He's working on allowing VR HMDs to be directly accessed from Linux VR apps without the windowing system getting in the way as is currently the case. Right now if plugging in the HTC Vive to a system running e.g. the AMDGPU driver, part of the desktop will appear on the headset by default.
Keith is working on Direct Rendering Manager changes for "display resource leasing" to get window managers out of the way or so that HMDs are never exposed to the windowing system. VR applications/games could directly use Linux KMS interfaces for driving the HMD.
For those interested in the technical approach being pursued, Keith has written a blog post outlining some of the current plans.