Comment 0 for bug 1804766

Hi,
for quite a while we had thought enabling opengl to go along the MIR for virglrenderer (bug 1657409), but missed that it is a prereq for using MDEVs as well.
This now become much more important as newer drivers (recent nvidia drivers, as well as kernel >4.16 for intel) made this much more available to users - and it would work just fine if qemu had opengl enabled.

Other than for virgl we don't need additional libraries to be promoted to MAIN.
Those we need for "just" opengl are already in MAIN for Ubuntu Desktop support.
So the change is as easy as adding a few build-deps and setting a config option.

The code is already in place, qemu 2.11 (Bionic) has all it needs for nvidia and 2.12 >=Cosmic has the code for Intel.
That said flipping this build option (no other change) would allow:
- >= 18.10 use vfio MDEVs for gpu's of nvidia and intel
- 18.04 use vfio MDEVs for gpu's of nvidia
- 18.04 + HWE kernel + later Cloud-Archive with qemu >2.12 use vfio MDEVs for intel gpus

I did a bunch of tests and found no related regressions.
And in terms of SRU terms this falls clearly under "enabling new HW/Feature in LTS" exception as the use of vfio-MDEV for gpus just wasn't as clear back then but becomes more and more important now.