[PATCH] drm/i915: Fix userptr so we do not have to worry about obj->mm.lock, v8.

[Thomas Hellström (Intel)]

On 3/25/21 10:23 AM, Maarten Lankhorst wrote:
> Instead of doing what we do currently, which will never work with
> PROVE_LOCKING, do the same as AMD does, and something similar to
> relocation slowpath. When all locks are dropped, we acquire the
> pages for pinning. When the locks are taken, we transfer those
> pages in .get_pages() to the bo. As a final check before installing
> the fences, we ensure that the mmu notifier was not called; if it is,
> we return -EAGAIN to userspace to signal it has to start over.
>
> Changes since v1:
> - Unbinding is done in submit_init only. submit_begin() removed.
> - MMU_NOTFIER -> MMU_NOTIFIER
> Changes since v2:
> - Make i915->mm.notifier a spinlock.
> Changes since v3:
> - Add WARN_ON if there are any page references left, should have been 0.
> - Return 0 on success in submit_init(), bug from spinlock conversion.
> - Release pvec outside of notifier_lock (Thomas).
> Changes since v4:
> - Mention why we're clearing eb->[i + 1].vma in the code. (Thomas)
> - Actually check all invalidations in eb_move_to_gpu. (Thomas)
> - Do not wait when process is exiting to fix gem_ctx_persistence.userptr.
> Changes since v5:
> - Clarify why check on PF_EXITING is (temporarily) required.
> Changes since v6:
> - Ensure userptr validity is checked in set_domain through a special path.
> Changes since v7:
> - Chane kvfree to kvfree().

v8: Change "Chane kvfree to kvfree()" to "Change kfree() to kvfree()" ? :)

/Thomas