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Based on kernel version 3.13. Page generated on 2014-01-20 22:03 EST.

1	                          Kernel Parameters
2	                          ~~~~~~~~~~~~~~~~~
3	
4	The following is a consolidated list of the kernel parameters as implemented
5	(mostly) by the __setup() macro and sorted into English Dictionary order
6	(defined as ignoring all punctuation and sorting digits before letters in a
7	case insensitive manner), and with descriptions where known.
8	
9	Module parameters for loadable modules are specified only as the
10	parameter name with optional '=' and value as appropriate, such as:
11	
12		modprobe usbcore blinkenlights=1
13	
14	Module parameters for modules that are built into the kernel image
15	are specified on the kernel command line with the module name plus
16	'.' plus parameter name, with '=' and value if appropriate, such as:
17	
18		usbcore.blinkenlights=1
19	
20	Hyphens (dashes) and underscores are equivalent in parameter names, so
21		log_buf_len=1M print-fatal-signals=1
22	can also be entered as
23		log-buf-len=1M print_fatal_signals=1
24	
25	
26	This document may not be entirely up to date and comprehensive. The command
27	"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
28	module. Loadable modules, after being loaded into the running kernel, also
29	reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
30	parameters may be changed at runtime by the command
31	"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
32	
33	The parameters listed below are only valid if certain kernel build options were
34	enabled and if respective hardware is present. The text in square brackets at
35	the beginning of each description states the restrictions within which a
36	parameter is applicable:
37	
38		ACPI	ACPI support is enabled.
39		AGP	AGP (Accelerated Graphics Port) is enabled.
40		ALSA	ALSA sound support is enabled.
41		APIC	APIC support is enabled.
42		APM	Advanced Power Management support is enabled.
43		ARM	ARM architecture is enabled.
44		AVR32	AVR32 architecture is enabled.
45		AX25	Appropriate AX.25 support is enabled.
46		BLACKFIN Blackfin architecture is enabled.
47		CLK	Common clock infrastructure is enabled.
48		CMA	Contiguous Memory Area support is enabled.
49		DRM	Direct Rendering Management support is enabled.
50		DYNAMIC_DEBUG Build in debug messages and enable them at runtime
51		EDD	BIOS Enhanced Disk Drive Services (EDD) is enabled
52		EFI	EFI Partitioning (GPT) is enabled
53		EIDE	EIDE/ATAPI support is enabled.
54		EVM	Extended Verification Module
55		FB	The frame buffer device is enabled.
56		FTRACE	Function tracing enabled.
57		GCOV	GCOV profiling is enabled.
58		HW	Appropriate hardware is enabled.
59		IA-64	IA-64 architecture is enabled.
60		IMA     Integrity measurement architecture is enabled.
61		IOSCHED	More than one I/O scheduler is enabled.
62		IP_PNP	IP DHCP, BOOTP, or RARP is enabled.
63		IPV6	IPv6 support is enabled.
64		ISAPNP	ISA PnP code is enabled.
65		ISDN	Appropriate ISDN support is enabled.
66		JOY	Appropriate joystick support is enabled.
67		KGDB	Kernel debugger support is enabled.
68		KVM	Kernel Virtual Machine support is enabled.
69		LIBATA  Libata driver is enabled
70		LP	Printer support is enabled.
71		LOOP	Loopback device support is enabled.
72		M68k	M68k architecture is enabled.
73				These options have more detailed description inside of
74				Documentation/m68k/kernel-options.txt.
75		MDA	MDA console support is enabled.
76		MIPS	MIPS architecture is enabled.
77		MOUSE	Appropriate mouse support is enabled.
78		MSI	Message Signaled Interrupts (PCI).
79		MTD	MTD (Memory Technology Device) support is enabled.
80		NET	Appropriate network support is enabled.
81		NUMA	NUMA support is enabled.
82		NFS	Appropriate NFS support is enabled.
83		OSS	OSS sound support is enabled.
84		PV_OPS	A paravirtualized kernel is enabled.
85		PARIDE	The ParIDE (parallel port IDE) subsystem is enabled.
86		PARISC	The PA-RISC architecture is enabled.
87		PCI	PCI bus support is enabled.
88		PCIE	PCI Express support is enabled.
89		PCMCIA	The PCMCIA subsystem is enabled.
90		PNP	Plug & Play support is enabled.
91		PPC	PowerPC architecture is enabled.
92		PPT	Parallel port support is enabled.
93		PS2	Appropriate PS/2 support is enabled.
94		RAM	RAM disk support is enabled.
95		S390	S390 architecture is enabled.
96		SCSI	Appropriate SCSI support is enabled.
97				A lot of drivers have their options described inside
98				the Documentation/scsi/ sub-directory.
99		SECURITY Different security models are enabled.
100		SELINUX SELinux support is enabled.
101		APPARMOR AppArmor support is enabled.
102		SERIAL	Serial support is enabled.
103		SH	SuperH architecture is enabled.
104		SMP	The kernel is an SMP kernel.
105		SPARC	Sparc architecture is enabled.
106		SWSUSP	Software suspend (hibernation) is enabled.
107		SUSPEND	System suspend states are enabled.
108		TPM	TPM drivers are enabled.
109		TS	Appropriate touchscreen support is enabled.
110		UMS	USB Mass Storage support is enabled.
111		USB	USB support is enabled.
112		USBHID	USB Human Interface Device support is enabled.
113		V4L	Video For Linux support is enabled.
114		VMMIO   Driver for memory mapped virtio devices is enabled.
115		VGA	The VGA console has been enabled.
116		VT	Virtual terminal support is enabled.
117		WDT	Watchdog support is enabled.
118		XT	IBM PC/XT MFM hard disk support is enabled.
119		X86-32	X86-32, aka i386 architecture is enabled.
120		X86-64	X86-64 architecture is enabled.
121				More X86-64 boot options can be found in
122				Documentation/x86/x86_64/boot-options.txt .
123		X86	Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
124		XEN	Xen support is enabled
125	
126	In addition, the following text indicates that the option:
127	
128		BUGS=	Relates to possible processor bugs on the said processor.
129		KNL	Is a kernel start-up parameter.
130		BOOT	Is a boot loader parameter.
131	
132	Parameters denoted with BOOT are actually interpreted by the boot
133	loader, and have no meaning to the kernel directly.
134	Do not modify the syntax of boot loader parameters without extreme
135	need or coordination with <Documentation/x86/boot.txt>.
136	
137	There are also arch-specific kernel-parameters not documented here.
138	See for example <Documentation/x86/x86_64/boot-options.txt>.
139	
140	Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
141	a trailing = on the name of any parameter states that that parameter will
142	be entered as an environment variable, whereas its absence indicates that
143	it will appear as a kernel argument readable via /proc/cmdline by programs
144	running once the system is up.
145	
146	The number of kernel parameters is not limited, but the length of the
147	complete command line (parameters including spaces etc.) is limited to
148	a fixed number of characters. This limit depends on the architecture
149	and is between 256 and 4096 characters. It is defined in the file
150	./include/asm/setup.h as COMMAND_LINE_SIZE.
151	
152	Finally, the [KMG] suffix is commonly described after a number of kernel
153	parameter values. These 'K', 'M', and 'G' letters represent the _binary_
154	multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
155	bytes respectively. Such letter suffixes can also be entirely omitted.
156	
157	
158		acpi=		[HW,ACPI,X86]
159				Advanced Configuration and Power Interface
160				Format: { force | off | strict | noirq | rsdt }
161				force -- enable ACPI if default was off
162				off -- disable ACPI if default was on
163				noirq -- do not use ACPI for IRQ routing
164				strict -- Be less tolerant of platforms that are not
165					strictly ACPI specification compliant.
166				rsdt -- prefer RSDT over (default) XSDT
167				copy_dsdt -- copy DSDT to memory
168	
169				See also Documentation/power/runtime_pm.txt, pci=noacpi
170	
171		acpi_rsdp=	[ACPI,EFI,KEXEC]
172				Pass the RSDP address to the kernel, mostly used
173				on machines running EFI runtime service to boot the
174				second kernel for kdump.
175	
176		acpi_apic_instance=	[ACPI, IOAPIC]
177				Format: <int>
178				2: use 2nd APIC table, if available
179				1,0: use 1st APIC table
180				default: 0
181	
182		acpi_backlight=	[HW,ACPI]
183				acpi_backlight=vendor
184				acpi_backlight=video
185				If set to vendor, prefer vendor specific driver
186				(e.g. thinkpad_acpi, sony_acpi, etc.) instead
187				of the ACPI video.ko driver.
188	
189		acpi.debug_layer=	[HW,ACPI,ACPI_DEBUG]
190		acpi.debug_level=	[HW,ACPI,ACPI_DEBUG]
191				Format: <int>
192				CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
193				debug output.  Bits in debug_layer correspond to a
194				_COMPONENT in an ACPI source file, e.g.,
195				    #define _COMPONENT ACPI_PCI_COMPONENT
196				Bits in debug_level correspond to a level in
197				ACPI_DEBUG_PRINT statements, e.g.,
198				    ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
199				The debug_level mask defaults to "info".  See
200				Documentation/acpi/debug.txt for more information about
201				debug layers and levels.
202	
203				Enable processor driver info messages:
204				    acpi.debug_layer=0x20000000
205				Enable PCI/PCI interrupt routing info messages:
206				    acpi.debug_layer=0x400000
207				Enable AML "Debug" output, i.e., stores to the Debug
208				object while interpreting AML:
209				    acpi.debug_layer=0xffffffff acpi.debug_level=0x2
210				Enable all messages related to ACPI hardware:
211				    acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
212	
213				Some values produce so much output that the system is
214				unusable.  The "log_buf_len" parameter may be useful
215				if you need to capture more output.
216	
217		acpi_irq_balance [HW,ACPI]
218				ACPI will balance active IRQs
219				default in APIC mode
220	
221		acpi_irq_nobalance [HW,ACPI]
222				ACPI will not move active IRQs (default)
223				default in PIC mode
224	
225		acpi_irq_isa=	[HW,ACPI] If irq_balance, mark listed IRQs used by ISA
226				Format: <irq>,<irq>...
227	
228		acpi_irq_pci=	[HW,ACPI] If irq_balance, clear listed IRQs for
229				use by PCI
230				Format: <irq>,<irq>...
231	
232		acpi_no_auto_ssdt	[HW,ACPI] Disable automatic loading of SSDT
233	
234		acpi_os_name=	[HW,ACPI] Tell ACPI BIOS the name of the OS
235				Format: To spoof as Windows 98: ="Microsoft Windows"
236	
237		acpi_osi=	[HW,ACPI] Modify list of supported OS interface strings
238				acpi_osi="string1"	# add string1
239				acpi_osi="!string2"	# remove string2
240				acpi_osi=!*		# remove all strings
241				acpi_osi=!		# disable all built-in OS vendor
242							  strings
243				acpi_osi=		# disable all strings
244	
245				'acpi_osi=!' can be used in combination with single or
246				multiple 'acpi_osi="string1"' to support specific OS
247				vendor string(s).  Note that such command can only
248				affect the default state of the OS vendor strings, thus
249				it cannot affect the default state of the feature group
250				strings and the current state of the OS vendor strings,
251				specifying it multiple times through kernel command line
252				is meaningless.  This command is useful when one do not
253				care about the state of the feature group strings which
254				should be controlled by the OSPM.
255				Examples:
256				  1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
257				     to 'acpi_osi="Windows 2000" acpi_osi=!', they all
258				     can make '_OSI("Windows 2000")' TRUE.
259	
260				'acpi_osi=' cannot be used in combination with other
261				'acpi_osi=' command lines, the _OSI method will not
262				exist in the ACPI namespace.  NOTE that such command can
263				only affect the _OSI support state, thus specifying it
264				multiple times through kernel command line is also
265				meaningless.
266				Examples:
267				  1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
268				     FALSE.
269	
270				'acpi_osi=!*' can be used in combination with single or
271				multiple 'acpi_osi="string1"' to support specific
272				string(s).  Note that such command can affect the
273				current state of both the OS vendor strings and the
274				feature group strings, thus specifying it multiple times
275				through kernel command line is meaningful.  But it may
276				still not able to affect the final state of a string if
277				there are quirks related to this string.  This command
278				is useful when one want to control the state of the
279				feature group strings to debug BIOS issues related to
280				the OSPM features.
281				Examples:
282				  1. 'acpi_osi="Module Device" acpi_osi=!*' can make
283				     '_OSI("Module Device")' FALSE.
284				  2. 'acpi_osi=!* acpi_osi="Module Device"' can make
285				     '_OSI("Module Device")' TRUE.
286				  3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
287				     equivalent to
288				     'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
289				     and
290				     'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
291				     they all will make '_OSI("Windows 2000")' TRUE.
292	
293		acpi_pm_good	[X86]
294				Override the pmtimer bug detection: force the kernel
295				to assume that this machine's pmtimer latches its value
296				and always returns good values.
297	
298		acpi_sci=	[HW,ACPI] ACPI System Control Interrupt trigger mode
299				Format: { level | edge | high | low }
300	
301		acpi_serialize	[HW,ACPI] force serialization of AML methods
302	
303		acpi_skip_timer_override [HW,ACPI]
304				Recognize and ignore IRQ0/pin2 Interrupt Override.
305				For broken nForce2 BIOS resulting in XT-PIC timer.
306	
307		acpi_sleep=	[HW,ACPI] Sleep options
308				Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
309					  old_ordering, nonvs, sci_force_enable }
310				See Documentation/power/video.txt for information on
311				s3_bios and s3_mode.
312				s3_beep is for debugging; it makes the PC's speaker beep
313				as soon as the kernel's real-mode entry point is called.
314				s4_nohwsig prevents ACPI hardware signature from being
315				used during resume from hibernation.
316				old_ordering causes the ACPI 1.0 ordering of the _PTS
317				control method, with respect to putting devices into
318				low power states, to be enforced (the ACPI 2.0 ordering
319				of _PTS is used by default).
320				nonvs prevents the kernel from saving/restoring the
321				ACPI NVS memory during suspend/hibernation and resume.
322				sci_force_enable causes the kernel to set SCI_EN directly
323				on resume from S1/S3 (which is against the ACPI spec,
324				but some broken systems don't work without it).
325	
326		acpi_use_timer_override [HW,ACPI]
327				Use timer override. For some broken Nvidia NF5 boards
328				that require a timer override, but don't have HPET
329	
330		acpi_enforce_resources=	[ACPI]
331				{ strict | lax | no }
332				Check for resource conflicts between native drivers
333				and ACPI OperationRegions (SystemIO and SystemMemory
334				only). IO ports and memory declared in ACPI might be
335				used by the ACPI subsystem in arbitrary AML code and
336				can interfere with legacy drivers.
337				strict (default): access to resources claimed by ACPI
338				is denied; legacy drivers trying to access reserved
339				resources will fail to bind to device using them.
340				lax: access to resources claimed by ACPI is allowed;
341				legacy drivers trying to access reserved resources
342				will bind successfully but a warning message is logged.
343				no: ACPI OperationRegions are not marked as reserved,
344				no further checks are performed.
345	
346		add_efi_memmap	[EFI; X86] Include EFI memory map in
347				kernel's map of available physical RAM.
348	
349		agp=		[AGP]
350				{ off | try_unsupported }
351				off: disable AGP support
352				try_unsupported: try to drive unsupported chipsets
353					(may crash computer or cause data corruption)
354	
355		ALSA		[HW,ALSA]
356				See Documentation/sound/alsa/alsa-parameters.txt
357	
358		alignment=	[KNL,ARM]
359				Allow the default userspace alignment fault handler
360				behaviour to be specified.  Bit 0 enables warnings,
361				bit 1 enables fixups, and bit 2 sends a segfault.
362	
363		align_va_addr=	[X86-64]
364				Align virtual addresses by clearing slice [14:12] when
365				allocating a VMA at process creation time. This option
366				gives you up to 3% performance improvement on AMD F15h
367				machines (where it is enabled by default) for a
368				CPU-intensive style benchmark, and it can vary highly in
369				a microbenchmark depending on workload and compiler.
370	
371				32: only for 32-bit processes
372				64: only for 64-bit processes
373				on: enable for both 32- and 64-bit processes
374				off: disable for both 32- and 64-bit processes
375	
376		alloc_snapshot	[FTRACE]
377				Allocate the ftrace snapshot buffer on boot up when the
378				main buffer is allocated. This is handy if debugging
379				and you need to use tracing_snapshot() on boot up, and
380				do not want to use tracing_snapshot_alloc() as it needs
381				to be done where GFP_KERNEL allocations are allowed.
382	
383		amd_iommu=	[HW,X86-64]
384				Pass parameters to the AMD IOMMU driver in the system.
385				Possible values are:
386				fullflush - enable flushing of IO/TLB entries when
387					    they are unmapped. Otherwise they are
388					    flushed before they will be reused, which
389					    is a lot of faster
390				off	  - do not initialize any AMD IOMMU found in
391					    the system
392				force_isolation - Force device isolation for all
393						  devices. The IOMMU driver is not
394						  allowed anymore to lift isolation
395						  requirements as needed. This option
396						  does not override iommu=pt
397	
398		amd_iommu_dump=	[HW,X86-64]
399				Enable AMD IOMMU driver option to dump the ACPI table
400				for AMD IOMMU. With this option enabled, AMD IOMMU
401				driver will print ACPI tables for AMD IOMMU during
402				IOMMU initialization.
403	
404		amijoy.map=	[HW,JOY] Amiga joystick support
405				Map of devices attached to JOY0DAT and JOY1DAT
406				Format: <a>,<b>
407				See also Documentation/input/joystick.txt
408	
409		analog.map=	[HW,JOY] Analog joystick and gamepad support
410				Specifies type or capabilities of an analog joystick
411				connected to one of 16 gameports
412				Format: <type1>,<type2>,..<type16>
413	
414		apc=		[HW,SPARC]
415				Power management functions (SPARCstation-4/5 + deriv.)
416				Format: noidle
417				Disable APC CPU standby support. SPARCstation-Fox does
418				not play well with APC CPU idle - disable it if you have
419				APC and your system crashes randomly.
420	
421		apic=		[APIC,X86-32] Advanced Programmable Interrupt Controller
422				Change the output verbosity whilst booting
423				Format: { quiet (default) | verbose | debug }
424				Change the amount of debugging information output
425				when initialising the APIC and IO-APIC components.
426	
427		autoconf=	[IPV6]
428				See Documentation/networking/ipv6.txt.
429	
430		show_lapic=	[APIC,X86] Advanced Programmable Interrupt Controller
431				Limit apic dumping. The parameter defines the maximal
432				number of local apics being dumped. Also it is possible
433				to set it to "all" by meaning -- no limit here.
434				Format: { 1 (default) | 2 | ... | all }.
435				The parameter valid if only apic=debug or
436				apic=verbose is specified.
437				Example: apic=debug show_lapic=all
438	
439		apm=		[APM] Advanced Power Management
440				See header of arch/x86/kernel/apm_32.c.
441	
442		arcrimi=	[HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
443				Format: <io>,<irq>,<nodeID>
444	
445		ataflop=	[HW,M68k]
446	
447		atarimouse=	[HW,MOUSE] Atari Mouse
448	
449		atkbd.extra=	[HW] Enable extra LEDs and keys on IBM RapidAccess,
450				EzKey and similar keyboards
451	
452		atkbd.reset=	[HW] Reset keyboard during initialization
453	
454		atkbd.set=	[HW] Select keyboard code set
455				Format: <int> (2 = AT (default), 3 = PS/2)
456	
457		atkbd.scroll=	[HW] Enable scroll wheel on MS Office and similar
458				keyboards
459	
460		atkbd.softraw=	[HW] Choose between synthetic and real raw mode
461				Format: <bool> (0 = real, 1 = synthetic (default))
462	
463		atkbd.softrepeat= [HW]
464				Use software keyboard repeat
465	
466		baycom_epp=	[HW,AX25]
467				Format: <io>,<mode>
468	
469		baycom_par=	[HW,AX25] BayCom Parallel Port AX.25 Modem
470				Format: <io>,<mode>
471				See header of drivers/net/hamradio/baycom_par.c.
472	
473		baycom_ser_fdx=	[HW,AX25]
474				BayCom Serial Port AX.25 Modem (Full Duplex Mode)
475				Format: <io>,<irq>,<mode>[,<baud>]
476				See header of drivers/net/hamradio/baycom_ser_fdx.c.
477	
478		baycom_ser_hdx=	[HW,AX25]
479				BayCom Serial Port AX.25 Modem (Half Duplex Mode)
480				Format: <io>,<irq>,<mode>
481				See header of drivers/net/hamradio/baycom_ser_hdx.c.
482	
483		blkdevparts=	Manual partition parsing of block device(s) for
484				embedded devices based on command line input.
485				See Documentation/block/cmdline-partition.txt
486	
487		boot_delay=	Milliseconds to delay each printk during boot.
488				Values larger than 10 seconds (10000) are changed to
489				no delay (0).
490				Format: integer
491	
492		bootmem_debug	[KNL] Enable bootmem allocator debug messages.
493	
494		bttv.card=	[HW,V4L] bttv (bt848 + bt878 based grabber cards)
495		bttv.radio=	Most important insmod options are available as
496				kernel args too.
497		bttv.pll=	See Documentation/video4linux/bttv/Insmod-options
498		bttv.tuner=
499	
500		bulk_remove=off	[PPC]  This parameter disables the use of the pSeries
501				firmware feature for flushing multiple hpte entries
502				at a time.
503	
504		c101=		[NET] Moxa C101 synchronous serial card
505	
506		cachesize=	[BUGS=X86-32] Override level 2 CPU cache size detection.
507				Sometimes CPU hardware bugs make them report the cache
508				size incorrectly. The kernel will attempt work arounds
509				to fix known problems, but for some CPUs it is not
510				possible to determine what the correct size should be.
511				This option provides an override for these situations.
512	
513		ccw_timeout_log [S390]
514				See Documentation/s390/CommonIO for details.
515	
516		cgroup_disable= [KNL] Disable a particular controller
517				Format: {name of the controller(s) to disable}
518					{Currently supported controllers - "memory"}
519	
520		checkreqprot	[SELINUX] Set initial checkreqprot flag value.
521				Format: { "0" | "1" }
522				See security/selinux/Kconfig help text.
523				0 -- check protection applied by kernel (includes
524					any implied execute protection).
525				1 -- check protection requested by application.
526				Default value is set via a kernel config option.
527				Value can be changed at runtime via
528					/selinux/checkreqprot.
529	
530		cio_ignore=	[S390]
531				See Documentation/s390/CommonIO for details.
532		clk_ignore_unused
533				[CLK]
534				Keep all clocks already enabled by bootloader on,
535				even if no driver has claimed them. This is useful
536				for debug and development, but should not be
537				needed on a platform with proper driver support.
538				For more information, see Documentation/clk.txt.
539	
540		clock=		[BUGS=X86-32, HW] gettimeofday clocksource override.
541				[Deprecated]
542				Forces specified clocksource (if available) to be used
543				when calculating gettimeofday(). If specified
544				clocksource is not available, it defaults to PIT.
545				Format: { pit | tsc | cyclone | pmtmr }
546	
547		clocksource=	Override the default clocksource
548				Format: <string>
549				Override the default clocksource and use the clocksource
550				with the name specified.
551				Some clocksource names to choose from, depending on
552				the platform:
553				[all] jiffies (this is the base, fallback clocksource)
554				[ACPI] acpi_pm
555				[ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
556					pxa_timer,timer3,32k_counter,timer0_1
557				[AVR32] avr32
558				[X86-32] pit,hpet,tsc;
559					scx200_hrt on Geode; cyclone on IBM x440
560				[MIPS] MIPS
561				[PARISC] cr16
562				[S390] tod
563				[SH] SuperH
564				[SPARC64] tick
565				[X86-64] hpet,tsc
566	
567		clearcpuid=BITNUM [X86]
568				Disable CPUID feature X for the kernel. See
569				arch/x86/include/asm/cpufeature.h for the valid bit
570				numbers. Note the Linux specific bits are not necessarily
571				stable over kernel options, but the vendor specific
572				ones should be.
573				Also note that user programs calling CPUID directly
574				or using the feature without checking anything
575				will still see it. This just prevents it from
576				being used by the kernel or shown in /proc/cpuinfo.
577				Also note the kernel might malfunction if you disable
578				some critical bits.
579	
580		cma=nn[MG]	[ARM,KNL]
581				Sets the size of kernel global memory area for contiguous
582				memory allocations. For more information, see
583				include/linux/dma-contiguous.h
584	
585		cmo_free_hint=	[PPC] Format: { yes | no }
586				Specify whether pages are marked as being inactive
587				when they are freed.  This is used in CMO environments
588				to determine OS memory pressure for page stealing by
589				a hypervisor.
590				Default: yes
591	
592		coherent_pool=nn[KMG]	[ARM,KNL]
593				Sets the size of memory pool for coherent, atomic dma
594				allocations, by default set to 256K.
595	
596		code_bytes	[X86] How many bytes of object code to print
597				in an oops report.
598				Range: 0 - 8192
599				Default: 64
600	
601		com20020=	[HW,NET] ARCnet - COM20020 chipset
602				Format:
603				<io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
604	
605		com90io=	[HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
606				Format: <io>[,<irq>]
607	
608		com90xx=	[HW,NET]
609				ARCnet - COM90xx chipset (memory-mapped buffers)
610				Format: <io>[,<irq>[,<memstart>]]
611	
612		condev=		[HW,S390] console device
613		conmode=
614	
615		console=	[KNL] Output console device and options.
616	
617			tty<n>	Use the virtual console device <n>.
618	
619			ttyS<n>[,options]
620			ttyUSB0[,options]
621				Use the specified serial port.  The options are of
622				the form "bbbbpnf", where "bbbb" is the baud rate,
623				"p" is parity ("n", "o", or "e"), "n" is number of
624				bits, and "f" is flow control ("r" for RTS or
625				omit it).  Default is "9600n8".
626	
627				See Documentation/serial-console.txt for more
628				information.  See
629				Documentation/networking/netconsole.txt for an
630				alternative.
631	
632			uart[8250],io,<addr>[,options]
633			uart[8250],mmio,<addr>[,options]
634				Start an early, polled-mode console on the 8250/16550
635				UART at the specified I/O port or MMIO address,
636				switching to the matching ttyS device later.  The
637				options are the same as for ttyS, above.
638			hvc<n>	Use the hypervisor console device <n>. This is for
639				both Xen and PowerPC hypervisors.
640	
641	                If the device connected to the port is not a TTY but a braille
642	                device, prepend "brl," before the device type, for instance
643				console=brl,ttyS0
644			For now, only VisioBraille is supported.
645	
646		consoleblank=	[KNL] The console blank (screen saver) timeout in
647				seconds. Defaults to 10*60 = 10mins. A value of 0
648				disables the blank timer.
649	
650		coredump_filter=
651				[KNL] Change the default value for
652				/proc/<pid>/coredump_filter.
653				See also Documentation/filesystems/proc.txt.
654	
655		cpuidle.off=1	[CPU_IDLE]
656				disable the cpuidle sub-system
657	
658		cpcihp_generic=	[HW,PCI] Generic port I/O CompactPCI driver
659				Format:
660				<first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
661	
662		crashkernel=size[KMG][@offset[KMG]]
663				[KNL] Using kexec, Linux can switch to a 'crash kernel'
664				upon panic. This parameter reserves the physical
665				memory region [offset, offset + size] for that kernel
666				image. If '@offset' is omitted, then a suitable offset
667				is selected automatically. Check
668				Documentation/kdump/kdump.txt for further details.
669	
670		crashkernel=range1:size1[,range2:size2,...][@offset]
671				[KNL] Same as above, but depends on the memory
672				in the running system. The syntax of range is
673				start-[end] where start and end are both
674				a memory unit (amount[KMG]). See also
675				Documentation/kdump/kdump.txt for an example.
676	
677		crashkernel=size[KMG],high
678				[KNL, x86_64] range could be above 4G. Allow kernel
679				to allocate physical memory region from top, so could
680				be above 4G if system have more than 4G ram installed.
681				Otherwise memory region will be allocated below 4G, if
682				available.
683				It will be ignored if crashkernel=X is specified.
684		crashkernel=size[KMG],low
685				[KNL, x86_64] range under 4G. When crashkernel=X,high
686				is passed, kernel could allocate physical memory region
687				above 4G, that cause second kernel crash on system
688				that require some amount of low memory, e.g. swiotlb
689				requires at least 64M+32K low memory.  Kernel would
690				try to allocate 72M below 4G automatically.
691				This one let user to specify own low range under 4G
692				for second kernel instead.
693				0: to disable low allocation.
694				It will be ignored when crashkernel=X,high is not used
695				or memory reserved is below 4G.
696	
697		cs89x0_dma=	[HW,NET]
698				Format: <dma>
699	
700		cs89x0_media=	[HW,NET]
701				Format: { rj45 | aui | bnc }
702	
703		dasd=		[HW,NET]
704				See header of drivers/s390/block/dasd_devmap.c.
705	
706		db9.dev[2|3]=	[HW,JOY] Multisystem joystick support via parallel port
707				(one device per port)
708				Format: <port#>,<type>
709				See also Documentation/input/joystick-parport.txt
710	
711		ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
712				time. See Documentation/dynamic-debug-howto.txt for
713				details.  Deprecated, see dyndbg.
714	
715		debug		[KNL] Enable kernel debugging (events log level).
716	
717		debug_locks_verbose=
718				[KNL] verbose self-tests
719				Format=<0|1>
720				Print debugging info while doing the locking API
721				self-tests.
722				We default to 0 (no extra messages), setting it to
723				1 will print _a lot_ more information - normally
724				only useful to kernel developers.
725	
726		debug_objects	[KNL] Enable object debugging
727	
728		no_debug_objects
729				[KNL] Disable object debugging
730	
731		debug_guardpage_minorder=
732				[KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
733				parameter allows control of the order of pages that will
734				be intentionally kept free (and hence protected) by the
735				buddy allocator. Bigger value increase the probability
736				of catching random memory corruption, but reduce the
737				amount of memory for normal system use. The maximum
738				possible value is MAX_ORDER/2.  Setting this parameter
739				to 1 or 2 should be enough to identify most random
740				memory corruption problems caused by bugs in kernel or
741				driver code when a CPU writes to (or reads from) a
742				random memory location. Note that there exists a class
743				of memory corruptions problems caused by buggy H/W or
744				F/W or by drivers badly programing DMA (basically when
745				memory is written at bus level and the CPU MMU is
746				bypassed) which are not detectable by
747				CONFIG_DEBUG_PAGEALLOC, hence this option will not help
748				tracking down these problems.
749	
750		debugpat	[X86] Enable PAT debugging
751	
752		decnet.addr=	[HW,NET]
753				Format: <area>[,<node>]
754				See also Documentation/networking/decnet.txt.
755	
756		default_hugepagesz=
757				[same as hugepagesz=] The size of the default
758				HugeTLB page size. This is the size represented by
759				the legacy /proc/ hugepages APIs, used for SHM, and
760				default size when mounting hugetlbfs filesystems.
761				Defaults to the default architecture's huge page size
762				if not specified.
763	
764		dhash_entries=	[KNL]
765				Set number of hash buckets for dentry cache.
766	
767		digi=		[HW,SERIAL]
768				IO parameters + enable/disable command.
769	
770		digiepca=	[HW,SERIAL]
771				See drivers/char/README.epca and
772				Documentation/serial/digiepca.txt.
773	
774		disable=	[IPV6]
775				See Documentation/networking/ipv6.txt.
776	
777		disable_ddw     [PPC/PSERIES]
778				Disable Dynamic DMA Window support. Use this if
779				to workaround buggy firmware.
780	
781		disable_ipv6=	[IPV6]
782				See Documentation/networking/ipv6.txt.
783	
784		disable_mtrr_cleanup [X86]
785				The kernel tries to adjust MTRR layout from continuous
786				to discrete, to make X server driver able to add WB
787				entry later. This parameter disables that.
788	
789		disable_mtrr_trim [X86, Intel and AMD only]
790				By default the kernel will trim any uncacheable
791				memory out of your available memory pool based on
792				MTRR settings.  This parameter disables that behavior,
793				possibly causing your machine to run very slowly.
794	
795		disable_timer_pin_1 [X86]
796				Disable PIN 1 of APIC timer
797				Can be useful to work around chipset bugs.
798	
799		dma_debug=off	If the kernel is compiled with DMA_API_DEBUG support,
800				this option disables the debugging code at boot.
801	
802		dma_debug_entries=<number>
803				This option allows to tune the number of preallocated
804				entries for DMA-API debugging code. One entry is
805				required per DMA-API allocation. Use this if the
806				DMA-API debugging code disables itself because the
807				architectural default is too low.
808	
809		dma_debug_driver=<driver_name>
810				With this option the DMA-API debugging driver
811				filter feature can be enabled at boot time. Just
812				pass the driver to filter for as the parameter.
813				The filter can be disabled or changed to another
814				driver later using sysfs.
815	
816		drm_kms_helper.edid_firmware=[<connector>:]<file>
817				Broken monitors, graphic adapters and KVMs may
818				send no or incorrect EDID data sets. This parameter
819				allows to specify an EDID data set in the
820				/lib/firmware directory that is used instead.
821				Generic built-in EDID data sets are used, if one of
822				edid/1024x768.bin, edid/1280x1024.bin,
823				edid/1680x1050.bin, or edid/1920x1080.bin is given
824				and no file with the same name exists. Details and
825				instructions how to build your own EDID data are
826				available in Documentation/EDID/HOWTO.txt. An EDID
827				data set will only be used for a particular connector,
828				if its name and a colon are prepended to the EDID
829				name.
830	
831		dscc4.setup=	[NET]
832	
833		dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
834		module.dyndbg[="val"]
835				Enable debug messages at boot time.  See
836				Documentation/dynamic-debug-howto.txt for details.
837	
838		earlycon=	[KNL] Output early console device and options.
839			uart[8250],io,<addr>[,options]
840			uart[8250],mmio,<addr>[,options]
841			uart[8250],mmio32,<addr>[,options]
842				Start an early, polled-mode console on the 8250/16550
843				UART at the specified I/O port or MMIO address.
844				MMIO inter-register address stride is either 8-bit
845				(mmio) or 32-bit (mmio32).
846				The options are the same as for ttyS, above.
847	
848		earlyprintk=	[X86,SH,BLACKFIN,ARM]
849				earlyprintk=vga
850				earlyprintk=efi
851				earlyprintk=xen
852				earlyprintk=serial[,ttySn[,baudrate]]
853				earlyprintk=serial[,0x...[,baudrate]]
854				earlyprintk=ttySn[,baudrate]
855				earlyprintk=dbgp[debugController#]
856	
857				earlyprintk is useful when the kernel crashes before
858				the normal console is initialized. It is not enabled by
859				default because it has some cosmetic problems.
860	
861				Append ",keep" to not disable it when the real console
862				takes over.
863	
864				Only one of vga, efi, serial, or usb debug port can
865				be used at a time.
866	
867				Currently only ttyS0 and ttyS1 may be specified by
868				name.  Other I/O ports may be explicitly specified
869				on some architectures (x86 and arm at least) by
870				replacing ttySn with an I/O port address, like this:
871					earlyprintk=serial,0x1008,115200
872				You can find the port for a given device in
873				/proc/tty/driver/serial:
874					2: uart:ST16650V2 port:00001008 irq:18 ...
875	
876				Interaction with the standard serial driver is not
877				very good.
878	
879				The VGA and EFI output is eventually overwritten by
880				the real console.
881	
882				The xen output can only be used by Xen PV guests.
883	
884		ekgdboc=	[X86,KGDB] Allow early kernel console debugging
885				ekgdboc=kbd
886	
887				This is designed to be used in conjunction with
888				the boot argument: earlyprintk=vga
889	
890		edd=		[EDD]
891				Format: {"off" | "on" | "skip[mbr]"}
892	
893		efi_no_storage_paranoia [EFI; X86]
894				Using this parameter you can use more than 50% of
895				your efi variable storage. Use this parameter only if
896				you are really sure that your UEFI does sane gc and
897				fulfills the spec otherwise your board may brick.
898	
899		eisa_irq_edge=	[PARISC,HW]
900				See header of drivers/parisc/eisa.c.
901	
902		elanfreq=	[X86-32]
903				See comment before function elanfreq_setup() in
904				arch/x86/kernel/cpu/cpufreq/elanfreq.c.
905	
906		elevator=	[IOSCHED]
907				Format: {"cfq" | "deadline" | "noop"}
908				See Documentation/block/cfq-iosched.txt and
909				Documentation/block/deadline-iosched.txt for details.
910	
911		elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
912				Specifies physical address of start of kernel core
913				image elf header and optionally the size. Generally
914				kexec loader will pass this option to capture kernel.
915				See Documentation/kdump/kdump.txt for details.
916	
917		enable_mtrr_cleanup [X86]
918				The kernel tries to adjust MTRR layout from continuous
919				to discrete, to make X server driver able to add WB
920				entry later. This parameter enables that.
921	
922		enable_timer_pin_1 [X86]
923				Enable PIN 1 of APIC timer
924				Can be useful to work around chipset bugs
925				(in particular on some ATI chipsets).
926				The kernel tries to set a reasonable default.
927	
928		enforcing	[SELINUX] Set initial enforcing status.
929				Format: {"0" | "1"}
930				See security/selinux/Kconfig help text.
931				0 -- permissive (log only, no denials).
932				1 -- enforcing (deny and log).
933				Default value is 0.
934				Value can be changed at runtime via /selinux/enforce.
935	
936		erst_disable	[ACPI]
937				Disable Error Record Serialization Table (ERST)
938				support.
939	
940		ether=		[HW,NET] Ethernet cards parameters
941				This option is obsoleted by the "netdev=" option, which
942				has equivalent usage. See its documentation for details.
943	
944		evm=		[EVM]
945				Format: { "fix" }
946				Permit 'security.evm' to be updated regardless of
947				current integrity status.
948	
949		failslab=
950		fail_page_alloc=
951		fail_make_request=[KNL]
952				General fault injection mechanism.
953				Format: <interval>,<probability>,<space>,<times>
954				See also Documentation/fault-injection/.
955	
956		floppy=		[HW]
957				See Documentation/blockdev/floppy.txt.
958	
959		force_pal_cache_flush
960				[IA-64] Avoid check_sal_cache_flush which may hang on
961				buggy SAL_CACHE_FLUSH implementations. Using this
962				parameter will force ia64_sal_cache_flush to call
963				ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
964	
965		ftrace=[tracer]
966				[FTRACE] will set and start the specified tracer
967				as early as possible in order to facilitate early
968				boot debugging.
969	
970		ftrace_dump_on_oops[=orig_cpu]
971				[FTRACE] will dump the trace buffers on oops.
972				If no parameter is passed, ftrace will dump
973				buffers of all CPUs, but if you pass orig_cpu, it will
974				dump only the buffer of the CPU that triggered the
975				oops.
976	
977		ftrace_filter=[function-list]
978				[FTRACE] Limit the functions traced by the function
979				tracer at boot up. function-list is a comma separated
980				list of functions. This list can be changed at run
981				time by the set_ftrace_filter file in the debugfs
982				tracing directory.
983	
984		ftrace_notrace=[function-list]
985				[FTRACE] Do not trace the functions specified in
986				function-list. This list can be changed at run time
987				by the set_ftrace_notrace file in the debugfs
988				tracing directory.
989	
990		ftrace_graph_filter=[function-list]
991				[FTRACE] Limit the top level callers functions traced
992				by the function graph tracer at boot up.
993				function-list is a comma separated list of functions
994				that can be changed at run time by the
995				set_graph_function file in the debugfs tracing directory.
996	
997		gamecon.map[2|3]=
998				[HW,JOY] Multisystem joystick and NES/SNES/PSX pad
999				support via parallel port (up to 5 devices per port)
1000				Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1001				See also Documentation/input/joystick-parport.txt
1002	
1003		gamma=		[HW,DRM]
1004	
1005		gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
1006				Format: off | on
1007				default: on
1008	
1009		gcov_persist=	[GCOV] When non-zero (default), profiling data for
1010				kernel modules is saved and remains accessible via
1011				debugfs, even when the module is unloaded/reloaded.
1012				When zero, profiling data is discarded and associated
1013				debugfs files are removed at module unload time.
1014	
1015		gpt		[EFI] Forces disk with valid GPT signature but
1016				invalid Protective MBR to be treated as GPT.
1017	
1018		grcan.enable0=	[HW] Configuration of physical interface 0. Determines
1019				the "Enable 0" bit of the configuration register.
1020				Format: 0 | 1
1021				Default: 0
1022		grcan.enable1=	[HW] Configuration of physical interface 1. Determines
1023				the "Enable 0" bit of the configuration register.
1024				Format: 0 | 1
1025				Default: 0
1026		grcan.select=	[HW] Select which physical interface to use.
1027				Format: 0 | 1
1028				Default: 0
1029		grcan.txsize=	[HW] Sets the size of the tx buffer.
1030				Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1031				Default: 1024
1032		grcan.rxsize=	[HW] Sets the size of the rx buffer.
1033				Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1034				Default: 1024
1035	
1036		hashdist=	[KNL,NUMA] Large hashes allocated during boot
1037				are distributed across NUMA nodes.  Defaults on
1038				for 64-bit NUMA, off otherwise.
1039				Format: 0 | 1 (for off | on)
1040	
1041		hcl=		[IA-64] SGI's Hardware Graph compatibility layer
1042	
1043		hd=		[EIDE] (E)IDE hard drive subsystem geometry
1044				Format: <cyl>,<head>,<sect>
1045	
1046		hest_disable	[ACPI]
1047				Disable Hardware Error Source Table (HEST) support;
1048				corresponding firmware-first mode error processing
1049				logic will be disabled.
1050	
1051		highmem=nn[KMG]	[KNL,BOOT] forces the highmem zone to have an exact
1052				size of <nn>. This works even on boxes that have no
1053				highmem otherwise. This also works to reduce highmem
1054				size on bigger boxes.
1055	
1056		highres=	[KNL] Enable/disable high resolution timer mode.
1057				Valid parameters: "on", "off"
1058				Default: "on"
1059	
1060		hisax=		[HW,ISDN]
1061				See Documentation/isdn/README.HiSax.
1062	
1063		hlt		[BUGS=ARM,SH]
1064	
1065		hpet=		[X86-32,HPET] option to control HPET usage
1066				Format: { enable (default) | disable | force |
1067					verbose }
1068				disable: disable HPET and use PIT instead
1069				force: allow force enabled of undocumented chips (ICH4,
1070					VIA, nVidia)
1071				verbose: show contents of HPET registers during setup
1072	
1073		hpet_mmap=	[X86, HPET_MMAP] Allow userspace to mmap HPET
1074				registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1075	
1076		hugepages=	[HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1077		hugepagesz=	[HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1078				On x86-64 and powerpc, this option can be specified
1079				multiple times interleaved with hugepages= to reserve
1080				huge pages of different sizes. Valid pages sizes on
1081				x86-64 are 2M (when the CPU supports "pse") and 1G
1082				(when the CPU supports the "pdpe1gb" cpuinfo flag)
1083				Note that 1GB pages can only be allocated at boot time
1084				using hugepages= and not freed afterwards.
1085	
1086		hvc_iucv=	[S390] Number of z/VM IUCV hypervisor console (HVC)
1087				       terminal devices. Valid values: 0..8
1088		hvc_iucv_allow=	[S390] Comma-separated list of z/VM user IDs.
1089				       If specified, z/VM IUCV HVC accepts connections
1090				       from listed z/VM user IDs only.
1091	
1092		hwthread_map=	[METAG] Comma-separated list of Linux cpu id to
1093				        hardware thread id mappings.
1094					Format: <cpu>:<hwthread>
1095	
1096		keep_bootcon	[KNL]
1097				Do not unregister boot console at start. This is only
1098				useful for debugging when something happens in the window
1099				between unregistering the boot console and initializing
1100				the real console.
1101	
1102		i2c_bus=	[HW] Override the default board specific I2C bus speed
1103				     or register an additional I2C bus that is not
1104				     registered from board initialization code.
1105				     Format:
1106				     <bus_id>,<clkrate>
1107	
1108		i8042.debug	[HW] Toggle i8042 debug mode
1109		i8042.direct	[HW] Put keyboard port into non-translated mode
1110		i8042.dumbkbd	[HW] Pretend that controller can only read data from
1111				     keyboard and cannot control its state
1112				     (Don't attempt to blink the leds)
1113		i8042.noaux	[HW] Don't check for auxiliary (== mouse) port
1114		i8042.nokbd	[HW] Don't check/create keyboard port
1115		i8042.noloop	[HW] Disable the AUX Loopback command while probing
1116				     for the AUX port
1117		i8042.nomux	[HW] Don't check presence of an active multiplexing
1118				     controller
1119		i8042.nopnp	[HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1120				     controllers
1121		i8042.notimeout	[HW] Ignore timeout condition signalled by controller
1122		i8042.reset	[HW] Reset the controller during init and cleanup
1123		i8042.unlock	[HW] Unlock (ignore) the keylock
1124	
1125		i810=		[HW,DRM]
1126	
1127		i8k.ignore_dmi	[HW] Continue probing hardware even if DMI data
1128				indicates that the driver is running on unsupported
1129				hardware.
1130		i8k.force	[HW] Activate i8k driver even if SMM BIOS signature
1131				does not match list of supported models.
1132		i8k.power_status
1133				[HW] Report power status in /proc/i8k
1134				(disabled by default)
1135		i8k.restricted	[HW] Allow controlling fans only if SYS_ADMIN
1136				capability is set.
1137	
1138		i915.invert_brightness=
1139				[DRM] Invert the sense of the variable that is used to
1140				set the brightness of the panel backlight. Normally a
1141				brightness value of 0 indicates backlight switched off,
1142				and the maximum of the brightness value sets the backlight
1143				to maximum brightness. If this parameter is set to 0
1144				(default) and the machine requires it, or this parameter
1145				is set to 1, a brightness value of 0 sets the backlight
1146				to maximum brightness, and the maximum of the brightness
1147				value switches the backlight off.
1148				-1 -- never invert brightness
1149				 0 -- machine default
1150				 1 -- force brightness inversion
1151	
1152		icn=		[HW,ISDN]
1153				Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1154	
1155		ide-core.nodma=	[HW] (E)IDE subsystem
1156				Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1157				.vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1158				.cdrom .chs .ignore_cable are additional options
1159				See Documentation/ide/ide.txt.
1160	
1161		ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1162				Claim all unknown PCI IDE storage controllers.
1163	
1164		idle=		[X86]
1165				Format: idle=poll, idle=halt, idle=nomwait
1166				Poll forces a polling idle loop that can slightly
1167				improve the performance of waking up a idle CPU, but
1168				will use a lot of power and make the system run hot.
1169				Not recommended.
1170				idle=halt: Halt is forced to be used for CPU idle.
1171				In such case C2/C3 won't be used again.
1172				idle=nomwait: Disable mwait for CPU C-states
1173	
1174		ignore_loglevel	[KNL]
1175				Ignore loglevel setting - this will print /all/
1176				kernel messages to the console. Useful for debugging.
1177				We also add it as printk module parameter, so users
1178				could change it dynamically, usually by
1179				/sys/module/printk/parameters/ignore_loglevel.
1180	
1181		ihash_entries=	[KNL]
1182				Set number of hash buckets for inode cache.
1183	
1184		ima_appraise=	[IMA] appraise integrity measurements
1185				Format: { "off" | "enforce" | "fix" }
1186				default: "enforce"
1187	
1188		ima_appraise_tcb [IMA]
1189				The builtin appraise policy appraises all files
1190				owned by uid=0.
1191	
1192		ima_hash=	[IMA]
1193				Format: { md5 | sha1 | rmd160 | sha256 | sha384
1194					   | sha512 | ... }
1195				default: "sha1"
1196	
1197				The list of supported hash algorithms is defined
1198				in crypto/hash_info.h.
1199	
1200		ima_tcb		[IMA]
1201				Load a policy which meets the needs of the Trusted
1202				Computing Base.  This means IMA will measure all
1203				programs exec'd, files mmap'd for exec, and all files
1204				opened for read by uid=0.
1205	
1206		ima_template=   [IMA]
1207				Select one of defined IMA measurements template formats.
1208				Formats: { "ima" | "ima-ng" }
1209				Default: "ima-ng"
1210	
1211		init=		[KNL]
1212				Format: <full_path>
1213				Run specified binary instead of /sbin/init as init
1214				process.
1215	
1216		initcall_debug	[KNL] Trace initcalls as they are executed.  Useful
1217				for working out where the kernel is dying during
1218				startup.
1219	
1220		initrd=		[BOOT] Specify the location of the initial ramdisk
1221	
1222		inport.irq=	[HW] Inport (ATI XL and Microsoft) busmouse driver
1223				Format: <irq>
1224	
1225		int_pln_enable  [x86] Enable power limit notification interrupt
1226	
1227		integrity_audit=[IMA]
1228				Format: { "0" | "1" }
1229				0 -- basic integrity auditing messages. (Default)
1230				1 -- additional integrity auditing messages.
1231	
1232		intel_iommu=	[DMAR] Intel IOMMU driver (DMAR) option
1233			on
1234				Enable intel iommu driver.
1235			off
1236				Disable intel iommu driver.
1237			igfx_off [Default Off]
1238				By default, gfx is mapped as normal device. If a gfx
1239				device has a dedicated DMAR unit, the DMAR unit is
1240				bypassed by not enabling DMAR with this option. In
1241				this case, gfx device will use physical address for
1242				DMA.
1243			forcedac [x86_64]
1244				With this option iommu will not optimize to look
1245				for io virtual address below 32-bit forcing dual
1246				address cycle on pci bus for cards supporting greater
1247				than 32-bit addressing. The default is to look
1248				for translation below 32-bit and if not available
1249				then look in the higher range.
1250			strict [Default Off]
1251				With this option on every unmap_single operation will
1252				result in a hardware IOTLB flush operation as opposed
1253				to batching them for performance.
1254			sp_off [Default Off]
1255				By default, super page will be supported if Intel IOMMU
1256				has the capability. With this option, super page will
1257				not be supported.
1258	
1259		intel_idle.max_cstate=	[KNL,HW,ACPI,X86]
1260				0	disables intel_idle and fall back on acpi_idle.
1261				1 to 6	specify maximum depth of C-state.
1262	
1263		intel_pstate=  [X86]
1264			       disable
1265			         Do not enable intel_pstate as the default
1266			         scaling driver for the supported processors
1267	
1268		intremap=	[X86-64, Intel-IOMMU]
1269				on	enable Interrupt Remapping (default)
1270				off	disable Interrupt Remapping
1271				nosid	disable Source ID checking
1272				no_x2apic_optout
1273					BIOS x2APIC opt-out request will be ignored
1274	
1275		iomem=		Disable strict checking of access to MMIO memory
1276			strict	regions from userspace.
1277			relaxed
1278	
1279		iommu=		[x86]
1280			off
1281			force
1282			noforce
1283			biomerge
1284			panic
1285			nopanic
1286			merge
1287			nomerge
1288			forcesac
1289			soft
1290			pt		[x86, IA-64]
1291	
1292	
1293		io7=		[HW] IO7 for Marvel based alpha systems
1294				See comment before marvel_specify_io7 in
1295				arch/alpha/kernel/core_marvel.c.
1296	
1297		io_delay=	[X86] I/O delay method
1298			0x80
1299				Standard port 0x80 based delay
1300			0xed
1301				Alternate port 0xed based delay (needed on some systems)
1302			udelay
1303				Simple two microseconds delay
1304			none
1305				No delay
1306	
1307		ip=		[IP_PNP]
1308				See Documentation/filesystems/nfs/nfsroot.txt.
1309	
1310		ip2=		[HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1311				See comment before ip2_setup() in
1312				drivers/char/ip2/ip2base.c.
1313	
1314		irqfixup	[HW]
1315				When an interrupt is not handled search all handlers
1316				for it. Intended to get systems with badly broken
1317				firmware running.
1318	
1319		irqpoll		[HW]
1320				When an interrupt is not handled search all handlers
1321				for it. Also check all handlers each timer
1322				interrupt. Intended to get systems with badly broken
1323				firmware running.
1324	
1325		isapnp=		[ISAPNP]
1326				Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1327	
1328		isolcpus=	[KNL,SMP] Isolate CPUs from the general scheduler.
1329				Format:
1330				<cpu number>,...,<cpu number>
1331				or
1332				<cpu number>-<cpu number>
1333				(must be a positive range in ascending order)
1334				or a mixture
1335				<cpu number>,...,<cpu number>-<cpu number>
1336	
1337				This option can be used to specify one or more CPUs
1338				to isolate from the general SMP balancing and scheduling
1339				algorithms. You can move a process onto or off an
1340				"isolated" CPU via the CPU affinity syscalls or cpuset.
1341				<cpu number> begins at 0 and the maximum value is
1342				"number of CPUs in system - 1".
1343	
1344				This option is the preferred way to isolate CPUs. The
1345				alternative -- manually setting the CPU mask of all
1346				tasks in the system -- can cause problems and
1347				suboptimal load balancer performance.
1348	
1349		iucv=		[HW,NET]
1350	
1351		ivrs_ioapic	[HW,X86_64]
1352				Provide an override to the IOAPIC-ID<->DEVICE-ID
1353				mapping provided in the IVRS ACPI table. For
1354				example, to map IOAPIC-ID decimal 10 to
1355				PCI device 00:14.0 write the parameter as:
1356					ivrs_ioapic[10]=00:14.0
1357	
1358		ivrs_hpet	[HW,X86_64]
1359				Provide an override to the HPET-ID<->DEVICE-ID
1360				mapping provided in the IVRS ACPI table. For
1361				example, to map HPET-ID decimal 0 to
1362				PCI device 00:14.0 write the parameter as:
1363					ivrs_hpet[0]=00:14.0
1364	
1365		js=		[HW,JOY] Analog joystick
1366				See Documentation/input/joystick.txt.
1367	
1368		keepinitrd	[HW,ARM]
1369	
1370		kernelcore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1371				specifies the amount of memory usable by the kernel
1372				for non-movable allocations.  The requested amount is
1373				spread evenly throughout all nodes in the system. The
1374				remaining memory in each node is used for Movable
1375				pages. In the event, a node is too small to have both
1376				kernelcore and Movable pages, kernelcore pages will
1377				take priority and other nodes will have a larger number
1378				of Movable pages.  The Movable zone is used for the
1379				allocation of pages that may be reclaimed or moved
1380				by the page migration subsystem.  This means that
1381				HugeTLB pages may not be allocated from this zone.
1382				Note that allocations like PTEs-from-HighMem still
1383				use the HighMem zone if it exists, and the Normal
1384				zone if it does not.
1385	
1386		kgdbdbgp=	[KGDB,HW] kgdb over EHCI usb debug port.
1387				Format: <Controller#>[,poll interval]
1388				The controller # is the number of the ehci usb debug
1389				port as it is probed via PCI.  The poll interval is
1390				optional and is the number seconds in between
1391				each poll cycle to the debug port in case you need
1392				the functionality for interrupting the kernel with
1393				gdb or control-c on the dbgp connection.  When
1394				not using this parameter you use sysrq-g to break into
1395				the kernel debugger.
1396	
1397		kgdboc=		[KGDB,HW] kgdb over consoles.
1398				Requires a tty driver that supports console polling,
1399				or a supported polling keyboard driver (non-usb).
1400				 Serial only format: <serial_device>[,baud]
1401				 keyboard only format: kbd
1402				 keyboard and serial format: kbd,<serial_device>[,baud]
1403				Optional Kernel mode setting:
1404				 kms, kbd format: kms,kbd
1405				 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1406	
1407		kgdbwait	[KGDB] Stop kernel execution and enter the
1408				kernel debugger at the earliest opportunity.
1409	
1410		kmac=		[MIPS] korina ethernet MAC address.
1411				Configure the RouterBoard 532 series on-chip
1412				Ethernet adapter MAC address.
1413	
1414		kmemleak=	[KNL] Boot-time kmemleak enable/disable
1415				Valid arguments: on, off
1416				Default: on
1417	
1418		kstack=N	[X86] Print N words from the kernel stack
1419				in oops dumps.
1420	
1421		kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1422				Default is 0 (don't ignore, but inject #GP)
1423	
1424		kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
1425				KVM MMU at runtime.
1426				Default is 0 (off)
1427	
1428		kvm-amd.nested=	[KVM,AMD] Allow nested virtualization in KVM/SVM.
1429				Default is 1 (enabled)
1430	
1431		kvm-amd.npt=	[KVM,AMD] Disable nested paging (virtualized MMU)
1432				for all guests.
1433				Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1434	
1435		kvm-intel.ept=	[KVM,Intel] Disable extended page tables
1436				(virtualized MMU) support on capable Intel chips.
1437				Default is 1 (enabled)
1438	
1439		kvm-intel.emulate_invalid_guest_state=
1440				[KVM,Intel] Enable emulation of invalid guest states
1441				Default is 0 (disabled)
1442	
1443		kvm-intel.flexpriority=
1444				[KVM,Intel] Disable FlexPriority feature (TPR shadow).
1445				Default is 1 (enabled)
1446	
1447		kvm-intel.nested=
1448				[KVM,Intel] Enable VMX nesting (nVMX).
1449				Default is 0 (disabled)
1450	
1451		kvm-intel.unrestricted_guest=
1452				[KVM,Intel] Disable unrestricted guest feature
1453				(virtualized real and unpaged mode) on capable
1454				Intel chips. Default is 1 (enabled)
1455	
1456		kvm-intel.vpid=	[KVM,Intel] Disable Virtual Processor Identification
1457				feature (tagged TLBs) on capable Intel chips.
1458				Default is 1 (enabled)
1459	
1460		l2cr=		[PPC]
1461	
1462		l3cr=		[PPC]
1463	
1464		lapic		[X86-32,APIC] Enable the local APIC even if BIOS
1465				disabled it.
1466	
1467		lapic=		[x86,APIC] "notscdeadline" Do not use TSC deadline
1468				value for LAPIC timer one-shot implementation. Default
1469				back to the programmable timer unit in the LAPIC.
1470	
1471		lapic_timer_c2_ok	[X86,APIC] trust the local apic timer
1472				in C2 power state.
1473	
1474		libata.dma=	[LIBATA] DMA control
1475				libata.dma=0	  Disable all PATA and SATA DMA
1476				libata.dma=1	  PATA and SATA Disk DMA only
1477				libata.dma=2	  ATAPI (CDROM) DMA only
1478				libata.dma=4	  Compact Flash DMA only
1479				Combinations also work, so libata.dma=3 enables DMA
1480				for disks and CDROMs, but not CFs.
1481	
1482		libata.ignore_hpa=	[LIBATA] Ignore HPA limit
1483				libata.ignore_hpa=0	  keep BIOS limits (default)
1484				libata.ignore_hpa=1	  ignore limits, using full disk
1485	
1486		libata.noacpi	[LIBATA] Disables use of ACPI in libata suspend/resume
1487				when set.
1488				Format: <int>
1489	
1490		libata.force=	[LIBATA] Force configurations.  The format is comma
1491				separated list of "[ID:]VAL" where ID is
1492				PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1493				matching port, link or device.  Basically, it matches
1494				the ATA ID string printed on console by libata.  If
1495				the whole ID part is omitted, the last PORT and DEVICE
1496				values are used.  If ID hasn't been specified yet, the
1497				configuration applies to all ports, links and devices.
1498	
1499				If only DEVICE is omitted, the parameter applies to
1500				the port and all links and devices behind it.  DEVICE
1501				number of 0 either selects the first device or the
1502				first fan-out link behind PMP device.  It does not
1503				select the host link.  DEVICE number of 15 selects the
1504				host link and device attached to it.
1505	
1506				The VAL specifies the configuration to force.  As long
1507				as there's no ambiguity shortcut notation is allowed.
1508				For example, both 1.5 and 1.5G would work for 1.5Gbps.
1509				The following configurations can be forced.
1510	
1511				* Cable type: 40c, 80c, short40c, unk, ign or sata.
1512				  Any ID with matching PORT is used.
1513	
1514				* SATA link speed limit: 1.5Gbps or 3.0Gbps.
1515	
1516				* Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1517				  udma[/][16,25,33,44,66,100,133] notation is also
1518				  allowed.
1519	
1520				* [no]ncq: Turn on or off NCQ.
1521	
1522				* nohrst, nosrst, norst: suppress hard, soft
1523	                          and both resets.
1524	
1525				* rstonce: only attempt one reset during
1526				  hot-unplug link recovery
1527	
1528				* dump_id: dump IDENTIFY data.
1529	
1530				* atapi_dmadir: Enable ATAPI DMADIR bridge support
1531	
1532				* disable: Disable this device.
1533	
1534				If there are multiple matching configurations changing
1535				the same attribute, the last one is used.
1536	
1537		memblock=debug	[KNL] Enable memblock debug messages.
1538	
1539		load_ramdisk=	[RAM] List of ramdisks to load from floppy
1540				See Documentation/blockdev/ramdisk.txt.
1541	
1542		lockd.nlm_grace_period=P  [NFS] Assign grace period.
1543				Format: <integer>
1544	
1545		lockd.nlm_tcpport=N	[NFS] Assign TCP port.
1546				Format: <integer>
1547	
1548		lockd.nlm_timeout=T	[NFS] Assign timeout value.
1549				Format: <integer>
1550	
1551		lockd.nlm_udpport=M	[NFS] Assign UDP port.
1552				Format: <integer>
1553	
1554		logibm.irq=	[HW,MOUSE] Logitech Bus Mouse Driver
1555				Format: <irq>
1556	
1557		loglevel=	All Kernel Messages with a loglevel smaller than the
1558				console loglevel will be printed to the console. It can
1559				also be changed with klogd or other programs. The
1560				loglevels are defined as follows:
1561	
1562				0 (KERN_EMERG)		system is unusable
1563				1 (KERN_ALERT)		action must be taken immediately
1564				2 (KERN_CRIT)		critical conditions
1565				3 (KERN_ERR)		error conditions
1566				4 (KERN_WARNING)	warning conditions
1567				5 (KERN_NOTICE)		normal but significant condition
1568				6 (KERN_INFO)		informational
1569				7 (KERN_DEBUG)		debug-level messages
1570	
1571		log_buf_len=n[KMG]	Sets the size of the printk ring buffer,
1572				in bytes.  n must be a power of two.  The default
1573				size is set in the kernel config file.
1574	
1575		logo.nologo	[FB] Disables display of the built-in Linux logo.
1576				This may be used to provide more screen space for
1577				kernel log messages and is useful when debugging
1578				kernel boot problems.
1579	
1580		lp=0		[LP]	Specify parallel ports to use, e.g,
1581		lp=port[,port...]	lp=none,parport0 (lp0 not configured, lp1 uses
1582		lp=reset		first parallel port). 'lp=0' disables the
1583		lp=auto			printer driver. 'lp=reset' (which can be
1584					specified in addition to the ports) causes
1585					attached printers to be reset. Using
1586					lp=port1,port2,... specifies the parallel ports
1587					to associate lp devices with, starting with
1588					lp0. A port specification may be 'none' to skip
1589					that lp device, or a parport name such as
1590					'parport0'. Specifying 'lp=auto' instead of a
1591					port specification list means that device IDs
1592					from each port should be examined, to see if
1593					an IEEE 1284-compliant printer is attached; if
1594					so, the driver will manage that printer.
1595					See also header of drivers/char/lp.c.
1596	
1597		lpj=n		[KNL]
1598				Sets loops_per_jiffy to given constant, thus avoiding
1599				time-consuming boot-time autodetection (up to 250 ms per
1600				CPU). 0 enables autodetection (default). To determine
1601				the correct value for your kernel, boot with normal
1602				autodetection and see what value is printed. Note that
1603				on SMP systems the preset will be applied to all CPUs,
1604				which is likely to cause problems if your CPUs need
1605				significantly divergent settings. An incorrect value
1606				will cause delays in the kernel to be wrong, leading to
1607				unpredictable I/O errors and other breakage. Although
1608				unlikely, in the extreme case this might damage your
1609				hardware.
1610	
1611		ltpc=		[NET]
1612				Format: <io>,<irq>,<dma>
1613	
1614		machvec=	[IA-64] Force the use of a particular machine-vector
1615				(machvec) in a generic kernel.
1616				Example: machvec=hpzx1_swiotlb
1617	
1618		machtype=	[Loongson] Share the same kernel image file between different
1619				 yeeloong laptop.
1620				Example: machtype=lemote-yeeloong-2f-7inch
1621	
1622		max_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory greater
1623				than or equal to this physical address is ignored.
1624	
1625		maxcpus=	[SMP] Maximum number of processors that	an SMP kernel
1626				should make use of.  maxcpus=n : n >= 0 limits the
1627				kernel to using 'n' processors.  n=0 is a special case,
1628				it is equivalent to "nosmp", which also disables
1629				the IO APIC.
1630	
1631		max_loop=	[LOOP] The number of loop block devices that get
1632		(loop.max_loop)	unconditionally pre-created at init time. The default
1633				number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1634				of statically allocating a predefined number, loop
1635				devices can be requested on-demand with the
1636				/dev/loop-control interface.
1637	
1638		mce		[X86-32] Machine Check Exception
1639	
1640		mce=option	[X86-64] See Documentation/x86/x86_64/boot-options.txt
1641	
1642		md=		[HW] RAID subsystems devices and level
1643				See Documentation/md.txt.
1644	
1645		mdacon=		[MDA]
1646				Format: <first>,<last>
1647				Specifies range of consoles to be captured by the MDA.
1648	
1649		mem=nn[KMG]	[KNL,BOOT] Force usage of a specific amount of memory
1650				Amount of memory to be used when the kernel is not able
1651				to see the whole system memory or for test.
1652				[X86] Work as limiting max address. Use together
1653				with memmap= to avoid physical address space collisions.
1654				Without memmap= PCI devices could be placed at addresses
1655				belonging to unused RAM.
1656	
1657		mem=nopentium	[BUGS=X86-32] Disable usage of 4MB pages for kernel
1658				memory.
1659	
1660		memchunk=nn[KMG]
1661				[KNL,SH] Allow user to override the default size for
1662				per-device physically contiguous DMA buffers.
1663	
1664		memmap=exactmap	[KNL,X86] Enable setting of an exact
1665				E820 memory map, as specified by the user.
1666				Such memmap=exactmap lines can be constructed based on
1667				BIOS output or other requirements. See the memmap=nn@ss
1668				option description.
1669	
1670		memmap=nn[KMG]@ss[KMG]
1671				[KNL] Force usage of a specific region of memory
1672				Region of memory to be used, from ss to ss+nn.
1673	
1674		memmap=nn[KMG]#ss[KMG]
1675				[KNL,ACPI] Mark specific memory as ACPI data.
1676				Region of memory to be used, from ss to ss+nn.
1677	
1678		memmap=nn[KMG]$ss[KMG]
1679				[KNL,ACPI] Mark specific memory as reserved.
1680				Region of memory to be used, from ss to ss+nn.
1681				Example: Exclude memory from 0x18690000-0x1869ffff
1682				         memmap=64K$0x18690000
1683				         or
1684				         memmap=0x10000$0x18690000
1685	
1686		memory_corruption_check=0/1 [X86]
1687				Some BIOSes seem to corrupt the first 64k of
1688				memory when doing things like suspend/resume.
1689				Setting this option will scan the memory
1690				looking for corruption.  Enabling this will
1691				both detect corruption and prevent the kernel
1692				from using the memory being corrupted.
1693				However, its intended as a diagnostic tool; if
1694				repeatable BIOS-originated corruption always
1695				affects the same memory, you can use memmap=
1696				to prevent the kernel from using that memory.
1697	
1698		memory_corruption_check_size=size [X86]
1699				By default it checks for corruption in the low
1700				64k, making this memory unavailable for normal
1701				use.  Use this parameter to scan for
1702				corruption in more or less memory.
1703	
1704		memory_corruption_check_period=seconds [X86]
1705				By default it checks for corruption every 60
1706				seconds.  Use this parameter to check at some
1707				other rate.  0 disables periodic checking.
1708	
1709		memtest=	[KNL,X86] Enable memtest
1710				Format: <integer>
1711				default : 0 <disable>
1712				Specifies the number of memtest passes to be
1713				performed. Each pass selects another test
1714				pattern from a given set of patterns. Memtest
1715				fills the memory with this pattern, validates
1716				memory contents and reserves bad memory
1717				regions that are detected.
1718	
1719		meye.*=		[HW] Set MotionEye Camera parameters
1720				See Documentation/video4linux/meye.txt.
1721	
1722		mfgpt_irq=	[IA-32] Specify the IRQ to use for the
1723				Multi-Function General Purpose Timers on AMD Geode
1724				platforms.
1725	
1726		mfgptfix	[X86-32] Fix MFGPT timers on AMD Geode platforms when
1727				the BIOS has incorrectly applied a workaround. TinyBIOS
1728				version 0.98 is known to be affected, 0.99 fixes the
1729				problem by letting the user disable the workaround.
1730	
1731		mga=		[HW,DRM]
1732	
1733		min_addr=nn[KMG]	[KNL,BOOT,ia64] All physical memory below this
1734				physical address is ignored.
1735	
1736		mini2440=	[ARM,HW,KNL]
1737				Format:[0..2][b][c][t]
1738				Default: "0tb"
1739				MINI2440 configuration specification:
1740				0 - The attached screen is the 3.5" TFT
1741				1 - The attached screen is the 7" TFT
1742				2 - The VGA Shield is attached (1024x768)
1743				Leaving out the screen size parameter will not load
1744				the TFT driver, and the framebuffer will be left
1745				unconfigured.
1746				b - Enable backlight. The TFT backlight pin will be
1747				linked to the kernel VESA blanking code and a GPIO
1748				LED. This parameter is not necessary when using the
1749				VGA shield.
1750				c - Enable the s3c camera interface.
1751				t - Reserved for enabling touchscreen support. The
1752				touchscreen support is not enabled in the mainstream
1753				kernel as of 2.6.30, a preliminary port can be found
1754				in the "bleeding edge" mini2440 support kernel at
1755				http://repo.or.cz/w/linux-2.6/mini2440.git
1756	
1757		mminit_loglevel=
1758				[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1759				parameter allows control of the logging verbosity for
1760				the additional memory initialisation checks. A value
1761				of 0 disables mminit logging and a level of 4 will
1762				log everything. Information is printed at KERN_DEBUG
1763				so loglevel=8 may also need to be specified.
1764	
1765		module.sig_enforce
1766				[KNL] When CONFIG_MODULE_SIG is set, this means that
1767				modules without (valid) signatures will fail to load.
1768				Note that if CONFIG_MODULE_SIG_FORCE is set, that
1769				is always true, so this option does nothing.
1770	
1771		mousedev.tap_time=
1772				[MOUSE] Maximum time between finger touching and
1773				leaving touchpad surface for touch to be considered
1774				a tap and be reported as a left button click (for
1775				touchpads working in absolute mode only).
1776				Format: <msecs>
1777		mousedev.xres=	[MOUSE] Horizontal screen resolution, used for devices
1778				reporting absolute coordinates, such as tablets
1779		mousedev.yres=	[MOUSE] Vertical screen resolution, used for devices
1780				reporting absolute coordinates, such as tablets
1781	
1782		movablecore=nn[KMG]	[KNL,X86,IA-64,PPC] This parameter
1783				is similar to kernelcore except it specifies the
1784				amount of memory used for migratable allocations.
1785				If both kernelcore and movablecore is specified,
1786				then kernelcore will be at *least* the specified
1787				value but may be more. If movablecore on its own
1788				is specified, the administrator must be careful
1789				that the amount of memory usable for all allocations
1790				is not too small.
1791	
1792		movable_node	[KNL,X86] Boot-time switch to enable the effects
1793				of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.
1794	
1795		MTD_Partition=	[MTD]
1796				Format: <name>,<region-number>,<size>,<offset>
1797	
1798		MTD_Region=	[MTD] Format:
1799				<name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1800	
1801		mtdparts=	[MTD]
1802				See drivers/mtd/cmdlinepart.c.
1803	
1804		multitce=off	[PPC]  This parameter disables the use of the pSeries
1805				firmware feature for updating multiple TCE entries
1806				at a time.
1807	
1808		onenand.bdry=	[HW,MTD] Flex-OneNAND Boundary Configuration
1809	
1810				Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1811	
1812				boundary - index of last SLC block on Flex-OneNAND.
1813					   The remaining blocks are configured as MLC blocks.
1814				lock	 - Configure if Flex-OneNAND boundary should be locked.
1815					   Once locked, the boundary cannot be changed.
1816					   1 indicates lock status, 0 indicates unlock status.
1817	
1818		mtdset=		[ARM]
1819				ARM/S3C2412 JIVE boot control
1820	
1821				See arch/arm/mach-s3c2412/mach-jive.c
1822	
1823		mtouchusb.raw_coordinates=
1824				[HW] Make the MicroTouch USB driver use raw coordinates
1825				('y', default) or cooked coordinates ('n')
1826	
1827		mtrr_chunk_size=nn[KMG] [X86]
1828				used for mtrr cleanup. It is largest continuous chunk
1829				that could hold holes aka. UC entries.
1830	
1831		mtrr_gran_size=nn[KMG] [X86]
1832				Used for mtrr cleanup. It is granularity of mtrr block.
1833				Default is 1.
1834				Large value could prevent small alignment from
1835				using up MTRRs.
1836	
1837		mtrr_spare_reg_nr=n [X86]
1838				Format: <integer>
1839				Range: 0,7 : spare reg number
1840				Default : 1
1841				Used for mtrr cleanup. It is spare mtrr entries number.
1842				Set to 2 or more if your graphical card needs more.
1843	
1844		n2=		[NET] SDL Inc. RISCom/N2 synchronous serial card
1845	
1846		netdev=		[NET] Network devices parameters
1847				Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1848				Note that mem_start is often overloaded to mean
1849				something different and driver-specific.
1850				This usage is only documented in each driver source
1851				file if at all.
1852	
1853		nf_conntrack.acct=
1854				[NETFILTER] Enable connection tracking flow accounting
1855				0 to disable accounting
1856				1 to enable accounting
1857				Default value is 0.
1858	
1859		nfsaddrs=	[NFS] Deprecated.  Use ip= instead.
1860				See Documentation/filesystems/nfs/nfsroot.txt.
1861	
1862		nfsroot=	[NFS] nfs root filesystem for disk-less boxes.
1863				See Documentation/filesystems/nfs/nfsroot.txt.
1864	
1865		nfsrootdebug	[NFS] enable nfsroot debugging messages.
1866				See Documentation/filesystems/nfs/nfsroot.txt.
1867	
1868		nfs.callback_tcpport=
1869				[NFS] set the TCP port on which the NFSv4 callback
1870				channel should listen.
1871	
1872		nfs.cache_getent=
1873				[NFS] sets the pathname to the program which is used
1874				to update the NFS client cache entries.
1875	
1876		nfs.cache_getent_timeout=
1877				[NFS] sets the timeout after which an attempt to
1878				update a cache entry is deemed to have failed.
1879	
1880		nfs.idmap_cache_timeout=
1881				[NFS] set the maximum lifetime for idmapper cache
1882				entries.
1883	
1884		nfs.enable_ino64=
1885				[NFS] enable 64-bit inode numbers.
1886				If zero, the NFS client will fake up a 32-bit inode
1887				number for the readdir() and stat() syscalls instead
1888				of returning the full 64-bit number.
1889				The default is to return 64-bit inode numbers.
1890	
1891		nfs.max_session_slots=
1892				[NFSv4.1] Sets the maximum number of session slots
1893				the client will attempt to negotiate with the server.
1894				This limits the number of simultaneous RPC requests
1895				that the client can send to the NFSv4.1 server.
1896				Note that there is little point in setting this
1897				value higher than the max_tcp_slot_table_limit.
1898	
1899		nfs.nfs4_disable_idmapping=
1900				[NFSv4] When set to the default of '1', this option
1901				ensures that both the RPC level authentication
1902				scheme and the NFS level operations agree to use
1903				numeric uids/gids if the mount is using the
1904				'sec=sys' security flavour. In effect it is
1905				disabling idmapping, which can make migration from
1906				legacy NFSv2/v3 systems to NFSv4 easier.
1907				Servers that do not support this mode of operation
1908				will be autodetected by the client, and it will fall
1909				back to using the idmapper.
1910				To turn off this behaviour, set the value to '0'.
1911		nfs.nfs4_unique_id=
1912				[NFS4] Specify an additional fixed unique ident-
1913				ification string that NFSv4 clients can insert into
1914				their nfs_client_id4 string.  This is typically a
1915				UUID that is generated at system install time.
1916	
1917		nfs.send_implementation_id =
1918				[NFSv4.1] Send client implementation identification
1919				information in exchange_id requests.
1920				If zero, no implementation identification information
1921				will be sent.
1922				The default is to send the implementation identification
1923				information.
1924		
1925		nfs.recover_lost_locks =
1926				[NFSv4] Attempt to recover locks that were lost due
1927				to a lease timeout on the server. Please note that
1928				doing this risks data corruption, since there are
1929				no guarantees that the file will remain unchanged
1930				after the locks are lost.
1931				If you want to enable the kernel legacy behaviour of
1932				attempting to recover these locks, then set this
1933				parameter to '1'.
1934				The default parameter value of '0' causes the kernel
1935				not to attempt recovery of lost locks.
1936	
1937		nfsd.nfs4_disable_idmapping=
1938				[NFSv4] When set to the default of '1', the NFSv4
1939				server will return only numeric uids and gids to
1940				clients using auth_sys, and will accept numeric uids
1941				and gids from such clients.  This is intended to ease
1942				migration from NFSv2/v3.
1943	
1944		objlayoutdriver.osd_login_prog=
1945				[NFS] [OBJLAYOUT] sets the pathname to the program which
1946				is used to automatically discover and login into new
1947				osd-targets. Please see:
1948				Documentation/filesystems/pnfs.txt for more explanations
1949	
1950		nmi_debug=	[KNL,AVR32,SH] Specify one or more actions to take
1951				when a NMI is triggered.
1952				Format: [state][,regs][,debounce][,die]
1953	
1954		nmi_watchdog=	[KNL,BUGS=X86] Debugging features for SMP kernels
1955				Format: [panic,][nopanic,][num]
1956				Valid num: 0
1957				0 - turn nmi_watchdog off
1958				When panic is specified, panic when an NMI watchdog
1959				timeout occurs (or 'nopanic' to override the opposite
1960				default).
1961				This is useful when you use a panic=... timeout and
1962				need the box quickly up again.
1963	
1964		netpoll.carrier_timeout=
1965				[NET] Specifies amount of time (in seconds) that
1966				netpoll should wait for a carrier. By default netpoll
1967				waits 4 seconds.
1968	
1969		no387		[BUGS=X86-32] Tells the kernel to use the 387 maths
1970				emulation library even if a 387 maths coprocessor
1971				is present.
1972	
1973		no_console_suspend
1974				[HW] Never suspend the console
1975				Disable suspending of consoles during suspend and
1976				hibernate operations.  Once disabled, debugging
1977				messages can reach various consoles while the rest
1978				of the system is being put to sleep (ie, while
1979				debugging driver suspend/resume hooks).  This may
1980				not work reliably with all consoles, but is known
1981				to work with serial and VGA consoles.
1982				To facilitate more flexible debugging, we also add
1983				console_suspend, a printk module parameter to control
1984				it. Users could use console_suspend (usually
1985				/sys/module/printk/parameters/console_suspend) to
1986				turn on/off it dynamically.
1987	
1988		noaliencache	[MM, NUMA, SLAB] Disables the allocation of alien
1989				caches in the slab allocator.  Saves per-node memory,
1990				but will impact performance.
1991	
1992		noalign		[KNL,ARM]
1993	
1994		noapic		[SMP,APIC] Tells the kernel to not make use of any
1995				IOAPICs that may be present in the system.
1996	
1997		noautogroup	Disable scheduler automatic task group creation.
1998	
1999		nobats		[PPC] Do not use BATs for mapping kernel lowmem
2000				on "Classic" PPC cores.
2001	
2002		nocache		[ARM]
2003	
2004		noclflush	[BUGS=X86] Don't use the CLFLUSH instruction
2005	
2006		nodelayacct	[KNL] Disable per-task delay accounting
2007	
2008		nodisconnect	[HW,SCSI,M68K] Disables SCSI disconnects.
2009	
2010		nodsp		[SH] Disable hardware DSP at boot time.
2011	
2012		noefi		[X86] Disable EFI runtime services support.
2013	
2014		noexec		[IA-64]
2015	
2016		noexec		[X86]
2017				On X86-32 available only on PAE configured kernels.
2018				noexec=on: enable non-executable mappings (default)
2019				noexec=off: disable non-executable mappings
2020	
2021		nosmap		[X86]
2022				Disable SMAP (Supervisor Mode Access Prevention)
2023				even if it is supported by processor.
2024	
2025		nosmep		[X86]
2026				Disable SMEP (Supervisor Mode Execution Prevention)
2027				even if it is supported by processor.
2028	
2029		noexec32	[X86-64]
2030				This affects only 32-bit executables.
2031				noexec32=on: enable non-executable mappings (default)
2032					read doesn't imply executable mappings
2033				noexec32=off: disable non-executable mappings
2034					read implies executable mappings
2035	
2036		nofpu		[SH] Disable hardware FPU at boot time.
2037	
2038		nofxsr		[BUGS=X86-32] Disables x86 floating point extended
2039				register save and restore. The kernel will only save
2040				legacy floating-point registers on task switch.
2041	
2042		noxsave		[BUGS=X86] Disables x86 extended register state save
2043				and restore using xsave. The kernel will fallback to
2044				enabling legacy floating-point and sse state.
2045	
2046		eagerfpu=	[X86]
2047				on	enable eager fpu restore
2048				off	disable eager fpu restore
2049				auto	selects the default scheme, which automatically
2050					enables eagerfpu restore for xsaveopt.
2051	
2052		nohlt		[BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
2053				wfi(ARM) instruction doesn't work correctly and not to
2054				use it. This is also useful when using JTAG debugger.
2055	
2056		no_file_caps	Tells the kernel not to honor file capabilities.  The
2057				only way then for a file to be executed with privilege
2058				is to be setuid root or executed by root.
2059	
2060		nohalt		[IA-64] Tells the kernel not to use the power saving
2061				function PAL_HALT_LIGHT when idle. This increases
2062				power-consumption. On the positive side, it reduces
2063				interrupt wake-up latency, which may improve performance
2064				in certain environments such as networked servers or
2065				real-time systems.
2066	
2067		nohz=		[KNL] Boottime enable/disable dynamic ticks
2068				Valid arguments: on, off
2069				Default: on
2070	
2071		nohz_full=	[KNL,BOOT]
2072				In kernels built with CONFIG_NO_HZ_FULL=y, set
2073				the specified list of CPUs whose tick will be stopped
2074				whenever possible. The boot CPU will be forced outside
2075				the range to maintain the timekeeping.
2076				The CPUs in this range must also be included in the
2077				rcu_nocbs= set.
2078	
2079		noiotrap	[SH] Disables trapped I/O port accesses.
2080	
2081		noirqdebug	[X86-32] Disables the code which attempts to detect and
2082				disable unhandled interrupt sources.
2083	
2084		no_timer_check	[X86,APIC] Disables the code which tests for
2085				broken timer IRQ sources.
2086	
2087		noisapnp	[ISAPNP] Disables ISA PnP code.
2088	
2089		noinitrd	[RAM] Tells the kernel not to load any configured
2090				initial RAM disk.
2091	
2092		nointremap	[X86-64, Intel-IOMMU] Do not enable interrupt
2093				remapping.
2094				[Deprecated - use intremap=off]
2095	
2096		nointroute	[IA-64]
2097	
2098		nojitter	[IA-64] Disables jitter checking for ITC timers.
2099	
2100		no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
2101	
2102		no-kvmapf	[X86,KVM] Disable paravirtualized asynchronous page
2103				fault handling.
2104	
2105		no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
2106				steal time is computed, but won't influence scheduler
2107				behaviour
2108	
2109		nolapic		[X86-32,APIC] Do not enable or use the local APIC.
2110	
2111		nolapic_timer	[X86-32,APIC] Do not use the local APIC timer.
2112	
2113		noltlbs		[PPC] Do not use large page/tlb entries for kernel
2114				lowmem mapping on PPC40x.
2115	
2116		nomca		[IA-64] Disable machine check abort handling
2117	
2118		nomce		[X86-32] Machine Check Exception
2119	
2120		nomfgpt		[X86-32] Disable Multi-Function General Purpose
2121				Timer usage (for AMD Geode machines).
2122	
2123		nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
2124				shutdown the other cpus.  Instead use the REBOOT_VECTOR
2125				irq.
2126	
2127		nomodule	Disable module load
2128	
2129		nopat		[X86] Disable PAT (page attribute table extension of
2130				pagetables) support.
2131	
2132		norandmaps	Don't use address space randomization.  Equivalent to
2133				echo 0 > /proc/sys/kernel/randomize_va_space
2134	
2135		noreplace-paravirt	[X86,IA-64,PV_OPS] Don't patch paravirt_ops
2136	
2137		noreplace-smp	[X86-32,SMP] Don't replace SMP instructions
2138				with UP alternatives
2139	
2140		nordrand	[X86] Disable the direct use of the RDRAND
2141				instruction even if it is supported by the
2142				processor.  RDRAND is still available to user
2143				space applications.
2144	
2145		noresume	[SWSUSP] Disables resume and restores original swap
2146				space.
2147	
2148		no-scroll	[VGA] Disables scrollback.
2149				This is required for the Braillex ib80-piezo Braille
2150				reader made by F.H. Papenmeier (Germany).
2151	
2152		nosbagart	[IA-64]
2153	
2154		nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
2155	
2156		nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
2157				and disable the IO APIC.  legacy for "maxcpus=0".
2158	
2159		nosoftlockup	[KNL] Disable the soft-lockup detector.
2160	
2161		nosync		[HW,M68K] Disables sync negotiation for all devices.
2162	
2163		notsc		[BUGS=X86-32] Disable Time Stamp Counter
2164	
2165		nousb		[USB] Disable the USB subsystem
2166	
2167		nowatchdog	[KNL] Disable the lockup detector (NMI watchdog).
2168	
2169		nowb		[ARM]
2170	
2171		nox2apic	[X86-64,APIC] Do not enable x2APIC mode.
2172	
2173		cpu0_hotplug	[X86] Turn on CPU0 hotplug feature when
2174				CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
2175				Some features depend on CPU0. Known dependencies are:
2176				1. Resume from suspend/hibernate depends on CPU0.
2177				Suspend/hibernate will fail if CPU0 is offline and you
2178				need to online CPU0 before suspend/hibernate.
2179				2. PIC interrupts also depend on CPU0. CPU0 can't be
2180				removed if a PIC interrupt is detected.
2181				It's said poweroff/reboot may depend on CPU0 on some
2182				machines although I haven't seen such issues so far
2183				after CPU0 is offline on a few tested machines.
2184				If the dependencies are under your control, you can
2185				turn on cpu0_hotplug.
2186	
2187		nptcg=		[IA-64] Override max number of concurrent global TLB
2188				purges which is reported from either PAL_VM_SUMMARY or
2189				SAL PALO.
2190	
2191		nr_cpus=	[SMP] Maximum number of processors that	an SMP kernel
2192				could support.  nr_cpus=n : n >= 1 limits the kernel to
2193				supporting 'n' processors. Later in runtime you can not
2194				use hotplug cpu feature to put more cpu back to online.
2195				just like you compile the kernel NR_CPUS=n
2196	
2197		nr_uarts=	[SERIAL] maximum number of UARTs to be registered.
2198	
2199		numa_balancing=	[KNL,X86] Enable or disable automatic NUMA balancing.
2200				Allowed values are enable and disable
2201	
2202		numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
2203				one of ['zone', 'node', 'default'] can be specified
2204				This can be set from sysctl after boot.
2205				See Documentation/sysctl/vm.txt for details.
2206	
2207		ohci1394_dma=early	[HW] enable debugging via the ohci1394 driver.
2208				See Documentation/debugging-via-ohci1394.txt for more
2209				info.
2210	
2211		olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
2212				Rather than timing out after 20 ms if an EC
2213				command is not properly ACKed, override the length
2214				of the timeout.  We have interrupts disabled while
2215				waiting for the ACK, so if this is set too high
2216				interrupts *may* be lost!
2217	
2218		omap_mux=	[OMAP] Override bootloader pin multiplexing.
2219				Format: <mux_mode0.mode_name=value>...
2220				For example, to override I2C bus2:
2221				omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
2222	
2223		oprofile.timer=	[HW]
2224				Use timer interrupt instead of performance counters
2225	
2226		oprofile.cpu_type=	Force an oprofile cpu type
2227				This might be useful if you have an older oprofile
2228				userland or if you want common events.
2229				Format: { arch_perfmon }
2230				arch_perfmon: [X86] Force use of architectural
2231					perfmon on Intel CPUs instead of the
2232					CPU specific event set.
2233				timer: [X86] Force use of architectural NMI
2234					timer mode (see also oprofile.timer
2235					for generic hr timer mode)
2236					[s390] Force legacy basic mode sampling
2237	                                (report cpu_type "timer")
2238	
2239		oops=panic	Always panic on oopses. Default is to just kill the
2240				process, but there is a small probability of
2241				deadlocking the machine.
2242				This will also cause panics on machine check exceptions.
2243				Useful together with panic=30 to trigger a reboot.
2244	
2245		OSS		[HW,OSS]
2246				See Documentation/sound/oss/oss-parameters.txt
2247	
2248		panic=		[KNL] Kernel behaviour on panic: delay <timeout>
2249				timeout > 0: seconds before rebooting
2250				timeout = 0: wait forever
2251				timeout < 0: reboot immediately
2252				Format: <timeout>
2253	
2254		parkbd.port=	[HW] Parallel port number the keyboard adapter is
2255				connected to, default is 0.
2256				Format: <parport#>
2257		parkbd.mode=	[HW] Parallel port keyboard adapter mode of operation,
2258				0 for XT, 1 for AT (default is AT).
2259				Format: <mode>
2260	
2261		parport=	[HW,PPT] Specify parallel ports. 0 disables.
2262				Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2263				Use 'auto' to force the driver to use any
2264				IRQ/DMA settings detected (the default is to
2265				ignore detected IRQ/DMA settings because of
2266				possible conflicts). You can specify the base
2267				address, IRQ, and DMA settings; IRQ and DMA
2268				should be numbers, or 'auto' (for using detected
2269				settings on that particular port), or 'nofifo'
2270				(to avoid using a FIFO even if it is detected).
2271				Parallel ports are assigned in the order they
2272				are specified on the command line, starting
2273				with parport0.
2274	
2275		parport_init_mode=	[HW,PPT]
2276				Configure VIA parallel port to operate in
2277				a specific mode. This is necessary on Pegasos
2278				computer where firmware has no options for setting
2279				up parallel port mode and sets it to spp.
2280				Currently this function knows 686a and 8231 chips.
2281				Format: [spp|ps2|epp|ecp|ecpepp]
2282	
2283		pause_on_oops=
2284				Halt all CPUs after the first oops has been printed for
2285				the specified number of seconds.  This is to be used if
2286				your oopses keep scrolling off the screen.
2287	
2288		pcbit=		[HW,ISDN]
2289	
2290		pcd.		[PARIDE]
2291				See header of drivers/block/paride/pcd.c.
2292				See also Documentation/blockdev/paride.txt.
2293	
2294		pci=option[,option...]	[PCI] various PCI subsystem options:
2295			earlydump	[X86] dump PCI config space before the kernel
2296				        changes anything
2297			off		[X86] don't probe for the PCI bus
2298			bios		[X86-32] force use of PCI BIOS, don't access
2299					the hardware directly. Use this if your machine
2300					has a non-standard PCI host bridge.
2301			nobios		[X86-32] disallow use of PCI BIOS, only direct
2302					hardware access methods are allowed. Use this
2303					if you experience crashes upon bootup and you
2304					suspect they are caused by the BIOS.
2305			conf1		[X86] Force use of PCI Configuration
2306					Mechanism 1.
2307			conf2		[X86] Force use of PCI Configuration
2308					Mechanism 2.
2309			noaer		[PCIE] If the PCIEAER kernel config parameter is
2310					enabled, this kernel boot option can be used to
2311					disable the use of PCIE advanced error reporting.
2312			nodomains	[PCI] Disable support for multiple PCI
2313					root domains (aka PCI segments, in ACPI-speak).
2314			nommconf	[X86] Disable use of MMCONFIG for PCI
2315					Configuration
2316			check_enable_amd_mmconf [X86] check for and enable
2317					properly configured MMIO access to PCI
2318					config space on AMD family 10h CPU
2319			nomsi		[MSI] If the PCI_MSI kernel config parameter is
2320					enabled, this kernel boot option can be used to
2321					disable the use of MSI interrupts system-wide.
2322			noioapicquirk	[APIC] Disable all boot interrupt quirks.
2323					Safety option to keep boot IRQs enabled. This
2324					should never be necessary.
2325			ioapicreroute	[APIC] Enable rerouting of boot IRQs to the
2326					primary IO-APIC for bridges that cannot disable
2327					boot IRQs. This fixes a source of spurious IRQs
2328					when the system masks IRQs.
2329			noioapicreroute	[APIC] Disable workaround that uses the
2330					boot IRQ equivalent of an IRQ that connects to
2331					a chipset where boot IRQs cannot be disabled.
2332					The opposite of ioapicreroute.
2333			biosirq		[X86-32] Use PCI BIOS calls to get the interrupt
2334					routing table. These calls are known to be buggy
2335					on several machines and they hang the machine
2336					when used, but on other computers it's the only
2337					way to get the interrupt routing table. Try
2338					this option if the kernel is unable to allocate
2339					IRQs or discover secondary PCI buses on your
2340					motherboard.
2341			rom		[X86] Assign address space to expansion ROMs.
2342					Use with caution as certain devices share
2343					address decoders between ROMs and other
2344					resources.
2345			norom		[X86] Do not assign address space to
2346					expansion ROMs that do not already have
2347					BIOS assigned address ranges.
2348			nobar		[X86] Do not assign address space to the
2349					BARs that weren't assigned by the BIOS.
2350			irqmask=0xMMMM	[X86] Set a bit mask of IRQs allowed to be
2351					assigned automatically to PCI devices. You can
2352					make the kernel exclude IRQs of your ISA cards
2353					this way.
2354			pirqaddr=0xAAAAA	[X86] Specify the physical address
2355					of the PIRQ table (normally generated
2356					by the BIOS) if it is outside the
2357					F0000h-100000h range.
2358			lastbus=N	[X86] Scan all buses thru bus #N. Can be
2359					useful if the kernel is unable to find your
2360					secondary buses and you want to tell it
2361					explicitly which ones they are.
2362			assign-busses	[X86] Always assign all PCI bus
2363					numbers ourselves, overriding
2364					whatever the firmware may have done.
2365			usepirqmask	[X86] Honor the possible IRQ mask stored
2366					in the BIOS $PIR table. This is needed on
2367					some systems with broken BIOSes, notably
2368					some HP Pavilion N5400 and Omnibook XE3
2369					notebooks. This will have no effect if ACPI
2370					IRQ routing is enabled.
2371			noacpi		[X86] Do not use ACPI for IRQ routing
2372					or for PCI scanning.
2373			use_crs		[X86] Use PCI host bridge window information
2374					from ACPI.  On BIOSes from 2008 or later, this
2375					is enabled by default.  If you need to use this,
2376					please report a bug.
2377			nocrs		[X86] Ignore PCI host bridge windows from ACPI.
2378				        If you need to use this, please report a bug.
2379			routeirq	Do IRQ routing for all PCI devices.
2380					This is normally done in pci_enable_device(),
2381					so this option is a temporary workaround
2382					for broken drivers that don't call it.
2383			skip_isa_align	[X86] do not align io start addr, so can
2384					handle more pci cards
2385			firmware	[ARM] Do not re-enumerate the bus but instead
2386					just use the configuration from the
2387					bootloader. This is currently used on
2388					IXP2000 systems where the bus has to be
2389					configured a certain way for adjunct CPUs.
2390			noearly		[X86] Don't do any early type 1 scanning.
2391					This might help on some broken boards which
2392					machine check when some devices' config space
2393					is read. But various workarounds are disabled
2394					and some IOMMU drivers will not work.
2395			bfsort		Sort PCI devices into breadth-first order.
2396					This sorting is done to get a device
2397					order compatible with older (<= 2.4) kernels.
2398			nobfsort	Don't sort PCI devices into breadth-first order.
2399			pcie_bus_tune_off	Disable PCIe MPS (Max Payload Size)
2400					tuning and use the BIOS-configured MPS defaults.
2401			pcie_bus_safe	Set every device's MPS to the largest value
2402					supported by all devices below the root complex.
2403			pcie_bus_perf	Set device MPS to the largest allowable MPS
2404					based on its parent bus. Also set MRRS (Max
2405					Read Request Size) to the largest supported
2406					value (no larger than the MPS that the device
2407					or bus can support) for best performance.
2408			pcie_bus_peer2peer	Set every device's MPS to 128B, which
2409					every device is guaranteed to support. This
2410					configuration allows peer-to-peer DMA between
2411					any pair of devices, possibly at the cost of
2412					reduced performance.  This also guarantees
2413					that hot-added devices will work.
2414			cbiosize=nn[KMG]	The fixed amount of bus space which is
2415					reserved for the CardBus bridge's IO window.
2416					The default value is 256 bytes.
2417			cbmemsize=nn[KMG]	The fixed amount of bus space which is
2418					reserved for the CardBus bridge's memory
2419					window. The default value is 64 megabytes.
2420			resource_alignment=
2421					Format:
2422					[<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2423					Specifies alignment and device to reassign
2424					aligned memory resources.
2425					If <order of align> is not specified,
2426					PAGE_SIZE is used as alignment.
2427					PCI-PCI bridge can be specified, if resource
2428					windows need to be expanded.
2429			ecrc=		Enable/disable PCIe ECRC (transaction layer
2430					end-to-end CRC checking).
2431					bios: Use BIOS/firmware settings. This is the
2432					the default.
2433					off: Turn ECRC off
2434					on: Turn ECRC on.
2435			hpiosize=nn[KMG]	The fixed amount of bus space which is
2436					reserved for hotplug bridge's IO window.
2437					Default size is 256 bytes.
2438			hpmemsize=nn[KMG]	The fixed amount of bus space which is
2439					reserved for hotplug bridge's memory window.
2440					Default size is 2 megabytes.
2441			realloc=	Enable/disable reallocating PCI bridge resources
2442					if allocations done by BIOS are too small to
2443					accommodate resources required by all child
2444					devices.
2445					off: Turn realloc off
2446					on: Turn realloc on
2447			realloc		same as realloc=on
2448			noari		do not use PCIe ARI.
2449			pcie_scan_all	Scan all possible PCIe devices.  Otherwise we
2450					only look for one device below a PCIe downstream
2451					port.
2452	
2453		pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power
2454				Management.
2455			off	Disable ASPM.
2456			force	Enable ASPM even on devices that claim not to support it.
2457				WARNING: Forcing ASPM on may cause system lockups.
2458	
2459		pcie_hp=	[PCIE] PCI Express Hotplug driver options:
2460			nomsi	Do not use MSI for PCI Express Native Hotplug (this
2461				makes all PCIe ports use INTx for hotplug services).
2462	
2463		pcie_ports=	[PCIE] PCIe ports handling:
2464			auto	Ask the BIOS whether or not to use native PCIe services
2465				associated with PCIe ports (PME, hot-plug, AER).  Use
2466				them only if that is allowed by the BIOS.
2467			native	Use native PCIe services associated with PCIe ports
2468				unconditionally.
2469			compat	Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2470				ports driver.
2471	
2472		pcie_pme=	[PCIE,PM] Native PCIe PME signaling options:
2473			nomsi	Do not use MSI for native PCIe PME signaling (this makes
2474				all PCIe root ports use INTx for all services).
2475	
2476		pcmv=		[HW,PCMCIA] BadgePAD 4
2477	
2478		pd.		[PARIDE]
2479				See Documentation/blockdev/paride.txt.
2480	
2481		pdcchassis=	[PARISC,HW] Disable/Enable PDC Chassis Status codes at
2482				boot time.
2483				Format: { 0 | 1 }
2484				See arch/parisc/kernel/pdc_chassis.c
2485	
2486		percpu_alloc=	Select which percpu first chunk allocator to use.
2487				Currently supported values are "embed" and "page".
2488				Archs may support subset or none of the	selections.
2489				See comments in mm/percpu.c for details on each
2490				allocator.  This parameter is primarily	for debugging
2491				and performance comparison.
2492	
2493		pf.		[PARIDE]
2494				See Documentation/blockdev/paride.txt.
2495	
2496		pg.		[PARIDE]
2497				See Documentation/blockdev/paride.txt.
2498	
2499		pirq=		[SMP,APIC] Manual mp-table setup
2500				See Documentation/x86/i386/IO-APIC.txt.
2501	
2502		plip=		[PPT,NET] Parallel port network link
2503				Format: { parport<nr> | timid | 0 }
2504				See also Documentation/parport.txt.
2505	
2506		pmtmr=		[X86] Manual setup of pmtmr I/O Port.
2507				Override pmtimer IOPort with a hex value.
2508				e.g. pmtmr=0x508
2509	
2510		pnp.debug=1	[PNP]
2511				Enable PNP debug messages (depends on the
2512				CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2513				via /sys/module/pnp/parameters/debug.  We always show
2514				current resource usage; turning this on also shows
2515				possible settings and some assignment information.
2516	
2517		pnpacpi=	[ACPI]
2518				{ off }
2519	
2520		pnpbios=	[ISAPNP]
2521				{ on | off | curr | res | no-curr | no-res }
2522	
2523		pnp_reserve_irq=
2524				[ISAPNP] Exclude IRQs for the autoconfiguration
2525	
2526		pnp_reserve_dma=
2527				[ISAPNP] Exclude DMAs for the autoconfiguration
2528	
2529		pnp_reserve_io=	[ISAPNP] Exclude I/O ports for the autoconfiguration
2530				Ranges are in pairs (I/O port base and size).
2531	
2532		pnp_reserve_mem=
2533				[ISAPNP] Exclude memory regions for the
2534				autoconfiguration.
2535				Ranges are in pairs (memory base and size).
2536	
2537		ports=		[IP_VS_FTP] IPVS ftp helper module
2538				Default is 21.
2539				Up to 8 (IP_VS_APP_MAX_PORTS) ports
2540				may be specified.
2541				Format: <port>,<port>....
2542	
2543		print-fatal-signals=
2544				[KNL] debug: print fatal signals
2545	
2546				If enabled, warn about various signal handling
2547				related application anomalies: too many signals,
2548				too many POSIX.1 timers, fatal signals causing a
2549				coredump - etc.
2550	
2551				If you hit the warning due to signal overflow,
2552				you might want to try "ulimit -i unlimited".
2553	
2554				default: off.
2555	
2556		printk.always_kmsg_dump=
2557				Trigger kmsg_dump for cases other than kernel oops or
2558				panics
2559				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2560				default: disabled
2561	
2562		printk.time=	Show timing data prefixed to each printk message line
2563				Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2564	
2565		processor.max_cstate=	[HW,ACPI]
2566				Limit processor to maximum C-state
2567				max_cstate=9 overrides any DMI blacklist limit.
2568	
2569		processor.nocst	[HW,ACPI]
2570				Ignore the _CST method to determine C-states,
2571				instead using the legacy FADT method
2572	
2573		profile=	[KNL] Enable kernel profiling via /proc/profile
2574				Format: [schedule,]<number>
2575				Param: "schedule" - profile schedule points.
2576				Param: <number> - step/bucket size as a power of 2 for
2577					statistical time based profiling.
2578				Param: "sleep" - profile D-state sleeping (millisecs).
2579					Requires CONFIG_SCHEDSTATS
2580				Param: "kvm" - profile VM exits.
2581	
2582		prompt_ramdisk=	[RAM] List of RAM disks to prompt for floppy disk
2583				before loading.
2584				See Documentation/blockdev/ramdisk.txt.
2585	
2586		psmouse.proto=	[HW,MOUSE] Highest PS2 mouse protocol extension to
2587				probe for; one of (bare|imps|exps|lifebook|any).
2588		psmouse.rate=	[HW,MOUSE] Set desired mouse report rate, in reports
2589				per second.
2590		psmouse.resetafter=	[HW,MOUSE]
2591				Try to reset the device after so many bad packets
2592				(0 = never).
2593		psmouse.resolution=
2594				[HW,MOUSE] Set desired mouse resolution, in dpi.
2595		psmouse.smartscroll=
2596				[HW,MOUSE] Controls Logitech smartscroll autorepeat.
2597				0 = disabled, 1 = enabled (default).
2598	
2599		pstore.backend=	Specify the name of the pstore backend to use
2600	
2601		pt.		[PARIDE]
2602				See Documentation/blockdev/paride.txt.
2603	
2604		pty.legacy_count=
2605				[KNL] Number of legacy pty's. Overwrites compiled-in
2606				default number.
2607	
2608		quiet		[KNL] Disable most log messages
2609	
2610		r128=		[HW,DRM]
2611	
2612		raid=		[HW,RAID]
2613				See Documentation/md.txt.
2614	
2615		ramdisk_blocksize=	[RAM]
2616				See Documentation/blockdev/ramdisk.txt.
2617	
2618		ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
2619				See Documentation/blockdev/ramdisk.txt.
2620	
2621		rcu_nocbs=	[KNL]
2622				In kernels built with CONFIG_RCU_NOCB_CPU=y, set
2623				the specified list of CPUs to be no-callback CPUs.
2624				Invocation of these CPUs' RCU callbacks will
2625				be offloaded to "rcuox/N" kthreads created for
2626				that purpose, where "x" is "b" for RCU-bh, "p"
2627				for RCU-preempt, and "s" for RCU-sched, and "N"
2628				is the CPU number.  This reduces OS jitter on the
2629				offloaded CPUs, which can be useful for HPC and
2630	
2631				real-time workloads.  It can also improve energy
2632				efficiency for asymmetric multiprocessors.
2633	
2634		rcu_nocb_poll	[KNL]
2635				Rather than requiring that offloaded CPUs
2636				(specified by rcu_nocbs= above) explicitly
2637				awaken the corresponding "rcuoN" kthreads,
2638				make these kthreads poll for callbacks.
2639				This improves the real-time response for the
2640				offloaded CPUs by relieving them of the need to
2641				wake up the corresponding kthread, but degrades
2642				energy efficiency by requiring that the kthreads
2643				periodically wake up to do the polling.
2644	
2645		rcutree.blimit=	[KNL]
2646				Set maximum number of finished RCU callbacks to process
2647				in one batch.
2648	
2649		rcutree.rcu_fanout_leaf= [KNL]
2650				Increase the number of CPUs assigned to each
2651				leaf rcu_node structure.  Useful for very large
2652				systems.
2653	
2654		rcutree.jiffies_till_first_fqs= [KNL]
2655				Set delay from grace-period initialization to
2656				first attempt to force quiescent states.
2657				Units are jiffies, minimum value is zero,
2658				and maximum value is HZ.
2659	
2660		rcutree.jiffies_till_next_fqs= [KNL]
2661				Set delay between subsequent attempts to force
2662				quiescent states.  Units are jiffies, minimum
2663				value is one, and maximum value is HZ.
2664	
2665		rcutree.qhimark= [KNL]
2666				Set threshold of queued
2667				RCU callbacks over which batch limiting is disabled.
2668	
2669		rcutree.qlowmark= [KNL]
2670				Set threshold of queued RCU callbacks below which
2671				batch limiting is re-enabled.
2672	
2673		rcutree.rcu_idle_gp_delay= [KNL]
2674				Set wakeup interval for idle CPUs that have
2675				RCU callbacks (RCU_FAST_NO_HZ=y).
2676	
2677		rcutree.rcu_idle_lazy_gp_delay= [KNL]
2678				Set wakeup interval for idle CPUs that have
2679				only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
2680				Lazy RCU callbacks are those which RCU can
2681				prove do nothing more than free memory.
2682	
2683		rcutorture.fqs_duration= [KNL]
2684				Set duration of force_quiescent_state bursts.
2685	
2686		rcutorture.fqs_holdoff= [KNL]
2687				Set holdoff time within force_quiescent_state bursts.
2688	
2689		rcutorture.fqs_stutter= [KNL]
2690				Set wait time between force_quiescent_state bursts.
2691	
2692		rcutorture.gp_exp= [KNL]
2693				Use expedited update-side primitives.
2694	
2695		rcutorture.gp_normal= [KNL]
2696				Use normal (non-expedited) update-side primitives.
2697				If both gp_exp and gp_normal are set, do both.
2698				If neither gp_exp nor gp_normal are set, still
2699				do both.
2700	
2701		rcutorture.n_barrier_cbs= [KNL]
2702				Set callbacks/threads for rcu_barrier() testing.
2703	
2704		rcutorture.nfakewriters= [KNL]
2705				Set number of concurrent RCU writers.  These just
2706				stress RCU, they don't participate in the actual
2707				test, hence the "fake".
2708	
2709		rcutorture.nreaders= [KNL]
2710				Set number of RCU readers.
2711	
2712		rcutorture.object_debug= [KNL]
2713				Enable debug-object double-call_rcu() testing.
2714	
2715		rcutorture.onoff_holdoff= [KNL]
2716				Set time (s) after boot for CPU-hotplug testing.
2717	
2718		rcutorture.onoff_interval= [KNL]
2719				Set time (s) between CPU-hotplug operations, or
2720				zero to disable CPU-hotplug testing.
2721	
2722		rcutorture.rcutorture_runnable= [BOOT]
2723				Start rcutorture running at boot time.
2724	
2725		rcutorture.shuffle_interval= [KNL]
2726				Set task-shuffle interval (s).  Shuffling tasks
2727				allows some CPUs to go into dyntick-idle mode
2728				during the rcutorture test.
2729	
2730		rcutorture.shutdown_secs= [KNL]
2731				Set time (s) after boot system shutdown.  This
2732				is useful for hands-off automated testing.
2733	
2734		rcutorture.stall_cpu= [KNL]
2735				Duration of CPU stall (s) to test RCU CPU stall
2736				warnings, zero to disable.
2737	
2738		rcutorture.stall_cpu_holdoff= [KNL]
2739				Time to wait (s) after boot before inducing stall.
2740	
2741		rcutorture.stat_interval= [KNL]
2742				Time (s) between statistics printk()s.
2743	
2744		rcutorture.stutter= [KNL]
2745				Time (s) to stutter testing, for example, specifying
2746				five seconds causes the test to run for five seconds,
2747				wait for five seconds, and so on.  This tests RCU's
2748				ability to transition abruptly to and from idle.
2749	
2750		rcutorture.test_boost= [KNL]
2751				Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
2752				"Maybe" means test if the RCU implementation
2753				under test support RCU priority boosting.
2754	
2755		rcutorture.test_boost_duration= [KNL]
2756				Duration (s) of each individual boost test.
2757	
2758		rcutorture.test_boost_interval= [KNL]
2759				Interval (s) between each boost test.
2760	
2761		rcutorture.test_no_idle_hz= [KNL]
2762				Test RCU's dyntick-idle handling.  See also the
2763				rcutorture.shuffle_interval parameter.
2764	
2765		rcutorture.torture_type= [KNL]
2766				Specify the RCU implementation to test.
2767	
2768		rcutorture.verbose= [KNL]
2769				Enable additional printk() statements.
2770	
2771		rcupdate.rcu_expedited= [KNL]
2772				Use expedited grace-period primitives, for
2773				example, synchronize_rcu_expedited() instead
2774				of synchronize_rcu().  This reduces latency,
2775				but can increase CPU utilization, degrade
2776				real-time latency, and degrade energy efficiency.
2777	
2778		rcupdate.rcu_cpu_stall_suppress= [KNL]
2779				Suppress RCU CPU stall warning messages.
2780	
2781		rcupdate.rcu_cpu_stall_timeout= [KNL]
2782				Set timeout for RCU CPU stall warning messages.
2783	
2784		rdinit=		[KNL]
2785				Format: <full_path>
2786				Run specified binary instead of /init from the ramdisk,
2787				used for early userspace startup. See initrd.
2788	
2789		reboot=		[KNL]
2790				Format (x86 or x86_64):
2791					[w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
2792					[[,]s[mp]#### \
2793					[[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
2794					[[,]f[orce]
2795				Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
2796				      reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
2797				      reboot_force is either force or not specified,
2798				      reboot_cpu is s[mp]#### with #### being the processor
2799						to be used for rebooting.
2800	
2801		relax_domain_level=
2802				[KNL, SMP] Set scheduler's default relax_domain_level.
2803				See Documentation/cgroups/cpusets.txt.
2804	
2805		reserve=	[KNL,BUGS] Force the kernel to ignore some iomem area
2806	
2807		reservetop=	[X86-32]
2808				Format: nn[KMG]
2809				Reserves a hole at the top of the kernel virtual
2810				address space.
2811	
2812		reservelow=	[X86]
2813				Format: nn[K]
2814				Set the amount of memory to reserve for BIOS at
2815				the bottom of the address space.
2816	
2817		reset_devices	[KNL] Force drivers to reset the underlying device
2818				during initialization.
2819	
2820		resume=		[SWSUSP]
2821				Specify the partition device for software suspend
2822				Format:
2823				{/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2824	
2825		resume_offset=	[SWSUSP]
2826				Specify the offset from the beginning of the partition
2827				given by "resume=" at which the swap header is located,
2828				in <PAGE_SIZE> units (needed only for swap files).
2829				See  Documentation/power/swsusp-and-swap-files.txt
2830	
2831		resumedelay=	[HIBERNATION] Delay (in seconds) to pause before attempting to
2832				read the resume files
2833	
2834		resumewait	[HIBERNATION] Wait (indefinitely) for resume device to show up.
2835				Useful for devices that are detected asynchronously
2836				(e.g. USB and MMC devices).
2837	
2838		hibernate=	[HIBERNATION]
2839			noresume	Don't check if there's a hibernation image
2840					present during boot.
2841			nocompress	Don't compress/decompress hibernation images.
2842	
2843		retain_initrd	[RAM] Keep initrd memory after extraction
2844	
2845		rhash_entries=	[KNL,NET]
2846				Set number of hash buckets for route cache
2847	
2848		riscom8=	[HW,SERIAL]
2849				Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2850	
2851		ro		[KNL] Mount root device read-only on boot
2852	
2853		root=		[KNL] Root filesystem
2854				See name_to_dev_t comment in init/do_mounts.c.
2855	
2856		rootdelay=	[KNL] Delay (in seconds) to pause before attempting to
2857				mount the root filesystem
2858	
2859		rootflags=	[KNL] Set root filesystem mount option string
2860	
2861		rootfstype=	[KNL] Set root filesystem type
2862	
2863		rootwait	[KNL] Wait (indefinitely) for root device to show up.
2864				Useful for devices that are detected asynchronously
2865				(e.g. USB and MMC devices).
2866	
2867		rproc_mem=nn[KMG][@address]
2868				[KNL,ARM,CMA] Remoteproc physical memory block.
2869				Memory area to be used by remote processor image,
2870				managed by CMA.
2871	
2872		rw		[KNL] Mount root device read-write on boot
2873	
2874		S		[KNL] Run init in single mode
2875	
2876		sa1100ir	[NET]
2877				See drivers/net/irda/sa1100_ir.c.
2878	
2879		sbni=		[NET] Granch SBNI12 leased line adapter
2880	
2881		sched_debug	[KNL] Enables verbose scheduler debug messages.
2882	
2883		skew_tick=	[KNL] Offset the periodic timer tick per cpu to mitigate
2884				xtime_lock contention on larger systems, and/or RCU lock
2885				contention on all systems with CONFIG_MAXSMP set.
2886				Format: { "0" | "1" }
2887				0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2888				1 -- enable.
2889				Note: increases power consumption, thus should only be
2890				enabled if running jitter sensitive (HPC/RT) workloads.
2891	
2892		security=	[SECURITY] Choose a security module to enable at boot.
2893				If this boot parameter is not specified, only the first
2894				security module asking for security registration will be
2895				loaded. An invalid security module name will be treated
2896				as if no module has been chosen.
2897	
2898		selinux=	[SELINUX] Disable or enable SELinux at boot time.
2899				Format: { "0" | "1" }
2900				See security/selinux/Kconfig help text.
2901				0 -- disable.
2902				1 -- enable.
2903				Default value is set via kernel config option.
2904				If enabled at boot time, /selinux/disable can be used
2905				later to disable prior to initial policy load.
2906	
2907		apparmor=	[APPARMOR] Disable or enable AppArmor at boot time
2908				Format: { "0" | "1" }
2909				See security/apparmor/Kconfig help text
2910				0 -- disable.
2911				1 -- enable.
2912				Default value is set via kernel config option.
2913	
2914		serialnumber	[BUGS=X86-32]
2915	
2916		shapers=	[NET]
2917				Maximal number of shapers.
2918	
2919		show_msr=	[x86] show boot-time MSR settings
2920				Format: { <integer> }
2921				Show boot-time (BIOS-initialized) MSR settings.
2922				The parameter means the number of CPUs to show,
2923				for example 1 means boot CPU only.
2924	
2925		simeth=		[IA-64]
2926		simscsi=
2927	
2928		slram=		[HW,MTD]
2929	
2930		slab_max_order=	[MM, SLAB]
2931				Determines the maximum allowed order for slabs.
2932				A high setting may cause OOMs due to memory
2933				fragmentation.  Defaults to 1 for systems with
2934				more than 32MB of RAM, 0 otherwise.
2935	
2936		slub_debug[=options[,slabs]]	[MM, SLUB]
2937				Enabling slub_debug allows one to determine the
2938				culprit if slab objects become corrupted. Enabling
2939				slub_debug can create guard zones around objects and
2940				may poison objects when not in use. Also tracks the
2941				last alloc / free. For more information see
2942				Documentation/vm/slub.txt.
2943	
2944		slub_max_order= [MM, SLUB]
2945				Determines the maximum allowed order for slabs.
2946				A high setting may cause OOMs due to memory
2947				fragmentation. For more information see
2948				Documentation/vm/slub.txt.
2949	
2950		slub_min_objects=	[MM, SLUB]
2951				The minimum number of objects per slab. SLUB will
2952				increase the slab order up to slub_max_order to
2953				generate a sufficiently large slab able to contain
2954				the number of objects indicated. The higher the number
2955				of objects the smaller the overhead of tracking slabs
2956				and the less frequently locks need to be acquired.
2957				For more information see Documentation/vm/slub.txt.
2958	
2959		slub_min_order=	[MM, SLUB]
2960				Determines the minimum page order for slabs. Must be
2961				lower than slub_max_order.
2962				For more information see Documentation/vm/slub.txt.
2963	
2964		slub_nomerge	[MM, SLUB]
2965				Disable merging of slabs with similar size. May be
2966				necessary if there is some reason to distinguish
2967				allocs to different slabs. Debug options disable
2968				merging on their own.
2969				For more information see Documentation/vm/slub.txt.
2970	
2971		smart2=		[HW]
2972				Format: <io1>[,<io2>[,...,<io8>]]
2973	
2974		smsc-ircc2.nopnp	[HW] Don't use PNP to discover SMC devices
2975		smsc-ircc2.ircc_cfg=	[HW] Device configuration I/O port
2976		smsc-ircc2.ircc_sir=	[HW] SIR base I/O port
2977		smsc-ircc2.ircc_fir=	[HW] FIR base I/O port
2978		smsc-ircc2.ircc_irq=	[HW] IRQ line
2979		smsc-ircc2.ircc_dma=	[HW] DMA channel
2980		smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2981					0: Toshiba Satellite 1800 (GP data pin select)
2982					1: Fast pin select (default)
2983					2: ATC IRMode
2984	
2985		softlockup_panic=
2986				[KNL] Should the soft-lockup detector generate panics.
2987				Format: <integer>
2988	
2989		sonypi.*=	[HW] Sony Programmable I/O Control Device driver
2990				See Documentation/laptops/sonypi.txt
2991	
2992		specialix=	[HW,SERIAL] Specialix multi-serial port adapter
2993				See Documentation/serial/specialix.txt.
2994	
2995		spia_io_base=	[HW,MTD]
2996		spia_fio_base=
2997		spia_pedr=
2998		spia_peddr=
2999	
3000		stacktrace	[FTRACE]
3001				Enabled the stack tracer on boot up.
3002	
3003		stacktrace_filter=[function-list]
3004				[FTRACE] Limit the functions that the stack tracer
3005				will trace at boot up. function-list is a comma separated
3006				list of functions. This list can be changed at run
3007				time by the stack_trace_filter file in the debugfs
3008				tracing directory. Note, this enables stack tracing
3009				and the stacktrace above is not needed.
3010	
3011		sti=		[PARISC,HW]
3012				Format: <num>
3013				Set the STI (builtin display/keyboard on the HP-PARISC
3014				machines) console (graphic card) which should be used
3015				as the initial boot-console.
3016				See also comment in drivers/video/console/sticore.c.
3017	
3018		sti_font=	[HW]
3019				See comment in drivers/video/console/sticore.c.
3020	
3021		stifb=		[HW]
3022				Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
3023	
3024		sunrpc.min_resvport=
3025		sunrpc.max_resvport=
3026				[NFS,SUNRPC]
3027				SunRPC servers often require that client requests
3028				originate from a privileged port (i.e. a port in the
3029				range 0 < portnr < 1024).
3030				An administrator who wishes to reserve some of these
3031				ports for other uses may adjust the range that the
3032				kernel's sunrpc client considers to be privileged
3033				using these two parameters to set the minimum and
3034				maximum port values.
3035	
3036		sunrpc.pool_mode=
3037				[NFS]
3038				Control how the NFS server code allocates CPUs to
3039				service thread pools.  Depending on how many NICs
3040				you have and where their interrupts are bound, this
3041				option will affect which CPUs will do NFS serving.
3042				Note: this parameter cannot be changed while the
3043				NFS server is running.
3044	
3045				auto	    the server chooses an appropriate mode
3046					    automatically using heuristics
3047				global	    a single global pool contains all CPUs
3048				percpu	    one pool for each CPU
3049				pernode	    one pool for each NUMA node (equivalent
3050					    to global on non-NUMA machines)
3051	
3052		sunrpc.tcp_slot_table_entries=
3053		sunrpc.udp_slot_table_entries=
3054				[NFS,SUNRPC]
3055				Sets the upper limit on the number of simultaneous
3056				RPC calls that can be sent from the client to a
3057				server. Increasing these values may allow you to
3058				improve throughput, but will also increase the
3059				amount of memory reserved for use by the client.
3060	
3061		swapaccount=[0|1]
3062				[KNL] Enable accounting of swap in memory resource
3063				controller if no parameter or 1 is given or disable
3064				it if 0 is given (See Documentation/cgroups/memory.txt)
3065	
3066		swiotlb=	[IA-64] Number of I/O TLB slabs
3067	
3068		switches=	[HW,M68k]
3069	
3070		sysfs.deprecated=0|1 [KNL]
3071				Enable/disable old style sysfs layout for old udev
3072				on older distributions. When this option is enabled
3073				very new udev will not work anymore. When this option
3074				is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
3075				in older udev will not work anymore.
3076				Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
3077				the kernel configuration.
3078	
3079		sysrq_always_enabled
3080				[KNL]
3081				Ignore sysrq setting - this boot parameter will
3082				neutralize any effect of /proc/sys/kernel/sysrq.
3083				Useful for debugging.
3084	
3085		tdfx=		[HW,DRM]
3086	
3087		test_suspend=	[SUSPEND]
3088				Specify "mem" (for Suspend-to-RAM) or "standby" (for
3089				standby suspend) as the system sleep state to briefly
3090				enter during system startup.  The system is woken from
3091				this state using a wakeup-capable RTC alarm.
3092	
3093		thash_entries=	[KNL,NET]
3094				Set number of hash buckets for TCP connection
3095	
3096		thermal.act=	[HW,ACPI]
3097				-1: disable all active trip points in all thermal zones
3098				<degrees C>: override all lowest active trip points
3099	
3100		thermal.crt=	[HW,ACPI]
3101				-1: disable all critical trip points in all thermal zones
3102				<degrees C>: override all critical trip points
3103	
3104		thermal.nocrt=	[HW,ACPI]
3105				Set to disable actions on ACPI thermal zone
3106				critical and hot trip points.
3107	
3108		thermal.off=	[HW,ACPI]
3109				1: disable ACPI thermal control
3110	
3111		thermal.psv=	[HW,ACPI]
3112				-1: disable all passive trip points
3113				<degrees C>: override all passive trip points to this
3114				value
3115	
3116		thermal.tzp=	[HW,ACPI]
3117				Specify global default ACPI thermal zone polling rate
3118				<deci-seconds>: poll all this frequency
3119				0: no polling (default)
3120	
3121		threadirqs	[KNL]
3122				Force threading of all interrupt handlers except those
3123				marked explicitly IRQF_NO_THREAD.
3124	
3125		tmem		[KNL,XEN]
3126				Enable the Transcendent memory driver if built-in.
3127	
3128		tmem.cleancache=0|1 [KNL, XEN]
3129				Default is on (1). Disable the usage of the cleancache
3130				API to send anonymous pages to the hypervisor.
3131	
3132		tmem.frontswap=0|1 [KNL, XEN]
3133				Default is on (1). Disable the usage of the frontswap
3134				API to send swap pages to the hypervisor. If disabled
3135				the selfballooning and selfshrinking are force disabled.
3136	
3137		tmem.selfballooning=0|1 [KNL, XEN]
3138				Default is on (1). Disable the driving of swap pages
3139				to the hypervisor.
3140	
3141		tmem.selfshrinking=0|1 [KNL, XEN]
3142				Default is on (1). Partial swapoff that immediately
3143				transfers pages from Xen hypervisor back to the
3144				kernel based on different criteria.
3145	
3146		topology=	[S390]
3147				Format: {off | on}
3148				Specify if the kernel should make use of the cpu
3149				topology information if the hardware supports this.
3150				The scheduler will make use of this information and
3151				e.g. base its process migration decisions on it.
3152				Default is on.
3153	
3154		tp720=		[HW,PS2]
3155	
3156		tpm_suspend_pcr=[HW,TPM]
3157				Format: integer pcr id
3158				Specify that at suspend time, the tpm driver
3159				should extend the specified pcr with zeros,
3160				as a workaround for some chips which fail to
3161				flush the last written pcr on TPM_SaveState.
3162				This will guarantee that all the other pcrs
3163				are saved.
3164	
3165		trace_buf_size=nn[KMG]
3166				[FTRACE] will set tracing buffer size.
3167	
3168		trace_event=[event-list]
3169				[FTRACE] Set and start specified trace events in order
3170				to facilitate early boot debugging.
3171				See also Documentation/trace/events.txt
3172	
3173		trace_options=[option-list]
3174				[FTRACE] Enable or disable tracer options at boot.
3175				The option-list is a comma delimited list of options
3176				that can be enabled or disabled just as if you were
3177				to echo the option name into
3178	
3179				    /sys/kernel/debug/tracing/trace_options
3180	
3181				For example, to enable stacktrace option (to dump the
3182				stack trace of each event), add to the command line:
3183	
3184				      trace_options=stacktrace
3185	
3186				See also Documentation/trace/ftrace.txt "trace options"
3187				section.
3188	
3189		traceoff_on_warning
3190				[FTRACE] enable this option to disable tracing when a
3191				warning is hit. This turns off "tracing_on". Tracing can
3192				be enabled again by echoing '1' into the "tracing_on"
3193				file located in /sys/kernel/debug/tracing/
3194	
3195				This option is useful, as it disables the trace before
3196				the WARNING dump is called, which prevents the trace to
3197				be filled with content caused by the warning output.
3198	
3199				This option can also be set at run time via the sysctl
3200				option:  kernel/traceoff_on_warning
3201	
3202		transparent_hugepage=
3203				[KNL]
3204				Format: [always|madvise|never]
3205				Can be used to control the default behavior of the system
3206				with respect to transparent hugepages.
3207				See Documentation/vm/transhuge.txt for more details.
3208	
3209		tsc=		Disable clocksource stability checks for TSC.
3210				Format: <string>
3211				[x86] reliable: mark tsc clocksource as reliable, this
3212				disables clocksource verification at runtime, as well
3213				as the stability checks done at bootup.	Used to enable
3214				high-resolution timer mode on older hardware, and in
3215				virtualized environment.
3216				[x86] noirqtime: Do not use TSC to do irq accounting.
3217				Used to run time disable IRQ_TIME_ACCOUNTING on any
3218				platforms where RDTSC is slow and this accounting
3219				can add overhead.
3220	
3221		turbografx.map[2|3]=	[HW,JOY]
3222				TurboGraFX parallel port interface
3223				Format:
3224				<port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
3225				See also Documentation/input/joystick-parport.txt
3226	
3227		udbg-immortal	[PPC] When debugging early kernel crashes that
3228				happen after console_init() and before a proper 
3229				console driver takes over, this boot options might
3230				help "seeing" what's going on.
3231	
3232		uhash_entries=	[KNL,NET]
3233				Set number of hash buckets for UDP/UDP-Lite connections
3234	
3235		uhci-hcd.ignore_oc=
3236				[USB] Ignore overcurrent events (default N).
3237				Some badly-designed motherboards generate lots of
3238				bogus events, for ports that aren't wired to
3239				anything.  Set this parameter to avoid log spamming.
3240				Note that genuine overcurrent events won't be
3241				reported either.
3242	
3243		unknown_nmi_panic
3244				[X86] Cause panic on unknown NMI.
3245	
3246		usbcore.authorized_default=
3247				[USB] Default USB device authorization:
3248				(default -1 = authorized except for wireless USB,
3249				0 = not authorized, 1 = authorized)
3250	
3251		usbcore.autosuspend=
3252				[USB] The autosuspend time delay (in seconds) used
3253				for newly-detected USB devices (default 2).  This
3254				is the time required before an idle device will be
3255				autosuspended.  Devices for which the delay is set
3256				to a negative value won't be autosuspended at all.
3257	
3258		usbcore.usbfs_snoop=
3259				[USB] Set to log all usbfs traffic (default 0 = off).
3260	
3261		usbcore.blinkenlights=
3262				[USB] Set to cycle leds on hubs (default 0 = off).
3263	
3264		usbcore.old_scheme_first=
3265				[USB] Start with the old device initialization
3266				scheme (default 0 = off).
3267	
3268		usbcore.usbfs_memory_mb=
3269				[USB] Memory limit (in MB) for buffers allocated by
3270				usbfs (default = 16, 0 = max = 2047).
3271	
3272		usbcore.use_both_schemes=
3273				[USB] Try the other device initialization scheme
3274				if the first one fails (default 1 = enabled).
3275	
3276		usbcore.initial_descriptor_timeout=
3277				[USB] Specifies timeout for the initial 64-byte
3278	                        USB_REQ_GET_DESCRIPTOR request in milliseconds
3279				(default 5000 = 5.0 seconds).
3280	
3281		usbhid.mousepoll=
3282				[USBHID] The interval which mice are to be polled at.
3283	
3284		usb-storage.delay_use=
3285				[UMS] The delay in seconds before a new device is
3286				scanned for Logical Units (default 5).
3287	
3288		usb-storage.quirks=
3289				[UMS] A list of quirks entries to supplement or
3290				override the built-in unusual_devs list.  List
3291				entries are separated by commas.  Each entry has
3292				the form VID:PID:Flags where VID and PID are Vendor
3293				and Product ID values (4-digit hex numbers) and
3294				Flags is a set of characters, each corresponding
3295				to a common usb-storage quirk flag as follows:
3296					a = SANE_SENSE (collect more than 18 bytes
3297						of sense data);
3298					b = BAD_SENSE (don't collect more than 18
3299						bytes of sense data);
3300					c = FIX_CAPACITY (decrease the reported
3301						device capacity by one sector);
3302					d = NO_READ_DISC_INFO (don't use
3303						READ_DISC_INFO command);
3304					e = NO_READ_CAPACITY_16 (don't use
3305						READ_CAPACITY_16 command);
3306					h = CAPACITY_HEURISTICS (decrease the
3307						reported device capacity by one
3308						sector if the number is odd);
3309					i = IGNORE_DEVICE (don't bind to this
3310						device);
3311					l = NOT_LOCKABLE (don't try to lock and
3312						unlock ejectable media);
3313					m = MAX_SECTORS_64 (don't transfer more
3314						than 64 sectors = 32 KB at a time);
3315					n = INITIAL_READ10 (force a retry of the
3316						initial READ(10) command);
3317					o = CAPACITY_OK (accept the capacity
3318						reported by the device);
3319					p = WRITE_CACHE (the device cache is ON
3320						by default);
3321					r = IGNORE_RESIDUE (the device reports
3322						bogus residue values);
3323					s = SINGLE_LUN (the device has only one
3324						Logical Unit);
3325					w = NO_WP_DETECT (don't test whether the
3326						medium is write-protected).
3327				Example: quirks=0419:aaf5:rl,0421:0433:rc
3328	
3329		user_debug=	[KNL,ARM]
3330				Format: <int>
3331				See arch/arm/Kconfig.debug help text.
3332					 1 - undefined instruction events
3333					 2 - system calls
3334					 4 - invalid data aborts
3335					 8 - SIGSEGV faults
3336					16 - SIGBUS faults
3337				Example: user_debug=31
3338	
3339		userpte=
3340				[X86] Flags controlling user PTE allocations.
3341	
3342					nohigh = do not allocate PTE pages in
3343						HIGHMEM regardless of setting
3344						of CONFIG_HIGHPTE.
3345	
3346		vdso=		[X86,SH]
3347				vdso=2: enable compat VDSO (default with COMPAT_VDSO)
3348				vdso=1: enable VDSO (default)
3349				vdso=0: disable VDSO mapping
3350	
3351		vdso32=		[X86]
3352				vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
3353				vdso32=1: enable 32-bit VDSO (default)
3354				vdso32=0: disable 32-bit VDSO mapping
3355	
3356		vector=		[IA-64,SMP]
3357				vector=percpu: enable percpu vector domain
3358	
3359		video=		[FB] Frame buffer configuration
3360				See Documentation/fb/modedb.txt.
3361	
3362		video.brightness_switch_enabled= [0,1]
3363				If set to 1, on receiving an ACPI notify event
3364				generated by hotkey, video driver will adjust brightness
3365				level and then send out the event to user space through
3366				the allocated input device; If set to 0, video driver
3367				will only send out the event without touching backlight
3368				brightness level.
3369				default: 1
3370	
3371		virtio_mmio.device=
3372				[VMMIO] Memory mapped virtio (platform) device.
3373	
3374					<size>@<baseaddr>:<irq>[:<id>]
3375				where:
3376					<size>     := size (can use standard suffixes
3377							like K, M and G)
3378					<baseaddr> := physical base address
3379					<irq>      := interrupt number (as passed to
3380							request_irq())
3381					<id>       := (optional) platform device id
3382				example:
3383					virtio_mmio.device=1K@0x100b0000:48:7
3384	
3385				Can be used multiple times for multiple devices.
3386	
3387		vga=		[BOOT,X86-32] Select a particular video mode
3388				See Documentation/x86/boot.txt and
3389				Documentation/svga.txt.
3390				Use vga=ask for menu.
3391				This is actually a boot loader parameter; the value is
3392				passed to the kernel using a special protocol.
3393	
3394		vmalloc=nn[KMG]	[KNL,BOOT] Forces the vmalloc area to have an exact
3395				size of <nn>. This can be used to increase the
3396				minimum size (128MB on x86). It can also be used to
3397				decrease the size and leave more room for directly
3398				mapped kernel RAM.
3399	
3400		vmhalt=		[KNL,S390] Perform z/VM CP command after system halt.
3401				Format: <command>
3402	
3403		vmpanic=	[KNL,S390] Perform z/VM CP command after kernel panic.
3404				Format: <command>
3405	
3406		vmpoff=		[KNL,S390] Perform z/VM CP command after power off.
3407				Format: <command>
3408	
3409		vsyscall=	[X86-64]
3410				Controls the behavior of vsyscalls (i.e. calls to
3411				fixed addresses of 0xffffffffff600x00 from legacy
3412				code).  Most statically-linked binaries and older
3413				versions of glibc use these calls.  Because these
3414				functions are at fixed addresses, they make nice
3415				targets for exploits that can control RIP.
3416	
3417				emulate     [default] Vsyscalls turn into traps and are
3418				            emulated reasonably safely.
3419	
3420				native      Vsyscalls are native syscall instructions.
3421				            This is a little bit faster than trapping
3422				            and makes a few dynamic recompilers work
3423				            better than they would in emulation mode.
3424				            It also makes exploits much easier to write.
3425	
3426				none        Vsyscalls don't work at all.  This makes
3427				            them quite hard to use for exploits but
3428				            might break your system.
3429	
3430		vt.color=	[VT] Default text color.
3431				Format: 0xYX, X = foreground, Y = background.
3432				Default: 0x07 = light gray on black.
3433	
3434		vt.cur_default=	[VT] Default cursor shape.
3435				Format: 0xCCBBAA, where AA, BB, and CC are the same as
3436				the parameters of the <Esc>[?A;B;Cc escape sequence;
3437				see VGA-softcursor.txt. Default: 2 = underline.
3438	
3439		vt.default_blu=	[VT]
3440				Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3441				Change the default blue palette of the console.
3442				This is a 16-member array composed of values
3443				ranging from 0-255.
3444	
3445		vt.default_grn=	[VT]
3446				Format: <green0>,<green1>,<green2>,...,<green15>
3447				Change the default green palette of the console.
3448				This is a 16-member array composed of values
3449				ranging from 0-255.
3450	
3451		vt.default_red=	[VT]
3452				Format: <red0>,<red1>,<red2>,...,<red15>
3453				Change the default red palette of the console.
3454				This is a 16-member array composed of values
3455				ranging from 0-255.
3456	
3457		vt.default_utf8=
3458				[VT]
3459				Format=<0|1>
3460				Set system-wide default UTF-8 mode for all tty's.
3461				Default is 1, i.e. UTF-8 mode is enabled for all
3462				newly opened terminals.
3463	
3464		vt.global_cursor_default=
3465				[VT]
3466				Format=<-1|0|1>
3467				Set system-wide default for whether a cursor
3468				is shown on new VTs. Default is -1,
3469				i.e. cursors will be created by default unless
3470				overridden by individual drivers. 0 will hide
3471				cursors, 1 will display them.
3472	
3473		vt.italic=	[VT] Default color for italic text; 0-15.
3474				Default: 2 = green.
3475	
3476		vt.underline=	[VT] Default color for underlined text; 0-15.
3477				Default: 3 = cyan.
3478	
3479		watchdog timers	[HW,WDT] For information on watchdog timers,
3480				see Documentation/watchdog/watchdog-parameters.txt
3481				or other driver-specific files in the
3482				Documentation/watchdog/ directory.
3483	
3484		workqueue.disable_numa
3485				By default, all work items queued to unbound
3486				workqueues are affine to the NUMA nodes they're
3487				issued on, which results in better behavior in
3488				general.  If NUMA affinity needs to be disabled for
3489				whatever reason, this option can be used.  Note
3490				that this also can be controlled per-workqueue for
3491				workqueues visible under /sys/bus/workqueue/.
3492	
3493		workqueue.power_efficient
3494				Per-cpu workqueues are generally preferred because
3495				they show better performance thanks to cache
3496				locality; unfortunately, per-cpu workqueues tend to
3497				be more power hungry than unbound workqueues.
3498	
3499				Enabling this makes the per-cpu workqueues which
3500				were observed to contribute significantly to power
3501				consumption unbound, leading to measurably lower
3502				power usage at the cost of small performance
3503				overhead.
3504	
3505				The default value of this parameter is determined by
3506				the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
3507	
3508		x2apic_phys	[X86-64,APIC] Use x2apic physical mode instead of
3509				default x2apic cluster mode on platforms
3510				supporting x2apic.
3511	
3512		x86_intel_mid_timer= [X86-32,APBT]
3513				Choose timer option for x86 Intel MID platform.
3514				Two valid options are apbt timer only and lapic timer
3515				plus one apbt timer for broadcast timer.
3516				x86_intel_mid_timer=apbt_only | lapic_and_apbt
3517	
3518		xen_emul_unplug=		[HW,X86,XEN]
3519				Unplug Xen emulated devices
3520				Format: [unplug0,][unplug1]
3521				ide-disks -- unplug primary master IDE devices
3522				aux-ide-disks -- unplug non-primary-master IDE devices
3523				nics -- unplug network devices
3524				all -- unplug all emulated devices (NICs and IDE disks)
3525				unnecessary -- unplugging emulated devices is
3526					unnecessary even if the host did not respond to
3527					the unplug protocol
3528				never -- do not unplug even if version check succeeds
3529	
3530		xen_nopvspin	[X86,XEN]
3531				Disables the ticketlock slowpath using Xen PV
3532				optimizations.
3533	
3534		xirc2ps_cs=	[NET,PCMCIA]
3535				Format:
3536				<irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3537	
3538	______________________________________________________________________
3539	
3540	TODO:
3541	
3542		Add more DRM drivers.
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