Kernel-3.10.0-957.el7_kernel-parameters

                      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.
CLK    Common clock infrastructure is enabled.
CMA    Contiguous Memory Area support 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.
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.
RDT    Intel Resource Director Technology.
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.
VMMIO   Driver for memory mapped virtio devices 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)
X86_UV    SGI UV support is enabled.
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_force_table_verification    [HW,ACPI]
        Enable table checksum verification during early stage.
        By default, this is disabled due to x86 early mapping
        size limitation.

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_static_ssdt    [HW,ACPI]
        Disable installation of static SSDTs at early boot time
        By default, SSDTs contained in the RSDT/XSDT will be
        installed automatically and they will appear under
        /sys/firmware/acpi/tables.
        This option turns off this feature.
        Note that specifying this option does not affect
        dynamic table installation which will install SSDT
        tables to /sys/firmware/acpi/tables/dynamic.

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.

acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
           kernels.

acpi_mask_gpe=  [HW,ACPI]
        Due to the existence of _Lxx/_Exx, some GPEs triggered
        by unsupported hardware/firmware features can result in
        GPE floodings that cannot be automatically disabled by
        the GPE dispatcher.
        This facility can be used to prevent such uncontrolled
        GPE floodings.
        Format: <int>
        Support masking of GPEs numbered from 0x00 to 0x7f.

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

alloc_snapshot    [FTRACE]
        Allocate the ftrace snapshot buffer on boot up when the
        main buffer is allocated. This is handy if debugging
        and you need to use tracing_snapshot() on boot up, and
        do not want to use tracing_snapshot_alloc() as it needs
        to be done where GFP_KERNEL allocations are allowed.

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
        force_isolation - Force device isolation for all
                  devices. The IOMMU driver is not
                  allowed anymore to lift isolation
                  requirements as needed. This option
                  does not override iommu=pt

amd_iommu_dump=    [HW,X86-64]
        Enable AMD IOMMU driver option to dump the ACPI table
        for AMD IOMMU. With this option enabled, AMD IOMMU
        driver will print ACPI tables for AMD IOMMU during
        IOMMU initialization.

amd_iommu_intr=    [HW,X86-64]
        Specifies one of the following AMD IOMMU interrupt
        remapping modes:
        legacy     - Use legacy interrupt remapping mode.
        vapic      - Use virtual APIC mode, which allows IOMMU
                     to inject interrupts directly into guest.
                     This mode requires kvm-amd.avic=1.
                     (Default when IOMMU HW support is present.)

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.

apic_extnmi=    [APIC,X86] External NMI delivery setting
        Format: { bsp (default) | all | none }
        bsp:  External NMI is delivered only to CPU 0
        all:  External NMIs are broadcast to all CPUs as a
              backup of CPU 0
        none: External NMI is masked for all CPUs. This is
              useful so that a dump capture kernel won't be
              shot down by NMI

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

bau=        [X86_UV] Enable the BAU on SGI UV.  The default
        behavior is to disable the BAU (i.e. bau=0).
        Format: { "0" | "1" }
        0 - Disable the BAU.
        1 - Enable the BAU.
        unset - Disable the BAU.

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.

ca_keys=    [KEYS] This parameter identifies a specific key(s) on
        the system trusted keyring to be used for certificate
        trust validation.
        format: { id:<keyid> | builtin }

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.
clk_ignore_unused
        [CLK]
        Keep all clocks already enabled by bootloader on,
        even if no driver has claimed them. This is useful
        for debug and development, but should not be
        needed on a platform with proper driver support.
        For more information, see Documentation/clk.txt.

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/cpufeatures.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.

cma=nn[MG]    [ARM,KNL]
        Sets the size of kernel global memory area for contiguous
        memory allocations. For more information, see
        include/linux/dma-contiguous.h

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

coherent_pool=nn[KMG]    [ARM,KNL]
        Sets the size of memory pool for coherent, atomic dma
        allocations, by default set to 256K.

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.
    hvc<n>    Use the hypervisor console device <n>. This is for
        both Xen and PowerPC hypervisors.

            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

cpu_init_udelay=N
        [X86] Delay for N microsec between assert and de-assert
        of APIC INIT to start processors.  This delay occurs
        on every CPU online, such as boot, and resume from suspend.
        Default: 10000

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.

crashkernel=size[KMG],high
        [KNL, x86_64] range could be above 4G. Allow kernel
        to allocate physical memory region from top, so could
        be above 4G if system have more than 4G ram installed.
        Otherwise memory region will be allocated below 4G, if
        available.
        It will be ignored if crashkernel=X is specified.
crashkernel=size[KMG],low
        [KNL, x86_64] range under 4G. When crashkernel=X,high
        is passed, kernel could allocate physical memory region
        above 4G, that cause second kernel crash on system
        that require some amount of low memory, e.g. swiotlb
        requires at least 64M+32K low memory.  Kernel would
        try to allocate 72M below 4G automatically.
        This one let user to specify own low range under 4G
        for second kernel instead.
        0: to disable low allocation.
        It will be ignored when crashkernel=X,high is not used
        or memory reserved is below 4G.

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.  Deprecated, see dyndbg.

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.

debug_pagealloc=
        [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
        parameter enables the feature at boot time. In
        default, it is disabled. We can avoid allocating huge
        chunk of memory for debug pagealloc if we don't enable
        it at boot time and the system will work mostly same
        with the kernel built without CONFIG_DEBUG_PAGEALLOC.
        on: enable the feature

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.

hardened_usercopy=
                    [KNL] Under CONFIG_HARDENED_USERCOPY, whether
                    hardening is enabled for this boot. Hardened
                    usercopy checking is used to protect the kernel
                    from reading or writing beyond known memory
                    allocation boundaries as a proactive defense
                    against bounds-checking flaws in the kernel's
                    copy_to_user()/copy_from_user() interface.
            on      Perform hardened usercopy checks (default).
            off     Disable hardened usercopy checks.

disable_cpu_apicid= [X86,APIC,SMP]
        Format: <int>
        The number of initial APIC ID for the
        corresponding CPU to be disabled at boot,
        mostly used for the kdump 2nd kernel to
        disable BSP to wake up multiple CPUs without
        causing system reset or hang due to sending
        INIT from AP to BSP.

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.

dis_ucode_ldr    [X86] Disable the microcode loader.

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.

drm_kms_helper.edid_firmware=[<connector>:]<file>
        Broken monitors, graphic adapters and KVMs may
        send no or incorrect EDID data sets. This parameter
        allows to specify an EDID data set in the
        /lib/firmware directory that is used instead.
        Generic built-in EDID data sets are used, if one of
        edid/1024x768.bin, edid/1280x1024.bin,
        edid/1680x1050.bin, or edid/1920x1080.bin is given
        and no file with the same name exists. Details and
        instructions how to build your own EDID data are
        available in Documentation/EDID/HOWTO.txt. An EDID
        data set will only be used for a particular connector,
        if its name and a colon are prepended to the EDID
        name.

dscc4.setup=    [NET]

dyndbg[="val"]        [KNL,DYNAMIC_DEBUG]
module.dyndbg[="val"]
        Enable debug messages at boot time.  See
        Documentation/dynamic-debug-howto.txt for details.

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,ARM]
        earlyprintk=vga
        earlyprintk=efi
        earlyprintk=xen
        earlyprintk=serial[,ttySn[,baudrate]]
        earlyprintk=serial[,0x...[,baudrate]]
        earlyprintk=ttySn[,baudrate]
        earlyprintk=dbgp[debugController#]

        earlyprintk is useful when the kernel crashes before
        the normal console is initialized. It is not enabled by
        default because it has some cosmetic problems.

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

        Only one of vga, efi, serial, or usb debug port can
        be used at a time.

        Currently only ttyS0 and ttyS1 may be specified by
        name.  Other I/O ports may be explicitly specified
        on some architectures (x86 and arm at least) by
        replacing ttySn with an I/O port address, like this:
            earlyprintk=serial,0x1008,115200
        You can find the port for a given device in
        /proc/tty/driver/serial:
            2: uart:ST16650V2 port:00001008 irq:18 ...

        Interaction with the standard serial driver is not
        very good.

        The VGA and EFI output is eventually overwritten by
        the real console.

        The xen output can only be used by Xen PV guests.

edac_report=    [HW,EDAC] Control how to report EDAC event
        Format: {"on" | "off" | "force"}
        on: enable EDAC to report H/W event. May be overridden
        by other higher priority error reporting module.
        off: disable H/W event reporting through EDAC.
        force: enforce the use of EDAC to report H/W event.
        default: on.

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]"}

efi=        [EFI]
        Format: { "old_map" }
        old_map [X86-64]: switch to the old ioremap-based EFI
        runtime services mapping. 32-bit still uses this one by
        default.

efi_no_storage_paranoia [EFI; X86]
        Using this parameter you can use more than 50% of
        your efi variable storage. Use this parameter only if
        you are really sure that your UEFI does sane gc and
        fulfills the spec otherwise your board may brick.

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.

ftrace_graph_max_depth=<uint>
        [FTRACE] Used with the function graph tracer. This is
        the max depth it will trace into a function. This value
        can be changed at run time by the max_graph_depth file
        in the tracefs tracing directory. default: 0 (no limit)

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.

grcan.enable0=    [HW] Configuration of physical interface 0. Determines
        the "Enable 0" bit of the configuration register.
        Format: 0 | 1
        Default: 0
grcan.enable1=    [HW] Configuration of physical interface 1. Determines
        the "Enable 0" bit of the configuration register.
        Format: 0 | 1
        Default: 0
grcan.select=    [HW] Select which physical interface to use.
        Format: 0 | 1
        Default: 0
grcan.txsize=    [HW] Sets the size of the tx buffer.
        Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
        Default: 1024
grcan.rxsize=    [HW] Sets the size of the rx buffer.
        Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
        Default: 1024

hardlockup_all_cpu_backtrace=
        [KNL] Should the hard-lockup detector generate
        backtraces on all cpus.
        Format: <integer>

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

hpet_mmap=    [X86, HPET_MMAP] option to expose HPET MMAP to
        userspace.  By default this is disabled. Values are
        0(disabled) or 1(enabled).

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.

hwthread_map=    [METAG] Comma-separated list of Linux cpu id to
                hardware thread id mappings.
            Format: <cpu>:<hwthread>

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 controller
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.

i915.invert_brightness=
        [DRM] Invert the sense of the variable that is used to
        set the brightness of the panel backlight. Normally a
        brightness value of 0 indicates backlight switched off,
        and the maximum of the brightness value sets the backlight
        to maximum brightness. If this parameter is set to 0
        (default) and the machine requires it, or this parameter
        is set to 1, a brightness value of 0 sets the backlight
        to maximum brightness, and the maximum of the brightness
        value switches the backlight off.
        -1 -- never invert brightness
         0 -- machine default
         1 -- force brightness inversion

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=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=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.

shadowman    [KNL] SHADOWMAN.

ima_appraise=    [IMA] appraise integrity measurements
        Format: { "off" | "enforce" | "fix" }
        default: "enforce"

ima_appraise_tcb [IMA]
        The builtin appraise policy appraises all files
        owned by uid=0.

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.

initcall_blacklist=  [KNL] Do not execute a comma-separated list of
        initcall functions.  Useful for debugging built-in
        modules and initcalls.

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

init_pkru=    [x86] Specify the default memory protection keys rights
        register contents for all processes.  0x55555554 by
        default (disallow access to all but pkey 0).  Can
        override in debugfs after boot.

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

int_pln_enable  [x86] Enable power limit notification interrupt

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.
    ecs_off [Default Off]
        By default, extended context tables will be supported if
        the hardware advertises that it has support both for the
        extended tables themselves, and also PASID support. With
        this option set, extended tables will not be used even
        on hardware which claims to support them.

intel_idle.max_cstate=    [KNL,HW,ACPI,X86]
        0    disables intel_idle and fall back on acpi_idle.
        1 to 6    specify maximum depth of C-state.

intel_pstate=  [X86]
           disable
             Do not enable intel_pstate as the default
             scaling driver for the supported processors
           passive
         Use intel_pstate as a scaling driver, but configure it
         to work with generic cpufreq governors (instead of
         enabling its internal governor).  This mode cannot be
         used along with the hardware-managed P-states (HWP)
         feature.
           force
         Enable intel_pstate on systems that prohibit it by default
         in favor of acpi-cpufreq. Forcing the intel_pstate driver
         instead of acpi-cpufreq may disable platform features, such
         as thermal controls and power capping, that rely on ACPI
         P-States information being indicated to OSPM and therefore
         should be used with caution. This option does not work with
         processors that aren't supported by the intel_pstate driver
         or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
           no_hwp
             Do not enable hardware P state control (HWP)
         if available.
    hwp_only
        Only load intel_pstate on systems which support
        hardware P state control (HWP) if available.
    support_acpi_ppc
        Enforce ACPI _PPC performance limits. If the Fixed ACPI
        Description Table, specifies preferred power management
        profile as "Enterprise Server" or "Performance Server",
        then this feature is turned on by default.

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
        nopost    disable Interrupt Posting

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]
    nobypass    [PPC/POWERNV]
        Disable IOMMU bypass, using IOMMU for PCI devices.


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.

irqaffinity=    [SMP] Set the default irq affinity mask
        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>

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]

ivrs_ioapic    [HW,X86_64]
        Provide an override to the IOAPIC-ID<->DEVICE-ID
        mapping provided in the IVRS ACPI table. For
        example, to map IOAPIC-ID decimal 10 to
        PCI device 00:14.0 write the parameter as:
            ivrs_ioapic[10]=00:14.0

ivrs_hpet    [HW,X86_64]
        Provide an override to the HPET-ID<->DEVICE-ID
        mapping provided in the IVRS ACPI table. For
        example, to map HPET-ID decimal 0 to
        PCI device 00:14.0 write the parameter as:
            ivrs_hpet[0]=00:14.0

ivrs_acpihid    [HW,X86_64]
        Provide an override to the ACPI-HID:UID<->DEVICE-ID
        mapping provided in the IVRS ACPI table. For
        example, to map UART-HID:UID AMD0020:0 to
        PCI device 00:14.5 write the parameter as:
            ivrs_acpihid[00:14.5]=AMD0020:0

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

nokaslr        [KNL]
        When CONFIG_RANDOMIZE_BASE is set, this disables
        kernel and module base offset ASLR (Address Space
        Layout Randomization).

keepinitrd    [HW,ARM]

kernelcore=    [KNL,X86,IA-64,PPC]
        Format: nn[KMGTPE] | "mirror"
        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.

        Instead of specifying the amount of memory (nn[KMGTPE]),
        you can specify "mirror" option. In case "mirror"
        option is specified, mirrored (reliable) memory is used
        for non-movable allocations and remaining memory is used
        for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
        so you can NOT specify nn[KMGTPE] and "mirror" at the same
        time.

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

kpti        [X86-64] Enable kernel page table isolation.

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

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.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
        CVE-2018-3620.

        Valid arguments: never, cond, always

        always: L1D cache flush on every VMENTER.
        cond:    Flush L1D on VMENTER only when the code between
            VMEXIT and VMENTER can leak host memory.
        never:    Disables the mitigation

        Default is cond (do L1 cache flush in specific instances)

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

l1tf=           [X86] Control mitigation of the L1TF vulnerability on
              affected CPUs

        The kernel PTE inversion protection is unconditionally
        enabled and cannot be disabled.

        full
            Provides all available mitigations for the
            L1TF vulnerability. Disables SMT and
            enables all mitigations in the
            hypervisors, i.e. unconditional L1D flush.

            SMT control and L1D flush control via the
            sysfs interface is still possible after
            boot.  Hypervisors will issue a warning
            when the first VM is started in a
            potentially insecure configuration,
            i.e. SMT enabled or L1D flush disabled.

        full,force
            Same as 'full', but disables SMT and L1D
            flush runtime control. Implies the
            'nosmt=force' command line option.
            (i.e. sysfs control of SMT is disabled.)

        flush
            Leaves SMT enabled and enables the default
            hypervisor mitigation, i.e. conditional
            L1D flush.

            SMT control and L1D flush control via the
            sysfs interface is still possible after
            boot.  Hypervisors will issue a warning
            when the first VM is started in a
            potentially insecure configuration,
            i.e. SMT enabled or L1D flush disabled.

        flush,nosmt

            Disables SMT and enables the default
            hypervisor mitigation.

            SMT control and L1D flush control via the
            sysfs interface is still possible after
            boot.  Hypervisors will issue a warning
            when the first VM is started in a
            potentially insecure configuration,
            i.e. SMT enabled or L1D flush disabled.

        flush,nowarn
            Same as 'flush', but hypervisors will not
            warn when a VM is started in a potentially
            insecure configuration.

        off
            Disables hypervisor mitigations and doesn't
            emit any warnings.

        Default is 'flush'.

        For details see: Documentation/admin-guide/l1tf.rst

l2cr=        [PPC]

l3cr=        [PPC]

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

lapic=        [x86,APIC] "notscdeadline" Do not use TSC deadline
        value for LAPIC timer one-shot implementation. Default
        back to the programmable timer unit in the LAPIC.

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.

        * [no]ncqtrim: Turn off queued DSM TRIM.

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

        * rstonce: only attempt one reset during
          hot-unplug link recovery

        * dump_id: dump IDENTIFY data.

        * atapi_dmadir: Enable ATAPI DMADIR bridge support

        * disable: Disable this device.

        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.

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] Work as limiting max address. 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.
        If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
        which limits max address to nn[KMG].
        Multiple different regions can be specified,
        comma delimited.
        Example:
            memmap=100M@2G,100M#3G,1G!1024G

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$0x18690000
        Some bootloaders may need an escape character before '$',
        like Grub2, otherwise '$' and the following number
        will be eaten.

memmap=nn[KMG]!ss[KMG]
        [KNL,X86] Mark specific memory as protected.
        Region of memory to be used, from ss to ss+nn.
        The memory region may be marked as e820 type 12 (0xc)
        and is NVDIMM or ADR memory.

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.

mem_encrypt=    [X86-64] AMD Secure Memory Encryption (SME) control
        Valid arguments: on, off
        Default (depends on kernel configuration option):
          on  (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
          off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
        mem_encrypt=on:        Activate SME
        mem_encrypt=off:    Do not activate SME

        Refer to Documentation/x86/amd-memory-encryption.txt
        for details on when memory encryption can be activated.

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.

module.sig_enforce
        [KNL] When CONFIG_MODULE_SIG is set, this means that
        modules without (valid) signatures will fail to load.
        Note that if CONFIG_MODULE_SIG_FORCE is set, that
        is always true, so this option does nothing.

module_blacklist=  [KNL] Do not load a comma-separated list of
        modules.  Useful for debugging problem modules.

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.

movable_node    [KNL,X86] Boot-time switch to enable the effects
        of CONFIG_MOVABLE_NODE=y. See mm/Kconfig for details.

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.max_session_slots=
        [NFSv4.1] Sets the maximum number of session slots
        the client will attempt to negotiate with the server.
        This limits the number of simultaneous RPC requests
        that the client can send to the NFSv4.1 server.
        Note that there is little point in setting this
        value higher than the max_tcp_slot_table_limit.

nfs.nfs4_disable_idmapping=
        [NFSv4] When set to the default of '1', this option
        ensures that both the RPC level authentication
        scheme and the NFS level operations agree to use
        numeric uids/gids if the mount is using the
        'sec=sys' security flavour. In effect it is
        disabling idmapping, which can make migration from
        legacy NFSv2/v3 systems to NFSv4 easier.
        Servers that do not support this mode of operation
        will be autodetected by the client, and it will fall
        back to using the idmapper.
        To turn off this behaviour, set the value to '0'.
nfs.nfs4_unique_id=
        [NFS4] Specify an additional fixed unique ident-
        ification string that NFSv4 clients can insert into
        their nfs_client_id4 string.  This is typically a
        UUID that is generated at system install time.

nfs.send_implementation_id =
        [NFSv4.1] Send client implementation identification
        information in exchange_id requests.
        If zero, no implementation identification information
        will be sent.
        The default is to send the implementation identification
        information.

nfs.recover_lost_locks =
        [NFSv4] Attempt to recover locks that were lost due
        to a lease timeout on the server. Please note that
        doing this risks data corruption, since there are
        no guarantees that the file will remain unchanged
        after the locks are lost.
        If you want to enable the kernel legacy behaviour of
        attempting to recover these locks, then set this
        parameter to '1'.
        The default parameter value of '0' causes the kernel
        not to attempt recovery of lost locks.

nfs4.layoutstats_timer =
        [NFSv4.2] Change the rate at which the kernel sends
        layoutstats to the pNFS metadata server.

        Setting this to value to 0 causes the kernel to use
        whatever value is the default set by the layout
        driver. A non-zero value sets the minimum interval
        in seconds between layoutstats transmissions.

nfsd.nfs4_disable_idmapping=
        [NFSv4] When set to the default of '1', the NFSv4
        server will return only numeric uids and gids to
        clients using auth_sys, and will accept numeric uids
        and gids from such clients.  This is intended to ease
        migration from NFSv2/v3.

objlayoutdriver.osd_login_prog=
        [NFS] [OBJLAYOUT] sets the pathname to the program which
        is used to automatically discover and login into new
        osd-targets. Please see:
        Documentation/filesystems/pnfs.txt for more explanations

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 or 1
        0 - turn nmi_watchdog off
        1 - turn nmi_watchdog on
        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.

        These settings can be accessed at runtime via
        the nmi_watchdog and hardlockup_panic sysctls.

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        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

nosmap        [X86]
        Disable SMAP (Supervisor Mode Access Prevention)
        even if it is supported by processor.

nosmep        [X86]
        Disable SMEP (Supervisor Mode Execution Prevention)
        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.

nohugeiomap    [KNL,x86] Disable kernel huge I/O mappings.

nosmt        [KNL,S390] Disable symmetric multithreading (SMT).
        Equivalent to smt=1.

        [KNL,x86] Disable symmetric multithreading (SMT).
        nosmt=force: Force disable SMT, cannot be undone
                 via the sysfs control file.

nospectre_v2    [X86] Disable all mitigations for the Spectre variant 2
        (indirect branch prediction) vulnerability. System may
        allow data leaks with this option, which is equivalent
        to spectre_v2=off.

nospec_store_bypass_disable
        [HW] Disable all mitigations for the Speculative Store Bypass vulnerability

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.

noxsaveopt    [X86] Disables xsaveopt used in saving x86 extended
        register states. The kernel will fall back to use
        xsave to save the states. By using this parameter,
        performance of saving the states is degraded because
        xsave doesn't support modified optimization while
        xsaveopt supports it on xsaveopt enabled systems.

noxsaves    [X86] Disables xsaves and xrstors used in saving and
        restoring x86 extended register state in compacted
        form of xsave area. The kernel will fall back to use
        xsaveopt and xrstor to save and restore the states
        in standard form of xsave area. By using this
        parameter, xsave area per process might occupy more
        memory on xsaves enabled systems.

nompx           [X86] Disables Intel Memory Protection Extensions.
        See Documentation/x86/intel_mpx.txt for more
        information about the feature.

nopku        [X86] Disable Memory Protection Keys CPU feature found
        in some Intel CPUs.

eagerfpu=    [X86]
        on    enable eager fpu restore
        off    disable eager fpu restore
        auto    selects the default scheme, which automatically
            enables eagerfpu restore for xsaveopt.

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_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.

nohibernate    [HIBERNATION] Disable hibernation and resume.

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

nohz_full=    [KNL,BOOT]
        In kernels built with CONFIG_NO_HZ_FULL=y, set
        the specified list of CPUs whose tick will be stopped
        whenever possible. The boot CPU will be forced outside
        the range to maintain the timekeeping.
        The CPUs in this range must also be included in the
        rcu_nocbs= set.

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-vmw-sched-clock
        [X86,PV_OPS] Disable paravirtualized VMware scheduler
        clock and use the default one.

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

nopti        [X86-64] Disable kernel page table isolation.

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).

nonmi_ipi    [X86] Disable using NMI IPIs during panic/reboot to
        shutdown the other cpus.  Instead use the REBOOT_VECTOR
        irq.

nomodule    Disable module load

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

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 both lockup detectors, i.e.
                    soft-lockup and NMI watchdog (hard-lockup).

nowb        [ARM]

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

cpu0_hotplug    [X86] Turn on CPU0 hotplug feature when
        CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
        Some features depend on CPU0. Known dependencies are:
        1. Resume from suspend/hibernate depends on CPU0.
        Suspend/hibernate will fail if CPU0 is offline and you
        need to online CPU0 before suspend/hibernate.
        2. PIC interrupts also depend on CPU0. CPU0 can't be
        removed if a PIC interrupt is detected.
        It's said poweroff/reboot may depend on CPU0 on some
        machines although I haven't seen such issues so far
        after CPU0 is offline on a few tested machines.
        If the dependencies are under your control, you can
        turn on cpu0_hotplug.

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_balancing=    [KNL,X86] Enable or disable automatic NUMA balancing.
        Allowed values are enable and disable

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>

panic_on_warn    panic() instead of WARN().  Useful to cause kdump
        on a WARN().

crash_kexec_post_notifiers
        Run kdump after running panic-notifiers and dumping
        kmsg. This only for the users who doubt kdump always
        succeeds in any situation.
        Note that this also increases risks of kdump failure,
        because some panic notifiers can make the crashed
        kernel more unstable.

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.
    pcie_bus_tune_off    Disable PCIe MPS (Max Payload Size)
            tuning and use the BIOS-configured MPS defaults.
    pcie_bus_safe    Set every device's MPS to the largest value
            supported by all devices below the root complex.
    pcie_bus_perf    Set device MPS to the largest allowable MPS
            based on its parent bus. Also set MRRS (Max
            Read Request Size) to the largest supported
            value (no larger than the MPS that the device
            or bus can support) for best performance.
    pcie_bus_peer2peer    Set every device's MPS to 128B, which
            every device is guaranteed to support. This
            configuration allows peer-to-peer DMA between
            any pair of devices, possibly at the cost of
            reduced performance.  This also guarantees
            that hot-added devices will work.
    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.
    hpiosize=nn[KMG]    The fixed amount of bus space which is
            reserved for hotplug bridge's IO window.
            Default size is 256 bytes.
    hpmemsize=nn[KMG]    The fixed amount of bus space which is
            reserved for hotplug bridge's memory window.
            Default size is 2 megabytes.
    hpbussize=nn    The minimum amount of additional bus numbers
            reserved for buses below a hotplug bridge.
            Default is 1.
    realloc=    Enable/disable reallocating PCI bridge resources
            if allocations done by BIOS are too small to
            accommodate resources required by all child
            devices.
            off: Turn realloc off
            on: Turn realloc on
    realloc        same as realloc=on
    noari        do not use PCIe ARI.
    pcie_scan_all    Scan all possible PCIe devices.  Otherwise we
            only look for one device below a PCIe downstream
            port.

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_hp=    [PCIE] PCI Express Hotplug driver options:
    nomsi    Do not use MSI for PCI Express Native Hotplug (this
        makes all PCIe ports use INTx for hotplug services).

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_port_pm=    [PCIE] PCIe port power management handling:
    off    Disable power management of all PCIe ports
    force    Forcibly enable power management of all PCIe ports

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.always_kmsg_dump=
        Trigger kmsg_dump for cases other than kernel oops or
        panics
        Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
        default: disabled

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.

rcu_nocbs=    [KNL,BOOT]
        In kernels built with CONFIG_RCU_NOCB_CPU=y, set
        the specified list of CPUs to be no-callback CPUs.
        Invocation of these CPUs' RCU callbacks will
        be offloaded to "rcuox/N" kthreads created for
        that purpose, where "x" is "b" for RCU-bh, "p"
        for RCU-preempt, and "s" for RCU-sched, and "N"
        is the CPU number.  This reduces OS jitter on the
        offloaded CPUs, which can be useful for HPC and

        real-time workloads.  It can also improve energy
        efficiency for asymmetric multiprocessors.

rcu_nocb_poll    [KNL,BOOT]
        Rather than requiring that offloaded CPUs
        (specified by rcu_nocbs= above) explicitly
        awaken the corresponding "rcuoN" kthreads,
        make these kthreads poll for callbacks.
        This improves the real-time response for the
        offloaded CPUs by relieving them of the need to
        wake up the corresponding kthread, but degrades
        energy efficiency by requiring that the kthreads
        periodically wake up to do the polling.

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

rcutree.fanout_leaf=    [KNL,BOOT]
        Increase the number of CPUs assigned to each
        leaf rcu_node structure.  Useful for very large
        systems.

rcutree.jiffies_till_first_fqs= [KNL,BOOT]
        Set delay from grace-period initialization to
        first attempt to force quiescent states.
        Units are jiffies, minimum value is zero,
        and maximum value is HZ.

rcutree.jiffies_till_next_fqs= [KNL,BOOT]
        Set delay between subsequent attempts to force
        quiescent states.  Units are jiffies, minimum
        value is one, and maximum value is HZ.

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

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

rcutree.rcu_cpu_stall_suppress=    [KNL,BOOT]
        Suppress RCU CPU stall warning messages.

rcutree.rcu_cpu_stall_timeout= [KNL,BOOT]
        Set timeout for RCU CPU stall warning messages.

rcutree.rcu_idle_gp_delay=    [KNL,BOOT]
        Set wakeup interval for idle CPUs that have
        RCU callbacks (RCU_FAST_NO_HZ=y).

rcutree.rcu_idle_lazy_gp_delay=    [KNL,BOOT]
        Set wakeup interval for idle CPUs that have
        only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
        Lazy RCU callbacks are those which RCU can
        prove do nothing more than free memory.

rcutorture.fqs_duration= [KNL,BOOT]
        Set duration of force_quiescent_state bursts.

rcutorture.fqs_holdoff= [KNL,BOOT]
        Set holdoff time within force_quiescent_state bursts.

rcutorture.fqs_stutter= [KNL,BOOT]
        Set wait time between force_quiescent_state bursts.

rcutorture.irqreader= [KNL,BOOT]
        Test RCU readers from irq handlers.

rcutorture.n_barrier_cbs= [KNL,BOOT]
        Set callbacks/threads for rcu_barrier() testing.

rcutorture.nfakewriters= [KNL,BOOT]
        Set number of concurrent RCU writers.  These just
        stress RCU, they don't participate in the actual
        test, hence the "fake".

rcutorture.nreaders= [KNL,BOOT]
        Set number of RCU readers.

rcutorture.onoff_holdoff= [KNL,BOOT]
        Set time (s) after boot for CPU-hotplug testing.

rcutorture.onoff_interval= [KNL,BOOT]
        Set time (s) between CPU-hotplug operations, or
        zero to disable CPU-hotplug testing.

rcutorture.shuffle_interval= [KNL,BOOT]
        Set task-shuffle interval (s).  Shuffling tasks
        allows some CPUs to go into dyntick-idle mode
        during the rcutorture test.

rcutorture.shutdown_secs= [KNL,BOOT]
        Set time (s) after boot system shutdown.  This
        is useful for hands-off automated testing.

rcutorture.stall_cpu= [KNL,BOOT]
        Duration of CPU stall (s) to test RCU CPU stall
        warnings, zero to disable.

rcutorture.stall_cpu_holdoff= [KNL,BOOT]
        Time to wait (s) after boot before inducing stall.

rcutorture.stat_interval= [KNL,BOOT]
        Time (s) between statistics printk()s.

rcutorture.stutter= [KNL,BOOT]
        Time (s) to stutter testing, for example, specifying
        five seconds causes the test to run for five seconds,
        wait for five seconds, and so on.  This tests RCU's
        ability to transition abruptly to and from idle.

rcutorture.test_boost= [KNL,BOOT]
        Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
        "Maybe" means test if the RCU implementation
        under test support RCU priority boosting.

rcutorture.test_boost_duration= [KNL,BOOT]
        Duration (s) of each individual boost test.

rcutorture.test_boost_interval= [KNL,BOOT]
        Interval (s) between each boost test.

rcutorture.test_no_idle_hz= [KNL,BOOT]
        Test RCU's dyntick-idle handling.  See also the
        rcutorture.shuffle_interval parameter.

rcutorture.torture_type= [KNL,BOOT]
        Specify the RCU implementation to test.

rcutorture.verbose= [KNL,BOOT]
        Enable additional printk() statements.

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

rdt=        [HW,X86,RDT]
        Turn on/off individual RDT features. List is:
        cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
        mba.
        E.g. to turn on cmt and turn off mba use:
            rdt=cmt,!mba

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
        Format:
        {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}

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.
    no        Disable hibernation and resume.

retain_initrd    [RAM] Keep initrd memory after extraction

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

ring3mwait=disable
        [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
        CPUs.

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).

rproc_mem=nn[KMG][@address]
        [KNL,ARM,CMA] Remoteproc physical memory block.
        Memory area to be used by remote processor image,
        managed by CMA.

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

S        [KNL] Run init in single mode

s390_iommu=    [HW,S390]
        Set s390 IOTLB flushing mode
    strict
        With strict flushing every unmap operation will result in
        an IOTLB flush. Default is lazy flushing before reuse,
        which is faster.

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

sbni=        [NET] Granch SBNI12 leased line adapter

sched_debug    [KNL] Enables verbose scheduler debug messages.

schedstats=    [KNL,X86] Enable or disable scheduled statistics.
        Allowed values are enable and disable. This feature
        incurs a small amount of overhead in the scheduler
        but is useful for debugging and performance tuning.

skew_tick=    [KNL] Offset the periodic timer tick per cpu to mitigate
        xtime_lock contention on larger systems, and/or RCU lock
        contention on all systems with CONFIG_MAXSMP set.
        Format: { "0" | "1" }
        0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
        1 -- enable.
        Note: increases power consumption, thus should only be
        enabled if running jitter sensitive (HPC/RT) workloads.

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]

slab_max_order=    [MM, SLAB]
        Determines the maximum allowed order for slabs.
        A high setting may cause OOMs due to memory
        fragmentation.  Defaults to 1 for systems with
        more than 32MB of RAM, 0 otherwise.

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 minimum 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>]]

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>

softlockup_all_cpu_backtrace=
        [KNL] Should the soft-lockup detector generate
        backtraces on all cpus.
        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.

spectre_v2=    [X86] Control mitigation of Spectre variant 2
        (indirect branch speculation) vulnerability.

        on   - unconditionally enable
        off  - unconditionally disable
        auto - kernel detects whether your CPU model is
               vulnerable

        Selecting 'on' will, and 'auto' may, choose a
        mitigation method at run time according to the
        CPU, the available microcode, the setting of the
        CONFIG_RETPOLINE configuration option, and the
        compiler with which the kernel was built.

        Specific mitigations can also be selected manually:

        retpoline      - replace indirect branches
        ibrs          - Intel: Indirect Branch Restricted Speculation (kernel)
        ibrs_always      - Intel: Indirect Branch Restricted Speculation (kernel and user space)

        Not specifying this option is equivalent to
        spectre_v2=auto.

spec_store_bypass_disable=
        [HW] Control Speculative Store Bypass (SSB) Disable mitigation
        (Speculative Store Bypass vulnerability)

        Certain CPUs are vulnerable to an exploit against a
        a common industry wide performance optimization known
        as "Speculative Store Bypass" in which recent stores
        to the same memory location may not be observed by
        later loads during speculative execution. The idea
        is that such stores are unlikely and that they can
        be detected prior to instruction retirement at the
        end of a particular speculation execution window.

        In vulnerable processors, the speculatively forwarded
        store can be used in a cache side channel attack, for
        example to read memory to which the attacker does not
        directly have access (e.g. inside sandboxed code).

        This parameter controls whether the Speculative Store
        Bypass optimization is used.

        on      - Unconditionally disable Speculative Store Bypass
        off     - Unconditionally enable Speculative Store Bypass
        auto    - Kernel detects whether the CPU model contains an
              implementation of Speculative Store Bypass and
              picks the most appropriate mitigation. If the
              CPU is vulnerable, the default mitigation is
              architecture and Kconfig dependent. See below.
        prctl   - Control Speculative Store Bypass for a thread
              via prctl. Speculative Store Bypass is enabled
              for a process by default. The state of the control
              is inherited on fork.
        seccomp - Same as "prctl" above, but all seccomp threads
              will disable SSB unless they explicitly opt out.

        Not specifying this option is equivalent to
        spec_store_bypass_disable=auto.

        Default mitigations:
        X86:    If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"

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

stack_guard_gap=    [MM]
        override the default stack gap protection. The value
        is in page units and it defines how many pages prior
        to (for stacks growing down) resp. after (for stacks
        growing up) the main stack are reserved for no other
        mapping. Default value is 256 pages.

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

stacktrace_filter=[function-list]
        [FTRACE] Limit the functions that the stack tracer
        will trace at boot up. function-list is a comma separated
        list of functions. This list can be changed at run
        time by the stack_trace_filter file in the debugfs
        tracing directory. Note, this enables stack tracing
        and the stacktrace above is not needed.

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.svc_rpc_per_connection_limit=
        [NFS,SUNRPC]
        Limit the number of requests that the server will
        process in parallel from a single connection.
        The default value is 0 (no limit).

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.

suspend.pm_test_delay=
        [SUSPEND]
        Sets the number of seconds to remain in a suspend test
        mode before resuming the system (see
        /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
        is set. Default value is 5.

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 explicitly IRQF_NO_THREAD.

tmem        [KNL,XEN]
        Enable the Transcendent memory driver if built-in.

tmem.cleancache=0|1 [KNL, XEN]
        Default is on (1). Disable the usage of the cleancache
        API to send anonymous pages to the hypervisor.

tmem.frontswap=0|1 [KNL, XEN]
        Default is on (1). Disable the usage of the frontswap
        API to send swap pages to the hypervisor. If disabled
        the selfballooning and selfshrinking are force disabled.

tmem.selfballooning=0|1 [KNL, XEN]
        Default is on (1). Disable the driving of swap pages
        to the hypervisor.

tmem.selfshrinking=0|1 [KNL, XEN]
        Default is on (1). Partial swapoff that immediately
        transfers pages from Xen hypervisor back to the
        kernel based on different criteria.

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.

topology_updates= [KNL, PPC, NUMA]
        Format: {off}
        Specify if the kernel should ignore (off)
        topology updates sent by the hypervisor to this
        LPAR.

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

trace_options=[option-list]
        [FTRACE] Enable or disable tracer options at boot.
        The option-list is a comma delimited list of options
        that can be enabled or disabled just as if you were
        to echo the option name into

            /sys/kernel/debug/tracing/trace_options

        For example, to enable stacktrace option (to dump the
        stack trace of each event), add to the command line:

              trace_options=stacktrace

        See also Documentation/trace/ftrace.txt "trace options"
        section.

traceoff_on_warning
        [FTRACE] enable this option to disable tracing when a
        warning is hit. This turns off "tracing_on". Tracing can
        be enabled again by echoing '1' into the "tracing_on"
        file located in /sys/kernel/debug/tracing/

        This option is useful, as it disables the trace before
        the WARNING dump is called, which prevents the trace to
        be filled with content caused by the warning output.

        This option can also be set at run time via the sysctl
        option:  kernel/traceoff_on_warning

transparent_hugepage=
        [KNL]
        Format: [always|madvise|never]
        Can be used to control the default behavior of the system
        with respect to transparent hugepages.
        See Documentation/vm/transhuge.txt for more details.

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.usbfs_snoop_max=
        [USB] Maximum number of bytes to snoop in each URB
        (default = 65536).

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);
            f = NO_REPORT_OPCODES (don't use report opcodes
                command, uas only);
            g = MAX_SECTORS_240 (don't transfer more than
                240 sectors at a time, uas only);
            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);
            j = NO_REPORT_LUNS (don't use report luns
                command, uas only);
            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);
            p = WRITE_CACHE (the device cache is ON
                by default);
            r = IGNORE_RESIDUE (the device reports
                bogus residue values);
            s = SINGLE_LUN (the device has only one
                Logical Unit);
            t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
                commands, uas only);
            u = IGNORE_UAS (don't bind to the uas driver);
            w = NO_WP_DETECT (don't test whether the
                medium is write-protected).
            y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
                even if the device claims no cache)
        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.

video.brightness_switch_enabled= [0,1]
        If set to 1, on receiving an ACPI notify event
        generated by hotkey, video driver will adjust brightness
        level and then send out the event to user space through
        the allocated input device; If set to 0, video driver
        will only send out the event without touching backlight
        brightness level.
        default: 1

virtio_mmio.device=
        [VMMIO] Memory mapped virtio (platform) device.

            <size>@<baseaddr>:<irq>[:<id>]
        where:
            <size>     := size (can use standard suffixes
                    like K, M and G)
            <baseaddr> := physical base address
            <irq>      := interrupt number (as passed to
                    request_irq())
            <id>       := (optional) platform device id
        example:
            virtio_mmio.device=1K@0x100b0000:48:7

        Can be used multiple times for multiple devices.

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.

workqueue.watchdog_thresh=
        If CONFIG_WQ_WATCHDOG is configured, workqueue can
        warn stall conditions and dump internal state to
        help debugging.  0 disables workqueue stall
        detection; otherwise, it's the stall threshold
        duration in seconds.  The default value is 30 and
        it can be updated at runtime by writing to the
        corresponding sysfs file.

workqueue.disable_numa
        By default, all work items queued to unbound
        workqueues are affine to the NUMA nodes they're
        issued on, which results in better behavior in
        general.  If NUMA affinity needs to be disabled for
        whatever reason, this option can be used.  Note
        that this also can be controlled per-workqueue for
        workqueues visible under /sys/bus/workqueue/.

workqueue.power_efficient
        Per-cpu workqueues are generally preferred because
        they show better performance thanks to cache
        locality; unfortunately, per-cpu workqueues tend to
        be more power hungry than unbound workqueues.

        Enabling this makes the per-cpu workqueues which
        were observed to contribute significantly to power
        consumption unbound, leading to measurably lower
        power usage at the cost of small performance
        overhead.

        The default value of this parameter is determined by
        the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.

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

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.