qdisk error with rbd

[Antoine Perdaens <a.perdaens@xxxxxxxxx>]

Hello all,

Our current setup is based on Xen 4.11 + Qemu 3.1 with rbd disks, an example of 
a disk that works : 
"vdev=xvda1,backendtype=qdisk,target=rbd:rbd-pool/disk-02-root:id=rbd”.

The same setup with Qemu 5.0 gives this error in /var/log/xen/qemu-dm-* : 
"qemu-system-i386: failed to create 'qdisk' device '51713': failed to create 
drive: Could not open 'rbd:rbd-pool/disk-02-root:id=rbd': No such file or 
directory”


Looking at the source in xen-block.c it looks like the driver is forced to 
“file” which wouldn’t work for other type of block devices.

It looks like a regression with the xen-disk introduction.

Regards,
Antoine