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    SubjectRe: [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by VM instructions
    On Tue, Jan 12, 2021 at 9:59 AM Sean Christopherson <seanjc@google.com> wrote:
    >
    > On Tue, Jan 12, 2021, Sean Christopherson wrote:
    > > On Tue, Jan 12, 2021, Wei Huang wrote:
    > > > From: Bandan Das <bsd@redhat.com>
    > > >
    > > > While running VM related instructions (VMRUN/VMSAVE/VMLOAD), some AMD
    > > > CPUs check EAX against reserved memory regions (e.g. SMM memory on host)
    > > > before checking VMCB's instruction intercept.
    > >
    > > It would be very helpful to list exactly which CPUs are/aren't affected, even if
    > > that just means stating something like "all CPUs before XYZ". Given patch 2/2,
    > > I assume it's all CPUs without the new CPUID flag?
    >
    > Ah, despite calling this an 'errata', the bad behavior is explicitly documented
    > in the APM, i.e. it's an architecture bug, not a silicon bug.
    >
    > Can you reword the changelog to make it clear that the premature #GP is the
    > correct architectural behavior for CPUs without the new CPUID flag?

    Andrew Cooper points out that there may be a nicer workaround. Make
    sure that the SMRAM and HT region (FFFD00000000 - FFFFFFFFFFFF) are
    marked as reserved in the guest, too.

    --Andy

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