From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932404Ab3GDL1M (ORCPT ); Thu, 4 Jul 2013 07:27:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:2696 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753041Ab3GDL1L (ORCPT ); Thu, 4 Jul 2013 07:27:11 -0400 From: Denys Vlasenko To: Gleb Natapov , linux-kernel@vger.kernel.org Cc: Denys Vlasenko , Paolo Bonzini , Avi Kivity Subject: [PATCH v2] x86/kvm/emulate.c: simplify NOP (opcode 0x90) check Date: Thu, 4 Jul 2013 13:27:00 +0200 Message-Id: <1372937220-27856-1-git-send-email-dvlasenk@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We do not need to check for reg == RAX for opcodes 0x91...0x97. Signed-off-by: Denys Vlasenko CC: Paolo Bonzini CC: Avi Kivity Signed-off-by: Denys Vlasenko CC: Paolo Bonzini CC: Avi Kivity --- arch/x86/kvm/emulate.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 2bc1e81..2dc48a1 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4544,9 +4544,14 @@ special_insn: case 0x8d: /* lea r16/r32, m */ ctxt->dst.val = ctxt->src.addr.mem.ea; break; - case 0x90 ... 0x97: /* nop / xchg reg, rax */ + case 0x90: /* nop / xchg reg, rax */ + /* Not all opcodes 90 are NOPs, only ones which refer to RAX */ + /* For example, 49 90 is xchg %rax,%r8 */ + /* Bare 90 and 40 90 (redundant REX prefix) are nop */ if (ctxt->dst.addr.reg == reg_rmw(ctxt, VCPU_REGS_RAX)) break; + /* Fall through */ + case 0x91 ... 0x97: /* xchg reg, rax */ rc = em_xchg(ctxt); break; case 0x98: /* cbw/cwde/cdqe */ -- 1.8.1.4