From: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
This stops "CMP r/m, reg" to write back the data into memory.
Pointed out by Avi.
The writeback suppression now covers CMP, CMPS, SCAS.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>
---
Changelog v1->v2: moved the line just after the cmp label.
arch/x86/kvm/emulate.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 3e8b4ab..db48e91 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3671,6 +3671,7 @@ special_insn:
break;
case 0x38 ... 0x3d:
cmp: /* cmp */
+ c->dst.type = OP_NONE; /* Disable writeback. */
emulate_2op_SrcV("cmp", c->src, c->dst, ctxt->eflags);
break;
case 0x40 ... 0x47: /* inc r16/r32 */
@@ -3797,7 +3798,6 @@ special_insn:
rc = emulate_popf(ctxt, ops, &c->dst.val, c->op_bytes);
break;
case 0xa6 ... 0xa7: /* cmps */
- c->dst.type = OP_NONE; /* Disable writeback. */
goto cmp;
case 0xa8 ... 0xa9: /* test ax, imm */
goto test;
--
1.7.1
--
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