boot time.
3672
3673	mtrr_chunk_size=nn[KMG,X86,EARLY]
3674			used for mtrr cleanup. It is largest continuous chunk
3675			that could hold holes aka. UC entries.
3676
3677	mtrr_gran_size=nn[KMG,X86,EARLY]
3678			Used for mtrr cleanup. It is granularity of mtrr block.
3679			Default is 1.
3680			Large value could prevent small alignment from
3681			using up MTRRs.
3682
3683	mtrr_spare_reg_nr=n [X86,EARLY]
3684			Format: <integer>
3685			Range: 0,7 : spare reg number
3686			Default : 1
3687			Used for mtrr cleanup. It is spare mtrr entries number.
3688			Set to 2 or more if your graphical card needs more.
3689
3690	multitce=off	[PPC]  This parameter disables the use of the pSeries
3691			firmware feature for updating multiple TCE entries
3692			at a time.
3693
3694	n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
3695
3696	netdev=		[NET] Network devices parameters
3697			Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3698			Note that mem_start is often overloaded to mean
3699			something different and driver-specific.
3700			This usage is only documented in each driver source
3701			file if at all.
3702
3703	netpoll.carrier_timeout=
3704			[NET] Specifies amount of time (in seconds) that
3705			netpoll should wait for a carrier. By default netpoll
3706			waits 4 seconds.
3707
3708	nf_conntrack.acct=
3709			[NETFILTER] Enable connection tracking flow accounting
3710			0 to disable accounting
3711			1 to enable accounting
3712			Default value is 0.
3713
3714	nfs.cache_getent=
3715			[NFS] sets the pathname to the program which is used
3716			to update the NFS client cache entries.
3717
3718	nfs.cache_getent_timeout=
3719			[NFS] sets the timeout after which an attempt to
3720			update a cache entry is deemed to have failed.
3721
3722	nfs.callback_nr_threads=
3723			[NFSv4] set the total number of threads that the
3724			NFS client will assign to service NFSv4 callback
3725			requests.
3726
3727	nfs.callback_tcpport=
3728			[NFS] set the TCP port on which the NFSv4 callback
3729			channel should listen.
3730
3731	nfs.delay_retrans=
3732			[NFS] specifies the number of times the NFSv4 client
3733			retries the request before returning an EAGAIN error,
3734			after a reply of NFS4ERR_DELAY from the server.
3735			Only applies if the softerr mount option is enabled,
3736			and the specified value is >= 0.
3737
3738	nfs.enable_ino64=
3739			[NFS] enable 64-bit inode numbers.
3740			If zero, the NFS client will fake up a 32-bit inode
3741			number for the readdir() and stat() syscalls instead
3742			of returning the full 64-bit number.
3743			The default is to return 64-bit inode numbers.
3744
3745	nfs.idmap_cache_timeout=
3746			[NFS] set the maximum lifetime for idmapper cache
3747			entries.
3748
3749	nfs.max_session_cb_slots=
3750			[NFSv4.1] Sets the maximum number of session
3751			slots the client will assign to the callback
3752			channel. This determines the maximum number of
3753			callbacks the client will process in parallel for
3754			a particular server.
3755
3756	nfs.max_session_slots=
3757			[NFSv4.1] Sets the maximum number of session slots
3758			the client will attempt to negotiate with the server.
3759			This limits the number of simultaneous RPC requests
3760			that the client can send to the NFSv4.1 server.
3761			Note that there is little point in setting this
3762			value higher than the max_tcp_slot_table_limit.
3763
3764	nfs.nfs4_disable_idmapping=
3765			[NFSv4] When set to the default of '1', this option
3766			ensures that both the RPC level authentication
3767			scheme and the NFS level operations agree to use
3768			numeric uids/gids if the mount is using the
3769			'sec=sys' security flavour. In effect it is
3770			disabling idmapping, which can make migration from
3771			legacy NFSv2/v3 systems to NFSv4 easier.
3772			Servers that do not support this mode of operation
3773			will be autodetected by the client, and it will fall
3774			back to using the idmapper.
3775			To turn off this behaviour, set the value to '0'.
3776
3777	nfs.nfs4_unique_id=
3778			[NFS4] Specify an additional fixed unique ident-
3779			ification string that NFSv4 clients can insert into
3780			their nfs_client_id4 string.  This is typically a
3781			UUID that is generated at system install time.
3782
3783	nfs.recover_lost_locks=
3784			[NFSv4] Attempt to recover locks that were lost due
3785			to a lease timeout on the server. Please note that
3786			doing this risks data corruption, since there are
3787			no guarantees that the file will remain unchanged
3788			after the locks are lost.
3789			If you want to enable the kernel legacy behaviour of
3790			attempting to recover these locks, then set this
3791			parameter to '1'.
3792			The default parameter value of '0' causes the kernel
3793			not to attempt recovery of lost locks.
3794
3795	nfs.send_implementation_id=
3796			[NFSv4.1] Send client implementation identification
3797			information in exchange_id requests.
3798			If zero, no implementation identification information
3799			will be sent.
3800			The default is to send the implementation identification
3801			information.
3802
3803	nfs4.layoutstats_timer=
3804			[NFSv4.2] Change the rate at which the kernel sends
3805			layoutstats to the pNFS metadata server.
3806
3807			Setting this to value to 0 causes the kernel to use
3808			whatever value is the default set by the layout
3809			driver. A non-zero value sets the minimum interval
3810			in seconds between layoutstats transmissions.
3811
3812	nfsd.inter_copy_offload_enable=
3813			[NFSv4.2] When set to 1, the server will support
3814			server-to-server copies for which this server is
3815			the destination of the copy.
3816
3817	nfsd.nfs4_disable_idmapping=
3818			[NFSv4] When set to the default of '1', the NFSv4
3819			server will return only numeric uids and gids to
3820			clients using auth_sys, and will accept numeric uids
3821			and gids from such clients.  This is intended to ease
3822			migration from NFSv2/v3.
3823
3824	nfsd.nfsd4_ssc_umount_timeout=
3825			[NFSv4.2] When used as the destination of a
3826			server-to-server copy, knfsd temporarily mounts
3827			the source server.  It caches the mount in case
3828			it will be needed again, and discards it if not
3829			used for the number of milliseconds specified by
3830			this parameter.
3831
3832	nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
3833			See Documentation/admin-guide/nfs/nfsroot.rst.
3834
3835	nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
3836			See Documentation/admin-guide/nfs/nfsroot.rst.
3837
3838	nfsrootdebug	[NFS] enable nfsroot debugging messages.
3839			See Documentation/admin-guide/nfs/nfsroot.rst.
3840
3841	nmi_backtrace.backtrace_idle [KNL]
3842			Dump stacks even of idle CPUs in response to an
3843			NMI stack-backtrace request.
3844
3845	nmi_debug=	[KNL,SH] Specify one or more actions to take
3846			when a NMI is triggered.
3847			Format: [state][,regs][,debounce][,die]
3848
3849	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
3850			Format: [panic,][nopanic,][rNNN,][num]
3851			Valid num: 0 or 1
3852			0 - turn hardlockup detector in nmi_watchdog off
3853			1 - turn hardlockup detector in nmi_watchdog on
3854			rNNN - configure the watchdog with raw perf event 0xNNN
3855
3856			When panic is specified, panic when an NMI watchdog
3857			timeout occurs (or 'nopanic' to not panic on an NMI
3858			watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3859			To disable both hard and soft lockup detectors,
3860			please see 'nowatchdog'.
3861			This is useful when you use a panic=... timeout and
3862			need the box quickly up again.
3863
3864			These settings can be accessed at runtime via
3865			the nmi_watchdog and hardlockup_panic sysctls.
3866
3867	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
3868			emulation library even if a 387 maths coprocessor
3869			is present.
3870
3871	no4lvl		[RISCV,EARLY] Disable 4-level and 5-level paging modes.
3872			Forces kernel to use 3-level paging instead.
3873
3874	no5lvl		[X86-64,RISCV,EARLY] Disable 5-level paging mode. Forces
3875			kernel to use 4-level paging instead.
3876
3877	noalign		[KNL,ARM]
3878
3879	noapic		[SMP,APIC,EARLY] Tells the kernel to not make use of any
3880			IOAPICs that may be present in the system.
3881
3882	noautogroup	Disable scheduler automatic task group creation.
3883
3884	nocache		[ARM,EARLY]
3885
3886	no_console_suspend
3887			[HW] Never suspend the console
3888			Disable suspending of consoles during suspend and
3889			hibernate operations.  Once disabled, debugging
3890			messages can reach various consoles while the rest
3891			of the system is being put to sleep (ie, while
3892			debugging driver suspend/resume hooks).  This may
3893			not work reliably with all consoles, but is known
3894			to work with serial and VGA consoles.
3895			To facilitate more flexible debugging, we also add
3896			console_suspend, a printk module parameter to control
3897			it. Users could use console_suspend (usually
3898			/sys/module/printk/parameters/console_suspend) to
3899			turn on/off it dynamically.
3900
3901	no_debug_objects
3902			[KNL,EARLY] Disable object debugging
3903
3904	nodsp		[SH] Disable hardware DSP at boot time.
3905
3906	noefi		[EFI,EARLY] Disable EFI runtime services support.
3907
3908	no_entry_flush  [PPC,EARLY] Don't flush the L1-D cache when entering the kernel.
3909
3910	noexec32	[X86-64]
3911			This affects only 32-bit executables.
3912			noexec32=on: enable non-executable mappings (default)
3913				read doesn't imply executable mappings
3914			noexec32=off: disable non-executable mappings
3915				read implies executable mappings
3916
3917	no_file_caps	Tells the kernel not to honor file capabilities.  The
3918			only way then for a file to be executed with privilege
3919			is to be setuid root or executed by root.
3920
3921	nofpu		[MIPS,SH] Disable hardware FPU at boot time.
3922
3923	nofsgsbase	[X86] Disables FSGSBASE instructions.
3924
3925	nofxsr		[BUGS=X86-32] Disables x86 floating point extended
3926			register save and restore. The kernel will only save
3927			legacy floating-point registers on task switch.
3928
3929	no_hash_pointers
3930			[KNL,EARLY]
3931			Force pointers printed to the console or buffers to be
3932			unhashed.  By default, when a pointer is printed via %p
3933			format string, that pointer is "hashed", i.e. obscured
3934			by hashing the pointer value.  This is a security feature
3935			that hides actual kernel addresses from unprivileged
3936			users, but it also makes debugging the kernel more
3937			difficult since unequal pointers can no longer be
3938			compared.  However, if this command-line option is
3939			specified, then all normal pointers will have their true
3940			value printed. This option should only be specified when
3941			debugging the kernel.  Please do not use on production
3942			kernels.
3943
3944	nohibernate	[HIBERNATION] Disable hibernation and resume.
3945
3946	nohlt		[ARM,ARM64,MICROBLAZE,MIPS,PPC,RISCV,SH] Forces the kernel to
3947			busy wait in do_idle() and not use the arch_cpu_idle()
3948			implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
3949			to be effective. This is useful on platforms where the
3950			sleep(SH) or wfi(ARM,ARM64) instructions do not work
3951			correctly or when doing power measurements to evaluate
3952			the impact of the sleep instructions. This is also
3953			useful when using JTAG debugger.
3954
3955	nohugeiomap	[KNL,X86,PPC,ARM64,EARLY] Disable kernel huge I/O mappings.
3956
3957	nohugevmalloc	[KNL,X86,PPC,ARM64,EARLY] Disable kernel huge vmalloc mappings.
3958
3959	nohz=		[KNL] Boottime enable/disable dynamic ticks
3960			Valid arguments: on, off
3961			Default: on
3962
3963	nohz_full=	[KNL,BOOT,SMP,ISOL]
3964			The argument is a cpu list, as described above.
3965			In kernels built with CONFIG_NO_HZ_FULL=y, set
3966			the specified list of CPUs whose tick will be stopped
3967			whenever possible. The boot CPU will be forced outside
3968			the range to maintain the timekeeping.  Any CPUs
3969			in this list will have their RCU callbacks offloaded,
3970			just as if they had also been called out in the
3971			rcu_nocbs= boot parameter.
3972
3973			Note that this argument takes precedence over
3974			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
3975
3976	noinitrd	[RAM] Tells the kernel not to load any configured
3977			initial RAM disk.
3978
3979	nointremap	[X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
3980			remapping.
3981			[Deprecated - use intremap=off]
3982
3983	noinvpcid	[X86,EARLY] Disable the INVPCID cpu feature.
3984
3985	noiotrap	[SH] Disables trapped I/O port accesses.
3986
3987	noirqdebug	[X86-32] Disables the code which attempts to detect and
3988			disable unhandled interrupt sources.
3989
3990	noisapnp	[ISAPNP] Disables ISA PnP code.
3991
3992	nokaslr		[KNL,EARLY]
3993			When CONFIG_RANDOMIZE_BASE is set, this disables
3994			kernel and module base offset ASLR (Address Space
3995			Layout Randomization).
3996
3997	no-kvmapf	[X86,KVM,EARLY] Disable paravirtualized asynchronous page
3998			fault handling.
3999
4000	no-kvmclock	[X86,KVM,EARLY] Disable paravirtualized KVM clock driver
4001
4002	nolapic		[X86-32,APIC,EARLY] Do not enable or use the local APIC.
4003
4004	nolapic_timer	[X86-32,APIC,EARLY] Do not use the local APIC timer.
4005
4006	nomce		[X86-32] Disable Machine Check Exception
4007
4008	nomfgpt		[X86-32] Disable Multi-Function General Purpose
4009			Timer usage (for AMD Geode machines).
4010
4011	nomodeset	Disable kernel modesetting. Most systems' firmware
4012			sets up a display mode and provides framebuffer memory
4013			for output. With nomodeset, DRM and fbdev drivers will
4014			not load if they could possibly displace the pre-
4015			initialized output. Only the system framebuffer will
4016			be available for use. The respective drivers will not
4017			perform display-mode changes or accelerated rendering.
4018
4019			Useful as error fallback, or for testing and debugging.
4020
4021	nomodule	Disable module load
4022
4023	nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
4024			shutdown the other cpus.  Instead use the REBOOT_VECTOR
4025			irq.
4026
4027	nopat		[X86,EARLY] Disable PAT (page attribute table extension of
4028			pagetables) support.
4029
4030	nopcid		[X86-64,EARLY] Disable the PCID cpu feature.
4031
4032	nopku		[X86] Disable Memory Protection Keys CPU feature found
4033			in some Intel CPUs.
4034
4035	nopti		[X86-64,EARLY]
4036			Equivalent to pti=off
4037
4038	nopv=		[X86,XEN,KVM,HYPER_V,VMWARE,EARLY]
4039			Disables the PV optimizations forcing the guest to run
4040			as generic guest with no PV drivers. Currently support
4041			XEN HVM, KVM, HYPER_V and VMWARE guest.
4042
4043	nopvspin	[X86,XEN,KVM,EARLY]
4044			Disables the qspinlock slow path using PV optimizations
4045			which allow the hypervisor to 'idle' the guest on lock
4046			contention.
4047
4048	norandmaps	Don't use address space randomization.  Equivalent to
4049			echo 0 > /proc/sys/kernel/randomize_va_space
4050
4051	noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
4052			with UP alternatives
4053
4054	noresume	[SWSUSP] Disables resume and restores original swap
4055			space.
4056
4057	no-scroll	[VGA] Disables scrollback.
4058			This is required for the Braillex ib80-piezo Braille
4059			reader made by F.H. Papenmeier (Germany).
4060
4061	nosgx		[X86-64,SGX,EARLY] Disables Intel SGX kernel support.
4062
4063	nosmap		[PPC,EARLY]
4064			Disable SMAP (Supervisor Mode Access Prevention)
4065			even if it is supported by processor.
4066
4067	nosmep		[PPC64s,EARLY]
4068			Disable SMEP (Supervisor Mode Execution Prevention)
4069			even if it is supported by processor.
4070
4071	nosmp		[SMP,EARLY] Tells an SMP kernel to act as a UP kernel,
4072			and disable the IO APIC.  legacy for "maxcpus=0".
4073
4074	nosmt		[KNL,MIPS,PPC,S390,EARLY] Disable symmetric multithreading (SMT).
4075			Equivalent to smt=1.
4076
4077			[KNL,X86,PPC] Disable symmetric multithreading (SMT).
4078			nosmt=force: Force disable SMT, cannot be undone
4079				     via the sysfs control file.
4080
4081	nosoftlockup	[KNL] Disable the soft-lockup detector.
4082
4083	nospec_store_bypass_disable
4084			[HW,EARLY] Disable all mitigations for the Speculative
4085			Store Bypass vulnerability
4086
4087	nospectre_bhb	[ARM64,EARLY] Disable all mitigations for Spectre-BHB (branch
4088			history injection) vulnerability. System may allow data leaks
4089			with this option.
4090
4091	nospectre_v1	[X86,PPC,EARLY] Disable mitigations for Spectre Variant 1
4092			(bounds check bypass). With this option data leaks are
4093			possible in the system.
4094
4095	nospectre_v2	[X86,PPC_E500,ARM64,EARLY] Disable all mitigations
4096			for the Spectre variant 2 (indirect branch
4097			prediction) vulnerability. System may allow data
4098			leaks with this option.
4099
4100	no-steal-acc	[X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY]
4101			Disable paravirtualized steal time accounting. steal time
4102			is computed, but won't influence scheduler behaviour
4103
4104	nosync		[HW,M68K] Disables sync negotiation for all devices.
4105
4106	no_timer_check	[X86,APIC] Disables the code which tests for
4107			broken timer IRQ sources.
4108
4109	no_uaccess_flush
4110	                [PPC,EARLY] Don't flush the L1-D cache after accessing user data.
4111
4112	novmcoredd	[KNL,KDUMP]
4113			Disable device dump. Device dump allows drivers to
4114			append dump data to vmcore so you can collect driver
4115			specified debug info.  Drivers can append the data
4116			without any limit and this data is stored in memory,
4117			so this may cause significant memory stress.  Disabling
4118			device dump can help save memory but the driver debug
4119			data will be no longer available.  This parameter
4120			is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
4121			is set.
4122
4123	no-vmw-sched-clock
4124			[X86,PV_OPS,EARLY] Disable paravirtualized VMware
4125			scheduler clock and use the default one.
4126
4127	nowatchdog	[KNL] Disable both lockup detectors, i.e.
4128			soft-lockup and NMI watchdog (hard-lockup).
4129
4130	nowb		[ARM,EARLY]
4131
4132	nox2apic	[X86-64,APIC,EARLY] Do not enable x2APIC mode.
4133
4134			NOTE: this parameter will be ignored on systems with the
4135			LEGACY_XAPIC_DISABLED bit set in the
4136			IA32_XAPIC_DISABLE_STATUS MSR.
4137
4138	noxsave		[BUGS=X86] Disables x86 extended register state save
4139			and restore using xsave. The kernel will fallback to
4140			enabling legacy floating-point and sse state.
4141
4142	noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
4143			register states. The kernel will fall back to use
4144			xsave to save the states. By using this parameter,
4145			performance of saving the states is degraded because
4146			xsave doesn't support modified optimization while
4147			xsaveopt supports it on xsaveopt enabled systems.
4148
4149	noxsaves	[X86] Disables xsaves and xrstors used in saving and
4150			restoring x86 extended register state in compacted
4151			form of xsave area. The kernel will fall back to use
4152			xsaveopt and xrstor to save and restore the states
4153			in standard form of xsave area. By using this
4154			parameter, xsave area per process might occupy more
4155			memory on xsaves enabled systems.
4156
4157	nr_cpus=	[SMP,EARLY] Maximum number of processors that an SMP kernel
4158			could support.  nr_cpus=n : n >= 1 limits the kernel to
4159			support 'n' processors. It could be larger than the
4160			number of already plugged CPU during bootup, later in
4161			runtime you can physically add extra cpu until it reaches
4162			n. So during boot up some boot time memory for per-cpu
4163			variables need be pre-allocated for later physical cpu
4164			hot plugging.
4165
4166	nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
4167
4168	numa=off 	[KNL, ARM64, PPC, RISCV, SPARC, X86, EARLY]
4169			Disable NUMA, Only set up a single NUMA node
4170			spanning all memory.
4171
4172	numa=fake=<size>[MG]
4173			[KNL, ARM64, RISCV, X86, EARLY]
4174			If given as a memory unit, fills all system RAM with
4175			nodes of size interleaved over physical nodes.
4176
4177	numa=fake=<N>
4178			[KNL, ARM64, RISCV, X86, EARLY]
4179			If given as an integer, fills all system RAM with N
4180			fake nodes interleaved over physical nodes.
4181
4182	numa=fake=<N>U
4183			[KNL, ARM64, RISCV, X86, EARLY]
4184			If given as an integer followed by 'U', it will
4185			divide each physical node into N emulated nodes.
4186
4187	numa_balancing=	[KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4188			NUMA balancing.
4189			Allowed values are enable and disable
4190
4191	numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4192			'node', 'default' can be specified
4193			This can be set from sysctl after boot.
4194			See Documentation/admin-guide/sysctl/vm.rst for details.
4195
4196	ohci1394_dma=early	[HW,EARLY] enable debugging via the ohci1394 driver.
4197			See Documentation/core-api/debugging-via-ohci1394.rst for more
4198			info.
4199
4200	olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4201			Rather than timing out after 20 ms if an EC
4202			command is not properly ACKed, override the length
4203			of the timeout.  We have interrupts disabled while
4204			waiting for the ACK, so if this is set too high
4205			interrupts *may* be lost!
4206
4207	omap_mux=	[OMAP] Override bootloader pin multiplexing.
4208			Format: <mux_mode0.mode_name=value>...
4209			For example, to override I2C bus2:
4210			omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4211
4212	onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
4213
4214			Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4215
4216			boundary - index of last SLC block on Flex-OneNAND.
4217				   The remaining blocks are configured as MLC blocks.
4218			lock	 - Configure if Flex-OneNAND boundary should be locked.
4219				   Once locked, the boundary cannot be changed.
4220				   1 indicates lock status, 0 indicates unlock status.
4221
4222	oops=panic	[KNL,EARLY]
4223			Always panic on oopses. Default is to just kill the
4224			process, but there is a small probability of
4225			deadlocking the machine.
4226			This will also cause panics on machine check exceptions.
4227			Useful together with panic=30 to trigger a reboot.
4228
4229	page_alloc.shuffle=
4230			[KNL] Boolean flag to control whether the page allocator
4231			should randomize its free lists. This parameter can be
4232			used to enable/disable page randomization. The state of
4233			the flag can be read from sysfs at:
4234			/sys/module/page_alloc/parameters/shuffle.
4235			This parameter is only available if CONFIG_SHUFFLE_PAGE_ALLOCATOR=y.
4236
4237	page_owner=	[KNL,EARLY] Boot-time page_owner enabling option.
4238			Storage of the information about who allocated
4239			each page is disabled in default. With this switch,
4240			we can turn it on.
4241			on: enable the feature
4242
4243	page_poison=	[KNL,EARLY] Boot-time parameter changing the state of
4244			poisoning on the buddy allocator, available with
4245			CONFIG_PAGE_POISONING=y.
4246			off: turn off poisoning (default)
4247			on: turn on poisoning
4248
4249	page_reporting.page_reporting_order=
4250			[KNL] Minimal page reporting order
4251			Format: <integer>
4252			Adjust the minimal page reporting order. The page
4253			reporting is disabled when it exceeds MAX_PAGE_ORDER.
4254
4255	panic=		[KNL] Kernel behaviour on panic: delay <timeout>
4256			timeout > 0: seconds before rebooting
4257			timeout = 0: wait forever
4258			timeout < 0: reboot immediately
4259			Format: <timeout>
4260
4261	panic_on_taint=	[KNL,EARLY]
4262			Bitmask for conditionally calling panic() in add_taint()
4263			Format: <hex>[,nousertaint]
4264			Hexadecimal bitmask representing the set of TAINT flags
4265			that will cause the kernel to panic when add_taint() is
4266			called with any of the flags in this set.
4267			The optional switch "nousertaint" can be utilized to
4268			prevent userspace forced crashes by writing to sysctl
4269			/proc/sys/kernel/tainted any flagset matching with the
4270			bitmask set on panic_on_taint.
4271			See Documentation/admin-guide/tainted-kernels.rst for
4272			extra details on the taint flags that users can pick
4273			to compose the bitmask to assign to panic_on_taint.
4274
4275	panic_on_warn=1	panic() instead of WARN().  Useful to cause kdump
4276			on a WARN().
4277
4278	panic_print=	Bitmask for printing system info when panic happens.
4279			User can chose combination of the following bits:
4280			bit 0: print all tasks info
4281			bit 1: print system memory info
4282			bit 2: print timer info
4283			bit 3: print locks info if CONFIG_LOCKDEP is on
4284			bit 4: print ftrace buffer
4285			bit 5: print all printk messages in buffer
4286			bit 6: print all CPUs backtrace (if available in the arch)
4287			bit 7: print only tasks in uninterruptible (blocked) state
4288			*Be aware* that this option may print a _lot_ of lines,
4289			so there are risks of losing older messages in the log.
4290			Use this option carefully, maybe worth to setup a
4291			bigger log buffer with "log_buf_len" along with this.
4292
4293	parkbd.port=	[HW] Parallel port number the keyboard adapter is
4294			connected to, default is 0.
4295			Format: <parport#>
4296	parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
4297			0 for XT, 1 for AT (default is AT).
4298			Format: <mode>
4299
4300	parport=	[HW,PPT] Specify parallel ports. 0 disables.
4301			Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4302			Use 'auto' to force the driver to use any
4303			IRQ/DMA settings detected (the default is to
4304			ignore detected IRQ/DMA settings because of
4305			possible conflicts). You can specify the base
4306			address, IRQ, and DMA settings; IRQ and DMA
4307			should be numbers, or 'auto' (for using detected
4308			settings on that particular port), or 'nofifo'
4309			(to avoid using a FIFO even if it is detected).
4310			Parallel ports are assigned in the order they
4311			are specified on the command line, starting
4312			with parport0.
4313
4314	parport_init_mode=	[HW,PPT]
4315			Configure VIA parallel port to operate in
4316			a specific mode. This is necessary on Pegasos
4317			computer where firmware has no options for setting
4318			up parallel port mode and sets it to spp.
4319			Currently this function knows 686a and 8231 chips.
4320			Format: [spp|ps2|epp|ecp|ecpepp]
4321
4322	pata_legacy.all=	[HW,LIBATA]
4323			Format: <int>
4324			Set to non-zero to probe primary and secondary ISA
4325			port ranges on PCI systems where no PCI PATA device
4326			has been found at either range.  Disabled by default.
4327
4328	pata_legacy.autospeed=	[HW,LIBATA]
4329			Format: <int>
4330			Set to non-zero if a chip is present that snoops speed
4331			changes.  Disabled by default.
4332
4333	pata_legacy.ht6560a=	[HW,LIBATA]
4334			Format: <int>
4335			Set to 1, 2, or 3 for HT 6560A on the primary channel,
4336			the secondary channel, or both channels respectively.
4337			Disabled by default.
4338
4339	pata_legacy.ht6560b=	[HW,LIBATA]
4340			Format: <int>
4341			Set to 1, 2, or 3 for HT 6560B on the primary channel,
4342			the secondary channel, or both channels respectively.
4343			Disabled by default.
4344
4345	pata_legacy.iordy_mask=	[HW,LIBATA]
4346			Format: <int>
4347			IORDY enable mask.  Set individual bits to allow IORDY
4348			for the respective channel.  Bit 0 is for the first
4349			legacy channel handled by this driver, bit 1 is for
4350			the second channel, and so on.  The sequence will often
4351			correspond to the primary legacy channel, the secondary
4352			legacy channel, and so on, but the handling of a PCI
4353			bus and the use of other driver options may interfere
4354			with the sequence.  By default IORDY is allowed across
4355			all channels.
4356
4357	pata_legacy.opti82c46x=	[HW,LIBATA]
4358			Format: <int>
4359			Set to 1, 2, or 3 for Opti 82c611A on the primary
4360			channel, the secondary channel, or both channels
4361			respectively.  Disabled by default.
4362
4363	pata_legacy.opti82c611a=	[HW,LIBATA]
4364			Format: <int>
4365			Set to 1, 2, or 3 for Opti 82c465MV on the primary
4366			channel, the secondary channel, or both channels
4367			respectively.  Disabled by default.
4368
4369	pata_legacy.pio_mask=	[HW,LIBATA]
4370			Format: <int>
4371			PIO mode mask for autospeed devices.  Set individual
4372			bits to allow the use of the respective PIO modes.
4373			Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4374			All modes allowed by default.
4375
4376	pata_legacy.probe_all=	[HW,LIBATA]
4377			Format: <int>
4378			Set to non-zero to probe tertiary and further ISA
4379			port ranges on PCI systems.  Disabled by default.
4380
4381	pata_legacy.probe_mask=	[HW,LIBATA]
4382			Format: <int>
4383			Probe mask for legacy ISA PATA ports.  Depending on
4384			platform configuration and the use of other driver
4385			options up to 6 legacy ports are supported: 0x1f0,
4386			0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4387			of individual ports can be disabled by setting the
4388			corresponding bits in the mask to 1.  Bit 0 is for
4389			the first port in the list above (0x1f0), and so on.
4390			By default all supported ports are probed.
4391
4392	pata_legacy.qdi=	[HW,LIBATA]
4393			Format: <int>
4394			Set to non-zero to probe QDI controllers.  By default
4395			set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4396
4397	pata_legacy.winbond=	[HW,LIBATA]
4398			Format: <int>
4399			Set to non-zero to probe Winbond controllers.  Use
4400			the standard I/O port (0x130) if 1, otherwise the
4401			value given is the I/O port to use (typically 0x1b0).
4402			By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4403			0 otherwise.
4404
4405	pata_platform.pio_mask=	[HW,LIBATA]
4406			Format: <int>
4407			Supported PIO mode mask.  Set individual bits to allow
4408			the use of the respective PIO modes.  Bit 0 is for
4409			mode 0, bit 1 is for mode 1, and so on.  Mode 0 only
4410			allowed by default.
4411
4412	pause_on_oops=<int>
4413			Halt all CPUs after the first oops has been printed for
4414			the specified number of seconds.  This is to be used if
4415			your oopses keep scrolling off the screen.
4416
4417	pcbit=		[HW,ISDN]
4418
4419	pci=option[,option...]	[PCI,EARLY] various PCI subsystem options.
4420
4421				Some options herein operate on a specific device
4422				or a set of devices (<pci_dev>). These are
4423				specified in one of the following formats:
4424
4425				[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4426				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4427
4428				Note: the first format specifies a PCI
4429				bus/device/function address which may change
4430				if new hardware is inserted, if motherboard
4431				firmware changes, or due to changes caused
4432				by other kernel parameters. If the
4433				domain is left unspecified, it is
4434				taken to be zero. Optionally, a path
4435				to a device through multiple device/function
4436				addresses can be specified after the base
4437				address (this is more robust against
4438				renumbering issues).  The second format
4439				selects devices using IDs from the
4440				configuration space which may match multiple
4441				devices in the system.
4442
4443		earlydump	dump PCI config space before the kernel
4444				changes anything
4445		off		[X86] don't probe for the PCI bus
4446		bios		[X86-32] force use of PCI BIOS, don't access
4447				the hardware directly. Use this if your machine
4448				has a non-standard PCI host bridge.
4449		nobios		[X86-32] disallow use of PCI BIOS, only direct
4450				hardware access methods are allowed. Use this
4451				if you experience crashes upon bootup and you
4452				suspect they are caused by the BIOS.
4453		conf1		[X86] Force use of PCI Configuration Access
4454				Mechanism 1 (config address in IO port 0xCF8,
4455				data in IO port 0xCFC, both 32-bit).
4456		conf2		[X86] Force use of PCI Configuration Access
4457				Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4458				the function, IO port 0xCFA, also 8-bit, sets
4459				bus number. The config space is then accessed
4460				through ports 0xC000-0xCFFF).
4461				See http://wiki.osdev.org/PCI for more info
4462				on the configuration access mechanisms.
4463		noaer		[PCIE] If the PCIEAER kernel config parameter is
4464				enabled, this kernel boot option can be used to
4465				disable the use of PCIE advanced error reporting.
4466		nodomains	[PCI] Disable support for multiple PCI
4467				root domains (aka PCI segments, in ACPI-speak).
4468		nommconf	[X86] Disable use of MMCONFIG for PCI
4469				Configuration
4470		check_enable_amd_mmconf [X86] check for and enable
4471				properly configured MMIO access to PCI
4472				config space on AMD family 10h CPU
4473		nomsi		[MSI] If the PCI_MSI kernel config parameter is
4474				enabled, this kernel boot option can be used to
4475				disable the use of MSI interrupts system-wide.
4476		noioapicquirk	[APIC] Disable all boot interrupt quirks.
4477				Safety option to keep boot IRQs enabled. This
4478				should never be necessary.
4479		ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
4480				primary IO-APIC for bridges that cannot disable
4481				boot IRQs. This fixes a source of spurious IRQs
4482				when the system masks IRQs.
4483		noioapicreroute	[APIC] Disable workaround that uses the
4484				boot IRQ equivalent of an IRQ that connects to
4485				a chipset where boot IRQs cannot be disabled.
4486				The opposite of ioapicreroute.
4487		biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
4488				routing table. These calls are known to be buggy
4489				on several machines and they hang the machine
4490				when used, but on other computers it's the only
4491				way to get the interrupt routing table. Try
4492				this option if the kernel is unable to allocate
4493				IRQs or discover secondary PCI buses on your
4494				motherboard.
4495		rom		[X86] Assign address space to expansion ROMs.
4496				Use with caution as certain devices share
4497				address decoders between ROMs and other
4498				resources.
4499		norom		[X86] Do not assign address space to
4500				expansion ROMs that do not already have
4501				BIOS assigned address ranges.
4502		nobar		[X86] Do not assign address space to the
4503				BARs that weren't assigned by the BIOS.
4504		irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
4505				assigned automatically to PCI devices. You can
4506				make the kernel exclude IRQs of your ISA cards
4507				this way.
4508		pirqaddr=0xAAAAA	[X86] Specify the physical address
4509				of the PIRQ table (normally generated
4510				by the BIOS) if it is outside the
4511				F0000h-100000h range.
4512		lastbus=N	[X86] Scan all buses thru bus #N. Can be
4513				useful if the kernel is unable to find your
4514				secondary buses and you want to tell it
4515				explicitly which ones they are.
4516		assign-busses	[X86] Always assign all PCI bus
4517				numbers ourselves, overriding
4518				whatever the firmware may have done.
4519		usepirqmask	[X86] Honor the possible IRQ mask stored
4520				in the BIOS $PIR table. This is needed on
4521				some systems with broken BIOSes, notably
4522				some HP Pavilion N5400 and Omnibook XE3
4523				notebooks. This will have no effect if ACPI
4524				IRQ routing is enabled.
4525		noacpi		[X86] Do not use ACPI for IRQ routing
4526				or for PCI scanning.
4527		use_crs		[X86] Use PCI host bridge window information
4528				from ACPI.  On BIOSes from 2008 or later, this
4529				is enabled by default.  If you need to use this,
4530				please report a bug.
4531		nocrs		[X86] Ignore PCI host bridge windows from ACPI.
4532				If you need to use this, please report a bug.
4533		use_e820	[X86] Use E820 reservations to exclude parts of
4534				PCI host bridge windows. This is a workaround
4535				for BIOS defects in host bridge _CRS methods.
4536				If you need to use this, please report a bug to
4537				<linux-pci@vger.kernel.org>.
4538		no_e820		[X86] Ignore E820 reservations for PCI host
4539				bridge windows. This is the default on modern
4540				hardware. If you need to use this, please report
4541				a bug to <linux-pci@vger.kernel.org>.
4542		routeirq	Do IRQ routing for all PCI devices.
4543				This is normally done in pci_enable_device(),
4544				so this option is a temporary workaround
4545				for broken drivers that don't call it.
4546		skip_isa_align	[X86] do not align io start addr, so can
4547				handle more pci cards
4548		noearly		[X86] Don't do any early type 1 scanning.
4549				This might help on some broken boards which
4550				machine check when some devices' config space
4551				is read. But various workarounds are disabled
4552				and some IOMMU drivers will not work.
4553		bfsort		Sort PCI devices into breadth-first order.
4554				This sorting is done to get a device
4555				order compatible with older (<= 2.4) kernels.
4556		nobfsort	Don't sort PCI devices into breadth-first order.
4557		pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
4558				tuning and use the BIOS-configured MPS defaults.
4559		pcie_bus_safe	Set every device's MPS to the largest value
4560				supported by all devices below the root complex.
4561		pcie_bus_perf	Set device MPS to the largest allowable MPS
4562				based on its parent bus. Also set MRRS (Max
4563				Read Request Size) to the largest supported
4564				value (no larger than the MPS that the device
4565				or bus can support) for best performance.
4566		pcie_bus_peer2peer	Set every device's MPS to 128B, which
4567				every device is guaranteed to support. This
4568				configuration allows peer-to-peer DMA between
4569				any pair of devices, possibly at the cost of
4570				reduced performance.  This also guarantees
4571				that hot-added devices will work.
4572		cbiosize=nn[KMG]	The fixed amount of bus space which is
4573				reserved for the CardBus bridge's IO window.
4574				The default value is 256 bytes.
4575		cbmemsize=nn[KMG]	The fixed amount of bus space which is
4576				reserved for the CardBus bridge's memory
4577				window. The default value is 64 megabytes.
4578		resource_alignment=
4579				Format:
4580				[<order of align>@]<pci_dev>[; ...]
4581				Specifies alignment and device to reassign
4582				aligned memory resources. How to
4583				specify the device is described above.
4584				If <order of align> is not specified,
4585				PAGE_SIZE is used as alignment.
4586				A PCI-PCI bridge can be specified if resource
4587				windows need to be expanded.
4588				To specify the alignment for several
4589				instances of a device, the PCI vendor,
4590				device, subvendor, and subdevice may be
4591				specified, e.g., 12@pci:8086:9c22:103c:198f
4592				for 4096-byte alignment.
4593		ecrc=		Enable/disable PCIe ECRC (transaction layer
4594				end-to-end CRC checking). Only effective if
4595				OS has native AER control (either granted by
4596				ACPI _OSC or forced via "pcie_ports=native")
4597				bios: Use BIOS/firmware settings. This is the
4598				the default.
4599				off: Turn ECRC off
4600				on: Turn ECRC on.
4601		hpiosize=nn[KMG]	The fixed amount of bus space which is
4602				reserved for hotplug bridge's IO window.
4603				Default size is 256 bytes.
4604		hpmmiosize=nn[KMG]	The fixed amount of bus space which is
4605				reserved for hotplug bridge's MMIO window.
4606				Default size is 2 megabytes.
4607		hpmmioprefsize=nn[KMG]	The fixed amount of bus space which is
4608				reserved for hotplug bridge's MMIO_PREF window.
4609				Default size is 2 megabytes.
4610		hpmemsize=nn[KMG]	The fixed amount of bus space which is
4611				reserved for hotplug bridge's MMIO and
4612				MMIO_PREF window.
4613				Default size is 2 megabytes.
4614		hpbussize=nn	The minimum amount of additional bus numbers
4615				reserved for buses below a hotplug bridge.
4616				Default is 1.
4617		realloc=	Enable/disable reallocating PCI bridge resources
4618				if allocations done by BIOS are too small to
4619				accommodate resources required by all child
4620				devices.
4621				off: Turn realloc off
4622				on: Turn realloc on
4623		realloc		same as realloc=on
4624		noari		do not use PCIe ARI.
4625		noats		[PCIE, Intel-IOMMU, AMD-IOMMU]
4626				do not use PCIe ATS (and IOMMU device IOTLB).
4627		pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
4628				only look for one device below a PCIe downstream
4629				port.
4630		big_root_window	Try to add a big 64bit memory window to the PCIe
4631				root complex on AMD CPUs. Some GFX hardware
4632				can resize a BAR to allow access to all VRAM.
4633				Adding the window is slightly risky (it may
4634				conflict with unreported devices), so this
4635				taints the kernel.
4636		disable_acs_redir=<pci_dev>[; ...]
4637				Specify one or more PCI devices (in the format
4638				specified above) separated by semicolons.
4639				Each device specified will have the PCI ACS
4640				redirect capabilities forced off which will
4641				allow P2P traffic between devices through
4642				bridges without forcing it upstream. Note:
4643				this removes isolation between devices and
4644				may put more devices in an IOMMU group.
4645		config_acs=
4646				Format:
4647				<ACS flags>@<pci_dev>[; ...]
4648				Specify one or more PCI devices (in the format
4649				specified above) optionally prepended with flags
4650				and separated by semicolons. The respective
4651				capabilities will be enabled, disabled or
4652				unchanged based on what is specified in
4653				flags.
4654
4655				ACS Flags is defined as follows:
4656				  bit-0 : ACS Source Validation
4657				  bit-1 : ACS Translation Blocking
4658				  bit-2 : ACS P2P Request Redirect
4659				  bit-3 : ACS P2P Completion Redirect
4660				  bit-4 : ACS Upstream Forwarding
4661				  bit-5 : ACS P2P Egress Control
4662				  bit-6 : ACS Direct Translated P2P
4663				Each bit can be marked as:
4664				  '0' – force disabled
4665				  '1' – force enabled
4666				  'x' – unchanged
4667				For example,
4668				  pci=config_acs=10x
4669				would configure all devices that support
4670				ACS to enable P2P Request Redirect, disable
4671				Translation Blocking, and leave Source
4672				Validation unchanged from whatever power-up
4673				or firmware set it to.
4674
4675				Note: this may remove isolation between devices
4676				and may put more devices in an IOMMU group.
4677		force_floating	[S390] Force usage of floating interrupts.
4678		nomio		[S390] Do not use MIO instructions.
4679		norid		[S390] ignore the RID field and force use of
4680				one PCI domain per PCI function
4681
4682	pcie_aspm=	[PCIE] Forcibly enable or ignore PCIe Active State Power
4683			Management.
4684		off	Don't touch ASPM configuration at all.  Leave any
4685			configuration done by firmware unchanged.
4686		force	Enable ASPM even on devices that claim not to support it.
4687			WARNING: Forcing ASPM on may cause system lockups.
4688
4689	pcie_ports=	[PCIE] PCIe port services handling:
4690		native	Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4691			even if the platform doesn't give the OS permission to
4692			use them.  This may cause conflicts if the platform
4693			also tries to use these services.
4694		dpc-native	Use native PCIe service for DPC only.  May
4695				cause conflicts if firmware uses AER or DPC.
4696		compat	Disable native PCIe services (PME, AER, DPC, PCIe
4697			hotplug).
4698
4699	pcie_port_pm=	[PCIE] PCIe port power management handling:
4700		off	Disable power management of all PCIe ports
4701		force	Forcibly enable power management of all PCIe ports
4702
4703	pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
4704		nomsi	Do not use MSI for native PCIe PME signaling (this makes
4705			all PCIe root ports use INTx for all services).
4706
4707	pcmv=		[HW,PCMCIA] BadgePAD 4
4708
4709	pd_ignore_unused
4710			[PM]
4711			Keep all power-domains already enabled by bootloader on,
4712			even if no driver has claimed them. This is useful
4713			for debug and development, but should not be
4714			needed on a platform with proper driver support.
4715
4716	pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
4717			boot time.
4718			Format: { 0 | 1 }
4719			See arch/parisc/kernel/pdc_chassis.c
4720
4721	percpu_alloc=	[MM,EARLY]
4722			Select which percpu first chunk allocator to use.
4723			Currently supported values are "embed" and "page".
4724			Archs may support subset or none of the	selections.
4725			See comments in mm/percpu.c for details on each
4726			allocator.  This parameter is primarily	for debugging
4727			and performance comparison.
4728
4729	pirq=		[SMP,APIC] Manual mp-table setup
4730			See Documentation/arch/x86/i386/IO-APIC.rst.
4731
4732	plip=		[PPT,NET] Parallel port network link
4733			Format: { parport<nr> | timid | 0 }
4734			See also Documentation/admin-guide/parport.rst.
4735
4736	pmtmr=		[X86] Manual setup of pmtmr I/O Port.
4737			Override pmtimer IOPort with a hex value.
4738			e.g. pmtmr=0x508
4739
4740	pmu_override=	[PPC] Override the PMU.
4741			This option takes over the PMU facility, so it is no
4742			longer usable by perf. Setting this option starts the
4743			PMU counters by setting MMCR0 to 0 (the FC bit is
4744			cleared). If a number is given, then MMCR1 is set to
4745			that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4746			remains 0.
4747
4748	pm_debug_messages	[SUSPEND,KNL]
4749			Enable suspend/resume debug messages during boot up.
4750
4751	pnp.debug=1	[PNP]
4752			Enable PNP debug messages (depends on the
4753			CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
4754			via /sys/module/pnp/parameters/debug.  We always show
4755			current resource usage; turning this on also shows
4756			possible settings and some assignment information.
4757
4758	pnpacpi=	[ACPI]
4759			{ off }
4760
4761	pnpbios=	[ISAPNP]
4762			{ on | off | curr | res | no-curr | no-res }
4763
4764	pnp_reserve_irq=
4765			[ISAPNP] Exclude IRQs for the autoconfiguration
4766
4767	pnp_reserve_dma=
4768			[ISAPNP] Exclude DMAs for the autoconfiguration
4769
4770	pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
4771			Ranges are in pairs (I/O port base and size).
4772
4773	pnp_reserve_mem=
4774			[ISAPNP] Exclude memory regions for the
4775			autoconfiguration.
4776			Ranges are in pairs (memory base and size).
4777
4778	ports=		[IP_VS_FTP] IPVS ftp helper module
4779			Default is 21.
4780			Up to 8 (IP_VS_APP_MAX_PORTS) ports
4781			may be specified.
4782			Format: <port>,<port>....
4783
4784	possible_cpus=  [SMP,S390,X86]
4785			Format: <unsigned int>
4786			Set the number of possible CPUs, overriding the
4787			regular discovery mechanisms (such as ACPI/FW, etc).
4788
4789	powersave=off	[PPC] This option disables power saving features.
4790			It specifically disables cpuidle and sets the
4791			platform machine description specific power_save
4792			function to NULL. On Idle the CPU just reduces
4793			execution priority.
4794
4795	ppc_strict_facility_enable
4796			[PPC,ENABLE] This option catches any kernel floating point,
4797			Altivec, VSX and SPE outside of regions specifically
4798			allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4799			There is some performance impact when enabling this.
4800
4801	ppc_tm=		[PPC,EARLY]
4802			Format: {"off"}
4803			Disable Hardware Transactional Memory
4804
4805	preempt=	[KNL]
4806			Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4807			none - Limited to cond_resched() calls
4808			voluntary - Limited to cond_resched() and might_sleep() calls
4809			full - Any section that isn't explicitly preempt disabled
4810			       can be preempted anytime.  Tasks will also yield
4811			       contended spinlocks (if the critical section isn't
4812			       explicitly preempt disabled beyond the lock itself).
4813
4814	print-fatal-signals=
4815			[KNL] debug: print fatal signals
4816
4817			If enabled, warn about various signal handling
4818			related application anomalies: too many signals,
4819			too many POSIX.1 timers, fatal signals causing a
4820			coredump - etc.
4821
4822			If you hit the warning due to signal overflow,
4823			you might want to try "ulimit -i unlimited".
4824
4825			default: off.
4826
4827	printk.always_kmsg_dump=
4828			Trigger kmsg_dump for cases other than kernel oops or
4829			panics
4830			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
4831			default: disabled
4832
4833	printk.console_no_auto_verbose=
4834			Disable console loglevel raise on oops, panic
4835			or lockdep-detected issues (only if lock debug is on).
4836			With an exception to setups with low baudrate on
4837			serial console, keeping this 0 is a good choice
4838			in order to provide more debug information.
4839			Format: <bool>
4840			default: 0 (auto_verbose is enabled)
4841
4842	printk.devkmsg={on,off,ratelimit}
4843			Control writing to /dev/kmsg.
4844			on - unlimited logging to /dev/kmsg from userspace
4845			off - logging to /dev/kmsg disabled
4846			ratelimit - ratelimit the logging
4847			Default: ratelimit
4848
4849	printk.time=	Show timing data prefixed to each printk message line
4850			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
4851
4852	proc_mem.force_override= [KNL]
4853			Format: {always | ptrace | never}
4854			Traditionally /proc/pid/mem allows memory permissions to be
4855			overridden without restrictions. This option may be set to
4856			restrict that. Can be one of:
4857			- 'always': traditional behavior always allows mem overrides.
4858			- 'ptrace': only allow mem overrides for active ptracers.
4859			- 'never':  never allow mem overrides.
4860			If not specified, default is the CONFIG_PROC_MEM_* choice.
4861
4862	processor.max_cstate=	[HW,ACPI]
4863			Limit processor to maximum C-state
4864			max_cstate=9 overrides any DMI blacklist limit.
4865
4866	processor.nocst	[HW,ACPI]
4867			Ignore the _CST method to determine C-states,
4868			instead using the legacy FADT method
4869
4870	profile=	[KNL] Enable kernel profiling via /proc/profile
4871			Format: [<profiletype>,]<number>
4872			Param: <profiletype>: "schedule" or "kvm"
4873				[defaults to kernel profiling]
4874			Param: "schedule" - profile schedule points.
4875			Param: "kvm" - profile VM exits.
4876			Param: <number> - step/bucket size as a power of 2 for
4877				statistical time based profiling.
4878
4879	prompt_ramdisk=	[RAM] [Deprecated]
4880
4881	prot_virt=	[S390] enable hosting protected virtual machines
4882			isolated from the hypervisor (if hardware supports
4883			that). If enabled, the default kernel base address
4884			might be overridden even when Kernel Address Space
4885			Layout Randomization is disabled.
4886			Format: <bool>
4887
4888	psi=		[KNL] Enable or disable pressure stall information
4889			tracking.
4890			Format: <bool>
4891
4892	psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
4893			probe for; one of (bare|imps|exps|lifebook|any).
4894	psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
4895			per second.
4896	psmouse.resetafter=	[HW,MOUSE]
4897			Try to reset the device after so many bad packets
4898			(0 = never).
4899	psmouse.resolution=
4900			[HW,MOUSE] Set desired mouse resolution, in dpi.
4901	psmouse.smartscroll=
4902			[HW,MOUSE] Controls Logitech smartscroll autorepeat.
4903			0 = disabled, 1 = enabled (default).
4904
4905	pstore.backend=	Specify the name of the pstore backend to use
4906
4907	pti=		[X86-64] Control Page Table Isolation of user and
4908			kernel address spaces.  Disabling this feature
4909			removes hardening, but improves performance of
4910			system calls and interrupts.
4911
4912			on   - unconditionally enable
4913			off  - unconditionally disable
4914			auto - kernel detects whether your CPU model is
4915			       vulnerable to issues that PTI mitigates
4916
4917			Not specifying this option is equivalent to pti=auto.
4918
4919	pty.legacy_count=
4920			[KNL] Number of legacy pty's. Overwrites compiled-in
4921			default number.
4922
4923	quiet		[KNL,EARLY] Disable most log messages
4924
4925	r128=		[HW,DRM]
4926
4927	radix_hcall_invalidate=on  [PPC/PSERIES]
4928			Disable RADIX GTSE feature and use hcall for TLB
4929			invalidate.
4930
4931	raid=		[HW,RAID]
4932			See Documentation/admin-guide/md.rst.
4933
4934	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
4935			See Documentation/admin-guide/blockdev/ramdisk.rst.
4936
4937	ramdisk_start=	[RAM] RAM disk image start address
4938
4939	random.trust_cpu=off
4940			[KNL,EARLY] Disable trusting the use of the CPU's
4941			random number generator (if available) to
4942			initialize the kernel's RNG.
4943
4944	random.trust_bootloader=off
4945			[KNL,EARLY] Disable trusting the use of the a seed
4946			passed by the bootloader (if available) to
4947			initialize the kernel's RNG.
4948
4949	randomize_kstack_offset=
4950			[KNL,EARLY] Enable or disable kernel stack offset
4951			randomization, which provides roughly 5 bits of
4952			entropy, frustrating memory corruption attacks
4953			that depend on stack address determinism or
4954			cross-syscall address exposures. This is only
4955			available on architectures that have defined
4956			CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4957			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
4958			Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4959
4960	ras=option[,option,...]	[KNL] RAS-specific options
4961
4962		cec_disable	[X86]
4963				Disable the Correctable Errors Collector,
4964				see CONFIG_RAS_CEC help text.
4965
4966	rcu_nocbs[=cpu-list]
4967			[KNL] The optional argument is a cpu list,
4968			as described above.
4969
4970			In kernels built with CONFIG_RCU_NOCB_CPU=y,
4971			enable the no-callback CPU mode, which prevents
4972			such CPUs' callbacks from being invoked in
4973			softirq context.  Invocation of such CPUs' RCU
4974			callbacks will instead be offloaded to "rcuox/N"
4975			kthreads created for that purpose, where "x" is
4976			"p" for RCU-preempt, "s" for RCU-sched, and "g"
4977			for the kthreads that mediate grace periods; and
4978			"N" is the CPU number. This reduces OS jitter on
4979			the offloaded CPUs, which can be useful for HPC
4980			and real-time workloads.  It can also improve
4981			energy efficiency for asymmetric multiprocessors.
4982
4983			If a cpulist is passed as an argument, the specified
4984			list of	CPUs is set to no-callback mode from boot.
4985
4986			Otherwise, if the '=' sign and the cpulist
4987			arguments are omitted, no CPU will be set to
4988			no-callback mode from boot but the mode may be
4989			toggled at runtime via cpusets.
4990
4991			Note that this argument takes precedence over
4992			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4993
4994	rcu_nocb_poll	[KNL]
4995			Rather than requiring that offloaded CPUs
4996			(specified by rcu_nocbs= above) explicitly
4997			awaken the corresponding "rcuoN" kthreads,
4998			make these kthreads poll for callbacks.
4999			This improves the real-time response for the
5000			offloaded CPUs by relieving them of the need to
5001			wake up the corresponding kthread, but degrades
5002			energy efficiency by requiring that the kthreads
5003			periodically wake up to do the polling.
5004
5005	rcutree.blimit=	[KNL]
5006			Set maximum number of finished RCU callbacks to
5007			process in one batch.
5008
5009	rcutree.csd_lock_suppress_rcu_stall=	[KNL]
5010			Do only a one-line RCU CPU stall warning when
5011			there is an ongoing too-long CSD-lock wait.
5012
5013	rcutree.do_rcu_barrier=	[KNL]
5014			Request a call to rcu_barrier().  This is
5015			throttled so that userspace tests can safely
5016			hammer on the sysfs variable if they so choose.
5017			If triggered before the RCU grace-period machinery
5018			is fully active, this will error out with EAGAIN.
5019
5020	rcutree.dump_tree=	[KNL]
5021			Dump the structure of the rcu_node combining tree
5022			out at early boot.  This is used for diagnostic
5023			purposes, to verify correct tree setup.
5024
5025	rcutree.gp_cleanup_delay=	[KNL]
5026			Set the number of jiffies to delay each step of
5027			RCU grace-period cleanup.
5028
5029	rcutree.gp_init_delay=	[KNL]
5030			Set the number of jiffies to delay each step of
5031			RCU grace-period initialization.
5032
5033	rcutree.gp_preinit_delay=	[KNL]
5034			Set the number of jiffies to delay each step of
5035			RCU grace-period pre-initialization, that is,
5036			the propagation of recent CPU-hotplug changes up
5037			the rcu_node combining tree.
5038
5039	rcutree.jiffies_till_first_fqs= [KNL]
5040			Set delay from grace-period initialization to
5041			first attempt to force quiescent states.
5042			Units are jiffies, minimum value is zero,
5043			and maximum value is HZ.
5044
5045	rcutree.jiffies_till_next_fqs= [KNL]
5046			Set delay between subsequent attempts to force
5047			quiescent states.  Units are jiffies, minimum
5048			value is one, and maximum value is HZ.
5049
5050	rcutree.jiffies_till_sched_qs= [KNL]
5051			Set required age in jiffies for a
5052			given grace period before RCU starts
5053			soliciting quiescent-state help from
5054			rcu_note_context_switch() and cond_resched().
5055			If not specified, the kernel will calculate
5056			a value based on the most recent settings
5057			of rcutree.jiffies_till_first_fqs
5058			and rcutree.jiffies_till_next_fqs.
5059			This calculated value may be viewed in
5060			rcutree.jiffies_to_sched_qs.  Any attempt to set
5061			rcutree.jiffies_to_sched_qs will be cheerfully
5062			overwritten.
5063
5064	rcutree.kthread_prio= 	 [KNL,BOOT]
5065			Set the SCHED_FIFO priority of the RCU per-CPU
5066			kthreads (rcuc/N). This value is also used for
5067			the priority of the RCU boost threads (rcub/N)
5068			and for the RCU grace-period kthreads (rcu_bh,
5069			rcu_preempt, and rcu_sched). If RCU_BOOST is
5070			set, valid values are 1-99 and the default is 1
5071			(the least-favored priority).  Otherwise, when
5072			RCU_BOOST is not set, valid values are 0-99 and
5073			the default is zero (non-realtime operation).
5074			When RCU_NOCB_CPU is set, also adjust the
5075			priority of NOCB callback kthreads.
5076
5077	rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5078			On callback-offloaded (rcu_nocbs) CPUs,
5079			RCU reduces the lock contention that would
5080			otherwise be caused by callback floods through
5081			use of the ->nocb_bypass list.	However, in the
5082			common non-flooded case, RCU queues directly to
5083			the main ->cblist in order to avoid the extra
5084			overhead of the ->nocb_bypass list and its lock.
5085			But if there are too many callbacks queued during
5086			a single jiffy, RCU pre-queues the callbacks into
5087			the ->nocb_bypass queue.  The definition of "too
5088			many" is supplied by this kernel boot parameter.
5089
5090	rcutree.nohz_full_patience_delay= [KNL]
5091			On callback-offloaded (rcu_nocbs) CPUs, avoid
5092			disturbing RCU unless the grace period has
5093			reached the specified age in milliseconds.
5094			Defaults to zero.  Large values will be capped
5095			at five seconds.  All values will be rounded down
5096			to the nearest value representable by jiffies.
5097
5098	rcutree.qhimark= [KNL]
5099			Set threshold of queued RCU callbacks beyond which
5100			batch limiting is disabled.
5101
5102	rcutree.qlowmark= [KNL]
5103			Set threshold of queued RCU callbacks below which
5104			batch limiting is re-enabled.
5105
5106	rcutree.qovld= [KNL]
5107			Set threshold of queued RCU callbacks beyond which
5108			RCU's force-quiescent-state scan will aggressively
5109			enlist help from cond_resched() and sched IPIs to
5110			help CPUs more quickly reach quiescent states.
5111			Set to less than zero to make this be set based
5112			on rcutree.qhimark at boot time and to zero to
5113			disable more aggressive help enlistment.
5114
5115	rcutree.rcu_delay_page_cache_fill_msec= [KNL]
5116			Set the page-cache refill delay (in milliseconds)
5117			in response to low-memory conditions.  The range
5118			of permitted values is in the range 0:100000.
5119
5120	rcutree.rcu_divisor= [KNL]
5121			Set the shift-right count to use to compute
5122			the callback-invocation batch limit bl from
5123			the number of callbacks queued on this CPU.
5124			The result will be bounded below by the value of
5125			the rcutree.blimit kernel parameter.  Every bl
5126			callbacks, the softirq handler will exit in
5127			order to allow the CPU to do other work.
5128
5129			Please note that this callback-invocation batch
5130			limit applies only to non-offloaded callback
5131			invocation.  Offloaded callbacks are instead
5132			invoked in the context of an rcuoc kthread, which
5133			scheduler will preempt as it does any other task.
5134
5135	rcutree.rcu_fanout_exact= [KNL]
5136			Disable autobalancing of the rcu_node combining
5137			tree.  This is used by rcutorture, and might
5138			possibly be useful for architectures having high
5139			cache-to-cache transfer latencies.
5140
5141	rcutree.rcu_fanout_leaf= [KNL]
5142			Change the number of CPUs assigned to each
5143			leaf rcu_node structure.  Useful for very
5144			large systems, which will choose the value 64,
5145			and for NUMA systems with large remote-access
5146			latencies, which will choose a value aligned
5147			with the appropriate hardware boundaries.
5148
5149	rcutree.rcu_min_cached_objs= [KNL]
5150			Minimum number of objects which are cached and
5151			maintained per one CPU. Object size is equal
5152			to PAGE_SIZE. The cache allows to reduce the
5153			pressure to page allocator, also it makes the
5154			whole algorithm to behave better in low memory
5155			condition.
5156
5157	rcutree.rcu_nocb_gp_stride= [KNL]
5158			Set the number of NOCB callback kthreads in
5159			each group, which defaults to the square root
5160			of the number of CPUs.	Larger numbers reduce
5161			the wakeup overhead on the global grace-period
5162			kthread, but increases that same overhead on
5163			each group's NOCB grace-period kthread.
5164
5165	rcutree.rcu_kick_kthreads= [KNL]
5166			Cause the grace-period kthread to get an extra
5167			wake_up() if it sleeps three times longer than
5168			it should at force-quiescent-state time.
5169			This wake_up() will be accompanied by a
5170			WARN_ONCE() splat and an ftrace_dump().
5171
5172	rcutree.rcu_resched_ns= [KNL]
5173			Limit the time spend invoking a batch of RCU
5174			callbacks to the specified number of nanoseconds.
5175			By default, this limit is checked only once
5176			every 32 callbacks in order to limit the pain
5177			inflicted by local_clock() overhead.
5178
5179	rcutree.rcu_unlock_delay= [KNL]
5180			In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5181			this specifies an rcu_read_unlock()-time delay
5182			in microseconds.  This defaults to zero.
5183			Larger delays increase the probability of
5184			catching RCU pointer leaks, that is, buggy use
5185			of RCU-protected pointers after the relevant
5186			rcu_read_unlock() has completed.
5187
5188	rcutree.sysrq_rcu= [KNL]
5189			Commandeer a sysrq key to dump out Tree RCU's
5190			rcu_node tree with an eye towards determining
5191			why a new grace period has not yet started.
5192
5193	rcutree.use_softirq=	[KNL]
5194			If set to zero, move all RCU_SOFTIRQ processing to
5195			per-CPU rcuc kthreads.  Defaults to a non-zero
5196			value, meaning that RCU_SOFTIRQ is used by default.
5197			Specify rcutree.use_softirq=0 to use rcuc kthreads.
5198
5199			But note that CONFIG_PREEMPT_RT=y kernels disable
5200			this kernel boot parameter, forcibly setting it
5201			to zero.
5202
5203	rcutree.enable_rcu_lazy= [KNL]
5204			To save power, batch RCU callbacks and flush after
5205			delay, memory pressure or callback list growing too
5206			big.
5207
5208	rcutree.rcu_normal_wake_from_gp= [KNL]
5209			Reduces a latency of synchronize_rcu() call. This approach
5210			maintains its own track of synchronize_rcu() callers, so it
5211			does not interact with regular callbacks because it does not
5212			use a call_rcu[_hurry]() path. Please note, this is for a
5213			normal grace period.
5214
5215			How to enable it:
5216
5217			echo 1 > /sys/module/rcutree/parameters/rcu_normal_wake_from_gp
5218			or pass a boot parameter "rcutree.rcu_normal_wake_from_gp=1"
5219
5220			Default is 0.
5221
5222	rcuscale.gp_async= [KNL]
5223			Measure performance of asynchronous
5224			grace-period primitives such as call_rcu().
5225
5226	rcuscale.gp_async_max= [KNL]
5227			Specify the maximum number of outstanding
5228			callbacks per writer thread.  When a writer
5229			thread exceeds this limit, it invokes the
5230			corresponding flavor of rcu_barrier() to allow
5231			previously posted callbacks to drain.
5232
5233	rcuscale.gp_exp= [KNL]
5234			Measure performance of expedited synchronous
5235			grace-period primitives.
5236
5237	rcuscale.holdoff= [KNL]
5238			Set test-start holdoff period.  The purpose of
5239			this parameter is to delay the start of the
5240			test until boot completes in order to avoid
5241			interference.
5242
5243	rcuscale.kfree_by_call_rcu= [KNL]
5244			In kernels built with CONFIG_RCU_LAZY=y, test
5245			call_rcu() instead of kfree_rcu().
5246
5247	rcuscale.kfree_mult= [KNL]
5248			Instead of allocating an object of size kfree_obj,
5249			allocate one of kfree_mult * sizeof(kfree_obj).
5250			Defaults to 1.
5251
5252	rcuscale.kfree_rcu_test= [KNL]
5253			Set to measure performance of kfree_rcu() flooding.
5254
5255	rcuscale.kfree_rcu_test_double= [KNL]
5256			Test the double-argument variant of kfree_rcu().
5257			If this parameter has the same value as
5258			rcuscale.kfree_rcu_test_single, both the single-
5259			and double-argument variants are tested.
5260
5261	rcuscale.kfree_rcu_test_single= [KNL]
5262			Test the single-argument variant of kfree_rcu().
5263			If this parameter has the same value as
5264			rcuscale.kfree_rcu_test_double, both the single-
5265			and double-argument variants are tested.
5266
5267	rcuscale.kfree_nthreads= [KNL]
5268			The number of threads running loops of kfree_rcu().
5269
5270	rcuscale.kfree_alloc_num= [KNL]
5271			Number of allocations and frees done in an iteration.
5272
5273	rcuscale.kfree_loops= [KNL]
5274			Number of loops doing rcuscale.kfree_alloc_num number
5275			of allocations and frees.
5276
5277	rcuscale.minruntime= [KNL]
5278			Set the minimum test run time in seconds.  This
5279			does not affect the data-collection interval,
5280			but instead allows better measurement of things
5281			like CPU consumption.
5282
5283	rcuscale.nreaders= [KNL]
5284			Set number of RCU readers.  The value -1 selects
5285			N, where N is the number of CPUs.  A value
5286			"n" less than -1 selects N-n+1, where N is again
5287			the number of CPUs.  For example, -2 selects N
5288			(the number of CPUs), -3 selects N+1, and so on.
5289			A value of "n" less than or equal to -N selects
5290			a single reader.
5291
5292	rcuscale.nwriters= [KNL]
5293			Set number of RCU writers.  The values operate
5294			the same as for rcuscale.nreaders.
5295			N, where N is the number of CPUs
5296
5297	rcuscale.scale_type= [KNL]
5298			Specify the RCU implementation to test.
5299
5300	rcuscale.shutdown= [KNL]
5301			Shut the system down after performance tests
5302			complete.  This is useful for hands-off automated
5303			testing.
5304
5305	rcuscale.verbose= [KNL]
5306			Enable additional printk() statements.
5307
5308	rcuscale.writer_holdoff= [KNL]
5309			Write-side holdoff between grace periods,
5310			in microseconds.  The default of zero says
5311			no holdoff.
5312
5313	rcuscale.writer_holdoff_jiffies= [KNL]
5314			Additional write-side holdoff between grace
5315			periods, but in jiffies.  The default of zero
5316			says no holdoff.
5317
5318	rcutorture.fqs_duration= [KNL]
5319			Set duration of force_quiescent_state bursts
5320			in microseconds.
5321
5322	rcutorture.fqs_holdoff= [KNL]
5323			Set holdoff time within force_quiescent_state bursts
5324			in microseconds.
5325
5326	rcutorture.fqs_stutter= [KNL]
5327			Set wait time between force_quiescent_state bursts
5328			in seconds.
5329
5330	rcutorture.fwd_progress= [KNL]
5331			Specifies the number of kthreads to be used
5332			for  RCU grace-period forward-progress testing
5333			for the types of RCU supporting this notion.
5334			Defaults to 1 kthread, values less than zero or
5335			greater than the number of CPUs cause the number
5336			of CPUs to be used.
5337
5338	rcutorture.fwd_progress_div= [KNL]
5339			Specify the fraction of a CPU-stall-warning
5340			period to do tight-loop forward-progress testing.
5341
5342	rcutorture.fwd_progress_holdoff= [KNL]
5343			Number of seconds to wait between successive
5344			forward-progress tests.
5345
5346	rcutorture.fwd_progress_need_resched= [KNL]
5347			Enclose cond_resched() calls within checks for
5348			need_resched() during tight-loop forward-progress
5349			testing.
5350
5351	rcutorture.gp_cond= [KNL]
5352			Use conditional/asynchronous update-side
5353			primitives, if available.
5354
5355	rcutorture.gp_exp= [KNL]
5356			Use expedited update-side primitives, if available.
5357
5358	rcutorture.gp_normal= [KNL]
5359			Use normal (non-expedited) asynchronous
5360			update-side primitives, if available.
5361
5362	rcutorture.gp_sync= [KNL]
5363			Use normal (non-expedited) synchronous
5364			update-side primitives, if available.  If all
5365			of rcutorture.gp_cond=, rcutorture.gp_exp=,
5366			rcutorture.gp_normal=, and rcutorture.gp_sync=
5367			are zero, rcutorture acts as if is interpreted
5368			they are all non-zero.
5369
5370	rcutorture.irqreader= [KNL]
5371			Run RCU readers from irq handlers, or, more
5372			accurately, from a timer handler.  Not all RCU
5373			flavors take kindly to this sort of thing.
5374
5375	rcutorture.leakpointer= [KNL]
5376			Leak an RCU-protected pointer out of the reader.
5377			This can of course result in splats, and is
5378			intended to test the ability of things like
5379			CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5380			such leaks.
5381
5382	rcutorture.n_barrier_cbs= [KNL]
5383			Set callbacks/threads for rcu_barrier() testing.
5384
5385	rcutorture.nfakewriters= [KNL]
5386			Set number of concurrent RCU writers.  These just
5387			stress RCU, they don't participate in the actual
5388			test, hence the "fake".
5389
5390	rcutorture.nocbs_nthreads= [KNL]
5391			Set number of RCU callback-offload togglers.
5392			Zero (the default) disables toggling.
5393
5394	rcutorture.nocbs_toggle= [KNL]
5395			Set the delay in milliseconds between successive
5396			callback-offload toggling attempts.
5397
5398	rcutorture.nreaders= [KNL]
5399			Set number of RCU readers.  The value -1 selects
5400			N-1, where N is the number of CPUs.  A value
5401			"n" less than -1 selects N-n-2, where N is again
5402			the number of CPUs.  For example, -2 selects N
5403			(the number of CPUs), -3 selects N+1, and so on.
5404
5405	rcutorture.object_debug= [KNL]
5406			Enable debug-object double-call_rcu() testing.
5407
5408	rcutorture.onoff_holdoff= [KNL]
5409			Set time (s) after boot for CPU-hotplug testing.
5410
5411	rcutorture.onoff_interval= [KNL]
5412			Set time (jiffies) between CPU-hotplug operations,
5413			or zero to disable CPU-hotplug testing.
5414
5415	rcutorture.read_exit= [KNL]
5416			Set the number of read-then-exit kthreads used
5417			to test the interaction of RCU updaters and
5418			task-exit processing.
5419
5420	rcutorture.read_exit_burst= [KNL]
5421			The number of times in a given read-then-exit
5422			episode that a set of read-then-exit kthreads
5423			is spawned.
5424
5425	rcutorture.read_exit_delay= [KNL]
5426			The delay, in seconds, between successive
5427			read-then-exit testing episodes.
5428
5429	rcutorture.shuffle_interval= [KNL]
5430			Set task-shuffle interval (s).  Shuffling tasks
5431			allows some CPUs to go into dyntick-idle mode
5432			during the rcutorture test.
5433
5434	rcutorture.shutdown_secs= [KNL]
5435			Set time (s) after boot system shutdown.  This
5436			is useful for hands-off automated testing.
5437
5438	rcutorture.stall_cpu= [KNL]
5439			Duration of CPU stall (s) to test RCU CPU stall
5440			warnings, zero to disable.
5441
5442	rcutorture.stall_cpu_block= [KNL]
5443			Sleep while stalling if set.  This will result
5444			in warnings from preemptible RCU in addition to
5445			any other stall-related activity.  Note that
5446			in kernels built with CONFIG_PREEMPTION=n and
5447			CONFIG_PREEMPT_COUNT=y, this parameter will
5448			cause the CPU to pass through a quiescent state.
5449			Given CONFIG_PREEMPTION=n, this will suppress
5450			RCU CPU stall warnings, but will instead result
5451			in scheduling-while-atomic splats.
5452
5453			Use of this module parameter results in splats.
5454
5455
5456	rcutorture.stall_cpu_holdoff= [KNL]
5457			Time to wait (s) after boot before inducing stall.
5458
5459	rcutorture.stall_cpu_irqsoff= [KNL]
5460			Disable interrupts while stalling if set, but only
5461			on the first stall in the set.
5462
5463	rcutorture.stall_cpu_repeat= [KNL]
5464			Number of times to repeat the stall sequence,
5465			so that rcutorture.stall_cpu_repeat=3 will result
5466			in four stall sequences.
5467
5468	rcutorture.stall_gp_kthread= [KNL]
5469			Duration (s) of forced sleep within RCU
5470			grace-period kthread to test RCU CPU stall
5471			warnings, zero to disable.  If both stall_cpu
5472			and stall_gp_kthread are specified, the
5473			kthread is starved first, then the CPU.
5474
5475	rcutorture.stat_interval= [KNL]
5476			Time (s) between statistics printk()s.
5477
5478	rcutorture.stutter= [KNL]
5479			Time (s) to stutter testing, for example, specifying
5480			five seconds causes the test to run for five seconds,
5481			wait for five seconds, and so on.  This tests RCU's
5482			ability to transition abruptly to and from idle.
5483
5484	rcutorture.test_boost= [KNL]
5485			Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
5486			"Maybe" means test if the RCU implementation
5487			under test support RCU priority boosting.
5488
5489	rcutorture.test_boost_duration= [KNL]
5490			Duration (s) of each individual boost test.
5491
5492	rcutorture.test_boost_interval= [KNL]
5493			Interval (s) between each boost test.
5494
5495	rcutorture.test_no_idle_hz= [KNL]
5496			Test RCU's dyntick-idle handling.  See also the
5497			rcutorture.shuffle_interval parameter.
5498
5499	rcutorture.torture_type= [KNL]
5500			Specify the RCU implementation to test.
5501
5502	rcutorture.verbose= [KNL]
5503			Enable additional printk() statements.
5504
5505	rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5506			Dump ftrace buffer after reporting RCU CPU
5507			stall warning.
5508
5509	rcupdate.rcu_cpu_stall_notifiers= [KNL]
5510			Provide RCU CPU stall notifiers, but see the
5511			warnings in the RCU_CPU_STALL_NOTIFIER Kconfig
5512			option's help text.  TL;DR:  You almost certainly
5513			do not want rcupdate.rcu_cpu_stall_notifiers.
5514
5515	rcupdate.rcu_cpu_stall_suppress= [KNL]
5516			Suppress RCU CPU stall warning messages.
5517
5518	rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5519			Suppress RCU CPU stall warning messages and
5520			rcutorture writer stall warnings that occur
5521			during early boot, that is, during the time
5522			before the init task is spawned.
5523
5524	rcupdate.rcu_cpu_stall_timeout= [KNL]
5525			Set timeout for RCU CPU stall warning messages.
5526			The value is in seconds and the maximum allowed
5527			value is 300 seconds.
5528
5529	rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5530			Set timeout for expedited RCU CPU stall warning
5531			messages.  The value is in milliseconds
5532			and the maximum allowed value is 21000
5533			milliseconds. Please note that this value is
5534			adjusted to an arch timer tick resolution.
5535			Setting this to zero causes the value from
5536			rcupdate.rcu_cpu_stall_timeout to be used (after
5537			conversion from seconds to milliseconds).
5538
5539	rcupdate.rcu_cpu_stall_cputime= [KNL]
5540			Provide statistics on the cputime and count of
5541			interrupts and tasks during the sampling period. For
5542			multiple continuous RCU stalls, all sampling periods
5543			begin at half of the first RCU stall timeout.
5544
5545	rcupdate.rcu_exp_stall_task_details= [KNL]
5546			Print stack dumps of any tasks blocking the
5547			current expedited RCU grace period during an
5548			expedited RCU CPU stall warning.
5549
5550	rcupdate.rcu_expedited= [KNL]
5551			Use expedited grace-period primitives, for
5552			example, synchronize_rcu_expedited() instead
5553			of synchronize_rcu().  This reduces latency,
5554			but can increase CPU utilization, degrade
5555			real-time latency, and degrade energy efficiency.
5556			No effect on CONFIG_TINY_RCU kernels.
5557
5558	rcupdate.rcu_normal= [KNL]
5559			Use only normal grace-period primitives,
5560			for example, synchronize_rcu() instead of
5561			synchronize_rcu_expedited().  This improves
5562			real-time latency, CPU utilization, and
5563			energy efficiency, but can expose users to
5564			increased grace-period latency.  This parameter
5565			overrides rcupdate.rcu_expedited.  No effect on
5566			CONFIG_TINY_RCU kernels.
5567
5568	rcupdate.rcu_normal_after_boot= [KNL]
5569			Once boot has completed (that is, after
5570			rcu_end_inkernel_boot() has been invoked), use
5571			only normal grace-period primitives.  No effect
5572			on CONFIG_TINY_RCU kernels.
5573
5574			But note that CONFIG_PREEMPT_RT=y kernels enables
5575			this kernel boot parameter, forcibly setting
5576			it to the value one, that is, converting any
5577			post-boot attempt at an expedited RCU grace
5578			period to instead use normal non-expedited
5579			grace-period processing.
5580
5581	rcupdate.rcu_task_collapse_lim= [KNL]
5582			Set the maximum number of callbacks present
5583			at the beginning of a grace period that allows
5584			the RCU Tasks flavors to collapse back to using
5585			a single callback queue.  This switching only
5586			occurs when rcupdate.rcu_task_enqueue_lim is
5587			set to the default value of -1.
5588
5589	rcupdate.rcu_task_contend_lim= [KNL]
5590			Set the minimum number of callback-queuing-time
5591			lock-contention events per jiffy required to
5592			cause the RCU Tasks flavors to switch to per-CPU
5593			callback queuing.  This switching only occurs
5594			when rcupdate.rcu_task_enqueue_lim is set to
5595			the default value of -1.
5596
5597	rcupdate.rcu_task_enqueue_lim= [KNL]
5598			Set the number of callback queues to use for the
5599			RCU Tasks family of RCU flavors.  The default
5600			of -1 allows this to be automatically (and
5601			dynamically) adjusted.	This parameter is intended
5602			for use in testing.
5603
5604	rcupdate.rcu_task_ipi_delay= [KNL]
5605			Set time in jiffies during which RCU tasks will
5606			avoid sending IPIs, starting with the beginning
5607			of a given grace period.  Setting a large
5608			number avoids disturbing real-time workloads,
5609			but lengthens grace periods.
5610
5611	rcupdate.rcu_task_lazy_lim= [KNL]
5612			Number of callbacks on a given CPU that will
5613			cancel laziness on that CPU.  Use -1 to disable
5614			cancellation of laziness, but be advised that
5615			doing so increases the danger of OOM due to
5616			callback flooding.
5617
5618	rcupdate.rcu_task_stall_info= [KNL]
5619			Set initial timeout in jiffies for RCU task stall
5620			informational messages, which give some indication
5621			of the problem for those not patient enough to
5622			wait for ten minutes.  Informational messages are
5623			only printed prior to the stall-warning message
5624			for a given grace period. Disable with a value
5625			less than or equal to zero.  Defaults to ten
5626			seconds.  A change in value does not take effect
5627			until the beginning of the next grace period.
5628
5629	rcupdate.rcu_task_stall_info_mult= [KNL]
5630			Multiplier for time interval between successive
5631			RCU task stall informational messages for a given
5632			RCU tasks grace period.  This value is clamped
5633			to one through ten, inclusive.	It defaults to
5634			the value three, so that the first informational
5635			message is printed 10 seconds into the grace
5636			period, the second at 40 seconds, the third at
5637			160 seconds, and then the stall warning at 600
5638			seconds would prevent a fourth at 640 seconds.
5639
5640	rcupdate.rcu_task_stall_timeout= [KNL]
5641			Set timeout in jiffies for RCU task stall
5642			warning messages.  Disable with a value less
5643			than or equal to zero.	Defaults to ten minutes.
5644			A change in value does not take effect until
5645			the beginning of the next grace period.
5646
5647	rcupdate.rcu_tasks_lazy_ms= [KNL]
5648			Set timeout in milliseconds RCU Tasks asynchronous
5649			callback batching for call_rcu_tasks().
5650			A negative value will take the default.  A value
5651			of zero will disable batching.	Batching is
5652			always disabled for synchronize_rcu_tasks().
5653
5654	rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
5655			Set timeout in milliseconds RCU Tasks
5656			Trace asynchronous callback batching for
5657			call_rcu_tasks_trace().  A negative value
5658			will take the default.	A value of zero will
5659			disable batching.  Batching is always disabled
5660			for synchronize_rcu_tasks_trace().
5661
5662	rcupdate.rcu_self_test= [KNL]
5663			Run the RCU early boot self tests
5664
5665	rdinit=		[KNL]
5666			Format: <full_path>
5667			Run specified binary instead of /init from the ramdisk,
5668			used for early userspace startup. See initrd.
5669
5670	rdrand=		[X86,EARLY]
5671			force - Override the decision by the kernel to hide the
5672				advertisement of RDRAND support (this affects
5673				certain AMD processors because of buggy BIOS
5674				support, specifically around the suspend/resume
5675				path).
5676
5677	rdt=		[HW,X86,RDT]
5678			Turn on/off individual RDT features. List is:
5679			cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5680			mba, smba, bmec.
5681			E.g. to turn on cmt and turn off mba use:
5682				rdt=cmt,!mba
5683
5684	reboot=		[KNL]
5685			Format (x86 or x86_64):
5686				[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
5687				[[,]s[mp]#### \
5688				[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5689				[[,]f[orce]
5690			Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5691					(prefix with 'panic_' to set mode for panic
5692					reboot only),
5693			      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5694			      reboot_force is either force or not specified,
5695			      reboot_cpu is s[mp]#### with #### being the processor
5696					to be used for rebooting.
5697
5698	refscale.holdoff= [KNL]
5699			Set test-start holdoff period.  The purpose of
5700			this parameter is to delay the start of the
5701			test until boot completes in order to avoid
5702			interference.
5703
5704	refscale.lookup_instances= [KNL]
5705			Number of data elements to use for the forms of
5706			SLAB_TYPESAFE_BY_RCU testing.  A negative number
5707			is negated and multiplied by nr_cpu_ids, while
5708			zero specifies nr_cpu_ids.
5709
5710	refscale.loops= [KNL]
5711			Set the number of loops over the synchronization
5712			primitive under test.  Increasing this number
5713			reduces noise due to loop start/end overhead,
5714			but the default has already reduced the per-pass
5715			noise to a handful of picoseconds on ca. 2020
5716			x86 laptops.
5717
5718	refscale.nreaders= [KNL]
5719			Set number of readers.  The default value of -1
5720			selects N, where N is roughly 75% of the number
5721			of CPUs.  A value of zero is an interesting choice.
5722
5723	refscale.nruns= [KNL]
5724			Set number of runs, each of which is dumped onto
5725			the console log.
5726
5727	refscale.readdelay= [KNL]
5728			Set the read-side critical-section duration,
5729			measured in microseconds.
5730
5731	refscale.scale_type= [KNL]
5732			Specify the read-protection implementation to test.
5733
5734	refscale.shutdown= [KNL]
5735			Shut down the system at the end of the performance
5736			test.  This defaults to 1 (shut it down) when
5737			refscale is built into the kernel and to 0 (leave
5738			it running) when refscale is built as a module.
5739
5740	refscale.verbose= [KNL]
5741			Enable additional printk() statements.
5742
5743	refscale.verbose_batched= [KNL]
5744			Batch the additional printk() statements.  If zero
5745			(the default) or negative, print everything.  Otherwise,
5746			print every Nth verbose statement, where N is the value
5747			specified.
5748
5749	regulator_ignore_unused
5750			[REGULATOR]
5751			Prevents regulator framework from disabling regulators
5752			that are unused, due no driver claiming them. This may
5753			be useful for debug and development, but should not be
5754			needed on a platform with proper driver support.
5755
5756	relax_domain_level=
5757			[KNL, SMP] Set scheduler's default relax_domain_level.
5758			See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5759
5760	reserve=	[KNL,BUGS] Force kernel to ignore I/O ports or memory
5761			Format: <base1>,<size1>[,<base2>,<size2>,...]
5762			Reserve I/O ports or memory so the kernel won't use
5763			them.  If <base> is less than 0x10000, the region
5764			is assumed to be I/O ports; otherwise it is memory.
5765
5766	reserve_mem=	[RAM]
5767			Format: nn[KNG]:<align>:<label>
5768			Reserve physical memory and label it with a name that
5769			other subsystems can use to access it. This is typically
5770			used for systems that do not wipe the RAM, and this command
5771			line will try to reserve the same physical memory on
5772			soft reboots. Note, it is not guaranteed to be the same
5773			location. For example, if anything about the system changes
5774			or if booting a different kernel. It can also fail if KASLR
5775			places the kernel at the location of where the RAM reservation
5776			was from a previous boot, the new reservation will be at a
5777			different location.
5778			Any subsystem using this feature must add a way to verify
5779			that the contents of the physical memory is from a previous
5780			boot, as there may be cases where the memory will not be
5781			located at the same location.
5782
5783			The format is size:align:label for example, to request
5784			12 megabytes of 4096 alignment for ramoops:
5785
5786			reserve_mem=12M:4096:oops ramoops.mem_name=oops
5787
5788	reservetop=	[X86-32,EARLY]
5789			Format: nn[KMG]
5790			Reserves a hole at the top of the kernel virtual
5791			address space.
5792
5793	reset_devices	[KNL] Force drivers to reset the underlying device
5794			during initialization.
5795
5796	resume=		[SWSUSP]
5797			Specify the partition device for software suspend
5798			Format:
5799			{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5800
5801	resume_offset=	[SWSUSP]
5802			Specify the offset from the beginning of the partition
5803			given by "resume=" at which the swap header is located,
5804			in <PAGE_SIZE> units (needed only for swap files).
5805			See  Documentation/power/swsusp-and-swap-files.rst
5806
5807	resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
5808			read the resume files
5809
5810	resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
5811			Useful for devices that are detected asynchronously
5812			(e.g. USB and MMC devices).
5813
5814	retain_initrd	[RAM] Keep initrd memory after extraction. After boot, it will
5815			be accessible via /sys/firmware/initrd.
5816
5817	retbleed=	[X86] Control mitigation of RETBleed (Arbitrary
5818			Speculative Code Execution with Return Instructions)
5819			vulnerability.
5820
5821			AMD-based UNRET and IBPB mitigations alone do not stop
5822			sibling threads from influencing the predictions of other
5823			sibling threads. For that reason, STIBP is used on pro-
5824			cessors that support it, and mitigate SMT on processors
5825			that don't.
5826
5827			off          - no mitigation
5828			auto         - automatically select a migitation
5829			auto,nosmt   - automatically select a mitigation,
5830				       disabling SMT if necessary for
5831				       the full mitigation (only on Zen1
5832				       and older without STIBP).
5833			ibpb         - On AMD, mitigate short speculation
5834				       windows on basic block boundaries too.
5835				       Safe, highest perf impact. It also
5836				       enables STIBP if present. Not suitable
5837				       on Intel.
5838			ibpb,nosmt   - Like "ibpb" above but will disable SMT
5839				       when STIBP is not available. This is
5840				       the alternative for systems which do not
5841				       have STIBP.
5842			unret        - Force enable untrained return thunks,
5843				       only effective on AMD f15h-f17h based
5844				       systems.
5845			unret,nosmt  - Like unret, but will disable SMT when STIBP
5846				       is not available. This is the alternative for
5847				       systems which do not have STIBP.
5848
5849			Selecting 'auto' will choose a mitigation method at run
5850			time according to the CPU.
5851
5852			Not specifying this option is equivalent to retbleed=auto.
5853
5854	rfkill.default_state=
5855		0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
5856			etc. communication is blocked by default.
5857		1	Unblocked.
5858
5859	rfkill.master_switch_mode=
5860		0	The "airplane mode" button does nothing.
5861		1	The "airplane mode" button toggles between everything
5862			blocked and the previous configuration.
5863		2	The "airplane mode" button toggles between everything
5864			blocked and everything unblocked.
5865
5866	ring3mwait=disable
5867			[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5868			CPUs.
5869
5870	riscv_isa_fallback [RISCV,EARLY]
5871			When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
5872			falling back to detecting extension support by parsing
5873			"riscv,isa" property on devicetree systems when the
5874			replacement properties are not found. See the Kconfig
5875			entry for RISCV_ISA_FALLBACK.
5876
5877	ro		[KNL] Mount root device read-only on boot
5878
5879	rodata=		[KNL,EARLY]
5880		on	Mark read-only kernel memory as read-only (default).
5881		off	Leave read-only kernel memory writable for debugging.
5882		full	Mark read-only kernel memory and aliases as read-only
5883		        [arm64]
5884
5885	rockchip.usb_uart
5886			[EARLY]
5887			Enable the uart passthrough on the designated usb port
5888			on Rockchip SoCs. When active, the signals of the
5889			debug-uart get routed to the D+ and D- pins of the usb
5890			port and the regular usb controller gets disabled.
5891
5892	root=		[KNL] Root filesystem
5893			Usually this a a block device specifier of some kind,
5894			see the early_lookup_bdev comment in
5895			block/early-lookup.c for details.
5896			Alternatively this can be "ram" for the legacy initial
5897			ramdisk, "nfs" and "cifs" for root on a network file
5898			system, or "mtd" and "ubi" for mounting from raw flash.
5899
5900	rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
5901			mount the root filesystem
5902
5903	rootflags=	[KNL] Set root filesystem mount option string
5904
5905	rootfstype=	[KNL] Set root filesystem type
5906
5907	rootwait	[KNL] Wait (indefinitely) for root device to show up.
5908			Useful for devices that are detected asynchronously
5909			(e.g. USB and MMC devices).
5910
5911	rootwait=	[KNL] Maximum time (in seconds) to wait for root device
5912			to show up before attempting to mount the root
5913			filesystem.
5914
5915	rproc_mem=nn[KMG][@address]
5916			[KNL,ARM,CMA] Remoteproc physical memory block.
5917			Memory area to be used by remote processor image,
5918			managed by CMA.
5919
5920	rw		[KNL] Mount root device read-write on boot
5921
5922	S		[KNL] Run init in single mode
5923
5924	s390_iommu=	[HW,S390]
5925			Set s390 IOTLB flushing mode
5926		strict
5927			With strict flushing every unmap operation will result
5928			in an IOTLB flush. Default is lazy flushing before
5929			reuse, which is faster. Deprecated, equivalent to
5930			iommu.strict=1.
5931
5932	s390_iommu_aperture=	[KNL,S390]
5933			Specifies the size of the per device DMA address space
5934			accessible through the DMA and IOMMU APIs as a decimal
5935			factor of the size of main memory.
5936			The default is 1 meaning that one can concurrently use
5937			as many DMA addresses as physical memory is installed,
5938			if supported by hardware, and thus map all of memory
5939			once. With a value of 2 one can map all of memory twice
5940			and so on. As a special case a factor of 0 imposes no
5941			restrictions other than those given by hardware at the
5942			cost of significant additional memory use for tables.
5943
5944	sa1100ir	[NET]
5945			See drivers/net/irda/sa1100_ir.c.
5946
5947	sched_verbose	[KNL,EARLY] Enables verbose scheduler debug messages.
5948
5949	schedstats=	[KNL,X86] Enable or disable scheduled statistics.
5950			Allowed values are enable and disable. This feature
5951			incurs a small amount of overhead in the scheduler
5952			but is useful for debugging and performance tuning.
5953
5954	sched_thermal_decay_shift=
5955			[Deprecated]
5956			[KNL, SMP] Set a decay shift for scheduler thermal
5957			pressure signal. Thermal pressure signal follows the
5958			default decay period of other scheduler pelt
5959			signals(usually 32 ms but configurable). Setting
5960			sched_thermal_decay_shift will left shift the decay
5961			period for the thermal pressure signal by the shift
5962			value.
5963			i.e. with the default pelt decay period of 32 ms
5964			sched_thermal_decay_shift   thermal pressure decay pr
5965				1			64 ms
5966				2			128 ms
5967			and so on.
5968			Format: integer between 0 and 10
5969			Default is 0.
5970
5971	scftorture.holdoff= [KNL]
5972			Number of seconds to hold off before starting
5973			test.  Defaults to zero for module insertion and
5974			to 10 seconds for built-in smp_call_function()
5975			tests.
5976
5977	scftorture.longwait= [KNL]
5978			Request ridiculously long waits randomly selected
5979			up to the chosen limit in seconds.  Zero (the
5980			default) disables this feature.  Please note
5981			that requesting even small non-zero numbers of
5982			seconds can result in RCU CPU stall warnings,
5983			softlockup complaints, and so on.
5984
5985	scftorture.nthreads= [KNL]
5986			Number of kthreads to spawn to invoke the
5987			smp_call_function() family of functions.
5988			The default of -1 specifies a number of kthreads
5989			equal to the number of CPUs.
5990
5991	scftorture.onoff_holdoff= [KNL]
5992			Number seconds to wait after the start of the
5993			test before initiating CPU-hotplug operations.
5994
5995	scftorture.onoff_interval= [KNL]
5996			Number seconds to wait between successive
5997			CPU-hotplug operations.  Specifying zero (which
5998			is the default) disables CPU-hotplug operations.
5999
6000	scftorture.shutdown_secs= [KNL]
6001			The number of seconds following the start of the
6002			test after which to shut down the system.  The
6003			default of zero avoids shutting down the system.
6004			Non-zero values are useful for automated tests.
6005
6006	scftorture.stat_interval= [KNL]
6007			The number of seconds between outputting the
6008			current test statistics to the console.  A value
6009			of zero disables statistics output.
6010
6011	scftorture.stutter_cpus= [KNL]
6012			The number of jiffies to wait between each change
6013			to the set of CPUs under test.
6014
6015	scftorture.use_cpus_read_lock= [KNL]
6016			Use use_cpus_read_lock() instead of the default
6017			preempt_disable() to disable CPU hotplug
6018			while invoking one of the smp_call_function*()
6019			functions.
6020
6021	scftorture.verbose= [KNL]
6022			Enable additional printk() statements.
6023
6024	scftorture.weight_single= [KNL]
6025			The probability weighting to use for the
6026			smp_call_function_single() function with a zero
6027			"wait" parameter.  A value of -1 selects the
6028			default if all other weights are -1.  However,
6029			if at least one weight has some other value, a
6030			value of -1 will instead select a weight of zero.
6031
6032	scftorture.weight_single_wait= [KNL]
6033			The probability weighting to use for the
6034			smp_call_function_single() function with a
6035			non-zero "wait" parameter.  See weight_single.
6036
6037	scftorture.weight_many= [KNL]
6038			The probability weighting to use for the
6039			smp_call_function_many() function with a zero
6040			"wait" parameter.  See weight_single.
6041			Note well that setting a high probability for
6042			this weighting can place serious IPI load
6043			on the system.
6044
6045	scftorture.weight_many_wait= [KNL]
6046			The probability weighting to use for the
6047			smp_call_function_many() function with a
6048			non-zero "wait" parameter.  See weight_single
6049			and weight_many.
6050
6051	scftorture.weight_all= [KNL]
6052			The probability weighting to use for the
6053			smp_call_function_all() function with a zero
6054			"wait" parameter.  See weight_single and
6055			weight_many.
6056
6057	scftorture.weight_all_wait= [KNL]
6058			The probability weighting to use for the
6059			smp_call_function_all() function with a
6060			non-zero "wait" parameter.  See weight_single
6061			and weight_many.
6062
6063	skew_tick=	[KNL,EARLY] Offset the periodic timer tick per cpu to mitigate
6064			xtime_lock contention on larger systems, and/or RCU lock
6065			contention on all systems with CONFIG_MAXSMP set.
6066			Format: { "0" | "1" }
6067			0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6068			1 -- enable.
6069			Note: increases power consumption, thus should only be
6070			enabled if running jitter sensitive (HPC/RT) workloads.
6071
6072	security=	[SECURITY] Choose a legacy "major" security module to
6073			enable at boot. This has been deprecated by the
6074			"lsm=" parameter.
6075
6076	selinux=	[SELINUX] Disable or enable SELinux at boot time.
6077			Format: { "0" | "1" }
6078			See security/selinux/Kconfig help text.
6079			0 -- disable.
6080			1 -- enable.
6081			Default value is 1.
6082
6083	serialnumber	[BUGS=X86-32]
6084
6085	sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
6086
6087	shapers=	[NET]
6088			Maximal number of shapers.
6089
6090	show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
6091			Limit apic dumping. The parameter defines the maximal
6092			number of local apics being dumped. Also it is possible
6093			to set it to "all" by meaning -- no limit here.
6094			Format: { 1 (default) | 2 | ... | all }.
6095			The parameter valid if only apic=debug or
6096			apic=verbose is specified.
6097			Example: apic=debug show_lapic=all
6098
6099	slab_debug[=options[,slabs][;[options[,slabs]]...]	[MM]
6100			Enabling slab_debug allows one to determine the
6101			culprit if slab objects become corrupted. Enabling
6102			slab_debug can create guard zones around objects and
6103			may poison objects when not in use. Also tracks the
6104			last alloc / free. For more information see
6105			Documentation/mm/slub.rst.
6106			(slub_debug legacy name also accepted for now)
6107
6108	slab_max_order= [MM]
6109			Determines the maximum allowed order for slabs.
6110			A high setting may cause OOMs due to memory
6111			fragmentation. For more information see
6112			Documentation/mm/slub.rst.
6113			(slub_max_order legacy name also accepted for now)
6114
6115	slab_merge	[MM]
6116			Enable merging of slabs with similar size when the
6117			kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
6118			(slub_merge legacy name also accepted for now)
6119
6120	slab_min_objects=	[MM]
6121			The minimum number of objects per slab. SLUB will
6122			increase the slab order up to slab_max_order to
6123			generate a sufficiently large slab able to contain
6124			the number of objects indicated. The higher the number
6125			of objects the smaller the overhead of tracking slabs
6126			and the less frequently locks need to be acquired.
6127			For more information see Documentation/mm/slub.rst.
6128			(slub_min_objects legacy name also accepted for now)
6129
6130	slab_min_order=	[MM]
6131			Determines the minimum page order for slabs. Must be
6132			lower or equal to slab_max_order. For more information see
6133			Documentation/mm/slub.rst.
6134			(slub_min_order legacy name also accepted for now)
6135
6136	slab_nomerge	[MM]
6137			Disable merging of slabs with similar size. May be
6138			necessary if there is some reason to distinguish
6139			allocs to different slabs, especially in hardened
6140			environments where the risk of heap overflows and
6141			layout control by attackers can usually be
6142			frustrated by disabling merging. This will reduce
6143			most of the exposure of a heap attack to a single
6144			cache (risks via metadata attacks are mostly
6145			unchanged). Debug options disable merging on their
6146			own.
6147			For more information see Documentation/mm/slub.rst.
6148			(slub_nomerge legacy name also accepted for now)
6149
6150	slram=		[HW,MTD]
6151
6152	smart2=		[HW]
6153			Format: <io1>[,<io2>[,...,<io8>]]
6154
6155	smp.csd_lock_timeout= [KNL]
6156			Specify the period of time in milliseconds
6157			that smp_call_function() and friends will wait
6158			for a CPU to release the CSD lock.  This is
6159			useful when diagnosing bugs involving CPUs
6160			disabling interrupts for extended periods
6161			of time.  Defaults to 5,000 milliseconds, and
6162			setting a value of zero disables this feature.
6163			This feature may be more efficiently disabled
6164			using the csdlock_debug- kernel parameter.
6165
6166	smp.panic_on_ipistall= [KNL]
6167			If a csd_lock_timeout extends for more than
6168			the specified number of milliseconds, panic the
6169			system.  By default, let CSD-lock acquisition
6170			take as long as they take.  Specifying 300,000
6171			for this value provides a 5-minute timeout.
6172
6173	smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
6174	smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
6175	smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
6176	smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
6177	smsc-ircc2.ircc_irq=	[HW] IRQ line
6178	smsc-ircc2.ircc_dma=	[HW] DMA channel
6179	smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6180				0: Toshiba Satellite 1800 (GP data pin select)
6181				1: Fast pin select (default)
6182				2: ATC IRMode
6183
6184	smt=		[KNL,MIPS,S390,EARLY] Set the maximum number of threads
6185			(logical CPUs) to use per physical CPU on systems
6186			capable of symmetric multithreading (SMT). Will
6187			be capped to the actual hardware limit.
6188			Format: <integer>
6189			Default: -1 (no limit)
6190
6191	softlockup_panic=
6192			[KNL] Should the soft-lockup detector generate panics.
6193			Format: 0 | 1
6194
6195			A value of 1 instructs the soft-lockup detector
6196			to panic the machine when a soft-lockup occurs. It is
6197			also controlled by the kernel.softlockup_panic sysctl
6198			and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6199			respective build-time switch to that functionality.
6200
6201	softlockup_all_cpu_backtrace=
6202			[KNL] Should the soft-lockup detector generate
6203			backtraces on all cpus.
6204			Format: 0 | 1
6205
6206	sonypi.*=	[HW] Sony Programmable I/O Control Device driver
6207			See Documentation/admin-guide/laptops/sonypi.rst
6208
6209	spectre_bhi=	[X86] Control mitigation of Branch History Injection
6210			(BHI) vulnerability.  This setting affects the
6211			deployment of the HW BHI control and the SW BHB
6212			clearing sequence.
6213
6214			on     - (default) Enable the HW or SW mitigation as
6215				 needed.  This protects the kernel from
6216				 both syscalls and VMs.
6217			vmexit - On systems which don't have the HW mitigation
6218				 available, enable the SW mitigation on vmexit
6219				 ONLY.  On such systems, the host kernel is
6220				 protected from VM-originated BHI attacks, but
6221				 may still be vulnerable to syscall attacks.
6222			off    - Disable the mitigation.
6223
6224	spectre_v2=	[X86,EARLY] Control mitigation of Spectre variant 2
6225			(indirect branch speculation) vulnerability.
6226			The default operation protects the kernel from
6227			user space attacks.
6228
6229			on   - unconditionally enable, implies
6230			       spectre_v2_user=on
6231			off  - unconditionally disable, implies
6232			       spectre_v2_user=off
6233			auto - kernel detects whether your CPU model is
6234			       vulnerable
6235
6236			Selecting 'on' will, and 'auto' may, choose a
6237			mitigation method at run time according to the
6238			CPU, the available microcode, the setting of the
6239			CONFIG_MITIGATION_RETPOLINE configuration option,
6240			and the compiler with which the kernel was built.
6241
6242			Selecting 'on' will also enable the mitigation
6243			against user space to user space task attacks.
6244
6245			Selecting 'off' will disable both the kernel and
6246			the user space protections.
6247
6248			Specific mitigations can also be selected manually:
6249
6250			retpoline	  - replace indirect branches
6251			retpoline,generic - Retpolines
6252			retpoline,lfence  - LFENCE; indirect branch
6253			retpoline,amd     - alias for retpoline,lfence
6254			eibrs		  - Enhanced/Auto IBRS
6255			eibrs,retpoline   - Enhanced/Auto IBRS + Retpolines
6256			eibrs,lfence      - Enhanced/Auto IBRS + LFENCE
6257			ibrs		  - use IBRS to protect kernel
6258
6259			Not specifying this option is equivalent to
6260			spectre_v2=auto.
6261
6262	spectre_v2_user=
6263			[X86] Control mitigation of Spectre variant 2
6264		        (indirect branch speculation) vulnerability between
6265		        user space tasks
6266
6267			on	- Unconditionally enable mitigations. Is
6268				  enforced by spectre_v2=on
6269
6270			off     - Unconditionally disable mitigations. Is
6271				  enforced by spectre_v2=off
6272
6273			prctl   - Indirect branch speculation is enabled,
6274				  but mitigation can be enabled via prctl
6275				  per thread.  The mitigation control state
6276				  is inherited on fork.
6277
6278			prctl,ibpb
6279				- Like "prctl" above, but only STIBP is
6280				  controlled per thread. IBPB is issued
6281				  always when switching between different user
6282				  space processes.
6283
6284			seccomp
6285				- Same as "prctl" above, but all seccomp
6286				  threads will enable the mitigation unless
6287				  they explicitly opt out.
6288
6289			seccomp,ibpb
6290				- Like "seccomp" above, but only STIBP is
6291				  controlled per thread. IBPB is issued
6292				  always when switching between different
6293				  user space processes.
6294
6295			auto    - Kernel selects the mitigation depending on
6296				  the available CPU features and vulnerability.
6297
6298			Default mitigation: "prctl"
6299
6300			Not specifying this option is equivalent to
6301			spectre_v2_user=auto.
6302
6303	spec_rstack_overflow=
6304			[X86,EARLY] Control RAS overflow mitigation on AMD Zen CPUs
6305
6306			off		- Disable mitigation
6307			microcode	- Enable microcode mitigation only
6308			safe-ret	- Enable sw-only safe RET mitigation (default)
6309			ibpb		- Enable mitigation by issuing IBPB on
6310					  kernel entry
6311			ibpb-vmexit	- Issue IBPB only on VMEXIT
6312					  (cloud-specific mitigation)
6313
6314	spec_store_bypass_disable=
6315			[HW,EARLY] Control Speculative Store Bypass (SSB) Disable mitigation
6316			(Speculative Store Bypass vulnerability)
6317
6318			Certain CPUs are vulnerable to an exploit against a
6319			a common industry wide performance optimization known
6320			as "Speculative Store Bypass" in which recent stores
6321			to the same memory location may not be observed by
6322			later loads during speculative execution. The idea
6323			is that such stores are unlikely and that they can
6324			be detected prior to instruction retirement at the
6325			end of a particular speculation execution window.
6326
6327			In vulnerable processors, the speculatively forwarded
6328			store can be used in a cache side channel attack, for
6329			example to read memory to which the attacker does not
6330			directly have access (e.g. inside sandboxed code).
6331
6332			This parameter controls whether the Speculative Store
6333			Bypass optimization is used.
6334
6335			On x86 the options are:
6336
6337			on      - Unconditionally disable Speculative Store Bypass
6338			off     - Unconditionally enable Speculative Store Bypass
6339			auto    - Kernel detects whether the CPU model contains an
6340				  implementation of Speculative Store Bypass and
6341				  picks the most appropriate mitigation. If the
6342				  CPU is not vulnerable, "off" is selected. If the
6343				  CPU is vulnerable the default mitigation is
6344				  architecture and Kconfig dependent. See below.
6345			prctl   - Control Speculative Store Bypass per thread
6346				  via prctl. Speculative Store Bypass is enabled
6347				  for a process by default. The state of the control
6348				  is inherited on fork.
6349			seccomp - Same as "prctl" above, but all seccomp threads
6350				  will disable SSB unless they explicitly opt out.
6351
6352			Default mitigations:
6353			X86:	"prctl"
6354
6355			On powerpc the options are:
6356
6357			on,auto - On Power8 and Power9 insert a store-forwarding
6358				  barrier on kernel entry and exit. On Power7
6359				  perform a software flush on kernel entry and
6360				  exit.
6361			off	- No action.
6362
6363			Not specifying this option is equivalent to
6364			spec_store_bypass_disable=auto.
6365
6366	split_lock_detect=
6367			[X86] Enable split lock detection or bus lock detection
6368
6369			When enabled (and if hardware support is present), atomic
6370			instructions that access data across cache line
6371			boundaries will result in an alignment check exception
6372			for split lock detection or a debug exception for
6373			bus lock detection.
6374
6375			off	- not enabled
6376
6377			warn	- the kernel will emit rate-limited warnings
6378				  about applications triggering the #AC
6379				  exception or the #DB exception. This mode is
6380				  the default on CPUs that support split lock
6381				  detection or bus lock detection. Default
6382				  behavior is by #AC if both features are
6383				  enabled in hardware.
6384
6385			fatal	- the kernel will send SIGBUS to applications
6386				  that trigger the #AC exception or the #DB
6387				  exception. Default behavior is by #AC if
6388				  both features are enabled in hardware.
6389
6390			ratelimit:N -
6391				  Set system wide rate limit to N bus locks
6392				  per second for bus lock detection.
6393				  0 < N <= 1000.
6394
6395				  N/A for split lock detection.
6396
6397
6398			If an #AC exception is hit in the kernel or in
6399			firmware (i.e. not while executing in user mode)
6400			the kernel will oops in either "warn" or "fatal"
6401			mode.
6402
6403			#DB exception for bus lock is triggered only when
6404			CPL > 0.
6405
6406	srbds=		[X86,INTEL,EARLY]
6407			Control the Special Register Buffer Data Sampling
6408			(SRBDS) mitigation.
6409
6410			Certain CPUs are vulnerable to an MDS-like
6411			exploit which can leak bits from the random
6412			number generator.
6413
6414			By default, this issue is mitigated by
6415			microcode.  However, the microcode fix can cause
6416			the RDRAND and RDSEED instructions to become
6417			much slower.  Among other effects, this will
6418			result in reduced throughput from /dev/urandom.
6419
6420			The microcode mitigation can be disabled with
6421			the following option:
6422
6423			off:    Disable mitigation and remove
6424				performance impact to RDRAND and RDSEED
6425
6426	srcutree.big_cpu_lim [KNL]
6427			Specifies the number of CPUs constituting a
6428			large system, such that srcu_struct structures
6429			should immediately allocate an srcu_node array.
6430			This kernel-boot parameter defaults to 128,
6431			but takes effect only when the low-order four
6432			bits of srcutree.convert_to_big is equal to 3
6433			(decide at boot).
6434
6435	srcutree.convert_to_big [KNL]
6436			Specifies under what conditions an SRCU tree
6437			srcu_struct structure will be converted to big
6438			form, that is, with an rcu_node tree:
6439
6440				   0:  Never.
6441				   1:  At init_srcu_struct() time.
6442				   2:  When rcutorture decides to.
6443				   3:  Decide at boot time (default).
6444				0x1X:  Above plus if high contention.
6445
6446			Either way, the srcu_node tree will be sized based
6447			on the actual runtime number of CPUs (nr_cpu_ids)
6448			instead of the compile-time CONFIG_NR_CPUS.
6449
6450	srcutree.counter_wrap_check [KNL]
6451			Specifies how frequently to check for
6452			grace-period sequence counter wrap for the
6453			srcu_data structure's ->srcu_gp_seq_needed field.
6454			The greater the number of bits set in this kernel
6455			parameter, the less frequently counter wrap will
6456			be checked for.  Note that the bottom two bits
6457			are ignored.
6458
6459	srcutree.exp_holdoff [KNL]
6460			Specifies how many nanoseconds must elapse
6461			since the end of the last SRCU grace period for
6462			a given srcu_struct until the next normal SRCU
6463			grace period will be considered for automatic
6464			expediting.  Set to zero to disable automatic
6465			expediting.
6466
6467	srcutree.srcu_max_nodelay [KNL]
6468			Specifies the number of no-delay instances
6469			per jiffy for which the SRCU grace period
6470			worker thread will be rescheduled with zero
6471			delay. Beyond this limit, worker thread will
6472			be rescheduled with a sleep delay of one jiffy.
6473
6474	srcutree.srcu_max_nodelay_phase [KNL]
6475			Specifies the per-grace-period phase, number of
6476			non-sleeping polls of readers. Beyond this limit,
6477			grace period worker thread will be rescheduled
6478			with a sleep delay of one jiffy, between each
6479			rescan of the readers, for a grace period phase.
6480
6481	srcutree.srcu_retry_check_delay [KNL]
6482			Specifies number of microseconds of non-sleeping
6483			delay between each non-sleeping poll of readers.
6484
6485	srcutree.small_contention_lim [KNL]
6486			Specifies the number of update-side contention
6487			events per jiffy will be tolerated before
6488			initiating a conversion of an srcu_struct
6489			structure to big form.	Note that the value of
6490			srcutree.convert_to_big must have the 0x10 bit
6491			set for contention-based conversions to occur.
6492
6493	ssbd=		[ARM64,HW,EARLY]
6494			Speculative Store Bypass Disable control
6495
6496			On CPUs that are vulnerable to the Speculative
6497			Store Bypass vulnerability and offer a
6498			firmware based mitigation, this parameter
6499			indicates how the mitigation should be used:
6500
6501			force-on:  Unconditionally enable mitigation for
6502				   for both kernel and userspace
6503			force-off: Unconditionally disable mitigation for
6504				   for both kernel and userspace
6505			kernel:    Always enable mitigation in the
6506				   kernel, and offer a prctl interface
6507				   to allow userspace to register its
6508				   interest in being mitigated too.
6509
6510	stack_guard_gap=	[MM]
6511			override the default stack gap protection. The value
6512			is in page units and it defines how many pages prior
6513			to (for stacks growing down) resp. after (for stacks
6514			growing up) the main stack are reserved for no other
6515			mapping. Default value is 256 pages.
6516
6517	stack_depot_disable= [KNL,EARLY]
6518			Setting this to true through kernel command line will
6519			disable the stack depot thereby saving the static memory
6520			consumed by the stack hash table. By default this is set
6521			to false.
6522
6523	stacktrace	[FTRACE]
6524			Enabled the stack tracer on boot up.
6525
6526	stacktrace_filter=[function-list]
6527			[FTRACE] Limit the functions that the stack tracer
6528			will trace at boot up. function-list is a comma-separated
6529			list of functions. This list can be changed at run
6530			time by the stack_trace_filter file in the debugfs
6531			tracing directory. Note, this enables stack tracing
6532			and the stacktrace above is not needed.
6533
6534	sti=		[PARISC,HW]
6535			Format: <num>
6536			Set the STI (builtin display/keyboard on the HP-PARISC
6537			machines) console (graphic card) which should be used
6538			as the initial boot-console.
6539			See also comment in drivers/video/console/sticore.c.
6540
6541	sti_font=	[HW]
6542			See comment in drivers/video/console/sticore.c.
6543
6544	stifb=		[HW]
6545			Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6546
6547        strict_sas_size=
6548			[X86]
6549			Format: <bool>
6550			Enable or disable strict sigaltstack size checks
6551			against the required signal frame size which
6552			depends on the supported FPU features. This can
6553			be used to filter out binaries which have
6554			not yet been made aware of AT_MINSIGSTKSZ.
6555
6556	stress_hpt	[PPC,EARLY]
6557			Limits the number of kernel HPT entries in the hash
6558			page table to increase the rate of hash page table
6559			faults on kernel addresses.
6560
6561	stress_slb	[PPC,EARLY]
6562			Limits the number of kernel SLB entries, and flushes
6563			them frequently to increase the rate of SLB faults
6564			on kernel addresses.
6565
6566	sunrpc.min_resvport=
6567	sunrpc.max_resvport=
6568			[NFS,SUNRPC]
6569			SunRPC servers often require that client requests
6570			originate from a privileged port (i.e. a port in the
6571			range 0 < portnr < 1024).
6572			An administrator who wishes to reserve some of these
6573			ports for other uses may adjust the range that the
6574			kernel's sunrpc client considers to be privileged
6575			using these two parameters to set the minimum and
6576			maximum port values.
6577
6578	sunrpc.svc_rpc_per_connection_limit=
6579			[NFS,SUNRPC]
6580			Limit the number of requests that the server will
6581			process in parallel from a single connection.
6582			The default value is 0 (no limit).
6583
6584	sunrpc.pool_mode=
6585			[NFS]
6586			Control how the NFS server code allocates CPUs to
6587			service thread pools.  Depending on how many NICs
6588			you have and where their interrupts are bound, this
6589			option will affect which CPUs will do NFS serving.
6590			Note: this parameter cannot be changed while the
6591			NFS server is running.
6592
6593			auto	    the server chooses an appropriate mode
6594				    automatically using heuristics
6595			global	    a single global pool contains all CPUs
6596			percpu	    one pool for each CPU
6597			pernode	    one pool for each NUMA node (equivalent
6598				    to global on non-NUMA machines)
6599
6600	sunrpc.tcp_slot_table_entries=
6601	sunrpc.udp_slot_table_entries=
6602			[NFS,SUNRPC]
6603			Sets the upper limit on the number of simultaneous
6604			RPC calls that can be sent from the client to a
6605			server. Increasing these values may allow you to
6606			improve throughput, but will also increase the
6607			amount of memory reserved for use by the client.
6608
6609	suspend.pm_test_delay=
6610			[SUSPEND]
6611			Sets the number of seconds to remain in a suspend test
6612			mode before resuming the system (see
6613			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6614			is set. Default value is 5.
6615
6616	svm=		[PPC]
6617			Format: { on | off | y | n | 1 | 0 }
6618			This parameter controls use of the Protected
6619			Execution Facility on pSeries.
6620
6621	swiotlb=	[ARM,PPC,MIPS,X86,S390,EARLY]
6622			Format: { <int> [,<int>] | force | noforce }
6623			<int> -- Number of I/O TLB slabs
6624			<int> -- Second integer after comma. Number of swiotlb
6625				 areas with their own lock. Will be rounded up
6626				 to a power of 2.
6627			force -- force using of bounce buffers even if they
6628			         wouldn't be automatically used by the kernel
6629			noforce -- Never use bounce buffers (for debugging)
6630
6631	switches=	[HW,M68k,EARLY]
6632
6633	sysctl.*=	[KNL]
6634			Set a sysctl parameter, right before loading the init
6635			process, as if the value was written to the respective
6636			/proc/sys/... file. Both '.' and '/' are recognized as
6637			separators. Unrecognized parameters and invalid values
6638			are reported in the kernel log. Sysctls registered
6639			later by a loaded module cannot be set this way.
6640			Example: sysctl.vm.swappiness=40
6641
6642	sysrq_always_enabled
6643			[KNL]
6644			Ignore sysrq setting - this boot parameter will
6645			neutralize any effect of /proc/sys/kernel/sysrq.
6646			Useful for debugging.
6647
6648	tcpmhash_entries= [KNL,NET]
6649			Set the number of tcp_metrics_hash slots.
6650			Default value is 8192 or 16384 depending on total
6651			ram pages. This is used to specify the TCP metrics
6652			cache size. See Documentation/networking/ip-sysctl.rst
6653			"tcp_no_metrics_save" section for more details.
6654
6655	tdfx=		[HW,DRM]
6656
6657	test_suspend=	[SUSPEND]
6658			Format: { "mem" | "standby" | "freeze" }[,N]
6659			Specify "mem" (for Suspend-to-RAM) or "standby" (for
6660			standby suspend) or "freeze" (for suspend type freeze)
6661			as the system sleep state during system startup with
6662			the optional capability to repeat N number of times.
6663			The system is woken from this state using a
6664			wakeup-capable RTC alarm.
6665
6666	thash_entries=	[KNL,NET]
6667			Set number of hash buckets for TCP connection
6668
6669	thermal.act=	[HW,ACPI]
6670			-1: disable all active trip points in all thermal zones
6671			<degrees C>: override all lowest active trip points
6672
6673	thermal.crt=	[HW,ACPI]
6674			-1: disable all critical trip points in all thermal zones
6675			<degrees C>: override all critical trip points
6676
6677	thermal.off=	[HW,ACPI]
6678			1: disable ACPI thermal control
6679
6680	thermal.psv=	[HW,ACPI]
6681			-1: disable all passive trip points
6682			<degrees C>: override all passive trip points to this
6683			value
6684
6685	thermal.tzp=	[HW,ACPI]
6686			Specify global default ACPI thermal zone polling rate
6687			<deci-seconds>: poll all this frequency
6688			0: no polling (default)
6689
6690	thp_anon=	[KNL]
6691			Format: <size>[KMG],<size>[KMG]:<state>;<size>[KMG]-<size>[KMG]:<state>
6692			state is one of "always", "madvise", "never" or "inherit".
6693			Control the default behavior of the system with respect
6694			to anonymous transparent hugepages.
6695			Can be used multiple times for multiple anon THP sizes.
6696			See Documentation/admin-guide/mm/transhuge.rst for more
6697			details.
6698
6699	threadirqs	[KNL,EARLY]
6700			Force threading of all interrupt handlers except those
6701			marked explicitly IRQF_NO_THREAD.
6702
6703	topology=	[S390,EARLY]
6704			Format: {off | on}
6705			Specify if the kernel should make use of the cpu
6706			topology information if the hardware supports this.
6707			The scheduler will make use of this information and
6708			e.g. base its process migration decisions on it.
6709			Default is on.
6710
6711	torture.disable_onoff_at_boot= [KNL]
6712			Prevent the CPU-hotplug component of torturing
6713			until after init has spawned.
6714
6715	torture.ftrace_dump_at_shutdown= [KNL]
6716			Dump the ftrace buffer at torture-test shutdown,
6717			even if there were no errors.  This can be a
6718			very costly operation when many torture tests
6719			are running concurrently, especially on systems
6720			with rotating-rust storage.
6721
6722	torture.verbose_sleep_frequency= [KNL]
6723			Specifies how many verbose printk()s should be
6724			emitted between each sleep.  The default of zero
6725			disables verbose-printk() sleeping.
6726
6727	torture.verbose_sleep_duration= [KNL]
6728			Duration of each verbose-printk() sleep in jiffies.
6729
6730	tpm_suspend_pcr=[HW,TPM]
6731			Format: integer pcr id
6732			Specify that at suspend time, the tpm driver
6733			should extend the specified pcr with zeros,
6734			as a workaround for some chips which fail to
6735			flush the last written pcr on TPM_SaveState.
6736			This will guarantee that all the other pcrs
6737			are saved.
6738
6739	tpm_tis.interrupts= [HW,TPM]
6740			Enable interrupts for the MMIO based physical layer
6741			for the FIFO interface. By default it is set to false
6742			(0). For more information about TPM hardware interfaces
6743			defined by Trusted Computing Group (TCG) see
6744			https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
6745
6746	tp_printk	[FTRACE]
6747			Have the tracepoints sent to printk as well as the
6748			tracing ring buffer. This is useful for early boot up
6749			where the system hangs or reboots and does not give the
6750			option for reading the tracing buffer or performing a
6751			ftrace_dump_on_oops.
6752
6753			To turn off having tracepoints sent to printk,
6754			 echo 0 > /proc/sys/kernel/tracepoint_printk
6755			Note, echoing 1 into this file without the
6756			tp_printk kernel cmdline option has no effect.
6757
6758			The tp_printk_stop_on_boot (see below) can also be used
6759			to stop the printing of events to console at
6760			late_initcall_sync.
6761
6762			** CAUTION **
6763
6764			Having tracepoints sent to printk() and activating high
6765			frequency tracepoints such as irq or sched, can cause
6766			the system to live lock.
6767
6768	tp_printk_stop_on_boot [FTRACE]
6769			When tp_printk (above) is set, it can cause a lot of noise
6770			on the console. It may be useful to only include the
6771			printing of events during boot up, as user space may
6772			make the system inoperable.
6773
6774			This command line option will stop the printing of events
6775			to console at the late_initcall_sync() time frame.
6776
6777	trace_buf_size=nn[KMG]
6778			[FTRACE] will set tracing buffer size on each cpu.
6779
6780	trace_clock=	[FTRACE] Set the clock used for tracing events
6781			at boot up.
6782			local - Use the per CPU time stamp counter
6783				(converted into nanoseconds). Fast, but
6784				depending on the architecture, may not be
6785				in sync between CPUs.
6786			global - Event time stamps are synchronize across
6787				CPUs. May be slower than the local clock,
6788				but better for some race conditions.
6789			counter - Simple counting of events (1, 2, ..)
6790				note, some counts may be skipped due to the
6791				infrastructure grabbing the clock more than
6792				once per event.
6793			uptime - Use jiffies as the time stamp.
6794			perf - Use the same clock that perf uses.
6795			mono - Use ktime_get_mono_fast_ns() for time stamps.
6796			mono_raw - Use ktime_get_raw_fast_ns() for time
6797				stamps.
6798			boot - Use ktime_get_boot_fast_ns() for time stamps.
6799			Architectures may add more clocks. See
6800			Documentation/trace/ftrace.rst for more details.
6801
6802	trace_event=[event-list]
6803			[FTRACE] Set and start specified trace events in order
6804			to facilitate early boot debugging. The event-list is a
6805			comma-separated list of trace events to enable. See
6806			also Documentation/trace/events.rst
6807
6808	trace_instance=[instance-info]
6809			[FTRACE] Create a ring buffer instance early in boot up.
6810			This will be listed in:
6811
6812				/sys/kernel/tracing/instances
6813
6814			Events can be enabled at the time the instance is created
6815			via:
6816
6817				trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
6818
6819			Note, the "<system*>:" portion is optional if the event is
6820			unique.
6821
6822				trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
6823
6824			will enable the "sched_switch" event (note, the "sched:" is optional, and
6825			the same thing would happen if it was left off). The irq_handler_entry
6826			event, and all events under the "initcall" system.
6827
6828			Flags can be added to the instance to modify its behavior when it is
6829			created. The flags are separated by '^'.
6830
6831			The available flags are:
6832
6833			    traceoff	- Have the tracing instance tracing disabled after it is created.
6834			    traceprintk	- Have trace_printk() write into this trace instance
6835					  (note, "printk" and "trace_printk" can also be used)
6836
6837				trace_instance=foo^traceoff^traceprintk,sched,irq
6838
6839			The flags must come before the defined events.
6840
6841			If memory has been reserved (see memmap for x86), the instance
6842			can use that memory:
6843
6844				memmap=12M$0x284500000 trace_instance=boot_map@0x284500000:12M
6845
6846			The above will create a "boot_map" instance that uses the physical
6847			memory at 0x284500000 that is 12Megs. The per CPU buffers of that
6848			instance will be split up accordingly.
6849
6850			Alternatively, the memory can be reserved by the reserve_mem option:
6851
6852				reserve_mem=12M:4096:trace trace_instance=boot_map@trace
6853
6854			This will reserve 12 megabytes at boot up with a 4096 byte alignment
6855			and place the ring buffer in this memory. Note that due to KASLR, the
6856			memory may not be the same location each time, which will not preserve
6857			the buffer content.
6858
6859			Also note that the layout of the ring buffer data may change between
6860			kernel versions where the validator will fail and reset the ring buffer
6861			if the layout is not the same as the previous kernel.
6862
6863			If the ring buffer is used for persistent bootups and has events enabled,
6864			it is recommend to disable tracing so that events from a previous boot do not
6865			mix with events of the current boot (unless you are debugging a random crash
6866			at boot up).
6867
6868				reserve_mem=12M:4096:trace trace_instance=boot_map^traceoff^traceprintk@trace,sched,irq
6869
6870			See also Documentation/trace/debugging.rst
6871
6872
6873	trace_options=[option-list]
6874			[FTRACE] Enable or disable tracer options at boot.
6875			The option-list is a comma delimited list of options
6876			that can be enabled or disabled just as if you were
6877			to echo the option name into
6878
6879			    /sys/kernel/tracing/trace_options
6880
6881			For example, to enable stacktrace option (to dump the
6882			stack trace of each event), add to the command line:
6883
6884			      trace_options=stacktrace
6885
6886			See also Documentation/trace/ftrace.rst "trace options"
6887			section.
6888
6889	trace_trigger=[trigger-list]
6890			[FTRACE] Add a event trigger on specific events.
6891			Set a trigger on top of a specific event, with an optional
6892			filter.
6893
6894			The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
6895			Where more than one trigger may be specified that are comma deliminated.
6896
6897			For example:
6898
6899			  trace_trigger="sched_switch.stacktrace if prev_state == 2"
6900
6901			The above will enable the "stacktrace" trigger on the "sched_switch"
6902			event but only trigger it if the "prev_state" of the "sched_switch"
6903			event is "2" (TASK_UNINTERUPTIBLE).
6904
6905			See also "Event triggers" in Documentation/trace/events.rst
6906
6907
6908	traceoff_on_warning
6909			[FTRACE] enable this option to disable tracing when a
6910			warning is hit. This turns off "tracing_on". Tracing can
6911			be enabled again by echoing '1' into the "tracing_on"
6912			file located in /sys/kernel/tracing/
6913
6914			This option is useful, as it disables the trace before
6915			the WARNING dump is called, which prevents the trace to
6916			be filled with content caused by the warning output.
6917
6918			This option can also be set at run time via the sysctl
6919			option:  kernel/traceoff_on_warning
6920
6921	transparent_hugepage=
6922			[KNL]
6923			Format: [always|madvise|never]
6924			Can be used to control the default behavior of the system
6925			with respect to transparent hugepages.
6926			See Documentation/admin-guide/mm/transhuge.rst
6927			for more details.
6928
6929	trusted.source=	[KEYS]
6930			Format: <string>
6931			This parameter identifies the trust source as a backend
6932			for trusted keys implementation. Supported trust
6933			sources:
6934			- "tpm"
6935			- "tee"
6936			- "caam"
6937			- "dcp"
6938			If not specified then it defaults to iterating through
6939			the trust source list starting with TPM and assigns the
6940			first trust source as a backend which is initialized
6941			successfully during iteration.
6942
6943	trusted.rng=	[KEYS]
6944			Format: <string>
6945			The RNG used to generate key material for trusted keys.
6946			Can be one of:
6947			- "kernel"
6948			- the same value as trusted.source: "tpm" or "tee"
6949			- "default"
6950			If not specified, "default" is used. In this case,
6951			the RNG's choice is left to each individual trust source.
6952
6953	trusted.dcp_use_otp_key
6954			This is intended to be used in combination with
6955			trusted.source=dcp and will select the DCP OTP key
6956			instead of the DCP UNIQUE key blob encryption.
6957
6958	trusted.dcp_skip_zk_test
6959			This is intended to be used in combination with
6960			trusted.source=dcp and will disable the check if the
6961			blob key is all zeros. This is helpful for situations where
6962			having this key zero'ed is acceptable. E.g. in testing
6963			scenarios.
6964
6965	tsc=		Disable clocksource stability checks for TSC.
6966			Format: <string>
6967			[x86] reliable: mark tsc clocksource as reliable, this
6968			disables clocksource verification at runtime, as well
6969			as the stability checks done at bootup.	Used to enable
6970			high-resolution timer mode on older hardware, and in
6971			virtualized environment.
6972			[x86] noirqtime: Do not use TSC to do irq accounting.
6973			Used to run time disable IRQ_TIME_ACCOUNTING on any
6974			platforms where RDTSC is slow and this accounting
6975			can add overhead.
6976			[x86] unstable: mark the TSC clocksource as unstable, this
6977			marks the TSC unconditionally unstable at bootup and
6978			avoids any further wobbles once the TSC watchdog notices.
6979			[x86] nowatchdog: disable clocksource watchdog. Used
6980			in situations with strict latency requirements (where
6981			interruptions from clocksource watchdog are not
6982			acceptable).
6983			[x86] recalibrate: force recalibration against a HW timer
6984			(HPET or PM timer) on systems whose TSC frequency was
6985			obtained from HW or FW using either an MSR or CPUID(0x15).
6986			Warn if the difference is more than 500 ppm.
6987			[x86] watchdog: Use TSC as the watchdog clocksource with
6988			which to check other HW timers (HPET or PM timer), but
6989			only on systems where TSC has been deemed trustworthy.
6990			This will be suppressed by an earlier tsc=nowatchdog and
6991			can be overridden by a later tsc=nowatchdog.  A console
6992			message will flag any such suppression or overriding.
6993
6994	tsc_early_khz=  [X86,EARLY] Skip early TSC calibration and use the given
6995			value instead. Useful when the early TSC frequency discovery
6996			procedure is not reliable, such as on overclocked systems
6997			with CPUID.16h support and partial CPUID.15h support.
6998			Format: <unsigned int>
6999
7000	tsx=		[X86] Control Transactional Synchronization
7001			Extensions (TSX) feature in Intel processors that
7002			support TSX control.
7003
7004			This parameter controls the TSX feature. The options are:
7005
7006			on	- Enable TSX on the system. Although there are
7007				mitigations for all known security vulnerabilities,
7008				TSX has been known to be an accelerator for
7009				several previous speculation-related CVEs, and
7010				so there may be unknown	security risks associated
7011				with leaving it enabled.
7012
7013			off	- Disable TSX on the system. (Note that this
7014				option takes effect only on newer CPUs which are
7015				not vulnerable to MDS, i.e., have
7016				MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
7017				the new IA32_TSX_CTRL MSR through a microcode
7018				update. This new MSR allows for the reliable
7019				deactivation of the TSX functionality.)
7020
7021			auto	- Disable TSX if X86_BUG_TAA is present,
7022				  otherwise enable TSX on the system.
7023
7024			Not specifying this option is equivalent to tsx=off.
7025
7026			See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7027			for more details.
7028
7029	tsx_async_abort= [X86,INTEL,EARLY] Control mitigation for the TSX Async
7030			Abort (TAA) vulnerability.
7031
7032			Similar to Micro-architectural Data Sampling (MDS)
7033			certain CPUs that support Transactional
7034			Synchronization Extensions (TSX) are vulnerable to an
7035			exploit against CPU internal buffers which can forward
7036			information to a disclosure gadget under certain
7037			conditions.
7038
7039			In vulnerable processors, the speculatively forwarded
7040			data can be used in a cache side channel attack, to
7041			access data to which the attacker does not have direct
7042			access.
7043
7044			This parameter controls the TAA mitigation.  The
7045			options are:
7046
7047			full       - Enable TAA mitigation on vulnerable CPUs
7048				     if TSX is enabled.
7049
7050			full,nosmt - Enable TAA mitigation and disable SMT on
7051				     vulnerable CPUs. If TSX is disabled, SMT
7052				     is not disabled because CPU is not
7053				     vulnerable to cross-thread TAA attacks.
7054			off        - Unconditionally disable TAA mitigation
7055
7056			On MDS-affected machines, tsx_async_abort=off can be
7057			prevented by an active MDS mitigation as both vulnerabilities
7058			are mitigated with the same mechanism so in order to disable
7059			this mitigation, you need to specify mds=off too.
7060
7061			Not specifying this option is equivalent to
7062			tsx_async_abort=full.  On CPUs which are MDS affected
7063			and deploy MDS mitigation, TAA mitigation is not
7064			required and doesn't provide any additional
7065			mitigation.
7066
7067			For details see:
7068			Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
7069
7070	turbografx.map[2|3]=	[HW,JOY]
7071			TurboGraFX parallel port interface
7072			Format:
7073			<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
7074			See also Documentation/input/devices/joystick-parport.rst
7075
7076	udbg-immortal	[PPC] When debugging early kernel crashes that
7077			happen after console_init() and before a proper
7078			console driver takes over, this boot options might
7079			help "seeing" what's going on.
7080
7081	uhash_entries=	[KNL,NET]
7082			Set number of hash buckets for UDP/UDP-Lite connections
7083
7084	uhci-hcd.ignore_oc=
7085			[USB] Ignore overcurrent events (default N).
7086			Some badly-designed motherboards generate lots of
7087			bogus events, for ports that aren't wired to
7088			anything.  Set this parameter to avoid log spamming.
7089			Note that genuine overcurrent events won't be
7090			reported either.
7091
7092	unknown_nmi_panic
7093			[X86] Cause panic on unknown NMI.
7094
7095	unwind_debug	[X86-64,EARLY]
7096			Enable unwinder debug output.  This can be
7097			useful for debugging certain unwinder error
7098			conditions, including corrupt stacks and
7099			bad/missing unwinder metadata.
7100
7101	usbcore.authorized_default=
7102			[USB] Default USB device authorization:
7103			(default -1 = authorized (same as 1),
7104			0 = not authorized, 1 = authorized, 2 = authorized
7105			if device connected to internal port)
7106
7107	usbcore.autosuspend=
7108			[USB] The autosuspend time delay (in seconds) used
7109			for newly-detected USB devices (default 2).  This
7110			is the time required before an idle device will be
7111			autosuspended.  Devices for which the delay is set
7112			to a negative value won't be autosuspended at all.
7113
7114	usbcore.usbfs_snoop=
7115			[USB] Set to log all usbfs traffic (default 0 = off).
7116
7117	usbcore.usbfs_snoop_max=
7118			[USB] Maximum number of bytes to snoop in each URB
7119			(default = 65536).
7120
7121	usbcore.blinkenlights=
7122			[USB] Set to cycle leds on hubs (default 0 = off).
7123
7124	usbcore.old_scheme_first=
7125			[USB] Start with the old device initialization
7126			scheme (default 0 = off).
7127
7128	usbcore.usbfs_memory_mb=
7129			[USB] Memory limit (in MB) for buffers allocated by
7130			usbfs (default = 16, 0 = max = 2047).
7131
7132	usbcore.use_both_schemes=
7133			[USB] Try the other device initialization scheme
7134			if the first one fails (default 1 = enabled).
7135
7136	usbcore.initial_descriptor_timeout=
7137			[USB] Specifies timeout for the initial 64-byte
7138			USB_REQ_GET_DESCRIPTOR request in milliseconds
7139			(default 5000 = 5.0 seconds).
7140
7141	usbcore.nousb	[USB] Disable the USB subsystem
7142
7143	usbcore.quirks=
7144			[USB] A list of quirk entries to augment the built-in
7145			usb core quirk list. List entries are separated by
7146			commas. Each entry has the form
7147			VendorID:ProductID:Flags. The IDs are 4-digit hex
7148			numbers and Flags is a set of letters. Each letter
7149			will change the built-in quirk; setting it if it is
7150			clear and clearing it if it is set. The letters have
7151			the following meanings:
7152				a = USB_QUIRK_STRING_FETCH_255 (string
7153					descriptors must not be fetched using
7154					a 255-byte read);
7155				b = USB_QUIRK_RESET_RESUME (device can't resume
7156					correctly so reset it instead);
7157				c = USB_QUIRK_NO_SET_INTF (device can't handle
7158					Set-Interface requests);
7159				d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7160					handle its Configuration or Interface
7161					strings);
7162				e = USB_QUIRK_RESET (device can't be reset
7163					(e.g morph devices), don't use reset);
7164				f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7165					more interface descriptions than the
7166					bNumInterfaces count, and can't handle
7167					talking to these interfaces);
7168				g = USB_QUIRK_DELAY_INIT (device needs a pause
7169					during initialization, after we read
7170					the device descriptor);
7171				h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7172					high speed and super speed interrupt
7173					endpoints, the USB 2.0 and USB 3.0 spec
7174					require the interval in microframes (1
7175					microframe = 125 microseconds) to be
7176					calculated as interval = 2 ^
7177					(bInterval-1).
7178					Devices with this quirk report their
7179					bInterval as the result of this
7180					calculation instead of the exponent
7181					variable used in the calculation);
7182				i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7183					handle device_qualifier descriptor
7184					requests);
7185				j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7186					generates spurious wakeup, ignore
7187					remote wakeup capability);
7188				k = USB_QUIRK_NO_LPM (device can't handle Link
7189					Power Management);
7190				l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7191					(Device reports its bInterval as linear
7192					frames instead of the USB 2.0
7193					calculation);
7194				m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7195					to be disconnected before suspend to
7196					prevent spurious wakeup);
7197				n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7198					pause after every control message);
7199				o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7200					delay after resetting its port);
7201				p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT
7202					(Reduce timeout of the SET_ADDRESS
7203					request from 5000 ms to 500 ms);
7204			Example: quirks=0781:5580:bk,0a5c:5834:gij
7205
7206	usbhid.mousepoll=
7207			[USBHID] The interval which mice are to be polled at.
7208
7209	usbhid.jspoll=
7210			[USBHID] The interval which joysticks are to be polled at.
7211
7212	usbhid.kbpoll=
7213			[USBHID] The interval which keyboards are to be polled at.
7214
7215	usb-storage.delay_use=
7216			[UMS] The delay in seconds before a new device is
7217			scanned for Logical Units (default 1).
7218			Optionally the delay in milliseconds if the value has
7219			suffix with "ms".
7220			Example: delay_use=2567ms
7221
7222	usb-storage.quirks=
7223			[UMS] A list of quirks entries to supplement or
7224			override the built-in unusual_devs list.  List
7225			entries are separated by commas.  Each entry has
7226			the form VID:PID:Flags where VID and PID are Vendor
7227			and Product ID values (4-digit hex numbers) and
7228			Flags is a set of characters, each corresponding
7229			to a common usb-storage quirk flag as follows:
7230				a = SANE_SENSE (collect more than 18 bytes
7231					of sense data, not on uas);
7232				b = BAD_SENSE (don't collect more than 18
7233					bytes of sense data, not on uas);
7234				c = FIX_CAPACITY (decrease the reported
7235					device capacity by one sector);
7236				d = NO_READ_DISC_INFO (don't use
7237					READ_DISC_INFO command, not on uas);
7238				e = NO_READ_CAPACITY_16 (don't use
7239					READ_CAPACITY_16 command);
7240				f = NO_REPORT_OPCODES (don't use report opcodes
7241					command, uas only);
7242				g = MAX_SECTORS_240 (don't transfer more than
7243					240 sectors at a time, uas only);
7244				h = CAPACITY_HEURISTICS (decrease the
7245					reported device capacity by one
7246					sector if the number is odd);
7247				i = IGNORE_DEVICE (don't bind to this
7248					device);
7249				j = NO_REPORT_LUNS (don't use report luns
7250					command, uas only);
7251				k = NO_SAME (do not use WRITE_SAME, uas only)
7252				l = NOT_LOCKABLE (don't try to lock and
7253					unlock ejectable media, not on uas);
7254				m = MAX_SECTORS_64 (don't transfer more
7255					than 64 sectors = 32 KB at a time,
7256					not on uas);
7257				n = INITIAL_READ10 (force a retry of the
7258					initial READ(10) command, not on uas);
7259				o = CAPACITY_OK (accept the capacity
7260					reported by the device, not on uas);
7261				p = WRITE_CACHE (the device cache is ON
7262					by default, not on uas);
7263				r = IGNORE_RESIDUE (the device reports
7264					bogus residue values, not on uas);
7265				s = SINGLE_LUN (the device has only one
7266					Logical Unit);
7267				t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7268					commands, uas only);
7269				u = IGNORE_UAS (don't bind to the uas driver);
7270				w = NO_WP_DETECT (don't test whether the
7271					medium is write-protected).
7272				y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7273					even if the device claims no cache,
7274					not on uas)
7275			Example: quirks=0419:aaf5:rl,0421:0433:rc
7276
7277	user_debug=	[KNL,ARM]
7278			Format: <int>
7279			See arch/arm/Kconfig.debug help text.
7280				 1 - undefined instruction events
7281				 2 - system calls
7282				 4 - invalid data aborts
7283				 8 - SIGSEGV faults
7284				16 - SIGBUS faults
7285			Example: user_debug=31
7286
7287	userpte=
7288			[X86,EARLY] Flags controlling user PTE allocations.
7289
7290				nohigh = do not allocate PTE pages in
7291					HIGHMEM regardless of setting
7292					of CONFIG_HIGHPTE.
7293
7294	vdso=		[X86,SH,SPARC]
7295			On X86_32, this is an alias for vdso32=.  Otherwise:
7296
7297			vdso=1: enable VDSO (the default)
7298			vdso=0: disable VDSO mapping
7299
7300	vdso32=		[X86] Control the 32-bit vDSO
7301			vdso32=1: enable 32-bit VDSO
7302			vdso32=0 or vdso32=2: disable 32-bit VDSO
7303
7304			See the help text for CONFIG_COMPAT_VDSO for more
7305			details.  If CONFIG_COMPAT_VDSO is set, the default is
7306			vdso32=0; otherwise, the default is vdso32=1.
7307
7308			For compatibility with older kernels, vdso32=2 is an
7309			alias for vdso32=0.
7310
7311			Try vdso32=0 if you encounter an error that says:
7312			dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7313
7314	video=		[FB,EARLY] Frame buffer configuration
7315			See Documentation/fb/modedb.rst.
7316
7317	video.brightness_switch_enabled= [ACPI]
7318			Format: [0|1]
7319			If set to 1, on receiving an ACPI notify event
7320			generated by hotkey, video driver will adjust brightness
7321			level and then send out the event to user space through
7322			the allocated input device. If set to 0, video driver
7323			will only send out the event without touching backlight
7324			brightness level.
7325			default: 1
7326
7327	virtio_mmio.device=
7328			[VMMIO] Memory mapped virtio (platform) device.
7329
7330				<size>@<baseaddr>:<irq>[:<id>]
7331			where:
7332				<size>     := size (can use standard suffixes
7333						like K, M and G)
7334				<baseaddr> := physical base address
7335				<irq>      := interrupt number (as passed to
7336						request_irq())
7337				<id>       := (optional) platform device id
7338			example:
7339				virtio_mmio.device=1K@0x100b0000:48:7
7340
7341			Can be used multiple times for multiple devices.
7342
7343	vga=		[BOOT,X86-32] Select a particular video mode
7344			See Documentation/arch/x86/boot.rst and
7345			Documentation/admin-guide/svga.rst.
7346			Use vga=ask for menu.
7347			This is actually a boot loader parameter; the value is
7348			passed to the kernel using a special protocol.
7349
7350	vm_debug[=options]	[KNL] Available with CONFIG_DEBUG_VM=y.
7351			May slow down system boot speed, especially when
7352			enabled on systems with a large amount of memory.
7353			All options are enabled by default, and this
7354			interface is meant to allow for selectively
7355			enabling or disabling specific virtual memory
7356			debugging features.
7357
7358			Available options are:
7359			  P	Enable page structure init time poisoning
7360			  -	Disable all of the above options
7361
7362	vmalloc=nn[KMG]	[KNL,BOOT,EARLY] Forces the vmalloc area to have an
7363			exact size of <nn>. This can be used to increase
7364			the minimum size (128MB on x86, arm32 platforms).
7365			It can also be used to decrease the size and leave more room
7366			for directly mapped kernel RAM. Note that this parameter does
7367			not exist on many other platforms (including arm64, alpha,
7368			loongarch, arc, csky, hexagon, microblaze, mips, nios2, openrisc,
7369			parisc, m64k, powerpc, riscv, sh, um, xtensa, s390, sparc).
7370
7371	vmcp_cma=nn[MG]	[KNL,S390,EARLY]
7372			Sets the memory size reserved for contiguous memory
7373			allocations for the vmcp device driver.
7374
7375	vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
7376			Format: <command>
7377
7378	vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
7379			Format: <command>
7380
7381	vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
7382			Format: <command>
7383
7384	vsyscall=	[X86-64,EARLY]
7385			Controls the behavior of vsyscalls (i.e. calls to
7386			fixed addresses of 0xffffffffff600x00 from legacy
7387			code).  Most statically-linked binaries and older
7388			versions of glibc use these calls.  Because these
7389			functions are at fixed addresses, they make nice
7390			targets for exploits that can control RIP.
7391
7392			emulate     Vsyscalls turn into traps and are emulated
7393			            reasonably safely.  The vsyscall page is
7394				    readable.
7395
7396			xonly       [default] Vsyscalls turn into traps and are
7397			            emulated reasonably safely.  The vsyscall
7398				    page is not readable.
7399
7400			none        Vsyscalls don't work at all.  This makes
7401			            them quite hard to use for exploits but
7402			            might break your system.
7403
7404	vt.color=	[VT] Default text color.
7405			Format: 0xYX, X = foreground, Y = background.
7406			Default: 0x07 = light gray on black.
7407
7408	vt.cur_default=	[VT] Default cursor shape.
7409			Format: 0xCCBBAA, where AA, BB, and CC are the same as
7410			the parameters of the <Esc>[?A;B;Cc escape sequence;
7411			see VGA-softcursor.txt. Default: 2 = underline.
7412
7413	vt.default_blu=	[VT]
7414			Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7415			Change the default blue palette of the console.
7416			This is a 16-member array composed of values
7417			ranging from 0-255.
7418
7419	vt.default_grn=	[VT]
7420			Format: <green0>,<green1>,<green2>,...,<green15>
7421			Change the default green palette of the console.
7422			This is a 16-member array composed of values
7423			ranging from 0-255.
7424
7425	vt.default_red=	[VT]
7426			Format: <red0>,<red1>,<red2>,...,<red15>
7427			Change the default red palette of the console.
7428			This is a 16-member array composed of values
7429			ranging from 0-255.
7430
7431	vt.default_utf8=
7432			[VT]
7433			Format=<0|1>
7434			Set system-wide default UTF-8 mode for all tty's.
7435			Default is 1, i.e. UTF-8 mode is enabled for all
7436			newly opened terminals.
7437
7438	vt.global_cursor_default=
7439			[VT]
7440			Format=<-1|0|1>
7441			Set system-wide default for whether a cursor
7442			is shown on new VTs. Default is -1,
7443			i.e. cursors will be created by default unless
7444			overridden by individual drivers. 0 will hide
7445			cursors, 1 will display them.
7446
7447	vt.italic=	[VT] Default color for italic text; 0-15.
7448			Default: 2 = green.
7449
7450	vt.underline=	[VT] Default color for underlined text; 0-15.
7451			Default: 3 = cyan.
7452
7453	watchdog timers	[HW,WDT] For information on watchdog timers,
7454			see Documentation/watchdog/watchdog-parameters.rst
7455			or other driver-specific files in the
7456			Documentation/watchdog/ directory.
7457
7458	watchdog_thresh=
7459			[KNL]
7460			Set the hard lockup detector stall duration
7461			threshold in seconds. The soft lockup detector
7462			threshold is set to twice the value. A value of 0
7463			disables both lockup detectors. Default is 10
7464			seconds.
7465
7466	workqueue.unbound_cpus=
7467			[KNL,SMP] Specify to constrain one or some CPUs
7468			to use in unbound workqueues.
7469			Format: <cpu-list>
7470			By default, all online CPUs are available for
7471			unbound workqueues.
7472
7473	workqueue.watchdog_thresh=
7474			If CONFIG_WQ_WATCHDOG is configured, workqueue can
7475			warn stall conditions and dump internal state to
7476			help debugging.  0 disables workqueue stall
7477			detection; otherwise, it's the stall threshold
7478			duration in seconds.  The default value is 30 and
7479			it can be updated at runtime by writing to the
7480			corresponding sysfs file.
7481
7482	workqueue.panic_on_stall=<uint>
7483			Panic when workqueue stall is detected by
7484			CONFIG_WQ_WATCHDOG. It sets the number times of the
7485			stall to trigger panic.
7486
7487			The default is 0, which disables the panic on stall.
7488
7489	workqueue.cpu_intensive_thresh_us=
7490			Per-cpu work items which run for longer than this
7491			threshold are automatically considered CPU intensive
7492			and excluded from concurrency management to prevent
7493			them from noticeably delaying other per-cpu work
7494			items. Default is 10000 (10ms).
7495
7496			If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
7497			will report the work functions which violate this
7498			threshold repeatedly. They are likely good
7499			candidates for using WQ_UNBOUND workqueues instead.
7500
7501	workqueue.cpu_intensive_warning_thresh=<uint>
7502			If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
7503			will report the work functions which violate the
7504			intensive_threshold_us repeatedly. In order to prevent
7505			spurious warnings, start printing only after a work
7506			function has violated this threshold number of times.
7507
7508			The default is 4 times. 0 disables the warning.
7509
7510	workqueue.power_efficient
7511			Per-cpu workqueues are generally preferred because
7512			they show better performance thanks to cache
7513			locality; unfortunately, per-cpu workqueues tend to
7514			be more power hungry than unbound workqueues.
7515
7516			Enabling this makes the per-cpu workqueues which
7517			were observed to contribute significantly to power
7518			consumption unbound, leading to measurably lower
7519			power usage at the cost of small performance
7520			overhead.
7521
7522			The default value of this parameter is determined by
7523			the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7524
7525        workqueue.default_affinity_scope=
7526			Select the default affinity scope to use for unbound
7527			workqueues. Can be one of "cpu", "smt", "cache",
7528			"numa" and "system". Default is "cache". For more
7529			information, see the Affinity Scopes section in
7530			Documentation/core-api/workqueue.rst.
7531
7532			This can be changed after boot by writing to the
7533			matching /sys/module/workqueue/parameters file. All
7534			workqueues with the "default" affinity scope will be
7535			updated accordingly.
7536
7537	workqueue.debug_force_rr_cpu
7538			Workqueue used to implicitly guarantee that work
7539			items queued without explicit CPU specified are put
7540			on the local CPU.  This guarantee is no longer true
7541			and while local CPU is still preferred work items
7542			may be put on foreign CPUs.  This debug option
7543			forces round-robin CPU selection to flush out
7544			usages which depend on the now broken guarantee.
7545			When enabled, memory and cache locality will be
7546			impacted.
7547
7548	writecombine=	[LOONGARCH,EARLY] Control the MAT (Memory Access
7549			Type) of ioremap_wc().
7550
7551			on   - Enable writecombine, use WUC for ioremap_wc()
7552			off  - Disable writecombine, use SUC for ioremap_wc()
7553
7554	x2apic_phys	[X86-64,APIC,EARLY] Use x2apic physical mode instead of
7555			default x2apic cluster mode on platforms
7556			supporting x2apic.
7557
7558	xen_512gb_limit		[KNL,X86-64,XEN]
7559			Restricts the kernel running paravirtualized under Xen
7560			to use only up to 512 GB of RAM. The reason to do so is
7561			crash analysis tools and Xen tools for doing domain
7562			save/restore/migration must be enabled to handle larger
7563			domains.
7564
7565	xen_emul_unplug=		[HW,X86,XEN,EARLY]
7566			Unplug Xen emulated devices
7567			Format: [unplug0,][unplug1]
7568			ide-disks -- unplug primary master IDE devices
7569			aux-ide-disks -- unplug non-primary-master IDE devices
7570			nics -- unplug network devices
7571			all -- unplug all emulated devices (NICs and IDE disks)
7572			unnecessary -- unplugging emulated devices is
7573				unnecessary even if the host did not respond to
7574				the unplug protocol
7575			never -- do not unplug even if version check succeeds
7576
7577	xen_legacy_crash	[X86,XEN,EARLY]
7578			Crash from Xen panic notifier, without executing late
7579			panic() code such as dumping handler.
7580
7581	xen_mc_debug	[X86,XEN,EARLY]
7582			Enable multicall debugging when running as a Xen PV guest.
7583			Enabling this feature will reduce performance a little
7584			bit, so it should only be enabled for obtaining extended
7585			debug data in case of multicall errors.
7586
7587	xen_msr_safe=	[X86,XEN,EARLY]
7588			Format: <bool>
7589			Select whether to always use non-faulting (safe) MSR
7590			access functions when running as Xen PV guest. The
7591			default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
7592
7593	xen_nopv	[X86]
7594			Disables the PV optimizations forcing the HVM guest to
7595			run as generic HVM guest with no PV drivers.
7596			This option is obsoleted by the "nopv" option, which
7597			has equivalent effect for XEN platform.
7598
7599	xen_no_vector_callback
7600			[KNL,X86,XEN,EARLY] Disable the vector callback for Xen
7601			event channel interrupts.
7602
7603	xen_scrub_pages=	[XEN]
7604			Boolean option to control scrubbing pages before giving them back
7605			to Xen, for use by other domains. Can be also changed at runtime
7606			with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7607			Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7608
7609	xen_timer_slop=	[X86-64,XEN,EARLY]
7610			Set the timer slop (in nanoseconds) for the virtual Xen
7611			timers (default is 100000). This adjusts the minimum
7612			delta of virtualized Xen timers, where lower values
7613			improve timer resolution at the expense of processing
7614			more timer interrupts.
7615
7616	xen.balloon_boot_timeout= [XEN]
7617			The time (in seconds) to wait before giving up to boot
7618			in case initial ballooning fails to free enough memory.
7619			Applies only when running as HVM or PVH guest and
7620			started with less memory configured than allowed at
7621			max. Default is 180.
7622
7623	xen.event_eoi_delay=	[XEN]
7624			How long to delay EOI handling in case of event
7625			storms (jiffies). Default is 10.
7626
7627	xen.event_loop_timeout=	[XEN]
7628			After which time (jiffies) the event handling loop
7629			should start to delay EOI handling. Default is 2.
7630
7631	xen.fifo_events=	[XEN]
7632			Boolean parameter to disable using fifo event handling
7633			even if available. Normally fifo event handling is
7634			preferred over the 2-level event handling, as it is
7635			fairer and the number of possible event channels is
7636			much higher. Default is on (use fifo events).
7637
7638	xirc2ps_cs=	[NET,PCMCIA]
7639			Format:
7640			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7641
7642	xive=		[PPC]
7643			By default on POWER9 and above, the kernel will
7644			natively use the XIVE interrupt controller. This option
7645			allows the fallback firmware mode to be used:
7646
7647			off       Fallback to firmware control of XIVE interrupt
7648				  controller on both pseries and powernv
7649				  platforms. Only useful on POWER9 and above.
7650
7651	xive.store-eoi=off	[PPC]
7652			By default on POWER10 and above, the kernel will use
7653			stores for EOI handling when the XIVE interrupt mode
7654			is active. This option allows the XIVE driver to use
7655			loads instead, as on POWER9.
7656
7657	xhci-hcd.quirks		[USB,KNL]
7658			A hex value specifying bitmask with supplemental xhci
7659			host controller quirks. Meaning of each bit can be
7660			consulted in header drivers/usb/host/xhci.h.
7661
7662	xmon		[PPC,EARLY]
7663			Format: { early | on | rw | ro | off }
7664			Controls if xmon debugger is enabled. Default is off.
7665			Passing only "xmon" is equivalent to "xmon=early".
7666			early	Call xmon as early as possible on boot; xmon
7667				debugger is called from setup_arch().
7668			on	xmon debugger hooks will be installed so xmon
7669				is only called on a kernel crash. Default mode,
7670				i.e. either "ro" or "rw" mode, is controlled
7671				with CONFIG_XMON_DEFAULT_RO_MODE.
7672			rw	xmon debugger hooks will be installed so xmon
7673				is called only on a kernel crash, mode is write,
7674				meaning SPR registers, memory and, other data
7675				can be written using xmon commands.
7676			ro 	same as "rw" option above but SPR registers,
7677				memory, and other data can't be written using
7678				xmon commands.
7679			off	xmon is disabled.
7680