[Intel-gfx] [PATCH 06/17] drm/i915/ringbuffer: Serialize load of PD_DIR

[Chris Wilson]

Quoting Chris Wilson (2018-06-10 20:43:14)
> After triggering the mm switch with a load of PD_DIR, which may be
> deferred unto the MI_SET_CONTEXT on rcs, serialise the next commands
> with that load by posting a read of PD_DIR (or else those subsequent
> commands may access the stale page tables).

My stress test failed over night. Much improved MTBF, but not eliminated
yet. Next step is to follow the STORE_REG_MEM with an
engine->emit_flush(EMIT_INVALIDATE).

I think we are indeed on the right track, and that these are much more
than random delays.
-Chris