Re: [PATCH 01/10] drm/i915/guc: Precompute GuC shared data offset

[Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>]

On 05/10/17 02:33, Chris Wilson wrote:
> Quoting Michał Winiarski (2017-10-05 10:13:40)
>> We're using first page of kernel context state to share data with GuC,
>> let's precompute the ggtt offset at GuC initialization time rather than
>> everytime we're using GuC actions.
> 
> So LRC_GUCSHR_PN is still 0. Plans for that to change?
> 

This is a requirement from the GuC side. GuC expects each context to 
have that extra page before the PPHWSP and it uses it to dump some 
per-lrc info, part of which is for internal use and part is info for the 
host (although we don't need/use it).
On certain events (reset/preempt/suspend etc) GuC will dump extra info 
and this is done in the page provided in the H2G. I think we use the one 
of the default ctx just for simplicity, but it should be possible to use 
a different one, possibly not attached to any lrc if needed, but I'm not 
sure if this has ever been tested.

-Daniele

> Atm, we should be changing one pointer deref for another...
> -Chris
>>
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