Documentation/gpu: VM_BIND locking document

Add the first version of the VM_BIND locking document which is
intended to be part of the xe driver upstreaming agreement.

The document describes and discuss the locking used during exec-
functions, evicton and for userptr gpu-vmas. Intention is to be using the
same nomenclature as the drm-vm-bind-async.rst.

v2:
- s/gvm/gpu_vm/g (Rodrigo Vivi)
- Clarify the userptr seqlock with a pointer to mm/mmu_notifier.c
  (Rodrigo Vivi)
- Adjust commit message accordingly.
- Add SPDX license header.

v3:
- Large update to align with the drm_gpuvm manager locking
- Add "Efficient userptr gpu_vma exec function iteration" section
- Add "Locking at bind- and unbind time" section.

v4:
- Fix tabs vs space errors by untabifying (Rodrigo Vivi)
- Minor style fixes and typos (Rodrigo Vivi)
- Clarify situations where stale GPU mappings are occurring and how
  access through these mappings are blocked. (Rodrigo Vivi)
- Insert into the toctree in implementation_guidelines.rst

v5:
- Add a section about recoverable page-faults.
- Use local references to other documentation where possible
  (Bagas Sanjaya)
- General documentation fixes and typos (Danilo Krummrich and
  Boris Brezillon)
- Improve the documentation around locks that need to be grabbed from the
  dm-fence critical section (Boris Brezillon)
- Add more references to the DRM GPUVM helpers (Danilo Krummrich and
  Boriz Brezillon)
- Update the rfc/xe.rst document.

v6:
- Rework wording to improve readability (Boris Brezillon, Rodrigo Vivi,
  Bagas Sanjaya)
- Various minor fixes across the document (Boris Brezillon)

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Danilo Krummrich <dakr@redhat.com>
Acked-by: John Hubbard <jhubbard@nvidia.com> # Documentation/core-api/pin_user_pages.rst changes
Link: https://patchwork.freedesktop.org/patch/msgid/20231129090637.2629-1-thomas.hellstrom@linux.intel.com

1 files changed, 5 insertions, 0 deletions

diff --git a/Documentation/gpu/rfc/xe.rst b/Documentation/gpu/rfc/xe.rst
index c29113a0ac30..ceb21219d52e 100644
--- a/Documentation/gpu/rfc/xe.rst
+++ b/Documentation/gpu/rfc/xe.rst
@@ -123,10 +123,15 @@ Documentation should include:
 
  * O(1) complexity under VM_BIND.
 
+The document is now included in the drm documentation :doc:`here </gpu/drm-vm-bind-async>`.
+
 Some parts of userptr like mmu_notifiers should become GPUVA or DRM helpers when
 the second driver supporting VM_BIND+userptr appears. Details to be defined when
 the time comes.
 
+The DRM GPUVM helpers do not yet include the userptr parts, but discussions
+about implementing them are ongoing.
+
 Long running compute: minimal data structure/scaffolding
 --------------------------------------------------------
 The generic scheduler code needs to include the handling of endless compute