[Intel-gfx] [PATCH 35/39] drm/i915: Keep contexts pinned until after the next kernel context switch

[Chris Wilson]

Quoting Chris Wilson (2019-03-13 14:43:57)
> We need to keep the context image pinned in memory until after the GPU
> has finished writing into it. Since it continues to write as we signal
> the final breadcrumb, we need to keep it pinned until the request after
> it is complete. Currently we know the order in which requests execute on
> each engine, and so to remove that presumption we need to identify a
> request/context-switch we know must occur after our completion. Any
> request queued after the signal must imply a context switch, for
> simplicity we use a fresh request from the kernel context.

I'm not happy with the preallocation scheme for the active barrier yet.
But the general picture is here.
-Chris