KVM: MMU: skip invalid sp when unprotect page

In kvm_mmu_unprotect_page(), the invalid sp can be skipped

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index d3cd102..3ac5115 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -1629,7 +1629,7 @@
 	bucket = &kvm->arch.mmu_page_hash[index];
 restart:
 	hlist_for_each_entry_safe(sp, node, n, bucket, hash_link)
-		if (sp->gfn == gfn && !sp->role.direct) {
+		if (sp->gfn == gfn && !sp->role.direct && !sp->role.invalid) {
 			pgprintk("%s: gfn %lx role %x\n", __func__, gfn,
 				 sp->role.word);
 			r = 1;