Re: [PATCH 03/15] KVM: SVM: Inject #UD on RDTSCP when it should be disabled in the guest

[Jim Mattson]

On Tue, May 4, 2021 at 2:57 PM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 04/05/21 23:53, Sean Christopherson wrote:
> >> Does the right thing happen here if the vCPU is in guest mode when
> >> userspace decides to toggle the CPUID.80000001H:EDX.RDTSCP bit on or
> >> off?
> > I hate our terminology.  By "guest mode", do you mean running the vCPU, or do
> > you specifically mean running in L2?
> >
>
> Guest mode should mean L2.
>
> (I wonder if we should have a capability that says "KVM_SET_CPUID2 can
> only be called prior to KVM_RUN").

It would certainly make it easier to reason about potential security issues.