[Qemu-devel] [PATCH 5/6] target-i386: Make x86 mfence and lfence illegal without SSE2

[Stefan Hajnoczi]

From: Martin Simmons <address@hidden>

While trying to use qemu -cpu pentium3 to test for incorrect uses of certain
SSE2 instructions, I found that QEMU allowed the mfence and lfence
instructions to be executed even though Pentium 3 doesn't support them.

According to the processor specs (and experience on a real Pentium 3), these
instructions are only available with SSE2, but QEMU is checking for SSE.  The
check for the related sfence instruction is correct (it works with SSE).

This trival patch fixes the test.

Signed-off-by: Martin Simmons <address@hidden>
Signed-off-by: Stefan Hajnoczi <address@hidden>
---
 target-i386/translate.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/target-i386/translate.c b/target-i386/translate.c
index 199302e..10bd72a 100644
--- a/target-i386/translate.c
+++ b/target-i386/translate.c
@@ -7538,7 +7538,7 @@ static target_ulong disas_insn(DisasContext *s, 
target_ulong pc_start)
             break;
         case 5: /* lfence */
         case 6: /* mfence */
-            if ((modrm & 0xc7) != 0xc0 || !(s->cpuid_features & CPUID_SSE))
+            if ((modrm & 0xc7) != 0xc0 || !(s->cpuid_features & CPUID_SSE2))
                 goto illegal_op;
             break;
         case 7: /* sfence / clflush */
-- 
1.7.4.4