KVM: MMU: fix walking shadow page table

Properly check the last mapping, and do not walk to the next level if last spte
is met

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/mmu.c

@@ -1517,10 +1517,6 @@ static bool shadow_walk_okay(struct kvm_shadow_walk_iterator *iterator)
 	if (iterator->level < PT_PAGE_TABLE_LEVEL)
 		return false;
 
-	if (iterator->level == PT_PAGE_TABLE_LEVEL)
-		if (is_large_pte(*iterator->sptep))
-			return false;
-
 	iterator->index = SHADOW_PT_INDEX(iterator->addr, iterator->level);
 	iterator->sptep	= ((u64 *)__va(iterator->shadow_addr)) + iterator->index;
 	return true;
@@ -1528,6 +1524,11 @@ static bool shadow_walk_okay(struct kvm_shadow_walk_iterator *iterator)
 
 static void shadow_walk_next(struct kvm_shadow_walk_iterator *iterator)
 {
+	if (is_last_spte(*iterator->sptep, iterator->level)) {
+		iterator->level = 0;
+		return;
+	}
+
 	iterator->shadow_addr = *iterator->sptep & PT64_BASE_ADDR_MASK;
 	--iterator->level;
 }