[Fedora-xen] where are disk config docs?

[Tom Horsley]

There are apparently an awful lot of different ways to define
disks for VMs, but there are apparently no docs describing
them anywhere :-). Where do folks find out how to do all the
things I see references to in the mailing lists (xenblk drivers,
tap:aio, xvda, I can find millions of hits on google, mostly
in patches, but I can't find anything resembling documentation).