When updating accessed and dirty bits, check that the new SPTE is present
before attempting to query its A/D bits. Failure to confirm the SPTE is
present can theoretically cause a false negative, e.g. if a MMIO SPTE
replaces a "real" SPTE and somehow the PFNs magically match.
Realistically, this is all but guaranteed to be a benign bug. Fix it up
primarily so that a future patch can tweak the MMU_WARN_ON checking A/D
status to fire if the SPTE is not-present.
Fixes:
f8e144971c68 ("kvm: x86/mmu: Add access tracking for tdp_mmu")
Cc: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <
20210225204749.1512652-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
static void handle_changed_spte_acc_track(u64 old_spte, u64 new_spte, int level)
{
- bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte);
-
if (!is_shadow_present_pte(old_spte) || !is_last_spte(old_spte, level))
return;
if (is_accessed_spte(old_spte) &&
- (!is_accessed_spte(new_spte) || pfn_changed))
+ (!is_shadow_present_pte(new_spte) || !is_accessed_spte(new_spte) ||
+ spte_to_pfn(old_spte) != spte_to_pfn(new_spte)))
kvm_set_pfn_accessed(spte_to_pfn(old_spte));
}
if (was_leaf && is_dirty_spte(old_spte) &&
- (!is_dirty_spte(new_spte) || pfn_changed))
+ (!is_present || !is_dirty_spte(new_spte) || pfn_changed))
kvm_set_pfn_dirty(spte_to_pfn(old_spte));
/*