1	acpi=		[HW,ACPI,X86,ARM64]
2			Advanced Configuration and Power Interface
3			Format: { force | on | off | strict | noirq | rsdt |
4				  copy_dsdt }
5			force -- enable ACPI if default was off
6			on -- enable ACPI but allow fallback to DT [arm64]
7			off -- disable ACPI if default was on
8			noirq -- do not use ACPI for IRQ routing
9			strict -- Be less tolerant of platforms that are not
10				strictly ACPI specification compliant.
11			rsdt -- prefer RSDT over (default) XSDT
12			copy_dsdt -- copy DSDT to memory
13			For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
14			are available
15
16			See also Documentation/power/runtime_pm.txt, pci=noacpi
17
18	acpi_apic_instance=	[ACPI, IOAPIC]
19			Format: <int>
20			2: use 2nd APIC table, if available
21			1,0: use 1st APIC table
22			default: 0
23
24	acpi_backlight=	[HW,ACPI]
25			acpi_backlight=vendor
26			acpi_backlight=video
27			If set to vendor, prefer vendor specific driver
28			(e.g. thinkpad_acpi, sony_acpi, etc.) instead
29			of the ACPI video.ko driver.
30
31	acpi_force_32bit_fadt_addr
32			force FADT to use 32 bit addresses rather than the
33			64 bit X_* addresses. Some firmware have broken 64
34			bit addresses for force ACPI ignore these and use
35			the older legacy 32 bit addresses.
36
37	acpica_no_return_repair [HW, ACPI]
38			Disable AML predefined validation mechanism
39			This mechanism can repair the evaluation result to make
40			the return objects more ACPI specification compliant.
41			This option is useful for developers to identify the
42			root cause of an AML interpreter issue when the issue
43			has something to do with the repair mechanism.
44
45	acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
46	acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
47			Format: <int>
48			CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
49			debug output.  Bits in debug_layer correspond to a
50			_COMPONENT in an ACPI source file, e.g.,
51			    #define _COMPONENT ACPI_PCI_COMPONENT
52			Bits in debug_level correspond to a level in
53			ACPI_DEBUG_PRINT statements, e.g.,
54			    ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
55			The debug_level mask defaults to "info".  See
56			Documentation/acpi/debug.txt for more information about
57			debug layers and levels.
58
59			Enable processor driver info messages:
60			    acpi.debug_layer=0x20000000
61			Enable PCI/PCI interrupt routing info messages:
62			    acpi.debug_layer=0x400000
63			Enable AML "Debug" output, i.e., stores to the Debug
64			object while interpreting AML:
65			    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
66			Enable all messages related to ACPI hardware:
67			    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
68
69			Some values produce so much output that the system is
70			unusable.  The "log_buf_len" parameter may be useful
71			if you need to capture more output.
72
73	acpi_enforce_resources=	[ACPI]
74			{ strict | lax | no }
75			Check for resource conflicts between native drivers
76			and ACPI OperationRegions (SystemIO and SystemMemory
77			only). IO ports and memory declared in ACPI might be
78			used by the ACPI subsystem in arbitrary AML code and
79			can interfere with legacy drivers.
80			strict (default): access to resources claimed by ACPI
81			is denied; legacy drivers trying to access reserved
82			resources will fail to bind to device using them.
83			lax: access to resources claimed by ACPI is allowed;
84			legacy drivers trying to access reserved resources
85			will bind successfully but a warning message is logged.
86			no: ACPI OperationRegions are not marked as reserved,
87			no further checks are performed.
88
89	acpi_force_table_verification	[HW,ACPI]
90			Enable table checksum verification during early stage.
91			By default, this is disabled due to x86 early mapping
92			size limitation.
93
94	acpi_irq_balance [HW,ACPI]
95			ACPI will balance active IRQs
96			default in APIC mode
97
98	acpi_irq_nobalance [HW,ACPI]
99			ACPI will not move active IRQs (default)
100			default in PIC mode
101
102	acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
103			Format: <irq>,<irq>...
104
105	acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
106			use by PCI
107			Format: <irq>,<irq>...
108
109	acpi_mask_gpe=	[HW,ACPI]
110			Due to the existence of _Lxx/_Exx, some GPEs triggered
111			by unsupported hardware/firmware features can result in
112			GPE floodings that cannot be automatically disabled by
113			the GPE dispatcher.
114			This facility can be used to prevent such uncontrolled
115			GPE floodings.
116			Format: <int>
117
118	acpi_no_auto_serialize	[HW,ACPI]
119			Disable auto-serialization of AML methods
120			AML control methods that contain the opcodes to create
121			named objects will be marked as "Serialized" by the
122			auto-serialization feature.
123			This feature is enabled by default.
124			This option allows to turn off the feature.
125
126	acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
127			   kernels.
128
129	acpi_no_static_ssdt	[HW,ACPI]
130			Disable installation of static SSDTs at early boot time
131			By default, SSDTs contained in the RSDT/XSDT will be
132			installed automatically and they will appear under
133			/sys/firmware/acpi/tables.
134			This option turns off this feature.
135			Note that specifying this option does not affect
136			dynamic table installation which will install SSDT
137			tables to /sys/firmware/acpi/tables/dynamic.
138
139	acpi_rsdp=	[ACPI,EFI,KEXEC]
140			Pass the RSDP address to the kernel, mostly used
141			on machines running EFI runtime service to boot the
142			second kernel for kdump.
143
144	acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
145			Format: To spoof as Windows 98: ="Microsoft Windows"
146
147	acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
148			of 2 which is mandated by ACPI 6) as the supported ACPI
149			specification revision (when using this switch, it may
150			be necessary to carry out a cold reboot _twice_ in a
151			row to make it take effect on the platform firmware).
152
153	acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
154			acpi_osi="string1"	# add string1
155			acpi_osi="!string2"	# remove string2
156			acpi_osi=!*		# remove all strings
157			acpi_osi=!		# disable all built-in OS vendor
158						  strings
159			acpi_osi=!!		# enable all built-in OS vendor
160						  strings
161			acpi_osi=		# disable all strings
162
163			'acpi_osi=!' can be used in combination with single or
164			multiple 'acpi_osi="string1"' to support specific OS
165			vendor string(s).  Note that such command can only
166			affect the default state of the OS vendor strings, thus
167			it cannot affect the default state of the feature group
168			strings and the current state of the OS vendor strings,
169			specifying it multiple times through kernel command line
170			is meaningless.  This command is useful when one do not
171			care about the state of the feature group strings which
172			should be controlled by the OSPM.
173			Examples:
174			  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
175			     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
176			     can make '_OSI("Windows 2000")' TRUE.
177
178			'acpi_osi=' cannot be used in combination with other
179			'acpi_osi=' command lines, the _OSI method will not
180			exist in the ACPI namespace.  NOTE that such command can
181			only affect the _OSI support state, thus specifying it
182			multiple times through kernel command line is also
183			meaningless.
184			Examples:
185			  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
186			     FALSE.
187
188			'acpi_osi=!*' can be used in combination with single or
189			multiple 'acpi_osi="string1"' to support specific
190			string(s).  Note that such command can affect the
191			current state of both the OS vendor strings and the
192			feature group strings, thus specifying it multiple times
193			through kernel command line is meaningful.  But it may
194			still not able to affect the final state of a string if
195			there are quirks related to this string.  This command
196			is useful when one want to control the state of the
197			feature group strings to debug BIOS issues related to
198			the OSPM features.
199			Examples:
200			  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
201			     '_OSI("Module Device")' FALSE.
202			  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
203			     '_OSI("Module Device")' TRUE.
204			  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
205			     equivalent to
206			     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
207			     and
208			     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
209			     they all will make '_OSI("Windows 2000")' TRUE.
210
211	acpi_pm_good	[X86]
212			Override the pmtimer bug detection: force the kernel
213			to assume that this machine's pmtimer latches its value
214			and always returns good values.
215
216	acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
217			Format: { level | edge | high | low }
218
219	acpi_skip_timer_override [HW,ACPI]
220			Recognize and ignore IRQ0/pin2 Interrupt Override.
221			For broken nForce2 BIOS resulting in XT-PIC timer.
222
223	acpi_sleep=	[HW,ACPI] Sleep options
224			Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
225				  old_ordering, nonvs, sci_force_enable, nobl }
226			See Documentation/power/video.txt for information on
227			s3_bios and s3_mode.
228			s3_beep is for debugging; it makes the PC's speaker beep
229			as soon as the kernel's real-mode entry point is called.
230			s4_nohwsig prevents ACPI hardware signature from being
231			used during resume from hibernation.
232			old_ordering causes the ACPI 1.0 ordering of the _PTS
233			control method, with respect to putting devices into
234			low power states, to be enforced (the ACPI 2.0 ordering
235			of _PTS is used by default).
236			nonvs prevents the kernel from saving/restoring the
237			ACPI NVS memory during suspend/hibernation and resume.
238			sci_force_enable causes the kernel to set SCI_EN directly
239			on resume from S1/S3 (which is against the ACPI spec,
240			but some broken systems don't work without it).
241			nobl causes the internal blacklist of systems known to
242			behave incorrectly in some ways with respect to system
243			suspend and resume to be ignored (use wisely).
244
245	acpi_use_timer_override [HW,ACPI]
246			Use timer override. For some broken Nvidia NF5 boards
247			that require a timer override, but don't have HPET
248
249	add_efi_memmap	[EFI; X86] Include EFI memory map in
250			kernel's map of available physical RAM.
251
252	agp=		[AGP]
253			{ off | try_unsupported }
254			off: disable AGP support
255			try_unsupported: try to drive unsupported chipsets
256				(may crash computer or cause data corruption)
257
258	ALSA		[HW,ALSA]
259			See Documentation/sound/alsa-configuration.rst
260
261	alignment=	[KNL,ARM]
262			Allow the default userspace alignment fault handler
263			behaviour to be specified.  Bit 0 enables warnings,
264			bit 1 enables fixups, and bit 2 sends a segfault.
265
266	align_va_addr=	[X86-64]
267			Align virtual addresses by clearing slice [14:12] when
268			allocating a VMA at process creation time. This option
269			gives you up to 3% performance improvement on AMD F15h
270			machines (where it is enabled by default) for a
271			CPU-intensive style benchmark, and it can vary highly in
272			a microbenchmark depending on workload and compiler.
273
274			32: only for 32-bit processes
275			64: only for 64-bit processes
276			on: enable for both 32- and 64-bit processes
277			off: disable for both 32- and 64-bit processes
278
279	alloc_snapshot	[FTRACE]
280			Allocate the ftrace snapshot buffer on boot up when the
281			main buffer is allocated. This is handy if debugging
282			and you need to use tracing_snapshot() on boot up, and
283			do not want to use tracing_snapshot_alloc() as it needs
284			to be done where GFP_KERNEL allocations are allowed.
285
286	amd_iommu=	[HW,X86-64]
287			Pass parameters to the AMD IOMMU driver in the system.
288			Possible values are:
289			fullflush - enable flushing of IO/TLB entries when
290				    they are unmapped. Otherwise they are
291				    flushed before they will be reused, which
292				    is a lot of faster
293			off	  - do not initialize any AMD IOMMU found in
294				    the system
295			force_isolation - Force device isolation for all
296					  devices. The IOMMU driver is not
297					  allowed anymore to lift isolation
298					  requirements as needed. This option
299					  does not override iommu=pt
300
301	amd_iommu_dump=	[HW,X86-64]
302			Enable AMD IOMMU driver option to dump the ACPI table
303			for AMD IOMMU. With this option enabled, AMD IOMMU
304			driver will print ACPI tables for AMD IOMMU during
305			IOMMU initialization.
306
307	amd_iommu_intr=	[HW,X86-64]
308			Specifies one of the following AMD IOMMU interrupt
309			remapping modes:
310			legacy     - Use legacy interrupt remapping mode.
311			vapic      - Use virtual APIC mode, which allows IOMMU
312			             to inject interrupts directly into guest.
313			             This mode requires kvm-amd.avic=1.
314			             (Default when IOMMU HW support is present.)
315
316	amijoy.map=	[HW,JOY] Amiga joystick support
317			Map of devices attached to JOY0DAT and JOY1DAT
318			Format: <a>,<b>
319			See also Documentation/input/joydev/joystick.rst
320
321	analog.map=	[HW,JOY] Analog joystick and gamepad support
322			Specifies type or capabilities of an analog joystick
323			connected to one of 16 gameports
324			Format: <type1>,<type2>,..<type16>
325
326	apc=		[HW,SPARC]
327			Power management functions (SPARCstation-4/5 + deriv.)
328			Format: noidle
329			Disable APC CPU standby support. SPARCstation-Fox does
330			not play well with APC CPU idle - disable it if you have
331			APC and your system crashes randomly.
332
333	apic=		[APIC,X86] Advanced Programmable Interrupt Controller
334			Change the output verbosity while booting
335			Format: { quiet (default) | verbose | debug }
336			Change the amount of debugging information output
337			when initialising the APIC and IO-APIC components.
338			For X86-32, this can also be used to specify an APIC
339			driver name.
340			Format: apic=driver_name
341			Examples: apic=bigsmp
342
343	apic_extnmi=	[APIC,X86] External NMI delivery setting
344			Format: { bsp (default) | all | none }
345			bsp:  External NMI is delivered only to CPU 0
346			all:  External NMIs are broadcast to all CPUs as a
347			      backup of CPU 0
348			none: External NMI is masked for all CPUs. This is
349			      useful so that a dump capture kernel won't be
350			      shot down by NMI
351
352	autoconf=	[IPV6]
353			See Documentation/networking/ipv6.txt.
354
355	show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
356			Limit apic dumping. The parameter defines the maximal
357			number of local apics being dumped. Also it is possible
358			to set it to "all" by meaning -- no limit here.
359			Format: { 1 (default) | 2 | ... | all }.
360			The parameter valid if only apic=debug or
361			apic=verbose is specified.
362			Example: apic=debug show_lapic=all
363
364	apm=		[APM] Advanced Power Management
365			See header of arch/x86/kernel/apm_32.c.
366
367	arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
368			Format: <io>,<irq>,<nodeID>
369
370	ataflop=	[HW,M68k]
371
372	atarimouse=	[HW,MOUSE] Atari Mouse
373
374	atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
375			EzKey and similar keyboards
376
377	atkbd.reset=	[HW] Reset keyboard during initialization
378
379	atkbd.set=	[HW] Select keyboard code set
380			Format: <int> (2 = AT (default), 3 = PS/2)
381
382	atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
383			keyboards
384
385	atkbd.softraw=	[HW] Choose between synthetic and real raw mode
386			Format: <bool> (0 = real, 1 = synthetic (default))
387
388	atkbd.softrepeat= [HW]
389			Use software keyboard repeat
390
391	audit=		[KNL] Enable the audit sub-system
392			Format: { "0" | "1" | "off" | "on" }
393			0 | off - kernel audit is disabled and can not be
394			    enabled until the next reboot
395			unset - kernel audit is initialized but disabled and
396			    will be fully enabled by the userspace auditd.
397			1 | on - kernel audit is initialized and partially
398			    enabled, storing at most audit_backlog_limit
399			    messages in RAM until it is fully enabled by the
400			    userspace auditd.
401			Default: unset
402
403	audit_backlog_limit= [KNL] Set the audit queue size limit.
404			Format: <int> (must be >=0)
405			Default: 64
406
407	bau=		[X86_UV] Enable the BAU on SGI UV.  The default
408			behavior is to disable the BAU (i.e. bau=0).
409			Format: { "0" | "1" }
410			0 - Disable the BAU.
411			1 - Enable the BAU.
412			unset - Disable the BAU.
413
414	baycom_epp=	[HW,AX25]
415			Format: <io>,<mode>
416
417	baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
418			Format: <io>,<mode>
419			See header of drivers/net/hamradio/baycom_par.c.
420
421	baycom_ser_fdx=	[HW,AX25]
422			BayCom Serial Port AX.25 Modem (Full Duplex Mode)
423			Format: <io>,<irq>,<mode>[,<baud>]
424			See header of drivers/net/hamradio/baycom_ser_fdx.c.
425
426	baycom_ser_hdx=	[HW,AX25]
427			BayCom Serial Port AX.25 Modem (Half Duplex Mode)
428			Format: <io>,<irq>,<mode>
429			See header of drivers/net/hamradio/baycom_ser_hdx.c.
430
431	blkdevparts=	Manual partition parsing of block device(s) for
432			embedded devices based on command line input.
433			See Documentation/block/cmdline-partition.txt
434
435	boot_delay=	Milliseconds to delay each printk during boot.
436			Values larger than 10 seconds (10000) are changed to
437			no delay (0).
438			Format: integer
439
440	bootmem_debug	[KNL] Enable bootmem allocator debug messages.
441
442	bert_disable	[ACPI]
443			Disable BERT OS support on buggy BIOSes.
444
445	bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
446	bttv.radio=	Most important insmod options are available as
447			kernel args too.
448	bttv.pll=	See Documentation/media/v4l-drivers/bttv.rst
449	bttv.tuner=
450
451	bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
452			firmware feature for flushing multiple hpte entries
453			at a time.
454
455	c101=		[NET] Moxa C101 synchronous serial card
456
457	cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
458			Sometimes CPU hardware bugs make them report the cache
459			size incorrectly. The kernel will attempt work arounds
460			to fix known problems, but for some CPUs it is not
461			possible to determine what the correct size should be.
462			This option provides an override for these situations.
463
464	carrier_timeout=
465			[NET] Specifies amount of time (in seconds) that
466			the kernel should wait for a network carrier. By default
467			it waits 120 seconds.
468
469	ca_keys=	[KEYS] This parameter identifies a specific key(s) on
470			the system trusted keyring to be used for certificate
471			trust validation.
472			format: { id:<keyid> | builtin }
473
474	cca=		[MIPS] Override the kernel pages' cache coherency
475			algorithm.  Accepted values range from 0 to 7
476			inclusive. See arch/mips/include/asm/pgtable-bits.h
477			for platform specific values (SB1, Loongson3 and
478			others).
479
480	ccw_timeout_log	[S390]
481			See Documentation/s390/CommonIO for details.
482
483	cgroup_disable=	[KNL] Disable a particular controller
484			Format: {name of the controller(s) to disable}
485			The effects of cgroup_disable=foo are:
486			- foo isn't auto-mounted if you mount all cgroups in
487			  a single hierarchy
488			- foo isn't visible as an individually mountable
489			  subsystem
490			{Currently only "memory" controller deal with this and
491			cut the overhead, others just disable the usage. So
492			only cgroup_disable=memory is actually worthy}
493
494	cgroup_no_v1=	[KNL] Disable cgroup controllers and named hierarchies in v1
495			Format: { { controller | "all" | "named" }
496			          [,{ controller | "all" | "named" }...] }
497			Like cgroup_disable, but only applies to cgroup v1;
498			the blacklisted controllers remain available in cgroup2.
499			"all" blacklists all controllers and "named" disables
500			named mounts. Specifying both "all" and "named" disables
501			all v1 hierarchies.
502
503	cgroup.memory=	[KNL] Pass options to the cgroup memory controller.
504			Format: <string>
505			nosocket -- Disable socket memory accounting.
506			nokmem -- Disable kernel memory accounting.
507
508	checkreqprot	[SELINUX] Set initial checkreqprot flag value.
509			Format: { "0" | "1" }
510			See security/selinux/Kconfig help text.
511			0 -- check protection applied by kernel (includes
512				any implied execute protection).
513			1 -- check protection requested by application.
514			Default value is set via a kernel config option.
515			Value can be changed at runtime via
516				/selinux/checkreqprot.
517
518	cio_ignore=	[S390]
519			See Documentation/s390/CommonIO for details.
520	clk_ignore_unused
521			[CLK]
522			Prevents the clock framework from automatically gating
523			clocks that have not been explicitly enabled by a Linux
524			device driver but are enabled in hardware at reset or
525			by the bootloader/firmware. Note that this does not
526			force such clocks to be always-on nor does it reserve
527			those clocks in any way. This parameter is useful for
528			debug and development, but should not be needed on a
529			platform with proper driver support.  For more
530			information, see Documentation/driver-api/clk.rst.
531
532	clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
533			[Deprecated]
534			Forces specified clocksource (if available) to be used
535			when calculating gettimeofday(). If specified
536			clocksource is not available, it defaults to PIT.
537			Format: { pit | tsc | cyclone | pmtmr }
538
539	clocksource=	Override the default clocksource
540			Format: <string>
541			Override the default clocksource and use the clocksource
542			with the name specified.
543			Some clocksource names to choose from, depending on
544			the platform:
545			[all] jiffies (this is the base, fallback clocksource)
546			[ACPI] acpi_pm
547			[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
548				pxa_timer,timer3,32k_counter,timer0_1
549			[X86-32] pit,hpet,tsc;
550				scx200_hrt on Geode; cyclone on IBM x440
551			[MIPS] MIPS
552			[PARISC] cr16
553			[S390] tod
554			[SH] SuperH
555			[SPARC64] tick
556			[X86-64] hpet,tsc
557
558	clocksource.arm_arch_timer.evtstrm=
559			[ARM,ARM64]
560			Format: <bool>
561			Enable/disable the eventstream feature of the ARM
562			architected timer so that code using WFE-based polling
563			loops can be debugged more effectively on production
564			systems.
565
566	clearcpuid=BITNUM [X86]
567			Disable CPUID feature X for the kernel. See
568			arch/x86/include/asm/cpufeatures.h for the valid bit
569			numbers. Note the Linux specific bits are not necessarily
570			stable over kernel options, but the vendor specific
571			ones should be.
572			Also note that user programs calling CPUID directly
573			or using the feature without checking anything
574			will still see it. This just prevents it from
575			being used by the kernel or shown in /proc/cpuinfo.
576			Also note the kernel might malfunction if you disable
577			some critical bits.
578
579	cma=nn[MG]@[start[MG][-end[MG]]]
580			[ARM,X86,KNL]
581			Sets the size of kernel global memory area for
582			contiguous memory allocations and optionally the
583			placement constraint by the physical address range of
584			memory allocations. A value of 0 disables CMA
585			altogether. For more information, see
586			include/linux/dma-contiguous.h
587
588	cmo_free_hint=	[PPC] Format: { yes | no }
589			Specify whether pages are marked as being inactive
590			when they are freed.  This is used in CMO environments
591			to determine OS memory pressure for page stealing by
592			a hypervisor.
593			Default: yes
594
595	coherent_pool=nn[KMG]	[ARM,KNL]
596			Sets the size of memory pool for coherent, atomic dma
597			allocations, by default set to 256K.
598
599	com20020=	[HW,NET] ARCnet - COM20020 chipset
600			Format:
601			<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
602
603	com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
604			Format: <io>[,<irq>]
605
606	com90xx=	[HW,NET]
607			ARCnet - COM90xx chipset (memory-mapped buffers)
608			Format: <io>[,<irq>[,<memstart>]]
609
610	condev=		[HW,S390] console device
611	conmode=
612
613	console=	[KNL] Output console device and options.
614
615		tty<n>	Use the virtual console device <n>.
616
617		ttyS<n>[,options]
618		ttyUSB0[,options]
619			Use the specified serial port.  The options are of
620			the form "bbbbpnf", where "bbbb" is the baud rate,
621			"p" is parity ("n", "o", or "e"), "n" is number of
622			bits, and "f" is flow control ("r" for RTS or
623			omit it).  Default is "9600n8".
624
625			See Documentation/admin-guide/serial-console.rst for more
626			information.  See
627			Documentation/networking/netconsole.txt for an
628			alternative.
629
630		uart[8250],io,<addr>[,options]
631		uart[8250],mmio,<addr>[,options]
632		uart[8250],mmio16,<addr>[,options]
633		uart[8250],mmio32,<addr>[,options]
634		uart[8250],0x<addr>[,options]
635			Start an early, polled-mode console on the 8250/16550
636			UART at the specified I/O port or MMIO address,
637			switching to the matching ttyS device later.
638			MMIO inter-register address stride is either 8-bit
639			(mmio), 16-bit (mmio16), or 32-bit (mmio32).
640			If none of [io|mmio|mmio16|mmio32], <addr> is assumed
641			to be equivalent to 'mmio'. 'options' are specified in
642			the same format described for ttyS above; if unspecified,
643			the h/w is not re-initialized.
644
645		hvc<n>	Use the hypervisor console device <n>. This is for
646			both Xen and PowerPC hypervisors.
647
648		If the device connected to the port is not a TTY but a braille
649		device, prepend "brl," before the device type, for instance
650			console=brl,ttyS0
651		For now, only VisioBraille is supported.
652
653	console_msg_format=
654			[KNL] Change console messages format
655		default
656			By default we print messages on consoles in
657			"[time stamp] text\n" format (time stamp may not be
658			printed, depending on CONFIG_PRINTK_TIME or
659			`printk_time' param).
660		syslog
661			Switch to syslog format: "<%u>[time stamp] text\n"
662			IOW, each message will have a facility and loglevel
663			prefix. The format is similar to one used by syslog()
664			syscall, or to executing "dmesg -S --raw" or to reading
665			from /proc/kmsg.
666
667	consoleblank=	[KNL] The console blank (screen saver) timeout in
668			seconds. A value of 0 disables the blank timer.
669			Defaults to 0.
670
671	coredump_filter=
672			[KNL] Change the default value for
673			/proc/<pid>/coredump_filter.
674			See also Documentation/filesystems/proc.txt.
675
676	coresight_cpu_debug.enable
677			[ARM,ARM64]
678			Format: <bool>
679			Enable/disable the CPU sampling based debugging.
680			0: default value, disable debugging
681			1: enable debugging at boot time
682
683	cpuidle.off=1	[CPU_IDLE]
684			disable the cpuidle sub-system
685
686	cpuidle.governor=
687			[CPU_IDLE] Name of the cpuidle governor to use.
688
689	cpufreq.off=1	[CPU_FREQ]
690			disable the cpufreq sub-system
691
692	cpu_init_udelay=N
693			[X86] Delay for N microsec between assert and de-assert
694			of APIC INIT to start processors.  This delay occurs
695			on every CPU online, such as boot, and resume from suspend.
696			Default: 10000
697
698	cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
699			Format:
700			<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
701
702	crashkernel=size[KMG][@offset[KMG]]
703			[KNL] Using kexec, Linux can switch to a 'crash kernel'
704			upon panic. This parameter reserves the physical
705			memory region [offset, offset + size] for that kernel
706			image. If '@offset' is omitted, then a suitable offset
707			is selected automatically.
708			[KNL, x86_64] select a region under 4G first, and
709			fall back to reserve region above 4G when '@offset'
710			hasn't been specified.
711			See Documentation/kdump/kdump.txt for further details.
712
713	crashkernel=range1:size1[,range2:size2,...][@offset]
714			[KNL] Same as above, but depends on the memory
715			in the running system. The syntax of range is
716			start-[end] where start and end are both
717			a memory unit (amount[KMG]). See also
718			Documentation/kdump/kdump.txt for an example.
719
720	crashkernel=size[KMG],high
721			[KNL, x86_64] range could be above 4G. Allow kernel
722			to allocate physical memory region from top, so could
723			be above 4G if system have more than 4G ram installed.
724			Otherwise memory region will be allocated below 4G, if
725			available.
726			It will be ignored if crashkernel=X is specified.
727	crashkernel=size[KMG],low
728			[KNL, x86_64] range under 4G. When crashkernel=X,high
729			is passed, kernel could allocate physical memory region
730			above 4G, that cause second kernel crash on system
731			that require some amount of low memory, e.g. swiotlb
732			requires at least 64M+32K low memory, also enough extra
733			low memory is needed to make sure DMA buffers for 32-bit
734			devices won't run out. Kernel would try to allocate at
735			at least 256M below 4G automatically.
736			This one let user to specify own low range under 4G
737			for second kernel instead.
738			0: to disable low allocation.
739			It will be ignored when crashkernel=X,high is not used
740			or memory reserved is below 4G.
741
742	cryptomgr.notests
743			[KNL] Disable crypto self-tests
744
745	cs89x0_dma=	[HW,NET]
746			Format: <dma>
747
748	cs89x0_media=	[HW,NET]
749			Format: { rj45 | aui | bnc }
750
751	dasd=		[HW,NET]
752			See header of drivers/s390/block/dasd_devmap.c.
753
754	db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
755			(one device per port)
756			Format: <port#>,<type>
757			See also Documentation/input/devices/joystick-parport.rst
758
759	ddebug_query=	[KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
760			time. See
761			Documentation/admin-guide/dynamic-debug-howto.rst for
762			details.  Deprecated, see dyndbg.
763
764	debug		[KNL] Enable kernel debugging (events log level).
765
766	debug_boot_weak_hash
767			[KNL] Enable printing [hashed] pointers early in the
768			boot sequence.  If enabled, we use a weak hash instead
769			of siphash to hash pointers.  Use this option if you are
770			seeing instances of '(___ptrval___)') and need to see a
771			value (hashed pointer) instead. Cryptographically
772			insecure, please do not use on production kernels.
773
774	debug_locks_verbose=
775			[KNL] verbose self-tests
776			Format=<0|1>
777			Print debugging info while doing the locking API
778			self-tests.
779			We default to 0 (no extra messages), setting it to
780			1 will print _a lot_ more information - normally
781			only useful to kernel developers.
782
783	debug_objects	[KNL] Enable object debugging
784
785	no_debug_objects
786			[KNL] Disable object debugging
787
788	debug_guardpage_minorder=
789			[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
790			parameter allows control of the order of pages that will
791			be intentionally kept free (and hence protected) by the
792			buddy allocator. Bigger value increase the probability
793			of catching random memory corruption, but reduce the
794			amount of memory for normal system use. The maximum
795			possible value is MAX_ORDER/2.  Setting this parameter
796			to 1 or 2 should be enough to identify most random
797			memory corruption problems caused by bugs in kernel or
798			driver code when a CPU writes to (or reads from) a
799			random memory location. Note that there exists a class
800			of memory corruptions problems caused by buggy H/W or
801			F/W or by drivers badly programing DMA (basically when
802			memory is written at bus level and the CPU MMU is
803			bypassed) which are not detectable by
804			CONFIG_DEBUG_PAGEALLOC, hence this option will not help
805			tracking down these problems.
806
807	debug_pagealloc=
808			[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
809			parameter enables the feature at boot time. In
810			default, it is disabled. We can avoid allocating huge
811			chunk of memory for debug pagealloc if we don't enable
812			it at boot time and the system will work mostly same
813			with the kernel built without CONFIG_DEBUG_PAGEALLOC.
814			on: enable the feature
815
816	debugpat	[X86] Enable PAT debugging
817
818	decnet.addr=	[HW,NET]
819			Format: <area>[,<node>]
820			See also Documentation/networking/decnet.txt.
821
822	default_hugepagesz=
823			[same as hugepagesz=] The size of the default
824			HugeTLB page size. This is the size represented by
825			the legacy /proc/ hugepages APIs, used for SHM, and
826			default size when mounting hugetlbfs filesystems.
827			Defaults to the default architecture's huge page size
828			if not specified.
829
830	deferred_probe_timeout=
831			[KNL] Debugging option to set a timeout in seconds for
832			deferred probe to give up waiting on dependencies to
833			probe. Only specific dependencies (subsystems or
834			drivers) that have opted in will be ignored. A timeout of 0
835			will timeout at the end of initcalls. This option will also
836			dump out devices still on the deferred probe list after
837			retrying.
838
839	dhash_entries=	[KNL]
840			Set number of hash buckets for dentry cache.
841
842	disable_1tb_segments [PPC]
843			Disables the use of 1TB hash page table segments. This
844			causes the kernel to fall back to 256MB segments which
845			can be useful when debugging issues that require an SLB
846			miss to occur.
847
848	disable=	[IPV6]
849			See Documentation/networking/ipv6.txt.
850
851	hardened_usercopy=
852                        [KNL] Under CONFIG_HARDENED_USERCOPY, whether
853                        hardening is enabled for this boot. Hardened
854                        usercopy checking is used to protect the kernel
855                        from reading or writing beyond known memory
856                        allocation boundaries as a proactive defense
857                        against bounds-checking flaws in the kernel's
858                        copy_to_user()/copy_from_user() interface.
859                on      Perform hardened usercopy checks (default).
860                off     Disable hardened usercopy checks.
861
862	disable_radix	[PPC]
863			Disable RADIX MMU mode on POWER9
864
865	disable_cpu_apicid= [X86,APIC,SMP]
866			Format: <int>
867			The number of initial APIC ID for the
868			corresponding CPU to be disabled at boot,
869			mostly used for the kdump 2nd kernel to
870			disable BSP to wake up multiple CPUs without
871			causing system reset or hang due to sending
872			INIT from AP to BSP.
873
874	perf_v4_pmi=	[X86,INTEL]
875			Format: <bool>
876			Disable Intel PMU counter freezing feature.
877			The feature only exists starting from
878			Arch Perfmon v4 (Skylake and newer).
879
880	disable_ddw	[PPC/PSERIES]
881			Disable Dynamic DMA Window support. Use this if
882			to workaround buggy firmware.
883
884	disable_ipv6=	[IPV6]
885			See Documentation/networking/ipv6.txt.
886
887	disable_mtrr_cleanup [X86]
888			The kernel tries to adjust MTRR layout from continuous
889			to discrete, to make X server driver able to add WB
890			entry later. This parameter disables that.
891
892	disable_mtrr_trim [X86, Intel and AMD only]
893			By default the kernel will trim any uncacheable
894			memory out of your available memory pool based on
895			MTRR settings.  This parameter disables that behavior,
896			possibly causing your machine to run very slowly.
897
898	disable_timer_pin_1 [X86]
899			Disable PIN 1 of APIC timer
900			Can be useful to work around chipset bugs.
901
902	dis_ucode_ldr	[X86] Disable the microcode loader.
903
904	dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
905			this option disables the debugging code at boot.
906
907	dma_debug_entries=<number>
908			This option allows to tune the number of preallocated
909			entries for DMA-API debugging code. One entry is
910			required per DMA-API allocation. Use this if the
911			DMA-API debugging code disables itself because the
912			architectural default is too low.
913
914	dma_debug_driver=<driver_name>
915			With this option the DMA-API debugging driver
916			filter feature can be enabled at boot time. Just
917			pass the driver to filter for as the parameter.
918			The filter can be disabled or changed to another
919			driver later using sysfs.
920
921	driver_async_probe=  [KNL]
922			List of driver names to be probed asynchronously.
923			Format: <driver_name1>,<driver_name2>...
924
925	drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
926			Broken monitors, graphic adapters, KVMs and EDIDless
927			panels may send no or incorrect EDID data sets.
928			This parameter allows to specify an EDID data sets
929			in the /lib/firmware directory that are used instead.
930			Generic built-in EDID data sets are used, if one of
931			edid/1024x768.bin, edid/1280x1024.bin,
932			edid/1680x1050.bin, or edid/1920x1080.bin is given
933			and no file with the same name exists. Details and
934			instructions how to build your own EDID data are
935			available in Documentation/EDID/HOWTO.txt. An EDID
936			data set will only be used for a particular connector,
937			if its name and a colon are prepended to the EDID
938			name. Each connector may use a unique EDID data
939			set by separating the files with a comma.  An EDID
940			data set with no connector name will be used for
941			any connectors not explicitly specified.
942
943	dscc4.setup=	[NET]
944
945	dt_cpu_ftrs=	[PPC]
946			Format: {"off" | "known"}
947			Control how the dt_cpu_ftrs device-tree binding is
948			used for CPU feature discovery and setup (if it
949			exists).
950			off: Do not use it, fall back to legacy cpu table.
951			known: Do not pass through unknown features to guests
952			or userspace, only those that the kernel is aware of.
953
954	dump_apple_properties	[X86]
955			Dump name and content of EFI device properties on
956			x86 Macs.  Useful for driver authors to determine
957			what data is available or for reverse-engineering.
958
959	dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
960	module.dyndbg[="val"]
961			Enable debug messages at boot time.  See
962			Documentation/admin-guide/dynamic-debug-howto.rst
963			for details.
964
965	nompx		[X86] Disables Intel Memory Protection Extensions.
966			See Documentation/x86/intel_mpx.txt for more
967			information about the feature.
968
969	nopku		[X86] Disable Memory Protection Keys CPU feature found
970			in some Intel CPUs.
971
972	module.async_probe [KNL]
973			Enable asynchronous probe on this module.
974
975	early_ioremap_debug [KNL]
976			Enable debug messages in early_ioremap support. This
977			is useful for tracking down temporary early mappings
978			which are not unmapped.
979
980	earlycon=	[KNL] Output early console device and options.
981
982			[ARM64] The early console is determined by the
983			stdout-path property in device tree's chosen node,
984			or determined by the ACPI SPCR table.
985
986			[X86] When used with no options the early console is
987			determined by the ACPI SPCR table.
988
989		cdns,<addr>[,options]
990			Start an early, polled-mode console on a Cadence
991			(xuartps) serial port at the specified address. Only
992			supported option is baud rate. If baud rate is not
993			specified, the serial port must already be setup and
994			configured.
995
996		uart[8250],io,<addr>[,options]
997		uart[8250],mmio,<addr>[,options]
998		uart[8250],mmio32,<addr>[,options]
999		uart[8250],mmio32be,<addr>[,options]
1000		uart[8250],0x<addr>[,options]
1001			Start an early, polled-mode console on the 8250/16550
1002			UART at the specified I/O port or MMIO address.
1003			MMIO inter-register address stride is either 8-bit
1004			(mmio) or 32-bit (mmio32 or mmio32be).
1005			If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1006			to be equivalent to 'mmio'. 'options' are specified
1007			in the same format described for "console=ttyS<n>"; if
1008			unspecified, the h/w is not initialized.
1009
1010		pl011,<addr>
1011		pl011,mmio32,<addr>
1012			Start an early, polled-mode console on a pl011 serial
1013			port at the specified address. The pl011 serial port
1014			must already be setup and configured. Options are not
1015			yet supported.  If 'mmio32' is specified, then only
1016			the driver will use only 32-bit accessors to read/write
1017			the device registers.
1018
1019		meson,<addr>
1020			Start an early, polled-mode console on a meson serial
1021			port at the specified address. The serial port must
1022			already be setup and configured. Options are not yet
1023			supported.
1024
1025		msm_serial,<addr>
1026			Start an early, polled-mode console on an msm serial
1027			port at the specified address. The serial port
1028			must already be setup and configured. Options are not
1029			yet supported.
1030
1031		msm_serial_dm,<addr>
1032			Start an early, polled-mode console on an msm serial
1033			dm port at the specified address. The serial port
1034			must already be setup and configured. Options are not
1035			yet supported.
1036
1037		owl,<addr>
1038			Start an early, polled-mode console on a serial port
1039			of an Actions Semi SoC, such as S500 or S900, at the
1040			specified address. The serial port must already be
1041			setup and configured. Options are not yet supported.
1042
1043		rda,<addr>
1044			Start an early, polled-mode console on a serial port
1045			of an RDA Micro SoC, such as RDA8810PL, at the
1046			specified address. The serial port must already be
1047			setup and configured. Options are not yet supported.
1048
1049		smh	Use ARM semihosting calls for early console.
1050
1051		s3c2410,<addr>
1052		s3c2412,<addr>
1053		s3c2440,<addr>
1054		s3c6400,<addr>
1055		s5pv210,<addr>
1056		exynos4210,<addr>
1057			Use early console provided by serial driver available
1058			on Samsung SoCs, requires selecting proper type and
1059			a correct base address of the selected UART port. The
1060			serial port must already be setup and configured.
1061			Options are not yet supported.
1062
1063		lantiq,<addr>
1064			Start an early, polled-mode console on a lantiq serial
1065			(lqasc) port at the specified address. The serial port
1066			must already be setup and configured. Options are not
1067			yet supported.
1068
1069		lpuart,<addr>
1070		lpuart32,<addr>
1071			Use early console provided by Freescale LP UART driver
1072			found on Freescale Vybrid and QorIQ LS1021A processors.
1073			A valid base address must be provided, and the serial
1074			port must already be setup and configured.
1075
1076		ar3700_uart,<addr>
1077			Start an early, polled-mode console on the
1078			Armada 3700 serial port at the specified
1079			address. The serial port must already be setup
1080			and configured. Options are not yet supported.
1081
1082		qcom_geni,<addr>
1083			Start an early, polled-mode console on a Qualcomm
1084			Generic Interface (GENI) based serial port at the
1085			specified address. The serial port must already be
1086			setup and configured. Options are not yet supported.
1087
1088		efifb,[options]
1089			Start an early, unaccelerated console on the EFI
1090			memory mapped framebuffer (if available). On cache
1091			coherent non-x86 systems that use system memory for
1092			the framebuffer, pass the 'ram' option so that it is
1093			mapped with the correct attributes.
1094
1095	earlyprintk=	[X86,SH,ARM,M68k,S390]
1096			earlyprintk=vga
1097			earlyprintk=sclp
1098			earlyprintk=xen
1099			earlyprintk=serial[,ttySn[,baudrate]]
1100			earlyprintk=serial[,0x...[,baudrate]]
1101			earlyprintk=ttySn[,baudrate]
1102			earlyprintk=dbgp[debugController#]
1103			earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1104			earlyprintk=xdbc[xhciController#]
1105
1106			earlyprintk is useful when the kernel crashes before
1107			the normal console is initialized. It is not enabled by
1108			default because it has some cosmetic problems.
1109
1110			Append ",keep" to not disable it when the real console
1111			takes over.
1112
1113			Only one of vga, efi, serial, or usb debug port can
1114			be used at a time.
1115
1116			Currently only ttyS0 and ttyS1 may be specified by
1117			name.  Other I/O ports may be explicitly specified
1118			on some architectures (x86 and arm at least) by
1119			replacing ttySn with an I/O port address, like this:
1120				earlyprintk=serial,0x1008,115200
1121			You can find the port for a given device in
1122			/proc/tty/driver/serial:
1123				2: uart:ST16650V2 port:00001008 irq:18 ...
1124
1125			Interaction with the standard serial driver is not
1126			very good.
1127
1128			The VGA and EFI output is eventually overwritten by
1129			the real console.
1130
1131			The xen output can only be used by Xen PV guests.
1132
1133			The sclp output can only be used on s390.
1134
1135			The optional "force" to "pciserial" enables use of a
1136			PCI device even when its classcode is not of the
1137			UART class.
1138
1139	edac_report=	[HW,EDAC] Control how to report EDAC event
1140			Format: {"on" | "off" | "force"}
1141			on: enable EDAC to report H/W event. May be overridden
1142			by other higher priority error reporting module.
1143			off: disable H/W event reporting through EDAC.
1144			force: enforce the use of EDAC to report H/W event.
1145			default: on.
1146
1147	ekgdboc=	[X86,KGDB] Allow early kernel console debugging
1148			ekgdboc=kbd
1149
1150			This is designed to be used in conjunction with
1151			the boot argument: earlyprintk=vga
1152
1153	edd=		[EDD]
1154			Format: {"off" | "on" | "skip[mbr]"}
1155
1156	efi=		[EFI]
1157			Format: { "old_map", "nochunk", "noruntime", "debug" }
1158			old_map [X86-64]: switch to the old ioremap-based EFI
1159			runtime services mapping. 32-bit still uses this one by
1160			default.
1161			nochunk: disable reading files in "chunks" in the EFI
1162			boot stub, as chunking can cause problems with some
1163			firmware implementations.
1164			noruntime : disable EFI runtime services support
1165			debug: enable misc debug output
1166
1167	efi_no_storage_paranoia [EFI; X86]
1168			Using this parameter you can use more than 50% of
1169			your efi variable storage. Use this parameter only if
1170			you are really sure that your UEFI does sane gc and
1171			fulfills the spec otherwise your board may brick.
1172
1173	efi_fake_mem=	nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1174			Add arbitrary attribute to specific memory range by
1175			updating original EFI memory map.
1176			Region of memory which aa attribute is added to is
1177			from ss to ss+nn.
1178			If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1179			is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1180			attribute is added to range 0x100000000-0x180000000 and
1181			0x10a0000000-0x1120000000.
1182
1183			Using this parameter you can do debugging of EFI memmap
1184			related feature. For example, you can do debugging of
1185			Address Range Mirroring feature even if your box
1186			doesn't support it.
1187
1188	efivar_ssdt=	[EFI; X86] Name of an EFI variable that contains an SSDT
1189			that is to be dynamically loaded by Linux. If there are
1190			multiple variables with the same name but with different
1191			vendor GUIDs, all of them will be loaded. See
1192			Documentation/acpi/ssdt-overlays.txt for details.
1193
1194
1195	eisa_irq_edge=	[PARISC,HW]
1196			See header of drivers/parisc/eisa.c.
1197
1198	elanfreq=	[X86-32]
1199			See comment before function elanfreq_setup() in
1200			arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1201
1202	elevator=	[IOSCHED]
1203			Format: { "mq-deadline" | "kyber" | "bfq" }
1204			See Documentation/block/deadline-iosched.txt,
1205			Documentation/block/kyber-iosched.txt and
1206			Documentation/block/bfq-iosched.txt for details.
1207
1208	elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1209			Specifies physical address of start of kernel core
1210			image elf header and optionally the size. Generally
1211			kexec loader will pass this option to capture kernel.
1212			See Documentation/kdump/kdump.txt for details.
1213
1214	enable_mtrr_cleanup [X86]
1215			The kernel tries to adjust MTRR layout from continuous
1216			to discrete, to make X server driver able to add WB
1217			entry later. This parameter enables that.
1218
1219	enable_timer_pin_1 [X86]
1220			Enable PIN 1 of APIC timer
1221			Can be useful to work around chipset bugs
1222			(in particular on some ATI chipsets).
1223			The kernel tries to set a reasonable default.
1224
1225	enforcing	[SELINUX] Set initial enforcing status.
1226			Format: {"0" | "1"}
1227			See security/selinux/Kconfig help text.
1228			0 -- permissive (log only, no denials).
1229			1 -- enforcing (deny and log).
1230			Default value is 0.
1231			Value can be changed at runtime via /selinux/enforce.
1232
1233	erst_disable	[ACPI]
1234			Disable Error Record Serialization Table (ERST)
1235			support.
1236
1237	ether=		[HW,NET] Ethernet cards parameters
1238			This option is obsoleted by the "netdev=" option, which
1239			has equivalent usage. See its documentation for details.
1240
1241	evm=		[EVM]
1242			Format: { "fix" }
1243			Permit 'security.evm' to be updated regardless of
1244			current integrity status.
1245
1246	failslab=
1247	fail_page_alloc=
1248	fail_make_request=[KNL]
1249			General fault injection mechanism.
1250			Format: <interval>,<probability>,<space>,<times>
1251			See also Documentation/fault-injection/.
1252
1253	floppy=		[HW]
1254			See Documentation/blockdev/floppy.txt.
1255
1256	force_pal_cache_flush
1257			[IA-64] Avoid check_sal_cache_flush which may hang on
1258			buggy SAL_CACHE_FLUSH implementations. Using this
1259			parameter will force ia64_sal_cache_flush to call
1260			ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1261
1262	forcepae	[X86-32]
1263			Forcefully enable Physical Address Extension (PAE).
1264			Many Pentium M systems disable PAE but may have a
1265			functionally usable PAE implementation.
1266			Warning: use of this parameter will taint the kernel
1267			and may cause unknown problems.
1268
1269	ftrace=[tracer]
1270			[FTRACE] will set and start the specified tracer
1271			as early as possible in order to facilitate early
1272			boot debugging.
1273
1274	ftrace_dump_on_oops[=orig_cpu]
1275			[FTRACE] will dump the trace buffers on oops.
1276			If no parameter is passed, ftrace will dump
1277			buffers of all CPUs, but if you pass orig_cpu, it will
1278			dump only the buffer of the CPU that triggered the
1279			oops.
1280
1281	ftrace_filter=[function-list]
1282			[FTRACE] Limit the functions traced by the function
1283			tracer at boot up. function-list is a comma separated
1284			list of functions. This list can be changed at run
1285			time by the set_ftrace_filter file in the debugfs
1286			tracing directory.
1287
1288	ftrace_notrace=[function-list]
1289			[FTRACE] Do not trace the functions specified in
1290			function-list. This list can be changed at run time
1291			by the set_ftrace_notrace file in the debugfs
1292			tracing directory.
1293
1294	ftrace_graph_filter=[function-list]
1295			[FTRACE] Limit the top level callers functions traced
1296			by the function graph tracer at boot up.
1297			function-list is a comma separated list of functions
1298			that can be changed at run time by the
1299			set_graph_function file in the debugfs tracing directory.
1300
1301	ftrace_graph_notrace=[function-list]
1302			[FTRACE] Do not trace from the functions specified in
1303			function-list.  This list is a comma separated list of
1304			functions that can be changed at run time by the
1305			set_graph_notrace file in the debugfs tracing directory.
1306
1307	ftrace_graph_max_depth=<uint>
1308			[FTRACE] Used with the function graph tracer. This is
1309			the max depth it will trace into a function. This value
1310			can be changed at run time by the max_graph_depth file
1311			in the tracefs tracing directory. default: 0 (no limit)
1312
1313	gamecon.map[2|3]=
1314			[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1315			support via parallel port (up to 5 devices per port)
1316			Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1317			See also Documentation/input/devices/joystick-parport.rst
1318
1319	gamma=		[HW,DRM]
1320
1321	gart_fix_e820=	[X86_64] disable the fix e820 for K8 GART
1322			Format: off | on
1323			default: on
1324
1325	gcov_persist=	[GCOV] When non-zero (default), profiling data for
1326			kernel modules is saved and remains accessible via
1327			debugfs, even when the module is unloaded/reloaded.
1328			When zero, profiling data is discarded and associated
1329			debugfs files are removed at module unload time.
1330
1331	goldfish	[X86] Enable the goldfish android emulator platform.
1332			Don't use this when you are not running on the
1333			android emulator
1334
1335	gpt		[EFI] Forces disk with valid GPT signature but
1336			invalid Protective MBR to be treated as GPT. If the
1337			primary GPT is corrupted, it enables the backup/alternate
1338			GPT to be used instead.
1339
1340	grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1341			the "Enable 0" bit of the configuration register.
1342			Format: 0 | 1
1343			Default: 0
1344	grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1345			the "Enable 0" bit of the configuration register.
1346			Format: 0 | 1
1347			Default: 0
1348	grcan.select=	[HW] Select which physical interface to use.
1349			Format: 0 | 1
1350			Default: 0
1351	grcan.txsize=	[HW] Sets the size of the tx buffer.
1352			Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1353			Default: 1024
1354	grcan.rxsize=	[HW] Sets the size of the rx buffer.
1355			Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1356			Default: 1024
1357
1358	gpio-mockup.gpio_mockup_ranges
1359			[HW] Sets the ranges of gpiochip of for this device.
1360			Format: <start1>,<end1>,<start2>,<end2>...
1361
1362	hardlockup_all_cpu_backtrace=
1363			[KNL] Should the hard-lockup detector generate
1364			backtraces on all cpus.
1365			Format: <integer>
1366
1367	hashdist=	[KNL,NUMA] Large hashes allocated during boot
1368			are distributed across NUMA nodes.  Defaults on
1369			for 64-bit NUMA, off otherwise.
1370			Format: 0 | 1 (for off | on)
1371
1372	hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1373
1374	hd=		[EIDE] (E)IDE hard drive subsystem geometry
1375			Format: <cyl>,<head>,<sect>
1376
1377	hest_disable	[ACPI]
1378			Disable Hardware Error Source Table (HEST) support;
1379			corresponding firmware-first mode error processing
1380			logic will be disabled.
1381
1382	highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1383			size of <nn>. This works even on boxes that have no
1384			highmem otherwise. This also works to reduce highmem
1385			size on bigger boxes.
1386
1387	highres=	[KNL] Enable/disable high resolution timer mode.
1388			Valid parameters: "on", "off"
1389			Default: "on"
1390
1391	hisax=		[HW,ISDN]
1392			See Documentation/isdn/README.HiSax.
1393
1394	hlt		[BUGS=ARM,SH]
1395
1396	hpet=		[X86-32,HPET] option to control HPET usage
1397			Format: { enable (default) | disable | force |
1398				verbose }
1399			disable: disable HPET and use PIT instead
1400			force: allow force enabled of undocumented chips (ICH4,
1401				VIA, nVidia)
1402			verbose: show contents of HPET registers during setup
1403
1404	hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1405			registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1406
1407	hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1408	hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1409			On x86-64 and powerpc, this option can be specified
1410			multiple times interleaved with hugepages= to reserve
1411			huge pages of different sizes. Valid pages sizes on
1412			x86-64 are 2M (when the CPU supports "pse") and 1G
1413			(when the CPU supports the "pdpe1gb" cpuinfo flag).
1414
1415	hung_task_panic=
1416			[KNL] Should the hung task detector generate panics.
1417			Format: <integer>
1418
1419			A nonzero value instructs the kernel to panic when a
1420			hung task is detected. The default value is controlled
1421			by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1422			option. The value selected by this boot parameter can
1423			be changed later by the kernel.hung_task_panic sysctl.
1424
1425	hvc_iucv=	[S390]	Number of z/VM IUCV hypervisor console (HVC)
1426				terminal devices. Valid values: 0..8
1427	hvc_iucv_allow=	[S390]	Comma-separated list of z/VM user IDs.
1428				If specified, z/VM IUCV HVC accepts connections
1429				from listed z/VM user IDs only.
1430
1431	hv_nopvspin	[X86,HYPER_V] Disables the paravirt spinlock optimizations
1432				      which allow the hypervisor to 'idle' the
1433				      guest on lock contention.
1434
1435	keep_bootcon	[KNL]
1436			Do not unregister boot console at start. This is only
1437			useful for debugging when something happens in the window
1438			between unregistering the boot console and initializing
1439			the real console.
1440
1441	i2c_bus=	[HW]	Override the default board specific I2C bus speed
1442				or register an additional I2C bus that is not
1443				registered from board initialization code.
1444				Format:
1445				<bus_id>,<clkrate>
1446
1447	i8042.debug	[HW] Toggle i8042 debug mode
1448	i8042.unmask_kbd_data
1449			[HW] Enable printing of interrupt data from the KBD port
1450			     (disabled by default, and as a pre-condition
1451			     requires that i8042.debug=1 be enabled)
1452	i8042.direct	[HW] Put keyboard port into non-translated mode
1453	i8042.dumbkbd	[HW] Pretend that controller can only read data from
1454			     keyboard and cannot control its state
1455			     (Don't attempt to blink the leds)
1456	i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1457	i8042.nokbd	[HW] Don't check/create keyboard port
1458	i8042.noloop	[HW] Disable the AUX Loopback command while probing
1459			     for the AUX port
1460	i8042.nomux	[HW] Don't check presence of an active multiplexing
1461			     controller
1462	i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1463			     controllers
1464	i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1465	i8042.reset	[HW] Reset the controller during init, cleanup and
1466			     suspend-to-ram transitions, only during s2r
1467			     transitions, or never reset
1468			Format: { 1 | Y | y | 0 | N | n }
1469			1, Y, y: always reset controller
1470			0, N, n: don't ever reset controller
1471			Default: only on s2r transitions on x86; most other
1472			architectures force reset to be always executed
1473	i8042.unlock	[HW] Unlock (ignore) the keylock
1474	i8042.kbdreset	[HW] Reset device connected to KBD port
1475
1476	i810=		[HW,DRM]
1477
1478	i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1479			indicates that the driver is running on unsupported
1480			hardware.
1481	i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1482			does not match list of supported models.
1483	i8k.power_status
1484			[HW] Report power status in /proc/i8k
1485			(disabled by default)
1486	i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1487			capability is set.
1488
1489	i915.invert_brightness=
1490			[DRM] Invert the sense of the variable that is used to
1491			set the brightness of the panel backlight. Normally a
1492			brightness value of 0 indicates backlight switched off,
1493			and the maximum of the brightness value sets the backlight
1494			to maximum brightness. If this parameter is set to 0
1495			(default) and the machine requires it, or this parameter
1496			is set to 1, a brightness value of 0 sets the backlight
1497			to maximum brightness, and the maximum of the brightness
1498			value switches the backlight off.
1499			-1 -- never invert brightness
1500			 0 -- machine default
1501			 1 -- force brightness inversion
1502
1503	icn=		[HW,ISDN]
1504			Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1505
1506	ide-core.nodma=	[HW] (E)IDE subsystem
1507			Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1508			.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1509			.cdrom .chs .ignore_cable are additional options
1510			See Documentation/ide/ide.txt.
1511
1512	ide-generic.probe-mask= [HW] (E)IDE subsystem
1513			Format: <int>
1514			Probe mask for legacy ISA IDE ports.  Depending on
1515			platform up to 6 ports are supported, enabled by
1516			setting corresponding bits in the mask to 1.  The
1517			default value is 0x0, which has a special meaning.
1518			On systems that have PCI, it triggers scanning the
1519			PCI bus for the first and the second port, which
1520			are then probed.  On systems without PCI the value
1521			of 0x0 enables probing the two first ports as if it
1522			was 0x3.
1523
1524	ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1525			Claim all unknown PCI IDE storage controllers.
1526
1527	idle=		[X86]
1528			Format: idle=poll, idle=halt, idle=nomwait
1529			Poll forces a polling idle loop that can slightly
1530			improve the performance of waking up a idle CPU, but
1531			will use a lot of power and make the system run hot.
1532			Not recommended.
1533			idle=halt: Halt is forced to be used for CPU idle.
1534			In such case C2/C3 won't be used again.
1535			idle=nomwait: Disable mwait for CPU C-states
1536
1537	ieee754=	[MIPS] Select IEEE Std 754 conformance mode
1538			Format: { strict | legacy | 2008 | relaxed }
1539			Default: strict
1540
1541			Choose which programs will be accepted for execution
1542			based on the IEEE 754 NaN encoding(s) supported by
1543			the FPU and the NaN encoding requested with the value
1544			of an ELF file header flag individually set by each
1545			binary.  Hardware implementations are permitted to
1546			support either or both of the legacy and the 2008 NaN
1547			encoding mode.
1548
1549			Available settings are as follows:
1550			strict	accept binaries that request a NaN encoding
1551				supported by the FPU
1552			legacy	only accept legacy-NaN binaries, if supported
1553				by the FPU
1554			2008	only accept 2008-NaN binaries, if supported
1555				by the FPU
1556			relaxed	accept any binaries regardless of whether
1557				supported by the FPU
1558
1559			The FPU emulator is always able to support both NaN
1560			encodings, so if no FPU hardware is present or it has
1561			been disabled with 'nofpu', then the settings of
1562			'legacy' and '2008' strap the emulator accordingly,
1563			'relaxed' straps the emulator for both legacy-NaN and
1564			2008-NaN, whereas 'strict' enables legacy-NaN only on
1565			legacy processors and both NaN encodings on MIPS32 or
1566			MIPS64 CPUs.
1567
1568			The setting for ABS.fmt/NEG.fmt instruction execution
1569			mode generally follows that for the NaN encoding,
1570			except where unsupported by hardware.
1571
1572	ignore_loglevel	[KNL]
1573			Ignore loglevel setting - this will print /all/
1574			kernel messages to the console. Useful for debugging.
1575			We also add it as printk module parameter, so users
1576			could change it dynamically, usually by
1577			/sys/module/printk/parameters/ignore_loglevel.
1578
1579	ignore_rlimit_data
1580			Ignore RLIMIT_DATA setting for data mappings,
1581			print warning at first misuse.  Can be changed via
1582			/sys/module/kernel/parameters/ignore_rlimit_data.
1583
1584	ihash_entries=	[KNL]
1585			Set number of hash buckets for inode cache.
1586
1587	ima_appraise=	[IMA] appraise integrity measurements
1588			Format: { "off" | "enforce" | "fix" | "log" }
1589			default: "enforce"
1590
1591	ima_appraise_tcb [IMA] Deprecated.  Use ima_policy= instead.
1592			The builtin appraise policy appraises all files
1593			owned by uid=0.
1594
1595	ima_canonical_fmt [IMA]
1596			Use the canonical format for the binary runtime
1597			measurements, instead of host native format.
1598
1599	ima_hash=	[IMA]
1600			Format: { md5 | sha1 | rmd160 | sha256 | sha384
1601				   | sha512 | ... }
1602			default: "sha1"
1603
1604			The list of supported hash algorithms is defined
1605			in crypto/hash_info.h.
1606
1607	ima_policy=	[IMA]
1608			The builtin policies to load during IMA setup.
1609			Format: "tcb | appraise_tcb | secure_boot |
1610				 fail_securely"
1611
1612			The "tcb" policy measures all programs exec'd, files
1613			mmap'd for exec, and all files opened with the read
1614			mode bit set by either the effective uid (euid=0) or
1615			uid=0.
1616
1617			The "appraise_tcb" policy appraises the integrity of
1618			all files owned by root.
1619
1620			The "secure_boot" policy appraises the integrity
1621			of files (eg. kexec kernel image, kernel modules,
1622			firmware, policy, etc) based on file signatures.
1623
1624			The "fail_securely" policy forces file signature
1625			verification failure also on privileged mounted
1626			filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
1627			flag.
1628
1629	ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
1630			Load a policy which meets the needs of the Trusted
1631			Computing Base.  This means IMA will measure all
1632			programs exec'd, files mmap'd for exec, and all files
1633			opened for read by uid=0.
1634
1635	ima_template=	[IMA]
1636			Select one of defined IMA measurements template formats.
1637			Formats: { "ima" | "ima-ng" | "ima-sig" }
1638			Default: "ima-ng"
1639
1640	ima_template_fmt=
1641			[IMA] Define a custom template format.
1642			Format: { "field1|...|fieldN" }
1643
1644	ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1645			Format: <min_file_size>
1646			Set the minimal file size for using asynchronous hash.
1647			If left unspecified, ahash usage is disabled.
1648
1649			ahash performance varies for different data sizes on
1650			different crypto accelerators. This option can be used
1651			to achieve the best performance for a particular HW.
1652
1653	ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1654			Format: <bufsize>
1655			Set hashing buffer size. Default: 4k.
1656
1657			ahash performance varies for different chunk sizes on
1658			different crypto accelerators. This option can be used
1659			to achieve best performance for particular HW.
1660
1661	init=		[KNL]
1662			Format: <full_path>
1663			Run specified binary instead of /sbin/init as init
1664			process.
1665
1666	initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1667			for working out where the kernel is dying during
1668			startup.
1669
1670	initcall_blacklist=  [KNL] Do not execute a comma-separated list of
1671			initcall functions.  Useful for debugging built-in
1672			modules and initcalls.
1673
1674	initrd=		[BOOT] Specify the location of the initial ramdisk
1675
1676	init_pkru=	[x86] Specify the default memory protection keys rights
1677			register contents for all processes.  0x55555554 by
1678			default (disallow access to all but pkey 0).  Can
1679			override in debugfs after boot.
1680
1681	inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1682			Format: <irq>
1683
1684	int_pln_enable	[x86] Enable power limit notification interrupt
1685
1686	integrity_audit=[IMA]
1687			Format: { "0" | "1" }
1688			0 -- basic integrity auditing messages. (Default)
1689			1 -- additional integrity auditing messages.
1690
1691	intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1692		on
1693			Enable intel iommu driver.
1694		off
1695			Disable intel iommu driver.
1696		igfx_off [Default Off]
1697			By default, gfx is mapped as normal device. If a gfx
1698			device has a dedicated DMAR unit, the DMAR unit is
1699			bypassed by not enabling DMAR with this option. In
1700			this case, gfx device will use physical address for
1701			DMA.
1702		forcedac [x86_64]
1703			With this option iommu will not optimize to look
1704			for io virtual address below 32-bit forcing dual
1705			address cycle on pci bus for cards supporting greater
1706			than 32-bit addressing. The default is to look
1707			for translation below 32-bit and if not available
1708			then look in the higher range.
1709		strict [Default Off]
1710			With this option on every unmap_single operation will
1711			result in a hardware IOTLB flush operation as opposed
1712			to batching them for performance.
1713		sp_off [Default Off]
1714			By default, super page will be supported if Intel IOMMU
1715			has the capability. With this option, super page will
1716			not be supported.
1717		sm_on [Default Off]
1718			By default, scalable mode will be disabled even if the
1719			hardware advertises that it has support for the scalable
1720			mode translation. With this option set, scalable mode
1721			will be used on hardware which claims to support it.
1722		tboot_noforce [Default Off]
1723			Do not force the Intel IOMMU enabled under tboot.
1724			By default, tboot will force Intel IOMMU on, which
1725			could harm performance of some high-throughput
1726			devices like 40GBit network cards, even if identity
1727			mapping is enabled.
1728			Note that using this option lowers the security
1729			provided by tboot because it makes the system
1730			vulnerable to DMA attacks.
1731
1732	intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1733			0	disables intel_idle and fall back on acpi_idle.
1734			1 to 9	specify maximum depth of C-state.
1735
1736	intel_pstate=	[X86]
1737			disable
1738			  Do not enable intel_pstate as the default
1739			  scaling driver for the supported processors
1740			passive
1741			  Use intel_pstate as a scaling driver, but configure it
1742			  to work with generic cpufreq governors (instead of
1743			  enabling its internal governor).  This mode cannot be
1744			  used along with the hardware-managed P-states (HWP)
1745			  feature.
1746			force
1747			  Enable intel_pstate on systems that prohibit it by default
1748			  in favor of acpi-cpufreq. Forcing the intel_pstate driver
1749			  instead of acpi-cpufreq may disable platform features, such
1750			  as thermal controls and power capping, that rely on ACPI
1751			  P-States information being indicated to OSPM and therefore
1752			  should be used with caution. This option does not work with
1753			  processors that aren't supported by the intel_pstate driver
1754			  or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1755			no_hwp
1756			  Do not enable hardware P state control (HWP)
1757			  if available.
1758			hwp_only
1759			  Only load intel_pstate on systems which support
1760			  hardware P state control (HWP) if available.
1761			support_acpi_ppc
1762			  Enforce ACPI _PPC performance limits. If the Fixed ACPI
1763			  Description Table, specifies preferred power management
1764			  profile as "Enterprise Server" or "Performance Server",
1765			  then this feature is turned on by default.
1766			per_cpu_perf_limits
1767			  Allow per-logical-CPU P-State performance control limits using
1768			  cpufreq sysfs interface
1769
1770	intremap=	[X86-64, Intel-IOMMU]
1771			on	enable Interrupt Remapping (default)
1772			off	disable Interrupt Remapping
1773			nosid	disable Source ID checking
1774			no_x2apic_optout
1775				BIOS x2APIC opt-out request will be ignored
1776			nopost	disable Interrupt Posting
1777
1778	iomem=		Disable strict checking of access to MMIO memory
1779		strict	regions from userspace.
1780		relaxed
1781
1782	iommu=		[x86]
1783		off
1784		force
1785		noforce
1786		biomerge
1787		panic
1788		nopanic
1789		merge
1790		nomerge
1791		soft
1792		pt		[x86]
1793		nopt		[x86]
1794		nobypass	[PPC/POWERNV]
1795			Disable IOMMU bypass, using IOMMU for PCI devices.
1796
1797	iommu.strict=	[ARM64] Configure TLB invalidation behaviour
1798			Format: { "0" | "1" }
1799			0 - Lazy mode.
1800			  Request that DMA unmap operations use deferred
1801			  invalidation of hardware TLBs, for increased
1802			  throughput at the cost of reduced device isolation.
1803			  Will fall back to strict mode if not supported by
1804			  the relevant IOMMU driver.
1805			1 - Strict mode (default).
1806			  DMA unmap operations invalidate IOMMU hardware TLBs
1807			  synchronously.
1808
1809	iommu.passthrough=
1810			[ARM64] Configure DMA to bypass the IOMMU by default.
1811			Format: { "0" | "1" }
1812			0 - Use IOMMU translation for DMA.
1813			1 - Bypass the IOMMU for DMA.
1814			unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
1815
1816	io7=		[HW] IO7 for Marvel based alpha systems
1817			See comment before marvel_specify_io7 in
1818			arch/alpha/kernel/core_marvel.c.
1819
1820	io_delay=	[X86] I/O delay method
1821		0x80
1822			Standard port 0x80 based delay
1823		0xed
1824			Alternate port 0xed based delay (needed on some systems)
1825		udelay
1826			Simple two microseconds delay
1827		none
1828			No delay
1829
1830	ip=		[IP_PNP]
1831			See Documentation/filesystems/nfs/nfsroot.txt.
1832
1833	ipcmni_extend	[KNL] Extend the maximum number of unique System V
1834			IPC identifiers from 32,768 to 16,777,216.
1835
1836	irqaffinity=	[SMP] Set the default irq affinity mask
1837			The argument is a cpu list, as described above.
1838
1839	irqchip.gicv2_force_probe=
1840			[ARM, ARM64]
1841			Format: <bool>
1842			Force the kernel to look for the second 4kB page
1843			of a GICv2 controller even if the memory range
1844			exposed by the device tree is too small.
1845
1846	irqchip.gicv3_nolpi=
1847			[ARM, ARM64]
1848			Force the kernel to ignore the availability of
1849			LPIs (and by consequence ITSs). Intended for system
1850			that use the kernel as a bootloader, and thus want
1851			to let secondary kernels in charge of setting up
1852			LPIs.
1853
1854	irqchip.gicv3_pseudo_nmi= [ARM64]
1855			Enables support for pseudo-NMIs in the kernel. This
1856			requires the kernel to be built with
1857			CONFIG_ARM64_PSEUDO_NMI.
1858
1859	irqfixup	[HW]
1860			When an interrupt is not handled search all handlers
1861			for it. Intended to get systems with badly broken
1862			firmware running.
1863
1864	irqpoll		[HW]
1865			When an interrupt is not handled search all handlers
1866			for it. Also check all handlers each timer
1867			interrupt. Intended to get systems with badly broken
1868			firmware running.
1869
1870	isapnp=		[ISAPNP]
1871			Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1872
1873	isolcpus=	[KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
1874			[Deprecated - use cpusets instead]
1875			Format: [flag-list,]<cpu-list>
1876
1877			Specify one or more CPUs to isolate from disturbances
1878			specified in the flag list (default: domain):
1879
1880			nohz
1881			  Disable the tick when a single task runs.
1882
1883			  A residual 1Hz tick is offloaded to workqueues, which you
1884			  need to affine to housekeeping through the global
1885			  workqueue's affinity configured via the
1886			  /sys/devices/virtual/workqueue/cpumask sysfs file, or
1887			  by using the 'domain' flag described below.
1888
1889			  NOTE: by default the global workqueue runs on all CPUs,
1890			  so to protect individual CPUs the 'cpumask' file has to
1891			  be configured manually after bootup.
1892
1893			domain
1894			  Isolate from the general SMP balancing and scheduling
1895			  algorithms. Note that performing domain isolation this way
1896			  is irreversible: it's not possible to bring back a CPU to
1897			  the domains once isolated through isolcpus. It's strongly
1898			  advised to use cpusets instead to disable scheduler load
1899			  balancing through the "cpuset.sched_load_balance" file.
1900			  It offers a much more flexible interface where CPUs can
1901			  move in and out of an isolated set anytime.
1902
1903			  You can move a process onto or off an "isolated" CPU via
1904			  the CPU affinity syscalls or cpuset.
1905			  <cpu number> begins at 0 and the maximum value is
1906			  "number of CPUs in system - 1".
1907
1908			The format of <cpu-list> is described above.
1909
1910
1911
1912	iucv=		[HW,NET]
1913
1914	ivrs_ioapic	[HW,X86_64]
1915			Provide an override to the IOAPIC-ID<->DEVICE-ID
1916			mapping provided in the IVRS ACPI table. For
1917			example, to map IOAPIC-ID decimal 10 to
1918			PCI device 00:14.0 write the parameter as:
1919				ivrs_ioapic[10]=00:14.0
1920
1921	ivrs_hpet	[HW,X86_64]
1922			Provide an override to the HPET-ID<->DEVICE-ID
1923			mapping provided in the IVRS ACPI table. For
1924			example, to map HPET-ID decimal 0 to
1925			PCI device 00:14.0 write the parameter as:
1926				ivrs_hpet[0]=00:14.0
1927
1928	ivrs_acpihid	[HW,X86_64]
1929			Provide an override to the ACPI-HID:UID<->DEVICE-ID
1930			mapping provided in the IVRS ACPI table. For
1931			example, to map UART-HID:UID AMD0020:0 to
1932			PCI device 00:14.5 write the parameter as:
1933				ivrs_acpihid[00:14.5]=AMD0020:0
1934
1935	js=		[HW,JOY] Analog joystick
1936			See Documentation/input/joydev/joystick.rst.
1937
1938	nokaslr		[KNL]
1939			When CONFIG_RANDOMIZE_BASE is set, this disables
1940			kernel and module base offset ASLR (Address Space
1941			Layout Randomization).
1942
1943	kasan_multi_shot
1944			[KNL] Enforce KASAN (Kernel Address Sanitizer) to print
1945			report on every invalid memory access. Without this
1946			parameter KASAN will print report only for the first
1947			invalid access.
1948
1949	keepinitrd	[HW,ARM]
1950
1951	kernelcore=	[KNL,X86,IA-64,PPC]
1952			Format: nn[KMGTPE] | nn% | "mirror"
1953			This parameter specifies the amount of memory usable by
1954			the kernel for non-movable allocations.  The requested
1955			amount is spread evenly throughout all nodes in the
1956			system as ZONE_NORMAL.  The remaining memory is used for
1957			movable memory in its own zone, ZONE_MOVABLE.  In the
1958			event, a node is too small to have both ZONE_NORMAL and
1959			ZONE_MOVABLE, kernelcore memory will take priority and
1960			other nodes will have a larger ZONE_MOVABLE.
1961
1962			ZONE_MOVABLE is used for the allocation of pages that
1963			may be reclaimed or moved by the page migration
1964			subsystem.  Note that allocations like PTEs-from-HighMem
1965			still use the HighMem zone if it exists, and the Normal
1966			zone if it does not.
1967
1968			It is possible to specify the exact amount of memory in
1969			the form of "nn[KMGTPE]", a percentage of total system
1970			memory in the form of "nn%", or "mirror".  If "mirror"
1971			option is specified, mirrored (reliable) memory is used
1972			for non-movable allocations and remaining memory is used
1973			for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
1974			are exclusive, so you cannot specify multiple forms.
1975
1976	kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1977			Format: <Controller#>[,poll interval]
1978			The controller # is the number of the ehci usb debug
1979			port as it is probed via PCI.  The poll interval is
1980			optional and is the number seconds in between
1981			each poll cycle to the debug port in case you need
1982			the functionality for interrupting the kernel with
1983			gdb or control-c on the dbgp connection.  When
1984			not using this parameter you use sysrq-g to break into
1985			the kernel debugger.
1986
1987	kgdboc=		[KGDB,HW] kgdb over consoles.
1988			Requires a tty driver that supports console polling,
1989			or a supported polling keyboard driver (non-usb).
1990			 Serial only format: <serial_device>[,baud]
1991			 keyboard only format: kbd
1992			 keyboard and serial format: kbd,<serial_device>[,baud]
1993			Optional Kernel mode setting:
1994			 kms, kbd format: kms,kbd
1995			 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1996
1997	kgdbwait	[KGDB] Stop kernel execution and enter the
1998			kernel debugger at the earliest opportunity.
1999
2000	kmac=		[MIPS] korina ethernet MAC address.
2001			Configure the RouterBoard 532 series on-chip
2002			Ethernet adapter MAC address.
2003
2004	kmemleak=	[KNL] Boot-time kmemleak enable/disable
2005			Valid arguments: on, off
2006			Default: on
2007			Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2008			the default is off.
2009
2010	kpti=		[ARM64] Control page table isolation of user
2011			and kernel address spaces.
2012			Default: enabled on cores which need mitigation.
2013			0: force disabled
2014			1: force enabled
2015
2016	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2017			Default is 0 (don't ignore, but inject #GP)
2018
2019	kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2020				   Default is false (don't support).
2021
2022	kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
2023			KVM MMU at runtime.
2024			Default is 0 (off)
2025
2026	kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
2027			Default is 1 (enabled)
2028
2029	kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
2030			for all guests.
2031			Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2032
2033	kvm-arm.vgic_v3_group0_trap=
2034			[KVM,ARM] Trap guest accesses to GICv3 group-0
2035			system registers
2036
2037	kvm-arm.vgic_v3_group1_trap=
2038			[KVM,ARM] Trap guest accesses to GICv3 group-1
2039			system registers
2040
2041	kvm-arm.vgic_v3_common_trap=
2042			[KVM,ARM] Trap guest accesses to GICv3 common
2043			system registers
2044
2045	kvm-arm.vgic_v4_enable=
2046			[KVM,ARM] Allow use of GICv4 for direct injection of
2047			LPIs.
2048
2049	kvm-intel.ept=	[KVM,Intel] Disable extended page tables
2050			(virtualized MMU) support on capable Intel chips.
2051			Default is 1 (enabled)
2052
2053	kvm-intel.emulate_invalid_guest_state=
2054			[KVM,Intel] Enable emulation of invalid guest states
2055			Default is 0 (disabled)
2056
2057	kvm-intel.flexpriority=
2058			[KVM,Intel] Disable FlexPriority feature (TPR shadow).
2059			Default is 1 (enabled)
2060
2061	kvm-intel.nested=
2062			[KVM,Intel] Enable VMX nesting (nVMX).
2063			Default is 0 (disabled)
2064
2065	kvm-intel.unrestricted_guest=
2066			[KVM,Intel] Disable unrestricted guest feature
2067			(virtualized real and unpaged mode) on capable
2068			Intel chips. Default is 1 (enabled)
2069
2070	kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2071			CVE-2018-3620.
2072
2073			Valid arguments: never, cond, always
2074
2075			always: L1D cache flush on every VMENTER.
2076			cond:	Flush L1D on VMENTER only when the code between
2077				VMEXIT and VMENTER can leak host memory.
2078			never:	Disables the mitigation
2079
2080			Default is cond (do L1 cache flush in specific instances)
2081
2082	kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
2083			feature (tagged TLBs) on capable Intel chips.
2084			Default is 1 (enabled)
2085
2086	l1tf=           [X86] Control mitigation of the L1TF vulnerability on
2087			      affected CPUs
2088
2089			The kernel PTE inversion protection is unconditionally
2090			enabled and cannot be disabled.
2091
2092			full
2093				Provides all available mitigations for the
2094				L1TF vulnerability. Disables SMT and
2095				enables all mitigations in the
2096				hypervisors, i.e. unconditional L1D flush.
2097
2098				SMT control and L1D flush control via the
2099				sysfs interface is still possible after
2100				boot.  Hypervisors will issue a warning
2101				when the first VM is started in a
2102				potentially insecure configuration,
2103				i.e. SMT enabled or L1D flush disabled.
2104
2105			full,force
2106				Same as 'full', but disables SMT and L1D
2107				flush runtime control. Implies the
2108				'nosmt=force' command line option.
2109				(i.e. sysfs control of SMT is disabled.)
2110
2111			flush
2112				Leaves SMT enabled and enables the default
2113				hypervisor mitigation, i.e. conditional
2114				L1D flush.
2115
2116				SMT control and L1D flush control via the
2117				sysfs interface is still possible after
2118				boot.  Hypervisors will issue a warning
2119				when the first VM is started in a
2120				potentially insecure configuration,
2121				i.e. SMT enabled or L1D flush disabled.
2122
2123			flush,nosmt
2124
2125				Disables SMT and enables the default
2126				hypervisor mitigation.
2127
2128				SMT control and L1D flush control via the
2129				sysfs interface is still possible after
2130				boot.  Hypervisors will issue a warning
2131				when the first VM is started in a
2132				potentially insecure configuration,
2133				i.e. SMT enabled or L1D flush disabled.
2134
2135			flush,nowarn
2136				Same as 'flush', but hypervisors will not
2137				warn when a VM is started in a potentially
2138				insecure configuration.
2139
2140			off
2141				Disables hypervisor mitigations and doesn't
2142				emit any warnings.
2143				It also drops the swap size and available
2144				RAM limit restriction on both hypervisor and
2145				bare metal.
2146
2147			Default is 'flush'.
2148
2149			For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2150
2151	l2cr=		[PPC]
2152
2153	l3cr=		[PPC]
2154
2155	lapic		[X86-32,APIC] Enable the local APIC even if BIOS
2156			disabled it.
2157
2158	lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
2159			value for LAPIC timer one-shot implementation. Default
2160			back to the programmable timer unit in the LAPIC.
2161
2162	lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
2163			in C2 power state.
2164
2165	libata.dma=	[LIBATA] DMA control
2166			libata.dma=0	  Disable all PATA and SATA DMA
2167			libata.dma=1	  PATA and SATA Disk DMA only
2168			libata.dma=2	  ATAPI (CDROM) DMA only
2169			libata.dma=4	  Compact Flash DMA only
2170			Combinations also work, so libata.dma=3 enables DMA
2171			for disks and CDROMs, but not CFs.
2172
2173	libata.ignore_hpa=	[LIBATA] Ignore HPA limit
2174			libata.ignore_hpa=0	  keep BIOS limits (default)
2175			libata.ignore_hpa=1	  ignore limits, using full disk
2176
2177	libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
2178			when set.
2179			Format: <int>
2180
2181	libata.force=	[LIBATA] Force configurations.  The format is comma
2182			separated list of "[ID:]VAL" where ID is
2183			PORT[.DEVICE].  PORT and DEVICE are decimal numbers
2184			matching port, link or device.  Basically, it matches
2185			the ATA ID string printed on console by libata.  If
2186			the whole ID part is omitted, the last PORT and DEVICE
2187			values are used.  If ID hasn't been specified yet, the
2188			configuration applies to all ports, links and devices.
2189
2190			If only DEVICE is omitted, the parameter applies to
2191			the port and all links and devices behind it.  DEVICE
2192			number of 0 either selects the first device or the
2193			first fan-out link behind PMP device.  It does not
2194			select the host link.  DEVICE number of 15 selects the
2195			host link and device attached to it.
2196
2197			The VAL specifies the configuration to force.  As long
2198			as there's no ambiguity shortcut notation is allowed.
2199			For example, both 1.5 and 1.5G would work for 1.5Gbps.
2200			The following configurations can be forced.
2201
2202			* Cable type: 40c, 80c, short40c, unk, ign or sata.
2203			  Any ID with matching PORT is used.
2204
2205			* SATA link speed limit: 1.5Gbps or 3.0Gbps.
2206
2207			* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2208			  udma[/][16,25,33,44,66,100,133] notation is also
2209			  allowed.
2210
2211			* [no]ncq: Turn on or off NCQ.
2212
2213			* [no]ncqtrim: Turn off queued DSM TRIM.
2214
2215			* nohrst, nosrst, norst: suppress hard, soft
2216			  and both resets.
2217
2218			* rstonce: only attempt one reset during
2219			  hot-unplug link recovery
2220
2221			* dump_id: dump IDENTIFY data.
2222
2223			* atapi_dmadir: Enable ATAPI DMADIR bridge support
2224
2225			* disable: Disable this device.
2226
2227			If there are multiple matching configurations changing
2228			the same attribute, the last one is used.
2229
2230	memblock=debug	[KNL] Enable memblock debug messages.
2231
2232	load_ramdisk=	[RAM] List of ramdisks to load from floppy
2233			See Documentation/blockdev/ramdisk.txt.
2234
2235	lockd.nlm_grace_period=P  [NFS] Assign grace period.
2236			Format: <integer>
2237
2238	lockd.nlm_tcpport=N	[NFS] Assign TCP port.
2239			Format: <integer>
2240
2241	lockd.nlm_timeout=T	[NFS] Assign timeout value.
2242			Format: <integer>
2243
2244	lockd.nlm_udpport=M	[NFS] Assign UDP port.
2245			Format: <integer>
2246
2247	locktorture.nreaders_stress= [KNL]
2248			Set the number of locking read-acquisition kthreads.
2249			Defaults to being automatically set based on the
2250			number of online CPUs.
2251
2252	locktorture.nwriters_stress= [KNL]
2253			Set the number of locking write-acquisition kthreads.
2254
2255	locktorture.onoff_holdoff= [KNL]
2256			Set time (s) after boot for CPU-hotplug testing.
2257
2258	locktorture.onoff_interval= [KNL]
2259			Set time (s) between CPU-hotplug operations, or
2260			zero to disable CPU-hotplug testing.
2261
2262	locktorture.shuffle_interval= [KNL]
2263			Set task-shuffle interval (jiffies).  Shuffling
2264			tasks allows some CPUs to go into dyntick-idle
2265			mode during the locktorture test.
2266
2267	locktorture.shutdown_secs= [KNL]
2268			Set time (s) after boot system shutdown.  This
2269			is useful for hands-off automated testing.
2270
2271	locktorture.stat_interval= [KNL]
2272			Time (s) between statistics printk()s.
2273
2274	locktorture.stutter= [KNL]
2275			Time (s) to stutter testing, for example,
2276			specifying five seconds causes the test to run for
2277			five seconds, wait for five seconds, and so on.
2278			This tests the locking primitive's ability to
2279			transition abruptly to and from idle.
2280
2281	locktorture.torture_type= [KNL]
2282			Specify the locking implementation to test.
2283
2284	locktorture.verbose= [KNL]
2285			Enable additional printk() statements.
2286
2287	logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
2288			Format: <irq>
2289
2290	loglevel=	All Kernel Messages with a loglevel smaller than the
2291			console loglevel will be printed to the console. It can
2292			also be changed with klogd or other programs. The
2293			loglevels are defined as follows:
2294
2295			0 (KERN_EMERG)		system is unusable
2296			1 (KERN_ALERT)		action must be taken immediately
2297			2 (KERN_CRIT)		critical conditions
2298			3 (KERN_ERR)		error conditions
2299			4 (KERN_WARNING)	warning conditions
2300			5 (KERN_NOTICE)		normal but significant condition
2301			6 (KERN_INFO)		informational
2302			7 (KERN_DEBUG)		debug-level messages
2303
2304	log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
2305			in bytes.  n must be a power of two and greater
2306			than the minimal size. The minimal size is defined
2307			by LOG_BUF_SHIFT kernel config parameter. There is
2308			also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2309			that allows to increase the default size depending on
2310			the number of CPUs. See init/Kconfig for more details.
2311
2312	logo.nologo	[FB] Disables display of the built-in Linux logo.
2313			This may be used to provide more screen space for
2314			kernel log messages and is useful when debugging
2315			kernel boot problems.
2316
2317	lp=0		[LP]	Specify parallel ports to use, e.g,
2318	lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
2319	lp=reset		first parallel port). 'lp=0' disables the
2320	lp=auto			printer driver. 'lp=reset' (which can be
2321				specified in addition to the ports) causes
2322				attached printers to be reset. Using
2323				lp=port1,port2,... specifies the parallel ports
2324				to associate lp devices with, starting with
2325				lp0. A port specification may be 'none' to skip
2326				that lp device, or a parport name such as
2327				'parport0'. Specifying 'lp=auto' instead of a
2328				port specification list means that device IDs
2329				from each port should be examined, to see if
2330				an IEEE 1284-compliant printer is attached; if
2331				so, the driver will manage that printer.
2332				See also header of drivers/char/lp.c.
2333
2334	lpj=n		[KNL]
2335			Sets loops_per_jiffy to given constant, thus avoiding
2336			time-consuming boot-time autodetection (up to 250 ms per
2337			CPU). 0 enables autodetection (default). To determine
2338			the correct value for your kernel, boot with normal
2339			autodetection and see what value is printed. Note that
2340			on SMP systems the preset will be applied to all CPUs,
2341			which is likely to cause problems if your CPUs need
2342			significantly divergent settings. An incorrect value
2343			will cause delays in the kernel to be wrong, leading to
2344			unpredictable I/O errors and other breakage. Although
2345			unlikely, in the extreme case this might damage your
2346			hardware.
2347
2348	ltpc=		[NET]
2349			Format: <io>,<irq>,<dma>
2350
2351	lsm.debug	[SECURITY] Enable LSM initialization debugging output.
2352
2353	lsm=lsm1,...,lsmN
2354			[SECURITY] Choose order of LSM initialization. This
2355			overrides CONFIG_LSM, and the "security=" parameter.
2356
2357	machvec=	[IA-64] Force the use of a particular machine-vector
2358			(machvec) in a generic kernel.
2359			Example: machvec=hpzx1_swiotlb
2360
2361	machtype=	[Loongson] Share the same kernel image file between different
2362			 yeeloong laptop.
2363			Example: machtype=lemote-yeeloong-2f-7inch
2364
2365	max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
2366			than or equal to this physical address is ignored.
2367
2368	maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
2369			will bring up during bootup.  maxcpus=n : n >= 0 limits
2370			the kernel to bring up 'n' processors. Surely after
2371			bootup you can bring up the other plugged cpu by executing
2372			"echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2373			only takes effect during system bootup.
2374			While n=0 is a special case, it is equivalent to "nosmp",
2375			which also disables the IO APIC.
2376
2377	max_loop=	[LOOP] The number of loop block devices that get
2378	(loop.max_loop)	unconditionally pre-created at init time. The default
2379			number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2380			of statically allocating a predefined number, loop
2381			devices can be requested on-demand with the
2382			/dev/loop-control interface.
2383
2384	mce		[X86-32] Machine Check Exception
2385
2386	mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
2387
2388	md=		[HW] RAID subsystems devices and level
2389			See Documentation/admin-guide/md.rst.
2390
2391	mdacon=		[MDA]
2392			Format: <first>,<last>
2393			Specifies range of consoles to be captured by the MDA.
2394
2395	mds=		[X86,INTEL]
2396			Control mitigation for the Micro-architectural Data
2397			Sampling (MDS) vulnerability.
2398
2399			Certain CPUs are vulnerable to an exploit against CPU
2400			internal buffers which can forward information to a
2401			disclosure gadget under certain conditions.
2402
2403			In vulnerable processors, the speculatively
2404			forwarded data can be used in a cache side channel
2405			attack, to access data to which the attacker does
2406			not have direct access.
2407
2408			This parameter controls the MDS mitigation. The
2409			options are:
2410
2411			full       - Enable MDS mitigation on vulnerable CPUs
2412			full,nosmt - Enable MDS mitigation and disable
2413				     SMT on vulnerable CPUs
2414			off        - Unconditionally disable MDS mitigation
2415
2416			Not specifying this option is equivalent to
2417			mds=full.
2418
2419			For details see: Documentation/admin-guide/hw-vuln/mds.rst
2420
2421	mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
2422			Amount of memory to be used when the kernel is not able
2423			to see the whole system memory or for test.
2424			[X86] Work as limiting max address. Use together
2425			with memmap= to avoid physical address space collisions.
2426			Without memmap= PCI devices could be placed at addresses
2427			belonging to unused RAM.
2428
2429	mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
2430			memory.
2431
2432	memchunk=nn[KMG]
2433			[KNL,SH] Allow user to override the default size for
2434			per-device physically contiguous DMA buffers.
2435
2436	memhp_default_state=online/offline
2437			[KNL] Set the initial state for the memory hotplug
2438			onlining policy. If not specified, the default value is
2439			set according to the
2440			CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
2441			option.
2442			See Documentation/memory-hotplug.txt.
2443
2444	memmap=exactmap	[KNL,X86] Enable setting of an exact
2445			E820 memory map, as specified by the user.
2446			Such memmap=exactmap lines can be constructed based on
2447			BIOS output or other requirements. See the memmap=nn@ss
2448			option description.
2449
2450	memmap=nn[KMG]@ss[KMG]
2451			[KNL] Force usage of a specific region of memory.
2452			Region of memory to be used is from ss to ss+nn.
2453			If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
2454			which limits max address to nn[KMG].
2455			Multiple different regions can be specified,
2456			comma delimited.
2457			Example:
2458				memmap=100M@2G,100M#3G,1G!1024G
2459
2460	memmap=nn[KMG]#ss[KMG]
2461			[KNL,ACPI] Mark specific memory as ACPI data.
2462			Region of memory to be marked is from ss to ss+nn.
2463
2464	memmap=nn[KMG]$ss[KMG]
2465			[KNL,ACPI] Mark specific memory as reserved.
2466			Region of memory to be reserved is from ss to ss+nn.
2467			Example: Exclude memory from 0x18690000-0x1869ffff
2468			         memmap=64K$0x18690000
2469			         or
2470			         memmap=0x10000$0x18690000
2471			Some bootloaders may need an escape character before '$',
2472			like Grub2, otherwise '$' and the following number
2473			will be eaten.
2474
2475	memmap=nn[KMG]!ss[KMG]
2476			[KNL,X86] Mark specific memory as protected.
2477			Region of memory to be used, from ss to ss+nn.
2478			The memory region may be marked as e820 type 12 (0xc)
2479			and is NVDIMM or ADR memory.
2480
2481	memmap=<size>%<offset>-<oldtype>+<newtype>
2482			[KNL,ACPI] Convert memory within the specified region
2483			from <oldtype> to <newtype>. If "-<oldtype>" is left
2484			out, the whole region will be marked as <newtype>,
2485			even if previously unavailable. If "+<newtype>" is left
2486			out, matching memory will be removed. Types are
2487			specified as e820 types, e.g., 1 = RAM, 2 = reserved,
2488			3 = ACPI, 12 = PRAM.
2489
2490	memory_corruption_check=0/1 [X86]
2491			Some BIOSes seem to corrupt the first 64k of
2492			memory when doing things like suspend/resume.
2493			Setting this option will scan the memory
2494			looking for corruption.  Enabling this will
2495			both detect corruption and prevent the kernel
2496			from using the memory being corrupted.
2497			However, its intended as a diagnostic tool; if
2498			repeatable BIOS-originated corruption always
2499			affects the same memory, you can use memmap=
2500			to prevent the kernel from using that memory.
2501
2502	memory_corruption_check_size=size [X86]
2503			By default it checks for corruption in the low
2504			64k, making this memory unavailable for normal
2505			use.  Use this parameter to scan for
2506			corruption in more or less memory.
2507
2508	memory_corruption_check_period=seconds [X86]
2509			By default it checks for corruption every 60
2510			seconds.  Use this parameter to check at some
2511			other rate.  0 disables periodic checking.
2512
2513	memtest=	[KNL,X86,ARM,PPC] Enable memtest
2514			Format: <integer>
2515			default : 0 <disable>
2516			Specifies the number of memtest passes to be
2517			performed. Each pass selects another test
2518			pattern from a given set of patterns. Memtest
2519			fills the memory with this pattern, validates
2520			memory contents and reserves bad memory
2521			regions that are detected.
2522
2523	mem_encrypt=	[X86-64] AMD Secure Memory Encryption (SME) control
2524			Valid arguments: on, off
2525			Default (depends on kernel configuration option):
2526			  on  (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
2527			  off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
2528			mem_encrypt=on:		Activate SME
2529			mem_encrypt=off:	Do not activate SME
2530
2531			Refer to Documentation/x86/amd-memory-encryption.txt
2532			for details on when memory encryption can be activated.
2533
2534	mem_sleep_default=	[SUSPEND] Default system suspend mode:
2535			s2idle  - Suspend-To-Idle
2536			shallow - Power-On Suspend or equivalent (if supported)
2537			deep    - Suspend-To-RAM or equivalent (if supported)
2538			See Documentation/admin-guide/pm/sleep-states.rst.
2539
2540	meye.*=		[HW] Set MotionEye Camera parameters
2541			See Documentation/media/v4l-drivers/meye.rst.
2542
2543	mfgpt_irq=	[IA-32] Specify the IRQ to use for the
2544			Multi-Function General Purpose Timers on AMD Geode
2545			platforms.
2546
2547	mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
2548			the BIOS has incorrectly applied a workaround. TinyBIOS
2549			version 0.98 is known to be affected, 0.99 fixes the
2550			problem by letting the user disable the workaround.
2551
2552	mga=		[HW,DRM]
2553
2554	min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
2555			physical address is ignored.
2556
2557	mini2440=	[ARM,HW,KNL]
2558			Format:[0..2][b][c][t]
2559			Default: "0tb"
2560			MINI2440 configuration specification:
2561			0 - The attached screen is the 3.5" TFT
2562			1 - The attached screen is the 7" TFT
2563			2 - The VGA Shield is attached (1024x768)
2564			Leaving out the screen size parameter will not load
2565			the TFT driver, and the framebuffer will be left
2566			unconfigured.
2567			b - Enable backlight. The TFT backlight pin will be
2568			linked to the kernel VESA blanking code and a GPIO
2569			LED. This parameter is not necessary when using the
2570			VGA shield.
2571			c - Enable the s3c camera interface.
2572			t - Reserved for enabling touchscreen support. The
2573			touchscreen support is not enabled in the mainstream
2574			kernel as of 2.6.30, a preliminary port can be found
2575			in the "bleeding edge" mini2440 support kernel at
2576			http://repo.or.cz/w/linux-2.6/mini2440.git
2577
2578	mitigations=
2579			[X86,PPC,S390,ARM64] Control optional mitigations for
2580			CPU vulnerabilities.  This is a set of curated,
2581			arch-independent options, each of which is an
2582			aggregation of existing arch-specific options.
2583
2584			off
2585				Disable all optional CPU mitigations.  This
2586				improves system performance, but it may also
2587				expose users to several CPU vulnerabilities.
2588				Equivalent to: nopti [X86,PPC]
2589					       kpti=0 [ARM64]
2590					       nospectre_v1 [PPC]
2591					       nobp=0 [S390]
2592					       nospectre_v2 [X86,PPC,S390,ARM64]
2593					       spectre_v2_user=off [X86]
2594					       spec_store_bypass_disable=off [X86,PPC]
2595					       ssbd=force-off [ARM64]
2596					       l1tf=off [X86]
2597					       mds=off [X86]
2598
2599			auto (default)
2600				Mitigate all CPU vulnerabilities, but leave SMT
2601				enabled, even if it's vulnerable.  This is for
2602				users who don't want to be surprised by SMT
2603				getting disabled across kernel upgrades, or who
2604				have other ways of avoiding SMT-based attacks.
2605				Equivalent to: (default behavior)
2606
2607			auto,nosmt
2608				Mitigate all CPU vulnerabilities, disabling SMT
2609				if needed.  This is for users who always want to
2610				be fully mitigated, even if it means losing SMT.
2611				Equivalent to: l1tf=flush,nosmt [X86]
2612					       mds=full,nosmt [X86]
2613
2614	mminit_loglevel=
2615			[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2616			parameter allows control of the logging verbosity for
2617			the additional memory initialisation checks. A value
2618			of 0 disables mminit logging and a level of 4 will
2619			log everything. Information is printed at KERN_DEBUG
2620			so loglevel=8 may also need to be specified.
2621
2622	module.sig_enforce
2623			[KNL] When CONFIG_MODULE_SIG is set, this means that
2624			modules without (valid) signatures will fail to load.
2625			Note that if CONFIG_MODULE_SIG_FORCE is set, that
2626			is always true, so this option does nothing.
2627
2628	module_blacklist=  [KNL] Do not load a comma-separated list of
2629			modules.  Useful for debugging problem modules.
2630
2631	mousedev.tap_time=
2632			[MOUSE] Maximum time between finger touching and
2633			leaving touchpad surface for touch to be considered
2634			a tap and be reported as a left button click (for
2635			touchpads working in absolute mode only).
2636			Format: <msecs>
2637	mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
2638			reporting absolute coordinates, such as tablets
2639	mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
2640			reporting absolute coordinates, such as tablets
2641
2642	movablecore=	[KNL,X86,IA-64,PPC]
2643			Format: nn[KMGTPE] | nn%
2644			This parameter is the complement to kernelcore=, it
2645			specifies the amount of memory used for migratable
2646			allocations.  If both kernelcore and movablecore is
2647			specified, then kernelcore will be at *least* the
2648			specified value but may be more.  If movablecore on its
2649			own is specified, the administrator must be careful
2650			that the amount of memory usable for all allocations
2651			is not too small.
2652
2653	movable_node	[KNL] Boot-time switch to make hotplugable memory
2654			NUMA nodes to be movable. This means that the memory
2655			of such nodes will be usable only for movable
2656			allocations which rules out almost all kernel
2657			allocations. Use with caution!
2658
2659	MTD_Partition=	[MTD]
2660			Format: <name>,<region-number>,<size>,<offset>
2661
2662	MTD_Region=	[MTD] Format:
2663			<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2664
2665	mtdparts=	[MTD]
2666			See drivers/mtd/cmdlinepart.c.
2667
2668	multitce=off	[PPC]  This parameter disables the use of the pSeries
2669			firmware feature for updating multiple TCE entries
2670			at a time.
2671
2672	onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
2673
2674			Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2675
2676			boundary - index of last SLC block on Flex-OneNAND.
2677				   The remaining blocks are configured as MLC blocks.
2678			lock	 - Configure if Flex-OneNAND boundary should be locked.
2679				   Once locked, the boundary cannot be changed.
2680				   1 indicates lock status, 0 indicates unlock status.
2681
2682	mtdset=		[ARM]
2683			ARM/S3C2412 JIVE boot control
2684
2685			See arch/arm/mach-s3c2412/mach-jive.c
2686
2687	mtouchusb.raw_coordinates=
2688			[HW] Make the MicroTouch USB driver use raw coordinates
2689			('y', default) or cooked coordinates ('n')
2690
2691	mtrr_chunk_size=nn[KMG] [X86]
2692			used for mtrr cleanup. It is largest continuous chunk
2693			that could hold holes aka. UC entries.
2694
2695	mtrr_gran_size=nn[KMG] [X86]
2696			Used for mtrr cleanup. It is granularity of mtrr block.
2697			Default is 1.
2698			Large value could prevent small alignment from
2699			using up MTRRs.
2700
2701	mtrr_spare_reg_nr=n [X86]
2702			Format: <integer>
2703			Range: 0,7 : spare reg number
2704			Default : 1
2705			Used for mtrr cleanup. It is spare mtrr entries number.
2706			Set to 2 or more if your graphical card needs more.
2707
2708	n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
2709
2710	netdev=		[NET] Network devices parameters
2711			Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2712			Note that mem_start is often overloaded to mean
2713			something different and driver-specific.
2714			This usage is only documented in each driver source
2715			file if at all.
2716
2717	nf_conntrack.acct=
2718			[NETFILTER] Enable connection tracking flow accounting
2719			0 to disable accounting
2720			1 to enable accounting
2721			Default value is 0.
2722
2723	nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
2724			See Documentation/filesystems/nfs/nfsroot.txt.
2725
2726	nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
2727			See Documentation/filesystems/nfs/nfsroot.txt.
2728
2729	nfsrootdebug	[NFS] enable nfsroot debugging messages.
2730			See Documentation/filesystems/nfs/nfsroot.txt.
2731
2732	nfs.callback_nr_threads=
2733			[NFSv4] set the total number of threads that the
2734			NFS client will assign to service NFSv4 callback
2735			requests.
2736
2737	nfs.callback_tcpport=
2738			[NFS] set the TCP port on which the NFSv4 callback
2739			channel should listen.
2740
2741	nfs.cache_getent=
2742			[NFS] sets the pathname to the program which is used
2743			to update the NFS client cache entries.
2744
2745	nfs.cache_getent_timeout=
2746			[NFS] sets the timeout after which an attempt to
2747			update a cache entry is deemed to have failed.
2748
2749	nfs.idmap_cache_timeout=
2750			[NFS] set the maximum lifetime for idmapper cache
2751			entries.
2752
2753	nfs.enable_ino64=
2754			[NFS] enable 64-bit inode numbers.
2755			If zero, the NFS client will fake up a 32-bit inode
2756			number for the readdir() and stat() syscalls instead
2757			of returning the full 64-bit number.
2758			The default is to return 64-bit inode numbers.
2759
2760	nfs.max_session_cb_slots=
2761			[NFSv4.1] Sets the maximum number of session
2762			slots the client will assign to the callback
2763			channel. This determines the maximum number of
2764			callbacks the client will process in parallel for
2765			a particular server.
2766
2767	nfs.max_session_slots=
2768			[NFSv4.1] Sets the maximum number of session slots
2769			the client will attempt to negotiate with the server.
2770			This limits the number of simultaneous RPC requests
2771			that the client can send to the NFSv4.1 server.
2772			Note that there is little point in setting this
2773			value higher than the max_tcp_slot_table_limit.
2774
2775	nfs.nfs4_disable_idmapping=
2776			[NFSv4] When set to the default of '1', this option
2777			ensures that both the RPC level authentication
2778			scheme and the NFS level operations agree to use
2779			numeric uids/gids if the mount is using the
2780			'sec=sys' security flavour. In effect it is
2781			disabling idmapping, which can make migration from
2782			legacy NFSv2/v3 systems to NFSv4 easier.
2783			Servers that do not support this mode of operation
2784			will be autodetected by the client, and it will fall
2785			back to using the idmapper.
2786			To turn off this behaviour, set the value to '0'.
2787	nfs.nfs4_unique_id=
2788			[NFS4] Specify an additional fixed unique ident-
2789			ification string that NFSv4 clients can insert into
2790			their nfs_client_id4 string.  This is typically a
2791			UUID that is generated at system install time.
2792
2793	nfs.send_implementation_id =
2794			[NFSv4.1] Send client implementation identification
2795			information in exchange_id requests.
2796			If zero, no implementation identification information
2797			will be sent.
2798			The default is to send the implementation identification
2799			information.
2800
2801	nfs.recover_lost_locks =
2802			[NFSv4] Attempt to recover locks that were lost due
2803			to a lease timeout on the server. Please note that
2804			doing this risks data corruption, since there are
2805			no guarantees that the file will remain unchanged
2806			after the locks are lost.
2807			If you want to enable the kernel legacy behaviour of
2808			attempting to recover these locks, then set this
2809			parameter to '1'.
2810			The default parameter value of '0' causes the kernel
2811			not to attempt recovery of lost locks.
2812
2813	nfs4.layoutstats_timer =
2814			[NFSv4.2] Change the rate at which the kernel sends
2815			layoutstats to the pNFS metadata server.
2816
2817			Setting this to value to 0 causes the kernel to use
2818			whatever value is the default set by the layout
2819			driver. A non-zero value sets the minimum interval
2820			in seconds between layoutstats transmissions.
2821
2822	nfsd.nfs4_disable_idmapping=
2823			[NFSv4] When set to the default of '1', the NFSv4
2824			server will return only numeric uids and gids to
2825			clients using auth_sys, and will accept numeric uids
2826			and gids from such clients.  This is intended to ease
2827			migration from NFSv2/v3.
2828
2829	nmi_debug=	[KNL,SH] Specify one or more actions to take
2830			when a NMI is triggered.
2831			Format: [state][,regs][,debounce][,die]
2832
2833	nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2834			Format: [panic,][nopanic,][num]
2835			Valid num: 0 or 1
2836			0 - turn hardlockup detector in nmi_watchdog off
2837			1 - turn hardlockup detector in nmi_watchdog on
2838			When panic is specified, panic when an NMI watchdog
2839			timeout occurs (or 'nopanic' to override the opposite
2840			default). To disable both hard and soft lockup detectors,
2841			please see 'nowatchdog'.
2842			This is useful when you use a panic=... timeout and
2843			need the box quickly up again.
2844
2845			These settings can be accessed at runtime via
2846			the nmi_watchdog and hardlockup_panic sysctls.
2847
2848	netpoll.carrier_timeout=
2849			[NET] Specifies amount of time (in seconds) that
2850			netpoll should wait for a carrier. By default netpoll
2851			waits 4 seconds.
2852
2853	no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
2854			emulation library even if a 387 maths coprocessor
2855			is present.
2856
2857	no5lvl		[X86-64] Disable 5-level paging mode. Forces
2858			kernel to use 4-level paging instead.
2859
2860	no_console_suspend
2861			[HW] Never suspend the console
2862			Disable suspending of consoles during suspend and
2863			hibernate operations.  Once disabled, debugging
2864			messages can reach various consoles while the rest
2865			of the system is being put to sleep (ie, while
2866			debugging driver suspend/resume hooks).  This may
2867			not work reliably with all consoles, but is known
2868			to work with serial and VGA consoles.
2869			To facilitate more flexible debugging, we also add
2870			console_suspend, a printk module parameter to control
2871			it. Users could use console_suspend (usually
2872			/sys/module/printk/parameters/console_suspend) to
2873			turn on/off it dynamically.
2874
2875	noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
2876			caches in the slab allocator.  Saves per-node memory,
2877			but will impact performance.
2878
2879	noalign		[KNL,ARM]
2880
2881	noaltinstr	[S390] Disables alternative instructions patching
2882			(CPU alternatives feature).
2883
2884	noapic		[SMP,APIC] Tells the kernel to not make use of any
2885			IOAPICs that may be present in the system.
2886
2887	noautogroup	Disable scheduler automatic task group creation.
2888
2889	nobats		[PPC] Do not use BATs for mapping kernel lowmem
2890			on "Classic" PPC cores.
2891
2892	nocache		[ARM]
2893
2894	noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2895
2896	nodelayacct	[KNL] Disable per-task delay accounting
2897
2898	nodsp		[SH] Disable hardware DSP at boot time.
2899
2900	noefi		Disable EFI runtime services support.
2901
2902	noexec		[IA-64]
2903
2904	noexec		[X86]
2905			On X86-32 available only on PAE configured kernels.
2906			noexec=on: enable non-executable mappings (default)
2907			noexec=off: disable non-executable mappings
2908
2909	nosmap		[X86,PPC]
2910			Disable SMAP (Supervisor Mode Access Prevention)
2911			even if it is supported by processor.
2912
2913	nosmep		[X86,PPC]
2914			Disable SMEP (Supervisor Mode Execution Prevention)
2915			even if it is supported by processor.
2916
2917	noexec32	[X86-64]
2918			This affects only 32-bit executables.
2919			noexec32=on: enable non-executable mappings (default)
2920				read doesn't imply executable mappings
2921			noexec32=off: disable non-executable mappings
2922				read implies executable mappings
2923
2924	nofpu		[MIPS,SH] Disable hardware FPU at boot time.
2925
2926	nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2927			register save and restore. The kernel will only save
2928			legacy floating-point registers on task switch.
2929
2930	nohugeiomap	[KNL,x86] Disable kernel huge I/O mappings.
2931
2932	nosmt		[KNL,S390] Disable symmetric multithreading (SMT).
2933			Equivalent to smt=1.
2934
2935			[KNL,x86] Disable symmetric multithreading (SMT).
2936			nosmt=force: Force disable SMT, cannot be undone
2937				     via the sysfs control file.
2938
2939	nospectre_v1	[PPC] Disable mitigations for Spectre Variant 1 (bounds
2940			check bypass). With this option data leaks are possible
2941			in the system.
2942
2943	nospectre_v2	[X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
2944			the Spectre variant 2 (indirect branch prediction)
2945			vulnerability. System may allow data leaks with this
2946			option.
2947
2948	nospec_store_bypass_disable
2949			[HW] Disable all mitigations for the Speculative Store Bypass vulnerability
2950
2951	noxsave		[BUGS=X86] Disables x86 extended register state save
2952			and restore using xsave. The kernel will fallback to
2953			enabling legacy floating-point and sse state.
2954
2955	noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
2956			register states. The kernel will fall back to use
2957			xsave to save the states. By using this parameter,
2958			performance of saving the states is degraded because
2959			xsave doesn't support modified optimization while
2960			xsaveopt supports it on xsaveopt enabled systems.
2961
2962	noxsaves	[X86] Disables xsaves and xrstors used in saving and
2963			restoring x86 extended register state in compacted
2964			form of xsave area. The kernel will fall back to use
2965			xsaveopt and xrstor to save and restore the states
2966			in standard form of xsave area. By using this
2967			parameter, xsave area per process might occupy more
2968			memory on xsaves enabled systems.
2969
2970	nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2971			wfi(ARM) instruction doesn't work correctly and not to
2972			use it. This is also useful when using JTAG debugger.
2973
2974	no_file_caps	Tells the kernel not to honor file capabilities.  The
2975			only way then for a file to be executed with privilege
2976			is to be setuid root or executed by root.
2977
2978	nohalt		[IA-64] Tells the kernel not to use the power saving
2979			function PAL_HALT_LIGHT when idle. This increases
2980			power-consumption. On the positive side, it reduces
2981			interrupt wake-up latency, which may improve performance
2982			in certain environments such as networked servers or
2983			real-time systems.
2984
2985	nohibernate	[HIBERNATION] Disable hibernation and resume.
2986
2987	nohz=		[KNL] Boottime enable/disable dynamic ticks
2988			Valid arguments: on, off
2989			Default: on
2990
2991	nohz_full=	[KNL,BOOT,SMP,ISOL]
2992			The argument is a cpu list, as described above.
2993			In kernels built with CONFIG_NO_HZ_FULL=y, set
2994			the specified list of CPUs whose tick will be stopped
2995			whenever possible. The boot CPU will be forced outside
2996			the range to maintain the timekeeping.  Any CPUs
2997			in this list will have their RCU callbacks offloaded,
2998			just as if they had also been called out in the
2999			rcu_nocbs= boot parameter.
3000
3001	noiotrap	[SH] Disables trapped I/O port accesses.
3002
3003	noirqdebug	[X86-32] Disables the code which attempts to detect and
3004			disable unhandled interrupt sources.
3005
3006	no_timer_check	[X86,APIC] Disables the code which tests for
3007			broken timer IRQ sources.
3008
3009	noisapnp	[ISAPNP] Disables ISA PnP code.
3010
3011	noinitrd	[RAM] Tells the kernel not to load any configured
3012			initial RAM disk.
3013
3014	nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
3015			remapping.
3016			[Deprecated - use intremap=off]
3017
3018	nointroute	[IA-64]
3019
3020	noinvpcid	[X86] Disable the INVPCID cpu feature.
3021
3022	nojitter	[IA-64] Disables jitter checking for ITC timers.
3023
3024	no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
3025
3026	no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
3027			fault handling.
3028
3029	no-vmw-sched-clock
3030			[X86,PV_OPS] Disable paravirtualized VMware scheduler
3031			clock and use the default one.
3032
3033	no-steal-acc	[X86,KVM] Disable paravirtualized steal time accounting.
3034			steal time is computed, but won't influence scheduler
3035			behaviour
3036
3037	nolapic		[X86-32,APIC] Do not enable or use the local APIC.
3038
3039	nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
3040
3041	noltlbs		[PPC] Do not use large page/tlb entries for kernel
3042			lowmem mapping on PPC40x and PPC8xx
3043
3044	nomca		[IA-64] Disable machine check abort handling
3045
3046	nomce		[X86-32] Disable Machine Check Exception
3047
3048	nomfgpt		[X86-32] Disable Multi-Function General Purpose
3049			Timer usage (for AMD Geode machines).
3050
3051	nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
3052			shutdown the other cpus.  Instead use the REBOOT_VECTOR
3053			irq.
3054
3055	nomodule	Disable module load
3056
3057	nopat		[X86] Disable PAT (page attribute table extension of
3058			pagetables) support.
3059
3060	nopcid		[X86-64] Disable the PCID cpu feature.
3061
3062	norandmaps	Don't use address space randomization.  Equivalent to
3063			echo 0 > /proc/sys/kernel/randomize_va_space
3064
3065	noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
3066			with UP alternatives
3067
3068	nordrand	[X86] Disable kernel use of the RDRAND and
3069			RDSEED instructions even if they are supported
3070			by the processor.  RDRAND and RDSEED are still
3071			available to user space applications.
3072
3073	noresume	[SWSUSP] Disables resume and restores original swap
3074			space.
3075
3076	no-scroll	[VGA] Disables scrollback.
3077			This is required for the Braillex ib80-piezo Braille
3078			reader made by F.H. Papenmeier (Germany).
3079
3080	nosbagart	[IA-64]
3081
3082	nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
3083
3084	nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
3085			and disable the IO APIC.  legacy for "maxcpus=0".
3086
3087	nosoftlockup	[KNL] Disable the soft-lockup detector.
3088
3089	nosync		[HW,M68K] Disables sync negotiation for all devices.
3090
3091	nowatchdog	[KNL] Disable both lockup detectors, i.e.
3092			soft-lockup and NMI watchdog (hard-lockup).
3093
3094	nowb		[ARM]
3095
3096	nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
3097
3098	cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
3099			CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
3100			Some features depend on CPU0. Known dependencies are:
3101			1. Resume from suspend/hibernate depends on CPU0.
3102			Suspend/hibernate will fail if CPU0 is offline and you
3103			need to online CPU0 before suspend/hibernate.
3104			2. PIC interrupts also depend on CPU0. CPU0 can't be
3105			removed if a PIC interrupt is detected.
3106			It's said poweroff/reboot may depend on CPU0 on some
3107			machines although I haven't seen such issues so far
3108			after CPU0 is offline on a few tested machines.
3109			If the dependencies are under your control, you can
3110			turn on cpu0_hotplug.
3111
3112	nps_mtm_hs_ctr=	[KNL,ARC]
3113			This parameter sets the maximum duration, in
3114			cycles, each HW thread of the CTOP can run
3115			without interruptions, before HW switches it.
3116			The actual maximum duration is 16 times this
3117			parameter's value.
3118			Format: integer between 1 and 255
3119			Default: 255
3120
3121	nptcg=		[IA-64] Override max number of concurrent global TLB
3122			purges which is reported from either PAL_VM_SUMMARY or
3123			SAL PALO.
3124
3125	nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
3126			could support.  nr_cpus=n : n >= 1 limits the kernel to
3127			support 'n' processors. It could be larger than the
3128			number of already plugged CPU during bootup, later in
3129			runtime you can physically add extra cpu until it reaches
3130			n. So during boot up some boot time memory for per-cpu
3131			variables need be pre-allocated for later physical cpu
3132			hot plugging.
3133
3134	nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
3135
3136	numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
3137			Allowed values are enable and disable
3138
3139	numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
3140			'node', 'default' can be specified
3141			This can be set from sysctl after boot.
3142			See Documentation/sysctl/vm.txt for details.
3143
3144	ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
3145			See Documentation/debugging-via-ohci1394.txt for more
3146			info.
3147
3148	olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
3149			Rather than timing out after 20 ms if an EC
3150			command is not properly ACKed, override the length
3151			of the timeout.  We have interrupts disabled while
3152			waiting for the ACK, so if this is set too high
3153			interrupts *may* be lost!
3154
3155	omap_mux=	[OMAP] Override bootloader pin multiplexing.
3156			Format: <mux_mode0.mode_name=value>...
3157			For example, to override I2C bus2:
3158			omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
3159
3160	oprofile.timer=	[HW]
3161			Use timer interrupt instead of performance counters
3162
3163	oprofile.cpu_type=	Force an oprofile cpu type
3164			This might be useful if you have an older oprofile
3165			userland or if you want common events.
3166			Format: { arch_perfmon }
3167			arch_perfmon: [X86] Force use of architectural
3168				perfmon on Intel CPUs instead of the
3169				CPU specific event set.
3170			timer: [X86] Force use of architectural NMI
3171				timer mode (see also oprofile.timer
3172				for generic hr timer mode)
3173
3174	oops=panic	Always panic on oopses. Default is to just kill the
3175			process, but there is a small probability of
3176			deadlocking the machine.
3177			This will also cause panics on machine check exceptions.
3178			Useful together with panic=30 to trigger a reboot.
3179
3180	page_alloc.shuffle=
3181			[KNL] Boolean flag to control whether the page allocator
3182			should randomize its free lists. The randomization may
3183			be automatically enabled if the kernel detects it is
3184			running on a platform with a direct-mapped memory-side
3185			cache, and this parameter can be used to
3186			override/disable that behavior. The state of the flag
3187			can be read from sysfs at:
3188			/sys/module/page_alloc/parameters/shuffle.
3189
3190	page_owner=	[KNL] Boot-time page_owner enabling option.
3191			Storage of the information about who allocated
3192			each page is disabled in default. With this switch,
3193			we can turn it on.
3194			on: enable the feature
3195
3196	page_poison=	[KNL] Boot-time parameter changing the state of
3197			poisoning on the buddy allocator, available with
3198			CONFIG_PAGE_POISONING=y.
3199			off: turn off poisoning (default)
3200			on: turn on poisoning
3201
3202	panic=		[KNL] Kernel behaviour on panic: delay <timeout>
3203			timeout > 0: seconds before rebooting
3204			timeout = 0: wait forever
3205			timeout < 0: reboot immediately
3206			Format: <timeout>
3207
3208	panic_print=	Bitmask for printing system info when panic happens.
3209			User can chose combination of the following bits:
3210			bit 0: print all tasks info
3211			bit 1: print system memory info
3212			bit 2: print timer info
3213			bit 3: print locks info if CONFIG_LOCKDEP is on
3214			bit 4: print ftrace buffer
3215			bit 5: print all printk messages in buffer
3216
3217	panic_on_warn	panic() instead of WARN().  Useful to cause kdump
3218			on a WARN().
3219
3220	crash_kexec_post_notifiers
3221			Run kdump after running panic-notifiers and dumping
3222			kmsg. This only for the users who doubt kdump always
3223			succeeds in any situation.
3224			Note that this also increases risks of kdump failure,
3225			because some panic notifiers can make the crashed
3226			kernel more unstable.
3227
3228	parkbd.port=	[HW] Parallel port number the keyboard adapter is
3229			connected to, default is 0.
3230			Format: <parport#>
3231	parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
3232			0 for XT, 1 for AT (default is AT).
3233			Format: <mode>
3234
3235	parport=	[HW,PPT] Specify parallel ports. 0 disables.
3236			Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
3237			Use 'auto' to force the driver to use any
3238			IRQ/DMA settings detected (the default is to
3239			ignore detected IRQ/DMA settings because of
3240			possible conflicts). You can specify the base
3241			address, IRQ, and DMA settings; IRQ and DMA
3242			should be numbers, or 'auto' (for using detected
3243			settings on that particular port), or 'nofifo'
3244			(to avoid using a FIFO even if it is detected).
3245			Parallel ports are assigned in the order they
3246			are specified on the command line, starting
3247			with parport0.
3248
3249	parport_init_mode=	[HW,PPT]
3250			Configure VIA parallel port to operate in
3251			a specific mode. This is necessary on Pegasos
3252			computer where firmware has no options for setting
3253			up parallel port mode and sets it to spp.
3254			Currently this function knows 686a and 8231 chips.
3255			Format: [spp|ps2|epp|ecp|ecpepp]
3256
3257	pause_on_oops=
3258			Halt all CPUs after the first oops has been printed for
3259			the specified number of seconds.  This is to be used if
3260			your oopses keep scrolling off the screen.
3261
3262	pcbit=		[HW,ISDN]
3263
3264	pcd.		[PARIDE]
3265			See header of drivers/block/paride/pcd.c.
3266			See also Documentation/blockdev/paride.txt.
3267
3268	pci=option[,option...]	[PCI] various PCI subsystem options.
3269
3270				Some options herein operate on a specific device
3271				or a set of devices (<pci_dev>). These are
3272				specified in one of the following formats:
3273
3274				[<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
3275				pci:<vendor>:<device>[:<subvendor>:<subdevice>]
3276
3277				Note: the first format specifies a PCI
3278				bus/device/function address which may change
3279				if new hardware is inserted, if motherboard
3280				firmware changes, or due to changes caused
3281				by other kernel parameters. If the
3282				domain is left unspecified, it is
3283				taken to be zero. Optionally, a path
3284				to a device through multiple device/function
3285				addresses can be specified after the base
3286				address (this is more robust against
3287				renumbering issues).  The second format
3288				selects devices using IDs from the
3289				configuration space which may match multiple
3290				devices in the system.
3291
3292		earlydump	dump PCI config space before the kernel
3293				changes anything
3294		off		[X86] don't probe for the PCI bus
3295		bios		[X86-32] force use of PCI BIOS, don't access
3296				the hardware directly. Use this if your machine
3297				has a non-standard PCI host bridge.
3298		nobios		[X86-32] disallow use of PCI BIOS, only direct
3299				hardware access methods are allowed. Use this
3300				if you experience crashes upon bootup and you
3301				suspect they are caused by the BIOS.
3302		conf1		[X86] Force use of PCI Configuration Access
3303				Mechanism 1 (config address in IO port 0xCF8,
3304				data in IO port 0xCFC, both 32-bit).
3305		conf2		[X86] Force use of PCI Configuration Access
3306				Mechanism 2 (IO port 0xCF8 is an 8-bit port for
3307				the function, IO port 0xCFA, also 8-bit, sets
3308				bus number. The config space is then accessed
3309				through ports 0xC000-0xCFFF).
3310				See http://wiki.osdev.org/PCI for more info
3311				on the configuration access mechanisms.
3312		noaer		[PCIE] If the PCIEAER kernel config parameter is
3313				enabled, this kernel boot option can be used to
3314				disable the use of PCIE advanced error reporting.
3315		nodomains	[PCI] Disable support for multiple PCI
3316				root domains (aka PCI segments, in ACPI-speak).
3317		nommconf	[X86] Disable use of MMCONFIG for PCI
3318				Configuration
3319		check_enable_amd_mmconf [X86] check for and enable
3320				properly configured MMIO access to PCI
3321				config space on AMD family 10h CPU
3322		nomsi		[MSI] If the PCI_MSI kernel config parameter is
3323				enabled, this kernel boot option can be used to
3324				disable the use of MSI interrupts system-wide.
3325		noioapicquirk	[APIC] Disable all boot interrupt quirks.
3326				Safety option to keep boot IRQs enabled. This
3327				should never be necessary.
3328		ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
3329				primary IO-APIC for bridges that cannot disable
3330				boot IRQs. This fixes a source of spurious IRQs
3331				when the system masks IRQs.
3332		noioapicreroute	[APIC] Disable workaround that uses the
3333				boot IRQ equivalent of an IRQ that connects to
3334				a chipset where boot IRQs cannot be disabled.
3335				The opposite of ioapicreroute.
3336		biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
3337				routing table. These calls are known to be buggy
3338				on several machines and they hang the machine
3339				when used, but on other computers it's the only
3340				way to get the interrupt routing table. Try
3341				this option if the kernel is unable to allocate
3342				IRQs or discover secondary PCI buses on your
3343				motherboard.
3344		rom		[X86] Assign address space to expansion ROMs.
3345				Use with caution as certain devices share
3346				address decoders between ROMs and other
3347				resources.
3348		norom		[X86] Do not assign address space to
3349				expansion ROMs that do not already have
3350				BIOS assigned address ranges.
3351		nobar		[X86] Do not assign address space to the
3352				BARs that weren't assigned by the BIOS.
3353		irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
3354				assigned automatically to PCI devices. You can
3355				make the kernel exclude IRQs of your ISA cards
3356				this way.
3357		pirqaddr=0xAAAAA	[X86] Specify the physical address
3358				of the PIRQ table (normally generated
3359				by the BIOS) if it is outside the
3360				F0000h-100000h range.
3361		lastbus=N	[X86] Scan all buses thru bus #N. Can be
3362				useful if the kernel is unable to find your
3363				secondary buses and you want to tell it
3364				explicitly which ones they are.
3365		assign-busses	[X86] Always assign all PCI bus
3366				numbers ourselves, overriding
3367				whatever the firmware may have done.
3368		usepirqmask	[X86] Honor the possible IRQ mask stored
3369				in the BIOS $PIR table. This is needed on
3370				some systems with broken BIOSes, notably
3371				some HP Pavilion N5400 and Omnibook XE3
3372				notebooks. This will have no effect if ACPI
3373				IRQ routing is enabled.
3374		noacpi		[X86] Do not use ACPI for IRQ routing
3375				or for PCI scanning.
3376		use_crs		[X86] Use PCI host bridge window information
3377				from ACPI.  On BIOSes from 2008 or later, this
3378				is enabled by default.  If you need to use this,
3379				please report a bug.
3380		nocrs		[X86] Ignore PCI host bridge windows from ACPI.
3381				If you need to use this, please report a bug.
3382		routeirq	Do IRQ routing for all PCI devices.
3383				This is normally done in pci_enable_device(),
3384				so this option is a temporary workaround
3385				for broken drivers that don't call it.
3386		skip_isa_align	[X86] do not align io start addr, so can
3387				handle more pci cards
3388		noearly		[X86] Don't do any early type 1 scanning.
3389				This might help on some broken boards which
3390				machine check when some devices' config space
3391				is read. But various workarounds are disabled
3392				and some IOMMU drivers will not work.
3393		bfsort		Sort PCI devices into breadth-first order.
3394				This sorting is done to get a device
3395				order compatible with older (<= 2.4) kernels.
3396		nobfsort	Don't sort PCI devices into breadth-first order.
3397		pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
3398				tuning and use the BIOS-configured MPS defaults.
3399		pcie_bus_safe	Set every device's MPS to the largest value
3400				supported by all devices below the root complex.
3401		pcie_bus_perf	Set device MPS to the largest allowable MPS
3402				based on its parent bus. Also set MRRS (Max
3403				Read Request Size) to the largest supported
3404				value (no larger than the MPS that the device
3405				or bus can support) for best performance.
3406		pcie_bus_peer2peer	Set every device's MPS to 128B, which
3407				every device is guaranteed to support. This
3408				configuration allows peer-to-peer DMA between
3409				any pair of devices, possibly at the cost of
3410				reduced performance.  This also guarantees
3411				that hot-added devices will work.
3412		cbiosize=nn[KMG]	The fixed amount of bus space which is
3413				reserved for the CardBus bridge's IO window.
3414				The default value is 256 bytes.
3415		cbmemsize=nn[KMG]	The fixed amount of bus space which is
3416				reserved for the CardBus bridge's memory
3417				window. The default value is 64 megabytes.
3418		resource_alignment=
3419				Format:
3420				[<order of align>@]<pci_dev>[; ...]
3421				Specifies alignment and device to reassign
3422				aligned memory resources. How to
3423				specify the device is described above.
3424				If <order of align> is not specified,
3425				PAGE_SIZE is used as alignment.
3426				PCI-PCI bridge can be specified, if resource
3427				windows need to be expanded.
3428				To specify the alignment for several
3429				instances of a device, the PCI vendor,
3430				device, subvendor, and subdevice may be
3431				specified, e.g., 4096@pci:8086:9c22:103c:198f
3432		ecrc=		Enable/disable PCIe ECRC (transaction layer
3433				end-to-end CRC checking).
3434				bios: Use BIOS/firmware settings. This is the
3435				the default.
3436				off: Turn ECRC off
3437				on: Turn ECRC on.
3438		hpiosize=nn[KMG]	The fixed amount of bus space which is
3439				reserved for hotplug bridge's IO window.
3440				Default size is 256 bytes.
3441		hpmemsize=nn[KMG]	The fixed amount of bus space which is
3442				reserved for hotplug bridge's memory window.
3443				Default size is 2 megabytes.
3444		hpbussize=nn	The minimum amount of additional bus numbers
3445				reserved for buses below a hotplug bridge.
3446				Default is 1.
3447		realloc=	Enable/disable reallocating PCI bridge resources
3448				if allocations done by BIOS are too small to
3449				accommodate resources required by all child
3450				devices.
3451				off: Turn realloc off
3452				on: Turn realloc on
3453		realloc		same as realloc=on
3454		noari		do not use PCIe ARI.
3455		noats		[PCIE, Intel-IOMMU, AMD-IOMMU]
3456				do not use PCIe ATS (and IOMMU device IOTLB).
3457		pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
3458				only look for one device below a PCIe downstream
3459				port.
3460		big_root_window	Try to add a big 64bit memory window to the PCIe
3461				root complex on AMD CPUs. Some GFX hardware
3462				can resize a BAR to allow access to all VRAM.
3463				Adding the window is slightly risky (it may
3464				conflict with unreported devices), so this
3465				taints the kernel.
3466		disable_acs_redir=<pci_dev>[; ...]
3467				Specify one or more PCI devices (in the format
3468				specified above) separated by semicolons.
3469				Each device specified will have the PCI ACS
3470				redirect capabilities forced off which will
3471				allow P2P traffic between devices through
3472				bridges without forcing it upstream. Note:
3473				this removes isolation between devices and
3474				may put more devices in an IOMMU group.
3475		force_floating	[S390] Force usage of floating interrupts.
3476		nomio		[S390] Do not use MIO instructions.
3477
3478	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
3479			Management.
3480		off	Disable ASPM.
3481		force	Enable ASPM even on devices that claim not to support it.
3482			WARNING: Forcing ASPM on may cause system lockups.
3483
3484	pcie_ports=	[PCIE] PCIe port services handling:
3485		native	Use native PCIe services (PME, AER, DPC, PCIe hotplug)
3486			even if the platform doesn't give the OS permission to
3487			use them.  This may cause conflicts if the platform
3488			also tries to use these services.
3489		compat	Disable native PCIe services (PME, AER, DPC, PCIe
3490			hotplug).
3491
3492	pcie_port_pm=	[PCIE] PCIe port power management handling:
3493		off	Disable power management of all PCIe ports
3494		force	Forcibly enable power management of all PCIe ports
3495
3496	pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
3497		nomsi	Do not use MSI for native PCIe PME signaling (this makes
3498			all PCIe root ports use INTx for all services).
3499
3500	pcmv=		[HW,PCMCIA] BadgePAD 4
3501
3502	pd_ignore_unused
3503			[PM]
3504			Keep all power-domains already enabled by bootloader on,
3505			even if no driver has claimed them. This is useful
3506			for debug and development, but should not be
3507			needed on a platform with proper driver support.
3508
3509	pd.		[PARIDE]
3510			See Documentation/blockdev/paride.txt.
3511
3512	pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
3513			boot time.
3514			Format: { 0 | 1 }
3515			See arch/parisc/kernel/pdc_chassis.c
3516
3517	percpu_alloc=	Select which percpu first chunk allocator to use.
3518			Currently supported values are "embed" and "page".
3519			Archs may support subset or none of the	selections.
3520			See comments in mm/percpu.c for details on each
3521			allocator.  This parameter is primarily	for debugging
3522			and performance comparison.
3523
3524	pf.		[PARIDE]
3525			See Documentation/blockdev/paride.txt.
3526
3527	pg.		[PARIDE]
3528			See Documentation/blockdev/paride.txt.
3529
3530	pirq=		[SMP,APIC] Manual mp-table setup
3531			See Documentation/x86/i386/IO-APIC.txt.
3532
3533	plip=		[PPT,NET] Parallel port network link
3534			Format: { parport<nr> | timid | 0 }
3535			See also Documentation/admin-guide/parport.rst.
3536
3537	pmtmr=		[X86] Manual setup of pmtmr I/O Port.
3538			Override pmtimer IOPort with a hex value.
3539			e.g. pmtmr=0x508
3540
3541	pnp.debug=1	[PNP]
3542			Enable PNP debug messages (depends on the
3543			CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
3544			via /sys/module/pnp/parameters/debug.  We always show
3545			current resource usage; turning this on also shows
3546			possible settings and some assignment information.
3547
3548	pnpacpi=	[ACPI]
3549			{ off }
3550
3551	pnpbios=	[ISAPNP]
3552			{ on | off | curr | res | no-curr | no-res }
3553
3554	pnp_reserve_irq=
3555			[ISAPNP] Exclude IRQs for the autoconfiguration
3556
3557	pnp_reserve_dma=
3558			[ISAPNP] Exclude DMAs for the autoconfiguration
3559
3560	pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
3561			Ranges are in pairs (I/O port base and size).
3562
3563	pnp_reserve_mem=
3564			[ISAPNP] Exclude memory regions for the
3565			autoconfiguration.
3566			Ranges are in pairs (memory base and size).
3567
3568	ports=		[IP_VS_FTP] IPVS ftp helper module
3569			Default is 21.
3570			Up to 8 (IP_VS_APP_MAX_PORTS) ports
3571			may be specified.
3572			Format: <port>,<port>....
3573
3574	powersave=off	[PPC] This option disables power saving features.
3575			It specifically disables cpuidle and sets the
3576			platform machine description specific power_save
3577			function to NULL. On Idle the CPU just reduces
3578			execution priority.
3579
3580	ppc_strict_facility_enable
3581			[PPC] This option catches any kernel floating point,
3582			Altivec, VSX and SPE outside of regions specifically
3583			allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3584			There is some performance impact when enabling this.
3585
3586	ppc_tm=		[PPC]
3587			Format: {"off"}
3588			Disable Hardware Transactional Memory
3589
3590	print-fatal-signals=
3591			[KNL] debug: print fatal signals
3592
3593			If enabled, warn about various signal handling
3594			related application anomalies: too many signals,
3595			too many POSIX.1 timers, fatal signals causing a
3596			coredump - etc.
3597
3598			If you hit the warning due to signal overflow,
3599			you might want to try "ulimit -i unlimited".
3600
3601			default: off.
3602
3603	printk.always_kmsg_dump=
3604			Trigger kmsg_dump for cases other than kernel oops or
3605			panics
3606			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
3607			default: disabled
3608
3609	printk.devkmsg={on,off,ratelimit}
3610			Control writing to /dev/kmsg.
3611			on - unlimited logging to /dev/kmsg from userspace
3612			off - logging to /dev/kmsg disabled
3613			ratelimit - ratelimit the logging
3614			Default: ratelimit
3615
3616	printk.time=	Show timing data prefixed to each printk message line
3617			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
3618
3619	processor.max_cstate=	[HW,ACPI]
3620			Limit processor to maximum C-state
3621			max_cstate=9 overrides any DMI blacklist limit.
3622
3623	processor.nocst	[HW,ACPI]
3624			Ignore the _CST method to determine C-states,
3625			instead using the legacy FADT method
3626
3627	profile=	[KNL] Enable kernel profiling via /proc/profile
3628			Format: [<profiletype>,]<number>
3629			Param: <profiletype>: "schedule", "sleep", or "kvm"
3630				[defaults to kernel profiling]
3631			Param: "schedule" - profile schedule points.
3632			Param: "sleep" - profile D-state sleeping (millisecs).
3633				Requires CONFIG_SCHEDSTATS
3634			Param: "kvm" - profile VM exits.
3635			Param: <number> - step/bucket size as a power of 2 for
3636				statistical time based profiling.
3637
3638	prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
3639			before loading.
3640			See Documentation/blockdev/ramdisk.txt.
3641
3642	psi=		[KNL] Enable or disable pressure stall information
3643			tracking.
3644			Format: <bool>
3645
3646	psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
3647			probe for; one of (bare|imps|exps|lifebook|any).
3648	psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
3649			per second.
3650	psmouse.resetafter=	[HW,MOUSE]
3651			Try to reset the device after so many bad packets
3652			(0 = never).
3653	psmouse.resolution=
3654			[HW,MOUSE] Set desired mouse resolution, in dpi.
3655	psmouse.smartscroll=
3656			[HW,MOUSE] Controls Logitech smartscroll autorepeat.
3657			0 = disabled, 1 = enabled (default).
3658
3659	pstore.backend=	Specify the name of the pstore backend to use
3660
3661	pt.		[PARIDE]
3662			See Documentation/blockdev/paride.txt.
3663
3664	pti=		[X86_64] Control Page Table Isolation of user and
3665			kernel address spaces.  Disabling this feature
3666			removes hardening, but improves performance of
3667			system calls and interrupts.
3668
3669			on   - unconditionally enable
3670			off  - unconditionally disable
3671			auto - kernel detects whether your CPU model is
3672			       vulnerable to issues that PTI mitigates
3673
3674			Not specifying this option is equivalent to pti=auto.
3675
3676	nopti		[X86_64]
3677			Equivalent to pti=off
3678
3679	pty.legacy_count=
3680			[KNL] Number of legacy pty's. Overwrites compiled-in
3681			default number.
3682
3683	quiet		[KNL] Disable most log messages
3684
3685	r128=		[HW,DRM]
3686
3687	raid=		[HW,RAID]
3688			See Documentation/admin-guide/md.rst.
3689
3690	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
3691			See Documentation/blockdev/ramdisk.txt.
3692
3693	random.trust_cpu={on,off}
3694			[KNL] Enable or disable trusting the use of the
3695			CPU's random number generator (if available) to
3696			fully seed the kernel's CRNG. Default is controlled
3697			by CONFIG_RANDOM_TRUST_CPU.
3698
3699	ras=option[,option,...]	[KNL] RAS-specific options
3700
3701		cec_disable	[X86]
3702				Disable the Correctable Errors Collector,
3703				see CONFIG_RAS_CEC help text.
3704
3705	rcu_nocbs=	[KNL]
3706			The argument is a cpu list, as described above,
3707			except that the string "all" can be used to
3708			specify every CPU on the system.
3709
3710			In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3711			the specified list of CPUs to be no-callback CPUs.
3712			Invocation of these CPUs' RCU callbacks will be
3713			offloaded to "rcuox/N" kthreads created for that
3714			purpose, where "x" is "p" for RCU-preempt, and
3715			"s" for RCU-sched, and "N" is the CPU number.
3716			This reduces OS jitter on the offloaded CPUs,
3717			which can be useful for HPC and real-time
3718			workloads.  It can also improve energy efficiency
3719			for asymmetric multiprocessors.
3720
3721	rcu_nocb_poll	[KNL]
3722			Rather than requiring that offloaded CPUs
3723			(specified by rcu_nocbs= above) explicitly
3724			awaken the corresponding "rcuoN" kthreads,
3725			make these kthreads poll for callbacks.
3726			This improves the real-time response for the
3727			offloaded CPUs by relieving them of the need to
3728			wake up the corresponding kthread, but degrades
3729			energy efficiency by requiring that the kthreads
3730			periodically wake up to do the polling.
3731
3732	rcutree.blimit=	[KNL]
3733			Set maximum number of finished RCU callbacks to
3734			process in one batch.
3735
3736	rcutree.dump_tree=	[KNL]
3737			Dump the structure of the rcu_node combining tree
3738			out at early boot.  This is used for diagnostic
3739			purposes, to verify correct tree setup.
3740
3741	rcutree.gp_cleanup_delay=	[KNL]
3742			Set the number of jiffies to delay each step of
3743			RCU grace-period cleanup.
3744
3745	rcutree.gp_init_delay=	[KNL]
3746			Set the number of jiffies to delay each step of
3747			RCU grace-period initialization.
3748
3749	rcutree.gp_preinit_delay=	[KNL]
3750			Set the number of jiffies to delay each step of
3751			RCU grace-period pre-initialization, that is,
3752			the propagation of recent CPU-hotplug changes up
3753			the rcu_node combining tree.
3754
3755	rcutree.rcu_fanout_exact= [KNL]
3756			Disable autobalancing of the rcu_node combining
3757			tree.  This is used by rcutorture, and might
3758			possibly be useful for architectures having high
3759			cache-to-cache transfer latencies.
3760
3761	rcutree.rcu_fanout_leaf= [KNL]
3762			Change the number of CPUs assigned to each
3763			leaf rcu_node structure.  Useful for very
3764			large systems, which will choose the value 64,
3765			and for NUMA systems with large remote-access
3766			latencies, which will choose a value aligned
3767			with the appropriate hardware boundaries.
3768
3769	rcutree.jiffies_till_first_fqs= [KNL]
3770			Set delay from grace-period initialization to
3771			first attempt to force quiescent states.
3772			Units are jiffies, minimum value is zero,
3773			and maximum value is HZ.
3774
3775	rcutree.jiffies_till_next_fqs= [KNL]
3776			Set delay between subsequent attempts to force
3777			quiescent states.  Units are jiffies, minimum
3778			value is one, and maximum value is HZ.
3779
3780	rcutree.jiffies_till_sched_qs= [KNL]
3781			Set required age in jiffies for a
3782			given grace period before RCU starts
3783			soliciting quiescent-state help from
3784			rcu_note_context_switch() and cond_resched().
3785			If not specified, the kernel will calculate
3786			a value based on the most recent settings
3787			of rcutree.jiffies_till_first_fqs
3788			and rcutree.jiffies_till_next_fqs.
3789			This calculated value may be viewed in
3790			rcutree.jiffies_to_sched_qs.  Any attempt to set
3791			rcutree.jiffies_to_sched_qs will be cheerfully
3792			overwritten.
3793
3794	rcutree.kthread_prio= 	 [KNL,BOOT]
3795			Set the SCHED_FIFO priority of the RCU per-CPU
3796			kthreads (rcuc/N). This value is also used for
3797			the priority of the RCU boost threads (rcub/N)
3798			and for the RCU grace-period kthreads (rcu_bh,
3799			rcu_preempt, and rcu_sched). If RCU_BOOST is
3800			set, valid values are 1-99 and the default is 1
3801			(the least-favored priority).  Otherwise, when
3802			RCU_BOOST is not set, valid values are 0-99 and
3803			the default is zero (non-realtime operation).
3804
3805	rcutree.rcu_nocb_leader_stride= [KNL]
3806			Set the number of NOCB kthread groups, which
3807			defaults to the square root of the number of
3808			CPUs.  Larger numbers reduces the wakeup overhead
3809			on the per-CPU grace-period kthreads, but increases
3810			that same overhead on each group's leader.
3811
3812	rcutree.qhimark= [KNL]
3813			Set threshold of queued RCU callbacks beyond which
3814			batch limiting is disabled.
3815
3816	rcutree.qlowmark= [KNL]
3817			Set threshold of queued RCU callbacks below which
3818			batch limiting is re-enabled.
3819
3820	rcutree.rcu_idle_gp_delay= [KNL]
3821			Set wakeup interval for idle CPUs that have
3822			RCU callbacks (RCU_FAST_NO_HZ=y).
3823
3824	rcutree.rcu_idle_lazy_gp_delay= [KNL]
3825			Set wakeup interval for idle CPUs that have
3826			only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3827			Lazy RCU callbacks are those which RCU can
3828			prove do nothing more than free memory.
3829
3830	rcutree.rcu_kick_kthreads= [KNL]
3831			Cause the grace-period kthread to get an extra
3832			wake_up() if it sleeps three times longer than
3833			it should at force-quiescent-state time.
3834			This wake_up() will be accompanied by a
3835			WARN_ONCE() splat and an ftrace_dump().
3836
3837	rcutree.sysrq_rcu= [KNL]
3838			Commandeer a sysrq key to dump out Tree RCU's
3839			rcu_node tree with an eye towards determining
3840			why a new grace period has not yet started.
3841
3842	rcuperf.gp_async= [KNL]
3843			Measure performance of asynchronous
3844			grace-period primitives such as call_rcu().
3845
3846	rcuperf.gp_async_max= [KNL]
3847			Specify the maximum number of outstanding
3848			callbacks per writer thread.  When a writer
3849			thread exceeds this limit, it invokes the
3850			corresponding flavor of rcu_barrier() to allow
3851			previously posted callbacks to drain.
3852
3853	rcuperf.gp_exp= [KNL]
3854			Measure performance of expedited synchronous
3855			grace-period primitives.
3856
3857	rcuperf.holdoff= [KNL]
3858			Set test-start holdoff period.  The purpose of
3859			this parameter is to delay the start of the
3860			test until boot completes in order to avoid
3861			interference.
3862
3863	rcuperf.nreaders= [KNL]
3864			Set number of RCU readers.  The value -1 selects
3865			N, where N is the number of CPUs.  A value
3866			"n" less than -1 selects N-n+1, where N is again
3867			the number of CPUs.  For example, -2 selects N
3868			(the number of CPUs), -3 selects N+1, and so on.
3869			A value of "n" less than or equal to -N selects
3870			a single reader.
3871
3872	rcuperf.nwriters= [KNL]
3873			Set number of RCU writers.  The values operate
3874			the same as for rcuperf.nreaders.
3875			N, where N is the number of CPUs
3876
3877	rcuperf.perf_type= [KNL]
3878			Specify the RCU implementation to test.
3879
3880	rcuperf.shutdown= [KNL]
3881			Shut the system down after performance tests
3882			complete.  This is useful for hands-off automated
3883			testing.
3884
3885	rcuperf.verbose= [KNL]
3886			Enable additional printk() statements.
3887
3888	rcuperf.writer_holdoff= [KNL]
3889			Write-side holdoff between grace periods,
3890			in microseconds.  The default of zero says
3891			no holdoff.
3892
3893	rcutorture.fqs_duration= [KNL]
3894			Set duration of force_quiescent_state bursts
3895			in microseconds.
3896
3897	rcutorture.fqs_holdoff= [KNL]
3898			Set holdoff time within force_quiescent_state bursts
3899			in microseconds.
3900
3901	rcutorture.fqs_stutter= [KNL]
3902			Set wait time between force_quiescent_state bursts
3903			in seconds.
3904
3905	rcutorture.fwd_progress= [KNL]
3906			Enable RCU grace-period forward-progress testing
3907			for the types of RCU supporting this notion.
3908
3909	rcutorture.fwd_progress_div= [KNL]
3910			Specify the fraction of a CPU-stall-warning
3911			period to do tight-loop forward-progress testing.
3912
3913	rcutorture.fwd_progress_holdoff= [KNL]
3914			Number of seconds to wait between successive
3915			forward-progress tests.
3916
3917	rcutorture.fwd_progress_need_resched= [KNL]
3918			Enclose cond_resched() calls within checks for
3919			need_resched() during tight-loop forward-progress
3920			testing.
3921
3922	rcutorture.gp_cond= [KNL]
3923			Use conditional/asynchronous update-side
3924			primitives, if available.
3925
3926	rcutorture.gp_exp= [KNL]
3927			Use expedited update-side primitives, if available.
3928
3929	rcutorture.gp_normal= [KNL]
3930			Use normal (non-expedited) asynchronous
3931			update-side primitives, if available.
3932
3933	rcutorture.gp_sync= [KNL]
3934			Use normal (non-expedited) synchronous
3935			update-side primitives, if available.  If all
3936			of rcutorture.gp_cond=, rcutorture.gp_exp=,
3937			rcutorture.gp_normal=, and rcutorture.gp_sync=
3938			are zero, rcutorture acts as if is interpreted
3939			they are all non-zero.
3940
3941	rcutorture.n_barrier_cbs= [KNL]
3942			Set callbacks/threads for rcu_barrier() testing.
3943
3944	rcutorture.nfakewriters= [KNL]
3945			Set number of concurrent RCU writers.  These just
3946			stress RCU, they don't participate in the actual
3947			test, hence the "fake".
3948
3949	rcutorture.nreaders= [KNL]
3950			Set number of RCU readers.  The value -1 selects
3951			N-1, where N is the number of CPUs.  A value
3952			"n" less than -1 selects N-n-2, where N is again
3953			the number of CPUs.  For example, -2 selects N
3954			(the number of CPUs), -3 selects N+1, and so on.
3955
3956	rcutorture.object_debug= [KNL]
3957			Enable debug-object double-call_rcu() testing.
3958
3959	rcutorture.onoff_holdoff= [KNL]
3960			Set time (s) after boot for CPU-hotplug testing.
3961
3962	rcutorture.onoff_interval= [KNL]
3963			Set time (jiffies) between CPU-hotplug operations,
3964			or zero to disable CPU-hotplug testing.
3965
3966	rcutorture.shuffle_interval= [KNL]
3967			Set task-shuffle interval (s).  Shuffling tasks
3968			allows some CPUs to go into dyntick-idle mode
3969			during the rcutorture test.
3970
3971	rcutorture.shutdown_secs= [KNL]
3972			Set time (s) after boot system shutdown.  This
3973			is useful for hands-off automated testing.
3974
3975	rcutorture.stall_cpu= [KNL]
3976			Duration of CPU stall (s) to test RCU CPU stall
3977			warnings, zero to disable.
3978
3979	rcutorture.stall_cpu_holdoff= [KNL]
3980			Time to wait (s) after boot before inducing stall.
3981
3982	rcutorture.stall_cpu_irqsoff= [KNL]
3983			Disable interrupts while stalling if set.
3984
3985	rcutorture.stat_interval= [KNL]
3986			Time (s) between statistics printk()s.
3987
3988	rcutorture.stutter= [KNL]
3989			Time (s) to stutter testing, for example, specifying
3990			five seconds causes the test to run for five seconds,
3991			wait for five seconds, and so on.  This tests RCU's
3992			ability to transition abruptly to and from idle.
3993
3994	rcutorture.test_boost= [KNL]
3995			Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
3996			"Maybe" means test if the RCU implementation
3997			under test support RCU priority boosting.
3998
3999	rcutorture.test_boost_duration= [KNL]
4000			Duration (s) of each individual boost test.
4001
4002	rcutorture.test_boost_interval= [KNL]
4003			Interval (s) between each boost test.
4004
4005	rcutorture.test_no_idle_hz= [KNL]
4006			Test RCU's dyntick-idle handling.  See also the
4007			rcutorture.shuffle_interval parameter.
4008
4009	rcutorture.torture_type= [KNL]
4010			Specify the RCU implementation to test.
4011
4012	rcutorture.verbose= [KNL]
4013			Enable additional printk() statements.
4014
4015	rcupdate.rcu_cpu_stall_suppress= [KNL]
4016			Suppress RCU CPU stall warning messages.
4017
4018	rcupdate.rcu_cpu_stall_timeout= [KNL]
4019			Set timeout for RCU CPU stall warning messages.
4020
4021	rcupdate.rcu_expedited= [KNL]
4022			Use expedited grace-period primitives, for
4023			example, synchronize_rcu_expedited() instead
4024			of synchronize_rcu().  This reduces latency,
4025			but can increase CPU utilization, degrade
4026			real-time latency, and degrade energy efficiency.
4027			No effect on CONFIG_TINY_RCU kernels.
4028
4029	rcupdate.rcu_normal= [KNL]
4030			Use only normal grace-period primitives,
4031			for example, synchronize_rcu() instead of
4032			synchronize_rcu_expedited().  This improves
4033			real-time latency, CPU utilization, and
4034			energy efficiency, but can expose users to
4035			increased grace-period latency.  This parameter
4036			overrides rcupdate.rcu_expedited.  No effect on
4037			CONFIG_TINY_RCU kernels.
4038
4039	rcupdate.rcu_normal_after_boot= [KNL]
4040			Once boot has completed (that is, after
4041			rcu_end_inkernel_boot() has been invoked), use
4042			only normal grace-period primitives.  No effect
4043			on CONFIG_TINY_RCU kernels.
4044
4045	rcupdate.rcu_task_stall_timeout= [KNL]
4046			Set timeout in jiffies for RCU task stall warning
4047			messages.  Disable with a value less than or equal
4048			to zero.
4049
4050	rcupdate.rcu_self_test= [KNL]
4051			Run the RCU early boot self tests
4052
4053	rdinit=		[KNL]
4054			Format: <full_path>
4055			Run specified binary instead of /init from the ramdisk,
4056			used for early userspace startup. See initrd.
4057
4058	rdt=		[HW,X86,RDT]
4059			Turn on/off individual RDT features. List is:
4060			cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
4061			mba.
4062			E.g. to turn on cmt and turn off mba use:
4063				rdt=cmt,!mba
4064
4065	reboot=		[KNL]
4066			Format (x86 or x86_64):
4067				[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
4068				[[,]s[mp]#### \
4069				[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
4070				[[,]f[orce]
4071			Where reboot_mode is one of warm (soft) or cold (hard) or gpio
4072					(prefix with 'panic_' to set mode for panic
4073					reboot only),
4074			      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
4075			      reboot_force is either force or not specified,
4076			      reboot_cpu is s[mp]#### with #### being the processor
4077					to be used for rebooting.
4078
4079	relax_domain_level=
4080			[KNL, SMP] Set scheduler's default relax_domain_level.
4081			See Documentation/cgroup-v1/cpusets.txt.
4082
4083	reserve=	[KNL,BUGS] Force kernel to ignore I/O ports or memory
4084			Format: <base1>,<size1>[,<base2>,<size2>,...]
4085			Reserve I/O ports or memory so the kernel won't use
4086			them.  If <base> is less than 0x10000, the region
4087			is assumed to be I/O ports; otherwise it is memory.
4088
4089	reservetop=	[X86-32]
4090			Format: nn[KMG]
4091			Reserves a hole at the top of the kernel virtual
4092			address space.
4093
4094	reservelow=	[X86]
4095			Format: nn[K]
4096			Set the amount of memory to reserve for BIOS at
4097			the bottom of the address space.
4098
4099	reset_devices	[KNL] Force drivers to reset the underlying device
4100			during initialization.
4101
4102	resume=		[SWSUSP]
4103			Specify the partition device for software suspend
4104			Format:
4105			{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
4106
4107	resume_offset=	[SWSUSP]
4108			Specify the offset from the beginning of the partition
4109			given by "resume=" at which the swap header is located,
4110			in <PAGE_SIZE> units (needed only for swap files).
4111			See  Documentation/power/swsusp-and-swap-files.txt
4112
4113	resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
4114			read the resume files
4115
4116	resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
4117			Useful for devices that are detected asynchronously
4118			(e.g. USB and MMC devices).
4119
4120	hibernate=	[HIBERNATION]
4121		noresume	Don't check if there's a hibernation image
4122				present during boot.
4123		nocompress	Don't compress/decompress hibernation images.
4124		no		Disable hibernation and resume.
4125		protect_image	Turn on image protection during restoration
4126				(that will set all pages holding image data
4127				during restoration read-only).
4128
4129	retain_initrd	[RAM] Keep initrd memory after extraction
4130
4131	rfkill.default_state=
4132		0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
4133			etc. communication is blocked by default.
4134		1	Unblocked.
4135
4136	rfkill.master_switch_mode=
4137		0	The "airplane mode" button does nothing.
4138		1	The "airplane mode" button toggles between everything
4139			blocked and the previous configuration.
4140		2	The "airplane mode" button toggles between everything
4141			blocked and everything unblocked.
4142
4143	rhash_entries=	[KNL,NET]
4144			Set number of hash buckets for route cache
4145
4146	ring3mwait=disable
4147			[KNL] Disable ring 3 MONITOR/MWAIT feature on supported
4148			CPUs.
4149
4150	ro		[KNL] Mount root device read-only on boot
4151
4152	rodata=		[KNL]
4153		on	Mark read-only kernel memory as read-only (default).
4154		off	Leave read-only kernel memory writable for debugging.
4155
4156	rockchip.usb_uart
4157			Enable the uart passthrough on the designated usb port
4158			on Rockchip SoCs. When active, the signals of the
4159			debug-uart get routed to the D+ and D- pins of the usb
4160			port and the regular usb controller gets disabled.
4161
4162	root=		[KNL] Root filesystem
4163			See name_to_dev_t comment in init/do_mounts.c.
4164
4165	rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
4166			mount the root filesystem
4167
4168	rootflags=	[KNL] Set root filesystem mount option string
4169
4170	rootfstype=	[KNL] Set root filesystem type
4171
4172	rootwait	[KNL] Wait (indefinitely) for root device to show up.
4173			Useful for devices that are detected asynchronously
4174			(e.g. USB and MMC devices).
4175
4176	rproc_mem=nn[KMG][@address]
4177			[KNL,ARM,CMA] Remoteproc physical memory block.
4178			Memory area to be used by remote processor image,
4179			managed by CMA.
4180
4181	rw		[KNL] Mount root device read-write on boot
4182
4183	S		[KNL] Run init in single mode
4184
4185	s390_iommu=	[HW,S390]
4186			Set s390 IOTLB flushing mode
4187		strict
4188			With strict flushing every unmap operation will result in
4189			an IOTLB flush. Default is lazy flushing before reuse,
4190			which is faster.
4191
4192	sa1100ir	[NET]
4193			See drivers/net/irda/sa1100_ir.c.
4194
4195	sbni=		[NET] Granch SBNI12 leased line adapter
4196
4197	sched_debug	[KNL] Enables verbose scheduler debug messages.
4198
4199	schedstats=	[KNL,X86] Enable or disable scheduled statistics.
4200			Allowed values are enable and disable. This feature
4201			incurs a small amount of overhead in the scheduler
4202			but is useful for debugging and performance tuning.
4203
4204	skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
4205			xtime_lock contention on larger systems, and/or RCU lock
4206			contention on all systems with CONFIG_MAXSMP set.
4207			Format: { "0" | "1" }
4208			0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
4209			1 -- enable.
4210			Note: increases power consumption, thus should only be
4211			enabled if running jitter sensitive (HPC/RT) workloads.
4212
4213	security=	[SECURITY] Choose a legacy "major" security module to
4214			enable at boot. This has been deprecated by the
4215			"lsm=" parameter.
4216
4217	selinux=	[SELINUX] Disable or enable SELinux at boot time.
4218			Format: { "0" | "1" }
4219			See security/selinux/Kconfig help text.
4220			0 -- disable.
4221			1 -- enable.
4222			Default value is set via kernel config option.
4223			If enabled at boot time, /selinux/disable can be used
4224			later to disable prior to initial policy load.
4225
4226	apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
4227			Format: { "0" | "1" }
4228			See security/apparmor/Kconfig help text
4229			0 -- disable.
4230			1 -- enable.
4231			Default value is set via kernel config option.
4232
4233	serialnumber	[BUGS=X86-32]
4234
4235	shapers=	[NET]
4236			Maximal number of shapers.
4237
4238	simeth=		[IA-64]
4239	simscsi=
4240
4241	slram=		[HW,MTD]
4242
4243	slab_nomerge	[MM]
4244			Disable merging of slabs with similar size. May be
4245			necessary if there is some reason to distinguish
4246			allocs to different slabs, especially in hardened
4247			environments where the risk of heap overflows and
4248			layout control by attackers can usually be
4249			frustrated by disabling merging. This will reduce
4250			most of the exposure of a heap attack to a single
4251			cache (risks via metadata attacks are mostly
4252			unchanged). Debug options disable merging on their
4253			own.
4254			For more information see Documentation/vm/slub.rst.
4255
4256	slab_max_order=	[MM, SLAB]
4257			Determines the maximum allowed order for slabs.
4258			A high setting may cause OOMs due to memory
4259			fragmentation.  Defaults to 1 for systems with
4260			more than 32MB of RAM, 0 otherwise.
4261
4262	slub_debug[=options[,slabs]]	[MM, SLUB]
4263			Enabling slub_debug allows one to determine the
4264			culprit if slab objects become corrupted. Enabling
4265			slub_debug can create guard zones around objects and
4266			may poison objects when not in use. Also tracks the
4267			last alloc / free. For more information see
4268			Documentation/vm/slub.rst.
4269
4270	slub_memcg_sysfs=	[MM, SLUB]
4271			Determines whether to enable sysfs directories for
4272			memory cgroup sub-caches. 1 to enable, 0 to disable.
4273			The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
4274			Enabling this can lead to a very high number of	debug
4275			directories and files being created under
4276			/sys/kernel/slub.
4277
4278	slub_max_order= [MM, SLUB]
4279			Determines the maximum allowed order for slabs.
4280			A high setting may cause OOMs due to memory
4281			fragmentation. For more information see
4282			Documentation/vm/slub.rst.
4283
4284	slub_min_objects=	[MM, SLUB]
4285			The minimum number of objects per slab. SLUB will
4286			increase the slab order up to slub_max_order to
4287			generate a sufficiently large slab able to contain
4288			the number of objects indicated. The higher the number
4289			of objects the smaller the overhead of tracking slabs
4290			and the less frequently locks need to be acquired.
4291			For more information see Documentation/vm/slub.rst.
4292
4293	slub_min_order=	[MM, SLUB]
4294			Determines the minimum page order for slabs. Must be
4295			lower than slub_max_order.
4296			For more information see Documentation/vm/slub.rst.
4297
4298	slub_nomerge	[MM, SLUB]
4299			Same with slab_nomerge. This is supported for legacy.
4300			See slab_nomerge for more information.
4301
4302	smart2=		[HW]
4303			Format: <io1>[,<io2>[,...,<io8>]]
4304
4305	smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
4306	smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
4307	smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
4308	smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
4309	smsc-ircc2.ircc_irq=	[HW] IRQ line
4310	smsc-ircc2.ircc_dma=	[HW] DMA channel
4311	smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
4312				0: Toshiba Satellite 1800 (GP data pin select)
4313				1: Fast pin select (default)
4314				2: ATC IRMode
4315
4316	smt		[KNL,S390] Set the maximum number of threads (logical
4317			CPUs) to use per physical CPU on systems capable of
4318			symmetric multithreading (SMT). Will be capped to the
4319			actual hardware limit.
4320			Format: <integer>
4321			Default: -1 (no limit)
4322
4323	softlockup_panic=
4324			[KNL] Should the soft-lockup detector generate panics.
4325			Format: <integer>
4326
4327			A nonzero value instructs the soft-lockup detector
4328			to panic the machine when a soft-lockup occurs. This
4329			is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
4330			which is the respective build-time switch to that
4331			functionality.
4332
4333	softlockup_all_cpu_backtrace=
4334			[KNL] Should the soft-lockup detector generate
4335			backtraces on all cpus.
4336			Format: <integer>
4337
4338	sonypi.*=	[HW] Sony Programmable I/O Control Device driver
4339			See Documentation/laptops/sonypi.txt
4340
4341	spectre_v2=	[X86] Control mitigation of Spectre variant 2
4342			(indirect branch speculation) vulnerability.
4343			The default operation protects the kernel from
4344			user space attacks.
4345
4346			on   - unconditionally enable, implies
4347			       spectre_v2_user=on
4348			off  - unconditionally disable, implies
4349			       spectre_v2_user=off
4350			auto - kernel detects whether your CPU model is
4351			       vulnerable
4352
4353			Selecting 'on' will, and 'auto' may, choose a
4354			mitigation method at run time according to the
4355			CPU, the available microcode, the setting of the
4356			CONFIG_RETPOLINE configuration option, and the
4357			compiler with which the kernel was built.
4358
4359			Selecting 'on' will also enable the mitigation
4360			against user space to user space task attacks.
4361
4362			Selecting 'off' will disable both the kernel and
4363			the user space protections.
4364
4365			Specific mitigations can also be selected manually:
4366
4367			retpoline	  - replace indirect branches
4368			retpoline,generic - google's original retpoline
4369			retpoline,amd     - AMD-specific minimal thunk
4370
4371			Not specifying this option is equivalent to
4372			spectre_v2=auto.
4373
4374	spectre_v2_user=
4375			[X86] Control mitigation of Spectre variant 2
4376		        (indirect branch speculation) vulnerability between
4377		        user space tasks
4378
4379			on	- Unconditionally enable mitigations. Is
4380				  enforced by spectre_v2=on
4381
4382			off     - Unconditionally disable mitigations. Is
4383				  enforced by spectre_v2=off
4384
4385			prctl   - Indirect branch speculation is enabled,
4386				  but mitigation can be enabled via prctl
4387				  per thread.  The mitigation control state
4388				  is inherited on fork.
4389
4390			prctl,ibpb
4391				- Like "prctl" above, but only STIBP is
4392				  controlled per thread. IBPB is issued
4393				  always when switching between different user
4394				  space processes.
4395
4396			seccomp
4397				- Same as "prctl" above, but all seccomp
4398				  threads will enable the mitigation unless
4399				  they explicitly opt out.
4400
4401			seccomp,ibpb
4402				- Like "seccomp" above, but only STIBP is
4403				  controlled per thread. IBPB is issued
4404				  always when switching between different
4405				  user space processes.
4406
4407			auto    - Kernel selects the mitigation depending on
4408				  the available CPU features and vulnerability.
4409
4410			Default mitigation:
4411			If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
4412
4413			Not specifying this option is equivalent to
4414			spectre_v2_user=auto.
4415
4416	spec_store_bypass_disable=
4417			[HW] Control Speculative Store Bypass (SSB) Disable mitigation
4418			(Speculative Store Bypass vulnerability)
4419
4420			Certain CPUs are vulnerable to an exploit against a
4421			a common industry wide performance optimization known
4422			as "Speculative Store Bypass" in which recent stores
4423			to the same memory location may not be observed by
4424			later loads during speculative execution. The idea
4425			is that such stores are unlikely and that they can
4426			be detected prior to instruction retirement at the
4427			end of a particular speculation execution window.
4428
4429			In vulnerable processors, the speculatively forwarded
4430			store can be used in a cache side channel attack, for
4431			example to read memory to which the attacker does not
4432			directly have access (e.g. inside sandboxed code).
4433
4434			This parameter controls whether the Speculative Store
4435			Bypass optimization is used.
4436
4437			On x86 the options are:
4438
4439			on      - Unconditionally disable Speculative Store Bypass
4440			off     - Unconditionally enable Speculative Store Bypass
4441			auto    - Kernel detects whether the CPU model contains an
4442				  implementation of Speculative Store Bypass and
4443				  picks the most appropriate mitigation. If the
4444				  CPU is not vulnerable, "off" is selected. If the
4445				  CPU is vulnerable the default mitigation is
4446				  architecture and Kconfig dependent. See below.
4447			prctl   - Control Speculative Store Bypass per thread
4448				  via prctl. Speculative Store Bypass is enabled
4449				  for a process by default. The state of the control
4450				  is inherited on fork.
4451			seccomp - Same as "prctl" above, but all seccomp threads
4452				  will disable SSB unless they explicitly opt out.
4453
4454			Default mitigations:
4455			X86:	If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
4456
4457			On powerpc the options are:
4458
4459			on,auto - On Power8 and Power9 insert a store-forwarding
4460				  barrier on kernel entry and exit. On Power7
4461				  perform a software flush on kernel entry and
4462				  exit.
4463			off	- No action.
4464
4465			Not specifying this option is equivalent to
4466			spec_store_bypass_disable=auto.
4467
4468	spia_io_base=	[HW,MTD]
4469	spia_fio_base=
4470	spia_pedr=
4471	spia_peddr=
4472
4473	srcutree.counter_wrap_check [KNL]
4474			Specifies how frequently to check for
4475			grace-period sequence counter wrap for the
4476			srcu_data structure's ->srcu_gp_seq_needed field.
4477			The greater the number of bits set in this kernel
4478			parameter, the less frequently counter wrap will
4479			be checked for.  Note that the bottom two bits
4480			are ignored.
4481
4482	srcutree.exp_holdoff [KNL]
4483			Specifies how many nanoseconds must elapse
4484			since the end of the last SRCU grace period for
4485			a given srcu_struct until the next normal SRCU
4486			grace period will be considered for automatic
4487			expediting.  Set to zero to disable automatic
4488			expediting.
4489
4490	ssbd=		[ARM64,HW]
4491			Speculative Store Bypass Disable control
4492
4493			On CPUs that are vulnerable to the Speculative
4494			Store Bypass vulnerability and offer a
4495			firmware based mitigation, this parameter
4496			indicates how the mitigation should be used:
4497
4498			force-on:  Unconditionally enable mitigation for
4499				   for both kernel and userspace
4500			force-off: Unconditionally disable mitigation for
4501				   for both kernel and userspace
4502			kernel:    Always enable mitigation in the
4503				   kernel, and offer a prctl interface
4504				   to allow userspace to register its
4505				   interest in being mitigated too.
4506
4507	stack_guard_gap=	[MM]
4508			override the default stack gap protection. The value
4509			is in page units and it defines how many pages prior
4510			to (for stacks growing down) resp. after (for stacks
4511			growing up) the main stack are reserved for no other
4512			mapping. Default value is 256 pages.
4513
4514	stacktrace	[FTRACE]
4515			Enabled the stack tracer on boot up.
4516
4517	stacktrace_filter=[function-list]
4518			[FTRACE] Limit the functions that the stack tracer
4519			will trace at boot up. function-list is a comma separated
4520			list of functions. This list can be changed at run
4521			time by the stack_trace_filter file in the debugfs
4522			tracing directory. Note, this enables stack tracing
4523			and the stacktrace above is not needed.
4524
4525	sti=		[PARISC,HW]
4526			Format: <num>
4527			Set the STI (builtin display/keyboard on the HP-PARISC
4528			machines) console (graphic card) which should be used
4529			as the initial boot-console.
4530			See also comment in drivers/video/console/sticore.c.
4531
4532	sti_font=	[HW]
4533			See comment in drivers/video/console/sticore.c.
4534
4535	stifb=		[HW]
4536			Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
4537
4538	sunrpc.min_resvport=
4539	sunrpc.max_resvport=
4540			[NFS,SUNRPC]
4541			SunRPC servers often require that client requests
4542			originate from a privileged port (i.e. a port in the
4543			range 0 < portnr < 1024).
4544			An administrator who wishes to reserve some of these
4545			ports for other uses may adjust the range that the
4546			kernel's sunrpc client considers to be privileged
4547			using these two parameters to set the minimum and
4548			maximum port values.
4549
4550	sunrpc.svc_rpc_per_connection_limit=
4551			[NFS,SUNRPC]
4552			Limit the number of requests that the server will
4553			process in parallel from a single connection.
4554			The default value is 0 (no limit).
4555
4556	sunrpc.pool_mode=
4557			[NFS]
4558			Control how the NFS server code allocates CPUs to
4559			service thread pools.  Depending on how many NICs
4560			you have and where their interrupts are bound, this
4561			option will affect which CPUs will do NFS serving.
4562			Note: this parameter cannot be changed while the
4563			NFS server is running.
4564
4565			auto	    the server chooses an appropriate mode
4566				    automatically using heuristics
4567			global	    a single global pool contains all CPUs
4568			percpu	    one pool for each CPU
4569			pernode	    one pool for each NUMA node (equivalent
4570				    to global on non-NUMA machines)
4571
4572	sunrpc.tcp_slot_table_entries=
4573	sunrpc.udp_slot_table_entries=
4574			[NFS,SUNRPC]
4575			Sets the upper limit on the number of simultaneous
4576			RPC calls that can be sent from the client to a
4577			server. Increasing these values may allow you to
4578			improve throughput, but will also increase the
4579			amount of memory reserved for use by the client.
4580
4581	suspend.pm_test_delay=
4582			[SUSPEND]
4583			Sets the number of seconds to remain in a suspend test
4584			mode before resuming the system (see
4585			/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
4586			is set. Default value is 5.
4587
4588	swapaccount=[0|1]
4589			[KNL] Enable accounting of swap in memory resource
4590			controller if no parameter or 1 is given or disable
4591			it if 0 is given (See Documentation/cgroup-v1/memory.txt)
4592
4593	swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
4594			Format: { <int> | force | noforce }
4595			<int> -- Number of I/O TLB slabs
4596			force -- force using of bounce buffers even if they
4597			         wouldn't be automatically used by the kernel
4598			noforce -- Never use bounce buffers (for debugging)
4599
4600	switches=	[HW,M68k]
4601
4602	sysfs.deprecated=0|1 [KNL]
4603			Enable/disable old style sysfs layout for old udev
4604			on older distributions. When this option is enabled
4605			very new udev will not work anymore. When this option
4606			is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4607			in older udev will not work anymore.
4608			Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4609			the kernel configuration.
4610
4611	sysrq_always_enabled
4612			[KNL]
4613			Ignore sysrq setting - this boot parameter will
4614			neutralize any effect of /proc/sys/kernel/sysrq.
4615			Useful for debugging.
4616
4617	tcpmhash_entries= [KNL,NET]
4618			Set the number of tcp_metrics_hash slots.
4619			Default value is 8192 or 16384 depending on total
4620			ram pages. This is used to specify the TCP metrics
4621			cache size. See Documentation/networking/ip-sysctl.txt
4622			"tcp_no_metrics_save" section for more details.
4623
4624	tdfx=		[HW,DRM]
4625
4626	test_suspend=	[SUSPEND][,N]
4627			Specify "mem" (for Suspend-to-RAM) or "standby" (for
4628			standby suspend) or "freeze" (for suspend type freeze)
4629			as the system sleep state during system startup with
4630			the optional capability to repeat N number of times.
4631			The system is woken from this state using a
4632			wakeup-capable RTC alarm.
4633
4634	thash_entries=	[KNL,NET]
4635			Set number of hash buckets for TCP connection
4636
4637	thermal.act=	[HW,ACPI]
4638			-1: disable all active trip points in all thermal zones
4639			<degrees C>: override all lowest active trip points
4640
4641	thermal.crt=	[HW,ACPI]
4642			-1: disable all critical trip points in all thermal zones
4643			<degrees C>: override all critical trip points
4644
4645	thermal.nocrt=	[HW,ACPI]
4646			Set to disable actions on ACPI thermal zone
4647			critical and hot trip points.
4648
4649	thermal.off=	[HW,ACPI]
4650			1: disable ACPI thermal control
4651
4652	thermal.psv=	[HW,ACPI]
4653			-1: disable all passive trip points
4654			<degrees C>: override all passive trip points to this
4655			value
4656
4657	thermal.tzp=	[HW,ACPI]
4658			Specify global default ACPI thermal zone polling rate
4659			<deci-seconds>: poll all this frequency
4660			0: no polling (default)
4661
4662	threadirqs	[KNL]
4663			Force threading of all interrupt handlers except those
4664			marked explicitly IRQF_NO_THREAD.
4665
4666	tmem		[KNL,XEN]
4667			Enable the Transcendent memory driver if built-in.
4668
4669	tmem.cleancache=0|1 [KNL, XEN]
4670			Default is on (1). Disable the usage of the cleancache
4671			API to send anonymous pages to the hypervisor.
4672
4673	tmem.frontswap=0|1 [KNL, XEN]
4674			Default is on (1). Disable the usage of the frontswap
4675			API to send swap pages to the hypervisor. If disabled
4676			the selfballooning and selfshrinking are force disabled.
4677
4678	tmem.selfballooning=0|1 [KNL, XEN]
4679			Default is on (1). Disable the driving of swap pages
4680			to the hypervisor.
4681
4682	tmem.selfshrinking=0|1 [KNL, XEN]
4683			Default is on (1). Partial swapoff that immediately
4684			transfers pages from Xen hypervisor back to the
4685			kernel based on different criteria.
4686
4687	topology=	[S390]
4688			Format: {off | on}
4689			Specify if the kernel should make use of the cpu
4690			topology information if the hardware supports this.
4691			The scheduler will make use of this information and
4692			e.g. base its process migration decisions on it.
4693			Default is on.
4694
4695	topology_updates= [KNL, PPC, NUMA]
4696			Format: {off}
4697			Specify if the kernel should ignore (off)
4698			topology updates sent by the hypervisor to this
4699			LPAR.
4700
4701	tp720=		[HW,PS2]
4702
4703	tpm_suspend_pcr=[HW,TPM]
4704			Format: integer pcr id
4705			Specify that at suspend time, the tpm driver
4706			should extend the specified pcr with zeros,
4707			as a workaround for some chips which fail to
4708			flush the last written pcr on TPM_SaveState.
4709			This will guarantee that all the other pcrs
4710			are saved.
4711
4712	trace_buf_size=nn[KMG]
4713			[FTRACE] will set tracing buffer size on each cpu.
4714
4715	trace_event=[event-list]
4716			[FTRACE] Set and start specified trace events in order
4717			to facilitate early boot debugging. The event-list is a
4718			comma separated list of trace events to enable. See
4719			also Documentation/trace/events.rst
4720
4721	trace_options=[option-list]
4722			[FTRACE] Enable or disable tracer options at boot.
4723			The option-list is a comma delimited list of options
4724			that can be enabled or disabled just as if you were
4725			to echo the option name into
4726
4727			    /sys/kernel/debug/tracing/trace_options
4728
4729			For example, to enable stacktrace option (to dump the
4730			stack trace of each event), add to the command line:
4731
4732			      trace_options=stacktrace
4733
4734			See also Documentation/trace/ftrace.rst "trace options"
4735			section.
4736
4737	tp_printk[FTRACE]
4738			Have the tracepoints sent to printk as well as the
4739			tracing ring buffer. This is useful for early boot up
4740			where the system hangs or reboots and does not give the
4741			option for reading the tracing buffer or performing a
4742			ftrace_dump_on_oops.
4743
4744			To turn off having tracepoints sent to printk,
4745			 echo 0 > /proc/sys/kernel/tracepoint_printk
4746			Note, echoing 1 into this file without the
4747			tracepoint_printk kernel cmdline option has no effect.
4748
4749			** CAUTION **
4750
4751			Having tracepoints sent to printk() and activating high
4752			frequency tracepoints such as irq or sched, can cause
4753			the system to live lock.
4754
4755	traceoff_on_warning
4756			[FTRACE] enable this option to disable tracing when a
4757			warning is hit. This turns off "tracing_on". Tracing can
4758			be enabled again by echoing '1' into the "tracing_on"
4759			file located in /sys/kernel/debug/tracing/
4760
4761			This option is useful, as it disables the trace before
4762			the WARNING dump is called, which prevents the trace to
4763			be filled with content caused by the warning output.
4764
4765			This option can also be set at run time via the sysctl
4766			option:  kernel/traceoff_on_warning
4767
4768	transparent_hugepage=
4769			[KNL]
4770			Format: [always|madvise|never]
4771			Can be used to control the default behavior of the system
4772			with respect to transparent hugepages.
4773			See Documentation/admin-guide/mm/transhuge.rst
4774			for more details.
4775
4776	tsc=		Disable clocksource stability checks for TSC.
4777			Format: <string>
4778			[x86] reliable: mark tsc clocksource as reliable, this
4779			disables clocksource verification at runtime, as well
4780			as the stability checks done at bootup.	Used to enable
4781			high-resolution timer mode on older hardware, and in
4782			virtualized environment.
4783			[x86] noirqtime: Do not use TSC to do irq accounting.
4784			Used to run time disable IRQ_TIME_ACCOUNTING on any
4785			platforms where RDTSC is slow and this accounting
4786			can add overhead.
4787			[x86] unstable: mark the TSC clocksource as unstable, this
4788			marks the TSC unconditionally unstable at bootup and
4789			avoids any further wobbles once the TSC watchdog notices.
4790			[x86] nowatchdog: disable clocksource watchdog. Used
4791			in situations with strict latency requirements (where
4792			interruptions from clocksource watchdog are not
4793			acceptable).
4794
4795	turbografx.map[2|3]=	[HW,JOY]
4796			TurboGraFX parallel port interface
4797			Format:
4798			<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4799			See also Documentation/input/devices/joystick-parport.rst
4800
4801	udbg-immortal	[PPC] When debugging early kernel crashes that
4802			happen after console_init() and before a proper
4803			console driver takes over, this boot options might
4804			help "seeing" what's going on.
4805
4806	uhash_entries=	[KNL,NET]
4807			Set number of hash buckets for UDP/UDP-Lite connections
4808
4809	uhci-hcd.ignore_oc=
4810			[USB] Ignore overcurrent events (default N).
4811			Some badly-designed motherboards generate lots of
4812			bogus events, for ports that aren't wired to
4813			anything.  Set this parameter to avoid log spamming.
4814			Note that genuine overcurrent events won't be
4815			reported either.
4816
4817	unknown_nmi_panic
4818			[X86] Cause panic on unknown NMI.
4819
4820	usbcore.authorized_default=
4821			[USB] Default USB device authorization:
4822			(default -1 = authorized except for wireless USB,
4823			0 = not authorized, 1 = authorized, 2 = authorized
4824			if device connected to internal port)
4825
4826	usbcore.autosuspend=
4827			[USB] The autosuspend time delay (in seconds) used
4828			for newly-detected USB devices (default 2).  This
4829			is the time required before an idle device will be
4830			autosuspended.  Devices for which the delay is set
4831			to a negative value won't be autosuspended at all.
4832
4833	usbcore.usbfs_snoop=
4834			[USB] Set to log all usbfs traffic (default 0 = off).
4835
4836	usbcore.usbfs_snoop_max=
4837			[USB] Maximum number of bytes to snoop in each URB
4838			(default = 65536).
4839
4840	usbcore.blinkenlights=
4841			[USB] Set to cycle leds on hubs (default 0 = off).
4842
4843	usbcore.old_scheme_first=
4844			[USB] Start with the old device initialization
4845			scheme,  applies only to low and full-speed devices
4846			 (default 0 = off).
4847
4848	usbcore.usbfs_memory_mb=
4849			[USB] Memory limit (in MB) for buffers allocated by
4850			usbfs (default = 16, 0 = max = 2047).
4851
4852	usbcore.use_both_schemes=
4853			[USB] Try the other device initialization scheme
4854			if the first one fails (default 1 = enabled).
4855
4856	usbcore.initial_descriptor_timeout=
4857			[USB] Specifies timeout for the initial 64-byte
4858			USB_REQ_GET_DESCRIPTOR request in milliseconds
4859			(default 5000 = 5.0 seconds).
4860
4861	usbcore.nousb	[USB] Disable the USB subsystem
4862
4863	usbcore.quirks=
4864			[USB] A list of quirk entries to augment the built-in
4865			usb core quirk list. List entries are separated by
4866			commas. Each entry has the form
4867			VendorID:ProductID:Flags. The IDs are 4-digit hex
4868			numbers and Flags is a set of letters. Each letter
4869			will change the built-in quirk; setting it if it is
4870			clear and clearing it if it is set. The letters have
4871			the following meanings:
4872				a = USB_QUIRK_STRING_FETCH_255 (string
4873					descriptors must not be fetched using
4874					a 255-byte read);
4875				b = USB_QUIRK_RESET_RESUME (device can't resume
4876					correctly so reset it instead);
4877				c = USB_QUIRK_NO_SET_INTF (device can't handle
4878					Set-Interface requests);
4879				d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
4880					handle its Configuration or Interface
4881					strings);
4882				e = USB_QUIRK_RESET (device can't be reset
4883					(e.g morph devices), don't use reset);
4884				f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
4885					more interface descriptions than the
4886					bNumInterfaces count, and can't handle
4887					talking to these interfaces);
4888				g = USB_QUIRK_DELAY_INIT (device needs a pause
4889					during initialization, after we read
4890					the device descriptor);
4891				h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
4892					high speed and super speed interrupt
4893					endpoints, the USB 2.0 and USB 3.0 spec
4894					require the interval in microframes (1
4895					microframe = 125 microseconds) to be
4896					calculated as interval = 2 ^
4897					(bInterval-1).
4898					Devices with this quirk report their
4899					bInterval as the result of this
4900					calculation instead of the exponent
4901					variable used in the calculation);
4902				i = USB_QUIRK_DEVICE_QUALIFIER (device can't
4903					handle device_qualifier descriptor
4904					requests);
4905				j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
4906					generates spurious wakeup, ignore
4907					remote wakeup capability);
4908				k = USB_QUIRK_NO_LPM (device can't handle Link
4909					Power Management);
4910				l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
4911					(Device reports its bInterval as linear
4912					frames instead of the USB 2.0
4913					calculation);
4914				m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
4915					to be disconnected before suspend to
4916					prevent spurious wakeup);
4917				n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
4918					pause after every control message);
4919				o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
4920					delay after resetting its port);
4921			Example: quirks=0781:5580:bk,0a5c:5834:gij
4922
4923	usbhid.mousepoll=
4924			[USBHID] The interval which mice are to be polled at.
4925
4926	usbhid.jspoll=
4927			[USBHID] The interval which joysticks are to be polled at.
4928
4929	usbhid.kbpoll=
4930			[USBHID] The interval which keyboards are to be polled at.
4931
4932	usb-storage.delay_use=
4933			[UMS] The delay in seconds before a new device is
4934			scanned for Logical Units (default 1).
4935
4936	usb-storage.quirks=
4937			[UMS] A list of quirks entries to supplement or
4938			override the built-in unusual_devs list.  List
4939			entries are separated by commas.  Each entry has
4940			the form VID:PID:Flags where VID and PID are Vendor
4941			and Product ID values (4-digit hex numbers) and
4942			Flags is a set of characters, each corresponding
4943			to a common usb-storage quirk flag as follows:
4944				a = SANE_SENSE (collect more than 18 bytes
4945					of sense data);
4946				b = BAD_SENSE (don't collect more than 18
4947					bytes of sense data);
4948				c = FIX_CAPACITY (decrease the reported
4949					device capacity by one sector);
4950				d = NO_READ_DISC_INFO (don't use
4951					READ_DISC_INFO command);
4952				e = NO_READ_CAPACITY_16 (don't use
4953					READ_CAPACITY_16 command);
4954				f = NO_REPORT_OPCODES (don't use report opcodes
4955					command, uas only);
4956				g = MAX_SECTORS_240 (don't transfer more than
4957					240 sectors at a time, uas only);
4958				h = CAPACITY_HEURISTICS (decrease the
4959					reported device capacity by one
4960					sector if the number is odd);
4961				i = IGNORE_DEVICE (don't bind to this
4962					device);
4963				j = NO_REPORT_LUNS (don't use report luns
4964					command, uas only);
4965				l = NOT_LOCKABLE (don't try to lock and
4966					unlock ejectable media);
4967				m = MAX_SECTORS_64 (don't transfer more
4968					than 64 sectors = 32 KB at a time);
4969				n = INITIAL_READ10 (force a retry of the
4970					initial READ(10) command);
4971				o = CAPACITY_OK (accept the capacity
4972					reported by the device);
4973				p = WRITE_CACHE (the device cache is ON
4974					by default);
4975				r = IGNORE_RESIDUE (the device reports
4976					bogus residue values);
4977				s = SINGLE_LUN (the device has only one
4978					Logical Unit);
4979				t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4980					commands, uas only);
4981				u = IGNORE_UAS (don't bind to the uas driver);
4982				w = NO_WP_DETECT (don't test whether the
4983					medium is write-protected).
4984				y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
4985					even if the device claims no cache)
4986			Example: quirks=0419:aaf5:rl,0421:0433:rc
4987
4988	user_debug=	[KNL,ARM]
4989			Format: <int>
4990			See arch/arm/Kconfig.debug help text.
4991				 1 - undefined instruction events
4992				 2 - system calls
4993				 4 - invalid data aborts
4994				 8 - SIGSEGV faults
4995				16 - SIGBUS faults
4996			Example: user_debug=31
4997
4998	userpte=
4999			[X86] Flags controlling user PTE allocations.
5000
5001				nohigh = do not allocate PTE pages in
5002					HIGHMEM regardless of setting
5003					of CONFIG_HIGHPTE.
5004
5005	vdso=		[X86,SH]
5006			On X86_32, this is an alias for vdso32=.  Otherwise:
5007
5008			vdso=1: enable VDSO (the default)
5009			vdso=0: disable VDSO mapping
5010
5011	vdso32=		[X86] Control the 32-bit vDSO
5012			vdso32=1: enable 32-bit VDSO
5013			vdso32=0 or vdso32=2: disable 32-bit VDSO
5014
5015			See the help text for CONFIG_COMPAT_VDSO for more
5016			details.  If CONFIG_COMPAT_VDSO is set, the default is
5017			vdso32=0; otherwise, the default is vdso32=1.
5018
5019			For compatibility with older kernels, vdso32=2 is an
5020			alias for vdso32=0.
5021
5022			Try vdso32=0 if you encounter an error that says:
5023			dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
5024
5025	vector=		[IA-64,SMP]
5026			vector=percpu: enable percpu vector domain
5027
5028	video=		[FB] Frame buffer configuration
5029			See Documentation/fb/modedb.txt.
5030
5031	video.brightness_switch_enabled= [0,1]
5032			If set to 1, on receiving an ACPI notify event
5033			generated by hotkey, video driver will adjust brightness
5034			level and then send out the event to user space through
5035			the allocated input device; If set to 0, video driver
5036			will only send out the event without touching backlight
5037			brightness level.
5038			default: 1
5039
5040	virtio_mmio.device=
5041			[VMMIO] Memory mapped virtio (platform) device.
5042
5043				<size>@<baseaddr>:<irq>[:<id>]
5044			where:
5045				<size>     := size (can use standard suffixes
5046						like K, M and G)
5047				<baseaddr> := physical base address
5048				<irq>      := interrupt number (as passed to
5049						request_irq())
5050				<id>       := (optional) platform device id
5051			example:
5052				virtio_mmio.device=1K@0x100b0000:48:7
5053
5054			Can be used multiple times for multiple devices.
5055
5056	vga=		[BOOT,X86-32] Select a particular video mode
5057			See Documentation/x86/boot.txt and
5058			Documentation/svga.txt.
5059			Use vga=ask for menu.
5060			This is actually a boot loader parameter; the value is
5061			passed to the kernel using a special protocol.
5062
5063	vm_debug[=options]	[KNL] Available with CONFIG_DEBUG_VM=y.
5064			May slow down system boot speed, especially when
5065			enabled on systems with a large amount of memory.
5066			All options are enabled by default, and this
5067			interface is meant to allow for selectively
5068			enabling or disabling specific virtual memory
5069			debugging features.
5070
5071			Available options are:
5072			  P	Enable page structure init time poisoning
5073			  -	Disable all of the above options
5074
5075	vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
5076			size of <nn>. This can be used to increase the
5077			minimum size (128MB on x86). It can also be used to
5078			decrease the size and leave more room for directly
5079			mapped kernel RAM.
5080
5081	vmcp_cma=nn[MG]	[KNL,S390]
5082			Sets the memory size reserved for contiguous memory
5083			allocations for the vmcp device driver.
5084
5085	vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
5086			Format: <command>
5087
5088	vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
5089			Format: <command>
5090
5091	vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
5092			Format: <command>
5093
5094	vsyscall=	[X86-64]
5095			Controls the behavior of vsyscalls (i.e. calls to
5096			fixed addresses of 0xffffffffff600x00 from legacy
5097			code).  Most statically-linked binaries and older
5098			versions of glibc use these calls.  Because these
5099			functions are at fixed addresses, they make nice
5100			targets for exploits that can control RIP.
5101
5102			emulate     [default] Vsyscalls turn into traps and are
5103			            emulated reasonably safely.
5104
5105			native      Vsyscalls are native syscall instructions.
5106			            This is a little bit faster than trapping
5107			            and makes a few dynamic recompilers work
5108			            better than they would in emulation mode.
5109			            It also makes exploits much easier to write.
5110
5111			none        Vsyscalls don't work at all.  This makes
5112			            them quite hard to use for exploits but
5113			            might break your system.
5114
5115	vt.color=	[VT] Default text color.
5116			Format: 0xYX, X = foreground, Y = background.
5117			Default: 0x07 = light gray on black.
5118
5119	vt.cur_default=	[VT] Default cursor shape.
5120			Format: 0xCCBBAA, where AA, BB, and CC are the same as
5121			the parameters of the <Esc>[?A;B;Cc escape sequence;
5122			see VGA-softcursor.txt. Default: 2 = underline.
5123
5124	vt.default_blu=	[VT]
5125			Format: <blue0>,<blue1>,<blue2>,...,<blue15>
5126			Change the default blue palette of the console.
5127			This is a 16-member array composed of values
5128			ranging from 0-255.
5129
5130	vt.default_grn=	[VT]
5131			Format: <green0>,<green1>,<green2>,...,<green15>
5132			Change the default green palette of the console.
5133			This is a 16-member array composed of values
5134			ranging from 0-255.
5135
5136	vt.default_red=	[VT]
5137			Format: <red0>,<red1>,<red2>,...,<red15>
5138			Change the default red palette of the console.
5139			This is a 16-member array composed of values
5140			ranging from 0-255.
5141
5142	vt.default_utf8=
5143			[VT]
5144			Format=<0|1>
5145			Set system-wide default UTF-8 mode for all tty's.
5146			Default is 1, i.e. UTF-8 mode is enabled for all
5147			newly opened terminals.
5148
5149	vt.global_cursor_default=
5150			[VT]
5151			Format=<-1|0|1>
5152			Set system-wide default for whether a cursor
5153			is shown on new VTs. Default is -1,
5154			i.e. cursors will be created by default unless
5155			overridden by individual drivers. 0 will hide
5156			cursors, 1 will display them.
5157
5158	vt.italic=	[VT] Default color for italic text; 0-15.
5159			Default: 2 = green.
5160
5161	vt.underline=	[VT] Default color for underlined text; 0-15.
5162			Default: 3 = cyan.
5163
5164	watchdog timers	[HW,WDT] For information on watchdog timers,
5165			see Documentation/watchdog/watchdog-parameters.txt
5166			or other driver-specific files in the
5167			Documentation/watchdog/ directory.
5168
5169	watchdog_thresh=
5170			[KNL]
5171			Set the hard lockup detector stall duration
5172			threshold in seconds. The soft lockup detector
5173			threshold is set to twice the value. A value of 0
5174			disables both lockup detectors. Default is 10
5175			seconds.
5176
5177	workqueue.watchdog_thresh=
5178			If CONFIG_WQ_WATCHDOG is configured, workqueue can
5179			warn stall conditions and dump internal state to
5180			help debugging.  0 disables workqueue stall
5181			detection; otherwise, it's the stall threshold
5182			duration in seconds.  The default value is 30 and
5183			it can be updated at runtime by writing to the
5184			corresponding sysfs file.
5185
5186	workqueue.disable_numa
5187			By default, all work items queued to unbound
5188			workqueues are affine to the NUMA nodes they're
5189			issued on, which results in better behavior in
5190			general.  If NUMA affinity needs to be disabled for
5191			whatever reason, this option can be used.  Note
5192			that this also can be controlled per-workqueue for
5193			workqueues visible under /sys/bus/workqueue/.
5194
5195	workqueue.power_efficient
5196			Per-cpu workqueues are generally preferred because
5197			they show better performance thanks to cache
5198			locality; unfortunately, per-cpu workqueues tend to
5199			be more power hungry than unbound workqueues.
5200
5201			Enabling this makes the per-cpu workqueues which
5202			were observed to contribute significantly to power
5203			consumption unbound, leading to measurably lower
5204			power usage at the cost of small performance
5205			overhead.
5206
5207			The default value of this parameter is determined by
5208			the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
5209
5210	workqueue.debug_force_rr_cpu
5211			Workqueue used to implicitly guarantee that work
5212			items queued without explicit CPU specified are put
5213			on the local CPU.  This guarantee is no longer true
5214			and while local CPU is still preferred work items
5215			may be put on foreign CPUs.  This debug option
5216			forces round-robin CPU selection to flush out
5217			usages which depend on the now broken guarantee.
5218			When enabled, memory and cache locality will be
5219			impacted.
5220
5221	x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
5222			default x2apic cluster mode on platforms
5223			supporting x2apic.
5224
5225	x86_intel_mid_timer= [X86-32,APBT]
5226			Choose timer option for x86 Intel MID platform.
5227			Two valid options are apbt timer only and lapic timer
5228			plus one apbt timer for broadcast timer.
5229			x86_intel_mid_timer=apbt_only | lapic_and_apbt
5230
5231	xen_512gb_limit		[KNL,X86-64,XEN]
5232			Restricts the kernel running paravirtualized under Xen
5233			to use only up to 512 GB of RAM. The reason to do so is
5234			crash analysis tools and Xen tools for doing domain
5235			save/restore/migration must be enabled to handle larger
5236			domains.
5237
5238	xen_emul_unplug=		[HW,X86,XEN]
5239			Unplug Xen emulated devices
5240			Format: [unplug0,][unplug1]
5241			ide-disks -- unplug primary master IDE devices
5242			aux-ide-disks -- unplug non-primary-master IDE devices
5243			nics -- unplug network devices
5244			all -- unplug all emulated devices (NICs and IDE disks)
5245			unnecessary -- unplugging emulated devices is
5246				unnecessary even if the host did not respond to
5247				the unplug protocol
5248			never -- do not unplug even if version check succeeds
5249
5250	xen_nopvspin	[X86,XEN]
5251			Disables the ticketlock slowpath using Xen PV
5252			optimizations.
5253
5254	xen_nopv	[X86]
5255			Disables the PV optimizations forcing the HVM guest to
5256			run as generic HVM guest with no PV drivers.
5257
5258	xen_scrub_pages=	[XEN]
5259			Boolean option to control scrubbing pages before giving them back
5260			to Xen, for use by other domains. Can be also changed at runtime
5261			with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
5262			Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
5263
5264	xen_timer_slop=	[X86-64,XEN]
5265			Set the timer slop (in nanoseconds) for the virtual Xen
5266			timers (default is 100000). This adjusts the minimum
5267			delta of virtualized Xen timers, where lower values
5268			improve timer resolution at the expense of processing
5269			more timer interrupts.
5270
5271	xirc2ps_cs=	[NET,PCMCIA]
5272			Format:
5273			<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
5274
5275	xhci-hcd.quirks		[USB,KNL]
5276			A hex value specifying bitmask with supplemental xhci
5277			host controller quirks. Meaning of each bit can be
5278			consulted in header drivers/usb/host/xhci.h.
5279