Fedora xen - Jan 2009 - Shutdown VM when host goes down?

Hi,

I managed to migrate my F8 host with Xen to F10 with KVM and Xenner. So far 
this was easier than expected. :-) Of course there are some smaller issues 
(Xenner does not work with SElinux, NetworkManager does not support bridges) 
but now there is only one real issue left:

How can I automatically shut down all running VMs when my host machine goes 
down? All VMs do poweroff if I press the ''shutdown'' button in
virt-manager. So
I guess it''s just a matter of sending this signal to all running VMs
and
waiting a bit.

Thank you very much,
fs