https://github.com/airlied/mesa/tree/radv-wip-steamvr
The external memory code will be going upstream to master once I clean it up a bit, the semaphore hack is waiting on kernel
changes, and the NIR shader hack is waiting on a new SteamVR build that removes the bad use of SPIR-V.
I've run Serious SAM TFE in VR mode on this branch.