[v4,5/6] KVM: MMU: combine guest pte read between walk and pte prefetch

Commit Message

Xiao Guangrong July 3, 2010, 10:31 a.m. UTC

None

Patch

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 3350c02..e617e93 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -291,6 +291,20 @@  static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
 		     gpte_to_gfn(gpte), pfn, true, true);
 }
 
+static bool FNAME(check_level_mapping)(struct kvm_vcpu *vcpu,
+				       struct guest_walker *gw, int level)
+{
+	pt_element_t curr_pte;
+	int r;
+
+	r = kvm_read_guest_atomic(vcpu->kvm, gw->pte_gpa[level - 1],
+				     &curr_pte, sizeof(curr_pte));
+	if (r || curr_pte != gw->ptes[level - 1])
+		return false;
+
+	return true;
+}
+
 /*
  * Fetch a shadow pte for a specific level in the paging hierarchy.
  */
@@ -304,11 +318,9 @@  static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 	u64 spte, *sptep = NULL;
 	int direct;
 	gfn_t table_gfn;
-	int r;
 	int level;
-	bool dirty = is_dirty_gpte(gw->ptes[gw->level - 1]);
+	bool dirty = is_dirty_gpte(gw->ptes[gw->level - 1]), check = true;
 	unsigned direct_access;
-	pt_element_t curr_pte;
 	struct kvm_shadow_walk_iterator iterator;
 
 	if (!is_present_gpte(gw->ptes[gw->level - 1]))
@@ -322,6 +334,12 @@  static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 		level = iterator.level;
 		sptep = iterator.sptep;
 		if (iterator.level == hlevel) {
+			if (check && level == gw->level &&
+			      !FNAME(check_level_mapping)(vcpu, gw, hlevel)) {
+				kvm_release_pfn_clean(pfn);
+				break;
+			}
+
 			mmu_set_spte(vcpu, sptep, access,
 				     gw->pte_access & access,
 				     user_fault, write_fault,
@@ -376,10 +394,10 @@  static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 		sp = kvm_mmu_get_page(vcpu, table_gfn, addr, level-1,
 					       direct, access, sptep);
 		if (!direct) {
-			r = kvm_read_guest_atomic(vcpu->kvm,
-						  gw->pte_gpa[level - 2],
-						  &curr_pte, sizeof(curr_pte));
-			if (r || curr_pte != gw->ptes[level - 2]) {
+			if (hlevel == level - 1)
+				check = false;
+
+			if (!FNAME(check_level_mapping)(vcpu, gw, level - 1)) {
 				kvm_mmu_put_page(sp, sptep);
 				kvm_release_pfn_clean(pfn);
 				sptep = NULL;