Description of problem:
In order to be a good guest when running under a Xen hypervisor as a fully-virtualized domains, we should have the PV-on-HVM drivers available in the Fedora kernel.  Unfortunately, these drivers are not yet upstream, so we have to first get them accepted upstream, and then port them (or just inherit them) to Fedora.  The good news is that much of the infrastructure for getting these working (xenbus, xen-blkfront, xen-netfront) is already in upstream, so it's a matter of getting the rest of the glue pulled together and accepted.