Hi guys,
I just updated my kernel version for dom0 from 3.13.10 to 3.14.5 (both 
gentoo hardened sources) when one of my virtual machines still running 
on 3.13.10 suddenly froze. At that time I was about to update the kernel 
for my domU when it froze. My XEN version is 4.3.2.

I then tried to shutdown the domU from the dom0 (xl shutdown name) which 
seemingly worked (shutdown messages appeard on the console for the 
domU). A restart threw an error message which I missed to record . In xl 
list however, the old domU line was still there with a name of (null) 
and a state of "--ps-d".

Shutdown of other domUs to be able to restart the machine resulted in 
the same xl list output: name as (null) and "--ps-d" state, although 
according to their log files under /var/lo/xen-consoles they seem to 
stop correctly. What I however noted was that the LVMs for all domUs 
were still open after their shutdown and they [blkback.N.xvdayN] were 
still available in the process list on dom0.

Investigation then revealed that the messages as per the attached file 
had been recorded in dmesg on dom0.

For now I have decided to switch back to kernel version 3.13.10 which 
was running absolutely stable for a number of weeks.

I am more than happy to provide further information if needed.

Thanks Atom2