[Intel-gfx] [PATCH 0/7] Commit early to GuC

[Daniele Ceraolo Spurio]

On 1/15/2020 12:40 AM, Chris Wilson wrote:
> Quoting Daniele Ceraolo Spurio (2020-01-15 01:31:36)
>> We currently wait until we attempt to load the GuC to confirm if we're
>> in GuC mode or not, at which point a lot of the engine setup has already
>> happened and needs to be updated for GuC submission. To allow us to get
>> the setup done directly into GuC mode, we need to commit to using GuC
>> as soon as possible.
> I think this is the wrong direction; as I thought the goal was to allow
> delayed loading of firmware, even going as far as allowing the system to
> run a browser for the user to get the firmware first. I may be

We do indeed want to keep supporting execlists mode even as some HW 
features move to the GuC to allow the user to get to the binaries, but 
we don't want to switch between the 2 modes without a reboot. Switching 
between the 2 modes is not a HW capability that we're committed to; the 
guc->elsp transition is already not possible, while the elsp->guc one 
still seems to work, but who knows for how long it will?

This series is also not really changing the commitment at the 
implementation level, just making it "official" and acting based on 
that. Even without these patches, if the blobs are on the system we will 
attempt to get into GuC mode unless we get an allocation failure or 
something similar, in which case it is extremely likely that the 
fall-back to non-guc will not work either.

> completely wrong about that, but imho I never want to have to build
> firmware images into the kernel.

I do 100% agree with this statement, although I'm not sure how this 
relates to the series. Are you planning to pull some of the engine setup 
to an even earlier point?

>
> The transition from execlists to guc could be just set-wedged; delete
> old engines, build guc engines. [This should also work for guc -> guc.]
> Throwing away context state is ugly, but simple enough.

As mentioned above, we can't switch between elsp and GuC modes so this 
transition would have to be done before the first submission to HW. Why 
not go directly in GuC mode then?

Daniele

> -Chris