linux-kernel - [PATCH 1/9] KVM: x86: Mark VEX-prefix instructions emulation as unimplemented

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Message-Id: <1401723251-8034-2-git-send-email-namit@cs.technion.ac.il>
Date:	Mon,  2 Jun 2014 18:34:03 +0300
From:	Nadav Amit <namit@...technion.ac.il>
To:	pbonzini@...hat.com
Cc:	gleb@...nel.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Nadav Amit <namit@...technion.ac.il>
Subject: [PATCH 1/9] KVM: x86: Mark VEX-prefix instructions emulation as unimplemented

Currently the emulator does not recognize vex-prefix instructions.  However, it
may incorrectly decode lgdt/lidt instructions and try to execute them. This
patch returns unhandlable error on their emulation.

Signed-off-by: Nadav Amit <namit@...technion.ac.il>
---
 arch/x86/kvm/emulate.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index e4e833d..8ec4a3e 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4314,6 +4314,13 @@ done_prefixes:
 	if (ctxt->d & ModRM)
 		ctxt->modrm = insn_fetch(u8, ctxt);
 
+	/* vex-prefix instructions are not implemented */
+	if (ctxt->opcode_len == 1 && (ctxt->b == 0xc5 || ctxt->b == 0xc4) &&
+	    (mode == X86EMUL_MODE_PROT64 ||
+	    (mode >= X86EMUL_MODE_PROT16 && (ctxt->modrm & 0x80)))) {
+		ctxt->d = NotImpl;
+	}
+
 	while (ctxt->d & GroupMask) {
 		switch (ctxt->d & GroupMask) {
 		case Group:
-- 
1.9.1

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