Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758833Ab3FCPmR (ORCPT ); Mon, 3 Jun 2013 11:42:17 -0400 Received: from mail-ea0-f182.google.com ([209.85.215.182]:64565 "EHLO mail-ea0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756694Ab3FCPmN (ORCPT ); Mon, 3 Jun 2013 11:42:13 -0400 MIME-Version: 1.0 In-Reply-To: <51A77FA8.6010007@redhat.com> References: <1369924555-30216-1-git-send-email-pbonzini@redhat.com> <51A7717D.6030203@redhat.com> <51A77FA8.6010007@redhat.com> Date: Mon, 3 Jun 2013 18:42:11 +0300 Message-ID: Subject: Re: [PATCH] KVM: fix sil/dil/bpl/spl in the mod/rm fields From: Avi Kivity To: Paolo Bonzini Cc: kvm , linux-kernel@vger.kernel.org, gnatapov@redhat.com Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1891 Lines: 44 On Thu, May 30, 2013 at 7:34 PM, Paolo Bonzini wrote: > Il 30/05/2013 17:34, Paolo Bonzini ha scritto: >> Il 30/05/2013 16:35, Paolo Bonzini ha scritto: >>> The x86-64 extended low-byte registers were fetched correctly from reg, >>> but not from mod/rm. >>> >>> This fixes another bug in the boot of RHEL5.9 64-bit, but it is still >>> not enough. >> >> Well, it is enough but it takes 2 minutes to reach the point where >> hardware virtualization is used. It is doing a lot of stuff in >> emulation mode because FS and GS have leftovers from the A20 test: >> >> FS =0000 0000000000000000 0000ffff 00009300 DPL=0 DS16 [-WA] >> GS =ffff 00000000000ffff0 0000ffff 00009300 DPL=0 DS16 [-WA] >> >> 0x00000000000113be: in $0x92,%al >> 0x00000000000113c0: or $0x2,%al >> 0x00000000000113c2: out %al,$0x92 >> 0x00000000000113c4: xor %ax,%ax >> 0x00000000000113c6: mov %ax,%fs >> 0x00000000000113c8: dec %ax >> 0x00000000000113c9: mov %ax,%gs >> 0x00000000000113cb: inc %ax >> 0x00000000000113cc: mov %ax,%fs:0x200 >> 0x00000000000113d0: cmp %gs:0x210,%ax >> 0x00000000000113d5: je 0x113cb >> >> The DPL < RPL test fails. Any ideas? Should we introduce a new >> intermediate value for emulate_invalid_guest_state (0=none, 1=some, 2=full)? > > One idea could be to replace invalid descriptors with NULL ones. Then > you can intercept this in the #GP handler and trigger emulation for that > instruction only. Won't work, vmx won't let you enter in such a configuration. Maybe you can detect the exact code sequence (%eip, some instructions, register state) and clear %fs and %gs. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/