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Commit a01994f5 authored by Peter Zijlstra's avatar Peter Zijlstra
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x86/perf: Default set FREEZE_ON_SMI for all

Kyle reported that rr[0] has started to malfunction on Comet Lake and
later CPUs due to EFI starting to make use of CPL3 [1] and the PMU
event filtering not distinguishing between regular CPL3 and SMM CPL3.

Since this is a privilege violation, default disable SMM visibility
where possible.

Administrators wanting to observe SMM cycles can easily change this
using the sysfs attribute while regular users don't have access to
this file.

[0] https://rr-project.org/

[1] See the Intel white paper "Trustworthy SMM on the Intel vPro Platform"
at https://bugzilla.kernel.org/attachment.cgi?id=300300

, particularly the
end of page 5.

Reported-by: default avatarKyle Huey <me@kylehuey.com>
Suggested-by: default avatarAndrew Cooper <Andrew.Cooper3@citrix.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@kernel.org
Link: https://lkml.kernel.org/r/YfKChjX61OW4CkYm@hirez.programming.kicks-ass.net
parent 26291c54
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