Buggy kvm crashes with kernel panic if xen started inside a kvm machine. kvm needs the -no-kvm-pit, this argument is not available with libvirt. I have tested the following workaround on ubuntu 9.04 Rename kvm cd /usr/bin mv kvm kvm.orig Use the following script instead the original kvm #!/bin/sh exec kvm.orig -no-kvm-pit $* Do not forget chmod +x kvm Have fun, Thomas