[Intel-gfx] [PATCH 25/66] drm/i915/gem: Reintroduce multiple passes for reloc processing

[Thomas Hellström (Intel)]

On 7/15/20 1:51 PM, Chris Wilson wrote:
> The prospect of locking the entire submission sequence under a wide
> ww_mutex re-imposes some key restrictions, in particular that we must
> not call copy_(from|to)_user underneath the mutex (as the faulthandlers
> themselves may need to take the ww_mutex). To satisfy this requirement,
> we need to split the relocation handling into multiple phases again.
> After dropping the reservations, we need to allocate enough buffer space
> to both copy the relocations from userspace into, and serve as the
> relocation command buffer. Once we have finished copying the
> relocations, we can then re-aquire all the objects for the execbuf and
> rebind them, including our new relocations objects. After we have bound
> all the new and old objects into their final locations, we can then
> convert the relocation entries into the GPU commands to update the
> relocated vma. Finally, once it is all over and we have dropped the
> ww_mutex for the last time, we can then complete the update of the user
> relocation entries.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

Tvrtko had some issues with this patch when submitted as part of a 
previous series, and they don't seem addressed.

/Thomas