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author | Jiri Kosina <jkosina@suse.cz> | 2018-07-13 16:23:25 +0200 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2018-07-13 16:29:56 +0200 |
commit | d90a7a0ec83fb86622cd7dae23255d3c50a99ec8 (patch) | |
tree | 45fe6653256fa6726df0f4070d5ccf99b6bd4ce2 /Documentation/ABI/testing/sysfs-devices-system-cpu | |
parent | fee0aede6f4739c87179eca76136f83210953b86 (diff) | |
download | linux-stable-d90a7a0ec83fb86622cd7dae23255d3c50a99ec8.tar.gz linux-stable-d90a7a0ec83fb86622cd7dae23255d3c50a99ec8.tar.bz2 linux-stable-d90a7a0ec83fb86622cd7dae23255d3c50a99ec8.zip |
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
Diffstat (limited to 'Documentation/ABI/testing/sysfs-devices-system-cpu')
-rw-r--r-- | Documentation/ABI/testing/sysfs-devices-system-cpu | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index 65d9b844ecfd..73318225a368 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -476,6 +476,7 @@ What: /sys/devices/system/cpu/vulnerabilities /sys/devices/system/cpu/vulnerabilities/spectre_v1 /sys/devices/system/cpu/vulnerabilities/spectre_v2 /sys/devices/system/cpu/vulnerabilities/spec_store_bypass + /sys/devices/system/cpu/vulnerabilities/l1tf Date: January 2018 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> Description: Information about CPU vulnerabilities @@ -488,6 +489,9 @@ Description: Information about CPU vulnerabilities "Vulnerable" CPU is affected and no mitigation in effect "Mitigation: $M" CPU is affected and mitigation $M is in effect + Details about the l1tf file can be found in + Documentation/admin-guide/l1tf.rst + What: /sys/devices/system/cpu/smt /sys/devices/system/cpu/smt/active /sys/devices/system/cpu/smt/control |