From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aurelien Jarno Subject: Re: Data corruption in guest using KVM Date: Sat, 21 Jul 2007 19:54:04 +0200 Message-ID: <20070721175404.GA3665@hall.aurel32.net> References: <20070721172248.GA1555@hall.aurel32.net> <46A24675.1010506@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Anthony Liguori Return-path: Content-Disposition: inline In-Reply-To: <46A24675.1010506-rdkfGonbjUSkNkDKm+mE6A@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org On Sat, Jul 21, 2007 at 12:46:29PM -0500, Anthony Liguori wrote: > Aurelien Jarno wrote: > >Hi all, > > > >For a long time I am seeing data corruption in guests when using KVM, > >but I am convinced only since today that the problem comes from KVM. > > > >The symptoms are a few bytes that are mangled to 0x00 in a file that has > >been written. For now I have only seen 2 or 4 consecutive bytes mangled, > >but that may due to statistics given the limited samples. > > > >The problem appears very rarely. I am only seeing it when doing huge > >compilations (for example gcc or glibc), and not for every build. Note > >that I am only detecting build failures, so I can miss some corruptions. > > > >Note that I have observed the problem on GNU/Linux, GNU/kFreeBSD and > >plain FreeBSD, for both 32 and 64-bit guests. I always used 64-bit > >hosts, and I have seen the problem on both Core 2 and Athlon 64 CPU > >(always multi-core). > > > >I have never seen such corruptions using QEMU, so I would say the > >problem does not comes from the disk emulation, though it may be due to > >statistics. Note that I have made a lot of compilation in a MIPS QEMU > >guest (a few hundred of hours), without any problem. This platform uses > >the same IDE controller as the one in KVM. > > > >Does anybody have seen the same kind of problem? Without a way to > >reproduce the corruption, I think it will be very difficult to debug > >the problem. > > > > What sort of disk are you using (qcow2?) > I am using raw files for the disk in all cases. Note that I have just seen a three bytes corruption. Building the glibc seems to be a good way to reproduce the bug, as a lot of source files are generated on the fly during the build, and as GCC does not like source files with 0x00. I will try to do the same compilation using a NFS mount, to see if it comes or not from the IDE controller emulation. Regards, Aurelien -- .''`. Aurelien Jarno | GPG: 1024D/F1BCDB73 : :' : Debian developer | Electrical Engineer `. `' aurel32-8fiUuRrzOP0dnm+yROfE0A@public.gmane.org | aurelien-rXXEIb44qovR7s880joybQ@public.gmane.org `- people.debian.org/~aurel32 | www.aurel32.net ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/