[gorkish]

A soft-gpu driver backed by real hardware "somewhere else" is a beautiful piece of software! While it certainly has application in virtual machines, and may even be "optimal" for some use cases like desktop gaming, it's ultimately doesn't fit with the modern definition of "virtualization --

I am talking about virtualization in the sense of being able to divide the hardware resources of a system into isolated domains and give control of those resources to guest operating systems. Passing API calls from guest to host for execution inside of the host domain is not that. A GPU providing a bunch of PCIe virtual functions which are individually mapped to guests interacting directly with the hardware is that.

GPU virtualization should be the base implementation and paravirtualization/HLE/api-passthrough can still sit on top as a fast-path when the compromises of doing it that way can be justified.

[AshamedCaptain]

I would say the complete opposite. The only reason one may have to use a real GPU driver backed by a partitioned GPU is precisely desktop gaming, as there you are more interested in performance than anything else and the arbitrary limits set by your GPU vendor (e.g. 1 partition only) may not impact you at all.

If you want to really divide hardware resources, then as I argue in the other thread doing it in software is clearly a much more sensible way to go. You are not subject to the whims of the GPU vendor and the OS, rather than the firmware, control the partition boundaries. Same as what has been done in practically every other virtualized device (CPUs, memory, etc.). We never expected the hardware to need to partition itself; I'd even have a hard time calling that "virtualization" at all. Plus, the way hardware is designed these days, it is highly unlikely that the PCI virtual functions of a GPU function as an effective security boundary. If it wasn't for performance, using hardware partitioning would never be a worthwhile tradeoff.