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SubjectRe: [PATCH 0/3] KVM: x86: Revert dirty tracking for GPRs
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On 23/01/21 00:50, Sean Christopherson wrote:
> This is effectively belated feedback on the SEV-ES series. My primary
> interest is to revert the GPR dirty/available tracking, as it's pure
> overhead for non-SEV-ES VMs, and even for SEV-ES I suspect the dirty
> tracking is at best lost in the noise, and possibly even a net negative.
>
> My original plan was to submit patches 1+3 as patch 1, taking a few
> creative liberties with the GHCB spec to justify writing the GHCB GPRs
> after every VMGEXIT. But, since KVM is effectively writing the GHCB GPRs
> on every VMRUN, I feel confident in saying that my interpretation of the
> spec has already been proven correct.
>
> The SEV-ES changes are effectively compile tested only, but unless I've
> overlooked a code path, patch 1 is a nop. Patch 3 definitely needs
> testing.
>
> Paolo, I'd really like to get patches 1 and 2 into 5.11, the code cost of
> the dirty/available tracking is not trivial.
>
> Sean Christopherson (3):
> KVM: SVM: Unconditionally sync GPRs to GHCB on VMRUN of SEV-ES guest
> KVM: x86: Revert "KVM: x86: Mark GPRs dirty when written"
> KVM: SVM: Sync GPRs to the GHCB only after VMGEXIT
>
> arch/x86/kvm/kvm_cache_regs.h | 51 +++++++++++++++++------------------
> arch/x86/kvm/svm/sev.c | 14 +++++-----
> arch/x86/kvm/svm/svm.h | 1 +
> 3 files changed, 34 insertions(+), 32 deletions(-)
>

Queued 1-2, thanks! Yes, these should be in 5.11.

Paolo

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