So, even if the almost ready Xen 4.0 release will for the first time abandon the ancient non-paravirtops dom0 patches in favor of paravirtops-based ones, the inclusion in mainline is still not close to happen, contrary to what one might naively have guessed.
(FWIW, I'm currently running Slackware 13.0 as a dom0 through the SUSE patches, rebased for kernel.org 2.6.31 by A . Lyon)