[PATCH 3/8] drm/amdgpu: Implement mmap as GEM object function

[Christian König]

Am 06.04.21 um 14:52 schrieb Thomas Zimmermann:
> Hi
>
> Am 06.04.21 um 14:42 schrieb Christian König:
>> Hi Thomas,
>>
>> Am 06.04.21 um 13:55 schrieb Thomas Zimmermann:
>>> Hi
>>>
>>> Am 06.04.21 um 12:56 schrieb Christian König:
>>>>>
>>>>> In the end I went with the semantics I found in amdgpu_mmap() and 
>>>>> handled KFD specially. Let me know if this requires to be changed.
>>>>
>>>> Well the question is where is the call to 
>>>> drm_vma_node_verify_access() now? Cause that needs to be skipped 
>>>> for KFD BOs.
>>>
>>> I see. It's now drm_vma_node_is_allowed(); called by drm_gem_mmap(). 
>>> [1] So drm_gem_mmap() cannot be used by amdgpu.
>>>
>>> If I understand the code at [2] correctly, KFD objects don't use the 
>>> GEM ioctl interfaces, but they still use the internal GEM object 
>>> that is part of the TTM BO. In this case, amdgpu could have its own 
>>> version of drm_gem_mmap(), which calls drm_gem_mmap_obj(), [3] which 
>>> in turn handles the mmap details via GEM object functions.
>>
>> Correct, well we could cleanup the KFD to use the GEM functions as well.
>
> The KFD code already calls amdgpu_gem_object_create(). It should have 
> the object-functions pointer set for use with mmap. Not sure what the 
> use of drm_vma_node_is_allowed() would involve.

The KFD allows BOs to be mmaped with different offsets than what's used 
in the DRM node.

So drm_vma_node_is_allowed() would return false as far as I know.

Regards,
Christian.

>
> Best regards
> Thomas
>
>>
>> Felix what exactly was your objections to using this?
>>
>> Regards,
>> Christian.
>>
>>>
>>> drm_gem_prime_mmap() doesn't do any additional verification.
>>>
>>> Best regards
>>> Thomas
>>>
>>> [1] 
>>> https://elixir.bootlin.com/linux/v5.11.11/source/drivers/gpu/drm/drm_gem.c#L1156 
>>>
>>> [2] 
>>> https://elixir.bootlin.com/linux/v5.11.11/source/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c#L1224 
>>>
>>> [3] 
>>> https://elixir.bootlin.com/linux/v5.12-rc6/source/drivers/gpu/drm/drm_gem.c#L1053 
>>>
>>>
>>>
>>>>
>>>> Regards,
>>>> Christian.
>>>>
>>>>>
>>>>> Best regards
>>>>> Thomas
>>>>>
>>>>>>> -
>>>>>>>   int amdgpu_copy_buffer(struct amdgpu_ring *ring, uint64_t 
>>>>>>> src_offset,
>>>>>>>                  uint64_t dst_offset, uint32_t byte_count,
>>>>>>>                  struct dma_resv *resv,
>>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h 
>>>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>>>>>>> index dec0db8b0b13..6e51faad7371 100644
>>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>>>>>>> @@ -146,7 +146,6 @@ int amdgpu_fill_buffer(struct amdgpu_bo *bo,
>>>>>>>               struct dma_resv *resv,
>>>>>>>               struct dma_fence **fence);
>>>>>>> -int amdgpu_mmap(struct file *filp, struct vm_area_struct *vma);
>>>>>>>   int amdgpu_ttm_alloc_gart(struct ttm_buffer_object *bo);
>>>>>>>   int amdgpu_ttm_recover_gart(struct ttm_buffer_object *tbo);
>>>>>>>   uint64_t amdgpu_ttm_domain_start(struct amdgpu_device *adev, 
>>>>>>> uint32_t type);
>>>>>>
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>>>>>
>>>>
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