Mailing the story:
Set up Xen 4.0.1 & Libvirt 0.8.3 on top of Ubuntu 10.10 Desktop
Following bellow is brief instruction of mentioned set up loading xen back-end, evtchn, gntdev devices separately from pvops kernel 2.6.32.24 under Xen 4.0.1 on top Ubuntu Maverick Meerkat Desktop. Due to Desktop environment we have first to disable Network Manager and restart networking manually updating /etc/network/interfaces.