From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757816AbXLWO4l (ORCPT ); Sun, 23 Dec 2007 09:56:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755843AbXLWOvy (ORCPT ); Sun, 23 Dec 2007 09:51:54 -0500 Received: from il.qumranet.com ([82.166.9.18]:35897 "EHLO il.qumranet.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752957AbXLWOvm (ORCPT ); Sun, 23 Dec 2007 09:51:42 -0500 From: Avi Kivity To: linux-kernel@vger.kernel.org, kvm-devel@lists.sourceforge.net Cc: Laurent Vivier Subject: [PATCH 17/50] KVM: x86 emulator: Any legacy prefix after a REX prefix nullifies its effect Date: Sun, 23 Dec 2007 16:51:02 +0200 Message-Id: <1198421495-31481-18-git-send-email-avi@qumranet.com> X-Mailer: git-send-email 1.5.3.7 In-Reply-To: <1198421495-31481-1-git-send-email-avi@qumranet.com> References: <1198421495-31481-1-git-send-email-avi@qumranet.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Laurent Vivier This patch modifies the management of REX prefix according behavior I saw in Xen 3.1. In Xen, this modification has been introduced by Jan Beulich. http://lists.xensource.com/archives/html/xen-changelog/2007-01/msg00081.html Signed-off-by: Laurent Vivier Signed-off-by: Avi Kivity --- drivers/kvm/x86_emulate.c | 24 +++++++++++++++--------- 1 files changed, 15 insertions(+), 9 deletions(-) diff --git a/drivers/kvm/x86_emulate.c b/drivers/kvm/x86_emulate.c index fe50317..e6b213b 100644 --- a/drivers/kvm/x86_emulate.c +++ b/drivers/kvm/x86_emulate.c @@ -521,7 +521,6 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) { struct decode_cache *c = &ctxt->decode; u8 sib, rex_prefix = 0; - unsigned int i; int rc = 0; int mode = ctxt->mode; int index_reg = 0, base_reg = 0, scale, rip_relative = 0; @@ -551,7 +550,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) } /* Legacy prefixes. */ - for (i = 0; i < 8; i++) { + for (;;) { switch (c->b = insn_fetch(u8, 1, c->eip)) { case 0x66: /* operand-size override */ c->op_bytes ^= 6; /* switch between 2/4 bytes */ @@ -582,6 +581,11 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) case 0x36: /* SS override */ c->override_base = &ctxt->ss_base; break; + case 0x40 ... 0x4f: /* REX */ + if (mode != X86EMUL_MODE_PROT64) + goto done_prefixes; + rex_prefix = c->b; + continue; case 0xf0: /* LOCK */ c->lock_prefix = 1; break; @@ -592,19 +596,21 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops) default: goto done_prefixes; } + + /* Any legacy prefix after a REX prefix nullifies its effect. */ + + rex_prefix = 0; } done_prefixes: /* REX prefix. */ - if ((mode == X86EMUL_MODE_PROT64) && ((c->b & 0xf0) == 0x40)) { - rex_prefix = c->b; - if (c->b & 8) + if (rex_prefix) { + if (rex_prefix & 8) c->op_bytes = 8; /* REX.W */ - c->modrm_reg = (c->b & 4) << 1; /* REX.R */ - index_reg = (c->b & 2) << 2; /* REX.X */ - c->modrm_rm = base_reg = (c->b & 1) << 3; /* REG.B */ - c->b = insn_fetch(u8, 1, c->eip); + c->modrm_reg = (rex_prefix & 4) << 1; /* REX.R */ + index_reg = (rex_prefix & 2) << 2; /* REX.X */ + c->modrm_rm = base_reg = (rex_prefix & 1) << 3; /* REG.B */ } /* Opcode byte(s). */ -- 1.5.3.7