From: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Date: Tue, 12 Apr 2011 15:24:55 +0000 (+0900)
Subject: KVM: x86 emulator: Disable writeback for CMP emulation
X-Git-Tag: MMI-PSA29.97-13-9~19664^2~71
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=575e7c1417d41dd72ddf2a49965f833ce9352e92;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git

KVM: x86 emulator: Disable writeback for CMP emulation

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@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>
---

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 2ec69bc85846..1e0e3f8156f8 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;