From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752255AbbJTNWa (ORCPT ); Tue, 20 Oct 2015 09:22:30 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:36219 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751100AbbJTNW1 (ORCPT ); Tue, 20 Oct 2015 09:22:27 -0400 Subject: Re: [Xen-devel] PROBLEM: kernel panic xsave_init To: John Doe , 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> Cc: Ingo Molnar , x86@kernel.org, xen-devel@lists.xen.org, linux-kernel@vger.kernel.org From: Boris Ostrovsky Message-ID: <56264008.8090800@oracle.com> Date: Tue, 20 Oct 2015 09:22:16 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <56262F81.804@gmail.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: aserv0022.oracle.com [141.146.126.234] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/20/2015 08:11 AM, John Doe wrote: > On 20/10/2015 11:51, Jan Beulich wrote: >>>>> On 19.10.15 at 18:25, wrote: >>> On 10/19/2015 06:16 AM, John Doe wrote: >>>>>> [ 0.000000] general protection fault: 0000 [#1] SMP >>>>>> [ 0.000000] Modules linked in: >>>>>> [ 0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted >>> 4.1.9-6.pvops.qubes.x86_64 #1 >>>>>> [ 0.000000] Hardware name: To Be Filled By O.E.M. To Be Filled By >>> O.E.M./Z170 Extreme4, BIOS P1.80 09/18/2015 >>>>>> [ 0.000000] task: ffffffff81c154c0 ti: ffffffff81c00000 task.ti: >>> ffffffff81c00000 >>>>>> [ 0.000000] RIP: e030:[] [] >>> xstate_enable_boot_cpu+0xde/0x288 >>>>>> [ 0.000000] RSP: e02b:ffffffff81c03de8 EFLAGS: 00010046 >>>>>> [ 0.000000] RAX: 000000000000001f RBX: 0000000000000008 RCX: >>> 0000000000000000 >>>>>> [ 0.000000] RDX: 0000000000000000 RSI: 000000000000001f RDI: >>> 0000000000042660 >>> >>> >>> It would be good to see what's at ffffffff81d58fad. My guess would be >>> that it's xsetbv. >>> >>> If it is then you probably want to make sure you are running hypervisor >>> that has commit e8121c54 ("x86/xsave: enable support for new ISA >>> extensions"). Looks like the first version that has it is 4.5 and you >>> seem to be running 4.4.2. >>> >>> Copying Jan to see if there are plans to backport this (probably not >>> since it's a new feature). >> >> Hmm, if there are features getting exposed that lead to crashes like >> this, then while we wouldn't normally backport enhancements, we >> may need to consider adding a one-off patch to hide respective >> features to that stable branch. But first we of course need to >> understand what is going on here. 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. With this being a new processor (Skylake) it would be logical to have these bits provided by CPUID. >> >> Jan >> > > I will try with 4.6.0 asap, unfortunately the 4.4.2 image i have is not > built with debug enabled and i'm unable to run gdb at boot, i'm building > a new one right now. You should be able to use 'gdb /proc/kcore' and look at the instruction at (and around) 0xffffffff81d58fad. > If you need anything else please be very step-specific since i'm not > very practical at this. You can also try adding cpuid=['0xd,0:eax=00000000000000000000000000000111'] to your config file and see if it helps. -boris