Where does this feature stand currently? It pops up under a couple of names and proposed implementations (e.g., "qemu-xen stubdomains", "qemu-upstream stubdom, Linux", and "qemu-upstream stubdom, BSD libc"), so it seems likely I missed something.

If I understand this email from Sept 2013 (http://lists.xen.org/archives/html/xen-devel/2013-09/msg02881.html), qemu-xen stubdomains might have made it into 4.4 if the schedule had been slipped a little, suggesting some active effort. On the other hand, the same email designated the efforts attached to Anthony and Ian as "prognosis: ?". Anthony released a patchset/branch about a year ago, but that got sidelined in favor of getting Xen on ARM. However, I did not identify any more recent patches.

It remains appealing to make use of the more recent developments in qemu-upstream, but with the isolation provided by a stubdomain. The many improvements made in teasing driver domains out of dom0 strengthen this appeal (for example, using OpenSolaris as a ZFS-based storage domain).

What are the most recent patches or repository for this feature?

Thanks,

Eric