Re: [PATCH v2 1/7] drm/i915/gen8: Add infrastructure to initialize WA batch buffers

["Siluvery, Arun" <arun.siluvery@linux.intel.com>]

On 01/06/2015 11:22, Daniel, Thomas wrote:
>>
>> Indeed, allocating an extra scratch page in the context would simplify
>> vma/mm management. A trick might be to allocate the scratch page at the
>> start, then offset the lrc regs etc - that would then be consistent
>> amongst gen and be easy enough to extend if we need more per-context
>> scratch space in future.
>> -Chris
>
> Yes, I think we already have another use for more per-context space at the start.  The GuC is planning to do this.  Arun, you probably should work with Alex Dai and Dave Gordon to avoid conflicts here.
>
> Thomas.
>

Thanks for the heads-up Thomas.
I have discussed with Dave and agreed to share this page;
GuC probably doesn't need whole page so first half is reserved for it's 
use and second half is used for WA.

I have modified my patches to use context page for applying these WA and 
don't see any issues.

During the discussions Dave proposed another approach. Even though these 
WA are called per context they are only initialized once and not changed 
afterwards, same set of WA are applied for each context so instead of 
adding them in each context, does it make sense to create a separate 
page and share across all contexts? but ofcourse GuC will anyway add a 
new page to context so I might as well share that page.

Chris/Dave, do you see any problems with sharing page with GuC or you 
prefer to allocate a separate page for these WA and share across all 
contexts? Please give your comments.

regards
Arun


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