2009-10-22 11:45:20 +08:00
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What: /sys/devices/system/cpu/
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Date: pre-git history
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description:
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A collection of both global and individual CPU attributes
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Individual CPU attributes are contained in subdirectories
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named by the kernel's logical CPU number, e.g.:
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/sys/devices/system/cpu/cpu#/
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2009-10-22 11:45:25 +08:00
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What: /sys/devices/system/cpu/kernel_max
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/sys/devices/system/cpu/offline
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/sys/devices/system/cpu/online
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/sys/devices/system/cpu/possible
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/sys/devices/system/cpu/present
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Date: December 2008
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: CPU topology files that describe kernel limits related to
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hotplug. Briefly:
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kernel_max: the maximum cpu index allowed by the kernel
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configuration.
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offline: cpus that are not online because they have been
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HOTPLUGGED off or exceed the limit of cpus allowed by the
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kernel configuration (kernel_max above).
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online: cpus that are online and being scheduled.
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possible: cpus that have been allocated resources and can be
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brought online if they are present.
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present: cpus that have been identified as being present in
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the system.
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See Documentation/cputopology.txt for more information.
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2009-11-26 01:23:25 +08:00
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What: /sys/devices/system/cpu/probe
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/sys/devices/system/cpu/release
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Date: November 2009
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: Dynamic addition and removal of CPU's. This is not hotplug
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removal, this is meant complete removal/addition of the CPU
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from the system.
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probe: writes to this file will dynamically add a CPU to the
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system. Information written to the file to add CPU's is
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architecture specific.
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release: writes to this file dynamically remove a CPU from
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the system. Information writtento the file to remove CPU's
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is architecture specific.
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2009-10-22 12:15:30 +08:00
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2009-12-15 09:59:09 +08:00
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What: /sys/devices/system/cpu/cpu#/node
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Date: October 2009
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Contact: Linux memory management mailing list <linux-mm@kvack.org>
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Description: Discover NUMA node a CPU belongs to
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When CONFIG_NUMA is enabled, a symbolic link that points
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to the corresponding NUMA node directory.
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For example, the following symlink is created for cpu42
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in NUMA node 2:
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/sys/devices/system/cpu/cpu42/node2 -> ../../node/node2
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2009-10-22 11:45:31 +08:00
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What: /sys/devices/system/cpu/cpu#/topology/core_id
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/sys/devices/system/cpu/cpu#/topology/core_siblings
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/sys/devices/system/cpu/cpu#/topology/core_siblings_list
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/sys/devices/system/cpu/cpu#/topology/physical_package_id
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/sys/devices/system/cpu/cpu#/topology/thread_siblings
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/sys/devices/system/cpu/cpu#/topology/thread_siblings_list
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Date: December 2008
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: CPU topology files that describe a logical CPU's relationship
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to other cores and threads in the same physical package.
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One cpu# directory is created per logical CPU in the system,
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e.g. /sys/devices/system/cpu/cpu42/.
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Briefly, the files above are:
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core_id: the CPU core ID of cpu#. Typically it is the
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hardware platform's identifier (rather than the kernel's).
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The actual value is architecture and platform dependent.
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core_siblings: internal kernel map of cpu#'s hardware threads
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within the same physical_package_id.
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core_siblings_list: human-readable list of the logical CPU
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numbers within the same physical_package_id as cpu#.
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physical_package_id: physical package id of cpu#. Typically
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corresponds to a physical socket number, but the actual value
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is architecture and platform dependent.
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thread_siblings: internel kernel map of cpu#'s hardware
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threads within the same core as cpu#
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thread_siblings_list: human-readable list of cpu#'s hardware
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threads within the same core as cpu#
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See Documentation/cputopology.txt for more information.
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2009-10-22 11:45:41 +08:00
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What: /sys/devices/system/cpu/cpuidle/current_driver
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/sys/devices/system/cpu/cpuidle/current_governer_ro
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2018-02-07 21:34:36 +08:00
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/sys/devices/system/cpu/cpuidle/available_governors
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/sys/devices/system/cpu/cpuidle/current_governor
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2009-10-22 11:45:41 +08:00
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Date: September 2007
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: Discover cpuidle policy and mechanism
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Various CPUs today support multiple idle levels that are
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differentiated by varying exit latencies and power
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consumption during idle.
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Idle policy (governor) is differentiated from idle mechanism
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(driver)
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2018-02-07 21:34:36 +08:00
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current_driver: (RO) displays current idle mechanism
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2009-10-22 11:45:41 +08:00
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2018-02-07 21:34:36 +08:00
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current_governor_ro: (RO) displays current idle policy
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With the cpuidle_sysfs_switch boot option enabled (meant for
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developer testing), the following three attributes are visible
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instead:
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current_driver: same as described above
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available_governors: (RO) displays a space separated list of
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available governors
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current_governor: (RW) displays current idle policy. Users can
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switch the governor at runtime by writing to this file.
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2009-10-22 11:45:41 +08:00
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See files in Documentation/cpuidle/ for more information.
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2018-02-07 21:34:36 +08:00
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What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/name
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/sys/devices/system/cpu/cpuX/cpuidle/stateN/latency
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/sys/devices/system/cpu/cpuX/cpuidle/stateN/power
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/sys/devices/system/cpu/cpuX/cpuidle/stateN/time
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/sys/devices/system/cpu/cpuX/cpuidle/stateN/usage
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Date: September 2007
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KernelVersion: v2.6.24
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Contact: Linux power management list <linux-pm@vger.kernel.org>
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Description:
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The directory /sys/devices/system/cpu/cpuX/cpuidle contains per
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logical CPU specific cpuidle information for each online cpu X.
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The processor idle states which are available for use have the
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following attributes:
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name: (RO) Name of the idle state (string).
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latency: (RO) The latency to exit out of this idle state (in
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microseconds).
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power: (RO) The power consumed while in this idle state (in
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milliwatts).
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time: (RO) The total time spent in this idle state (in microseconds).
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usage: (RO) Number of times this state was entered (a count).
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What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/desc
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Date: February 2008
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KernelVersion: v2.6.25
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Contact: Linux power management list <linux-pm@vger.kernel.org>
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Description:
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(RO) A small description about the idle state (string).
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What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/disable
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Date: March 2012
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KernelVersion: v3.10
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Contact: Linux power management list <linux-pm@vger.kernel.org>
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Description:
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(RW) Option to disable this idle state (bool). The behavior and
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the effect of the disable variable depends on the implementation
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of a particular governor. In the ladder governor, for example,
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it is not coherent, i.e. if one is disabling a light state, then
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all deeper states are disabled as well, but the disable variable
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does not reflect it. Likewise, if one enables a deep state but a
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lighter state still is disabled, then this has no effect.
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What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/residency
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Date: March 2014
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KernelVersion: v3.15
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Contact: Linux power management list <linux-pm@vger.kernel.org>
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Description:
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(RO) Display the target residency i.e. the minimum amount of
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time (in microseconds) this cpu should spend in this idle state
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to make the transition worth the effort.
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2018-03-14 19:27:21 +08:00
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What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/
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Date: March 2018
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KernelVersion: v4.17
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Contact: Linux power management list <linux-pm@vger.kernel.org>
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Description:
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Idle state usage statistics related to suspend-to-idle.
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This attribute group is only present for states that can be
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used in suspend-to-idle with suspended timekeeping.
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What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/time
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Date: March 2018
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KernelVersion: v4.17
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Contact: Linux power management list <linux-pm@vger.kernel.org>
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Description:
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Total time spent by the CPU in suspend-to-idle (with scheduler
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tick suspended) after requesting this state.
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What: /sys/devices/system/cpu/cpuX/cpuidle/stateN/s2idle/usage
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Date: March 2018
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KernelVersion: v4.17
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Contact: Linux power management list <linux-pm@vger.kernel.org>
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Description:
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Total number of times this state has been requested by the CPU
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while entering suspend-to-idle.
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2018-02-07 21:34:36 +08:00
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2009-10-22 11:45:46 +08:00
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What: /sys/devices/system/cpu/cpu#/cpufreq/*
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Date: pre-git history
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2014-04-22 13:12:05 +08:00
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Contact: linux-pm@vger.kernel.org
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2009-10-22 11:45:46 +08:00
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Description: Discover and change clock speed of CPUs
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Clock scaling allows you to change the clock speed of the
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CPUs on the fly. This is a nice method to save battery
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power, because the lower the clock speed, the less power
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the CPU consumes.
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There are many knobs to tweak in this directory.
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See files in Documentation/cpu-freq/ for more information.
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2013-06-27 15:08:54 +08:00
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What: /sys/devices/system/cpu/cpu#/cpufreq/freqdomain_cpus
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Date: June 2013
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2014-04-22 13:12:05 +08:00
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Contact: linux-pm@vger.kernel.org
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2013-06-27 15:08:54 +08:00
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Description: Discover CPUs in the same CPU frequency coordination domain
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freqdomain_cpus is the list of CPUs (online+offline) that share
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the same clock/freq domain (possibly at the hardware level).
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That information may be hidden from the cpufreq core and the
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value of related_cpus may be different from freqdomain_cpus. This
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attribute is useful for user space DVFS controllers to get better
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power/performance results for platforms using acpi-cpufreq.
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This file is only present if the acpi-cpufreq driver is in use.
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2011-05-16 21:39:48 +08:00
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What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1}
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Date: August 2008
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2009-04-09 21:31:53 +08:00
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KernelVersion: 2.6.27
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2015-05-18 16:07:16 +08:00
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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2011-05-16 21:39:48 +08:00
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Description: Disable L3 cache indices
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These files exist in every CPU's cache/index3 directory. Each
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cache_disable_{0,1} file corresponds to one disable slot which
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can be used to disable a cache index. Reading from these files
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on a processor with this functionality will return the currently
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disabled index for that node. There is one L3 structure per
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node, or per internal node on MCM machines. Writing a valid
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index to one of these files will cause the specificed cache
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index to be disabled.
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All AMD processors with L3 caches provide this functionality.
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For details, see BKDGs at
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http://developer.amd.com/documentation/guides/Pages/default.aspx
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2012-09-04 16:28:07 +08:00
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What: /sys/devices/system/cpu/cpufreq/boost
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Date: August 2012
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: Processor frequency boosting control
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This switch controls the boost setting for the whole system.
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Boosting allows the CPU and the firmware to run at a frequency
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beyound it's nominal limit.
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2017-10-11 01:36:16 +08:00
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More details can be found in
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Documentation/admin-guide/pm/cpufreq.rst
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2013-03-28 16:16:45 +08:00
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What: /sys/devices/system/cpu/cpu#/crash_notes
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/sys/devices/system/cpu/cpu#/crash_notes_size
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Date: April 2013
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Contact: kexec@lists.infradead.org
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Description: address and size of the percpu note.
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crash_notes: the physical address of the memory that holds the
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note of cpu#.
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crash_notes_size: size of the note of cpu#.
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2014-01-06 20:54:26 +08:00
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What: /sys/devices/system/cpu/intel_pstate/max_perf_pct
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/sys/devices/system/cpu/intel_pstate/min_perf_pct
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/sys/devices/system/cpu/intel_pstate/no_turbo
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Date: February 2013
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Contact: linux-pm@vger.kernel.org
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Description: Parameters for the Intel P-state driver
|
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Logic for selecting the current P-state in Intel
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Sandybridge+ processors. The three knobs control
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limits for the P-state that will be requested by the
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driver.
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max_perf_pct: limits the maximum P state that will be requested by
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the driver stated as a percentage of the available performance.
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min_perf_pct: limits the minimum P state that will be requested by
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the driver stated as a percentage of the available performance.
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no_turbo: limits the driver to selecting P states below the turbo
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frequency range.
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2017-10-11 01:36:16 +08:00
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More details can be found in
|
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Documentation/admin-guide/pm/intel_pstate.rst
|
2014-09-30 21:48:25 +08:00
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What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below>
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Date: July 2014(documented, existed before August 2008)
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Contact: Sudeep Holla <sudeep.holla@arm.com>
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Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: Parameters for the CPU cache attributes
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allocation_policy:
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- WriteAllocate: allocate a memory location to a cache line
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on a cache miss because of a write
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- ReadAllocate: allocate a memory location to a cache line
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on a cache miss because of a read
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- ReadWriteAllocate: both writeallocate and readallocate
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attributes: LEGACY used only on IA64 and is same as write_policy
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coherency_line_size: the minimum amount of data in bytes that gets
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transferred from memory to cache
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2015-05-08 21:45:34 +08:00
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level: the cache hierarchy in the multi-level cache configuration
|
2014-09-30 21:48:25 +08:00
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number_of_sets: total number of sets in the cache, a set is a
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collection of cache lines with the same cache index
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physical_line_partition: number of physical cache line per cache tag
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shared_cpu_list: the list of logical cpus sharing the cache
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shared_cpu_map: logical cpu mask containing the list of cpus sharing
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the cache
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size: the total cache size in kB
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type:
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- Instruction: cache that only holds instructions
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- Data: cache that only caches data
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- Unified: cache that holds both data and instructions
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ways_of_associativity: degree of freedom in placing a particular block
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of memory in the cache
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write_policy:
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- WriteThrough: data is written to both the cache line
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and to the block in the lower-level memory
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- WriteBack: data is written only to the cache line and
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the modified cache line is written to main
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memory only when it is replaced
|
2016-03-22 21:27:09 +08:00
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|
2016-10-22 21:19:48 +08:00
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What: /sys/devices/system/cpu/cpu*/cache/index*/id
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Date: September 2016
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Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
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Description: Cache id
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The id provides a unique number for a specific instance of
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a cache of a particular type. E.g. there may be a level
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|
3 unified cache on each socket in a server and we may
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assign them ids 0, 1, 2, ...
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Note that id value can be non-contiguous. E.g. level 1
|
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caches typically exist per core, but there may not be a
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|
power of two cores on a socket, so these caches may be
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numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ...
|
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|
2016-03-22 21:27:09 +08:00
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|
|
What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats
|
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|
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat
|
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/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat
|
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|
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle
|
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|
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap
|
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|
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp
|
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|
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault
|
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|
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent
|
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|
|
/sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset
|
|
|
|
|
Date: March 2016
|
|
|
|
|
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
|
|
|
|
|
Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
|
|
|
|
|
Description: POWERNV CPUFreq driver's frequency throttle stats directory and
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|
|
|
attributes
|
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|
|
|
|
|
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|
|
'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency
|
|
|
|
|
throttle stat attributes for the chip. The throttle stats of a cpu
|
|
|
|
|
is common across all the cpus belonging to a chip. Below are the
|
|
|
|
|
throttle attributes exported in the 'throttle_stats' directory:
|
|
|
|
|
|
|
|
|
|
- turbo_stat : This file gives the total number of times the max
|
|
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|
|
frequency is throttled to lower frequency in turbo (at and above
|
|
|
|
|
nominal frequency) range of frequencies.
|
|
|
|
|
|
|
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|
|
- sub_turbo_stat : This file gives the total number of times the
|
|
|
|
|
max frequency is throttled to lower frequency in sub-turbo(below
|
|
|
|
|
nominal frequency) range of frequencies.
|
|
|
|
|
|
|
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|
|
- unthrottle : This file gives the total number of times the max
|
|
|
|
|
frequency is unthrottled after being throttled.
|
|
|
|
|
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|
|
- powercap : This file gives the total number of times the max
|
|
|
|
|
frequency is throttled due to 'Power Capping'.
|
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|
|
|
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|
|
- overtemp : This file gives the total number of times the max
|
|
|
|
|
frequency is throttled due to 'CPU Over Temperature'.
|
|
|
|
|
|
|
|
|
|
- supply_fault : This file gives the total number of times the
|
|
|
|
|
max frequency is throttled due to 'Power Supply Failure'.
|
|
|
|
|
|
|
|
|
|
- overcurrent : This file gives the total number of times the
|
|
|
|
|
max frequency is throttled due to 'Overcurrent'.
|
|
|
|
|
|
|
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|
|
- occ_reset : This file gives the total number of times the max
|
|
|
|
|
frequency is throttled due to 'OCC Reset'.
|
|
|
|
|
|
|
|
|
|
The sysfs attributes representing different throttle reasons like
|
|
|
|
|
powercap, overtemp, supply_fault, overcurrent and occ_reset map to
|
|
|
|
|
the reasons provided by OCC firmware for throttling the frequency.
|
|
|
|
|
|
|
|
|
|
What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats
|
|
|
|
|
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat
|
|
|
|
|
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat
|
|
|
|
|
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle
|
|
|
|
|
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap
|
|
|
|
|
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp
|
|
|
|
|
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault
|
|
|
|
|
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent
|
|
|
|
|
/sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset
|
|
|
|
|
Date: March 2016
|
|
|
|
|
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
|
|
|
|
|
Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
|
|
|
|
|
Description: POWERNV CPUFreq driver's frequency throttle stats directory and
|
|
|
|
|
attributes
|
|
|
|
|
|
|
|
|
|
'policyX/throttle_stats' directory and all the attributes are same as
|
|
|
|
|
the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and
|
|
|
|
|
attributes which give the frequency throttle information of the chip.
|
2016-07-08 23:01:13 +08:00
|
|
|
|
|
|
|
|
What: /sys/devices/system/cpu/cpuX/regs/
|
|
|
|
|
/sys/devices/system/cpu/cpuX/regs/identification/
|
|
|
|
|
/sys/devices/system/cpu/cpuX/regs/identification/midr_el1
|
|
|
|
|
/sys/devices/system/cpu/cpuX/regs/identification/revidr_el1
|
|
|
|
|
Date: June 2016
|
|
|
|
|
Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org>
|
|
|
|
|
Description: AArch64 CPU registers
|
|
|
|
|
'identification' directory exposes the CPU ID registers for
|
|
|
|
|
identifying model and revision of the CPU.
|
2017-03-27 21:18:18 +08:00
|
|
|
|
|
|
|
|
What: /sys/devices/system/cpu/cpu#/cpu_capacity
|
|
|
|
|
Date: December 2016
|
|
|
|
|
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
|
|
|
|
|
Description: information about CPUs heterogeneity.
|
|
|
|
|
|
|
|
|
|
cpu_capacity: capacity of cpu#.
|
2018-01-08 05:48:00 +08:00
|
|
|
|
|
|
|
|
What: /sys/devices/system/cpu/vulnerabilities
|
|
|
|
|
/sys/devices/system/cpu/vulnerabilities/meltdown
|
|
|
|
|
/sys/devices/system/cpu/vulnerabilities/spectre_v1
|
|
|
|
|
/sys/devices/system/cpu/vulnerabilities/spectre_v2
|
2018-04-26 10:04:20 +08:00
|
|
|
/sys/devices/system/cpu/vulnerabilities/spec_store_bypass
|
x86/bugs, kvm: Introduce boot-time control of L1TF mitigations
Introduce the 'l1tf=' kernel command line option to allow for boot-time
switching of mitigation that is used on processors affected by L1TF.
The possible values are:
full
Provides all available mitigations for the L1TF vulnerability. Disables
SMT and enables all mitigations in the hypervisors. SMT control via
/sys/devices/system/cpu/smt/control 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 control. Implies the 'nosmt=force'
command line option. sysfs control of SMT and the hypervisor flush
control is disabled.
flush
Leaves SMT enabled and enables the conditional hypervisor mitigation.
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 conditional hypervisor mitigation. SMT
control via /sys/devices/system/cpu/smt/control is still possible
after boot. If SMT is reenabled or flushing disabled at runtime
hypervisors will issue a warning.
flush,nowarn
Same as 'flush', but hypervisors will not warn when
a VM is started in a potentially insecure configuration.
off
Disables hypervisor mitigations and doesn't emit any warnings.
Default is 'flush'.
Let KVM adhere to these semantics, which means:
- 'lt1f=full,force' : Performe L1D flushes. No runtime control
possible.
- 'l1tf=full'
- 'l1tf-flush'
- 'l1tf=flush,nosmt' : Perform L1D flushes and warn on VM start if
SMT has been runtime enabled or L1D flushing
has been run-time enabled
- 'l1tf=flush,nowarn' : Perform L1D flushes and no warnings are emitted.
- 'l1tf=off' : L1D flushes are not performed and no warnings
are emitted.
KVM can always override the L1D flushing behavior using its 'vmentry_l1d_flush'
module parameter except when lt1f=full,force is set.
This makes KVM's private 'nosmt' option redundant, and as it is a bit
non-systematic anyway (this is something to control globally, not on
hypervisor level), remove that option.
Add the missing Documentation entry for the l1tf vulnerability sysfs file
while at it.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20180713142323.202758176@linutronix.de
2018-07-13 22:23:25 +08:00
|
|
|
/sys/devices/system/cpu/vulnerabilities/l1tf
|
2018-01-09 23:02:51 +08:00
|
|
|
Date: January 2018
|
2018-01-08 05:48:00 +08:00
|
|
|
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
|
|
|
|
|
Description: Information about CPU vulnerabilities
|
|
|
|
|
|
|
|
|
|
The files are named after the code names of CPU
|
|
|
|
|
vulnerabilities. The output of those files reflects the
|
|
|
|
|
state of the CPUs in the system. Possible output values:
|
|
|
|
|
|
|
|
|
|
"Not affected" CPU is not affected by the vulnerability
|
|
|
|
|
"Vulnerable" CPU is affected and no mitigation in effect
|
2018-01-09 23:02:51 +08:00
|
|
|
"Mitigation: $M" CPU is affected and mitigation $M is in effect
|
2018-05-29 23:48:27 +08:00
|
|
|
|
x86/bugs, kvm: Introduce boot-time control of L1TF mitigations
Introduce the 'l1tf=' kernel command line option to allow for boot-time
switching of mitigation that is used on processors affected by L1TF.
The possible values are:
full
Provides all available mitigations for the L1TF vulnerability. Disables
SMT and enables all mitigations in the hypervisors. SMT control via
/sys/devices/system/cpu/smt/control 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 control. Implies the 'nosmt=force'
command line option. sysfs control of SMT and the hypervisor flush
control is disabled.
flush
Leaves SMT enabled and enables the conditional hypervisor mitigation.
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 conditional hypervisor mitigation. SMT
control via /sys/devices/system/cpu/smt/control is still possible
after boot. If SMT is reenabled or flushing disabled at runtime
hypervisors will issue a warning.
flush,nowarn
Same as 'flush', but hypervisors will not warn when
a VM is started in a potentially insecure configuration.
off
Disables hypervisor mitigations and doesn't emit any warnings.
Default is 'flush'.
Let KVM adhere to these semantics, which means:
- 'lt1f=full,force' : Performe L1D flushes. No runtime control
possible.
- 'l1tf=full'
- 'l1tf-flush'
- 'l1tf=flush,nosmt' : Perform L1D flushes and warn on VM start if
SMT has been runtime enabled or L1D flushing
has been run-time enabled
- 'l1tf=flush,nowarn' : Perform L1D flushes and no warnings are emitted.
- 'l1tf=off' : L1D flushes are not performed and no warnings
are emitted.
KVM can always override the L1D flushing behavior using its 'vmentry_l1d_flush'
module parameter except when lt1f=full,force is set.
This makes KVM's private 'nosmt' option redundant, and as it is a bit
non-systematic anyway (this is something to control globally, not on
hypervisor level), remove that option.
Add the missing Documentation entry for the l1tf vulnerability sysfs file
while at it.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20180713142323.202758176@linutronix.de
2018-07-13 22:23:25 +08:00
|
|
|
Details about the l1tf file can be found in
|
|
|
|
|
Documentation/admin-guide/l1tf.rst
|
|
|
|
|
|
2018-05-29 23:48:27 +08:00
|
|
|
What: /sys/devices/system/cpu/smt
|
|
|
|
|
/sys/devices/system/cpu/smt/active
|
|
|
|
|
/sys/devices/system/cpu/smt/control
|
|
|
|
|
Date: June 2018
|
|
|
|
|
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
|
|
|
|
|
Description: Control Symetric Multi Threading (SMT)
|
|
|
|
|
|
|
|
|
|
active: Tells whether SMT is active (enabled and siblings online)
|
|
|
|
|
|
|
|
|
|
control: Read/write interface to control SMT. Possible
|
|
|
|
|
values:
|
|
|
|
|
|
|
|
|
|
"on" SMT is enabled
|
|
|
|
|
"off" SMT is disabled
|
|
|
|
|
"forceoff" SMT is force disabled. Cannot be changed.
|
|
|
|
|
"notsupported" SMT is not supported by the CPU
|
|
|
|
|
|
|
|
|
|
If control status is "forceoff" or "notsupported" writes
|
|
|
|
|
are rejected.
|