Re: [PATCH 0/7] KVM: x86: expose CVE-2017-5715 ("Spectre variant 2") mitigations to guest

[Thomas Gleixner]

On Mon, 8 Jan 2018, Paolo Bonzini wrote:

> This series allows guests to use the MSR_IA32_SPEC_CTRL and
> MSR_IA32_PRED_CMD model specific registers that were added as mitigations
> for CVE-2017-5715.
> 
> These are only the KVM specific parts of the fix.  It does *not* yet
> include any protection for reading host memory from the guest, because
> that would be done in the same way as the rest of Linux.  So there is no
> IBRS *usage* here, no retpolines, no stuffing of the return stack buffer.
> (KVM already includes a fix to clear all registers on vmexit, which is
> enough to block Google Project Zero's PoC exploit).
> 
> However, I am including the changes to use IBPB (indirect branch
> predictor barrier) if available.  That occurs only when there is a VCPU
> switch on a physical CPU, thus it has a small impact on performance.
> 
> The patches are a bit hackish because the relevant cpufeatures have
> not been included yet, and because I wanted to make the patches easier
> to backport to distro kernels if desired, but I would still like to
> have them in 4.16.
> 
> Please review.

CC'ing x86@xxxxxxxxxx on this would have been asked too much, right?