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Based on kernel version 3.19. Page generated on 2015-02-13 21:21 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	This document may not be entirely up to date and comprehensive. The command
37	"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
38	module. Loadable modules, after being loaded into the running kernel, also
39	reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
40	parameters may be changed at runtime by the command
41	"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
43	The parameters listed below are only valid if certain kernel build options were
44	enabled and if respective hardware is present. The text in square brackets at
45	the beginning of each description states the restrictions within which a
46	parameter is applicable:
48		ACPI	ACPI support is enabled.
49		AGP	AGP (Accelerated Graphics Port) is enabled.
50		ALSA	ALSA sound support is enabled.
51		APIC	APIC support is enabled.
52		APM	Advanced Power Management support is enabled.
53		ARM	ARM architecture is enabled.
54		AVR32	AVR32 architecture is enabled.
55		AX25	Appropriate AX.25 support is enabled.
56		BLACKFIN Blackfin architecture is enabled.
57		CLK	Common clock infrastructure is enabled.
58		CMA	Contiguous Memory Area support is enabled.
59		DRM	Direct Rendering Management support is enabled.
60		DYNAMIC_DEBUG Build in debug messages and enable them at runtime
61		EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
62		EFI	EFI Partitioning (GPT) is enabled
63		EIDE	EIDE/ATAPI support is enabled.
64		EVM	Extended Verification Module
65		FB	The frame buffer device is enabled.
66		FTRACE	Function tracing enabled.
67		GCOV	GCOV profiling is enabled.
68		HW	Appropriate hardware is enabled.
69		IA-64	IA-64 architecture is enabled.
70		IMA     Integrity measurement architecture is enabled.
71		IOSCHED	More than one I/O scheduler is enabled.
72		IP_PNP	IP DHCP, BOOTP, or RARP is enabled.
73		IPV6	IPv6 support is enabled.
74		ISAPNP	ISA PnP code is enabled.
75		ISDN	Appropriate ISDN support is enabled.
76		JOY	Appropriate joystick support is enabled.
77		KGDB	Kernel debugger support is enabled.
78		KVM	Kernel Virtual Machine support is enabled.
79		LIBATA  Libata driver is enabled
80		LP	Printer support is enabled.
81		LOOP	Loopback device support is enabled.
82		M68k	M68k architecture is enabled.
83				These options have more detailed description inside of
84				Documentation/m68k/kernel-options.txt.
85		MDA	MDA console support is enabled.
86		MIPS	MIPS architecture is enabled.
87		MOUSE	Appropriate mouse support is enabled.
88		MSI	Message Signaled Interrupts (PCI).
89		MTD	MTD (Memory Technology Device) support is enabled.
90		NET	Appropriate network support is enabled.
91		NUMA	NUMA support is enabled.
92		NFS	Appropriate NFS support is enabled.
93		OSS	OSS sound support is enabled.
94		PV_OPS	A paravirtualized kernel is enabled.
95		PARIDE	The ParIDE (parallel port IDE) subsystem is enabled.
96		PARISC	The PA-RISC architecture is enabled.
97		PCI	PCI bus support is enabled.
98		PCIE	PCI Express support is enabled.
99		PCMCIA	The PCMCIA subsystem is enabled.
100		PNP	Plug & Play support is enabled.
101		PPC	PowerPC architecture is enabled.
102		PPT	Parallel port support is enabled.
103		PS2	Appropriate PS/2 support is enabled.
104		RAM	RAM disk support is enabled.
105		S390	S390 architecture is enabled.
106		SCSI	Appropriate SCSI support is enabled.
107				A lot of drivers have their options described inside
108				the Documentation/scsi/ sub-directory.
109		SECURITY Different security models are enabled.
110		SELINUX SELinux support is enabled.
111		APPARMOR AppArmor support is enabled.
112		SERIAL	Serial support is enabled.
113		SH	SuperH architecture is enabled.
114		SMP	The kernel is an SMP kernel.
115		SPARC	Sparc architecture is enabled.
116		SWSUSP	Software suspend (hibernation) is enabled.
117		SUSPEND	System suspend states are enabled.
118		TPM	TPM drivers are enabled.
119		TS	Appropriate touchscreen support is enabled.
120		UMS	USB Mass Storage support is enabled.
121		USB	USB support is enabled.
122		USBHID	USB Human Interface Device support is enabled.
123		V4L	Video For Linux support is enabled.
124		VMMIO   Driver for memory mapped virtio devices is enabled.
125		VGA	The VGA console has been enabled.
126		VT	Virtual terminal support is enabled.
127		WDT	Watchdog support is enabled.
128		XT	IBM PC/XT MFM hard disk support is enabled.
129		X86-32	X86-32, aka i386 architecture is enabled.
130		X86-64	X86-64 architecture is enabled.
131				More X86-64 boot options can be found in
132				Documentation/x86/x86_64/boot-options.txt .
133		X86	Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
134		XEN	Xen support is enabled
136	In addition, the following text indicates that the option:
138		BUGS=	Relates to possible processor bugs on the said processor.
139		KNL	Is a kernel start-up parameter.
140		BOOT	Is a boot loader parameter.
142	Parameters denoted with BOOT are actually interpreted by the boot
143	loader, and have no meaning to the kernel directly.
144	Do not modify the syntax of boot loader parameters without extreme
145	need or coordination with <Documentation/x86/boot.txt>.
147	There are also arch-specific kernel-parameters not documented here.
148	See for example <Documentation/x86/x86_64/boot-options.txt>.
150	Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
151	a trailing = on the name of any parameter states that that parameter will
152	be entered as an environment variable, whereas its absence indicates that
153	it will appear as a kernel argument readable via /proc/cmdline by programs
154	running once the system is up.
156	The number of kernel parameters is not limited, but the length of the
157	complete command line (parameters including spaces etc.) is limited to
158	a fixed number of characters. This limit depends on the architecture
159	and is between 256 and 4096 characters. It is defined in the file
160	./include/asm/setup.h as COMMAND_LINE_SIZE.
162	Finally, the [KMG] suffix is commonly described after a number of kernel
163	parameter values. These 'K', 'M', and 'G' letters represent the _binary_
164	multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
165	bytes respectively. Such letter suffixes can also be entirely omitted.
168		acpi=		[HW,ACPI,X86]
169				Advanced Configuration and Power Interface
170				Format: { force | off | strict | noirq | rsdt }
171				force -- enable ACPI if default was off
172				off -- disable ACPI if default was on
173				noirq -- do not use ACPI for IRQ routing
174				strict -- Be less tolerant of platforms that are not
175					strictly ACPI specification compliant.
176				rsdt -- prefer RSDT over (default) XSDT
177				copy_dsdt -- copy DSDT to memory
179				See also Documentation/power/runtime_pm.txt, pci=noacpi
181		acpi_rsdp=	[ACPI,EFI,KEXEC]
182				Pass the RSDP address to the kernel, mostly used
183				on machines running EFI runtime service to boot the
184				second kernel for kdump.
186		acpi_apic_instance=	[ACPI, IOAPIC]
187				Format: <int>
188				2: use 2nd APIC table, if available
189				1,0: use 1st APIC table
190				default: 0
192		acpi_backlight=	[HW,ACPI]
193				acpi_backlight=vendor
194				acpi_backlight=video
195				If set to vendor, prefer vendor specific driver
196				(e.g. thinkpad_acpi, sony_acpi, etc.) instead
197				of the ACPI video.ko driver.
199		acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
200		acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
201				Format: <int>
202				CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
203				debug output.  Bits in debug_layer correspond to a
204				_COMPONENT in an ACPI source file, e.g.,
206				Bits in debug_level correspond to a level in
207				ACPI_DEBUG_PRINT statements, e.g.,
209				The debug_level mask defaults to "info".  See
210				Documentation/acpi/debug.txt for more information about
211				debug layers and levels.
213				Enable processor driver info messages:
214				    acpi.debug_layer=0x20000000
215				Enable PCI/PCI interrupt routing info messages:
216				    acpi.debug_layer=0x400000
217				Enable AML "Debug" output, i.e., stores to the Debug
218				object while interpreting AML:
219				    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
220				Enable all messages related to ACPI hardware:
221				    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
223				Some values produce so much output that the system is
224				unusable.  The "log_buf_len" parameter may be useful
225				if you need to capture more output.
227		acpi_force_table_verification	[HW,ACPI]
228				Enable table checksum verification during early stage.
229				By default, this is disabled due to x86 early mapping
230				size limitation.
232		acpi_irq_balance [HW,ACPI]
233				ACPI will balance active IRQs
234				default in APIC mode
236		acpi_irq_nobalance [HW,ACPI]
237				ACPI will not move active IRQs (default)
238				default in PIC mode
240		acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
241				Format: <irq>,<irq>...
243		acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
244				use by PCI
245				Format: <irq>,<irq>...
247		acpi_no_auto_serialize	[HW,ACPI]
248				Disable auto-serialization of AML methods
249				AML control methods that contain the opcodes to create
250				named objects will be marked as "Serialized" by the
251				auto-serialization feature.
252				This feature is enabled by default.
253				This option allows to turn off the feature.
255		acpi_no_static_ssdt	[HW,ACPI]
256				Disable installation of static SSDTs at early boot time
257				By default, SSDTs contained in the RSDT/XSDT will be
258				installed automatically and they will appear under
259				/sys/firmware/acpi/tables.
260				This option turns off this feature.
261				Note that specifying this option does not affect
262				dynamic table installation which will install SSDT
263				tables to /sys/firmware/acpi/tables/dynamic.
265		acpica_no_return_repair [HW, ACPI]
266				Disable AML predefined validation mechanism
267				This mechanism can repair the evaluation result to make
268				the return objects more ACPI specification compliant.
269				This option is useful for developers to identify the
270				root cause of an AML interpreter issue when the issue
271				has something to do with the repair mechanism.
273		acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
274				Format: To spoof as Windows 98: ="Microsoft Windows"
276		acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
277				acpi_osi="string1"	# add string1
278				acpi_osi="!string2"	# remove string2
279				acpi_osi=!*		# remove all strings
280				acpi_osi=!		# disable all built-in OS vendor
281							  strings
282				acpi_osi=		# disable all strings
284				'acpi_osi=!' can be used in combination with single or
285				multiple 'acpi_osi="string1"' to support specific OS
286				vendor string(s).  Note that such command can only
287				affect the default state of the OS vendor strings, thus
288				it cannot affect the default state of the feature group
289				strings and the current state of the OS vendor strings,
290				specifying it multiple times through kernel command line
291				is meaningless.  This command is useful when one do not
292				care about the state of the feature group strings which
293				should be controlled by the OSPM.
294				Examples:
295				  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
296				     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
297				     can make '_OSI("Windows 2000")' TRUE.
299				'acpi_osi=' cannot be used in combination with other
300				'acpi_osi=' command lines, the _OSI method will not
301				exist in the ACPI namespace.  NOTE that such command can
302				only affect the _OSI support state, thus specifying it
303				multiple times through kernel command line is also
304				meaningless.
305				Examples:
306				  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
307				     FALSE.
309				'acpi_osi=!*' can be used in combination with single or
310				multiple 'acpi_osi="string1"' to support specific
311				string(s).  Note that such command can affect the
312				current state of both the OS vendor strings and the
313				feature group strings, thus specifying it multiple times
314				through kernel command line is meaningful.  But it may
315				still not able to affect the final state of a string if
316				there are quirks related to this string.  This command
317				is useful when one want to control the state of the
318				feature group strings to debug BIOS issues related to
319				the OSPM features.
320				Examples:
321				  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
322				     '_OSI("Module Device")' FALSE.
323				  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
324				     '_OSI("Module Device")' TRUE.
325				  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
326				     equivalent to
327				     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
328				     and
329				     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
330				     they all will make '_OSI("Windows 2000")' TRUE.
332		acpi_pm_good	[X86]
333				Override the pmtimer bug detection: force the kernel
334				to assume that this machine's pmtimer latches its value
335				and always returns good values.
337		acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
338				Format: { level | edge | high | low }
340		acpi_skip_timer_override [HW,ACPI]
341				Recognize and ignore IRQ0/pin2 Interrupt Override.
342				For broken nForce2 BIOS resulting in XT-PIC timer.
344		acpi_sleep=	[HW,ACPI] Sleep options
345				Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
346					  old_ordering, nonvs, sci_force_enable }
347				See Documentation/power/video.txt for information on
348				s3_bios and s3_mode.
349				s3_beep is for debugging; it makes the PC's speaker beep
350				as soon as the kernel's real-mode entry point is called.
351				s4_nohwsig prevents ACPI hardware signature from being
352				used during resume from hibernation.
353				old_ordering causes the ACPI 1.0 ordering of the _PTS
354				control method, with respect to putting devices into
355				low power states, to be enforced (the ACPI 2.0 ordering
356				of _PTS is used by default).
357				nonvs prevents the kernel from saving/restoring the
358				ACPI NVS memory during suspend/hibernation and resume.
359				sci_force_enable causes the kernel to set SCI_EN directly
360				on resume from S1/S3 (which is against the ACPI spec,
361				but some broken systems don't work without it).
363		acpi_use_timer_override [HW,ACPI]
364				Use timer override. For some broken Nvidia NF5 boards
365				that require a timer override, but don't have HPET
367		acpi_enforce_resources=	[ACPI]
368				{ strict | lax | no }
369				Check for resource conflicts between native drivers
370				and ACPI OperationRegions (SystemIO and SystemMemory
371				only). IO ports and memory declared in ACPI might be
372				used by the ACPI subsystem in arbitrary AML code and
373				can interfere with legacy drivers.
374				strict (default): access to resources claimed by ACPI
375				is denied; legacy drivers trying to access reserved
376				resources will fail to bind to device using them.
377				lax: access to resources claimed by ACPI is allowed;
378				legacy drivers trying to access reserved resources
379				will bind successfully but a warning message is logged.
380				no: ACPI OperationRegions are not marked as reserved,
381				no further checks are performed.
383		acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
384				   kernels.
386		add_efi_memmap	[EFI; X86] Include EFI memory map in
387				kernel's map of available physical RAM.
389		agp=		[AGP]
390				{ off | try_unsupported }
391				off: disable AGP support
392				try_unsupported: try to drive unsupported chipsets
393					(may crash computer or cause data corruption)
395		ALSA		[HW,ALSA]
396				See Documentation/sound/alsa/alsa-parameters.txt
398		alignment=	[KNL,ARM]
399				Allow the default userspace alignment fault handler
400				behaviour to be specified.  Bit 0 enables warnings,
401				bit 1 enables fixups, and bit 2 sends a segfault.
403		align_va_addr=	[X86-64]
404				Align virtual addresses by clearing slice [14:12] when
405				allocating a VMA at process creation time. This option
406				gives you up to 3% performance improvement on AMD F15h
407				machines (where it is enabled by default) for a
408				CPU-intensive style benchmark, and it can vary highly in
409				a microbenchmark depending on workload and compiler.
411				32: only for 32-bit processes
412				64: only for 64-bit processes
413				on: enable for both 32- and 64-bit processes
414				off: disable for both 32- and 64-bit processes
416		alloc_snapshot	[FTRACE]
417				Allocate the ftrace snapshot buffer on boot up when the
418				main buffer is allocated. This is handy if debugging
419				and you need to use tracing_snapshot() on boot up, and
420				do not want to use tracing_snapshot_alloc() as it needs
421				to be done where GFP_KERNEL allocations are allowed.
423		amd_iommu=	[HW,X86-64]
424				Pass parameters to the AMD IOMMU driver in the system.
425				Possible values are:
426				fullflush - enable flushing of IO/TLB entries when
427					    they are unmapped. Otherwise they are
428					    flushed before they will be reused, which
429					    is a lot of faster
430				off	  - do not initialize any AMD IOMMU found in
431					    the system
432				force_isolation - Force device isolation for all
433						  devices. The IOMMU driver is not
434						  allowed anymore to lift isolation
435						  requirements as needed. This option
436						  does not override iommu=pt
438		amd_iommu_dump=	[HW,X86-64]
439				Enable AMD IOMMU driver option to dump the ACPI table
440				for AMD IOMMU. With this option enabled, AMD IOMMU
441				driver will print ACPI tables for AMD IOMMU during
442				IOMMU initialization.
444		amijoy.map=	[HW,JOY] Amiga joystick support
445				Map of devices attached to JOY0DAT and JOY1DAT
446				Format: <a>,<b>
447				See also Documentation/input/joystick.txt
449		analog.map=	[HW,JOY] Analog joystick and gamepad support
450				Specifies type or capabilities of an analog joystick
451				connected to one of 16 gameports
452				Format: <type1>,<type2>,..<type16>
454		apc=		[HW,SPARC]
455				Power management functions (SPARCstation-4/5 + deriv.)
456				Format: noidle
457				Disable APC CPU standby support. SPARCstation-Fox does
458				not play well with APC CPU idle - disable it if you have
459				APC and your system crashes randomly.
461		apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
462				Change the output verbosity whilst booting
463				Format: { quiet (default) | verbose | debug }
464				Change the amount of debugging information output
465				when initialising the APIC and IO-APIC components.
467		autoconf=	[IPV6]
468				See Documentation/networking/ipv6.txt.
470		show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
471				Limit apic dumping. The parameter defines the maximal
472				number of local apics being dumped. Also it is possible
473				to set it to "all" by meaning -- no limit here.
474				Format: { 1 (default) | 2 | ... | all }.
475				The parameter valid if only apic=debug or
476				apic=verbose is specified.
477				Example: apic=debug show_lapic=all
479		apm=		[APM] Advanced Power Management
480				See header of arch/x86/kernel/apm_32.c.
482		arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
483				Format: <io>,<irq>,<nodeID>
485		ataflop=	[HW,M68k]
487		atarimouse=	[HW,MOUSE] Atari Mouse
489		atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
490				EzKey and similar keyboards
492		atkbd.reset=	[HW] Reset keyboard during initialization
494		atkbd.set=	[HW] Select keyboard code set
495				Format: <int> (2 = AT (default), 3 = PS/2)
497		atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
498				keyboards
500		atkbd.softraw=	[HW] Choose between synthetic and real raw mode
501				Format: <bool> (0 = real, 1 = synthetic (default))
503		atkbd.softrepeat= [HW]
504				Use software keyboard repeat
506		audit=		[KNL] Enable the audit sub-system
507				Format: { "0" | "1" } (0 = disabled, 1 = enabled)
508				0 - kernel audit is disabled and can not be enabled
509				    until the next reboot
510				unset - kernel audit is initialized but disabled and
511				    will be fully enabled by the userspace auditd.
512				1 - kernel audit is initialized and partially enabled,
513				    storing at most audit_backlog_limit messages in
514				    RAM until it is fully enabled by the userspace
515				    auditd.
516				Default: unset
518		audit_backlog_limit= [KNL] Set the audit queue size limit.
519				Format: <int> (must be >=0)
520				Default: 64
522		baycom_epp=	[HW,AX25]
523				Format: <io>,<mode>
525		baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
526				Format: <io>,<mode>
527				See header of drivers/net/hamradio/baycom_par.c.
529		baycom_ser_fdx=	[HW,AX25]
530				BayCom Serial Port AX.25 Modem (Full Duplex Mode)
531				Format: <io>,<irq>,<mode>[,<baud>]
532				See header of drivers/net/hamradio/baycom_ser_fdx.c.
534		baycom_ser_hdx=	[HW,AX25]
535				BayCom Serial Port AX.25 Modem (Half Duplex Mode)
536				Format: <io>,<irq>,<mode>
537				See header of drivers/net/hamradio/baycom_ser_hdx.c.
539		blkdevparts=	Manual partition parsing of block device(s) for
540				embedded devices based on command line input.
541				See Documentation/block/cmdline-partition.txt
543		boot_delay=	Milliseconds to delay each printk during boot.
544				Values larger than 10 seconds (10000) are changed to
545				no delay (0).
546				Format: integer
548		bootmem_debug	[KNL] Enable bootmem allocator debug messages.
550		bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
551		bttv.radio=	Most important insmod options are available as
552				kernel args too.
553		bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
554		bttv.tuner=
556		bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
557				firmware feature for flushing multiple hpte entries
558				at a time.
560		c101=		[NET] Moxa C101 synchronous serial card
562		cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
563				Sometimes CPU hardware bugs make them report the cache
564				size incorrectly. The kernel will attempt work arounds
565				to fix known problems, but for some CPUs it is not
566				possible to determine what the correct size should be.
567				This option provides an override for these situations.
569		ca_keys=	[KEYS] This parameter identifies a specific key(s) on
570				the system trusted keyring to be used for certificate
571				trust validation.
572				format: { id:<keyid> | builtin }
574		cca=		[MIPS] Override the kernel pages' cache coherency
575				algorithm.  Accepted values range from 0 to 7
576				inclusive. See arch/mips/include/asm/pgtable-bits.h
577				for platform specific values (SB1, Loongson3 and
578				others).
580		ccw_timeout_log [S390]
581				See Documentation/s390/CommonIO for details.
583		cgroup_disable= [KNL] Disable a particular controller
584				Format: {name of the controller(s) to disable}
585				The effects of cgroup_disable=foo are:
586				- foo isn't auto-mounted if you mount all cgroups in
587				  a single hierarchy
588				- foo isn't visible as an individually mountable
589				  subsystem
590				{Currently only "memory" controller deal with this and
591				cut the overhead, others just disable the usage. So
592				only cgroup_disable=memory is actually worthy}
594		checkreqprot	[SELINUX] Set initial checkreqprot flag value.
595				Format: { "0" | "1" }
596				See security/selinux/Kconfig help text.
597				0 -- check protection applied by kernel (includes
598					any implied execute protection).
599				1 -- check protection requested by application.
600				Default value is set via a kernel config option.
601				Value can be changed at runtime via
602					/selinux/checkreqprot.
604		cio_ignore=	[S390]
605				See Documentation/s390/CommonIO for details.
606		clk_ignore_unused
607				[CLK]
608				Prevents the clock framework from automatically gating
609				clocks that have not been explicitly enabled by a Linux
610				device driver but are enabled in hardware at reset or
611				by the bootloader/firmware. Note that this does not
612				force such clocks to be always-on nor does it reserve
613				those clocks in any way. This parameter is useful for
614				debug and development, but should not be needed on a
615				platform with proper driver support.  For more
616				information, see Documentation/clk.txt.
618		clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
619				[Deprecated]
620				Forces specified clocksource (if available) to be used
621				when calculating gettimeofday(). If specified
622				clocksource is not available, it defaults to PIT.
623				Format: { pit | tsc | cyclone | pmtmr }
625		clocksource=	Override the default clocksource
626				Format: <string>
627				Override the default clocksource and use the clocksource
628				with the name specified.
629				Some clocksource names to choose from, depending on
630				the platform:
631				[all] jiffies (this is the base, fallback clocksource)
632				[ACPI] acpi_pm
633				[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
634					pxa_timer,timer3,32k_counter,timer0_1
635				[AVR32] avr32
636				[X86-32] pit,hpet,tsc;
637					scx200_hrt on Geode; cyclone on IBM x440
638				[MIPS] MIPS
639				[PARISC] cr16
640				[S390] tod
641				[SH] SuperH
642				[SPARC64] tick
643				[X86-64] hpet,tsc
645		clearcpuid=BITNUM [X86]
646				Disable CPUID feature X for the kernel. See
647				arch/x86/include/asm/cpufeature.h for the valid bit
648				numbers. Note the Linux specific bits are not necessarily
649				stable over kernel options, but the vendor specific
650				ones should be.
651				Also note that user programs calling CPUID directly
652				or using the feature without checking anything
653				will still see it. This just prevents it from
654				being used by the kernel or shown in /proc/cpuinfo.
655				Also note the kernel might malfunction if you disable
656				some critical bits.
658		cma=nn[MG]@[start[MG][-end[MG]]]
659				[ARM,X86,KNL]
660				Sets the size of kernel global memory area for
661				contiguous memory allocations and optionally the
662				placement constraint by the physical address range of
663				memory allocations. A value of 0 disables CMA
664				altogether. For more information, see
665				include/linux/dma-contiguous.h
667		cmo_free_hint=	[PPC] Format: { yes | no }
668				Specify whether pages are marked as being inactive
669				when they are freed.  This is used in CMO environments
670				to determine OS memory pressure for page stealing by
671				a hypervisor.
672				Default: yes
674		coherent_pool=nn[KMG]	[ARM,KNL]
675				Sets the size of memory pool for coherent, atomic dma
676				allocations, by default set to 256K.
678		code_bytes	[X86] How many bytes of object code to print
679				in an oops report.
680				Range: 0 - 8192
681				Default: 64
683		com20020=	[HW,NET] ARCnet - COM20020 chipset
684				Format:
685				<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
687		com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
688				Format: <io>[,<irq>]
690		com90xx=	[HW,NET]
691				ARCnet - COM90xx chipset (memory-mapped buffers)
692				Format: <io>[,<irq>[,<memstart>]]
694		condev=		[HW,S390] console device
695		conmode=
697		console=	[KNL] Output console device and options.
699			tty<n>	Use the virtual console device <n>.
701			ttyS<n>[,options]
702			ttyUSB0[,options]
703				Use the specified serial port.  The options are of
704				the form "bbbbpnf", where "bbbb" is the baud rate,
705				"p" is parity ("n", "o", or "e"), "n" is number of
706				bits, and "f" is flow control ("r" for RTS or
707				omit it).  Default is "9600n8".
709				See Documentation/serial-console.txt for more
710				information.  See
711				Documentation/networking/netconsole.txt for an
712				alternative.
714			uart[8250],io,<addr>[,options]
715			uart[8250],mmio,<addr>[,options]
716				Start an early, polled-mode console on the 8250/16550
717				UART at the specified I/O port or MMIO address,
718				switching to the matching ttyS device later.  The
719				options are the same as for ttyS, above.
720			hvc<n>	Use the hypervisor console device <n>. This is for
721				both Xen and PowerPC hypervisors.
723	                If the device connected to the port is not a TTY but a braille
724	                device, prepend "brl," before the device type, for instance
725				console=brl,ttyS0
726			For now, only VisioBraille is supported.
728		consoleblank=	[KNL] The console blank (screen saver) timeout in
729				seconds. Defaults to 10*60 = 10mins. A value of 0
730				disables the blank timer.
732		coredump_filter=
733				[KNL] Change the default value for
734				/proc/<pid>/coredump_filter.
735				See also Documentation/filesystems/proc.txt.
737		cpuidle.off=1	[CPU_IDLE]
738				disable the cpuidle sub-system
740		cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
741				Format:
742				<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
744		crashkernel=size[KMG][@offset[KMG]]
745				[KNL] Using kexec, Linux can switch to a 'crash kernel'
746				upon panic. This parameter reserves the physical
747				memory region [offset, offset + size] for that kernel
748				image. If '@offset' is omitted, then a suitable offset
749				is selected automatically. Check
750				Documentation/kdump/kdump.txt for further details.
752		crashkernel=range1:size1[,range2:size2,...][@offset]
753				[KNL] Same as above, but depends on the memory
754				in the running system. The syntax of range is
755				start-[end] where start and end are both
756				a memory unit (amount[KMG]). See also
757				Documentation/kdump/kdump.txt for an example.
759		crashkernel=size[KMG],high
760				[KNL, x86_64] range could be above 4G. Allow kernel
761				to allocate physical memory region from top, so could
762				be above 4G if system have more than 4G ram installed.
763				Otherwise memory region will be allocated below 4G, if
764				available.
765				It will be ignored if crashkernel=X is specified.
766		crashkernel=size[KMG],low
767				[KNL, x86_64] range under 4G. When crashkernel=X,high
768				is passed, kernel could allocate physical memory region
769				above 4G, that cause second kernel crash on system
770				that require some amount of low memory, e.g. swiotlb
771				requires at least 64M+32K low memory.  Kernel would
772				try to allocate 72M below 4G automatically.
773				This one let user to specify own low range under 4G
774				for second kernel instead.
775				0: to disable low allocation.
776				It will be ignored when crashkernel=X,high is not used
777				or memory reserved is below 4G.
779		cs89x0_dma=	[HW,NET]
780				Format: <dma>
782		cs89x0_media=	[HW,NET]
783				Format: { rj45 | aui | bnc }
785		dasd=		[HW,NET]
786				See header of drivers/s390/block/dasd_devmap.c.
788		db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
789				(one device per port)
790				Format: <port#>,<type>
791				See also Documentation/input/joystick-parport.txt
793		ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
794				time. See Documentation/dynamic-debug-howto.txt for
795				details.  Deprecated, see dyndbg.
797		debug		[KNL] Enable kernel debugging (events log level).
799		debug_locks_verbose=
800				[KNL] verbose self-tests
801				Format=<0|1>
802				Print debugging info while doing the locking API
803				self-tests.
804				We default to 0 (no extra messages), setting it to
805				1 will print _a lot_ more information - normally
806				only useful to kernel developers.
808		debug_objects	[KNL] Enable object debugging
810		no_debug_objects
811				[KNL] Disable object debugging
813		debug_guardpage_minorder=
814				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
815				parameter allows control of the order of pages that will
816				be intentionally kept free (and hence protected) by the
817				buddy allocator. Bigger value increase the probability
818				of catching random memory corruption, but reduce the
819				amount of memory for normal system use. The maximum
820				possible value is MAX_ORDER/2.  Setting this parameter
821				to 1 or 2 should be enough to identify most random
822				memory corruption problems caused by bugs in kernel or
823				driver code when a CPU writes to (or reads from) a
824				random memory location. Note that there exists a class
825				of memory corruptions problems caused by buggy H/W or
826				F/W or by drivers badly programing DMA (basically when
827				memory is written at bus level and the CPU MMU is
828				bypassed) which are not detectable by
829				CONFIG_DEBUG_PAGEALLOC, hence this option will not help
830				tracking down these problems.
832		debug_pagealloc=
833				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
834				parameter enables the feature at boot time. In
835				default, it is disabled. We can avoid allocating huge
836				chunk of memory for debug pagealloc if we don't enable
837				it at boot time and the system will work mostly same
838				with the kernel built without CONFIG_DEBUG_PAGEALLOC.
839				on: enable the feature
841		debugpat	[X86] Enable PAT debugging
843		decnet.addr=	[HW,NET]
844				Format: <area>[,<node>]
845				See also Documentation/networking/decnet.txt.
847		default_hugepagesz=
848				[same as hugepagesz=] The size of the default
849				HugeTLB page size. This is the size represented by
850				the legacy /proc/ hugepages APIs, used for SHM, and
851				default size when mounting hugetlbfs filesystems.
852				Defaults to the default architecture's huge page size
853				if not specified.
855		dhash_entries=	[KNL]
856				Set number of hash buckets for dentry cache.
858		disable=	[IPV6]
859				See Documentation/networking/ipv6.txt.
861		disable_cpu_apicid= [X86,APIC,SMP]
862				Format: <int>
863				The number of initial APIC ID for the
864				corresponding CPU to be disabled at boot,
865				mostly used for the kdump 2nd kernel to
866				disable BSP to wake up multiple CPUs without
867				causing system reset or hang due to sending
868				INIT from AP to BSP.
870		disable_ddw     [PPC/PSERIES]
871				Disable Dynamic DMA Window support. Use this if
872				to workaround buggy firmware.
874		disable_ipv6=	[IPV6]
875				See Documentation/networking/ipv6.txt.
877		disable_mtrr_cleanup [X86]
878				The kernel tries to adjust MTRR layout from continuous
879				to discrete, to make X server driver able to add WB
880				entry later. This parameter disables that.
882		disable_mtrr_trim [X86, Intel and AMD only]
883				By default the kernel will trim any uncacheable
884				memory out of your available memory pool based on
885				MTRR settings.  This parameter disables that behavior,
886				possibly causing your machine to run very slowly.
888		disable_timer_pin_1 [X86]
889				Disable PIN 1 of APIC timer
890				Can be useful to work around chipset bugs.
892		dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
893				this option disables the debugging code at boot.
895		dma_debug_entries=<number>
896				This option allows to tune the number of preallocated
897				entries for DMA-API debugging code. One entry is
898				required per DMA-API allocation. Use this if the
899				DMA-API debugging code disables itself because the
900				architectural default is too low.
902		dma_debug_driver=<driver_name>
903				With this option the DMA-API debugging driver
904				filter feature can be enabled at boot time. Just
905				pass the driver to filter for as the parameter.
906				The filter can be disabled or changed to another
907				driver later using sysfs.
909		drm_kms_helper.edid_firmware=[<connector>:]<file>
910				Broken monitors, graphic adapters and KVMs may
911				send no or incorrect EDID data sets. This parameter
912				allows to specify an EDID data set in the
913				/lib/firmware directory that is used instead.
914				Generic built-in EDID data sets are used, if one of
915				edid/1024x768.bin, edid/1280x1024.bin,
916				edid/1680x1050.bin, or edid/1920x1080.bin is given
917				and no file with the same name exists. Details and
918				instructions how to build your own EDID data are
919				available in Documentation/EDID/HOWTO.txt. An EDID
920				data set will only be used for a particular connector,
921				if its name and a colon are prepended to the EDID
922				name.
924		dscc4.setup=	[NET]
926		dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
927		module.dyndbg[="val"]
928				Enable debug messages at boot time.  See
929				Documentation/dynamic-debug-howto.txt for details.
931		early_ioremap_debug [KNL]
932				Enable debug messages in early_ioremap support. This
933				is useful for tracking down temporary early mappings
934				which are not unmapped.
936		earlycon=	[KNL] Output early console device and options.
938			cdns,<addr>
939				Start an early, polled-mode console on a cadence serial
940				port at the specified address. The cadence serial port
941				must already be setup and configured. Options are not
942				yet supported.
944			uart[8250],io,<addr>[,options]
945			uart[8250],mmio,<addr>[,options]
946			uart[8250],mmio32,<addr>[,options]
947				Start an early, polled-mode console on the 8250/16550
948				UART at the specified I/O port or MMIO address.
949				MMIO inter-register address stride is either 8-bit
950				(mmio) or 32-bit (mmio32).
951				The options are the same as for ttyS, above.
953			pl011,<addr>
954				Start an early, polled-mode console on a pl011 serial
955				port at the specified address. The pl011 serial port
956				must already be setup and configured. Options are not
957				yet supported.
959			msm_serial,<addr>
960				Start an early, polled-mode console on an msm serial
961				port at the specified address. The serial port
962				must already be setup and configured. Options are not
963				yet supported.
965			msm_serial_dm,<addr>
966				Start an early, polled-mode console on an msm serial
967				dm port at the specified address. The serial port
968				must already be setup and configured. Options are not
969				yet supported.
971			smh	Use ARM semihosting calls for early console.
973		earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
974				earlyprintk=vga
975				earlyprintk=efi
976				earlyprintk=xen
977				earlyprintk=serial[,ttySn[,baudrate]]
978				earlyprintk=serial[,0x...[,baudrate]]
979				earlyprintk=ttySn[,baudrate]
980				earlyprintk=dbgp[debugController#]
982				earlyprintk is useful when the kernel crashes before
983				the normal console is initialized. It is not enabled by
984				default because it has some cosmetic problems.
986				Append ",keep" to not disable it when the real console
987				takes over.
989				Only one of vga, efi, serial, or usb debug port can
990				be used at a time.
992				Currently only ttyS0 and ttyS1 may be specified by
993				name.  Other I/O ports may be explicitly specified
994				on some architectures (x86 and arm at least) by
995				replacing ttySn with an I/O port address, like this:
996					earlyprintk=serial,0x1008,115200
997				You can find the port for a given device in
998				/proc/tty/driver/serial:
999					2: uart:ST16650V2 port:00001008 irq:18 ...
1001				Interaction with the standard serial driver is not
1002				very good.
1004				The VGA and EFI output is eventually overwritten by
1005				the real console.
1007				The xen output can only be used by Xen PV guests.
1009		edac_report=	[HW,EDAC] Control how to report EDAC event
1010				Format: {"on" | "off" | "force"}
1011				on: enable EDAC to report H/W event. May be overridden
1012				by other higher priority error reporting module.
1013				off: disable H/W event reporting through EDAC.
1014				force: enforce the use of EDAC to report H/W event.
1015				default: on.
1017		ekgdboc=	[X86,KGDB] Allow early kernel console debugging
1018				ekgdboc=kbd
1020				This is designed to be used in conjunction with
1021				the boot argument: earlyprintk=vga
1023		edd=		[EDD]
1024				Format: {"off" | "on" | "skip[mbr]"}
1026		efi=		[EFI]
1027				Format: { "old_map", "nochunk", "noruntime" }
1028				old_map [X86-64]: switch to the old ioremap-based EFI
1029				runtime services mapping. 32-bit still uses this one by
1030				default.
1031				nochunk: disable reading files in "chunks" in the EFI
1032				boot stub, as chunking can cause problems with some
1033				firmware implementations.
1034				noruntime : disable EFI runtime services support
1036		efi_no_storage_paranoia [EFI; X86]
1037				Using this parameter you can use more than 50% of
1038				your efi variable storage. Use this parameter only if
1039				you are really sure that your UEFI does sane gc and
1040				fulfills the spec otherwise your board may brick.
1042		eisa_irq_edge=	[PARISC,HW]
1043				See header of drivers/parisc/eisa.c.
1045		elanfreq=	[X86-32]
1046				See comment before function elanfreq_setup() in
1047				arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1049		elevator=	[IOSCHED]
1050				Format: {"cfq" | "deadline" | "noop"}
1051				See Documentation/block/cfq-iosched.txt and
1052				Documentation/block/deadline-iosched.txt for details.
1054		elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1055				Specifies physical address of start of kernel core
1056				image elf header and optionally the size. Generally
1057				kexec loader will pass this option to capture kernel.
1058				See Documentation/kdump/kdump.txt for details.
1060		enable_mtrr_cleanup [X86]
1061				The kernel tries to adjust MTRR layout from continuous
1062				to discrete, to make X server driver able to add WB
1063				entry later. This parameter enables that.
1065		enable_timer_pin_1 [X86]
1066				Enable PIN 1 of APIC timer
1067				Can be useful to work around chipset bugs
1068				(in particular on some ATI chipsets).
1069				The kernel tries to set a reasonable default.
1071		enforcing	[SELINUX] Set initial enforcing status.
1072				Format: {"0" | "1"}
1073				See security/selinux/Kconfig help text.
1074				0 -- permissive (log only, no denials).
1075				1 -- enforcing (deny and log).
1076				Default value is 0.
1077				Value can be changed at runtime via /selinux/enforce.
1079		erst_disable	[ACPI]
1080				Disable Error Record Serialization Table (ERST)
1081				support.
1083		ether=		[HW,NET] Ethernet cards parameters
1084				This option is obsoleted by the "netdev=" option, which
1085				has equivalent usage. See its documentation for details.
1087		evm=		[EVM]
1088				Format: { "fix" }
1089				Permit 'security.evm' to be updated regardless of
1090				current integrity status.
1092		failslab=
1093		fail_page_alloc=
1094		fail_make_request=[KNL]
1095				General fault injection mechanism.
1096				Format: <interval>,<probability>,<space>,<times>
1097				See also Documentation/fault-injection/.
1099		floppy=		[HW]
1100				See Documentation/blockdev/floppy.txt.
1102		force_pal_cache_flush
1103				[IA-64] Avoid check_sal_cache_flush which may hang on
1104				buggy SAL_CACHE_FLUSH implementations. Using this
1105				parameter will force ia64_sal_cache_flush to call
1106				ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1108		forcepae [X86-32]
1109				Forcefully enable Physical Address Extension (PAE).
1110				Many Pentium M systems disable PAE but may have a
1111				functionally usable PAE implementation.
1112				Warning: use of this parameter will taint the kernel
1113				and may cause unknown problems.
1115		ftrace=[tracer]
1116				[FTRACE] will set and start the specified tracer
1117				as early as possible in order to facilitate early
1118				boot debugging.
1120		ftrace_dump_on_oops[=orig_cpu]
1121				[FTRACE] will dump the trace buffers on oops.
1122				If no parameter is passed, ftrace will dump
1123				buffers of all CPUs, but if you pass orig_cpu, it will
1124				dump only the buffer of the CPU that triggered the
1125				oops.
1127		ftrace_filter=[function-list]
1128				[FTRACE] Limit the functions traced by the function
1129				tracer at boot up. function-list is a comma separated
1130				list of functions. This list can be changed at run
1131				time by the set_ftrace_filter file in the debugfs
1132				tracing directory.
1134		ftrace_notrace=[function-list]
1135				[FTRACE] Do not trace the functions specified in
1136				function-list. This list can be changed at run time
1137				by the set_ftrace_notrace file in the debugfs
1138				tracing directory.
1140		ftrace_graph_filter=[function-list]
1141				[FTRACE] Limit the top level callers functions traced
1142				by the function graph tracer at boot up.
1143				function-list is a comma separated list of functions
1144				that can be changed at run time by the
1145				set_graph_function file in the debugfs tracing directory.
1147		ftrace_graph_notrace=[function-list]
1148				[FTRACE] Do not trace from the functions specified in
1149				function-list.  This list is a comma separated list of
1150				functions that can be changed at run time by the
1151				set_graph_notrace file in the debugfs tracing directory.
1153		gamecon.map[2|3]=
1154				[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1155				support via parallel port (up to 5 devices per port)
1156				Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1157				See also Documentation/input/joystick-parport.txt
1159		gamma=		[HW,DRM]
1161		gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
1162				Format: off | on
1163				default: on
1165		gcov_persist=	[GCOV] When non-zero (default), profiling data for
1166				kernel modules is saved and remains accessible via
1167				debugfs, even when the module is unloaded/reloaded.
1168				When zero, profiling data is discarded and associated
1169				debugfs files are removed at module unload time.
1171		gpt		[EFI] Forces disk with valid GPT signature but
1172				invalid Protective MBR to be treated as GPT. If the
1173				primary GPT is corrupted, it enables the backup/alternate
1174				GPT to be used instead.
1176		grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1177				the "Enable 0" bit of the configuration register.
1178				Format: 0 | 1
1179				Default: 0
1180		grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1181				the "Enable 0" bit of the configuration register.
1182				Format: 0 | 1
1183				Default: 0
1184		grcan.select=	[HW] Select which physical interface to use.
1185				Format: 0 | 1
1186				Default: 0
1187		grcan.txsize=	[HW] Sets the size of the tx buffer.
1188				Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1189				Default: 1024
1190		grcan.rxsize=	[HW] Sets the size of the rx buffer.
1191				Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1192				Default: 1024
1194		hashdist=	[KNL,NUMA] Large hashes allocated during boot
1195				are distributed across NUMA nodes.  Defaults on
1196				for 64-bit NUMA, off otherwise.
1197				Format: 0 | 1 (for off | on)
1199		hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1201		hd=		[EIDE] (E)IDE hard drive subsystem geometry
1202				Format: <cyl>,<head>,<sect>
1204		hest_disable	[ACPI]
1205				Disable Hardware Error Source Table (HEST) support;
1206				corresponding firmware-first mode error processing
1207				logic will be disabled.
1209		highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1210				size of <nn>. This works even on boxes that have no
1211				highmem otherwise. This also works to reduce highmem
1212				size on bigger boxes.
1214		highres=	[KNL] Enable/disable high resolution timer mode.
1215				Valid parameters: "on", "off"
1216				Default: "on"
1218		hisax=		[HW,ISDN]
1219				See Documentation/isdn/README.HiSax.
1221		hlt		[BUGS=ARM,SH]
1223		hpet=		[X86-32,HPET] option to control HPET usage
1224				Format: { enable (default) | disable | force |
1225					verbose }
1226				disable: disable HPET and use PIT instead
1227				force: allow force enabled of undocumented chips (ICH4,
1228					VIA, nVidia)
1229				verbose: show contents of HPET registers during setup
1231		hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1232				registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1234		hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1235		hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1236				On x86-64 and powerpc, this option can be specified
1237				multiple times interleaved with hugepages= to reserve
1238				huge pages of different sizes. Valid pages sizes on
1239				x86-64 are 2M (when the CPU supports "pse") and 1G
1240				(when the CPU supports the "pdpe1gb" cpuinfo flag).
1242		hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
1243				       terminal devices. Valid values: 0..8
1244		hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
1245				       If specified, z/VM IUCV HVC accepts connections
1246				       from listed z/VM user IDs only.
1248		hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
1249				        hardware thread id mappings.
1250					Format: <cpu>:<hwthread>
1252		keep_bootcon	[KNL]
1253				Do not unregister boot console at start. This is only
1254				useful for debugging when something happens in the window
1255				between unregistering the boot console and initializing
1256				the real console.
1258		i2c_bus=	[HW] Override the default board specific I2C bus speed
1259				     or register an additional I2C bus that is not
1260				     registered from board initialization code.
1261				     Format:
1262				     <bus_id>,<clkrate>
1264		i8042.debug	[HW] Toggle i8042 debug mode
1265		i8042.direct	[HW] Put keyboard port into non-translated mode
1266		i8042.dumbkbd	[HW] Pretend that controller can only read data from
1267				     keyboard and cannot control its state
1268				     (Don't attempt to blink the leds)
1269		i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1270		i8042.nokbd	[HW] Don't check/create keyboard port
1271		i8042.noloop	[HW] Disable the AUX Loopback command while probing
1272				     for the AUX port
1273		i8042.nomux	[HW] Don't check presence of an active multiplexing
1274				     controller
1275		i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1276				     controllers
1277		i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1278		i8042.reset	[HW] Reset the controller during init and cleanup
1279		i8042.unlock	[HW] Unlock (ignore) the keylock
1280		i8042.kbdreset  [HW] Reset device connected to KBD port
1282		i810=		[HW,DRM]
1284		i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1285				indicates that the driver is running on unsupported
1286				hardware.
1287		i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1288				does not match list of supported models.
1289		i8k.power_status
1290				[HW] Report power status in /proc/i8k
1291				(disabled by default)
1292		i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1293				capability is set.
1295		i915.invert_brightness=
1296				[DRM] Invert the sense of the variable that is used to
1297				set the brightness of the panel backlight. Normally a
1298				brightness value of 0 indicates backlight switched off,
1299				and the maximum of the brightness value sets the backlight
1300				to maximum brightness. If this parameter is set to 0
1301				(default) and the machine requires it, or this parameter
1302				is set to 1, a brightness value of 0 sets the backlight
1303				to maximum brightness, and the maximum of the brightness
1304				value switches the backlight off.
1305				-1 -- never invert brightness
1306				 0 -- machine default
1307				 1 -- force brightness inversion
1309		icn=		[HW,ISDN]
1310				Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1312		ide-core.nodma=	[HW] (E)IDE subsystem
1313				Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1314				.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1315				.cdrom .chs .ignore_cable are additional options
1316				See Documentation/ide/ide.txt.
1318		ide-generic.probe-mask= [HW] (E)IDE subsystem
1319				Format: <int>
1320				Probe mask for legacy ISA IDE ports.  Depending on
1321				platform up to 6 ports are supported, enabled by
1322				setting corresponding bits in the mask to 1.  The
1323				default value is 0x0, which has a special meaning.
1324				On systems that have PCI, it triggers scanning the
1325				PCI bus for the first and the second port, which
1326				are then probed.  On systems without PCI the value
1327				of 0x0 enables probing the two first ports as if it
1328				was 0x3.
1330		ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1331				Claim all unknown PCI IDE storage controllers.
1333		idle=		[X86]
1334				Format: idle=poll, idle=halt, idle=nomwait
1335				Poll forces a polling idle loop that can slightly
1336				improve the performance of waking up a idle CPU, but
1337				will use a lot of power and make the system run hot.
1338				Not recommended.
1339				idle=halt: Halt is forced to be used for CPU idle.
1340				In such case C2/C3 won't be used again.
1341				idle=nomwait: Disable mwait for CPU C-states
1343		ignore_loglevel	[KNL]
1344				Ignore loglevel setting - this will print /all/
1345				kernel messages to the console. Useful for debugging.
1346				We also add it as printk module parameter, so users
1347				could change it dynamically, usually by
1348				/sys/module/printk/parameters/ignore_loglevel.
1350		ihash_entries=	[KNL]
1351				Set number of hash buckets for inode cache.
1353		ima_appraise=	[IMA] appraise integrity measurements
1354				Format: { "off" | "enforce" | "fix" | "log" }
1355				default: "enforce"
1357		ima_appraise_tcb [IMA]
1358				The builtin appraise policy appraises all files
1359				owned by uid=0.
1361		ima_hash=	[IMA]
1362				Format: { md5 | sha1 | rmd160 | sha256 | sha384
1363					   | sha512 | ... }
1364				default: "sha1"
1366				The list of supported hash algorithms is defined
1367				in crypto/hash_info.h.
1369		ima_tcb		[IMA]
1370				Load a policy which meets the needs of the Trusted
1371				Computing Base.  This means IMA will measure all
1372				programs exec'd, files mmap'd for exec, and all files
1373				opened for read by uid=0.
1375		ima_template=   [IMA]
1376				Select one of defined IMA measurements template formats.
1377				Formats: { "ima" | "ima-ng" }
1378				Default: "ima-ng"
1380		ima_template_fmt=
1381		                [IMA] Define a custom template format.
1382				Format: { "field1|...|fieldN" }
1384		ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1385				Format: <min_file_size>
1386				Set the minimal file size for using asynchronous hash.
1387				If left unspecified, ahash usage is disabled.
1389				ahash performance varies for different data sizes on
1390				different crypto accelerators. This option can be used
1391				to achieve the best performance for a particular HW.
1393		ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1394				Format: <bufsize>
1395				Set hashing buffer size. Default: 4k.
1397				ahash performance varies for different chunk sizes on
1398				different crypto accelerators. This option can be used
1399				to achieve best performance for particular HW.
1401		init=		[KNL]
1402				Format: <full_path>
1403				Run specified binary instead of /sbin/init as init
1404				process.
1406		initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1407				for working out where the kernel is dying during
1408				startup.
1410		initcall_blacklist=  [KNL] Do not execute a comma-separated list of
1411				initcall functions.  Useful for debugging built-in
1412				modules and initcalls.
1414		initrd=		[BOOT] Specify the location of the initial ramdisk
1416		inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1417				Format: <irq>
1419		int_pln_enable  [x86] Enable power limit notification interrupt
1421		integrity_audit=[IMA]
1422				Format: { "0" | "1" }
1423				0 -- basic integrity auditing messages. (Default)
1424				1 -- additional integrity auditing messages.
1426		intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1427			on
1428				Enable intel iommu driver.
1429			off
1430				Disable intel iommu driver.
1431			igfx_off [Default Off]
1432				By default, gfx is mapped as normal device. If a gfx
1433				device has a dedicated DMAR unit, the DMAR unit is
1434				bypassed by not enabling DMAR with this option. In
1435				this case, gfx device will use physical address for
1436				DMA.
1437			forcedac [x86_64]
1438				With this option iommu will not optimize to look
1439				for io virtual address below 32-bit forcing dual
1440				address cycle on pci bus for cards supporting greater
1441				than 32-bit addressing. The default is to look
1442				for translation below 32-bit and if not available
1443				then look in the higher range.
1444			strict [Default Off]
1445				With this option on every unmap_single operation will
1446				result in a hardware IOTLB flush operation as opposed
1447				to batching them for performance.
1448			sp_off [Default Off]
1449				By default, super page will be supported if Intel IOMMU
1450				has the capability. With this option, super page will
1451				not be supported.
1453		intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1454				0	disables intel_idle and fall back on acpi_idle.
1455				1 to 6	specify maximum depth of C-state.
1457		intel_pstate=  [X86]
1458			       disable
1459			         Do not enable intel_pstate as the default
1460			         scaling driver for the supported processors
1461			       force
1462				 Enable intel_pstate on systems that prohibit it by default
1463				 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1464				 instead of acpi-cpufreq may disable platform features, such
1465				 as thermal controls and power capping, that rely on ACPI
1466				 P-States information being indicated to OSPM and therefore
1467				 should be used with caution. This option does not work with
1468				 processors that aren't supported by the intel_pstate driver
1469				 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1470			       no_hwp
1471			         Do not enable hardware P state control (HWP)
1472				 if available.
1474		intremap=	[X86-64, Intel-IOMMU]
1475				on	enable Interrupt Remapping (default)
1476				off	disable Interrupt Remapping
1477				nosid	disable Source ID checking
1478				no_x2apic_optout
1479					BIOS x2APIC opt-out request will be ignored
1481		iomem=		Disable strict checking of access to MMIO memory
1482			strict	regions from userspace.
1483			relaxed
1485		iommu=		[x86]
1486			off
1487			force
1488			noforce
1489			biomerge
1490			panic
1491			nopanic
1492			merge
1493			nomerge
1494			forcesac
1495			soft
1496			pt		[x86, IA-64]
1499		io7=		[HW] IO7 for Marvel based alpha systems
1500				See comment before marvel_specify_io7 in
1501				arch/alpha/kernel/core_marvel.c.
1503		io_delay=	[X86] I/O delay method
1504			0x80
1505				Standard port 0x80 based delay
1506			0xed
1507				Alternate port 0xed based delay (needed on some systems)
1508			udelay
1509				Simple two microseconds delay
1510			none
1511				No delay
1513		ip=		[IP_PNP]
1514				See Documentation/filesystems/nfs/nfsroot.txt.
1516		irqfixup	[HW]
1517				When an interrupt is not handled search all handlers
1518				for it. Intended to get systems with badly broken
1519				firmware running.
1521		irqpoll		[HW]
1522				When an interrupt is not handled search all handlers
1523				for it. Also check all handlers each timer
1524				interrupt. Intended to get systems with badly broken
1525				firmware running.
1527		isapnp=		[ISAPNP]
1528				Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1530		isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1531				Format:
1532				<cpu number>,...,<cpu number>
1533				or
1534				<cpu number>-<cpu number>
1535				(must be a positive range in ascending order)
1536				or a mixture
1537				<cpu number>,...,<cpu number>-<cpu number>
1539				This option can be used to specify one or more CPUs
1540				to isolate from the general SMP balancing and scheduling
1541				algorithms. You can move a process onto or off an
1542				"isolated" CPU via the CPU affinity syscalls or cpuset.
1543				<cpu number> begins at 0 and the maximum value is
1544				"number of CPUs in system - 1".
1546				This option is the preferred way to isolate CPUs. The
1547				alternative -- manually setting the CPU mask of all
1548				tasks in the system -- can cause problems and
1549				suboptimal load balancer performance.
1551		iucv=		[HW,NET]
1553		ivrs_ioapic	[HW,X86_64]
1554				Provide an override to the IOAPIC-ID<->DEVICE-ID
1555				mapping provided in the IVRS ACPI table. For
1556				example, to map IOAPIC-ID decimal 10 to
1557				PCI device 00:14.0 write the parameter as:
1558					ivrs_ioapic[10]=00:14.0
1560		ivrs_hpet	[HW,X86_64]
1561				Provide an override to the HPET-ID<->DEVICE-ID
1562				mapping provided in the IVRS ACPI table. For
1563				example, to map HPET-ID decimal 0 to
1564				PCI device 00:14.0 write the parameter as:
1565					ivrs_hpet[0]=00:14.0
1567		js=		[HW,JOY] Analog joystick
1568				See Documentation/input/joystick.txt.
1570		kaslr/nokaslr	[X86]
1571				Enable/disable kernel and module base offset ASLR
1572				(Address Space Layout Randomization) if built into
1573				the kernel. When CONFIG_HIBERNATION is selected,
1574				kASLR is disabled by default. When kASLR is enabled,
1575				hibernation will be disabled.
1577		keepinitrd	[HW,ARM]
1579		kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1580				specifies the amount of memory usable by the kernel
1581				for non-movable allocations.  The requested amount is
1582				spread evenly throughout all nodes in the system. The
1583				remaining memory in each node is used for Movable
1584				pages. In the event, a node is too small to have both
1585				kernelcore and Movable pages, kernelcore pages will
1586				take priority and other nodes will have a larger number
1587				of Movable pages.  The Movable zone is used for the
1588				allocation of pages that may be reclaimed or moved
1589				by the page migration subsystem.  This means that
1590				HugeTLB pages may not be allocated from this zone.
1591				Note that allocations like PTEs-from-HighMem still
1592				use the HighMem zone if it exists, and the Normal
1593				zone if it does not.
1595		kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1596				Format: <Controller#>[,poll interval]
1597				The controller # is the number of the ehci usb debug
1598				port as it is probed via PCI.  The poll interval is
1599				optional and is the number seconds in between
1600				each poll cycle to the debug port in case you need
1601				the functionality for interrupting the kernel with
1602				gdb or control-c on the dbgp connection.  When
1603				not using this parameter you use sysrq-g to break into
1604				the kernel debugger.
1606		kgdboc=		[KGDB,HW] kgdb over consoles.
1607				Requires a tty driver that supports console polling,
1608				or a supported polling keyboard driver (non-usb).
1609				 Serial only format: <serial_device>[,baud]
1610				 keyboard only format: kbd
1611				 keyboard and serial format: kbd,<serial_device>[,baud]
1612				Optional Kernel mode setting:
1613				 kms, kbd format: kms,kbd
1614				 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1616		kgdbwait	[KGDB] Stop kernel execution and enter the
1617				kernel debugger at the earliest opportunity.
1619		kmac=		[MIPS] korina ethernet MAC address.
1620				Configure the RouterBoard 532 series on-chip
1621				Ethernet adapter MAC address.
1623		kmemleak=	[KNL] Boot-time kmemleak enable/disable
1624				Valid arguments: on, off
1625				Default: on
1627				the default is off.
1629		kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
1630				Valid arguments: 0, 1, 2
1631				kmemcheck=0 (disabled)
1632				kmemcheck=1 (enabled)
1633				kmemcheck=2 (one-shot mode)
1634				Default: 2 (one-shot mode)
1636		kstack=N	[X86] Print N words from the kernel stack
1637				in oops dumps.
1639		kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1640				Default is 0 (don't ignore, but inject #GP)
1642		kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
1643				KVM MMU at runtime.
1644				Default is 0 (off)
1646		kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1647				Default is 1 (enabled)
1649		kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
1650				for all guests.
1651				Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1653		kvm-intel.ept=	[KVM,Intel] Disable extended page tables
1654				(virtualized MMU) support on capable Intel chips.
1655				Default is 1 (enabled)
1657		kvm-intel.emulate_invalid_guest_state=
1658				[KVM,Intel] Enable emulation of invalid guest states
1659				Default is 0 (disabled)
1661		kvm-intel.flexpriority=
1662				[KVM,Intel] Disable FlexPriority feature (TPR shadow).
1663				Default is 1 (enabled)
1665		kvm-intel.nested=
1666				[KVM,Intel] Enable VMX nesting (nVMX).
1667				Default is 0 (disabled)
1669		kvm-intel.unrestricted_guest=
1670				[KVM,Intel] Disable unrestricted guest feature
1671				(virtualized real and unpaged mode) on capable
1672				Intel chips. Default is 1 (enabled)
1674		kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
1675				feature (tagged TLBs) on capable Intel chips.
1676				Default is 1 (enabled)
1678		l2cr=		[PPC]
1680		l3cr=		[PPC]
1682		lapic		[X86-32,APIC] Enable the local APIC even if BIOS
1683				disabled it.
1685		lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
1686				value for LAPIC timer one-shot implementation. Default
1687				back to the programmable timer unit in the LAPIC.
1689		lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1690				in C2 power state.
1692		libata.dma=	[LIBATA] DMA control
1693				libata.dma=0	  Disable all PATA and SATA DMA
1694				libata.dma=1	  PATA and SATA Disk DMA only
1695				libata.dma=2	  ATAPI (CDROM) DMA only
1696				libata.dma=4	  Compact Flash DMA only
1697				Combinations also work, so libata.dma=3 enables DMA
1698				for disks and CDROMs, but not CFs.
1700		libata.ignore_hpa=	[LIBATA] Ignore HPA limit
1701				libata.ignore_hpa=0	  keep BIOS limits (default)
1702				libata.ignore_hpa=1	  ignore limits, using full disk
1704		libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
1705				when set.
1706				Format: <int>
1708		libata.force=	[LIBATA] Force configurations.  The format is comma
1709				separated list of "[ID:]VAL" where ID is
1710				PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1711				matching port, link or device.  Basically, it matches
1712				the ATA ID string printed on console by libata.  If
1713				the whole ID part is omitted, the last PORT and DEVICE
1714				values are used.  If ID hasn't been specified yet, the
1715				configuration applies to all ports, links and devices.
1717				If only DEVICE is omitted, the parameter applies to
1718				the port and all links and devices behind it.  DEVICE
1719				number of 0 either selects the first device or the
1720				first fan-out link behind PMP device.  It does not
1721				select the host link.  DEVICE number of 15 selects the
1722				host link and device attached to it.
1724				The VAL specifies the configuration to force.  As long
1725				as there's no ambiguity shortcut notation is allowed.
1726				For example, both 1.5 and 1.5G would work for 1.5Gbps.
1727				The following configurations can be forced.
1729				* Cable type: 40c, 80c, short40c, unk, ign or sata.
1730				  Any ID with matching PORT is used.
1732				* SATA link speed limit: 1.5Gbps or 3.0Gbps.
1734				* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1735				  udma[/][16,25,33,44,66,100,133] notation is also
1736				  allowed.
1738				* [no]ncq: Turn on or off NCQ.
1740				* nohrst, nosrst, norst: suppress hard, soft
1741	                          and both resets.
1743				* rstonce: only attempt one reset during
1744				  hot-unplug link recovery
1746				* dump_id: dump IDENTIFY data.
1748				* atapi_dmadir: Enable ATAPI DMADIR bridge support
1750				* disable: Disable this device.
1752				If there are multiple matching configurations changing
1753				the same attribute, the last one is used.
1755		memblock=debug	[KNL] Enable memblock debug messages.
1757		load_ramdisk=	[RAM] List of ramdisks to load from floppy
1758				See Documentation/blockdev/ramdisk.txt.
1760		lockd.nlm_grace_period=P  [NFS] Assign grace period.
1761				Format: <integer>
1763		lockd.nlm_tcpport=N	[NFS] Assign TCP port.
1764				Format: <integer>
1766		lockd.nlm_timeout=T	[NFS] Assign timeout value.
1767				Format: <integer>
1769		lockd.nlm_udpport=M	[NFS] Assign UDP port.
1770				Format: <integer>
1772		locktorture.nreaders_stress= [KNL]
1773				Set the number of locking read-acquisition kthreads.
1774				Defaults to being automatically set based on the
1775				number of online CPUs.
1777		locktorture.nwriters_stress= [KNL]
1778				Set the number of locking write-acquisition kthreads.
1780		locktorture.onoff_holdoff= [KNL]
1781				Set time (s) after boot for CPU-hotplug testing.
1783		locktorture.onoff_interval= [KNL]
1784				Set time (s) between CPU-hotplug operations, or
1785				zero to disable CPU-hotplug testing.
1787		locktorture.shuffle_interval= [KNL]
1788				Set task-shuffle interval (jiffies).  Shuffling
1789				tasks allows some CPUs to go into dyntick-idle
1790				mode during the locktorture test.
1792		locktorture.shutdown_secs= [KNL]
1793				Set time (s) after boot system shutdown.  This
1794				is useful for hands-off automated testing.
1796		locktorture.stat_interval= [KNL]
1797				Time (s) between statistics printk()s.
1799		locktorture.stutter= [KNL]
1800				Time (s) to stutter testing, for example,
1801				specifying five seconds causes the test to run for
1802				five seconds, wait for five seconds, and so on.
1803				This tests the locking primitive's ability to
1804				transition abruptly to and from idle.
1806		locktorture.torture_runnable= [BOOT]
1807				Start locktorture running at boot time.
1809		locktorture.torture_type= [KNL]
1810				Specify the locking implementation to test.
1812		locktorture.verbose= [KNL]
1813				Enable additional printk() statements.
1815		logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
1816				Format: <irq>
1818		loglevel=	All Kernel Messages with a loglevel smaller than the
1819				console loglevel will be printed to the console. It can
1820				also be changed with klogd or other programs. The
1821				loglevels are defined as follows:
1823				0 (KERN_EMERG)		system is unusable
1824				1 (KERN_ALERT)		action must be taken immediately
1825				2 (KERN_CRIT)		critical conditions
1826				3 (KERN_ERR)		error conditions
1827				4 (KERN_WARNING)	warning conditions
1828				5 (KERN_NOTICE)		normal but significant condition
1829				6 (KERN_INFO)		informational
1830				7 (KERN_DEBUG)		debug-level messages
1832		log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
1833				in bytes.  n must be a power of two and greater
1834				than the minimal size. The minimal size is defined
1835				by LOG_BUF_SHIFT kernel config parameter. There is
1836				also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1837				that allows to increase the default size depending on
1838				the number of CPUs. See init/Kconfig for more details.
1840		logo.nologo	[FB] Disables display of the built-in Linux logo.
1841				This may be used to provide more screen space for
1842				kernel log messages and is useful when debugging
1843				kernel boot problems.
1845		lp=0		[LP]	Specify parallel ports to use, e.g,
1846		lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
1847		lp=reset		first parallel port). 'lp=0' disables the
1848		lp=auto			printer driver. 'lp=reset' (which can be
1849					specified in addition to the ports) causes
1850					attached printers to be reset. Using
1851					lp=port1,port2,... specifies the parallel ports
1852					to associate lp devices with, starting with
1853					lp0. A port specification may be 'none' to skip
1854					that lp device, or a parport name such as
1855					'parport0'. Specifying 'lp=auto' instead of a
1856					port specification list means that device IDs
1857					from each port should be examined, to see if
1858					an IEEE 1284-compliant printer is attached; if
1859					so, the driver will manage that printer.
1860					See also header of drivers/char/lp.c.
1862		lpj=n		[KNL]
1863				Sets loops_per_jiffy to given constant, thus avoiding
1864				time-consuming boot-time autodetection (up to 250 ms per
1865				CPU). 0 enables autodetection (default). To determine
1866				the correct value for your kernel, boot with normal
1867				autodetection and see what value is printed. Note that
1868				on SMP systems the preset will be applied to all CPUs,
1869				which is likely to cause problems if your CPUs need
1870				significantly divergent settings. An incorrect value
1871				will cause delays in the kernel to be wrong, leading to
1872				unpredictable I/O errors and other breakage. Although
1873				unlikely, in the extreme case this might damage your
1874				hardware.
1876		ltpc=		[NET]
1877				Format: <io>,<irq>,<dma>
1879		machvec=	[IA-64] Force the use of a particular machine-vector
1880				(machvec) in a generic kernel.
1881				Example: machvec=hpzx1_swiotlb
1883		machtype=	[Loongson] Share the same kernel image file between different
1884				 yeeloong laptop.
1885				Example: machtype=lemote-yeeloong-2f-7inch
1887		max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
1888				than or equal to this physical address is ignored.
1890		maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
1891				should make use of.  maxcpus=n : n >= 0 limits the
1892				kernel to using 'n' processors.  n=0 is a special case,
1893				it is equivalent to "nosmp", which also disables
1894				the IO APIC.
1896		max_loop=	[LOOP] The number of loop block devices that get
1897		(loop.max_loop)	unconditionally pre-created at init time. The default
1898				number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1899				of statically allocating a predefined number, loop
1900				devices can be requested on-demand with the
1901				/dev/loop-control interface.
1903		mce		[X86-32] Machine Check Exception
1905		mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
1907		md=		[HW] RAID subsystems devices and level
1908				See Documentation/md.txt.
1910		mdacon=		[MDA]
1911				Format: <first>,<last>
1912				Specifies range of consoles to be captured by the MDA.
1914		mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
1915				Amount of memory to be used when the kernel is not able
1916				to see the whole system memory or for test.
1917				[X86] Work as limiting max address. Use together
1918				with memmap= to avoid physical address space collisions.
1919				Without memmap= PCI devices could be placed at addresses
1920				belonging to unused RAM.
1922		mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
1923				memory.
1925		memchunk=nn[KMG]
1926				[KNL,SH] Allow user to override the default size for
1927				per-device physically contiguous DMA buffers.
1929		memmap=exactmap	[KNL,X86] Enable setting of an exact
1930				E820 memory map, as specified by the user.
1931				Such memmap=exactmap lines can be constructed based on
1932				BIOS output or other requirements. See the memmap=nn@ss
1933				option description.
1935		memmap=nn[KMG]@ss[KMG]
1936				[KNL] Force usage of a specific region of memory.
1937				Region of memory to be used is from ss to ss+nn.
1939		memmap=nn[KMG]#ss[KMG]
1940				[KNL,ACPI] Mark specific memory as ACPI data.
1941				Region of memory to be marked is from ss to ss+nn.
1943		memmap=nn[KMG]$ss[KMG]
1944				[KNL,ACPI] Mark specific memory as reserved.
1945				Region of memory to be reserved is from ss to ss+nn.
1946				Example: Exclude memory from 0x18690000-0x1869ffff
1947				         memmap=64K$0x18690000
1948				         or
1949				         memmap=0x10000$0x18690000
1951		memory_corruption_check=0/1 [X86]
1952				Some BIOSes seem to corrupt the first 64k of
1953				memory when doing things like suspend/resume.
1954				Setting this option will scan the memory
1955				looking for corruption.  Enabling this will
1956				both detect corruption and prevent the kernel
1957				from using the memory being corrupted.
1958				However, its intended as a diagnostic tool; if
1959				repeatable BIOS-originated corruption always
1960				affects the same memory, you can use memmap=
1961				to prevent the kernel from using that memory.
1963		memory_corruption_check_size=size [X86]
1964				By default it checks for corruption in the low
1965				64k, making this memory unavailable for normal
1966				use.  Use this parameter to scan for
1967				corruption in more or less memory.
1969		memory_corruption_check_period=seconds [X86]
1970				By default it checks for corruption every 60
1971				seconds.  Use this parameter to check at some
1972				other rate.  0 disables periodic checking.
1974		memtest=	[KNL,X86] Enable memtest
1975				Format: <integer>
1976				default : 0 <disable>
1977				Specifies the number of memtest passes to be
1978				performed. Each pass selects another test
1979				pattern from a given set of patterns. Memtest
1980				fills the memory with this pattern, validates
1981				memory contents and reserves bad memory
1982				regions that are detected.
1984		meye.*=		[HW] Set MotionEye Camera parameters
1985				See Documentation/video4linux/meye.txt.
1987		mfgpt_irq=	[IA-32] Specify the IRQ to use for the
1988				Multi-Function General Purpose Timers on AMD Geode
1989				platforms.
1991		mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
1992				the BIOS has incorrectly applied a workaround. TinyBIOS
1993				version 0.98 is known to be affected, 0.99 fixes the
1994				problem by letting the user disable the workaround.
1996		mga=		[HW,DRM]
1998		min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
1999				physical address is ignored.
2001		mini2440=	[ARM,HW,KNL]
2002				Format:[0..2][b][c][t]
2003				Default: "0tb"
2004				MINI2440 configuration specification:
2005				0 - The attached screen is the 3.5" TFT
2006				1 - The attached screen is the 7" TFT
2007				2 - The VGA Shield is attached (1024x768)
2008				Leaving out the screen size parameter will not load
2009				the TFT driver, and the framebuffer will be left
2010				unconfigured.
2011				b - Enable backlight. The TFT backlight pin will be
2012				linked to the kernel VESA blanking code and a GPIO
2013				LED. This parameter is not necessary when using the
2014				VGA shield.
2015				c - Enable the s3c camera interface.
2016				t - Reserved for enabling touchscreen support. The
2017				touchscreen support is not enabled in the mainstream
2018				kernel as of 2.6.30, a preliminary port can be found
2019				in the "bleeding edge" mini2440 support kernel at
2020				http://repo.or.cz/w/linux-2.6/mini2440.git
2022		mminit_loglevel=
2023				[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2024				parameter allows control of the logging verbosity for
2025				the additional memory initialisation checks. A value
2026				of 0 disables mminit logging and a level of 4 will
2027				log everything. Information is printed at KERN_DEBUG
2028				so loglevel=8 may also need to be specified.
2030		module.sig_enforce
2031				[KNL] When CONFIG_MODULE_SIG is set, this means that
2032				modules without (valid) signatures will fail to load.
2033				Note that if CONFIG_MODULE_SIG_FORCE is set, that
2034				is always true, so this option does nothing.
2036		mousedev.tap_time=
2037				[MOUSE] Maximum time between finger touching and
2038				leaving touchpad surface for touch to be considered
2039				a tap and be reported as a left button click (for
2040				touchpads working in absolute mode only).
2041				Format: <msecs>
2042		mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
2043				reporting absolute coordinates, such as tablets
2044		mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
2045				reporting absolute coordinates, such as tablets
2047		movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
2048				is similar to kernelcore except it specifies the
2049				amount of memory used for migratable allocations.
2050				If both kernelcore and movablecore is specified,
2051				then kernelcore will be at *least* the specified
2052				value but may be more. If movablecore on its own
2053				is specified, the administrator must be careful
2054				that the amount of memory usable for all allocations
2055				is not too small.
2057		movable_node	[KNL,X86] Boot-time switch to enable the effects
2058				of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2060		MTD_Partition=	[MTD]
2061				Format: <name>,<region-number>,<size>,<offset>
2063		MTD_Region=	[MTD] Format:
2064				<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2066		mtdparts=	[MTD]
2067				See drivers/mtd/cmdlinepart.c.
2069		multitce=off	[PPC]  This parameter disables the use of the pSeries
2070				firmware feature for updating multiple TCE entries
2071				at a time.
2073		onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
2075				Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2077				boundary - index of last SLC block on Flex-OneNAND.
2078					   The remaining blocks are configured as MLC blocks.
2079				lock	 - Configure if Flex-OneNAND boundary should be locked.
2080					   Once locked, the boundary cannot be changed.
2081					   1 indicates lock status, 0 indicates unlock status.
2083		mtdset=		[ARM]
2084				ARM/S3C2412 JIVE boot control
2086				See arch/arm/mach-s3c2412/mach-jive.c
2088		mtouchusb.raw_coordinates=
2089				[HW] Make the MicroTouch USB driver use raw coordinates
2090				('y', default) or cooked coordinates ('n')
2092		mtrr_chunk_size=nn[KMG] [X86]
2093				used for mtrr cleanup. It is largest continuous chunk
2094				that could hold holes aka. UC entries.
2096		mtrr_gran_size=nn[KMG] [X86]
2097				Used for mtrr cleanup. It is granularity of mtrr block.
2098				Default is 1.
2099				Large value could prevent small alignment from
2100				using up MTRRs.
2102		mtrr_spare_reg_nr=n [X86]
2103				Format: <integer>
2104				Range: 0,7 : spare reg number
2105				Default : 1
2106				Used for mtrr cleanup. It is spare mtrr entries number.
2107				Set to 2 or more if your graphical card needs more.
2109		n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
2111		netdev=		[NET] Network devices parameters
2112				Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2113				Note that mem_start is often overloaded to mean
2114				something different and driver-specific.
2115				This usage is only documented in each driver source
2116				file if at all.
2118		nf_conntrack.acct=
2119				[NETFILTER] Enable connection tracking flow accounting
2120				0 to disable accounting
2121				1 to enable accounting
2122				Default value is 0.
2124		nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
2125				See Documentation/filesystems/nfs/nfsroot.txt.
2127		nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
2128				See Documentation/filesystems/nfs/nfsroot.txt.
2130		nfsrootdebug	[NFS] enable nfsroot debugging messages.
2131				See Documentation/filesystems/nfs/nfsroot.txt.
2133		nfs.callback_tcpport=
2134				[NFS] set the TCP port on which the NFSv4 callback
2135				channel should listen.
2137		nfs.cache_getent=
2138				[NFS] sets the pathname to the program which is used
2139				to update the NFS client cache entries.
2141		nfs.cache_getent_timeout=
2142				[NFS] sets the timeout after which an attempt to
2143				update a cache entry is deemed to have failed.
2145		nfs.idmap_cache_timeout=
2146				[NFS] set the maximum lifetime for idmapper cache
2147				entries.
2149		nfs.enable_ino64=
2150				[NFS] enable 64-bit inode numbers.
2151				If zero, the NFS client will fake up a 32-bit inode
2152				number for the readdir() and stat() syscalls instead
2153				of returning the full 64-bit number.
2154				The default is to return 64-bit inode numbers.
2156		nfs.max_session_slots=
2157				[NFSv4.1] Sets the maximum number of session slots
2158				the client will attempt to negotiate with the server.
2159				This limits the number of simultaneous RPC requests
2160				that the client can send to the NFSv4.1 server.
2161				Note that there is little point in setting this
2162				value higher than the max_tcp_slot_table_limit.
2164		nfs.nfs4_disable_idmapping=
2165				[NFSv4] When set to the default of '1', this option
2166				ensures that both the RPC level authentication
2167				scheme and the NFS level operations agree to use
2168				numeric uids/gids if the mount is using the
2169				'sec=sys' security flavour. In effect it is
2170				disabling idmapping, which can make migration from
2171				legacy NFSv2/v3 systems to NFSv4 easier.
2172				Servers that do not support this mode of operation
2173				will be autodetected by the client, and it will fall
2174				back to using the idmapper.
2175				To turn off this behaviour, set the value to '0'.
2176		nfs.nfs4_unique_id=
2177				[NFS4] Specify an additional fixed unique ident-
2178				ification string that NFSv4 clients can insert into
2179				their nfs_client_id4 string.  This is typically a
2180				UUID that is generated at system install time.
2182		nfs.send_implementation_id =
2183				[NFSv4.1] Send client implementation identification
2184				information in exchange_id requests.
2185				If zero, no implementation identification information
2186				will be sent.
2187				The default is to send the implementation identification
2188				information.
2190		nfs.recover_lost_locks =
2191				[NFSv4] Attempt to recover locks that were lost due
2192				to a lease timeout on the server. Please note that
2193				doing this risks data corruption, since there are
2194				no guarantees that the file will remain unchanged
2195				after the locks are lost.
2196				If you want to enable the kernel legacy behaviour of
2197				attempting to recover these locks, then set this
2198				parameter to '1'.
2199				The default parameter value of '0' causes the kernel
2200				not to attempt recovery of lost locks.
2202		nfsd.nfs4_disable_idmapping=
2203				[NFSv4] When set to the default of '1', the NFSv4
2204				server will return only numeric uids and gids to
2205				clients using auth_sys, and will accept numeric uids
2206				and gids from such clients.  This is intended to ease
2207				migration from NFSv2/v3.
2209		objlayoutdriver.osd_login_prog=
2210				[NFS] [OBJLAYOUT] sets the pathname to the program which
2211				is used to automatically discover and login into new
2212				osd-targets. Please see:
2213				Documentation/filesystems/pnfs.txt for more explanations
2215		nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
2216				when a NMI is triggered.
2217				Format: [state][,regs][,debounce][,die]
2219		nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2220				Format: [panic,][nopanic,][num]
2221				Valid num: 0
2222				0 - turn nmi_watchdog off
2223				When panic is specified, panic when an NMI watchdog
2224				timeout occurs (or 'nopanic' to override the opposite
2225				default).
2226				This is useful when you use a panic=... timeout and
2227				need the box quickly up again.
2229		netpoll.carrier_timeout=
2230				[NET] Specifies amount of time (in seconds) that
2231				netpoll should wait for a carrier. By default netpoll
2232				waits 4 seconds.
2234		no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
2235				emulation library even if a 387 maths coprocessor
2236				is present.
2238		no_console_suspend
2239				[HW] Never suspend the console
2240				Disable suspending of consoles during suspend and
2241				hibernate operations.  Once disabled, debugging
2242				messages can reach various consoles while the rest
2243				of the system is being put to sleep (ie, while
2244				debugging driver suspend/resume hooks).  This may
2245				not work reliably with all consoles, but is known
2246				to work with serial and VGA consoles.
2247				To facilitate more flexible debugging, we also add
2248				console_suspend, a printk module parameter to control
2249				it. Users could use console_suspend (usually
2250				/sys/module/printk/parameters/console_suspend) to
2251				turn on/off it dynamically.
2253		noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
2254				caches in the slab allocator.  Saves per-node memory,
2255				but will impact performance.
2257		noalign		[KNL,ARM]
2259		noapic		[SMP,APIC] Tells the kernel to not make use of any
2260				IOAPICs that may be present in the system.
2262		noautogroup	Disable scheduler automatic task group creation.
2264		nobats		[PPC] Do not use BATs for mapping kernel lowmem
2265				on "Classic" PPC cores.
2267		nocache		[ARM]
2269		noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2271		nodelayacct	[KNL] Disable per-task delay accounting
2273		nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.
2275		nodsp		[SH] Disable hardware DSP at boot time.
2277		noefi		Disable EFI runtime services support.
2279		noexec		[IA-64]
2281		noexec		[X86]
2282				On X86-32 available only on PAE configured kernels.
2283				noexec=on: enable non-executable mappings (default)
2284				noexec=off: disable non-executable mappings
2286		nosmap		[X86]
2287				Disable SMAP (Supervisor Mode Access Prevention)
2288				even if it is supported by processor.
2290		nosmep		[X86]
2291				Disable SMEP (Supervisor Mode Execution Prevention)
2292				even if it is supported by processor.
2294		noexec32	[X86-64]
2295				This affects only 32-bit executables.
2296				noexec32=on: enable non-executable mappings (default)
2297					read doesn't imply executable mappings
2298				noexec32=off: disable non-executable mappings
2299					read implies executable mappings
2301		nofpu		[SH] Disable hardware FPU at boot time.
2303		nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2304				register save and restore. The kernel will only save
2305				legacy floating-point registers on task switch.
2307		noxsave		[BUGS=X86] Disables x86 extended register state save
2308				and restore using xsave. The kernel will fallback to
2309				enabling legacy floating-point and sse state.
2311		noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
2312				register states. The kernel will fall back to use
2313				xsave to save the states. By using this parameter,
2314				performance of saving the states is degraded because
2315				xsave doesn't support modified optimization while
2316				xsaveopt supports it on xsaveopt enabled systems.
2318		noxsaves	[X86] Disables xsaves and xrstors used in saving and
2319				restoring x86 extended register state in compacted
2320				form of xsave area. The kernel will fall back to use
2321				xsaveopt and xrstor to save and restore the states
2322				in standard form of xsave area. By using this
2323				parameter, xsave area per process might occupy more
2324				memory on xsaves enabled systems.
2326		eagerfpu=	[X86]
2327				on	enable eager fpu restore
2328				off	disable eager fpu restore
2329				auto	selects the default scheme, which automatically
2330					enables eagerfpu restore for xsaveopt.
2332		nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2333				wfi(ARM) instruction doesn't work correctly and not to
2334				use it. This is also useful when using JTAG debugger.
2336		no_file_caps	Tells the kernel not to honor file capabilities.  The
2337				only way then for a file to be executed with privilege
2338				is to be setuid root or executed by root.
2340		nohalt		[IA-64] Tells the kernel not to use the power saving
2341				function PAL_HALT_LIGHT when idle. This increases
2342				power-consumption. On the positive side, it reduces
2343				interrupt wake-up latency, which may improve performance
2344				in certain environments such as networked servers or
2345				real-time systems.
2347		nohibernate	[HIBERNATION] Disable hibernation and resume.
2349		nohz=		[KNL] Boottime enable/disable dynamic ticks
2350				Valid arguments: on, off
2351				Default: on
2353		nohz_full=	[KNL,BOOT]
2354				In kernels built with CONFIG_NO_HZ_FULL=y, set
2355				the specified list of CPUs whose tick will be stopped
2356				whenever possible. The boot CPU will be forced outside
2357				the range to maintain the timekeeping.
2358				The CPUs in this range must also be included in the
2359				rcu_nocbs= set.
2361		noiotrap	[SH] Disables trapped I/O port accesses.
2363		noirqdebug	[X86-32] Disables the code which attempts to detect and
2364				disable unhandled interrupt sources.
2366		no_timer_check	[X86,APIC] Disables the code which tests for
2367				broken timer IRQ sources.
2369		noisapnp	[ISAPNP] Disables ISA PnP code.
2371		noinitrd	[RAM] Tells the kernel not to load any configured
2372				initial RAM disk.
2374		nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
2375				remapping.
2376				[Deprecated - use intremap=off]
2378		nointroute	[IA-64]
2380		nojitter	[IA-64] Disables jitter checking for ITC timers.
2382		no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
2384		no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
2385				fault handling.
2387		no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
2388				steal time is computed, but won't influence scheduler
2389				behaviour
2391		nolapic		[X86-32,APIC] Do not enable or use the local APIC.
2393		nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2395		noltlbs		[PPC] Do not use large page/tlb entries for kernel
2396				lowmem mapping on PPC40x.
2398		nomca		[IA-64] Disable machine check abort handling
2400		nomce		[X86-32] Machine Check Exception
2402		nomfgpt		[X86-32] Disable Multi-Function General Purpose
2403				Timer usage (for AMD Geode machines).
2405		nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
2406				shutdown the other cpus.  Instead use the REBOOT_VECTOR
2407				irq.
2409		nomodule	Disable module load
2411		nopat		[X86] Disable PAT (page attribute table extension of
2412				pagetables) support.
2414		norandmaps	Don't use address space randomization.  Equivalent to
2415				echo 0 > /proc/sys/kernel/randomize_va_space
2417		noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2419		noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2420				with UP alternatives
2422		nordrand	[X86] Disable kernel use of the RDRAND and
2423				RDSEED instructions even if they are supported
2424				by the processor.  RDRAND and RDSEED are still
2425				available to user space applications.
2427		noresume	[SWSUSP] Disables resume and restores original swap
2428				space.
2430		no-scroll	[VGA] Disables scrollback.
2431				This is required for the Braillex ib80-piezo Braille
2432				reader made by F.H. Papenmeier (Germany).
2434		nosbagart	[IA-64]
2436		nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2438		nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
2439				and disable the IO APIC.  legacy for "maxcpus=0".
2441		nosoftlockup	[KNL] Disable the soft-lockup detector.
2443		nosync		[HW,M68K] Disables sync negotiation for all devices.
2445		notsc		[BUGS=X86-32] Disable Time Stamp Counter
2447		nousb		[USB] Disable the USB subsystem
2449		nowatchdog	[KNL] Disable the lockup detector (NMI watchdog).
2451		nowb		[ARM]
2453		nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
2455		cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
2457				Some features depend on CPU0. Known dependencies are:
2458				1. Resume from suspend/hibernate depends on CPU0.
2459				Suspend/hibernate will fail if CPU0 is offline and you
2460				need to online CPU0 before suspend/hibernate.
2461				2. PIC interrupts also depend on CPU0. CPU0 can't be
2462				removed if a PIC interrupt is detected.
2463				It's said poweroff/reboot may depend on CPU0 on some
2464				machines although I haven't seen such issues so far
2465				after CPU0 is offline on a few tested machines.
2466				If the dependencies are under your control, you can
2467				turn on cpu0_hotplug.
2469		nptcg=		[IA-64] Override max number of concurrent global TLB
2470				purges which is reported from either PAL_VM_SUMMARY or
2471				SAL PALO.
2473		nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
2474				could support.  nr_cpus=n : n >= 1 limits the kernel to
2475				supporting 'n' processors. Later in runtime you can not
2476				use hotplug cpu feature to put more cpu back to online.
2477				just like you compile the kernel NR_CPUS=n
2479		nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
2481		numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
2482				Allowed values are enable and disable
2484		numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2485				one of ['zone', 'node', 'default'] can be specified
2486				This can be set from sysctl after boot.
2487				See Documentation/sysctl/vm.txt for details.
2489		ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
2490				See Documentation/debugging-via-ohci1394.txt for more
2491				info.
2493		olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2494				Rather than timing out after 20 ms if an EC
2495				command is not properly ACKed, override the length
2496				of the timeout.  We have interrupts disabled while
2497				waiting for the ACK, so if this is set too high
2498				interrupts *may* be lost!
2500		omap_mux=	[OMAP] Override bootloader pin multiplexing.
2501				Format: <mux_mode0.mode_name=value>...
2502				For example, to override I2C bus2:
2503				omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2505		oprofile.timer=	[HW]
2506				Use timer interrupt instead of performance counters
2508		oprofile.cpu_type=	Force an oprofile cpu type
2509				This might be useful if you have an older oprofile
2510				userland or if you want common events.
2511				Format: { arch_perfmon }
2512				arch_perfmon: [X86] Force use of architectural
2513					perfmon on Intel CPUs instead of the
2514					CPU specific event set.
2515				timer: [X86] Force use of architectural NMI
2516					timer mode (see also oprofile.timer
2517					for generic hr timer mode)
2518					[s390] Force legacy basic mode sampling
2519	                                (report cpu_type "timer")
2521		oops=panic	Always panic on oopses. Default is to just kill the
2522				process, but there is a small probability of
2523				deadlocking the machine.
2524				This will also cause panics on machine check exceptions.
2525				Useful together with panic=30 to trigger a reboot.
2527		OSS		[HW,OSS]
2528				See Documentation/sound/oss/oss-parameters.txt
2530		page_owner=	[KNL] Boot-time page_owner enabling option.
2531				Storage of the information about who allocated
2532				each page is disabled in default. With this switch,
2533				we can turn it on.
2534				on: enable the feature
2536		panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2537				timeout > 0: seconds before rebooting
2538				timeout = 0: wait forever
2539				timeout < 0: reboot immediately
2540				Format: <timeout>
2542		panic_on_warn	panic() instead of WARN().  Useful to cause kdump
2543				on a WARN().
2545		crash_kexec_post_notifiers
2546				Run kdump after running panic-notifiers and dumping
2547				kmsg. This only for the users who doubt kdump always
2548				succeeds in any situation.
2549				Note that this also increases risks of kdump failure,
2550				because some panic notifiers can make the crashed
2551				kernel more unstable.
2553		parkbd.port=	[HW] Parallel port number the keyboard adapter is
2554				connected to, default is 0.
2555				Format: <parport#>
2556		parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
2557				0 for XT, 1 for AT (default is AT).
2558				Format: <mode>
2560		parport=	[HW,PPT] Specify parallel ports. 0 disables.
2561				Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2562				Use 'auto' to force the driver to use any
2563				IRQ/DMA settings detected (the default is to
2564				ignore detected IRQ/DMA settings because of
2565				possible conflicts). You can specify the base
2566				address, IRQ, and DMA settings; IRQ and DMA
2567				should be numbers, or 'auto' (for using detected
2568				settings on that particular port), or 'nofifo'
2569				(to avoid using a FIFO even if it is detected).
2570				Parallel ports are assigned in the order they
2571				are specified on the command line, starting
2572				with parport0.
2574		parport_init_mode=	[HW,PPT]
2575				Configure VIA parallel port to operate in
2576				a specific mode. This is necessary on Pegasos
2577				computer where firmware has no options for setting
2578				up parallel port mode and sets it to spp.
2579				Currently this function knows 686a and 8231 chips.
2580				Format: [spp|ps2|epp|ecp|ecpepp]
2582		pause_on_oops=
2583				Halt all CPUs after the first oops has been printed for
2584				the specified number of seconds.  This is to be used if
2585				your oopses keep scrolling off the screen.
2587		pcbit=		[HW,ISDN]
2589		pcd.		[PARIDE]
2590				See header of drivers/block/paride/pcd.c.
2591				See also Documentation/blockdev/paride.txt.
2593		pci=option[,option...]	[PCI] various PCI subsystem options:
2594			earlydump	[X86] dump PCI config space before the kernel
2595				        changes anything
2596			off		[X86] don't probe for the PCI bus
2597			bios		[X86-32] force use of PCI BIOS, don't access
2598					the hardware directly. Use this if your machine
2599					has a non-standard PCI host bridge.
2600			nobios		[X86-32] disallow use of PCI BIOS, only direct
2601					hardware access methods are allowed. Use this
2602					if you experience crashes upon bootup and you
2603					suspect they are caused by the BIOS.
2604			conf1		[X86] Force use of PCI Configuration
2605					Mechanism 1.
2606			conf2		[X86] Force use of PCI Configuration
2607					Mechanism 2.
2608			noaer		[PCIE] If the PCIEAER kernel config parameter is
2609					enabled, this kernel boot option can be used to
2610					disable the use of PCIE advanced error reporting.
2611			nodomains	[PCI] Disable support for multiple PCI
2612					root domains (aka PCI segments, in ACPI-speak).
2613			nommconf	[X86] Disable use of MMCONFIG for PCI
2614					Configuration
2615			check_enable_amd_mmconf [X86] check for and enable
2616					properly configured MMIO access to PCI
2617					config space on AMD family 10h CPU
2618			nomsi		[MSI] If the PCI_MSI kernel config parameter is
2619					enabled, this kernel boot option can be used to
2620					disable the use of MSI interrupts system-wide.
2621			noioapicquirk	[APIC] Disable all boot interrupt quirks.
2622					Safety option to keep boot IRQs enabled. This
2623					should never be necessary.
2624			ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
2625					primary IO-APIC for bridges that cannot disable
2626					boot IRQs. This fixes a source of spurious IRQs
2627					when the system masks IRQs.
2628			noioapicreroute	[APIC] Disable workaround that uses the
2629					boot IRQ equivalent of an IRQ that connects to
2630					a chipset where boot IRQs cannot be disabled.
2631					The opposite of ioapicreroute.
2632			biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
2633					routing table. These calls are known to be buggy
2634					on several machines and they hang the machine
2635					when used, but on other computers it's the only
2636					way to get the interrupt routing table. Try
2637					this option if the kernel is unable to allocate
2638					IRQs or discover secondary PCI buses on your
2639					motherboard.
2640			rom		[X86] Assign address space to expansion ROMs.
2641					Use with caution as certain devices share
2642					address decoders between ROMs and other
2643					resources.
2644			norom		[X86] Do not assign address space to
2645					expansion ROMs that do not already have
2646					BIOS assigned address ranges.
2647			nobar		[X86] Do not assign address space to the
2648					BARs that weren't assigned by the BIOS.
2649			irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
2650					assigned automatically to PCI devices. You can
2651					make the kernel exclude IRQs of your ISA cards
2652					this way.
2653			pirqaddr=0xAAAAA	[X86] Specify the physical address
2654					of the PIRQ table (normally generated
2655					by the BIOS) if it is outside the
2656					F0000h-100000h range.
2657			lastbus=N	[X86] Scan all buses thru bus #N. Can be
2658					useful if the kernel is unable to find your
2659					secondary buses and you want to tell it
2660					explicitly which ones they are.
2661			assign-busses	[X86] Always assign all PCI bus
2662					numbers ourselves, overriding
2663					whatever the firmware may have done.
2664			usepirqmask	[X86] Honor the possible IRQ mask stored
2665					in the BIOS $PIR table. This is needed on
2666					some systems with broken BIOSes, notably
2667					some HP Pavilion N5400 and Omnibook XE3
2668					notebooks. This will have no effect if ACPI
2669					IRQ routing is enabled.
2670			noacpi		[X86] Do not use ACPI for IRQ routing
2671					or for PCI scanning.
2672			use_crs		[X86] Use PCI host bridge window information
2673					from ACPI.  On BIOSes from 2008 or later, this
2674					is enabled by default.  If you need to use this,
2675					please report a bug.
2676			nocrs		[X86] Ignore PCI host bridge windows from ACPI.
2677				        If you need to use this, please report a bug.
2678			routeirq	Do IRQ routing for all PCI devices.
2679					This is normally done in pci_enable_device(),
2680					so this option is a temporary workaround
2681					for broken drivers that don't call it.
2682			skip_isa_align	[X86] do not align io start addr, so can
2683					handle more pci cards
2684			firmware	[ARM] Do not re-enumerate the bus but instead
2685					just use the configuration from the
2686					bootloader. This is currently used on
2687					IXP2000 systems where the bus has to be
2688					configured a certain way for adjunct CPUs.
2689			noearly		[X86] Don't do any early type 1 scanning.
2690					This might help on some broken boards which
2691					machine check when some devices' config space
2692					is read. But various workarounds are disabled
2693					and some IOMMU drivers will not work.
2694			bfsort		Sort PCI devices into breadth-first order.
2695					This sorting is done to get a device
2696					order compatible with older (<= 2.4) kernels.
2697			nobfsort	Don't sort PCI devices into breadth-first order.
2698			pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
2699					tuning and use the BIOS-configured MPS defaults.
2700			pcie_bus_safe	Set every device's MPS to the largest value
2701					supported by all devices below the root complex.
2702			pcie_bus_perf	Set device MPS to the largest allowable MPS
2703					based on its parent bus. Also set MRRS (Max
2704					Read Request Size) to the largest supported
2705					value (no larger than the MPS that the device
2706					or bus can support) for best performance.
2707			pcie_bus_peer2peer	Set every device's MPS to 128B, which
2708					every device is guaranteed to support. This
2709					configuration allows peer-to-peer DMA between
2710					any pair of devices, possibly at the cost of
2711					reduced performance.  This also guarantees
2712					that hot-added devices will work.
2713			cbiosize=nn[KMG]	The fixed amount of bus space which is
2714					reserved for the CardBus bridge's IO window.
2715					The default value is 256 bytes.
2716			cbmemsize=nn[KMG]	The fixed amount of bus space which is
2717					reserved for the CardBus bridge's memory
2718					window. The default value is 64 megabytes.
2719			resource_alignment=
2720					Format:
2721					[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2722					Specifies alignment and device to reassign
2723					aligned memory resources.
2724					If <order of align> is not specified,
2725					PAGE_SIZE is used as alignment.
2726					PCI-PCI bridge can be specified, if resource
2727					windows need to be expanded.
2728			ecrc=		Enable/disable PCIe ECRC (transaction layer
2729					end-to-end CRC checking).
2730					bios: Use BIOS/firmware settings. This is the
2731					the default.
2732					off: Turn ECRC off
2733					on: Turn ECRC on.
2734			hpiosize=nn[KMG]	The fixed amount of bus space which is
2735					reserved for hotplug bridge's IO window.
2736					Default size is 256 bytes.
2737			hpmemsize=nn[KMG]	The fixed amount of bus space which is
2738					reserved for hotplug bridge's memory window.
2739					Default size is 2 megabytes.
2740			realloc=	Enable/disable reallocating PCI bridge resources
2741					if allocations done by BIOS are too small to
2742					accommodate resources required by all child
2743					devices.
2744					off: Turn realloc off
2745					on: Turn realloc on
2746			realloc		same as realloc=on
2747			noari		do not use PCIe ARI.
2748			pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
2749					only look for one device below a PCIe downstream
2750					port.
2752		pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
2753				Management.
2754			off	Disable ASPM.
2755			force	Enable ASPM even on devices that claim not to support it.
2756				WARNING: Forcing ASPM on may cause system lockups.
2758		pcie_hp=	[PCIE] PCI Express Hotplug driver options:
2759			nomsi	Do not use MSI for PCI Express Native Hotplug (this
2760				makes all PCIe ports use INTx for hotplug services).
2762		pcie_ports=	[PCIE] PCIe ports handling:
2763			auto	Ask the BIOS whether or not to use native PCIe services
2764				associated with PCIe ports (PME, hot-plug, AER).  Use
2765				them only if that is allowed by the BIOS.
2766			native	Use native PCIe services associated with PCIe ports
2767				unconditionally.
2768			compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2769				ports driver.
2771		pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
2772			nomsi	Do not use MSI for native PCIe PME signaling (this makes
2773				all PCIe root ports use INTx for all services).
2775		pcmv=		[HW,PCMCIA] BadgePAD 4
2777		pd_ignore_unused
2778				[PM]
2779				Keep all power-domains already enabled by bootloader on,
2780				even if no driver has claimed them. This is useful
2781				for debug and development, but should not be
2782				needed on a platform with proper driver support.
2784		pd.		[PARIDE]
2785				See Documentation/blockdev/paride.txt.
2787		pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
2788				boot time.
2789				Format: { 0 | 1 }
2790				See arch/parisc/kernel/pdc_chassis.c
2792		percpu_alloc=	Select which percpu first chunk allocator to use.
2793				Currently supported values are "embed" and "page".
2794				Archs may support subset or none of the	selections.
2795				See comments in mm/percpu.c for details on each
2796				allocator.  This parameter is primarily	for debugging
2797				and performance comparison.
2799		pf.		[PARIDE]
2800				See Documentation/blockdev/paride.txt.
2802		pg.		[PARIDE]
2803				See Documentation/blockdev/paride.txt.
2805		pirq=		[SMP,APIC] Manual mp-table setup
2806				See Documentation/x86/i386/IO-APIC.txt.
2808		plip=		[PPT,NET] Parallel port network link
2809				Format: { parport<nr> | timid | 0 }
2810				See also Documentation/parport.txt.
2812		pmtmr=		[X86] Manual setup of pmtmr I/O Port.
2813				Override pmtimer IOPort with a hex value.
2814				e.g. pmtmr=0x508
2816		pnp.debug=1	[PNP]
2817				Enable PNP debug messages (depends on the
2818				CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2819				via /sys/module/pnp/parameters/debug.  We always show
2820				current resource usage; turning this on also shows
2821				possible settings and some assignment information.
2823		pnpacpi=	[ACPI]
2824				{ off }
2826		pnpbios=	[ISAPNP]
2827				{ on | off | curr | res | no-curr | no-res }
2829		pnp_reserve_irq=
2830				[ISAPNP] Exclude IRQs for the autoconfiguration
2832		pnp_reserve_dma=
2833				[ISAPNP] Exclude DMAs for the autoconfiguration
2835		pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
2836				Ranges are in pairs (I/O port base and size).
2838		pnp_reserve_mem=
2839				[ISAPNP] Exclude memory regions for the
2840				autoconfiguration.
2841				Ranges are in pairs (memory base and size).
2843		ports=		[IP_VS_FTP] IPVS ftp helper module
2844				Default is 21.
2845				Up to 8 (IP_VS_APP_MAX_PORTS) ports
2846				may be specified.
2847				Format: <port>,<port>....
2849		print-fatal-signals=
2850				[KNL] debug: print fatal signals
2852				If enabled, warn about various signal handling
2853				related application anomalies: too many signals,
2854				too many POSIX.1 timers, fatal signals causing a
2855				coredump - etc.
2857				If you hit the warning due to signal overflow,
2858				you might want to try "ulimit -i unlimited".
2860				default: off.
2862		printk.always_kmsg_dump=
2863				Trigger kmsg_dump for cases other than kernel oops or
2864				panics
2865				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2866				default: disabled
2868		printk.time=	Show timing data prefixed to each printk message line
2869				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2871		processor.max_cstate=	[HW,ACPI]
2872				Limit processor to maximum C-state
2873				max_cstate=9 overrides any DMI blacklist limit.
2875		processor.nocst	[HW,ACPI]
2876				Ignore the _CST method to determine C-states,
2877				instead using the legacy FADT method
2879		profile=	[KNL] Enable kernel profiling via /proc/profile
2880				Format: [schedule,]<number>
2881				Param: "schedule" - profile schedule points.
2882				Param: <number> - step/bucket size as a power of 2 for
2883					statistical time based profiling.
2884				Param: "sleep" - profile D-state sleeping (millisecs).
2885					Requires CONFIG_SCHEDSTATS
2886				Param: "kvm" - profile VM exits.
2888		prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
2889				before loading.
2890				See Documentation/blockdev/ramdisk.txt.
2892		psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
2893				probe for; one of (bare|imps|exps|lifebook|any).
2894		psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
2895				per second.
2896		psmouse.resetafter=	[HW,MOUSE]
2897				Try to reset the device after so many bad packets
2898				(0 = never).
2899		psmouse.resolution=
2900				[HW,MOUSE] Set desired mouse resolution, in dpi.
2901		psmouse.smartscroll=
2902				[HW,MOUSE] Controls Logitech smartscroll autorepeat.
2903				0 = disabled, 1 = enabled (default).
2905		pstore.backend=	Specify the name of the pstore backend to use
2907		pt.		[PARIDE]
2908				See Documentation/blockdev/paride.txt.
2910		pty.legacy_count=
2911				[KNL] Number of legacy pty's. Overwrites compiled-in
2912				default number.
2914		quiet		[KNL] Disable most log messages
2916		r128=		[HW,DRM]
2918		raid=		[HW,RAID]
2919				See Documentation/md.txt.
2921		ramdisk_blocksize=	[RAM]
2922				See Documentation/blockdev/ramdisk.txt.
2924		ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
2925				See Documentation/blockdev/ramdisk.txt.
2927		rcu_nocbs=	[KNL]
2928				In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2929				the specified list of CPUs to be no-callback CPUs.
2930				Invocation of these CPUs' RCU callbacks will
2931				be offloaded to "rcuox/N" kthreads created for
2932				that purpose, where "x" is "b" for RCU-bh, "p"
2933				for RCU-preempt, and "s" for RCU-sched, and "N"
2934				is the CPU number.  This reduces OS jitter on the
2935				offloaded CPUs, which can be useful for HPC and
2936				real-time workloads.  It can also improve energy
2937				efficiency for asymmetric multiprocessors.
2939		rcu_nocb_poll	[KNL]
2940				Rather than requiring that offloaded CPUs
2941				(specified by rcu_nocbs= above) explicitly
2942				awaken the corresponding "rcuoN" kthreads,
2943				make these kthreads poll for callbacks.
2944				This improves the real-time response for the
2945				offloaded CPUs by relieving them of the need to
2946				wake up the corresponding kthread, but degrades
2947				energy efficiency by requiring that the kthreads
2948				periodically wake up to do the polling.
2950		rcutree.blimit=	[KNL]
2951				Set maximum number of finished RCU callbacks to
2952				process in one batch.
2954		rcutree.rcu_fanout_leaf= [KNL]
2955				Increase the number of CPUs assigned to each
2956				leaf rcu_node structure.  Useful for very large
2957				systems.
2959		rcutree.jiffies_till_sched_qs= [KNL]
2960				Set required age in jiffies for a
2961				given grace period before RCU starts
2962				soliciting quiescent-state help from
2963				rcu_note_context_switch().
2965		rcutree.jiffies_till_first_fqs= [KNL]
2966				Set delay from grace-period initialization to
2967				first attempt to force quiescent states.
2968				Units are jiffies, minimum value is zero,
2969				and maximum value is HZ.
2971		rcutree.jiffies_till_next_fqs= [KNL]
2972				Set delay between subsequent attempts to force
2973				quiescent states.  Units are jiffies, minimum
2974				value is one, and maximum value is HZ.
2976		rcutree.kthread_prio= 	 [KNL,BOOT]
2977				Set the SCHED_FIFO priority of the RCU
2978				per-CPU kthreads (rcuc/N). This value is also
2979				used for the priority of the RCU boost threads
2980				(rcub/N). Valid values are 1-99 and the default
2981				is 1 (the least-favored priority).
2983		rcutree.rcu_nocb_leader_stride= [KNL]
2984				Set the number of NOCB kthread groups, which
2985				defaults to the square root of the number of
2986				CPUs.  Larger numbers reduces the wakeup overhead
2987				on the per-CPU grace-period kthreads, but increases
2988				that same overhead on each group's leader.
2990		rcutree.qhimark= [KNL]
2991				Set threshold of queued RCU callbacks beyond which
2992				batch limiting is disabled.
2994		rcutree.qlowmark= [KNL]
2995				Set threshold of queued RCU callbacks below which
2996				batch limiting is re-enabled.
2998		rcutree.rcu_idle_gp_delay= [KNL]
2999				Set wakeup interval for idle CPUs that have
3000				RCU callbacks (RCU_FAST_NO_HZ=y).
3002		rcutree.rcu_idle_lazy_gp_delay= [KNL]
3003				Set wakeup interval for idle CPUs that have
3004				only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3005				Lazy RCU callbacks are those which RCU can
3006				prove do nothing more than free memory.
3008		rcutorture.cbflood_inter_holdoff= [KNL]
3009				Set holdoff time (jiffies) between successive
3010				callback-flood tests.
3012		rcutorture.cbflood_intra_holdoff= [KNL]
3013				Set holdoff time (jiffies) between successive
3014				bursts of callbacks within a given callback-flood
3015				test.
3017		rcutorture.cbflood_n_burst= [KNL]
3018				Set the number of bursts making up a given
3019				callback-flood test.  Set this to zero to
3020				disable callback-flood testing.
3022		rcutorture.cbflood_n_per_burst= [KNL]
3023				Set the number of callbacks to be registered
3024				in a given burst of a callback-flood test.
3026		rcutorture.fqs_duration= [KNL]
3027				Set duration of force_quiescent_state bursts.
3029		rcutorture.fqs_holdoff= [KNL]
3030				Set holdoff time within force_quiescent_state bursts.
3032		rcutorture.fqs_stutter= [KNL]
3033				Set wait time between force_quiescent_state bursts.
3035		rcutorture.gp_exp= [KNL]
3036				Use expedited update-side primitives.
3038		rcutorture.gp_normal= [KNL]
3039				Use normal (non-expedited) update-side primitives.
3040				If both gp_exp and gp_normal are set, do both.
3041				If neither gp_exp nor gp_normal are set, still
3042				do both.
3044		rcutorture.n_barrier_cbs= [KNL]
3045				Set callbacks/threads for rcu_barrier() testing.
3047		rcutorture.nfakewriters= [KNL]
3048				Set number of concurrent RCU writers.  These just
3049				stress RCU, they don't participate in the actual
3050				test, hence the "fake".
3052		rcutorture.nreaders= [KNL]
3053				Set number of RCU readers.
3055		rcutorture.object_debug= [KNL]
3056				Enable debug-object double-call_rcu() testing.
3058		rcutorture.onoff_holdoff= [KNL]
3059				Set time (s) after boot for CPU-hotplug testing.
3061		rcutorture.onoff_interval= [KNL]
3062				Set time (s) between CPU-hotplug operations, or
3063				zero to disable CPU-hotplug testing.
3065		rcutorture.torture_runnable= [BOOT]
3066				Start rcutorture running at boot time.
3068		rcutorture.shuffle_interval= [KNL]
3069				Set task-shuffle interval (s).  Shuffling tasks
3070				allows some CPUs to go into dyntick-idle mode
3071				during the rcutorture test.
3073		rcutorture.shutdown_secs= [KNL]
3074				Set time (s) after boot system shutdown.  This
3075				is useful for hands-off automated testing.
3077		rcutorture.stall_cpu= [KNL]
3078				Duration of CPU stall (s) to test RCU CPU stall
3079				warnings, zero to disable.
3081		rcutorture.stall_cpu_holdoff= [KNL]
3082				Time to wait (s) after boot before inducing stall.
3084		rcutorture.stat_interval= [KNL]
3085				Time (s) between statistics printk()s.
3087		rcutorture.stutter= [KNL]
3088				Time (s) to stutter testing, for example, specifying
3089				five seconds causes the test to run for five seconds,
3090				wait for five seconds, and so on.  This tests RCU's
3091				ability to transition abruptly to and from idle.
3093		rcutorture.test_boost= [KNL]
3094				Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
3095				"Maybe" means test if the RCU implementation
3096				under test support RCU priority boosting.
3098		rcutorture.test_boost_duration= [KNL]
3099				Duration (s) of each individual boost test.
3101		rcutorture.test_boost_interval= [KNL]
3102				Interval (s) between each boost test.
3104		rcutorture.test_no_idle_hz= [KNL]
3105				Test RCU's dyntick-idle handling.  See also the
3106				rcutorture.shuffle_interval parameter.
3108		rcutorture.torture_type= [KNL]
3109				Specify the RCU implementation to test.
3111		rcutorture.verbose= [KNL]
3112				Enable additional printk() statements.
3114		rcupdate.rcu_expedited= [KNL]
3115				Use expedited grace-period primitives, for
3116				example, synchronize_rcu_expedited() instead
3117				of synchronize_rcu().  This reduces latency,
3118				but can increase CPU utilization, degrade
3119				real-time latency, and degrade energy efficiency.
3121		rcupdate.rcu_cpu_stall_suppress= [KNL]
3122				Suppress RCU CPU stall warning messages.
3124		rcupdate.rcu_cpu_stall_timeout= [KNL]
3125				Set timeout for RCU CPU stall warning messages.
3127		rcupdate.rcu_task_stall_timeout= [KNL]
3128				Set timeout in jiffies for RCU task stall warning
3129				messages.  Disable with a value less than or equal
3130				to zero.
3132		rcupdate.rcu_self_test= [KNL]
3133				Run the RCU early boot self tests
3135		rcupdate.rcu_self_test_bh= [KNL]
3136				Run the RCU bh early boot self tests
3138		rcupdate.rcu_self_test_sched= [KNL]
3139				Run the RCU sched early boot self tests
3141		rdinit=		[KNL]
3142				Format: <full_path>
3143				Run specified binary instead of /init from the ramdisk,
3144				used for early userspace startup. See initrd.
3146		reboot=		[KNL]
3147				Format (x86 or x86_64):
3148					[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3149					[[,]s[mp]#### \
3150					[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3151					[[,]f[orce]
3152				Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3153				      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3154				      reboot_force is either force or not specified,
3155				      reboot_cpu is s[mp]#### with #### being the processor
3156						to be used for rebooting.
3158		relax_domain_level=
3159				[KNL, SMP] Set scheduler's default relax_domain_level.
3160				See Documentation/cgroups/cpusets.txt.
3162		relative_sleep_states=
3163				[SUSPEND] Use sleep state labeling where the deepest
3164				state available other than hibernation is always "mem".
3165				Format: { "0" | "1" }
3166				0 -- Traditional sleep state labels.
3167				1 -- Relative sleep state labels.
3169		reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
3171		reservetop=	[X86-32]
3172				Format: nn[KMG]
3173				Reserves a hole at the top of the kernel virtual
3174				address space.
3176		reservelow=	[X86]
3177				Format: nn[K]
3178				Set the amount of memory to reserve for BIOS at
3179				the bottom of the address space.
3181		reset_devices	[KNL] Force drivers to reset the underlying device
3182				during initialization.
3184		resume=		[SWSUSP]
3185				Specify the partition device for software suspend
3186				Format:
3187				{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3189		resume_offset=	[SWSUSP]
3190				Specify the offset from the beginning of the partition
3191				given by "resume=" at which the swap header is located,
3192				in <PAGE_SIZE> units (needed only for swap files).
3193				See  Documentation/power/swsusp-and-swap-files.txt
3195		resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
3196				read the resume files
3198		resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
3199				Useful for devices that are detected asynchronously
3200				(e.g. USB and MMC devices).
3202		hibernate=	[HIBERNATION]
3203			noresume	Don't check if there's a hibernation image
3204					present during boot.
3205			nocompress	Don't compress/decompress hibernation images.
3206			no		Disable hibernation and resume.
3208		retain_initrd	[RAM] Keep initrd memory after extraction
3210		rhash_entries=	[KNL,NET]
3211				Set number of hash buckets for route cache
3213		ro		[KNL] Mount root device read-only on boot
3215		root=		[KNL] Root filesystem
3216				See name_to_dev_t comment in init/do_mounts.c.
3218		rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
3219				mount the root filesystem
3221		rootflags=	[KNL] Set root filesystem mount option string
3223		rootfstype=	[KNL] Set root filesystem type
3225		rootwait	[KNL] Wait (indefinitely) for root device to show up.
3226				Useful for devices that are detected asynchronously
3227				(e.g. USB and MMC devices).
3229		rproc_mem=nn[KMG][@address]
3230				[KNL,ARM,CMA] Remoteproc physical memory block.
3231				Memory area to be used by remote processor image,
3232				managed by CMA.
3234		rw		[KNL] Mount root device read-write on boot
3236		S		[KNL] Run init in single mode
3238		s390_iommu=	[HW,S390]
3239				Set s390 IOTLB flushing mode
3240			strict
3241				With strict flushing every unmap operation will result in
3242				an IOTLB flush. Default is lazy flushing before reuse,
3243				which is faster.
3245		sa1100ir	[NET]
3246				See drivers/net/irda/sa1100_ir.c.
3248		sbni=		[NET] Granch SBNI12 leased line adapter
3250		sched_debug	[KNL] Enables verbose scheduler debug messages.
3252		skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
3253				xtime_lock contention on larger systems, and/or RCU lock
3254				contention on all systems with CONFIG_MAXSMP set.
3255				Format: { "0" | "1" }
3256				0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3257				1 -- enable.
3258				Note: increases power consumption, thus should only be
3259				enabled if running jitter sensitive (HPC/RT) workloads.
3261		security=	[SECURITY] Choose a security module to enable at boot.
3262				If this boot parameter is not specified, only the first
3263				security module asking for security registration will be
3264				loaded. An invalid security module name will be treated
3265				as if no module has been chosen.
3267		selinux=	[SELINUX] Disable or enable SELinux at boot time.
3268				Format: { "0" | "1" }
3269				See security/selinux/Kconfig help text.
3270				0 -- disable.
3271				1 -- enable.
3272				Default value is set via kernel config option.
3273				If enabled at boot time, /selinux/disable can be used
3274				later to disable prior to initial policy load.
3276		apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
3277				Format: { "0" | "1" }
3278				See security/apparmor/Kconfig help text
3279				0 -- disable.
3280				1 -- enable.
3281				Default value is set via kernel config option.
3283		serialnumber	[BUGS=X86-32]
3285		shapers=	[NET]
3286				Maximal number of shapers.
3288		show_msr=	[x86] show boot-time MSR settings
3289				Format: { <integer> }
3290				Show boot-time (BIOS-initialized) MSR settings.
3291				The parameter means the number of CPUs to show,
3292				for example 1 means boot CPU only.
3294		simeth=		[IA-64]
3295		simscsi=
3297		slram=		[HW,MTD]
3299		slab_nomerge	[MM]
3300				Disable merging of slabs with similar size. May be
3301				necessary if there is some reason to distinguish
3302				allocs to different slabs. Debug options disable
3303				merging on their own.
3304				For more information see Documentation/vm/slub.txt.
3306		slab_max_order=	[MM, SLAB]
3307				Determines the maximum allowed order for slabs.
3308				A high setting may cause OOMs due to memory
3309				fragmentation.  Defaults to 1 for systems with
3310				more than 32MB of RAM, 0 otherwise.
3312		slub_debug[=options[,slabs]]	[MM, SLUB]
3313				Enabling slub_debug allows one to determine the
3314				culprit if slab objects become corrupted. Enabling
3315				slub_debug can create guard zones around objects and
3316				may poison objects when not in use. Also tracks the
3317				last alloc / free. For more information see
3318				Documentation/vm/slub.txt.
3320		slub_max_order= [MM, SLUB]
3321				Determines the maximum allowed order for slabs.
3322				A high setting may cause OOMs due to memory
3323				fragmentation. For more information see
3324				Documentation/vm/slub.txt.
3326		slub_min_objects=	[MM, SLUB]
3327				The minimum number of objects per slab. SLUB will
3328				increase the slab order up to slub_max_order to
3329				generate a sufficiently large slab able to contain
3330				the number of objects indicated. The higher the number
3331				of objects the smaller the overhead of tracking slabs
3332				and the less frequently locks need to be acquired.
3333				For more information see Documentation/vm/slub.txt.
3335		slub_min_order=	[MM, SLUB]
3336				Determines the minimum page order for slabs. Must be
3337				lower than slub_max_order.
3338				For more information see Documentation/vm/slub.txt.
3340		slub_nomerge	[MM, SLUB]
3341				Same with slab_nomerge. This is supported for legacy.
3342				See slab_nomerge for more information.
3344		smart2=		[HW]
3345				Format: <io1>[,<io2>[,...,<io8>]]
3347		smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
3348		smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
3349		smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
3350		smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
3351		smsc-ircc2.ircc_irq=	[HW] IRQ line
3352		smsc-ircc2.ircc_dma=	[HW] DMA channel
3353		smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3354					0: Toshiba Satellite 1800 (GP data pin select)
3355					1: Fast pin select (default)
3356					2: ATC IRMode
3358		softlockup_panic=
3359				[KNL] Should the soft-lockup detector generate panics.
3360				Format: <integer>
3362		softlockup_all_cpu_backtrace=
3363				[KNL] Should the soft-lockup detector generate
3364				backtraces on all cpus.
3365				Format: <integer>
3367		sonypi.*=	[HW] Sony Programmable I/O Control Device driver
3368				See Documentation/laptops/sonypi.txt
3370		spia_io_base=	[HW,MTD]
3371		spia_fio_base=
3372		spia_pedr=
3373		spia_peddr=
3375		stacktrace	[FTRACE]
3376				Enabled the stack tracer on boot up.
3378		stacktrace_filter=[function-list]
3379				[FTRACE] Limit the functions that the stack tracer
3380				will trace at boot up. function-list is a comma separated
3381				list of functions. This list can be changed at run
3382				time by the stack_trace_filter file in the debugfs
3383				tracing directory. Note, this enables stack tracing
3384				and the stacktrace above is not needed.
3386		sti=		[PARISC,HW]
3387				Format: <num>
3388				Set the STI (builtin display/keyboard on the HP-PARISC
3389				machines) console (graphic card) which should be used
3390				as the initial boot-console.
3391				See also comment in drivers/video/console/sticore.c.
3393		sti_font=	[HW]
3394				See comment in drivers/video/console/sticore.c.
3396		stifb=		[HW]
3397				Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3399		sunrpc.min_resvport=
3400		sunrpc.max_resvport=
3401				[NFS,SUNRPC]
3402				SunRPC servers often require that client requests
3403				originate from a privileged port (i.e. a port in the
3404				range 0 < portnr < 1024).
3405				An administrator who wishes to reserve some of these
3406				ports for other uses may adjust the range that the
3407				kernel's sunrpc client considers to be privileged
3408				using these two parameters to set the minimum and
3409				maximum port values.
3411		sunrpc.pool_mode=
3412				[NFS]
3413				Control how the NFS server code allocates CPUs to
3414				service thread pools.  Depending on how many NICs
3415				you have and where their interrupts are bound, this
3416				option will affect which CPUs will do NFS serving.
3417				Note: this parameter cannot be changed while the
3418				NFS server is running.
3420				auto	    the server chooses an appropriate mode
3421					    automatically using heuristics
3422				global	    a single global pool contains all CPUs
3423				percpu	    one pool for each CPU
3424				pernode	    one pool for each NUMA node (equivalent
3425					    to global on non-NUMA machines)
3427		sunrpc.tcp_slot_table_entries=
3428		sunrpc.udp_slot_table_entries=
3429				[NFS,SUNRPC]
3430				Sets the upper limit on the number of simultaneous
3431				RPC calls that can be sent from the client to a
3432				server. Increasing these values may allow you to
3433				improve throughput, but will also increase the
3434				amount of memory reserved for use by the client.
3436		swapaccount=[0|1]
3437				[KNL] Enable accounting of swap in memory resource
3438				controller if no parameter or 1 is given or disable
3439				it if 0 is given (See Documentation/cgroups/memory.txt)
3441		swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
3442				Format: { <int> | force }
3443				<int> -- Number of I/O TLB slabs
3444				force -- force using of bounce buffers even if they
3445				         wouldn't be automatically used by the kernel
3447		switches=	[HW,M68k]
3449		sysfs.deprecated=0|1 [KNL]
3450				Enable/disable old style sysfs layout for old udev
3451				on older distributions. When this option is enabled
3452				very new udev will not work anymore. When this option
3453				is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3454				in older udev will not work anymore.
3455				Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3456				the kernel configuration.
3458		sysrq_always_enabled
3459				[KNL]
3460				Ignore sysrq setting - this boot parameter will
3461				neutralize any effect of /proc/sys/kernel/sysrq.
3462				Useful for debugging.
3464		tcpmhash_entries= [KNL,NET]
3465				Set the number of tcp_metrics_hash slots.
3466				Default value is 8192 or 16384 depending on total
3467				ram pages. This is used to specify the TCP metrics
3468				cache size. See Documentation/networking/ip-sysctl.txt
3469				"tcp_no_metrics_save" section for more details.
3471		tdfx=		[HW,DRM]
3473		test_suspend=	[SUSPEND][,N]
3474				Specify "mem" (for Suspend-to-RAM) or "standby" (for
3475				standby suspend) or "freeze" (for suspend type freeze)
3476				as the system sleep state during system startup with
3477				the optional capability to repeat N number of times.
3478				The system is woken from this state using a
3479				wakeup-capable RTC alarm.
3481		thash_entries=	[KNL,NET]
3482				Set number of hash buckets for TCP connection
3484		thermal.act=	[HW,ACPI]
3485				-1: disable all active trip points in all thermal zones
3486				<degrees C>: override all lowest active trip points
3488		thermal.crt=	[HW,ACPI]
3489				-1: disable all critical trip points in all thermal zones
3490				<degrees C>: override all critical trip points
3492		thermal.nocrt=	[HW,ACPI]
3493				Set to disable actions on ACPI thermal zone
3494				critical and hot trip points.
3496		thermal.off=	[HW,ACPI]
3497				1: disable ACPI thermal control
3499		thermal.psv=	[HW,ACPI]
3500				-1: disable all passive trip points
3501				<degrees C>: override all passive trip points to this
3502				value
3504		thermal.tzp=	[HW,ACPI]
3505				Specify global default ACPI thermal zone polling rate
3506				<deci-seconds>: poll all this frequency
3507				0: no polling (default)
3509		threadirqs	[KNL]
3510				Force threading of all interrupt handlers except those
3511				marked explicitly IRQF_NO_THREAD.
3513		tmem		[KNL,XEN]
3514				Enable the Transcendent memory driver if built-in.
3516		tmem.cleancache=0|1 [KNL, XEN]
3517				Default is on (1). Disable the usage of the cleancache
3518				API to send anonymous pages to the hypervisor.
3520		tmem.frontswap=0|1 [KNL, XEN]
3521				Default is on (1). Disable the usage of the frontswap
3522				API to send swap pages to the hypervisor. If disabled
3523				the selfballooning and selfshrinking are force disabled.
3525		tmem.selfballooning=0|1 [KNL, XEN]
3526				Default is on (1). Disable the driving of swap pages
3527				to the hypervisor.
3529		tmem.selfshrinking=0|1 [KNL, XEN]
3530				Default is on (1). Partial swapoff that immediately
3531				transfers pages from Xen hypervisor back to the
3532				kernel based on different criteria.
3534		topology=	[S390]
3535				Format: {off | on}
3536				Specify if the kernel should make use of the cpu
3537				topology information if the hardware supports this.
3538				The scheduler will make use of this information and
3539				e.g. base its process migration decisions on it.
3540				Default is on.
3542		topology_updates= [KNL, PPC, NUMA]
3543				Format: {off}
3544				Specify if the kernel should ignore (off)
3545				topology updates sent by the hypervisor to this
3546				LPAR.
3548		tp720=		[HW,PS2]
3550		tpm_suspend_pcr=[HW,TPM]
3551				Format: integer pcr id
3552				Specify that at suspend time, the tpm driver
3553				should extend the specified pcr with zeros,
3554				as a workaround for some chips which fail to
3555				flush the last written pcr on TPM_SaveState.
3556				This will guarantee that all the other pcrs
3557				are saved.
3559		trace_buf_size=nn[KMG]
3560				[FTRACE] will set tracing buffer size on each cpu.
3562		trace_event=[event-list]
3563				[FTRACE] Set and start specified trace events in order
3564				to facilitate early boot debugging.
3565				See also Documentation/trace/events.txt
3567		trace_options=[option-list]
3568				[FTRACE] Enable or disable tracer options at boot.
3569				The option-list is a comma delimited list of options
3570				that can be enabled or disabled just as if you were
3571				to echo the option name into
3573				    /sys/kernel/debug/tracing/trace_options
3575				For example, to enable stacktrace option (to dump the
3576				stack trace of each event), add to the command line:
3578				      trace_options=stacktrace
3580				See also Documentation/trace/ftrace.txt "trace options"
3581				section.
3583		tp_printk[FTRACE]
3584				Have the tracepoints sent to printk as well as the
3585				tracing ring buffer. This is useful for early boot up
3586				where the system hangs or reboots and does not give the
3587				option for reading the tracing buffer or performing a
3588				ftrace_dump_on_oops.
3590				To turn off having tracepoints sent to printk,
3591				 echo 0 > /proc/sys/kernel/tracepoint_printk
3592				Note, echoing 1 into this file without the
3593				tracepoint_printk kernel cmdline option has no effect.
3595				** CAUTION **
3597				Having tracepoints sent to printk() and activating high
3598				frequency tracepoints such as irq or sched, can cause
3599				the system to live lock.
3601		traceoff_on_warning
3602				[FTRACE] enable this option to disable tracing when a
3603				warning is hit. This turns off "tracing_on". Tracing can
3604				be enabled again by echoing '1' into the "tracing_on"
3605				file located in /sys/kernel/debug/tracing/
3607				This option is useful, as it disables the trace before
3608				the WARNING dump is called, which prevents the trace to
3609				be filled with content caused by the warning output.
3611				This option can also be set at run time via the sysctl
3612				option:  kernel/traceoff_on_warning
3614		transparent_hugepage=
3615				[KNL]
3616				Format: [always|madvise|never]
3617				Can be used to control the default behavior of the system
3618				with respect to transparent hugepages.
3619				See Documentation/vm/transhuge.txt for more details.
3621		tsc=		Disable clocksource stability checks for TSC.
3622				Format: <string>
3623				[x86] reliable: mark tsc clocksource as reliable, this
3624				disables clocksource verification at runtime, as well
3625				as the stability checks done at bootup.	Used to enable
3626				high-resolution timer mode on older hardware, and in
3627				virtualized environment.
3628				[x86] noirqtime: Do not use TSC to do irq accounting.
3629				Used to run time disable IRQ_TIME_ACCOUNTING on any
3630				platforms where RDTSC is slow and this accounting
3631				can add overhead.
3633		turbografx.map[2|3]=	[HW,JOY]
3634				TurboGraFX parallel port interface
3635				Format:
3636				<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3637				See also Documentation/input/joystick-parport.txt
3639		udbg-immortal	[PPC] When debugging early kernel crashes that
3640				happen after console_init() and before a proper 
3641				console driver takes over, this boot options might
3642				help "seeing" what's going on.
3644		uhash_entries=	[KNL,NET]
3645				Set number of hash buckets for UDP/UDP-Lite connections
3647		uhci-hcd.ignore_oc=
3648				[USB] Ignore overcurrent events (default N).
3649				Some badly-designed motherboards generate lots of
3650				bogus events, for ports that aren't wired to
3651				anything.  Set this parameter to avoid log spamming.
3652				Note that genuine overcurrent events won't be
3653				reported either.
3655		unknown_nmi_panic
3656				[X86] Cause panic on unknown NMI.
3658		usbcore.authorized_default=
3659				[USB] Default USB device authorization:
3660				(default -1 = authorized except for wireless USB,
3661				0 = not authorized, 1 = authorized)
3663		usbcore.autosuspend=
3664				[USB] The autosuspend time delay (in seconds) used
3665				for newly-detected USB devices (default 2).  This
3666				is the time required before an idle device will be
3667				autosuspended.  Devices for which the delay is set
3668				to a negative value won't be autosuspended at all.
3670		usbcore.usbfs_snoop=
3671				[USB] Set to log all usbfs traffic (default 0 = off).
3673		usbcore.blinkenlights=
3674				[USB] Set to cycle leds on hubs (default 0 = off).
3676		usbcore.old_scheme_first=
3677				[USB] Start with the old device initialization
3678				scheme (default 0 = off).
3680		usbcore.usbfs_memory_mb=
3681				[USB] Memory limit (in MB) for buffers allocated by
3682				usbfs (default = 16, 0 = max = 2047).
3684		usbcore.use_both_schemes=
3685				[USB] Try the other device initialization scheme
3686				if the first one fails (default 1 = enabled).
3688		usbcore.initial_descriptor_timeout=
3689				[USB] Specifies timeout for the initial 64-byte
3690	                        USB_REQ_GET_DESCRIPTOR request in milliseconds
3691				(default 5000 = 5.0 seconds).
3693		usbhid.mousepoll=
3694				[USBHID] The interval which mice are to be polled at.
3696		usb-storage.delay_use=
3697				[UMS] The delay in seconds before a new device is
3698				scanned for Logical Units (default 1).
3700		usb-storage.quirks=
3701				[UMS] A list of quirks entries to supplement or
3702				override the built-in unusual_devs list.  List
3703				entries are separated by commas.  Each entry has
3704				the form VID:PID:Flags where VID and PID are Vendor
3705				and Product ID values (4-digit hex numbers) and
3706				Flags is a set of characters, each corresponding
3707				to a common usb-storage quirk flag as follows:
3708					a = SANE_SENSE (collect more than 18 bytes
3709						of sense data);
3710					b = BAD_SENSE (don't collect more than 18
3711						bytes of sense data);
3712					c = FIX_CAPACITY (decrease the reported
3713						device capacity by one sector);
3714					d = NO_READ_DISC_INFO (don't use
3715						READ_DISC_INFO command);
3716					e = NO_READ_CAPACITY_16 (don't use
3717						READ_CAPACITY_16 command);
3718					f = NO_REPORT_OPCODES (don't use report opcodes
3719						command, uas only);
3720					h = CAPACITY_HEURISTICS (decrease the
3721						reported device capacity by one
3722						sector if the number is odd);
3723					i = IGNORE_DEVICE (don't bind to this
3724						device);
3725					l = NOT_LOCKABLE (don't try to lock and
3726						unlock ejectable media);
3727					m = MAX_SECTORS_64 (don't transfer more
3728						than 64 sectors = 32 KB at a time);
3729					n = INITIAL_READ10 (force a retry of the
3730						initial READ(10) command);
3731					o = CAPACITY_OK (accept the capacity
3732						reported by the device);
3733					p = WRITE_CACHE (the device cache is ON
3734						by default);
3735					r = IGNORE_RESIDUE (the device reports
3736						bogus residue values);
3737					s = SINGLE_LUN (the device has only one
3738						Logical Unit);
3739					t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3740						commands, uas only);
3741					u = IGNORE_UAS (don't bind to the uas driver);
3742					w = NO_WP_DETECT (don't test whether the
3743						medium is write-protected).
3744				Example: quirks=0419:aaf5:rl,0421:0433:rc
3746		user_debug=	[KNL,ARM]
3747				Format: <int>
3748				See arch/arm/Kconfig.debug help text.
3749					 1 - undefined instruction events
3750					 2 - system calls
3751					 4 - invalid data aborts
3752					 8 - SIGSEGV faults
3753					16 - SIGBUS faults
3754				Example: user_debug=31
3756		userpte=
3757				[X86] Flags controlling user PTE allocations.
3759					nohigh = do not allocate PTE pages in
3760						HIGHMEM regardless of setting
3761						of CONFIG_HIGHPTE.
3763		vdso=		[X86,SH]
3764				On X86_32, this is an alias for vdso32=.  Otherwise:
3766				vdso=1: enable VDSO (the default)
3767				vdso=0: disable VDSO mapping
3769		vdso32=		[X86] Control the 32-bit vDSO
3770				vdso32=1: enable 32-bit VDSO
3771				vdso32=0 or vdso32=2: disable 32-bit VDSO
3773				See the help text for CONFIG_COMPAT_VDSO for more
3774				details.  If CONFIG_COMPAT_VDSO is set, the default is
3775				vdso32=0; otherwise, the default is vdso32=1.
3777				For compatibility with older kernels, vdso32=2 is an
3778				alias for vdso32=0.
3780				Try vdso32=0 if you encounter an error that says:
3781				dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3783		vector=		[IA-64,SMP]
3784				vector=percpu: enable percpu vector domain
3786		video=		[FB] Frame buffer configuration
3787				See Documentation/fb/modedb.txt.
3789		video.brightness_switch_enabled= [0,1]
3790				If set to 1, on receiving an ACPI notify event
3791				generated by hotkey, video driver will adjust brightness
3792				level and then send out the event to user space through
3793				the allocated input device; If set to 0, video driver
3794				will only send out the event without touching backlight
3795				brightness level.
3796				default: 1
3798		virtio_mmio.device=
3799				[VMMIO] Memory mapped virtio (platform) device.
3801					<size>@<baseaddr>:<irq>[:<id>]
3802				where:
3803					<size>     := size (can use standard suffixes
3804							like K, M and G)
3805					<baseaddr> := physical base address
3806					<irq>      := interrupt number (as passed to
3807							request_irq())
3808					<id>       := (optional) platform device id
3809				example:
3810					virtio_mmio.device=1K@0x100b0000:48:7
3812				Can be used multiple times for multiple devices.
3814		vga=		[BOOT,X86-32] Select a particular video mode
3815				See Documentation/x86/boot.txt and
3816				Documentation/svga.txt.
3817				Use vga=ask for menu.
3818				This is actually a boot loader parameter; the value is
3819				passed to the kernel using a special protocol.
3821		vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
3822				size of <nn>. This can be used to increase the
3823				minimum size (128MB on x86). It can also be used to
3824				decrease the size and leave more room for directly
3825				mapped kernel RAM.
3827		vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
3828				Format: <command>
3830		vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
3831				Format: <command>
3833		vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
3834				Format: <command>
3836		vsyscall=	[X86-64]
3837				Controls the behavior of vsyscalls (i.e. calls to
3838				fixed addresses of 0xffffffffff600x00 from legacy
3839				code).  Most statically-linked binaries and older
3840				versions of glibc use these calls.  Because these
3841				functions are at fixed addresses, they make nice
3842				targets for exploits that can control RIP.
3844				emulate     [default] Vsyscalls turn into traps and are
3845				            emulated reasonably safely.
3847				native      Vsyscalls are native syscall instructions.
3848				            This is a little bit faster than trapping
3849				            and makes a few dynamic recompilers work
3850				            better than they would in emulation mode.
3851				            It also makes exploits much easier to write.
3853				none        Vsyscalls don't work at all.  This makes
3854				            them quite hard to use for exploits but
3855				            might break your system.
3857		vt.color=	[VT] Default text color.
3858				Format: 0xYX, X = foreground, Y = background.
3859				Default: 0x07 = light gray on black.
3861		vt.cur_default=	[VT] Default cursor shape.
3862				Format: 0xCCBBAA, where AA, BB, and CC are the same as
3863				the parameters of the <Esc>[?A;B;Cc escape sequence;
3864				see VGA-softcursor.txt. Default: 2 = underline.
3866		vt.default_blu=	[VT]
3867				Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3868				Change the default blue palette of the console.
3869				This is a 16-member array composed of values
3870				ranging from 0-255.
3872		vt.default_grn=	[VT]
3873				Format: <green0>,<green1>,<green2>,...,<green15>
3874				Change the default green palette of the console.
3875				This is a 16-member array composed of values
3876				ranging from 0-255.
3878		vt.default_red=	[VT]
3879				Format: <red0>,<red1>,<red2>,...,<red15>
3880				Change the default red palette of the console.
3881				This is a 16-member array composed of values
3882				ranging from 0-255.
3884		vt.default_utf8=
3885				[VT]
3886				Format=<0|1>
3887				Set system-wide default UTF-8 mode for all tty's.
3888				Default is 1, i.e. UTF-8 mode is enabled for all
3889				newly opened terminals.
3891		vt.global_cursor_default=
3892				[VT]
3893				Format=<-1|0|1>
3894				Set system-wide default for whether a cursor
3895				is shown on new VTs. Default is -1,
3896				i.e. cursors will be created by default unless
3897				overridden by individual drivers. 0 will hide
3898				cursors, 1 will display them.
3900		vt.italic=	[VT] Default color for italic text; 0-15.
3901				Default: 2 = green.
3903		vt.underline=	[VT] Default color for underlined text; 0-15.
3904				Default: 3 = cyan.
3906		watchdog timers	[HW,WDT] For information on watchdog timers,
3907				see Documentation/watchdog/watchdog-parameters.txt
3908				or other driver-specific files in the
3909				Documentation/watchdog/ directory.
3911		workqueue.disable_numa
3912				By default, all work items queued to unbound
3913				workqueues are affine to the NUMA nodes they're
3914				issued on, which results in better behavior in
3915				general.  If NUMA affinity needs to be disabled for
3916				whatever reason, this option can be used.  Note
3917				that this also can be controlled per-workqueue for
3918				workqueues visible under /sys/bus/workqueue/.
3920		workqueue.power_efficient
3921				Per-cpu workqueues are generally preferred because
3922				they show better performance thanks to cache
3923				locality; unfortunately, per-cpu workqueues tend to
3924				be more power hungry than unbound workqueues.
3926				Enabling this makes the per-cpu workqueues which
3927				were observed to contribute significantly to power
3928				consumption unbound, leading to measurably lower
3929				power usage at the cost of small performance
3930				overhead.
3932				The default value of this parameter is determined by
3933				the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3935		x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
3936				default x2apic cluster mode on platforms
3937				supporting x2apic.
3939		x86_intel_mid_timer= [X86-32,APBT]
3940				Choose timer option for x86 Intel MID platform.
3941				Two valid options are apbt timer only and lapic timer
3942				plus one apbt timer for broadcast timer.
3943				x86_intel_mid_timer=apbt_only | lapic_and_apbt
3945		xen_emul_unplug=		[HW,X86,XEN]
3946				Unplug Xen emulated devices
3947				Format: [unplug0,][unplug1]
3948				ide-disks -- unplug primary master IDE devices
3949				aux-ide-disks -- unplug non-primary-master IDE devices
3950				nics -- unplug network devices
3951				all -- unplug all emulated devices (NICs and IDE disks)
3952				unnecessary -- unplugging emulated devices is
3953					unnecessary even if the host did not respond to
3954					the unplug protocol
3955				never -- do not unplug even if version check succeeds
3957		xen_nopvspin	[X86,XEN]
3958				Disables the ticketlock slowpath using Xen PV
3959				optimizations.
3961		xen_nopv	[X86]
3962				Disables the PV optimizations forcing the HVM guest to
3963				run as generic HVM guest with no PV drivers.
3965		xirc2ps_cs=	[NET,PCMCIA]
3966				Format:
3967				<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3969	______________________________________________________________________
3971	TODO:
3973		Add more DRM drivers.
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