Using disk XML <disk type='block' device='cdrom'> <driver name='qemu' type='raw'/> <source dev='/dev/sr0'/> <target dev='hdc' bus='ide'/> <readonly/> <address type='drive' controller='0' bus='1' target='0' unit='0'/> </disk> And no media in the host CDROM, booting fails like: error: cannot open file '/dev/sr0': No medium found This is coming from: qemu_command.c:qemuDomainDetermineDiskChain->virStorageFileGetMetadata Easy-ish fix is to use O_NONBLOCK when opening the path, but then trying to read the non-existing file header later on just fails with an i/o error. qemu has handled this for a while by trying to detect host devices and altering open flags appropriately, see the *probe* functions here: http://git.qemu.org/?p=qemu.git;a=blob;f=block/raw-posix.c This is something we explicitly made work in qemu in the past due to user request, so it'd be nice to get it working again.
Still relevant with libvirt 1.1.3 in fedora 20, but given that no one else has complained in 2 releases, moving it to the upstream tracker
Fixed upstream with v1.2.3-173-g9556681: commit 955668138873f2dd9b2e9989fecaddb33dc149c7 Author: Martin Kletzander <mkletzan> Date: Wed Apr 16 17:31:50 2014 +0200 qemu: don't check for backing chains for formats w/o snapshot support