Re: [PATCH 05/15] KVM: VMX: Disable preemption when probing user return MSRs

[Jim Mattson]

On Tue, May 4, 2021 at 10:17 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> Disable preemption when probing a user return MSR via RDSMR/WRMSR.  If
> the MSR holds a different value per logical CPU, the WRMSR could corrupt
> the host's value if KVM is preempted between the RDMSR and WRMSR, and
> then rescheduled on a different CPU.
>
> Opportunistically land the helper in common x86, SVM will use the helper
> in a future commit.
>
> Fixes: 4be534102624 ("KVM: VMX: Initialize vmx->guest_msrs[] right after allocation")
> Cc: stable@xxxxxxxxxxxxxxx
> Cc: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-by: Jim Mattson <jmattson@xxxxxxxxxx>