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x86: deduplicate the spectre_v2_user documentation

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This would need updating to make prctl be the new default, but it's
simpler to delete it and refer to the dup.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20201105001406.13005-2-aarcange@redhat.com
This commit is contained in:
Andrea Arcangeli 2020-11-04 19:14:06 -05:00 • committed by Kees Cook
parent 2f46993d83
commit d9bbdbf324
1 changed files with 2 additions and 49 deletions
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51
Documentation/admin-guide/hw-vuln/spectre.rst
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@ -593,61 +593,14 @@ kernel command line.
Not specifying this option is equivalent to Not specifying this option is equivalent to
spectre_v2=auto. spectre_v2=auto.
For user space mitigation:
spectre_v2_user=
[X86] Control mitigation of Spectre variant 2
(indirect branch speculation) vulnerability between
user space tasks
on
Unconditionally enable mitigations. Is
enforced by spectre_v2=on
off
Unconditionally disable mitigations. Is
enforced by spectre_v2=off
prctl
Indirect branch speculation is enabled,
but mitigation can be enabled via prctl
per thread. The mitigation control state
is inherited on fork.
prctl,ibpb
Like "prctl" above, but only STIBP is
controlled per thread. IBPB is issued
always when switching between different user
space processes.
seccomp
Same as "prctl" above, but all seccomp
threads will enable the mitigation unless
they explicitly opt out.
seccomp,ibpb
Like "seccomp" above, but only STIBP is
controlled per thread. IBPB is issued
always when switching between different
user space processes.
auto
Kernel selects the mitigation depending on
the available CPU features and vulnerability.
Default mitigation:
If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
Not specifying this option is equivalent to
spectre_v2_user=auto.
In general the kernel by default selects In general the kernel by default selects
reasonable mitigations for the current CPU. To reasonable mitigations for the current CPU. To
disable Spectre variant 2 mitigations, boot with disable Spectre variant 2 mitigations, boot with
spectre_v2=off. Spectre variant 1 mitigations spectre_v2=off. Spectre variant 1 mitigations
cannot be disabled. cannot be disabled.
For spectre_v2_user see :doc:`/admin-guide/kernel-parameters`.
Mitigation selection guide Mitigation selection guide
-------------------------- --------------------------