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

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