Re: [PATCH v3 7/9] KVM: VMX: Add guest physical address check in EPT violation and misconfig

Jim Mattson
2021-01-15T19:37:19Z

On Fri, Oct 23, 2020 at 10:43 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 23/10/20 19:23, Jim Mattson wrote:
> >> The information that we need is _not_ that provided by the advanced
> >> VM-exit information (or by a page walk). If a page is neither writable
> >> nor executable, the advanced information doesn't say if the injected #PF
> >> should be a W=1 or a F=1 fault. We need the information in bits 0..2 of
> >> the exit qualification for the final access, which however is not
> >> available for the paging-structure access.
> >>
> > Are you planning to extend the emulator, then, to support all
> > instructions? I'm not sure where you are going with this.
>
> I'm going to fix the bit 8=1 case, but for bit 8=0 there's not much that
> you can do. In all likelihood the guest is buggy anyway.

Did this drop off your radar? Are you still planning to fix the bit8=1
case to use advanced EPT exit qualification information? Or did I just
miss it?

> It would be possible to only do the decode part of the emulator to get
> the PFEC (matching the GVA from the vmexit to the memory operand, for
> example, and retrying if the instruction is unexpected). Then one would
> only need enough VEX/EVEX parsing to process the decoding.
>
> Paolo
>