Merge tag 'docs-5.7-2' of git://git.lwn.net/linux

[sfrench/cifs-2.6.git] / Documentation / admin-guide / kernel-parameters.txt

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f7899914f32a9454c26ddf156e8b2a16cc342791..2ad7d7c26060451776ba0afd1c42f3cbc34ed6f6 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -22,11 +22,13 @@
                        default: 0
 
        acpi_backlight= [HW,ACPI]
                        default: 0
 
        acpi_backlight= [HW,ACPI]

-                       acpi_backlight=vendor
-                       acpi_backlight=video
-                       If set to vendor, prefer vendor specific driver
+                       { 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.
                        (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
 
        acpi_force_32bit_fadt_addr
                        force FADT to use 32 bit addresses rather than the


@@ -136,6 +138,10 @@
                        dynamic table installation which will install SSDT
                        tables to /sys/firmware/acpi/tables/dynamic.
 
                        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
        acpi_rsdp=      [ACPI,EFI,KEXEC]
                        Pass the RSDP address to the kernel, mostly used
                        on machines running EFI runtime service to boot the


@@ -446,6 +452,9 @@
        bert_disable    [ACPI]
                        Disable BERT OS support on buggy BIOSes.
 
        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.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
        bttv.radio=     Most important insmod options are available as
                        kernel args too.


@@ -518,6 +527,7 @@
                        Default value is set via a kernel config option.
                        Value can be changed at runtime via
                                /sys/fs/selinux/checkreqprot.
                        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.
 
        cio_ignore=     [S390]
                        See Documentation/s390/common_io.rst for details.


@@ -1352,6 +1362,24 @@
                        can be changed at run time by the max_graph_depth file
                        in the tracefs tracing directory. default: 0 (no limit)
 
                        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.
+

        gamecon.map[2|3]=
                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
                        support via parallel port (up to 5 devices per port)
        gamecon.map[2|3]=
                        [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
                        support via parallel port (up to 5 devices per port)


@@ -2541,13 +2569,22 @@
                        For details see: Documentation/admin-guide/hw-vuln/mds.rst
 
        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
                        For details see: Documentation/admin-guide/hw-vuln/mds.rst
 
        mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory

-                       Amount of memory to be used when the kernel is not able
-                       to see the whole system memory or for test.
+                       Amount of memory to be used in cases as follows:
+
+                       1 for test;
+                       2 when the kernel is not able to see the whole system memory;
+                       3 memory that lies after 'mem=' boundary is excluded from
+                        the hypervisor, then assigned to KVM guests.
+

                        [X86] Work as limiting max address. Use together
                        with memmap= to avoid physical address space collisions.
                        Without memmap= PCI devices could be placed at addresses
                        belonging to unused RAM.
 
                        [X86] Work as limiting max address. Use together
                        with memmap= to avoid physical address space collisions.
                        Without memmap= PCI devices could be placed at addresses
                        belonging to unused RAM.
 

+                       Note that this only takes effects during boot time since
+                       in above case 3, memory may need be hot added after boot
+                       if system memory of hypervisor is not sufficient.
+

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


@@ -3172,7 +3209,7 @@
                        [X86,PV_OPS] Disable paravirtualized VMware scheduler
                        clock and use the default one.
 
                        [X86,PV_OPS] Disable paravirtualized VMware scheduler
                        clock and use the default one.
 

-       no-steal-acc    [X86,KVM,ARM64] Disable paravirtualized steal time
+       no-steal-acc    [X86,PV_OPS,ARM64] Disable paravirtualized steal time

                        accounting. steal time is computed, but won't
                        influence scheduler behaviour
 
                        accounting. steal time is computed, but won't
                        influence scheduler behaviour
 


@@ -3283,12 +3320,6 @@
                        This can be set from sysctl after boot.
                        See Documentation/admin-guide/sysctl/vm.rst for details.
 
                        This can be set from sysctl after boot.
                        See Documentation/admin-guide/sysctl/vm.rst for details.
 

-       of_devlink      [OF, KNL] Create device links between consumer and
-                       supplier devices by scanning the devictree to infer the
-                       consumer/supplier relationships.  A consumer device
-                       will not be probed until all the supplier devices have
-                       probed successfully.
-

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


@@ -3696,6 +3727,9 @@
                        Override pmtimer IOPort with a hex value.
                        e.g. pmtmr=0x508
 
                        Override pmtimer IOPort with a hex value.
                        e.g. pmtmr=0x508
 

+       pm_debug_messages       [SUSPEND,KNL]
+                       Enable suspend/resume debug messages during boot up.
+

        pnp.debug=1     [PNP]
                        Enable PNP debug messages (depends on the
                        CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
        pnp.debug=1     [PNP]
                        Enable PNP debug messages (depends on the
                        CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time


@@ -3797,6 +3831,11 @@
                        before loading.
                        See Documentation/admin-guide/blockdev/ramdisk.rst.
 
                        before loading.
                        See Documentation/admin-guide/blockdev/ramdisk.rst.
 

+       prot_virt=      [S390] enable hosting protected virtual machines
+                       isolated from the hypervisor (if hardware supports
+                       that).
+                       Format: <bool>
+

        psi=            [KNL] Enable or disable pressure stall information
                        tracking.
                        Format: <bool>
        psi=            [KNL] Enable or disable pressure stall information
                        tracking.
                        Format: <bool>


@@ -3982,6 +4021,15 @@
                        Set threshold of queued RCU callbacks below which
                        batch limiting is re-enabled.
 
                        Set threshold of queued RCU callbacks below which
                        batch limiting is re-enabled.
 

+       rcutree.qovld= [KNL]
+                       Set threshold of queued RCU callbacks beyond which
+                       RCU's force-quiescent-state scan will aggressively
+                       enlist help from cond_resched() and sched IPIs to
+                       help CPUs more quickly reach quiescent states.
+                       Set to less than zero to make this be set based
+                       on rcutree.qhimark at boot time and to zero to
+                       disable more aggressive help enlistment.
+

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


@@ -4197,6 +4245,12 @@
        rcupdate.rcu_cpu_stall_suppress= [KNL]
                        Suppress RCU CPU stall warning messages.
 
        rcupdate.rcu_cpu_stall_suppress= [KNL]
                        Suppress RCU CPU stall warning messages.
 

+       rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
+                       Suppress RCU CPU stall warning messages and
+                       rcutorture writer stall warnings that occur
+                       during early boot, that is, during the time
+                       before the init task is spawned.
+

        rcupdate.rcu_cpu_stall_timeout= [KNL]
                        Set timeout for RCU CPU stall warning messages.
 
        rcupdate.rcu_cpu_stall_timeout= [KNL]
                        Set timeout for RCU CPU stall warning messages.
 


@@ -4390,6 +4444,22 @@
                        incurs a small amount of overhead in the scheduler
                        but is useful for debugging and performance tuning.
 
                        incurs a small amount of overhead in the scheduler
                        but is useful for debugging and performance tuning.
 

+       sched_thermal_decay_shift=
+                       [KNL, SMP] Set a decay shift for scheduler thermal
+                       pressure signal. Thermal pressure signal follows the
+                       default decay period of other scheduler pelt
+                       signals(usually 32 ms but configurable). Setting
+                       sched_thermal_decay_shift will left shift the decay
+                       period for the thermal pressure signal by the shift
+                       value.
+                       i.e. with the default pelt decay period of 32 ms
+                       sched_thermal_decay_shift   thermal pressure decay pr
+                               1                       64 ms
+                               2                       128 ms
+                       and so on.
+                       Format: integer between 0 and 10
+                       Default is 0.
+

        skew_tick=      [KNL] Offset the periodic timer tick per cpu to mitigate
                        xtime_lock contention on larger systems, and/or RCU lock
                        contention on all systems with CONFIG_MAXSMP set.
        skew_tick=      [KNL] Offset the periodic timer tick per cpu to mitigate
                        xtime_lock contention on larger systems, and/or RCU lock
                        contention on all systems with CONFIG_MAXSMP set.


@@ -4657,6 +4727,28 @@
        spia_pedr=
        spia_peddr=
 
        spia_pedr=
        spia_peddr=
 

+       split_lock_detect=
+                       [X86] Enable split lock detection
+
+                       When enabled (and if hardware support is present), atomic
+                       instructions that access data across cache line
+                       boundaries will result in an alignment check exception.
+
+                       off     - not enabled
+
+                       warn    - the kernel will emit rate limited warnings
+                                 about applications triggering the #AC
+                                 exception. This mode is the default on CPUs
+                                 that supports split lock detection.
+
+                       fatal   - the kernel will send SIGBUS to applications
+                                 that trigger the #AC exception.
+
+                       If an #AC exception is hit in the kernel or in
+                       firmware (i.e. not while executing in user mode)
+                       the kernel will oops in either "warn" or "fatal"
+                       mode.
+

        srcutree.counter_wrap_check [KNL]
                        Specifies how frequently to check for
                        grace-period sequence counter wrap for the
        srcutree.counter_wrap_check [KNL]
                        Specifies how frequently to check for
                        grace-period sequence counter wrap for the


@@ -4869,6 +4961,10 @@
                        topology updates sent by the hypervisor to this
                        LPAR.
 
                        topology updates sent by the hypervisor to this
                        LPAR.
 

+       torture.disable_onoff_at_boot= [KNL]
+                       Prevent the CPU-hotplug component of torturing
+                       until after init has spawned.
+

        tp720=          [HW,PS2]
 
        tpm_suspend_pcr=[HW,TPM]
        tp720=          [HW,PS2]
 
        tpm_suspend_pcr=[HW,TPM]