[Intel-gfx] [PATCH 02/18] drm/i915: Flush pages on acquisition

[Chris Wilson]

Quoting Chris Wilson (2019-03-20 12:35:51)
> The cost of the extra flushes is a worry, but not enough for me to be
> concerned about. I think the convention that get_pages == coherent on
> gpu improves quite a bit of our internal rummaging around and prevents
> the ABI nightmare of mmap_gtt/mmap_offset. Will this flush remain inside
> set_pages()? No, I don't think it will as pushing it into the callers
> outside of the mm.lock itself makes sense, but I didn't think that was
> of paramount importance compared to the uABI and can be done later.

Fwiw, the proxy object is one where we do want to move the clflush into
the caller (to avoid it on the proxy object)! So, it turns out to be
something I can't indefinitely postpone. (But that object also
desperately wants to break away from the whole object at once design.)
-Chris