From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:47200) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QRvEb-0004Ob-PX for qemu-devel@nongnu.org; Wed, 01 Jun 2011 19:53:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QRvEa-0002C3-4F for qemu-devel@nongnu.org; Wed, 01 Jun 2011 19:53:57 -0400 Received: from mx1.redhat.com ([209.132.183.28]:23159) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QRnP1-0003dY-5x for qemu-devel@nongnu.org; Wed, 01 Jun 2011 11:32:11 -0400 From: Markus Armbruster References: <1305808412-16994-1-git-send-email-kwolf@redhat.com> <1305808412-16994-6-git-send-email-kwolf@redhat.com> <20110526181208.46aba2ae@doriath> <20110601104456.5469329b@doriath> <4DE64690.8020500@redhat.com> Date: Wed, 01 Jun 2011 17:32:06 +0200 In-Reply-To: <4DE64690.8020500@redhat.com> (Kevin Wolf's message of "Wed, 01 Jun 2011 16:02:56 +0200") Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] [PATCH 05/18] ide: Turn debug messages into assertions List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: Stefan Hajnoczi , qemu-devel@nongnu.org, Luiz Capitulino Kevin Wolf writes: > Am 01.06.2011 15:44, schrieb Luiz Capitulino: >> On Thu, 26 May 2011 18:12:08 -0300 >> Luiz Capitulino wrote: >> >>> On Thu, 19 May 2011 14:33:19 +0200 >>> Kevin Wolf wrote: >>> >>>> These printfs aren't really debug messages, but clearly indicate a bug if they >>>> ever become effective. >>> >>> Then we have a bug somewhere, starting a VM with: >>> >>> # qemu -hda disks/test.img -enable-kvm -m 1G -cdrom /dev/sr0 >>> >>> Where the host's CDROM is empty, triggers one of these asserts: >>> >>> qmp-unstable/hw/ide/pci.c:299: bmdma_cmd_writeb: Assertion `bm->bus->dma->aiocb == ((void *)0)' >> >> I found out why this is happening. I'm passing '-snapshot' to the command-line, >> sorry for not mentioning it (I forgot I was using my devel alias). > > And suddenly it's reproducible. :-) > > I'll have a look. > >> I also found out that /usr/bin/eject in the guest won't work when >> -snapshot is used. Shouldn't qemu ignore this flag when using cdrom >> passthrough? > > "Won't work" means that it works like with a CD-ROM image? That would be > what I expect, as you end up having a qcow2 image with -snapshot. With a qcow2 stacked onto the host_cdrom. The block layer forwards the guest's eject only if the top driver has a bdrv_eject() method. Which qcow2 doesn't have. I guess bdrv_eject() fails with -ENOTSUP, and cmd_start_stop_unit() reports a funny error to the guest. > Not sure what's the best way of fixing this. Maybe just ignoring > -snapshot for read-only block devices? Why not, the combination is pointless. > Or we could try and forward the > eject request to the backing file if the format driver doesn't handle it. For what it's worth, the "raw" driver forwards manually.