Kevin Wolf <kw...@redhat.com> writes: > Am 01.06.2011 15:44, schrieb Luiz Capitulino: >> On Thu, 26 May 2011 18:12:08 -0300 >> Luiz Capitulino <lcapitul...@redhat.com> wrote: >> >>> On Thu, 19 May 2011 14:33:19 +0200 >>> Kevin Wolf <kw...@redhat.com> 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.
