[PATCH] drm/amdkfd: remove unnecessary cpu domain validation

[Christian König]

Am 03.03.25 um 22:01 schrieb Felix Kuehling:
> On 2025-03-03 13:48, Christian König wrote:
>> Am 03.03.25 um 19:45 schrieb James Zhu:
>>> before move to GTT domain.
>> That might not be unnecessary. We sometimes intentionally move BOs to the CPU domain to invalidate all VM mappings.
> We discussed this in our VM sync meeting this morning, and I wasn't 100% sure either. In this case it's causing a nearly live-lock of mutual evictions when two processes share the same BO and have both their eviction fences on the shared reservation object.
>
> I was thinking the VM invalidation should be taken care of by the DMABuf move notifier, so this explicit invalidation seemed redundant. Is there a way we can test or otherwise verify that we're not missing anything?

We used this hack to validate into system domain and then GTT for userptrs, but I can't think of any reason to do this for DMA-buf imports.

Regards,
Christian.

>
> Thanks,
>   Felix
>
>
>> Christian.
>>
>>> Signed-off-by: James Zhu <James.Zhu at amd.com>
>>> ---
>>>  drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c | 6 ------
>>>  1 file changed, 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>> index 62ca12e94581..2ac6d4fa0601 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd_gpuvm.c
>>> @@ -595,12 +595,6 @@ kfd_mem_dmamap_dmabuf(struct kfd_mem_attachment *attachment)
>>>  {
>>>  	struct ttm_operation_ctx ctx = {.interruptible = true};
>>>  	struct amdgpu_bo *bo = attachment->bo_va->base.bo;
>>> -	int ret;
>>> -
>>> -	amdgpu_bo_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_CPU);
>>> -	ret = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
>>> -	if (ret)
>>> -		return ret;
>>>  
>>>  	amdgpu_bo_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_GTT);
>>>  	return ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);