Using blkback works for me, e.g. <driver name='phy'...>.
what is the diff to 'qemu'?
What xl config did you use? It doesn't work for me if I specify qdisk and readonly. E.g. the following does not work "backendtype=qdisk,format=raw,vdev=xvdz,access=ro,target=..."
"phy:/dev/mapper/keys,xvdz,r" Greetz
