From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752654AbbJUARF (ORCPT ); Tue, 20 Oct 2015 20:17:05 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:38645 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751457AbbJUARD (ORCPT ); Tue, 20 Oct 2015 20:17:03 -0400 Subject: Re: [Xen-devel] PROBLEM: kernel panic xsave_init To: Boris Ostrovsky , Jan Beulich References: <562430E6.6010205@gmail.com> <20151019075618.GA22488@gmail.com> <5624C2FB.6080605@gmail.com> <56251973.9010603@oracle.com> <56262AD802000078000ACAA1@prv-mh.provo.novell.com> <56262F81.804@gmail.com> <56264008.8090800@oracle.com> <5626613002000078000ACE3B@prv-mh.provo.novell.com> <56264F5D.9000104@oracle.com> Cc: Ingo Molnar , x86@kernel.org, xen-devel@lists.xen.org, linux-kernel@vger.kernel.org From: John Doe X-Enigmail-Draft-Status: N1110 Message-ID: <5626D97C.1060609@gmail.com> Date: Wed, 21 Oct 2015 02:17:00 +0200 MIME-Version: 1.0 In-Reply-To: <56264F5D.9000104@oracle.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 20/10/2015 16:27, Boris Ostrovsky wrote: > On 10/20/2015 09:43 AM, Jan Beulich wrote: >>>>> On 20.10.15 at 15:22, wrote: >>> The reason I think its this commit is that RAX, RDX and RCX look very >>> much like arguments to xsetbv (which xstate_enable_boot_cpu() executes) >>> and RAX value is 0x1f, which has two new bits that this commit defined. >> That would be the two MPX related bits, yet us (luckily) white listing >> leaf 7 in pv_cpuid(), it is quite easy to validate that we don't expose >> this feature to PV(H) guests. > > Oh, so something like > > cpuid=['0x7:ebx=xxxxxxxxxxxxxxxxx0xxxxxxxxxxxxxx'] > > (bit 14 as zero) for John to try then. > > > -boris > >> Sadly the story is different for HVM >> guests (where the leaf handling uses black listing), but the register >> dump here clearly points to a PV guest (or Dom0). >> >> Jan >> > Jan the dump is taken from serial connection to Dom0, it does crash during boot. I just tried with xen 4.6.0 and it booted properly without xsave=0. Running gdb against /proc/kcore, with a x/10x 0xffffffff81d58fad i just get null bytes, with both xen4.4.3 (xsave=0) and 4.6.0. Tomorrow i will send you the gdb output and i will try to run it during the boot process. J.