[Mesa-stable] Backport L3 cache control patches to 11.1

[Mark Janes]

Kenneth Graunke <kenneth at whitecape.org> writes:

> On Thursday, January 14, 2016 4:50:17 PM PST Mark Janes wrote:
>> Changes to the L3 configuration by non-mesa (eg, media) programs
>> interfere with mesa.  This affects media playback in ChromeOS.
>> 
>> Luckily, Curro made Mesa L3-aware in preparation for compute shaders.
>> His patches resolve media playback issues in ChromeOS.
>> 
>> Please backport the following commits to 11.1:
>
> I disagree, we should not backport these to Mesa stable releases.
>
> They are risky, have known regressions, and actually only work around
> bugs in other projects.

I wasn't aware of the regression.  For reference:

https://bugs.freedesktop.org/show_bug.cgi?id=93540
https://bugs.freedesktop.org/show_bug.cgi?id=93599

> libva needs to use a hardware context to protect itself from other
> userspace processes.  The kernel needs to initialize L3 as part of
> the golden context (the default state of new contexts).
>
> The Chrome team is welcome to carry patches with known caveats if
> they want, but I'm not comfortable shipping this upstream.

I doubt the Chrome team would want to ship their product with this
issue.

> --Ken