From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753452AbeCVKHN (ORCPT ); Thu, 22 Mar 2018 06:07:13 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:51110 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750982AbeCVKHL (ORCPT ); Thu, 22 Mar 2018 06:07:11 -0400 Subject: Re: [PATCH] KVM: X86: Fix the decoding of segment overrides in 64bit mode To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= References: <1521707651-9375-1-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini Message-ID: Date: Thu, 22 Mar 2018 11:07:08 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <1521707651-9375-1-git-send-email-wanpengli@tencent.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/03/2018 09:34, Wanpeng Li wrote: > From: Wanpeng Li > > Explicit segment overides other than %fs and %gs are documented as ignored by > both Intel and AMD. > > In practice, this means that: > > * Explicit uses of %ss don't actually yield #SS[0] for non-canonical > memory references. > * Explicit uses of %{e,c,d}s don't override %rbp/%rsp-based memory references > to yield #GP[0] for non-canonical memory references. > > Cc: Paolo Bonzini > Cc: Radim Krčmář > Signed-off-by: Wanpeng Li > --- > arch/x86/kvm/emulate.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index dd88158..5091255 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -5148,8 +5148,10 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) > case 0x2e: /* CS override */ > case 0x36: /* SS override */ > case 0x3e: /* DS override */ > - has_seg_override = true; > - ctxt->seg_override = (ctxt->b >> 3) & 3; > + if (mode != X86EMUL_MODE_PROT64) { > + has_seg_override = true; > + ctxt->seg_override = (ctxt->b >> 3) & 3; > + } > break; > case 0x64: /* FS override */ > case 0x65: /* GS override */ > Testcase, please... Paolo