From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753037Ab3L3BTZ (ORCPT ); Sun, 29 Dec 2013 20:19:25 -0500 Received: from terminus.zytor.com ([198.137.202.10]:49511 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752770Ab3L3BTY (ORCPT ); Sun, 29 Dec 2013 20:19:24 -0500 Message-ID: <52C0C9F4.50101@zytor.com> Date: Sun, 29 Dec 2013 17:18:44 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: halfdog , Thomas Gleixner , Ingo Molnar CC: x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: Sanitize CPU-state when switching from virtual-8086 mode to other task References: <52BF4A80.3010503@halfdog.net> <52BF8AEE.6020904@zytor.com> <52C089AC.4000401@halfdog.net> In-Reply-To: <52C089AC.4000401@halfdog.net> X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/29/2013 12:44 PM, halfdog wrote: > H. Peter Anvin wrote: >> On 12/28/2013 02:02 PM, halfdog wrote: >>> It seems that missing CPU-state sanitation during task >>> switching triggers kernel-panic. This might be related to >>> unhandled FPU-errors. See [1] for POC and serial console log >>> of OOPs. Due to missing real 32-bit x86-hardware it is not >>> clear, if this issue might be related to subtle differences in >>> virtual-8086 mode handling when inside a virtualbox guest. >>> > >> This oops happens inside the guest? Either way, I would be >> *very* skeptical of Virtualbox in this case. > >> You can run a 32-bit kernel on 64-bit hardware, you know... > > I know, but hardware was occupied with long-running simulation. > > With the initial POC, there might be a timing issue involved, with > different process layout, exception does not occur in swith_to but > sometimes on other locations. > > I created a new random-code testcase [1] , which works around that > problem. When booted a Debian initrd and tried id, OOPSes are > fired like wild but at least system does not lock up immediately. > Still in VirtualBox? -hpa