From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754642AbYILNcu (ORCPT ); Fri, 12 Sep 2008 09:32:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751788AbYILNcl (ORCPT ); Fri, 12 Sep 2008 09:32:41 -0400 Received: from agminet01.oracle.com ([141.146.126.228]:35238 "EHLO agminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751521AbYILNcl (ORCPT ); Fri, 12 Sep 2008 09:32:41 -0400 Subject: Re: kernel BUG at drivers/pci/intel-iommu.c:1373! From: Chris Mason To: mgross@linux.intel.com Cc: linux-kernel , David Woodhouse , Jens Axboe In-Reply-To: <20080909161903.GA14986@linux.intel.com> References: <1220883964.8537.27.camel@think.oraclecorp.com> <20080909161903.GA14986@linux.intel.com> Content-Type: text/plain Date: Fri, 12 Sep 2008 09:32:30 -0400 Message-Id: <1221226350.28506.0.camel@think.oraclecorp.com> Mime-Version: 1.0 X-Mailer: Evolution 2.22.2 Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAQAAAAI= X-Brightmail-Tracker: AAAAAQAAAAI= X-Whitelist: TRUE X-Whitelist: TRUE Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2008-09-09 at 09:19 -0700, mark gross wrote: > On Mon, Sep 08, 2008 at 10:26:04AM -0400, Chris Mason wrote: > > Hello everyone, > > > > I originally hit this with btrfs and assumed I was doing something > > wrong, but it looks like it is a generic problem. The stack trace at > > the bottom of this email came from the following setup: > > > > mdadm --create /dev/md0 --level=1 --raid-devices=4 --assume-clean /dev/sd[cdef] > > mkfs.ext4dev /dev/md0 50000000 > > mount /dev/md0 /mnt > > synctest -t 100 -F -f -u /mnt > > > > synctest is an old benchmark from akpm that I dug up to test the btrfs > > fsync code. google doesn't seem to know much about it anymore, so I've > > tossed it up here: > > > > http://oss.oracle.com/~mason/synctest/synctest.c > > > > The important part is that I have a software raid1 volume with 4 drives > > and that I'm hammering on it has hard as I can with synchronous writes > > from 100 procs. > > > > MD uses bio_clone to make copies of bios for each device in the mirror > > set. So, using 4 devices means each bio is cloned 3 times, greatly > > increases the chances that I'll send down the same page in different > > bios to different devices. > > > > Ext4 needs about 10 minutes to trigger on top of MD. Btrfs needs about > > 30 seconds when it controls the 4 devices itself. > > > > I've been told this BUG in the io-mmu code comes when someone tries to > > map a page into the iommu that has already been mapped. It seems like > > that is a natural result of bio_clone, and not an inherent race in the > > code. But, I've just said everything I know about the iommu code, so my > > guesses don't mean much. > > I have a bad feeling about this. Can you retest booting with a kernel > parrameter "intel_iommu=strict"? Sorry, I'm going to have to try this again after the plumber's conf. -chris