I am using libvirt on Ubuntu 10.04 Server and the following versions of these packages:
libvirt-bin, libvirt0, python-libvirt - 0.7.5-5ubuntu27.22
qemu-kvm 0.12.3+noroms-0ubuntu9.18

Recently, when restarting a VM (either by issuing "sudo reboot" on a Linux guest or choosing "Restart" from the Start Menu on a Windows guest) the VM shuts down and remains off rather than simply restarting. I cannot test "virsh restart <domain>" on this server as the version of libvirt does not appear to support restarting - see https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/368962

I do not receive any errors in /var/log when the shutdown occurs. Powering the VM back on works, however I would prefer to have hot restart working so VMs that are automatically rebooted to install updates will come back up automatically. Do you have any suggestions on how to debug this behavior?