Re: [PATCH] drm/i915/ppgtt: Load address space after mi_set_context

[Michel Thierry <michel.thierry@intel.com>]

On 9/12/2014 4:40 PM, Chris Wilson wrote:
> On Fri, Sep 12, 2014 at 06:35:10PM +0300, Ville Syrjälä wrote:
>> On Fri, Sep 12, 2014 at 04:10:01PM +0100, Michel Thierry wrote:
>>> From: Ben Widawsky <benjamin.widawsky@intel.com>
>>>
>>> The simple explanation is, the docs say to do this for GEN8. Perhaps we
>>> want to do this for GEN7 too, I am not certain.
>>>
>>> PDPs are saved and restored with context. Contexts (without execlists)
>>> only exist on the render ring. The docs say that PDPs are not power
>>> context save/restored.  I've learned that this actually means something
>>> which SW doesn't care about. So pretend the statement doesn't exist.
>>> For non RCS, nothing changes.
>
> Hang on. This is exactly what I was worried about... Which PDPs are
> saved with context? Why doesn't this mean that we aren't overwitting
> PDPs in use on other rings when RCS loads a new context?
> -Chris
>

I was wondering the same when I read Ben's original comment. Could this 
be GEN8 specific?