mm: more intensive memory corruption debugging

[deliverable/linux.git] / Documentation / kernel-parameters.txt

                          Kernel Parameters
                          ~~~~~~~~~~~~~~~~~

The following is a consolidated list of the kernel parameters as implemented
(mostly) by the __setup() macro and sorted into English Dictionary order
(defined as ignoring all punctuation and sorting digits before letters in a
case insensitive manner), and with descriptions where known.

Module parameters for loadable modules are specified only as the
parameter name with optional '=' and value as appropriate, such as:

        modprobe usbcore blinkenlights=1

Module parameters for modules that are built into the kernel image
are specified on the kernel command line with the module name plus
'.' plus parameter name, with '=' and value if appropriate, such as:

        usbcore.blinkenlights=1

Hyphens (dashes) and underscores are equivalent in parameter names, so
        log_buf_len=1M print-fatal-signals=1
can also be entered as
        log-buf-len=1M print_fatal_signals=1


This document may not be entirely up to date and comprehensive. The command
"modinfo -p ${modulename}" shows a current list of all parameters of a loadable
module. Loadable modules, after being loaded into the running kernel, also
reveal their parameters in /sys/module/${modulename}/parameters/. Some of these
parameters may be changed at runtime by the command
"echo -n ${value} > /sys/module/${modulename}/parameters/${parm}".

The parameters listed below are only valid if certain kernel build options were
enabled and if respective hardware is present. The text in square brackets at
the beginning of each description states the restrictions within which a
parameter is applicable:

        ACPI    ACPI support is enabled.
        AGP     AGP (Accelerated Graphics Port) is enabled.
        ALSA    ALSA sound support is enabled.
        APIC    APIC support is enabled.
        APM     Advanced Power Management support is enabled.
        ARM     ARM architecture is enabled.
        AVR32   AVR32 architecture is enabled.
        AX25    Appropriate AX.25 support is enabled.
        BLACKFIN Blackfin architecture is enabled.
        DRM     Direct Rendering Management support is enabled.
        DYNAMIC_DEBUG Build in debug messages and enable them at runtime
        EDD     BIOS Enhanced Disk Drive Services (EDD) is enabled
        EFI     EFI Partitioning (GPT) is enabled
        EIDE    EIDE/ATAPI support is enabled.
        EVM     Extended Verification Module
        FB      The frame buffer device is enabled.
        FTRACE  Function tracing enabled.
        GCOV    GCOV profiling is enabled.
        HW      Appropriate hardware is enabled.
        IA-64   IA-64 architecture is enabled.
        IMA     Integrity measurement architecture is enabled.
        IOSCHED More than one I/O scheduler is enabled.
        IP_PNP  IP DHCP, BOOTP, or RARP is enabled.
        IPV6    IPv6 support is enabled.
        ISAPNP  ISA PnP code is enabled.
        ISDN    Appropriate ISDN support is enabled.
        JOY     Appropriate joystick support is enabled.
        KGDB    Kernel debugger support is enabled.
        KVM     Kernel Virtual Machine support is enabled.
        LIBATA  Libata driver is enabled
        LP      Printer support is enabled.
        LOOP    Loopback device support is enabled.
        M68k    M68k architecture is enabled.
                        These options have more detailed description inside of
                        Documentation/m68k/kernel-options.txt.
        MCA     MCA bus support is enabled.
        MDA     MDA console support is enabled.
        MIPS    MIPS architecture is enabled.
        MOUSE   Appropriate mouse support is enabled.
        MSI     Message Signaled Interrupts (PCI).
        MTD     MTD (Memory Technology Device) support is enabled.
        NET     Appropriate network support is enabled.
        NUMA    NUMA support is enabled.
        NFS     Appropriate NFS support is enabled.
        OSS     OSS sound support is enabled.
        PV_OPS  A paravirtualized kernel is enabled.
        PARIDE  The ParIDE (parallel port IDE) subsystem is enabled.
        PARISC  The PA-RISC architecture is enabled.
        PCI     PCI bus support is enabled.
        PCIE    PCI Express support is enabled.
        PCMCIA  The PCMCIA subsystem is enabled.
        PNP     Plug & Play support is enabled.
        PPC     PowerPC architecture is enabled.
        PPT     Parallel port support is enabled.
        PS2     Appropriate PS/2 support is enabled.
        RAM     RAM disk support is enabled.
        S390    S390 architecture is enabled.
        SCSI    Appropriate SCSI support is enabled.
                        A lot of drivers have their options described inside
                        the Documentation/scsi/ sub-directory.
        SECURITY Different security models are enabled.
        SELINUX SELinux support is enabled.
        APPARMOR AppArmor support is enabled.
        SERIAL  Serial support is enabled.
        SH      SuperH architecture is enabled.
        SMP     The kernel is an SMP kernel.
        SPARC   Sparc architecture is enabled.
        SWSUSP  Software suspend (hibernation) is enabled.
        SUSPEND System suspend states are enabled.
        TPM     TPM drivers are enabled.
        TS      Appropriate touchscreen support is enabled.
        UMS     USB Mass Storage support is enabled.
        USB     USB support is enabled.
        USBHID  USB Human Interface Device support is enabled.
        V4L     Video For Linux support is enabled.
        VGA     The VGA console has been enabled.
        VT      Virtual terminal support is enabled.
        WDT     Watchdog support is enabled.
        XT      IBM PC/XT MFM hard disk support is enabled.
        X86-32  X86-32, aka i386 architecture is enabled.
        X86-64  X86-64 architecture is enabled.
                        More X86-64 boot options can be found in
                        Documentation/x86/x86_64/boot-options.txt .
        X86     Either 32-bit or 64-bit x86 (same as X86-32+X86-64)
        XEN     Xen support is enabled

In addition, the following text indicates that the option:

        BUGS=   Relates to possible processor bugs on the said processor.
        KNL     Is a kernel start-up parameter.
        BOOT    Is a boot loader parameter.

Parameters denoted with BOOT are actually interpreted by the boot
loader, and have no meaning to the kernel directly.
Do not modify the syntax of boot loader parameters without extreme
need or coordination with <Documentation/x86/boot.txt>.

There are also arch-specific kernel-parameters not documented here.
See for example <Documentation/x86/x86_64/boot-options.txt>.

Note that ALL kernel parameters listed below are CASE SENSITIVE, and that
a trailing = on the name of any parameter states that that parameter will
be entered as an environment variable, whereas its absence indicates that
it will appear as a kernel argument readable via /proc/cmdline by programs
running once the system is up.

The number of kernel parameters is not limited, but the length of the
complete command line (parameters including spaces etc.) is limited to
a fixed number of characters. This limit depends on the architecture
and is between 256 and 4096 characters. It is defined in the file
./include/asm/setup.h as COMMAND_LINE_SIZE.

Finally, the [KMG] suffix is commonly described after a number of kernel
parameter values. These 'K', 'M', and 'G' letters represent the _binary_
multipliers 'Kilo', 'Mega', and 'Giga', equalling 2^10, 2^20, and 2^30
bytes respectively. Such letter suffixes can also be entirely omitted.


        acpi=           [HW,ACPI,X86]
                        Advanced Configuration and Power Interface
                        Format: { force | off | strict | noirq | rsdt }
                        force -- enable ACPI if default was off
                        off -- disable ACPI if default was on
                        noirq -- do not use ACPI for IRQ routing
                        strict -- Be less tolerant of platforms that are not
                                strictly ACPI specification compliant.
                        rsdt -- prefer RSDT over (default) XSDT
                        copy_dsdt -- copy DSDT to memory

                        See also Documentation/power/runtime_pm.txt, pci=noacpi

        acpi_rsdp=      [ACPI,EFI,KEXEC]
                        Pass the RSDP address to the kernel, mostly used
                        on machines running EFI runtime service to boot the
                        second kernel for kdump.

        acpi_apic_instance=     [ACPI, IOAPIC]
                        Format: <int>
                        2: use 2nd APIC table, if available
                        1,0: use 1st APIC table
                        default: 0

        acpi_backlight= [HW,ACPI]
                        acpi_backlight=vendor
                        acpi_backlight=video
                        If set to vendor, prefer vendor specific driver
                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
                        of the ACPI video.ko driver.

        acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
        acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
                        Format: <int>
                        CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
                        debug output.  Bits in debug_layer correspond to a
                        _COMPONENT in an ACPI source file, e.g.,
                            #define _COMPONENT ACPI_PCI_COMPONENT
                        Bits in debug_level correspond to a level in
                        ACPI_DEBUG_PRINT statements, e.g.,
                            ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
                        The debug_level mask defaults to "info".  See
                        Documentation/acpi/debug.txt for more information about
                        debug layers and levels.

                        Enable processor driver info messages:
                            acpi.debug_layer=0x20000000
                        Enable PCI/PCI interrupt routing info messages:
                            acpi.debug_layer=0x400000
                        Enable AML "Debug" output, i.e., stores to the Debug
                        object while interpreting AML:
                            acpi.debug_layer=0xffffffff acpi.debug_level=0x2
                        Enable all messages related to ACPI hardware:
                            acpi.debug_layer=0x2 acpi.debug_level=0xffffffff

                        Some values produce so much output that the system is
                        unusable.  The "log_buf_len" parameter may be useful
                        if you need to capture more output.

        acpi_irq_balance [HW,ACPI]
                        ACPI will balance active IRQs
                        default in APIC mode

        acpi_irq_nobalance [HW,ACPI]
                        ACPI will not move active IRQs (default)
                        default in PIC mode

        acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
                        Format: <irq>,<irq>...

        acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
                        use by PCI
                        Format: <irq>,<irq>...

        acpi_no_auto_ssdt       [HW,ACPI] Disable automatic loading of SSDT

        acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
                        Format: To spoof as Windows 98: ="Microsoft Windows"

        acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
                        acpi_osi="string1"      # add string1 -- only one string
                        acpi_osi="!string2"     # remove built-in string2
                        acpi_osi=               # disable all strings

        acpi_pm_good    [X86]
                        Override the pmtimer bug detection: force the kernel
                        to assume that this machine's pmtimer latches its value
                        and always returns good values.

        acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
                        Format: { level | edge | high | low }

        acpi_serialize  [HW,ACPI] force serialization of AML methods

        acpi_skip_timer_override [HW,ACPI]
                        Recognize and ignore IRQ0/pin2 Interrupt Override.
                        For broken nForce2 BIOS resulting in XT-PIC timer.

        acpi_sleep=     [HW,ACPI] Sleep options
                        Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
                                  old_ordering, nonvs, sci_force_enable }
                        See Documentation/power/video.txt for information on
                        s3_bios and s3_mode.
                        s3_beep is for debugging; it makes the PC's speaker beep
                        as soon as the kernel's real-mode entry point is called.
                        s4_nohwsig prevents ACPI hardware signature from being
                        used during resume from hibernation.
                        old_ordering causes the ACPI 1.0 ordering of the _PTS
                        control method, with respect to putting devices into
                        low power states, to be enforced (the ACPI 2.0 ordering
                        of _PTS is used by default).
                        nonvs prevents the kernel from saving/restoring the
                        ACPI NVS memory during suspend/hibernation and resume.
                        sci_force_enable causes the kernel to set SCI_EN directly
                        on resume from S1/S3 (which is against the ACPI spec,
                        but some broken systems don't work without it).

        acpi_use_timer_override [HW,ACPI]
                        Use timer override. For some broken Nvidia NF5 boards
                        that require a timer override, but don't have HPET

        acpi_enforce_resources= [ACPI]
                        { strict | lax | no }
                        Check for resource conflicts between native drivers
                        and ACPI OperationRegions (SystemIO and SystemMemory
                        only). IO ports and memory declared in ACPI might be
                        used by the ACPI subsystem in arbitrary AML code and
                        can interfere with legacy drivers.
                        strict (default): access to resources claimed by ACPI
                        is denied; legacy drivers trying to access reserved
                        resources will fail to bind to device using them.
                        lax: access to resources claimed by ACPI is allowed;
                        legacy drivers trying to access reserved resources
                        will bind successfully but a warning message is logged.
                        no: ACPI OperationRegions are not marked as reserved,
                        no further checks are performed.

        add_efi_memmap  [EFI; X86] Include EFI memory map in
                        kernel's map of available physical RAM.

        agp=            [AGP]
                        { off | try_unsupported }
                        off: disable AGP support
                        try_unsupported: try to drive unsupported chipsets
                                (may crash computer or cause data corruption)

        ALSA            [HW,ALSA]
                        See Documentation/sound/alsa/alsa-parameters.txt

        alignment=      [KNL,ARM]
                        Allow the default userspace alignment fault handler
                        behaviour to be specified.  Bit 0 enables warnings,
                        bit 1 enables fixups, and bit 2 sends a segfault.

        align_va_addr=  [X86-64]
                        Align virtual addresses by clearing slice [14:12] when
                        allocating a VMA at process creation time. This option
                        gives you up to 3% performance improvement on AMD F15h
                        machines (where it is enabled by default) for a
                        CPU-intensive style benchmark, and it can vary highly in
                        a microbenchmark depending on workload and compiler.

                        32: only for 32-bit processes
                        64: only for 64-bit processes
                        on: enable for both 32- and 64-bit processes
                        off: disable for both 32- and 64-bit processes

        amd_iommu=      [HW,X86-64]
                        Pass parameters to the AMD IOMMU driver in the system.
                        Possible values are:
                        fullflush - enable flushing of IO/TLB entries when
                                    they are unmapped. Otherwise they are
                                    flushed before they will be reused, which
                                    is a lot of faster
                        off       - do not initialize any AMD IOMMU found in
                                    the system

        amijoy.map=     [HW,JOY] Amiga joystick support
                        Map of devices attached to JOY0DAT and JOY1DAT
                        Format: <a>,<b>
                        See also Documentation/input/joystick.txt

        analog.map=     [HW,JOY] Analog joystick and gamepad support
                        Specifies type or capabilities of an analog joystick
                        connected to one of 16 gameports
                        Format: <type1>,<type2>,..<type16>

        apc=            [HW,SPARC]
                        Power management functions (SPARCstation-4/5 + deriv.)
                        Format: noidle
                        Disable APC CPU standby support. SPARCstation-Fox does
                        not play well with APC CPU idle - disable it if you have
                        APC and your system crashes randomly.

        apic=           [APIC,X86-32] Advanced Programmable Interrupt Controller
                        Change the output verbosity whilst booting
                        Format: { quiet (default) | verbose | debug }
                        Change the amount of debugging information output
                        when initialising the APIC and IO-APIC components.

        autoconf=       [IPV6]
                        See Documentation/networking/ipv6.txt.

        show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
                        Limit apic dumping. The parameter defines the maximal
                        number of local apics being dumped. Also it is possible
                        to set it to "all" by meaning -- no limit here.
                        Format: { 1 (default) | 2 | ... | all }.
                        The parameter valid if only apic=debug or
                        apic=verbose is specified.
                        Example: apic=debug show_lapic=all

        apm=            [APM] Advanced Power Management
                        See header of arch/x86/kernel/apm_32.c.

        arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
                        Format: <io>,<irq>,<nodeID>

        ataflop=        [HW,M68k]

        atarimouse=     [HW,MOUSE] Atari Mouse

        atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
                        EzKey and similar keyboards

        atkbd.reset=    [HW] Reset keyboard during initialization

        atkbd.set=      [HW] Select keyboard code set
                        Format: <int> (2 = AT (default), 3 = PS/2)

        atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
                        keyboards

        atkbd.softraw=  [HW] Choose between synthetic and real raw mode
                        Format: <bool> (0 = real, 1 = synthetic (default))

        atkbd.softrepeat= [HW]
                        Use software keyboard repeat

        autotest        [IA-64]

        baycom_epp=     [HW,AX25]
                        Format: <io>,<mode>

        baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
                        Format: <io>,<mode>
                        See header of drivers/net/hamradio/baycom_par.c.

        baycom_ser_fdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Full Duplex Mode)
                        Format: <io>,<irq>,<mode>[,<baud>]
                        See header of drivers/net/hamradio/baycom_ser_fdx.c.

        baycom_ser_hdx= [HW,AX25]
                        BayCom Serial Port AX.25 Modem (Half Duplex Mode)
                        Format: <io>,<irq>,<mode>
                        See header of drivers/net/hamradio/baycom_ser_hdx.c.

        boot_delay=     Milliseconds to delay each printk during boot.
                        Values larger than 10 seconds (10000) are changed to
                        no delay (0).
                        Format: integer

        bootmem_debug   [KNL] Enable bootmem allocator debug messages.

        bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
        bttv.radio=     Most important insmod options are available as
                        kernel args too.
        bttv.pll=       See Documentation/video4linux/bttv/Insmod-options
        bttv.tuner=

        bulk_remove=off [PPC]  This parameter disables the use of the pSeries
                        firmware feature for flushing multiple hpte entries
                        at a time.

        c101=           [NET] Moxa C101 synchronous serial card

        cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
                        Sometimes CPU hardware bugs make them report the cache
                        size incorrectly. The kernel will attempt work arounds
                        to fix known problems, but for some CPUs it is not
                        possible to determine what the correct size should be.
                        This option provides an override for these situations.

        capability.disable=
                        [SECURITY] Disable capabilities.  This would normally
                        be used only if an alternative security model is to be
                        configured.  Potentially dangerous and should only be
                        used if you are entirely sure of the consequences.

        ccw_timeout_log [S390]
                        See Documentation/s390/CommonIO for details.

        cgroup_disable= [KNL] Disable a particular controller
                        Format: {name of the controller(s) to disable}
                                {Currently supported controllers - "memory"}

        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
                        Format: { "0" | "1" }
                        See security/selinux/Kconfig help text.
                        0 -- check protection applied by kernel (includes
                                any implied execute protection).
                        1 -- check protection requested by application.
                        Default value is set via a kernel config option.
                        Value can be changed at runtime via
                                /selinux/checkreqprot.

        cio_ignore=     [S390]
                        See Documentation/s390/CommonIO for details.

        clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
                        [Deprecated]
                        Forces specified clocksource (if available) to be used
                        when calculating gettimeofday(). If specified
                        clocksource is not available, it defaults to PIT.
                        Format: { pit | tsc | cyclone | pmtmr }

        clocksource=    Override the default clocksource
                        Format: <string>
                        Override the default clocksource and use the clocksource
                        with the name specified.
                        Some clocksource names to choose from, depending on
                        the platform:
                        [all] jiffies (this is the base, fallback clocksource)
                        [ACPI] acpi_pm
                        [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
                                pxa_timer,timer3,32k_counter,timer0_1
                        [AVR32] avr32
                        [X86-32] pit,hpet,tsc;
                                scx200_hrt on Geode; cyclone on IBM x440
                        [MIPS] MIPS
                        [PARISC] cr16
                        [S390] tod
                        [SH] SuperH
                        [SPARC64] tick
                        [X86-64] hpet,tsc

        clearcpuid=BITNUM [X86]
                        Disable CPUID feature X for the kernel. See
                        arch/x86/include/asm/cpufeature.h for the valid bit
                        numbers. Note the Linux specific bits are not necessarily
                        stable over kernel options, but the vendor specific
                        ones should be.
                        Also note that user programs calling CPUID directly
                        or using the feature without checking anything
                        will still see it. This just prevents it from
                        being used by the kernel or shown in /proc/cpuinfo.
                        Also note the kernel might malfunction if you disable
                        some critical bits.

        cmo_free_hint=  [PPC] Format: { yes | no }
                        Specify whether pages are marked as being inactive
                        when they are freed.  This is used in CMO environments
                        to determine OS memory pressure for page stealing by
                        a hypervisor.
                        Default: yes

        code_bytes      [X86] How many bytes of object code to print
                        in an oops report.
                        Range: 0 - 8192
                        Default: 64

        com20020=       [HW,NET] ARCnet - COM20020 chipset
                        Format:
                        <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]

        com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
                        Format: <io>[,<irq>]

        com90xx=        [HW,NET]
                        ARCnet - COM90xx chipset (memory-mapped buffers)
                        Format: <io>[,<irq>[,<memstart>]]

        condev=         [HW,S390] console device
        conmode=

        console=        [KNL] Output console device and options.

                tty<n>  Use the virtual console device <n>.

                ttyS<n>[,options]
                ttyUSB0[,options]
                        Use the specified serial port.  The options are of
                        the form "bbbbpnf", where "bbbb" is the baud rate,
                        "p" is parity ("n", "o", or "e"), "n" is number of
                        bits, and "f" is flow control ("r" for RTS or
                        omit it).  Default is "9600n8".

                        See Documentation/serial-console.txt for more
                        information.  See
                        Documentation/networking/netconsole.txt for an
                        alternative.

                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                        Start an early, polled-mode console on the 8250/16550
                        UART at the specified I/O port or MMIO address,
                        switching to the matching ttyS device later.  The
                        options are the same as for ttyS, above.

                If the device connected to the port is not a TTY but a braille
                device, prepend "brl," before the device type, for instance
                        console=brl,ttyS0
                For now, only VisioBraille is supported.

        consoleblank=   [KNL] The console blank (screen saver) timeout in
                        seconds. Defaults to 10*60 = 10mins. A value of 0
                        disables the blank timer.

        coredump_filter=
                        [KNL] Change the default value for
                        /proc/<pid>/coredump_filter.
                        See also Documentation/filesystems/proc.txt.

        cpuidle.off=1   [CPU_IDLE]
                        disable the cpuidle sub-system

        cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
                        Format:
                        <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]

        crashkernel=size[KMG][@offset[KMG]]
                        [KNL] Using kexec, Linux can switch to a 'crash kernel'
                        upon panic. This parameter reserves the physical
                        memory region [offset, offset + size] for that kernel
                        image. If '@offset' is omitted, then a suitable offset
                        is selected automatically. Check
                        Documentation/kdump/kdump.txt for further details.

        crashkernel=range1:size1[,range2:size2,...][@offset]
                        [KNL] Same as above, but depends on the memory
                        in the running system. The syntax of range is
                        start-[end] where start and end are both
                        a memory unit (amount[KMG]). See also
                        Documentation/kdump/kdump.txt for an example.

        cs89x0_dma=     [HW,NET]
                        Format: <dma>

        cs89x0_media=   [HW,NET]
                        Format: { rj45 | aui | bnc }

        dasd=           [HW,NET]
                        See header of drivers/s390/block/dasd_devmap.c.

        db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
                        (one device per port)
                        Format: <port#>,<type>
                        See also Documentation/input/joystick-parport.txt

        ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
                        time. See Documentation/dynamic-debug-howto.txt for
                        details.

        debug           [KNL] Enable kernel debugging (events log level).

        debug_locks_verbose=
                        [KNL] verbose self-tests
                        Format=<0|1>
                        Print debugging info while doing the locking API
                        self-tests.
                        We default to 0 (no extra messages), setting it to
                        1 will print _a lot_ more information - normally
                        only useful to kernel developers.

        debug_objects   [KNL] Enable object debugging

        no_debug_objects
                        [KNL] Disable object debugging

        debug_guardpage_minorder=
                        [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
                        parameter allows control of the order of pages that will
                        be intentionally kept free (and hence protected) by the
                        buddy allocator. Bigger value increase the probability
                        of catching random memory corruption, but reduce the
                        amount of memory for normal system use. The maximum
                        possible value is MAX_ORDER/2.  Setting this parameter
                        to 1 or 2 should be enough to identify most random
                        memory corruption problems caused by bugs in kernel or
                        driver code when a CPU writes to (or reads from) a
                        random memory location. Note that there exists a class
                        of memory corruptions problems caused by buggy H/W or
                        F/W or by drivers badly programing DMA (basically when
                        memory is written at bus level and the CPU MMU is
                        bypassed) which are not detectable by
                        CONFIG_DEBUG_PAGEALLOC, hence this option will not help
                        tracking down these problems.

        debugpat        [X86] Enable PAT debugging

        decnet.addr=    [HW,NET]
                        Format: <area>[,<node>]
                        See also Documentation/networking/decnet.txt.

        default_hugepagesz=
                        [same as hugepagesz=] The size of the default
                        HugeTLB page size. This is the size represented by
                        the legacy /proc/ hugepages APIs, used for SHM, and
                        default size when mounting hugetlbfs filesystems.
                        Defaults to the default architecture's huge page size
                        if not specified.

        dhash_entries=  [KNL]
                        Set number of hash buckets for dentry cache.

        digi=           [HW,SERIAL]
                        IO parameters + enable/disable command.

        digiepca=       [HW,SERIAL]
                        See drivers/char/README.epca and
                        Documentation/serial/digiepca.txt.

        disable=        [IPV6]
                        See Documentation/networking/ipv6.txt.

        disable_ddw     [PPC/PSERIES]
                        Disable Dynamic DMA Window support. Use this if
                        to workaround buggy firmware.

        disable_ipv6=   [IPV6]
                        See Documentation/networking/ipv6.txt.

        disable_mtrr_cleanup [X86]
                        The kernel tries to adjust MTRR layout from continuous
                        to discrete, to make X server driver able to add WB
                        entry later. This parameter disables that.

        disable_mtrr_trim [X86, Intel and AMD only]
                        By default the kernel will trim any uncacheable
                        memory out of your available memory pool based on
                        MTRR settings.  This parameter disables that behavior,
                        possibly causing your machine to run very slowly.

        disable_timer_pin_1 [X86]
                        Disable PIN 1 of APIC timer
                        Can be useful to work around chipset bugs.

        dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
                        this option disables the debugging code at boot.

        dma_debug_entries=<number>
                        This option allows to tune the number of preallocated
                        entries for DMA-API debugging code. One entry is
                        required per DMA-API allocation. Use this if the
                        DMA-API debugging code disables itself because the
                        architectural default is too low.

        dma_debug_driver=<driver_name>
                        With this option the DMA-API debugging driver
                        filter feature can be enabled at boot time. Just
                        pass the driver to filter for as the parameter.
                        The filter can be disabled or changed to another
                        driver later using sysfs.

        dscc4.setup=    [NET]

        earlycon=       [KNL] Output early console device and options.
                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                uart[8250],mmio32,<addr>[,options]
                        Start an early, polled-mode console on the 8250/16550
                        UART at the specified I/O port or MMIO address.
                        MMIO inter-register address stride is either 8-bit
                        (mmio) or 32-bit (mmio32).
                        The options are the same as for ttyS, above.

        earlyprintk=    [X86,SH,BLACKFIN]
                        earlyprintk=vga
                        earlyprintk=serial[,ttySn[,baudrate]]
                        earlyprintk=ttySn[,baudrate]
                        earlyprintk=dbgp[debugController#]

                        Append ",keep" to not disable it when the real console
                        takes over.

                        Only vga or serial or usb debug port at a time.

                        Currently only ttyS0 and ttyS1 are supported.

                        Interaction with the standard serial driver is not
                        very good.

                        The VGA output is eventually overwritten by the real
                        console.

        ekgdboc=        [X86,KGDB] Allow early kernel console debugging
                        ekgdboc=kbd

                        This is designed to be used in conjunction with
                        the boot argument: earlyprintk=vga

        edd=            [EDD]
                        Format: {"off" | "on" | "skip[mbr]"}

        eisa_irq_edge=  [PARISC,HW]
                        See header of drivers/parisc/eisa.c.

        elanfreq=       [X86-32]
                        See comment before function elanfreq_setup() in
                        arch/x86/kernel/cpu/cpufreq/elanfreq.c.

        elevator=       [IOSCHED]
                        Format: {"cfq" | "deadline" | "noop"}
                        See Documentation/block/cfq-iosched.txt and
                        Documentation/block/deadline-iosched.txt for details.

        elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
                        Specifies physical address of start of kernel core
                        image elf header and optionally the size. Generally
                        kexec loader will pass this option to capture kernel.
                        See Documentation/kdump/kdump.txt for details.

        enable_mtrr_cleanup [X86]
                        The kernel tries to adjust MTRR layout from continuous
                        to discrete, to make X server driver able to add WB
                        entry later. This parameter enables that.

        enable_timer_pin_1 [X86]
                        Enable PIN 1 of APIC timer
                        Can be useful to work around chipset bugs
                        (in particular on some ATI chipsets).
                        The kernel tries to set a reasonable default.

        enforcing       [SELINUX] Set initial enforcing status.
                        Format: {"0" | "1"}
                        See security/selinux/Kconfig help text.
                        0 -- permissive (log only, no denials).
                        1 -- enforcing (deny and log).
                        Default value is 0.
                        Value can be changed at runtime via /selinux/enforce.

        erst_disable    [ACPI]
                        Disable Error Record Serialization Table (ERST)
                        support.

        ether=          [HW,NET] Ethernet cards parameters
                        This option is obsoleted by the "netdev=" option, which
                        has equivalent usage. See its documentation for details.

        evm=            [EVM]
                        Format: { "fix" }
                        Permit 'security.evm' to be updated regardless of
                        current integrity status.

        failslab=
        fail_page_alloc=
        fail_make_request=[KNL]
                        General fault injection mechanism.
                        Format: <interval>,<probability>,<space>,<times>
                        See also Documentation/fault-injection/.

        floppy=         [HW]
                        See Documentation/blockdev/floppy.txt.

        force_pal_cache_flush
                        [IA-64] Avoid check_sal_cache_flush which may hang on
                        buggy SAL_CACHE_FLUSH implementations. Using this
                        parameter will force ia64_sal_cache_flush to call
                        ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.

        ftrace=[tracer]
                        [FTRACE] will set and start the specified tracer
                        as early as possible in order to facilitate early
                        boot debugging.

        ftrace_dump_on_oops[=orig_cpu]
                        [FTRACE] will dump the trace buffers on oops.
                        If no parameter is passed, ftrace will dump
                        buffers of all CPUs, but if you pass orig_cpu, it will
                        dump only the buffer of the CPU that triggered the
                        oops.

        ftrace_filter=[function-list]
                        [FTRACE] Limit the functions traced by the function
                        tracer at boot up. function-list is a comma separated
                        list of functions. This list can be changed at run
                        time by the set_ftrace_filter file in the debugfs
                        tracing directory.

        ftrace_notrace=[function-list]
                        [FTRACE] Do not trace the functions specified in
                        function-list. This list can be changed at run time
                        by the set_ftrace_notrace file in the debugfs
                        tracing directory.

        ftrace_graph_filter=[function-list]
                        [FTRACE] Limit the top level callers functions traced
                        by the function graph tracer at boot up.
                        function-list is a comma separated list of functions
                        that can be changed at run time by the
                        set_graph_function file in the debugfs tracing directory.

        gamecon.map[2|3]=
                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
                        support via parallel port (up to 5 devices per port)
                        Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
                        See also Documentation/input/joystick-parport.txt

        gamma=          [HW,DRM]

        gart_fix_e820=  [X86_64] disable the fix e820 for K8 GART
                        Format: off | on
                        default: on

        gcov_persist=   [GCOV] When non-zero (default), profiling data for
                        kernel modules is saved and remains accessible via
                        debugfs, even when the module is unloaded/reloaded.
                        When zero, profiling data is discarded and associated
                        debugfs files are removed at module unload time.

        gpt             [EFI] Forces disk with valid GPT signature but
                        invalid Protective MBR to be treated as GPT.

        hashdist=       [KNL,NUMA] Large hashes allocated during boot
                        are distributed across NUMA nodes.  Defaults on
                        for 64-bit NUMA, off otherwise.
                        Format: 0 | 1 (for off | on)

        hcl=            [IA-64] SGI's Hardware Graph compatibility layer

        hd=             [EIDE] (E)IDE hard drive subsystem geometry
                        Format: <cyl>,<head>,<sect>

        hest_disable    [ACPI]
                        Disable Hardware Error Source Table (HEST) support;
                        corresponding firmware-first mode error processing
                        logic will be disabled.

        highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
                        size of <nn>. This works even on boxes that have no
                        highmem otherwise. This also works to reduce highmem
                        size on bigger boxes.

        highres=        [KNL] Enable/disable high resolution timer mode.
                        Valid parameters: "on", "off"
                        Default: "on"

        hisax=          [HW,ISDN]
                        See Documentation/isdn/README.HiSax.

        hlt             [BUGS=ARM,SH]

        hpet=           [X86-32,HPET] option to control HPET usage
                        Format: { enable (default) | disable | force |
                                verbose }
                        disable: disable HPET and use PIT instead
                        force: allow force enabled of undocumented chips (ICH4,
                                VIA, nVidia)
                        verbose: show contents of HPET registers during setup

        hugepages=      [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
        hugepagesz=     [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
                        On x86-64 and powerpc, this option can be specified
                        multiple times interleaved with hugepages= to reserve
                        huge pages of different sizes. Valid pages sizes on
                        x86-64 are 2M (when the CPU supports "pse") and 1G
                        (when the CPU supports the "pdpe1gb" cpuinfo flag)
                        Note that 1GB pages can only be allocated at boot time
                        using hugepages= and not freed afterwards.

        hvc_iucv=       [S390] Number of z/VM IUCV hypervisor console (HVC)
                               terminal devices. Valid values: 0..8
        hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
                               If specified, z/VM IUCV HVC accepts connections
                               from listed z/VM user IDs only.

        keep_bootcon    [KNL]
                        Do not unregister boot console at start. This is only
                        useful for debugging when something happens in the window
                        between unregistering the boot console and initializing
                        the real console.

        i2c_bus=        [HW] Override the default board specific I2C bus speed
                             or register an additional I2C bus that is not
                             registered from board initialization code.
                             Format:
                             <bus_id>,<clkrate>

        i8042.debug     [HW] Toggle i8042 debug mode
        i8042.direct    [HW] Put keyboard port into non-translated mode
        i8042.dumbkbd   [HW] Pretend that controller can only read data from
                             keyboard and cannot control its state
                             (Don't attempt to blink the leds)
        i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
        i8042.nokbd     [HW] Don't check/create keyboard port
        i8042.noloop    [HW] Disable the AUX Loopback command while probing
                             for the AUX port
        i8042.nomux     [HW] Don't check presence of an active multiplexing
                             controller
        i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
                             controllers
        i8042.notimeout [HW] Ignore timeout condition signalled by conroller
        i8042.reset     [HW] Reset the controller during init and cleanup
        i8042.unlock    [HW] Unlock (ignore) the keylock

        i810=           [HW,DRM]

        i8k.ignore_dmi  [HW] Continue probing hardware even if DMI data
                        indicates that the driver is running on unsupported
                        hardware.
        i8k.force       [HW] Activate i8k driver even if SMM BIOS signature
                        does not match list of supported models.
        i8k.power_status
                        [HW] Report power status in /proc/i8k
                        (disabled by default)
        i8k.restricted  [HW] Allow controlling fans only if SYS_ADMIN
                        capability is set.

        icn=            [HW,ISDN]
                        Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]

        ide-core.nodma= [HW] (E)IDE subsystem
                        Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
                        .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
                        .cdrom .chs .ignore_cable are additional options
                        See Documentation/ide/ide.txt.

        ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
                        Claim all unknown PCI IDE storage controllers.

        idle=           [X86]
                        Format: idle=poll, idle=mwait, idle=halt, idle=nomwait
                        Poll forces a polling idle loop that can slightly
                        improve the performance of waking up a idle CPU, but
                        will use a lot of power and make the system run hot.
                        Not recommended.
                        idle=mwait: On systems which support MONITOR/MWAIT but
                        the kernel chose to not use it because it doesn't save
                        as much power as a normal idle loop, use the
                        MONITOR/MWAIT idle loop anyways. Performance should be
                        the same as idle=poll.
                        idle=halt: Halt is forced to be used for CPU idle.
                        In such case C2/C3 won't be used again.
                        idle=nomwait: Disable mwait for CPU C-states

        ignore_loglevel [KNL]
                        Ignore loglevel setting - this will print /all/
                        kernel messages to the console. Useful for debugging.
                        We also add it as printk module parameter, so users
                        could change it dynamically, usually by
                        /sys/module/printk/parameters/ignore_loglevel.

        ihash_entries=  [KNL]
                        Set number of hash buckets for inode cache.

        ima_audit=      [IMA]
                        Format: { "0" | "1" }
                        0 -- integrity auditing messages. (Default)
                        1 -- enable informational integrity auditing messages.

        ima_hash=       [IMA]
                        Format: { "sha1" | "md5" }
                        default: "sha1"

        ima_tcb         [IMA]
                        Load a policy which meets the needs of the Trusted
                        Computing Base.  This means IMA will measure all
                        programs exec'd, files mmap'd for exec, and all files
                        opened for read by uid=0.

        init=           [KNL]
                        Format: <full_path>
                        Run specified binary instead of /sbin/init as init
                        process.

        initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
                        for working out where the kernel is dying during
                        startup.

        initrd=         [BOOT] Specify the location of the initial ramdisk

        inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
                        Format: <irq>

        intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
                on
                        Enable intel iommu driver.
                off
                        Disable intel iommu driver.
                igfx_off [Default Off]
                        By default, gfx is mapped as normal device. If a gfx
                        device has a dedicated DMAR unit, the DMAR unit is
                        bypassed by not enabling DMAR with this option. In
                        this case, gfx device will use physical address for
                        DMA.
                forcedac [x86_64]
                        With this option iommu will not optimize to look
                        for io virtual address below 32-bit forcing dual
                        address cycle on pci bus for cards supporting greater
                        than 32-bit addressing. The default is to look
                        for translation below 32-bit and if not available
                        then look in the higher range.
                strict [Default Off]
                        With this option on every unmap_single operation will
                        result in a hardware IOTLB flush operation as opposed
                        to batching them for performance.
                sp_off [Default Off]
                        By default, super page will be supported if Intel IOMMU
                        has the capability. With this option, super page will
                        not be supported.
        intremap=       [X86-64, Intel-IOMMU]
                        on      enable Interrupt Remapping (default)
                        off     disable Interrupt Remapping
                        nosid   disable Source ID checking
                        no_x2apic_optout
                                BIOS x2APIC opt-out request will be ignored

        inttest=        [IA-64]

        iomem=          Disable strict checking of access to MMIO memory
                strict  regions from userspace.
                relaxed

        iommu=          [x86]
                off
                force
                noforce
                biomerge
                panic
                nopanic
                merge
                nomerge
                forcesac
                soft
                pt      [x86, IA-64]

        io7=            [HW] IO7 for Marvel based alpha systems
                        See comment before marvel_specify_io7 in
                        arch/alpha/kernel/core_marvel.c.

        io_delay=       [X86] I/O delay method
                0x80
                        Standard port 0x80 based delay
                0xed
                        Alternate port 0xed based delay (needed on some systems)
                udelay
                        Simple two microseconds delay
                none
                        No delay

        ip=             [IP_PNP]
                        See Documentation/filesystems/nfs/nfsroot.txt.

        ip2=            [HW] Set IO/IRQ pairs for up to 4 IntelliPort boards
                        See comment before ip2_setup() in
                        drivers/char/ip2/ip2base.c.

        irqfixup        [HW]
                        When an interrupt is not handled search all handlers
                        for it. Intended to get systems with badly broken
                        firmware running.

        irqpoll         [HW]
                        When an interrupt is not handled search all handlers
                        for it. Also check all handlers each timer
                        interrupt. Intended to get systems with badly broken
                        firmware running.

        isapnp=         [ISAPNP]
                        Format: <RDP>,<reset>,<pci_scan>,<verbosity>

        isolcpus=       [KNL,SMP] Isolate CPUs from the general scheduler.
                        Format:
                        <cpu number>,...,<cpu number>
                        or
                        <cpu number>-<cpu number>
                        (must be a positive range in ascending order)
                        or a mixture
                        <cpu number>,...,<cpu number>-<cpu number>

                        This option can be used to specify one or more CPUs
                        to isolate from the general SMP balancing and scheduling
                        algorithms. You can move a process onto or off an
                        "isolated" CPU via the CPU affinity syscalls or cpuset.
                        <cpu number> begins at 0 and the maximum value is
                        "number of CPUs in system - 1".

                        This option is the preferred way to isolate CPUs. The
                        alternative -- manually setting the CPU mask of all
                        tasks in the system -- can cause problems and
                        suboptimal load balancer performance.

        iucv=           [HW,NET]

        js=             [HW,JOY] Analog joystick
                        See Documentation/input/joystick.txt.

        keepinitrd      [HW,ARM]

        kernelcore=nn[KMG]      [KNL,X86,IA-64,PPC] This parameter
                        specifies the amount of memory usable by the kernel
                        for non-movable allocations.  The requested amount is
                        spread evenly throughout all nodes in the system. The
                        remaining memory in each node is used for Movable
                        pages. In the event, a node is too small to have both
                        kernelcore and Movable pages, kernelcore pages will
                        take priority and other nodes will have a larger number
                        of kernelcore pages.  The Movable zone is used for the
                        allocation of pages that may be reclaimed or moved
                        by the page migration subsystem.  This means that
                        HugeTLB pages may not be allocated from this zone.
                        Note that allocations like PTEs-from-HighMem still
                        use the HighMem zone if it exists, and the Normal
                        zone if it does not.

        kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
                        Format: <Controller#>[,poll interval]
                        The controller # is the number of the ehci usb debug
                        port as it is probed via PCI.  The poll interval is
                        optional and is the number seconds in between
                        each poll cycle to the debug port in case you need
                        the functionality for interrupting the kernel with
                        gdb or control-c on the dbgp connection.  When
                        not using this parameter you use sysrq-g to break into
                        the kernel debugger.

        kgdboc=         [KGDB,HW] kgdb over consoles.
                        Requires a tty driver that supports console polling,
                        or a supported polling keyboard driver (non-usb).
                         Serial only format: <serial_device>[,baud]
                         keyboard only format: kbd
                         keyboard and serial format: kbd,<serial_device>[,baud]
                        Optional Kernel mode setting:
                         kms, kbd format: kms,kbd
                         kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]

        kgdbwait        [KGDB] Stop kernel execution and enter the
                        kernel debugger at the earliest opportunity.

        kmac=           [MIPS] korina ethernet MAC address.
                        Configure the RouterBoard 532 series on-chip
                        Ethernet adapter MAC address.

        kmemleak=       [KNL] Boot-time kmemleak enable/disable
                        Valid arguments: on, off
                        Default: on

        kstack=N        [X86] Print N words from the kernel stack
                        in oops dumps.

        kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
                        Default is 0 (don't ignore, but inject #GP)

        kvm.oos_shadow= [KVM] Disable out-of-sync shadow paging.
                        Default is 1 (enabled)

        kvm.mmu_audit=  [KVM] This is a R/W parameter which allows audit
                        KVM MMU at runtime.
                        Default is 0 (off)

        kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
                        Default is 1 (enabled)

        kvm-amd.npt=    [KVM,AMD] Disable nested paging (virtualized MMU)
                        for all guests.
                        Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.

        kvm-intel.ept=  [KVM,Intel] Disable extended page tables
                        (virtualized MMU) support on capable Intel chips.
                        Default is 1 (enabled)

        kvm-intel.emulate_invalid_guest_state=
                        [KVM,Intel] Enable emulation of invalid guest states
                        Default is 0 (disabled)

        kvm-intel.flexpriority=
                        [KVM,Intel] Disable FlexPriority feature (TPR shadow).
                        Default is 1 (enabled)

        kvm-intel.nested=
                        [KVM,Intel] Enable VMX nesting (nVMX).
                        Default is 0 (disabled)

        kvm-intel.unrestricted_guest=
                        [KVM,Intel] Disable unrestricted guest feature
                        (virtualized real and unpaged mode) on capable
                        Intel chips. Default is 1 (enabled)

        kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
                        feature (tagged TLBs) on capable Intel chips.
                        Default is 1 (enabled)

        l2cr=           [PPC]

        l3cr=           [PPC]

        lapic           [X86-32,APIC] Enable the local APIC even if BIOS
                        disabled it.

        lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
                        in C2 power state.

        libata.dma=     [LIBATA] DMA control
                        libata.dma=0      Disable all PATA and SATA DMA
                        libata.dma=1      PATA and SATA Disk DMA only
                        libata.dma=2      ATAPI (CDROM) DMA only
                        libata.dma=4      Compact Flash DMA only
                        Combinations also work, so libata.dma=3 enables DMA
                        for disks and CDROMs, but not CFs.

        libata.ignore_hpa=      [LIBATA] Ignore HPA limit
                        libata.ignore_hpa=0       keep BIOS limits (default)
                        libata.ignore_hpa=1       ignore limits, using full disk

        libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
                        when set.
                        Format: <int>

        libata.force=   [LIBATA] Force configurations.  The format is comma
                        separated list of "[ID:]VAL" where ID is
                        PORT[.DEVICE].  PORT and DEVICE are decimal numbers
                        matching port, link or device.  Basically, it matches
                        the ATA ID string printed on console by libata.  If
                        the whole ID part is omitted, the last PORT and DEVICE
                        values are used.  If ID hasn't been specified yet, the
                        configuration applies to all ports, links and devices.

                        If only DEVICE is omitted, the parameter applies to
                        the port and all links and devices behind it.  DEVICE
                        number of 0 either selects the first device or the
                        first fan-out link behind PMP device.  It does not
                        select the host link.  DEVICE number of 15 selects the
                        host link and device attached to it.

                        The VAL specifies the configuration to force.  As long
                        as there's no ambiguity shortcut notation is allowed.
                        For example, both 1.5 and 1.5G would work for 1.5Gbps.
                        The following configurations can be forced.

                        * Cable type: 40c, 80c, short40c, unk, ign or sata.
                          Any ID with matching PORT is used.

                        * SATA link speed limit: 1.5Gbps or 3.0Gbps.

                        * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
                          udma[/][16,25,33,44,66,100,133] notation is also
                          allowed.

                        * [no]ncq: Turn on or off NCQ.

                        * nohrst, nosrst, norst: suppress hard, soft
                          and both resets.

                        * dump_id: dump IDENTIFY data.

                        If there are multiple matching configurations changing
                        the same attribute, the last one is used.

        memblock=debug  [KNL] Enable memblock debug messages.

        load_ramdisk=   [RAM] List of ramdisks to load from floppy
                        See Documentation/blockdev/ramdisk.txt.

        lockd.nlm_grace_period=P  [NFS] Assign grace period.
                        Format: <integer>

        lockd.nlm_tcpport=N     [NFS] Assign TCP port.
                        Format: <integer>

        lockd.nlm_timeout=T     [NFS] Assign timeout value.
                        Format: <integer>

        lockd.nlm_udpport=M     [NFS] Assign UDP port.
                        Format: <integer>

        logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
                        Format: <irq>

        loglevel=       All Kernel Messages with a loglevel smaller than the
                        console loglevel will be printed to the console. It can
                        also be changed with klogd or other programs. The
                        loglevels are defined as follows:

                        0 (KERN_EMERG)          system is unusable
                        1 (KERN_ALERT)          action must be taken immediately
                        2 (KERN_CRIT)           critical conditions
                        3 (KERN_ERR)            error conditions
                        4 (KERN_WARNING)        warning conditions
                        5 (KERN_NOTICE)         normal but significant condition
                        6 (KERN_INFO)           informational
                        7 (KERN_DEBUG)          debug-level messages

        log_buf_len=n[KMG]      Sets the size of the printk ring buffer,
                        in bytes.  n must be a power of two.  The default
                        size is set in the kernel config file.

        logo.nologo     [FB] Disables display of the built-in Linux logo.
                        This may be used to provide more screen space for
                        kernel log messages and is useful when debugging
                        kernel boot problems.

        lp=0            [LP]    Specify parallel ports to use, e.g,
        lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
        lp=reset                first parallel port). 'lp=0' disables the
        lp=auto                 printer driver. 'lp=reset' (which can be
                                specified in addition to the ports) causes
                                attached printers to be reset. Using
                                lp=port1,port2,... specifies the parallel ports
                                to associate lp devices with, starting with
                                lp0. A port specification may be 'none' to skip
                                that lp device, or a parport name such as
                                'parport0'. Specifying 'lp=auto' instead of a
                                port specification list means that device IDs
                                from each port should be examined, to see if
                                an IEEE 1284-compliant printer is attached; if
                                so, the driver will manage that printer.
                                See also header of drivers/char/lp.c.

        lpj=n           [KNL]
                        Sets loops_per_jiffy to given constant, thus avoiding
                        time-consuming boot-time autodetection (up to 250 ms per
                        CPU). 0 enables autodetection (default). To determine
                        the correct value for your kernel, boot with normal
                        autodetection and see what value is printed. Note that
                        on SMP systems the preset will be applied to all CPUs,
                        which is likely to cause problems if your CPUs need
                        significantly divergent settings. An incorrect value
                        will cause delays in the kernel to be wrong, leading to
                        unpredictable I/O errors and other breakage. Although
                        unlikely, in the extreme case this might damage your
                        hardware.

        ltpc=           [NET]
                        Format: <io>,<irq>,<dma>

        machvec=        [IA-64] Force the use of a particular machine-vector
                        (machvec) in a generic kernel.
                        Example: machvec=hpzx1_swiotlb

        machtype=       [Loongson] Share the same kernel image file between different
                         yeeloong laptop.
                        Example: machtype=lemote-yeeloong-2f-7inch

        max_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory greater
                        than or equal to this physical address is ignored.

        maxcpus=        [SMP] Maximum number of processors that an SMP kernel
                        should make use of.  maxcpus=n : n >= 0 limits the
                        kernel to using 'n' processors.  n=0 is a special case,
                        it is equivalent to "nosmp", which also disables
                        the IO APIC.

        max_loop=       [LOOP] The number of loop block devices that get
        (loop.max_loop) unconditionally pre-created at init time. The default
                        number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
                        of statically allocating a predefined number, loop
                        devices can be requested on-demand with the
                        /dev/loop-control interface.

        mcatest=        [IA-64]

        mce             [X86-32] Machine Check Exception

        mce=option      [X86-64] See Documentation/x86/x86_64/boot-options.txt

        md=             [HW] RAID subsystems devices and level
                        See Documentation/md.txt.

        mdacon=         [MDA]
                        Format: <first>,<last>
                        Specifies range of consoles to be captured by the MDA.

        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
                        Amount of memory to be used when the kernel is not able
                        to see the whole system memory or for test.
                        [X86-32] Use together with memmap= to avoid physical
                        address space collisions. Without memmap= PCI devices
                        could be placed at addresses belonging to unused RAM.

        mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
                        memory.

        memchunk=nn[KMG]
                        [KNL,SH] Allow user to override the default size for
                        per-device physically contiguous DMA buffers.

        memmap=exactmap [KNL,X86] Enable setting of an exact
                        E820 memory map, as specified by the user.
                        Such memmap=exactmap lines can be constructed based on
                        BIOS output or other requirements. See the memmap=nn@ss
                        option description.

        memmap=nn[KMG]@ss[KMG]
                        [KNL] Force usage of a specific region of memory
                        Region of memory to be used, from ss to ss+nn.

        memmap=nn[KMG]#ss[KMG]
                        [KNL,ACPI] Mark specific memory as ACPI data.
                        Region of memory to be used, from ss to ss+nn.

        memmap=nn[KMG]$ss[KMG]
                        [KNL,ACPI] Mark specific memory as reserved.
                        Region of memory to be used, from ss to ss+nn.
                        Example: Exclude memory from 0x18690000-0x1869ffff
                                 memmap=64K$0x18690000
                                 or
                                 memmap=0x10000$0x18690000

        memory_corruption_check=0/1 [X86]
                        Some BIOSes seem to corrupt the first 64k of
                        memory when doing things like suspend/resume.
                        Setting this option will scan the memory
                        looking for corruption.  Enabling this will
                        both detect corruption and prevent the kernel
                        from using the memory being corrupted.
                        However, its intended as a diagnostic tool; if
                        repeatable BIOS-originated corruption always
                        affects the same memory, you can use memmap=
                        to prevent the kernel from using that memory.

        memory_corruption_check_size=size [X86]
                        By default it checks for corruption in the low
                        64k, making this memory unavailable for normal
                        use.  Use this parameter to scan for
                        corruption in more or less memory.

        memory_corruption_check_period=seconds [X86]
                        By default it checks for corruption every 60
                        seconds.  Use this parameter to check at some
                        other rate.  0 disables periodic checking.

        memtest=        [KNL,X86] Enable memtest
                        Format: <integer>
                        default : 0 <disable>
                        Specifies the number of memtest passes to be
                        performed. Each pass selects another test
                        pattern from a given set of patterns. Memtest
                        fills the memory with this pattern, validates
                        memory contents and reserves bad memory
                        regions that are detected.

        meye.*=         [HW] Set MotionEye Camera parameters
                        See Documentation/video4linux/meye.txt.

        mfgpt_irq=      [IA-32] Specify the IRQ to use for the
                        Multi-Function General Purpose Timers on AMD Geode
                        platforms.

        mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
                        the BIOS has incorrectly applied a workaround. TinyBIOS
                        version 0.98 is known to be affected, 0.99 fixes the
                        problem by letting the user disable the workaround.

        mga=            [HW,DRM]

        min_addr=nn[KMG]        [KNL,BOOT,ia64] All physical memory below this
                        physical address is ignored.

        mini2440=       [ARM,HW,KNL]
                        Format:[0..2][b][c][t]
                        Default: "0tb"
                        MINI2440 configuration specification:
                        0 - The attached screen is the 3.5" TFT
                        1 - The attached screen is the 7" TFT
                        2 - The VGA Shield is attached (1024x768)
                        Leaving out the screen size parameter will not load
                        the TFT driver, and the framebuffer will be left
                        unconfigured.
                        b - Enable backlight. The TFT backlight pin will be
                        linked to the kernel VESA blanking code and a GPIO
                        LED. This parameter is not necessary when using the
                        VGA shield.
                        c - Enable the s3c camera interface.
                        t - Reserved for enabling touchscreen support. The
                        touchscreen support is not enabled in the mainstream
                        kernel as of 2.6.30, a preliminary port can be found
                        in the "bleeding edge" mini2440 support kernel at
                        http://repo.or.cz/w/linux-2.6/mini2440.git

        mminit_loglevel=
                        [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
                        parameter allows control of the logging verbosity for
                        the additional memory initialisation checks. A value
                        of 0 disables mminit logging and a level of 4 will
                        log everything. Information is printed at KERN_DEBUG
                        so loglevel=8 may also need to be specified.

        mousedev.tap_time=
                        [MOUSE] Maximum time between finger touching and
                        leaving touchpad surface for touch to be considered
                        a tap and be reported as a left button click (for
                        touchpads working in absolute mode only).
                        Format: <msecs>
        mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
                        reporting absolute coordinates, such as tablets
        mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
                        reporting absolute coordinates, such as tablets

        movablecore=nn[KMG]     [KNL,X86,IA-64,PPC] This parameter
                        is similar to kernelcore except it specifies the
                        amount of memory used for migratable allocations.
                        If both kernelcore and movablecore is specified,
                        then kernelcore will be at *least* the specified
                        value but may be more. If movablecore on its own
                        is specified, the administrator must be careful
                        that the amount of memory usable for all allocations
                        is not too small.

        MTD_Partition=  [MTD]
                        Format: <name>,<region-number>,<size>,<offset>

        MTD_Region=     [MTD] Format:
                        <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]

        mtdparts=       [MTD]
                        See drivers/mtd/cmdlinepart.c.

        multitce=off    [PPC]  This parameter disables the use of the pSeries
                        firmware feature for updating multiple TCE entries
                        at a time.

        onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration

                        Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]

                        boundary - index of last SLC block on Flex-OneNAND.
                                   The remaining blocks are configured as MLC blocks.
                        lock     - Configure if Flex-OneNAND boundary should be locked.
                                   Once locked, the boundary cannot be changed.
                                   1 indicates lock status, 0 indicates unlock status.

        mtdset=         [ARM]
                        ARM/S3C2412 JIVE boot control

                        See arch/arm/mach-s3c2412/mach-jive.c

        mtouchusb.raw_coordinates=
                        [HW] Make the MicroTouch USB driver use raw coordinates
                        ('y', default) or cooked coordinates ('n')

        mtrr_chunk_size=nn[KMG] [X86]
                        used for mtrr cleanup. It is largest continuous chunk
                        that could hold holes aka. UC entries.

        mtrr_gran_size=nn[KMG] [X86]
                        Used for mtrr cleanup. It is granularity of mtrr block.
                        Default is 1.
                        Large value could prevent small alignment from
                        using up MTRRs.

        mtrr_spare_reg_nr=n [X86]
                        Format: <integer>
                        Range: 0,7 : spare reg number
                        Default : 1
                        Used for mtrr cleanup. It is spare mtrr entries number.
                        Set to 2 or more if your graphical card needs more.

        n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card

        netdev=         [NET] Network devices parameters
                        Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
                        Note that mem_start is often overloaded to mean
                        something different and driver-specific.
                        This usage is only documented in each driver source
                        file if at all.

        nf_conntrack.acct=
                        [NETFILTER] Enable connection tracking flow accounting
                        0 to disable accounting
                        1 to enable accounting
                        Default value is 0.

        nfsaddrs=       [NFS] Deprecated.  Use ip= instead.
                        See Documentation/filesystems/nfs/nfsroot.txt.

        nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
                        See Documentation/filesystems/nfs/nfsroot.txt.

        nfsrootdebug    [NFS] enable nfsroot debugging messages.
                        See Documentation/filesystems/nfs/nfsroot.txt.

        nfs.callback_tcpport=
                        [NFS] set the TCP port on which the NFSv4 callback
                        channel should listen.

        nfs.cache_getent=
                        [NFS] sets the pathname to the program which is used
                        to update the NFS client cache entries.

        nfs.cache_getent_timeout=
                        [NFS] sets the timeout after which an attempt to
                        update a cache entry is deemed to have failed.

        nfs.idmap_cache_timeout=
                        [NFS] set the maximum lifetime for idmapper cache
                        entries.

        nfs.enable_ino64=
                        [NFS] enable 64-bit inode numbers.
                        If zero, the NFS client will fake up a 32-bit inode
                        number for the readdir() and stat() syscalls instead
                        of returning the full 64-bit number.
                        The default is to return 64-bit inode numbers.

        nfs.nfs4_disable_idmapping=
                        [NFSv4] When set, this option disables the NFSv4
                        idmapper on the client, but only if the mount
                        is using the 'sec=sys' security flavour. This may
                        make migration from legacy NFSv2/v3 systems easier
                        provided that the server has the appropriate support.
                        The default is to always enable NFSv4 idmapping.

        nmi_debug=      [KNL,AVR32,SH] Specify one or more actions to take
                        when a NMI is triggered.
                        Format: [state][,regs][,debounce][,die]

        nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
                        Format: [panic,][nopanic,][num]
                        Valid num: 0
                        0 - turn nmi_watchdog off
                        When panic is specified, panic when an NMI watchdog
                        timeout occurs (or 'nopanic' to override the opposite
                        default).
                        This is useful when you use a panic=... timeout and
                        need the box quickly up again.

        netpoll.carrier_timeout=
                        [NET] Specifies amount of time (in seconds) that
                        netpoll should wait for a carrier. By default netpoll
                        waits 4 seconds.

        no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
                        emulation library even if a 387 maths coprocessor
                        is present.

        no_console_suspend
                        [HW] Never suspend the console
                        Disable suspending of consoles during suspend and
                        hibernate operations.  Once disabled, debugging
                        messages can reach various consoles while the rest
                        of the system is being put to sleep (ie, while
                        debugging driver suspend/resume hooks).  This may
                        not work reliably with all consoles, but is known
                        to work with serial and VGA consoles.
                        To facilitate more flexible debugging, we also add
                        console_suspend, a printk module parameter to control
                        it. Users could use console_suspend (usually
                        /sys/module/printk/parameters/console_suspend) to
                        turn on/off it dynamically.

        noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
                        caches in the slab allocator.  Saves per-node memory,
                        but will impact performance.

        noalign         [KNL,ARM]

        noapic          [SMP,APIC] Tells the kernel to not make use of any
                        IOAPICs that may be present in the system.

        noautogroup     Disable scheduler automatic task group creation.

        nobats          [PPC] Do not use BATs for mapping kernel lowmem
                        on "Classic" PPC cores.

        nocache         [ARM]

        noclflush       [BUGS=X86] Don't use the CLFLUSH instruction

        nodelayacct     [KNL] Disable per-task delay accounting

        nodisconnect    [HW,SCSI,M68K] Disables SCSI disconnects.

        nodsp           [SH] Disable hardware DSP at boot time.

        noefi           [X86] Disable EFI runtime services support.

        noexec          [IA-64]

        noexec          [X86]
                        On X86-32 available only on PAE configured kernels.
                        noexec=on: enable non-executable mappings (default)
                        noexec=off: disable non-executable mappings

        nosmep          [X86]
                        Disable SMEP (Supervisor Mode Execution Protection)
                        even if it is supported by processor.

        noexec32        [X86-64]
                        This affects only 32-bit executables.
                        noexec32=on: enable non-executable mappings (default)
                                read doesn't imply executable mappings
                        noexec32=off: disable non-executable mappings
                                read implies executable mappings

        nofpu           [SH] Disable hardware FPU at boot time.

        nofxsr          [BUGS=X86-32] Disables x86 floating point extended
                        register save and restore. The kernel will only save
                        legacy floating-point registers on task switch.

        noxsave         [BUGS=X86] Disables x86 extended register state save
                        and restore using xsave. The kernel will fallback to
                        enabling legacy floating-point and sse state.

        nohlt           [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
                        wfi(ARM) instruction doesn't work correctly and not to
                        use it. This is also useful when using JTAG debugger.

        no-hlt          [BUGS=X86-32] Tells the kernel that the hlt
                        instruction doesn't work correctly and not to
                        use it.

        no_file_caps    Tells the kernel not to honor file capabilities.  The
                        only way then for a file to be executed with privilege
                        is to be setuid root or executed by root.

        nohalt          [IA-64] Tells the kernel not to use the power saving
                        function PAL_HALT_LIGHT when idle. This increases
                        power-consumption. On the positive side, it reduces
                        interrupt wake-up latency, which may improve performance
                        in certain environments such as networked servers or
                        real-time systems.

        nohz=           [KNL] Boottime enable/disable dynamic ticks
                        Valid arguments: on, off
                        Default: on

        noiotrap        [SH] Disables trapped I/O port accesses.

        noirqdebug      [X86-32] Disables the code which attempts to detect and
                        disable unhandled interrupt sources.

        no_timer_check  [X86,APIC] Disables the code which tests for
                        broken timer IRQ sources.

        noisapnp        [ISAPNP] Disables ISA PnP code.

        noinitrd        [RAM] Tells the kernel not to load any configured
                        initial RAM disk.

        nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
                        remapping.
                        [Deprecated - use intremap=off]

        nointroute      [IA-64]

        nojitter        [IA-64] Disables jitter checking for ITC timers.

        no-kvmclock     [X86,KVM] Disable paravirtualized KVM clock driver

        no-kvmapf       [X86,KVM] Disable paravirtualized asynchronous page
                        fault handling.

        no-steal-acc    [X86,KVM] Disable paravirtualized steal time accounting.
                        steal time is computed, but won't influence scheduler
                        behaviour

        nolapic         [X86-32,APIC] Do not enable or use the local APIC.

        nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.

        noltlbs         [PPC] Do not use large page/tlb entries for kernel
                        lowmem mapping on PPC40x.

        nomca           [IA-64] Disable machine check abort handling

        nomce           [X86-32] Machine Check Exception

        nomfgpt         [X86-32] Disable Multi-Function General Purpose
                        Timer usage (for AMD Geode machines).

        nopat           [X86] Disable PAT (page attribute table extension of
                        pagetables) support.

        norandmaps      Don't use address space randomization.  Equivalent to
                        echo 0 > /proc/sys/kernel/randomize_va_space

        noreplace-paravirt      [X86,IA-64,PV_OPS] Don't patch paravirt_ops

        noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
                        with UP alternatives

        noresidual      [PPC] Don't use residual data on PReP machines.

        nordrand        [X86] Disable the direct use of the RDRAND
                        instruction even if it is supported by the
                        processor.  RDRAND is still available to user
                        space applications.

        noresume        [SWSUSP] Disables resume and restores original swap
                        space.

        no-scroll       [VGA] Disables scrollback.
                        This is required for the Braillex ib80-piezo Braille
                        reader made by F.H. Papenmeier (Germany).

        nosbagart       [IA-64]

        nosep           [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.

        nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
                        and disable the IO APIC.  legacy for "maxcpus=0".

        nosoftlockup    [KNL] Disable the soft-lockup detector.

        nosync          [HW,M68K] Disables sync negotiation for all devices.

        notsc           [BUGS=X86-32] Disable Time Stamp Counter

        nousb           [USB] Disable the USB subsystem

        nowatchdog      [KNL] Disable the lockup detector (NMI watchdog).

        nowb            [ARM]

        nox2apic        [X86-64,APIC] Do not enable x2APIC mode.

        nptcg=          [IA-64] Override max number of concurrent global TLB
                        purges which is reported from either PAL_VM_SUMMARY or
                        SAL PALO.

        nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
                        could support.  nr_cpus=n : n >= 1 limits the kernel to
                        supporting 'n' processors. Later in runtime you can not
                        use hotplug cpu feature to put more cpu back to online.
                        just like you compile the kernel NR_CPUS=n

        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.

        numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
                        one of ['zone', 'node', 'default'] can be specified
                        This can be set from sysctl after boot.
                        See Documentation/sysctl/vm.txt for details.

        ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
                        See Documentation/debugging-via-ohci1394.txt for more
                        info.

        olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
                        Rather than timing out after 20 ms if an EC
                        command is not properly ACKed, override the length
                        of the timeout.  We have interrupts disabled while
                        waiting for the ACK, so if this is set too high
                        interrupts *may* be lost!

        omap_mux=       [OMAP] Override bootloader pin multiplexing.
                        Format: <mux_mode0.mode_name=value>...
                        For example, to override I2C bus2:
                        omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100

        oprofile.timer= [HW]
                        Use timer interrupt instead of performance counters

        oprofile.cpu_type=      Force an oprofile cpu type
                        This might be useful if you have an older oprofile
                        userland or if you want common events.
                        Format: { arch_perfmon }
                        arch_perfmon: [X86] Force use of architectural
                                perfmon on Intel CPUs instead of the
                                CPU specific event set.
                        timer: [X86] Force use of architectural NMI
                                timer mode (see also oprofile.timer
                                for generic hr timer mode)
                                [s390] Force legacy basic mode sampling
                                (report cpu_type "timer")

        oops=panic      Always panic on oopses. Default is to just kill the
                        process, but there is a small probability of
                        deadlocking the machine.
                        This will also cause panics on machine check exceptions.
                        Useful together with panic=30 to trigger a reboot.

        OSS             [HW,OSS]
                        See Documentation/sound/oss/oss-parameters.txt

        panic=          [KNL] Kernel behaviour on panic: delay <timeout>
                        timeout > 0: seconds before rebooting
                        timeout = 0: wait forever
                        timeout < 0: reboot immediately
                        Format: <timeout>

        parkbd.port=    [HW] Parallel port number the keyboard adapter is
                        connected to, default is 0.
                        Format: <parport#>
        parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
                        0 for XT, 1 for AT (default is AT).
                        Format: <mode>

        parport=        [HW,PPT] Specify parallel ports. 0 disables.
                        Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
                        Use 'auto' to force the driver to use any
                        IRQ/DMA settings detected (the default is to
                        ignore detected IRQ/DMA settings because of
                        possible conflicts). You can specify the base
                        address, IRQ, and DMA settings; IRQ and DMA
                        should be numbers, or 'auto' (for using detected
                        settings on that particular port), or 'nofifo'
                        (to avoid using a FIFO even if it is detected).
                        Parallel ports are assigned in the order they
                        are specified on the command line, starting
                        with parport0.

        parport_init_mode=      [HW,PPT]
                        Configure VIA parallel port to operate in
                        a specific mode. This is necessary on Pegasos
                        computer where firmware has no options for setting
                        up parallel port mode and sets it to spp.
                        Currently this function knows 686a and 8231 chips.
                        Format: [spp|ps2|epp|ecp|ecpepp]

        pause_on_oops=
                        Halt all CPUs after the first oops has been printed for
                        the specified number of seconds.  This is to be used if
                        your oopses keep scrolling off the screen.

        pcbit=          [HW,ISDN]

        pcd.            [PARIDE]
                        See header of drivers/block/paride/pcd.c.
                        See also Documentation/blockdev/paride.txt.

        pci=option[,option...]  [PCI] various PCI subsystem options:
                earlydump       [X86] dump PCI config space before the kernel
                                changes anything
                off             [X86] don't probe for the PCI bus
                bios            [X86-32] force use of PCI BIOS, don't access
                                the hardware directly. Use this if your machine
                                has a non-standard PCI host bridge.
                nobios          [X86-32] disallow use of PCI BIOS, only direct
                                hardware access methods are allowed. Use this
                                if you experience crashes upon bootup and you
                                suspect they are caused by the BIOS.
                conf1           [X86] Force use of PCI Configuration
                                Mechanism 1.
                conf2           [X86] Force use of PCI Configuration
                                Mechanism 2.
                noaer           [PCIE] If the PCIEAER kernel config parameter is
                                enabled, this kernel boot option can be used to
                                disable the use of PCIE advanced error reporting.
                nodomains       [PCI] Disable support for multiple PCI
                                root domains (aka PCI segments, in ACPI-speak).
                nommconf        [X86] Disable use of MMCONFIG for PCI
                                Configuration
                check_enable_amd_mmconf [X86] check for and enable
                                properly configured MMIO access to PCI
                                config space on AMD family 10h CPU
                nomsi           [MSI] If the PCI_MSI kernel config parameter is
                                enabled, this kernel boot option can be used to
                                disable the use of MSI interrupts system-wide.
                noioapicquirk   [APIC] Disable all boot interrupt quirks.
                                Safety option to keep boot IRQs enabled. This
                                should never be necessary.
                ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
                                primary IO-APIC for bridges that cannot disable
                                boot IRQs. This fixes a source of spurious IRQs
                                when the system masks IRQs.
                noioapicreroute [APIC] Disable workaround that uses the
                                boot IRQ equivalent of an IRQ that connects to
                                a chipset where boot IRQs cannot be disabled.
                                The opposite of ioapicreroute.
                biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
                                routing table. These calls are known to be buggy
                                on several machines and they hang the machine
                                when used, but on other computers it's the only
                                way to get the interrupt routing table. Try
                                this option if the kernel is unable to allocate
                                IRQs or discover secondary PCI buses on your
                                motherboard.
                rom             [X86] Assign address space to expansion ROMs.
                                Use with caution as certain devices share
                                address decoders between ROMs and other
                                resources.
                norom           [X86] Do not assign address space to
                                expansion ROMs that do not already have
                                BIOS assigned address ranges.
                nobar           [X86] Do not assign address space to the
                                BARs that weren't assigned by the BIOS.
                irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
                                assigned automatically to PCI devices. You can
                                make the kernel exclude IRQs of your ISA cards
                                this way.
                pirqaddr=0xAAAAA        [X86] Specify the physical address
                                of the PIRQ table (normally generated
                                by the BIOS) if it is outside the
                                F0000h-100000h range.
                lastbus=N       [X86] Scan all buses thru bus #N. Can be
                                useful if the kernel is unable to find your
                                secondary buses and you want to tell it
                                explicitly which ones they are.
                assign-busses   [X86] Always assign all PCI bus
                                numbers ourselves, overriding
                                whatever the firmware may have done.
                usepirqmask     [X86] Honor the possible IRQ mask stored
                                in the BIOS $PIR table. This is needed on
                                some systems with broken BIOSes, notably
                                some HP Pavilion N5400 and Omnibook XE3
                                notebooks. This will have no effect if ACPI
                                IRQ routing is enabled.
                noacpi          [X86] Do not use ACPI for IRQ routing
                                or for PCI scanning.
                use_crs         [X86] Use PCI host bridge window information
                                from ACPI.  On BIOSes from 2008 or later, this
                                is enabled by default.  If you need to use this,
                                please report a bug.
                nocrs           [X86] Ignore PCI host bridge windows from ACPI.
                                If you need to use this, please report a bug.
                routeirq        Do IRQ routing for all PCI devices.
                                This is normally done in pci_enable_device(),
                                so this option is a temporary workaround
                                for broken drivers that don't call it.
                skip_isa_align  [X86] do not align io start addr, so can
                                handle more pci cards
                firmware        [ARM] Do not re-enumerate the bus but instead
                                just use the configuration from the
                                bootloader. This is currently used on
                                IXP2000 systems where the bus has to be
                                configured a certain way for adjunct CPUs.
                noearly         [X86] Don't do any early type 1 scanning.
                                This might help on some broken boards which
                                machine check when some devices' config space
                                is read. But various workarounds are disabled
                                and some IOMMU drivers will not work.
                bfsort          Sort PCI devices into breadth-first order.
                                This sorting is done to get a device
                                order compatible with older (<= 2.4) kernels.
                nobfsort        Don't sort PCI devices into breadth-first order.
                cbiosize=nn[KMG]        The fixed amount of bus space which is
                                reserved for the CardBus bridge's IO window.
                                The default value is 256 bytes.
                cbmemsize=nn[KMG]       The fixed amount of bus space which is
                                reserved for the CardBus bridge's memory
                                window. The default value is 64 megabytes.
                resource_alignment=
                                Format:
                                [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
                                Specifies alignment and device to reassign
                                aligned memory resources.
                                If <order of align> is not specified,
                                PAGE_SIZE is used as alignment.
                                PCI-PCI bridge can be specified, if resource
                                windows need to be expanded.
                ecrc=           Enable/disable PCIe ECRC (transaction layer
                                end-to-end CRC checking).
                                bios: Use BIOS/firmware settings. This is the
                                the default.
                                off: Turn ECRC off
                                on: Turn ECRC on.
                realloc         reallocate PCI resources if allocations done by BIOS
                                are erroneous.

        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
                        Management.
                off     Disable ASPM.
                force   Enable ASPM even on devices that claim not to support it.
                        WARNING: Forcing ASPM on may cause system lockups.

        pcie_ports=     [PCIE] PCIe ports handling:
                auto    Ask the BIOS whether or not to use native PCIe services
                        associated with PCIe ports (PME, hot-plug, AER).  Use
                        them only if that is allowed by the BIOS.
                native  Use native PCIe services associated with PCIe ports
                        unconditionally.
                compat  Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
                        ports driver.

        pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
                nomsi   Do not use MSI for native PCIe PME signaling (this makes
                        all PCIe root ports use INTx for all services).

        pcmv=           [HW,PCMCIA] BadgePAD 4

        pd.             [PARIDE]
                        See Documentation/blockdev/paride.txt.

        pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
                        boot time.
                        Format: { 0 | 1 }
                        See arch/parisc/kernel/pdc_chassis.c

        percpu_alloc=   Select which percpu first chunk allocator to use.
                        Currently supported values are "embed" and "page".
                        Archs may support subset or none of the selections.
                        See comments in mm/percpu.c for details on each
                        allocator.  This parameter is primarily for debugging
                        and performance comparison.

        pf.             [PARIDE]
                        See Documentation/blockdev/paride.txt.

        pg.             [PARIDE]
                        See Documentation/blockdev/paride.txt.

        pirq=           [SMP,APIC] Manual mp-table setup
                        See Documentation/x86/i386/IO-APIC.txt.

        plip=           [PPT,NET] Parallel port network link
                        Format: { parport<nr> | timid | 0 }
                        See also Documentation/parport.txt.

        pmtmr=          [X86] Manual setup of pmtmr I/O Port.
                        Override pmtimer IOPort with a hex value.
                        e.g. pmtmr=0x508

        pnp.debug=1     [PNP]
                        Enable PNP debug messages (depends on the
                        CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
                        via /sys/module/pnp/parameters/debug.  We always show
                        current resource usage; turning this on also shows
                        possible settings and some assignment information.

        pnpacpi=        [ACPI]
                        { off }

        pnpbios=        [ISAPNP]
                        { on | off | curr | res | no-curr | no-res }

        pnp_reserve_irq=
                        [ISAPNP] Exclude IRQs for the autoconfiguration

        pnp_reserve_dma=
                        [ISAPNP] Exclude DMAs for the autoconfiguration

        pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
                        Ranges are in pairs (I/O port base and size).

        pnp_reserve_mem=
                        [ISAPNP] Exclude memory regions for the
                        autoconfiguration.
                        Ranges are in pairs (memory base and size).

        ports=          [IP_VS_FTP] IPVS ftp helper module
                        Default is 21.
                        Up to 8 (IP_VS_APP_MAX_PORTS) ports
                        may be specified.
                        Format: <port>,<port>....

        print-fatal-signals=
                        [KNL] debug: print fatal signals

                        If enabled, warn about various signal handling
                        related application anomalies: too many signals,
                        too many POSIX.1 timers, fatal signals causing a
                        coredump - etc.

                        If you hit the warning due to signal overflow,
                        you might want to try "ulimit -i unlimited".

                        default: off.

        printk.time=    Show timing data prefixed to each printk message line
                        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)

        processor.max_cstate=   [HW,ACPI]
                        Limit processor to maximum C-state
                        max_cstate=9 overrides any DMI blacklist limit.

        processor.nocst [HW,ACPI]
                        Ignore the _CST method to determine C-states,
                        instead using the legacy FADT method

        profile=        [KNL] Enable kernel profiling via /proc/profile
                        Format: [schedule,]<number>
                        Param: "schedule" - profile schedule points.
                        Param: <number> - step/bucket size as a power of 2 for
                                statistical time based profiling.
                        Param: "sleep" - profile D-state sleeping (millisecs).
                                Requires CONFIG_SCHEDSTATS
                        Param: "kvm" - profile VM exits.

        prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
                        before loading.
                        See Documentation/blockdev/ramdisk.txt.

        psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
                        probe for; one of (bare|imps|exps|lifebook|any).
        psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
                        per second.
        psmouse.resetafter=     [HW,MOUSE]
                        Try to reset the device after so many bad packets
                        (0 = never).
        psmouse.resolution=
                        [HW,MOUSE] Set desired mouse resolution, in dpi.
        psmouse.smartscroll=
                        [HW,MOUSE] Controls Logitech smartscroll autorepeat.
                        0 = disabled, 1 = enabled (default).

        pstore.backend= Specify the name of the pstore backend to use

        pt.             [PARIDE]
                        See Documentation/blockdev/paride.txt.

        pty.legacy_count=
                        [KNL] Number of legacy pty's. Overwrites compiled-in
                        default number.

        quiet           [KNL] Disable most log messages

        r128=           [HW,DRM]

        raid=           [HW,RAID]
                        See Documentation/md.txt.

        ramdisk_blocksize=      [RAM]
                        See Documentation/blockdev/ramdisk.txt.

        ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
                        See Documentation/blockdev/ramdisk.txt.

        rcupdate.blimit=        [KNL,BOOT]
                        Set maximum number of finished RCU callbacks to process
                        in one batch.

        rcupdate.qhimark=       [KNL,BOOT]
                        Set threshold of queued
                        RCU callbacks over which batch limiting is disabled.

        rcupdate.qlowmark=      [KNL,BOOT]
                        Set threshold of queued RCU callbacks below which
                        batch limiting is re-enabled.

        rdinit=         [KNL]
                        Format: <full_path>
                        Run specified binary instead of /init from the ramdisk,
                        used for early userspace startup. See initrd.

        reboot=         [BUGS=X86-32,BUGS=ARM,BUGS=IA-64] Rebooting mode
                        Format: <reboot_mode>[,<reboot_mode2>[,...]]
                        See arch/*/kernel/reboot.c or arch/*/kernel/process.c

        relax_domain_level=
                        [KNL, SMP] Set scheduler's default relax_domain_level.
                        See Documentation/cgroups/cpusets.txt.

        reserve=        [KNL,BUGS] Force the kernel to ignore some iomem area

        reservetop=     [X86-32]
                        Format: nn[KMG]
                        Reserves a hole at the top of the kernel virtual
                        address space.

        reservelow=     [X86]
                        Format: nn[K]
                        Set the amount of memory to reserve for BIOS at
                        the bottom of the address space.

        reset_devices   [KNL] Force drivers to reset the underlying device
                        during initialization.

        resume=         [SWSUSP]
                        Specify the partition device for software suspend

        resume_offset=  [SWSUSP]
                        Specify the offset from the beginning of the partition
                        given by "resume=" at which the swap header is located,
                        in <PAGE_SIZE> units (needed only for swap files).
                        See  Documentation/power/swsusp-and-swap-files.txt

        resumedelay=    [HIBERNATION] Delay (in seconds) to pause before attempting to
                        read the resume files

        resumewait      [HIBERNATION] Wait (indefinitely) for resume device to show up.
                        Useful for devices that are detected asynchronously
                        (e.g. USB and MMC devices).

        hibernate=      [HIBERNATION]
                noresume        Don't check if there's a hibernation image
                                present during boot.
                nocompress      Don't compress/decompress hibernation images.

        retain_initrd   [RAM] Keep initrd memory after extraction

        rhash_entries=  [KNL,NET]
                        Set number of hash buckets for route cache

        riscom8=        [HW,SERIAL]
                        Format: <io_board1>[,<io_board2>[,...<io_boardN>]]

        ro              [KNL] Mount root device read-only on boot

        root=           [KNL] Root filesystem
                        See name_to_dev_t comment in init/do_mounts.c.

        rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
                        mount the root filesystem

        rootflags=      [KNL] Set root filesystem mount option string

        rootfstype=     [KNL] Set root filesystem type

        rootwait        [KNL] Wait (indefinitely) for root device to show up.
                        Useful for devices that are detected asynchronously
                        (e.g. USB and MMC devices).

        rw              [KNL] Mount root device read-write on boot

        S               [KNL] Run init in single mode

        sa1100ir        [NET]
                        See drivers/net/irda/sa1100_ir.c.

        sbni=           [NET] Granch SBNI12 leased line adapter

        sched_debug     [KNL] Enables verbose scheduler debug messages.

        security=       [SECURITY] Choose a security module to enable at boot.
                        If this boot parameter is not specified, only the first
                        security module asking for security registration will be
                        loaded. An invalid security module name will be treated
                        as if no module has been chosen.

        selinux=        [SELINUX] Disable or enable SELinux at boot time.
                        Format: { "0" | "1" }
                        See security/selinux/Kconfig help text.
                        0 -- disable.
                        1 -- enable.
                        Default value is set via kernel config option.
                        If enabled at boot time, /selinux/disable can be used
                        later to disable prior to initial policy load.

        apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
                        Format: { "0" | "1" }
                        See security/apparmor/Kconfig help text
                        0 -- disable.
                        1 -- enable.
                        Default value is set via kernel config option.

        serialnumber    [BUGS=X86-32]

        shapers=        [NET]
                        Maximal number of shapers.

        show_msr=       [x86] show boot-time MSR settings
                        Format: { <integer> }
                        Show boot-time (BIOS-initialized) MSR settings.
                        The parameter means the number of CPUs to show,
                        for example 1 means boot CPU only.

        simeth=         [IA-64]
        simscsi=

        slram=          [HW,MTD]

        slub_debug[=options[,slabs]]    [MM, SLUB]
                        Enabling slub_debug allows one to determine the
                        culprit if slab objects become corrupted. Enabling
                        slub_debug can create guard zones around objects and
                        may poison objects when not in use. Also tracks the
                        last alloc / free. For more information see
                        Documentation/vm/slub.txt.

        slub_max_order= [MM, SLUB]
                        Determines the maximum allowed order for slabs.
                        A high setting may cause OOMs due to memory
                        fragmentation. For more information see
                        Documentation/vm/slub.txt.

        slub_min_objects=       [MM, SLUB]
                        The minimum number of objects per slab. SLUB will
                        increase the slab order up to slub_max_order to
                        generate a sufficiently large slab able to contain
                        the number of objects indicated. The higher the number
                        of objects the smaller the overhead of tracking slabs
                        and the less frequently locks need to be acquired.
                        For more information see Documentation/vm/slub.txt.

        slub_min_order= [MM, SLUB]
                        Determines the mininum page order for slabs. Must be
                        lower than slub_max_order.
                        For more information see Documentation/vm/slub.txt.

        slub_nomerge    [MM, SLUB]
                        Disable merging of slabs with similar size. May be
                        necessary if there is some reason to distinguish
                        allocs to different slabs. Debug options disable
                        merging on their own.
                        For more information see Documentation/vm/slub.txt.

        smart2=         [HW]
                        Format: <io1>[,<io2>[,...,<io8>]]

        smp-alt-once    [X86-32,SMP] On a hotplug CPU system, only
                        attempt to substitute SMP alternatives once at boot.

        smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
        smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
        smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
        smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
        smsc-ircc2.ircc_irq=    [HW] IRQ line
        smsc-ircc2.ircc_dma=    [HW] DMA channel
        smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
                                0: Toshiba Satellite 1800 (GP data pin select)
                                1: Fast pin select (default)
                                2: ATC IRMode

        softlockup_panic=
                        [KNL] Should the soft-lockup detector generate panics.
                        Format: <integer>

        sonypi.*=       [HW] Sony Programmable I/O Control Device driver
                        See Documentation/laptops/sonypi.txt

        specialix=      [HW,SERIAL] Specialix multi-serial port adapter
                        See Documentation/serial/specialix.txt.

        spia_io_base=   [HW,MTD]
        spia_fio_base=
        spia_pedr=
        spia_peddr=

        stacktrace      [FTRACE]
                        Enabled the stack tracer on boot up.

        sti=            [PARISC,HW]
                        Format: <num>
                        Set the STI (builtin display/keyboard on the HP-PARISC
                        machines) console (graphic card) which should be used
                        as the initial boot-console.
                        See also comment in drivers/video/console/sticore.c.

        sti_font=       [HW]
                        See comment in drivers/video/console/sticore.c.

        stifb=          [HW]
                        Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]

        sunrpc.min_resvport=
        sunrpc.max_resvport=
                        [NFS,SUNRPC]
                        SunRPC servers often require that client requests
                        originate from a privileged port (i.e. a port in the
                        range 0 < portnr < 1024).
                        An administrator who wishes to reserve some of these
                        ports for other uses may adjust the range that the
                        kernel's sunrpc client considers to be privileged
                        using these two parameters to set the minimum and
                        maximum port values.

        sunrpc.pool_mode=
                        [NFS]
                        Control how the NFS server code allocates CPUs to
                        service thread pools.  Depending on how many NICs
                        you have and where their interrupts are bound, this
                        option will affect which CPUs will do NFS serving.
                        Note: this parameter cannot be changed while the
                        NFS server is running.

                        auto        the server chooses an appropriate mode
                                    automatically using heuristics
                        global      a single global pool contains all CPUs
                        percpu      one pool for each CPU
                        pernode     one pool for each NUMA node (equivalent
                                    to global on non-NUMA machines)

        sunrpc.tcp_slot_table_entries=
        sunrpc.udp_slot_table_entries=
                        [NFS,SUNRPC]
                        Sets the upper limit on the number of simultaneous
                        RPC calls that can be sent from the client to a
                        server. Increasing these values may allow you to
                        improve throughput, but will also increase the
                        amount of memory reserved for use by the client.

        swapaccount[=0|1]
                        [KNL] Enable accounting of swap in memory resource
                        controller if no parameter or 1 is given or disable
                        it if 0 is given (See Documentation/cgroups/memory.txt)

        swiotlb=        [IA-64] Number of I/O TLB slabs

        switches=       [HW,M68k]

        sysfs.deprecated=0|1 [KNL]
                        Enable/disable old style sysfs layout for old udev
                        on older distributions. When this option is enabled
                        very new udev will not work anymore. When this option
                        is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
                        in older udev will not work anymore.
                        Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
                        the kernel configuration.

        sysrq_always_enabled
                        [KNL]
                        Ignore sysrq setting - this boot parameter will
                        neutralize any effect of /proc/sys/kernel/sysrq.
                        Useful for debugging.

        tdfx=           [HW,DRM]

        test_suspend=   [SUSPEND]
                        Specify "mem" (for Suspend-to-RAM) or "standby" (for
                        standby suspend) as the system sleep state to briefly
                        enter during system startup.  The system is woken from
                        this state using a wakeup-capable RTC alarm.

        thash_entries=  [KNL,NET]
                        Set number of hash buckets for TCP connection

        thermal.act=    [HW,ACPI]
                        -1: disable all active trip points in all thermal zones
                        <degrees C>: override all lowest active trip points

        thermal.crt=    [HW,ACPI]
                        -1: disable all critical trip points in all thermal zones
                        <degrees C>: override all critical trip points

        thermal.nocrt=  [HW,ACPI]
                        Set to disable actions on ACPI thermal zone
                        critical and hot trip points.

        thermal.off=    [HW,ACPI]
                        1: disable ACPI thermal control

        thermal.psv=    [HW,ACPI]
                        -1: disable all passive trip points
                        <degrees C>: override all passive trip points to this
                        value

        thermal.tzp=    [HW,ACPI]
                        Specify global default ACPI thermal zone polling rate
                        <deci-seconds>: poll all this frequency
                        0: no polling (default)

        threadirqs      [KNL]
                        Force threading of all interrupt handlers except those
                        marked explicitely IRQF_NO_THREAD.

        topology=       [S390]
                        Format: {off | on}
                        Specify if the kernel should make use of the cpu
                        topology information if the hardware supports this.
                        The scheduler will make use of this information and
                        e.g. base its process migration decisions on it.
                        Default is on.

        tp720=          [HW,PS2]

        tpm_suspend_pcr=[HW,TPM]
                        Format: integer pcr id
                        Specify that at suspend time, the tpm driver
                        should extend the specified pcr with zeros,
                        as a workaround for some chips which fail to
                        flush the last written pcr on TPM_SaveState.
                        This will guarantee that all the other pcrs
                        are saved.

        trace_buf_size=nn[KMG]
                        [FTRACE] will set tracing buffer size.

        trace_event=[event-list]
                        [FTRACE] Set and start specified trace events in order
                        to facilitate early boot debugging.
                        See also Documentation/trace/events.txt

        tsc=            Disable clocksource stability checks for TSC.
                        Format: <string>
                        [x86] reliable: mark tsc clocksource as reliable, this
                        disables clocksource verification at runtime, as well
                        as the stability checks done at bootup. Used to enable
                        high-resolution timer mode on older hardware, and in
                        virtualized environment.
                        [x86] noirqtime: Do not use TSC to do irq accounting.
                        Used to run time disable IRQ_TIME_ACCOUNTING on any
                        platforms where RDTSC is slow and this accounting
                        can add overhead.

        turbografx.map[2|3]=    [HW,JOY]
                        TurboGraFX parallel port interface
                        Format:
                        <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
                        See also Documentation/input/joystick-parport.txt

        udbg-immortal   [PPC] When debugging early kernel crashes that
                        happen after console_init() and before a proper 
                        console driver takes over, this boot options might
                        help "seeing" what's going on.

        uhash_entries=  [KNL,NET]
                        Set number of hash buckets for UDP/UDP-Lite connections

        uhci-hcd.ignore_oc=
                        [USB] Ignore overcurrent events (default N).
                        Some badly-designed motherboards generate lots of
                        bogus events, for ports that aren't wired to
                        anything.  Set this parameter to avoid log spamming.
                        Note that genuine overcurrent events won't be
                        reported either.

        unknown_nmi_panic
                        [X86] Cause panic on unknown NMI.

        usbcore.authorized_default=
                        [USB] Default USB device authorization:
                        (default -1 = authorized except for wireless USB,
                        0 = not authorized, 1 = authorized)

        usbcore.autosuspend=
                        [USB] The autosuspend time delay (in seconds) used
                        for newly-detected USB devices (default 2).  This
                        is the time required before an idle device will be
                        autosuspended.  Devices for which the delay is set
                        to a negative value won't be autosuspended at all.

        usbcore.usbfs_snoop=
                        [USB] Set to log all usbfs traffic (default 0 = off).

        usbcore.blinkenlights=
                        [USB] Set to cycle leds on hubs (default 0 = off).

        usbcore.old_scheme_first=
                        [USB] Start with the old device initialization
                        scheme (default 0 = off).

        usbcore.usbfs_memory_mb=
                        [USB] Memory limit (in MB) for buffers allocated by
                        usbfs (default = 16, 0 = max = 2047).

        usbcore.use_both_schemes=
                        [USB] Try the other device initialization scheme
                        if the first one fails (default 1 = enabled).

        usbcore.initial_descriptor_timeout=
                        [USB] Specifies timeout for the initial 64-byte
                        USB_REQ_GET_DESCRIPTOR request in milliseconds
                        (default 5000 = 5.0 seconds).

        usbhid.mousepoll=
                        [USBHID] The interval which mice are to be polled at.

        usb-storage.delay_use=
                        [UMS] The delay in seconds before a new device is
                        scanned for Logical Units (default 5).

        usb-storage.quirks=
                        [UMS] A list of quirks entries to supplement or
                        override the built-in unusual_devs list.  List
                        entries are separated by commas.  Each entry has
                        the form VID:PID:Flags where VID and PID are Vendor
                        and Product ID values (4-digit hex numbers) and
                        Flags is a set of characters, each corresponding
                        to a common usb-storage quirk flag as follows:
                                a = SANE_SENSE (collect more than 18 bytes
                                        of sense data);
                                b = BAD_SENSE (don't collect more than 18
                                        bytes of sense data);
                                c = FIX_CAPACITY (decrease the reported
                                        device capacity by one sector);
                                d = NO_READ_DISC_INFO (don't use
                                        READ_DISC_INFO command);
                                e = NO_READ_CAPACITY_16 (don't use
                                        READ_CAPACITY_16 command);
                                h = CAPACITY_HEURISTICS (decrease the
                                        reported device capacity by one
                                        sector if the number is odd);
                                i = IGNORE_DEVICE (don't bind to this
                                        device);
                                l = NOT_LOCKABLE (don't try to lock and
                                        unlock ejectable media);
                                m = MAX_SECTORS_64 (don't transfer more
                                        than 64 sectors = 32 KB at a time);
                                n = INITIAL_READ10 (force a retry of the
                                        initial READ(10) command);
                                o = CAPACITY_OK (accept the capacity
                                        reported by the device);
                                r = IGNORE_RESIDUE (the device reports
                                        bogus residue values);
                                s = SINGLE_LUN (the device has only one
                                        Logical Unit);
                                w = NO_WP_DETECT (don't test whether the
                                        medium is write-protected).
                        Example: quirks=0419:aaf5:rl,0421:0433:rc

        user_debug=     [KNL,ARM]
                        Format: <int>
                        See arch/arm/Kconfig.debug help text.
                                 1 - undefined instruction events
                                 2 - system calls
                                 4 - invalid data aborts
                                 8 - SIGSEGV faults
                                16 - SIGBUS faults
                        Example: user_debug=31

        userpte=
                        [X86] Flags controlling user PTE allocations.

                                nohigh = do not allocate PTE pages in
                                        HIGHMEM regardless of setting
                                        of CONFIG_HIGHPTE.

        vdso=           [X86,SH]
                        vdso=2: enable compat VDSO (default with COMPAT_VDSO)
                        vdso=1: enable VDSO (default)
                        vdso=0: disable VDSO mapping

        vdso32=         [X86]
                        vdso32=2: enable compat VDSO (default with COMPAT_VDSO)
                        vdso32=1: enable 32-bit VDSO (default)
                        vdso32=0: disable 32-bit VDSO mapping

        vector=         [IA-64,SMP]
                        vector=percpu: enable percpu vector domain

        video=          [FB] Frame buffer configuration
                        See Documentation/fb/modedb.txt.

        vga=            [BOOT,X86-32] Select a particular video mode
                        See Documentation/x86/boot.txt and
                        Documentation/svga.txt.
                        Use vga=ask for menu.
                        This is actually a boot loader parameter; the value is
                        passed to the kernel using a special protocol.

        vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
                        size of <nn>. This can be used to increase the
                        minimum size (128MB on x86). It can also be used to
                        decrease the size and leave more room for directly
                        mapped kernel RAM.

        vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
                        Format: <command>

        vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
                        Format: <command>

        vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
                        Format: <command>

        vsyscall=       [X86-64]
                        Controls the behavior of vsyscalls (i.e. calls to
                        fixed addresses of 0xffffffffff600x00 from legacy
                        code).  Most statically-linked binaries and older
                        versions of glibc use these calls.  Because these
                        functions are at fixed addresses, they make nice
                        targets for exploits that can control RIP.

                        emulate     [default] Vsyscalls turn into traps and are
                                    emulated reasonably safely.

                        native      Vsyscalls are native syscall instructions.
                                    This is a little bit faster than trapping
                                    and makes a few dynamic recompilers work
                                    better than they would in emulation mode.
                                    It also makes exploits much easier to write.

                        none        Vsyscalls don't work at all.  This makes
                                    them quite hard to use for exploits but
                                    might break your system.

        vt.cur_default= [VT] Default cursor shape.
                        Format: 0xCCBBAA, where AA, BB, and CC are the same as
                        the parameters of the <Esc>[?A;B;Cc escape sequence;
                        see VGA-softcursor.txt. Default: 2 = underline.

        vt.default_blu= [VT]
                        Format: <blue0>,<blue1>,<blue2>,...,<blue15>
                        Change the default blue palette of the console.
                        This is a 16-member array composed of values
                        ranging from 0-255.

        vt.default_grn= [VT]
                        Format: <green0>,<green1>,<green2>,...,<green15>
                        Change the default green palette of the console.
                        This is a 16-member array composed of values
                        ranging from 0-255.

        vt.default_red= [VT]
                        Format: <red0>,<red1>,<red2>,...,<red15>
                        Change the default red palette of the console.
                        This is a 16-member array composed of values
                        ranging from 0-255.

        vt.default_utf8=
                        [VT]
                        Format=<0|1>
                        Set system-wide default UTF-8 mode for all tty's.
                        Default is 1, i.e. UTF-8 mode is enabled for all
                        newly opened terminals.

        vt.global_cursor_default=
                        [VT]
                        Format=<-1|0|1>
                        Set system-wide default for whether a cursor
                        is shown on new VTs. Default is -1,
                        i.e. cursors will be created by default unless
                        overridden by individual drivers. 0 will hide
                        cursors, 1 will display them.

        watchdog timers [HW,WDT] For information on watchdog timers,
                        see Documentation/watchdog/watchdog-parameters.txt
                        or other driver-specific files in the
                        Documentation/watchdog/ directory.

        x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
                        default x2apic cluster mode on platforms
                        supporting x2apic.

        x86_mrst_timer= [X86-32,APBT]
                        Choose timer option for x86 Moorestown MID platform.
                        Two valid options are apbt timer only and lapic timer
                        plus one apbt timer for broadcast timer.
                        x86_mrst_timer=apbt_only | lapic_and_apbt

        xd=             [HW,XT] Original XT pre-IDE (RLL encoded) disks.
        xd_geo=         See header of drivers/block/xd.c.

        xen_emul_unplug=                [HW,X86,XEN]
                        Unplug Xen emulated devices
                        Format: [unplug0,][unplug1]
                        ide-disks -- unplug primary master IDE devices
                        aux-ide-disks -- unplug non-primary-master IDE devices
                        nics -- unplug network devices
                        all -- unplug all emulated devices (NICs and IDE disks)
                        unnecessary -- unplugging emulated devices is
                                unnecessary even if the host did not respond to
                                the unplug protocol
                        never -- do not unplug even if version check succeeds

        xirc2ps_cs=     [NET,PCMCIA]
                        Format:
                        <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]

______________________________________________________________________

TODO:

        Add more DRM drivers.