| Message ID | 20211120045046.3940942-6-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86/mmu: Overhaul TDP MMU zapping and flushing | expand |
On Fri, Nov 19, 2021 at 8:51 PM Sean Christopherson <seanjc@google.com> wrote: > > Explicitly check for preset SPTEs when clearing dirty bits in the TDP > MMU. This isn't strictly required for correctness, as setting the dirty > bit in a defunct SPTE will not change the SPTE from !PRESENT to PRESENT. > However, the guarded MMU_WARN_ON() in spte_ad_need_write_protect() would > complain if anyone actually turned on KVM's MMU debugging. > > Fixes: a6a0b05da9f3 ("kvm: x86/mmu: Support dirty logging for the TDP MMU") > Cc: Ben Gardon <bgardon@google.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> Reviewed-by: Ben Gardon <bgardon@google.com> > --- > arch/x86/kvm/mmu/tdp_mmu.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > index 1db8496259ad..c575df121b19 100644 > --- a/arch/x86/kvm/mmu/tdp_mmu.c > +++ b/arch/x86/kvm/mmu/tdp_mmu.c > @@ -1246,6 +1246,9 @@ static bool clear_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, > if (tdp_mmu_iter_cond_resched(kvm, &iter, false, true)) > continue; > > + if (!is_shadow_present_pte(iter.old_spte)) > + continue; > + > if (spte_ad_need_write_protect(iter.old_spte)) { > if (is_writable_pte(iter.old_spte)) > new_spte = iter.old_spte & ~PT_WRITABLE_MASK; > -- > 2.34.0.rc2.393.gf8c9666880-goog >
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 1db8496259ad..c575df121b19 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1246,6 +1246,9 @@ static bool clear_dirty_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root, if (tdp_mmu_iter_cond_resched(kvm, &iter, false, true)) continue; + if (!is_shadow_present_pte(iter.old_spte)) + continue; + if (spte_ad_need_write_protect(iter.old_spte)) { if (is_writable_pte(iter.old_spte)) new_spte = iter.old_spte & ~PT_WRITABLE_MASK;
Explicitly check for preset SPTEs when clearing dirty bits in the TDP MMU. This isn't strictly required for correctness, as setting the dirty bit in a defunct SPTE will not change the SPTE from !PRESENT to PRESENT. However, the guarded MMU_WARN_ON() in spte_ad_need_write_protect() would complain if anyone actually turned on KVM's MMU debugging. Fixes: a6a0b05da9f3 ("kvm: x86/mmu: Support dirty logging for the TDP MMU") Cc: Ben Gardon <bgardon@google.com> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/mmu/tdp_mmu.c | 3 +++ 1 file changed, 3 insertions(+)