KVM: x86/mmu: Fix TDP MMU zap collapsible SPTEs

There is a bug in the TDP MMU function to zap SPTEs which could be
replaced with a larger mapping which prevents the function from doing
anything. Fix this by correctly zapping the last level SPTEs.

Cc: stable@vger.kernel.org
Fixes: 14881998566d ("kvm: x86/mmu: Support disabling dirty logging for the tdp MMU")
Signed-off-by: Ben Gardon <bgardon@google.com>
Message-Id: <20210202185734.1680553-11-bgardon@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 2ef8615f9dba87bca72d4912df6e4cd9394def56..b56d604809b8afdf2d7080e4cf471ed649e675d7 100644 (file)
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1049,8 +1049,8 @@ bool kvm_tdp_mmu_slot_set_dirty(struct kvm *kvm, struct kvm_memory_slot *slot)
 }
 
 /*
- * Clear non-leaf entries (and free associated page tables) which could
- * be replaced by large mappings, for GFNs within the slot.
+ * Clear leaf entries which could be replaced by large mappings, for
+ * GFNs within the slot.
  */
 static void zap_collapsible_spte_range(struct kvm *kvm,
                                       struct kvm_mmu_page *root,
@@ -1062,7 +1062,7 @@ static void zap_collapsible_spte_range(struct kvm *kvm,
 
        tdp_root_for_each_pte(iter, root, start, end) {
                if (!is_shadow_present_pte(iter.old_spte) ||
-                   is_last_spte(iter.old_spte, iter.level))
+                   !is_last_spte(iter.old_spte, iter.level))
                        continue;
 
                pfn = spte_to_pfn(iter.old_spte);