Comment 1 for bug 1297224

Supporting flexible locations of qemu and alternate location for the ovmf BIOS would allow to get rid of patches. So sounds useful. Note that the 14.04 (Trusty) release of Ubuntu (as well as the 13.10 (Saucy) release) were not using the Xen version of qemu for xl but the generic upstream qemu (compiled with Xen support).

To push deprecation of xend in 14.04, xl was made the default toolstack. In order to not completely break users of xend it still ships with xend support and this will not get removed in the 14.04 release. This could be something to try in the next release. If Xen-4.5 is ready by then its gone anyway and in case we stick with 4.4 we could stop using --with-xend. Probably depending on upstream to decide whether the old device-model should go, too.

Blktap(2) is not installed by default. It has been a bunch of separate packages for a while. The default is to use upmstream qemu. Not sure whether qdisk refers to a specific interface. Normally IDE is specified and blkfront is used after unplug.