Daniel, imagine hardware that can only do what Windows does: future fences signalled by userspace whenever userspace wants, and no kernel queues like we have today.
Hmm, that sounds kinda like what we're trying to do for Libre-SOC's gpu which is basically where the cpu (exactly the same cores as the gpu) runs a user-space software renderer with extra instructions to make it go fast, so the kernel only gets involved for futex-wait or for video scan-out. This causes problems when figuring out how to interact with dma-fences for interoperability...
Jacob Lifshay