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Based on kernel version 4.9. Page generated on 2016-12-21 14:34 EST.

1	                          Kernel Parameters
2	                          ~~~~~~~~~~~~~~~~~
4	The following is a consolidated list of the kernel parameters as
5	implemented by the __setup(), core_param() and module_param() macros
6	and sorted into English Dictionary order (defined as ignoring all
7	punctuation and sorting digits before letters in a case insensitive
8	manner), and with descriptions where known.
10	The kernel parses parameters from the kernel command line up to "--";
11	if it doesn't recognize a parameter and it doesn't contain a '.', the
12	parameter gets passed to init: parameters with '=' go into init's
13	environment, others are passed as command line arguments to init.
14	Everything after "--" is passed as an argument to init.
16	Module parameters can be specified in two ways: via the kernel command
17	line with a module name prefix, or via modprobe, e.g.:
19		(kernel command line) usbcore.blinkenlights=1
20		(modprobe command line) modprobe usbcore blinkenlights=1
22	Parameters for modules which are built into the kernel need to be
23	specified on the kernel command line.  modprobe looks through the
24	kernel command line (/proc/cmdline) and collects module parameters
25	when it loads a module, so the kernel command line can be used for
26	loadable modules too.
28	Hyphens (dashes) and underscores are equivalent in parameter names, so
29		log_buf_len=1M print-fatal-signals=1
30	can also be entered as
31		log-buf-len=1M print_fatal_signals=1
33	Double-quotes can be used to protect spaces in values, e.g.:
34		param="spaces in here"
36	cpu lists:
37	----------
39	Some kernel parameters take a list of CPUs as a value, e.g.  isolcpus,
40	nohz_full, irqaffinity, rcu_nocbs.  The format of this list is:
42		<cpu number>,...,<cpu number>
44	or
46		<cpu number>-<cpu number>
47		(must be a positive range in ascending order)
49	or a mixture
51	<cpu number>,...,<cpu number>-<cpu number>
53	Note that for the special case of a range one can split the range into equal
54	sized groups and for each group use some amount from the beginning of that
55	group:
57		<cpu number>-cpu number>:<used size>/<group size>
59	For example one can add to the command line following parameter:
61		isolcpus=1,2,10-20,100-2000:2/25
63	where the final item represents CPUs 100,101,125,126,150,151,...
67	This document may not be entirely up to date and comprehensive. The command
68	"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
69	module. Loadable modules, after being loaded into the running kernel, also
70	reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
71	parameters may be changed at runtime by the command
72	"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
74	The parameters listed below are only valid if certain kernel build options were
75	enabled and if respective hardware is present. The text in square brackets at
76	the beginning of each description states the restrictions within which a
77	parameter is applicable:
79		ACPI	ACPI support is enabled.
80		AGP	AGP (Accelerated Graphics Port) is enabled.
81		ALSA	ALSA sound support is enabled.
82		APIC	APIC support is enabled.
83		APM	Advanced Power Management support is enabled.
84		ARM	ARM architecture is enabled.
85		AVR32	AVR32 architecture is enabled.
86		AX25	Appropriate AX.25 support is enabled.
87		BLACKFIN Blackfin architecture is enabled.
88		CLK	Common clock infrastructure is enabled.
89		CMA	Contiguous Memory Area support is enabled.
90		DRM	Direct Rendering Management support is enabled.
91		DYNAMIC_DEBUG Build in debug messages and enable them at runtime
92		EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
93		EFI	EFI Partitioning (GPT) is enabled
94		EIDE	EIDE/ATAPI support is enabled.
95		EVM	Extended Verification Module
96		FB	The frame buffer device is enabled.
97		FTRACE	Function tracing enabled.
98		GCOV	GCOV profiling is enabled.
99		HW	Appropriate hardware is enabled.
100		IA-64	IA-64 architecture is enabled.
101		IMA     Integrity measurement architecture is enabled.
102		IOSCHED	More than one I/O scheduler is enabled.
103		IP_PNP	IP DHCP, BOOTP, or RARP is enabled.
104		IPV6	IPv6 support is enabled.
105		ISAPNP	ISA PnP code is enabled.
106		ISDN	Appropriate ISDN support is enabled.
107		JOY	Appropriate joystick support is enabled.
108		KGDB	Kernel debugger support is enabled.
109		KVM	Kernel Virtual Machine support is enabled.
110		LIBATA  Libata driver is enabled
111		LP	Printer support is enabled.
112		LOOP	Loopback device support is enabled.
113		M68k	M68k architecture is enabled.
114				These options have more detailed description inside of
115				Documentation/m68k/kernel-options.txt.
116		MDA	MDA console support is enabled.
117		MIPS	MIPS architecture is enabled.
118		MOUSE	Appropriate mouse support is enabled.
119		MSI	Message Signaled Interrupts (PCI).
120		MTD	MTD (Memory Technology Device) support is enabled.
121		NET	Appropriate network support is enabled.
122		NUMA	NUMA support is enabled.
123		NFS	Appropriate NFS support is enabled.
124		OSS	OSS sound support is enabled.
125		PV_OPS	A paravirtualized kernel is enabled.
126		PARIDE	The ParIDE (parallel port IDE) subsystem is enabled.
127		PARISC	The PA-RISC architecture is enabled.
128		PCI	PCI bus support is enabled.
129		PCIE	PCI Express support is enabled.
130		PCMCIA	The PCMCIA subsystem is enabled.
131		PNP	Plug & Play support is enabled.
132		PPC	PowerPC architecture is enabled.
133		PPT	Parallel port support is enabled.
134		PS2	Appropriate PS/2 support is enabled.
135		RAM	RAM disk support is enabled.
136		S390	S390 architecture is enabled.
137		SCSI	Appropriate SCSI support is enabled.
138				A lot of drivers have their options described inside
139				the Documentation/scsi/ sub-directory.
140		SECURITY Different security models are enabled.
141		SELINUX SELinux support is enabled.
142		APPARMOR AppArmor support is enabled.
143		SERIAL	Serial support is enabled.
144		SH	SuperH architecture is enabled.
145		SMP	The kernel is an SMP kernel.
146		SPARC	Sparc architecture is enabled.
147		SWSUSP	Software suspend (hibernation) is enabled.
148		SUSPEND	System suspend states are enabled.
149		TPM	TPM drivers are enabled.
150		TS	Appropriate touchscreen support is enabled.
151		UMS	USB Mass Storage support is enabled.
152		USB	USB support is enabled.
153		USBHID	USB Human Interface Device support is enabled.
154		V4L	Video For Linux support is enabled.
155		VMMIO   Driver for memory mapped virtio devices is enabled.
156		VGA	The VGA console has been enabled.
157		VT	Virtual terminal support is enabled.
158		WDT	Watchdog support is enabled.
159		XT	IBM PC/XT MFM hard disk support is enabled.
160		X86-32	X86-32, aka i386 architecture is enabled.
161		X86-64	X86-64 architecture is enabled.
162				More X86-64 boot options can be found in
163				Documentation/x86/x86_64/boot-options.txt .
164		X86	Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
165		X86_UV	SGI UV support is enabled.
166		XEN	Xen support is enabled
168	In addition, the following text indicates that the option:
170		BUGS=	Relates to possible processor bugs on the said processor.
171		KNL	Is a kernel start-up parameter.
172		BOOT	Is a boot loader parameter.
174	Parameters denoted with BOOT are actually interpreted by the boot
175	loader, and have no meaning to the kernel directly.
176	Do not modify the syntax of boot loader parameters without extreme
177	need or coordination with <Documentation/x86/boot.txt>.
179	There are also arch-specific kernel-parameters not documented here.
180	See for example <Documentation/x86/x86_64/boot-options.txt>.
182	Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
183	a trailing = on the name of any parameter states that that parameter will
184	be entered as an environment variable, whereas its absence indicates that
185	it will appear as a kernel argument readable via /proc/cmdline by programs
186	running once the system is up.
188	The number of kernel parameters is not limited, but the length of the
189	complete command line (parameters including spaces etc.) is limited to
190	a fixed number of characters. This limit depends on the architecture
191	and is between 256 and 4096 characters. It is defined in the file
192	./include/asm/setup.h as COMMAND_LINE_SIZE.
194	Finally, the [KMG] suffix is commonly described after a number of kernel
195	parameter values. These 'K', 'M', and 'G' letters represent the _binary_
196	multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
197	bytes respectively. Such letter suffixes can also be entirely omitted.
200		acpi=		[HW,ACPI,X86,ARM64]
201				Advanced Configuration and Power Interface
202				Format: { force | on | off | strict | noirq | rsdt |
203					  copy_dsdt }
204				force -- enable ACPI if default was off
205				on -- enable ACPI but allow fallback to DT [arm64]
206				off -- disable ACPI if default was on
207				noirq -- do not use ACPI for IRQ routing
208				strict -- Be less tolerant of platforms that are not
209					strictly ACPI specification compliant.
210				rsdt -- prefer RSDT over (default) XSDT
211				copy_dsdt -- copy DSDT to memory
212				For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
213				are available
215				See also Documentation/power/runtime_pm.txt, pci=noacpi
217		acpi_apic_instance=	[ACPI, IOAPIC]
218				Format: <int>
219				2: use 2nd APIC table, if available
220				1,0: use 1st APIC table
221				default: 0
223		acpi_backlight=	[HW,ACPI]
224				acpi_backlight=vendor
225				acpi_backlight=video
226				If set to vendor, prefer vendor specific driver
227				(e.g. thinkpad_acpi, sony_acpi, etc.) instead
228				of the ACPI video.ko driver.
230		acpi_force_32bit_fadt_addr
231				force FADT to use 32 bit addresses rather than the
232				64 bit X_* addresses. Some firmware have broken 64
233				bit addresses for force ACPI ignore these and use
234				the older legacy 32 bit addresses.
236		acpica_no_return_repair [HW, ACPI]
237				Disable AML predefined validation mechanism
238				This mechanism can repair the evaluation result to make
239				the return objects more ACPI specification compliant.
240				This option is useful for developers to identify the
241				root cause of an AML interpreter issue when the issue
242				has something to do with the repair mechanism.
244		acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
245		acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
246				Format: <int>
247				CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
248				debug output.  Bits in debug_layer correspond to a
249				_COMPONENT in an ACPI source file, e.g.,
251				Bits in debug_level correspond to a level in
252				ACPI_DEBUG_PRINT statements, e.g.,
254				The debug_level mask defaults to "info".  See
255				Documentation/acpi/debug.txt for more information about
256				debug layers and levels.
258				Enable processor driver info messages:
259				    acpi.debug_layer=0x20000000
260				Enable PCI/PCI interrupt routing info messages:
261				    acpi.debug_layer=0x400000
262				Enable AML "Debug" output, i.e., stores to the Debug
263				object while interpreting AML:
264				    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
265				Enable all messages related to ACPI hardware:
266				    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
268				Some values produce so much output that the system is
269				unusable.  The "log_buf_len" parameter may be useful
270				if you need to capture more output.
272		acpi_enforce_resources=	[ACPI]
273				{ strict | lax | no }
274				Check for resource conflicts between native drivers
275				and ACPI OperationRegions (SystemIO and SystemMemory
276				only). IO ports and memory declared in ACPI might be
277				used by the ACPI subsystem in arbitrary AML code and
278				can interfere with legacy drivers.
279				strict (default): access to resources claimed by ACPI
280				is denied; legacy drivers trying to access reserved
281				resources will fail to bind to device using them.
282				lax: access to resources claimed by ACPI is allowed;
283				legacy drivers trying to access reserved resources
284				will bind successfully but a warning message is logged.
285				no: ACPI OperationRegions are not marked as reserved,
286				no further checks are performed.
288		acpi_force_table_verification	[HW,ACPI]
289				Enable table checksum verification during early stage.
290				By default, this is disabled due to x86 early mapping
291				size limitation.
293		acpi_irq_balance [HW,ACPI]
294				ACPI will balance active IRQs
295				default in APIC mode
297		acpi_irq_nobalance [HW,ACPI]
298				ACPI will not move active IRQs (default)
299				default in PIC mode
301		acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
302				Format: <irq>,<irq>...
304		acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
305				use by PCI
306				Format: <irq>,<irq>...
308		acpi_no_auto_serialize	[HW,ACPI]
309				Disable auto-serialization of AML methods
310				AML control methods that contain the opcodes to create
311				named objects will be marked as "Serialized" by the
312				auto-serialization feature.
313				This feature is enabled by default.
314				This option allows to turn off the feature.
316		acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
317				   kernels.
319		acpi_no_static_ssdt	[HW,ACPI]
320				Disable installation of static SSDTs at early boot time
321				By default, SSDTs contained in the RSDT/XSDT will be
322				installed automatically and they will appear under
323				/sys/firmware/acpi/tables.
324				This option turns off this feature.
325				Note that specifying this option does not affect
326				dynamic table installation which will install SSDT
327				tables to /sys/firmware/acpi/tables/dynamic.
329		acpi_rsdp=	[ACPI,EFI,KEXEC]
330				Pass the RSDP address to the kernel, mostly used
331				on machines running EFI runtime service to boot the
332				second kernel for kdump.
334		acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
335				Format: To spoof as Windows 98: ="Microsoft Windows"
337		acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
338				of 2 which is mandated by ACPI 6) as the supported ACPI
339				specification revision (when using this switch, it may
340				be necessary to carry out a cold reboot _twice_ in a
341				row to make it take effect on the platform firmware).
343		acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
344				acpi_osi="string1"	# add string1
345				acpi_osi="!string2"	# remove string2
346				acpi_osi=!*		# remove all strings
347				acpi_osi=!		# disable all built-in OS vendor
348							  strings
349				acpi_osi=!!		# enable all built-in OS vendor
350							  strings
351				acpi_osi=		# disable all strings
353				'acpi_osi=!' can be used in combination with single or
354				multiple 'acpi_osi="string1"' to support specific OS
355				vendor string(s).  Note that such command can only
356				affect the default state of the OS vendor strings, thus
357				it cannot affect the default state of the feature group
358				strings and the current state of the OS vendor strings,
359				specifying it multiple times through kernel command line
360				is meaningless.  This command is useful when one do not
361				care about the state of the feature group strings which
362				should be controlled by the OSPM.
363				Examples:
364				  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
365				     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
366				     can make '_OSI("Windows 2000")' TRUE.
368				'acpi_osi=' cannot be used in combination with other
369				'acpi_osi=' command lines, the _OSI method will not
370				exist in the ACPI namespace.  NOTE that such command can
371				only affect the _OSI support state, thus specifying it
372				multiple times through kernel command line is also
373				meaningless.
374				Examples:
375				  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
376				     FALSE.
378				'acpi_osi=!*' can be used in combination with single or
379				multiple 'acpi_osi="string1"' to support specific
380				string(s).  Note that such command can affect the
381				current state of both the OS vendor strings and the
382				feature group strings, thus specifying it multiple times
383				through kernel command line is meaningful.  But it may
384				still not able to affect the final state of a string if
385				there are quirks related to this string.  This command
386				is useful when one want to control the state of the
387				feature group strings to debug BIOS issues related to
388				the OSPM features.
389				Examples:
390				  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
391				     '_OSI("Module Device")' FALSE.
392				  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
393				     '_OSI("Module Device")' TRUE.
394				  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
395				     equivalent to
396				     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
397				     and
398				     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
399				     they all will make '_OSI("Windows 2000")' TRUE.
401		acpi_pm_good	[X86]
402				Override the pmtimer bug detection: force the kernel
403				to assume that this machine's pmtimer latches its value
404				and always returns good values.
406		acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
407				Format: { level | edge | high | low }
409		acpi_skip_timer_override [HW,ACPI]
410				Recognize and ignore IRQ0/pin2 Interrupt Override.
411				For broken nForce2 BIOS resulting in XT-PIC timer.
413		acpi_sleep=	[HW,ACPI] Sleep options
414				Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
415					  old_ordering, nonvs, sci_force_enable }
416				See Documentation/power/video.txt for information on
417				s3_bios and s3_mode.
418				s3_beep is for debugging; it makes the PC's speaker beep
419				as soon as the kernel's real-mode entry point is called.
420				s4_nohwsig prevents ACPI hardware signature from being
421				used during resume from hibernation.
422				old_ordering causes the ACPI 1.0 ordering of the _PTS
423				control method, with respect to putting devices into
424				low power states, to be enforced (the ACPI 2.0 ordering
425				of _PTS is used by default).
426				nonvs prevents the kernel from saving/restoring the
427				ACPI NVS memory during suspend/hibernation and resume.
428				sci_force_enable causes the kernel to set SCI_EN directly
429				on resume from S1/S3 (which is against the ACPI spec,
430				but some broken systems don't work without it).
432		acpi_use_timer_override [HW,ACPI]
433				Use timer override. For some broken Nvidia NF5 boards
434				that require a timer override, but don't have HPET
436		add_efi_memmap	[EFI; X86] Include EFI memory map in
437				kernel's map of available physical RAM.
439		agp=		[AGP]
440				{ off | try_unsupported }
441				off: disable AGP support
442				try_unsupported: try to drive unsupported chipsets
443					(may crash computer or cause data corruption)
445		ALSA		[HW,ALSA]
446				See Documentation/sound/alsa/alsa-parameters.txt
448		alignment=	[KNL,ARM]
449				Allow the default userspace alignment fault handler
450				behaviour to be specified.  Bit 0 enables warnings,
451				bit 1 enables fixups, and bit 2 sends a segfault.
453		align_va_addr=	[X86-64]
454				Align virtual addresses by clearing slice [14:12] when
455				allocating a VMA at process creation time. This option
456				gives you up to 3% performance improvement on AMD F15h
457				machines (where it is enabled by default) for a
458				CPU-intensive style benchmark, and it can vary highly in
459				a microbenchmark depending on workload and compiler.
461				32: only for 32-bit processes
462				64: only for 64-bit processes
463				on: enable for both 32- and 64-bit processes
464				off: disable for both 32- and 64-bit processes
466		alloc_snapshot	[FTRACE]
467				Allocate the ftrace snapshot buffer on boot up when the
468				main buffer is allocated. This is handy if debugging
469				and you need to use tracing_snapshot() on boot up, and
470				do not want to use tracing_snapshot_alloc() as it needs
471				to be done where GFP_KERNEL allocations are allowed.
473		amd_iommu=	[HW,X86-64]
474				Pass parameters to the AMD IOMMU driver in the system.
475				Possible values are:
476				fullflush - enable flushing of IO/TLB entries when
477					    they are unmapped. Otherwise they are
478					    flushed before they will be reused, which
479					    is a lot of faster
480				off	  - do not initialize any AMD IOMMU found in
481					    the system
482				force_isolation - Force device isolation for all
483						  devices. The IOMMU driver is not
484						  allowed anymore to lift isolation
485						  requirements as needed. This option
486						  does not override iommu=pt
488		amd_iommu_dump=	[HW,X86-64]
489				Enable AMD IOMMU driver option to dump the ACPI table
490				for AMD IOMMU. With this option enabled, AMD IOMMU
491				driver will print ACPI tables for AMD IOMMU during
492				IOMMU initialization.
494		amd_iommu_intr=	[HW,X86-64]
495				Specifies one of the following AMD IOMMU interrupt
496				remapping modes:
497				legacy     - Use legacy interrupt remapping mode.
498				vapic      - Use virtual APIC mode, which allows IOMMU
499				             to inject interrupts directly into guest.
500				             This mode requires kvm-amd.avic=1.
501				             (Default when IOMMU HW support is present.)
503		amijoy.map=	[HW,JOY] Amiga joystick support
504				Map of devices attached to JOY0DAT and JOY1DAT
505				Format: <a>,<b>
506				See also Documentation/input/joystick.txt
508		analog.map=	[HW,JOY] Analog joystick and gamepad support
509				Specifies type or capabilities of an analog joystick
510				connected to one of 16 gameports
511				Format: <type1>,<type2>,..<type16>
513		apc=		[HW,SPARC]
514				Power management functions (SPARCstation-4/5 + deriv.)
515				Format: noidle
516				Disable APC CPU standby support. SPARCstation-Fox does
517				not play well with APC CPU idle - disable it if you have
518				APC and your system crashes randomly.
520		apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
521				Change the output verbosity whilst booting
522				Format: { quiet (default) | verbose | debug }
523				Change the amount of debugging information output
524				when initialising the APIC and IO-APIC components.
526		apic_extnmi=	[APIC,X86] External NMI delivery setting
527				Format: { bsp (default) | all | none }
528				bsp:  External NMI is delivered only to CPU 0
529				all:  External NMIs are broadcast to all CPUs as a
530				      backup of CPU 0
531				none: External NMI is masked for all CPUs. This is
532				      useful so that a dump capture kernel won't be
533				      shot down by NMI
535		autoconf=	[IPV6]
536				See Documentation/networking/ipv6.txt.
538		show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
539				Limit apic dumping. The parameter defines the maximal
540				number of local apics being dumped. Also it is possible
541				to set it to "all" by meaning -- no limit here.
542				Format: { 1 (default) | 2 | ... | all }.
543				The parameter valid if only apic=debug or
544				apic=verbose is specified.
545				Example: apic=debug show_lapic=all
547		apm=		[APM] Advanced Power Management
548				See header of arch/x86/kernel/apm_32.c.
550		arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
551				Format: <io>,<irq>,<nodeID>
553		ataflop=	[HW,M68k]
555		atarimouse=	[HW,MOUSE] Atari Mouse
557		atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
558				EzKey and similar keyboards
560		atkbd.reset=	[HW] Reset keyboard during initialization
562		atkbd.set=	[HW] Select keyboard code set
563				Format: <int> (2 = AT (default), 3 = PS/2)
565		atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
566				keyboards
568		atkbd.softraw=	[HW] Choose between synthetic and real raw mode
569				Format: <bool> (0 = real, 1 = synthetic (default))
571		atkbd.softrepeat= [HW]
572				Use software keyboard repeat
574		audit=		[KNL] Enable the audit sub-system
575				Format: { "0" | "1" } (0 = disabled, 1 = enabled)
576				0 - kernel audit is disabled and can not be enabled
577				    until the next reboot
578				unset - kernel audit is initialized but disabled and
579				    will be fully enabled by the userspace auditd.
580				1 - kernel audit is initialized and partially enabled,
581				    storing at most audit_backlog_limit messages in
582				    RAM until it is fully enabled by the userspace
583				    auditd.
584				Default: unset
586		audit_backlog_limit= [KNL] Set the audit queue size limit.
587				Format: <int> (must be >=0)
588				Default: 64
590		bau=		[X86_UV] Enable the BAU on SGI UV.  The default
591				behavior is to disable the BAU (i.e. bau=0).
592				Format: { "0" | "1" }
593				0 - Disable the BAU.
594				1 - Enable the BAU.
595				unset - Disable the BAU.
597		baycom_epp=	[HW,AX25]
598				Format: <io>,<mode>
600		baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
601				Format: <io>,<mode>
602				See header of drivers/net/hamradio/baycom_par.c.
604		baycom_ser_fdx=	[HW,AX25]
605				BayCom Serial Port AX.25 Modem (Full Duplex Mode)
606				Format: <io>,<irq>,<mode>[,<baud>]
607				See header of drivers/net/hamradio/baycom_ser_fdx.c.
609		baycom_ser_hdx=	[HW,AX25]
610				BayCom Serial Port AX.25 Modem (Half Duplex Mode)
611				Format: <io>,<irq>,<mode>
612				See header of drivers/net/hamradio/baycom_ser_hdx.c.
614		blkdevparts=	Manual partition parsing of block device(s) for
615				embedded devices based on command line input.
616				See Documentation/block/cmdline-partition.txt
618		boot_delay=	Milliseconds to delay each printk during boot.
619				Values larger than 10 seconds (10000) are changed to
620				no delay (0).
621				Format: integer
623		bootmem_debug	[KNL] Enable bootmem allocator debug messages.
625		bert_disable	[ACPI]
626				Disable BERT OS support on buggy BIOSes.
628		bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
629		bttv.radio=	Most important insmod options are available as
630				kernel args too.
631		bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
632		bttv.tuner=
634		bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
635				firmware feature for flushing multiple hpte entries
636				at a time.
638		c101=		[NET] Moxa C101 synchronous serial card
640		cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
641				Sometimes CPU hardware bugs make them report the cache
642				size incorrectly. The kernel will attempt work arounds
643				to fix known problems, but for some CPUs it is not
644				possible to determine what the correct size should be.
645				This option provides an override for these situations.
647		ca_keys=	[KEYS] This parameter identifies a specific key(s) on
648				the system trusted keyring to be used for certificate
649				trust validation.
650				format: { id:<keyid> | builtin }
652		cca=		[MIPS] Override the kernel pages' cache coherency
653				algorithm.  Accepted values range from 0 to 7
654				inclusive. See arch/mips/include/asm/pgtable-bits.h
655				for platform specific values (SB1, Loongson3 and
656				others).
658		ccw_timeout_log [S390]
659				See Documentation/s390/CommonIO for details.
661		cgroup_disable= [KNL] Disable a particular controller
662				Format: {name of the controller(s) to disable}
663				The effects of cgroup_disable=foo are:
664				- foo isn't auto-mounted if you mount all cgroups in
665				  a single hierarchy
666				- foo isn't visible as an individually mountable
667				  subsystem
668				{Currently only "memory" controller deal with this and
669				cut the overhead, others just disable the usage. So
670				only cgroup_disable=memory is actually worthy}
672		cgroup_no_v1=	[KNL] Disable one, multiple, all cgroup controllers in v1
673				Format: { controller[,controller...] | "all" }
674				Like cgroup_disable, but only applies to cgroup v1;
675				the blacklisted controllers remain available in cgroup2.
677		cgroup.memory=	[KNL] Pass options to the cgroup memory controller.
678				Format: <string>
679				nosocket -- Disable socket memory accounting.
680				nokmem -- Disable kernel memory accounting.
682		checkreqprot	[SELINUX] Set initial checkreqprot flag value.
683				Format: { "0" | "1" }
684				See security/selinux/Kconfig help text.
685				0 -- check protection applied by kernel (includes
686					any implied execute protection).
687				1 -- check protection requested by application.
688				Default value is set via a kernel config option.
689				Value can be changed at runtime via
690					/selinux/checkreqprot.
692		cio_ignore=	[S390]
693				See Documentation/s390/CommonIO for details.
694		clk_ignore_unused
695				[CLK]
696				Prevents the clock framework from automatically gating
697				clocks that have not been explicitly enabled by a Linux
698				device driver but are enabled in hardware at reset or
699				by the bootloader/firmware. Note that this does not
700				force such clocks to be always-on nor does it reserve
701				those clocks in any way. This parameter is useful for
702				debug and development, but should not be needed on a
703				platform with proper driver support.  For more
704				information, see Documentation/clk.txt.
706		clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
707				[Deprecated]
708				Forces specified clocksource (if available) to be used
709				when calculating gettimeofday(). If specified
710				clocksource is not available, it defaults to PIT.
711				Format: { pit | tsc | cyclone | pmtmr }
713		clocksource=	Override the default clocksource
714				Format: <string>
715				Override the default clocksource and use the clocksource
716				with the name specified.
717				Some clocksource names to choose from, depending on
718				the platform:
719				[all] jiffies (this is the base, fallback clocksource)
720				[ACPI] acpi_pm
721				[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
722					pxa_timer,timer3,32k_counter,timer0_1
723				[AVR32] avr32
724				[X86-32] pit,hpet,tsc;
725					scx200_hrt on Geode; cyclone on IBM x440
726				[MIPS] MIPS
727				[PARISC] cr16
728				[S390] tod
729				[SH] SuperH
730				[SPARC64] tick
731				[X86-64] hpet,tsc
733		clocksource.arm_arch_timer.evtstrm=
734				[ARM,ARM64]
735				Format: <bool>
736				Enable/disable the eventstream feature of the ARM
737				architected timer so that code using WFE-based polling
738				loops can be debugged more effectively on production
739				systems.
741		clocksource.arm_arch_timer.fsl-a008585=
742				[ARM64]
743				Format: <bool>
744				Enable/disable the workaround of Freescale/NXP
745				erratum A-008585.  This can be useful for KVM
746				guests, if the guest device tree doesn't show the
747				erratum.  If unspecified, the workaround is
748				enabled based on the device tree.
750		clearcpuid=BITNUM [X86]
751				Disable CPUID feature X for the kernel. See
752				arch/x86/include/asm/cpufeatures.h for the valid bit
753				numbers. Note the Linux specific bits are not necessarily
754				stable over kernel options, but the vendor specific
755				ones should be.
756				Also note that user programs calling CPUID directly
757				or using the feature without checking anything
758				will still see it. This just prevents it from
759				being used by the kernel or shown in /proc/cpuinfo.
760				Also note the kernel might malfunction if you disable
761				some critical bits.
763		cma=nn[MG]@[start[MG][-end[MG]]]
764				[ARM,X86,KNL]
765				Sets the size of kernel global memory area for
766				contiguous memory allocations and optionally the
767				placement constraint by the physical address range of
768				memory allocations. A value of 0 disables CMA
769				altogether. For more information, see
770				include/linux/dma-contiguous.h
772		cmo_free_hint=	[PPC] Format: { yes | no }
773				Specify whether pages are marked as being inactive
774				when they are freed.  This is used in CMO environments
775				to determine OS memory pressure for page stealing by
776				a hypervisor.
777				Default: yes
779		coherent_pool=nn[KMG]	[ARM,KNL]
780				Sets the size of memory pool for coherent, atomic dma
781				allocations, by default set to 256K.
783		code_bytes	[X86] How many bytes of object code to print
784				in an oops report.
785				Range: 0 - 8192
786				Default: 64
788		com20020=	[HW,NET] ARCnet - COM20020 chipset
789				Format:
790				<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
792		com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
793				Format: <io>[,<irq>]
795		com90xx=	[HW,NET]
796				ARCnet - COM90xx chipset (memory-mapped buffers)
797				Format: <io>[,<irq>[,<memstart>]]
799		condev=		[HW,S390] console device
800		conmode=
802		console=	[KNL] Output console device and options.
804			tty<n>	Use the virtual console device <n>.
806			ttyS<n>[,options]
807			ttyUSB0[,options]
808				Use the specified serial port.  The options are of
809				the form "bbbbpnf", where "bbbb" is the baud rate,
810				"p" is parity ("n", "o", or "e"), "n" is number of
811				bits, and "f" is flow control ("r" for RTS or
812				omit it).  Default is "9600n8".
814				See Documentation/serial-console.txt for more
815				information.  See
816				Documentation/networking/netconsole.txt for an
817				alternative.
819			uart[8250],io,<addr>[,options]
820			uart[8250],mmio,<addr>[,options]
821			uart[8250],mmio16,<addr>[,options]
822			uart[8250],mmio32,<addr>[,options]
823			uart[8250],0x<addr>[,options]
824				Start an early, polled-mode console on the 8250/16550
825				UART at the specified I/O port or MMIO address,
826				switching to the matching ttyS device later.
827				MMIO inter-register address stride is either 8-bit
828				(mmio), 16-bit (mmio16), or 32-bit (mmio32).
829				If none of [io|mmio|mmio16|mmio32], <addr> is assumed
830				to be equivalent to 'mmio'. 'options' are specified in
831				the same format described for ttyS above; if unspecified,
832				the h/w is not re-initialized.
834			hvc<n>	Use the hypervisor console device <n>. This is for
835				both Xen and PowerPC hypervisors.
837	                If the device connected to the port is not a TTY but a braille
838	                device, prepend "brl," before the device type, for instance
839				console=brl,ttyS0
840			For now, only VisioBraille is supported.
842		consoleblank=	[KNL] The console blank (screen saver) timeout in
843				seconds. Defaults to 10*60 = 10mins. A value of 0
844				disables the blank timer.
846		coredump_filter=
847				[KNL] Change the default value for
848				/proc/<pid>/coredump_filter.
849				See also Documentation/filesystems/proc.txt.
851		cpuidle.off=1	[CPU_IDLE]
852				disable the cpuidle sub-system
854		cpu_init_udelay=N
855				[X86] Delay for N microsec between assert and de-assert
856				of APIC INIT to start processors.  This delay occurs
857				on every CPU online, such as boot, and resume from suspend.
858				Default: 10000
860		cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
861				Format:
862				<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
864		crashkernel=size[KMG][@offset[KMG]]
865				[KNL] Using kexec, Linux can switch to a 'crash kernel'
866				upon panic. This parameter reserves the physical
867				memory region [offset, offset + size] for that kernel
868				image. If '@offset' is omitted, then a suitable offset
869				is selected automatically. Check
870				Documentation/kdump/kdump.txt for further details.
872		crashkernel=range1:size1[,range2:size2,...][@offset]
873				[KNL] Same as above, but depends on the memory
874				in the running system. The syntax of range is
875				start-[end] where start and end are both
876				a memory unit (amount[KMG]). See also
877				Documentation/kdump/kdump.txt for an example.
879		crashkernel=size[KMG],high
880				[KNL, x86_64] range could be above 4G. Allow kernel
881				to allocate physical memory region from top, so could
882				be above 4G if system have more than 4G ram installed.
883				Otherwise memory region will be allocated below 4G, if
884				available.
885				It will be ignored if crashkernel=X is specified.
886		crashkernel=size[KMG],low
887				[KNL, x86_64] range under 4G. When crashkernel=X,high
888				is passed, kernel could allocate physical memory region
889				above 4G, that cause second kernel crash on system
890				that require some amount of low memory, e.g. swiotlb
891				requires at least 64M+32K low memory, also enough extra
892				low memory is needed to make sure DMA buffers for 32-bit
893				devices won't run out. Kernel would try to allocate at
894				at least 256M below 4G automatically.
895				This one let user to specify own low range under 4G
896				for second kernel instead.
897				0: to disable low allocation.
898				It will be ignored when crashkernel=X,high is not used
899				or memory reserved is below 4G.
901		cryptomgr.notests
902	                        [KNL] Disable crypto self-tests
904		cs89x0_dma=	[HW,NET]
905				Format: <dma>
907		cs89x0_media=	[HW,NET]
908				Format: { rj45 | aui | bnc }
910		dasd=		[HW,NET]
911				See header of drivers/s390/block/dasd_devmap.c.
913		db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
914				(one device per port)
915				Format: <port#>,<type>
916				See also Documentation/input/joystick-parport.txt
918		ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
919				time. See Documentation/dynamic-debug-howto.txt for
920				details.  Deprecated, see dyndbg.
922		debug		[KNL] Enable kernel debugging (events log level).
924		debug_locks_verbose=
925				[KNL] verbose self-tests
926				Format=<0|1>
927				Print debugging info while doing the locking API
928				self-tests.
929				We default to 0 (no extra messages), setting it to
930				1 will print _a lot_ more information - normally
931				only useful to kernel developers.
933		debug_objects	[KNL] Enable object debugging
935		no_debug_objects
936				[KNL] Disable object debugging
938		debug_guardpage_minorder=
939				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
940				parameter allows control of the order of pages that will
941				be intentionally kept free (and hence protected) by the
942				buddy allocator. Bigger value increase the probability
943				of catching random memory corruption, but reduce the
944				amount of memory for normal system use. The maximum
945				possible value is MAX_ORDER/2.  Setting this parameter
946				to 1 or 2 should be enough to identify most random
947				memory corruption problems caused by bugs in kernel or
948				driver code when a CPU writes to (or reads from) a
949				random memory location. Note that there exists a class
950				of memory corruptions problems caused by buggy H/W or
951				F/W or by drivers badly programing DMA (basically when
952				memory is written at bus level and the CPU MMU is
953				bypassed) which are not detectable by
954				CONFIG_DEBUG_PAGEALLOC, hence this option will not help
955				tracking down these problems.
957		debug_pagealloc=
958				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
959				parameter enables the feature at boot time. In
960				default, it is disabled. We can avoid allocating huge
961				chunk of memory for debug pagealloc if we don't enable
962				it at boot time and the system will work mostly same
963				with the kernel built without CONFIG_DEBUG_PAGEALLOC.
964				on: enable the feature
966		debugpat	[X86] Enable PAT debugging
968		decnet.addr=	[HW,NET]
969				Format: <area>[,<node>]
970				See also Documentation/networking/decnet.txt.
972		default_hugepagesz=
973				[same as hugepagesz=] The size of the default
974				HugeTLB page size. This is the size represented by
975				the legacy /proc/ hugepages APIs, used for SHM, and
976				default size when mounting hugetlbfs filesystems.
977				Defaults to the default architecture's huge page size
978				if not specified.
980		dhash_entries=	[KNL]
981				Set number of hash buckets for dentry cache.
983		disable_1tb_segments [PPC]
984				Disables the use of 1TB hash page table segments. This
985				causes the kernel to fall back to 256MB segments which
986				can be useful when debugging issues that require an SLB
987				miss to occur.
989		disable=	[IPV6]
990				See Documentation/networking/ipv6.txt.
992		disable_radix	[PPC]
993				Disable RADIX MMU mode on POWER9
995		disable_cpu_apicid= [X86,APIC,SMP]
996				Format: <int>
997				The number of initial APIC ID for the
998				corresponding CPU to be disabled at boot,
999				mostly used for the kdump 2nd kernel to
1000				disable BSP to wake up multiple CPUs without
1001				causing system reset or hang due to sending
1002				INIT from AP to BSP.
1004		disable_ddw     [PPC/PSERIES]
1005				Disable Dynamic DMA Window support. Use this if
1006				to workaround buggy firmware.
1008		disable_ipv6=	[IPV6]
1009				See Documentation/networking/ipv6.txt.
1011		disable_mtrr_cleanup [X86]
1012				The kernel tries to adjust MTRR layout from continuous
1013				to discrete, to make X server driver able to add WB
1014				entry later. This parameter disables that.
1016		disable_mtrr_trim [X86, Intel and AMD only]
1017				By default the kernel will trim any uncacheable
1018				memory out of your available memory pool based on
1019				MTRR settings.  This parameter disables that behavior,
1020				possibly causing your machine to run very slowly.
1022		disable_timer_pin_1 [X86]
1023				Disable PIN 1 of APIC timer
1024				Can be useful to work around chipset bugs.
1026		dis_ucode_ldr	[X86] Disable the microcode loader.
1028		dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
1029				this option disables the debugging code at boot.
1031		dma_debug_entries=<number>
1032				This option allows to tune the number of preallocated
1033				entries for DMA-API debugging code. One entry is
1034				required per DMA-API allocation. Use this if the
1035				DMA-API debugging code disables itself because the
1036				architectural default is too low.
1038		dma_debug_driver=<driver_name>
1039				With this option the DMA-API debugging driver
1040				filter feature can be enabled at boot time. Just
1041				pass the driver to filter for as the parameter.
1042				The filter can be disabled or changed to another
1043				driver later using sysfs.
1045		drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1046				Broken monitors, graphic adapters, KVMs and EDIDless
1047				panels may send no or incorrect EDID data sets.
1048				This parameter allows to specify an EDID data sets
1049				in the /lib/firmware directory that are used instead.
1050				Generic built-in EDID data sets are used, if one of
1051				edid/1024x768.bin, edid/1280x1024.bin,
1052				edid/1680x1050.bin, or edid/1920x1080.bin is given
1053				and no file with the same name exists. Details and
1054				instructions how to build your own EDID data are
1055				available in Documentation/EDID/HOWTO.txt. An EDID
1056				data set will only be used for a particular connector,
1057				if its name and a colon are prepended to the EDID
1058				name. Each connector may use a unique EDID data
1059				set by separating the files with a comma.  An EDID
1060				data set with no connector name will be used for
1061				any connectors not explicitly specified.
1063		dscc4.setup=	[NET]
1065		dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
1066		module.dyndbg[="val"]
1067				Enable debug messages at boot time.  See
1068				Documentation/dynamic-debug-howto.txt for details.
1070		nompx		[X86] Disables Intel Memory Protection Extensions.
1071				See Documentation/x86/intel_mpx.txt for more
1072				information about the feature.
1074		nopku		[X86] Disable Memory Protection Keys CPU feature found
1075				in some Intel CPUs.
1077		eagerfpu=	[X86]
1078				on	enable eager fpu restore
1079				off	disable eager fpu restore
1080				auto	selects the default scheme, which automatically
1081					enables eagerfpu restore for xsaveopt.
1083		module.async_probe [KNL]
1084				Enable asynchronous probe on this module.
1086		early_ioremap_debug [KNL]
1087				Enable debug messages in early_ioremap support. This
1088				is useful for tracking down temporary early mappings
1089				which are not unmapped.
1091		earlycon=	[KNL] Output early console device and options.
1093				When used with no options, the early console is
1094				determined by the stdout-path property in device
1095				tree's chosen node.
1097			cdns,<addr>[,options]
1098				Start an early, polled-mode console on a Cadence
1099				(xuartps) serial port at the specified address. Only
1100				supported option is baud rate. If baud rate is not
1101				specified, the serial port must already be setup and
1102				configured.
1104			uart[8250],io,<addr>[,options]
1105			uart[8250],mmio,<addr>[,options]
1106			uart[8250],mmio32,<addr>[,options]
1107			uart[8250],mmio32be,<addr>[,options]
1108			uart[8250],0x<addr>[,options]
1109				Start an early, polled-mode console on the 8250/16550
1110				UART at the specified I/O port or MMIO address.
1111				MMIO inter-register address stride is either 8-bit
1112				(mmio) or 32-bit (mmio32 or mmio32be).
1113				If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1114				to be equivalent to 'mmio'. 'options' are specified
1115				in the same format described for "console=ttyS<n>"; if
1116				unspecified, the h/w is not initialized.
1118			pl011,<addr>
1119			pl011,mmio32,<addr>
1120				Start an early, polled-mode console on a pl011 serial
1121				port at the specified address. The pl011 serial port
1122				must already be setup and configured. Options are not
1123				yet supported.  If 'mmio32' is specified, then only
1124				the driver will use only 32-bit accessors to read/write
1125				the device registers.
1127			meson,<addr>
1128				Start an early, polled-mode console on a meson serial
1129				port at the specified address. The serial port must
1130				already be setup and configured. Options are not yet
1131				supported.
1133			msm_serial,<addr>
1134				Start an early, polled-mode console on an msm serial
1135				port at the specified address. The serial port
1136				must already be setup and configured. Options are not
1137				yet supported.
1139			msm_serial_dm,<addr>
1140				Start an early, polled-mode console on an msm serial
1141				dm port at the specified address. The serial port
1142				must already be setup and configured. Options are not
1143				yet supported.
1145			smh	Use ARM semihosting calls for early console.
1147			s3c2410,<addr>
1148			s3c2412,<addr>
1149			s3c2440,<addr>
1150			s3c6400,<addr>
1151			s5pv210,<addr>
1152			exynos4210,<addr>
1153				Use early console provided by serial driver available
1154				on Samsung SoCs, requires selecting proper type and
1155				a correct base address of the selected UART port. The
1156				serial port must already be setup and configured.
1157				Options are not yet supported.
1159			lpuart,<addr>
1160			lpuart32,<addr>
1161				Use early console provided by Freescale LP UART driver
1162				found on Freescale Vybrid and QorIQ LS1021A processors.
1163				A valid base address must be provided, and the serial
1164				port must already be setup and configured.
1166			armada3700_uart,<addr>
1167				Start an early, polled-mode console on the
1168				Armada 3700 serial port at the specified
1169				address. The serial port must already be setup
1170				and configured. Options are not yet supported.
1172		earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
1173				earlyprintk=vga
1174				earlyprintk=efi
1175				earlyprintk=xen
1176				earlyprintk=serial[,ttySn[,baudrate]]
1177				earlyprintk=serial[,0x...[,baudrate]]
1178				earlyprintk=ttySn[,baudrate]
1179				earlyprintk=dbgp[debugController#]
1180				earlyprintk=pciserial,bus:device.function[,baudrate]
1182				earlyprintk is useful when the kernel crashes before
1183				the normal console is initialized. It is not enabled by
1184				default because it has some cosmetic problems.
1186				Append ",keep" to not disable it when the real console
1187				takes over.
1189				Only one of vga, efi, serial, or usb debug port can
1190				be used at a time.
1192				Currently only ttyS0 and ttyS1 may be specified by
1193				name.  Other I/O ports may be explicitly specified
1194				on some architectures (x86 and arm at least) by
1195				replacing ttySn with an I/O port address, like this:
1196					earlyprintk=serial,0x1008,115200
1197				You can find the port for a given device in
1198				/proc/tty/driver/serial:
1199					2: uart:ST16650V2 port:00001008 irq:18 ...
1201				Interaction with the standard serial driver is not
1202				very good.
1204				The VGA and EFI output is eventually overwritten by
1205				the real console.
1207				The xen output can only be used by Xen PV guests.
1209		edac_report=	[HW,EDAC] Control how to report EDAC event
1210				Format: {"on" | "off" | "force"}
1211				on: enable EDAC to report H/W event. May be overridden
1212				by other higher priority error reporting module.
1213				off: disable H/W event reporting through EDAC.
1214				force: enforce the use of EDAC to report H/W event.
1215				default: on.
1217		ekgdboc=	[X86,KGDB] Allow early kernel console debugging
1218				ekgdboc=kbd
1220				This is designed to be used in conjunction with
1221				the boot argument: earlyprintk=vga
1223		edd=		[EDD]
1224				Format: {"off" | "on" | "skip[mbr]"}
1226		efi=		[EFI]
1227				Format: { "old_map", "nochunk", "noruntime", "debug" }
1228				old_map [X86-64]: switch to the old ioremap-based EFI
1229				runtime services mapping. 32-bit still uses this one by
1230				default.
1231				nochunk: disable reading files in "chunks" in the EFI
1232				boot stub, as chunking can cause problems with some
1233				firmware implementations.
1234				noruntime : disable EFI runtime services support
1235				debug: enable misc debug output
1237		efi_no_storage_paranoia [EFI; X86]
1238				Using this parameter you can use more than 50% of
1239				your efi variable storage. Use this parameter only if
1240				you are really sure that your UEFI does sane gc and
1241				fulfills the spec otherwise your board may brick.
1243		efi_fake_mem=	nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
1244				Add arbitrary attribute to specific memory range by
1245				updating original EFI memory map.
1246				Region of memory which aa attribute is added to is
1247				from ss to ss+nn.
1248				If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
1249				is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
1250				attribute is added to range 0x100000000-0x180000000 and
1251				0x10a0000000-0x1120000000.
1253				Using this parameter you can do debugging of EFI memmap
1254				related feature. For example, you can do debugging of
1255				Address Range Mirroring feature even if your box
1256				doesn't support it.
1258		efivar_ssdt=	[EFI; X86] Name of an EFI variable that contains an SSDT
1259				that is to be dynamically loaded by Linux. If there are
1260				multiple variables with the same name but with different
1261				vendor GUIDs, all of them will be loaded. See
1262				Documentation/acpi/ssdt-overlays.txt for details.
1265		eisa_irq_edge=	[PARISC,HW]
1266				See header of drivers/parisc/eisa.c.
1268		elanfreq=	[X86-32]
1269				See comment before function elanfreq_setup() in
1270				arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1272		elevator=	[IOSCHED]
1273				Format: {"cfq" | "deadline" | "noop"}
1274				See Documentation/block/cfq-iosched.txt and
1275				Documentation/block/deadline-iosched.txt for details.
1277		elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1278				Specifies physical address of start of kernel core
1279				image elf header and optionally the size. Generally
1280				kexec loader will pass this option to capture kernel.
1281				See Documentation/kdump/kdump.txt for details.
1283		enable_mtrr_cleanup [X86]
1284				The kernel tries to adjust MTRR layout from continuous
1285				to discrete, to make X server driver able to add WB
1286				entry later. This parameter enables that.
1288		enable_timer_pin_1 [X86]
1289				Enable PIN 1 of APIC timer
1290				Can be useful to work around chipset bugs
1291				(in particular on some ATI chipsets).
1292				The kernel tries to set a reasonable default.
1294		enforcing	[SELINUX] Set initial enforcing status.
1295				Format: {"0" | "1"}
1296				See security/selinux/Kconfig help text.
1297				0 -- permissive (log only, no denials).
1298				1 -- enforcing (deny and log).
1299				Default value is 0.
1300				Value can be changed at runtime via /selinux/enforce.
1302		erst_disable	[ACPI]
1303				Disable Error Record Serialization Table (ERST)
1304				support.
1306		ether=		[HW,NET] Ethernet cards parameters
1307				This option is obsoleted by the "netdev=" option, which
1308				has equivalent usage. See its documentation for details.
1310		evm=		[EVM]
1311				Format: { "fix" }
1312				Permit 'security.evm' to be updated regardless of
1313				current integrity status.
1315		failslab=
1316		fail_page_alloc=
1317		fail_make_request=[KNL]
1318				General fault injection mechanism.
1319				Format: <interval>,<probability>,<space>,<times>
1320				See also Documentation/fault-injection/.
1322		floppy=		[HW]
1323				See Documentation/blockdev/floppy.txt.
1325		force_pal_cache_flush
1326				[IA-64] Avoid check_sal_cache_flush which may hang on
1327				buggy SAL_CACHE_FLUSH implementations. Using this
1328				parameter will force ia64_sal_cache_flush to call
1329				ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1331		forcepae [X86-32]
1332				Forcefully enable Physical Address Extension (PAE).
1333				Many Pentium M systems disable PAE but may have a
1334				functionally usable PAE implementation.
1335				Warning: use of this parameter will taint the kernel
1336				and may cause unknown problems.
1338		ftrace=[tracer]
1339				[FTRACE] will set and start the specified tracer
1340				as early as possible in order to facilitate early
1341				boot debugging.
1343		ftrace_dump_on_oops[=orig_cpu]
1344				[FTRACE] will dump the trace buffers on oops.
1345				If no parameter is passed, ftrace will dump
1346				buffers of all CPUs, but if you pass orig_cpu, it will
1347				dump only the buffer of the CPU that triggered the
1348				oops.
1350		ftrace_filter=[function-list]
1351				[FTRACE] Limit the functions traced by the function
1352				tracer at boot up. function-list is a comma separated
1353				list of functions. This list can be changed at run
1354				time by the set_ftrace_filter file in the debugfs
1355				tracing directory.
1357		ftrace_notrace=[function-list]
1358				[FTRACE] Do not trace the functions specified in
1359				function-list. This list can be changed at run time
1360				by the set_ftrace_notrace file in the debugfs
1361				tracing directory.
1363		ftrace_graph_filter=[function-list]
1364				[FTRACE] Limit the top level callers functions traced
1365				by the function graph tracer at boot up.
1366				function-list is a comma separated list of functions
1367				that can be changed at run time by the
1368				set_graph_function file in the debugfs tracing directory.
1370		ftrace_graph_notrace=[function-list]
1371				[FTRACE] Do not trace from the functions specified in
1372				function-list.  This list is a comma separated list of
1373				functions that can be changed at run time by the
1374				set_graph_notrace file in the debugfs tracing directory.
1376		gamecon.map[2|3]=
1377				[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1378				support via parallel port (up to 5 devices per port)
1379				Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1380				See also Documentation/input/joystick-parport.txt
1382		gamma=		[HW,DRM]
1384		gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
1385				Format: off | on
1386				default: on
1388		gcov_persist=	[GCOV] When non-zero (default), profiling data for
1389				kernel modules is saved and remains accessible via
1390				debugfs, even when the module is unloaded/reloaded.
1391				When zero, profiling data is discarded and associated
1392				debugfs files are removed at module unload time.
1394		gpt		[EFI] Forces disk with valid GPT signature but
1395				invalid Protective MBR to be treated as GPT. If the
1396				primary GPT is corrupted, it enables the backup/alternate
1397				GPT to be used instead.
1399		grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1400				the "Enable 0" bit of the configuration register.
1401				Format: 0 | 1
1402				Default: 0
1403		grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1404				the "Enable 0" bit of the configuration register.
1405				Format: 0 | 1
1406				Default: 0
1407		grcan.select=	[HW] Select which physical interface to use.
1408				Format: 0 | 1
1409				Default: 0
1410		grcan.txsize=	[HW] Sets the size of the tx buffer.
1411				Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1412				Default: 1024
1413		grcan.rxsize=	[HW] Sets the size of the rx buffer.
1414				Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1415				Default: 1024
1417		gpio-mockup.gpio_mockup_ranges
1418				[HW] Sets the ranges of gpiochip of for this device.
1419				Format: <start1>,<end1>,<start2>,<end2>...
1421		hardlockup_all_cpu_backtrace=
1422				[KNL] Should the hard-lockup detector generate
1423				backtraces on all cpus.
1424				Format: <integer>
1426		hashdist=	[KNL,NUMA] Large hashes allocated during boot
1427				are distributed across NUMA nodes.  Defaults on
1428				for 64-bit NUMA, off otherwise.
1429				Format: 0 | 1 (for off | on)
1431		hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1433		hd=		[EIDE] (E)IDE hard drive subsystem geometry
1434				Format: <cyl>,<head>,<sect>
1436		hest_disable	[ACPI]
1437				Disable Hardware Error Source Table (HEST) support;
1438				corresponding firmware-first mode error processing
1439				logic will be disabled.
1441		highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1442				size of <nn>. This works even on boxes that have no
1443				highmem otherwise. This also works to reduce highmem
1444				size on bigger boxes.
1446		highres=	[KNL] Enable/disable high resolution timer mode.
1447				Valid parameters: "on", "off"
1448				Default: "on"
1450		hisax=		[HW,ISDN]
1451				See Documentation/isdn/README.HiSax.
1453		hlt		[BUGS=ARM,SH]
1455		hpet=		[X86-32,HPET] option to control HPET usage
1456				Format: { enable (default) | disable | force |
1457					verbose }
1458				disable: disable HPET and use PIT instead
1459				force: allow force enabled of undocumented chips (ICH4,
1460					VIA, nVidia)
1461				verbose: show contents of HPET registers during setup
1463		hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1464				registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1466		hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1467		hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1468				On x86-64 and powerpc, this option can be specified
1469				multiple times interleaved with hugepages= to reserve
1470				huge pages of different sizes. Valid pages sizes on
1471				x86-64 are 2M (when the CPU supports "pse") and 1G
1472				(when the CPU supports the "pdpe1gb" cpuinfo flag).
1474		hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
1475				       terminal devices. Valid values: 0..8
1476		hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
1477				       If specified, z/VM IUCV HVC accepts connections
1478				       from listed z/VM user IDs only.
1480		hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
1481				        hardware thread id mappings.
1482					Format: <cpu>:<hwthread>
1484		keep_bootcon	[KNL]
1485				Do not unregister boot console at start. This is only
1486				useful for debugging when something happens in the window
1487				between unregistering the boot console and initializing
1488				the real console.
1490		i2c_bus=	[HW] Override the default board specific I2C bus speed
1491				     or register an additional I2C bus that is not
1492				     registered from board initialization code.
1493				     Format:
1494				     <bus_id>,<clkrate>
1496		i8042.debug	[HW] Toggle i8042 debug mode
1497		i8042.unmask_kbd_data
1498				[HW] Enable printing of interrupt data from the KBD port
1499				     (disabled by default, and as a pre-condition
1500				     requires that i8042.debug=1 be enabled)
1501		i8042.direct	[HW] Put keyboard port into non-translated mode
1502		i8042.dumbkbd	[HW] Pretend that controller can only read data from
1503				     keyboard and cannot control its state
1504				     (Don't attempt to blink the leds)
1505		i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1506		i8042.nokbd	[HW] Don't check/create keyboard port
1507		i8042.noloop	[HW] Disable the AUX Loopback command while probing
1508				     for the AUX port
1509		i8042.nomux	[HW] Don't check presence of an active multiplexing
1510				     controller
1511		i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1512				     controllers
1513		i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1514		i8042.reset	[HW] Reset the controller during init, cleanup and
1515				     suspend-to-ram transitions, only during s2r
1516				     transitions, or never reset
1517				Format: { 1 | Y | y | 0 | N | n }
1518				1, Y, y: always reset controller
1519				0, N, n: don't ever reset controller
1520				Default: only on s2r transitions on x86; most other
1521				architectures force reset to be always executed
1522		i8042.unlock	[HW] Unlock (ignore) the keylock
1523		i8042.kbdreset  [HW] Reset device connected to KBD port
1525		i810=		[HW,DRM]
1527		i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1528				indicates that the driver is running on unsupported
1529				hardware.
1530		i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1531				does not match list of supported models.
1532		i8k.power_status
1533				[HW] Report power status in /proc/i8k
1534				(disabled by default)
1535		i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1536				capability is set.
1538		i915.invert_brightness=
1539				[DRM] Invert the sense of the variable that is used to
1540				set the brightness of the panel backlight. Normally a
1541				brightness value of 0 indicates backlight switched off,
1542				and the maximum of the brightness value sets the backlight
1543				to maximum brightness. If this parameter is set to 0
1544				(default) and the machine requires it, or this parameter
1545				is set to 1, a brightness value of 0 sets the backlight
1546				to maximum brightness, and the maximum of the brightness
1547				value switches the backlight off.
1548				-1 -- never invert brightness
1549				 0 -- machine default
1550				 1 -- force brightness inversion
1552		icn=		[HW,ISDN]
1553				Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1555		ide-core.nodma=	[HW] (E)IDE subsystem
1556				Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1557				.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1558				.cdrom .chs .ignore_cable are additional options
1559				See Documentation/ide/ide.txt.
1561		ide-generic.probe-mask= [HW] (E)IDE subsystem
1562				Format: <int>
1563				Probe mask for legacy ISA IDE ports.  Depending on
1564				platform up to 6 ports are supported, enabled by
1565				setting corresponding bits in the mask to 1.  The
1566				default value is 0x0, which has a special meaning.
1567				On systems that have PCI, it triggers scanning the
1568				PCI bus for the first and the second port, which
1569				are then probed.  On systems without PCI the value
1570				of 0x0 enables probing the two first ports as if it
1571				was 0x3.
1573		ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1574				Claim all unknown PCI IDE storage controllers.
1576		idle=		[X86]
1577				Format: idle=poll, idle=halt, idle=nomwait
1578				Poll forces a polling idle loop that can slightly
1579				improve the performance of waking up a idle CPU, but
1580				will use a lot of power and make the system run hot.
1581				Not recommended.
1582				idle=halt: Halt is forced to be used for CPU idle.
1583				In such case C2/C3 won't be used again.
1584				idle=nomwait: Disable mwait for CPU C-states
1586		ieee754=	[MIPS] Select IEEE Std 754 conformance mode
1587				Format: { strict | legacy | 2008 | relaxed }
1588				Default: strict
1590				Choose which programs will be accepted for execution
1591				based on the IEEE 754 NaN encoding(s) supported by
1592				the FPU and the NaN encoding requested with the value
1593				of an ELF file header flag individually set by each
1594				binary.  Hardware implementations are permitted to
1595				support either or both of the legacy and the 2008 NaN
1596				encoding mode.
1598				Available settings are as follows:
1599				strict	accept binaries that request a NaN encoding
1600					supported by the FPU
1601				legacy	only accept legacy-NaN binaries, if supported
1602					by the FPU
1603				2008	only accept 2008-NaN binaries, if supported
1604					by the FPU
1605				relaxed	accept any binaries regardless of whether
1606					supported by the FPU
1608				The FPU emulator is always able to support both NaN
1609				encodings, so if no FPU hardware is present or it has
1610				been disabled with 'nofpu', then the settings of
1611				'legacy' and '2008' strap the emulator accordingly,
1612				'relaxed' straps the emulator for both legacy-NaN and
1613				2008-NaN, whereas 'strict' enables legacy-NaN only on
1614				legacy processors and both NaN encodings on MIPS32 or
1615				MIPS64 CPUs.
1617				The setting for ABS.fmt/NEG.fmt instruction execution
1618				mode generally follows that for the NaN encoding,
1619				except where unsupported by hardware.
1621		ignore_loglevel	[KNL]
1622				Ignore loglevel setting - this will print /all/
1623				kernel messages to the console. Useful for debugging.
1624				We also add it as printk module parameter, so users
1625				could change it dynamically, usually by
1626				/sys/module/printk/parameters/ignore_loglevel.
1628		ignore_rlimit_data
1629				Ignore RLIMIT_DATA setting for data mappings,
1630				print warning at first misuse.  Can be changed via
1631				/sys/module/kernel/parameters/ignore_rlimit_data.
1633		ihash_entries=	[KNL]
1634				Set number of hash buckets for inode cache.
1636		ima_appraise=	[IMA] appraise integrity measurements
1637				Format: { "off" | "enforce" | "fix" | "log" }
1638				default: "enforce"
1640		ima_appraise_tcb [IMA]
1641				The builtin appraise policy appraises all files
1642				owned by uid=0.
1644		ima_hash=	[IMA]
1645				Format: { md5 | sha1 | rmd160 | sha256 | sha384
1646					   | sha512 | ... }
1647				default: "sha1"
1649				The list of supported hash algorithms is defined
1650				in crypto/hash_info.h.
1652		ima_policy=	[IMA]
1653				The builtin measurement policy to load during IMA
1654				setup.  Specyfing "tcb" as the value, measures all
1655				programs exec'd, files mmap'd for exec, and all files
1656				opened with the read mode bit set by either the
1657				effective uid (euid=0) or uid=0.
1658				Format: "tcb"
1660		ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
1661				Load a policy which meets the needs of the Trusted
1662				Computing Base.  This means IMA will measure all
1663				programs exec'd, files mmap'd for exec, and all files
1664				opened for read by uid=0.
1666		ima_template=   [IMA]
1667				Select one of defined IMA measurements template formats.
1668				Formats: { "ima" | "ima-ng" | "ima-sig" }
1669				Default: "ima-ng"
1671		ima_template_fmt=
1672		                [IMA] Define a custom template format.
1673				Format: { "field1|...|fieldN" }
1675		ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1676				Format: <min_file_size>
1677				Set the minimal file size for using asynchronous hash.
1678				If left unspecified, ahash usage is disabled.
1680				ahash performance varies for different data sizes on
1681				different crypto accelerators. This option can be used
1682				to achieve the best performance for a particular HW.
1684		ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1685				Format: <bufsize>
1686				Set hashing buffer size. Default: 4k.
1688				ahash performance varies for different chunk sizes on
1689				different crypto accelerators. This option can be used
1690				to achieve best performance for particular HW.
1692		init=		[KNL]
1693				Format: <full_path>
1694				Run specified binary instead of /sbin/init as init
1695				process.
1697		initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1698				for working out where the kernel is dying during
1699				startup.
1701		initcall_blacklist=  [KNL] Do not execute a comma-separated list of
1702				initcall functions.  Useful for debugging built-in
1703				modules and initcalls.
1705		initrd=		[BOOT] Specify the location of the initial ramdisk
1707		init_pkru=	[x86] Specify the default memory protection keys rights
1708				register contents for all processes.  0x55555554 by
1709				default (disallow access to all but pkey 0).  Can
1710				override in debugfs after boot.
1712		inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1713				Format: <irq>
1715		int_pln_enable  [x86] Enable power limit notification interrupt
1717		integrity_audit=[IMA]
1718				Format: { "0" | "1" }
1719				0 -- basic integrity auditing messages. (Default)
1720				1 -- additional integrity auditing messages.
1722		intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1723			on
1724				Enable intel iommu driver.
1725			off
1726				Disable intel iommu driver.
1727			igfx_off [Default Off]
1728				By default, gfx is mapped as normal device. If a gfx
1729				device has a dedicated DMAR unit, the DMAR unit is
1730				bypassed by not enabling DMAR with this option. In
1731				this case, gfx device will use physical address for
1732				DMA.
1733			forcedac [x86_64]
1734				With this option iommu will not optimize to look
1735				for io virtual address below 32-bit forcing dual
1736				address cycle on pci bus for cards supporting greater
1737				than 32-bit addressing. The default is to look
1738				for translation below 32-bit and if not available
1739				then look in the higher range.
1740			strict [Default Off]
1741				With this option on every unmap_single operation will
1742				result in a hardware IOTLB flush operation as opposed
1743				to batching them for performance.
1744			sp_off [Default Off]
1745				By default, super page will be supported if Intel IOMMU
1746				has the capability. With this option, super page will
1747				not be supported.
1748			ecs_off [Default Off]
1749				By default, extended context tables will be supported if
1750				the hardware advertises that it has support both for the
1751				extended tables themselves, and also PASID support. With
1752				this option set, extended tables will not be used even
1753				on hardware which claims to support them.
1755		intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1756				0	disables intel_idle and fall back on acpi_idle.
1757				1 to 9	specify maximum depth of C-state.
1759		intel_pstate=  [X86]
1760			       disable
1761			         Do not enable intel_pstate as the default
1762			         scaling driver for the supported processors
1763			       force
1764				 Enable intel_pstate on systems that prohibit it by default
1765				 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1766				 instead of acpi-cpufreq may disable platform features, such
1767				 as thermal controls and power capping, that rely on ACPI
1768				 P-States information being indicated to OSPM and therefore
1769				 should be used with caution. This option does not work with
1770				 processors that aren't supported by the intel_pstate driver
1771				 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1772			       no_hwp
1773			         Do not enable hardware P state control (HWP)
1774				 if available.
1775			hwp_only
1776				Only load intel_pstate on systems which support
1777				hardware P state control (HWP) if available.
1778			support_acpi_ppc
1779				Enforce ACPI _PPC performance limits. If the Fixed ACPI
1780				Description Table, specifies preferred power management
1781				profile as "Enterprise Server" or "Performance Server",
1782				then this feature is turned on by default.
1784		intremap=	[X86-64, Intel-IOMMU]
1785				on	enable Interrupt Remapping (default)
1786				off	disable Interrupt Remapping
1787				nosid	disable Source ID checking
1788				no_x2apic_optout
1789					BIOS x2APIC opt-out request will be ignored
1790				nopost	disable Interrupt Posting
1792		iomem=		Disable strict checking of access to MMIO memory
1793			strict	regions from userspace.
1794			relaxed
1796		iommu=		[x86]
1797			off
1798			force
1799			noforce
1800			biomerge
1801			panic
1802			nopanic
1803			merge
1804			nomerge
1805			forcesac
1806			soft
1807			pt		[x86, IA-64]
1808			nobypass	[PPC/POWERNV]
1809				Disable IOMMU bypass, using IOMMU for PCI devices.
1812		io7=		[HW] IO7 for Marvel based alpha systems
1813				See comment before marvel_specify_io7 in
1814				arch/alpha/kernel/core_marvel.c.
1816		io_delay=	[X86] I/O delay method
1817			0x80
1818				Standard port 0x80 based delay
1819			0xed
1820				Alternate port 0xed based delay (needed on some systems)
1821			udelay
1822				Simple two microseconds delay
1823			none
1824				No delay
1826		ip=		[IP_PNP]
1827				See Documentation/filesystems/nfs/nfsroot.txt.
1829		irqaffinity=	[SMP] Set the default irq affinity mask
1830				The argument is a cpu list, as described above.
1832		irqfixup	[HW]
1833				When an interrupt is not handled search all handlers
1834				for it. Intended to get systems with badly broken
1835				firmware running.
1837		irqpoll		[HW]
1838				When an interrupt is not handled search all handlers
1839				for it. Also check all handlers each timer
1840				interrupt. Intended to get systems with badly broken
1841				firmware running.
1843		isapnp=		[ISAPNP]
1844				Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1846		isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1847				The argument is a cpu list, as described above.
1849				This option can be used to specify one or more CPUs
1850				to isolate from the general SMP balancing and scheduling
1851				algorithms. You can move a process onto or off an
1852				"isolated" CPU via the CPU affinity syscalls or cpuset.
1853				<cpu number> begins at 0 and the maximum value is
1854				"number of CPUs in system - 1".
1856				This option is the preferred way to isolate CPUs. The
1857				alternative -- manually setting the CPU mask of all
1858				tasks in the system -- can cause problems and
1859				suboptimal load balancer performance.
1861		iucv=		[HW,NET]
1863		ivrs_ioapic	[HW,X86_64]
1864				Provide an override to the IOAPIC-ID<->DEVICE-ID
1865				mapping provided in the IVRS ACPI table. For
1866				example, to map IOAPIC-ID decimal 10 to
1867				PCI device 00:14.0 write the parameter as:
1868					ivrs_ioapic[10]=00:14.0
1870		ivrs_hpet	[HW,X86_64]
1871				Provide an override to the HPET-ID<->DEVICE-ID
1872				mapping provided in the IVRS ACPI table. For
1873				example, to map HPET-ID decimal 0 to
1874				PCI device 00:14.0 write the parameter as:
1875					ivrs_hpet[0]=00:14.0
1877		ivrs_acpihid	[HW,X86_64]
1878				Provide an override to the ACPI-HID:UID<->DEVICE-ID
1879				mapping provided in the IVRS ACPI table. For
1880				example, to map UART-HID:UID AMD0020:0 to
1881				PCI device 00:14.5 write the parameter as:
1882					ivrs_acpihid[00:14.5]=AMD0020:0
1884		js=		[HW,JOY] Analog joystick
1885				See Documentation/input/joystick.txt.
1887		nokaslr		[KNL]
1888				When CONFIG_RANDOMIZE_BASE is set, this disables
1889				kernel and module base offset ASLR (Address Space
1890				Layout Randomization).
1892		keepinitrd	[HW,ARM]
1894		kernelcore=	[KNL,X86,IA-64,PPC]
1895				Format: nn[KMGTPE] | "mirror"
1896				This parameter
1897				specifies the amount of memory usable by the kernel
1898				for non-movable allocations.  The requested amount is
1899				spread evenly throughout all nodes in the system. The
1900				remaining memory in each node is used for Movable
1901				pages. In the event, a node is too small to have both
1902				kernelcore and Movable pages, kernelcore pages will
1903				take priority and other nodes will have a larger number
1904				of Movable pages.  The Movable zone is used for the
1905				allocation of pages that may be reclaimed or moved
1906				by the page migration subsystem.  This means that
1907				HugeTLB pages may not be allocated from this zone.
1908				Note that allocations like PTEs-from-HighMem still
1909				use the HighMem zone if it exists, and the Normal
1910				zone if it does not.
1912				Instead of specifying the amount of memory (nn[KMGTPE]),
1913				you can specify "mirror" option. In case "mirror"
1914				option is specified, mirrored (reliable) memory is used
1915				for non-movable allocations and remaining memory is used
1916				for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
1917				so you can NOT specify nn[KMGTPE] and "mirror" at the same
1918				time.
1920		kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1921				Format: <Controller#>[,poll interval]
1922				The controller # is the number of the ehci usb debug
1923				port as it is probed via PCI.  The poll interval is
1924				optional and is the number seconds in between
1925				each poll cycle to the debug port in case you need
1926				the functionality for interrupting the kernel with
1927				gdb or control-c on the dbgp connection.  When
1928				not using this parameter you use sysrq-g to break into
1929				the kernel debugger.
1931		kgdboc=		[KGDB,HW] kgdb over consoles.
1932				Requires a tty driver that supports console polling,
1933				or a supported polling keyboard driver (non-usb).
1934				 Serial only format: <serial_device>[,baud]
1935				 keyboard only format: kbd
1936				 keyboard and serial format: kbd,<serial_device>[,baud]
1937				Optional Kernel mode setting:
1938				 kms, kbd format: kms,kbd
1939				 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1941		kgdbwait	[KGDB] Stop kernel execution and enter the
1942				kernel debugger at the earliest opportunity.
1944		kmac=		[MIPS] korina ethernet MAC address.
1945				Configure the RouterBoard 532 series on-chip
1946				Ethernet adapter MAC address.
1948		kmemleak=	[KNL] Boot-time kmemleak enable/disable
1949				Valid arguments: on, off
1950				Default: on
1952				the default is off.
1954		kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
1955				Valid arguments: 0, 1, 2
1956				kmemcheck=0 (disabled)
1957				kmemcheck=1 (enabled)
1958				kmemcheck=2 (one-shot mode)
1959				Default: 2 (one-shot mode)
1961		kstack=N	[X86] Print N words from the kernel stack
1962				in oops dumps.
1964		kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1965				Default is 0 (don't ignore, but inject #GP)
1967		kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
1968				KVM MMU at runtime.
1969				Default is 0 (off)
1971		kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1972				Default is 1 (enabled)
1974		kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
1975				for all guests.
1976				Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1978		kvm-intel.ept=	[KVM,Intel] Disable extended page tables
1979				(virtualized MMU) support on capable Intel chips.
1980				Default is 1 (enabled)
1982		kvm-intel.emulate_invalid_guest_state=
1983				[KVM,Intel] Enable emulation of invalid guest states
1984				Default is 0 (disabled)
1986		kvm-intel.flexpriority=
1987				[KVM,Intel] Disable FlexPriority feature (TPR shadow).
1988				Default is 1 (enabled)
1990		kvm-intel.nested=
1991				[KVM,Intel] Enable VMX nesting (nVMX).
1992				Default is 0 (disabled)
1994		kvm-intel.unrestricted_guest=
1995				[KVM,Intel] Disable unrestricted guest feature
1996				(virtualized real and unpaged mode) on capable
1997				Intel chips. Default is 1 (enabled)
1999		kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
2000				feature (tagged TLBs) on capable Intel chips.
2001				Default is 1 (enabled)
2003		l2cr=		[PPC]
2005		l3cr=		[PPC]
2007		lapic		[X86-32,APIC] Enable the local APIC even if BIOS
2008				disabled it.
2010		lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
2011				value for LAPIC timer one-shot implementation. Default
2012				back to the programmable timer unit in the LAPIC.
2014		lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
2015				in C2 power state.
2017		libata.dma=	[LIBATA] DMA control
2018				libata.dma=0	  Disable all PATA and SATA DMA
2019				libata.dma=1	  PATA and SATA Disk DMA only
2020				libata.dma=2	  ATAPI (CDROM) DMA only
2021				libata.dma=4	  Compact Flash DMA only
2022				Combinations also work, so libata.dma=3 enables DMA
2023				for disks and CDROMs, but not CFs.
2025		libata.ignore_hpa=	[LIBATA] Ignore HPA limit
2026				libata.ignore_hpa=0	  keep BIOS limits (default)
2027				libata.ignore_hpa=1	  ignore limits, using full disk
2029		libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
2030				when set.
2031				Format: <int>
2033		libata.force=	[LIBATA] Force configurations.  The format is comma
2034				separated list of "[ID:]VAL" where ID is
2035				PORT[.DEVICE].  PORT and DEVICE are decimal numbers
2036				matching port, link or device.  Basically, it matches
2037				the ATA ID string printed on console by libata.  If
2038				the whole ID part is omitted, the last PORT and DEVICE
2039				values are used.  If ID hasn't been specified yet, the
2040				configuration applies to all ports, links and devices.
2042				If only DEVICE is omitted, the parameter applies to
2043				the port and all links and devices behind it.  DEVICE
2044				number of 0 either selects the first device or the
2045				first fan-out link behind PMP device.  It does not
2046				select the host link.  DEVICE number of 15 selects the
2047				host link and device attached to it.
2049				The VAL specifies the configuration to force.  As long
2050				as there's no ambiguity shortcut notation is allowed.
2051				For example, both 1.5 and 1.5G would work for 1.5Gbps.
2052				The following configurations can be forced.
2054				* Cable type: 40c, 80c, short40c, unk, ign or sata.
2055				  Any ID with matching PORT is used.
2057				* SATA link speed limit: 1.5Gbps or 3.0Gbps.
2059				* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2060				  udma[/][16,25,33,44,66,100,133] notation is also
2061				  allowed.
2063				* [no]ncq: Turn on or off NCQ.
2065				* [no]ncqtrim: Turn off queued DSM TRIM.
2067				* nohrst, nosrst, norst: suppress hard, soft
2068	                          and both resets.
2070				* rstonce: only attempt one reset during
2071				  hot-unplug link recovery
2073				* dump_id: dump IDENTIFY data.
2075				* atapi_dmadir: Enable ATAPI DMADIR bridge support
2077				* disable: Disable this device.
2079				If there are multiple matching configurations changing
2080				the same attribute, the last one is used.
2082		memblock=debug	[KNL] Enable memblock debug messages.
2084		load_ramdisk=	[RAM] List of ramdisks to load from floppy
2085				See Documentation/blockdev/ramdisk.txt.
2087		lockd.nlm_grace_period=P  [NFS] Assign grace period.
2088				Format: <integer>
2090		lockd.nlm_tcpport=N	[NFS] Assign TCP port.
2091				Format: <integer>
2093		lockd.nlm_timeout=T	[NFS] Assign timeout value.
2094				Format: <integer>
2096		lockd.nlm_udpport=M	[NFS] Assign UDP port.
2097				Format: <integer>
2099		locktorture.nreaders_stress= [KNL]
2100				Set the number of locking read-acquisition kthreads.
2101				Defaults to being automatically set based on the
2102				number of online CPUs.
2104		locktorture.nwriters_stress= [KNL]
2105				Set the number of locking write-acquisition kthreads.
2107		locktorture.onoff_holdoff= [KNL]
2108				Set time (s) after boot for CPU-hotplug testing.
2110		locktorture.onoff_interval= [KNL]
2111				Set time (s) between CPU-hotplug operations, or
2112				zero to disable CPU-hotplug testing.
2114		locktorture.shuffle_interval= [KNL]
2115				Set task-shuffle interval (jiffies).  Shuffling
2116				tasks allows some CPUs to go into dyntick-idle
2117				mode during the locktorture test.
2119		locktorture.shutdown_secs= [KNL]
2120				Set time (s) after boot system shutdown.  This
2121				is useful for hands-off automated testing.
2123		locktorture.stat_interval= [KNL]
2124				Time (s) between statistics printk()s.
2126		locktorture.stutter= [KNL]
2127				Time (s) to stutter testing, for example,
2128				specifying five seconds causes the test to run for
2129				five seconds, wait for five seconds, and so on.
2130				This tests the locking primitive's ability to
2131				transition abruptly to and from idle.
2133		locktorture.torture_runnable= [BOOT]
2134				Start locktorture running at boot time.
2136		locktorture.torture_type= [KNL]
2137				Specify the locking implementation to test.
2139		locktorture.verbose= [KNL]
2140				Enable additional printk() statements.
2142		logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
2143				Format: <irq>
2145		loglevel=	All Kernel Messages with a loglevel smaller than the
2146				console loglevel will be printed to the console. It can
2147				also be changed with klogd or other programs. The
2148				loglevels are defined as follows:
2150				0 (KERN_EMERG)		system is unusable
2151				1 (KERN_ALERT)		action must be taken immediately
2152				2 (KERN_CRIT)		critical conditions
2153				3 (KERN_ERR)		error conditions
2154				4 (KERN_WARNING)	warning conditions
2155				5 (KERN_NOTICE)		normal but significant condition
2156				6 (KERN_INFO)		informational
2157				7 (KERN_DEBUG)		debug-level messages
2159		log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
2160				in bytes.  n must be a power of two and greater
2161				than the minimal size. The minimal size is defined
2162				by LOG_BUF_SHIFT kernel config parameter. There is
2163				also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
2164				that allows to increase the default size depending on
2165				the number of CPUs. See init/Kconfig for more details.
2167		logo.nologo	[FB] Disables display of the built-in Linux logo.
2168				This may be used to provide more screen space for
2169				kernel log messages and is useful when debugging
2170				kernel boot problems.
2172		lp=0		[LP]	Specify parallel ports to use, e.g,
2173		lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
2174		lp=reset		first parallel port). 'lp=0' disables the
2175		lp=auto			printer driver. 'lp=reset' (which can be
2176					specified in addition to the ports) causes
2177					attached printers to be reset. Using
2178					lp=port1,port2,... specifies the parallel ports
2179					to associate lp devices with, starting with
2180					lp0. A port specification may be 'none' to skip
2181					that lp device, or a parport name such as
2182					'parport0'. Specifying 'lp=auto' instead of a
2183					port specification list means that device IDs
2184					from each port should be examined, to see if
2185					an IEEE 1284-compliant printer is attached; if
2186					so, the driver will manage that printer.
2187					See also header of drivers/char/lp.c.
2189		lpj=n		[KNL]
2190				Sets loops_per_jiffy to given constant, thus avoiding
2191				time-consuming boot-time autodetection (up to 250 ms per
2192				CPU). 0 enables autodetection (default). To determine
2193				the correct value for your kernel, boot with normal
2194				autodetection and see what value is printed. Note that
2195				on SMP systems the preset will be applied to all CPUs,
2196				which is likely to cause problems if your CPUs need
2197				significantly divergent settings. An incorrect value
2198				will cause delays in the kernel to be wrong, leading to
2199				unpredictable I/O errors and other breakage. Although
2200				unlikely, in the extreme case this might damage your
2201				hardware.
2203		ltpc=		[NET]
2204				Format: <io>,<irq>,<dma>
2206		machvec=	[IA-64] Force the use of a particular machine-vector
2207				(machvec) in a generic kernel.
2208				Example: machvec=hpzx1_swiotlb
2210		machtype=	[Loongson] Share the same kernel image file between different
2211				 yeeloong laptop.
2212				Example: machtype=lemote-yeeloong-2f-7inch
2214		max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
2215				than or equal to this physical address is ignored.
2217		maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
2218				will bring up during bootup.  maxcpus=n : n >= 0 limits
2219				the kernel to bring up 'n' processors. Surely after
2220				bootup you can bring up the other plugged cpu by executing
2221				"echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
2222				only takes effect during system bootup.
2223				While n=0 is a special case, it is equivalent to "nosmp",
2224				which also disables the IO APIC.
2226		max_loop=	[LOOP] The number of loop block devices that get
2227		(loop.max_loop)	unconditionally pre-created at init time. The default
2228				number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
2229				of statically allocating a predefined number, loop
2230				devices can be requested on-demand with the
2231				/dev/loop-control interface.
2233		mce		[X86-32] Machine Check Exception
2235		mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
2237		md=		[HW] RAID subsystems devices and level
2238				See Documentation/md.txt.
2240		mdacon=		[MDA]
2241				Format: <first>,<last>
2242				Specifies range of consoles to be captured by the MDA.
2244		mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
2245				Amount of memory to be used when the kernel is not able
2246				to see the whole system memory or for test.
2247				[X86] Work as limiting max address. Use together
2248				with memmap= to avoid physical address space collisions.
2249				Without memmap= PCI devices could be placed at addresses
2250				belonging to unused RAM.
2252		mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
2253				memory.
2255		memchunk=nn[KMG]
2256				[KNL,SH] Allow user to override the default size for
2257				per-device physically contiguous DMA buffers.
2259	        memhp_default_state=online/offline
2260				[KNL] Set the initial state for the memory hotplug
2261				onlining policy. If not specified, the default value is
2262				set according to the
2264				option.
2265				See Documentation/memory-hotplug.txt.
2267		memmap=exactmap	[KNL,X86] Enable setting of an exact
2268				E820 memory map, as specified by the user.
2269				Such memmap=exactmap lines can be constructed based on
2270				BIOS output or other requirements. See the memmap=nn@ss
2271				option description.
2273		memmap=nn[KMG]@ss[KMG]
2274				[KNL] Force usage of a specific region of memory.
2275				Region of memory to be used is from ss to ss+nn.
2277		memmap=nn[KMG]#ss[KMG]
2278				[KNL,ACPI] Mark specific memory as ACPI data.
2279				Region of memory to be marked is from ss to ss+nn.
2281		memmap=nn[KMG]$ss[KMG]
2282				[KNL,ACPI] Mark specific memory as reserved.
2283				Region of memory to be reserved is from ss to ss+nn.
2284				Example: Exclude memory from 0x18690000-0x1869ffff
2285				         memmap=64K$0x18690000
2286				         or
2287				         memmap=0x10000$0x18690000
2289		memmap=nn[KMG]!ss[KMG]
2290				[KNL,X86] Mark specific memory as protected.
2291				Region of memory to be used, from ss to ss+nn.
2292				The memory region may be marked as e820 type 12 (0xc)
2293				and is NVDIMM or ADR memory.
2295		memory_corruption_check=0/1 [X86]
2296				Some BIOSes seem to corrupt the first 64k of
2297				memory when doing things like suspend/resume.
2298				Setting this option will scan the memory
2299				looking for corruption.  Enabling this will
2300				both detect corruption and prevent the kernel
2301				from using the memory being corrupted.
2302				However, its intended as a diagnostic tool; if
2303				repeatable BIOS-originated corruption always
2304				affects the same memory, you can use memmap=
2305				to prevent the kernel from using that memory.
2307		memory_corruption_check_size=size [X86]
2308				By default it checks for corruption in the low
2309				64k, making this memory unavailable for normal
2310				use.  Use this parameter to scan for
2311				corruption in more or less memory.
2313		memory_corruption_check_period=seconds [X86]
2314				By default it checks for corruption every 60
2315				seconds.  Use this parameter to check at some
2316				other rate.  0 disables periodic checking.
2318		memtest=	[KNL,X86,ARM] Enable memtest
2319				Format: <integer>
2320				default : 0 <disable>
2321				Specifies the number of memtest passes to be
2322				performed. Each pass selects another test
2323				pattern from a given set of patterns. Memtest
2324				fills the memory with this pattern, validates
2325				memory contents and reserves bad memory
2326				regions that are detected.
2328		meye.*=		[HW] Set MotionEye Camera parameters
2329				See Documentation/video4linux/meye.txt.
2331		mfgpt_irq=	[IA-32] Specify the IRQ to use for the
2332				Multi-Function General Purpose Timers on AMD Geode
2333				platforms.
2335		mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
2336				the BIOS has incorrectly applied a workaround. TinyBIOS
2337				version 0.98 is known to be affected, 0.99 fixes the
2338				problem by letting the user disable the workaround.
2340		mga=		[HW,DRM]
2342		min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
2343				physical address is ignored.
2345		mini2440=	[ARM,HW,KNL]
2346				Format:[0..2][b][c][t]
2347				Default: "0tb"
2348				MINI2440 configuration specification:
2349				0 - The attached screen is the 3.5" TFT
2350				1 - The attached screen is the 7" TFT
2351				2 - The VGA Shield is attached (1024x768)
2352				Leaving out the screen size parameter will not load
2353				the TFT driver, and the framebuffer will be left
2354				unconfigured.
2355				b - Enable backlight. The TFT backlight pin will be
2356				linked to the kernel VESA blanking code and a GPIO
2357				LED. This parameter is not necessary when using the
2358				VGA shield.
2359				c - Enable the s3c camera interface.
2360				t - Reserved for enabling touchscreen support. The
2361				touchscreen support is not enabled in the mainstream
2362				kernel as of 2.6.30, a preliminary port can be found
2363				in the "bleeding edge" mini2440 support kernel at
2364				http://repo.or.cz/w/linux-2.6/mini2440.git
2366		mminit_loglevel=
2367				[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2368				parameter allows control of the logging verbosity for
2369				the additional memory initialisation checks. A value
2370				of 0 disables mminit logging and a level of 4 will
2371				log everything. Information is printed at KERN_DEBUG
2372				so loglevel=8 may also need to be specified.
2374		module.sig_enforce
2375				[KNL] When CONFIG_MODULE_SIG is set, this means that
2376				modules without (valid) signatures will fail to load.
2377				Note that if CONFIG_MODULE_SIG_FORCE is set, that
2378				is always true, so this option does nothing.
2380		module_blacklist=  [KNL] Do not load a comma-separated list of
2381				modules.  Useful for debugging problem modules.
2383		mousedev.tap_time=
2384				[MOUSE] Maximum time between finger touching and
2385				leaving touchpad surface for touch to be considered
2386				a tap and be reported as a left button click (for
2387				touchpads working in absolute mode only).
2388				Format: <msecs>
2389		mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
2390				reporting absolute coordinates, such as tablets
2391		mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
2392				reporting absolute coordinates, such as tablets
2394		movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
2395				is similar to kernelcore except it specifies the
2396				amount of memory used for migratable allocations.
2397				If both kernelcore and movablecore is specified,
2398				then kernelcore will be at *least* the specified
2399				value but may be more. If movablecore on its own
2400				is specified, the administrator must be careful
2401				that the amount of memory usable for all allocations
2402				is not too small.
2404		movable_node	[KNL,X86] Boot-time switch to enable the effects
2405				of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2407		MTD_Partition=	[MTD]
2408				Format: <name>,<region-number>,<size>,<offset>
2410		MTD_Region=	[MTD] Format:
2411				<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2413		mtdparts=	[MTD]
2414				See drivers/mtd/cmdlinepart.c.
2416		multitce=off	[PPC]  This parameter disables the use of the pSeries
2417				firmware feature for updating multiple TCE entries
2418				at a time.
2420		onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
2422				Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2424				boundary - index of last SLC block on Flex-OneNAND.
2425					   The remaining blocks are configured as MLC blocks.
2426				lock	 - Configure if Flex-OneNAND boundary should be locked.
2427					   Once locked, the boundary cannot be changed.
2428					   1 indicates lock status, 0 indicates unlock status.
2430		mtdset=		[ARM]
2431				ARM/S3C2412 JIVE boot control
2433				See arch/arm/mach-s3c2412/mach-jive.c
2435		mtouchusb.raw_coordinates=
2436				[HW] Make the MicroTouch USB driver use raw coordinates
2437				('y', default) or cooked coordinates ('n')
2439		mtrr_chunk_size=nn[KMG] [X86]
2440				used for mtrr cleanup. It is largest continuous chunk
2441				that could hold holes aka. UC entries.
2443		mtrr_gran_size=nn[KMG] [X86]
2444				Used for mtrr cleanup. It is granularity of mtrr block.
2445				Default is 1.
2446				Large value could prevent small alignment from
2447				using up MTRRs.
2449		mtrr_spare_reg_nr=n [X86]
2450				Format: <integer>
2451				Range: 0,7 : spare reg number
2452				Default : 1
2453				Used for mtrr cleanup. It is spare mtrr entries number.
2454				Set to 2 or more if your graphical card needs more.
2456		n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
2458		netdev=		[NET] Network devices parameters
2459				Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2460				Note that mem_start is often overloaded to mean
2461				something different and driver-specific.
2462				This usage is only documented in each driver source
2463				file if at all.
2465		nf_conntrack.acct=
2466				[NETFILTER] Enable connection tracking flow accounting
2467				0 to disable accounting
2468				1 to enable accounting
2469				Default value is 0.
2471		nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
2472				See Documentation/filesystems/nfs/nfsroot.txt.
2474		nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
2475				See Documentation/filesystems/nfs/nfsroot.txt.
2477		nfsrootdebug	[NFS] enable nfsroot debugging messages.
2478				See Documentation/filesystems/nfs/nfsroot.txt.
2480		nfs.callback_nr_threads=
2481				[NFSv4] set the total number of threads that the
2482				NFS client will assign to service NFSv4 callback
2483				requests.
2485		nfs.callback_tcpport=
2486				[NFS] set the TCP port on which the NFSv4 callback
2487				channel should listen.
2489		nfs.cache_getent=
2490				[NFS] sets the pathname to the program which is used
2491				to update the NFS client cache entries.
2493		nfs.cache_getent_timeout=
2494				[NFS] sets the timeout after which an attempt to
2495				update a cache entry is deemed to have failed.
2497		nfs.idmap_cache_timeout=
2498				[NFS] set the maximum lifetime for idmapper cache
2499				entries.
2501		nfs.enable_ino64=
2502				[NFS] enable 64-bit inode numbers.
2503				If zero, the NFS client will fake up a 32-bit inode
2504				number for the readdir() and stat() syscalls instead
2505				of returning the full 64-bit number.
2506				The default is to return 64-bit inode numbers.
2508		nfs.max_session_cb_slots=
2509				[NFSv4.1] Sets the maximum number of session
2510				slots the client will assign to the callback
2511				channel. This determines the maximum number of
2512				callbacks the client will process in parallel for
2513				a particular server.
2515		nfs.max_session_slots=
2516				[NFSv4.1] Sets the maximum number of session slots
2517				the client will attempt to negotiate with the server.
2518				This limits the number of simultaneous RPC requests
2519				that the client can send to the NFSv4.1 server.
2520				Note that there is little point in setting this
2521				value higher than the max_tcp_slot_table_limit.
2523		nfs.nfs4_disable_idmapping=
2524				[NFSv4] When set to the default of '1', this option
2525				ensures that both the RPC level authentication
2526				scheme and the NFS level operations agree to use
2527				numeric uids/gids if the mount is using the
2528				'sec=sys' security flavour. In effect it is
2529				disabling idmapping, which can make migration from
2530				legacy NFSv2/v3 systems to NFSv4 easier.
2531				Servers that do not support this mode of operation
2532				will be autodetected by the client, and it will fall
2533				back to using the idmapper.
2534				To turn off this behaviour, set the value to '0'.
2535		nfs.nfs4_unique_id=
2536				[NFS4] Specify an additional fixed unique ident-
2537				ification string that NFSv4 clients can insert into
2538				their nfs_client_id4 string.  This is typically a
2539				UUID that is generated at system install time.
2541		nfs.send_implementation_id =
2542				[NFSv4.1] Send client implementation identification
2543				information in exchange_id requests.
2544				If zero, no implementation identification information
2545				will be sent.
2546				The default is to send the implementation identification
2547				information.
2549		nfs.recover_lost_locks =
2550				[NFSv4] Attempt to recover locks that were lost due
2551				to a lease timeout on the server. Please note that
2552				doing this risks data corruption, since there are
2553				no guarantees that the file will remain unchanged
2554				after the locks are lost.
2555				If you want to enable the kernel legacy behaviour of
2556				attempting to recover these locks, then set this
2557				parameter to '1'.
2558				The default parameter value of '0' causes the kernel
2559				not to attempt recovery of lost locks.
2561		nfs4.layoutstats_timer =
2562				[NFSv4.2] Change the rate at which the kernel sends
2563				layoutstats to the pNFS metadata server.
2565				Setting this to value to 0 causes the kernel to use
2566				whatever value is the default set by the layout
2567				driver. A non-zero value sets the minimum interval
2568				in seconds between layoutstats transmissions.
2570		nfsd.nfs4_disable_idmapping=
2571				[NFSv4] When set to the default of '1', the NFSv4
2572				server will return only numeric uids and gids to
2573				clients using auth_sys, and will accept numeric uids
2574				and gids from such clients.  This is intended to ease
2575				migration from NFSv2/v3.
2577		objlayoutdriver.osd_login_prog=
2578				[NFS] [OBJLAYOUT] sets the pathname to the program which
2579				is used to automatically discover and login into new
2580				osd-targets. Please see:
2581				Documentation/filesystems/pnfs.txt for more explanations
2583		nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
2584				when a NMI is triggered.
2585				Format: [state][,regs][,debounce][,die]
2587		nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2588				Format: [panic,][nopanic,][num]
2589				Valid num: 0 or 1
2590				0 - turn hardlockup detector in nmi_watchdog off
2591				1 - turn hardlockup detector in nmi_watchdog on
2592				When panic is specified, panic when an NMI watchdog
2593				timeout occurs (or 'nopanic' to override the opposite
2594				default). To disable both hard and soft lockup detectors,
2595				please see 'nowatchdog'.
2596				This is useful when you use a panic=... timeout and
2597				need the box quickly up again.
2599		netpoll.carrier_timeout=
2600				[NET] Specifies amount of time (in seconds) that
2601				netpoll should wait for a carrier. By default netpoll
2602				waits 4 seconds.
2604		no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
2605				emulation library even if a 387 maths coprocessor
2606				is present.
2608		no_console_suspend
2609				[HW] Never suspend the console
2610				Disable suspending of consoles during suspend and
2611				hibernate operations.  Once disabled, debugging
2612				messages can reach various consoles while the rest
2613				of the system is being put to sleep (ie, while
2614				debugging driver suspend/resume hooks).  This may
2615				not work reliably with all consoles, but is known
2616				to work with serial and VGA consoles.
2617				To facilitate more flexible debugging, we also add
2618				console_suspend, a printk module parameter to control
2619				it. Users could use console_suspend (usually
2620				/sys/module/printk/parameters/console_suspend) to
2621				turn on/off it dynamically.
2623		noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
2624				caches in the slab allocator.  Saves per-node memory,
2625				but will impact performance.
2627		noalign		[KNL,ARM]
2629		noapic		[SMP,APIC] Tells the kernel to not make use of any
2630				IOAPICs that may be present in the system.
2632		noautogroup	Disable scheduler automatic task group creation.
2634		nobats		[PPC] Do not use BATs for mapping kernel lowmem
2635				on "Classic" PPC cores.
2637		nocache		[ARM]
2639		noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2641		nodelayacct	[KNL] Disable per-task delay accounting
2643		nodsp		[SH] Disable hardware DSP at boot time.
2645		noefi		Disable EFI runtime services support.
2647		noexec		[IA-64]
2649		noexec		[X86]
2650				On X86-32 available only on PAE configured kernels.
2651				noexec=on: enable non-executable mappings (default)
2652				noexec=off: disable non-executable mappings
2654		nosmap		[X86]
2655				Disable SMAP (Supervisor Mode Access Prevention)
2656				even if it is supported by processor.
2658		nosmep		[X86]
2659				Disable SMEP (Supervisor Mode Execution Prevention)
2660				even if it is supported by processor.
2662		noexec32	[X86-64]
2663				This affects only 32-bit executables.
2664				noexec32=on: enable non-executable mappings (default)
2665					read doesn't imply executable mappings
2666				noexec32=off: disable non-executable mappings
2667					read implies executable mappings
2669		nofpu		[MIPS,SH] Disable hardware FPU at boot time.
2671		nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2672				register save and restore. The kernel will only save
2673				legacy floating-point registers on task switch.
2675		nohugeiomap	[KNL,x86] Disable kernel huge I/O mappings.
2677		nosmt		[KNL,S390] Disable symmetric multithreading (SMT).
2678				Equivalent to smt=1.
2680		noxsave		[BUGS=X86] Disables x86 extended register state save
2681				and restore using xsave. The kernel will fallback to
2682				enabling legacy floating-point and sse state.
2684		noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
2685				register states. The kernel will fall back to use
2686				xsave to save the states. By using this parameter,
2687				performance of saving the states is degraded because
2688				xsave doesn't support modified optimization while
2689				xsaveopt supports it on xsaveopt enabled systems.
2691		noxsaves	[X86] Disables xsaves and xrstors used in saving and
2692				restoring x86 extended register state in compacted
2693				form of xsave area. The kernel will fall back to use
2694				xsaveopt and xrstor to save and restore the states
2695				in standard form of xsave area. By using this
2696				parameter, xsave area per process might occupy more
2697				memory on xsaves enabled systems.
2699		nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2700				wfi(ARM) instruction doesn't work correctly and not to
2701				use it. This is also useful when using JTAG debugger.
2703		no_file_caps	Tells the kernel not to honor file capabilities.  The
2704				only way then for a file to be executed with privilege
2705				is to be setuid root or executed by root.
2707		nohalt		[IA-64] Tells the kernel not to use the power saving
2708				function PAL_HALT_LIGHT when idle. This increases
2709				power-consumption. On the positive side, it reduces
2710				interrupt wake-up latency, which may improve performance
2711				in certain environments such as networked servers or
2712				real-time systems.
2714		nohibernate	[HIBERNATION] Disable hibernation and resume.
2716		nohz=		[KNL] Boottime enable/disable dynamic ticks
2717				Valid arguments: on, off
2718				Default: on
2720		nohz_full=	[KNL,BOOT]
2721				The argument is a cpu list, as described above.
2722				In kernels built with CONFIG_NO_HZ_FULL=y, set
2723				the specified list of CPUs whose tick will be stopped
2724				whenever possible. The boot CPU will be forced outside
2725				the range to maintain the timekeeping.
2726				The CPUs in this range must also be included in the
2727				rcu_nocbs= set.
2729		noiotrap	[SH] Disables trapped I/O port accesses.
2731		noirqdebug	[X86-32] Disables the code which attempts to detect and
2732				disable unhandled interrupt sources.
2734		no_timer_check	[X86,APIC] Disables the code which tests for
2735				broken timer IRQ sources.
2737		noisapnp	[ISAPNP] Disables ISA PnP code.
2739		noinitrd	[RAM] Tells the kernel not to load any configured
2740				initial RAM disk.
2742		nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
2743				remapping.
2744				[Deprecated - use intremap=off]
2746		nointroute	[IA-64]
2748		noinvpcid	[X86] Disable the INVPCID cpu feature.
2750		nojitter	[IA-64] Disables jitter checking for ITC timers.
2752		no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
2754		no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
2755				fault handling.
2757		no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
2758				steal time is computed, but won't influence scheduler
2759				behaviour
2761		nolapic		[X86-32,APIC] Do not enable or use the local APIC.
2763		nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2765		noltlbs		[PPC] Do not use large page/tlb entries for kernel
2766				lowmem mapping on PPC40x and PPC8xx
2768		nomca		[IA-64] Disable machine check abort handling
2770		nomce		[X86-32] Disable Machine Check Exception
2772		nomfgpt		[X86-32] Disable Multi-Function General Purpose
2773				Timer usage (for AMD Geode machines).
2775		nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
2776				shutdown the other cpus.  Instead use the REBOOT_VECTOR
2777				irq.
2779		nomodule	Disable module load
2781		nopat		[X86] Disable PAT (page attribute table extension of
2782				pagetables) support.
2784		norandmaps	Don't use address space randomization.  Equivalent to
2785				echo 0 > /proc/sys/kernel/randomize_va_space
2787		noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2789		noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2790				with UP alternatives
2792		nordrand	[X86] Disable kernel use of the RDRAND and
2793				RDSEED instructions even if they are supported
2794				by the processor.  RDRAND and RDSEED are still
2795				available to user space applications.
2797		noresume	[SWSUSP] Disables resume and restores original swap
2798				space.
2800		no-scroll	[VGA] Disables scrollback.
2801				This is required for the Braillex ib80-piezo Braille
2802				reader made by F.H. Papenmeier (Germany).
2804		nosbagart	[IA-64]
2806		nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2808		nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
2809				and disable the IO APIC.  legacy for "maxcpus=0".
2811		nosoftlockup	[KNL] Disable the soft-lockup detector.
2813		nosync		[HW,M68K] Disables sync negotiation for all devices.
2815		notsc		[BUGS=X86-32] Disable Time Stamp Counter
2817		nowatchdog	[KNL] Disable both lockup detectors, i.e.
2818	                        soft-lockup and NMI watchdog (hard-lockup).
2820		nowb		[ARM]
2822		nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
2824		cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
2826				Some features depend on CPU0. Known dependencies are:
2827				1. Resume from suspend/hibernate depends on CPU0.
2828				Suspend/hibernate will fail if CPU0 is offline and you
2829				need to online CPU0 before suspend/hibernate.
2830				2. PIC interrupts also depend on CPU0. CPU0 can't be
2831				removed if a PIC interrupt is detected.
2832				It's said poweroff/reboot may depend on CPU0 on some
2833				machines although I haven't seen such issues so far
2834				after CPU0 is offline on a few tested machines.
2835				If the dependencies are under your control, you can
2836				turn on cpu0_hotplug.
2838		nptcg=		[IA-64] Override max number of concurrent global TLB
2839				purges which is reported from either PAL_VM_SUMMARY or
2840				SAL PALO.
2842		nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
2843				could support.  nr_cpus=n : n >= 1 limits the kernel to
2844				support 'n' processors. It could be larger than the
2845				number of already plugged CPU during bootup, later in
2846				runtime you can physically add extra cpu until it reaches
2847				n. So during boot up some boot time memory for per-cpu
2848				variables need be pre-allocated for later physical cpu
2849				hot plugging.
2851		nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
2853		numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
2854				Allowed values are enable and disable
2856		numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2857				one of ['zone', 'node', 'default'] can be specified
2858				This can be set from sysctl after boot.
2859				See Documentation/sysctl/vm.txt for details.
2861		ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
2862				See Documentation/debugging-via-ohci1394.txt for more
2863				info.
2865		olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2866				Rather than timing out after 20 ms if an EC
2867				command is not properly ACKed, override the length
2868				of the timeout.  We have interrupts disabled while
2869				waiting for the ACK, so if this is set too high
2870				interrupts *may* be lost!
2872		omap_mux=	[OMAP] Override bootloader pin multiplexing.
2873				Format: <mux_mode0.mode_name=value>...
2874				For example, to override I2C bus2:
2875				omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2877		oprofile.timer=	[HW]
2878				Use timer interrupt instead of performance counters
2880		oprofile.cpu_type=	Force an oprofile cpu type
2881				This might be useful if you have an older oprofile
2882				userland or if you want common events.
2883				Format: { arch_perfmon }
2884				arch_perfmon: [X86] Force use of architectural
2885					perfmon on Intel CPUs instead of the
2886					CPU specific event set.
2887				timer: [X86] Force use of architectural NMI
2888					timer mode (see also oprofile.timer
2889					for generic hr timer mode)
2891		oops=panic	Always panic on oopses. Default is to just kill the
2892				process, but there is a small probability of
2893				deadlocking the machine.
2894				This will also cause panics on machine check exceptions.
2895				Useful together with panic=30 to trigger a reboot.
2897		OSS		[HW,OSS]
2898				See Documentation/sound/oss/oss-parameters.txt
2900		page_owner=	[KNL] Boot-time page_owner enabling option.
2901				Storage of the information about who allocated
2902				each page is disabled in default. With this switch,
2903				we can turn it on.
2904				on: enable the feature
2906		page_poison=	[KNL] Boot-time parameter changing the state of
2907				poisoning on the buddy allocator.
2908				off: turn off poisoning
2909				on: turn on poisoning
2911		panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2912				timeout > 0: seconds before rebooting
2913				timeout = 0: wait forever
2914				timeout < 0: reboot immediately
2915				Format: <timeout>
2917		panic_on_warn	panic() instead of WARN().  Useful to cause kdump
2918				on a WARN().
2920		crash_kexec_post_notifiers
2921				Run kdump after running panic-notifiers and dumping
2922				kmsg. This only for the users who doubt kdump always
2923				succeeds in any situation.
2924				Note that this also increases risks of kdump failure,
2925				because some panic notifiers can make the crashed
2926				kernel more unstable.
2928		parkbd.port=	[HW] Parallel port number the keyboard adapter is
2929				connected to, default is 0.
2930				Format: <parport#>
2931		parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
2932				0 for XT, 1 for AT (default is AT).
2933				Format: <mode>
2935		parport=	[HW,PPT] Specify parallel ports. 0 disables.
2936				Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2937				Use 'auto' to force the driver to use any
2938				IRQ/DMA settings detected (the default is to
2939				ignore detected IRQ/DMA settings because of
2940				possible conflicts). You can specify the base
2941				address, IRQ, and DMA settings; IRQ and DMA
2942				should be numbers, or 'auto' (for using detected
2943				settings on that particular port), or 'nofifo'
2944				(to avoid using a FIFO even if it is detected).
2945				Parallel ports are assigned in the order they
2946				are specified on the command line, starting
2947				with parport0.
2949		parport_init_mode=	[HW,PPT]
2950				Configure VIA parallel port to operate in
2951				a specific mode. This is necessary on Pegasos
2952				computer where firmware has no options for setting
2953				up parallel port mode and sets it to spp.
2954				Currently this function knows 686a and 8231 chips.
2955				Format: [spp|ps2|epp|ecp|ecpepp]
2957		pause_on_oops=
2958				Halt all CPUs after the first oops has been printed for
2959				the specified number of seconds.  This is to be used if
2960				your oopses keep scrolling off the screen.
2962		pcbit=		[HW,ISDN]
2964		pcd.		[PARIDE]
2965				See header of drivers/block/paride/pcd.c.
2966				See also Documentation/blockdev/paride.txt.
2968		pci=option[,option...]	[PCI] various PCI subsystem options:
2969			earlydump	[X86] dump PCI config space before the kernel
2970				        changes anything
2971			off		[X86] don't probe for the PCI bus
2972			bios		[X86-32] force use of PCI BIOS, don't access
2973					the hardware directly. Use this if your machine
2974					has a non-standard PCI host bridge.
2975			nobios		[X86-32] disallow use of PCI BIOS, only direct
2976					hardware access methods are allowed. Use this
2977					if you experience crashes upon bootup and you
2978					suspect they are caused by the BIOS.
2979			conf1		[X86] Force use of PCI Configuration Access
2980					Mechanism 1 (config address in IO port 0xCF8,
2981					data in IO port 0xCFC, both 32-bit).
2982			conf2		[X86] Force use of PCI Configuration Access
2983					Mechanism 2 (IO port 0xCF8 is an 8-bit port for
2984					the function, IO port 0xCFA, also 8-bit, sets
2985					bus number. The config space is then accessed
2986					through ports 0xC000-0xCFFF).
2987					See http://wiki.osdev.org/PCI for more info
2988					on the configuration access mechanisms.
2989			noaer		[PCIE] If the PCIEAER kernel config parameter is
2990					enabled, this kernel boot option can be used to
2991					disable the use of PCIE advanced error reporting.
2992			nodomains	[PCI] Disable support for multiple PCI
2993					root domains (aka PCI segments, in ACPI-speak).
2994			nommconf	[X86] Disable use of MMCONFIG for PCI
2995					Configuration
2996			check_enable_amd_mmconf [X86] check for and enable
2997					properly configured MMIO access to PCI
2998					config space on AMD family 10h CPU
2999			nomsi		[MSI] If the PCI_MSI kernel config parameter is
3000					enabled, this kernel boot option can be used to
3001					disable the use of MSI interrupts system-wide.
3002			noioapicquirk	[APIC] Disable all boot interrupt quirks.
3003					Safety option to keep boot IRQs enabled. This
3004					should never be necessary.
3005			ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
3006					primary IO-APIC for bridges that cannot disable
3007					boot IRQs. This fixes a source of spurious IRQs
3008					when the system masks IRQs.
3009			noioapicreroute	[APIC] Disable workaround that uses the
3010					boot IRQ equivalent of an IRQ that connects to
3011					a chipset where boot IRQs cannot be disabled.
3012					The opposite of ioapicreroute.
3013			biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
3014					routing table. These calls are known to be buggy
3015					on several machines and they hang the machine
3016					when used, but on other computers it's the only
3017					way to get the interrupt routing table. Try
3018					this option if the kernel is unable to allocate
3019					IRQs or discover secondary PCI buses on your
3020					motherboard.
3021			rom		[X86] Assign address space to expansion ROMs.
3022					Use with caution as certain devices share
3023					address decoders between ROMs and other
3024					resources.
3025			norom		[X86] Do not assign address space to
3026					expansion ROMs that do not already have
3027					BIOS assigned address ranges.
3028			nobar		[X86] Do not assign address space to the
3029					BARs that weren't assigned by the BIOS.
3030			irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
3031					assigned automatically to PCI devices. You can
3032					make the kernel exclude IRQs of your ISA cards
3033					this way.
3034			pirqaddr=0xAAAAA	[X86] Specify the physical address
3035					of the PIRQ table (normally generated
3036					by the BIOS) if it is outside the
3037					F0000h-100000h range.
3038			lastbus=N	[X86] Scan all buses thru bus #N. Can be
3039					useful if the kernel is unable to find your
3040					secondary buses and you want to tell it
3041					explicitly which ones they are.
3042			assign-busses	[X86] Always assign all PCI bus
3043					numbers ourselves, overriding
3044					whatever the firmware may have done.
3045			usepirqmask	[X86] Honor the possible IRQ mask stored
3046					in the BIOS $PIR table. This is needed on
3047					some systems with broken BIOSes, notably
3048					some HP Pavilion N5400 and Omnibook XE3
3049					notebooks. This will have no effect if ACPI
3050					IRQ routing is enabled.
3051			noacpi		[X86] Do not use ACPI for IRQ routing
3052					or for PCI scanning.
3053			use_crs		[X86] Use PCI host bridge window information
3054					from ACPI.  On BIOSes from 2008 or later, this
3055					is enabled by default.  If you need to use this,
3056					please report a bug.
3057			nocrs		[X86] Ignore PCI host bridge windows from ACPI.
3058				        If you need to use this, please report a bug.
3059			routeirq	Do IRQ routing for all PCI devices.
3060					This is normally done in pci_enable_device(),
3061					so this option is a temporary workaround
3062					for broken drivers that don't call it.
3063			skip_isa_align	[X86] do not align io start addr, so can
3064					handle more pci cards
3065			noearly		[X86] Don't do any early type 1 scanning.
3066					This might help on some broken boards which
3067					machine check when some devices' config space
3068					is read. But various workarounds are disabled
3069					and some IOMMU drivers will not work.
3070			bfsort		Sort PCI devices into breadth-first order.
3071					This sorting is done to get a device
3072					order compatible with older (<= 2.4) kernels.
3073			nobfsort	Don't sort PCI devices into breadth-first order.
3074			pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
3075					tuning and use the BIOS-configured MPS defaults.
3076			pcie_bus_safe	Set every device's MPS to the largest value
3077					supported by all devices below the root complex.
3078			pcie_bus_perf	Set device MPS to the largest allowable MPS
3079					based on its parent bus. Also set MRRS (Max
3080					Read Request Size) to the largest supported
3081					value (no larger than the MPS that the device
3082					or bus can support) for best performance.
3083			pcie_bus_peer2peer	Set every device's MPS to 128B, which
3084					every device is guaranteed to support. This
3085					configuration allows peer-to-peer DMA between
3086					any pair of devices, possibly at the cost of
3087					reduced performance.  This also guarantees
3088					that hot-added devices will work.
3089			cbiosize=nn[KMG]	The fixed amount of bus space which is
3090					reserved for the CardBus bridge's IO window.
3091					The default value is 256 bytes.
3092			cbmemsize=nn[KMG]	The fixed amount of bus space which is
3093					reserved for the CardBus bridge's memory
3094					window. The default value is 64 megabytes.
3095			resource_alignment=
3096					Format:
3097					[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
3098					[<order of align>@]pci:<vendor>:<device>\
3099							[:<subvendor>:<subdevice>][; ...]
3100					Specifies alignment and device to reassign
3101					aligned memory resources.
3102					If <order of align> is not specified,
3103					PAGE_SIZE is used as alignment.
3104					PCI-PCI bridge can be specified, if resource
3105					windows need to be expanded.
3106					To specify the alignment for several
3107					instances of a device, the PCI vendor,
3108					device, subvendor, and subdevice may be
3109					specified, e.g., 4096@pci:8086:9c22:103c:198f
3110			ecrc=		Enable/disable PCIe ECRC (transaction layer
3111					end-to-end CRC checking).
3112					bios: Use BIOS/firmware settings. This is the
3113					the default.
3114					off: Turn ECRC off
3115					on: Turn ECRC on.
3116			hpiosize=nn[KMG]	The fixed amount of bus space which is
3117					reserved for hotplug bridge's IO window.
3118					Default size is 256 bytes.
3119			hpmemsize=nn[KMG]	The fixed amount of bus space which is
3120					reserved for hotplug bridge's memory window.
3121					Default size is 2 megabytes.
3122			hpbussize=nn	The minimum amount of additional bus numbers
3123					reserved for buses below a hotplug bridge.
3124					Default is 1.
3125			realloc=	Enable/disable reallocating PCI bridge resources
3126					if allocations done by BIOS are too small to
3127					accommodate resources required by all child
3128					devices.
3129					off: Turn realloc off
3130					on: Turn realloc on
3131			realloc		same as realloc=on
3132			noari		do not use PCIe ARI.
3133			pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
3134					only look for one device below a PCIe downstream
3135					port.
3137		pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
3138				Management.
3139			off	Disable ASPM.
3140			force	Enable ASPM even on devices that claim not to support it.
3141				WARNING: Forcing ASPM on may cause system lockups.
3143		pcie_hp=	[PCIE] PCI Express Hotplug driver options:
3144			nomsi	Do not use MSI for PCI Express Native Hotplug (this
3145				makes all PCIe ports use INTx for hotplug services).
3147		pcie_ports=	[PCIE] PCIe ports handling:
3148			auto	Ask the BIOS whether or not to use native PCIe services
3149				associated with PCIe ports (PME, hot-plug, AER).  Use
3150				them only if that is allowed by the BIOS.
3151			native	Use native PCIe services associated with PCIe ports
3152				unconditionally.
3153			compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
3154				ports driver.
3156		pcie_port_pm=	[PCIE] PCIe port power management handling:
3157			off	Disable power management of all PCIe ports
3158			force	Forcibly enable power management of all PCIe ports
3160		pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
3161			nomsi	Do not use MSI for native PCIe PME signaling (this makes
3162				all PCIe root ports use INTx for all services).
3164		pcmv=		[HW,PCMCIA] BadgePAD 4
3166		pd_ignore_unused
3167				[PM]
3168				Keep all power-domains already enabled by bootloader on,
3169				even if no driver has claimed them. This is useful
3170				for debug and development, but should not be
3171				needed on a platform with proper driver support.
3173		pd.		[PARIDE]
3174				See Documentation/blockdev/paride.txt.
3176		pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
3177				boot time.
3178				Format: { 0 | 1 }
3179				See arch/parisc/kernel/pdc_chassis.c
3181		percpu_alloc=	Select which percpu first chunk allocator to use.
3182				Currently supported values are "embed" and "page".
3183				Archs may support subset or none of the	selections.
3184				See comments in mm/percpu.c for details on each
3185				allocator.  This parameter is primarily	for debugging
3186				and performance comparison.
3188		pf.		[PARIDE]
3189				See Documentation/blockdev/paride.txt.
3191		pg.		[PARIDE]
3192				See Documentation/blockdev/paride.txt.
3194		pirq=		[SMP,APIC] Manual mp-table setup
3195				See Documentation/x86/i386/IO-APIC.txt.
3197		plip=		[PPT,NET] Parallel port network link
3198				Format: { parport<nr> | timid | 0 }
3199				See also Documentation/parport.txt.
3201		pmtmr=		[X86] Manual setup of pmtmr I/O Port.
3202				Override pmtimer IOPort with a hex value.
3203				e.g. pmtmr=0x508
3205		pnp.debug=1	[PNP]
3206				Enable PNP debug messages (depends on the
3207				CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
3208				via /sys/module/pnp/parameters/debug.  We always show
3209				current resource usage; turning this on also shows
3210				possible settings and some assignment information.
3212		pnpacpi=	[ACPI]
3213				{ off }
3215		pnpbios=	[ISAPNP]
3216				{ on | off | curr | res | no-curr | no-res }
3218		pnp_reserve_irq=
3219				[ISAPNP] Exclude IRQs for the autoconfiguration
3221		pnp_reserve_dma=
3222				[ISAPNP] Exclude DMAs for the autoconfiguration
3224		pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
3225				Ranges are in pairs (I/O port base and size).
3227		pnp_reserve_mem=
3228				[ISAPNP] Exclude memory regions for the
3229				autoconfiguration.
3230				Ranges are in pairs (memory base and size).
3232		ports=		[IP_VS_FTP] IPVS ftp helper module
3233				Default is 21.
3234				Up to 8 (IP_VS_APP_MAX_PORTS) ports
3235				may be specified.
3236				Format: <port>,<port>....
3238		ppc_strict_facility_enable
3239				[PPC] This option catches any kernel floating point,
3240				Altivec, VSX and SPE outside of regions specifically
3241				allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
3242				There is some performance impact when enabling this.
3244		print-fatal-signals=
3245				[KNL] debug: print fatal signals
3247				If enabled, warn about various signal handling
3248				related application anomalies: too many signals,
3249				too many POSIX.1 timers, fatal signals causing a
3250				coredump - etc.
3252				If you hit the warning due to signal overflow,
3253				you might want to try "ulimit -i unlimited".
3255				default: off.
3257		printk.always_kmsg_dump=
3258				Trigger kmsg_dump for cases other than kernel oops or
3259				panics
3260				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
3261				default: disabled
3263		printk.devkmsg={on,off,ratelimit}
3264				Control writing to /dev/kmsg.
3265				on - unlimited logging to /dev/kmsg from userspace
3266				off - logging to /dev/kmsg disabled
3267				ratelimit - ratelimit the logging
3268				Default: ratelimit
3270		printk.time=	Show timing data prefixed to each printk message line
3271				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
3273		processor.max_cstate=	[HW,ACPI]
3274				Limit processor to maximum C-state
3275				max_cstate=9 overrides any DMI blacklist limit.
3277		processor.nocst	[HW,ACPI]
3278				Ignore the _CST method to determine C-states,
3279				instead using the legacy FADT method
3281		profile=	[KNL] Enable kernel profiling via /proc/profile
3282				Format: [schedule,]<number>
3283				Param: "schedule" - profile schedule points.
3284				Param: <number> - step/bucket size as a power of 2 for
3285					statistical time based profiling.
3286				Param: "sleep" - profile D-state sleeping (millisecs).
3287					Requires CONFIG_SCHEDSTATS
3288				Param: "kvm" - profile VM exits.
3290		prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
3291				before loading.
3292				See Documentation/blockdev/ramdisk.txt.
3294		psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
3295				probe for; one of (bare|imps|exps|lifebook|any).
3296		psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
3297				per second.
3298		psmouse.resetafter=	[HW,MOUSE]
3299				Try to reset the device after so many bad packets
3300				(0 = never).
3301		psmouse.resolution=
3302				[HW,MOUSE] Set desired mouse resolution, in dpi.
3303		psmouse.smartscroll=
3304				[HW,MOUSE] Controls Logitech smartscroll autorepeat.
3305				0 = disabled, 1 = enabled (default).
3307		pstore.backend=	Specify the name of the pstore backend to use
3309		pt.		[PARIDE]
3310				See Documentation/blockdev/paride.txt.
3312		pty.legacy_count=
3313				[KNL] Number of legacy pty's. Overwrites compiled-in
3314				default number.
3316		quiet		[KNL] Disable most log messages
3318		r128=		[HW,DRM]
3320		raid=		[HW,RAID]
3321				See Documentation/md.txt.
3323		ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
3324				See Documentation/blockdev/ramdisk.txt.
3326		rcu_nocbs=	[KNL]
3327				The argument is a cpu list, as described above.
3329				In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3330				the specified list of CPUs to be no-callback CPUs.
3331				Invocation of these CPUs' RCU callbacks will
3332				be offloaded to "rcuox/N" kthreads created for
3333				that purpose, where "x" is "b" for RCU-bh, "p"
3334				for RCU-preempt, and "s" for RCU-sched, and "N"
3335				is the CPU number.  This reduces OS jitter on the
3336				offloaded CPUs, which can be useful for HPC and
3337				real-time workloads.  It can also improve energy
3338				efficiency for asymmetric multiprocessors.
3340		rcu_nocb_poll	[KNL]
3341				Rather than requiring that offloaded CPUs
3342				(specified by rcu_nocbs= above) explicitly
3343				awaken the corresponding "rcuoN" kthreads,
3344				make these kthreads poll for callbacks.
3345				This improves the real-time response for the
3346				offloaded CPUs by relieving them of the need to
3347				wake up the corresponding kthread, but degrades
3348				energy efficiency by requiring that the kthreads
3349				periodically wake up to do the polling.
3351		rcutree.blimit=	[KNL]
3352				Set maximum number of finished RCU callbacks to
3353				process in one batch.
3355		rcutree.dump_tree=	[KNL]
3356				Dump the structure of the rcu_node combining tree
3357				out at early boot.  This is used for diagnostic
3358				purposes, to verify correct tree setup.
3360		rcutree.gp_cleanup_delay=	[KNL]
3361				Set the number of jiffies to delay each step of
3362				RCU grace-period cleanup.  This only has effect
3365		rcutree.gp_init_delay=	[KNL]
3366				Set the number of jiffies to delay each step of
3367				RCU grace-period initialization.  This only has
3369				is set.
3371		rcutree.gp_preinit_delay=	[KNL]
3372				Set the number of jiffies to delay each step of
3373				RCU grace-period pre-initialization, that is,
3374				the propagation of recent CPU-hotplug changes up
3375				the rcu_node combining tree.  This only has effect
3378		rcutree.rcu_fanout_exact= [KNL]
3379				Disable autobalancing of the rcu_node combining
3380				tree.  This is used by rcutorture, and might
3381				possibly be useful for architectures having high
3382				cache-to-cache transfer latencies.
3384		rcutree.rcu_fanout_leaf= [KNL]
3385				Change the number of CPUs assigned to each
3386				leaf rcu_node structure.  Useful for very
3387				large systems, which will choose the value 64,
3388				and for NUMA systems with large remote-access
3389				latencies, which will choose a value aligned
3390				with the appropriate hardware boundaries.
3392		rcutree.jiffies_till_sched_qs= [KNL]
3393				Set required age in jiffies for a
3394				given grace period before RCU starts
3395				soliciting quiescent-state help from
3396				rcu_note_context_switch().
3398		rcutree.jiffies_till_first_fqs= [KNL]
3399				Set delay from grace-period initialization to
3400				first attempt to force quiescent states.
3401				Units are jiffies, minimum value is zero,
3402				and maximum value is HZ.
3404		rcutree.jiffies_till_next_fqs= [KNL]
3405				Set delay between subsequent attempts to force
3406				quiescent states.  Units are jiffies, minimum
3407				value is one, and maximum value is HZ.
3409		rcutree.kthread_prio= 	 [KNL,BOOT]
3410				Set the SCHED_FIFO priority of the RCU per-CPU
3411				kthreads (rcuc/N). This value is also used for
3412				the priority of the RCU boost threads (rcub/N)
3413				and for the RCU grace-period kthreads (rcu_bh,
3414				rcu_preempt, and rcu_sched). If RCU_BOOST is
3415				set, valid values are 1-99 and the default is 1
3416				(the least-favored priority).  Otherwise, when
3417				RCU_BOOST is not set, valid values are 0-99 and
3418				the default is zero (non-realtime operation).
3420		rcutree.rcu_nocb_leader_stride= [KNL]
3421				Set the number of NOCB kthread groups, which
3422				defaults to the square root of the number of
3423				CPUs.  Larger numbers reduces the wakeup overhead
3424				on the per-CPU grace-period kthreads, but increases
3425				that same overhead on each group's leader.
3427		rcutree.qhimark= [KNL]
3428				Set threshold of queued RCU callbacks beyond which
3429				batch limiting is disabled.
3431		rcutree.qlowmark= [KNL]
3432				Set threshold of queued RCU callbacks below which
3433				batch limiting is re-enabled.
3435		rcutree.rcu_idle_gp_delay= [KNL]
3436				Set wakeup interval for idle CPUs that have
3437				RCU callbacks (RCU_FAST_NO_HZ=y).
3439		rcutree.rcu_idle_lazy_gp_delay= [KNL]
3440				Set wakeup interval for idle CPUs that have
3441				only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3442				Lazy RCU callbacks are those which RCU can
3443				prove do nothing more than free memory.
3445		rcuperf.gp_exp= [KNL]
3446				Measure performance of expedited synchronous
3447				grace-period primitives.
3449		rcuperf.holdoff= [KNL]
3450				Set test-start holdoff period.  The purpose of
3451				this parameter is to delay the start of the
3452				test until boot completes in order to avoid
3453				interference.
3455		rcuperf.nreaders= [KNL]
3456				Set number of RCU readers.  The value -1 selects
3457				N, where N is the number of CPUs.  A value
3458				"n" less than -1 selects N-n+1, where N is again
3459				the number of CPUs.  For example, -2 selects N
3460				(the number of CPUs), -3 selects N+1, and so on.
3461				A value of "n" less than or equal to -N selects
3462				a single reader.
3464		rcuperf.nwriters= [KNL]
3465				Set number of RCU writers.  The values operate
3466				the same as for rcuperf.nreaders.
3467				N, where N is the number of CPUs
3469		rcuperf.perf_runnable= [BOOT]
3470				Start rcuperf running at boot time.
3472		rcuperf.shutdown= [KNL]
3473				Shut the system down after performance tests
3474				complete.  This is useful for hands-off automated
3475				testing.
3477		rcuperf.perf_type= [KNL]
3478				Specify the RCU implementation to test.
3480		rcuperf.verbose= [KNL]
3481				Enable additional printk() statements.
3483		rcutorture.cbflood_inter_holdoff= [KNL]
3484				Set holdoff time (jiffies) between successive
3485				callback-flood tests.
3487		rcutorture.cbflood_intra_holdoff= [KNL]
3488				Set holdoff time (jiffies) between successive
3489				bursts of callbacks within a given callback-flood
3490				test.
3492		rcutorture.cbflood_n_burst= [KNL]
3493				Set the number of bursts making up a given
3494				callback-flood test.  Set this to zero to
3495				disable callback-flood testing.
3497		rcutorture.cbflood_n_per_burst= [KNL]
3498				Set the number of callbacks to be registered
3499				in a given burst of a callback-flood test.
3501		rcutorture.fqs_duration= [KNL]
3502				Set duration of force_quiescent_state bursts
3503				in microseconds.
3505		rcutorture.fqs_holdoff= [KNL]
3506				Set holdoff time within force_quiescent_state bursts
3507				in microseconds.
3509		rcutorture.fqs_stutter= [KNL]
3510				Set wait time between force_quiescent_state bursts
3511				in seconds.
3513		rcutorture.gp_cond= [KNL]
3514				Use conditional/asynchronous update-side
3515				primitives, if available.
3517		rcutorture.gp_exp= [KNL]
3518				Use expedited update-side primitives, if available.
3520		rcutorture.gp_normal= [KNL]
3521				Use normal (non-expedited) asynchronous
3522				update-side primitives, if available.
3524		rcutorture.gp_sync= [KNL]
3525				Use normal (non-expedited) synchronous
3526				update-side primitives, if available.  If all
3527				of rcutorture.gp_cond=, rcutorture.gp_exp=,
3528				rcutorture.gp_normal=, and rcutorture.gp_sync=
3529				are zero, rcutorture acts as if is interpreted
3530				they are all non-zero.
3532		rcutorture.n_barrier_cbs= [KNL]
3533				Set callbacks/threads for rcu_barrier() testing.
3535		rcutorture.nfakewriters= [KNL]
3536				Set number of concurrent RCU writers.  These just
3537				stress RCU, they don't participate in the actual
3538				test, hence the "fake".
3540		rcutorture.nreaders= [KNL]
3541				Set number of RCU readers.  The value -1 selects
3542				N-1, where N is the number of CPUs.  A value
3543				"n" less than -1 selects N-n-2, where N is again
3544				the number of CPUs.  For example, -2 selects N
3545				(the number of CPUs), -3 selects N+1, and so on.
3547		rcutorture.object_debug= [KNL]
3548				Enable debug-object double-call_rcu() testing.
3550		rcutorture.onoff_holdoff= [KNL]
3551				Set time (s) after boot for CPU-hotplug testing.
3553		rcutorture.onoff_interval= [KNL]
3554				Set time (s) between CPU-hotplug operations, or
3555				zero to disable CPU-hotplug testing.
3557		rcutorture.shuffle_interval= [KNL]
3558				Set task-shuffle interval (s).  Shuffling tasks
3559				allows some CPUs to go into dyntick-idle mode
3560				during the rcutorture test.
3562		rcutorture.shutdown_secs= [KNL]
3563				Set time (s) after boot system shutdown.  This
3564				is useful for hands-off automated testing.
3566		rcutorture.stall_cpu= [KNL]
3567				Duration of CPU stall (s) to test RCU CPU stall
3568				warnings, zero to disable.
3570		rcutorture.stall_cpu_holdoff= [KNL]
3571				Time to wait (s) after boot before inducing stall.
3573		rcutorture.stat_interval= [KNL]
3574				Time (s) between statistics printk()s.
3576		rcutorture.stutter= [KNL]
3577				Time (s) to stutter testing, for example, specifying
3578				five seconds causes the test to run for five seconds,
3579				wait for five seconds, and so on.  This tests RCU's
3580				ability to transition abruptly to and from idle.
3582		rcutorture.test_boost= [KNL]
3583				Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
3584				"Maybe" means test if the RCU implementation
3585				under test support RCU priority boosting.
3587		rcutorture.test_boost_duration= [KNL]
3588				Duration (s) of each individual boost test.
3590		rcutorture.test_boost_interval= [KNL]
3591				Interval (s) between each boost test.
3593		rcutorture.test_no_idle_hz= [KNL]
3594				Test RCU's dyntick-idle handling.  See also the
3595				rcutorture.shuffle_interval parameter.
3597		rcutorture.torture_runnable= [BOOT]
3598				Start rcutorture running at boot time.
3600		rcutorture.torture_type= [KNL]
3601				Specify the RCU implementation to test.
3603		rcutorture.verbose= [KNL]
3604				Enable additional printk() statements.
3606		rcupdate.rcu_cpu_stall_suppress= [KNL]
3607				Suppress RCU CPU stall warning messages.
3609		rcupdate.rcu_cpu_stall_timeout= [KNL]
3610				Set timeout for RCU CPU stall warning messages.
3612		rcupdate.rcu_expedited= [KNL]
3613				Use expedited grace-period primitives, for
3614				example, synchronize_rcu_expedited() instead
3615				of synchronize_rcu().  This reduces latency,
3616				but can increase CPU utilization, degrade
3617				real-time latency, and degrade energy efficiency.
3618				No effect on CONFIG_TINY_RCU kernels.
3620		rcupdate.rcu_normal= [KNL]
3621				Use only normal grace-period primitives,
3622				for example, synchronize_rcu() instead of
3623				synchronize_rcu_expedited().  This improves
3624				real-time latency, CPU utilization, and
3625				energy efficiency, but can expose users to
3626				increased grace-period latency.  This parameter
3627				overrides rcupdate.rcu_expedited.  No effect on
3628				CONFIG_TINY_RCU kernels.
3630		rcupdate.rcu_normal_after_boot= [KNL]
3631				Once boot has completed (that is, after
3632				rcu_end_inkernel_boot() has been invoked), use
3633				only normal grace-period primitives.  No effect
3634				on CONFIG_TINY_RCU kernels.
3636		rcupdate.rcu_task_stall_timeout= [KNL]
3637				Set timeout in jiffies for RCU task stall warning
3638				messages.  Disable with a value less than or equal
3639				to zero.
3641		rcupdate.rcu_self_test= [KNL]
3642				Run the RCU early boot self tests
3644		rcupdate.rcu_self_test_bh= [KNL]
3645				Run the RCU bh early boot self tests
3647		rcupdate.rcu_self_test_sched= [KNL]
3648				Run the RCU sched early boot self tests
3650		rdinit=		[KNL]
3651				Format: <full_path>
3652				Run specified binary instead of /init from the ramdisk,
3653				used for early userspace startup. See initrd.
3655		reboot=		[KNL]
3656				Format (x86 or x86_64):
3657					[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3658					[[,]s[mp]#### \
3659					[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3660					[[,]f[orce]
3661				Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3662				      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3663				      reboot_force is either force or not specified,
3664				      reboot_cpu is s[mp]#### with #### being the processor
3665						to be used for rebooting.
3667		relax_domain_level=
3668				[KNL, SMP] Set scheduler's default relax_domain_level.
3669				See Documentation/cgroup-v1/cpusets.txt.
3671		relative_sleep_states=
3672				[SUSPEND] Use sleep state labeling where the deepest
3673				state available other than hibernation is always "mem".
3674				Format: { "0" | "1" }
3675				0 -- Traditional sleep state labels.
3676				1 -- Relative sleep state labels.
3678		reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
3680		reservetop=	[X86-32]
3681				Format: nn[KMG]
3682				Reserves a hole at the top of the kernel virtual
3683				address space.
3685		reservelow=	[X86]
3686				Format: nn[K]
3687				Set the amount of memory to reserve for BIOS at
3688				the bottom of the address space.
3690		reset_devices	[KNL] Force drivers to reset the underlying device
3691				during initialization.
3693		resume=		[SWSUSP]
3694				Specify the partition device for software suspend
3695				Format:
3696				{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3698		resume_offset=	[SWSUSP]
3699				Specify the offset from the beginning of the partition
3700				given by "resume=" at which the swap header is located,
3701				in <PAGE_SIZE> units (needed only for swap files).
3702				See  Documentation/power/swsusp-and-swap-files.txt
3704		resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
3705				read the resume files
3707		resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
3708				Useful for devices that are detected asynchronously
3709				(e.g. USB and MMC devices).
3711		hibernate=	[HIBERNATION]
3712			noresume	Don't check if there's a hibernation image
3713					present during boot.
3714			nocompress	Don't compress/decompress hibernation images.
3715			no		Disable hibernation and resume.
3716			protect_image	Turn on image protection during restoration
3717					(that will set all pages holding image data
3718					during restoration read-only).
3720		retain_initrd	[RAM] Keep initrd memory after extraction
3722		rfkill.default_state=
3723			0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
3724				etc. communication is blocked by default.
3725			1	Unblocked.
3727		rfkill.master_switch_mode=
3728			0	The "airplane mode" button does nothing.
3729			1	The "airplane mode" button toggles between everything
3730				blocked and the previous configuration.
3731			2	The "airplane mode" button toggles between everything
3732				blocked and everything unblocked.
3734		rhash_entries=	[KNL,NET]
3735				Set number of hash buckets for route cache
3737		ro		[KNL] Mount root device read-only on boot
3739		rodata=		[KNL]
3740			on	Mark read-only kernel memory as read-only (default).
3741			off	Leave read-only kernel memory writable for debugging.
3743		rockchip.usb_uart
3744				Enable the uart passthrough on the designated usb port
3745				on Rockchip SoCs. When active, the signals of the
3746				debug-uart get routed to the D+ and D- pins of the usb
3747				port and the regular usb controller gets disabled.
3749		root=		[KNL] Root filesystem
3750				See name_to_dev_t comment in init/do_mounts.c.
3752		rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
3753				mount the root filesystem
3755		rootflags=	[KNL] Set root filesystem mount option string
3757		rootfstype=	[KNL] Set root filesystem type
3759		rootwait	[KNL] Wait (indefinitely) for root device to show up.
3760				Useful for devices that are detected asynchronously
3761				(e.g. USB and MMC devices).
3763		rproc_mem=nn[KMG][@address]
3764				[KNL,ARM,CMA] Remoteproc physical memory block.
3765				Memory area to be used by remote processor image,
3766				managed by CMA.
3768		rw		[KNL] Mount root device read-write on boot
3770		S		[KNL] Run init in single mode
3772		s390_iommu=	[HW,S390]
3773				Set s390 IOTLB flushing mode
3774			strict
3775				With strict flushing every unmap operation will result in
3776				an IOTLB flush. Default is lazy flushing before reuse,
3777				which is faster.
3779		sa1100ir	[NET]
3780				See drivers/net/irda/sa1100_ir.c.
3782		sbni=		[NET] Granch SBNI12 leased line adapter
3784		sched_debug	[KNL] Enables verbose scheduler debug messages.
3786		schedstats=	[KNL,X86] Enable or disable scheduled statistics.
3787				Allowed values are enable and disable. This feature
3788				incurs a small amount of overhead in the scheduler
3789				but is useful for debugging and performance tuning.
3791		skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
3792				xtime_lock contention on larger systems, and/or RCU lock
3793				contention on all systems with CONFIG_MAXSMP set.
3794				Format: { "0" | "1" }
3795				0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3796				1 -- enable.
3797				Note: increases power consumption, thus should only be
3798				enabled if running jitter sensitive (HPC/RT) workloads.
3800		security=	[SECURITY] Choose a security module to enable at boot.
3801				If this boot parameter is not specified, only the first
3802				security module asking for security registration will be
3803				loaded. An invalid security module name will be treated
3804				as if no module has been chosen.
3806		selinux=	[SELINUX] Disable or enable SELinux at boot time.
3807				Format: { "0" | "1" }
3808				See security/selinux/Kconfig help text.
3809				0 -- disable.
3810				1 -- enable.
3811				Default value is set via kernel config option.
3812				If enabled at boot time, /selinux/disable can be used
3813				later to disable prior to initial policy load.
3815		apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
3816				Format: { "0" | "1" }
3817				See security/apparmor/Kconfig help text
3818				0 -- disable.
3819				1 -- enable.
3820				Default value is set via kernel config option.
3822		serialnumber	[BUGS=X86-32]
3824		shapers=	[NET]
3825				Maximal number of shapers.
3827		show_msr=	[x86] show boot-time MSR settings
3828				Format: { <integer> }
3829				Show boot-time (BIOS-initialized) MSR settings.
3830				The parameter means the number of CPUs to show,
3831				for example 1 means boot CPU only.
3833		simeth=		[IA-64]
3834		simscsi=
3836		slram=		[HW,MTD]
3838		slab_nomerge	[MM]
3839				Disable merging of slabs with similar size. May be
3840				necessary if there is some reason to distinguish
3841				allocs to different slabs. Debug options disable
3842				merging on their own.
3843				For more information see Documentation/vm/slub.txt.
3845		slab_max_order=	[MM, SLAB]
3846				Determines the maximum allowed order for slabs.
3847				A high setting may cause OOMs due to memory
3848				fragmentation.  Defaults to 1 for systems with
3849				more than 32MB of RAM, 0 otherwise.
3851		slub_debug[=options[,slabs]]	[MM, SLUB]
3852				Enabling slub_debug allows one to determine the
3853				culprit if slab objects become corrupted. Enabling
3854				slub_debug can create guard zones around objects and
3855				may poison objects when not in use. Also tracks the
3856				last alloc / free. For more information see
3857				Documentation/vm/slub.txt.
3859		slub_max_order= [MM, SLUB]
3860				Determines the maximum allowed order for slabs.
3861				A high setting may cause OOMs due to memory
3862				fragmentation. For more information see
3863				Documentation/vm/slub.txt.
3865		slub_min_objects=	[MM, SLUB]
3866				The minimum number of objects per slab. SLUB will
3867				increase the slab order up to slub_max_order to
3868				generate a sufficiently large slab able to contain
3869				the number of objects indicated. The higher the number
3870				of objects the smaller the overhead of tracking slabs
3871				and the less frequently locks need to be acquired.
3872				For more information see Documentation/vm/slub.txt.
3874		slub_min_order=	[MM, SLUB]
3875				Determines the minimum page order for slabs. Must be
3876				lower than slub_max_order.
3877				For more information see Documentation/vm/slub.txt.
3879		slub_nomerge	[MM, SLUB]
3880				Same with slab_nomerge. This is supported for legacy.
3881				See slab_nomerge for more information.
3883		smart2=		[HW]
3884				Format: <io1>[,<io2>[,...,<io8>]]
3886		smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
3887		smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
3888		smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
3889		smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
3890		smsc-ircc2.ircc_irq=	[HW] IRQ line
3891		smsc-ircc2.ircc_dma=	[HW] DMA channel
3892		smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3893					0: Toshiba Satellite 1800 (GP data pin select)
3894					1: Fast pin select (default)
3895					2: ATC IRMode
3897		smt		[KNL,S390] Set the maximum number of threads (logical
3898				CPUs) to use per physical CPU on systems capable of
3899				symmetric multithreading (SMT). Will be capped to the
3900				actual hardware limit.
3901				Format: <integer>
3902				Default: -1 (no limit)
3904		softlockup_panic=
3905				[KNL] Should the soft-lockup detector generate panics.
3906				Format: <integer>
3908		softlockup_all_cpu_backtrace=
3909				[KNL] Should the soft-lockup detector generate
3910				backtraces on all cpus.
3911				Format: <integer>
3913		sonypi.*=	[HW] Sony Programmable I/O Control Device driver
3914				See Documentation/laptops/sonypi.txt
3916		spia_io_base=	[HW,MTD]
3917		spia_fio_base=
3918		spia_pedr=
3919		spia_peddr=
3921		stacktrace	[FTRACE]
3922				Enabled the stack tracer on boot up.
3924		stacktrace_filter=[function-list]
3925				[FTRACE] Limit the functions that the stack tracer
3926				will trace at boot up. function-list is a comma separated
3927				list of functions. This list can be changed at run
3928				time by the stack_trace_filter file in the debugfs
3929				tracing directory. Note, this enables stack tracing
3930				and the stacktrace above is not needed.
3932		sti=		[PARISC,HW]
3933				Format: <num>
3934				Set the STI (builtin display/keyboard on the HP-PARISC
3935				machines) console (graphic card) which should be used
3936				as the initial boot-console.
3937				See also comment in drivers/video/console/sticore.c.
3939		sti_font=	[HW]
3940				See comment in drivers/video/console/sticore.c.
3942		stifb=		[HW]
3943				Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3945		sunrpc.min_resvport=
3946		sunrpc.max_resvport=
3947				[NFS,SUNRPC]
3948				SunRPC servers often require that client requests
3949				originate from a privileged port (i.e. a port in the
3950				range 0 < portnr < 1024).
3951				An administrator who wishes to reserve some of these
3952				ports for other uses may adjust the range that the
3953				kernel's sunrpc client considers to be privileged
3954				using these two parameters to set the minimum and
3955				maximum port values.
3957		sunrpc.svc_rpc_per_connection_limit=
3958				[NFS,SUNRPC]
3959				Limit the number of requests that the server will
3960				process in parallel from a single connection.
3961				The default value is 0 (no limit).
3963		sunrpc.pool_mode=
3964				[NFS]
3965				Control how the NFS server code allocates CPUs to
3966				service thread pools.  Depending on how many NICs
3967				you have and where their interrupts are bound, this
3968				option will affect which CPUs will do NFS serving.
3969				Note: this parameter cannot be changed while the
3970				NFS server is running.
3972				auto	    the server chooses an appropriate mode
3973					    automatically using heuristics
3974				global	    a single global pool contains all CPUs
3975				percpu	    one pool for each CPU
3976				pernode	    one pool for each NUMA node (equivalent
3977					    to global on non-NUMA machines)
3979		sunrpc.tcp_slot_table_entries=
3980		sunrpc.udp_slot_table_entries=
3981				[NFS,SUNRPC]
3982				Sets the upper limit on the number of simultaneous
3983				RPC calls that can be sent from the client to a
3984				server. Increasing these values may allow you to
3985				improve throughput, but will also increase the
3986				amount of memory reserved for use by the client.
3988		suspend.pm_test_delay=
3989				[SUSPEND]
3990				Sets the number of seconds to remain in a suspend test
3991				mode before resuming the system (see
3992				/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3993				is set. Default value is 5.
3995		swapaccount=[0|1]
3996				[KNL] Enable accounting of swap in memory resource
3997				controller if no parameter or 1 is given or disable
3998				it if 0 is given (See Documentation/cgroup-v1/memory.txt)
4000		swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
4001				Format: { <int> | force }
4002				<int> -- Number of I/O TLB slabs
4003				force -- force using of bounce buffers even if they
4004				         wouldn't be automatically used by the kernel
4006		switches=	[HW,M68k]
4008		sysfs.deprecated=0|1 [KNL]
4009				Enable/disable old style sysfs layout for old udev
4010				on older distributions. When this option is enabled
4011				very new udev will not work anymore. When this option
4012				is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
4013				in older udev will not work anymore.
4014				Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
4015				the kernel configuration.
4017		sysrq_always_enabled
4018				[KNL]
4019				Ignore sysrq setting - this boot parameter will
4020				neutralize any effect of /proc/sys/kernel/sysrq.
4021				Useful for debugging.
4023		tcpmhash_entries= [KNL,NET]
4024				Set the number of tcp_metrics_hash slots.
4025				Default value is 8192 or 16384 depending on total
4026				ram pages. This is used to specify the TCP metrics
4027				cache size. See Documentation/networking/ip-sysctl.txt
4028				"tcp_no_metrics_save" section for more details.
4030		tdfx=		[HW,DRM]
4032		test_suspend=	[SUSPEND][,N]
4033				Specify "mem" (for Suspend-to-RAM) or "standby" (for
4034				standby suspend) or "freeze" (for suspend type freeze)
4035				as the system sleep state during system startup with
4036				the optional capability to repeat N number of times.
4037				The system is woken from this state using a
4038				wakeup-capable RTC alarm.
4040		thash_entries=	[KNL,NET]
4041				Set number of hash buckets for TCP connection
4043		thermal.act=	[HW,ACPI]
4044				-1: disable all active trip points in all thermal zones
4045				<degrees C>: override all lowest active trip points
4047		thermal.crt=	[HW,ACPI]
4048				-1: disable all critical trip points in all thermal zones
4049				<degrees C>: override all critical trip points
4051		thermal.nocrt=	[HW,ACPI]
4052				Set to disable actions on ACPI thermal zone
4053				critical and hot trip points.
4055		thermal.off=	[HW,ACPI]
4056				1: disable ACPI thermal control
4058		thermal.psv=	[HW,ACPI]
4059				-1: disable all passive trip points
4060				<degrees C>: override all passive trip points to this
4061				value
4063		thermal.tzp=	[HW,ACPI]
4064				Specify global default ACPI thermal zone polling rate
4065				<deci-seconds>: poll all this frequency
4066				0: no polling (default)
4068		threadirqs	[KNL]
4069				Force threading of all interrupt handlers except those
4070				marked explicitly IRQF_NO_THREAD.
4072		tmem		[KNL,XEN]
4073				Enable the Transcendent memory driver if built-in.
4075		tmem.cleancache=0|1 [KNL, XEN]
4076				Default is on (1). Disable the usage of the cleancache
4077				API to send anonymous pages to the hypervisor.
4079		tmem.frontswap=0|1 [KNL, XEN]
4080				Default is on (1). Disable the usage of the frontswap
4081				API to send swap pages to the hypervisor. If disabled
4082				the selfballooning and selfshrinking are force disabled.
4084		tmem.selfballooning=0|1 [KNL, XEN]
4085				Default is on (1). Disable the driving of swap pages
4086				to the hypervisor.
4088		tmem.selfshrinking=0|1 [KNL, XEN]
4089				Default is on (1). Partial swapoff that immediately
4090				transfers pages from Xen hypervisor back to the
4091				kernel based on different criteria.
4093		topology=	[S390]
4094				Format: {off | on}
4095				Specify if the kernel should make use of the cpu
4096				topology information if the hardware supports this.
4097				The scheduler will make use of this information and
4098				e.g. base its process migration decisions on it.
4099				Default is on.
4101		topology_updates= [KNL, PPC, NUMA]
4102				Format: {off}
4103				Specify if the kernel should ignore (off)
4104				topology updates sent by the hypervisor to this
4105				LPAR.
4107		tp720=		[HW,PS2]
4109		tpm_suspend_pcr=[HW,TPM]
4110				Format: integer pcr id
4111				Specify that at suspend time, the tpm driver
4112				should extend the specified pcr with zeros,
4113				as a workaround for some chips which fail to
4114				flush the last written pcr on TPM_SaveState.
4115				This will guarantee that all the other pcrs
4116				are saved.
4118		trace_buf_size=nn[KMG]
4119				[FTRACE] will set tracing buffer size on each cpu.
4121		trace_event=[event-list]
4122				[FTRACE] Set and start specified trace events in order
4123				to facilitate early boot debugging. The event-list is a
4124				comma separated list of trace events to enable. See
4125				also Documentation/trace/events.txt
4127		trace_options=[option-list]
4128				[FTRACE] Enable or disable tracer options at boot.
4129				The option-list is a comma delimited list of options
4130				that can be enabled or disabled just as if you were
4131				to echo the option name into
4133				    /sys/kernel/debug/tracing/trace_options
4135				For example, to enable stacktrace option (to dump the
4136				stack trace of each event), add to the command line:
4138				      trace_options=stacktrace
4140				See also Documentation/trace/ftrace.txt "trace options"
4141				section.
4143		tp_printk[FTRACE]
4144				Have the tracepoints sent to printk as well as the
4145				tracing ring buffer. This is useful for early boot up
4146				where the system hangs or reboots and does not give the
4147				option for reading the tracing buffer or performing a
4148				ftrace_dump_on_oops.
4150				To turn off having tracepoints sent to printk,
4151				 echo 0 > /proc/sys/kernel/tracepoint_printk
4152				Note, echoing 1 into this file without the
4153				tracepoint_printk kernel cmdline option has no effect.
4155				** CAUTION **
4157				Having tracepoints sent to printk() and activating high
4158				frequency tracepoints such as irq or sched, can cause
4159				the system to live lock.
4161		traceoff_on_warning
4162				[FTRACE] enable this option to disable tracing when a
4163				warning is hit. This turns off "tracing_on". Tracing can
4164				be enabled again by echoing '1' into the "tracing_on"
4165				file located in /sys/kernel/debug/tracing/
4167				This option is useful, as it disables the trace before
4168				the WARNING dump is called, which prevents the trace to
4169				be filled with content caused by the warning output.
4171				This option can also be set at run time via the sysctl
4172				option:  kernel/traceoff_on_warning
4174		transparent_hugepage=
4175				[KNL]
4176				Format: [always|madvise|never]
4177				Can be used to control the default behavior of the system
4178				with respect to transparent hugepages.
4179				See Documentation/vm/transhuge.txt for more details.
4181		tsc=		Disable clocksource stability checks for TSC.
4182				Format: <string>
4183				[x86] reliable: mark tsc clocksource as reliable, this
4184				disables clocksource verification at runtime, as well
4185				as the stability checks done at bootup.	Used to enable
4186				high-resolution timer mode on older hardware, and in
4187				virtualized environment.
4188				[x86] noirqtime: Do not use TSC to do irq accounting.
4189				Used to run time disable IRQ_TIME_ACCOUNTING on any
4190				platforms where RDTSC is slow and this accounting
4191				can add overhead.
4193		turbografx.map[2|3]=	[HW,JOY]
4194				TurboGraFX parallel port interface
4195				Format:
4196				<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
4197				See also Documentation/input/joystick-parport.txt
4199		udbg-immortal	[PPC] When debugging early kernel crashes that
4200				happen after console_init() and before a proper 
4201				console driver takes over, this boot options might
4202				help "seeing" what's going on.
4204		uhash_entries=	[KNL,NET]
4205				Set number of hash buckets for UDP/UDP-Lite connections
4207		uhci-hcd.ignore_oc=
4208				[USB] Ignore overcurrent events (default N).
4209				Some badly-designed motherboards generate lots of
4210				bogus events, for ports that aren't wired to
4211				anything.  Set this parameter to avoid log spamming.
4212				Note that genuine overcurrent events won't be
4213				reported either.
4215		unknown_nmi_panic
4216				[X86] Cause panic on unknown NMI.
4218		usbcore.authorized_default=
4219				[USB] Default USB device authorization:
4220				(default -1 = authorized except for wireless USB,
4221				0 = not authorized, 1 = authorized)
4223		usbcore.autosuspend=
4224				[USB] The autosuspend time delay (in seconds) used
4225				for newly-detected USB devices (default 2).  This
4226				is the time required before an idle device will be
4227				autosuspended.  Devices for which the delay is set
4228				to a negative value won't be autosuspended at all.
4230		usbcore.usbfs_snoop=
4231				[USB] Set to log all usbfs traffic (default 0 = off).
4233		usbcore.usbfs_snoop_max=
4234				[USB] Maximum number of bytes to snoop in each URB
4235				(default = 65536).
4237		usbcore.blinkenlights=
4238				[USB] Set to cycle leds on hubs (default 0 = off).
4240		usbcore.old_scheme_first=
4241				[USB] Start with the old device initialization
4242				scheme (default 0 = off).
4244		usbcore.usbfs_memory_mb=
4245				[USB] Memory limit (in MB) for buffers allocated by
4246				usbfs (default = 16, 0 = max = 2047).
4248		usbcore.use_both_schemes=
4249				[USB] Try the other device initialization scheme
4250				if the first one fails (default 1 = enabled).
4252		usbcore.initial_descriptor_timeout=
4253				[USB] Specifies timeout for the initial 64-byte
4254	                        USB_REQ_GET_DESCRIPTOR request in milliseconds
4255				(default 5000 = 5.0 seconds).
4257		usbcore.nousb	[USB] Disable the USB subsystem
4259		usbhid.mousepoll=
4260				[USBHID] The interval which mice are to be polled at.
4262		usb-storage.delay_use=
4263				[UMS] The delay in seconds before a new device is
4264				scanned for Logical Units (default 1).
4266		usb-storage.quirks=
4267				[UMS] A list of quirks entries to supplement or
4268				override the built-in unusual_devs list.  List
4269				entries are separated by commas.  Each entry has
4270				the form VID:PID:Flags where VID and PID are Vendor
4271				and Product ID values (4-digit hex numbers) and
4272				Flags is a set of characters, each corresponding
4273				to a common usb-storage quirk flag as follows:
4274					a = SANE_SENSE (collect more than 18 bytes
4275						of sense data);
4276					b = BAD_SENSE (don't collect more than 18
4277						bytes of sense data);
4278					c = FIX_CAPACITY (decrease the reported
4279						device capacity by one sector);
4280					d = NO_READ_DISC_INFO (don't use
4281						READ_DISC_INFO command);
4282					e = NO_READ_CAPACITY_16 (don't use
4283						READ_CAPACITY_16 command);
4284					f = NO_REPORT_OPCODES (don't use report opcodes
4285						command, uas only);
4286					g = MAX_SECTORS_240 (don't transfer more than
4287						240 sectors at a time, uas only);
4288					h = CAPACITY_HEURISTICS (decrease the
4289						reported device capacity by one
4290						sector if the number is odd);
4291					i = IGNORE_DEVICE (don't bind to this
4292						device);
4293					j = NO_REPORT_LUNS (don't use report luns
4294						command, uas only);
4295					l = NOT_LOCKABLE (don't try to lock and
4296						unlock ejectable media);
4297					m = MAX_SECTORS_64 (don't transfer more
4298						than 64 sectors = 32 KB at a time);
4299					n = INITIAL_READ10 (force a retry of the
4300						initial READ(10) command);
4301					o = CAPACITY_OK (accept the capacity
4302						reported by the device);
4303					p = WRITE_CACHE (the device cache is ON
4304						by default);
4305					r = IGNORE_RESIDUE (the device reports
4306						bogus residue values);
4307					s = SINGLE_LUN (the device has only one
4308						Logical Unit);
4309					t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
4310						commands, uas only);
4311					u = IGNORE_UAS (don't bind to the uas driver);
4312					w = NO_WP_DETECT (don't test whether the
4313						medium is write-protected).
4315						even if the device claims no cache)
4316				Example: quirks=0419:aaf5:rl,0421:0433:rc
4318		user_debug=	[KNL,ARM]
4319				Format: <int>
4320				See arch/arm/Kconfig.debug help text.
4321					 1 - undefined instruction events
4322					 2 - system calls
4323					 4 - invalid data aborts
4324					 8 - SIGSEGV faults
4325					16 - SIGBUS faults
4326				Example: user_debug=31
4328		userpte=
4329				[X86] Flags controlling user PTE allocations.
4331					nohigh = do not allocate PTE pages in
4332						HIGHMEM regardless of setting
4333						of CONFIG_HIGHPTE.
4335		vdso=		[X86,SH]
4336				On X86_32, this is an alias for vdso32=.  Otherwise:
4338				vdso=1: enable VDSO (the default)
4339				vdso=0: disable VDSO mapping
4341		vdso32=		[X86] Control the 32-bit vDSO
4342				vdso32=1: enable 32-bit VDSO
4343				vdso32=0 or vdso32=2: disable 32-bit VDSO
4345				See the help text for CONFIG_COMPAT_VDSO for more
4346				details.  If CONFIG_COMPAT_VDSO is set, the default is
4347				vdso32=0; otherwise, the default is vdso32=1.
4349				For compatibility with older kernels, vdso32=2 is an
4350				alias for vdso32=0.
4352				Try vdso32=0 if you encounter an error that says:
4353				dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
4355		vector=		[IA-64,SMP]
4356				vector=percpu: enable percpu vector domain
4358		video=		[FB] Frame buffer configuration
4359				See Documentation/fb/modedb.txt.
4361		video.brightness_switch_enabled= [0,1]
4362				If set to 1, on receiving an ACPI notify event
4363				generated by hotkey, video driver will adjust brightness
4364				level and then send out the event to user space through
4365				the allocated input device; If set to 0, video driver
4366				will only send out the event without touching backlight
4367				brightness level.
4368				default: 1
4370		virtio_mmio.device=
4371				[VMMIO] Memory mapped virtio (platform) device.
4373					<size>@<baseaddr>:<irq>[:<id>]
4374				where:
4375					<size>     := size (can use standard suffixes
4376							like K, M and G)
4377					<baseaddr> := physical base address
4378					<irq>      := interrupt number (as passed to
4379							request_irq())
4380					<id>       := (optional) platform device id
4381				example:
4382					virtio_mmio.device=1K@0x100b0000:48:7
4384				Can be used multiple times for multiple devices.
4386		vga=		[BOOT,X86-32] Select a particular video mode
4387				See Documentation/x86/boot.txt and
4388				Documentation/svga.txt.
4389				Use vga=ask for menu.
4390				This is actually a boot loader parameter; the value is
4391				passed to the kernel using a special protocol.
4393		vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
4394				size of <nn>. This can be used to increase the
4395				minimum size (128MB on x86). It can also be used to
4396				decrease the size and leave more room for directly
4397				mapped kernel RAM.
4399		vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
4400				Format: <command>
4402		vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
4403				Format: <command>
4405		vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
4406				Format: <command>
4408		vsyscall=	[X86-64]
4409				Controls the behavior of vsyscalls (i.e. calls to
4410				fixed addresses of 0xffffffffff600x00 from legacy
4411				code).  Most statically-linked binaries and older
4412				versions of glibc use these calls.  Because these
4413				functions are at fixed addresses, they make nice
4414				targets for exploits that can control RIP.
4416				emulate     [default] Vsyscalls turn into traps and are
4417				            emulated reasonably safely.
4419				native      Vsyscalls are native syscall instructions.
4420				            This is a little bit faster than trapping
4421				            and makes a few dynamic recompilers work
4422				            better than they would in emulation mode.
4423				            It also makes exploits much easier to write.
4425				none        Vsyscalls don't work at all.  This makes
4426				            them quite hard to use for exploits but
4427				            might break your system.
4429		vt.color=	[VT] Default text color.
4430				Format: 0xYX, X = foreground, Y = background.
4431				Default: 0x07 = light gray on black.
4433		vt.cur_default=	[VT] Default cursor shape.
4434				Format: 0xCCBBAA, where AA, BB, and CC are the same as
4435				the parameters of the <Esc>[?A;B;Cc escape sequence;
4436				see VGA-softcursor.txt. Default: 2 = underline.
4438		vt.default_blu=	[VT]
4439				Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4440				Change the default blue palette of the console.
4441				This is a 16-member array composed of values
4442				ranging from 0-255.
4444		vt.default_grn=	[VT]
4445				Format: <green0>,<green1>,<green2>,...,<green15>
4446				Change the default green palette of the console.
4447				This is a 16-member array composed of values
4448				ranging from 0-255.
4450		vt.default_red=	[VT]
4451				Format: <red0>,<red1>,<red2>,...,<red15>
4452				Change the default red palette of the console.
4453				This is a 16-member array composed of values
4454				ranging from 0-255.
4456		vt.default_utf8=
4457				[VT]
4458				Format=<0|1>
4459				Set system-wide default UTF-8 mode for all tty's.
4460				Default is 1, i.e. UTF-8 mode is enabled for all
4461				newly opened terminals.
4463		vt.global_cursor_default=
4464				[VT]
4465				Format=<-1|0|1>
4466				Set system-wide default for whether a cursor
4467				is shown on new VTs. Default is -1,
4468				i.e. cursors will be created by default unless
4469				overridden by individual drivers. 0 will hide
4470				cursors, 1 will display them.
4472		vt.italic=	[VT] Default color for italic text; 0-15.
4473				Default: 2 = green.
4475		vt.underline=	[VT] Default color for underlined text; 0-15.
4476				Default: 3 = cyan.
4478		watchdog timers	[HW,WDT] For information on watchdog timers,
4479				see Documentation/watchdog/watchdog-parameters.txt
4480				or other driver-specific files in the
4481				Documentation/watchdog/ directory.
4483		workqueue.watchdog_thresh=
4484				If CONFIG_WQ_WATCHDOG is configured, workqueue can
4485				warn stall conditions and dump internal state to
4486				help debugging.  0 disables workqueue stall
4487				detection; otherwise, it's the stall threshold
4488				duration in seconds.  The default value is 30 and
4489				it can be updated at runtime by writing to the
4490				corresponding sysfs file.
4492		workqueue.disable_numa
4493				By default, all work items queued to unbound
4494				workqueues are affine to the NUMA nodes they're
4495				issued on, which results in better behavior in
4496				general.  If NUMA affinity needs to be disabled for
4497				whatever reason, this option can be used.  Note
4498				that this also can be controlled per-workqueue for
4499				workqueues visible under /sys/bus/workqueue/.
4501		workqueue.power_efficient
4502				Per-cpu workqueues are generally preferred because
4503				they show better performance thanks to cache
4504				locality; unfortunately, per-cpu workqueues tend to
4505				be more power hungry than unbound workqueues.
4507				Enabling this makes the per-cpu workqueues which
4508				were observed to contribute significantly to power
4509				consumption unbound, leading to measurably lower
4510				power usage at the cost of small performance
4511				overhead.
4513				The default value of this parameter is determined by
4514				the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4516		workqueue.debug_force_rr_cpu
4517				Workqueue used to implicitly guarantee that work
4518				items queued without explicit CPU specified are put
4519				on the local CPU.  This guarantee is no longer true
4520				and while local CPU is still preferred work items
4521				may be put on foreign CPUs.  This debug option
4522				forces round-robin CPU selection to flush out
4523				usages which depend on the now broken guarantee.
4524				When enabled, memory and cache locality will be
4525				impacted.
4527		x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
4528				default x2apic cluster mode on platforms
4529				supporting x2apic.
4531		x86_intel_mid_timer= [X86-32,APBT]
4532				Choose timer option for x86 Intel MID platform.
4533				Two valid options are apbt timer only and lapic timer
4534				plus one apbt timer for broadcast timer.
4535				x86_intel_mid_timer=apbt_only | lapic_and_apbt
4537		xen_512gb_limit		[KNL,X86-64,XEN]
4538				Restricts the kernel running paravirtualized under Xen
4539				to use only up to 512 GB of RAM. The reason to do so is
4540				crash analysis tools and Xen tools for doing domain
4541				save/restore/migration must be enabled to handle larger
4542				domains.
4544		xen_emul_unplug=		[HW,X86,XEN]
4545				Unplug Xen emulated devices
4546				Format: [unplug0,][unplug1]
4547				ide-disks -- unplug primary master IDE devices
4548				aux-ide-disks -- unplug non-primary-master IDE devices
4549				nics -- unplug network devices
4550				all -- unplug all emulated devices (NICs and IDE disks)
4551				unnecessary -- unplugging emulated devices is
4552					unnecessary even if the host did not respond to
4553					the unplug protocol
4554				never -- do not unplug even if version check succeeds
4556		xen_nopvspin	[X86,XEN]
4557				Disables the ticketlock slowpath using Xen PV
4558				optimizations.
4560		xen_nopv	[X86]
4561				Disables the PV optimizations forcing the HVM guest to
4562				run as generic HVM guest with no PV drivers.
4564		xirc2ps_cs=	[NET,PCMCIA]
4565				Format:
4566				<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4568	______________________________________________________________________
4570	TODO:
4572		Add more DRM drivers.
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