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Based on kernel version 4.3. Page generated on 2015-11-02 12:50 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_apic_instance=	[ACPI, IOAPIC]
183				Format: <int>
184				2: use 2nd APIC table, if available
185				1,0: use 1st APIC table
186				default: 0
188		acpi_backlight=	[HW,ACPI]
189				acpi_backlight=vendor
190				acpi_backlight=video
191				If set to vendor, prefer vendor specific driver
192				(e.g. thinkpad_acpi, sony_acpi, etc.) instead
193				of the ACPI video.ko driver.
195		acpica_no_return_repair [HW, ACPI]
196				Disable AML predefined validation mechanism
197				This mechanism can repair the evaluation result to make
198				the return objects more ACPI specification compliant.
199				This option is useful for developers to identify the
200				root cause of an AML interpreter issue when the issue
201				has something to do with the repair mechanism.
203		acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
204		acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
205				Format: <int>
206				CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
207				debug output.  Bits in debug_layer correspond to a
208				_COMPONENT in an ACPI source file, e.g.,
210				Bits in debug_level correspond to a level in
211				ACPI_DEBUG_PRINT statements, e.g.,
213				The debug_level mask defaults to "info".  See
214				Documentation/acpi/debug.txt for more information about
215				debug layers and levels.
217				Enable processor driver info messages:
218				    acpi.debug_layer=0x20000000
219				Enable PCI/PCI interrupt routing info messages:
220				    acpi.debug_layer=0x400000
221				Enable AML "Debug" output, i.e., stores to the Debug
222				object while interpreting AML:
223				    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
224				Enable all messages related to ACPI hardware:
225				    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
227				Some values produce so much output that the system is
228				unusable.  The "log_buf_len" parameter may be useful
229				if you need to capture more output.
231		acpi_enforce_resources=	[ACPI]
232				{ strict | lax | no }
233				Check for resource conflicts between native drivers
234				and ACPI OperationRegions (SystemIO and SystemMemory
235				only). IO ports and memory declared in ACPI might be
236				used by the ACPI subsystem in arbitrary AML code and
237				can interfere with legacy drivers.
238				strict (default): access to resources claimed by ACPI
239				is denied; legacy drivers trying to access reserved
240				resources will fail to bind to device using them.
241				lax: access to resources claimed by ACPI is allowed;
242				legacy drivers trying to access reserved resources
243				will bind successfully but a warning message is logged.
244				no: ACPI OperationRegions are not marked as reserved,
245				no further checks are performed.
247		acpi_force_table_verification	[HW,ACPI]
248				Enable table checksum verification during early stage.
249				By default, this is disabled due to x86 early mapping
250				size limitation.
252		acpi_irq_balance [HW,ACPI]
253				ACPI will balance active IRQs
254				default in APIC mode
256		acpi_irq_nobalance [HW,ACPI]
257				ACPI will not move active IRQs (default)
258				default in PIC mode
260		acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
261				Format: <irq>,<irq>...
263		acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
264				use by PCI
265				Format: <irq>,<irq>...
267		acpi_no_auto_serialize	[HW,ACPI]
268				Disable auto-serialization of AML methods
269				AML control methods that contain the opcodes to create
270				named objects will be marked as "Serialized" by the
271				auto-serialization feature.
272				This feature is enabled by default.
273				This option allows to turn off the feature.
275		acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
276				   kernels.
278		acpi_no_static_ssdt	[HW,ACPI]
279				Disable installation of static SSDTs at early boot time
280				By default, SSDTs contained in the RSDT/XSDT will be
281				installed automatically and they will appear under
282				/sys/firmware/acpi/tables.
283				This option turns off this feature.
284				Note that specifying this option does not affect
285				dynamic table installation which will install SSDT
286				tables to /sys/firmware/acpi/tables/dynamic.
288		acpi_rsdp=	[ACPI,EFI,KEXEC]
289				Pass the RSDP address to the kernel, mostly used
290				on machines running EFI runtime service to boot the
291				second kernel for kdump.
293		acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
294				Format: To spoof as Windows 98: ="Microsoft Windows"
296		acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
297				of 2 which is mandated by ACPI 6) as the supported ACPI
298				specification revision (when using this switch, it may
299				be necessary to carry out a cold reboot _twice_ in a
300				row to make it take effect on the platform firmware).
302		acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
303				acpi_osi="string1"	# add string1
304				acpi_osi="!string2"	# remove string2
305				acpi_osi=!*		# remove all strings
306				acpi_osi=!		# disable all built-in OS vendor
307							  strings
308				acpi_osi=		# disable all strings
310				'acpi_osi=!' can be used in combination with single or
311				multiple 'acpi_osi="string1"' to support specific OS
312				vendor string(s).  Note that such command can only
313				affect the default state of the OS vendor strings, thus
314				it cannot affect the default state of the feature group
315				strings and the current state of the OS vendor strings,
316				specifying it multiple times through kernel command line
317				is meaningless.  This command is useful when one do not
318				care about the state of the feature group strings which
319				should be controlled by the OSPM.
320				Examples:
321				  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
322				     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
323				     can make '_OSI("Windows 2000")' TRUE.
325				'acpi_osi=' cannot be used in combination with other
326				'acpi_osi=' command lines, the _OSI method will not
327				exist in the ACPI namespace.  NOTE that such command can
328				only affect the _OSI support state, thus specifying it
329				multiple times through kernel command line is also
330				meaningless.
331				Examples:
332				  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
333				     FALSE.
335				'acpi_osi=!*' can be used in combination with single or
336				multiple 'acpi_osi="string1"' to support specific
337				string(s).  Note that such command can affect the
338				current state of both the OS vendor strings and the
339				feature group strings, thus specifying it multiple times
340				through kernel command line is meaningful.  But it may
341				still not able to affect the final state of a string if
342				there are quirks related to this string.  This command
343				is useful when one want to control the state of the
344				feature group strings to debug BIOS issues related to
345				the OSPM features.
346				Examples:
347				  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
348				     '_OSI("Module Device")' FALSE.
349				  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
350				     '_OSI("Module Device")' TRUE.
351				  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
352				     equivalent to
353				     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
354				     and
355				     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
356				     they all will make '_OSI("Windows 2000")' TRUE.
358		acpi_pm_good	[X86]
359				Override the pmtimer bug detection: force the kernel
360				to assume that this machine's pmtimer latches its value
361				and always returns good values.
363		acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
364				Format: { level | edge | high | low }
366		acpi_skip_timer_override [HW,ACPI]
367				Recognize and ignore IRQ0/pin2 Interrupt Override.
368				For broken nForce2 BIOS resulting in XT-PIC timer.
370		acpi_sleep=	[HW,ACPI] Sleep options
371				Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
372					  old_ordering, nonvs, sci_force_enable }
373				See Documentation/power/video.txt for information on
374				s3_bios and s3_mode.
375				s3_beep is for debugging; it makes the PC's speaker beep
376				as soon as the kernel's real-mode entry point is called.
377				s4_nohwsig prevents ACPI hardware signature from being
378				used during resume from hibernation.
379				old_ordering causes the ACPI 1.0 ordering of the _PTS
380				control method, with respect to putting devices into
381				low power states, to be enforced (the ACPI 2.0 ordering
382				of _PTS is used by default).
383				nonvs prevents the kernel from saving/restoring the
384				ACPI NVS memory during suspend/hibernation and resume.
385				sci_force_enable causes the kernel to set SCI_EN directly
386				on resume from S1/S3 (which is against the ACPI spec,
387				but some broken systems don't work without it).
389		acpi_use_timer_override [HW,ACPI]
390				Use timer override. For some broken Nvidia NF5 boards
391				that require a timer override, but don't have HPET
393		add_efi_memmap	[EFI; X86] Include EFI memory map in
394				kernel's map of available physical RAM.
396		agp=		[AGP]
397				{ off | try_unsupported }
398				off: disable AGP support
399				try_unsupported: try to drive unsupported chipsets
400					(may crash computer or cause data corruption)
402		ALSA		[HW,ALSA]
403				See Documentation/sound/alsa/alsa-parameters.txt
405		alignment=	[KNL,ARM]
406				Allow the default userspace alignment fault handler
407				behaviour to be specified.  Bit 0 enables warnings,
408				bit 1 enables fixups, and bit 2 sends a segfault.
410		align_va_addr=	[X86-64]
411				Align virtual addresses by clearing slice [14:12] when
412				allocating a VMA at process creation time. This option
413				gives you up to 3% performance improvement on AMD F15h
414				machines (where it is enabled by default) for a
415				CPU-intensive style benchmark, and it can vary highly in
416				a microbenchmark depending on workload and compiler.
418				32: only for 32-bit processes
419				64: only for 64-bit processes
420				on: enable for both 32- and 64-bit processes
421				off: disable for both 32- and 64-bit processes
423		alloc_snapshot	[FTRACE]
424				Allocate the ftrace snapshot buffer on boot up when the
425				main buffer is allocated. This is handy if debugging
426				and you need to use tracing_snapshot() on boot up, and
427				do not want to use tracing_snapshot_alloc() as it needs
428				to be done where GFP_KERNEL allocations are allowed.
430		amd_iommu=	[HW,X86-64]
431				Pass parameters to the AMD IOMMU driver in the system.
432				Possible values are:
433				fullflush - enable flushing of IO/TLB entries when
434					    they are unmapped. Otherwise they are
435					    flushed before they will be reused, which
436					    is a lot of faster
437				off	  - do not initialize any AMD IOMMU found in
438					    the system
439				force_isolation - Force device isolation for all
440						  devices. The IOMMU driver is not
441						  allowed anymore to lift isolation
442						  requirements as needed. This option
443						  does not override iommu=pt
445		amd_iommu_dump=	[HW,X86-64]
446				Enable AMD IOMMU driver option to dump the ACPI table
447				for AMD IOMMU. With this option enabled, AMD IOMMU
448				driver will print ACPI tables for AMD IOMMU during
449				IOMMU initialization.
451		amijoy.map=	[HW,JOY] Amiga joystick support
452				Map of devices attached to JOY0DAT and JOY1DAT
453				Format: <a>,<b>
454				See also Documentation/input/joystick.txt
456		analog.map=	[HW,JOY] Analog joystick and gamepad support
457				Specifies type or capabilities of an analog joystick
458				connected to one of 16 gameports
459				Format: <type1>,<type2>,..<type16>
461		apc=		[HW,SPARC]
462				Power management functions (SPARCstation-4/5 + deriv.)
463				Format: noidle
464				Disable APC CPU standby support. SPARCstation-Fox does
465				not play well with APC CPU idle - disable it if you have
466				APC and your system crashes randomly.
468		apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
469				Change the output verbosity whilst booting
470				Format: { quiet (default) | verbose | debug }
471				Change the amount of debugging information output
472				when initialising the APIC and IO-APIC components.
474		autoconf=	[IPV6]
475				See Documentation/networking/ipv6.txt.
477		show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
478				Limit apic dumping. The parameter defines the maximal
479				number of local apics being dumped. Also it is possible
480				to set it to "all" by meaning -- no limit here.
481				Format: { 1 (default) | 2 | ... | all }.
482				The parameter valid if only apic=debug or
483				apic=verbose is specified.
484				Example: apic=debug show_lapic=all
486		apm=		[APM] Advanced Power Management
487				See header of arch/x86/kernel/apm_32.c.
489		arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
490				Format: <io>,<irq>,<nodeID>
492		ataflop=	[HW,M68k]
494		atarimouse=	[HW,MOUSE] Atari Mouse
496		atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
497				EzKey and similar keyboards
499		atkbd.reset=	[HW] Reset keyboard during initialization
501		atkbd.set=	[HW] Select keyboard code set
502				Format: <int> (2 = AT (default), 3 = PS/2)
504		atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
505				keyboards
507		atkbd.softraw=	[HW] Choose between synthetic and real raw mode
508				Format: <bool> (0 = real, 1 = synthetic (default))
510		atkbd.softrepeat= [HW]
511				Use software keyboard repeat
513		audit=		[KNL] Enable the audit sub-system
514				Format: { "0" | "1" } (0 = disabled, 1 = enabled)
515				0 - kernel audit is disabled and can not be enabled
516				    until the next reboot
517				unset - kernel audit is initialized but disabled and
518				    will be fully enabled by the userspace auditd.
519				1 - kernel audit is initialized and partially enabled,
520				    storing at most audit_backlog_limit messages in
521				    RAM until it is fully enabled by the userspace
522				    auditd.
523				Default: unset
525		audit_backlog_limit= [KNL] Set the audit queue size limit.
526				Format: <int> (must be >=0)
527				Default: 64
529		baycom_epp=	[HW,AX25]
530				Format: <io>,<mode>
532		baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
533				Format: <io>,<mode>
534				See header of drivers/net/hamradio/baycom_par.c.
536		baycom_ser_fdx=	[HW,AX25]
537				BayCom Serial Port AX.25 Modem (Full Duplex Mode)
538				Format: <io>,<irq>,<mode>[,<baud>]
539				See header of drivers/net/hamradio/baycom_ser_fdx.c.
541		baycom_ser_hdx=	[HW,AX25]
542				BayCom Serial Port AX.25 Modem (Half Duplex Mode)
543				Format: <io>,<irq>,<mode>
544				See header of drivers/net/hamradio/baycom_ser_hdx.c.
546		blkdevparts=	Manual partition parsing of block device(s) for
547				embedded devices based on command line input.
548				See Documentation/block/cmdline-partition.txt
550		boot_delay=	Milliseconds to delay each printk during boot.
551				Values larger than 10 seconds (10000) are changed to
552				no delay (0).
553				Format: integer
555		bootmem_debug	[KNL] Enable bootmem allocator debug messages.
557		bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
558		bttv.radio=	Most important insmod options are available as
559				kernel args too.
560		bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
561		bttv.tuner=
563		bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
564				firmware feature for flushing multiple hpte entries
565				at a time.
567		c101=		[NET] Moxa C101 synchronous serial card
569		cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
570				Sometimes CPU hardware bugs make them report the cache
571				size incorrectly. The kernel will attempt work arounds
572				to fix known problems, but for some CPUs it is not
573				possible to determine what the correct size should be.
574				This option provides an override for these situations.
576		ca_keys=	[KEYS] This parameter identifies a specific key(s) on
577				the system trusted keyring to be used for certificate
578				trust validation.
579				format: { id:<keyid> | builtin }
581		cca=		[MIPS] Override the kernel pages' cache coherency
582				algorithm.  Accepted values range from 0 to 7
583				inclusive. See arch/mips/include/asm/pgtable-bits.h
584				for platform specific values (SB1, Loongson3 and
585				others).
587		ccw_timeout_log [S390]
588				See Documentation/s390/CommonIO for details.
590		cgroup_disable= [KNL] Disable a particular controller
591				Format: {name of the controller(s) to disable}
592				The effects of cgroup_disable=foo are:
593				- foo isn't auto-mounted if you mount all cgroups in
594				  a single hierarchy
595				- foo isn't visible as an individually mountable
596				  subsystem
597				{Currently only "memory" controller deal with this and
598				cut the overhead, others just disable the usage. So
599				only cgroup_disable=memory is actually worthy}
601		checkreqprot	[SELINUX] Set initial checkreqprot flag value.
602				Format: { "0" | "1" }
603				See security/selinux/Kconfig help text.
604				0 -- check protection applied by kernel (includes
605					any implied execute protection).
606				1 -- check protection requested by application.
607				Default value is set via a kernel config option.
608				Value can be changed at runtime via
609					/selinux/checkreqprot.
611		cio_ignore=	[S390]
612				See Documentation/s390/CommonIO for details.
613		clk_ignore_unused
614				[CLK]
615				Prevents the clock framework from automatically gating
616				clocks that have not been explicitly enabled by a Linux
617				device driver but are enabled in hardware at reset or
618				by the bootloader/firmware. Note that this does not
619				force such clocks to be always-on nor does it reserve
620				those clocks in any way. This parameter is useful for
621				debug and development, but should not be needed on a
622				platform with proper driver support.  For more
623				information, see Documentation/clk.txt.
625		clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
626				[Deprecated]
627				Forces specified clocksource (if available) to be used
628				when calculating gettimeofday(). If specified
629				clocksource is not available, it defaults to PIT.
630				Format: { pit | tsc | cyclone | pmtmr }
632		clocksource=	Override the default clocksource
633				Format: <string>
634				Override the default clocksource and use the clocksource
635				with the name specified.
636				Some clocksource names to choose from, depending on
637				the platform:
638				[all] jiffies (this is the base, fallback clocksource)
639				[ACPI] acpi_pm
640				[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
641					pxa_timer,timer3,32k_counter,timer0_1
642				[AVR32] avr32
643				[X86-32] pit,hpet,tsc;
644					scx200_hrt on Geode; cyclone on IBM x440
645				[MIPS] MIPS
646				[PARISC] cr16
647				[S390] tod
648				[SH] SuperH
649				[SPARC64] tick
650				[X86-64] hpet,tsc
652		clearcpuid=BITNUM [X86]
653				Disable CPUID feature X for the kernel. See
654				arch/x86/include/asm/cpufeature.h for the valid bit
655				numbers. Note the Linux specific bits are not necessarily
656				stable over kernel options, but the vendor specific
657				ones should be.
658				Also note that user programs calling CPUID directly
659				or using the feature without checking anything
660				will still see it. This just prevents it from
661				being used by the kernel or shown in /proc/cpuinfo.
662				Also note the kernel might malfunction if you disable
663				some critical bits.
665		cma=nn[MG]@[start[MG][-end[MG]]]
666				[ARM,X86,KNL]
667				Sets the size of kernel global memory area for
668				contiguous memory allocations and optionally the
669				placement constraint by the physical address range of
670				memory allocations. A value of 0 disables CMA
671				altogether. For more information, see
672				include/linux/dma-contiguous.h
674		cmo_free_hint=	[PPC] Format: { yes | no }
675				Specify whether pages are marked as being inactive
676				when they are freed.  This is used in CMO environments
677				to determine OS memory pressure for page stealing by
678				a hypervisor.
679				Default: yes
681		coherent_pool=nn[KMG]	[ARM,KNL]
682				Sets the size of memory pool for coherent, atomic dma
683				allocations, by default set to 256K.
685		code_bytes	[X86] How many bytes of object code to print
686				in an oops report.
687				Range: 0 - 8192
688				Default: 64
690		com20020=	[HW,NET] ARCnet - COM20020 chipset
691				Format:
692				<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
694		com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
695				Format: <io>[,<irq>]
697		com90xx=	[HW,NET]
698				ARCnet - COM90xx chipset (memory-mapped buffers)
699				Format: <io>[,<irq>[,<memstart>]]
701		condev=		[HW,S390] console device
702		conmode=
704		console=	[KNL] Output console device and options.
706			tty<n>	Use the virtual console device <n>.
708			ttyS<n>[,options]
709			ttyUSB0[,options]
710				Use the specified serial port.  The options are of
711				the form "bbbbpnf", where "bbbb" is the baud rate,
712				"p" is parity ("n", "o", or "e"), "n" is number of
713				bits, and "f" is flow control ("r" for RTS or
714				omit it).  Default is "9600n8".
716				See Documentation/serial-console.txt for more
717				information.  See
718				Documentation/networking/netconsole.txt for an
719				alternative.
721			uart[8250],io,<addr>[,options]
722			uart[8250],mmio,<addr>[,options]
723			uart[8250],mmio32,<addr>[,options]
724			uart[8250],0x<addr>[,options]
725				Start an early, polled-mode console on the 8250/16550
726				UART at the specified I/O port or MMIO address,
727				switching to the matching ttyS device later.
728				MMIO inter-register address stride is either 8-bit
729				(mmio) or 32-bit (mmio32).
730				If none of [io|mmio|mmio32], <addr> is assumed to be
731				equivalent to 'mmio'. 'options' are specified in the
732				same format described for ttyS above; if unspecified,
733				the h/w is not re-initialized.
735			hvc<n>	Use the hypervisor console device <n>. This is for
736				both Xen and PowerPC hypervisors.
738	                If the device connected to the port is not a TTY but a braille
739	                device, prepend "brl," before the device type, for instance
740				console=brl,ttyS0
741			For now, only VisioBraille is supported.
743		consoleblank=	[KNL] The console blank (screen saver) timeout in
744				seconds. Defaults to 10*60 = 10mins. A value of 0
745				disables the blank timer.
747		coredump_filter=
748				[KNL] Change the default value for
749				/proc/<pid>/coredump_filter.
750				See also Documentation/filesystems/proc.txt.
752		cpuidle.off=1	[CPU_IDLE]
753				disable the cpuidle sub-system
755		cpu_init_udelay=N
756				[X86] Delay for N microsec between assert and de-assert
757				of APIC INIT to start processors.  This delay occurs
758				on every CPU online, such as boot, and resume from suspend.
759				Default: 10000
761		cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
762				Format:
763				<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
765		crashkernel=size[KMG][@offset[KMG]]
766				[KNL] Using kexec, Linux can switch to a 'crash kernel'
767				upon panic. This parameter reserves the physical
768				memory region [offset, offset + size] for that kernel
769				image. If '@offset' is omitted, then a suitable offset
770				is selected automatically. Check
771				Documentation/kdump/kdump.txt for further details.
773		crashkernel=range1:size1[,range2:size2,...][@offset]
774				[KNL] Same as above, but depends on the memory
775				in the running system. The syntax of range is
776				start-[end] where start and end are both
777				a memory unit (amount[KMG]). See also
778				Documentation/kdump/kdump.txt for an example.
780		crashkernel=size[KMG],high
781				[KNL, x86_64] range could be above 4G. Allow kernel
782				to allocate physical memory region from top, so could
783				be above 4G if system have more than 4G ram installed.
784				Otherwise memory region will be allocated below 4G, if
785				available.
786				It will be ignored if crashkernel=X is specified.
787		crashkernel=size[KMG],low
788				[KNL, x86_64] range under 4G. When crashkernel=X,high
789				is passed, kernel could allocate physical memory region
790				above 4G, that cause second kernel crash on system
791				that require some amount of low memory, e.g. swiotlb
792				requires at least 64M+32K low memory.  Kernel would
793				try to allocate 72M below 4G automatically.
794				This one let user to specify own low range under 4G
795				for second kernel instead.
796				0: to disable low allocation.
797				It will be ignored when crashkernel=X,high is not used
798				or memory reserved is below 4G.
800		cs89x0_dma=	[HW,NET]
801				Format: <dma>
803		cs89x0_media=	[HW,NET]
804				Format: { rj45 | aui | bnc }
806		dasd=		[HW,NET]
807				See header of drivers/s390/block/dasd_devmap.c.
809		db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
810				(one device per port)
811				Format: <port#>,<type>
812				See also Documentation/input/joystick-parport.txt
814		ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
815				time. See Documentation/dynamic-debug-howto.txt for
816				details.  Deprecated, see dyndbg.
818		debug		[KNL] Enable kernel debugging (events log level).
820		debug_locks_verbose=
821				[KNL] verbose self-tests
822				Format=<0|1>
823				Print debugging info while doing the locking API
824				self-tests.
825				We default to 0 (no extra messages), setting it to
826				1 will print _a lot_ more information - normally
827				only useful to kernel developers.
829		debug_objects	[KNL] Enable object debugging
831		no_debug_objects
832				[KNL] Disable object debugging
834		debug_guardpage_minorder=
835				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
836				parameter allows control of the order of pages that will
837				be intentionally kept free (and hence protected) by the
838				buddy allocator. Bigger value increase the probability
839				of catching random memory corruption, but reduce the
840				amount of memory for normal system use. The maximum
841				possible value is MAX_ORDER/2.  Setting this parameter
842				to 1 or 2 should be enough to identify most random
843				memory corruption problems caused by bugs in kernel or
844				driver code when a CPU writes to (or reads from) a
845				random memory location. Note that there exists a class
846				of memory corruptions problems caused by buggy H/W or
847				F/W or by drivers badly programing DMA (basically when
848				memory is written at bus level and the CPU MMU is
849				bypassed) which are not detectable by
850				CONFIG_DEBUG_PAGEALLOC, hence this option will not help
851				tracking down these problems.
853		debug_pagealloc=
854				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
855				parameter enables the feature at boot time. In
856				default, it is disabled. We can avoid allocating huge
857				chunk of memory for debug pagealloc if we don't enable
858				it at boot time and the system will work mostly same
859				with the kernel built without CONFIG_DEBUG_PAGEALLOC.
860				on: enable the feature
862		debugpat	[X86] Enable PAT debugging
864		decnet.addr=	[HW,NET]
865				Format: <area>[,<node>]
866				See also Documentation/networking/decnet.txt.
868		default_hugepagesz=
869				[same as hugepagesz=] The size of the default
870				HugeTLB page size. This is the size represented by
871				the legacy /proc/ hugepages APIs, used for SHM, and
872				default size when mounting hugetlbfs filesystems.
873				Defaults to the default architecture's huge page size
874				if not specified.
876		dhash_entries=	[KNL]
877				Set number of hash buckets for dentry cache.
879		disable=	[IPV6]
880				See Documentation/networking/ipv6.txt.
882		disable_cpu_apicid= [X86,APIC,SMP]
883				Format: <int>
884				The number of initial APIC ID for the
885				corresponding CPU to be disabled at boot,
886				mostly used for the kdump 2nd kernel to
887				disable BSP to wake up multiple CPUs without
888				causing system reset or hang due to sending
889				INIT from AP to BSP.
891		disable_ddw     [PPC/PSERIES]
892				Disable Dynamic DMA Window support. Use this if
893				to workaround buggy firmware.
895		disable_ipv6=	[IPV6]
896				See Documentation/networking/ipv6.txt.
898		disable_mtrr_cleanup [X86]
899				The kernel tries to adjust MTRR layout from continuous
900				to discrete, to make X server driver able to add WB
901				entry later. This parameter disables that.
903		disable_mtrr_trim [X86, Intel and AMD only]
904				By default the kernel will trim any uncacheable
905				memory out of your available memory pool based on
906				MTRR settings.  This parameter disables that behavior,
907				possibly causing your machine to run very slowly.
909		disable_timer_pin_1 [X86]
910				Disable PIN 1 of APIC timer
911				Can be useful to work around chipset bugs.
913		dis_ucode_ldr	[X86] Disable the microcode loader.
915		dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
916				this option disables the debugging code at boot.
918		dma_debug_entries=<number>
919				This option allows to tune the number of preallocated
920				entries for DMA-API debugging code. One entry is
921				required per DMA-API allocation. Use this if the
922				DMA-API debugging code disables itself because the
923				architectural default is too low.
925		dma_debug_driver=<driver_name>
926				With this option the DMA-API debugging driver
927				filter feature can be enabled at boot time. Just
928				pass the driver to filter for as the parameter.
929				The filter can be disabled or changed to another
930				driver later using sysfs.
932		drm_kms_helper.edid_firmware=[<connector>:]<file>
933				Broken monitors, graphic adapters and KVMs may
934				send no or incorrect EDID data sets. This parameter
935				allows to specify an EDID data set in the
936				/lib/firmware directory that is used instead.
937				Generic built-in EDID data sets are used, if one of
938				edid/1024x768.bin, edid/1280x1024.bin,
939				edid/1680x1050.bin, or edid/1920x1080.bin is given
940				and no file with the same name exists. Details and
941				instructions how to build your own EDID data are
942				available in Documentation/EDID/HOWTO.txt. An EDID
943				data set will only be used for a particular connector,
944				if its name and a colon are prepended to the EDID
945				name.
947		dscc4.setup=	[NET]
949		dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
950		module.dyndbg[="val"]
951				Enable debug messages at boot time.  See
952				Documentation/dynamic-debug-howto.txt for details.
954		nompx		[X86] Disables Intel Memory Protection Extensions.
955				See Documentation/x86/intel_mpx.txt for more
956				information about the feature.
958		eagerfpu=	[X86]
959				on	enable eager fpu restore
960				off	disable eager fpu restore
961				auto	selects the default scheme, which automatically
962					enables eagerfpu restore for xsaveopt.
964		module.async_probe [KNL]
965				Enable asynchronous probe on this module.
967		early_ioremap_debug [KNL]
968				Enable debug messages in early_ioremap support. This
969				is useful for tracking down temporary early mappings
970				which are not unmapped.
972		earlycon=	[KNL] Output early console device and options.
974			cdns,<addr>
975				Start an early, polled-mode console on a cadence serial
976				port at the specified address. The cadence serial port
977				must already be setup and configured. Options are not
978				yet supported.
980			uart[8250],io,<addr>[,options]
981			uart[8250],mmio,<addr>[,options]
982			uart[8250],mmio32,<addr>[,options]
983			uart[8250],mmio32be,<addr>[,options]
984			uart[8250],0x<addr>[,options]
985				Start an early, polled-mode console on the 8250/16550
986				UART at the specified I/O port or MMIO address.
987				MMIO inter-register address stride is either 8-bit
988				(mmio) or 32-bit (mmio32 or mmio32be).
989				If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
990				to be equivalent to 'mmio'. 'options' are specified
991				in the same format described for "console=ttyS<n>"; if
992				unspecified, the h/w is not initialized.
994			pl011,<addr>
995				Start an early, polled-mode console on a pl011 serial
996				port at the specified address. The pl011 serial port
997				must already be setup and configured. Options are not
998				yet supported.
1000			msm_serial,<addr>
1001				Start an early, polled-mode console on an msm serial
1002				port at the specified address. The serial port
1003				must already be setup and configured. Options are not
1004				yet supported.
1006			msm_serial_dm,<addr>
1007				Start an early, polled-mode console on an msm serial
1008				dm port at the specified address. The serial port
1009				must already be setup and configured. Options are not
1010				yet supported.
1012			smh	Use ARM semihosting calls for early console.
1014			s3c2410,<addr>
1015			s3c2412,<addr>
1016			s3c2440,<addr>
1017			s3c6400,<addr>
1018			s5pv210,<addr>
1019			exynos4210,<addr>
1020				Use early console provided by serial driver available
1021				on Samsung SoCs, requires selecting proper type and
1022				a correct base address of the selected UART port. The
1023				serial port must already be setup and configured.
1024				Options are not yet supported.
1026		earlyprintk=	[X86,SH,BLACKFIN,ARM,M68k]
1027				earlyprintk=vga
1028				earlyprintk=efi
1029				earlyprintk=xen
1030				earlyprintk=serial[,ttySn[,baudrate]]
1031				earlyprintk=serial[,0x...[,baudrate]]
1032				earlyprintk=ttySn[,baudrate]
1033				earlyprintk=dbgp[debugController#]
1034				earlyprintk=pciserial,bus:device.function[,baudrate]
1036				earlyprintk is useful when the kernel crashes before
1037				the normal console is initialized. It is not enabled by
1038				default because it has some cosmetic problems.
1040				Append ",keep" to not disable it when the real console
1041				takes over.
1043				Only one of vga, efi, serial, or usb debug port can
1044				be used at a time.
1046				Currently only ttyS0 and ttyS1 may be specified by
1047				name.  Other I/O ports may be explicitly specified
1048				on some architectures (x86 and arm at least) by
1049				replacing ttySn with an I/O port address, like this:
1050					earlyprintk=serial,0x1008,115200
1051				You can find the port for a given device in
1052				/proc/tty/driver/serial:
1053					2: uart:ST16650V2 port:00001008 irq:18 ...
1055				Interaction with the standard serial driver is not
1056				very good.
1058				The VGA and EFI output is eventually overwritten by
1059				the real console.
1061				The xen output can only be used by Xen PV guests.
1063		edac_report=	[HW,EDAC] Control how to report EDAC event
1064				Format: {"on" | "off" | "force"}
1065				on: enable EDAC to report H/W event. May be overridden
1066				by other higher priority error reporting module.
1067				off: disable H/W event reporting through EDAC.
1068				force: enforce the use of EDAC to report H/W event.
1069				default: on.
1071		ekgdboc=	[X86,KGDB] Allow early kernel console debugging
1072				ekgdboc=kbd
1074				This is designed to be used in conjunction with
1075				the boot argument: earlyprintk=vga
1077		edd=		[EDD]
1078				Format: {"off" | "on" | "skip[mbr]"}
1080		efi=		[EFI]
1081				Format: { "old_map", "nochunk", "noruntime", "debug" }
1082				old_map [X86-64]: switch to the old ioremap-based EFI
1083				runtime services mapping. 32-bit still uses this one by
1084				default.
1085				nochunk: disable reading files in "chunks" in the EFI
1086				boot stub, as chunking can cause problems with some
1087				firmware implementations.
1088				noruntime : disable EFI runtime services support
1089				debug: enable misc debug output
1091		efi_no_storage_paranoia [EFI; X86]
1092				Using this parameter you can use more than 50% of
1093				your efi variable storage. Use this parameter only if
1094				you are really sure that your UEFI does sane gc and
1095				fulfills the spec otherwise your board may brick.
1097		eisa_irq_edge=	[PARISC,HW]
1098				See header of drivers/parisc/eisa.c.
1100		elanfreq=	[X86-32]
1101				See comment before function elanfreq_setup() in
1102				arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1104		elevator=	[IOSCHED]
1105				Format: {"cfq" | "deadline" | "noop"}
1106				See Documentation/block/cfq-iosched.txt and
1107				Documentation/block/deadline-iosched.txt for details.
1109		elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1110				Specifies physical address of start of kernel core
1111				image elf header and optionally the size. Generally
1112				kexec loader will pass this option to capture kernel.
1113				See Documentation/kdump/kdump.txt for details.
1115		enable_mtrr_cleanup [X86]
1116				The kernel tries to adjust MTRR layout from continuous
1117				to discrete, to make X server driver able to add WB
1118				entry later. This parameter enables that.
1120		enable_timer_pin_1 [X86]
1121				Enable PIN 1 of APIC timer
1122				Can be useful to work around chipset bugs
1123				(in particular on some ATI chipsets).
1124				The kernel tries to set a reasonable default.
1126		enforcing	[SELINUX] Set initial enforcing status.
1127				Format: {"0" | "1"}
1128				See security/selinux/Kconfig help text.
1129				0 -- permissive (log only, no denials).
1130				1 -- enforcing (deny and log).
1131				Default value is 0.
1132				Value can be changed at runtime via /selinux/enforce.
1134		erst_disable	[ACPI]
1135				Disable Error Record Serialization Table (ERST)
1136				support.
1138		ether=		[HW,NET] Ethernet cards parameters
1139				This option is obsoleted by the "netdev=" option, which
1140				has equivalent usage. See its documentation for details.
1142		evm=		[EVM]
1143				Format: { "fix" }
1144				Permit 'security.evm' to be updated regardless of
1145				current integrity status.
1147		failslab=
1148		fail_page_alloc=
1149		fail_make_request=[KNL]
1150				General fault injection mechanism.
1151				Format: <interval>,<probability>,<space>,<times>
1152				See also Documentation/fault-injection/.
1154		floppy=		[HW]
1155				See Documentation/blockdev/floppy.txt.
1157		force_pal_cache_flush
1158				[IA-64] Avoid check_sal_cache_flush which may hang on
1159				buggy SAL_CACHE_FLUSH implementations. Using this
1160				parameter will force ia64_sal_cache_flush to call
1161				ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1163		forcepae [X86-32]
1164				Forcefully enable Physical Address Extension (PAE).
1165				Many Pentium M systems disable PAE but may have a
1166				functionally usable PAE implementation.
1167				Warning: use of this parameter will taint the kernel
1168				and may cause unknown problems.
1170		ftrace=[tracer]
1171				[FTRACE] will set and start the specified tracer
1172				as early as possible in order to facilitate early
1173				boot debugging.
1175		ftrace_dump_on_oops[=orig_cpu]
1176				[FTRACE] will dump the trace buffers on oops.
1177				If no parameter is passed, ftrace will dump
1178				buffers of all CPUs, but if you pass orig_cpu, it will
1179				dump only the buffer of the CPU that triggered the
1180				oops.
1182		ftrace_filter=[function-list]
1183				[FTRACE] Limit the functions traced by the function
1184				tracer at boot up. function-list is a comma separated
1185				list of functions. This list can be changed at run
1186				time by the set_ftrace_filter file in the debugfs
1187				tracing directory.
1189		ftrace_notrace=[function-list]
1190				[FTRACE] Do not trace the functions specified in
1191				function-list. This list can be changed at run time
1192				by the set_ftrace_notrace file in the debugfs
1193				tracing directory.
1195		ftrace_graph_filter=[function-list]
1196				[FTRACE] Limit the top level callers functions traced
1197				by the function graph tracer at boot up.
1198				function-list is a comma separated list of functions
1199				that can be changed at run time by the
1200				set_graph_function file in the debugfs tracing directory.
1202		ftrace_graph_notrace=[function-list]
1203				[FTRACE] Do not trace from the functions specified in
1204				function-list.  This list is a comma separated list of
1205				functions that can be changed at run time by the
1206				set_graph_notrace file in the debugfs tracing directory.
1208		gamecon.map[2|3]=
1209				[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1210				support via parallel port (up to 5 devices per port)
1211				Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1212				See also Documentation/input/joystick-parport.txt
1214		gamma=		[HW,DRM]
1216		gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
1217				Format: off | on
1218				default: on
1220		gcov_persist=	[GCOV] When non-zero (default), profiling data for
1221				kernel modules is saved and remains accessible via
1222				debugfs, even when the module is unloaded/reloaded.
1223				When zero, profiling data is discarded and associated
1224				debugfs files are removed at module unload time.
1226		gpt		[EFI] Forces disk with valid GPT signature but
1227				invalid Protective MBR to be treated as GPT. If the
1228				primary GPT is corrupted, it enables the backup/alternate
1229				GPT to be used instead.
1231		grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1232				the "Enable 0" bit of the configuration register.
1233				Format: 0 | 1
1234				Default: 0
1235		grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1236				the "Enable 0" bit of the configuration register.
1237				Format: 0 | 1
1238				Default: 0
1239		grcan.select=	[HW] Select which physical interface to use.
1240				Format: 0 | 1
1241				Default: 0
1242		grcan.txsize=	[HW] Sets the size of the tx buffer.
1243				Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1244				Default: 1024
1245		grcan.rxsize=	[HW] Sets the size of the rx buffer.
1246				Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1247				Default: 1024
1249		hashdist=	[KNL,NUMA] Large hashes allocated during boot
1250				are distributed across NUMA nodes.  Defaults on
1251				for 64-bit NUMA, off otherwise.
1252				Format: 0 | 1 (for off | on)
1254		hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1256		hd=		[EIDE] (E)IDE hard drive subsystem geometry
1257				Format: <cyl>,<head>,<sect>
1259		hest_disable	[ACPI]
1260				Disable Hardware Error Source Table (HEST) support;
1261				corresponding firmware-first mode error processing
1262				logic will be disabled.
1264		highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1265				size of <nn>. This works even on boxes that have no
1266				highmem otherwise. This also works to reduce highmem
1267				size on bigger boxes.
1269		highres=	[KNL] Enable/disable high resolution timer mode.
1270				Valid parameters: "on", "off"
1271				Default: "on"
1273		hisax=		[HW,ISDN]
1274				See Documentation/isdn/README.HiSax.
1276		hlt		[BUGS=ARM,SH]
1278		hpet=		[X86-32,HPET] option to control HPET usage
1279				Format: { enable (default) | disable | force |
1280					verbose }
1281				disable: disable HPET and use PIT instead
1282				force: allow force enabled of undocumented chips (ICH4,
1283					VIA, nVidia)
1284				verbose: show contents of HPET registers during setup
1286		hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1287				registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1289		hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1290		hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1291				On x86-64 and powerpc, this option can be specified
1292				multiple times interleaved with hugepages= to reserve
1293				huge pages of different sizes. Valid pages sizes on
1294				x86-64 are 2M (when the CPU supports "pse") and 1G
1295				(when the CPU supports the "pdpe1gb" cpuinfo flag).
1297		hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
1298				       terminal devices. Valid values: 0..8
1299		hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
1300				       If specified, z/VM IUCV HVC accepts connections
1301				       from listed z/VM user IDs only.
1303		hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
1304				        hardware thread id mappings.
1305					Format: <cpu>:<hwthread>
1307		keep_bootcon	[KNL]
1308				Do not unregister boot console at start. This is only
1309				useful for debugging when something happens in the window
1310				between unregistering the boot console and initializing
1311				the real console.
1313		i2c_bus=	[HW] Override the default board specific I2C bus speed
1314				     or register an additional I2C bus that is not
1315				     registered from board initialization code.
1316				     Format:
1317				     <bus_id>,<clkrate>
1319		i8042.debug	[HW] Toggle i8042 debug mode
1320		i8042.unmask_kbd_data
1321				[HW] Enable printing of interrupt data from the KBD port
1322				     (disabled by default, and as a pre-condition
1323				     requires that i8042.debug=1 be enabled)
1324		i8042.direct	[HW] Put keyboard port into non-translated mode
1325		i8042.dumbkbd	[HW] Pretend that controller can only read data from
1326				     keyboard and cannot control its state
1327				     (Don't attempt to blink the leds)
1328		i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1329		i8042.nokbd	[HW] Don't check/create keyboard port
1330		i8042.noloop	[HW] Disable the AUX Loopback command while probing
1331				     for the AUX port
1332		i8042.nomux	[HW] Don't check presence of an active multiplexing
1333				     controller
1334		i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1335				     controllers
1336		i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1337		i8042.reset	[HW] Reset the controller during init and cleanup
1338		i8042.unlock	[HW] Unlock (ignore) the keylock
1339		i8042.kbdreset  [HW] Reset device connected to KBD port
1341		i810=		[HW,DRM]
1343		i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1344				indicates that the driver is running on unsupported
1345				hardware.
1346		i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1347				does not match list of supported models.
1348		i8k.power_status
1349				[HW] Report power status in /proc/i8k
1350				(disabled by default)
1351		i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1352				capability is set.
1354		i915.invert_brightness=
1355				[DRM] Invert the sense of the variable that is used to
1356				set the brightness of the panel backlight. Normally a
1357				brightness value of 0 indicates backlight switched off,
1358				and the maximum of the brightness value sets the backlight
1359				to maximum brightness. If this parameter is set to 0
1360				(default) and the machine requires it, or this parameter
1361				is set to 1, a brightness value of 0 sets the backlight
1362				to maximum brightness, and the maximum of the brightness
1363				value switches the backlight off.
1364				-1 -- never invert brightness
1365				 0 -- machine default
1366				 1 -- force brightness inversion
1368		icn=		[HW,ISDN]
1369				Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1371		ide-core.nodma=	[HW] (E)IDE subsystem
1372				Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1373				.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1374				.cdrom .chs .ignore_cable are additional options
1375				See Documentation/ide/ide.txt.
1377		ide-generic.probe-mask= [HW] (E)IDE subsystem
1378				Format: <int>
1379				Probe mask for legacy ISA IDE ports.  Depending on
1380				platform up to 6 ports are supported, enabled by
1381				setting corresponding bits in the mask to 1.  The
1382				default value is 0x0, which has a special meaning.
1383				On systems that have PCI, it triggers scanning the
1384				PCI bus for the first and the second port, which
1385				are then probed.  On systems without PCI the value
1386				of 0x0 enables probing the two first ports as if it
1387				was 0x3.
1389		ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1390				Claim all unknown PCI IDE storage controllers.
1392		idle=		[X86]
1393				Format: idle=poll, idle=halt, idle=nomwait
1394				Poll forces a polling idle loop that can slightly
1395				improve the performance of waking up a idle CPU, but
1396				will use a lot of power and make the system run hot.
1397				Not recommended.
1398				idle=halt: Halt is forced to be used for CPU idle.
1399				In such case C2/C3 won't be used again.
1400				idle=nomwait: Disable mwait for CPU C-states
1402		ignore_loglevel	[KNL]
1403				Ignore loglevel setting - this will print /all/
1404				kernel messages to the console. Useful for debugging.
1405				We also add it as printk module parameter, so users
1406				could change it dynamically, usually by
1407				/sys/module/printk/parameters/ignore_loglevel.
1409		ihash_entries=	[KNL]
1410				Set number of hash buckets for inode cache.
1412		ima_appraise=	[IMA] appraise integrity measurements
1413				Format: { "off" | "enforce" | "fix" | "log" }
1414				default: "enforce"
1416		ima_appraise_tcb [IMA]
1417				The builtin appraise policy appraises all files
1418				owned by uid=0.
1420		ima_hash=	[IMA]
1421				Format: { md5 | sha1 | rmd160 | sha256 | sha384
1422					   | sha512 | ... }
1423				default: "sha1"
1425				The list of supported hash algorithms is defined
1426				in crypto/hash_info.h.
1428		ima_policy=	[IMA]
1429				The builtin measurement policy to load during IMA
1430				setup.  Specyfing "tcb" as the value, measures all
1431				programs exec'd, files mmap'd for exec, and all files
1432				opened with the read mode bit set by either the
1433				effective uid (euid=0) or uid=0.
1434				Format: "tcb"
1436		ima_tcb		[IMA] Deprecated.  Use ima_policy= instead.
1437				Load a policy which meets the needs of the Trusted
1438				Computing Base.  This means IMA will measure all
1439				programs exec'd, files mmap'd for exec, and all files
1440				opened for read by uid=0.
1442		ima_template=   [IMA]
1443				Select one of defined IMA measurements template formats.
1444				Formats: { "ima" | "ima-ng" | "ima-sig" }
1445				Default: "ima-ng"
1447		ima_template_fmt=
1448		                [IMA] Define a custom template format.
1449				Format: { "field1|...|fieldN" }
1451		ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
1452				Format: <min_file_size>
1453				Set the minimal file size for using asynchronous hash.
1454				If left unspecified, ahash usage is disabled.
1456				ahash performance varies for different data sizes on
1457				different crypto accelerators. This option can be used
1458				to achieve the best performance for a particular HW.
1460		ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
1461				Format: <bufsize>
1462				Set hashing buffer size. Default: 4k.
1464				ahash performance varies for different chunk sizes on
1465				different crypto accelerators. This option can be used
1466				to achieve best performance for particular HW.
1468		init=		[KNL]
1469				Format: <full_path>
1470				Run specified binary instead of /sbin/init as init
1471				process.
1473		initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1474				for working out where the kernel is dying during
1475				startup.
1477		initcall_blacklist=  [KNL] Do not execute a comma-separated list of
1478				initcall functions.  Useful for debugging built-in
1479				modules and initcalls.
1481		initrd=		[BOOT] Specify the location of the initial ramdisk
1483		inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1484				Format: <irq>
1486		int_pln_enable  [x86] Enable power limit notification interrupt
1488		integrity_audit=[IMA]
1489				Format: { "0" | "1" }
1490				0 -- basic integrity auditing messages. (Default)
1491				1 -- additional integrity auditing messages.
1493		intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1494			on
1495				Enable intel iommu driver.
1496			off
1497				Disable intel iommu driver.
1498			igfx_off [Default Off]
1499				By default, gfx is mapped as normal device. If a gfx
1500				device has a dedicated DMAR unit, the DMAR unit is
1501				bypassed by not enabling DMAR with this option. In
1502				this case, gfx device will use physical address for
1503				DMA.
1504			forcedac [x86_64]
1505				With this option iommu will not optimize to look
1506				for io virtual address below 32-bit forcing dual
1507				address cycle on pci bus for cards supporting greater
1508				than 32-bit addressing. The default is to look
1509				for translation below 32-bit and if not available
1510				then look in the higher range.
1511			strict [Default Off]
1512				With this option on every unmap_single operation will
1513				result in a hardware IOTLB flush operation as opposed
1514				to batching them for performance.
1515			sp_off [Default Off]
1516				By default, super page will be supported if Intel IOMMU
1517				has the capability. With this option, super page will
1518				not be supported.
1519			ecs_off [Default Off]
1520				By default, extended context tables will be supported if
1521				the hardware advertises that it has support both for the
1522				extended tables themselves, and also PASID support. With
1523				this option set, extended tables will not be used even
1524				on hardware which claims to support them.
1526		intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1527				0	disables intel_idle and fall back on acpi_idle.
1528				1 to 6	specify maximum depth of C-state.
1530		intel_pstate=  [X86]
1531			       disable
1532			         Do not enable intel_pstate as the default
1533			         scaling driver for the supported processors
1534			       force
1535				 Enable intel_pstate on systems that prohibit it by default
1536				 in favor of acpi-cpufreq. Forcing the intel_pstate driver
1537				 instead of acpi-cpufreq may disable platform features, such
1538				 as thermal controls and power capping, that rely on ACPI
1539				 P-States information being indicated to OSPM and therefore
1540				 should be used with caution. This option does not work with
1541				 processors that aren't supported by the intel_pstate driver
1542				 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
1543			       no_hwp
1544			         Do not enable hardware P state control (HWP)
1545				 if available.
1546			hwp_only
1547				Only load intel_pstate on systems which support
1548				hardware P state control (HWP) if available.
1550		intremap=	[X86-64, Intel-IOMMU]
1551				on	enable Interrupt Remapping (default)
1552				off	disable Interrupt Remapping
1553				nosid	disable Source ID checking
1554				no_x2apic_optout
1555					BIOS x2APIC opt-out request will be ignored
1557		iomem=		Disable strict checking of access to MMIO memory
1558			strict	regions from userspace.
1559			relaxed
1561		iommu=		[x86]
1562			off
1563			force
1564			noforce
1565			biomerge
1566			panic
1567			nopanic
1568			merge
1569			nomerge
1570			forcesac
1571			soft
1572			pt		[x86, IA-64]
1573			nobypass	[PPC/POWERNV]
1574				Disable IOMMU bypass, using IOMMU for PCI devices.
1577		io7=		[HW] IO7 for Marvel based alpha systems
1578				See comment before marvel_specify_io7 in
1579				arch/alpha/kernel/core_marvel.c.
1581		io_delay=	[X86] I/O delay method
1582			0x80
1583				Standard port 0x80 based delay
1584			0xed
1585				Alternate port 0xed based delay (needed on some systems)
1586			udelay
1587				Simple two microseconds delay
1588			none
1589				No delay
1591		ip=		[IP_PNP]
1592				See Documentation/filesystems/nfs/nfsroot.txt.
1594		irqfixup	[HW]
1595				When an interrupt is not handled search all handlers
1596				for it. Intended to get systems with badly broken
1597				firmware running.
1599		irqpoll		[HW]
1600				When an interrupt is not handled search all handlers
1601				for it. Also check all handlers each timer
1602				interrupt. Intended to get systems with badly broken
1603				firmware running.
1605		isapnp=		[ISAPNP]
1606				Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1608		isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1609				Format:
1610				<cpu number>,...,<cpu number>
1611				or
1612				<cpu number>-<cpu number>
1613				(must be a positive range in ascending order)
1614				or a mixture
1615				<cpu number>,...,<cpu number>-<cpu number>
1617				This option can be used to specify one or more CPUs
1618				to isolate from the general SMP balancing and scheduling
1619				algorithms. You can move a process onto or off an
1620				"isolated" CPU via the CPU affinity syscalls or cpuset.
1621				<cpu number> begins at 0 and the maximum value is
1622				"number of CPUs in system - 1".
1624				This option is the preferred way to isolate CPUs. The
1625				alternative -- manually setting the CPU mask of all
1626				tasks in the system -- can cause problems and
1627				suboptimal load balancer performance.
1629		iucv=		[HW,NET]
1631		ivrs_ioapic	[HW,X86_64]
1632				Provide an override to the IOAPIC-ID<->DEVICE-ID
1633				mapping provided in the IVRS ACPI table. For
1634				example, to map IOAPIC-ID decimal 10 to
1635				PCI device 00:14.0 write the parameter as:
1636					ivrs_ioapic[10]=00:14.0
1638		ivrs_hpet	[HW,X86_64]
1639				Provide an override to the HPET-ID<->DEVICE-ID
1640				mapping provided in the IVRS ACPI table. For
1641				example, to map HPET-ID decimal 0 to
1642				PCI device 00:14.0 write the parameter as:
1643					ivrs_hpet[0]=00:14.0
1645		js=		[HW,JOY] Analog joystick
1646				See Documentation/input/joystick.txt.
1648		kaslr/nokaslr	[X86]
1649				Enable/disable kernel and module base offset ASLR
1650				(Address Space Layout Randomization) if built into
1651				the kernel. When CONFIG_HIBERNATION is selected,
1652				kASLR is disabled by default. When kASLR is enabled,
1653				hibernation will be disabled.
1655		keepinitrd	[HW,ARM]
1657		kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1658				specifies the amount of memory usable by the kernel
1659				for non-movable allocations.  The requested amount is
1660				spread evenly throughout all nodes in the system. The
1661				remaining memory in each node is used for Movable
1662				pages. In the event, a node is too small to have both
1663				kernelcore and Movable pages, kernelcore pages will
1664				take priority and other nodes will have a larger number
1665				of Movable pages.  The Movable zone is used for the
1666				allocation of pages that may be reclaimed or moved
1667				by the page migration subsystem.  This means that
1668				HugeTLB pages may not be allocated from this zone.
1669				Note that allocations like PTEs-from-HighMem still
1670				use the HighMem zone if it exists, and the Normal
1671				zone if it does not.
1673		kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1674				Format: <Controller#>[,poll interval]
1675				The controller # is the number of the ehci usb debug
1676				port as it is probed via PCI.  The poll interval is
1677				optional and is the number seconds in between
1678				each poll cycle to the debug port in case you need
1679				the functionality for interrupting the kernel with
1680				gdb or control-c on the dbgp connection.  When
1681				not using this parameter you use sysrq-g to break into
1682				the kernel debugger.
1684		kgdboc=		[KGDB,HW] kgdb over consoles.
1685				Requires a tty driver that supports console polling,
1686				or a supported polling keyboard driver (non-usb).
1687				 Serial only format: <serial_device>[,baud]
1688				 keyboard only format: kbd
1689				 keyboard and serial format: kbd,<serial_device>[,baud]
1690				Optional Kernel mode setting:
1691				 kms, kbd format: kms,kbd
1692				 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1694		kgdbwait	[KGDB] Stop kernel execution and enter the
1695				kernel debugger at the earliest opportunity.
1697		kmac=		[MIPS] korina ethernet MAC address.
1698				Configure the RouterBoard 532 series on-chip
1699				Ethernet adapter MAC address.
1701		kmemleak=	[KNL] Boot-time kmemleak enable/disable
1702				Valid arguments: on, off
1703				Default: on
1705				the default is off.
1707		kmemcheck=	[X86] Boot-time kmemcheck enable/disable/one-shot mode
1708				Valid arguments: 0, 1, 2
1709				kmemcheck=0 (disabled)
1710				kmemcheck=1 (enabled)
1711				kmemcheck=2 (one-shot mode)
1712				Default: 2 (one-shot mode)
1714		kstack=N	[X86] Print N words from the kernel stack
1715				in oops dumps.
1717		kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1718				Default is 0 (don't ignore, but inject #GP)
1720		kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
1721				KVM MMU at runtime.
1722				Default is 0 (off)
1724		kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1725				Default is 1 (enabled)
1727		kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
1728				for all guests.
1729				Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1731		kvm-intel.ept=	[KVM,Intel] Disable extended page tables
1732				(virtualized MMU) support on capable Intel chips.
1733				Default is 1 (enabled)
1735		kvm-intel.emulate_invalid_guest_state=
1736				[KVM,Intel] Enable emulation of invalid guest states
1737				Default is 0 (disabled)
1739		kvm-intel.flexpriority=
1740				[KVM,Intel] Disable FlexPriority feature (TPR shadow).
1741				Default is 1 (enabled)
1743		kvm-intel.nested=
1744				[KVM,Intel] Enable VMX nesting (nVMX).
1745				Default is 0 (disabled)
1747		kvm-intel.unrestricted_guest=
1748				[KVM,Intel] Disable unrestricted guest feature
1749				(virtualized real and unpaged mode) on capable
1750				Intel chips. Default is 1 (enabled)
1752		kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
1753				feature (tagged TLBs) on capable Intel chips.
1754				Default is 1 (enabled)
1756		l2cr=		[PPC]
1758		l3cr=		[PPC]
1760		lapic		[X86-32,APIC] Enable the local APIC even if BIOS
1761				disabled it.
1763		lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
1764				value for LAPIC timer one-shot implementation. Default
1765				back to the programmable timer unit in the LAPIC.
1767		lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1768				in C2 power state.
1770		libata.dma=	[LIBATA] DMA control
1771				libata.dma=0	  Disable all PATA and SATA DMA
1772				libata.dma=1	  PATA and SATA Disk DMA only
1773				libata.dma=2	  ATAPI (CDROM) DMA only
1774				libata.dma=4	  Compact Flash DMA only
1775				Combinations also work, so libata.dma=3 enables DMA
1776				for disks and CDROMs, but not CFs.
1778		libata.ignore_hpa=	[LIBATA] Ignore HPA limit
1779				libata.ignore_hpa=0	  keep BIOS limits (default)
1780				libata.ignore_hpa=1	  ignore limits, using full disk
1782		libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
1783				when set.
1784				Format: <int>
1786		libata.force=	[LIBATA] Force configurations.  The format is comma
1787				separated list of "[ID:]VAL" where ID is
1788				PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1789				matching port, link or device.  Basically, it matches
1790				the ATA ID string printed on console by libata.  If
1791				the whole ID part is omitted, the last PORT and DEVICE
1792				values are used.  If ID hasn't been specified yet, the
1793				configuration applies to all ports, links and devices.
1795				If only DEVICE is omitted, the parameter applies to
1796				the port and all links and devices behind it.  DEVICE
1797				number of 0 either selects the first device or the
1798				first fan-out link behind PMP device.  It does not
1799				select the host link.  DEVICE number of 15 selects the
1800				host link and device attached to it.
1802				The VAL specifies the configuration to force.  As long
1803				as there's no ambiguity shortcut notation is allowed.
1804				For example, both 1.5 and 1.5G would work for 1.5Gbps.
1805				The following configurations can be forced.
1807				* Cable type: 40c, 80c, short40c, unk, ign or sata.
1808				  Any ID with matching PORT is used.
1810				* SATA link speed limit: 1.5Gbps or 3.0Gbps.
1812				* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1813				  udma[/][16,25,33,44,66,100,133] notation is also
1814				  allowed.
1816				* [no]ncq: Turn on or off NCQ.
1818				* [no]ncqtrim: Turn off queued DSM TRIM.
1820				* nohrst, nosrst, norst: suppress hard, soft
1821	                          and both resets.
1823				* rstonce: only attempt one reset during
1824				  hot-unplug link recovery
1826				* dump_id: dump IDENTIFY data.
1828				* atapi_dmadir: Enable ATAPI DMADIR bridge support
1830				* disable: Disable this device.
1832				If there are multiple matching configurations changing
1833				the same attribute, the last one is used.
1835		memblock=debug	[KNL] Enable memblock debug messages.
1837		load_ramdisk=	[RAM] List of ramdisks to load from floppy
1838				See Documentation/blockdev/ramdisk.txt.
1840		lockd.nlm_grace_period=P  [NFS] Assign grace period.
1841				Format: <integer>
1843		lockd.nlm_tcpport=N	[NFS] Assign TCP port.
1844				Format: <integer>
1846		lockd.nlm_timeout=T	[NFS] Assign timeout value.
1847				Format: <integer>
1849		lockd.nlm_udpport=M	[NFS] Assign UDP port.
1850				Format: <integer>
1852		locktorture.nreaders_stress= [KNL]
1853				Set the number of locking read-acquisition kthreads.
1854				Defaults to being automatically set based on the
1855				number of online CPUs.
1857		locktorture.nwriters_stress= [KNL]
1858				Set the number of locking write-acquisition kthreads.
1860		locktorture.onoff_holdoff= [KNL]
1861				Set time (s) after boot for CPU-hotplug testing.
1863		locktorture.onoff_interval= [KNL]
1864				Set time (s) between CPU-hotplug operations, or
1865				zero to disable CPU-hotplug testing.
1867		locktorture.shuffle_interval= [KNL]
1868				Set task-shuffle interval (jiffies).  Shuffling
1869				tasks allows some CPUs to go into dyntick-idle
1870				mode during the locktorture test.
1872		locktorture.shutdown_secs= [KNL]
1873				Set time (s) after boot system shutdown.  This
1874				is useful for hands-off automated testing.
1876		locktorture.stat_interval= [KNL]
1877				Time (s) between statistics printk()s.
1879		locktorture.stutter= [KNL]
1880				Time (s) to stutter testing, for example,
1881				specifying five seconds causes the test to run for
1882				five seconds, wait for five seconds, and so on.
1883				This tests the locking primitive's ability to
1884				transition abruptly to and from idle.
1886		locktorture.torture_runnable= [BOOT]
1887				Start locktorture running at boot time.
1889		locktorture.torture_type= [KNL]
1890				Specify the locking implementation to test.
1892		locktorture.verbose= [KNL]
1893				Enable additional printk() statements.
1895		logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
1896				Format: <irq>
1898		loglevel=	All Kernel Messages with a loglevel smaller than the
1899				console loglevel will be printed to the console. It can
1900				also be changed with klogd or other programs. The
1901				loglevels are defined as follows:
1903				0 (KERN_EMERG)		system is unusable
1904				1 (KERN_ALERT)		action must be taken immediately
1905				2 (KERN_CRIT)		critical conditions
1906				3 (KERN_ERR)		error conditions
1907				4 (KERN_WARNING)	warning conditions
1908				5 (KERN_NOTICE)		normal but significant condition
1909				6 (KERN_INFO)		informational
1910				7 (KERN_DEBUG)		debug-level messages
1912		log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
1913				in bytes.  n must be a power of two and greater
1914				than the minimal size. The minimal size is defined
1915				by LOG_BUF_SHIFT kernel config parameter. There is
1916				also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
1917				that allows to increase the default size depending on
1918				the number of CPUs. See init/Kconfig for more details.
1920		logo.nologo	[FB] Disables display of the built-in Linux logo.
1921				This may be used to provide more screen space for
1922				kernel log messages and is useful when debugging
1923				kernel boot problems.
1925		lp=0		[LP]	Specify parallel ports to use, e.g,
1926		lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
1927		lp=reset		first parallel port). 'lp=0' disables the
1928		lp=auto			printer driver. 'lp=reset' (which can be
1929					specified in addition to the ports) causes
1930					attached printers to be reset. Using
1931					lp=port1,port2,... specifies the parallel ports
1932					to associate lp devices with, starting with
1933					lp0. A port specification may be 'none' to skip
1934					that lp device, or a parport name such as
1935					'parport0'. Specifying 'lp=auto' instead of a
1936					port specification list means that device IDs
1937					from each port should be examined, to see if
1938					an IEEE 1284-compliant printer is attached; if
1939					so, the driver will manage that printer.
1940					See also header of drivers/char/lp.c.
1942		lpj=n		[KNL]
1943				Sets loops_per_jiffy to given constant, thus avoiding
1944				time-consuming boot-time autodetection (up to 250 ms per
1945				CPU). 0 enables autodetection (default). To determine
1946				the correct value for your kernel, boot with normal
1947				autodetection and see what value is printed. Note that
1948				on SMP systems the preset will be applied to all CPUs,
1949				which is likely to cause problems if your CPUs need
1950				significantly divergent settings. An incorrect value
1951				will cause delays in the kernel to be wrong, leading to
1952				unpredictable I/O errors and other breakage. Although
1953				unlikely, in the extreme case this might damage your
1954				hardware.
1956		ltpc=		[NET]
1957				Format: <io>,<irq>,<dma>
1959		machvec=	[IA-64] Force the use of a particular machine-vector
1960				(machvec) in a generic kernel.
1961				Example: machvec=hpzx1_swiotlb
1963		machtype=	[Loongson] Share the same kernel image file between different
1964				 yeeloong laptop.
1965				Example: machtype=lemote-yeeloong-2f-7inch
1967		max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
1968				than or equal to this physical address is ignored.
1970		maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
1971				should make use of.  maxcpus=n : n >= 0 limits the
1972				kernel to using 'n' processors.  n=0 is a special case,
1973				it is equivalent to "nosmp", which also disables
1974				the IO APIC.
1976		max_loop=	[LOOP] The number of loop block devices that get
1977		(loop.max_loop)	unconditionally pre-created at init time. The default
1978				number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1979				of statically allocating a predefined number, loop
1980				devices can be requested on-demand with the
1981				/dev/loop-control interface.
1983		mce		[X86-32] Machine Check Exception
1985		mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
1987		md=		[HW] RAID subsystems devices and level
1988				See Documentation/md.txt.
1990		mdacon=		[MDA]
1991				Format: <first>,<last>
1992				Specifies range of consoles to be captured by the MDA.
1994		mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
1995				Amount of memory to be used when the kernel is not able
1996				to see the whole system memory or for test.
1997				[X86] Work as limiting max address. Use together
1998				with memmap= to avoid physical address space collisions.
1999				Without memmap= PCI devices could be placed at addresses
2000				belonging to unused RAM.
2002		mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
2003				memory.
2005		memchunk=nn[KMG]
2006				[KNL,SH] Allow user to override the default size for
2007				per-device physically contiguous DMA buffers.
2009		memmap=exactmap	[KNL,X86] Enable setting of an exact
2010				E820 memory map, as specified by the user.
2011				Such memmap=exactmap lines can be constructed based on
2012				BIOS output or other requirements. See the memmap=nn@ss
2013				option description.
2015		memmap=nn[KMG]@ss[KMG]
2016				[KNL] Force usage of a specific region of memory.
2017				Region of memory to be used is from ss to ss+nn.
2019		memmap=nn[KMG]#ss[KMG]
2020				[KNL,ACPI] Mark specific memory as ACPI data.
2021				Region of memory to be marked is from ss to ss+nn.
2023		memmap=nn[KMG]$ss[KMG]
2024				[KNL,ACPI] Mark specific memory as reserved.
2025				Region of memory to be reserved is from ss to ss+nn.
2026				Example: Exclude memory from 0x18690000-0x1869ffff
2027				         memmap=64K$0x18690000
2028				         or
2029				         memmap=0x10000$0x18690000
2031		memmap=nn[KMG]!ss[KMG]
2032				[KNL,X86] Mark specific memory as protected.
2033				Region of memory to be used, from ss to ss+nn.
2034				The memory region may be marked as e820 type 12 (0xc)
2035				and is NVDIMM or ADR memory.
2037		memory_corruption_check=0/1 [X86]
2038				Some BIOSes seem to corrupt the first 64k of
2039				memory when doing things like suspend/resume.
2040				Setting this option will scan the memory
2041				looking for corruption.  Enabling this will
2042				both detect corruption and prevent the kernel
2043				from using the memory being corrupted.
2044				However, its intended as a diagnostic tool; if
2045				repeatable BIOS-originated corruption always
2046				affects the same memory, you can use memmap=
2047				to prevent the kernel from using that memory.
2049		memory_corruption_check_size=size [X86]
2050				By default it checks for corruption in the low
2051				64k, making this memory unavailable for normal
2052				use.  Use this parameter to scan for
2053				corruption in more or less memory.
2055		memory_corruption_check_period=seconds [X86]
2056				By default it checks for corruption every 60
2057				seconds.  Use this parameter to check at some
2058				other rate.  0 disables periodic checking.
2060		memtest=	[KNL,X86,ARM] Enable memtest
2061				Format: <integer>
2062				default : 0 <disable>
2063				Specifies the number of memtest passes to be
2064				performed. Each pass selects another test
2065				pattern from a given set of patterns. Memtest
2066				fills the memory with this pattern, validates
2067				memory contents and reserves bad memory
2068				regions that are detected.
2070		meye.*=		[HW] Set MotionEye Camera parameters
2071				See Documentation/video4linux/meye.txt.
2073		mfgpt_irq=	[IA-32] Specify the IRQ to use for the
2074				Multi-Function General Purpose Timers on AMD Geode
2075				platforms.
2077		mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
2078				the BIOS has incorrectly applied a workaround. TinyBIOS
2079				version 0.98 is known to be affected, 0.99 fixes the
2080				problem by letting the user disable the workaround.
2082		mga=		[HW,DRM]
2084		min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
2085				physical address is ignored.
2087		mini2440=	[ARM,HW,KNL]
2088				Format:[0..2][b][c][t]
2089				Default: "0tb"
2090				MINI2440 configuration specification:
2091				0 - The attached screen is the 3.5" TFT
2092				1 - The attached screen is the 7" TFT
2093				2 - The VGA Shield is attached (1024x768)
2094				Leaving out the screen size parameter will not load
2095				the TFT driver, and the framebuffer will be left
2096				unconfigured.
2097				b - Enable backlight. The TFT backlight pin will be
2098				linked to the kernel VESA blanking code and a GPIO
2099				LED. This parameter is not necessary when using the
2100				VGA shield.
2101				c - Enable the s3c camera interface.
2102				t - Reserved for enabling touchscreen support. The
2103				touchscreen support is not enabled in the mainstream
2104				kernel as of 2.6.30, a preliminary port can be found
2105				in the "bleeding edge" mini2440 support kernel at
2106				http://repo.or.cz/w/linux-2.6/mini2440.git
2108		mminit_loglevel=
2109				[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
2110				parameter allows control of the logging verbosity for
2111				the additional memory initialisation checks. A value
2112				of 0 disables mminit logging and a level of 4 will
2113				log everything. Information is printed at KERN_DEBUG
2114				so loglevel=8 may also need to be specified.
2116		module.sig_enforce
2117				[KNL] When CONFIG_MODULE_SIG is set, this means that
2118				modules without (valid) signatures will fail to load.
2119				Note that if CONFIG_MODULE_SIG_FORCE is set, that
2120				is always true, so this option does nothing.
2122		mousedev.tap_time=
2123				[MOUSE] Maximum time between finger touching and
2124				leaving touchpad surface for touch to be considered
2125				a tap and be reported as a left button click (for
2126				touchpads working in absolute mode only).
2127				Format: <msecs>
2128		mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
2129				reporting absolute coordinates, such as tablets
2130		mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
2131				reporting absolute coordinates, such as tablets
2133		movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
2134				is similar to kernelcore except it specifies the
2135				amount of memory used for migratable allocations.
2136				If both kernelcore and movablecore is specified,
2137				then kernelcore will be at *least* the specified
2138				value but may be more. If movablecore on its own
2139				is specified, the administrator must be careful
2140				that the amount of memory usable for all allocations
2141				is not too small.
2143		movable_node	[KNL,X86] Boot-time switch to enable the effects
2144				of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
2146		MTD_Partition=	[MTD]
2147				Format: <name>,<region-number>,<size>,<offset>
2149		MTD_Region=	[MTD] Format:
2150				<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
2152		mtdparts=	[MTD]
2153				See drivers/mtd/cmdlinepart.c.
2155		multitce=off	[PPC]  This parameter disables the use of the pSeries
2156				firmware feature for updating multiple TCE entries
2157				at a time.
2159		onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
2161				Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
2163				boundary - index of last SLC block on Flex-OneNAND.
2164					   The remaining blocks are configured as MLC blocks.
2165				lock	 - Configure if Flex-OneNAND boundary should be locked.
2166					   Once locked, the boundary cannot be changed.
2167					   1 indicates lock status, 0 indicates unlock status.
2169		mtdset=		[ARM]
2170				ARM/S3C2412 JIVE boot control
2172				See arch/arm/mach-s3c2412/mach-jive.c
2174		mtouchusb.raw_coordinates=
2175				[HW] Make the MicroTouch USB driver use raw coordinates
2176				('y', default) or cooked coordinates ('n')
2178		mtrr_chunk_size=nn[KMG] [X86]
2179				used for mtrr cleanup. It is largest continuous chunk
2180				that could hold holes aka. UC entries.
2182		mtrr_gran_size=nn[KMG] [X86]
2183				Used for mtrr cleanup. It is granularity of mtrr block.
2184				Default is 1.
2185				Large value could prevent small alignment from
2186				using up MTRRs.
2188		mtrr_spare_reg_nr=n [X86]
2189				Format: <integer>
2190				Range: 0,7 : spare reg number
2191				Default : 1
2192				Used for mtrr cleanup. It is spare mtrr entries number.
2193				Set to 2 or more if your graphical card needs more.
2195		n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
2197		netdev=		[NET] Network devices parameters
2198				Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
2199				Note that mem_start is often overloaded to mean
2200				something different and driver-specific.
2201				This usage is only documented in each driver source
2202				file if at all.
2204		nf_conntrack.acct=
2205				[NETFILTER] Enable connection tracking flow accounting
2206				0 to disable accounting
2207				1 to enable accounting
2208				Default value is 0.
2210		nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
2211				See Documentation/filesystems/nfs/nfsroot.txt.
2213		nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
2214				See Documentation/filesystems/nfs/nfsroot.txt.
2216		nfsrootdebug	[NFS] enable nfsroot debugging messages.
2217				See Documentation/filesystems/nfs/nfsroot.txt.
2219		nfs.callback_tcpport=
2220				[NFS] set the TCP port on which the NFSv4 callback
2221				channel should listen.
2223		nfs.cache_getent=
2224				[NFS] sets the pathname to the program which is used
2225				to update the NFS client cache entries.
2227		nfs.cache_getent_timeout=
2228				[NFS] sets the timeout after which an attempt to
2229				update a cache entry is deemed to have failed.
2231		nfs.idmap_cache_timeout=
2232				[NFS] set the maximum lifetime for idmapper cache
2233				entries.
2235		nfs.enable_ino64=
2236				[NFS] enable 64-bit inode numbers.
2237				If zero, the NFS client will fake up a 32-bit inode
2238				number for the readdir() and stat() syscalls instead
2239				of returning the full 64-bit number.
2240				The default is to return 64-bit inode numbers.
2242		nfs.max_session_slots=
2243				[NFSv4.1] Sets the maximum number of session slots
2244				the client will attempt to negotiate with the server.
2245				This limits the number of simultaneous RPC requests
2246				that the client can send to the NFSv4.1 server.
2247				Note that there is little point in setting this
2248				value higher than the max_tcp_slot_table_limit.
2250		nfs.nfs4_disable_idmapping=
2251				[NFSv4] When set to the default of '1', this option
2252				ensures that both the RPC level authentication
2253				scheme and the NFS level operations agree to use
2254				numeric uids/gids if the mount is using the
2255				'sec=sys' security flavour. In effect it is
2256				disabling idmapping, which can make migration from
2257				legacy NFSv2/v3 systems to NFSv4 easier.
2258				Servers that do not support this mode of operation
2259				will be autodetected by the client, and it will fall
2260				back to using the idmapper.
2261				To turn off this behaviour, set the value to '0'.
2262		nfs.nfs4_unique_id=
2263				[NFS4] Specify an additional fixed unique ident-
2264				ification string that NFSv4 clients can insert into
2265				their nfs_client_id4 string.  This is typically a
2266				UUID that is generated at system install time.
2268		nfs.send_implementation_id =
2269				[NFSv4.1] Send client implementation identification
2270				information in exchange_id requests.
2271				If zero, no implementation identification information
2272				will be sent.
2273				The default is to send the implementation identification
2274				information.
2276		nfs.recover_lost_locks =
2277				[NFSv4] Attempt to recover locks that were lost due
2278				to a lease timeout on the server. Please note that
2279				doing this risks data corruption, since there are
2280				no guarantees that the file will remain unchanged
2281				after the locks are lost.
2282				If you want to enable the kernel legacy behaviour of
2283				attempting to recover these locks, then set this
2284				parameter to '1'.
2285				The default parameter value of '0' causes the kernel
2286				not to attempt recovery of lost locks.
2288		nfs4.layoutstats_timer =
2289				[NFSv4.2] Change the rate at which the kernel sends
2290				layoutstats to the pNFS metadata server.
2292				Setting this to value to 0 causes the kernel to use
2293				whatever value is the default set by the layout
2294				driver. A non-zero value sets the minimum interval
2295				in seconds between layoutstats transmissions.
2297		nfsd.nfs4_disable_idmapping=
2298				[NFSv4] When set to the default of '1', the NFSv4
2299				server will return only numeric uids and gids to
2300				clients using auth_sys, and will accept numeric uids
2301				and gids from such clients.  This is intended to ease
2302				migration from NFSv2/v3.
2304		objlayoutdriver.osd_login_prog=
2305				[NFS] [OBJLAYOUT] sets the pathname to the program which
2306				is used to automatically discover and login into new
2307				osd-targets. Please see:
2308				Documentation/filesystems/pnfs.txt for more explanations
2310		nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
2311				when a NMI is triggered.
2312				Format: [state][,regs][,debounce][,die]
2314		nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
2315				Format: [panic,][nopanic,][num]
2316				Valid num: 0 or 1
2317				0 - turn nmi_watchdog off
2318				1 - turn nmi_watchdog on
2319				When panic is specified, panic when an NMI watchdog
2320				timeout occurs (or 'nopanic' to override the opposite
2321				default).
2322				This is useful when you use a panic=... timeout and
2323				need the box quickly up again.
2325		netpoll.carrier_timeout=
2326				[NET] Specifies amount of time (in seconds) that
2327				netpoll should wait for a carrier. By default netpoll
2328				waits 4 seconds.
2330		no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
2331				emulation library even if a 387 maths coprocessor
2332				is present.
2334		no_console_suspend
2335				[HW] Never suspend the console
2336				Disable suspending of consoles during suspend and
2337				hibernate operations.  Once disabled, debugging
2338				messages can reach various consoles while the rest
2339				of the system is being put to sleep (ie, while
2340				debugging driver suspend/resume hooks).  This may
2341				not work reliably with all consoles, but is known
2342				to work with serial and VGA consoles.
2343				To facilitate more flexible debugging, we also add
2344				console_suspend, a printk module parameter to control
2345				it. Users could use console_suspend (usually
2346				/sys/module/printk/parameters/console_suspend) to
2347				turn on/off it dynamically.
2349		noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
2350				caches in the slab allocator.  Saves per-node memory,
2351				but will impact performance.
2353		noalign		[KNL,ARM]
2355		noapic		[SMP,APIC] Tells the kernel to not make use of any
2356				IOAPICs that may be present in the system.
2358		noautogroup	Disable scheduler automatic task group creation.
2360		nobats		[PPC] Do not use BATs for mapping kernel lowmem
2361				on "Classic" PPC cores.
2363		nocache		[ARM]
2365		noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2367		nodelayacct	[KNL] Disable per-task delay accounting
2369		nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.
2371		nodsp		[SH] Disable hardware DSP at boot time.
2373		noefi		Disable EFI runtime services support.
2375		noexec		[IA-64]
2377		noexec		[X86]
2378				On X86-32 available only on PAE configured kernels.
2379				noexec=on: enable non-executable mappings (default)
2380				noexec=off: disable non-executable mappings
2382		nosmap		[X86]
2383				Disable SMAP (Supervisor Mode Access Prevention)
2384				even if it is supported by processor.
2386		nosmep		[X86]
2387				Disable SMEP (Supervisor Mode Execution Prevention)
2388				even if it is supported by processor.
2390		noexec32	[X86-64]
2391				This affects only 32-bit executables.
2392				noexec32=on: enable non-executable mappings (default)
2393					read doesn't imply executable mappings
2394				noexec32=off: disable non-executable mappings
2395					read implies executable mappings
2397		nofpu		[MIPS,SH] Disable hardware FPU at boot time.
2399		nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2400				register save and restore. The kernel will only save
2401				legacy floating-point registers on task switch.
2403		nohugeiomap	[KNL,x86] Disable kernel huge I/O mappings.
2405		noxsave		[BUGS=X86] Disables x86 extended register state save
2406				and restore using xsave. The kernel will fallback to
2407				enabling legacy floating-point and sse state.
2409		noxsaveopt	[X86] Disables xsaveopt used in saving x86 extended
2410				register states. The kernel will fall back to use
2411				xsave to save the states. By using this parameter,
2412				performance of saving the states is degraded because
2413				xsave doesn't support modified optimization while
2414				xsaveopt supports it on xsaveopt enabled systems.
2416		noxsaves	[X86] Disables xsaves and xrstors used in saving and
2417				restoring x86 extended register state in compacted
2418				form of xsave area. The kernel will fall back to use
2419				xsaveopt and xrstor to save and restore the states
2420				in standard form of xsave area. By using this
2421				parameter, xsave area per process might occupy more
2422				memory on xsaves enabled systems.
2424		nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2425				wfi(ARM) instruction doesn't work correctly and not to
2426				use it. This is also useful when using JTAG debugger.
2428		no_file_caps	Tells the kernel not to honor file capabilities.  The
2429				only way then for a file to be executed with privilege
2430				is to be setuid root or executed by root.
2432		nohalt		[IA-64] Tells the kernel not to use the power saving
2433				function PAL_HALT_LIGHT when idle. This increases
2434				power-consumption. On the positive side, it reduces
2435				interrupt wake-up latency, which may improve performance
2436				in certain environments such as networked servers or
2437				real-time systems.
2439		nohibernate	[HIBERNATION] Disable hibernation and resume.
2441		nohz=		[KNL] Boottime enable/disable dynamic ticks
2442				Valid arguments: on, off
2443				Default: on
2445		nohz_full=	[KNL,BOOT]
2446				In kernels built with CONFIG_NO_HZ_FULL=y, set
2447				the specified list of CPUs whose tick will be stopped
2448				whenever possible. The boot CPU will be forced outside
2449				the range to maintain the timekeeping.
2450				The CPUs in this range must also be included in the
2451				rcu_nocbs= set.
2453		noiotrap	[SH] Disables trapped I/O port accesses.
2455		noirqdebug	[X86-32] Disables the code which attempts to detect and
2456				disable unhandled interrupt sources.
2458		no_timer_check	[X86,APIC] Disables the code which tests for
2459				broken timer IRQ sources.
2461		noisapnp	[ISAPNP] Disables ISA PnP code.
2463		noinitrd	[RAM] Tells the kernel not to load any configured
2464				initial RAM disk.
2466		nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
2467				remapping.
2468				[Deprecated - use intremap=off]
2470		nointroute	[IA-64]
2472		nojitter	[IA-64] Disables jitter checking for ITC timers.
2474		no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
2476		no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
2477				fault handling.
2479		no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
2480				steal time is computed, but won't influence scheduler
2481				behaviour
2483		nolapic		[X86-32,APIC] Do not enable or use the local APIC.
2485		nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2487		noltlbs		[PPC] Do not use large page/tlb entries for kernel
2488				lowmem mapping on PPC40x.
2490		nomca		[IA-64] Disable machine check abort handling
2492		nomce		[X86-32] Disable Machine Check Exception
2494		nomfgpt		[X86-32] Disable Multi-Function General Purpose
2495				Timer usage (for AMD Geode machines).
2497		nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
2498				shutdown the other cpus.  Instead use the REBOOT_VECTOR
2499				irq.
2501		nomodule	Disable module load
2503		nopat		[X86] Disable PAT (page attribute table extension of
2504				pagetables) support.
2506		norandmaps	Don't use address space randomization.  Equivalent to
2507				echo 0 > /proc/sys/kernel/randomize_va_space
2509		noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2511		noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2512				with UP alternatives
2514		nordrand	[X86] Disable kernel use of the RDRAND and
2515				RDSEED instructions even if they are supported
2516				by the processor.  RDRAND and RDSEED are still
2517				available to user space applications.
2519		noresume	[SWSUSP] Disables resume and restores original swap
2520				space.
2522		no-scroll	[VGA] Disables scrollback.
2523				This is required for the Braillex ib80-piezo Braille
2524				reader made by F.H. Papenmeier (Germany).
2526		nosbagart	[IA-64]
2528		nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2530		nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
2531				and disable the IO APIC.  legacy for "maxcpus=0".
2533		nosoftlockup	[KNL] Disable the soft-lockup detector.
2535		nosync		[HW,M68K] Disables sync negotiation for all devices.
2537		notsc		[BUGS=X86-32] Disable Time Stamp Counter
2539		nousb		[USB] Disable the USB subsystem
2541		nowatchdog	[KNL] Disable both lockup detectors, i.e.
2542	                        soft-lockup and NMI watchdog (hard-lockup).
2544		nowb		[ARM]
2546		nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
2548		cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
2550				Some features depend on CPU0. Known dependencies are:
2551				1. Resume from suspend/hibernate depends on CPU0.
2552				Suspend/hibernate will fail if CPU0 is offline and you
2553				need to online CPU0 before suspend/hibernate.
2554				2. PIC interrupts also depend on CPU0. CPU0 can't be
2555				removed if a PIC interrupt is detected.
2556				It's said poweroff/reboot may depend on CPU0 on some
2557				machines although I haven't seen such issues so far
2558				after CPU0 is offline on a few tested machines.
2559				If the dependencies are under your control, you can
2560				turn on cpu0_hotplug.
2562		nptcg=		[IA-64] Override max number of concurrent global TLB
2563				purges which is reported from either PAL_VM_SUMMARY or
2564				SAL PALO.
2566		nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
2567				could support.  nr_cpus=n : n >= 1 limits the kernel to
2568				supporting 'n' processors. Later in runtime you can not
2569				use hotplug cpu feature to put more cpu back to online.
2570				just like you compile the kernel NR_CPUS=n
2572		nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
2574		numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
2575				Allowed values are enable and disable
2577		numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2578				one of ['zone', 'node', 'default'] can be specified
2579				This can be set from sysctl after boot.
2580				See Documentation/sysctl/vm.txt for details.
2582		ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
2583				See Documentation/debugging-via-ohci1394.txt for more
2584				info.
2586		olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2587				Rather than timing out after 20 ms if an EC
2588				command is not properly ACKed, override the length
2589				of the timeout.  We have interrupts disabled while
2590				waiting for the ACK, so if this is set too high
2591				interrupts *may* be lost!
2593		omap_mux=	[OMAP] Override bootloader pin multiplexing.
2594				Format: <mux_mode0.mode_name=value>...
2595				For example, to override I2C bus2:
2596				omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2598		oprofile.timer=	[HW]
2599				Use timer interrupt instead of performance counters
2601		oprofile.cpu_type=	Force an oprofile cpu type
2602				This might be useful if you have an older oprofile
2603				userland or if you want common events.
2604				Format: { arch_perfmon }
2605				arch_perfmon: [X86] Force use of architectural
2606					perfmon on Intel CPUs instead of the
2607					CPU specific event set.
2608				timer: [X86] Force use of architectural NMI
2609					timer mode (see also oprofile.timer
2610					for generic hr timer mode)
2611					[s390] Force legacy basic mode sampling
2612	                                (report cpu_type "timer")
2614		oops=panic	Always panic on oopses. Default is to just kill the
2615				process, but there is a small probability of
2616				deadlocking the machine.
2617				This will also cause panics on machine check exceptions.
2618				Useful together with panic=30 to trigger a reboot.
2620		OSS		[HW,OSS]
2621				See Documentation/sound/oss/oss-parameters.txt
2623		page_owner=	[KNL] Boot-time page_owner enabling option.
2624				Storage of the information about who allocated
2625				each page is disabled in default. With this switch,
2626				we can turn it on.
2627				on: enable the feature
2629		panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2630				timeout > 0: seconds before rebooting
2631				timeout = 0: wait forever
2632				timeout < 0: reboot immediately
2633				Format: <timeout>
2635		panic_on_warn	panic() instead of WARN().  Useful to cause kdump
2636				on a WARN().
2638		crash_kexec_post_notifiers
2639				Run kdump after running panic-notifiers and dumping
2640				kmsg. This only for the users who doubt kdump always
2641				succeeds in any situation.
2642				Note that this also increases risks of kdump failure,
2643				because some panic notifiers can make the crashed
2644				kernel more unstable.
2646		parkbd.port=	[HW] Parallel port number the keyboard adapter is
2647				connected to, default is 0.
2648				Format: <parport#>
2649		parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
2650				0 for XT, 1 for AT (default is AT).
2651				Format: <mode>
2653		parport=	[HW,PPT] Specify parallel ports. 0 disables.
2654				Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2655				Use 'auto' to force the driver to use any
2656				IRQ/DMA settings detected (the default is to
2657				ignore detected IRQ/DMA settings because of
2658				possible conflicts). You can specify the base
2659				address, IRQ, and DMA settings; IRQ and DMA
2660				should be numbers, or 'auto' (for using detected
2661				settings on that particular port), or 'nofifo'
2662				(to avoid using a FIFO even if it is detected).
2663				Parallel ports are assigned in the order they
2664				are specified on the command line, starting
2665				with parport0.
2667		parport_init_mode=	[HW,PPT]
2668				Configure VIA parallel port to operate in
2669				a specific mode. This is necessary on Pegasos
2670				computer where firmware has no options for setting
2671				up parallel port mode and sets it to spp.
2672				Currently this function knows 686a and 8231 chips.
2673				Format: [spp|ps2|epp|ecp|ecpepp]
2675		pause_on_oops=
2676				Halt all CPUs after the first oops has been printed for
2677				the specified number of seconds.  This is to be used if
2678				your oopses keep scrolling off the screen.
2680		pcbit=		[HW,ISDN]
2682		pcd.		[PARIDE]
2683				See header of drivers/block/paride/pcd.c.
2684				See also Documentation/blockdev/paride.txt.
2686		pci=option[,option...]	[PCI] various PCI subsystem options:
2687			earlydump	[X86] dump PCI config space before the kernel
2688				        changes anything
2689			off		[X86] don't probe for the PCI bus
2690			bios		[X86-32] force use of PCI BIOS, don't access
2691					the hardware directly. Use this if your machine
2692					has a non-standard PCI host bridge.
2693			nobios		[X86-32] disallow use of PCI BIOS, only direct
2694					hardware access methods are allowed. Use this
2695					if you experience crashes upon bootup and you
2696					suspect they are caused by the BIOS.
2697			conf1		[X86] Force use of PCI Configuration
2698					Mechanism 1.
2699			conf2		[X86] Force use of PCI Configuration
2700					Mechanism 2.
2701			noaer		[PCIE] If the PCIEAER kernel config parameter is
2702					enabled, this kernel boot option can be used to
2703					disable the use of PCIE advanced error reporting.
2704			nodomains	[PCI] Disable support for multiple PCI
2705					root domains (aka PCI segments, in ACPI-speak).
2706			nommconf	[X86] Disable use of MMCONFIG for PCI
2707					Configuration
2708			check_enable_amd_mmconf [X86] check for and enable
2709					properly configured MMIO access to PCI
2710					config space on AMD family 10h CPU
2711			nomsi		[MSI] If the PCI_MSI kernel config parameter is
2712					enabled, this kernel boot option can be used to
2713					disable the use of MSI interrupts system-wide.
2714			noioapicquirk	[APIC] Disable all boot interrupt quirks.
2715					Safety option to keep boot IRQs enabled. This
2716					should never be necessary.
2717			ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
2718					primary IO-APIC for bridges that cannot disable
2719					boot IRQs. This fixes a source of spurious IRQs
2720					when the system masks IRQs.
2721			noioapicreroute	[APIC] Disable workaround that uses the
2722					boot IRQ equivalent of an IRQ that connects to
2723					a chipset where boot IRQs cannot be disabled.
2724					The opposite of ioapicreroute.
2725			biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
2726					routing table. These calls are known to be buggy
2727					on several machines and they hang the machine
2728					when used, but on other computers it's the only
2729					way to get the interrupt routing table. Try
2730					this option if the kernel is unable to allocate
2731					IRQs or discover secondary PCI buses on your
2732					motherboard.
2733			rom		[X86] Assign address space to expansion ROMs.
2734					Use with caution as certain devices share
2735					address decoders between ROMs and other
2736					resources.
2737			norom		[X86] Do not assign address space to
2738					expansion ROMs that do not already have
2739					BIOS assigned address ranges.
2740			nobar		[X86] Do not assign address space to the
2741					BARs that weren't assigned by the BIOS.
2742			irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
2743					assigned automatically to PCI devices. You can
2744					make the kernel exclude IRQs of your ISA cards
2745					this way.
2746			pirqaddr=0xAAAAA	[X86] Specify the physical address
2747					of the PIRQ table (normally generated
2748					by the BIOS) if it is outside the
2749					F0000h-100000h range.
2750			lastbus=N	[X86] Scan all buses thru bus #N. Can be
2751					useful if the kernel is unable to find your
2752					secondary buses and you want to tell it
2753					explicitly which ones they are.
2754			assign-busses	[X86] Always assign all PCI bus
2755					numbers ourselves, overriding
2756					whatever the firmware may have done.
2757			usepirqmask	[X86] Honor the possible IRQ mask stored
2758					in the BIOS $PIR table. This is needed on
2759					some systems with broken BIOSes, notably
2760					some HP Pavilion N5400 and Omnibook XE3
2761					notebooks. This will have no effect if ACPI
2762					IRQ routing is enabled.
2763			noacpi		[X86] Do not use ACPI for IRQ routing
2764					or for PCI scanning.
2765			use_crs		[X86] Use PCI host bridge window information
2766					from ACPI.  On BIOSes from 2008 or later, this
2767					is enabled by default.  If you need to use this,
2768					please report a bug.
2769			nocrs		[X86] Ignore PCI host bridge windows from ACPI.
2770				        If you need to use this, please report a bug.
2771			routeirq	Do IRQ routing for all PCI devices.
2772					This is normally done in pci_enable_device(),
2773					so this option is a temporary workaround
2774					for broken drivers that don't call it.
2775			skip_isa_align	[X86] do not align io start addr, so can
2776					handle more pci cards
2777			firmware	[ARM] Do not re-enumerate the bus but instead
2778					just use the configuration from the
2779					bootloader. This is currently used on
2780					IXP2000 systems where the bus has to be
2781					configured a certain way for adjunct CPUs.
2782			noearly		[X86] Don't do any early type 1 scanning.
2783					This might help on some broken boards which
2784					machine check when some devices' config space
2785					is read. But various workarounds are disabled
2786					and some IOMMU drivers will not work.
2787			bfsort		Sort PCI devices into breadth-first order.
2788					This sorting is done to get a device
2789					order compatible with older (<= 2.4) kernels.
2790			nobfsort	Don't sort PCI devices into breadth-first order.
2791			pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
2792					tuning and use the BIOS-configured MPS defaults.
2793			pcie_bus_safe	Set every device's MPS to the largest value
2794					supported by all devices below the root complex.
2795			pcie_bus_perf	Set device MPS to the largest allowable MPS
2796					based on its parent bus. Also set MRRS (Max
2797					Read Request Size) to the largest supported
2798					value (no larger than the MPS that the device
2799					or bus can support) for best performance.
2800			pcie_bus_peer2peer	Set every device's MPS to 128B, which
2801					every device is guaranteed to support. This
2802					configuration allows peer-to-peer DMA between
2803					any pair of devices, possibly at the cost of
2804					reduced performance.  This also guarantees
2805					that hot-added devices will work.
2806			cbiosize=nn[KMG]	The fixed amount of bus space which is
2807					reserved for the CardBus bridge's IO window.
2808					The default value is 256 bytes.
2809			cbmemsize=nn[KMG]	The fixed amount of bus space which is
2810					reserved for the CardBus bridge's memory
2811					window. The default value is 64 megabytes.
2812			resource_alignment=
2813					Format:
2814					[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2815					Specifies alignment and device to reassign
2816					aligned memory resources.
2817					If <order of align> is not specified,
2818					PAGE_SIZE is used as alignment.
2819					PCI-PCI bridge can be specified, if resource
2820					windows need to be expanded.
2821			ecrc=		Enable/disable PCIe ECRC (transaction layer
2822					end-to-end CRC checking).
2823					bios: Use BIOS/firmware settings. This is the
2824					the default.
2825					off: Turn ECRC off
2826					on: Turn ECRC on.
2827			hpiosize=nn[KMG]	The fixed amount of bus space which is
2828					reserved for hotplug bridge's IO window.
2829					Default size is 256 bytes.
2830			hpmemsize=nn[KMG]	The fixed amount of bus space which is
2831					reserved for hotplug bridge's memory window.
2832					Default size is 2 megabytes.
2833			realloc=	Enable/disable reallocating PCI bridge resources
2834					if allocations done by BIOS are too small to
2835					accommodate resources required by all child
2836					devices.
2837					off: Turn realloc off
2838					on: Turn realloc on
2839			realloc		same as realloc=on
2840			noari		do not use PCIe ARI.
2841			pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
2842					only look for one device below a PCIe downstream
2843					port.
2845		pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
2846				Management.
2847			off	Disable ASPM.
2848			force	Enable ASPM even on devices that claim not to support it.
2849				WARNING: Forcing ASPM on may cause system lockups.
2851		pcie_hp=	[PCIE] PCI Express Hotplug driver options:
2852			nomsi	Do not use MSI for PCI Express Native Hotplug (this
2853				makes all PCIe ports use INTx for hotplug services).
2855		pcie_ports=	[PCIE] PCIe ports handling:
2856			auto	Ask the BIOS whether or not to use native PCIe services
2857				associated with PCIe ports (PME, hot-plug, AER).  Use
2858				them only if that is allowed by the BIOS.
2859			native	Use native PCIe services associated with PCIe ports
2860				unconditionally.
2861			compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2862				ports driver.
2864		pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
2865			nomsi	Do not use MSI for native PCIe PME signaling (this makes
2866				all PCIe root ports use INTx for all services).
2868		pcmv=		[HW,PCMCIA] BadgePAD 4
2870		pd_ignore_unused
2871				[PM]
2872				Keep all power-domains already enabled by bootloader on,
2873				even if no driver has claimed them. This is useful
2874				for debug and development, but should not be
2875				needed on a platform with proper driver support.
2877		pd.		[PARIDE]
2878				See Documentation/blockdev/paride.txt.
2880		pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
2881				boot time.
2882				Format: { 0 | 1 }
2883				See arch/parisc/kernel/pdc_chassis.c
2885		percpu_alloc=	Select which percpu first chunk allocator to use.
2886				Currently supported values are "embed" and "page".
2887				Archs may support subset or none of the	selections.
2888				See comments in mm/percpu.c for details on each
2889				allocator.  This parameter is primarily	for debugging
2890				and performance comparison.
2892		pf.		[PARIDE]
2893				See Documentation/blockdev/paride.txt.
2895		pg.		[PARIDE]
2896				See Documentation/blockdev/paride.txt.
2898		pirq=		[SMP,APIC] Manual mp-table setup
2899				See Documentation/x86/i386/IO-APIC.txt.
2901		plip=		[PPT,NET] Parallel port network link
2902				Format: { parport<nr> | timid | 0 }
2903				See also Documentation/parport.txt.
2905		pmtmr=		[X86] Manual setup of pmtmr I/O Port.
2906				Override pmtimer IOPort with a hex value.
2907				e.g. pmtmr=0x508
2909		pnp.debug=1	[PNP]
2910				Enable PNP debug messages (depends on the
2911				CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2912				via /sys/module/pnp/parameters/debug.  We always show
2913				current resource usage; turning this on also shows
2914				possible settings and some assignment information.
2916		pnpacpi=	[ACPI]
2917				{ off }
2919		pnpbios=	[ISAPNP]
2920				{ on | off | curr | res | no-curr | no-res }
2922		pnp_reserve_irq=
2923				[ISAPNP] Exclude IRQs for the autoconfiguration
2925		pnp_reserve_dma=
2926				[ISAPNP] Exclude DMAs for the autoconfiguration
2928		pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
2929				Ranges are in pairs (I/O port base and size).
2931		pnp_reserve_mem=
2932				[ISAPNP] Exclude memory regions for the
2933				autoconfiguration.
2934				Ranges are in pairs (memory base and size).
2936		ports=		[IP_VS_FTP] IPVS ftp helper module
2937				Default is 21.
2938				Up to 8 (IP_VS_APP_MAX_PORTS) ports
2939				may be specified.
2940				Format: <port>,<port>....
2942		print-fatal-signals=
2943				[KNL] debug: print fatal signals
2945				If enabled, warn about various signal handling
2946				related application anomalies: too many signals,
2947				too many POSIX.1 timers, fatal signals causing a
2948				coredump - etc.
2950				If you hit the warning due to signal overflow,
2951				you might want to try "ulimit -i unlimited".
2953				default: off.
2955		printk.always_kmsg_dump=
2956				Trigger kmsg_dump for cases other than kernel oops or
2957				panics
2958				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2959				default: disabled
2961		printk.time=	Show timing data prefixed to each printk message line
2962				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2964		processor.max_cstate=	[HW,ACPI]
2965				Limit processor to maximum C-state
2966				max_cstate=9 overrides any DMI blacklist limit.
2968		processor.nocst	[HW,ACPI]
2969				Ignore the _CST method to determine C-states,
2970				instead using the legacy FADT method
2972		profile=	[KNL] Enable kernel profiling via /proc/profile
2973				Format: [schedule,]<number>
2974				Param: "schedule" - profile schedule points.
2975				Param: <number> - step/bucket size as a power of 2 for
2976					statistical time based profiling.
2977				Param: "sleep" - profile D-state sleeping (millisecs).
2978					Requires CONFIG_SCHEDSTATS
2979				Param: "kvm" - profile VM exits.
2981		prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
2982				before loading.
2983				See Documentation/blockdev/ramdisk.txt.
2985		psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
2986				probe for; one of (bare|imps|exps|lifebook|any).
2987		psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
2988				per second.
2989		psmouse.resetafter=	[HW,MOUSE]
2990				Try to reset the device after so many bad packets
2991				(0 = never).
2992		psmouse.resolution=
2993				[HW,MOUSE] Set desired mouse resolution, in dpi.
2994		psmouse.smartscroll=
2995				[HW,MOUSE] Controls Logitech smartscroll autorepeat.
2996				0 = disabled, 1 = enabled (default).
2998		pstore.backend=	Specify the name of the pstore backend to use
3000		pt.		[PARIDE]
3001				See Documentation/blockdev/paride.txt.
3003		pty.legacy_count=
3004				[KNL] Number of legacy pty's. Overwrites compiled-in
3005				default number.
3007		quiet		[KNL] Disable most log messages
3009		r128=		[HW,DRM]
3011		raid=		[HW,RAID]
3012				See Documentation/md.txt.
3014		ramdisk_blocksize=	[RAM]
3015				See Documentation/blockdev/ramdisk.txt.
3017		ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
3018				See Documentation/blockdev/ramdisk.txt.
3020		rcu_nocbs=	[KNL]
3021				In kernels built with CONFIG_RCU_NOCB_CPU=y, set
3022				the specified list of CPUs to be no-callback CPUs.
3023				Invocation of these CPUs' RCU callbacks will
3024				be offloaded to "rcuox/N" kthreads created for
3025				that purpose, where "x" is "b" for RCU-bh, "p"
3026				for RCU-preempt, and "s" for RCU-sched, and "N"
3027				is the CPU number.  This reduces OS jitter on the
3028				offloaded CPUs, which can be useful for HPC and
3029				real-time workloads.  It can also improve energy
3030				efficiency for asymmetric multiprocessors.
3032		rcu_nocb_poll	[KNL]
3033				Rather than requiring that offloaded CPUs
3034				(specified by rcu_nocbs= above) explicitly
3035				awaken the corresponding "rcuoN" kthreads,
3036				make these kthreads poll for callbacks.
3037				This improves the real-time response for the
3038				offloaded CPUs by relieving them of the need to
3039				wake up the corresponding kthread, but degrades
3040				energy efficiency by requiring that the kthreads
3041				periodically wake up to do the polling.
3043		rcutree.blimit=	[KNL]
3044				Set maximum number of finished RCU callbacks to
3045				process in one batch.
3047		rcutree.dump_tree=	[KNL]
3048				Dump the structure of the rcu_node combining tree
3049				out at early boot.  This is used for diagnostic
3050				purposes, to verify correct tree setup.
3052		rcutree.gp_cleanup_delay=	[KNL]
3053				Set the number of jiffies to delay each step of
3054				RCU grace-period cleanup.  This only has effect
3057		rcutree.gp_init_delay=	[KNL]
3058				Set the number of jiffies to delay each step of
3059				RCU grace-period initialization.  This only has
3061				is set.
3063		rcutree.gp_preinit_delay=	[KNL]
3064				Set the number of jiffies to delay each step of
3065				RCU grace-period pre-initialization, that is,
3066				the propagation of recent CPU-hotplug changes up
3067				the rcu_node combining tree.  This only has effect
3070		rcutree.rcu_fanout_exact= [KNL]
3071				Disable autobalancing of the rcu_node combining
3072				tree.  This is used by rcutorture, and might
3073				possibly be useful for architectures having high
3074				cache-to-cache transfer latencies.
3076		rcutree.rcu_fanout_leaf= [KNL]
3077				Increase the number of CPUs assigned to each
3078				leaf rcu_node structure.  Useful for very large
3079				systems.
3081		rcutree.jiffies_till_sched_qs= [KNL]
3082				Set required age in jiffies for a
3083				given grace period before RCU starts
3084				soliciting quiescent-state help from
3085				rcu_note_context_switch().
3087		rcutree.jiffies_till_first_fqs= [KNL]
3088				Set delay from grace-period initialization to
3089				first attempt to force quiescent states.
3090				Units are jiffies, minimum value is zero,
3091				and maximum value is HZ.
3093		rcutree.jiffies_till_next_fqs= [KNL]
3094				Set delay between subsequent attempts to force
3095				quiescent states.  Units are jiffies, minimum
3096				value is one, and maximum value is HZ.
3098		rcutree.kthread_prio= 	 [KNL,BOOT]
3099				Set the SCHED_FIFO priority of the RCU per-CPU
3100				kthreads (rcuc/N). This value is also used for
3101				the priority of the RCU boost threads (rcub/N)
3102				and for the RCU grace-period kthreads (rcu_bh,
3103				rcu_preempt, and rcu_sched). If RCU_BOOST is
3104				set, valid values are 1-99 and the default is 1
3105				(the least-favored priority).  Otherwise, when
3106				RCU_BOOST is not set, valid values are 0-99 and
3107				the default is zero (non-realtime operation).
3109		rcutree.rcu_nocb_leader_stride= [KNL]
3110				Set the number of NOCB kthread groups, which
3111				defaults to the square root of the number of
3112				CPUs.  Larger numbers reduces the wakeup overhead
3113				on the per-CPU grace-period kthreads, but increases
3114				that same overhead on each group's leader.
3116		rcutree.qhimark= [KNL]
3117				Set threshold of queued RCU callbacks beyond which
3118				batch limiting is disabled.
3120		rcutree.qlowmark= [KNL]
3121				Set threshold of queued RCU callbacks below which
3122				batch limiting is re-enabled.
3124		rcutree.rcu_idle_gp_delay= [KNL]
3125				Set wakeup interval for idle CPUs that have
3126				RCU callbacks (RCU_FAST_NO_HZ=y).
3128		rcutree.rcu_idle_lazy_gp_delay= [KNL]
3129				Set wakeup interval for idle CPUs that have
3130				only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
3131				Lazy RCU callbacks are those which RCU can
3132				prove do nothing more than free memory.
3134		rcutorture.cbflood_inter_holdoff= [KNL]
3135				Set holdoff time (jiffies) between successive
3136				callback-flood tests.
3138		rcutorture.cbflood_intra_holdoff= [KNL]
3139				Set holdoff time (jiffies) between successive
3140				bursts of callbacks within a given callback-flood
3141				test.
3143		rcutorture.cbflood_n_burst= [KNL]
3144				Set the number of bursts making up a given
3145				callback-flood test.  Set this to zero to
3146				disable callback-flood testing.
3148		rcutorture.cbflood_n_per_burst= [KNL]
3149				Set the number of callbacks to be registered
3150				in a given burst of a callback-flood test.
3152		rcutorture.fqs_duration= [KNL]
3153				Set duration of force_quiescent_state bursts
3154				in microseconds.
3156		rcutorture.fqs_holdoff= [KNL]
3157				Set holdoff time within force_quiescent_state bursts
3158				in microseconds.
3160		rcutorture.fqs_stutter= [KNL]
3161				Set wait time between force_quiescent_state bursts
3162				in seconds.
3164		rcutorture.gp_cond= [KNL]
3165				Use conditional/asynchronous update-side
3166				primitives, if available.
3168		rcutorture.gp_exp= [KNL]
3169				Use expedited update-side primitives, if available.
3171		rcutorture.gp_normal= [KNL]
3172				Use normal (non-expedited) asynchronous
3173				update-side primitives, if available.
3175		rcutorture.gp_sync= [KNL]
3176				Use normal (non-expedited) synchronous
3177				update-side primitives, if available.  If all
3178				of rcutorture.gp_cond=, rcutorture.gp_exp=,
3179				rcutorture.gp_normal=, and rcutorture.gp_sync=
3180				are zero, rcutorture acts as if is interpreted
3181				they are all non-zero.
3183		rcutorture.n_barrier_cbs= [KNL]
3184				Set callbacks/threads for rcu_barrier() testing.
3186		rcutorture.nfakewriters= [KNL]
3187				Set number of concurrent RCU writers.  These just
3188				stress RCU, they don't participate in the actual
3189				test, hence the "fake".
3191		rcutorture.nreaders= [KNL]
3192				Set number of RCU readers.  The value -1 selects
3193				N-1, where N is the number of CPUs.  A value
3194				"n" less than -1 selects N-n-2, where N is again
3195				the number of CPUs.  For example, -2 selects N
3196				(the number of CPUs), -3 selects N+1, and so on.
3198		rcutorture.object_debug= [KNL]
3199				Enable debug-object double-call_rcu() testing.
3201		rcutorture.onoff_holdoff= [KNL]
3202				Set time (s) after boot for CPU-hotplug testing.
3204		rcutorture.onoff_interval= [KNL]
3205				Set time (s) between CPU-hotplug operations, or
3206				zero to disable CPU-hotplug testing.
3208		rcutorture.shuffle_interval= [KNL]
3209				Set task-shuffle interval (s).  Shuffling tasks
3210				allows some CPUs to go into dyntick-idle mode
3211				during the rcutorture test.
3213		rcutorture.shutdown_secs= [KNL]
3214				Set time (s) after boot system shutdown.  This
3215				is useful for hands-off automated testing.
3217		rcutorture.stall_cpu= [KNL]
3218				Duration of CPU stall (s) to test RCU CPU stall
3219				warnings, zero to disable.
3221		rcutorture.stall_cpu_holdoff= [KNL]
3222				Time to wait (s) after boot before inducing stall.
3224		rcutorture.stat_interval= [KNL]
3225				Time (s) between statistics printk()s.
3227		rcutorture.stutter= [KNL]
3228				Time (s) to stutter testing, for example, specifying
3229				five seconds causes the test to run for five seconds,
3230				wait for five seconds, and so on.  This tests RCU's
3231				ability to transition abruptly to and from idle.
3233		rcutorture.test_boost= [KNL]
3234				Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
3235				"Maybe" means test if the RCU implementation
3236				under test support RCU priority boosting.
3238		rcutorture.test_boost_duration= [KNL]
3239				Duration (s) of each individual boost test.
3241		rcutorture.test_boost_interval= [KNL]
3242				Interval (s) between each boost test.
3244		rcutorture.test_no_idle_hz= [KNL]
3245				Test RCU's dyntick-idle handling.  See also the
3246				rcutorture.shuffle_interval parameter.
3248		rcutorture.torture_runnable= [BOOT]
3249				Start rcutorture running at boot time.
3251		rcutorture.torture_type= [KNL]
3252				Specify the RCU implementation to test.
3254		rcutorture.verbose= [KNL]
3255				Enable additional printk() statements.
3257		rcupdate.rcu_expedited= [KNL]
3258				Use expedited grace-period primitives, for
3259				example, synchronize_rcu_expedited() instead
3260				of synchronize_rcu().  This reduces latency,
3261				but can increase CPU utilization, degrade
3262				real-time latency, and degrade energy efficiency.
3264		rcupdate.rcu_cpu_stall_suppress= [KNL]
3265				Suppress RCU CPU stall warning messages.
3267		rcupdate.rcu_cpu_stall_timeout= [KNL]
3268				Set timeout for RCU CPU stall warning messages.
3270		rcupdate.rcu_task_stall_timeout= [KNL]
3271				Set timeout in jiffies for RCU task stall warning
3272				messages.  Disable with a value less than or equal
3273				to zero.
3275		rcupdate.rcu_self_test= [KNL]
3276				Run the RCU early boot self tests
3278		rcupdate.rcu_self_test_bh= [KNL]
3279				Run the RCU bh early boot self tests
3281		rcupdate.rcu_self_test_sched= [KNL]
3282				Run the RCU sched early boot self tests
3284		rdinit=		[KNL]
3285				Format: <full_path>
3286				Run specified binary instead of /init from the ramdisk,
3287				used for early userspace startup. See initrd.
3289		reboot=		[KNL]
3290				Format (x86 or x86_64):
3291					[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
3292					[[,]s[mp]#### \
3293					[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
3294					[[,]f[orce]
3295				Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
3296				      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
3297				      reboot_force is either force or not specified,
3298				      reboot_cpu is s[mp]#### with #### being the processor
3299						to be used for rebooting.
3301		relax_domain_level=
3302				[KNL, SMP] Set scheduler's default relax_domain_level.
3303				See Documentation/cgroups/cpusets.txt.
3305		relative_sleep_states=
3306				[SUSPEND] Use sleep state labeling where the deepest
3307				state available other than hibernation is always "mem".
3308				Format: { "0" | "1" }
3309				0 -- Traditional sleep state labels.
3310				1 -- Relative sleep state labels.
3312		reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
3314		reservetop=	[X86-32]
3315				Format: nn[KMG]
3316				Reserves a hole at the top of the kernel virtual
3317				address space.
3319		reservelow=	[X86]
3320				Format: nn[K]
3321				Set the amount of memory to reserve for BIOS at
3322				the bottom of the address space.
3324		reset_devices	[KNL] Force drivers to reset the underlying device
3325				during initialization.
3327		resume=		[SWSUSP]
3328				Specify the partition device for software suspend
3329				Format:
3330				{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
3332		resume_offset=	[SWSUSP]
3333				Specify the offset from the beginning of the partition
3334				given by "resume=" at which the swap header is located,
3335				in <PAGE_SIZE> units (needed only for swap files).
3336				See  Documentation/power/swsusp-and-swap-files.txt
3338		resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
3339				read the resume files
3341		resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
3342				Useful for devices that are detected asynchronously
3343				(e.g. USB and MMC devices).
3345		hibernate=	[HIBERNATION]
3346			noresume	Don't check if there's a hibernation image
3347					present during boot.
3348			nocompress	Don't compress/decompress hibernation images.
3349			no		Disable hibernation and resume.
3351		retain_initrd	[RAM] Keep initrd memory after extraction
3353		rfkill.default_state=
3354			0	"airplane mode".  All wifi, bluetooth, wimax, gps, fm,
3355				etc. communication is blocked by default.
3356			1	Unblocked.
3358		rfkill.master_switch_mode=
3359			0	The "airplane mode" button does nothing.
3360			1	The "airplane mode" button toggles between everything
3361				blocked and the previous configuration.
3362			2	The "airplane mode" button toggles between everything
3363				blocked and everything unblocked.
3365		rhash_entries=	[KNL,NET]
3366				Set number of hash buckets for route cache
3368		ro		[KNL] Mount root device read-only on boot
3370		root=		[KNL] Root filesystem
3371				See name_to_dev_t comment in init/do_mounts.c.
3373		rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
3374				mount the root filesystem
3376		rootflags=	[KNL] Set root filesystem mount option string
3378		rootfstype=	[KNL] Set root filesystem type
3380		rootwait	[KNL] Wait (indefinitely) for root device to show up.
3381				Useful for devices that are detected asynchronously
3382				(e.g. USB and MMC devices).
3384		rproc_mem=nn[KMG][@address]
3385				[KNL,ARM,CMA] Remoteproc physical memory block.
3386				Memory area to be used by remote processor image,
3387				managed by CMA.
3389		rw		[KNL] Mount root device read-write on boot
3391		S		[KNL] Run init in single mode
3393		s390_iommu=	[HW,S390]
3394				Set s390 IOTLB flushing mode
3395			strict
3396				With strict flushing every unmap operation will result in
3397				an IOTLB flush. Default is lazy flushing before reuse,
3398				which is faster.
3400		sa1100ir	[NET]
3401				See drivers/net/irda/sa1100_ir.c.
3403		sbni=		[NET] Granch SBNI12 leased line adapter
3405		sched_debug	[KNL] Enables verbose scheduler debug messages.
3407		skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
3408				xtime_lock contention on larger systems, and/or RCU lock
3409				contention on all systems with CONFIG_MAXSMP set.
3410				Format: { "0" | "1" }
3411				0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
3412				1 -- enable.
3413				Note: increases power consumption, thus should only be
3414				enabled if running jitter sensitive (HPC/RT) workloads.
3416		security=	[SECURITY] Choose a security module to enable at boot.
3417				If this boot parameter is not specified, only the first
3418				security module asking for security registration will be
3419				loaded. An invalid security module name will be treated
3420				as if no module has been chosen.
3422		selinux=	[SELINUX] Disable or enable SELinux at boot time.
3423				Format: { "0" | "1" }
3424				See security/selinux/Kconfig help text.
3425				0 -- disable.
3426				1 -- enable.
3427				Default value is set via kernel config option.
3428				If enabled at boot time, /selinux/disable can be used
3429				later to disable prior to initial policy load.
3431		apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
3432				Format: { "0" | "1" }
3433				See security/apparmor/Kconfig help text
3434				0 -- disable.
3435				1 -- enable.
3436				Default value is set via kernel config option.
3438		serialnumber	[BUGS=X86-32]
3440		shapers=	[NET]
3441				Maximal number of shapers.
3443		show_msr=	[x86] show boot-time MSR settings
3444				Format: { <integer> }
3445				Show boot-time (BIOS-initialized) MSR settings.
3446				The parameter means the number of CPUs to show,
3447				for example 1 means boot CPU only.
3449		simeth=		[IA-64]
3450		simscsi=
3452		slram=		[HW,MTD]
3454		slab_nomerge	[MM]
3455				Disable merging of slabs with similar size. May be
3456				necessary if there is some reason to distinguish
3457				allocs to different slabs. Debug options disable
3458				merging on their own.
3459				For more information see Documentation/vm/slub.txt.
3461		slab_max_order=	[MM, SLAB]
3462				Determines the maximum allowed order for slabs.
3463				A high setting may cause OOMs due to memory
3464				fragmentation.  Defaults to 1 for systems with
3465				more than 32MB of RAM, 0 otherwise.
3467		slub_debug[=options[,slabs]]	[MM, SLUB]
3468				Enabling slub_debug allows one to determine the
3469				culprit if slab objects become corrupted. Enabling
3470				slub_debug can create guard zones around objects and
3471				may poison objects when not in use. Also tracks the
3472				last alloc / free. For more information see
3473				Documentation/vm/slub.txt.
3475		slub_max_order= [MM, SLUB]
3476				Determines the maximum allowed order for slabs.
3477				A high setting may cause OOMs due to memory
3478				fragmentation. For more information see
3479				Documentation/vm/slub.txt.
3481		slub_min_objects=	[MM, SLUB]
3482				The minimum number of objects per slab. SLUB will
3483				increase the slab order up to slub_max_order to
3484				generate a sufficiently large slab able to contain
3485				the number of objects indicated. The higher the number
3486				of objects the smaller the overhead of tracking slabs
3487				and the less frequently locks need to be acquired.
3488				For more information see Documentation/vm/slub.txt.
3490		slub_min_order=	[MM, SLUB]
3491				Determines the minimum page order for slabs. Must be
3492				lower than slub_max_order.
3493				For more information see Documentation/vm/slub.txt.
3495		slub_nomerge	[MM, SLUB]
3496				Same with slab_nomerge. This is supported for legacy.
3497				See slab_nomerge for more information.
3499		smart2=		[HW]
3500				Format: <io1>[,<io2>[,...,<io8>]]
3502		smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
3503		smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
3504		smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
3505		smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
3506		smsc-ircc2.ircc_irq=	[HW] IRQ line
3507		smsc-ircc2.ircc_dma=	[HW] DMA channel
3508		smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
3509					0: Toshiba Satellite 1800 (GP data pin select)
3510					1: Fast pin select (default)
3511					2: ATC IRMode
3513		softlockup_panic=
3514				[KNL] Should the soft-lockup detector generate panics.
3515				Format: <integer>
3517		softlockup_all_cpu_backtrace=
3518				[KNL] Should the soft-lockup detector generate
3519				backtraces on all cpus.
3520				Format: <integer>
3522		sonypi.*=	[HW] Sony Programmable I/O Control Device driver
3523				See Documentation/laptops/sonypi.txt
3525		spia_io_base=	[HW,MTD]
3526		spia_fio_base=
3527		spia_pedr=
3528		spia_peddr=
3530		stacktrace	[FTRACE]
3531				Enabled the stack tracer on boot up.
3533		stacktrace_filter=[function-list]
3534				[FTRACE] Limit the functions that the stack tracer
3535				will trace at boot up. function-list is a comma separated
3536				list of functions. This list can be changed at run
3537				time by the stack_trace_filter file in the debugfs
3538				tracing directory. Note, this enables stack tracing
3539				and the stacktrace above is not needed.
3541		sti=		[PARISC,HW]
3542				Format: <num>
3543				Set the STI (builtin display/keyboard on the HP-PARISC
3544				machines) console (graphic card) which should be used
3545				as the initial boot-console.
3546				See also comment in drivers/video/console/sticore.c.
3548		sti_font=	[HW]
3549				See comment in drivers/video/console/sticore.c.
3551		stifb=		[HW]
3552				Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3554		sunrpc.min_resvport=
3555		sunrpc.max_resvport=
3556				[NFS,SUNRPC]
3557				SunRPC servers often require that client requests
3558				originate from a privileged port (i.e. a port in the
3559				range 0 < portnr < 1024).
3560				An administrator who wishes to reserve some of these
3561				ports for other uses may adjust the range that the
3562				kernel's sunrpc client considers to be privileged
3563				using these two parameters to set the minimum and
3564				maximum port values.
3566		sunrpc.pool_mode=
3567				[NFS]
3568				Control how the NFS server code allocates CPUs to
3569				service thread pools.  Depending on how many NICs
3570				you have and where their interrupts are bound, this
3571				option will affect which CPUs will do NFS serving.
3572				Note: this parameter cannot be changed while the
3573				NFS server is running.
3575				auto	    the server chooses an appropriate mode
3576					    automatically using heuristics
3577				global	    a single global pool contains all CPUs
3578				percpu	    one pool for each CPU
3579				pernode	    one pool for each NUMA node (equivalent
3580					    to global on non-NUMA machines)
3582		sunrpc.tcp_slot_table_entries=
3583		sunrpc.udp_slot_table_entries=
3584				[NFS,SUNRPC]
3585				Sets the upper limit on the number of simultaneous
3586				RPC calls that can be sent from the client to a
3587				server. Increasing these values may allow you to
3588				improve throughput, but will also increase the
3589				amount of memory reserved for use by the client.
3591		suspend.pm_test_delay=
3592				[SUSPEND]
3593				Sets the number of seconds to remain in a suspend test
3594				mode before resuming the system (see
3595				/sys/power/pm_test). Only available when CONFIG_PM_DEBUG
3596				is set. Default value is 5.
3598		swapaccount=[0|1]
3599				[KNL] Enable accounting of swap in memory resource
3600				controller if no parameter or 1 is given or disable
3601				it if 0 is given (See Documentation/cgroups/memory.txt)
3603		swiotlb=	[ARM,IA-64,PPC,MIPS,X86]
3604				Format: { <int> | force }
3605				<int> -- Number of I/O TLB slabs
3606				force -- force using of bounce buffers even if they
3607				         wouldn't be automatically used by the kernel
3609		switches=	[HW,M68k]
3611		sysfs.deprecated=0|1 [KNL]
3612				Enable/disable old style sysfs layout for old udev
3613				on older distributions. When this option is enabled
3614				very new udev will not work anymore. When this option
3615				is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3616				in older udev will not work anymore.
3617				Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3618				the kernel configuration.
3620		sysrq_always_enabled
3621				[KNL]
3622				Ignore sysrq setting - this boot parameter will
3623				neutralize any effect of /proc/sys/kernel/sysrq.
3624				Useful for debugging.
3626		tcpmhash_entries= [KNL,NET]
3627				Set the number of tcp_metrics_hash slots.
3628				Default value is 8192 or 16384 depending on total
3629				ram pages. This is used to specify the TCP metrics
3630				cache size. See Documentation/networking/ip-sysctl.txt
3631				"tcp_no_metrics_save" section for more details.
3633		tdfx=		[HW,DRM]
3635		test_suspend=	[SUSPEND][,N]
3636				Specify "mem" (for Suspend-to-RAM) or "standby" (for
3637				standby suspend) or "freeze" (for suspend type freeze)
3638				as the system sleep state during system startup with
3639				the optional capability to repeat N number of times.
3640				The system is woken from this state using a
3641				wakeup-capable RTC alarm.
3643		thash_entries=	[KNL,NET]
3644				Set number of hash buckets for TCP connection
3646		thermal.act=	[HW,ACPI]
3647				-1: disable all active trip points in all thermal zones
3648				<degrees C>: override all lowest active trip points
3650		thermal.crt=	[HW,ACPI]
3651				-1: disable all critical trip points in all thermal zones
3652				<degrees C>: override all critical trip points
3654		thermal.nocrt=	[HW,ACPI]
3655				Set to disable actions on ACPI thermal zone
3656				critical and hot trip points.
3658		thermal.off=	[HW,ACPI]
3659				1: disable ACPI thermal control
3661		thermal.psv=	[HW,ACPI]
3662				-1: disable all passive trip points
3663				<degrees C>: override all passive trip points to this
3664				value
3666		thermal.tzp=	[HW,ACPI]
3667				Specify global default ACPI thermal zone polling rate
3668				<deci-seconds>: poll all this frequency
3669				0: no polling (default)
3671		threadirqs	[KNL]
3672				Force threading of all interrupt handlers except those
3673				marked explicitly IRQF_NO_THREAD.
3675		tmem		[KNL,XEN]
3676				Enable the Transcendent memory driver if built-in.
3678		tmem.cleancache=0|1 [KNL, XEN]
3679				Default is on (1). Disable the usage of the cleancache
3680				API to send anonymous pages to the hypervisor.
3682		tmem.frontswap=0|1 [KNL, XEN]
3683				Default is on (1). Disable the usage of the frontswap
3684				API to send swap pages to the hypervisor. If disabled
3685				the selfballooning and selfshrinking are force disabled.
3687		tmem.selfballooning=0|1 [KNL, XEN]
3688				Default is on (1). Disable the driving of swap pages
3689				to the hypervisor.
3691		tmem.selfshrinking=0|1 [KNL, XEN]
3692				Default is on (1). Partial swapoff that immediately
3693				transfers pages from Xen hypervisor back to the
3694				kernel based on different criteria.
3696		topology=	[S390]
3697				Format: {off | on}
3698				Specify if the kernel should make use of the cpu
3699				topology information if the hardware supports this.
3700				The scheduler will make use of this information and
3701				e.g. base its process migration decisions on it.
3702				Default is on.
3704		topology_updates= [KNL, PPC, NUMA]
3705				Format: {off}
3706				Specify if the kernel should ignore (off)
3707				topology updates sent by the hypervisor to this
3708				LPAR.
3710		tp720=		[HW,PS2]
3712		tpm_suspend_pcr=[HW,TPM]
3713				Format: integer pcr id
3714				Specify that at suspend time, the tpm driver
3715				should extend the specified pcr with zeros,
3716				as a workaround for some chips which fail to
3717				flush the last written pcr on TPM_SaveState.
3718				This will guarantee that all the other pcrs
3719				are saved.
3721		trace_buf_size=nn[KMG]
3722				[FTRACE] will set tracing buffer size on each cpu.
3724		trace_event=[event-list]
3725				[FTRACE] Set and start specified trace events in order
3726				to facilitate early boot debugging.
3727				See also Documentation/trace/events.txt
3729		trace_options=[option-list]
3730				[FTRACE] Enable or disable tracer options at boot.
3731				The option-list is a comma delimited list of options
3732				that can be enabled or disabled just as if you were
3733				to echo the option name into
3735				    /sys/kernel/debug/tracing/trace_options
3737				For example, to enable stacktrace option (to dump the
3738				stack trace of each event), add to the command line:
3740				      trace_options=stacktrace
3742				See also Documentation/trace/ftrace.txt "trace options"
3743				section.
3745		tp_printk[FTRACE]
3746				Have the tracepoints sent to printk as well as the
3747				tracing ring buffer. This is useful for early boot up
3748				where the system hangs or reboots and does not give the
3749				option for reading the tracing buffer or performing a
3750				ftrace_dump_on_oops.
3752				To turn off having tracepoints sent to printk,
3753				 echo 0 > /proc/sys/kernel/tracepoint_printk
3754				Note, echoing 1 into this file without the
3755				tracepoint_printk kernel cmdline option has no effect.
3757				** CAUTION **
3759				Having tracepoints sent to printk() and activating high
3760				frequency tracepoints such as irq or sched, can cause
3761				the system to live lock.
3763		traceoff_on_warning
3764				[FTRACE] enable this option to disable tracing when a
3765				warning is hit. This turns off "tracing_on". Tracing can
3766				be enabled again by echoing '1' into the "tracing_on"
3767				file located in /sys/kernel/debug/tracing/
3769				This option is useful, as it disables the trace before
3770				the WARNING dump is called, which prevents the trace to
3771				be filled with content caused by the warning output.
3773				This option can also be set at run time via the sysctl
3774				option:  kernel/traceoff_on_warning
3776		transparent_hugepage=
3777				[KNL]
3778				Format: [always|madvise|never]
3779				Can be used to control the default behavior of the system
3780				with respect to transparent hugepages.
3781				See Documentation/vm/transhuge.txt for more details.
3783		tsc=		Disable clocksource stability checks for TSC.
3784				Format: <string>
3785				[x86] reliable: mark tsc clocksource as reliable, this
3786				disables clocksource verification at runtime, as well
3787				as the stability checks done at bootup.	Used to enable
3788				high-resolution timer mode on older hardware, and in
3789				virtualized environment.
3790				[x86] noirqtime: Do not use TSC to do irq accounting.
3791				Used to run time disable IRQ_TIME_ACCOUNTING on any
3792				platforms where RDTSC is slow and this accounting
3793				can add overhead.
3795		turbografx.map[2|3]=	[HW,JOY]
3796				TurboGraFX parallel port interface
3797				Format:
3798				<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3799				See also Documentation/input/joystick-parport.txt
3801		udbg-immortal	[PPC] When debugging early kernel crashes that
3802				happen after console_init() and before a proper 
3803				console driver takes over, this boot options might
3804				help "seeing" what's going on.
3806		uhash_entries=	[KNL,NET]
3807				Set number of hash buckets for UDP/UDP-Lite connections
3809		uhci-hcd.ignore_oc=
3810				[USB] Ignore overcurrent events (default N).
3811				Some badly-designed motherboards generate lots of
3812				bogus events, for ports that aren't wired to
3813				anything.  Set this parameter to avoid log spamming.
3814				Note that genuine overcurrent events won't be
3815				reported either.
3817		unknown_nmi_panic
3818				[X86] Cause panic on unknown NMI.
3820		usbcore.authorized_default=
3821				[USB] Default USB device authorization:
3822				(default -1 = authorized except for wireless USB,
3823				0 = not authorized, 1 = authorized)
3825		usbcore.autosuspend=
3826				[USB] The autosuspend time delay (in seconds) used
3827				for newly-detected USB devices (default 2).  This
3828				is the time required before an idle device will be
3829				autosuspended.  Devices for which the delay is set
3830				to a negative value won't be autosuspended at all.
3832		usbcore.usbfs_snoop=
3833				[USB] Set to log all usbfs traffic (default 0 = off).
3835		usbcore.blinkenlights=
3836				[USB] Set to cycle leds on hubs (default 0 = off).
3838		usbcore.old_scheme_first=
3839				[USB] Start with the old device initialization
3840				scheme (default 0 = off).
3842		usbcore.usbfs_memory_mb=
3843				[USB] Memory limit (in MB) for buffers allocated by
3844				usbfs (default = 16, 0 = max = 2047).
3846		usbcore.use_both_schemes=
3847				[USB] Try the other device initialization scheme
3848				if the first one fails (default 1 = enabled).
3850		usbcore.initial_descriptor_timeout=
3851				[USB] Specifies timeout for the initial 64-byte
3852	                        USB_REQ_GET_DESCRIPTOR request in milliseconds
3853				(default 5000 = 5.0 seconds).
3855		usbhid.mousepoll=
3856				[USBHID] The interval which mice are to be polled at.
3858		usb-storage.delay_use=
3859				[UMS] The delay in seconds before a new device is
3860				scanned for Logical Units (default 1).
3862		usb-storage.quirks=
3863				[UMS] A list of quirks entries to supplement or
3864				override the built-in unusual_devs list.  List
3865				entries are separated by commas.  Each entry has
3866				the form VID:PID:Flags where VID and PID are Vendor
3867				and Product ID values (4-digit hex numbers) and
3868				Flags is a set of characters, each corresponding
3869				to a common usb-storage quirk flag as follows:
3870					a = SANE_SENSE (collect more than 18 bytes
3871						of sense data);
3872					b = BAD_SENSE (don't collect more than 18
3873						bytes of sense data);
3874					c = FIX_CAPACITY (decrease the reported
3875						device capacity by one sector);
3876					d = NO_READ_DISC_INFO (don't use
3877						READ_DISC_INFO command);
3878					e = NO_READ_CAPACITY_16 (don't use
3879						READ_CAPACITY_16 command);
3880					f = NO_REPORT_OPCODES (don't use report opcodes
3881						command, uas only);
3882					g = MAX_SECTORS_240 (don't transfer more than
3883						240 sectors at a time, uas only);
3884					h = CAPACITY_HEURISTICS (decrease the
3885						reported device capacity by one
3886						sector if the number is odd);
3887					i = IGNORE_DEVICE (don't bind to this
3888						device);
3889					l = NOT_LOCKABLE (don't try to lock and
3890						unlock ejectable media);
3891					m = MAX_SECTORS_64 (don't transfer more
3892						than 64 sectors = 32 KB at a time);
3893					n = INITIAL_READ10 (force a retry of the
3894						initial READ(10) command);
3895					o = CAPACITY_OK (accept the capacity
3896						reported by the device);
3897					p = WRITE_CACHE (the device cache is ON
3898						by default);
3899					r = IGNORE_RESIDUE (the device reports
3900						bogus residue values);
3901					s = SINGLE_LUN (the device has only one
3902						Logical Unit);
3903					t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
3904						commands, uas only);
3905					u = IGNORE_UAS (don't bind to the uas driver);
3906					w = NO_WP_DETECT (don't test whether the
3907						medium is write-protected).
3908				Example: quirks=0419:aaf5:rl,0421:0433:rc
3910		user_debug=	[KNL,ARM]
3911				Format: <int>
3912				See arch/arm/Kconfig.debug help text.
3913					 1 - undefined instruction events
3914					 2 - system calls
3915					 4 - invalid data aborts
3916					 8 - SIGSEGV faults
3917					16 - SIGBUS faults
3918				Example: user_debug=31
3920		userpte=
3921				[X86] Flags controlling user PTE allocations.
3923					nohigh = do not allocate PTE pages in
3924						HIGHMEM regardless of setting
3925						of CONFIG_HIGHPTE.
3927		vdso=		[X86,SH]
3928				On X86_32, this is an alias for vdso32=.  Otherwise:
3930				vdso=1: enable VDSO (the default)
3931				vdso=0: disable VDSO mapping
3933		vdso32=		[X86] Control the 32-bit vDSO
3934				vdso32=1: enable 32-bit VDSO
3935				vdso32=0 or vdso32=2: disable 32-bit VDSO
3937				See the help text for CONFIG_COMPAT_VDSO for more
3938				details.  If CONFIG_COMPAT_VDSO is set, the default is
3939				vdso32=0; otherwise, the default is vdso32=1.
3941				For compatibility with older kernels, vdso32=2 is an
3942				alias for vdso32=0.
3944				Try vdso32=0 if you encounter an error that says:
3945				dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
3947		vector=		[IA-64,SMP]
3948				vector=percpu: enable percpu vector domain
3950		video=		[FB] Frame buffer configuration
3951				See Documentation/fb/modedb.txt.
3953		video.brightness_switch_enabled= [0,1]
3954				If set to 1, on receiving an ACPI notify event
3955				generated by hotkey, video driver will adjust brightness
3956				level and then send out the event to user space through
3957				the allocated input device; If set to 0, video driver
3958				will only send out the event without touching backlight
3959				brightness level.
3960				default: 1
3962		virtio_mmio.device=
3963				[VMMIO] Memory mapped virtio (platform) device.
3965					<size>@<baseaddr>:<irq>[:<id>]
3966				where:
3967					<size>     := size (can use standard suffixes
3968							like K, M and G)
3969					<baseaddr> := physical base address
3970					<irq>      := interrupt number (as passed to
3971							request_irq())
3972					<id>       := (optional) platform device id
3973				example:
3974					virtio_mmio.device=1K@0x100b0000:48:7
3976				Can be used multiple times for multiple devices.
3978		vga=		[BOOT,X86-32] Select a particular video mode
3979				See Documentation/x86/boot.txt and
3980				Documentation/svga.txt.
3981				Use vga=ask for menu.
3982				This is actually a boot loader parameter; the value is
3983				passed to the kernel using a special protocol.
3985		vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
3986				size of <nn>. This can be used to increase the
3987				minimum size (128MB on x86). It can also be used to
3988				decrease the size and leave more room for directly
3989				mapped kernel RAM.
3991		vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
3992				Format: <command>
3994		vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
3995				Format: <command>
3997		vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
3998				Format: <command>
4000		vsyscall=	[X86-64]
4001				Controls the behavior of vsyscalls (i.e. calls to
4002				fixed addresses of 0xffffffffff600x00 from legacy
4003				code).  Most statically-linked binaries and older
4004				versions of glibc use these calls.  Because these
4005				functions are at fixed addresses, they make nice
4006				targets for exploits that can control RIP.
4008				emulate     [default] Vsyscalls turn into traps and are
4009				            emulated reasonably safely.
4011				native      Vsyscalls are native syscall instructions.
4012				            This is a little bit faster than trapping
4013				            and makes a few dynamic recompilers work
4014				            better than they would in emulation mode.
4015				            It also makes exploits much easier to write.
4017				none        Vsyscalls don't work at all.  This makes
4018				            them quite hard to use for exploits but
4019				            might break your system.
4021		vt.color=	[VT] Default text color.
4022				Format: 0xYX, X = foreground, Y = background.
4023				Default: 0x07 = light gray on black.
4025		vt.cur_default=	[VT] Default cursor shape.
4026				Format: 0xCCBBAA, where AA, BB, and CC are the same as
4027				the parameters of the <Esc>[?A;B;Cc escape sequence;
4028				see VGA-softcursor.txt. Default: 2 = underline.
4030		vt.default_blu=	[VT]
4031				Format: <blue0>,<blue1>,<blue2>,...,<blue15>
4032				Change the default blue palette of the console.
4033				This is a 16-member array composed of values
4034				ranging from 0-255.
4036		vt.default_grn=	[VT]
4037				Format: <green0>,<green1>,<green2>,...,<green15>
4038				Change the default green palette of the console.
4039				This is a 16-member array composed of values
4040				ranging from 0-255.
4042		vt.default_red=	[VT]
4043				Format: <red0>,<red1>,<red2>,...,<red15>
4044				Change the default red palette of the console.
4045				This is a 16-member array composed of values
4046				ranging from 0-255.
4048		vt.default_utf8=
4049				[VT]
4050				Format=<0|1>
4051				Set system-wide default UTF-8 mode for all tty's.
4052				Default is 1, i.e. UTF-8 mode is enabled for all
4053				newly opened terminals.
4055		vt.global_cursor_default=
4056				[VT]
4057				Format=<-1|0|1>
4058				Set system-wide default for whether a cursor
4059				is shown on new VTs. Default is -1,
4060				i.e. cursors will be created by default unless
4061				overridden by individual drivers. 0 will hide
4062				cursors, 1 will display them.
4064		vt.italic=	[VT] Default color for italic text; 0-15.
4065				Default: 2 = green.
4067		vt.underline=	[VT] Default color for underlined text; 0-15.
4068				Default: 3 = cyan.
4070		watchdog timers	[HW,WDT] For information on watchdog timers,
4071				see Documentation/watchdog/watchdog-parameters.txt
4072				or other driver-specific files in the
4073				Documentation/watchdog/ directory.
4075		workqueue.disable_numa
4076				By default, all work items queued to unbound
4077				workqueues are affine to the NUMA nodes they're
4078				issued on, which results in better behavior in
4079				general.  If NUMA affinity needs to be disabled for
4080				whatever reason, this option can be used.  Note
4081				that this also can be controlled per-workqueue for
4082				workqueues visible under /sys/bus/workqueue/.
4084		workqueue.power_efficient
4085				Per-cpu workqueues are generally preferred because
4086				they show better performance thanks to cache
4087				locality; unfortunately, per-cpu workqueues tend to
4088				be more power hungry than unbound workqueues.
4090				Enabling this makes the per-cpu workqueues which
4091				were observed to contribute significantly to power
4092				consumption unbound, leading to measurably lower
4093				power usage at the cost of small performance
4094				overhead.
4096				The default value of this parameter is determined by
4097				the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
4099		x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
4100				default x2apic cluster mode on platforms
4101				supporting x2apic.
4103		x86_intel_mid_timer= [X86-32,APBT]
4104				Choose timer option for x86 Intel MID platform.
4105				Two valid options are apbt timer only and lapic timer
4106				plus one apbt timer for broadcast timer.
4107				x86_intel_mid_timer=apbt_only | lapic_and_apbt
4109		xen_512gb_limit		[KNL,X86-64,XEN]
4110				Restricts the kernel running paravirtualized under Xen
4111				to use only up to 512 GB of RAM. The reason to do so is
4112				crash analysis tools and Xen tools for doing domain
4113				save/restore/migration must be enabled to handle larger
4114				domains.
4116		xen_emul_unplug=		[HW,X86,XEN]
4117				Unplug Xen emulated devices
4118				Format: [unplug0,][unplug1]
4119				ide-disks -- unplug primary master IDE devices
4120				aux-ide-disks -- unplug non-primary-master IDE devices
4121				nics -- unplug network devices
4122				all -- unplug all emulated devices (NICs and IDE disks)
4123				unnecessary -- unplugging emulated devices is
4124					unnecessary even if the host did not respond to
4125					the unplug protocol
4126				never -- do not unplug even if version check succeeds
4128		xen_nopvspin	[X86,XEN]
4129				Disables the ticketlock slowpath using Xen PV
4130				optimizations.
4132		xen_nopv	[X86]
4133				Disables the PV optimizations forcing the HVM guest to
4134				run as generic HVM guest with no PV drivers.
4136		xirc2ps_cs=	[NET,PCMCIA]
4137				Format:
4138				<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
4140	______________________________________________________________________
4142	TODO:
4144		Add more DRM drivers.
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