x86/bugs: Rework spec_ctrl base and mask logic

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x86_spec_ctrL_mask is intended to mask out bits from a MSR_SPEC_CTRL value
which are not to be modified. However the implementation is not really used
and the bitmask was inverted to make a check easier, which was removed in
"x86/bugs: Remove x86_spec_ctrl_set()"

Aside of that it is missing the STIBP bit if it is supported by the
platform, so if the mask would be used in x86_virt_spec_ctrl() then it
would prevent a guest from setting STIBP.

Add the STIBP bit if supported and use the mask in x86_virt_spec_ctrl() to
sanitize the value which is supplied by the guest.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>

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This commit is contained in:

Thomas Gleixner 2018-05-12 20:10:00 +02:00

parent 4b59bdb569

commit be6fcb5478

1 changed files with 19 additions and 7 deletions

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arch/x86/kernel/cpu/bugs.c

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