Re: [PATCH drm-misc-next v7 4/7] drm/gpuvm: add an abstraction for a VM / BO combination

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On 10/31/23 12:25, Thomas Hellström wrote:
On Mon, 2023-10-23 at 22:16 +0200, Danilo Krummrich wrote:
Add an abstraction layer between the drm_gpuva mappings of a
particular
drm_gem_object and this GEM object itself. The abstraction represents
a
combination of a drm_gem_object and drm_gpuvm. The drm_gem_object
holds
a list of drm_gpuvm_bo structures (the structure representing this
abstraction), while each drm_gpuvm_bo contains list of mappings of
this
GEM object.

This has multiple advantages:

1) We can use the drm_gpuvm_bo structure to attach it to various
lists
    of the drm_gpuvm. This is useful for tracking external and evicted
    objects per VM, which is introduced in subsequent patches.

2) Finding mappings of a certain drm_gem_object mapped in a certain
    drm_gpuvm becomes much cheaper.

3) Drivers can derive and extend the structure to easily represent
    driver specific states of a BO for a certain GPUVM.

The idea of this abstraction was taken from amdgpu, hence the credit
for
this idea goes to the developers of amdgpu.

Cc: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
  drivers/gpu/drm/drm_gpuvm.c            | 335 +++++++++++++++++++++--
--
  drivers/gpu/drm/nouveau/nouveau_uvmm.c |  64 +++--
  include/drm/drm_gem.h                  |  32 +--
  include/drm/drm_gpuvm.h                | 188 +++++++++++++-
  4 files changed, 533 insertions(+), 86 deletions(-)

That checkpatch.pl error still remains as well.

I guess you refer to:

ERROR: do not use assignment in if condition
#633: FILE: drivers/gpu/drm/nouveau/nouveau_uvmm.c:1165:
+                       if (!(op->gem.obj = obj))

This was an intentional decision, since in this specific case it seems to
be more readable than the alternatives.

However, if we consider this to be a hard rule, which we never ever break,
I'm fine changing it too.


Thanks,
Thomas





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