Re: [PATCH v2 2/3] KVM: x86/mmu: Avoid collision with !PRESENT SPTEs in TDP MMU lpage stats

From: Mingwei Zhang
Date: Thu Jul 29 2021 - 15:01:15 EST

oh, definitely. Sorry for the confusion.

On Thu, Jul 29, 2021 at 11:34 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> On Mon, Jul 26, 2021, Mingwei Zhang wrote:
> > Factor in whether or not the old/new SPTEs are shadow-present when
> > adjusting the large page stats in the TDP MMU. A modified MMIO SPTE can
> > toggle the page size bit, as bit 7 is used to store the MMIO generation,
> > i.e. is_large_pte() can get a false positive when called on a MMIO SPTE.
> > Ditto for nuking SPTEs with REMOVED_SPTE, which sets bit 7 in its magic
> > value.
> >
> > Opportunistically move the logic below the check to verify at least one
> > of the old/new SPTEs is shadow present.
> >
> > Use is/was_leaf even though is/was_present would suffice. The code
> > generation is roughly equivalent since all flags need to be computed
> > prior to the code in question, and using the *_leaf flags will minimize
> > the diff in a future enhancement to account all pages, i.e. will change
> > the check to "is_leaf != was_leaf".
> >
> > Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> There's no hard rule for when to use Suggested-by vs. giving Author credit, but
> in this case, since you took the patch and changelog verbatim[*] (sans the missing
> tags below), it's more polite to take the full patch (with me as Author in
> this case) and add your SOB since you're posting the patch.
> Fixes: 1699f65c8b65 ("kvm/x86: Fix 'lpages' kvm stat for TDM MMU")
> Cc: stable@xxxxxxxxxxxxxxx
> [*]
> > Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>