[PATCH kvm-unit-tests 2/5] x86: test xadd with two identical operands

[Nadav Amit]

Previously, KVM emulated xadd incorrectly when the source and destination
operands were identical.  The expected result is that the register would hold
the sum (2x) and not the previous value (x).  This test checks this behavior.
It should be executed with a disabled unrestricted mode.

Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
---
 x86/realmode.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/x86/realmode.c b/x86/realmode.c
index dc4a1d3..10c3e03 100644
--- a/x86/realmode.c
+++ b/x86/realmode.c
@@ -1663,6 +1663,14 @@ void test_smsw(void)
 	report("smsw", R_AX | R_BX | R_CX, outregs.eax == outregs.ebx);
 }
 
+void test_xadd(void)
+{
+	MK_INSN(xadd, "xaddl %eax, %eax\n\t");
+	inregs.eax = 0x12345678;
+	exec_in_big_real_mode(&insn_xadd);
+	report("xadd", R_AX, outregs.eax == inregs.eax * 2);
+}
+
 
 void realmode_start(void)
 {
@@ -1712,6 +1720,7 @@ void realmode_start(void)
 	test_dr_mod();
 	test_smsw();
 	test_nopl();
+	test_xadd();
 	test_perf_loop();
 	test_perf_mov();
 	test_perf_arith();
-- 
1.9.1

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