linux/Documentation/kernel-parameters.txt
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   1                          Kernel Parameters
   2                          ~~~~~~~~~~~~~~~~~
   3
   4The 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
   7case insensitive manner), and with descriptions where known.
   8
   9Module parameters for loadable modules are specified only as the
  10parameter name with optional '=' and value as appropriate, such as:
  11
  12        modprobe usbcore blinkenlights=1
  13
  14Module parameters for modules that are built into the kernel image
  15are 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
  20Hyphens (dashes) and underscores are equivalent in parameter names, so
  21        log_buf_len=1M print-fatal-signals=1
  22can also be entered as
  23        log-buf-len=1M print_fatal_signals=1
  24
  25
  26This document may not be entirely up to date and comprehensive. The command
  27"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
  28module. Loadable modules, after being loaded into the running kernel, also
  29reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
  30parameters may be changed at runtime by the command
  31"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".
  32
  33The parameters listed below are only valid if certain kernel build options were
  34enabled and if respective hardware is present. The text in square brackets at
  35the beginning of each description states the restrictions within which a
  36parameter 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        DRM     Direct Rendering Management support is enabled.
  48        DYNAMIC_DEBUG Build in debug messages and enable them at runtime
  49        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
  50        EFI     EFI Partitioning (GPT) is enabled
  51        EIDE    EIDE/ATAPI support is enabled.
  52        EVM     Extended Verification Module
  53        FB      The frame buffer device is enabled.
  54        FTRACE  Function tracing enabled.
  55        GCOV    GCOV profiling is enabled.
  56        HW      Appropriate hardware is enabled.
  57        IA-64   IA-64 architecture is enabled.
  58        IMA     Integrity measurement architecture is enabled.
  59        IOSCHED More than one I/O scheduler is enabled.
  60        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
  61        IPV6    IPv6 support is enabled.
  62        ISAPNP  ISA PnP code is enabled.
  63        ISDN    Appropriate ISDN support is enabled.
  64        JOY     Appropriate joystick support is enabled.
  65        KGDB    Kernel debugger support is enabled.
  66        KVM     Kernel Virtual Machine support is enabled.
  67        LIBATA  Libata driver is enabled
  68        LP      Printer support is enabled.
  69        LOOP    Loopback device support is enabled.
  70        M68k    M68k architecture is enabled.
  71                        These options have more detailed description inside of
  72                        Documentation/m68k/kernel-options.txt.
  73        MDA     MDA console support is enabled.
  74        MIPS    MIPS architecture is enabled.
  75        MOUSE   Appropriate mouse support is enabled.
  76        MSI     Message Signaled Interrupts (PCI).
  77        MTD     MTD (Memory Technology Device) support is enabled.
  78        NET     Appropriate network support is enabled.
  79        NUMA    NUMA support is enabled.
  80        NFS     Appropriate NFS support is enabled.
  81        OSS     OSS sound support is enabled.
  82        PV_OPS  A paravirtualized kernel is enabled.
  83        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
  84        PARISC  The PA-RISC architecture is enabled.
  85        PCI     PCI bus support is enabled.
  86        PCIE    PCI Express support is enabled.
  87        PCMCIA  The PCMCIA subsystem is enabled.
  88        PNP     Plug & Play support is enabled.
  89        PPC     PowerPC architecture is enabled.
  90        PPT     Parallel port support is enabled.
  91        PS2     Appropriate PS/2 support is enabled.
  92        RAM     RAM disk support is enabled.
  93        S390    S390 architecture is enabled.
  94        SCSI    Appropriate SCSI support is enabled.
  95                        A lot of drivers have their options described inside
  96                        the Documentation/scsi/ sub-directory.
  97        SECURITY Different security models are enabled.
  98        SELINUX SELinux support is enabled.
  99        APPARMOR AppArmor support is enabled.
 100        SERIAL  Serial support is enabled.
 101        SH      SuperH architecture is enabled.
 102        SMP     The kernel is an SMP kernel.
 103        SPARC   Sparc architecture is enabled.
 104        SWSUSP  Software suspend (hibernation) is enabled.
 105        SUSPEND System suspend states are enabled.
 106        TPM     TPM drivers are enabled.
 107        TS      Appropriate touchscreen support is enabled.
 108        UMS     USB Mass Storage support is enabled.
 109        USB     USB support is enabled.
 110        USBHID  USB Human Interface Device support is enabled.
 111        V4L     Video For Linux support is enabled.
 112        VMMIO   Driver for memory mapped virtio devices is enabled.
 113        VGA     The VGA console has been enabled.
 114        VT      Virtual terminal support is enabled.
 115        WDT     Watchdog support is enabled.
 116        XT      IBM PC/XT MFM hard disk support is enabled.
 117        X86-32  X86-32, aka i386 architecture is enabled.
 118        X86-64  X86-64 architecture is enabled.
 119                        More X86-64 boot options can be found in
 120                        Documentation/x86/x86_64/boot-options.txt .
 121        X86     Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
 122        XEN     Xen support is enabled
 123
 124In addition, the following text indicates that the option:
 125
 126        BUGS=   Relates to possible processor bugs on the said processor.
 127        KNL     Is a kernel start-up parameter.
 128        BOOT    Is a boot loader parameter.
 129
 130Parameters denoted with BOOT are actually interpreted by the boot
 131loader, and have no meaning to the kernel directly.
 132Do not modify the syntax of boot loader parameters without extreme
 133need or coordination with <Documentation/x86/boot.txt>.
 134
 135There are also arch-specific kernel-parameters not documented here.
 136See for example <Documentation/x86/x86_64/boot-options.txt>.
 137
 138Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
 139a trailing = on the name of any parameter states that that parameter will
 140be entered as an environment variable, whereas its absence indicates that
 141it will appear as a kernel argument readable via /proc/cmdline by programs
 142running once the system is up.
 143
 144The number of kernel parameters is not limited, but the length of the
 145complete command line (parameters including spaces etc.) is limited to
 146a fixed number of characters. This limit depends on the architecture
 147and is between 256 and 4096 characters. It is defined in the file
 148./include/asm/setup.h as COMMAND_LINE_SIZE.
 149
 150Finally, the [KMG] suffix is commonly described after a number of kernel
 151parameter values. These 'K', 'M', and 'G' letters represent the _binary_
 152multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
 153bytes respectively. Such letter suffixes can also be entirely omitted.
 154
 155
 156        acpi=           [HW,ACPI,X86]
 157                        Advanced Configuration and Power Interface
 158                        Format: { force | off | strict | noirq | rsdt }
 159                        force -- enable ACPI if default was off
 160                        off -- disable ACPI if default was on
 161                        noirq -- do not use ACPI for IRQ routing
 162                        strict -- Be less tolerant of platforms that are not
 163                                strictly ACPI specification compliant.
 164                        rsdt -- prefer RSDT over (default) XSDT
 165                        copy_dsdt -- copy DSDT to memory
 166
 167                        See also Documentation/power/runtime_pm.txt, pci=noacpi
 168
 169        acpi_rsdp=      [ACPI,EFI,KEXEC]
 170                        Pass the RSDP address to the kernel, mostly used
 171                        on machines running EFI runtime service to boot the
 172                        second kernel for kdump.
 173
 174        acpi_apic_instance=     [ACPI, IOAPIC]
 175                        Format: <int>
 176                        2: use 2nd APIC table, if available
 177                        1,0: use 1st APIC table
 178                        default: 0
 179
 180        acpi_backlight= [HW,ACPI]
 181                        acpi_backlight=vendor
 182                        acpi_backlight=video
 183                        If set to vendor, prefer vendor specific driver
 184                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
 185                        of the ACPI video.ko driver.
 186
 187        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
 188        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
 189                        Format: <int>
 190                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
 191                        debug output.  Bits in debug_layer correspond to a
 192                        _COMPONENT in an ACPI source file, e.g.,
 193                            #define _COMPONENT ACPI_PCI_COMPONENT
 194                        Bits in debug_level correspond to a level in
 195                        ACPI_DEBUG_PRINT statements, e.g.,
 196                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
 197                        The debug_level mask defaults to "info".  See
 198                        Documentation/acpi/debug.txt for more information about
 199                        debug layers and levels.
 200
 201                        Enable processor driver info messages:
 202                            acpi.debug_layer=0x20000000
 203                        Enable PCI/PCI interrupt routing info messages:
 204                            acpi.debug_layer=0x400000
 205                        Enable AML "Debug" output, i.e., stores to the Debug
 206                        object while interpreting AML:
 207                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
 208                        Enable all messages related to ACPI hardware:
 209                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
 210
 211                        Some values produce so much output that the system is
 212                        unusable.  The "log_buf_len" parameter may be useful
 213                        if you need to capture more output.
 214
 215        acpi_irq_balance [HW,ACPI]
 216                        ACPI will balance active IRQs
 217                        default in APIC mode
 218
 219        acpi_irq_nobalance [HW,ACPI]
 220                        ACPI will not move active IRQs (default)
 221                        default in PIC mode
 222
 223        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
 224                        Format: <irq>,<irq>...
 225
 226        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
 227                        use by PCI
 228                        Format: <irq>,<irq>...
 229
 230        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT
 231
 232        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
 233                        Format: To spoof as Windows 98: ="Microsoft Windows"
 234
 235        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
 236                        acpi_osi="string1"      # add string1 -- only one string
 237                        acpi_osi="!string2"     # remove built-in string2
 238                        acpi_osi=               # disable all strings
 239
 240        acpi_pm_good    [X86]
 241                        Override the pmtimer bug detection: force the kernel
 242                        to assume that this machine's pmtimer latches its value
 243                        and always returns good values.
 244
 245        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
 246                        Format: { level | edge | high | low }
 247
 248        acpi_serialize  [HW,ACPI] force serialization of AML methods
 249
 250        acpi_skip_timer_override [HW,ACPI]
 251                        Recognize and ignore IRQ0/pin2 Interrupt Override.
 252                        For broken nForce2 BIOS resulting in XT-PIC timer.
 253
 254        acpi_sleep=     [HW,ACPI] Sleep options
 255                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
 256                                  old_ordering, nonvs, sci_force_enable }
 257                        See Documentation/power/video.txt for information on
 258                        s3_bios and s3_mode.
 259                        s3_beep is for debugging; it makes the PC's speaker beep
 260                        as soon as the kernel's real-mode entry point is called.
 261                        s4_nohwsig prevents ACPI hardware signature from being
 262                        used during resume from hibernation.
 263                        old_ordering causes the ACPI 1.0 ordering of the _PTS
 264                        control method, with respect to putting devices into
 265                        low power states, to be enforced (the ACPI 2.0 ordering
 266                        of _PTS is used by default).
 267                        nonvs prevents the kernel from saving/restoring the
 268                        ACPI NVS memory during suspend/hibernation and resume.
 269                        sci_force_enable causes the kernel to set SCI_EN directly
 270                        on resume from S1/S3 (which is against the ACPI spec,
 271                        but some broken systems don't work without it).
 272
 273        acpi_use_timer_override [HW,ACPI]
 274                        Use timer override. For some broken Nvidia NF5 boards
 275                        that require a timer override, but don't have HPET
 276
 277        acpi_enforce_resources= [ACPI]
 278                        { strict | lax | no }
 279                        Check for resource conflicts between native drivers
 280                        and ACPI OperationRegions (SystemIO and SystemMemory
 281                        only). IO ports and memory declared in ACPI might be
 282                        used by the ACPI subsystem in arbitrary AML code and
 283                        can interfere with legacy drivers.
 284                        strict (default): access to resources claimed by ACPI
 285                        is denied; legacy drivers trying to access reserved
 286                        resources will fail to bind to device using them.
 287                        lax: access to resources claimed by ACPI is allowed;
 288                        legacy drivers trying to access reserved resources
 289                        will bind successfully but a warning message is logged.
 290                        no: ACPI OperationRegions are not marked as reserved,
 291                        no further checks are performed.
 292
 293        add_efi_memmap  [EFI; X86] Include EFI memory map in
 294                        kernel's map of available physical RAM.
 295
 296        agp=            [AGP]
 297                        { off | try_unsupported }
 298                        off: disable AGP support
 299                        try_unsupported: try to drive unsupported chipsets
 300                                (may crash computer or cause data corruption)
 301
 302        ALSA            [HW,ALSA]
 303                        See Documentation/sound/alsa/alsa-parameters.txt
 304
 305        alignment=      [KNL,ARM]
 306                        Allow the default userspace alignment fault handler
 307                        behaviour to be specified.  Bit 0 enables warnings,
 308                        bit 1 enables fixups, and bit 2 sends a segfault.
 309
 310        align_va_addr=  [X86-64]
 311                        Align virtual addresses by clearing slice [14:12] when
 312                        allocating a VMA at process creation time. This option
 313                        gives you up to 3% performance improvement on AMD F15h
 314                        machines (where it is enabled by default) for a
 315                        CPU-intensive style benchmark, and it can vary highly in
 316                        a microbenchmark depending on workload and compiler.
 317
 318                        32: only for 32-bit processes
 319                        64: only for 64-bit processes
 320                        on: enable for both 32- and 64-bit processes
 321                        off: disable for both 32- and 64-bit processes
 322
 323        amd_iommu=      [HW,X86-64]
 324                        Pass parameters to the AMD IOMMU driver in the system.
 325                        Possible values are:
 326                        fullflush - enable flushing of IO/TLB entries when
 327                                    they are unmapped. Otherwise they are
 328                                    flushed before they will be reused, which
 329                                    is a lot of faster
 330                        off       - do not initialize any AMD IOMMU found in
 331                                    the system
 332                        force_isolation - Force device isolation for all
 333                                          devices. The IOMMU driver is not
 334                                          allowed anymore to lift isolation
 335                                          requirements as needed. This option
 336                                          does not override iommu=pt
 337
 338        amd_iommu_dump= [HW,X86-64]
 339                        Enable AMD IOMMU driver option to dump the ACPI table
 340                        for AMD IOMMU. With this option enabled, AMD IOMMU
 341                        driver will print ACPI tables for AMD IOMMU during
 342                        IOMMU initialization.
 343
 344        amijoy.map=     [HW,JOY] Amiga joystick support
 345                        Map of devices attached to JOY0DAT and JOY1DAT
 346                        Format: <a>,<b>
 347                        See also Documentation/input/joystick.txt
 348
 349        analog.map=     [HW,JOY] Analog joystick and gamepad support
 350                        Specifies type or capabilities of an analog joystick
 351                        connected to one of 16 gameports
 352                        Format: <type1>,<type2>,..<type16>
 353
 354        apc=            [HW,SPARC]
 355                        Power management functions (SPARCstation-4/5 + deriv.)
 356                        Format: noidle
 357                        Disable APC CPU standby support. SPARCstation-Fox does
 358                        not play well with APC CPU idle - disable it if you have
 359                        APC and your system crashes randomly.
 360
 361        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
 362                        Change the output verbosity whilst booting
 363                        Format: { quiet (default) | verbose | debug }
 364                        Change the amount of debugging information output
 365                        when initialising the APIC and IO-APIC components.
 366
 367        autoconf=       [IPV6]
 368                        See Documentation/networking/ipv6.txt.
 369
 370        show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
 371                        Limit apic dumping. The parameter defines the maximal
 372                        number of local apics being dumped. Also it is possible
 373                        to set it to "all" by meaning -- no limit here.
 374                        Format: { 1 (default) | 2 | ... | all }.
 375                        The parameter valid if only apic=debug or
 376                        apic=verbose is specified.
 377                        Example: apic=debug show_lapic=all
 378
 379        apm=            [APM] Advanced Power Management
 380                        See header of arch/x86/kernel/apm_32.c.
 381
 382        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
 383                        Format: <io>,<irq>,<nodeID>
 384
 385        ataflop=        [HW,M68k]
 386
 387        atarimouse=     [HW,MOUSE] Atari Mouse
 388
 389        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
 390                        EzKey and similar keyboards
 391
 392        atkbd.reset=    [HW] Reset keyboard during initialization
 393
 394        atkbd.set=      [HW] Select keyboard code set
 395                        Format: <int> (2 = AT (default), 3 = PS/2)
 396
 397        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
 398                        keyboards
 399
 400        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
 401                        Format: <bool> (0 = real, 1 = synthetic (default))
 402
 403        atkbd.softrepeat= [HW]
 404                        Use software keyboard repeat
 405
 406        baycom_epp=     [HW,AX25]
 407                        Format: <io>,<mode>
 408
 409        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
 410                        Format: <io>,<mode>
 411                        See header of drivers/net/hamradio/baycom_par.c.
 412
 413        baycom_ser_fdx= [HW,AX25]
 414                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
 415                        Format: <io>,<irq>,<mode>[,<baud>]
 416                        See header of drivers/net/hamradio/baycom_ser_fdx.c.
 417
 418        baycom_ser_hdx= [HW,AX25]
 419                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
 420                        Format: <io>,<irq>,<mode>
 421                        See header of drivers/net/hamradio/baycom_ser_hdx.c.
 422
 423        boot_delay=     Milliseconds to delay each printk during boot.
 424                        Values larger than 10 seconds (10000) are changed to
 425                        no delay (0).
 426                        Format: integer
 427
 428        bootmem_debug   [KNL] Enable bootmem allocator debug messages.
 429
 430        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
 431        bttv.radio=     Most important insmod options are available as
 432                        kernel args too.
 433        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
 434        bttv.tuner=
 435
 436        bulk_remove=off [PPC]  This parameter disables the use of the pSeries
 437                        firmware feature for flushing multiple hpte entries
 438                        at a time.
 439
 440        c101=           [NET] Moxa C101 synchronous serial card
 441
 442        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
 443                        Sometimes CPU hardware bugs make them report the cache
 444                        size incorrectly. The kernel will attempt work arounds
 445                        to fix known problems, but for some CPUs it is not
 446                        possible to determine what the correct size should be.
 447                        This option provides an override for these situations.
 448
 449        capability.disable=
 450                        [SECURITY] Disable capabilities.  This would normally
 451                        be used only if an alternative security model is to be
 452                        configured.  Potentially dangerous and should only be
 453                        used if you are entirely sure of the consequences.
 454
 455        ccw_timeout_log [S390]
 456                        See Documentation/s390/CommonIO for details.
 457
 458        cgroup_disable= [KNL] Disable a particular controller
 459                        Format: {name of the controller(s) to disable}
 460                                {Currently supported controllers - "memory"}
 461
 462        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
 463                        Format: { "0" | "1" }
 464                        See security/selinux/Kconfig help text.
 465                        0 -- check protection applied by kernel (includes
 466                                any implied execute protection).
 467                        1 -- check protection requested by application.
 468                        Default value is set via a kernel config option.
 469                        Value can be changed at runtime via
 470                                /selinux/checkreqprot.
 471
 472        cio_ignore=     [S390]
 473                        See Documentation/s390/CommonIO for details.
 474
 475        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
 476                        [Deprecated]
 477                        Forces specified clocksource (if available) to be used
 478                        when calculating gettimeofday(). If specified
 479                        clocksource is not available, it defaults to PIT.
 480                        Format: { pit | tsc | cyclone | pmtmr }
 481
 482        clocksource=    Override the default clocksource
 483                        Format: <string>
 484                        Override the default clocksource and use the clocksource
 485                        with the name specified.
 486                        Some clocksource names to choose from, depending on
 487                        the platform:
 488                        [all] jiffies (this is the base, fallback clocksource)
 489                        [ACPI] acpi_pm
 490                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
 491                                pxa_timer,timer3,32k_counter,timer0_1
 492                        [AVR32] avr32
 493                        [X86-32] pit,hpet,tsc;
 494                                scx200_hrt on Geode; cyclone on IBM x440
 495                        [MIPS] MIPS
 496                        [PARISC] cr16
 497                        [S390] tod
 498                        [SH] SuperH
 499                        [SPARC64] tick
 500                        [X86-64] hpet,tsc
 501
 502        clearcpuid=BITNUM [X86]
 503                        Disable CPUID feature X for the kernel. See
 504                        arch/x86/include/asm/cpufeature.h for the valid bit
 505                        numbers. Note the Linux specific bits are not necessarily
 506                        stable over kernel options, but the vendor specific
 507                        ones should be.
 508                        Also note that user programs calling CPUID directly
 509                        or using the feature without checking anything
 510                        will still see it. This just prevents it from
 511                        being used by the kernel or shown in /proc/cpuinfo.
 512                        Also note the kernel might malfunction if you disable
 513                        some critical bits.
 514
 515        cma=nn[MG]      [ARM,KNL]
 516                        Sets the size of kernel global memory area for contiguous
 517                        memory allocations. For more information, see
 518                        include/linux/dma-contiguous.h
 519
 520        cmo_free_hint=  [PPC] Format: { yes | no }
 521                        Specify whether pages are marked as being inactive
 522                        when they are freed.  This is used in CMO environments
 523                        to determine OS memory pressure for page stealing by
 524                        a hypervisor.
 525                        Default: yes
 526
 527        coherent_pool=nn[KMG]   [ARM,KNL]
 528                        Sets the size of memory pool for coherent, atomic dma
 529                        allocations if Contiguous Memory Allocator (CMA) is used.
 530
 531        code_bytes      [X86] How many bytes of object code to print
 532                        in an oops report.
 533                        Range: 0 - 8192
 534                        Default: 64
 535
 536        com20020=       [HW,NET] ARCnet - COM20020 chipset
 537                        Format:
 538                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
 539
 540        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
 541                        Format: <io>[,<irq>]
 542
 543        com90xx=        [HW,NET]
 544                        ARCnet - COM90xx chipset (memory-mapped buffers)
 545                        Format: <io>[,<irq>[,<memstart>]]
 546
 547        condev=         [HW,S390] console device
 548        conmode=
 549
 550        console=        [KNL] Output console device and options.
 551
 552                tty<n>  Use the virtual console device <n>.
 553
 554                ttyS<n>[,options]
 555                ttyUSB0[,options]
 556                        Use the specified serial port.  The options are of
 557                        the form "bbbbpnf", where "bbbb" is the baud rate,
 558                        "p" is parity ("n", "o", or "e"), "n" is number of
 559                        bits, and "f" is flow control ("r" for RTS or
 560                        omit it).  Default is "9600n8".
 561
 562                        See Documentation/serial-console.txt for more
 563                        information.  See
 564                        Documentation/networking/netconsole.txt for an
 565                        alternative.
 566
 567                uart[8250],io,<addr>[,options]
 568                uart[8250],mmio,<addr>[,options]
 569                        Start an early, polled-mode console on the 8250/16550
 570                        UART at the specified I/O port or MMIO address,
 571                        switching to the matching ttyS device later.  The
 572                        options are the same as for ttyS, above.
 573
 574                If the device connected to the port is not a TTY but a braille
 575                device, prepend "brl," before the device type, for instance
 576                        console=brl,ttyS0
 577                For now, only VisioBraille is supported.
 578
 579        consoleblank=   [KNL] The console blank (screen saver) timeout in
 580                        seconds. Defaults to 10*60 = 10mins. A value of 0
 581                        disables the blank timer.
 582
 583        coredump_filter=
 584                        [KNL] Change the default value for
 585                        /proc/<pid>/coredump_filter.
 586                        See also Documentation/filesystems/proc.txt.
 587
 588        cpuidle.off=1   [CPU_IDLE]
 589                        disable the cpuidle sub-system
 590
 591        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
 592                        Format:
 593                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
 594
 595        crashkernel=size[KMG][@offset[KMG]]
 596                        [KNL] Using kexec, Linux can switch to a 'crash kernel'
 597                        upon panic. This parameter reserves the physical
 598                        memory region [offset, offset + size] for that kernel
 599                        image. If '@offset' is omitted, then a suitable offset
 600                        is selected automatically. Check
 601                        Documentation/kdump/kdump.txt for further details.
 602
 603        crashkernel=range1:size1[,range2:size2,...][@offset]
 604                        [KNL] Same as above, but depends on the memory
 605                        in the running system. The syntax of range is
 606                        start-[end] where start and end are both
 607                        a memory unit (amount[KMG]). See also
 608                        Documentation/kdump/kdump.txt for an example.
 609
 610        cs89x0_dma=     [HW,NET]
 611                        Format: <dma>
 612
 613        cs89x0_media=   [HW,NET]
 614                        Format: { rj45 | aui | bnc }
 615
 616        dasd=           [HW,NET]
 617                        See header of drivers/s390/block/dasd_devmap.c.
 618
 619        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
 620                        (one device per port)
 621                        Format: <port#>,<type>
 622                        See also Documentation/input/joystick-parport.txt
 623
 624        ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
 625                        time. See Documentation/dynamic-debug-howto.txt for
 626                        details.  Deprecated, see dyndbg.
 627
 628        debug           [KNL] Enable kernel debugging (events log level).
 629
 630        debug_locks_verbose=
 631                        [KNL] verbose self-tests
 632                        Format=<0|1>
 633                        Print debugging info while doing the locking API
 634                        self-tests.
 635                        We default to 0 (no extra messages), setting it to
 636                        1 will print _a lot_ more information - normally
 637                        only useful to kernel developers.
 638
 639        debug_objects   [KNL] Enable object debugging
 640
 641        no_debug_objects
 642                        [KNL] Disable object debugging
 643
 644        debug_guardpage_minorder=
 645                        [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
 646                        parameter allows control of the order of pages that will
 647                        be intentionally kept free (and hence protected) by the
 648                        buddy allocator. Bigger value increase the probability
 649                        of catching random memory corruption, but reduce the
 650                        amount of memory for normal system use. The maximum
 651                        possible value is MAX_ORDER/2.  Setting this parameter
 652                        to 1 or 2 should be enough to identify most random
 653                        memory corruption problems caused by bugs in kernel or
 654                        driver code when a CPU writes to (or reads from) a
 655                        random memory location. Note that there exists a class
 656                        of memory corruptions problems caused by buggy H/W or
 657                        F/W or by drivers badly programing DMA (basically when
 658                        memory is written at bus level and the CPU MMU is
 659                        bypassed) which are not detectable by
 660                        CONFIG_DEBUG_PAGEALLOC, hence this option will not help
 661                        tracking down these problems.
 662
 663        debugpat        [X86] Enable PAT debugging
 664
 665        decnet.addr=    [HW,NET]
 666                        Format: <area>[,<node>]
 667                        See also Documentation/networking/decnet.txt.
 668
 669        default_hugepagesz=
 670                        [same as hugepagesz=] The size of the default
 671                        HugeTLB page size. This is the size represented by
 672                        the legacy /proc/ hugepages APIs, used for SHM, and
 673                        default size when mounting hugetlbfs filesystems.
 674                        Defaults to the default architecture's huge page size
 675                        if not specified.
 676
 677        dhash_entries=  [KNL]
 678                        Set number of hash buckets for dentry cache.
 679
 680        digi=           [HW,SERIAL]
 681                        IO parameters + enable/disable command.
 682
 683        digiepca=       [HW,SERIAL]
 684                        See drivers/char/README.epca and
 685                        Documentation/serial/digiepca.txt.
 686
 687        disable=        [IPV6]
 688                        See Documentation/networking/ipv6.txt.
 689
 690        disable_ddw     [PPC/PSERIES]
 691                        Disable Dynamic DMA Window support. Use this if
 692                        to workaround buggy firmware.
 693
 694        disable_ipv6=   [IPV6]
 695                        See Documentation/networking/ipv6.txt.
 696
 697        disable_mtrr_cleanup [X86]
 698                        The kernel tries to adjust MTRR layout from continuous
 699                        to discrete, to make X server driver able to add WB
 700                        entry later. This parameter disables that.
 701
 702        disable_mtrr_trim [X86, Intel and AMD only]
 703                        By default the kernel will trim any uncacheable
 704                        memory out of your available memory pool based on
 705                        MTRR settings.  This parameter disables that behavior,
 706                        possibly causing your machine to run very slowly.
 707
 708        disable_timer_pin_1 [X86]
 709                        Disable PIN 1 of APIC timer
 710                        Can be useful to work around chipset bugs.
 711
 712        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
 713                        this option disables the debugging code at boot.
 714
 715        dma_debug_entries=<number>
 716                        This option allows to tune the number of preallocated
 717                        entries for DMA-API debugging code. One entry is
 718                        required per DMA-API allocation. Use this if the
 719                        DMA-API debugging code disables itself because the
 720                        architectural default is too low.
 721
 722        dma_debug_driver=<driver_name>
 723                        With this option the DMA-API debugging driver
 724                        filter feature can be enabled at boot time. Just
 725                        pass the driver to filter for as the parameter.
 726                        The filter can be disabled or changed to another
 727                        driver later using sysfs.
 728
 729        drm_kms_helper.edid_firmware=[<connector>:]<file>
 730                        Broken monitors, graphic adapters and KVMs may
 731                        send no or incorrect EDID data sets. This parameter
 732                        allows to specify an EDID data set in the
 733                        /lib/firmware directory that is used instead.
 734                        Generic built-in EDID data sets are used, if one of
 735                        edid/1024x768.bin, edid/1280x1024.bin,
 736                        edid/1680x1050.bin, or edid/1920x1080.bin is given
 737                        and no file with the same name exists. Details and
 738                        instructions how to build your own EDID data are
 739                        available in Documentation/EDID/HOWTO.txt. An EDID
 740                        data set will only be used for a particular connector,
 741                        if its name and a colon are prepended to the EDID
 742                        name.
 743
 744        dscc4.setup=    [NET]
 745
 746        dyndbg[="val"]          [KNL,DYNAMIC_DEBUG]
 747        module.dyndbg[="val"]
 748                        Enable debug messages at boot time.  See
 749                        Documentation/dynamic-debug-howto.txt for details.
 750
 751        earlycon=       [KNL] Output early console device and options.
 752                uart[8250],io,<addr>[,options]
 753                uart[8250],mmio,<addr>[,options]
 754                uart[8250],mmio32,<addr>[,options]
 755                        Start an early, polled-mode console on the 8250/16550
 756                        UART at the specified I/O port or MMIO address.
 757                        MMIO inter-register address stride is either 8-bit
 758                        (mmio) or 32-bit (mmio32).
 759                        The options are the same as for ttyS, above.
 760
 761        earlyprintk=    [X86,SH,BLACKFIN]
 762                        earlyprintk=vga
 763                        earlyprintk=serial[,ttySn[,baudrate]]
 764                        earlyprintk=ttySn[,baudrate]
 765                        earlyprintk=dbgp[debugController#]
 766
 767                        Append ",keep" to not disable it when the real console
 768                        takes over.
 769
 770                        Only vga or serial or usb debug port at a time.
 771
 772                        Currently only ttyS0 and ttyS1 are supported.
 773
 774                        Interaction with the standard serial driver is not
 775                        very good.
 776
 777                        The VGA output is eventually overwritten by the real
 778                        console.
 779
 780        ekgdboc=        [X86,KGDB] Allow early kernel console debugging
 781                        ekgdboc=kbd
 782
 783                        This is designed to be used in conjunction with
 784                        the boot argument: earlyprintk=vga
 785
 786        edd=            [EDD]
 787                        Format: {"off" | "on" | "skip[mbr]"}
 788
 789        eisa_irq_edge=  [PARISC,HW]
 790                        See header of drivers/parisc/eisa.c.
 791
 792        elanfreq=       [X86-32]
 793                        See comment before function elanfreq_setup() in
 794                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.
 795
 796        elevator=       [IOSCHED]
 797                        Format: {"cfq" | "deadline" | "noop"}
 798                        See Documentation/block/cfq-iosched.txt and
 799                        Documentation/block/deadline-iosched.txt for details.
 800
 801        elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
 802                        Specifies physical address of start of kernel core
 803                        image elf header and optionally the size. Generally
 804                        kexec loader will pass this option to capture kernel.
 805                        See Documentation/kdump/kdump.txt for details.
 806
 807        enable_mtrr_cleanup [X86]
 808                        The kernel tries to adjust MTRR layout from continuous
 809                        to discrete, to make X server driver able to add WB
 810                        entry later. This parameter enables that.
 811
 812        enable_timer_pin_1 [X86]
 813                        Enable PIN 1 of APIC timer
 814                        Can be useful to work around chipset bugs
 815                        (in particular on some ATI chipsets).
 816                        The kernel tries to set a reasonable default.
 817
 818        enforcing       [SELINUX] Set initial enforcing status.
 819                        Format: {"0" | "1"}
 820                        See security/selinux/Kconfig help text.
 821                        0 -- permissive (log only, no denials).
 822                        1 -- enforcing (deny and log).
 823                        Default value is 0.
 824                        Value can be changed at runtime via /selinux/enforce.
 825
 826        erst_disable    [ACPI]
 827                        Disable Error Record Serialization Table (ERST)
 828                        support.
 829
 830        ether=          [HW,NET] Ethernet cards parameters
 831                        This option is obsoleted by the "netdev=" option, which
 832                        has equivalent usage. See its documentation for details.
 833
 834        evm=            [EVM]
 835                        Format: { "fix" }
 836                        Permit 'security.evm' to be updated regardless of
 837                        current integrity status.
 838
 839        failslab=
 840        fail_page_alloc=
 841        fail_make_request=[KNL]
 842                        General fault injection mechanism.
 843                        Format: <interval>,<probability>,<space>,<times>
 844                        See also Documentation/fault-injection/.
 845
 846        floppy=         [HW]
 847                        See Documentation/blockdev/floppy.txt.
 848
 849        force_pal_cache_flush
 850                        [IA-64] Avoid check_sal_cache_flush which may hang on
 851                        buggy SAL_CACHE_FLUSH implementations. Using this
 852                        parameter will force ia64_sal_cache_flush to call
 853                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
 854
 855        ftrace=[tracer]
 856                        [FTRACE] will set and start the specified tracer
 857                        as early as possible in order to facilitate early
 858                        boot debugging.
 859
 860        ftrace_dump_on_oops[=orig_cpu]
 861                        [FTRACE] will dump the trace buffers on oops.
 862                        If no parameter is passed, ftrace will dump
 863                        buffers of all CPUs, but if you pass orig_cpu, it will
 864                        dump only the buffer of the CPU that triggered the
 865                        oops.
 866
 867        ftrace_filter=[function-list]
 868                        [FTRACE] Limit the functions traced by the function
 869                        tracer at boot up. function-list is a comma separated
 870                        list of functions. This list can be changed at run
 871                        time by the set_ftrace_filter file in the debugfs
 872                        tracing directory.
 873
 874        ftrace_notrace=[function-list]
 875                        [FTRACE] Do not trace the functions specified in
 876                        function-list. This list can be changed at run time
 877                        by the set_ftrace_notrace file in the debugfs
 878                        tracing directory.
 879
 880        ftrace_graph_filter=[function-list]
 881                        [FTRACE] Limit the top level callers functions traced
 882                        by the function graph tracer at boot up.
 883                        function-list is a comma separated list of functions
 884                        that can be changed at run time by the
 885                        set_graph_function file in the debugfs tracing directory.
 886
 887        gamecon.map[2|3]=
 888                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
 889                        support via parallel port (up to 5 devices per port)
 890                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
 891                        See also Documentation/input/joystick-parport.txt
 892
 893        gamma=          [HW,DRM]
 894
 895        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
 896                        Format: off | on
 897                        default: on
 898
 899        gcov_persist=   [GCOV] When non-zero (default), profiling data for
 900                        kernel modules is saved and remains accessible via
 901                        debugfs, even when the module is unloaded/reloaded.
 902                        When zero, profiling data is discarded and associated
 903                        debugfs files are removed at module unload time.
 904
 905        gpt             [EFI] Forces disk with valid GPT signature but
 906                        invalid Protective MBR to be treated as GPT.
 907
 908        hashdist=       [KNL,NUMA] Large hashes allocated during boot
 909                        are distributed across NUMA nodes.  Defaults on
 910                        for 64-bit NUMA, off otherwise.
 911                        Format: 0 | 1 (for off | on)
 912
 913        hcl=            [IA-64] SGI's Hardware Graph compatibility layer
 914
 915        hd=             [EIDE] (E)IDE hard drive subsystem geometry
 916                        Format: <cyl>,<head>,<sect>
 917
 918        hest_disable    [ACPI]
 919                        Disable Hardware Error Source Table (HEST) support;
 920                        corresponding firmware-first mode error processing
 921                        logic will be disabled.
 922
 923        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
 924                        size of <nn>. This works even on boxes that have no
 925                        highmem otherwise. This also works to reduce highmem
 926                        size on bigger boxes.
 927
 928        highres=        [KNL] Enable/disable high resolution timer mode.
 929                        Valid parameters: "on", "off"
 930                        Default: "on"
 931
 932        hisax=          [HW,ISDN]
 933                        See Documentation/isdn/README.HiSax.
 934
 935        hlt             [BUGS=ARM,SH]
 936
 937        hpet=           [X86-32,HPET] option to control HPET usage
 938                        Format: { enable (default) | disable | force |
 939                                verbose }
 940                        disable: disable HPET and use PIT instead
 941                        force: allow force enabled of undocumented chips (ICH4,
 942                                VIA, nVidia)
 943                        verbose: show contents of HPET registers during setup
 944
 945        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
 946        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
 947                        On x86-64 and powerpc, this option can be specified
 948                        multiple times interleaved with hugepages= to reserve
 949                        huge pages of different sizes. Valid pages sizes on
 950                        x86-64 are 2M (when the CPU supports "pse") and 1G
 951                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
 952                        Note that 1GB pages can only be allocated at boot time
 953                        using hugepages= and not freed afterwards.
 954
 955        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
 956                               terminal devices. Valid values: 0..8
 957        hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
 958                               If specified, z/VM IUCV HVC accepts connections
 959                               from listed z/VM user IDs only.
 960
 961        keep_bootcon    [KNL]
 962                        Do not unregister boot console at start. This is only
 963                        useful for debugging when something happens in the window
 964                        between unregistering the boot console and initializing
 965                        the real console.
 966
 967        i2c_bus=        [HW] Override the default board specific I2C bus speed
 968                             or register an additional I2C bus that is not
 969                             registered from board initialization code.
 970                             Format:
 971                             <bus_id>,<clkrate>
 972
 973        i8042.debug     [HW] Toggle i8042 debug mode
 974        i8042.direct    [HW] Put keyboard port into non-translated mode
 975        i8042.dumbkbd   [HW] Pretend that controller can only read data from
 976                             keyboard and cannot control its state
 977                             (Don't attempt to blink the leds)
 978        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
 979        i8042.nokbd     [HW] Don't check/create keyboard port
 980        i8042.noloop    [HW] Disable the AUX Loopback command while probing
 981                             for the AUX port
 982        i8042.nomux     [HW] Don't check presence of an active multiplexing
 983                             controller
 984        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
 985                             controllers
 986        i8042.notimeout [HW] Ignore timeout condition signalled by controller
 987        i8042.reset     [HW] Reset the controller during init and cleanup
 988        i8042.unlock    [HW] Unlock (ignore) the keylock
 989
 990        i810=           [HW,DRM]
 991
 992        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
 993                        indicates that the driver is running on unsupported
 994                        hardware.
 995        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
 996                        does not match list of supported models.
 997        i8k.power_status
 998                        [HW] Report power status in /proc/i8k
 999                        (disabled by default)
1000        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
1001                        capability is set.
1002
1003        i915.invert_brightness=
1004                        [DRM] Invert the sense of the variable that is used to
1005                        set the brightness of the panel backlight. Normally a
1006                        brightness value of 0 indicates backlight switched off,
1007                        and the maximum of the brightness value sets the backlight
1008                        to maximum brightness. If this parameter is set to 0
1009                        (default) and the machine requires it, or this parameter
1010                        is set to 1, a brightness value of 0 sets the backlight
1011                        to maximum brightness, and the maximum of the brightness
1012                        value switches the backlight off.
1013                        -1 -- never invert brightness
1014                         0 -- machine default
1015                         1 -- force brightness inversion
1016
1017        icn=            [HW,ISDN]
1018                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1019
1020        ide-core.nodma= [HW] (E)IDE subsystem
1021                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
1022                        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
1023                        .cdrom .chs .ignore_cable are additional options
1024                        See Documentation/ide/ide.txt.
1025
1026        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
1027                        Claim all unknown PCI IDE storage controllers.
1028
1029        idle=           [X86]
1030                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
1031                        Poll forces a polling idle loop that can slightly
1032                        improve the performance of waking up a idle CPU, but
1033                        will use a lot of power and make the system run hot.
1034                        Not recommended.
1035                        idle=mwait: On systems which support MONITOR/MWAIT but
1036                        the kernel chose to not use it because it doesn't save
1037                        as much power as a normal idle loop, use the
1038                        MONITOR/MWAIT idle loop anyways. Performance should be
1039                        the same as idle=poll.
1040                        idle=halt: Halt is forced to be used for CPU idle.
1041                        In such case C2/C3 won't be used again.
1042                        idle=nomwait: Disable mwait for CPU C-states
1043
1044        ignore_loglevel [KNL]
1045                        Ignore loglevel setting - this will print /all/
1046                        kernel messages to the console. Useful for debugging.
1047                        We also add it as printk module parameter, so users
1048                        could change it dynamically, usually by
1049                        /sys/module/printk/parameters/ignore_loglevel.
1050
1051        ihash_entries=  [KNL]
1052                        Set number of hash buckets for inode cache.
1053
1054        ima_audit=      [IMA]
1055                        Format: { "0" | "1" }
1056                        0 -- integrity auditing messages. (Default)
1057                        1 -- enable informational integrity auditing messages.
1058
1059        ima_hash=       [IMA]
1060                        Format: { "sha1" | "md5" }
1061                        default: "sha1"
1062
1063        ima_tcb         [IMA]
1064                        Load a policy which meets the needs of the Trusted
1065                        Computing Base.  This means IMA will measure all
1066                        programs exec'd, files mmap'd for exec, and all files
1067                        opened for read by uid=0.
1068
1069        init=           [KNL]
1070                        Format: <full_path>
1071                        Run specified binary instead of /sbin/init as init
1072                        process.
1073
1074        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
1075                        for working out where the kernel is dying during
1076                        startup.
1077
1078        initrd=         [BOOT] Specify the location of the initial ramdisk
1079
1080        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
1081                        Format: <irq>
1082
1083        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
1084                on
1085                        Enable intel iommu driver.
1086                off
1087                        Disable intel iommu driver.
1088                igfx_off [Default Off]
1089                        By default, gfx is mapped as normal device. If a gfx
1090                        device has a dedicated DMAR unit, the DMAR unit is
1091                        bypassed by not enabling DMAR with this option. In
1092                        this case, gfx device will use physical address for
1093                        DMA.
1094                forcedac [x86_64]
1095                        With this option iommu will not optimize to look
1096                        for io virtual address below 32-bit forcing dual
1097                        address cycle on pci bus for cards supporting greater
1098                        than 32-bit addressing. The default is to look
1099                        for translation below 32-bit and if not available
1100                        then look in the higher range.
1101                strict [Default Off]
1102                        With this option on every unmap_single operation will
1103                        result in a hardware IOTLB flush operation as opposed
1104                        to batching them for performance.
1105                sp_off [Default Off]
1106                        By default, super page will be supported if Intel IOMMU
1107                        has the capability. With this option, super page will
1108                        not be supported.
1109
1110        intel_idle.max_cstate=  [KNL,HW,ACPI,X86]
1111                        0       disables intel_idle and fall back on acpi_idle.
1112                        1 to 6  specify maximum depth of C-state.
1113
1114        intremap=       [X86-64, Intel-IOMMU]
1115                        on      enable Interrupt Remapping (default)
1116                        off     disable Interrupt Remapping
1117                        nosid   disable Source ID checking
1118                        no_x2apic_optout
1119                                BIOS x2APIC opt-out request will be ignored
1120
1121        iomem=          Disable strict checking of access to MMIO memory
1122                strict  regions from userspace.
1123                relaxed
1124
1125        iommu=          [x86]
1126                off
1127                force
1128                noforce
1129                biomerge
1130                panic
1131                nopanic
1132                merge
1133                nomerge
1134                forcesac
1135                soft
1136                pt              [x86, IA-64]
1137                group_mf        [x86, IA-64]
1138
1139
1140        io7=            [HW] IO7 for Marvel based alpha systems
1141                        See comment before marvel_specify_io7 in
1142                        arch/alpha/kernel/core_marvel.c.
1143
1144        io_delay=       [X86] I/O delay method
1145                0x80
1146                        Standard port 0x80 based delay
1147                0xed
1148                        Alternate port 0xed based delay (needed on some systems)
1149                udelay
1150                        Simple two microseconds delay
1151                none
1152                        No delay
1153
1154        ip=             [IP_PNP]
1155                        See Documentation/filesystems/nfs/nfsroot.txt.
1156
1157        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
1158                        See comment before ip2_setup() in
1159                        drivers/char/ip2/ip2base.c.
1160
1161        irqfixup        [HW]
1162                        When an interrupt is not handled search all handlers
1163                        for it. Intended to get systems with badly broken
1164                        firmware running.
1165
1166        irqpoll         [HW]
1167                        When an interrupt is not handled search all handlers
1168                        for it. Also check all handlers each timer
1169                        interrupt. Intended to get systems with badly broken
1170                        firmware running.
1171
1172        isapnp=         [ISAPNP]
1173                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>
1174
1175        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
1176                        Format:
1177                        <cpu number>,...,<cpu number>
1178                        or
1179                        <cpu number>-<cpu number>
1180                        (must be a positive range in ascending order)
1181                        or a mixture
1182                        <cpu number>,...,<cpu number>-<cpu number>
1183
1184                        This option can be used to specify one or more CPUs
1185                        to isolate from the general SMP balancing and scheduling
1186                        algorithms. You can move a process onto or off an
1187                        "isolated" CPU via the CPU affinity syscalls or cpuset.
1188                        <cpu number> begins at 0 and the maximum value is
1189                        "number of CPUs in system - 1".
1190
1191                        This option is the preferred way to isolate CPUs. The
1192                        alternative -- manually setting the CPU mask of all
1193                        tasks in the system -- can cause problems and
1194                        suboptimal load balancer performance.
1195
1196        iucv=           [HW,NET]
1197
1198        js=             [HW,JOY] Analog joystick
1199                        See Documentation/input/joystick.txt.
1200
1201        keepinitrd      [HW,ARM]
1202
1203        kernelcore=nn[KMG]      [KNL,X86,IA-64,PPC] This parameter
1204                        specifies the amount of memory usable by the kernel
1205                        for non-movable allocations.  The requested amount is
1206                        spread evenly throughout all nodes in the system. The
1207                        remaining memory in each node is used for Movable
1208                        pages. In the event, a node is too small to have both
1209                        kernelcore and Movable pages, kernelcore pages will
1210                        take priority and other nodes will have a larger number
1211                        of kernelcore pages.  The Movable zone is used for the
1212                        allocation of pages that may be reclaimed or moved
1213                        by the page migration subsystem.  This means that
1214                        HugeTLB pages may not be allocated from this zone.
1215                        Note that allocations like PTEs-from-HighMem still
1216                        use the HighMem zone if it exists, and the Normal
1217                        zone if it does not.
1218
1219        kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
1220                        Format: <Controller#>[,poll interval]
1221                        The controller # is the number of the ehci usb debug
1222                        port as it is probed via PCI.  The poll interval is
1223                        optional and is the number seconds in between
1224                        each poll cycle to the debug port in case you need
1225                        the functionality for interrupting the kernel with
1226                        gdb or control-c on the dbgp connection.  When
1227                        not using this parameter you use sysrq-g to break into
1228                        the kernel debugger.
1229
1230        kgdboc=         [KGDB,HW] kgdb over consoles.
1231                        Requires a tty driver that supports console polling,
1232                        or a supported polling keyboard driver (non-usb).
1233                         Serial only format: <serial_device>[,baud]
1234                         keyboard only format: kbd
1235                         keyboard and serial format: kbd,<serial_device>[,baud]
1236                        Optional Kernel mode setting:
1237                         kms, kbd format: kms,kbd
1238                         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
1239
1240        kgdbwait        [KGDB] Stop kernel execution and enter the
1241                        kernel debugger at the earliest opportunity.
1242
1243        kmac=           [MIPS] korina ethernet MAC address.
1244                        Configure the RouterBoard 532 series on-chip
1245                        Ethernet adapter MAC address.
1246
1247        kmemleak=       [KNL] Boot-time kmemleak enable/disable
1248                        Valid arguments: on, off
1249                        Default: on
1250
1251        kstack=N        [X86] Print N words from the kernel stack
1252                        in oops dumps.
1253
1254        kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
1255                        Default is 0 (don't ignore, but inject #GP)
1256
1257        kvm.mmu_audit=  [KVM] This is a R/W parameter which allows audit
1258                        KVM MMU at runtime.
1259                        Default is 0 (off)
1260
1261        kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
1262                        Default is 1 (enabled)
1263
1264        kvm-amd.npt=    [KVM,AMD] Disable nested paging (virtualized MMU)
1265                        for all guests.
1266                        Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
1267
1268        kvm-intel.ept=  [KVM,Intel] Disable extended page tables
1269                        (virtualized MMU) support on capable Intel chips.
1270                        Default is 1 (enabled)
1271
1272        kvm-intel.emulate_invalid_guest_state=
1273                        [KVM,Intel] Enable emulation of invalid guest states
1274                        Default is 0 (disabled)
1275
1276        kvm-intel.flexpriority=
1277                        [KVM,Intel] Disable FlexPriority feature (TPR shadow).
1278                        Default is 1 (enabled)
1279
1280        kvm-intel.nested=
1281                        [KVM,Intel] Enable VMX nesting (nVMX).
1282                        Default is 0 (disabled)
1283
1284        kvm-intel.unrestricted_guest=
1285                        [KVM,Intel] Disable unrestricted guest feature
1286                        (virtualized real and unpaged mode) on capable
1287                        Intel chips. Default is 1 (enabled)
1288
1289        kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
1290                        feature (tagged TLBs) on capable Intel chips.
1291                        Default is 1 (enabled)
1292
1293        l2cr=           [PPC]
1294
1295        l3cr=           [PPC]
1296
1297        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
1298                        disabled it.
1299
1300        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
1301                        in C2 power state.
1302
1303        libata.dma=     [LIBATA] DMA control
1304                        libata.dma=0      Disable all PATA and SATA DMA
1305                        libata.dma=1      PATA and SATA Disk DMA only
1306                        libata.dma=2      ATAPI (CDROM) DMA only
1307                        libata.dma=4      Compact Flash DMA only
1308                        Combinations also work, so libata.dma=3 enables DMA
1309                        for disks and CDROMs, but not CFs.
1310
1311        libata.ignore_hpa=      [LIBATA] Ignore HPA limit
1312                        libata.ignore_hpa=0       keep BIOS limits (default)
1313                        libata.ignore_hpa=1       ignore limits, using full disk
1314
1315        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
1316                        when set.
1317                        Format: <int>
1318
1319        libata.force=   [LIBATA] Force configurations.  The format is comma
1320                        separated list of "[ID:]VAL" where ID is
1321                        PORT[.DEVICE].  PORT and DEVICE are decimal numbers
1322                        matching port, link or device.  Basically, it matches
1323                        the ATA ID string printed on console by libata.  If
1324                        the whole ID part is omitted, the last PORT and DEVICE
1325                        values are used.  If ID hasn't been specified yet, the
1326                        configuration applies to all ports, links and devices.
1327
1328                        If only DEVICE is omitted, the parameter applies to
1329                        the port and all links and devices behind it.  DEVICE
1330                        number of 0 either selects the first device or the
1331                        first fan-out link behind PMP device.  It does not
1332                        select the host link.  DEVICE number of 15 selects the
1333                        host link and device attached to it.
1334
1335                        The VAL specifies the configuration to force.  As long
1336                        as there's no ambiguity shortcut notation is allowed.
1337                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
1338                        The following configurations can be forced.
1339
1340                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
1341                          Any ID with matching PORT is used.
1342
1343                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.
1344
1345                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
1346                          udma[/][16,25,33,44,66,100,133] notation is also
1347                          allowed.
1348
1349                        * [no]ncq: Turn on or off NCQ.
1350
1351                        * nohrst, nosrst, norst: suppress hard, soft
1352                          and both resets.
1353
1354                        * dump_id: dump IDENTIFY data.
1355
1356                        If there are multiple matching configurations changing
1357                        the same attribute, the last one is used.
1358
1359        memblock=debug  [KNL] Enable memblock debug messages.
1360
1361        load_ramdisk=   [RAM] List of ramdisks to load from floppy
1362                        See Documentation/blockdev/ramdisk.txt.
1363
1364        lockd.nlm_grace_period=P  [NFS] Assign grace period.
1365                        Format: <integer>
1366
1367        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
1368                        Format: <integer>
1369
1370        lockd.nlm_timeout=T     [NFS] Assign timeout value.
1371                        Format: <integer>
1372
1373        lockd.nlm_udpport=M     [NFS] Assign UDP port.
1374                        Format: <integer>
1375
1376        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
1377                        Format: <irq>
1378
1379        loglevel=       All Kernel Messages with a loglevel smaller than the
1380                        console loglevel will be printed to the console. It can
1381                        also be changed with klogd or other programs. The
1382                        loglevels are defined as follows:
1383
1384                        0 (KERN_EMERG)          system is unusable
1385                        1 (KERN_ALERT)          action must be taken immediately
1386                        2 (KERN_CRIT)           critical conditions
1387                        3 (KERN_ERR)            error conditions
1388                        4 (KERN_WARNING)        warning conditions
1389                        5 (KERN_NOTICE)         normal but significant condition
1390                        6 (KERN_INFO)           informational
1391                        7 (KERN_DEBUG)          debug-level messages
1392
1393        log_buf_len=n[KMG]      Sets the size of the printk ring buffer,
1394                        in bytes.  n must be a power of two.  The default
1395                        size is set in the kernel config file.
1396
1397        logo.nologo     [FB] Disables display of the built-in Linux logo.
1398                        This may be used to provide more screen space for
1399                        kernel log messages and is useful when debugging
1400                        kernel boot problems.
1401
1402        lp=0            [LP]    Specify parallel ports to use, e.g,
1403        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
1404        lp=reset                first parallel port). 'lp=0' disables the
1405        lp=auto                 printer driver. 'lp=reset' (which can be
1406                                specified in addition to the ports) causes
1407                                attached printers to be reset. Using
1408                                lp=port1,port2,... specifies the parallel ports
1409                                to associate lp devices with, starting with
1410                                lp0. A port specification may be 'none' to skip
1411                                that lp device, or a parport name such as
1412                                'parport0'. Specifying 'lp=auto' instead of a
1413                                port specification list means that device IDs
1414                                from each port should be examined, to see if
1415                                an IEEE 1284-compliant printer is attached; if
1416                                so, the driver will manage that printer.
1417                                See also header of drivers/char/lp.c.
1418
1419        lpj=n           [KNL]
1420                        Sets loops_per_jiffy to given constant, thus avoiding
1421                        time-consuming boot-time autodetection (up to 250 ms per
1422                        CPU). 0 enables autodetection (default). To determine
1423                        the correct value for your kernel, boot with normal
1424                        autodetection and see what value is printed. Note that
1425                        on SMP systems the preset will be applied to all CPUs,
1426                        which is likely to cause problems if your CPUs need
1427                        significantly divergent settings. An incorrect value
1428                        will cause delays in the kernel to be wrong, leading to
1429                        unpredictable I/O errors and other breakage. Although
1430                        unlikely, in the extreme case this might damage your
1431                        hardware.
1432
1433        ltpc=           [NET]
1434                        Format: <io>,<irq>,<dma>
1435
1436        machvec=        [IA-64] Force the use of a particular machine-vector
1437                        (machvec) in a generic kernel.
1438                        Example: machvec=hpzx1_swiotlb
1439
1440        machtype=       [Loongson] Share the same kernel image file between different
1441                         yeeloong laptop.
1442                        Example: machtype=lemote-yeeloong-2f-7inch
1443
1444        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
1445                        than or equal to this physical address is ignored.
1446
1447        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
1448                        should make use of.  maxcpus=n : n >= 0 limits the
1449                        kernel to using 'n' processors.  n=0 is a special case,
1450                        it is equivalent to "nosmp", which also disables
1451                        the IO APIC.
1452
1453        max_loop=       [LOOP] The number of loop block devices that get
1454        (loop.max_loop) unconditionally pre-created at init time. The default
1455                        number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
1456                        of statically allocating a predefined number, loop
1457                        devices can be requested on-demand with the
1458                        /dev/loop-control interface.
1459
1460        mce             [X86-32] Machine Check Exception
1461
1462        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt
1463
1464        md=             [HW] RAID subsystems devices and level
1465                        See Documentation/md.txt.
1466
1467        mdacon=         [MDA]
1468                        Format: <first>,<last>
1469                        Specifies range of consoles to be captured by the MDA.
1470
1471        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
1472                        Amount of memory to be used when the kernel is not able
1473                        to see the whole system memory or for test.
1474                        [X86-32] Use together with memmap= to avoid physical
1475                        address space collisions. Without memmap= PCI devices
1476                        could be placed at addresses belonging to unused RAM.
1477
1478        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
1479                        memory.
1480
1481        memchunk=nn[KMG]
1482                        [KNL,SH] Allow user to override the default size for
1483                        per-device physically contiguous DMA buffers.
1484
1485        memmap=exactmap [KNL,X86] Enable setting of an exact
1486                        E820 memory map, as specified by the user.
1487                        Such memmap=exactmap lines can be constructed based on
1488                        BIOS output or other requirements. See the memmap=nn@ss
1489                        option description.
1490
1491        memmap=nn[KMG]@ss[KMG]
1492                        [KNL] Force usage of a specific region of memory
1493                        Region of memory to be used, from ss to ss+nn.
1494
1495        memmap=nn[KMG]#ss[KMG]
1496                        [KNL,ACPI] Mark specific memory as ACPI data.
1497                        Region of memory to be used, from ss to ss+nn.
1498
1499        memmap=nn[KMG]$ss[KMG]
1500                        [KNL,ACPI] Mark specific memory as reserved.
1501                        Region of memory to be used, from ss to ss+nn.
1502                        Example: Exclude memory from 0x18690000-0x1869ffff
1503                                 memmap=64K$0x18690000
1504                                 or
1505                                 memmap=0x10000$0x18690000
1506
1507        memory_corruption_check=0/1 [X86]
1508                        Some BIOSes seem to corrupt the first 64k of
1509                        memory when doing things like suspend/resume.
1510                        Setting this option will scan the memory
1511                        looking for corruption.  Enabling this will
1512                        both detect corruption and prevent the kernel
1513                        from using the memory being corrupted.
1514                        However, its intended as a diagnostic tool; if
1515                        repeatable BIOS-originated corruption always
1516                        affects the same memory, you can use memmap=
1517                        to prevent the kernel from using that memory.
1518
1519        memory_corruption_check_size=size [X86]
1520                        By default it checks for corruption in the low
1521                        64k, making this memory unavailable for normal
1522                        use.  Use this parameter to scan for
1523                        corruption in more or less memory.
1524
1525        memory_corruption_check_period=seconds [X86]
1526                        By default it checks for corruption every 60
1527                        seconds.  Use this parameter to check at some
1528                        other rate.  0 disables periodic checking.
1529
1530        memtest=        [KNL,X86] Enable memtest
1531                        Format: <integer>
1532                        default : 0 <disable>
1533                        Specifies the number of memtest passes to be
1534                        performed. Each pass selects another test
1535                        pattern from a given set of patterns. Memtest
1536                        fills the memory with this pattern, validates
1537                        memory contents and reserves bad memory
1538                        regions that are detected.
1539
1540        meye.*=         [HW] Set MotionEye Camera parameters
1541                        See Documentation/video4linux/meye.txt.
1542
1543        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
1544                        Multi-Function General Purpose Timers on AMD Geode
1545                        platforms.
1546
1547        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
1548                        the BIOS has incorrectly applied a workaround. TinyBIOS
1549                        version 0.98 is known to be affected, 0.99 fixes the
1550                        problem by letting the user disable the workaround.
1551
1552        mga=            [HW,DRM]
1553
1554        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
1555                        physical address is ignored.
1556
1557        mini2440=       [ARM,HW,KNL]
1558                        Format:[0..2][b][c][t]
1559                        Default: "0tb"
1560                        MINI2440 configuration specification:
1561                        0 - The attached screen is the 3.5" TFT
1562                        1 - The attached screen is the 7" TFT
1563                        2 - The VGA Shield is attached (1024x768)
1564                        Leaving out the screen size parameter will not load
1565                        the TFT driver, and the framebuffer will be left
1566                        unconfigured.
1567                        b - Enable backlight. The TFT backlight pin will be
1568                        linked to the kernel VESA blanking code and a GPIO
1569                        LED. This parameter is not necessary when using the
1570                        VGA shield.
1571                        c - Enable the s3c camera interface.
1572                        t - Reserved for enabling touchscreen support. The
1573                        touchscreen support is not enabled in the mainstream
1574                        kernel as of 2.6.30, a preliminary port can be found
1575                        in the "bleeding edge" mini2440 support kernel at
1576                        http://repo.or.cz/w/linux-2.6/mini2440.git
1577
1578        mminit_loglevel=
1579                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
1580                        parameter allows control of the logging verbosity for
1581                        the additional memory initialisation checks. A value
1582                        of 0 disables mminit logging and a level of 4 will
1583                        log everything. Information is printed at KERN_DEBUG
1584                        so loglevel=8 may also need to be specified.
1585
1586        mousedev.tap_time=
1587                        [MOUSE] Maximum time between finger touching and
1588                        leaving touchpad surface for touch to be considered
1589                        a tap and be reported as a left button click (for
1590                        touchpads working in absolute mode only).
1591                        Format: <msecs>
1592        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
1593                        reporting absolute coordinates, such as tablets
1594        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
1595                        reporting absolute coordinates, such as tablets
1596
1597        movablecore=nn[KMG]     [KNL,X86,IA-64,PPC] This parameter
1598                        is similar to kernelcore except it specifies the
1599                        amount of memory used for migratable allocations.
1600                        If both kernelcore and movablecore is specified,
1601                        then kernelcore will be at *least* the specified
1602                        value but may be more. If movablecore on its own
1603                        is specified, the administrator must be careful
1604                        that the amount of memory usable for all allocations
1605                        is not too small.
1606
1607        MTD_Partition=  [MTD]
1608                        Format: <name>,<region-number>,<size>,<offset>
1609
1610        MTD_Region=     [MTD] Format:
1611                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
1612
1613        mtdparts=       [MTD]
1614                        See drivers/mtd/cmdlinepart.c.
1615
1616        multitce=off    [PPC]  This parameter disables the use of the pSeries
1617                        firmware feature for updating multiple TCE entries
1618                        at a time.
1619
1620        onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration
1621
1622                        Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
1623
1624                        boundary - index of last SLC block on Flex-OneNAND.
1625                                   The remaining blocks are configured as MLC blocks.
1626                        lock     - Configure if Flex-OneNAND boundary should be locked.
1627                                   Once locked, the boundary cannot be changed.
1628                                   1 indicates lock status, 0 indicates unlock status.
1629
1630        mtdset=         [ARM]
1631                        ARM/S3C2412 JIVE boot control
1632
1633                        See arch/arm/mach-s3c2412/mach-jive.c
1634
1635        mtouchusb.raw_coordinates=
1636                        [HW] Make the MicroTouch USB driver use raw coordinates
1637                        ('y', default) or cooked coordinates ('n')
1638
1639        mtrr_chunk_size=nn[KMG] [X86]
1640                        used for mtrr cleanup. It is largest continuous chunk
1641                        that could hold holes aka. UC entries.
1642
1643        mtrr_gran_size=nn[KMG] [X86]
1644                        Used for mtrr cleanup. It is granularity of mtrr block.
1645                        Default is 1.
1646                        Large value could prevent small alignment from
1647                        using up MTRRs.
1648
1649        mtrr_spare_reg_nr=n [X86]
1650                        Format: <integer>
1651                        Range: 0,7 : spare reg number
1652                        Default : 1
1653                        Used for mtrr cleanup. It is spare mtrr entries number.
1654                        Set to 2 or more if your graphical card needs more.
1655
1656        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
1657
1658        netdev=         [NET] Network devices parameters
1659                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
1660                        Note that mem_start is often overloaded to mean
1661                        something different and driver-specific.
1662                        This usage is only documented in each driver source
1663                        file if at all.
1664
1665        nf_conntrack.acct=
1666                        [NETFILTER] Enable connection tracking flow accounting
1667                        0 to disable accounting
1668                        1 to enable accounting
1669                        Default value is 0.
1670
1671        nfsaddrs=       [NFS] Deprecated.  Use ip= instead.
1672                        See Documentation/filesystems/nfs/nfsroot.txt.
1673
1674        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
1675                        See Documentation/filesystems/nfs/nfsroot.txt.
1676
1677        nfsrootdebug    [NFS] enable nfsroot debugging messages.
1678                        See Documentation/filesystems/nfs/nfsroot.txt.
1679
1680        nfs.callback_tcpport=
1681                        [NFS] set the TCP port on which the NFSv4 callback
1682                        channel should listen.
1683
1684        nfs.cache_getent=
1685                        [NFS] sets the pathname to the program which is used
1686                        to update the NFS client cache entries.
1687
1688        nfs.cache_getent_timeout=
1689                        [NFS] sets the timeout after which an attempt to
1690                        update a cache entry is deemed to have failed.
1691
1692        nfs.idmap_cache_timeout=
1693                        [NFS] set the maximum lifetime for idmapper cache
1694                        entries.
1695
1696        nfs.enable_ino64=
1697                        [NFS] enable 64-bit inode numbers.
1698                        If zero, the NFS client will fake up a 32-bit inode
1699                        number for the readdir() and stat() syscalls instead
1700                        of returning the full 64-bit number.
1701                        The default is to return 64-bit inode numbers.
1702
1703        nfs.max_session_slots=
1704                        [NFSv4.1] Sets the maximum number of session slots
1705                        the client will attempt to negotiate with the server.
1706                        This limits the number of simultaneous RPC requests
1707                        that the client can send to the NFSv4.1 server.
1708                        Note that there is little point in setting this
1709                        value higher than the max_tcp_slot_table_limit.
1710
1711        nfs.nfs4_disable_idmapping=
1712                        [NFSv4] When set to the default of '1', this option
1713                        ensures that both the RPC level authentication
1714                        scheme and the NFS level operations agree to use
1715                        numeric uids/gids if the mount is using the
1716                        'sec=sys' security flavour. In effect it is
1717                        disabling idmapping, which can make migration from
1718                        legacy NFSv2/v3 systems to NFSv4 easier.
1719                        Servers that do not support this mode of operation
1720                        will be autodetected by the client, and it will fall
1721                        back to using the idmapper.
1722                        To turn off this behaviour, set the value to '0'.
1723
1724        nfs.send_implementation_id =
1725                        [NFSv4.1] Send client implementation identification
1726                        information in exchange_id requests.
1727                        If zero, no implementation identification information
1728                        will be sent.
1729                        The default is to send the implementation identification
1730                        information.
1731
1732        nfsd.nfs4_disable_idmapping=
1733                        [NFSv4] When set to the default of '1', the NFSv4
1734                        server will return only numeric uids and gids to
1735                        clients using auth_sys, and will accept numeric uids
1736                        and gids from such clients.  This is intended to ease
1737                        migration from NFSv2/v3.
1738
1739        objlayoutdriver.osd_login_prog=
1740                        [NFS] [OBJLAYOUT] sets the pathname to the program which
1741                        is used to automatically discover and login into new
1742                        osd-targets. Please see:
1743                        Documentation/filesystems/pnfs.txt for more explanations
1744
1745        nmi_debug=      [KNL,AVR32,SH] Specify one or more actions to take
1746                        when a NMI is triggered.
1747                        Format: [state][,regs][,debounce][,die]
1748
1749        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
1750                        Format: [panic,][nopanic,][num]
1751                        Valid num: 0
1752                        0 - turn nmi_watchdog off
1753                        When panic is specified, panic when an NMI watchdog
1754                        timeout occurs (or 'nopanic' to override the opposite
1755                        default).
1756                        This is useful when you use a panic=... timeout and
1757                        need the box quickly up again.
1758
1759        netpoll.carrier_timeout=
1760                        [NET] Specifies amount of time (in seconds) that
1761                        netpoll should wait for a carrier. By default netpoll
1762                        waits 4 seconds.
1763
1764        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
1765                        emulation library even if a 387 maths coprocessor
1766                        is present.
1767
1768        no_console_suspend
1769                        [HW] Never suspend the console
1770                        Disable suspending of consoles during suspend and
1771                        hibernate operations.  Once disabled, debugging
1772                        messages can reach various consoles while the rest
1773                        of the system is being put to sleep (ie, while
1774                        debugging driver suspend/resume hooks).  This may
1775                        not work reliably with all consoles, but is known
1776                        to work with serial and VGA consoles.
1777                        To facilitate more flexible debugging, we also add
1778                        console_suspend, a printk module parameter to control
1779                        it. Users could use console_suspend (usually
1780                        /sys/module/printk/parameters/console_suspend) to
1781                        turn on/off it dynamically.
1782
1783        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
1784                        caches in the slab allocator.  Saves per-node memory,
1785                        but will impact performance.
1786
1787        noalign         [KNL,ARM]
1788
1789        noapic          [SMP,APIC] Tells the kernel to not make use of any
1790                        IOAPICs that may be present in the system.
1791
1792        noautogroup     Disable scheduler automatic task group creation.
1793
1794        nobats          [PPC] Do not use BATs for mapping kernel lowmem
1795                        on "Classic" PPC cores.
1796
1797        nocache         [ARM]
1798
1799        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction
1800
1801        nodelayacct     [KNL] Disable per-task delay accounting
1802
1803        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.
1804
1805        nodsp           [SH] Disable hardware DSP at boot time.
1806
1807        noefi           [X86] Disable EFI runtime services support.
1808
1809        noexec          [IA-64]
1810
1811        noexec          [X86]
1812                        On X86-32 available only on PAE configured kernels.
1813                        noexec=on: enable non-executable mappings (default)
1814                        noexec=off: disable non-executable mappings
1815
1816        nosmep          [X86]
1817                        Disable SMEP (Supervisor Mode Execution Protection)
1818                        even if it is supported by processor.
1819
1820        noexec32        [X86-64]
1821                        This affects only 32-bit executables.
1822                        noexec32=on: enable non-executable mappings (default)
1823                                read doesn't imply executable mappings
1824                        noexec32=off: disable non-executable mappings
1825                                read implies executable mappings
1826
1827        nofpu           [SH] Disable hardware FPU at boot time.
1828
1829        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
1830                        register save and restore. The kernel will only save
1831                        legacy floating-point registers on task switch.
1832
1833        noxsave         [BUGS=X86] Disables x86 extended register state save
1834                        and restore using xsave. The kernel will fallback to
1835                        enabling legacy floating-point and sse state.
1836
1837        nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
1838                        wfi(ARM) instruction doesn't work correctly and not to
1839                        use it. This is also useful when using JTAG debugger.
1840
1841        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
1842                        instruction doesn't work correctly and not to
1843                        use it.
1844
1845        no_file_caps    Tells the kernel not to honor file capabilities.  The
1846                        only way then for a file to be executed with privilege
1847                        is to be setuid root or executed by root.
1848
1849        nohalt          [IA-64] Tells the kernel not to use the power saving
1850                        function PAL_HALT_LIGHT when idle. This increases
1851                        power-consumption. On the positive side, it reduces
1852                        interrupt wake-up latency, which may improve performance
1853                        in certain environments such as networked servers or
1854                        real-time systems.
1855
1856        nohz=           [KNL] Boottime enable/disable dynamic ticks
1857                        Valid arguments: on, off
1858                        Default: on
1859
1860        noiotrap        [SH] Disables trapped I/O port accesses.
1861
1862        noirqdebug      [X86-32] Disables the code which attempts to detect and
1863                        disable unhandled interrupt sources.
1864
1865        no_timer_check  [X86,APIC] Disables the code which tests for
1866                        broken timer IRQ sources.
1867
1868        noisapnp        [ISAPNP] Disables ISA PnP code.
1869
1870        noinitrd        [RAM] Tells the kernel not to load any configured
1871                        initial RAM disk.
1872
1873        nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
1874                        remapping.
1875                        [Deprecated - use intremap=off]
1876
1877        nointroute      [IA-64]
1878
1879        nojitter        [IA-64] Disables jitter checking for ITC timers.
1880
1881        no-kvmclock     [X86,KVM] Disable paravirtualized KVM clock driver
1882
1883        no-kvmapf       [X86,KVM] Disable paravirtualized asynchronous page
1884                        fault handling.
1885
1886        no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
1887                        steal time is computed, but won't influence scheduler
1888                        behaviour
1889
1890        nolapic         [X86-32,APIC] Do not enable or use the local APIC.
1891
1892        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
1893
1894        noltlbs         [PPC] Do not use large page/tlb entries for kernel
1895                        lowmem mapping on PPC40x.
1896
1897        nomca           [IA-64] Disable machine check abort handling
1898
1899        nomce           [X86-32] Machine Check Exception
1900
1901        nomfgpt         [X86-32] Disable Multi-Function General Purpose
1902                        Timer usage (for AMD Geode machines).
1903
1904        nonmi_ipi       [X86] Disable using NMI IPIs during panic/reboot to
1905                        shutdown the other cpus.  Instead use the REBOOT_VECTOR
1906                        irq.
1907
1908        nomodule        Disable module load
1909
1910        nopat           [X86] Disable PAT (page attribute table extension of
1911                        pagetables) support.
1912
1913        norandmaps      Don't use address space randomization.  Equivalent to
1914                        echo 0 > /proc/sys/kernel/randomize_va_space
1915
1916        noreplace-paravirt      [X86,IA-64,PV_OPS] Don't patch paravirt_ops
1917
1918        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
1919                        with UP alternatives
1920
1921        noresidual      [PPC] Don't use residual data on PReP machines.
1922
1923        nordrand        [X86] Disable the direct use of the RDRAND
1924                        instruction even if it is supported by the
1925                        processor.  RDRAND is still available to user
1926                        space applications.
1927
1928        noresume        [SWSUSP] Disables resume and restores original swap
1929                        space.
1930
1931        no-scroll       [VGA] Disables scrollback.
1932                        This is required for the Braillex ib80-piezo Braille
1933                        reader made by F.H. Papenmeier (Germany).
1934
1935        nosbagart       [IA-64]
1936
1937        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
1938
1939        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
1940                        and disable the IO APIC.  legacy for "maxcpus=0".
1941
1942        nosoftlockup    [KNL] Disable the soft-lockup detector.
1943
1944        nosync          [HW,M68K] Disables sync negotiation for all devices.
1945
1946        notsc           [BUGS=X86-32] Disable Time Stamp Counter
1947
1948        nousb           [USB] Disable the USB subsystem
1949
1950        nowatchdog      [KNL] Disable the lockup detector (NMI watchdog).
1951
1952        nowb            [ARM]
1953
1954        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
1955
1956        nptcg=          [IA-64] Override max number of concurrent global TLB
1957                        purges which is reported from either PAL_VM_SUMMARY or
1958                        SAL PALO.
1959
1960        nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
1961                        could support.  nr_cpus=n : n >= 1 limits the kernel to
1962                        supporting 'n' processors. Later in runtime you can not
1963                        use hotplug cpu feature to put more cpu back to online.
1964                        just like you compile the kernel NR_CPUS=n
1965
1966        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
1967
1968        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
1969                        one of ['zone', 'node', 'default'] can be specified
1970                        This can be set from sysctl after boot.
1971                        See Documentation/sysctl/vm.txt for details.
1972
1973        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
1974                        See Documentation/debugging-via-ohci1394.txt for more
1975                        info.
1976
1977        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
1978                        Rather than timing out after 20 ms if an EC
1979                        command is not properly ACKed, override the length
1980                        of the timeout.  We have interrupts disabled while
1981                        waiting for the ACK, so if this is set too high
1982                        interrupts *may* be lost!
1983
1984        omap_mux=       [OMAP] Override bootloader pin multiplexing.
1985                        Format: <mux_mode0.mode_name=value>...
1986                        For example, to override I2C bus2:
1987                        omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
1988
1989        oprofile.timer= [HW]
1990                        Use timer interrupt instead of performance counters
1991
1992        oprofile.cpu_type=      Force an oprofile cpu type
1993                        This might be useful if you have an older oprofile
1994                        userland or if you want common events.
1995                        Format: { arch_perfmon }
1996                        arch_perfmon: [X86] Force use of architectural
1997                                perfmon on Intel CPUs instead of the
1998                                CPU specific event set.
1999                        timer: [X86] Force use of architectural NMI
2000                                timer mode (see also oprofile.timer
2001                                for generic hr timer mode)
2002                                [s390] Force legacy basic mode sampling
2003                                (report cpu_type "timer")
2004
2005        oops=panic      Always panic on oopses. Default is to just kill the
2006                        process, but there is a small probability of
2007                        deadlocking the machine.
2008                        This will also cause panics on machine check exceptions.
2009                        Useful together with panic=30 to trigger a reboot.
2010
2011        OSS             [HW,OSS]
2012                        See Documentation/sound/oss/oss-parameters.txt
2013
2014        panic=          [KNL] Kernel behaviour on panic: delay <timeout>
2015                        timeout > 0: seconds before rebooting
2016                        timeout = 0: wait forever
2017                        timeout < 0: reboot immediately
2018                        Format: <timeout>
2019
2020        parkbd.port=    [HW] Parallel port number the keyboard adapter is
2021                        connected to, default is 0.
2022                        Format: <parport#>
2023        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
2024                        0 for XT, 1 for AT (default is AT).
2025                        Format: <mode>
2026
2027        parport=        [HW,PPT] Specify parallel ports. 0 disables.
2028                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
2029                        Use 'auto' to force the driver to use any
2030                        IRQ/DMA settings detected (the default is to
2031                        ignore detected IRQ/DMA settings because of
2032                        possible conflicts). You can specify the base
2033                        address, IRQ, and DMA settings; IRQ and DMA
2034                        should be numbers, or 'auto' (for using detected
2035                        settings on that particular port), or 'nofifo'
2036                        (to avoid using a FIFO even if it is detected).
2037                        Parallel ports are assigned in the order they
2038                        are specified on the command line, starting
2039                        with parport0.
2040
2041        parport_init_mode=      [HW,PPT]
2042                        Configure VIA parallel port to operate in
2043                        a specific mode. This is necessary on Pegasos
2044                        computer where firmware has no options for setting
2045                        up parallel port mode and sets it to spp.
2046                        Currently this function knows 686a and 8231 chips.
2047                        Format: [spp|ps2|epp|ecp|ecpepp]
2048
2049        pause_on_oops=
2050                        Halt all CPUs after the first oops has been printed for
2051                        the specified number of seconds.  This is to be used if
2052                        your oopses keep scrolling off the screen.
2053
2054        pcbit=          [HW,ISDN]
2055
2056        pcd.            [PARIDE]
2057                        See header of drivers/block/paride/pcd.c.
2058                        See also Documentation/blockdev/paride.txt.
2059
2060        pci=option[,option...]  [PCI] various PCI subsystem options:
2061                earlydump       [X86] dump PCI config space before the kernel
2062                                changes anything
2063                off             [X86] don't probe for the PCI bus
2064                bios            [X86-32] force use of PCI BIOS, don't access
2065                                the hardware directly. Use this if your machine
2066                                has a non-standard PCI host bridge.
2067                nobios          [X86-32] disallow use of PCI BIOS, only direct
2068                                hardware access methods are allowed. Use this
2069                                if you experience crashes upon bootup and you
2070                                suspect they are caused by the BIOS.
2071                conf1           [X86] Force use of PCI Configuration
2072                                Mechanism 1.
2073                conf2           [X86] Force use of PCI Configuration
2074                                Mechanism 2.
2075                noaer           [PCIE] If the PCIEAER kernel config parameter is
2076                                enabled, this kernel boot option can be used to
2077                                disable the use of PCIE advanced error reporting.
2078                nodomains       [PCI] Disable support for multiple PCI
2079                                root domains (aka PCI segments, in ACPI-speak).
2080                nommconf        [X86] Disable use of MMCONFIG for PCI
2081                                Configuration
2082                check_enable_amd_mmconf [X86] check for and enable
2083                                properly configured MMIO access to PCI
2084                                config space on AMD family 10h CPU
2085                nomsi           [MSI] If the PCI_MSI kernel config parameter is
2086                                enabled, this kernel boot option can be used to
2087                                disable the use of MSI interrupts system-wide.
2088                noioapicquirk   [APIC] Disable all boot interrupt quirks.
2089                                Safety option to keep boot IRQs enabled. This
2090                                should never be necessary.
2091                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
2092                                primary IO-APIC for bridges that cannot disable
2093                                boot IRQs. This fixes a source of spurious IRQs
2094                                when the system masks IRQs.
2095                noioapicreroute [APIC] Disable workaround that uses the
2096                                boot IRQ equivalent of an IRQ that connects to
2097                                a chipset where boot IRQs cannot be disabled.
2098                                The opposite of ioapicreroute.
2099                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
2100                                routing table. These calls are known to be buggy
2101                                on several machines and they hang the machine
2102                                when used, but on other computers it's the only
2103                                way to get the interrupt routing table. Try
2104                                this option if the kernel is unable to allocate
2105                                IRQs or discover secondary PCI buses on your
2106                                motherboard.
2107                rom             [X86] Assign address space to expansion ROMs.
2108                                Use with caution as certain devices share
2109                                address decoders between ROMs and other
2110                                resources.
2111                norom           [X86] Do not assign address space to
2112                                expansion ROMs that do not already have
2113                                BIOS assigned address ranges.
2114                nobar           [X86] Do not assign address space to the
2115                                BARs that weren't assigned by the BIOS.
2116                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
2117                                assigned automatically to PCI devices. You can
2118                                make the kernel exclude IRQs of your ISA cards
2119                                this way.
2120                pirqaddr=0xAAAAA        [X86] Specify the physical address
2121                                of the PIRQ table (normally generated
2122                                by the BIOS) if it is outside the
2123                                F0000h-100000h range.
2124                lastbus=N       [X86] Scan all buses thru bus #N. Can be
2125                                useful if the kernel is unable to find your
2126                                secondary buses and you want to tell it
2127                                explicitly which ones they are.
2128                assign-busses   [X86] Always assign all PCI bus
2129                                numbers ourselves, overriding
2130                                whatever the firmware may have done.
2131                usepirqmask     [X86] Honor the possible IRQ mask stored
2132                                in the BIOS $PIR table. This is needed on
2133                                some systems with broken BIOSes, notably
2134                                some HP Pavilion N5400 and Omnibook XE3
2135                                notebooks. This will have no effect if ACPI
2136                                IRQ routing is enabled.
2137                noacpi          [X86] Do not use ACPI for IRQ routing
2138                                or for PCI scanning.
2139                use_crs         [X86] Use PCI host bridge window information
2140                                from ACPI.  On BIOSes from 2008 or later, this
2141                                is enabled by default.  If you need to use this,
2142                                please report a bug.
2143                nocrs           [X86] Ignore PCI host bridge windows from ACPI.
2144                                If you need to use this, please report a bug.
2145                routeirq        Do IRQ routing for all PCI devices.
2146                                This is normally done in pci_enable_device(),
2147                                so this option is a temporary workaround
2148                                for broken drivers that don't call it.
2149                skip_isa_align  [X86] do not align io start addr, so can
2150                                handle more pci cards
2151                firmware        [ARM] Do not re-enumerate the bus but instead
2152                                just use the configuration from the
2153                                bootloader. This is currently used on
2154                                IXP2000 systems where the bus has to be
2155                                configured a certain way for adjunct CPUs.
2156                noearly         [X86] Don't do any early type 1 scanning.
2157                                This might help on some broken boards which
2158                                machine check when some devices' config space
2159                                is read. But various workarounds are disabled
2160                                and some IOMMU drivers will not work.
2161                bfsort          Sort PCI devices into breadth-first order.
2162                                This sorting is done to get a device
2163                                order compatible with older (<= 2.4) kernels.
2164                nobfsort        Don't sort PCI devices into breadth-first order.
2165                cbiosize=nn[KMG]        The fixed amount of bus space which is
2166                                reserved for the CardBus bridge's IO window.
2167                                The default value is 256 bytes.
2168                cbmemsize=nn[KMG]       The fixed amount of bus space which is
2169                                reserved for the CardBus bridge's memory
2170                                window. The default value is 64 megabytes.
2171                resource_alignment=
2172                                Format:
2173                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
2174                                Specifies alignment and device to reassign
2175                                aligned memory resources.
2176                                If <order of align> is not specified,
2177                                PAGE_SIZE is used as alignment.
2178                                PCI-PCI bridge can be specified, if resource
2179                                windows need to be expanded.
2180                ecrc=           Enable/disable PCIe ECRC (transaction layer
2181                                end-to-end CRC checking).
2182                                bios: Use BIOS/firmware settings. This is the
2183                                the default.
2184                                off: Turn ECRC off
2185                                on: Turn ECRC on.
2186                realloc=        Enable/disable reallocating PCI bridge resources
2187                                if allocations done by BIOS are too small to
2188                                accommodate resources required by all child
2189                                devices.
2190                                off: Turn realloc off
2191                                on: Turn realloc on
2192                realloc         same as realloc=on
2193                noari           do not use PCIe ARI.
2194                pcie_scan_all   Scan all possible PCIe devices.  Otherwise we
2195                                only look for one device below a PCIe downstream
2196                                port.
2197
2198        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
2199                        Management.
2200                off     Disable ASPM.
2201                force   Enable ASPM even on devices that claim not to support it.
2202                        WARNING: Forcing ASPM on may cause system lockups.
2203
2204        pcie_hp=        [PCIE] PCI Express Hotplug driver options:
2205                nomsi   Do not use MSI for PCI Express Native Hotplug (this
2206                        makes all PCIe ports use INTx for hotplug services).
2207
2208        pcie_ports=     [PCIE] PCIe ports handling:
2209                auto    Ask the BIOS whether or not to use native PCIe services
2210                        associated with PCIe ports (PME, hot-plug, AER).  Use
2211                        them only if that is allowed by the BIOS.
2212                native  Use native PCIe services associated with PCIe ports
2213                        unconditionally.
2214                compat  Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
2215                        ports driver.
2216
2217        pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
2218                nomsi   Do not use MSI for native PCIe PME signaling (this makes
2219                        all PCIe root ports use INTx for all services).
2220
2221        pcmv=           [HW,PCMCIA] BadgePAD 4
2222
2223        pd.             [PARIDE]
2224                        See Documentation/blockdev/paride.txt.
2225
2226        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
2227                        boot time.
2228                        Format: { 0 | 1 }
2229                        See arch/parisc/kernel/pdc_chassis.c
2230
2231        percpu_alloc=   Select which percpu first chunk allocator to use.
2232                        Currently supported values are "embed" and "page".
2233                        Archs may support subset or none of the selections.
2234                        See comments in mm/percpu.c for details on each
2235                        allocator.  This parameter is primarily for debugging
2236                        and performance comparison.
2237
2238        pf.             [PARIDE]
2239                        See Documentation/blockdev/paride.txt.
2240
2241        pg.             [PARIDE]
2242                        See Documentation/blockdev/paride.txt.
2243
2244        pirq=           [SMP,APIC] Manual mp-table setup
2245                        See Documentation/x86/i386/IO-APIC.txt.
2246
2247        plip=           [PPT,NET] Parallel port network link
2248                        Format: { parport<nr> | timid | 0 }
2249                        See also Documentation/parport.txt.
2250
2251        pmtmr=          [X86] Manual setup of pmtmr I/O Port.
2252                        Override pmtimer IOPort with a hex value.
2253                        e.g. pmtmr=0x508
2254
2255        pnp.debug=1     [PNP]
2256                        Enable PNP debug messages (depends on the
2257                        CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
2258                        via /sys/module/pnp/parameters/debug.  We always show
2259                        current resource usage; turning this on also shows
2260                        possible settings and some assignment information.
2261
2262        pnpacpi=        [ACPI]
2263                        { off }
2264
2265        pnpbios=        [ISAPNP]
2266                        { on | off | curr | res | no-curr | no-res }
2267
2268        pnp_reserve_irq=
2269                        [ISAPNP] Exclude IRQs for the autoconfiguration
2270
2271        pnp_reserve_dma=
2272                        [ISAPNP] Exclude DMAs for the autoconfiguration
2273
2274        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
2275                        Ranges are in pairs (I/O port base and size).
2276
2277        pnp_reserve_mem=
2278                        [ISAPNP] Exclude memory regions for the
2279                        autoconfiguration.
2280                        Ranges are in pairs (memory base and size).
2281
2282        ports=          [IP_VS_FTP] IPVS ftp helper module
2283                        Default is 21.
2284                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
2285                        may be specified.
2286                        Format: <port>,<port>....
2287
2288        print-fatal-signals=
2289                        [KNL] debug: print fatal signals
2290
2291                        If enabled, warn about various signal handling
2292                        related application anomalies: too many signals,
2293                        too many POSIX.1 timers, fatal signals causing a
2294                        coredump - etc.
2295
2296                        If you hit the warning due to signal overflow,
2297                        you might want to try "ulimit -i unlimited".
2298
2299                        default: off.
2300
2301        printk.always_kmsg_dump=
2302                        Trigger kmsg_dump for cases other than kernel oops or
2303                        panics
2304                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2305                        default: disabled
2306
2307        printk.time=    Show timing data prefixed to each printk message line
2308                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
2309
2310        processor.max_cstate=   [HW,ACPI]
2311                        Limit processor to maximum C-state
2312                        max_cstate=9 overrides any DMI blacklist limit.
2313
2314        processor.nocst [HW,ACPI]
2315                        Ignore the _CST method to determine C-states,
2316                        instead using the legacy FADT method
2317
2318        profile=        [KNL] Enable kernel profiling via /proc/profile
2319                        Format: [schedule,]<number>
2320                        Param: "schedule" - profile schedule points.
2321                        Param: <number> - step/bucket size as a power of 2 for
2322                                statistical time based profiling.
2323                        Param: "sleep" - profile D-state sleeping (millisecs).
2324                                Requires CONFIG_SCHEDSTATS
2325                        Param: "kvm" - profile VM exits.
2326
2327        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
2328                        before loading.
2329                        See Documentation/blockdev/ramdisk.txt.
2330
2331        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
2332                        probe for; one of (bare|imps|exps|lifebook|any).
2333        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
2334                        per second.
2335        psmouse.resetafter=     [HW,MOUSE]
2336                        Try to reset the device after so many bad packets
2337                        (0 = never).
2338        psmouse.resolution=
2339                        [HW,MOUSE] Set desired mouse resolution, in dpi.
2340        psmouse.smartscroll=
2341                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
2342                        0 = disabled, 1 = enabled (default).
2343
2344        pstore.backend= Specify the name of the pstore backend to use
2345
2346        pt.             [PARIDE]
2347                        See Documentation/blockdev/paride.txt.
2348
2349        pty.legacy_count=
2350                        [KNL] Number of legacy pty's. Overwrites compiled-in
2351                        default number.
2352
2353        quiet           [KNL] Disable most log messages
2354
2355        r128=           [HW,DRM]
2356
2357        raid=           [HW,RAID]
2358                        See Documentation/md.txt.
2359
2360        ramdisk_blocksize=      [RAM]
2361                        See Documentation/blockdev/ramdisk.txt.
2362
2363        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
2364                        See Documentation/blockdev/ramdisk.txt.
2365
2366        rcutree.blimit= [KNL,BOOT]
2367                        Set maximum number of finished RCU callbacks to process
2368                        in one batch.
2369
2370        rcutree.qhimark=        [KNL,BOOT]
2371                        Set threshold of queued
2372                        RCU callbacks over which batch limiting is disabled.
2373
2374        rcutree.qlowmark=       [KNL,BOOT]
2375                        Set threshold of queued RCU callbacks below which
2376                        batch limiting is re-enabled.
2377
2378        rcutree.rcu_cpu_stall_suppress= [KNL,BOOT]
2379                        Suppress RCU CPU stall warning messages.
2380
2381        rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
2382                        Set timeout for RCU CPU stall warning messages.
2383
2384        rcutorture.fqs_duration= [KNL,BOOT]
2385                        Set duration of force_quiescent_state bursts.
2386
2387        rcutorture.fqs_holdoff= [KNL,BOOT]
2388                        Set holdoff time within force_quiescent_state bursts.
2389
2390        rcutorture.fqs_stutter= [KNL,BOOT]
2391                        Set wait time between force_quiescent_state bursts.
2392
2393        rcutorture.irqreader= [KNL,BOOT]
2394                        Test RCU readers from irq handlers.
2395
2396        rcutorture.n_barrier_cbs= [KNL,BOOT]
2397                        Set callbacks/threads for rcu_barrier() testing.
2398
2399        rcutorture.nfakewriters= [KNL,BOOT]
2400                        Set number of concurrent RCU writers.  These just
2401                        stress RCU, they don't participate in the actual
2402                        test, hence the "fake".
2403
2404        rcutorture.nreaders= [KNL,BOOT]
2405                        Set number of RCU readers.
2406
2407        rcutorture.onoff_holdoff= [KNL,BOOT]
2408                        Set time (s) after boot for CPU-hotplug testing.
2409
2410        rcutorture.onoff_interval= [KNL,BOOT]
2411                        Set time (s) between CPU-hotplug operations, or
2412                        zero to disable CPU-hotplug testing.
2413
2414        rcutorture.shuffle_interval= [KNL,BOOT]
2415                        Set task-shuffle interval (s).  Shuffling tasks
2416                        allows some CPUs to go into dyntick-idle mode
2417                        during the rcutorture test.
2418
2419        rcutorture.shutdown_secs= [KNL,BOOT]
2420                        Set time (s) after boot system shutdown.  This
2421                        is useful for hands-off automated testing.
2422
2423        rcutorture.stall_cpu= [KNL,BOOT]
2424                        Duration of CPU stall (s) to test RCU CPU stall
2425                        warnings, zero to disable.
2426
2427        rcutorture.stall_cpu_holdoff= [KNL,BOOT]
2428                        Time to wait (s) after boot before inducing stall.
2429
2430        rcutorture.stat_interval= [KNL,BOOT]
2431                        Time (s) between statistics printk()s.
2432
2433        rcutorture.stutter= [KNL,BOOT]
2434                        Time (s) to stutter testing, for example, specifying
2435                        five seconds causes the test to run for five seconds,
2436                        wait for five seconds, and so on.  This tests RCU's
2437                        ability to transition abruptly to and from idle.
2438
2439        rcutorture.test_boost= [KNL,BOOT]
2440                        Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
2441                        "Maybe" means test if the RCU implementation
2442                        under test support RCU priority boosting.
2443
2444        rcutorture.test_boost_duration= [KNL,BOOT]
2445                        Duration (s) of each individual boost test.
2446
2447        rcutorture.test_boost_interval= [KNL,BOOT]
2448                        Interval (s) between each boost test.
2449
2450        rcutorture.test_no_idle_hz= [KNL,BOOT]
2451                        Test RCU's dyntick-idle handling.  See also the
2452                        rcutorture.shuffle_interval parameter.
2453
2454        rcutorture.torture_type= [KNL,BOOT]
2455                        Specify the RCU implementation to test.
2456
2457        rcutorture.verbose= [KNL,BOOT]
2458                        Enable additional printk() statements.
2459
2460        rdinit=         [KNL]
2461                        Format: <full_path>
2462                        Run specified binary instead of /init from the ramdisk,
2463                        used for early userspace startup. See initrd.
2464
2465        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
2466                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
2467                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c
2468
2469        relax_domain_level=
2470                        [KNL, SMP] Set scheduler's default relax_domain_level.
2471                        See Documentation/cgroups/cpusets.txt.
2472
2473        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area
2474
2475        reservetop=     [X86-32]
2476                        Format: nn[KMG]
2477                        Reserves a hole at the top of the kernel virtual
2478                        address space.
2479
2480        reservelow=     [X86]
2481                        Format: nn[K]
2482                        Set the amount of memory to reserve for BIOS at
2483                        the bottom of the address space.
2484
2485        reset_devices   [KNL] Force drivers to reset the underlying device
2486                        during initialization.
2487
2488        resume=         [SWSUSP]
2489                        Specify the partition device for software suspend
2490                        Format:
2491                        {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
2492
2493        resume_offset=  [SWSUSP]
2494                        Specify the offset from the beginning of the partition
2495                        given by "resume=" at which the swap header is located,
2496                        in <PAGE_SIZE> units (needed only for swap files).
2497                        See  Documentation/power/swsusp-and-swap-files.txt
2498
2499        resumedelay=    [HIBERNATION] Delay (in seconds) to pause before attempting to
2500                        read the resume files
2501
2502        resumewait      [HIBERNATION] Wait (indefinitely) for resume device to show up.
2503                        Useful for devices that are detected asynchronously
2504                        (e.g. USB and MMC devices).
2505
2506        hibernate=      [HIBERNATION]
2507                noresume        Don't check if there's a hibernation image
2508                                present during boot.
2509                nocompress      Don't compress/decompress hibernation images.
2510
2511        retain_initrd   [RAM] Keep initrd memory after extraction
2512
2513        rhash_entries=  [KNL,NET]
2514                        Set number of hash buckets for route cache
2515
2516        riscom8=        [HW,SERIAL]
2517                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]
2518
2519        ro              [KNL] Mount root device read-only on boot
2520
2521        root=           [KNL] Root filesystem
2522                        See name_to_dev_t comment in init/do_mounts.c.
2523
2524        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
2525                        mount the root filesystem
2526
2527        rootflags=      [KNL] Set root filesystem mount option string
2528
2529        rootfstype=     [KNL] Set root filesystem type
2530
2531        rootwait        [KNL] Wait (indefinitely) for root device to show up.
2532                        Useful for devices that are detected asynchronously
2533                        (e.g. USB and MMC devices).
2534
2535        rw              [KNL] Mount root device read-write on boot
2536
2537        S               [KNL] Run init in single mode
2538
2539        sa1100ir        [NET]
2540                        See drivers/net/irda/sa1100_ir.c.
2541
2542        sbni=           [NET] Granch SBNI12 leased line adapter
2543
2544        sched_debug     [KNL] Enables verbose scheduler debug messages.
2545
2546        skew_tick=      [KNL] Offset the periodic timer tick per cpu to mitigate
2547                        xtime_lock contention on larger systems, and/or RCU lock
2548                        contention on all systems with CONFIG_MAXSMP set.
2549                        Format: { "0" | "1" }
2550                        0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
2551                        1 -- enable.
2552                        Note: increases power consumption, thus should only be
2553                        enabled if running jitter sensitive (HPC/RT) workloads.
2554
2555        security=       [SECURITY] Choose a security module to enable at boot.
2556                        If this boot parameter is not specified, only the first
2557                        security module asking for security registration will be
2558                        loaded. An invalid security module name will be treated
2559                        as if no module has been chosen.
2560
2561        selinux=        [SELINUX] Disable or enable SELinux at boot time.
2562                        Format: { "0" | "1" }
2563                        See security/selinux/Kconfig help text.
2564                        0 -- disable.
2565                        1 -- enable.
2566                        Default value is set via kernel config option.
2567                        If enabled at boot time, /selinux/disable can be used
2568                        later to disable prior to initial policy load.
2569
2570        apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
2571                        Format: { "0" | "1" }
2572                        See security/apparmor/Kconfig help text
2573                        0 -- disable.
2574                        1 -- enable.
2575                        Default value is set via kernel config option.
2576
2577        serialnumber    [BUGS=X86-32]
2578
2579        shapers=        [NET]
2580                        Maximal number of shapers.
2581
2582        show_msr=       [x86] show boot-time MSR settings
2583                        Format: { <integer> }
2584                        Show boot-time (BIOS-initialized) MSR settings.
2585                        The parameter means the number of CPUs to show,
2586                        for example 1 means boot CPU only.
2587
2588        simeth=         [IA-64]
2589        simscsi=
2590
2591        slram=          [HW,MTD]
2592
2593        slab_max_order= [MM, SLAB]
2594                        Determines the maximum allowed order for slabs.
2595                        A high setting may cause OOMs due to memory
2596                        fragmentation.  Defaults to 1 for systems with
2597                        more than 32MB of RAM, 0 otherwise.
2598
2599        slub_debug[=options[,slabs]]    [MM, SLUB]
2600                        Enabling slub_debug allows one to determine the
2601                        culprit if slab objects become corrupted. Enabling
2602                        slub_debug can create guard zones around objects and
2603                        may poison objects when not in use. Also tracks the
2604                        last alloc / free. For more information see
2605                        Documentation/vm/slub.txt.
2606
2607        slub_max_order= [MM, SLUB]
2608                        Determines the maximum allowed order for slabs.
2609                        A high setting may cause OOMs due to memory
2610                        fragmentation. For more information see
2611                        Documentation/vm/slub.txt.
2612
2613        slub_min_objects=       [MM, SLUB]
2614                        The minimum number of objects per slab. SLUB will
2615                        increase the slab order up to slub_max_order to
2616                        generate a sufficiently large slab able to contain
2617                        the number of objects indicated. The higher the number
2618                        of objects the smaller the overhead of tracking slabs
2619                        and the less frequently locks need to be acquired.
2620                        For more information see Documentation/vm/slub.txt.
2621
2622        slub_min_order= [MM, SLUB]
2623                        Determines the minimum page order for slabs. Must be
2624                        lower than slub_max_order.
2625                        For more information see Documentation/vm/slub.txt.
2626
2627        slub_nomerge    [MM, SLUB]
2628                        Disable merging of slabs with similar size. May be
2629                        necessary if there is some reason to distinguish
2630                        allocs to different slabs. Debug options disable
2631                        merging on their own.
2632                        For more information see Documentation/vm/slub.txt.
2633
2634        smart2=         [HW]
2635                        Format: <io1>[,<io2>[,...,<io8>]]
2636
2637        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
2638                        attempt to substitute SMP alternatives once at boot.
2639
2640        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
2641        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
2642        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
2643        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
2644        smsc-ircc2.ircc_irq=    [HW] IRQ line
2645        smsc-ircc2.ircc_dma=    [HW] DMA channel
2646        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
2647                                0: Toshiba Satellite 1800 (GP data pin select)
2648                                1: Fast pin select (default)
2649                                2: ATC IRMode
2650
2651        softlockup_panic=
2652                        [KNL] Should the soft-lockup detector generate panics.
2653                        Format: <integer>
2654
2655        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
2656                        See Documentation/laptops/sonypi.txt
2657
2658        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
2659                        See Documentation/serial/specialix.txt.
2660
2661        spia_io_base=   [HW,MTD]
2662        spia_fio_base=
2663        spia_pedr=
2664        spia_peddr=
2665
2666        stacktrace      [FTRACE]
2667                        Enabled the stack tracer on boot up.
2668
2669        stacktrace_filter=[function-list]
2670                        [FTRACE] Limit the functions that the stack tracer
2671                        will trace at boot up. function-list is a comma separated
2672                        list of functions. This list can be changed at run
2673                        time by the stack_trace_filter file in the debugfs
2674                        tracing directory. Note, this enables stack tracing
2675                        and the stacktrace above is not needed.
2676
2677        sti=            [PARISC,HW]
2678                        Format: <num>
2679                        Set the STI (builtin display/keyboard on the HP-PARISC
2680                        machines) console (graphic card) which should be used
2681                        as the initial boot-console.
2682                        See also comment in drivers/video/console/sticore.c.
2683
2684        sti_font=       [HW]
2685                        See comment in drivers/video/console/sticore.c.
2686
2687        stifb=          [HW]
2688                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
2689
2690        sunrpc.min_resvport=
2691        sunrpc.max_resvport=
2692                        [NFS,SUNRPC]
2693                        SunRPC servers often require that client requests
2694                        originate from a privileged port (i.e. a port in the
2695                        range 0 < portnr < 1024).
2696                        An administrator who wishes to reserve some of these
2697                        ports for other uses may adjust the range that the
2698                        kernel's sunrpc client considers to be privileged
2699                        using these two parameters to set the minimum and
2700                        maximum port values.
2701
2702        sunrpc.pool_mode=
2703                        [NFS]
2704                        Control how the NFS server code allocates CPUs to
2705                        service thread pools.  Depending on how many NICs
2706                        you have and where their interrupts are bound, this
2707                        option will affect which CPUs will do NFS serving.
2708                        Note: this parameter cannot be changed while the
2709                        NFS server is running.
2710
2711                        auto        the server chooses an appropriate mode
2712                                    automatically using heuristics
2713                        global      a single global pool contains all CPUs
2714                        percpu      one pool for each CPU
2715                        pernode     one pool for each NUMA node (equivalent
2716                                    to global on non-NUMA machines)
2717
2718        sunrpc.tcp_slot_table_entries=
2719        sunrpc.udp_slot_table_entries=
2720                        [NFS,SUNRPC]
2721                        Sets the upper limit on the number of simultaneous
2722                        RPC calls that can be sent from the client to a
2723                        server. Increasing these values may allow you to
2724                        improve throughput, but will also increase the
2725                        amount of memory reserved for use by the client.
2726
2727        swapaccount[=0|1]
2728                        [KNL] Enable accounting of swap in memory resource
2729                        controller if no parameter or 1 is given or disable
2730                        it if 0 is given (See Documentation/cgroups/memory.txt)
2731
2732        swiotlb=        [IA-64] Number of I/O TLB slabs
2733
2734        switches=       [HW,M68k]
2735
2736        sysfs.deprecated=0|1 [KNL]
2737                        Enable/disable old style sysfs layout for old udev
2738                        on older distributions. When this option is enabled
2739                        very new udev will not work anymore. When this option
2740                        is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
2741                        in older udev will not work anymore.
2742                        Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
2743                        the kernel configuration.
2744
2745        sysrq_always_enabled
2746                        [KNL]
2747                        Ignore sysrq setting - this boot parameter will
2748                        neutralize any effect of /proc/sys/kernel/sysrq.
2749                        Useful for debugging.
2750
2751        tdfx=           [HW,DRM]
2752
2753        test_suspend=   [SUSPEND]
2754                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
2755                        standby suspend) as the system sleep state to briefly
2756                        enter during system startup.  The system is woken from
2757                        this state using a wakeup-capable RTC alarm.
2758
2759        thash_entries=  [KNL,NET]
2760                        Set number of hash buckets for TCP connection
2761
2762        thermal.act=    [HW,ACPI]
2763                        -1: disable all active trip points in all thermal zones
2764                        <degrees C>: override all lowest active trip points
2765
2766        thermal.crt=    [HW,ACPI]
2767                        -1: disable all critical trip points in all thermal zones
2768                        <degrees C>: override all critical trip points
2769
2770        thermal.nocrt=  [HW,ACPI]
2771                        Set to disable actions on ACPI thermal zone
2772                        critical and hot trip points.
2773
2774        thermal.off=    [HW,ACPI]
2775                        1: disable ACPI thermal control
2776
2777        thermal.psv=    [HW,ACPI]
2778                        -1: disable all passive trip points
2779                        <degrees C>: override all passive trip points to this
2780                        value
2781
2782        thermal.tzp=    [HW,ACPI]
2783                        Specify global default ACPI thermal zone polling rate
2784                        <deci-seconds>: poll all this frequency
2785                        0: no polling (default)
2786
2787        threadirqs      [KNL]
2788                        Force threading of all interrupt handlers except those
2789                        marked explicitly IRQF_NO_THREAD.
2790
2791        topology=       [S390]
2792                        Format: {off | on}
2793                        Specify if the kernel should make use of the cpu
2794                        topology information if the hardware supports this.
2795                        The scheduler will make use of this information and
2796                        e.g. base its process migration decisions on it.
2797                        Default is on.
2798
2799        tp720=          [HW,PS2]
2800
2801        tpm_suspend_pcr=[HW,TPM]
2802                        Format: integer pcr id
2803                        Specify that at suspend time, the tpm driver
2804                        should extend the specified pcr with zeros,
2805                        as a workaround for some chips which fail to
2806                        flush the last written pcr on TPM_SaveState.
2807                        This will guarantee that all the other pcrs
2808                        are saved.
2809
2810        trace_buf_size=nn[KMG]
2811                        [FTRACE] will set tracing buffer size.
2812
2813        trace_event=[event-list]
2814                        [FTRACE] Set and start specified trace events in order
2815                        to facilitate early boot debugging.
2816                        See also Documentation/trace/events.txt
2817
2818        transparent_hugepage=
2819                        [KNL]
2820                        Format: [always|madvise|never]
2821                        Can be used to control the default behavior of the system
2822                        with respect to transparent hugepages.
2823                        See Documentation/vm/transhuge.txt for more details.
2824
2825        tsc=            Disable clocksource stability checks for TSC.
2826                        Format: <string>
2827                        [x86] reliable: mark tsc clocksource as reliable, this
2828                        disables clocksource verification at runtime, as well
2829                        as the stability checks done at bootup. Used to enable
2830                        high-resolution timer mode on older hardware, and in
2831                        virtualized environment.
2832                        [x86] noirqtime: Do not use TSC to do irq accounting.
2833                        Used to run time disable IRQ_TIME_ACCOUNTING on any
2834                        platforms where RDTSC is slow and this accounting
2835                        can add overhead.
2836
2837        turbografx.map[2|3]=    [HW,JOY]
2838                        TurboGraFX parallel port interface
2839                        Format:
2840                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
2841                        See also Documentation/input/joystick-parport.txt
2842
2843        udbg-immortal   [PPC] When debugging early kernel crashes that
2844                        happen after console_init() and before a proper 
2845                        console driver takes over, this boot options might
2846                        help "seeing" what's going on.
2847
2848        uhash_entries=  [KNL,NET]
2849                        Set number of hash buckets for UDP/UDP-Lite connections
2850
2851        uhci-hcd.ignore_oc=
2852                        [USB] Ignore overcurrent events (default N).
2853                        Some badly-designed motherboards generate lots of
2854                        bogus events, for ports that aren't wired to
2855                        anything.  Set this parameter to avoid log spamming.
2856                        Note that genuine overcurrent events won't be
2857                        reported either.
2858
2859        unknown_nmi_panic
2860                        [X86] Cause panic on unknown NMI.
2861
2862        usbcore.authorized_default=
2863                        [USB] Default USB device authorization:
2864                        (default -1 = authorized except for wireless USB,
2865                        0 = not authorized, 1 = authorized)
2866
2867        usbcore.autosuspend=
2868                        [USB] The autosuspend time delay (in seconds) used
2869                        for newly-detected USB devices (default 2).  This
2870                        is the time required before an idle device will be
2871                        autosuspended.  Devices for which the delay is set
2872                        to a negative value won't be autosuspended at all.
2873
2874        usbcore.usbfs_snoop=
2875                        [USB] Set to log all usbfs traffic (default 0 = off).
2876
2877        usbcore.blinkenlights=
2878                        [USB] Set to cycle leds on hubs (default 0 = off).
2879
2880        usbcore.old_scheme_first=
2881                        [USB] Start with the old device initialization
2882                        scheme (default 0 = off).
2883
2884        usbcore.usbfs_memory_mb=
2885                        [USB] Memory limit (in MB) for buffers allocated by
2886                        usbfs (default = 16, 0 = max = 2047).
2887
2888        usbcore.use_both_schemes=
2889                        [USB] Try the other device initialization scheme
2890                        if the first one fails (default 1 = enabled).
2891
2892        usbcore.initial_descriptor_timeout=
2893                        [USB] Specifies timeout for the initial 64-byte
2894                        USB_REQ_GET_DESCRIPTOR request in milliseconds
2895                        (default 5000 = 5.0 seconds).
2896
2897        usbhid.mousepoll=
2898                        [USBHID] The interval which mice are to be polled at.
2899
2900        usb-storage.delay_use=
2901                        [UMS] The delay in seconds before a new device is
2902                        scanned for Logical Units (default 5).
2903
2904        usb-storage.quirks=
2905                        [UMS] A list of quirks entries to supplement or
2906                        override the built-in unusual_devs list.  List
2907                        entries are separated by commas.  Each entry has
2908                        the form VID:PID:Flags where VID and PID are Vendor
2909                        and Product ID values (4-digit hex numbers) and
2910                        Flags is a set of characters, each corresponding
2911                        to a common usb-storage quirk flag as follows:
2912                                a = SANE_SENSE (collect more than 18 bytes
2913                                        of sense data);
2914                                b = BAD_SENSE (don't collect more than 18
2915                                        bytes of sense data);
2916                                c = FIX_CAPACITY (decrease the reported
2917                                        device capacity by one sector);
2918                                d = NO_READ_DISC_INFO (don't use
2919                                        READ_DISC_INFO command);
2920                                e = NO_READ_CAPACITY_16 (don't use
2921                                        READ_CAPACITY_16 command);
2922                                h = CAPACITY_HEURISTICS (decrease the
2923                                        reported device capacity by one
2924                                        sector if the number is odd);
2925                                i = IGNORE_DEVICE (don't bind to this
2926                                        device);
2927                                l = NOT_LOCKABLE (don't try to lock and
2928                                        unlock ejectable media);
2929                                m = MAX_SECTORS_64 (don't transfer more
2930                                        than 64 sectors = 32 KB at a time);
2931                                n = INITIAL_READ10 (force a retry of the
2932                                        initial READ(10) command);
2933                                o = CAPACITY_OK (accept the capacity
2934                                        reported by the device);
2935                                r = IGNORE_RESIDUE (the device reports
2936                                        bogus residue values);
2937                                s = SINGLE_LUN (the device has only one
2938                                        Logical Unit);
2939                                w = NO_WP_DETECT (don't test whether the
2940                                        medium is write-protected).
2941                        Example: quirks=0419:aaf5:rl,0421:0433:rc
2942
2943        user_debug=     [KNL,ARM]
2944                        Format: <int>
2945                        See arch/arm/Kconfig.debug help text.
2946                                 1 - undefined instruction events
2947                                 2 - system calls
2948                                 4 - invalid data aborts
2949                                 8 - SIGSEGV faults
2950                                16 - SIGBUS faults
2951                        Example: user_debug=31
2952
2953        userpte=
2954                        [X86] Flags controlling user PTE allocations.
2955
2956                                nohigh = do not allocate PTE pages in
2957                                        HIGHMEM regardless of setting
2958                                        of CONFIG_HIGHPTE.
2959
2960        vdso=           [X86,SH]
2961                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
2962                        vdso=1: enable VDSO (default)
2963                        vdso=0: disable VDSO mapping
2964
2965        vdso32=         [X86]
2966                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
2967                        vdso32=1: enable 32-bit VDSO (default)
2968                        vdso32=0: disable 32-bit VDSO mapping
2969
2970        vector=         [IA-64,SMP]
2971                        vector=percpu: enable percpu vector domain
2972
2973        video=          [FB] Frame buffer configuration
2974                        See Documentation/fb/modedb.txt.
2975
2976        virtio_mmio.device=
2977                        [VMMIO] Memory mapped virtio (platform) device.
2978
2979                                <size>@<baseaddr>:<irq>[:<id>]
2980                        where:
2981                                <size>     := size (can use standard suffixes
2982                                                like K, M and G)
2983                                <baseaddr> := physical base address
2984                                <irq>      := interrupt number (as passed to
2985                                                request_irq())
2986                                <id>       := (optional) platform device id
2987                        example:
2988                                virtio_mmio.device=1K@0x100b0000:48:7
2989
2990                        Can be used multiple times for multiple devices.
2991
2992        vga=            [BOOT,X86-32] Select a particular video mode
2993                        See Documentation/x86/boot.txt and
2994                        Documentation/svga.txt.
2995                        Use vga=ask for menu.
2996                        This is actually a boot loader parameter; the value is
2997                        passed to the kernel using a special protocol.
2998
2999        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
3000                        size of <nn>. This can be used to increase the
3001                        minimum size (128MB on x86). It can also be used to
3002                        decrease the size and leave more room for directly
3003                        mapped kernel RAM.
3004
3005        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
3006                        Format: <command>
3007
3008        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
3009                        Format: <command>
3010
3011        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
3012                        Format: <command>
3013
3014        vsyscall=       [X86-64]
3015                        Controls the behavior of vsyscalls (i.e. calls to
3016                        fixed addresses of 0xffffffffff600x00 from legacy
3017                        code).  Most statically-linked binaries and older
3018                        versions of glibc use these calls.  Because these
3019                        functions are at fixed addresses, they make nice
3020                        targets for exploits that can control RIP.
3021
3022                        emulate     [default] Vsyscalls turn into traps and are
3023                                    emulated reasonably safely.
3024
3025                        native      Vsyscalls are native syscall instructions.
3026                                    This is a little bit faster than trapping
3027                                    and makes a few dynamic recompilers work
3028                                    better than they would in emulation mode.
3029                                    It also makes exploits much easier to write.
3030
3031                        none        Vsyscalls don't work at all.  This makes
3032                                    them quite hard to use for exploits but
3033                                    might break your system.
3034
3035        vt.cur_default= [VT] Default cursor shape.
3036                        Format: 0xCCBBAA, where AA, BB, and CC are the same as
3037                        the parameters of the <Esc>[?A;B;Cc escape sequence;
3038                        see VGA-softcursor.txt. Default: 2 = underline.
3039
3040        vt.default_blu= [VT]
3041                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
3042                        Change the default blue palette of the console.
3043                        This is a 16-member array composed of values
3044                        ranging from 0-255.
3045
3046        vt.default_grn= [VT]
3047                        Format: <green0>,<green1>,<green2>,...,<green15>
3048                        Change the default green palette of the console.
3049                        This is a 16-member array composed of values
3050                        ranging from 0-255.
3051
3052        vt.default_red= [VT]
3053                        Format: <red0>,<red1>,<red2>,...,<red15>
3054                        Change the default red palette of the console.
3055                        This is a 16-member array composed of values
3056                        ranging from 0-255.
3057
3058        vt.default_utf8=
3059                        [VT]
3060                        Format=<0|1>
3061                        Set system-wide default UTF-8 mode for all tty's.
3062                        Default is 1, i.e. UTF-8 mode is enabled for all
3063                        newly opened terminals.
3064
3065        vt.global_cursor_default=
3066                        [VT]
3067                        Format=<-1|0|1>
3068                        Set system-wide default for whether a cursor
3069                        is shown on new VTs. Default is -1,
3070                        i.e. cursors will be created by default unless
3071                        overridden by individual drivers. 0 will hide
3072                        cursors, 1 will display them.
3073
3074        watchdog timers [HW,WDT] For information on watchdog timers,
3075                        see Documentation/watchdog/watchdog-parameters.txt
3076                        or other driver-specific files in the
3077                        Documentation/watchdog/ directory.
3078
3079        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
3080                        default x2apic cluster mode on platforms
3081                        supporting x2apic.
3082
3083        x86_mrst_timer= [X86-32,APBT]
3084                        Choose timer option for x86 Moorestown MID platform.
3085                        Two valid options are apbt timer only and lapic timer
3086                        plus one apbt timer for broadcast timer.
3087                        x86_mrst_timer=apbt_only | lapic_and_apbt
3088
3089        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
3090        xd_geo=         See header of drivers/block/xd.c.
3091
3092        xen_emul_unplug=                [HW,X86,XEN]
3093                        Unplug Xen emulated devices
3094                        Format: [unplug0,][unplug1]
3095                        ide-disks -- unplug primary master IDE devices
3096                        aux-ide-disks -- unplug non-primary-master IDE devices
3097                        nics -- unplug network devices
3098                        all -- unplug all emulated devices (NICs and IDE disks)
3099                        unnecessary -- unplugging emulated devices is
3100                                unnecessary even if the host did not respond to
3101                                the unplug protocol
3102                        never -- do not unplug even if version check succeeds
3103
3104        xirc2ps_cs=     [NET,PCMCIA]
3105                        Format:
3106                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
3107
3108______________________________________________________________________
3109
3110TODO:
3111
3112        Add more DRM drivers.
3113
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