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Based on kernel version 4.1. Page generated on 2015-06-28 12:13 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,ARM64]
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
178				For ARM64, ONLY "acpi=off" or "acpi=force" are available
180				See also Documentation/power/runtime_pm.txt, pci=noacpi
182		acpi_rsdp=	[ACPI,EFI,KEXEC]
183				Pass the RSDP address to the kernel, mostly used
184				on machines running EFI runtime service to boot the
185				second kernel for kdump.
187		acpi_apic_instance=	[ACPI, IOAPIC]
188				Format: <int>
189				2: use 2nd APIC table, if available
190				1,0: use 1st APIC table
191				default: 0
193		acpi_backlight=	[HW,ACPI]
194				acpi_backlight=vendor
195				acpi_backlight=video
196				If set to vendor, prefer vendor specific driver
197				(e.g. thinkpad_acpi, sony_acpi, etc.) instead
198				of the ACPI video.ko driver.
200		acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
201		acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
202				Format: <int>
203				CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
204				debug output.  Bits in debug_layer correspond to a
205				_COMPONENT in an ACPI source file, e.g.,
207				Bits in debug_level correspond to a level in
208				ACPI_DEBUG_PRINT statements, e.g.,
210				The debug_level mask defaults to "info".  See
211				Documentation/acpi/debug.txt for more information about
212				debug layers and levels.
214				Enable processor driver info messages:
215				    acpi.debug_layer=0x20000000
216				Enable PCI/PCI interrupt routing info messages:
217				    acpi.debug_layer=0x400000
218				Enable AML "Debug" output, i.e., stores to the Debug
219				object while interpreting AML:
220				    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
221				Enable all messages related to ACPI hardware:
222				    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
224				Some values produce so much output that the system is
225				unusable.  The "log_buf_len" parameter may be useful
226				if you need to capture more output.
228		acpi_force_table_verification	[HW,ACPI]
229				Enable table checksum verification during early stage.
230				By default, this is disabled due to x86 early mapping
231				size limitation.
233		acpi_irq_balance [HW,ACPI]
234				ACPI will balance active IRQs
235				default in APIC mode
237		acpi_irq_nobalance [HW,ACPI]
238				ACPI will not move active IRQs (default)
239				default in PIC mode
241		acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
242				Format: <irq>,<irq>...
244		acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
245				use by PCI
246				Format: <irq>,<irq>...
248		acpi_no_auto_serialize	[HW,ACPI]
249				Disable auto-serialization of AML methods
250				AML control methods that contain the opcodes to create
251				named objects will be marked as "Serialized" by the
252				auto-serialization feature.
253				This feature is enabled by default.
254				This option allows to turn off the feature.
256		acpi_no_static_ssdt	[HW,ACPI]
257				Disable installation of static SSDTs at early boot time
258				By default, SSDTs contained in the RSDT/XSDT will be
259				installed automatically and they will appear under
260				/sys/firmware/acpi/tables.
261				This option turns off this feature.
262				Note that specifying this option does not affect
263				dynamic table installation which will install SSDT
264				tables to /sys/firmware/acpi/tables/dynamic.
266		acpica_no_return_repair [HW, ACPI]
267				Disable AML predefined validation mechanism
268				This mechanism can repair the evaluation result to make
269				the return objects more ACPI specification compliant.
270				This option is useful for developers to identify the
271				root cause of an AML interpreter issue when the issue
272				has something to do with the repair mechanism.
274		acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
275				Format: To spoof as Windows 98: ="Microsoft Windows"
277		acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
278				acpi_osi="string1"	# add string1
279				acpi_osi="!string2"	# remove string2
280				acpi_osi=!*		# remove all strings
281				acpi_osi=!		# disable all built-in OS vendor
282							  strings
283				acpi_osi=		# disable all strings
285				'acpi_osi=!' can be used in combination with single or
286				multiple 'acpi_osi="string1"' to support specific OS
287				vendor string(s).  Note that such command can only
288				affect the default state of the OS vendor strings, thus
289				it cannot affect the default state of the feature group
290				strings and the current state of the OS vendor strings,
291				specifying it multiple times through kernel command line
292				is meaningless.  This command is useful when one do not
293				care about the state of the feature group strings which
294				should be controlled by the OSPM.
295				Examples:
296				  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
297				     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
298				     can make '_OSI("Windows 2000")' TRUE.
300				'acpi_osi=' cannot be used in combination with other
301				'acpi_osi=' command lines, the _OSI method will not
302				exist in the ACPI namespace.  NOTE that such command can
303				only affect the _OSI support state, thus specifying it
304				multiple times through kernel command line is also
305				meaningless.
306				Examples:
307				  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
308				     FALSE.
310				'acpi_osi=!*' can be used in combination with single or
311				multiple 'acpi_osi="string1"' to support specific
312				string(s).  Note that such command can affect the
313				current state of both the OS vendor strings and the
314				feature group strings, thus specifying it multiple times
315				through kernel command line is meaningful.  But it may
316				still not able to affect the final state of a string if
317				there are quirks related to this string.  This command
318				is useful when one want to control the state of the
319				feature group strings to debug BIOS issues related to
320				the OSPM features.
321				Examples:
322				  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
323				     '_OSI("Module Device")' FALSE.
324				  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
325				     '_OSI("Module Device")' TRUE.
326				  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
327				     equivalent to
328				     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
329				     and
330				     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
331				     they all will make '_OSI("Windows 2000")' TRUE.
333		acpi_pm_good	[X86]
334				Override the pmtimer bug detection: force the kernel
335				to assume that this machine's pmtimer latches its value
336				and always returns good values.
338		acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
339				Format: { level | edge | high | low }
341		acpi_skip_timer_override [HW,ACPI]
342				Recognize and ignore IRQ0/pin2 Interrupt Override.
343				For broken nForce2 BIOS resulting in XT-PIC timer.
345		acpi_sleep=	[HW,ACPI] Sleep options
346				Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
347					  old_ordering, nonvs, sci_force_enable }
348				See Documentation/power/video.txt for information on
349				s3_bios and s3_mode.
350				s3_beep is for debugging; it makes the PC's speaker beep
351				as soon as the kernel's real-mode entry point is called.
352				s4_nohwsig prevents ACPI hardware signature from being
353				used during resume from hibernation.
354				old_ordering causes the ACPI 1.0 ordering of the _PTS
355				control method, with respect to putting devices into
356				low power states, to be enforced (the ACPI 2.0 ordering
357				of _PTS is used by default).
358				nonvs prevents the kernel from saving/restoring the
359				ACPI NVS memory during suspend/hibernation and resume.
360				sci_force_enable causes the kernel to set SCI_EN directly
361				on resume from S1/S3 (which is against the ACPI spec,
362				but some broken systems don't work without it).
364		acpi_use_timer_override [HW,ACPI]
365				Use timer override. For some broken Nvidia NF5 boards
366				that require a timer override, but don't have HPET
368		acpi_enforce_resources=	[ACPI]
369				{ strict | lax | no }
370				Check for resource conflicts between native drivers
371				and ACPI OperationRegions (SystemIO and SystemMemory
372				only). IO ports and memory declared in ACPI might be
373				used by the ACPI subsystem in arbitrary AML code and
374				can interfere with legacy drivers.
375				strict (default): access to resources claimed by ACPI
376				is denied; legacy drivers trying to access reserved
377				resources will fail to bind to device using them.
378				lax: access to resources claimed by ACPI is allowed;
379				legacy drivers trying to access reserved resources
380				will bind successfully but a warning message is logged.
381				no: ACPI OperationRegions are not marked as reserved,
382				no further checks are performed.
384		acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
385				   kernels.
387		add_efi_memmap	[EFI; X86] Include EFI memory map in
388				kernel's map of available physical RAM.
390		agp=		[AGP]
391				{ off | try_unsupported }
392				off: disable AGP support
393				try_unsupported: try to drive unsupported chipsets
394					(may crash computer or cause data corruption)
396		ALSA		[HW,ALSA]
397				See Documentation/sound/alsa/alsa-parameters.txt
399		alignment=	[KNL,ARM]
400				Allow the default userspace alignment fault handler
401				behaviour to be specified.  Bit 0 enables warnings,
402				bit 1 enables fixups, and bit 2 sends a segfault.
404		align_va_addr=	[X86-64]
405				Align virtual addresses by clearing slice [14:12] when
406				allocating a VMA at process creation time. This option
407				gives you up to 3% performance improvement on AMD F15h
408				machines (where it is enabled by default) for a
409				CPU-intensive style benchmark, and it can vary highly in
410				a microbenchmark depending on workload and compiler.
412				32: only for 32-bit processes
413				64: only for 64-bit processes
414				on: enable for both 32- and 64-bit processes
415				off: disable for both 32- and 64-bit processes
417		alloc_snapshot	[FTRACE]
418				Allocate the ftrace snapshot buffer on boot up when the
419				main buffer is allocated. This is handy if debugging
420				and you need to use tracing_snapshot() on boot up, and
421				do not want to use tracing_snapshot_alloc() as it needs
422				to be done where GFP_KERNEL allocations are allowed.
424		amd_iommu=	[HW,X86-64]
425				Pass parameters to the AMD IOMMU driver in the system.
426				Possible values are:
427				fullflush - enable flushing of IO/TLB entries when
428					    they are unmapped. Otherwise they are
429					    flushed before they will be reused, which
430					    is a lot of faster
431				off	  - do not initialize any AMD IOMMU found in
432					    the system
433				force_isolation - Force device isolation for all
434						  devices. The IOMMU driver is not
435						  allowed anymore to lift isolation
436						  requirements as needed. This option
437						  does not override iommu=pt
439		amd_iommu_dump=	[HW,X86-64]
440				Enable AMD IOMMU driver option to dump the ACPI table
441				for AMD IOMMU. With this option enabled, AMD IOMMU
442				driver will print ACPI tables for AMD IOMMU during
443				IOMMU initialization.
445		amijoy.map=	[HW,JOY] Amiga joystick support
446				Map of devices attached to JOY0DAT and JOY1DAT
447				Format: <a>,<b>
448				See also Documentation/input/joystick.txt
450		analog.map=	[HW,JOY] Analog joystick and gamepad support
451				Specifies type or capabilities of an analog joystick
452				connected to one of 16 gameports
453				Format: <type1>,<type2>,..<type16>
455		apc=		[HW,SPARC]
456				Power management functions (SPARCstation-4/5 + deriv.)
457				Format: noidle
458				Disable APC CPU standby support. SPARCstation-Fox does
459				not play well with APC CPU idle - disable it if you have
460				APC and your system crashes randomly.
462		apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
463				Change the output verbosity whilst booting
464				Format: { quiet (default) | verbose | debug }
465				Change the amount of debugging information output
466				when initialising the APIC and IO-APIC components.
468		autoconf=	[IPV6]
469				See Documentation/networking/ipv6.txt.
471		show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
472				Limit apic dumping. The parameter defines the maximal
473				number of local apics being dumped. Also it is possible
474				to set it to "all" by meaning -- no limit here.
475				Format: { 1 (default) | 2 | ... | all }.
476				The parameter valid if only apic=debug or
477				apic=verbose is specified.
478				Example: apic=debug show_lapic=all
480		apm=		[APM] Advanced Power Management
481				See header of arch/x86/kernel/apm_32.c.
483		arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
484				Format: <io>,<irq>,<nodeID>
486		ataflop=	[HW,M68k]
488		atarimouse=	[HW,MOUSE] Atari Mouse
490		atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
491				EzKey and similar keyboards
493		atkbd.reset=	[HW] Reset keyboard during initialization
495		atkbd.set=	[HW] Select keyboard code set
496				Format: <int> (2 = AT (default), 3 = PS/2)
498		atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
499				keyboards
501		atkbd.softraw=	[HW] Choose between synthetic and real raw mode
502				Format: <bool> (0 = real, 1 = synthetic (default))
504		atkbd.softrepeat= [HW]
505				Use software keyboard repeat
507		audit=		[KNL] Enable the audit sub-system
508				Format: { "0" | "1" } (0 = disabled, 1 = enabled)
509				0 - kernel audit is disabled and can not be enabled
510				    until the next reboot
511				unset - kernel audit is initialized but disabled and
512				    will be fully enabled by the userspace auditd.
513				1 - kernel audit is initialized and partially enabled,
514				    storing at most audit_backlog_limit messages in
515				    RAM until it is fully enabled by the userspace
516				    auditd.
517				Default: unset
519		audit_backlog_limit= [KNL] Set the audit queue size limit.
520				Format: <int> (must be >=0)
521				Default: 64
523		baycom_epp=	[HW,AX25]
524				Format: <io>,<mode>
526		baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
527				Format: <io>,<mode>
528				See header of drivers/net/hamradio/baycom_par.c.
530		baycom_ser_fdx=	[HW,AX25]
531				BayCom Serial Port AX.25 Modem (Full Duplex Mode)
532				Format: <io>,<irq>,<mode>[,<baud>]
533				See header of drivers/net/hamradio/baycom_ser_fdx.c.
535		baycom_ser_hdx=	[HW,AX25]
536				BayCom Serial Port AX.25 Modem (Half Duplex Mode)
537				Format: <io>,<irq>,<mode>
538				See header of drivers/net/hamradio/baycom_ser_hdx.c.
540		blkdevparts=	Manual partition parsing of block device(s) for
541				embedded devices based on command line input.
542				See Documentation/block/cmdline-partition.txt
544		boot_delay=	Milliseconds to delay each printk during boot.
545				Values larger than 10 seconds (10000) are changed to
546				no delay (0).
547				Format: integer
549		bootmem_debug	[KNL] Enable bootmem allocator debug messages.
551		bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
552		bttv.radio=	Most important insmod options are available as
553				kernel args too.
554		bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
555		bttv.tuner=
557		bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
558				firmware feature for flushing multiple hpte entries
559				at a time.
561		c101=		[NET] Moxa C101 synchronous serial card
563		cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
564				Sometimes CPU hardware bugs make them report the cache
565				size incorrectly. The kernel will attempt work arounds
566				to fix known problems, but for some CPUs it is not
567				possible to determine what the correct size should be.
568				This option provides an override for these situations.
570		ca_keys=	[KEYS] This parameter identifies a specific key(s) on
571				the system trusted keyring to be used for certificate
572				trust validation.
573				format: { id:<keyid> | builtin }
575		cca=		[MIPS] Override the kernel pages' cache coherency
576				algorithm.  Accepted values range from 0 to 7
577				inclusive. See arch/mips/include/asm/pgtable-bits.h
578				for platform specific values (SB1, Loongson3 and
579				others).
581		ccw_timeout_log [S390]
582				See Documentation/s390/CommonIO for details.
584		cgroup_disable= [KNL] Disable a particular controller
585				Format: {name of the controller(s) to disable}
586				The effects of cgroup_disable=foo are:
587				- foo isn't auto-mounted if you mount all cgroups in
588				  a single hierarchy
589				- foo isn't visible as an individually mountable
590				  subsystem
591				{Currently only "memory" controller deal with this and
592				cut the overhead, others just disable the usage. So
593				only cgroup_disable=memory is actually worthy}
595		checkreqprot	[SELINUX] Set initial checkreqprot flag value.
596				Format: { "0" | "1" }
597				See security/selinux/Kconfig help text.
598				0 -- check protection applied by kernel (includes
599					any implied execute protection).
600				1 -- check protection requested by application.
601				Default value is set via a kernel config option.
602				Value can be changed at runtime via
603					/selinux/checkreqprot.
605		cio_ignore=	[S390]
606				See Documentation/s390/CommonIO for details.
607		clk_ignore_unused
608				[CLK]
609				Prevents the clock framework from automatically gating
610				clocks that have not been explicitly enabled by a Linux
611				device driver but are enabled in hardware at reset or
612				by the bootloader/firmware. Note that this does not
613				force such clocks to be always-on nor does it reserve
614				those clocks in any way. This parameter is useful for
615				debug and development, but should not be needed on a
616				platform with proper driver support.  For more
617				information, see Documentation/clk.txt.
619		clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
620				[Deprecated]
621				Forces specified clocksource (if available) to be used
622				when calculating gettimeofday(). If specified
623				clocksource is not available, it defaults to PIT.
624				Format: { pit | tsc | cyclone | pmtmr }
626		clocksource=	Override the default clocksource
627				Format: <string>
628				Override the default clocksource and use the clocksource
629				with the name specified.
630				Some clocksource names to choose from, depending on
631				the platform:
632				[all] jiffies (this is the base, fallback clocksource)
633				[ACPI] acpi_pm
634				[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
635					pxa_timer,timer3,32k_counter,timer0_1
636				[AVR32] avr32
637				[X86-32] pit,hpet,tsc;
638					scx200_hrt on Geode; cyclone on IBM x440
639				[MIPS] MIPS
640				[PARISC] cr16
641				[S390] tod
642				[SH] SuperH
643				[SPARC64] tick
644				[X86-64] hpet,tsc
646		clearcpuid=BITNUM [X86]
647				Disable CPUID feature X for the kernel. See
648				arch/x86/include/asm/cpufeature.h for the valid bit
649				numbers. Note the Linux specific bits are not necessarily
650				stable over kernel options, but the vendor specific
651				ones should be.
652				Also note that user programs calling CPUID directly
653				or using the feature without checking anything
654				will still see it. This just prevents it from
655				being used by the kernel or shown in /proc/cpuinfo.
656				Also note the kernel might malfunction if you disable
657				some critical bits.
659		cma=nn[MG]@[start[MG][-end[MG]]]
660				[ARM,X86,KNL]
661				Sets the size of kernel global memory area for
662				contiguous memory allocations and optionally the
663				placement constraint by the physical address range of
664				memory allocations. A value of 0 disables CMA
665				altogether. For more information, see
666				include/linux/dma-contiguous.h
668		cmo_free_hint=	[PPC] Format: { yes | no }
669				Specify whether pages are marked as being inactive
670				when they are freed.  This is used in CMO environments
671				to determine OS memory pressure for page stealing by
672				a hypervisor.
673				Default: yes
675		coherent_pool=nn[KMG]	[ARM,KNL]
676				Sets the size of memory pool for coherent, atomic dma
677				allocations, by default set to 256K.
679		code_bytes	[X86] How many bytes of object code to print
680				in an oops report.
681				Range: 0 - 8192
682				Default: 64
684		com20020=	[HW,NET] ARCnet - COM20020 chipset
685				Format:
686				<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
688		com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
689				Format: <io>[,<irq>]
691		com90xx=	[HW,NET]
692				ARCnet - COM90xx chipset (memory-mapped buffers)
693				Format: <io>[,<irq>[,<memstart>]]
695		condev=		[HW,S390] console device
696		conmode=
698		console=	[KNL] Output console device and options.
700			tty<n>	Use the virtual console device <n>.
702			ttyS<n>[,options]
703			ttyUSB0[,options]
704				Use the specified serial port.  The options are of
705				the form "bbbbpnf", where "bbbb" is the baud rate,
706				"p" is parity ("n", "o", or "e"), "n" is number of
707				bits, and "f" is flow control ("r" for RTS or
708				omit it).  Default is "9600n8".
710				See Documentation/serial-console.txt for more
711				information.  See
712				Documentation/networking/netconsole.txt for an
713				alternative.
715			uart[8250],io,<addr>[,options]
716			uart[8250],mmio,<addr>[,options]
717			uart[8250],mmio32,<addr>[,options]
718			uart[8250],0x<addr>[,options]
719				Start an early, polled-mode console on the 8250/16550
720				UART at the specified I/O port or MMIO address,
721				switching to the matching ttyS device later.
722				MMIO inter-register address stride is either 8-bit
723				(mmio) or 32-bit (mmio32).
724				If none of [io|mmio|mmio32], <addr> is assumed to be
725				equivalent to 'mmio'. 'options' are specified in the
726				same format described for ttyS above; if unspecified,
727				the h/w is not re-initialized.
729			hvc<n>	Use the hypervisor console device <n>. This is for
730				both Xen and PowerPC hypervisors.
732	                If the device connected to the port is not a TTY but a braille
733	                device, prepend "brl," before the device type, for instance
734				console=brl,ttyS0
735			For now, only VisioBraille is supported.
737		consoleblank=	[KNL] The console blank (screen saver) timeout in
738				seconds. Defaults to 10*60 = 10mins. A value of 0
739				disables the blank timer.
741		coredump_filter=
742				[KNL] Change the default value for
743				/proc/<pid>/coredump_filter.
744				See also Documentation/filesystems/proc.txt.
746		cpuidle.off=1	[CPU_IDLE]
747				disable the cpuidle sub-system
749		cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
750				Format:
751				<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
753		crashkernel=size[KMG][@offset[KMG]]
754				[KNL] Using kexec, Linux can switch to a 'crash kernel'
755				upon panic. This parameter reserves the physical
756				memory region [offset, offset + size] for that kernel
757				image. If '@offset' is omitted, then a suitable offset
758				is selected automatically. Check
759				Documentation/kdump/kdump.txt for further details.
761		crashkernel=range1:size1[,range2:size2,...][@offset]
762				[KNL] Same as above, but depends on the memory
763				in the running system. The syntax of range is
764				start-[end] where start and end are both
765				a memory unit (amount[KMG]). See also
766				Documentation/kdump/kdump.txt for an example.
768		crashkernel=size[KMG],high
769				[KNL, x86_64] range could be above 4G. Allow kernel
770				to allocate physical memory region from top, so could
771				be above 4G if system have more than 4G ram installed.
772				Otherwise memory region will be allocated below 4G, if
773				available.
774				It will be ignored if crashkernel=X is specified.
775		crashkernel=size[KMG],low
776				[KNL, x86_64] range under 4G. When crashkernel=X,high
777				is passed, kernel could allocate physical memory region
778				above 4G, that cause second kernel crash on system
779				that require some amount of low memory, e.g. swiotlb
780				requires at least 64M+32K low memory.  Kernel would
781				try to allocate 72M below 4G automatically.
782				This one let user to specify own low range under 4G
783				for second kernel instead.
784				0: to disable low allocation.
785				It will be ignored when crashkernel=X,high is not used
786				or memory reserved is below 4G.
788		cs89x0_dma=	[HW,NET]
789				Format: <dma>
791		cs89x0_media=	[HW,NET]
792				Format: { rj45 | aui | bnc }
794		dasd=		[HW,NET]
795				See header of drivers/s390/block/dasd_devmap.c.
797		db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
798				(one device per port)
799				Format: <port#>,<type>
800				See also Documentation/input/joystick-parport.txt
802		ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
803				time. See Documentation/dynamic-debug-howto.txt for
804				details.  Deprecated, see dyndbg.
806		debug		[KNL] Enable kernel debugging (events log level).
808		debug_locks_verbose=
809				[KNL] verbose self-tests
810				Format=<0|1>
811				Print debugging info while doing the locking API
812				self-tests.
813				We default to 0 (no extra messages), setting it to
814				1 will print _a lot_ more information - normally
815				only useful to kernel developers.
817		debug_objects	[KNL] Enable object debugging
819		no_debug_objects
820				[KNL] Disable object debugging
822		debug_guardpage_minorder=
823				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
824				parameter allows control of the order of pages that will
825				be intentionally kept free (and hence protected) by the
826				buddy allocator. Bigger value increase the probability
827				of catching random memory corruption, but reduce the
828				amount of memory for normal system use. The maximum
829				possible value is MAX_ORDER/2.  Setting this parameter
830				to 1 or 2 should be enough to identify most random
831				memory corruption problems caused by bugs in kernel or
832				driver code when a CPU writes to (or reads from) a
833				random memory location. Note that there exists a class
834				of memory corruptions problems caused by buggy H/W or
835				F/W or by drivers badly programing DMA (basically when
836				memory is written at bus level and the CPU MMU is
837				bypassed) which are not detectable by
838				CONFIG_DEBUG_PAGEALLOC, hence this option will not help
839				tracking down these problems.
841		debug_pagealloc=
842				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
843				parameter enables the feature at boot time. In
844				default, it is disabled. We can avoid allocating huge
845				chunk of memory for debug pagealloc if we don't enable
846				it at boot time and the system will work mostly same
847				with the kernel built without CONFIG_DEBUG_PAGEALLOC.
848				on: enable the feature
850		debugpat	[X86] Enable PAT debugging
852		decnet.addr=	[HW,NET]
853				Format: <area>[,<node>]
854				See also Documentation/networking/decnet.txt.
856		default_hugepagesz=
857				[same as hugepagesz=] The size of the default
858				HugeTLB page size. This is the size represented by
859				the legacy /proc/ hugepages APIs, used for SHM, and
860				default size when mounting hugetlbfs filesystems.
861				Defaults to the default architecture's huge page size
862				if not specified.
864		dhash_entries=	[KNL]
865				Set number of hash buckets for dentry cache.
867		disable=	[IPV6]
868				See Documentation/networking/ipv6.txt.
870		disable_cpu_apicid= [X86,APIC,SMP]
871				Format: <int>
872				The number of initial APIC ID for the
873				corresponding CPU to be disabled at boot,
874				mostly used for the kdump 2nd kernel to
875				disable BSP to wake up multiple CPUs without
876				causing system reset or hang due to sending
877				INIT from AP to BSP.
879		disable_ddw     [PPC/PSERIES]
880				Disable Dynamic DMA Window support. Use this if
881				to workaround buggy firmware.
883		disable_ipv6=	[IPV6]
884				See Documentation/networking/ipv6.txt.
886		disable_mtrr_cleanup [X86]
887				The kernel tries to adjust MTRR layout from continuous
888				to discrete, to make X server driver able to add WB
889				entry later. This parameter disables that.
891		disable_mtrr_trim [X86, Intel and AMD only]
892				By default the kernel will trim any uncacheable
893				memory out of your available memory pool based on
894				MTRR settings.  This parameter disables that behavior,
895				possibly causing your machine to run very slowly.
897		disable_timer_pin_1 [X86]
898				Disable PIN 1 of APIC timer
899				Can be useful to work around chipset bugs.
901		dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
902				this option disables the debugging code at boot.
904		dma_debug_entries=<number>
905				This option allows to tune the number of preallocated
906				entries for DMA-API debugging code. One entry is
907				required per DMA-API allocation. Use this if the
908				DMA-API debugging code disables itself because the
909				architectural default is too low.
911		dma_debug_driver=<driver_name>
912				With this option the DMA-API debugging driver
913				filter feature can be enabled at boot time. Just
914				pass the driver to filter for as the parameter.
915				The filter can be disabled or changed to another
916				driver later using sysfs.
918		drm_kms_helper.edid_firmware=[<connector>:]<file>
919				Broken monitors, graphic adapters and KVMs may
920				send no or incorrect EDID data sets. This parameter
921				allows to specify an EDID data set in the
922				/lib/firmware directory that is used instead.
923				Generic built-in EDID data sets are used, if one of
924				edid/1024x768.bin, edid/1280x1024.bin,
925				edid/1680x1050.bin, or edid/1920x1080.bin is given
926				and no file with the same name exists. Details and
927				instructions how to build your own EDID data are
928				available in Documentation/EDID/HOWTO.txt. An EDID
929				data set will only be used for a particular connector,
930				if its name and a colon are prepended to the EDID
931				name.
933		dscc4.setup=	[NET]
935		dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
936		module.dyndbg[="val"]
937				Enable debug messages at boot time.  See
938				Documentation/dynamic-debug-howto.txt for details.
940		eagerfpu=	[X86]
941				on	enable eager fpu restore
942				off	disable eager fpu restore
943				auto	selects the default scheme, which automatically
944					enables eagerfpu restore for xsaveopt.
946		early_ioremap_debug [KNL]
947				Enable debug messages in early_ioremap support. This
948				is useful for tracking down temporary early mappings
949				which are not unmapped.
951		earlycon=	[KNL] Output early console device and options.
953			cdns,<addr>
954				Start an early, polled-mode console on a cadence serial
955				port at the specified address. The cadence serial port
956				must already be setup and configured. Options are not
957				yet supported.
959			uart[8250],io,<addr>[,options]
960			uart[8250],mmio,<addr>[,options]
961			uart[8250],mmio32,<addr>[,options]
962			uart[8250],0x<addr>[,options]
963				Start an early, polled-mode console on the 8250/16550
964				UART at the specified I/O port or MMIO address.
965				MMIO inter-register address stride is either 8-bit
966				(mmio) or 32-bit (mmio32).
967				If none of [io|mmio|mmio32], <addr> is assumed to be
968				equivalent to 'mmio'. 'options' are specified in the
969				same format described for "console=ttyS<n>"; if
970				unspecified, the h/w is not initialized.
972			pl011,<addr>
973				Start an early, polled-mode console on a pl011 serial
974				port at the specified address. The pl011 serial port
975				must already be setup and configured. Options are not
976				yet supported.
978			msm_serial,<addr>
979				Start an early, polled-mode console on an msm serial
980				port at the specified address. The serial port
981				must already be setup and configured. Options are not
982				yet supported.
984			msm_serial_dm,<addr>
985				Start an early, polled-mode console on an msm serial
986				dm port at the specified address. The serial port
987				must already be setup and configured. Options are not
988				yet supported.
990			smh	Use ARM semihosting calls for early console.
992			s3c2410,<addr>
993			s3c2412,<addr>
994			s3c2440,<addr>
995			s3c6400,<addr>
996			s5pv210,<addr>
997			exynos4210,<addr>
998				Use early console provided by serial driver available
999				on Samsung SoCs, requires selecting proper type and
1000				a correct base address of the selected UART port. The
1001				serial port must already be setup and configured.
1002				Options are not yet supported.
1004		earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
1005				earlyprintk=vga
1006				earlyprintk=efi
1007				earlyprintk=xen
1008				earlyprintk=serial[,ttySn[,baudrate]]
1009				earlyprintk=serial[,0x...[,baudrate]]
1010				earlyprintk=ttySn[,baudrate]
1011				earlyprintk=dbgp[debugController#]
1013				earlyprintk is useful when the kernel crashes before
1014				the normal console is initialized. It is not enabled by
1015				default because it has some cosmetic problems.
1017				Append ",keep" to not disable it when the real console
1018				takes over.
1020				Only one of vga, efi, serial, or usb debug port can
1021				be used at a time.
1023				Currently only ttyS0 and ttyS1 may be specified by
1024				name.  Other I/O ports may be explicitly specified
1025				on some architectures (x86 and arm at least) by
1026				replacing ttySn with an I/O port address, like this:
1027					earlyprintk=serial,0x1008,115200
1028				You can find the port for a given device in
1029				/proc/tty/driver/serial:
1030					2: uart:ST16650V2 port:00001008 irq:18 ...
1032				Interaction with the standard serial driver is not
1033				very good.
1035				The VGA and EFI output is eventually overwritten by
1036				the real console.
1038				The xen output can only be used by Xen PV guests.
1040		edac_report=	[HW,EDAC] Control how to report EDAC event
1041				Format: {"on" | "off" | "force"}
1042				on: enable EDAC to report H/W event. May be overridden
1043				by other higher priority error reporting module.
1044				off: disable H/W event reporting through EDAC.
1045				force: enforce the use of EDAC to report H/W event.
1046				default: on.
1048		ekgdboc=	[X86,KGDB] Allow early kernel console debugging
1049				ekgdboc=kbd
1051				This is designed to be used in conjunction with
1052				the boot argument: earlyprintk=vga
1054		edd=		[EDD]
1055				Format: {"off" | "on" | "skip[mbr]"}
1057		efi=		[EFI]
1058				Format: { "old_map", "nochunk", "noruntime", "debug" }
1059				old_map [X86-64]: switch to the old ioremap-based EFI
1060				runtime services mapping. 32-bit still uses this one by
1061				default.
1062				nochunk: disable reading files in "chunks" in the EFI
1063				boot stub, as chunking can cause problems with some
1064				firmware implementations.
1065				noruntime : disable EFI runtime services support
1066				debug: enable misc debug output
1068		efi_no_storage_paranoia [EFI; X86]
1069				Using this parameter you can use more than 50% of
1070				your efi variable storage. Use this parameter only if
1071				you are really sure that your UEFI does sane gc and
1072				fulfills the spec otherwise your board may brick.
1074		eisa_irq_edge=	[PARISC,HW]
1075				See header of drivers/parisc/eisa.c.
1077		elanfreq=	[X86-32]
1078				See comment before function elanfreq_setup() in
1079				arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1081		elevator=	[IOSCHED]
1082				Format: {"cfq" | "deadline" | "noop"}
1083				See Documentation/block/cfq-iosched.txt and
1084				Documentation/block/deadline-iosched.txt for details.
1086		elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1087				Specifies physical address of start of kernel core
1088				image elf header and optionally the size. Generally
1089				kexec loader will pass this option to capture kernel.
1090				See Documentation/kdump/kdump.txt for details.
1092		enable_mtrr_cleanup [X86]
1093				The kernel tries to adjust MTRR layout from continuous
1094				to discrete, to make X server driver able to add WB
1095				entry later. This parameter enables that.
1097		enable_timer_pin_1 [X86]
1098				Enable PIN 1 of APIC timer
1099				Can be useful to work around chipset bugs
1100				(in particular on some ATI chipsets).
1101				The kernel tries to set a reasonable default.
1103		enforcing	[SELINUX] Set initial enforcing status.
1104				Format: {"0" | "1"}
1105				See security/selinux/Kconfig help text.
1106				0 -- permissive (log only, no denials).
1107				1 -- enforcing (deny and log).
1108				Default value is 0.
1109				Value can be changed at runtime via /selinux/enforce.
1111		erst_disable	[ACPI]
1112				Disable Error Record Serialization Table (ERST)
1113				support.
1115		ether=		[HW,NET] Ethernet cards parameters
1116				This option is obsoleted by the "netdev=" option, which
1117				has equivalent usage. See its documentation for details.
1119		evm=		[EVM]
1120				Format: { "fix" }
1121				Permit 'security.evm' to be updated regardless of
1122				current integrity status.
1124		failslab=
1125		fail_page_alloc=
1126		fail_make_request=[KNL]
1127				General fault injection mechanism.
1128				Format: <interval>,<probability>,<space>,<times>
1129				See also Documentation/fault-injection/.
1131		floppy=		[HW]
1132				See Documentation/blockdev/floppy.txt.
1134		force_pal_cache_flush
1135				[IA-64] Avoid check_sal_cache_flush which may hang on
1136				buggy SAL_CACHE_FLUSH implementations. Using this
1137				parameter will force ia64_sal_cache_flush to call
1138				ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1140		forcepae [X86-32]
1141				Forcefully enable Physical Address Extension (PAE).
1142				Many Pentium M systems disable PAE but may have a
1143				functionally usable PAE implementation.
1144				Warning: use of this parameter will taint the kernel
1145				and may cause unknown problems.
1147		ftrace=[tracer]
1148				[FTRACE] will set and start the specified tracer
1149				as early as possible in order to facilitate early
1150				boot debugging.
1152		ftrace_dump_on_oops[=orig_cpu]
1153				[FTRACE] will dump the trace buffers on oops.
1154				If no parameter is passed, ftrace will dump
1155				buffers of all CPUs, but if you pass orig_cpu, it will
1156				dump only the buffer of the CPU that triggered the
1157				oops.
1159		ftrace_filter=[function-list]
1160				[FTRACE] Limit the functions traced by the function
1161				tracer at boot up. function-list is a comma separated
1162				list of functions. This list can be changed at run
1163				time by the set_ftrace_filter file in the debugfs
1164				tracing directory.
1166		ftrace_notrace=[function-list]
1167				[FTRACE] Do not trace the functions specified in
1168				function-list. This list can be changed at run time
1169				by the set_ftrace_notrace file in the debugfs
1170				tracing directory.
1172		ftrace_graph_filter=[function-list]
1173				[FTRACE] Limit the top level callers functions traced
1174				by the function graph tracer at boot up.
1175				function-list is a comma separated list of functions
1176				that can be changed at run time by the
1177				set_graph_function file in the debugfs tracing directory.
1179		ftrace_graph_notrace=[function-list]
1180				[FTRACE] Do not trace from the functions specified in
1181				function-list.  This list is a comma separated list of
1182				functions that can be changed at run time by the
1183				set_graph_notrace file in the debugfs tracing directory.
1185		gamecon.map[2|3]=
1186				[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1187				support via parallel port (up to 5 devices per port)
1188				Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1189				See also Documentation/input/joystick-parport.txt
1191		gamma=		[HW,DRM]
1193		gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
1194				Format: off | on
1195				default: on
1197		gcov_persist=	[GCOV] When non-zero (default), profiling data for
1198				kernel modules is saved and remains accessible via
1199				debugfs, even when the module is unloaded/reloaded.
1200				When zero, profiling data is discarded and associated
1201				debugfs files are removed at module unload time.
1203		gpt		[EFI] Forces disk with valid GPT signature but
1204				invalid Protective MBR to be treated as GPT. If the
1205				primary GPT is corrupted, it enables the backup/alternate
1206				GPT to be used instead.
1208		grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1209				the "Enable 0" bit of the configuration register.
1210				Format: 0 | 1
1211				Default: 0
1212		grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1213				the "Enable 0" bit of the configuration register.
1214				Format: 0 | 1
1215				Default: 0
1216		grcan.select=	[HW] Select which physical interface to use.
1217				Format: 0 | 1
1218				Default: 0
1219		grcan.txsize=	[HW] Sets the size of the tx buffer.
1220				Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1221				Default: 1024
1222		grcan.rxsize=	[HW] Sets the size of the rx buffer.
1223				Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1224				Default: 1024
1226		hashdist=	[KNL,NUMA] Large hashes allocated during boot
1227				are distributed across NUMA nodes.  Defaults on
1228				for 64-bit NUMA, off otherwise.
1229				Format: 0 | 1 (for off | on)
1231		hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1233		hd=		[EIDE] (E)IDE hard drive subsystem geometry
1234				Format: <cyl>,<head>,<sect>
1236		hest_disable	[ACPI]
1237				Disable Hardware Error Source Table (HEST) support;
1238				corresponding firmware-first mode error processing
1239				logic will be disabled.
1241		highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1242				size of <nn>. This works even on boxes that have no
1243				highmem otherwise. This also works to reduce highmem
1244				size on bigger boxes.
1246		highres=	[KNL] Enable/disable high resolution timer mode.
1247				Valid parameters: "on", "off"
1248				Default: "on"
1250		hisax=		[HW,ISDN]
1251				See Documentation/isdn/README.HiSax.
1253		hlt		[BUGS=ARM,SH]
1255		hpet=		[X86-32,HPET] option to control HPET usage
1256				Format: { enable (default) | disable | force |
1257					verbose }
1258				disable: disable HPET and use PIT instead
1259				force: allow force enabled of undocumented chips (ICH4,
1260					VIA, nVidia)
1261				verbose: show contents of HPET registers during setup
1263		hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1264				registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1266		hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1267		hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1268				On x86-64 and powerpc, this option can be specified
1269				multiple times interleaved with hugepages= to reserve
1270				huge pages of different sizes. Valid pages sizes on
1271				x86-64 are 2M (when the CPU supports "pse") and 1G
1272				(when the CPU supports the "pdpe1gb" cpuinfo flag).
1274		hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
1275				       terminal devices. Valid values: 0..8
1276		hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
1277				       If specified, z/VM IUCV HVC accepts connections
1278				       from listed z/VM user IDs only.
1280		hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
1281				        hardware thread id mappings.
1282					Format: <cpu>:<hwthread>
1284		keep_bootcon	[KNL]
1285				Do not unregister boot console at start. This is only
1286				useful for debugging when something happens in the window
1287				between unregistering the boot console and initializing
1288				the real console.
1290		i2c_bus=	[HW] Override the default board specific I2C bus speed
1291				     or register an additional I2C bus that is not
1292				     registered from board initialization code.
1293				     Format:
1294				     <bus_id>,<clkrate>
1296		i8042.debug	[HW] Toggle i8042 debug mode
1297		i8042.direct	[HW] Put keyboard port into non-translated mode
1298		i8042.dumbkbd	[HW] Pretend that controller can only read data from
1299				     keyboard and cannot control its state
1300				     (Don't attempt to blink the leds)
1301		i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1302		i8042.nokbd	[HW] Don't check/create keyboard port
1303		i8042.noloop	[HW] Disable the AUX Loopback command while probing
1304				     for the AUX port
1305		i8042.nomux	[HW] Don't check presence of an active multiplexing
1306				     controller
1307		i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1308				     controllers
1309		i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1310		i8042.reset	[HW] Reset the controller during init and cleanup
1311		i8042.unlock	[HW] Unlock (ignore) the keylock
1312		i8042.kbdreset  [HW] Reset device connected to KBD port
1314		i810=		[HW,DRM]
1316		i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1317				indicates that the driver is running on unsupported
1318				hardware.
1319		i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1320				does not match list of supported models.
1321		i8k.power_status
1322				[HW] Report power status in /proc/i8k
1323				(disabled by default)
1324		i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1325				capability is set.
1327		i915.invert_brightness=
1328				[DRM] Invert the sense of the variable that is used to
1329				set the brightness of the panel backlight. Normally a
1330				brightness value of 0 indicates backlight switched off,
1331				and the maximum of the brightness value sets the backlight
1332				to maximum brightness. If this parameter is set to 0
1333				(default) and the machine requires it, or this parameter
1334				is set to 1, a brightness value of 0 sets the backlight
1335				to maximum brightness, and the maximum of the brightness
1336				value switches the backlight off.
1337				-1 -- never invert brightness
1338				 0 -- machine default
1339				 1 -- force brightness inversion
1341		icn=		[HW,ISDN]
1342				Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1344		ide-core.nodma=	[HW] (E)IDE subsystem
1345				Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1346				.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1347				.cdrom .chs .ignore_cable are additional options
1348				See Documentation/ide/ide.txt.
1350		ide-generic.probe-mask= [HW] (E)IDE subsystem
1351				Format: <int>
1352				Probe mask for legacy ISA IDE ports.  Depending on
1353				platform up to 6 ports are supported, enabled by
1354				setting corresponding bits in the mask to 1.  The
1355				default value is 0x0, which has a special meaning.
1356				On systems that have PCI, it triggers scanning the
1357				PCI bus for the first and the second port, which
1358				are then probed.  On systems without PCI the value
1359				of 0x0 enables probing the two first ports as if it
1360				was 0x3.
1362		ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1363				Claim all unknown PCI IDE storage controllers.
1365		idle=		[X86]
1366				Format: idle=poll, idle=halt, idle=nomwait
1367				Poll forces a polling idle loop that can slightly
1368				improve the performance of waking up a idle CPU, but
1369				will use a lot of power and make the system run hot.
1370				Not recommended.
1371				idle=halt: Halt is forced to be used for CPU idle.
1372				In such case C2/C3 won't be used again.
1373				idle=nomwait: Disable mwait for CPU C-states
1375		ignore_loglevel	[KNL]
1376				Ignore loglevel setting - this will print /all/
1377				kernel messages to the console. Useful for debugging.
1378				We also add it as printk module parameter, so users
1379				could change it dynamically, usually by
1380				/sys/module/printk/parameters/ignore_loglevel.
1382		ihash_entries=	[KNL]
1383				Set number of hash buckets for inode cache.
1385		ima_appraise=	[IMA] appraise integrity measurements
1386				Format: { "off" | "enforce" | "fix" | "log" }
1387				default: "enforce"
1389		ima_appraise_tcb [IMA]
1390				The builtin appraise policy appraises all files
1391				owned by uid=0.
1393		ima_hash=	[IMA]
1394				Format: { md5 | sha1 | rmd160 | sha256 | sha384
1395					   | sha512 | ... }
1396				default: "sha1"
1398				The list of supported hash algorithms is defined
1399				in crypto/hash_info.h.
1401		ima_tcb		[IMA]
1402				Load a policy which meets the needs of the Trusted
1403				Computing Base.  This means IMA will measure all
1404				programs exec'd, files mmap'd for exec, and all files
1405				opened for read by uid=0.
1407		ima_template=   [IMA]
1408				Select one of defined IMA measurements template formats.
1409				Formats: { "ima" | "ima-ng" }
1410				Default: "ima-ng"
1412		ima_template_fmt=
1413		                [IMA] Define a custom template format.
1414				Format: { "field1|...|fieldN" }
1416		ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1417				Format: <min_file_size>
1418				Set the minimal file size for using asynchronous hash.
1419				If left unspecified, ahash usage is disabled.
1421				ahash performance varies for different data sizes on
1422				different crypto accelerators. This option can be used
1423				to achieve the best performance for a particular HW.
1425		ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1426				Format: <bufsize>
1427				Set hashing buffer size. Default: 4k.
1429				ahash performance varies for different chunk sizes on
1430				different crypto accelerators. This option can be used
1431				to achieve best performance for particular HW.
1433		init=		[KNL]
1434				Format: <full_path>
1435				Run specified binary instead of /sbin/init as init
1436				process.
1438		initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1439				for working out where the kernel is dying during
1440				startup.
1442		initcall_blacklist=  [KNL] Do not execute a comma-separated list of
1443				initcall functions.  Useful for debugging built-in
1444				modules and initcalls.
1446		initrd=		[BOOT] Specify the location of the initial ramdisk
1448		inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1449				Format: <irq>
1451		int_pln_enable  [x86] Enable power limit notification interrupt
1453		integrity_audit=[IMA]
1454				Format: { "0" | "1" }
1455				0 -- basic integrity auditing messages. (Default)
1456				1 -- additional integrity auditing messages.
1458		intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1459			on
1460				Enable intel iommu driver.
1461			off
1462				Disable intel iommu driver.
1463			igfx_off [Default Off]
1464				By default, gfx is mapped as normal device. If a gfx
1465				device has a dedicated DMAR unit, the DMAR unit is
1466				bypassed by not enabling DMAR with this option. In
1467				this case, gfx device will use physical address for
1468				DMA.
1469			forcedac [x86_64]
1470				With this option iommu will not optimize to look
1471				for io virtual address below 32-bit forcing dual
1472				address cycle on pci bus for cards supporting greater
1473				than 32-bit addressing. The default is to look
1474				for translation below 32-bit and if not available
1475				then look in the higher range.
1476			strict [Default Off]
1477				With this option on every unmap_single operation will
1478				result in a hardware IOTLB flush operation as opposed
1479				to batching them for performance.
1480			sp_off [Default Off]
1481				By default, super page will be supported if Intel IOMMU
1482				has the capability. With this option, super page will
1483				not be supported.
1484			ecs_off [Default Off]
1485				By default, extended context tables will be supported if
1486				the hardware advertises that it has support both for the
1487				extended tables themselves, and also PASID support. With
1488				this option set, extended tables will not be used even
1489				on hardware which claims to support them.
1491		intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1492				0	disables intel_idle and fall back on acpi_idle.
1493				1 to 6	specify maximum depth of C-state.
1495		intel_pstate=  [X86]
1496			       disable
1497			         Do not enable intel_pstate as the default
1498			         scaling driver for the supported processors
1499			       force
1500				 Enable intel_pstate on systems that prohibit it by default
1501				 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1502				 instead of acpi-cpufreq may disable platform features, such
1503				 as thermal controls and power capping, that rely on ACPI
1504				 P-States information being indicated to OSPM and therefore
1505				 should be used with caution. This option does not work with
1506				 processors that aren't supported by the intel_pstate driver
1507				 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1508			       no_hwp
1509			         Do not enable hardware P state control (HWP)
1510				 if available.
1511			hwp_only
1512				Only load intel_pstate on systems which support
1513				hardware P state control (HWP) if available.
1515		intremap=	[X86-64, Intel-IOMMU]
1516				on	enable Interrupt Remapping (default)
1517				off	disable Interrupt Remapping
1518				nosid	disable Source ID checking
1519				no_x2apic_optout
1520					BIOS x2APIC opt-out request will be ignored
1522		iomem=		Disable strict checking of access to MMIO memory
1523			strict	regions from userspace.
1524			relaxed
1526		iommu=		[x86]
1527			off
1528			force
1529			noforce
1530			biomerge
1531			panic
1532			nopanic
1533			merge
1534			nomerge
1535			forcesac
1536			soft
1537			pt		[x86, IA-64]
1538			nobypass	[PPC/POWERNV]
1539				Disable IOMMU bypass, using IOMMU for PCI devices.
1542		io7=		[HW] IO7 for Marvel based alpha systems
1543				See comment before marvel_specify_io7 in
1544				arch/alpha/kernel/core_marvel.c.
1546		io_delay=	[X86] I/O delay method
1547			0x80
1548				Standard port 0x80 based delay
1549			0xed
1550				Alternate port 0xed based delay (needed on some systems)
1551			udelay
1552				Simple two microseconds delay
1553			none
1554				No delay
1556		ip=		[IP_PNP]
1557				See Documentation/filesystems/nfs/nfsroot.txt.
1559		irqfixup	[HW]
1560				When an interrupt is not handled search all handlers
1561				for it. Intended to get systems with badly broken
1562				firmware running.
1564		irqpoll		[HW]
1565				When an interrupt is not handled search all handlers
1566				for it. Also check all handlers each timer
1567				interrupt. Intended to get systems with badly broken
1568				firmware running.
1570		isapnp=		[ISAPNP]
1571				Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1573		isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1574				Format:
1575				<cpu number>,...,<cpu number>
1576				or
1577				<cpu number>-<cpu number>
1578				(must be a positive range in ascending order)
1579				or a mixture
1580				<cpu number>,...,<cpu number>-<cpu number>
1582				This option can be used to specify one or more CPUs
1583				to isolate from the general SMP balancing and scheduling
1584				algorithms. You can move a process onto or off an
1585				"isolated" CPU via the CPU affinity syscalls or cpuset.
1586				<cpu number> begins at 0 and the maximum value is
1587				"number of CPUs in system - 1".
1589				This option is the preferred way to isolate CPUs. The
1590				alternative -- manually setting the CPU mask of all
1591				tasks in the system -- can cause problems and
1592				suboptimal load balancer performance.
1594		iucv=		[HW,NET]
1596		ivrs_ioapic	[HW,X86_64]
1597				Provide an override to the IOAPIC-ID<->DEVICE-ID
1598				mapping provided in the IVRS ACPI table. For
1599				example, to map IOAPIC-ID decimal 10 to
1600				PCI device 00:14.0 write the parameter as:
1601					ivrs_ioapic[10]=00:14.0
1603		ivrs_hpet	[HW,X86_64]
1604				Provide an override to the HPET-ID<->DEVICE-ID
1605				mapping provided in the IVRS ACPI table. For
1606				example, to map HPET-ID decimal 0 to
1607				PCI device 00:14.0 write the parameter as:
1608					ivrs_hpet[0]=00:14.0
1610		js=		[HW,JOY] Analog joystick
1611				See Documentation/input/joystick.txt.
1613		kaslr/nokaslr	[X86]
1614				Enable/disable kernel and module base offset ASLR
1615				(Address Space Layout Randomization) if built into
1616				the kernel. When CONFIG_HIBERNATION is selected,
1617				kASLR is disabled by default. When kASLR is enabled,
1618				hibernation will be disabled.
1620		keepinitrd	[HW,ARM]
1622		kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1623				specifies the amount of memory usable by the kernel
1624				for non-movable allocations.  The requested amount is
1625				spread evenly throughout all nodes in the system. The
1626				remaining memory in each node is used for Movable
1627				pages. In the event, a node is too small to have both
1628				kernelcore and Movable pages, kernelcore pages will
1629				take priority and other nodes will have a larger number
1630				of Movable pages.  The Movable zone is used for the
1631				allocation of pages that may be reclaimed or moved
1632				by the page migration subsystem.  This means that
1633				HugeTLB pages may not be allocated from this zone.
1634				Note that allocations like PTEs-from-HighMem still
1635				use the HighMem zone if it exists, and the Normal
1636				zone if it does not.
1638		kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1639				Format: <Controller#>[,poll interval]
1640				The controller # is the number of the ehci usb debug
1641				port as it is probed via PCI.  The poll interval is
1642				optional and is the number seconds in between
1643				each poll cycle to the debug port in case you need
1644				the functionality for interrupting the kernel with
1645				gdb or control-c on the dbgp connection.  When
1646				not using this parameter you use sysrq-g to break into
1647				the kernel debugger.
1649		kgdboc=		[KGDB,HW] kgdb over consoles.
1650				Requires a tty driver that supports console polling,
1651				or a supported polling keyboard driver (non-usb).
1652				 Serial only format: <serial_device>[,baud]
1653				 keyboard only format: kbd
1654				 keyboard and serial format: kbd,<serial_device>[,baud]
1655				Optional Kernel mode setting:
1656				 kms, kbd format: kms,kbd
1657				 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1659		kgdbwait	[KGDB] Stop kernel execution and enter the
1660				kernel debugger at the earliest opportunity.
1662		kmac=		[MIPS] korina ethernet MAC address.
1663				Configure the RouterBoard 532 series on-chip
1664				Ethernet adapter MAC address.
1666		kmemleak=	[KNL] Boot-time kmemleak enable/disable
1667				Valid arguments: on, off
1668				Default: on
1670				the default is off.
1672		kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
1673				Valid arguments: 0, 1, 2
1674				kmemcheck=0 (disabled)
1675				kmemcheck=1 (enabled)
1676				kmemcheck=2 (one-shot mode)
1677				Default: 2 (one-shot mode)
1679		kstack=N	[X86] Print N words from the kernel stack
1680				in oops dumps.
1682		kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1683				Default is 0 (don't ignore, but inject #GP)
1685		kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
1686				KVM MMU at runtime.
1687				Default is 0 (off)
1689		kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1690				Default is 1 (enabled)
1692		kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
1693				for all guests.
1694				Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1696		kvm-intel.ept=	[KVM,Intel] Disable extended page tables
1697				(virtualized MMU) support on capable Intel chips.
1698				Default is 1 (enabled)
1700		kvm-intel.emulate_invalid_guest_state=
1701				[KVM,Intel] Enable emulation of invalid guest states
1702				Default is 0 (disabled)
1704		kvm-intel.flexpriority=
1705				[KVM,Intel] Disable FlexPriority feature (TPR shadow).
1706				Default is 1 (enabled)
1708		kvm-intel.nested=
1709				[KVM,Intel] Enable VMX nesting (nVMX).
1710				Default is 0 (disabled)
1712		kvm-intel.unrestricted_guest=
1713				[KVM,Intel] Disable unrestricted guest feature
1714				(virtualized real and unpaged mode) on capable
1715				Intel chips. Default is 1 (enabled)
1717		kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
1718				feature (tagged TLBs) on capable Intel chips.
1719				Default is 1 (enabled)
1721		l2cr=		[PPC]
1723		l3cr=		[PPC]
1725		lapic		[X86-32,APIC] Enable the local APIC even if BIOS
1726				disabled it.
1728		lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
1729				value for LAPIC timer one-shot implementation. Default
1730				back to the programmable timer unit in the LAPIC.
1732		lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1733				in C2 power state.
1735		libata.dma=	[LIBATA] DMA control
1736				libata.dma=0	  Disable all PATA and SATA DMA
1737				libata.dma=1	  PATA and SATA Disk DMA only
1738				libata.dma=2	  ATAPI (CDROM) DMA only
1739				libata.dma=4	  Compact Flash DMA only
1740				Combinations also work, so libata.dma=3 enables DMA
1741				for disks and CDROMs, but not CFs.
1743		libata.ignore_hpa=	[LIBATA] Ignore HPA limit
1744				libata.ignore_hpa=0	  keep BIOS limits (default)
1745				libata.ignore_hpa=1	  ignore limits, using full disk
1747		libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
1748				when set.
1749				Format: <int>
1751		libata.force=	[LIBATA] Force configurations.  The format is comma
1752				separated list of "[ID:]VAL" where ID is
1753				PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1754				matching port, link or device.  Basically, it matches
1755				the ATA ID string printed on console by libata.  If
1756				the whole ID part is omitted, the last PORT and DEVICE
1757				values are used.  If ID hasn't been specified yet, the
1758				configuration applies to all ports, links and devices.
1760				If only DEVICE is omitted, the parameter applies to
1761				the port and all links and devices behind it.  DEVICE
1762				number of 0 either selects the first device or the
1763				first fan-out link behind PMP device.  It does not
1764				select the host link.  DEVICE number of 15 selects the
1765				host link and device attached to it.
1767				The VAL specifies the configuration to force.  As long
1768				as there's no ambiguity shortcut notation is allowed.
1769				For example, both 1.5 and 1.5G would work for 1.5Gbps.
1770				The following configurations can be forced.
1772				* Cable type: 40c, 80c, short40c, unk, ign or sata.
1773				  Any ID with matching PORT is used.
1775				* SATA link speed limit: 1.5Gbps or 3.0Gbps.
1777				* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1778				  udma[/][16,25,33,44,66,100,133] notation is also
1779				  allowed.
1781				* [no]ncq: Turn on or off NCQ.
1783				* nohrst, nosrst, norst: suppress hard, soft
1784	                          and both resets.
1786				* rstonce: only attempt one reset during
1787				  hot-unplug link recovery
1789				* dump_id: dump IDENTIFY data.
1791				* atapi_dmadir: Enable ATAPI DMADIR bridge support
1793				* disable: Disable this device.
1795				If there are multiple matching configurations changing
1796				the same attribute, the last one is used.
1798		memblock=debug	[KNL] Enable memblock debug messages.
1800		load_ramdisk=	[RAM] List of ramdisks to load from floppy
1801				See Documentation/blockdev/ramdisk.txt.
1803		lockd.nlm_grace_period=P  [NFS] Assign grace period.
1804				Format: <integer>
1806		lockd.nlm_tcpport=N	[NFS] Assign TCP port.
1807				Format: <integer>
1809		lockd.nlm_timeout=T	[NFS] Assign timeout value.
1810				Format: <integer>
1812		lockd.nlm_udpport=M	[NFS] Assign UDP port.
1813				Format: <integer>
1815		locktorture.nreaders_stress= [KNL]
1816				Set the number of locking read-acquisition kthreads.
1817				Defaults to being automatically set based on the
1818				number of online CPUs.
1820		locktorture.nwriters_stress= [KNL]
1821				Set the number of locking write-acquisition kthreads.
1823		locktorture.onoff_holdoff= [KNL]
1824				Set time (s) after boot for CPU-hotplug testing.
1826		locktorture.onoff_interval= [KNL]
1827				Set time (s) between CPU-hotplug operations, or
1828				zero to disable CPU-hotplug testing.
1830		locktorture.shuffle_interval= [KNL]
1831				Set task-shuffle interval (jiffies).  Shuffling
1832				tasks allows some CPUs to go into dyntick-idle
1833				mode during the locktorture test.
1835		locktorture.shutdown_secs= [KNL]
1836				Set time (s) after boot system shutdown.  This
1837				is useful for hands-off automated testing.
1839		locktorture.stat_interval= [KNL]
1840				Time (s) between statistics printk()s.
1842		locktorture.stutter= [KNL]
1843				Time (s) to stutter testing, for example,
1844				specifying five seconds causes the test to run for
1845				five seconds, wait for five seconds, and so on.
1846				This tests the locking primitive's ability to
1847				transition abruptly to and from idle.
1849		locktorture.torture_runnable= [BOOT]
1850				Start locktorture running at boot time.
1852		locktorture.torture_type= [KNL]
1853				Specify the locking implementation to test.
1855		locktorture.verbose= [KNL]
1856				Enable additional printk() statements.
1858		logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
1859				Format: <irq>
1861		loglevel=	All Kernel Messages with a loglevel smaller than the
1862				console loglevel will be printed to the console. It can
1863				also be changed with klogd or other programs. The
1864				loglevels are defined as follows:
1866				0 (KERN_EMERG)		system is unusable
1867				1 (KERN_ALERT)		action must be taken immediately
1868				2 (KERN_CRIT)		critical conditions
1869				3 (KERN_ERR)		error conditions
1870				4 (KERN_WARNING)	warning conditions
1871				5 (KERN_NOTICE)		normal but significant condition
1872				6 (KERN_INFO)		informational
1873				7 (KERN_DEBUG)		debug-level messages
1875		log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
1876				in bytes.  n must be a power of two and greater
1877				than the minimal size. The minimal size is defined
1878				by LOG_BUF_SHIFT kernel config parameter. There is
1879				also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1880				that allows to increase the default size depending on
1881				the number of CPUs. See init/Kconfig for more details.
1883		logo.nologo	[FB] Disables display of the built-in Linux logo.
1884				This may be used to provide more screen space for
1885				kernel log messages and is useful when debugging
1886				kernel boot problems.
1888		lp=0		[LP]	Specify parallel ports to use, e.g,
1889		lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
1890		lp=reset		first parallel port). 'lp=0' disables the
1891		lp=auto			printer driver. 'lp=reset' (which can be
1892					specified in addition to the ports) causes
1893					attached printers to be reset. Using
1894					lp=port1,port2,... specifies the parallel ports
1895					to associate lp devices with, starting with
1896					lp0. A port specification may be 'none' to skip
1897					that lp device, or a parport name such as
1898					'parport0'. Specifying 'lp=auto' instead of a
1899					port specification list means that device IDs
1900					from each port should be examined, to see if
1901					an IEEE 1284-compliant printer is attached; if
1902					so, the driver will manage that printer.
1903					See also header of drivers/char/lp.c.
1905		lpj=n		[KNL]
1906				Sets loops_per_jiffy to given constant, thus avoiding
1907				time-consuming boot-time autodetection (up to 250 ms per
1908				CPU). 0 enables autodetection (default). To determine
1909				the correct value for your kernel, boot with normal
1910				autodetection and see what value is printed. Note that
1911				on SMP systems the preset will be applied to all CPUs,
1912				which is likely to cause problems if your CPUs need
1913				significantly divergent settings. An incorrect value
1914				will cause delays in the kernel to be wrong, leading to
1915				unpredictable I/O errors and other breakage. Although
1916				unlikely, in the extreme case this might damage your
1917				hardware.
1919		ltpc=		[NET]
1920				Format: <io>,<irq>,<dma>
1922		machvec=	[IA-64] Force the use of a particular machine-vector
1923				(machvec) in a generic kernel.
1924				Example: machvec=hpzx1_swiotlb
1926		machtype=	[Loongson] Share the same kernel image file between different
1927				 yeeloong laptop.
1928				Example: machtype=lemote-yeeloong-2f-7inch
1930		max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
1931				than or equal to this physical address is ignored.
1933		maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
1934				should make use of.  maxcpus=n : n >= 0 limits the
1935				kernel to using 'n' processors.  n=0 is a special case,
1936				it is equivalent to "nosmp", which also disables
1937				the IO APIC.
1939		max_loop=	[LOOP] The number of loop block devices that get
1940		(loop.max_loop)	unconditionally pre-created at init time. The default
1941				number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1942				of statically allocating a predefined number, loop
1943				devices can be requested on-demand with the
1944				/dev/loop-control interface.
1946		mce		[X86-32] Machine Check Exception
1948		mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
1950		md=		[HW] RAID subsystems devices and level
1951				See Documentation/md.txt.
1953		mdacon=		[MDA]
1954				Format: <first>,<last>
1955				Specifies range of consoles to be captured by the MDA.
1957		mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
1958				Amount of memory to be used when the kernel is not able
1959				to see the whole system memory or for test.
1960				[X86] Work as limiting max address. Use together
1961				with memmap= to avoid physical address space collisions.
1962				Without memmap= PCI devices could be placed at addresses
1963				belonging to unused RAM.
1965		mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
1966				memory.
1968		memchunk=nn[KMG]
1969				[KNL,SH] Allow user to override the default size for
1970				per-device physically contiguous DMA buffers.
1972		memmap=exactmap	[KNL,X86] Enable setting of an exact
1973				E820 memory map, as specified by the user.
1974				Such memmap=exactmap lines can be constructed based on
1975				BIOS output or other requirements. See the memmap=nn@ss
1976				option description.
1978		memmap=nn[KMG]@ss[KMG]
1979				[KNL] Force usage of a specific region of memory.
1980				Region of memory to be used is from ss to ss+nn.
1982		memmap=nn[KMG]#ss[KMG]
1983				[KNL,ACPI] Mark specific memory as ACPI data.
1984				Region of memory to be marked is from ss to ss+nn.
1986		memmap=nn[KMG]$ss[KMG]
1987				[KNL,ACPI] Mark specific memory as reserved.
1988				Region of memory to be reserved is from ss to ss+nn.
1989				Example: Exclude memory from 0x18690000-0x1869ffff
1990				         memmap=64K$0x18690000
1991				         or
1992				         memmap=0x10000$0x18690000
1994		memmap=nn[KMG]!ss[KMG]
1995				[KNL,X86] Mark specific memory as protected.
1996				Region of memory to be used, from ss to ss+nn.
1997				The memory region may be marked as e820 type 12 (0xc)
1998				and is NVDIMM or ADR memory.
2000		memory_corruption_check=0/1 [X86]
2001				Some BIOSes seem to corrupt the first 64k of
2002				memory when doing things like suspend/resume.
2003				Setting this option will scan the memory
2004				looking for corruption.  Enabling this will
2005				both detect corruption and prevent the kernel
2006				from using the memory being corrupted.
2007				However, its intended as a diagnostic tool; if
2008				repeatable BIOS-originated corruption always
2009				affects the same memory, you can use memmap=
2010				to prevent the kernel from using that memory.
2012		memory_corruption_check_size=size [X86]
2013				By default it checks for corruption in the low
2014				64k, making this memory unavailable for normal
2015				use.  Use this parameter to scan for
2016				corruption in more or less memory.
2018		memory_corruption_check_period=seconds [X86]
2019				By default it checks for corruption every 60
2020				seconds.  Use this parameter to check at some
2021				other rate.  0 disables periodic checking.
2023		memtest=	[KNL,X86,ARM] Enable memtest
2024				Format: <integer>
2025				default : 0 <disable>
2026				Specifies the number of memtest passes to be
2027				performed. Each pass selects another test
2028				pattern from a given set of patterns. Memtest
2029				fills the memory with this pattern, validates
2030				memory contents and reserves bad memory
2031				regions that are detected.
2033		meye.*=		[HW] Set MotionEye Camera parameters
2034				See Documentation/video4linux/meye.txt.
2036		mfgpt_irq=	[IA-32] Specify the IRQ to use for the
2037				Multi-Function General Purpose Timers on AMD Geode
2038				platforms.
2040		mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
2041				the BIOS has incorrectly applied a workaround. TinyBIOS
2042				version 0.98 is known to be affected, 0.99 fixes the
2043				problem by letting the user disable the workaround.
2045		mga=		[HW,DRM]
2047		min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
2048				physical address is ignored.
2050		mini2440=	[ARM,HW,KNL]
2051				Format:[0..2][b][c][t]
2052				Default: "0tb"
2053				MINI2440 configuration specification:
2054				0 - The attached screen is the 3.5" TFT
2055				1 - The attached screen is the 7" TFT
2056				2 - The VGA Shield is attached (1024x768)
2057				Leaving out the screen size parameter will not load
2058				the TFT driver, and the framebuffer will be left
2059				unconfigured.
2060				b - Enable backlight. The TFT backlight pin will be
2061				linked to the kernel VESA blanking code and a GPIO
2062				LED. This parameter is not necessary when using the
2063				VGA shield.
2064				c - Enable the s3c camera interface.
2065				t - Reserved for enabling touchscreen support. The
2066				touchscreen support is not enabled in the mainstream
2067				kernel as of 2.6.30, a preliminary port can be found
2068				in the "bleeding edge" mini2440 support kernel at
2069				http://repo.or.cz/w/linux-2.6/mini2440.git
2071		mminit_loglevel=
2072				[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2073				parameter allows control of the logging verbosity for
2074				the additional memory initialisation checks. A value
2075				of 0 disables mminit logging and a level of 4 will
2076				log everything. Information is printed at KERN_DEBUG
2077				so loglevel=8 may also need to be specified.
2079		module.sig_enforce
2080				[KNL] When CONFIG_MODULE_SIG is set, this means that
2081				modules without (valid) signatures will fail to load.
2082				Note that if CONFIG_MODULE_SIG_FORCE is set, that
2083				is always true, so this option does nothing.
2085		mousedev.tap_time=
2086				[MOUSE] Maximum time between finger touching and
2087				leaving touchpad surface for touch to be considered
2088				a tap and be reported as a left button click (for
2089				touchpads working in absolute mode only).
2090				Format: <msecs>
2091		mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
2092				reporting absolute coordinates, such as tablets
2093		mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
2094				reporting absolute coordinates, such as tablets
2096		movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
2097				is similar to kernelcore except it specifies the
2098				amount of memory used for migratable allocations.
2099				If both kernelcore and movablecore is specified,
2100				then kernelcore will be at *least* the specified
2101				value but may be more. If movablecore on its own
2102				is specified, the administrator must be careful
2103				that the amount of memory usable for all allocations
2104				is not too small.
2106		movable_node	[KNL,X86] Boot-time switch to enable the effects
2107				of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2109		MTD_Partition=	[MTD]
2110				Format: <name>,<region-number>,<size>,<offset>
2112		MTD_Region=	[MTD] Format:
2113				<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2115		mtdparts=	[MTD]
2116				See drivers/mtd/cmdlinepart.c.
2118		multitce=off	[PPC]  This parameter disables the use of the pSeries
2119				firmware feature for updating multiple TCE entries
2120				at a time.
2122		onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
2124				Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2126				boundary - index of last SLC block on Flex-OneNAND.
2127					   The remaining blocks are configured as MLC blocks.
2128				lock	 - Configure if Flex-OneNAND boundary should be locked.
2129					   Once locked, the boundary cannot be changed.
2130					   1 indicates lock status, 0 indicates unlock status.
2132		mtdset=		[ARM]
2133				ARM/S3C2412 JIVE boot control
2135				See arch/arm/mach-s3c2412/mach-jive.c
2137		mtouchusb.raw_coordinates=
2138				[HW] Make the MicroTouch USB driver use raw coordinates
2139				('y', default) or cooked coordinates ('n')
2141		mtrr_chunk_size=nn[KMG] [X86]
2142				used for mtrr cleanup. It is largest continuous chunk
2143				that could hold holes aka. UC entries.
2145		mtrr_gran_size=nn[KMG] [X86]
2146				Used for mtrr cleanup. It is granularity of mtrr block.
2147				Default is 1.
2148				Large value could prevent small alignment from
2149				using up MTRRs.
2151		mtrr_spare_reg_nr=n [X86]
2152				Format: <integer>
2153				Range: 0,7 : spare reg number
2154				Default : 1
2155				Used for mtrr cleanup. It is spare mtrr entries number.
2156				Set to 2 or more if your graphical card needs more.
2158		n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
2160		netdev=		[NET] Network devices parameters
2161				Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2162				Note that mem_start is often overloaded to mean
2163				something different and driver-specific.
2164				This usage is only documented in each driver source
2165				file if at all.
2167		nf_conntrack.acct=
2168				[NETFILTER] Enable connection tracking flow accounting
2169				0 to disable accounting
2170				1 to enable accounting
2171				Default value is 0.
2173		nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
2174				See Documentation/filesystems/nfs/nfsroot.txt.
2176		nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
2177				See Documentation/filesystems/nfs/nfsroot.txt.
2179		nfsrootdebug	[NFS] enable nfsroot debugging messages.
2180				See Documentation/filesystems/nfs/nfsroot.txt.
2182		nfs.callback_tcpport=
2183				[NFS] set the TCP port on which the NFSv4 callback
2184				channel should listen.
2186		nfs.cache_getent=
2187				[NFS] sets the pathname to the program which is used
2188				to update the NFS client cache entries.
2190		nfs.cache_getent_timeout=
2191				[NFS] sets the timeout after which an attempt to
2192				update a cache entry is deemed to have failed.
2194		nfs.idmap_cache_timeout=
2195				[NFS] set the maximum lifetime for idmapper cache
2196				entries.
2198		nfs.enable_ino64=
2199				[NFS] enable 64-bit inode numbers.
2200				If zero, the NFS client will fake up a 32-bit inode
2201				number for the readdir() and stat() syscalls instead
2202				of returning the full 64-bit number.
2203				The default is to return 64-bit inode numbers.
2205		nfs.max_session_slots=
2206				[NFSv4.1] Sets the maximum number of session slots
2207				the client will attempt to negotiate with the server.
2208				This limits the number of simultaneous RPC requests
2209				that the client can send to the NFSv4.1 server.
2210				Note that there is little point in setting this
2211				value higher than the max_tcp_slot_table_limit.
2213		nfs.nfs4_disable_idmapping=
2214				[NFSv4] When set to the default of '1', this option
2215				ensures that both the RPC level authentication
2216				scheme and the NFS level operations agree to use
2217				numeric uids/gids if the mount is using the
2218				'sec=sys' security flavour. In effect it is
2219				disabling idmapping, which can make migration from
2220				legacy NFSv2/v3 systems to NFSv4 easier.
2221				Servers that do not support this mode of operation
2222				will be autodetected by the client, and it will fall
2223				back to using the idmapper.
2224				To turn off this behaviour, set the value to '0'.
2225		nfs.nfs4_unique_id=
2226				[NFS4] Specify an additional fixed unique ident-
2227				ification string that NFSv4 clients can insert into
2228				their nfs_client_id4 string.  This is typically a
2229				UUID that is generated at system install time.
2231		nfs.send_implementation_id =
2232				[NFSv4.1] Send client implementation identification
2233				information in exchange_id requests.
2234				If zero, no implementation identification information
2235				will be sent.
2236				The default is to send the implementation identification
2237				information.
2239		nfs.recover_lost_locks =
2240				[NFSv4] Attempt to recover locks that were lost due
2241				to a lease timeout on the server. Please note that
2242				doing this risks data corruption, since there are
2243				no guarantees that the file will remain unchanged
2244				after the locks are lost.
2245				If you want to enable the kernel legacy behaviour of
2246				attempting to recover these locks, then set this
2247				parameter to '1'.
2248				The default parameter value of '0' causes the kernel
2249				not to attempt recovery of lost locks.
2251		nfsd.nfs4_disable_idmapping=
2252				[NFSv4] When set to the default of '1', the NFSv4
2253				server will return only numeric uids and gids to
2254				clients using auth_sys, and will accept numeric uids
2255				and gids from such clients.  This is intended to ease
2256				migration from NFSv2/v3.
2258		objlayoutdriver.osd_login_prog=
2259				[NFS] [OBJLAYOUT] sets the pathname to the program which
2260				is used to automatically discover and login into new
2261				osd-targets. Please see:
2262				Documentation/filesystems/pnfs.txt for more explanations
2264		nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
2265				when a NMI is triggered.
2266				Format: [state][,regs][,debounce][,die]
2268		nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2269				Format: [panic,][nopanic,][num]
2270				Valid num: 0 or 1
2271				0 - turn nmi_watchdog off
2272				1 - turn nmi_watchdog on
2273				When panic is specified, panic when an NMI watchdog
2274				timeout occurs (or 'nopanic' to override the opposite
2275				default).
2276				This is useful when you use a panic=... timeout and
2277				need the box quickly up again.
2279		netpoll.carrier_timeout=
2280				[NET] Specifies amount of time (in seconds) that
2281				netpoll should wait for a carrier. By default netpoll
2282				waits 4 seconds.
2284		no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
2285				emulation library even if a 387 maths coprocessor
2286				is present.
2288		no_console_suspend
2289				[HW] Never suspend the console
2290				Disable suspending of consoles during suspend and
2291				hibernate operations.  Once disabled, debugging
2292				messages can reach various consoles while the rest
2293				of the system is being put to sleep (ie, while
2294				debugging driver suspend/resume hooks).  This may
2295				not work reliably with all consoles, but is known
2296				to work with serial and VGA consoles.
2297				To facilitate more flexible debugging, we also add
2298				console_suspend, a printk module parameter to control
2299				it. Users could use console_suspend (usually
2300				/sys/module/printk/parameters/console_suspend) to
2301				turn on/off it dynamically.
2303		noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
2304				caches in the slab allocator.  Saves per-node memory,
2305				but will impact performance.
2307		noalign		[KNL,ARM]
2309		noapic		[SMP,APIC] Tells the kernel to not make use of any
2310				IOAPICs that may be present in the system.
2312		noautogroup	Disable scheduler automatic task group creation.
2314		nobats		[PPC] Do not use BATs for mapping kernel lowmem
2315				on "Classic" PPC cores.
2317		nocache		[ARM]
2319		noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2321		nodelayacct	[KNL] Disable per-task delay accounting
2323		nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.
2325		nodsp		[SH] Disable hardware DSP at boot time.
2327		noefi		Disable EFI runtime services support.
2329		noexec		[IA-64]
2331		noexec		[X86]
2332				On X86-32 available only on PAE configured kernels.
2333				noexec=on: enable non-executable mappings (default)
2334				noexec=off: disable non-executable mappings
2336		nosmap		[X86]
2337				Disable SMAP (Supervisor Mode Access Prevention)
2338				even if it is supported by processor.
2340		nosmep		[X86]
2341				Disable SMEP (Supervisor Mode Execution Prevention)
2342				even if it is supported by processor.
2344		noexec32	[X86-64]
2345				This affects only 32-bit executables.
2346				noexec32=on: enable non-executable mappings (default)
2347					read doesn't imply executable mappings
2348				noexec32=off: disable non-executable mappings
2349					read implies executable mappings
2351		nofpu		[MIPS,SH] Disable hardware FPU at boot time.
2353		nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2354				register save and restore. The kernel will only save
2355				legacy floating-point registers on task switch.
2357		nohugeiomap	[KNL,x86] Disable kernel huge I/O mappings.
2359		noxsave		[BUGS=X86] Disables x86 extended register state save
2360				and restore using xsave. The kernel will fallback to
2361				enabling legacy floating-point and sse state.
2363		noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
2364				register states. The kernel will fall back to use
2365				xsave to save the states. By using this parameter,
2366				performance of saving the states is degraded because
2367				xsave doesn't support modified optimization while
2368				xsaveopt supports it on xsaveopt enabled systems.
2370		noxsaves	[X86] Disables xsaves and xrstors used in saving and
2371				restoring x86 extended register state in compacted
2372				form of xsave area. The kernel will fall back to use
2373				xsaveopt and xrstor to save and restore the states
2374				in standard form of xsave area. By using this
2375				parameter, xsave area per process might occupy more
2376				memory on xsaves enabled systems.
2378		nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2379				wfi(ARM) instruction doesn't work correctly and not to
2380				use it. This is also useful when using JTAG debugger.
2382		no_file_caps	Tells the kernel not to honor file capabilities.  The
2383				only way then for a file to be executed with privilege
2384				is to be setuid root or executed by root.
2386		nohalt		[IA-64] Tells the kernel not to use the power saving
2387				function PAL_HALT_LIGHT when idle. This increases
2388				power-consumption. On the positive side, it reduces
2389				interrupt wake-up latency, which may improve performance
2390				in certain environments such as networked servers or
2391				real-time systems.
2393		nohibernate	[HIBERNATION] Disable hibernation and resume.
2395		nohz=		[KNL] Boottime enable/disable dynamic ticks
2396				Valid arguments: on, off
2397				Default: on
2399		nohz_full=	[KNL,BOOT]
2400				In kernels built with CONFIG_NO_HZ_FULL=y, set
2401				the specified list of CPUs whose tick will be stopped
2402				whenever possible. The boot CPU will be forced outside
2403				the range to maintain the timekeeping.
2404				The CPUs in this range must also be included in the
2405				rcu_nocbs= set.
2407		noiotrap	[SH] Disables trapped I/O port accesses.
2409		noirqdebug	[X86-32] Disables the code which attempts to detect and
2410				disable unhandled interrupt sources.
2412		no_timer_check	[X86,APIC] Disables the code which tests for
2413				broken timer IRQ sources.
2415		noisapnp	[ISAPNP] Disables ISA PnP code.
2417		noinitrd	[RAM] Tells the kernel not to load any configured
2418				initial RAM disk.
2420		nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
2421				remapping.
2422				[Deprecated - use intremap=off]
2424		nointroute	[IA-64]
2426		nojitter	[IA-64] Disables jitter checking for ITC timers.
2428		no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
2430		no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
2431				fault handling.
2433		no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
2434				steal time is computed, but won't influence scheduler
2435				behaviour
2437		nolapic		[X86-32,APIC] Do not enable or use the local APIC.
2439		nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2441		noltlbs		[PPC] Do not use large page/tlb entries for kernel
2442				lowmem mapping on PPC40x.
2444		nomca		[IA-64] Disable machine check abort handling
2446		nomce		[X86-32] Machine Check Exception
2448		nomfgpt		[X86-32] Disable Multi-Function General Purpose
2449				Timer usage (for AMD Geode machines).
2451		nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
2452				shutdown the other cpus.  Instead use the REBOOT_VECTOR
2453				irq.
2455		nomodule	Disable module load
2457		nopat		[X86] Disable PAT (page attribute table extension of
2458				pagetables) support.
2460		norandmaps	Don't use address space randomization.  Equivalent to
2461				echo 0 > /proc/sys/kernel/randomize_va_space
2463		noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2465		noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2466				with UP alternatives
2468		nordrand	[X86] Disable kernel use of the RDRAND and
2469				RDSEED instructions even if they are supported
2470				by the processor.  RDRAND and RDSEED are still
2471				available to user space applications.
2473		noresume	[SWSUSP] Disables resume and restores original swap
2474				space.
2476		no-scroll	[VGA] Disables scrollback.
2477				This is required for the Braillex ib80-piezo Braille
2478				reader made by F.H. Papenmeier (Germany).
2480		nosbagart	[IA-64]
2482		nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2484		nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
2485				and disable the IO APIC.  legacy for "maxcpus=0".
2487		nosoftlockup	[KNL] Disable the soft-lockup detector.
2489		nosync		[HW,M68K] Disables sync negotiation for all devices.
2491		notsc		[BUGS=X86-32] Disable Time Stamp Counter
2493		nousb		[USB] Disable the USB subsystem
2495		nowatchdog	[KNL] Disable both lockup detectors, i.e.
2496	                        soft-lockup and NMI watchdog (hard-lockup).
2498		nowb		[ARM]
2500		nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
2502		cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
2504				Some features depend on CPU0. Known dependencies are:
2505				1. Resume from suspend/hibernate depends on CPU0.
2506				Suspend/hibernate will fail if CPU0 is offline and you
2507				need to online CPU0 before suspend/hibernate.
2508				2. PIC interrupts also depend on CPU0. CPU0 can't be
2509				removed if a PIC interrupt is detected.
2510				It's said poweroff/reboot may depend on CPU0 on some
2511				machines although I haven't seen such issues so far
2512				after CPU0 is offline on a few tested machines.
2513				If the dependencies are under your control, you can
2514				turn on cpu0_hotplug.
2516		nptcg=		[IA-64] Override max number of concurrent global TLB
2517				purges which is reported from either PAL_VM_SUMMARY or
2518				SAL PALO.
2520		nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
2521				could support.  nr_cpus=n : n >= 1 limits the kernel to
2522				supporting 'n' processors. Later in runtime you can not
2523				use hotplug cpu feature to put more cpu back to online.
2524				just like you compile the kernel NR_CPUS=n
2526		nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
2528		numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
2529				Allowed values are enable and disable
2531		numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2532				one of ['zone', 'node', 'default'] can be specified
2533				This can be set from sysctl after boot.
2534				See Documentation/sysctl/vm.txt for details.
2536		ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
2537				See Documentation/debugging-via-ohci1394.txt for more
2538				info.
2540		olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2541				Rather than timing out after 20 ms if an EC
2542				command is not properly ACKed, override the length
2543				of the timeout.  We have interrupts disabled while
2544				waiting for the ACK, so if this is set too high
2545				interrupts *may* be lost!
2547		omap_mux=	[OMAP] Override bootloader pin multiplexing.
2548				Format: <mux_mode0.mode_name=value>...
2549				For example, to override I2C bus2:
2550				omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2552		oprofile.timer=	[HW]
2553				Use timer interrupt instead of performance counters
2555		oprofile.cpu_type=	Force an oprofile cpu type
2556				This might be useful if you have an older oprofile
2557				userland or if you want common events.
2558				Format: { arch_perfmon }
2559				arch_perfmon: [X86] Force use of architectural
2560					perfmon on Intel CPUs instead of the
2561					CPU specific event set.
2562				timer: [X86] Force use of architectural NMI
2563					timer mode (see also oprofile.timer
2564					for generic hr timer mode)
2565					[s390] Force legacy basic mode sampling
2566	                                (report cpu_type "timer")
2568		oops=panic	Always panic on oopses. Default is to just kill the
2569				process, but there is a small probability of
2570				deadlocking the machine.
2571				This will also cause panics on machine check exceptions.
2572				Useful together with panic=30 to trigger a reboot.
2574		OSS		[HW,OSS]
2575				See Documentation/sound/oss/oss-parameters.txt
2577		page_owner=	[KNL] Boot-time page_owner enabling option.
2578				Storage of the information about who allocated
2579				each page is disabled in default. With this switch,
2580				we can turn it on.
2581				on: enable the feature
2583		panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2584				timeout > 0: seconds before rebooting
2585				timeout = 0: wait forever
2586				timeout < 0: reboot immediately
2587				Format: <timeout>
2589		panic_on_warn	panic() instead of WARN().  Useful to cause kdump
2590				on a WARN().
2592		crash_kexec_post_notifiers
2593				Run kdump after running panic-notifiers and dumping
2594				kmsg. This only for the users who doubt kdump always
2595				succeeds in any situation.
2596				Note that this also increases risks of kdump failure,
2597				because some panic notifiers can make the crashed
2598				kernel more unstable.
2600		parkbd.port=	[HW] Parallel port number the keyboard adapter is
2601				connected to, default is 0.
2602				Format: <parport#>
2603		parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
2604				0 for XT, 1 for AT (default is AT).
2605				Format: <mode>
2607		parport=	[HW,PPT] Specify parallel ports. 0 disables.
2608				Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2609				Use 'auto' to force the driver to use any
2610				IRQ/DMA settings detected (the default is to
2611				ignore detected IRQ/DMA settings because of
2612				possible conflicts). You can specify the base
2613				address, IRQ, and DMA settings; IRQ and DMA
2614				should be numbers, or 'auto' (for using detected
2615				settings on that particular port), or 'nofifo'
2616				(to avoid using a FIFO even if it is detected).
2617				Parallel ports are assigned in the order they
2618				are specified on the command line, starting
2619				with parport0.
2621		parport_init_mode=	[HW,PPT]
2622				Configure VIA parallel port to operate in
2623				a specific mode. This is necessary on Pegasos
2624				computer where firmware has no options for setting
2625				up parallel port mode and sets it to spp.
2626				Currently this function knows 686a and 8231 chips.
2627				Format: [spp|ps2|epp|ecp|ecpepp]
2629		pause_on_oops=
2630				Halt all CPUs after the first oops has been printed for
2631				the specified number of seconds.  This is to be used if
2632				your oopses keep scrolling off the screen.
2634		pcbit=		[HW,ISDN]
2636		pcd.		[PARIDE]
2637				See header of drivers/block/paride/pcd.c.
2638				See also Documentation/blockdev/paride.txt.
2640		pci=option[,option...]	[PCI] various PCI subsystem options:
2641			earlydump	[X86] dump PCI config space before the kernel
2642				        changes anything
2643			off		[X86] don't probe for the PCI bus
2644			bios		[X86-32] force use of PCI BIOS, don't access
2645					the hardware directly. Use this if your machine
2646					has a non-standard PCI host bridge.
2647			nobios		[X86-32] disallow use of PCI BIOS, only direct
2648					hardware access methods are allowed. Use this
2649					if you experience crashes upon bootup and you
2650					suspect they are caused by the BIOS.
2651			conf1		[X86] Force use of PCI Configuration
2652					Mechanism 1.
2653			conf2		[X86] Force use of PCI Configuration
2654					Mechanism 2.
2655			noaer		[PCIE] If the PCIEAER kernel config parameter is
2656					enabled, this kernel boot option can be used to
2657					disable the use of PCIE advanced error reporting.
2658			nodomains	[PCI] Disable support for multiple PCI
2659					root domains (aka PCI segments, in ACPI-speak).
2660			nommconf	[X86] Disable use of MMCONFIG for PCI
2661					Configuration
2662			check_enable_amd_mmconf [X86] check for and enable
2663					properly configured MMIO access to PCI
2664					config space on AMD family 10h CPU
2665			nomsi		[MSI] If the PCI_MSI kernel config parameter is
2666					enabled, this kernel boot option can be used to
2667					disable the use of MSI interrupts system-wide.
2668			noioapicquirk	[APIC] Disable all boot interrupt quirks.
2669					Safety option to keep boot IRQs enabled. This
2670					should never be necessary.
2671			ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
2672					primary IO-APIC for bridges that cannot disable
2673					boot IRQs. This fixes a source of spurious IRQs
2674					when the system masks IRQs.
2675			noioapicreroute	[APIC] Disable workaround that uses the
2676					boot IRQ equivalent of an IRQ that connects to
2677					a chipset where boot IRQs cannot be disabled.
2678					The opposite of ioapicreroute.
2679			biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
2680					routing table. These calls are known to be buggy
2681					on several machines and they hang the machine
2682					when used, but on other computers it's the only
2683					way to get the interrupt routing table. Try
2684					this option if the kernel is unable to allocate
2685					IRQs or discover secondary PCI buses on your
2686					motherboard.
2687			rom		[X86] Assign address space to expansion ROMs.
2688					Use with caution as certain devices share
2689					address decoders between ROMs and other
2690					resources.
2691			norom		[X86] Do not assign address space to
2692					expansion ROMs that do not already have
2693					BIOS assigned address ranges.
2694			nobar		[X86] Do not assign address space to the
2695					BARs that weren't assigned by the BIOS.
2696			irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
2697					assigned automatically to PCI devices. You can
2698					make the kernel exclude IRQs of your ISA cards
2699					this way.
2700			pirqaddr=0xAAAAA	[X86] Specify the physical address
2701					of the PIRQ table (normally generated
2702					by the BIOS) if it is outside the
2703					F0000h-100000h range.
2704			lastbus=N	[X86] Scan all buses thru bus #N. Can be
2705					useful if the kernel is unable to find your
2706					secondary buses and you want to tell it
2707					explicitly which ones they are.
2708			assign-busses	[X86] Always assign all PCI bus
2709					numbers ourselves, overriding
2710					whatever the firmware may have done.
2711			usepirqmask	[X86] Honor the possible IRQ mask stored
2712					in the BIOS $PIR table. This is needed on
2713					some systems with broken BIOSes, notably
2714					some HP Pavilion N5400 and Omnibook XE3
2715					notebooks. This will have no effect if ACPI
2716					IRQ routing is enabled.
2717			noacpi		[X86] Do not use ACPI for IRQ routing
2718					or for PCI scanning.
2719			use_crs		[X86] Use PCI host bridge window information
2720					from ACPI.  On BIOSes from 2008 or later, this
2721					is enabled by default.  If you need to use this,
2722					please report a bug.
2723			nocrs		[X86] Ignore PCI host bridge windows from ACPI.
2724				        If you need to use this, please report a bug.
2725			routeirq	Do IRQ routing for all PCI devices.
2726					This is normally done in pci_enable_device(),
2727					so this option is a temporary workaround
2728					for broken drivers that don't call it.
2729			skip_isa_align	[X86] do not align io start addr, so can
2730					handle more pci cards
2731			firmware	[ARM] Do not re-enumerate the bus but instead
2732					just use the configuration from the
2733					bootloader. This is currently used on
2734					IXP2000 systems where the bus has to be
2735					configured a certain way for adjunct CPUs.
2736			noearly		[X86] Don't do any early type 1 scanning.
2737					This might help on some broken boards which
2738					machine check when some devices' config space
2739					is read. But various workarounds are disabled
2740					and some IOMMU drivers will not work.
2741			bfsort		Sort PCI devices into breadth-first order.
2742					This sorting is done to get a device
2743					order compatible with older (<= 2.4) kernels.
2744			nobfsort	Don't sort PCI devices into breadth-first order.
2745			pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
2746					tuning and use the BIOS-configured MPS defaults.
2747			pcie_bus_safe	Set every device's MPS to the largest value
2748					supported by all devices below the root complex.
2749			pcie_bus_perf	Set device MPS to the largest allowable MPS
2750					based on its parent bus. Also set MRRS (Max
2751					Read Request Size) to the largest supported
2752					value (no larger than the MPS that the device
2753					or bus can support) for best performance.
2754			pcie_bus_peer2peer	Set every device's MPS to 128B, which
2755					every device is guaranteed to support. This
2756					configuration allows peer-to-peer DMA between
2757					any pair of devices, possibly at the cost of
2758					reduced performance.  This also guarantees
2759					that hot-added devices will work.
2760			cbiosize=nn[KMG]	The fixed amount of bus space which is
2761					reserved for the CardBus bridge's IO window.
2762					The default value is 256 bytes.
2763			cbmemsize=nn[KMG]	The fixed amount of bus space which is
2764					reserved for the CardBus bridge's memory
2765					window. The default value is 64 megabytes.
2766			resource_alignment=
2767					Format:
2768					[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2769					Specifies alignment and device to reassign
2770					aligned memory resources.
2771					If <order of align> is not specified,
2772					PAGE_SIZE is used as alignment.
2773					PCI-PCI bridge can be specified, if resource
2774					windows need to be expanded.
2775			ecrc=		Enable/disable PCIe ECRC (transaction layer
2776					end-to-end CRC checking).
2777					bios: Use BIOS/firmware settings. This is the
2778					the default.
2779					off: Turn ECRC off
2780					on: Turn ECRC on.
2781			hpiosize=nn[KMG]	The fixed amount of bus space which is
2782					reserved for hotplug bridge's IO window.
2783					Default size is 256 bytes.
2784			hpmemsize=nn[KMG]	The fixed amount of bus space which is
2785					reserved for hotplug bridge's memory window.
2786					Default size is 2 megabytes.
2787			realloc=	Enable/disable reallocating PCI bridge resources
2788					if allocations done by BIOS are too small to
2789					accommodate resources required by all child
2790					devices.
2791					off: Turn realloc off
2792					on: Turn realloc on
2793			realloc		same as realloc=on
2794			noari		do not use PCIe ARI.
2795			pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
2796					only look for one device below a PCIe downstream
2797					port.
2799		pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
2800				Management.
2801			off	Disable ASPM.
2802			force	Enable ASPM even on devices that claim not to support it.
2803				WARNING: Forcing ASPM on may cause system lockups.
2805		pcie_hp=	[PCIE] PCI Express Hotplug driver options:
2806			nomsi	Do not use MSI for PCI Express Native Hotplug (this
2807				makes all PCIe ports use INTx for hotplug services).
2809		pcie_ports=	[PCIE] PCIe ports handling:
2810			auto	Ask the BIOS whether or not to use native PCIe services
2811				associated with PCIe ports (PME, hot-plug, AER).  Use
2812				them only if that is allowed by the BIOS.
2813			native	Use native PCIe services associated with PCIe ports
2814				unconditionally.
2815			compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2816				ports driver.
2818		pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
2819			nomsi	Do not use MSI for native PCIe PME signaling (this makes
2820				all PCIe root ports use INTx for all services).
2822		pcmv=		[HW,PCMCIA] BadgePAD 4
2824		pd_ignore_unused
2825				[PM]
2826				Keep all power-domains already enabled by bootloader on,
2827				even if no driver has claimed them. This is useful
2828				for debug and development, but should not be
2829				needed on a platform with proper driver support.
2831		pd.		[PARIDE]
2832				See Documentation/blockdev/paride.txt.
2834		pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
2835				boot time.
2836				Format: { 0 | 1 }
2837				See arch/parisc/kernel/pdc_chassis.c
2839		percpu_alloc=	Select which percpu first chunk allocator to use.
2840				Currently supported values are "embed" and "page".
2841				Archs may support subset or none of the	selections.
2842				See comments in mm/percpu.c for details on each
2843				allocator.  This parameter is primarily	for debugging
2844				and performance comparison.
2846		pf.		[PARIDE]
2847				See Documentation/blockdev/paride.txt.
2849		pg.		[PARIDE]
2850				See Documentation/blockdev/paride.txt.
2852		pirq=		[SMP,APIC] Manual mp-table setup
2853				See Documentation/x86/i386/IO-APIC.txt.
2855		plip=		[PPT,NET] Parallel port network link
2856				Format: { parport<nr> | timid | 0 }
2857				See also Documentation/parport.txt.
2859		pmtmr=		[X86] Manual setup of pmtmr I/O Port.
2860				Override pmtimer IOPort with a hex value.
2861				e.g. pmtmr=0x508
2863		pnp.debug=1	[PNP]
2864				Enable PNP debug messages (depends on the
2865				CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2866				via /sys/module/pnp/parameters/debug.  We always show
2867				current resource usage; turning this on also shows
2868				possible settings and some assignment information.
2870		pnpacpi=	[ACPI]
2871				{ off }
2873		pnpbios=	[ISAPNP]
2874				{ on | off | curr | res | no-curr | no-res }
2876		pnp_reserve_irq=
2877				[ISAPNP] Exclude IRQs for the autoconfiguration
2879		pnp_reserve_dma=
2880				[ISAPNP] Exclude DMAs for the autoconfiguration
2882		pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
2883				Ranges are in pairs (I/O port base and size).
2885		pnp_reserve_mem=
2886				[ISAPNP] Exclude memory regions for the
2887				autoconfiguration.
2888				Ranges are in pairs (memory base and size).
2890		ports=		[IP_VS_FTP] IPVS ftp helper module
2891				Default is 21.
2892				Up to 8 (IP_VS_APP_MAX_PORTS) ports
2893				may be specified.
2894				Format: <port>,<port>....
2896		print-fatal-signals=
2897				[KNL] debug: print fatal signals
2899				If enabled, warn about various signal handling
2900				related application anomalies: too many signals,
2901				too many POSIX.1 timers, fatal signals causing a
2902				coredump - etc.
2904				If you hit the warning due to signal overflow,
2905				you might want to try "ulimit -i unlimited".
2907				default: off.
2909		printk.always_kmsg_dump=
2910				Trigger kmsg_dump for cases other than kernel oops or
2911				panics
2912				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2913				default: disabled
2915		printk.time=	Show timing data prefixed to each printk message line
2916				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2918		processor.max_cstate=	[HW,ACPI]
2919				Limit processor to maximum C-state
2920				max_cstate=9 overrides any DMI blacklist limit.
2922		processor.nocst	[HW,ACPI]
2923				Ignore the _CST method to determine C-states,
2924				instead using the legacy FADT method
2926		profile=	[KNL] Enable kernel profiling via /proc/profile
2927				Format: [schedule,]<number>
2928				Param: "schedule" - profile schedule points.
2929				Param: <number> - step/bucket size as a power of 2 for
2930					statistical time based profiling.
2931				Param: "sleep" - profile D-state sleeping (millisecs).
2932					Requires CONFIG_SCHEDSTATS
2933				Param: "kvm" - profile VM exits.
2935		prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
2936				before loading.
2937				See Documentation/blockdev/ramdisk.txt.
2939		psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
2940				probe for; one of (bare|imps|exps|lifebook|any).
2941		psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
2942				per second.
2943		psmouse.resetafter=	[HW,MOUSE]
2944				Try to reset the device after so many bad packets
2945				(0 = never).
2946		psmouse.resolution=
2947				[HW,MOUSE] Set desired mouse resolution, in dpi.
2948		psmouse.smartscroll=
2949				[HW,MOUSE] Controls Logitech smartscroll autorepeat.
2950				0 = disabled, 1 = enabled (default).
2952		pstore.backend=	Specify the name of the pstore backend to use
2954		pt.		[PARIDE]
2955				See Documentation/blockdev/paride.txt.
2957		pty.legacy_count=
2958				[KNL] Number of legacy pty's. Overwrites compiled-in
2959				default number.
2961		quiet		[KNL] Disable most log messages
2963		r128=		[HW,DRM]
2965		raid=		[HW,RAID]
2966				See Documentation/md.txt.
2968		ramdisk_blocksize=	[RAM]
2969				See Documentation/blockdev/ramdisk.txt.
2971		ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
2972				See Documentation/blockdev/ramdisk.txt.
2974		rcu_nocbs=	[KNL]
2975				In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2976				the specified list of CPUs to be no-callback CPUs.
2977				Invocation of these CPUs' RCU callbacks will
2978				be offloaded to "rcuox/N" kthreads created for
2979				that purpose, where "x" is "b" for RCU-bh, "p"
2980				for RCU-preempt, and "s" for RCU-sched, and "N"
2981				is the CPU number.  This reduces OS jitter on the
2982				offloaded CPUs, which can be useful for HPC and
2983				real-time workloads.  It can also improve energy
2984				efficiency for asymmetric multiprocessors.
2986		rcu_nocb_poll	[KNL]
2987				Rather than requiring that offloaded CPUs
2988				(specified by rcu_nocbs= above) explicitly
2989				awaken the corresponding "rcuoN" kthreads,
2990				make these kthreads poll for callbacks.
2991				This improves the real-time response for the
2992				offloaded CPUs by relieving them of the need to
2993				wake up the corresponding kthread, but degrades
2994				energy efficiency by requiring that the kthreads
2995				periodically wake up to do the polling.
2997		rcutree.blimit=	[KNL]
2998				Set maximum number of finished RCU callbacks to
2999				process in one batch.
3001		rcutree.gp_init_delay=	[KNL]
3002				Set the number of jiffies to delay each step of
3003				RCU grace-period initialization.  This only has
3004				effect when CONFIG_RCU_TORTURE_TEST_SLOW_INIT is
3005				set.
3007		rcutree.rcu_fanout_leaf= [KNL]
3008				Increase the number of CPUs assigned to each
3009				leaf rcu_node structure.  Useful for very large
3010				systems.
3012		rcutree.jiffies_till_sched_qs= [KNL]
3013				Set required age in jiffies for a
3014				given grace period before RCU starts
3015				soliciting quiescent-state help from
3016				rcu_note_context_switch().
3018		rcutree.jiffies_till_first_fqs= [KNL]
3019				Set delay from grace-period initialization to
3020				first attempt to force quiescent states.
3021				Units are jiffies, minimum value is zero,
3022				and maximum value is HZ.
3024		rcutree.jiffies_till_next_fqs= [KNL]
3025				Set delay between subsequent attempts to force
3026				quiescent states.  Units are jiffies, minimum
3027				value is one, and maximum value is HZ.
3029		rcutree.kthread_prio= 	 [KNL,BOOT]
3030				Set the SCHED_FIFO priority of the RCU per-CPU
3031				kthreads (rcuc/N). This value is also used for
3032				the priority of the RCU boost threads (rcub/N)
3033				and for the RCU grace-period kthreads (rcu_bh,
3034				rcu_preempt, and rcu_sched). If RCU_BOOST is
3035				set, valid values are 1-99 and the default is 1
3036				(the least-favored priority).  Otherwise, when
3037				RCU_BOOST is not set, valid values are 0-99 and
3038				the default is zero (non-realtime operation).
3040		rcutree.rcu_nocb_leader_stride= [KNL]
3041				Set the number of NOCB kthread groups, which
3042				defaults to the square root of the number of
3043				CPUs.  Larger numbers reduces the wakeup overhead
3044				on the per-CPU grace-period kthreads, but increases
3045				that same overhead on each group's leader.
3047		rcutree.qhimark= [KNL]
3048				Set threshold of queued RCU callbacks beyond which
3049				batch limiting is disabled.
3051		rcutree.qlowmark= [KNL]
3052				Set threshold of queued RCU callbacks below which
3053				batch limiting is re-enabled.
3055		rcutree.rcu_idle_gp_delay= [KNL]
3056				Set wakeup interval for idle CPUs that have
3057				RCU callbacks (RCU_FAST_NO_HZ=y).
3059		rcutree.rcu_idle_lazy_gp_delay= [KNL]
3060				Set wakeup interval for idle CPUs that have
3061				only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3062				Lazy RCU callbacks are those which RCU can
3063				prove do nothing more than free memory.
3065		rcutorture.cbflood_inter_holdoff= [KNL]
3066				Set holdoff time (jiffies) between successive
3067				callback-flood tests.
3069		rcutorture.cbflood_intra_holdoff= [KNL]
3070				Set holdoff time (jiffies) between successive
3071				bursts of callbacks within a given callback-flood
3072				test.
3074		rcutorture.cbflood_n_burst= [KNL]
3075				Set the number of bursts making up a given
3076				callback-flood test.  Set this to zero to
3077				disable callback-flood testing.
3079		rcutorture.cbflood_n_per_burst= [KNL]
3080				Set the number of callbacks to be registered
3081				in a given burst of a callback-flood test.
3083		rcutorture.fqs_duration= [KNL]
3084				Set duration of force_quiescent_state bursts.
3086		rcutorture.fqs_holdoff= [KNL]
3087				Set holdoff time within force_quiescent_state bursts.
3089		rcutorture.fqs_stutter= [KNL]
3090				Set wait time between force_quiescent_state bursts.
3092		rcutorture.gp_exp= [KNL]
3093				Use expedited update-side primitives.
3095		rcutorture.gp_normal= [KNL]
3096				Use normal (non-expedited) update-side primitives.
3097				If both gp_exp and gp_normal are set, do both.
3098				If neither gp_exp nor gp_normal are set, still
3099				do both.
3101		rcutorture.n_barrier_cbs= [KNL]
3102				Set callbacks/threads for rcu_barrier() testing.
3104		rcutorture.nfakewriters= [KNL]
3105				Set number of concurrent RCU writers.  These just
3106				stress RCU, they don't participate in the actual
3107				test, hence the "fake".
3109		rcutorture.nreaders= [KNL]
3110				Set number of RCU readers.
3112		rcutorture.object_debug= [KNL]
3113				Enable debug-object double-call_rcu() testing.
3115		rcutorture.onoff_holdoff= [KNL]
3116				Set time (s) after boot for CPU-hotplug testing.
3118		rcutorture.onoff_interval= [KNL]
3119				Set time (s) between CPU-hotplug operations, or
3120				zero to disable CPU-hotplug testing.
3122		rcutorture.torture_runnable= [BOOT]
3123				Start rcutorture running at boot time.
3125		rcutorture.shuffle_interval= [KNL]
3126				Set task-shuffle interval (s).  Shuffling tasks
3127				allows some CPUs to go into dyntick-idle mode
3128				during the rcutorture test.
3130		rcutorture.shutdown_secs= [KNL]
3131				Set time (s) after boot system shutdown.  This
3132				is useful for hands-off automated testing.
3134		rcutorture.stall_cpu= [KNL]
3135				Duration of CPU stall (s) to test RCU CPU stall
3136				warnings, zero to disable.
3138		rcutorture.stall_cpu_holdoff= [KNL]
3139				Time to wait (s) after boot before inducing stall.
3141		rcutorture.stat_interval= [KNL]
3142				Time (s) between statistics printk()s.
3144		rcutorture.stutter= [KNL]
3145				Time (s) to stutter testing, for example, specifying
3146				five seconds causes the test to run for five seconds,
3147				wait for five seconds, and so on.  This tests RCU's
3148				ability to transition abruptly to and from idle.
3150		rcutorture.test_boost= [KNL]
3151				Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
3152				"Maybe" means test if the RCU implementation
3153				under test support RCU priority boosting.
3155		rcutorture.test_boost_duration= [KNL]
3156				Duration (s) of each individual boost test.
3158		rcutorture.test_boost_interval= [KNL]
3159				Interval (s) between each boost test.
3161		rcutorture.test_no_idle_hz= [KNL]
3162				Test RCU's dyntick-idle handling.  See also the
3163				rcutorture.shuffle_interval parameter.
3165		rcutorture.torture_type= [KNL]
3166				Specify the RCU implementation to test.
3168		rcutorture.verbose= [KNL]
3169				Enable additional printk() statements.
3171		rcupdate.rcu_expedited= [KNL]
3172				Use expedited grace-period primitives, for
3173				example, synchronize_rcu_expedited() instead
3174				of synchronize_rcu().  This reduces latency,
3175				but can increase CPU utilization, degrade
3176				real-time latency, and degrade energy efficiency.
3178		rcupdate.rcu_cpu_stall_suppress= [KNL]
3179				Suppress RCU CPU stall warning messages.
3181		rcupdate.rcu_cpu_stall_timeout= [KNL]
3182				Set timeout for RCU CPU stall warning messages.
3184		rcupdate.rcu_task_stall_timeout= [KNL]
3185				Set timeout in jiffies for RCU task stall warning
3186				messages.  Disable with a value less than or equal
3187				to zero.
3189		rcupdate.rcu_self_test= [KNL]
3190				Run the RCU early boot self tests
3192		rcupdate.rcu_self_test_bh= [KNL]
3193				Run the RCU bh early boot self tests
3195		rcupdate.rcu_self_test_sched= [KNL]
3196				Run the RCU sched early boot self tests
3198		rdinit=		[KNL]
3199				Format: <full_path>
3200				Run specified binary instead of /init from the ramdisk,
3201				used for early userspace startup. See initrd.
3203		reboot=		[KNL]
3204				Format (x86 or x86_64):
3205					[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3206					[[,]s[mp]#### \
3207					[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3208					[[,]f[orce]
3209				Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3210				      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3211				      reboot_force is either force or not specified,
3212				      reboot_cpu is s[mp]#### with #### being the processor
3213						to be used for rebooting.
3215		relax_domain_level=
3216				[KNL, SMP] Set scheduler's default relax_domain_level.
3217				See Documentation/cgroups/cpusets.txt.
3219		relative_sleep_states=
3220				[SUSPEND] Use sleep state labeling where the deepest
3221				state available other than hibernation is always "mem".
3222				Format: { "0" | "1" }
3223				0 -- Traditional sleep state labels.
3224				1 -- Relative sleep state labels.
3226		reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
3228		reservetop=	[X86-32]
3229				Format: nn[KMG]
3230				Reserves a hole at the top of the kernel virtual
3231				address space.
3233		reservelow=	[X86]
3234				Format: nn[K]
3235				Set the amount of memory to reserve for BIOS at
3236				the bottom of the address space.
3238		reset_devices	[KNL] Force drivers to reset the underlying device
3239				during initialization.
3241		resume=		[SWSUSP]
3242				Specify the partition device for software suspend
3243				Format:
3244				{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3246		resume_offset=	[SWSUSP]
3247				Specify the offset from the beginning of the partition
3248				given by "resume=" at which the swap header is located,
3249				in <PAGE_SIZE> units (needed only for swap files).
3250				See  Documentation/power/swsusp-and-swap-files.txt
3252		resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
3253				read the resume files
3255		resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
3256				Useful for devices that are detected asynchronously
3257				(e.g. USB and MMC devices).
3259		hibernate=	[HIBERNATION]
3260			noresume	Don't check if there's a hibernation image
3261					present during boot.
3262			nocompress	Don't compress/decompress hibernation images.
3263			no		Disable hibernation and resume.
3265		retain_initrd	[RAM] Keep initrd memory after extraction
3267		rfkill.default_state=
3268			0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
3269				etc. communication is blocked by default.
3270			1	Unblocked.
3272		rfkill.master_switch_mode=
3273			0	The "airplane mode" button does nothing.
3274			1	The "airplane mode" button toggles between everything
3275				blocked and the previous configuration.
3276			2	The "airplane mode" button toggles between everything
3277				blocked and everything unblocked.
3279		rhash_entries=	[KNL,NET]
3280				Set number of hash buckets for route cache
3282		ro		[KNL] Mount root device read-only on boot
3284		root=		[KNL] Root filesystem
3285				See name_to_dev_t comment in init/do_mounts.c.
3287		rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
3288				mount the root filesystem
3290		rootflags=	[KNL] Set root filesystem mount option string
3292		rootfstype=	[KNL] Set root filesystem type
3294		rootwait	[KNL] Wait (indefinitely) for root device to show up.
3295				Useful for devices that are detected asynchronously
3296				(e.g. USB and MMC devices).
3298		rproc_mem=nn[KMG][@address]
3299				[KNL,ARM,CMA] Remoteproc physical memory block.
3300				Memory area to be used by remote processor image,
3301				managed by CMA.
3303		rw		[KNL] Mount root device read-write on boot
3305		S		[KNL] Run init in single mode
3307		s390_iommu=	[HW,S390]
3308				Set s390 IOTLB flushing mode
3309			strict
3310				With strict flushing every unmap operation will result in
3311				an IOTLB flush. Default is lazy flushing before reuse,
3312				which is faster.
3314		sa1100ir	[NET]
3315				See drivers/net/irda/sa1100_ir.c.
3317		sbni=		[NET] Granch SBNI12 leased line adapter
3319		sched_debug	[KNL] Enables verbose scheduler debug messages.
3321		skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
3322				xtime_lock contention on larger systems, and/or RCU lock
3323				contention on all systems with CONFIG_MAXSMP set.
3324				Format: { "0" | "1" }
3325				0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3326				1 -- enable.
3327				Note: increases power consumption, thus should only be
3328				enabled if running jitter sensitive (HPC/RT) workloads.
3330		security=	[SECURITY] Choose a security module to enable at boot.
3331				If this boot parameter is not specified, only the first
3332				security module asking for security registration will be
3333				loaded. An invalid security module name will be treated
3334				as if no module has been chosen.
3336		selinux=	[SELINUX] Disable or enable SELinux at boot time.
3337				Format: { "0" | "1" }
3338				See security/selinux/Kconfig help text.
3339				0 -- disable.
3340				1 -- enable.
3341				Default value is set via kernel config option.
3342				If enabled at boot time, /selinux/disable can be used
3343				later to disable prior to initial policy load.
3345		apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
3346				Format: { "0" | "1" }
3347				See security/apparmor/Kconfig help text
3348				0 -- disable.
3349				1 -- enable.
3350				Default value is set via kernel config option.
3352		serialnumber	[BUGS=X86-32]
3354		shapers=	[NET]
3355				Maximal number of shapers.
3357		show_msr=	[x86] show boot-time MSR settings
3358				Format: { <integer> }
3359				Show boot-time (BIOS-initialized) MSR settings.
3360				The parameter means the number of CPUs to show,
3361				for example 1 means boot CPU only.
3363		simeth=		[IA-64]
3364		simscsi=
3366		slram=		[HW,MTD]
3368		slab_nomerge	[MM]
3369				Disable merging of slabs with similar size. May be
3370				necessary if there is some reason to distinguish
3371				allocs to different slabs. Debug options disable
3372				merging on their own.
3373				For more information see Documentation/vm/slub.txt.
3375		slab_max_order=	[MM, SLAB]
3376				Determines the maximum allowed order for slabs.
3377				A high setting may cause OOMs due to memory
3378				fragmentation.  Defaults to 1 for systems with
3379				more than 32MB of RAM, 0 otherwise.
3381		slub_debug[=options[,slabs]]	[MM, SLUB]
3382				Enabling slub_debug allows one to determine the
3383				culprit if slab objects become corrupted. Enabling
3384				slub_debug can create guard zones around objects and
3385				may poison objects when not in use. Also tracks the
3386				last alloc / free. For more information see
3387				Documentation/vm/slub.txt.
3389		slub_max_order= [MM, SLUB]
3390				Determines the maximum allowed order for slabs.
3391				A high setting may cause OOMs due to memory
3392				fragmentation. For more information see
3393				Documentation/vm/slub.txt.
3395		slub_min_objects=	[MM, SLUB]
3396				The minimum number of objects per slab. SLUB will
3397				increase the slab order up to slub_max_order to
3398				generate a sufficiently large slab able to contain
3399				the number of objects indicated. The higher the number
3400				of objects the smaller the overhead of tracking slabs
3401				and the less frequently locks need to be acquired.
3402				For more information see Documentation/vm/slub.txt.
3404		slub_min_order=	[MM, SLUB]
3405				Determines the minimum page order for slabs. Must be
3406				lower than slub_max_order.
3407				For more information see Documentation/vm/slub.txt.
3409		slub_nomerge	[MM, SLUB]
3410				Same with slab_nomerge. This is supported for legacy.
3411				See slab_nomerge for more information.
3413		smart2=		[HW]
3414				Format: <io1>[,<io2>[,...,<io8>]]
3416		smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
3417		smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
3418		smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
3419		smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
3420		smsc-ircc2.ircc_irq=	[HW] IRQ line
3421		smsc-ircc2.ircc_dma=	[HW] DMA channel
3422		smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3423					0: Toshiba Satellite 1800 (GP data pin select)
3424					1: Fast pin select (default)
3425					2: ATC IRMode
3427		softlockup_panic=
3428				[KNL] Should the soft-lockup detector generate panics.
3429				Format: <integer>
3431		softlockup_all_cpu_backtrace=
3432				[KNL] Should the soft-lockup detector generate
3433				backtraces on all cpus.
3434				Format: <integer>
3436		sonypi.*=	[HW] Sony Programmable I/O Control Device driver
3437				See Documentation/laptops/sonypi.txt
3439		spia_io_base=	[HW,MTD]
3440		spia_fio_base=
3441		spia_pedr=
3442		spia_peddr=
3444		stacktrace	[FTRACE]
3445				Enabled the stack tracer on boot up.
3447		stacktrace_filter=[function-list]
3448				[FTRACE] Limit the functions that the stack tracer
3449				will trace at boot up. function-list is a comma separated
3450				list of functions. This list can be changed at run
3451				time by the stack_trace_filter file in the debugfs
3452				tracing directory. Note, this enables stack tracing
3453				and the stacktrace above is not needed.
3455		sti=		[PARISC,HW]
3456				Format: <num>
3457				Set the STI (builtin display/keyboard on the HP-PARISC
3458				machines) console (graphic card) which should be used
3459				as the initial boot-console.
3460				See also comment in drivers/video/console/sticore.c.
3462		sti_font=	[HW]
3463				See comment in drivers/video/console/sticore.c.
3465		stifb=		[HW]
3466				Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3468		sunrpc.min_resvport=
3469		sunrpc.max_resvport=
3470				[NFS,SUNRPC]
3471				SunRPC servers often require that client requests
3472				originate from a privileged port (i.e. a port in the
3473				range 0 < portnr < 1024).
3474				An administrator who wishes to reserve some of these
3475				ports for other uses may adjust the range that the
3476				kernel's sunrpc client considers to be privileged
3477				using these two parameters to set the minimum and
3478				maximum port values.
3480		sunrpc.pool_mode=
3481				[NFS]
3482				Control how the NFS server code allocates CPUs to
3483				service thread pools.  Depending on how many NICs
3484				you have and where their interrupts are bound, this
3485				option will affect which CPUs will do NFS serving.
3486				Note: this parameter cannot be changed while the
3487				NFS server is running.
3489				auto	    the server chooses an appropriate mode
3490					    automatically using heuristics
3491				global	    a single global pool contains all CPUs
3492				percpu	    one pool for each CPU
3493				pernode	    one pool for each NUMA node (equivalent
3494					    to global on non-NUMA machines)
3496		sunrpc.tcp_slot_table_entries=
3497		sunrpc.udp_slot_table_entries=
3498				[NFS,SUNRPC]
3499				Sets the upper limit on the number of simultaneous
3500				RPC calls that can be sent from the client to a
3501				server. Increasing these values may allow you to
3502				improve throughput, but will also increase the
3503				amount of memory reserved for use by the client.
3505		suspend.pm_test_delay=
3506				[SUSPEND]
3507				Sets the number of seconds to remain in a suspend test
3508				mode before resuming the system (see
3509				/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3510				is set. Default value is 5.
3512		swapaccount=[0|1]
3513				[KNL] Enable accounting of swap in memory resource
3514				controller if no parameter or 1 is given or disable
3515				it if 0 is given (See Documentation/cgroups/memory.txt)
3517		swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
3518				Format: { <int> | force }
3519				<int> -- Number of I/O TLB slabs
3520				force -- force using of bounce buffers even if they
3521				         wouldn't be automatically used by the kernel
3523		switches=	[HW,M68k]
3525		sysfs.deprecated=0|1 [KNL]
3526				Enable/disable old style sysfs layout for old udev
3527				on older distributions. When this option is enabled
3528				very new udev will not work anymore. When this option
3529				is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3530				in older udev will not work anymore.
3531				Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3532				the kernel configuration.
3534		sysrq_always_enabled
3535				[KNL]
3536				Ignore sysrq setting - this boot parameter will
3537				neutralize any effect of /proc/sys/kernel/sysrq.
3538				Useful for debugging.
3540		tcpmhash_entries= [KNL,NET]
3541				Set the number of tcp_metrics_hash slots.
3542				Default value is 8192 or 16384 depending on total
3543				ram pages. This is used to specify the TCP metrics
3544				cache size. See Documentation/networking/ip-sysctl.txt
3545				"tcp_no_metrics_save" section for more details.
3547		tdfx=		[HW,DRM]
3549		test_suspend=	[SUSPEND][,N]
3550				Specify "mem" (for Suspend-to-RAM) or "standby" (for
3551				standby suspend) or "freeze" (for suspend type freeze)
3552				as the system sleep state during system startup with
3553				the optional capability to repeat N number of times.
3554				The system is woken from this state using a
3555				wakeup-capable RTC alarm.
3557		thash_entries=	[KNL,NET]
3558				Set number of hash buckets for TCP connection
3560		thermal.act=	[HW,ACPI]
3561				-1: disable all active trip points in all thermal zones
3562				<degrees C>: override all lowest active trip points
3564		thermal.crt=	[HW,ACPI]
3565				-1: disable all critical trip points in all thermal zones
3566				<degrees C>: override all critical trip points
3568		thermal.nocrt=	[HW,ACPI]
3569				Set to disable actions on ACPI thermal zone
3570				critical and hot trip points.
3572		thermal.off=	[HW,ACPI]
3573				1: disable ACPI thermal control
3575		thermal.psv=	[HW,ACPI]
3576				-1: disable all passive trip points
3577				<degrees C>: override all passive trip points to this
3578				value
3580		thermal.tzp=	[HW,ACPI]
3581				Specify global default ACPI thermal zone polling rate
3582				<deci-seconds>: poll all this frequency
3583				0: no polling (default)
3585		threadirqs	[KNL]
3586				Force threading of all interrupt handlers except those
3587				marked explicitly IRQF_NO_THREAD.
3589		tmem		[KNL,XEN]
3590				Enable the Transcendent memory driver if built-in.
3592		tmem.cleancache=0|1 [KNL, XEN]
3593				Default is on (1). Disable the usage of the cleancache
3594				API to send anonymous pages to the hypervisor.
3596		tmem.frontswap=0|1 [KNL, XEN]
3597				Default is on (1). Disable the usage of the frontswap
3598				API to send swap pages to the hypervisor. If disabled
3599				the selfballooning and selfshrinking are force disabled.
3601		tmem.selfballooning=0|1 [KNL, XEN]
3602				Default is on (1). Disable the driving of swap pages
3603				to the hypervisor.
3605		tmem.selfshrinking=0|1 [KNL, XEN]
3606				Default is on (1). Partial swapoff that immediately
3607				transfers pages from Xen hypervisor back to the
3608				kernel based on different criteria.
3610		topology=	[S390]
3611				Format: {off | on}
3612				Specify if the kernel should make use of the cpu
3613				topology information if the hardware supports this.
3614				The scheduler will make use of this information and
3615				e.g. base its process migration decisions on it.
3616				Default is on.
3618		topology_updates= [KNL, PPC, NUMA]
3619				Format: {off}
3620				Specify if the kernel should ignore (off)
3621				topology updates sent by the hypervisor to this
3622				LPAR.
3624		tp720=		[HW,PS2]
3626		tpm_suspend_pcr=[HW,TPM]
3627				Format: integer pcr id
3628				Specify that at suspend time, the tpm driver
3629				should extend the specified pcr with zeros,
3630				as a workaround for some chips which fail to
3631				flush the last written pcr on TPM_SaveState.
3632				This will guarantee that all the other pcrs
3633				are saved.
3635		trace_buf_size=nn[KMG]
3636				[FTRACE] will set tracing buffer size on each cpu.
3638		trace_event=[event-list]
3639				[FTRACE] Set and start specified trace events in order
3640				to facilitate early boot debugging.
3641				See also Documentation/trace/events.txt
3643		trace_options=[option-list]
3644				[FTRACE] Enable or disable tracer options at boot.
3645				The option-list is a comma delimited list of options
3646				that can be enabled or disabled just as if you were
3647				to echo the option name into
3649				    /sys/kernel/debug/tracing/trace_options
3651				For example, to enable stacktrace option (to dump the
3652				stack trace of each event), add to the command line:
3654				      trace_options=stacktrace
3656				See also Documentation/trace/ftrace.txt "trace options"
3657				section.
3659		tp_printk[FTRACE]
3660				Have the tracepoints sent to printk as well as the
3661				tracing ring buffer. This is useful for early boot up
3662				where the system hangs or reboots and does not give the
3663				option for reading the tracing buffer or performing a
3664				ftrace_dump_on_oops.
3666				To turn off having tracepoints sent to printk,
3667				 echo 0 > /proc/sys/kernel/tracepoint_printk
3668				Note, echoing 1 into this file without the
3669				tracepoint_printk kernel cmdline option has no effect.
3671				** CAUTION **
3673				Having tracepoints sent to printk() and activating high
3674				frequency tracepoints such as irq or sched, can cause
3675				the system to live lock.
3677		traceoff_on_warning
3678				[FTRACE] enable this option to disable tracing when a
3679				warning is hit. This turns off "tracing_on". Tracing can
3680				be enabled again by echoing '1' into the "tracing_on"
3681				file located in /sys/kernel/debug/tracing/
3683				This option is useful, as it disables the trace before
3684				the WARNING dump is called, which prevents the trace to
3685				be filled with content caused by the warning output.
3687				This option can also be set at run time via the sysctl
3688				option:  kernel/traceoff_on_warning
3690		transparent_hugepage=
3691				[KNL]
3692				Format: [always|madvise|never]
3693				Can be used to control the default behavior of the system
3694				with respect to transparent hugepages.
3695				See Documentation/vm/transhuge.txt for more details.
3697		tsc=		Disable clocksource stability checks for TSC.
3698				Format: <string>
3699				[x86] reliable: mark tsc clocksource as reliable, this
3700				disables clocksource verification at runtime, as well
3701				as the stability checks done at bootup.	Used to enable
3702				high-resolution timer mode on older hardware, and in
3703				virtualized environment.
3704				[x86] noirqtime: Do not use TSC to do irq accounting.
3705				Used to run time disable IRQ_TIME_ACCOUNTING on any
3706				platforms where RDTSC is slow and this accounting
3707				can add overhead.
3709		turbografx.map[2|3]=	[HW,JOY]
3710				TurboGraFX parallel port interface
3711				Format:
3712				<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3713				See also Documentation/input/joystick-parport.txt
3715		udbg-immortal	[PPC] When debugging early kernel crashes that
3716				happen after console_init() and before a proper 
3717				console driver takes over, this boot options might
3718				help "seeing" what's going on.
3720		uhash_entries=	[KNL,NET]
3721				Set number of hash buckets for UDP/UDP-Lite connections
3723		uhci-hcd.ignore_oc=
3724				[USB] Ignore overcurrent events (default N).
3725				Some badly-designed motherboards generate lots of
3726				bogus events, for ports that aren't wired to
3727				anything.  Set this parameter to avoid log spamming.
3728				Note that genuine overcurrent events won't be
3729				reported either.
3731		unknown_nmi_panic
3732				[X86] Cause panic on unknown NMI.
3734		usbcore.authorized_default=
3735				[USB] Default USB device authorization:
3736				(default -1 = authorized except for wireless USB,
3737				0 = not authorized, 1 = authorized)
3739		usbcore.autosuspend=
3740				[USB] The autosuspend time delay (in seconds) used
3741				for newly-detected USB devices (default 2).  This
3742				is the time required before an idle device will be
3743				autosuspended.  Devices for which the delay is set
3744				to a negative value won't be autosuspended at all.
3746		usbcore.usbfs_snoop=
3747				[USB] Set to log all usbfs traffic (default 0 = off).
3749		usbcore.blinkenlights=
3750				[USB] Set to cycle leds on hubs (default 0 = off).
3752		usbcore.old_scheme_first=
3753				[USB] Start with the old device initialization
3754				scheme (default 0 = off).
3756		usbcore.usbfs_memory_mb=
3757				[USB] Memory limit (in MB) for buffers allocated by
3758				usbfs (default = 16, 0 = max = 2047).
3760		usbcore.use_both_schemes=
3761				[USB] Try the other device initialization scheme
3762				if the first one fails (default 1 = enabled).
3764		usbcore.initial_descriptor_timeout=
3765				[USB] Specifies timeout for the initial 64-byte
3766	                        USB_REQ_GET_DESCRIPTOR request in milliseconds
3767				(default 5000 = 5.0 seconds).
3769		usbhid.mousepoll=
3770				[USBHID] The interval which mice are to be polled at.
3772		usb-storage.delay_use=
3773				[UMS] The delay in seconds before a new device is
3774				scanned for Logical Units (default 1).
3776		usb-storage.quirks=
3777				[UMS] A list of quirks entries to supplement or
3778				override the built-in unusual_devs list.  List
3779				entries are separated by commas.  Each entry has
3780				the form VID:PID:Flags where VID and PID are Vendor
3781				and Product ID values (4-digit hex numbers) and
3782				Flags is a set of characters, each corresponding
3783				to a common usb-storage quirk flag as follows:
3784					a = SANE_SENSE (collect more than 18 bytes
3785						of sense data);
3786					b = BAD_SENSE (don't collect more than 18
3787						bytes of sense data);
3788					c = FIX_CAPACITY (decrease the reported
3789						device capacity by one sector);
3790					d = NO_READ_DISC_INFO (don't use
3791						READ_DISC_INFO command);
3792					e = NO_READ_CAPACITY_16 (don't use
3793						READ_CAPACITY_16 command);
3794					f = NO_REPORT_OPCODES (don't use report opcodes
3795						command, uas only);
3796					g = MAX_SECTORS_240 (don't transfer more than
3797						240 sectors at a time, uas only);
3798					h = CAPACITY_HEURISTICS (decrease the
3799						reported device capacity by one
3800						sector if the number is odd);
3801					i = IGNORE_DEVICE (don't bind to this
3802						device);
3803					l = NOT_LOCKABLE (don't try to lock and
3804						unlock ejectable media);
3805					m = MAX_SECTORS_64 (don't transfer more
3806						than 64 sectors = 32 KB at a time);
3807					n = INITIAL_READ10 (force a retry of the
3808						initial READ(10) command);
3809					o = CAPACITY_OK (accept the capacity
3810						reported by the device);
3811					p = WRITE_CACHE (the device cache is ON
3812						by default);
3813					r = IGNORE_RESIDUE (the device reports
3814						bogus residue values);
3815					s = SINGLE_LUN (the device has only one
3816						Logical Unit);
3817					t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3818						commands, uas only);
3819					u = IGNORE_UAS (don't bind to the uas driver);
3820					w = NO_WP_DETECT (don't test whether the
3821						medium is write-protected).
3822				Example: quirks=0419:aaf5:rl,0421:0433:rc
3824		user_debug=	[KNL,ARM]
3825				Format: <int>
3826				See arch/arm/Kconfig.debug help text.
3827					 1 - undefined instruction events
3828					 2 - system calls
3829					 4 - invalid data aborts
3830					 8 - SIGSEGV faults
3831					16 - SIGBUS faults
3832				Example: user_debug=31
3834		userpte=
3835				[X86] Flags controlling user PTE allocations.
3837					nohigh = do not allocate PTE pages in
3838						HIGHMEM regardless of setting
3839						of CONFIG_HIGHPTE.
3841		vdso=		[X86,SH]
3842				On X86_32, this is an alias for vdso32=.  Otherwise:
3844				vdso=1: enable VDSO (the default)
3845				vdso=0: disable VDSO mapping
3847		vdso32=		[X86] Control the 32-bit vDSO
3848				vdso32=1: enable 32-bit VDSO
3849				vdso32=0 or vdso32=2: disable 32-bit VDSO
3851				See the help text for CONFIG_COMPAT_VDSO for more
3852				details.  If CONFIG_COMPAT_VDSO is set, the default is
3853				vdso32=0; otherwise, the default is vdso32=1.
3855				For compatibility with older kernels, vdso32=2 is an
3856				alias for vdso32=0.
3858				Try vdso32=0 if you encounter an error that says:
3859				dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3861		vector=		[IA-64,SMP]
3862				vector=percpu: enable percpu vector domain
3864		video=		[FB] Frame buffer configuration
3865				See Documentation/fb/modedb.txt.
3867		video.brightness_switch_enabled= [0,1]
3868				If set to 1, on receiving an ACPI notify event
3869				generated by hotkey, video driver will adjust brightness
3870				level and then send out the event to user space through
3871				the allocated input device; If set to 0, video driver
3872				will only send out the event without touching backlight
3873				brightness level.
3874				default: 1
3876		virtio_mmio.device=
3877				[VMMIO] Memory mapped virtio (platform) device.
3879					<size>@<baseaddr>:<irq>[:<id>]
3880				where:
3881					<size>     := size (can use standard suffixes
3882							like K, M and G)
3883					<baseaddr> := physical base address
3884					<irq>      := interrupt number (as passed to
3885							request_irq())
3886					<id>       := (optional) platform device id
3887				example:
3888					virtio_mmio.device=1K@0x100b0000:48:7
3890				Can be used multiple times for multiple devices.
3892		vga=		[BOOT,X86-32] Select a particular video mode
3893				See Documentation/x86/boot.txt and
3894				Documentation/svga.txt.
3895				Use vga=ask for menu.
3896				This is actually a boot loader parameter; the value is
3897				passed to the kernel using a special protocol.
3899		vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
3900				size of <nn>. This can be used to increase the
3901				minimum size (128MB on x86). It can also be used to
3902				decrease the size and leave more room for directly
3903				mapped kernel RAM.
3905		vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
3906				Format: <command>
3908		vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
3909				Format: <command>
3911		vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
3912				Format: <command>
3914		vsyscall=	[X86-64]
3915				Controls the behavior of vsyscalls (i.e. calls to
3916				fixed addresses of 0xffffffffff600x00 from legacy
3917				code).  Most statically-linked binaries and older
3918				versions of glibc use these calls.  Because these
3919				functions are at fixed addresses, they make nice
3920				targets for exploits that can control RIP.
3922				emulate     [default] Vsyscalls turn into traps and are
3923				            emulated reasonably safely.
3925				native      Vsyscalls are native syscall instructions.
3926				            This is a little bit faster than trapping
3927				            and makes a few dynamic recompilers work
3928				            better than they would in emulation mode.
3929				            It also makes exploits much easier to write.
3931				none        Vsyscalls don't work at all.  This makes
3932				            them quite hard to use for exploits but
3933				            might break your system.
3935		vt.color=	[VT] Default text color.
3936				Format: 0xYX, X = foreground, Y = background.
3937				Default: 0x07 = light gray on black.
3939		vt.cur_default=	[VT] Default cursor shape.
3940				Format: 0xCCBBAA, where AA, BB, and CC are the same as
3941				the parameters of the <Esc>[?A;B;Cc escape sequence;
3942				see VGA-softcursor.txt. Default: 2 = underline.
3944		vt.default_blu=	[VT]
3945				Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3946				Change the default blue palette of the console.
3947				This is a 16-member array composed of values
3948				ranging from 0-255.
3950		vt.default_grn=	[VT]
3951				Format: <green0>,<green1>,<green2>,...,<green15>
3952				Change the default green palette of the console.
3953				This is a 16-member array composed of values
3954				ranging from 0-255.
3956		vt.default_red=	[VT]
3957				Format: <red0>,<red1>,<red2>,...,<red15>
3958				Change the default red palette of the console.
3959				This is a 16-member array composed of values
3960				ranging from 0-255.
3962		vt.default_utf8=
3963				[VT]
3964				Format=<0|1>
3965				Set system-wide default UTF-8 mode for all tty's.
3966				Default is 1, i.e. UTF-8 mode is enabled for all
3967				newly opened terminals.
3969		vt.global_cursor_default=
3970				[VT]
3971				Format=<-1|0|1>
3972				Set system-wide default for whether a cursor
3973				is shown on new VTs. Default is -1,
3974				i.e. cursors will be created by default unless
3975				overridden by individual drivers. 0 will hide
3976				cursors, 1 will display them.
3978		vt.italic=	[VT] Default color for italic text; 0-15.
3979				Default: 2 = green.
3981		vt.underline=	[VT] Default color for underlined text; 0-15.
3982				Default: 3 = cyan.
3984		watchdog timers	[HW,WDT] For information on watchdog timers,
3985				see Documentation/watchdog/watchdog-parameters.txt
3986				or other driver-specific files in the
3987				Documentation/watchdog/ directory.
3989		workqueue.disable_numa
3990				By default, all work items queued to unbound
3991				workqueues are affine to the NUMA nodes they're
3992				issued on, which results in better behavior in
3993				general.  If NUMA affinity needs to be disabled for
3994				whatever reason, this option can be used.  Note
3995				that this also can be controlled per-workqueue for
3996				workqueues visible under /sys/bus/workqueue/.
3998		workqueue.power_efficient
3999				Per-cpu workqueues are generally preferred because
4000				they show better performance thanks to cache
4001				locality; unfortunately, per-cpu workqueues tend to
4002				be more power hungry than unbound workqueues.
4004				Enabling this makes the per-cpu workqueues which
4005				were observed to contribute significantly to power
4006				consumption unbound, leading to measurably lower
4007				power usage at the cost of small performance
4008				overhead.
4010				The default value of this parameter is determined by
4011				the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4013		x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
4014				default x2apic cluster mode on platforms
4015				supporting x2apic.
4017		x86_intel_mid_timer= [X86-32,APBT]
4018				Choose timer option for x86 Intel MID platform.
4019				Two valid options are apbt timer only and lapic timer
4020				plus one apbt timer for broadcast timer.
4021				x86_intel_mid_timer=apbt_only | lapic_and_apbt
4023		xen_emul_unplug=		[HW,X86,XEN]
4024				Unplug Xen emulated devices
4025				Format: [unplug0,][unplug1]
4026				ide-disks -- unplug primary master IDE devices
4027				aux-ide-disks -- unplug non-primary-master IDE devices
4028				nics -- unplug network devices
4029				all -- unplug all emulated devices (NICs and IDE disks)
4030				unnecessary -- unplugging emulated devices is
4031					unnecessary even if the host did not respond to
4032					the unplug protocol
4033				never -- do not unplug even if version check succeeds
4035		xen_nopvspin	[X86,XEN]
4036				Disables the ticketlock slowpath using Xen PV
4037				optimizations.
4039		xen_nopv	[X86]
4040				Disables the PV optimizations forcing the HVM guest to
4041				run as generic HVM guest with no PV drivers.
4043		xirc2ps_cs=	[NET,PCMCIA]
4044				Format:
4045				<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4047	______________________________________________________________________
4049	TODO:
4051		Add more DRM drivers.
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