[Intel-gfx] [PATCH 6/7] drm/i915/ttm, drm/ttm: Introduce a TTM i915 gem object backend

[Thomas Hellström (Intel)]

On 5/11/21 3:58 PM, Christian König wrote:
> Am 11.05.21 um 15:25 schrieb Thomas Hellström:
>> Most logical place to introduce TTM buffer objects is as an i915
>> gem object backend. We need to add some ops to account for added
>> functionality like delayed delete and LRU list manipulation.
>>
>> Initially we support only LMEM and SYSTEM memory, but SYSTEM
>> (which in this case means evicted LMEM objects) is not
>> visible to i915 GEM yet. The plan is to move the i915 gem system region
>> over to the TTM system memory type in upcoming patches.
>>
>> We set up GPU bindings directly both from LMEM and from the system 
>> region,
>> as there is no need to use the legacy TTM_TT memory type. We reserve
>> that for future porting of GGTT bindings to TTM.
>>
>> There are some changes to TTM to allow for purging system memory buffer
>> objects and to refuse swapping of some objects: Unfortunately i915 gem
>> still relies heavily on short-term object pinning, and we've chosen to
>> keep short-term-pinned buffer objects on the TTM LRU lists for now,
>> meaning that we need some sort of mechanism to tell TTM they are not
>> swappable. A longer term goal is to get rid of the short-term pinning.
>
> Well just use the eviction_valuable interface for this.

Yes, we do that for vram/lmem eviction, but we have nothing similar for 
system swapping. Do I understand you correctly that you want me to add a 
call to eviction_valuable() also for that instead of swap_possible()?


>
> In general please make separate patches for the TTM changes and for 
> the i915 changes using them for easier review.

I'll respin with a split. Do you want me to do the same also for the 
other two patches that minmally touch TTM?

Thanks,

Thomas