From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Wolf Subject: Re: [Qemu-devel] qcow2 corruption observed, fixed by reverting old change Date: Wed, 11 Feb 2009 13:41:33 +0100 Message-ID: <4992C77D.4030104@suse.de> References: <20090211070049.GA27821@shareable.org> <4992A108.8070304@suse.de> <20090211114126.GC31997@shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: qemu-devel@nongnu.org, kvm-devel , Laurent Vivier To: Jamie Lokier Return-path: Received: from mx2.suse.de ([195.135.220.15]:54660 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755613AbZBKMec (ORCPT ); Wed, 11 Feb 2009 07:34:32 -0500 In-Reply-To: <20090211114126.GC31997@shareable.org> Sender: kvm-owner@vger.kernel.org List-ID: Jamie Lokier schrieb: > Kevin Wolf wrote: >> Jamie Lokier schrieb: >>> Although there are many ways to make Windows blue screen in KVM, in >>> this case I've narrowed it down to the difference in >>> qemu/block-qcow2.c between kvm-72 and kvm-73 (not -83). >> This must be one of SVN revisions 5003 to 5008 in upstream qemu. Can you >> narrow it down to one of these? I certainly don't feel like reviewing >> all of them once again. > > It's QEMU SVN delta 5005-5006, copied below. > > I've tested by applying the diffs up to QEMU SVN revs 5003 to 500, > onto kvm-72, and 5005-5006 is the diff which triggers the failed guest > boot, consistently. That's exactly what I was afraid of... It's the most difficult patch of the series. I'm adding Laurent to CC who wrote the patch series then, but I can imagine he wants to do different things in his spare time. Besides reviewing the code over and over again, I think the only real chance is that you can get a non-productive copy of your image and add some debug code so that we can see at least which code path is causing problems. > Aside from logic, the code mixes signed 32-bit with unsigned 64-bit > with unclear naming which would make me nervous. My host is 64-bit, > by the way. I would suspect that simply having a 64 bit host isn't enough to trigger the problem. These patches were in for half a year now without anyone noticing such failure. By the way and completely off-topic: Have you already tried to use the VHD patches? I would really like to know if they fix your problems. Kevin From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LXEIW-0007RE-Qe for qemu-devel@nongnu.org; Wed, 11 Feb 2009 07:34:36 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LXEIT-0007Qn-Q1 for qemu-devel@nongnu.org; Wed, 11 Feb 2009 07:34:35 -0500 Received: from [199.232.76.173] (port=55946 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LXEIT-0007Qj-KS for qemu-devel@nongnu.org; Wed, 11 Feb 2009 07:34:33 -0500 Received: from mx2.suse.de ([195.135.220.15]:54659) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LXEIT-0004cQ-7g for qemu-devel@nongnu.org; Wed, 11 Feb 2009 07:34:33 -0500 Message-ID: <4992C77D.4030104@suse.de> Date: Wed, 11 Feb 2009 13:41:33 +0100 From: Kevin Wolf MIME-Version: 1.0 Subject: Re: [Qemu-devel] qcow2 corruption observed, fixed by reverting old change References: <20090211070049.GA27821@shareable.org> <4992A108.8070304@suse.de> <20090211114126.GC31997@shareable.org> In-Reply-To: <20090211114126.GC31997@shareable.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jamie Lokier Cc: Laurent Vivier , qemu-devel@nongnu.org, kvm-devel Jamie Lokier schrieb: > Kevin Wolf wrote: >> Jamie Lokier schrieb: >>> Although there are many ways to make Windows blue screen in KVM, in >>> this case I've narrowed it down to the difference in >>> qemu/block-qcow2.c between kvm-72 and kvm-73 (not -83). >> This must be one of SVN revisions 5003 to 5008 in upstream qemu. Can you >> narrow it down to one of these? I certainly don't feel like reviewing >> all of them once again. > > It's QEMU SVN delta 5005-5006, copied below. > > I've tested by applying the diffs up to QEMU SVN revs 5003 to 500, > onto kvm-72, and 5005-5006 is the diff which triggers the failed guest > boot, consistently. That's exactly what I was afraid of... It's the most difficult patch of the series. I'm adding Laurent to CC who wrote the patch series then, but I can imagine he wants to do different things in his spare time. Besides reviewing the code over and over again, I think the only real chance is that you can get a non-productive copy of your image and add some debug code so that we can see at least which code path is causing problems. > Aside from logic, the code mixes signed 32-bit with unsigned 64-bit > with unclear naming which would make me nervous. My host is 64-bit, > by the way. I would suspect that simply having a 64 bit host isn't enough to trigger the problem. These patches were in for half a year now without anyone noticing such failure. By the way and completely off-topic: Have you already tried to use the VHD patches? I would really like to know if they fix your problems. Kevin