KVM: emulate: move around some checks

The only purpose of this patch is to make the next patch simpler
to review.  No semantic change.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/emulate.c

@@ -4388,12 +4388,15 @@ done_prefixes:
 		ctxt->d |= opcode.flags;
 	}
 
+	/* Unrecognised? */
+	if (ctxt->d == 0)
+		return EMULATION_FAILED;
+
 	ctxt->execute = opcode.u.execute;
 	ctxt->check_perm = opcode.check_perm;
 	ctxt->intercept = opcode.intercept;
 
-	/* Unrecognised? */
-	if (ctxt->d == 0 || (ctxt->d & NotImpl))
+	if (ctxt->d & NotImpl)
 		return EMULATION_FAILED;
 
 	if (!(ctxt->d & EmulateOnUD) && ctxt->ud)
@@ -4535,19 +4538,19 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
 
 	ctxt->mem_read.pos = 0;
 
-	if ((ctxt->mode == X86EMUL_MODE_PROT64 && (ctxt->d & No64)) ||
-			(ctxt->d & Undefined)) {
+	/* LOCK prefix is allowed only with some instructions */
+	if (ctxt->lock_prefix && (!(ctxt->d & Lock) || ctxt->dst.type != OP_MEM)) {
 		rc = emulate_ud(ctxt);
 		goto done;
 	}
 
-	/* LOCK prefix is allowed only with some instructions */
-	if (ctxt->lock_prefix && (!(ctxt->d & Lock) || ctxt->dst.type != OP_MEM)) {
+	if ((ctxt->d & SrcMask) == SrcMemFAddr && ctxt->src.type != OP_MEM) {
 		rc = emulate_ud(ctxt);
 		goto done;
 	}
 
-	if ((ctxt->d & SrcMask) == SrcMemFAddr && ctxt->src.type != OP_MEM) {
+	if ((ctxt->mode == X86EMUL_MODE_PROT64 && (ctxt->d & No64)) ||
+			(ctxt->d & Undefined)) {
 		rc = emulate_ud(ctxt);
 		goto done;
 	}