[Intel-gfx] [RFC PATCH 00/11] i915 HW context support

[Eugeni Dodonov]

On Tue, Feb 14, 2012 at 21:17, Adam Jackson <ajax at redhat.com> wrote:

> On 2/14/12 4:09 PM, Ben Widawsky wrote:
>
>  The IOCTLs defined here may also be used with ppgtt (real ppgtt) but the
>> interface may be insufficient for that. The contexts do provide a
>>
>>
> A... what?
>
> Series looks reasonable to me.  The one thing that makes me nervous is
> 4/11 mentioning the BIOS, which honestly seems like an insane thing to let
> your BIOS have _any_ say in, but then Intel sure does like to give the BIOS
> a chance to make the OS less functional.  The code in 7/11 effectively
> limits things to between 4k and 1M; does that actually make sense?  I can't
> imagine wanting to allocate only 4k if it turns out we'd always need at
> least (say) 32k.
>
> I have admittedly not read any of the docs on how this is meant to work,
> apologies if that'd answer this.
>

The high-level overview of this feature is that it adds support for having
a per-context set of GPU items the processes have access to. This is mostly
important for GL_ARB_Robustness [1] and GL_EXT_Transform_feedback [2].

So what it does is adding a possibility of having a different context id
for each set of operations. This way, what processes in one context_id do
should not affect the processes in another set. For GL_ARB_Robustness, it
could prevent one WebGL applications from taking down all the other users
of the GPU for example; and for GL_EXT_Transform_feedback it would allow
each process to have a way to store its own feedback data for different
stages of the pipeline. And so on.

As far as I know, it is also needed for full PPGTT support; but I don't
know this part good enough to give more in-depth answer (Daniel?)

(I hope it clarified the things a bit :))

[1] http://www.opengl.org/registry/specs/ARB/robustness.txt
[2] http://www.opengl.org/registry/specs/EXT/transform_feedback.txt

-- 
Eugeni Dodonov
 <http://eugeni.dodonov.net/>
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