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KVM: x86/mmu: Check for present SPTE when clearing dirty bit in TDP MMU 

Explicitly check for present 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: a6a0b05da9 ("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>
Message-Id: <20220226001546.360188-3-seanjc@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2022-02-26 00:15:20 +00:00 committed by Paolo Bonzini
parent 37b2a6510a
commit 3354ef5a59
1 changed files with 3 additions and 0 deletions
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3
arch/x86/kvm/mmu/tdp_mmu.c
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@ -1468,6 +1468,9 @@ retry:
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;