Re: [PATCH 1/4] KVM: X86: Fix tlb flush for tdp in kvm_invalidate_pcid()

[Jim Mattson]

On Thu, Oct 21, 2021 at 10:13 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 21/10/21 16:52, Sean Christopherson wrote:
> >> I think the EPT violation happens*after*  the cr3 write.  So the instruction to be
> >> emulated is not "cr3 write".  The emulation will queue fault into guest though,
> >> recursive EPT violation happens since the cr3 exceeds maxphyaddr limit.
> > Doh, you're correct.  I think my mind wandered into thinking about what would
> > happen with PDPTRs and forgot to get back to normal MOV CR3.
> >
> > So yeah, the only way to correctly handle this would be to intercept CR3 loads.
> > I'm guessing that would have a noticeable impact on guest performance.
>
> Ouch... yeah, allow_smaller_maxphyaddr already has bad performance, but
> intercepting CR3 loads would be another kind of slow.

Can we kill it? It's only half-baked as it is. Or are we committed to it now?