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x86/speculation/mds: Add mitigation control for MDS

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Now that the mitigations are in place, add a command line parameter to
control the mitigation, a mitigation selector function and a SMT update
mechanism.

This is the minimal straight forward initial implementation which just
provides an always on/off mode. The command line parameter is:

  mds=[full|off]

This is consistent with the existing mitigations for other speculative
hardware vulnerabilities.

The idle invocation is dynamically updated according to the SMT state of
the system similar to the dynamic update of the STIBP mitigation. The idle
mitigation is limited to CPUs which are only affected by MSBDS and not any
other variant, because the other variants cannot be mitigated on SMT
enabled systems.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Jon Masters <jcm@redhat.com>
Tested-by: Jon Masters <jcm@redhat.com>
This commit is contained in:
Thomas Gleixner
2019-02-18 22:04:08 +01:00
parent 07f07f55a2
commit bc1241700a
3 changed files with 97 additions and 0 deletions
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5
arch/x86/include/asm/processor.h
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@@ -992,4 +992,9 @@ enum l1tf_mitigations {
extern enum l1tf_mitigations l1tf_mitigation;
enum mds_mitigations {
MDS_MITIGATION_OFF,
MDS_MITIGATION_FULL,
};
#endif /* _ASM_X86_PROCESSOR_H */