From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LXIG4-0000eX-0C for qemu-devel@nongnu.org; Wed, 11 Feb 2009 11:48:20 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LXIG3-0000dB-01 for qemu-devel@nongnu.org; Wed, 11 Feb 2009 11:48:19 -0500 Received: from [199.232.76.173] (port=55186 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LXIG2-0000cv-Qb for qemu-devel@nongnu.org; Wed, 11 Feb 2009 11:48:18 -0500 Received: from mail2.shareable.org ([80.68.89.115]:36227) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LXIG2-0006Oi-FD for qemu-devel@nongnu.org; Wed, 11 Feb 2009 11:48:18 -0500 Date: Wed, 11 Feb 2009 16:48:14 +0000 From: Jamie Lokier Subject: Re: [Qemu-devel] qcow2 corruption observed, fixed by reverting old change Message-ID: <20090211164814.GA7161@shareable.org> References: <20090211070049.GA27821@shareable.org> <4992A108.8070304@suse.de> <20090211114126.GC31997@shareable.org> <4992C77D.4030104@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4992C77D.4030104@suse.de> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: Laurent Vivier , qemu-devel@nongnu.org, kvm-devel Kevin Wolf wrote: > 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. I have a copy of my image to reproduce the bug, so I can test patches including diagnostic patches. That's what I did to narrow it down. Being a company mail server, I can't send you the image of course. > > 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. It was just for clarity. If there are any bugs it's more likely to be truncation on a 32 bit host :-) I didn't see any mention of "long", so the code should behave the same on 64-bit and 32-bit hosts. > 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. Are those patches in kvm-83? I still have the image that was causing problems way back, and I'm converting it to raw now with kvm-83 to see if it now matches the raw image produced by VPC's own tool. Beyond checking that it reads ok, which it didn't before, I don't know how to test the VPC support properly, but I can try booting the image and see if it at least doesn't fsck^H^H^H^Hscandisk like it used to. I'm not using VPC images any more, we just install Windows into empty QCOW2 or raw images, like everyone else. :-) At some point I may test the VPC support with prebuilt images downloaded from Microsoft - you can too! -- Jamie