[Intel-gfx] [PATCH] drm/i915: Mark contents as dirty on a write fault

[Chris Wilson]

Quoting Chris Wilson (2019-09-20 13:22:13)
> Quoting Chris Wilson (2019-09-20 13:18:21)
> > Since dropping the set-to-gtt-domain in commit a679f58d0510 ("drm/i915:
> > Flush pages on acquisition"), we no longer mark the contents as dirty on
> > a write fault. This has the issue of us then not marking the pages as
> > dirty on releasing the buffer, which means the contents are not written
> > out to the swap device (should we ever pick that buffer as a victim).
> > Notably, this is visible in the dumb buffer interface used for cursors.
> > Having updated the cursor contents via mmap, and swapped away, if the
> > shrinker should evict the old cursor, upon next reuse, the cursor would
> > be invisible.
> 
> Hmm, I think the dumb interface may be missing a few steps around the
> place to ensure the contents are flushed.

No, it's fine. We do the flush in pinning pages, the only thing that was
dropped was then marking the content as dirty.
-Chris