Re: [PATCH v3 00/17] KVM: x86/pmu: Add support to enable Guest PEBS via DS

[Sean Christopherson]

On Fri, Jan 15, 2021, Andi Kleen wrote:
> > I'm asking about ucode/hardare.  Is the "guest pebs buffer write -> PEBS PMI"
> > guaranteed to be atomic?
> 
> Of course not.

So there's still a window where the guest could observe the bad counter index,
correct?