Comment 21 for bug 1248025

So Adam was giving me access to some Rackspace guests. I found that in those a xenfs was mounted to /proc/xen. This was done by the init script of xe-guest-utilities. I suspect this is something that works together with a XenServer host. There was also a nova-agent running which I could not find a package for. This was attached to /proc/xen/xenbus.
I can get libvirtd to run when I shut down all nova-agents, stop the xe utilities and unmoutn /proc/xen. So the problem is that having /proc/xen running, the initial checks of the libxl driver in libvirt are mislead to think the guest is a dom0. This would just abort loading the driver. But failing to read the capabilities returns an error from the driver load which seems fatal.
Maybe the solution will be as simple as either treating this as a soft failure, too or have a better check for that situation.

At least this gives a good lead to reproduce tomorrow and see whether newer versions of libvirt already handle that case. And if not, discuss and create a fix for upstream which we can pick into our releases.