KVM: x86 emulator: add LOOP/LOOPcc instruction emulation

index ac13831..46b7da8 100644
@@ -2320,7 +2320,7 @@ static struct opcode opcode_table[256] = {
 	/* 0xD8 - 0xDF */
 	N, N, N, N, N, N, N, N,
 	/* 0xE0 - 0xE7 */
-	N, N, N, N,
+	X3(D(SrcImmByte)), N,
 	D(ByteOp | SrcImmUByte | DstAcc), D(SrcImmUByte | DstAcc),
 	D(ByteOp | SrcAcc | DstImmUByte), D(SrcAcc | DstImmUByte),
 	/* 0xE8 - 0xEF */

@@ -3086,6 +3086,12 @@ special_insn:
 		c->src.val = c->regs[VCPU_REGS_RCX];
 		emulate_grp2(ctxt);
 		break;
+	case 0xe0 ... 0xe2:	/* loop/loopz/loopnz */
+		register_address_increment(c, &c->regs[VCPU_REGS_RCX], -1);
+		if (address_mask(c, c->regs[VCPU_REGS_RCX]) != 0 &&
+		    (c->b == 0xe2 || test_cc(c->b ^ 0x5, ctxt->eflags)))
+			jmp_rel(c, c->src.val);
+		break;
 	case 0xe4: 	/* inb */
 	case 0xe5: 	/* in */
 		goto do_io_in;

index 35f6a16..bedd175 100644
@@ -1194,6 +1194,48 @@ void test_idiv()
 		print_serial("idiv Test 3: PASS\n");
 }
 
+void test_loopcc(void)
+{
+	struct regs inregs = { 0 }, outregs;
+
+	MK_INSN(loop, "mov $10, %ecx\n\t"
+		      "1: inc %eax\n\t"
+		      "loop 1b\n\t");
+
+	MK_INSN(loope, "mov $10, %ecx\n\t"
+		       "mov $1, %eax\n\t"
+		       "1: dec %eax\n\t"
+		       "loope 1b\n\t");
+
+	MK_INSN(loopne, "mov $10, %ecx\n\t"
+		        "mov $5, %eax\n\t"
+		        "1: dec %eax\n\t"
+			"loopne 1b\n\t");
+
+	exec_in_big_real_mode(&inregs, &outregs,
+			insn_loop, insn_loop_end - insn_loop);
+	if(!regs_equal(&inregs, &outregs, R_AX) || outregs.eax != 10)
+		print_serial("LOOPcc short Test 1: FAIL\n");
+	else
+		print_serial("LOOPcc short Test 1: PASS\n");
+
+	exec_in_big_real_mode(&inregs, &outregs,
+			insn_loope, insn_loope_end - insn_loope);
+	if(!regs_equal(&inregs, &outregs, R_AX | R_CX) ||
+	   outregs.eax != -1 || outregs.ecx != 8)
+		print_serial("LOOPcc short Test 2: FAIL\n");
+	else
+		print_serial("LOOPcc short Test 2: PASS\n");
+
+	exec_in_big_real_mode(&inregs, &outregs,
+			insn_loopne, insn_loopne_end - insn_loopne);
+	if(!regs_equal(&inregs, &outregs, R_AX | R_CX) ||
+	   outregs.eax != 0 || outregs.ecx != 5)
+		print_serial("LOOPcc short Test 3: FAIL\n");
+	else
+		print_serial("LOOPcc short Test 3: PASS\n");
+}
+
 void realmode_start(void)
 {
 	test_null();

@@ -1221,6 +1263,7 @@ void realmode_start(void)
 	test_mul();
 	test_div();
 	test_idiv();
+	test_loopcc();
 
 	exit(0);
 }