On Thu, 2021-08-26 at 14:04 +0100, Tvrtko Ursulin wrote: > > On 26/08/2021 11:45, Thomas Hellström wrote: > > Pinned contexts, like the migrate contexts need reset after resume > > since their context image may have been lost. Also the GuC needs to > > register pinned contexts. > > So kernel context can get corrupt because we park the GPU with it > active. Blitter context for a different reason - which is that it is > used to copy itself over to smem, no? > > If that is correct, then why bother copying the blitter context in > the > first place and not just always re-create it on resume? > > That would be along the lines of marking the backing store as > "dontneed" > (however the exact mechanics of that look these days) so suspend can > skip them. I think that is marking the object with I915_BO_ALLOC_VOLATILE. However I assume this follows the rule of the internal backend objects: Contents are valid while pinned (or locked), and these images are indeed pinned on suspend so we need to come up with something else. Perhaps I915_BO_ALLOC_PM_NOSAVE for the context images (and engine status pages?) I915_BO_ALLOC_PM_MEMCPY for the migrate vm pagetables only. The latter will come in handy also for supporting small apertures where we need to pin these in the mappable area. > > > Add a list to struct intel_engine_cs where we add all pinned > > contexts on > > creation, and traverse that list at resume time to reset the pinned > > contexts. > > > > This fixes the kms_pipe_crc_basic@suspend-read-crc-pipe-a selftest > > for now, > > but proper LMEM backup / restore is needed for full suspend > > functionality. > > However, note that even with full LMEM backup / restore it may be > > desirable to keep the reset since backing up the migrate context > > images > > must happen using memcpy() after the migrate context has become > > inactive, > > and for performance- and other reasons we want to avoid memcpy() > > from > > LMEM. > > Hm I guess this talks about the issue - so are these images migrated > at > all today or not? My current WIP backs them up. But with something like the above flags, that's easily changed. Suggestions welcome. /Thomas
