Linux kernel 命令行参数一

The kernel’s command-line parameters

The following is a consolidated list of the kernel parameters as implemented by the __setup(), early_param(), core_param() and module_param() macros 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.

The kernel parses parameters from the kernel command line up to “--“; if it doesn’t recognize a parameter and it doesn’t contain a ‘.’, the parameter gets passed to init: parameters with ‘=’ go into init’s environment, others are passed as command line arguments to init. Everything after “--” is passed as an argument to init.

Module parameters can be specified in two ways: via the kernel command line with a module name prefix, or via modprobe, e.g.:

(kernel command line) usbcore.blinkenlights=1
(modprobe command line) modprobe usbcore blinkenlights=1

Parameters for modules which are built into the kernel need to be specified on the kernel command line. modprobe looks through the kernel command line (/proc/cmdline) and collects module parameters when it loads a module, so the kernel command line can be used for loadable modules too.

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

Double-quotes can be used to protect spaces in values, e.g.:

param="spaces in here"

cpu lists:

Some kernel parameters take a list of CPUs as a value, e.g. isolcpus, nohz_full, irqaffinity, rcu_nocbs. The format of this list is:

<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>

Note that for the special case of a range one can split the range into equal sized groups and for each group use some amount from the beginning of that group:

<cpu number>-<cpu number>:<used size>/<group size>

For example one can add to the command line following parameter:

isolcpus=1,2,10-20,100-2000:2/25

where the final item represents CPUs 100,101,125,126,150,151,…

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.
ARM64   ARM64 architecture is enabled.
AX25    Appropriate AX.25 support 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.
ISOL    CPU Isolation 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.rst.
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.
OF      Devicetree 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.rst.
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
XTENSA  xtensa architecture 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 <The Linux/x86 Boot Protocol>.

There are also arch-specific kernel-parameters not documented here. See for example <AMD64 Specific Boot Options>.

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’, equaling 2^10, 2^20, and 2^30 bytes respectively. Such letter suffixes can also be entirely omitted:

        acpi=           [HW,ACPI,X86,ARM64]
                        Advanced Configuration and Power Interface
                        Format: { force | on | off | strict | noirq | rsdt |
                                  copy_dsdt }
                        force -- enable ACPI if default was off
                        on -- enable ACPI but allow fallback to DT [arm64]
                        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
                        For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
                        are available

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

        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]
                        { vendor | video | native | none }
                        If set to vendor, prefer vendor-specific driver
                        (e.g. thinkpad_acpi, sony_acpi, etc.) instead
                        of the ACPI video.ko driver.
                        If set to video, use the ACPI video.ko driver.
                        If set to native, use the device's native backlight mode.
                        If set to none, disable the ACPI backlight interface.

        acpi_force_32bit_fadt_addr
                        force FADT to use 32 bit addresses rather than the
                        64 bit X_* addresses. Some firmware have broken 64
                        bit addresses for force ACPI ignore these and use
                        the older legacy 32 bit addresses.

        acpica_no_return_repair [HW, ACPI]
                        Disable AML predefined validation mechanism
                        This mechanism can repair the evaluation result to make
                        the return objects more ACPI specification compliant.
                        This option is useful for developers to identify the
                        root cause of an AML interpreter issue when the issue
                        has something to do with the repair mechanism.

        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/firmware-guide/acpi/debug.rst 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_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_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_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: <byte>

        acpi_no_auto_serialize  [HW,ACPI]
                        Disable auto-serialization of AML methods
                        AML control methods that contain the opcodes to create
                        named objects will be marked as "Serialized" by the
                        auto-serialization feature.
                        This feature is enabled by default.
                        This option allows to turn off the feature.

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

        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_no_watchdog        [HW,ACPI,WDT]
                        Ignore the ACPI-based watchdog interface (WDAT) and let
                        a native driver control the watchdog device instead.

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

        acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
                        of 2 which is mandated by ACPI 6) as the supported ACPI
                        specification revision (when using this switch, it may
                        be necessary to carry out a cold reboot _twice_ in a
                        row to make it take effect on the platform firmware).

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

                        'acpi_osi=!' can be used in combination with single or
                        multiple 'acpi_osi="string1"' to support specific OS
                        vendor string(s).  Note that such command can only
                        affect the default state of the OS vendor strings, thus
                        it cannot affect the default state of the feature group
                        strings and the current state of the OS vendor strings,
                        specifying it multiple times through kernel command line
                        is meaningless.  This command is useful when one do not
                        care about the state of the feature group strings which
                        should be controlled by the OSPM.
                        Examples:
                          1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
                             to 'acpi_osi="Windows 2000" acpi_osi=!', they all
                             can make '_OSI("Windows 2000")' TRUE.

                        'acpi_osi=' cannot be used in combination with other
                        'acpi_osi=' command lines, the _OSI method will not
                        exist in the ACPI namespace.  NOTE that such command can
                        only affect the _OSI support state, thus specifying it
                        multiple times through kernel command line is also
                        meaningless.
                        Examples:
                          1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
                             FALSE.

                        'acpi_osi=!*' can be used in combination with single or
                        multiple 'acpi_osi="string1"' to support specific
                        string(s).  Note that such command can affect the
                        current state of both the OS vendor strings and the
                        feature group strings, thus specifying it multiple times
                        through kernel command line is meaningful.  But it may
                        still not able to affect the final state of a string if
                        there are quirks related to this string.  This command
                        is useful when one want to control the state of the
                        feature group strings to debug BIOS issues related to
                        the OSPM features.
                        Examples:
                          1. 'acpi_osi="Module Device" acpi_osi=!*' can make
                             '_OSI("Module Device")' FALSE.
                          2. 'acpi_osi=!* acpi_osi="Module Device"' can make
                             '_OSI("Module Device")' TRUE.
                          3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
                             equivalent to
                             'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
                             and
                             'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
                             they all will make '_OSI("Windows 2000")' TRUE.

        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_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, nobl }
                        See Documentation/power/video.rst 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).
                        nobl causes the internal blacklist of systems known to
                        behave incorrectly in some ways with respect to system
                        suspend and resume to be ignored (use wisely).

        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

        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-configuration.rst

        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/joydev/joystick.rst

        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] Advanced Programmable Interrupt Controller
                        Change the output verbosity while booting
                        Format: { quiet (default) | verbose | debug }
                        Change the amount of debugging information output
                        when initialising the APIC and IO-APIC components.
                        For X86-32, this can also be used to specify an APIC
                        driver name.
                        Format: apic=driver_name
                        Examples: apic=bigsmp

        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.rst.

        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>

        arm64.nobti     [ARM64] Unconditionally disable Branch Target
                        Identification support

        arm64.nopauth   [ARM64] Unconditionally disable Pointer Authentication
                        support

        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

        audit=          [KNL] Enable the audit sub-system
                        Format: { "0" | "1" | "off" | "on" }
                        0 | off - kernel audit is disabled and can not be
                            enabled until the next reboot
                        unset - kernel audit is initialized but disabled and
                            will be fully enabled by the userspace auditd.
                        1 | on - kernel audit is initialized and partially
                            enabled, storing at most audit_backlog_limit
                            messages in RAM until it is fully enabled by the
                            userspace auditd.
                        Default: unset

        audit_backlog_limit= [KNL] Set the audit queue size limit.
                        Format: <int> (must be >=0)
                        Default: 64

        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.

        blkdevparts=    Manual partition parsing of block device(s) for
                        embedded devices based on command line input.
                        See Documentation/block/cmdline-partition.rst

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

        bootconfig      [KNL]
                        Extended command line options can be added to an initrd
                        and this will cause the kernel to look for it.

                        See Documentation/admin-guide/bootconfig.rst

        bert_disable    [ACPI]
                        Disable BERT OS support on buggy BIOSes.

        bgrt_disable    [ACPI][X86]
                        Disable BGRT to avoid flickering OEM logo.

        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/admin-guide/media/bttv.rst
        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.

        carrier_timeout=
                        [NET] Specifies amount of time (in seconds) that
                        the kernel should wait for a network carrier. By default
                        it waits 120 seconds.

        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 }

        cca=            [MIPS] Override the kernel pages' cache coherency
                        algorithm.  Accepted values range from 0 to 7
                        inclusive. See arch/mips/include/asm/pgtable-bits.h
                        for platform specific values (SB1, Loongson3 and
                        others).

        ccw_timeout_log [S390]
                        See Documentation/s390/common_io.rst for details.

        cgroup_disable= [KNL] Disable a particular controller
                        Format: {name of the controller(s) to disable}
                        The effects of cgroup_disable=foo are:
                        - foo isn't auto-mounted if you mount all cgroups in
                          a single hierarchy
                        - foo isn't visible as an individually mountable
                          subsystem
                        {Currently only "memory" controller deal with this and
                        cut the overhead, others just disable the usage. So
                        only cgroup_disable=memory is actually worthy}

        cgroup_no_v1=   [KNL] Disable cgroup controllers and named hierarchies in v1
                        Format: { { controller | "all" | "named" }
                                  [,{ controller | "all" | "named" }...] }
                        Like cgroup_disable, but only applies to cgroup v1;
                        the blacklisted controllers remain available in cgroup2.
                        "all" blacklists all controllers and "named" disables
                        named mounts. Specifying both "all" and "named" disables
                        all v1 hierarchies.

        cgroup.memory=  [KNL] Pass options to the cgroup memory controller.
                        Format: <string>
                        nosocket -- Disable socket memory accounting.
                        nokmem -- Disable kernel memory accounting.

        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
                                /sys/fs/selinux/checkreqprot.
                        Setting checkreqprot to 1 is deprecated.

        cio_ignore=     [S390]
                        See Documentation/s390/common_io.rst for details.
        clk_ignore_unused
                        [CLK]
                        Prevents the clock framework from automatically gating
                        clocks that have not been explicitly enabled by a Linux
                        device driver but are enabled in hardware at reset or
                        by the bootloader/firmware. Note that this does not
                        force such clocks to be always-on nor does it reserve
                        those clocks in any way. This parameter is useful for
                        debug and development, but should not be needed on a
                        platform with proper driver support.  For more
                        information, see Documentation/driver-api/clk.rst.

        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
                        [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

        clocksource.arm_arch_timer.evtstrm=
                        [ARM,ARM64]
                        Format: <bool>
                        Enable/disable the eventstream feature of the ARM
                        architected timer so that code using WFE-based polling
                        loops can be debugged more effectively on production
                        systems.

        clearcpuid=BITNUM[,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]@[start[MG][-end[MG]]]
                        [KNL,CMA]
                        Sets the size of kernel global memory area for
                        contiguous memory allocations and optionally the
                        placement constraint by the physical address range of
                        memory allocations. A value of 0 disables CMA
                        altogether. For more information, see
                        kernel/dma/contiguous.c

        cma_pernuma=nn[MG]
                        [ARM64,KNL,CMA]
                        Sets the size of kernel per-numa memory area for
                        contiguous memory allocations. A value of 0 disables
                        per-numa CMA altogether. And If this option is not
                        specificed, the default value is 0.
                        With per-numa CMA enabled, DMA users on node nid will
                        first try to allocate buffer from the pernuma area
                        which is located in node nid, if the allocation fails,
                        they will fallback to the global default memory area.

        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.

        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/admin-guide/serial-console.rst for more
                        information.  See
                        Documentation/networking/netconsole.rst for an
                        alternative.

                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                uart[8250],mmio16,<addr>[,options]
                uart[8250],mmio32,<addr>[,options]
                uart[8250],0x<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.
                        MMIO inter-register address stride is either 8-bit
                        (mmio), 16-bit (mmio16), or 32-bit (mmio32).
                        If none of [io|mmio|mmio16|mmio32], <addr> is assumed
                        to be equivalent to 'mmio'. 'options' are specified in
                        the same format described for ttyS above; if unspecified,
                        the h/w is not re-initialized.

                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.

        console_msg_format=
                        [KNL] Change console messages format
                default
                        By default we print messages on consoles in
                        "[time stamp] text\n" format (time stamp may not be
                        printed, depending on CONFIG_PRINTK_TIME or
                        `printk_time' param).
                syslog
                        Switch to syslog format: "<%u>[time stamp] text\n"
                        IOW, each message will have a facility and loglevel
                        prefix. The format is similar to one used by syslog()
                        syscall, or to executing "dmesg -S --raw" or to reading
                        from /proc/kmsg.

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

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

        coresight_cpu_debug.enable
                        [ARM,ARM64]
                        Format: <bool>
                        Enable/disable the CPU sampling based debugging.
                        0: default value, disable debugging
                        1: enable debugging at boot time

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

        cpuidle.governor=
                        [CPU_IDLE] Name of the cpuidle governor to use.

        cpufreq.off=1   [CPU_FREQ]
                        disable the cpufreq sub-system

        cpufreq.default_governor=
                        [CPU_FREQ] Name of the default cpufreq governor or
                        policy to use. This governor must be registered in the
                        kernel before the cpufreq driver probes.

        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.
                        [KNL, X86-64] Select a region under 4G first, and
                        fall back to reserve region above 4G when '@offset'
                        hasn't been specified.
                        See Documentation/admin-guide/kdump/kdump.rst 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/admin-guide/kdump/kdump.rst 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, also enough extra
                        low memory is needed to make sure DMA buffers for 32-bit
                        devices won't run out. Kernel would try to allocate at
                        at least 256M 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.

        cryptomgr.notests
                        [KNL] Disable crypto self-tests

        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/devices/joystick-parport.rst

        ddebug_query=   [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
                        time. See
                        Documentation/admin-guide/dynamic-debug-howto.rst for
                        details.  Deprecated, see dyndbg.

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

        debug_boot_weak_hash
                        [KNL] Enable printing [hashed] pointers early in the
                        boot sequence.  If enabled, we use a weak hash instead
                        of siphash to hash pointers.  Use this option if you are
                        seeing instances of '(___ptrval___)') and need to see a
                        value (hashed pointer) instead. Cryptographically
                        insecure, please do not use on production kernels.

        debug_locks_verbose=
                        [KNL] verbose locking self-tests
                        Format: <int>
                        Print debugging info while doing the locking API
                        self-tests.
                        Bitmask for the various LOCKTYPE_ tests. Defaults to 0
                        (no extra messages), setting it to -1 (all bits set)
                        will print _a_lot_ more information - normally only
                        useful to lockdep 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. By default, it is
                        disabled and the system will work mostly the same as a
                        kernel built without CONFIG_DEBUG_PAGEALLOC.
                        Note: to get most of debug_pagealloc error reports, it's
                        useful to also enable the page_owner functionality.
                        on: enable the feature

        debugfs=        [KNL] This parameter enables what is exposed to userspace
                        and debugfs internal clients.
                        Format: { on, no-mount, off }
                        on:     All functions are enabled.
                        no-mount:
                                Filesystem is not registered but kernel clients can
                                access APIs and a crashkernel can be used to read
                                its content. There is nothing to mount.
                        off:    Filesystem is not registered and clients
                                get a -EPERM as result when trying to register files
                                or directories within debugfs.
                                This is equivalent of the runtime functionality if
                                debugfs was not enabled in the kernel at all.
                        Default value is set in build-time with a kernel configuration.

        debugpat        [X86] Enable PAT debugging

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

        default_hugepagesz=
                        [HW] The size of the default HugeTLB page. This is
                        the size represented by the legacy /proc/ hugepages
                        APIs.  In addition, this is the default hugetlb size
                        used for shmget(), mmap() and mounting hugetlbfs
                        filesystems.  If not specified, defaults to the
                        architecture's default huge page size.  Huge page
                        sizes are architecture dependent.  See also
                        Documentation/admin-guide/mm/hugetlbpage.rst.
                        Format: size[KMG]

        deferred_probe_timeout=
                        [KNL] Debugging option to set a timeout in seconds for
                        deferred probe to give up waiting on dependencies to
                        probe. Only specific dependencies (subsystems or
                        drivers) that have opted in will be ignored. A timeout of 0
                        will timeout at the end of initcalls. This option will also
                        dump out devices still on the deferred probe list after
                        retrying.

        dfltcc=         [HW,S390]
                        Format: { on | off | def_only | inf_only | always }
                        on:       s390 zlib hardware support for compression on
                                  level 1 and decompression (default)
                        off:      No s390 zlib hardware support
                        def_only: s390 zlib hardware support for deflate
                                  only (compression on level 1)
                        inf_only: s390 zlib hardware support for inflate
                                  only (decompression)
                        always:   Same as 'on' but ignores the selected compression
                                  level always using hardware support (used for debugging)

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

        disable_1tb_segments [PPC]
                        Disables the use of 1TB hash page table segments. This
                        causes the kernel to fall back to 256MB segments which
                        can be useful when debugging issues that require an SLB
                        miss to occur.

        stress_slb      [PPC]
                        Limits the number of kernel SLB entries, and flushes
                        them frequently to increase the rate of SLB faults
                        on kernel addresses.

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

        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_radix   [PPC]
                        Disable RADIX MMU mode on POWER9

        radix_hcall_invalidate=on  [PPC/PSERIES]
                        Disable RADIX GTSE feature and use hcall for TLB
                        invalidate.

        disable_tlbie   [PPC]
                        Disable TLBIE instruction. Currently does not work
                        with KVM, with HASH MMU, or with coherent accelerators.

        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
                        to workaround buggy firmware.

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

        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.

        driver_async_probe=  [KNL]
                        List of driver names to be probed asynchronously.
                        Format: <driver_name1>,<driver_name2>...

        drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
                        Broken monitors, graphic adapters, KVMs and EDIDless
                        panels may send no or incorrect EDID data sets.
                        This parameter allows to specify an EDID data sets
                        in the /lib/firmware directory that are 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/admin-guide/edid.rst. An EDID
                        data set will only be used for a particular connector,
                        if its name and a colon are prepended to the EDID
                        name. Each connector may use a unique EDID data
                        set by separating the files with a comma.  An EDID
                        data set with no connector name will be used for
                        any connectors not explicitly specified.

        dscc4.setup=    [NET]

        dt_cpu_ftrs=    [PPC]
                        Format: {"off" | "known"}
                        Control how the dt_cpu_ftrs device-tree binding is
                        used for CPU feature discovery and setup (if it
                        exists).
                        off: Do not use it, fall back to legacy cpu table.
                        known: Do not pass through unknown features to guests
                        or userspace, only those that the kernel is aware of.

        dump_apple_properties   [X86]
                        Dump name and content of EFI device properties on
                        x86 Macs.  Useful for driver authors to determine
                        what data is available or for reverse-engineering.

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

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

        <module>.async_probe [KNL]
                        Enable asynchronous probe on this module.

        early_ioremap_debug [KNL]
                        Enable debug messages in early_ioremap support. This
                        is useful for tracking down temporary early mappings
                        which are not unmapped.

        earlycon=       [KNL] Output early console device and options.

                        When used with no options, the early console is
                        determined by stdout-path property in device tree's
                        chosen node or the ACPI SPCR table if supported by
                        the platform.

                cdns,<addr>[,options]
                        Start an early, polled-mode console on a Cadence
                        (xuartps) serial port at the specified address. Only
                        supported option is baud rate. If baud rate is not
                        specified, the serial port must already be setup and
                        configured.

                uart[8250],io,<addr>[,options]
                uart[8250],mmio,<addr>[,options]
                uart[8250],mmio32,<addr>[,options]
                uart[8250],mmio32be,<addr>[,options]
                uart[8250],0x<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 or mmio32be).
                        If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
                        to be equivalent to 'mmio'. 'options' are specified
                        in the same format described for "console=ttyS<n>"; if
                        unspecified, the h/w is not initialized.

                pl011,<addr>
                pl011,mmio32,<addr>
                        Start an early, polled-mode console on a pl011 serial
                        port at the specified address. The pl011 serial port
                        must already be setup and configured. Options are not
                        yet supported.  If 'mmio32' is specified, then only
                        the driver will use only 32-bit accessors to read/write
                        the device registers.

                meson,<addr>
                        Start an early, polled-mode console on a meson serial
                        port at the specified address. The serial port must
                        already be setup and configured. Options are not yet
                        supported.

                msm_serial,<addr>
                        Start an early, polled-mode console on an msm serial
                        port at the specified address. The serial port
                        must already be setup and configured. Options are not
                        yet supported.

                msm_serial_dm,<addr>
                        Start an early, polled-mode console on an msm serial
                        dm port at the specified address. The serial port
                        must already be setup and configured. Options are not
                        yet supported.

                owl,<addr>
                        Start an early, polled-mode console on a serial port
                        of an Actions Semi SoC, such as S500 or S900, at the
                        specified address. The serial port must already be
                        setup and configured. Options are not yet supported.

                rda,<addr>
                        Start an early, polled-mode console on a serial port
                        of an RDA Micro SoC, such as RDA8810PL, at the
                        specified address. The serial port must already be
                        setup and configured. Options are not yet supported.

                sbi
                        Use RISC-V SBI (Supervisor Binary Interface) for early
                        console.

                smh     Use ARM semihosting calls for early console.

                s3c2410,<addr>
                s3c2412,<addr>
                s3c2440,<addr>
                s3c6400,<addr>
                s5pv210,<addr>
                exynos4210,<addr>
                        Use early console provided by serial driver available
                        on Samsung SoCs, requires selecting proper type and
                        a correct base address of the selected UART port. The
                        serial port must already be setup and configured.
                        Options are not yet supported.

                lantiq,<addr>
                        Start an early, polled-mode console on a lantiq serial
                        (lqasc) port at the specified address. The serial port
                        must already be setup and configured. Options are not
                        yet supported.

                lpuart,<addr>
                lpuart32,<addr>
                        Use early console provided by Freescale LP UART driver
                        found on Freescale Vybrid and QorIQ LS1021A processors.
                        A valid base address must be provided, and the serial
                        port must already be setup and configured.

                ec_imx21,<addr>
                ec_imx6q,<addr>
                        Start an early, polled-mode, output-only console on the
                        Freescale i.MX UART at the specified address. The UART
                        must already be setup and configured.

                ar3700_uart,<addr>
                        Start an early, polled-mode console on the
                        Armada 3700 serial port at the specified
                        address. The serial port must already be setup
                        and configured. Options are not yet supported.

                qcom_geni,<addr>
                        Start an early, polled-mode console on a Qualcomm
                        Generic Interface (GENI) based serial port at the
                        specified address. The serial port must already be
                        setup and configured. Options are not yet supported.

                efifb,[options]
                        Start an early, unaccelerated console on the EFI
                        memory mapped framebuffer (if available). On cache
                        coherent non-x86 systems that use system memory for
                        the framebuffer, pass the 'ram' option so that it is
                        mapped with the correct attributes.

                linflex,<addr>
                        Use early console provided by Freescale LINFlexD UART
                        serial driver for NXP S32V234 SoCs. A valid base
                        address must be provided, and the serial port must
                        already be setup and configured.

        earlyprintk=    [X86,SH,ARM,M68k,S390]
                        earlyprintk=vga
                        earlyprintk=sclp
                        earlyprintk=xen
                        earlyprintk=serial[,ttySn[,baudrate]]
                        earlyprintk=serial[,0x...[,baudrate]]
                        earlyprintk=ttySn[,baudrate]
                        earlyprintk=dbgp[debugController#]
                        earlyprintk=pciserial[,force],bus:device.function[,baudrate]
                        earlyprintk=xdbc[xhciController#]

                        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.

                        The sclp output can only be used on s390.

                        The optional "force" to "pciserial" enables use of a
                        PCI device even when its classcode is not of the
                        UART class.

        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

                        This parameter works in place of the kgdboc parameter
                        but can only be used if the backing tty is available
                        very early in the boot process. For early debugging
                        via a serial port see kgdboc_earlycon instead.

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

        efi=            [EFI]
                        Format: { "debug", "disable_early_pci_dma",
                                  "nochunk", "noruntime", "nosoftreserve",
                                  "novamap", "no_disable_early_pci_dma" }
                        debug: enable misc debug output.
                        disable_early_pci_dma: disable the busmaster bit on all
                        PCI bridges while in the EFI boot stub.
                        nochunk: disable reading files in "chunks" in the EFI
                        boot stub, as chunking can cause problems with some
                        firmware implementations.
                        noruntime : disable EFI runtime services support
                        nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
                        attribute may cause the kernel to reserve the
                        memory range for a memory mapping driver to
                        claim. Specify efi=nosoftreserve to disable this
                        reservation and treat the memory by its base type
                        (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
                        novamap: do not call SetVirtualAddressMap().
                        no_disable_early_pci_dma: Leave the busmaster bit set
                        on all PCI bridges while in the EFI boot stub

        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.

        efi_fake_mem=   nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
                        Add arbitrary attribute to specific memory range by
                        updating original EFI memory map.
                        Region of memory which aa attribute is added to is
                        from ss to ss+nn.

                        If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
                        is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
                        attribute is added to range 0x100000000-0x180000000 and
                        0x10a0000000-0x1120000000.

                        If efi_fake_mem=8G@9G:0x40000 is specified, the
                        EFI_MEMORY_SP(0x40000) attribute is added to
                        range 0x240000000-0x43fffffff.

                        Using this parameter you can do debugging of EFI memmap
                        related features. For example, you can do debugging of
                        Address Range Mirroring feature even if your box
                        doesn't support it, or mark specific memory as
                        "soft reserved".

        efivar_ssdt=    [EFI; X86] Name of an EFI variable that contains an SSDT
                        that is to be dynamically loaded by Linux. If there are
                        multiple variables with the same name but with different
                        vendor GUIDs, all of them will be loaded. See
                        Documentation/admin-guide/acpi/ssdt-overlays.rst for details.


        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.

        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/admin-guide/kdump/kdump.rst 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
                        /sys/fs/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_usercopy=
        fail_page_alloc=
        fail_make_request=[KNL]
                        General fault injection mechanism.
                        Format: <interval>,<probability>,<space>,<times>
                        See also Documentation/fault-injection/.

        fb_tunnels=     [NET]
                        Format: { initns | none }
                        See Documentation/admin-guide/sysctl/net.rst for
                        fb_tunnels_only_for_init_ns

        floppy=         [HW]
                        See Documentation/admin-guide/blockdev/floppy.rst.

        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.

        forcepae        [X86-32]
                        Forcefully enable Physical Address Extension (PAE).
                        Many Pentium M systems disable PAE but may have a
                        functionally usable PAE implementation.
                        Warning: use of this parameter will taint the kernel
                        and may cause unknown problems.

        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_notrace=[function-list]
                        [FTRACE] Do not trace from the functions specified in
                        function-list.  This list is a comma-separated list of
                        functions that can be changed at run time by the
                        set_graph_notrace 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)

        fw_devlink=     [KNL] Create device links between consumer and supplier
                        devices by scanning the firmware to infer the
                        consumer/supplier relationships. This feature is
                        especially useful when drivers are loaded as modules as
                        it ensures proper ordering of tasks like device probing
                        (suppliers first, then consumers), supplier boot state
                        clean up (only after all consumers have probed),
                        suspend/resume & runtime PM (consumers first, then
                        suppliers).
                        Format: { off | permissive | on | rpm }
                        off --  Don't create device links from firmware info.
                        permissive -- Create device links from firmware info
                                but use it only for ordering boot state clean
                                up (sync_state() calls).
                        on --   Create device links from firmware info and use it
                                to enforce probe and suspend/resume ordering.
                        rpm --  Like "on", but also use to order runtime PM.

        fw_devlink.strict=<bool>
                        [KNL] Treat all inferred dependencies as mandatory
                        dependencies. This only applies for fw_devlink=on|rpm.
                        Format: <bool>

        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/devices/joystick-parport.rst

        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.

        goldfish        [X86] Enable the goldfish android emulator platform.
                        Don't use this when you are not running on the
                        android emulator

        gpt             [EFI] Forces disk with valid GPT signature but
                        invalid Protective MBR to be treated as GPT. If the
                        primary GPT is corrupted, it enables the backup/alternate
                        GPT to be used instead.

        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

        gpio-mockup.gpio_mockup_ranges
                        [HW] Sets the ranges of gpiochip of for this device.
                        Format: <start1>,<end1>,<start2>,<end2>...

        hardlockup_all_cpu_backtrace=
                        [KNL] Should the hard-lockup detector generate
                        backtraces on all cpus.
                        Format: 0 | 1

        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"

        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] Allow userspace to mmap HPET
                        registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.

        hugetlb_cma=    [HW,CMA] The size of a CMA area used for allocation
                        of gigantic hugepages.
                        Format: nn[KMGTPE]

                        Reserve a CMA area of given size and allocate gigantic
                        hugepages using the CMA allocator. If enabled, the
                        boot-time allocation of gigantic hugepages is skipped.

        hugepages=      [HW] Number of HugeTLB pages to allocate at boot.
                        If this follows hugepagesz (below), it specifies
                        the number of pages of hugepagesz to be allocated.
                        If this is the first HugeTLB parameter on the command
                        line, it specifies the number of pages to allocate for
                        the default huge page size.  See also
                        Documentation/admin-guide/mm/hugetlbpage.rst.
                        Format: <integer>

        hugepagesz=
                        [HW] The size of the HugeTLB pages.  This is used in
                        conjunction with hugepages (above) to allocate huge
                        pages of a specific size at boot.  The pair
                        hugepagesz=X hugepages=Y can be specified once for
                        each supported huge page size. Huge page sizes are
                        architecture dependent.  See also
                        Documentation/admin-guide/mm/hugetlbpage.rst.
                        Format: size[KMG]

        hung_task_panic=
                        [KNL] Should the hung task detector generate panics.
                        Format: 0 | 1

                        A value of 1 instructs the kernel to panic when a
                        hung task is detected. The default value is controlled
                        by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
                        option. The value selected by this boot parameter can
                        be changed later by the kernel.hung_task_panic sysctl.

        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.

        hv_nopvspin     [X86,HYPER_V] Disables the paravirt spinlock optimizations
                                      which allow the hypervisor to 'idle' the
                                      guest on lock contention.

        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.unmask_kbd_data
                        [HW] Enable printing of interrupt data from the KBD port
                             (disabled by default, and as a pre-condition
                             requires that i8042.debug=1 be enabled)
        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, cleanup and
                             suspend-to-ram transitions, only during s2r
                             transitions, or never reset
                        Format: { 1 | Y | y | 0 | N | n }
                        1, Y, y: always reset controller
                        0, N, n: don't ever reset controller
                        Default: only on s2r transitions on x86; most other
                        architectures force reset to be always executed
        i8042.unlock    [HW] Unlock (ignore) the keylock
        i8042.kbdreset  [HW] Reset device connected to KBD port

        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.rst.

        ide-generic.probe-mask= [HW] (E)IDE subsystem
                        Format: <int>
                        Probe mask for legacy ISA IDE ports.  Depending on
                        platform up to 6 ports are supported, enabled by
                        setting corresponding bits in the mask to 1.  The
                        default value is 0x0, which has a special meaning.
                        On systems that have PCI, it triggers scanning the
                        PCI bus for the first and the second port, which
                        are then probed.  On systems without PCI the value
                        of 0x0 enables probing the two first ports as if it
                        was 0x3.

        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

        idxd.sva=       [HW]
                        Format: <bool>
                        Allow force disabling of Shared Virtual Memory (SVA)
                        support for the idxd driver. By default it is set to
                        true (1).

        ieee754=        [MIPS] Select IEEE Std 754 conformance mode
                        Format: { strict | legacy | 2008 | relaxed }
                        Default: strict

                        Choose which programs will be accepted for execution
                        based on the IEEE 754 NaN encoding(s) supported by
                        the FPU and the NaN encoding requested with the value
                        of an ELF file header flag individually set by each
                        binary.  Hardware implementations are permitted to
                        support either or both of the legacy and the 2008 NaN
                        encoding mode.

                        Available settings are as follows:
                        strict  accept binaries that request a NaN encoding
                                supported by the FPU
                        legacy  only accept legacy-NaN binaries, if supported
                                by the FPU
                        2008    only accept 2008-NaN binaries, if supported
                                by the FPU
                        relaxed accept any binaries regardless of whether
                                supported by the FPU

                        The FPU emulator is always able to support both NaN
                        encodings, so if no FPU hardware is present or it has
                        been disabled with 'nofpu', then the settings of
                        'legacy' and '2008' strap the emulator accordingly,
                        'relaxed' straps the emulator for both legacy-NaN and
                        2008-NaN, whereas 'strict' enables legacy-NaN only on
                        legacy processors and both NaN encodings on MIPS32 or
                        MIPS64 CPUs.

                        The setting for ABS.fmt/NEG.fmt instruction execution
                        mode generally follows that for the NaN encoding,
                        except where unsupported by hardware.

        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.

        ignore_rlimit_data
                        Ignore RLIMIT_DATA setting for data mappings,
                        print warning at first misuse.  Can be changed via
                        /sys/module/kernel/parameters/ignore_rlimit_data.

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

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

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

        ima_canonical_fmt [IMA]
                        Use the canonical format for the binary runtime
                        measurements, instead of host native format.

        ima_hash=       [IMA]
                        Format: { md5 | sha1 | rmd160 | sha256 | sha384
                                   | sha512 | ... }
                        default: "sha1"

                        The list of supported hash algorithms is defined
                        in crypto/hash_info.h.

        ima_policy=     [IMA]
                        The builtin policies to load during IMA setup.
                        Format: "tcb | appraise_tcb | secure_boot |
                                 fail_securely | critical_data"

                        The "tcb" policy measures all programs exec'd, files
                        mmap'd for exec, and all files opened with the read
                        mode bit set by either the effective uid (euid=0) or
                        uid=0.

                        The "appraise_tcb" policy appraises the integrity of
                        all files owned by root.

                        The "secure_boot" policy appraises the integrity
                        of files (eg. kexec kernel image, kernel modules,
                        firmware, policy, etc) based on file signatures.

                        The "fail_securely" policy forces file signature
                        verification failure also on privileged mounted
                        filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
                        flag.

                        The "critical_data" policy measures kernel integrity
                        critical data.

        ima_tcb         [IMA] Deprecated.  Use ima_policy= instead.
                        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.

        ima_template=   [IMA]
                        Select one of defined IMA measurements template formats.
                        Formats: { "ima" | "ima-ng" | "ima-sig" }
                        Default: "ima-ng"

        ima_template_fmt=
                        [IMA] Define a custom template format.
                        Format: { "field1|...|fieldN" }

        ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
                        Format: <min_file_size>
                        Set the minimal file size for using asynchronous hash.
                        If left unspecified, ahash usage is disabled.

                        ahash performance varies for different data sizes on
                        different crypto accelerators. This option can be used
                        to achieve the best performance for a particular HW.

        ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
                        Format: <bufsize>
                        Set hashing buffer size. Default: 4k.

                        ahash performance varies for different chunk sizes on
                        different crypto accelerators. This option can be used
                        to achieve best performance for particular HW.

        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

        initrdmem=      [KNL] Specify a physical address and size from which to
                        load the initrd. If an initrd is compiled in or
                        specified in the bootparams, it takes priority over this
                        setting.
                        Format: ss[KMG],nn[KMG]
                        Default is 0, 0

        init_on_alloc=  [MM] Fill newly allocated pages and heap objects with
                        zeroes.
                        Format: 0 | 1
                        Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.

        init_on_free=   [MM] Fill freed pages and heap objects with zeroes.
                        Format: 0 | 1
                        Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.

        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

        integrity_audit=[IMA]
                        Format: { "0" | "1" }
                        0 -- basic integrity auditing messages. (Default)
                        1 -- additional integrity auditing messages.

        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.
                sm_on [Default Off]
                        By default, scalable mode will be disabled even if the
                        hardware advertises that it has support for the scalable
                        mode translation. With this option set, scalable mode
                        will be used on hardware which claims to support it.
                tboot_noforce [Default Off]
                        Do not force the Intel IOMMU enabled under tboot.
                        By default, tboot will force Intel IOMMU on, which
                        could harm performance of some high-throughput
                        devices like 40GBit network cards, even if identity
                        mapping is enabled.
                        Note that using this option lowers the security
                        provided by tboot because it makes the system
                        vulnerable to DMA attacks.

        intel_idle.max_cstate=  [KNL,HW,ACPI,X86]
                        0       disables intel_idle and fall back on acpi_idle.
                        1 to 9  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.
                        per_cpu_perf_limits
                          Allow per-logical-CPU P-State performance control limits using
                          cpufreq sysfs interface

        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
                soft
                pt              [X86]
                nopt            [X86]
                nobypass        [PPC/POWERNV]
                        Disable IOMMU bypass, using IOMMU for PCI devices.

        iommu.strict=   [ARM64] Configure TLB invalidation behaviour
                        Format: { "0" | "1" }
                        0 - Lazy mode.
                          Request that DMA unmap operations use deferred
                          invalidation of hardware TLBs, for increased
                          throughput at the cost of reduced device isolation.
                          Will fall back to strict mode if not supported by
                          the relevant IOMMU driver.
                        1 - Strict mode (default).
                          DMA unmap operations invalidate IOMMU hardware TLBs
                          synchronously.

        iommu.passthrough=
                        [ARM64, X86] Configure DMA to bypass the IOMMU by default.
                        Format: { "0" | "1" }
                        0 - Use IOMMU translation for DMA.
                        1 - Bypass the IOMMU for DMA.
                        unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.

        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/admin-guide/nfs/nfsroot.rst.

        ipcmni_extend   [KNL] Extend the maximum number of unique System V
                        IPC identifiers from 32,768 to 16,777,216.

        irqaffinity=    [SMP] Set the default irq affinity mask
                        The argument is a cpu list, as described above.

        irqchip.gicv2_force_probe=
                        [ARM, ARM64]
                        Format: <bool>
                        Force the kernel to look for the second 4kB page
                        of a GICv2 controller even if the memory range
                        exposed by the device tree is too small.

        irqchip.gicv3_nolpi=
                        [ARM, ARM64]
                        Force the kernel to ignore the availability of
                        LPIs (and by consequence ITSs). Intended for system
                        that use the kernel as a bootloader, and thus want
                        to let secondary kernels in charge of setting up
                        LPIs.

        irqchip.gicv3_pseudo_nmi= [ARM64]
                        Enables support for pseudo-NMIs in the kernel. This
                        requires the kernel to be built with
                        CONFIG_ARM64_PSEUDO_NMI.

        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,ISOL] Isolate a given set of CPUs from disturbance.
                        [Deprecated - use cpusets instead]
                        Format: [flag-list,]<cpu-list>

                        Specify one or more CPUs to isolate from disturbances
                        specified in the flag list (default: domain):

                        nohz
                          Disable the tick when a single task runs.

                          A residual 1Hz tick is offloaded to workqueues, which you
                          need to affine to housekeeping through the global
                          workqueue's affinity configured via the
                          /sys/devices/virtual/workqueue/cpumask sysfs file, or
                          by using the 'domain' flag described below.

                          NOTE: by default the global workqueue runs on all CPUs,
                          so to protect individual CPUs the 'cpumask' file has to
                          be configured manually after bootup.

                        domain
                          Isolate from the general SMP balancing and scheduling
                          algorithms. Note that performing domain isolation this way
                          is irreversible: it's not possible to bring back a CPU to
                          the domains once isolated through isolcpus. It's strongly
                          advised to use cpusets instead to disable scheduler load
                          balancing through the "cpuset.sched_load_balance" file.
                          It offers a much more flexible interface where CPUs can
                          move in and out of an isolated set anytime.

                          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".

                        managed_irq

                          Isolate from being targeted by managed interrupts
                          which have an interrupt mask containing isolated
                          CPUs. The affinity of managed interrupts is
                          handled by the kernel and cannot be changed via
                          the /proc/irq/* interfaces.

                          This isolation is best effort and only effective
                          if the automatically assigned interrupt mask of a
                          device queue contains isolated and housekeeping
                          CPUs. If housekeeping CPUs are online then such
                          interrupts are directed to the housekeeping CPU
                          so that IO submitted on the housekeeping CPU
                          cannot disturb the isolated CPU.

                          If a queue's affinity mask contains only isolated
                          CPUs then this parameter has no effect on the
                          interrupt routing decision, though interrupts are
                          only delivered when tasks running on those
                          isolated CPUs submit IO. IO submitted on
                          housekeeping CPUs has no influence on those
                          queues.

                        The format of <cpu-list> is described above.

        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/joydev/joystick.rst.

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

        kasan_multi_shot
                        [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
                        report on every invalid memory access. Without this
                        parameter KASAN will print report only for the first
                        invalid access.

        keepinitrd      [HW,ARM]

        kernelcore=     [KNL,X86,IA-64,PPC]
                        Format: nn[KMGTPE] | nn% | "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 as ZONE_NORMAL.  The remaining memory is used for
                        movable memory in its own zone, ZONE_MOVABLE.  In the
                        event, a node is too small to have both ZONE_NORMAL and
                        ZONE_MOVABLE, kernelcore memory will take priority and
                        other nodes will have a larger ZONE_MOVABLE.

                        ZONE_MOVABLE is used for the allocation of pages that
                        may be reclaimed or moved by the page migration
                        subsystem.  Note that allocations like PTEs-from-HighMem
                        still use the HighMem zone if it exists, and the Normal
                        zone if it does not.

                        It is possible to specify the exact amount of memory in
                        the form of "nn[KMGTPE]", a percentage of total system
                        memory in the form of "nn%", or "mirror".  If "mirror"
                        option is specified, mirrored (reliable) memory is used
                        for non-movable allocations and remaining memory is used
                        for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
                        are exclusive, so you cannot specify multiple forms.

        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]

        kgdboc_earlycon=        [KGDB,HW]
                        If the boot console provides the ability to read
                        characters and can work in polling mode, you can use
                        this parameter to tell kgdb to use it as a backend
                        until the normal console is registered. Intended to
                        be used together with the kgdboc parameter which
                        specifies the normal console to transition to.

                        The name of the early console should be specified
                        as the value of this parameter. Note that the name of
                        the early console might be different than the tty
                        name passed to kgdboc. It's OK to leave the value
                        blank and the first boot console that implements
                        read() will be picked.

        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
                        Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
                        the default is off.

        kprobe_event=[probe-list]
                        [FTRACE] Add kprobe events and enable at boot time.
                        The probe-list is a semicolon delimited list of probe
                        definitions. Each definition is same as kprobe_events
                        interface, but the parameters are comma delimited.
                        For example, to add a kprobe event on vfs_read with
                        arg1 and arg2, add to the command line;

                              kprobe_event=p,vfs_read,$arg1,$arg2

                        See also Documentation/trace/kprobetrace.rst "Kernel
                        Boot Parameter" section.

        kpti=           [ARM64] Control page table isolation of user
                        and kernel address spaces.
                        Default: enabled on cores which need mitigation.
                        0: force disabled
                        1: force enabled

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

        kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
                                   Default is false (don't support).

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

        kvm.nx_huge_pages=
                        [KVM] Controls the software workaround for the
                        X86_BUG_ITLB_MULTIHIT bug.
                        force   : Always deploy workaround.
                        off     : Never deploy workaround.
                        auto    : Deploy workaround based on the presence of
                                  X86_BUG_ITLB_MULTIHIT.

                        Default is 'auto'.

                        If the software workaround is enabled for the host,
                        guests do need not to enable it for nested guests.

        kvm.nx_huge_pages_recovery_ratio=
                        [KVM] Controls how many 4KiB pages are periodically zapped
                        back to huge pages.  0 disables the recovery, otherwise if
                        the value is N KVM will zap 1/Nth of the 4KiB pages every
                        minute.  The default is 60.

        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-arm.mode=
                        [KVM,ARM] Select one of KVM/arm64's modes of operation.

                        nvhe: Standard nVHE-based mode, without support for
                              protected guests.

                        protected: nVHE-based mode with support for guests whose
                                   state is kept private from the host.
                                   Not valid if the kernel is running in EL2.

                        Defaults to VHE/nVHE based on hardware support and
                        the value of CONFIG_ARM64_VHE.

        kvm-arm.vgic_v3_group0_trap=
                        [KVM,ARM] Trap guest accesses to GICv3 group-0
                        system registers

        kvm-arm.vgic_v3_group1_trap=
                        [KVM,ARM] Trap guest accesses to GICv3 group-1
                        system registers

        kvm-arm.vgic_v3_common_trap=
                        [KVM,ARM] Trap guest accesses to GICv3 common
                        system registers

        kvm-arm.vgic_v4_enable=
                        [KVM,ARM] Allow use of GICv4 for direct injection of
                        LPIs.

        kvm_cma_resv_ratio=n [PPC]
                        Reserves given percentage from system memory area for
                        contiguous memory allocation for KVM hash pagetable
                        allocation.
                        By default it reserves 5% of total system memory.
                        Format: <integer>
                        Default: 5

        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.
                                It also drops the swap size and available
                                RAM limit restriction on both hypervisor and
                                bare metal.

                        Default is 'flush'.

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

        l2cr=           [PPC]

        l3cr=           [PPC]

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

        lapic=          [X86,APIC] Do not use TSC deadline
                        value for LAPIC timer one-shot implementation. Default
                        back to the programmable timer unit in the LAPIC.
                        Format: notscdeadline

        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.

       
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