[RFC PATCH 00/97] Basic GuC submission support in the i915

[Dixit, Ashutosh]

On Sun, 09 May 2021 16:11:43 -0700, Jason Ekstrand wrote:
>
> Yes, landing GuC support may be the first step in removing execlist
> support. The inevitable reality is that GPU scheduling is coming and
> likely to be there only path in the not-too-distant future.  (See also
> the ongoing thread with AMD about fences.) I'm not going to pass
> judgement on whether or not this is a good thing.  I'm just reading the
> winds and, in my view, this is where things are headed for good or ill.
>
> In answer to the question above, the answer to "what do we gain from
> GuC?" may soon be, "you get to use your GPU."  We're not there yet and,
> again, I'm not necessarily advocating for it, but that is likely where
> things are headed.
>
> A firmware-based submission model isn't a bad design IMO and, aside from
> the firmware freedom issues, I think there are actual advantages to the
> model. Immediately, it'll unlock a few features like parallel submission
> (more on that in a bit) and long-running compute because they're
> implemented in GuC and the work to implement them properly in the
> execlist scheduler is highly non-trivial.  Longer term, it may (no
> guarantees) unlock some performance by getting the kernel out of the way.

I believe another main reason for GuC is support for HW based
virtualization like SRIOV. The only way to support SRIOV with execlists
would be to statically partition the GPU between VM's, any dynamic
partitioning needs something in HW.