Re: [PATCH v4 0/3] Introduce support for C linked list interfacing and GPU Buddy bindings

[Joel Fernandes <joelagnelf@nvidia.com>]

> On Dec 4, 2025, at 4:53 PM, Joel Fernandes <joelagnelf@nvidia.com> wrote:
> 
> This series combines a number of other series which build up to the same goal:
> to make it possible to use DRM buddy from nova-core rust code. See links to the
> different series below.
> 
> The git tree with all patches can be found at:
> git://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git (tag: clist-buddy-v4-20251204)

FYI - this series is rebased on linux-next to reduce conflicts, but I am happy to rebase on another tree if needed/requested.

Thanks,

 - Joel





> 
> Changes for v4:
> - Combined the clist and drm buddy series:
>  - A rust module (CList) to access circular linked lists from rust code.
>  - DRM buddy allocator bindings that were originally part of RFC.
>  - DRM buddy allocator one level up to drivers/gpu/ so it can be used by
>     GPU drivers (example, nova-core) that have usecases other than DRM.
> - Add Rust bindings for the GPU buddy allocator.
> 
> Notes from past cover letters about CList:
> 
> Introduction
> ============
> This patchset introduces an interface to iterate over doubly circular linked
> lists used in the kernel (allocated by C kernel code). The main usecase is
> iterating over the list of blocks provided by the GPU buddy allocator.
> 
> The series also moves the DRM buddy allocator one level up and adds Rust
> bindings for it, enabling GPU drivers like nova-core to use it.
> 
> A question may arise: Why not use rust list.rs for this?
> =========================================================
> Rust's list.rs is used to provide safe intrusive lists for Rust-allocated
> items. In doing so, it takes ownership of the items in the list and the links
> between list items. However, the usecase for GPU buddy allocator bindings, the
> C side allocates the items in the list, and also links the list together. Due
> to this, there is an ownership conflict making list.rs not the best abstraction
> for this usecase. What we need is a view of the list, not ownership of it.
> Further, the list links in a bindings usecase may come from C allocated
> objects, not from the Rust side.
> 
> Link to v2 (clist only): https://lore.kernel.org/all/20251111171315.2196103-4-joelagnelf@nvidia.com/
> 
> Notes and patches about DRM buddy code movement and DRM buddy bindings:
> 
> Link to RFC: https://lore.kernel.org/all/20251030190613.1224287-1-joelagnelf@nvidia.com/
> Link to DRM buddy move discussion: https://lore.kernel.org/all/20251124234432.1988476-1-joelagnelf@nvidia.com/
> 
> Joel Fernandes (3):
>  rust: clist: Add support to interface with C linked lists
>  gpu: Move DRM buddy allocator one level up
>  rust: gpu: Add GPU buddy allocator bindings
> 
> Documentation/gpu/drm-mm.rst                  |   10 +-
> MAINTAINERS                                   |    7 +
> drivers/gpu/Kconfig                           |   13 +
> drivers/gpu/Makefile                          |    2 +
> drivers/gpu/buddy.c                           | 1310 +++++++++++++++++
> drivers/gpu/drm/Kconfig                       |    1 +
> drivers/gpu/drm/Kconfig.debug                 |    4 +-
> drivers/gpu/drm/amd/amdgpu/Kconfig            |    1 +
> drivers/gpu/drm/amd/amdgpu/amdgpu_ras.c       |    2 +-
> .../gpu/drm/amd/amdgpu/amdgpu_res_cursor.h    |   12 +-
> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c  |   80 +-
> drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.h  |   20 +-
> drivers/gpu/drm/drm_buddy.c                   | 1287 +---------------
> drivers/gpu/drm/i915/Kconfig                  |    1 +
> drivers/gpu/drm/i915/i915_scatterlist.c       |   10 +-
> drivers/gpu/drm/i915/i915_ttm_buddy_manager.c |   55 +-
> drivers/gpu/drm/i915/i915_ttm_buddy_manager.h |    6 +-
> .../drm/i915/selftests/intel_memory_region.c  |   20 +-
> drivers/gpu/drm/tests/Makefile                |    1 -
> .../gpu/drm/ttm/tests/ttm_bo_validate_test.c  |    5 +-
> drivers/gpu/drm/ttm/tests/ttm_mock_manager.c  |   18 +-
> drivers/gpu/drm/ttm/tests/ttm_mock_manager.h  |    4 +-
> drivers/gpu/drm/xe/Kconfig                    |    1 +
> drivers/gpu/drm/xe/xe_res_cursor.h            |   34 +-
> drivers/gpu/drm/xe/xe_svm.c                   |   12 +-
> drivers/gpu/drm/xe/xe_ttm_vram_mgr.c          |   73 +-
> drivers/gpu/drm/xe/xe_ttm_vram_mgr_types.h    |    4 +-
> drivers/gpu/tests/Makefile                    |    3 +
> .../gpu_buddy_test.c}                         |  390 ++---
> drivers/gpu/tests/gpu_random.c                |   48 +
> drivers/gpu/tests/gpu_random.h                |   28 +
> drivers/video/Kconfig                         |    2 +
> include/drm/drm_buddy.h                       |  163 +-
> include/linux/gpu_buddy.h                     |  177 +++
> rust/bindings/bindings_helper.h               |   11 +
> rust/helpers/gpu.c                            |   23 +
> rust/helpers/helpers.c                        |    2 +
> rust/helpers/list.c                           |   12 +
> rust/kernel/clist.rs                          |  357 +++++
> rust/kernel/gpu/buddy.rs                      |  527 +++++++
> rust/kernel/gpu/mod.rs                        |    5 +
> rust/kernel/lib.rs                            |    3 +
> 42 files changed, 2944 insertions(+), 1800 deletions(-)
> create mode 100644 drivers/gpu/Kconfig
> create mode 100644 drivers/gpu/buddy.c
> create mode 100644 drivers/gpu/tests/Makefile
> rename drivers/gpu/{drm/tests/drm_buddy_test.c => tests/gpu_buddy_test.c} (68%)
> create mode 100644 drivers/gpu/tests/gpu_random.c
> create mode 100644 drivers/gpu/tests/gpu_random.h
> create mode 100644 include/linux/gpu_buddy.h
> create mode 100644 rust/helpers/gpu.c
> create mode 100644 rust/helpers/list.c
> create mode 100644 rust/kernel/clist.rs
> create mode 100644 rust/kernel/gpu/buddy.rs
> create mode 100644 rust/kernel/gpu/mod.rs
> 
> --
> 2.34.1
>