[Intel-gfx] [PATCH v5] drm/i915: Add soft-pinning API for execbuffer

[Chris Wilson]

On Mon, Jul 20, 2015 at 05:41:44PM +0100, Thomas Daniel wrote:
> From: Chris Wilson <chris at chris-wilson.co.uk>
> 
> Userspace can pass in an offset that it presumes the object is located
> at. The kernel will then do its utmost to fit the object into that
> location. The assumption is that userspace is handling its own object
> locations (for example along with full-ppgtt) and that the kernel will
> rarely have to make space for the user's requests.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> 
> v2: Fixed incorrect eviction found by Michal Winiarski - fix suggested by Chris
> Wilson.  Fixed incorrect error paths causing crash found by Michal Winiarski.
> (Not published externally)
> 
> v3: Rebased because of trivial conflict in object_bind_to_vm.  Fixed eviction
> to allow eviction of soft-pinned objects when another soft-pinned object used
> by a subsequent execbuffer overlaps reported by Michal Winiarski.
> (Not published externally)
> 
> v4: Moved soft-pinned objects to the front of ordered_vmas so that they are
> pinned first after an address conflict happens to avoid repeated conflicts in
> rare cases (Suggested by Chris Wilson).  Expanded comment on
> drm_i915_gem_exec_object2.offset to cover this new API.
> 
> v5: Added I915_PARAM_HAS_EXEC_SOFTPIN parameter for detecting this capability
> (Kristian). Added check for multiple pinnings on eviction (Akash). Made sure
> buffers are not considered misplaced without the user specifying
> EXEC_OBJECT_SUPPORTS_48BBADDRESS.  User must assume responsibility for any
> addressing workarounds.  Updated object2.offset field comment again to clarify
> NO_RELOC case (Chris).  checkpatch cleanup.

There are a couple of requirements we need first. One we have to be able
to use our vm on any engine, and the second is that without fixing the
list iterator in drm_mm using softpining ends up as a performance
regression.

It would be nice if people reviewed patches so that I can get those
fixes in.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre