linux-kernel - [PATCH 01/25] KVM: x86 emulator: Add std and cld instructions (opcodes 0xfc-0xfd)

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Message-Id: <1222616701-1206-2-git-send-email-avi@redhat.com>
Date:	Sun, 28 Sep 2008 18:44:37 +0300
From:	Avi Kivity <avi@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, Mohammed Gamal <m.gamal005@...il.com>
Subject: [PATCH 01/25] KVM: x86 emulator: Add std and cld instructions (opcodes 0xfc-0xfd)

From: Mohammed Gamal <m.gamal005@...il.com>

This adds the std and cld instructions to the emulator.

Encountered while running the BIOS with invalid guest
state emulation enabled.

Signed-off-by: Mohammed Gamal <m.gamal005@...il.com>
Signed-off-by: Avi Kivity <avi@...ranet.com>
---
 arch/x86/kvm/x86_emulate.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index 66e0bd6..944f1f4 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -187,7 +187,7 @@ static u16 opcode_table[256] = {
 	ImplicitOps, ImplicitOps, Group | Group3_Byte, Group | Group3,
 	/* 0xF8 - 0xFF */
 	ImplicitOps, 0, ImplicitOps, ImplicitOps,
-	0, 0, Group | Group4, Group | Group5,
+	ImplicitOps, ImplicitOps, Group | Group4, Group | Group5,
 };
 
 static u16 twobyte_table[256] = {
@@ -1762,6 +1762,14 @@ special_insn:
 		ctxt->eflags |= X86_EFLAGS_IF;
 		c->dst.type = OP_NONE;	/* Disable writeback. */
 		break;
+	case 0xfc: /* cld */
+		ctxt->eflags &= ~EFLG_DF;
+		c->dst.type = OP_NONE;	/* Disable writeback. */
+		break;
+	case 0xfd: /* std */
+		ctxt->eflags |= EFLG_DF;
+		c->dst.type = OP_NONE;	/* Disable writeback. */
+		break;
 	case 0xfe ... 0xff:	/* Grp4/Grp5 */
 		rc = emulate_grp45(ctxt, ops);
 		if (rc != 0)
-- 
1.6.0.1

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