linux-kernel - [PATCH] KVM: fix mov immediate emulation for 64-bit operands

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Message-Id: <E0EE2EE9-96C1-4354-BDCE-19E3AF2C0F30@gmail.com>
Date:	Sat, 7 Jan 2012 22:21:35 +0200
From:	Nadav Amit <nadav.amit@...il.com>
To:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: fix mov immediate emulation for 64-bit operands

MOV immediate instruction (opcodes 0xB8-0xBF) may take 64-bit operand.
The previous emulation implementation assumes the operand is no longer than 32.

Signed-off-by: Nadav Amit <nadav.amit@...il.com>
---
arch/x86/kvm/emulate.c |    6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 05a562b..65d1d31 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -3502,7 +3502,8 @@ static unsigned imm_size(struct x86_emulate_ctxt *ctxt)
	unsigned size;

	size = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes;
-	if (size == 8)
+	/* Immediates are usually no longer than 4 bytes */
+	if (size == 8 && ((ctxt->b & 0xF8) != 0xB8 || ctxt->twobyte))
		size = 4;
	return size;
}
@@ -3526,6 +3527,9 @@ static int decode_imm(struct x86_emulate_ctxt *ctxt, struct operand *op,
	case 4:
		op->val = insn_fetch(s32, ctxt);
		break;
+	case 8:
+		op->val = insn_fetch(s64, ctxt);
+		break;
	}
	if (!sign_extension) {
		switch (op->bytes) {
-- 
1.7.4.1


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