Xen users - Dec 2012 - using iso file as cdrom for pv domU is not working on xl toolstack (qdisk)

I have an issue on Xen 4.2+ (now on yesterday''s tip) where when I try
to
use an iso image as cdrom for a pv domU, it appears that the devices is 
an unusable state on the domU side.

DomU kernel output: http://bpaste.net/show/63482/
xen logs: http://bpaste.net/show/63490/
udevadm monitor output: http://bpaste.net/show/63481/

I can work around this issue easily by creating a loop back device for 
the iso file first and using that instead.

I suspect that qdisk should handle this situation, but I''m not sure how
to troubleshoot this.