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

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

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?

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);