Re: [PATCH drm-misc-next v5 0/6] [RFC] DRM GPUVM features

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

Hi, Danilo

On 9/28/23 21:16, Danilo Krummrich wrote:
> Currently GPUVM offers common infrastructure to track GPU VA allocations
> and mappings, generically connect GPU VA mappings to their backing
> buffers and perform more complex mapping operations on the GPU VA space.
>
> However, there are more design patterns commonly used by drivers, which
> can potentially be generalized in order to make GPUVM represent the
> basis of a VM implementation. In this context, this patch series aims at
> generalizing the following elements.
>
> 1) Provide a common dma-resv for GEM objects not being used outside of
>     this GPU-VM.
>
> 2) Provide tracking of external GEM objects (GEM objects which are
>     shared with other GPU-VMs).
>
> 3) Provide functions to efficiently lock all GEM objects dma-resv the
>     GPU-VM contains mappings of.
>
> 4) Provide tracking of evicted GEM objects the GPU-VM contains mappings
>     of, such that validation of evicted GEM objects is accelerated.
>
> 5) Provide some convinience functions for common patterns.
>
> The implementation introduces struct drm_gpuvm_bo, which serves as abstraction
> combining a struct drm_gpuvm and struct drm_gem_object, similar to what
> amdgpu does with struct amdgpu_bo_vm. While this adds a bit of complexity it
> improves the efficiency of tracking external and evicted GEM objects.
>
> This patch series is also available at [3].
>
> [1] https://gitlab.freedesktop.org/nouvelles/kernel/-/commits/gpuvm-next
>
> Changes in V2:
> ==============
>    - rename 'drm_gpuva_manager' -> 'drm_gpuvm' which generally leads to more
>      consistent naming
>    - properly separate commits (introduce common dma-resv, drm_gpuvm_bo
>      abstraction, etc.)
>    - remove maple tree for tracking external objects, use a list drm_gpuvm_bos
>      per drm_gpuvm instead
>    - rework dma-resv locking helpers (Thomas)
>    - add a locking helper for a given range of the VA space (Christian)
>    - make the GPUVA manager buildable as module, rather than drm_exec
>      builtin (Christian)
>
> Changes in V3:
> ==============
>    - rename missing function and files (Boris)
>    - warn if vm_obj->obj != obj in drm_gpuva_link() (Boris)
>    - don't expose drm_gpuvm_bo_destroy() (Boris)
>    - unlink VM_BO from GEM in drm_gpuvm_bo_destroy() rather than
>      drm_gpuva_unlink() and link within drm_gpuvm_bo_obtain() to keep
>      drm_gpuvm_bo instances unique
>    - add internal locking to external and evicted object lists to support drivers
>      updating the VA space from within the fence signalling critical path (Boris)
>    - unlink external objects and evicted objects from the GPUVM's list in
>      drm_gpuvm_bo_destroy()
>    - add more documentation and fix some kernel doc issues
>
> Changes in V4:
> ==============
>    - add a drm_gpuvm_resv() helper (Boris)
>    - add a drm_gpuvm::<list_name>::local_list field (Boris)
>    - remove drm_gpuvm_bo_get_unless_zero() helper (Boris)
>    - fix missing NULL assignment in get_next_vm_bo_from_list() (Boris)
>    - keep a drm_gem_object reference on potential vm_bo destroy (alternatively we
>      could free the vm_bo and drop the vm_bo's drm_gem_object reference through
>      async work)
>    - introduce DRM_GPUVM_RESV_PROTECTED flag to indicate external locking through
>      the corresponding dma-resv locks to optimize for drivers already holding
>      them when needed; add the corresponding lock_assert_held() calls (Thomas)
>    - make drm_gpuvm_bo_evict() per vm_bo and add a drm_gpuvm_bo_gem_evict()
>      helper (Thomas)
>    - pass a drm_gpuvm_bo in drm_gpuvm_ops::vm_bo_validate() (Thomas)
>    - documentation fixes
>
> Changes in V5:
> ==============
>    - use a root drm_gem_object provided by the driver as a base for the VM's
>      common dma-resv (Christian)
>    - provide a helper to allocate a "dummy" root GEM object in case a driver
>      specific root GEM object isn't available
>    - add a dedicated patch for nouveau to make use of the GPUVM's shared dma-resv
>    - improve documentation (Boris)
>    - the following patches are removed from the series, since they already landed
>      in drm-misc-next
>      - f72c2db47080 ("drm/gpuvm: rename struct drm_gpuva_manager to struct drm_gpuvm")
>      - fe7acaa727e1 ("drm/gpuvm: allow building as module")
>      - 78f54469b871 ("drm/nouveau: uvmm: rename 'umgr' to 'base'")
>
> Danilo Krummrich (6):
>    drm/gpuvm: add common dma-resv per struct drm_gpuvm
>    drm/gpuvm: add drm_gpuvm_flags to drm_gpuvm
>    drm/gpuvm: add an abstraction for a VM / BO combination
>    drm/gpuvm: track/lock/validate external/evicted objects
>    drm/nouveau: make use of the GPUVM's shared dma-resv
>    drm/nouveau: use GPUVM common infrastructure
>
>   drivers/gpu/drm/drm_gpuvm.c             | 1036 +++++++++++++++++++++--
>   drivers/gpu/drm/nouveau/nouveau_bo.c    |   15 +-
>   drivers/gpu/drm/nouveau/nouveau_bo.h    |    5 +
>   drivers/gpu/drm/nouveau/nouveau_exec.c  |   52 +-
>   drivers/gpu/drm/nouveau/nouveau_exec.h  |    4 -
>   drivers/gpu/drm/nouveau/nouveau_gem.c   |   10 +-
>   drivers/gpu/drm/nouveau/nouveau_sched.h |    4 +-
>   drivers/gpu/drm/nouveau/nouveau_uvmm.c  |  183 ++--
>   drivers/gpu/drm/nouveau/nouveau_uvmm.h  |    1 -
>   include/drm/drm_gem.h                   |   32 +-
>   include/drm/drm_gpuvm.h                 |  465 +++++++++-
>   11 files changed, 1625 insertions(+), 182 deletions(-)
>
>
> base-commit: a4ead6e37e3290cff399e2598d75e98777b69b37

One comment I had before on the GPUVM code in general was the licensing, 
but I'm not sure there was a reply. Is it possible to have this code 
dual MIT / GPLV2?

Thanks,

Thomas