KVM: MMU: Only indicate a fetch fault in page fault error code if nx is enabled

Bit 4 of the page fault error code is set only if EFER.NX is set.
Reviewed-by: NXiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: NAvi Kivity <avi@redhat.com>

arch/x86/kvm/paging_tmpl.h

@@ -245,7 +245,7 @@ static int FNAME(walk_addr)(struct guest_walker *walker,
 		walker->error_code |= PFERR_WRITE_MASK;
 	if (user_fault)
 		walker->error_code |= PFERR_USER_MASK;
-	if (fetch_fault)
+	if (fetch_fault && is_nx(vcpu))
 		walker->error_code |= PFERR_FETCH_MASK;
 	if (rsvd_fault)
 		walker->error_code |= PFERR_RSVD_MASK;