1 files changed, 23 insertions, 23 deletions

diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 7d03e9b7ccfa..913d52a7923e 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -707,8 +707,27 @@ static int FNAME(fetch)(struct kvm_vcpu *vcpu, gpa_t addr,
 		if (!is_shadow_present_pte(*it.sptep)) {
 			table_gfn = gw->table_gfn[it.level - 2];
 			access = gw->pt_access[it.level - 2];
-			sp = kvm_mmu_get_page(vcpu, table_gfn, addr, it.level-1,
-					      false, access);
+			sp = kvm_mmu_get_page(vcpu, table_gfn, addr,
+					      it.level-1, false, access);
+			/*
+			 * We must synchronize the pagetable before linking it
+			 * because the guest doesn't need to flush tlb when
+			 * the gpte is changed from non-present to present.
+			 * Otherwise, the guest may use the wrong mapping.
+			 *
+			 * For PG_LEVEL_4K, kvm_mmu_get_page() has already
+			 * synchronized it transiently via kvm_sync_page().
+			 *
+			 * For higher level pagetable, we synchronize it via
+			 * the slower mmu_sync_children().  If it needs to
+			 * break, some progress has been made; return
+			 * RET_PF_RETRY and retry on the next #PF.
+			 * KVM_REQ_MMU_SYNC is not necessary but it
+			 * expedites the process.
+			 */
+			if (sp->unsync_children &&
+			    mmu_sync_children(vcpu, sp, false))
+				return RET_PF_RETRY;
 		}
 
 		/*
@@ -1047,14 +1066,6 @@ static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gpa_t vaddr,
  * Using the cached information from sp->gfns is safe because:
  * - The spte has a reference to the struct page, so the pfn for a given gfn
  *   can't change unless all sptes pointing to it are nuked first.
- *
- * Note:
- *   We should flush all tlbs if spte is dropped even though guest is
- *   responsible for it. Since if we don't, kvm_mmu_notifier_invalidate_page
- *   and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't
- *   used by guest then tlbs are not flushed, so guest is allowed to access the
- *   freed pages.
- *   And we increase kvm->tlbs_dirty to delay tlbs flush in this case.
  */
 static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 {
@@ -1107,13 +1118,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 			return 0;
 
 		if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) {
-			/*
-			 * Update spte before increasing tlbs_dirty to make
-			 * sure no tlb flush is lost after spte is zapped; see
-			 * the comments in kvm_flush_remote_tlbs().
-			 */
-			smp_wmb();
-			vcpu->kvm->tlbs_dirty++;
+			set_spte_ret |= SET_SPTE_NEED_REMOTE_TLB_FLUSH;
 			continue;
 		}
 
@@ -1128,12 +1133,7 @@ static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
 
 		if (gfn != sp->gfns[i]) {
 			drop_spte(vcpu->kvm, &sp->spt[i]);
-			/*
-			 * The same as above where we are doing
-			 * prefetch_invalid_gpte().
-			 */
-			smp_wmb();
-			vcpu->kvm->tlbs_dirty++;
+			set_spte_ret |= SET_SPTE_NEED_REMOTE_TLB_FLUSH;
 			continue;
 		}