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

[Felix Kuehling <felix.kuehling@amd.com>]

On 2025-03-04 5:38, Christian König wrote:
>
> 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.

OK, I had the same intuition. In that case the patch is

Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>


>
> Regards,
> Christian.
>
>> Thanks,
>>   Felix
>>
>>
>>> Christian.
>>>
>>>> Signed-off-by: James Zhu <James.Zhu@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);