Re: [PATCH v2 3/4] drm/amdkfd: Move gfx9 MQD to VRAM domain

[Philip Yang <yangp@amd.com>]

On 2025-12-03 12:55, Kuehling, Felix wrote:
> On 2025-12-01 09:28, Philip Yang wrote:
>> To reduce queue switch latency further, move MQD to VRAM domain, add
>> AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS flag to allocate contiguous pages
>> using one buddy block.
>
> Why does it need to be contiguous? In the next patch you're mapping it 
> in the GART anyway.
Without AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS flag, amdgpu_bo_gpu_offset 
trigger this warning

     WARN_ON_ONCE(bo->tbo.resource->mem_type == TTM_PL_VRAM &&
              !(bo->flags & AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS));

This makes senses because we pass the FB aperture address to CP, this 
should be contiguous pages.

Regards,
Philip
>
> Regards,
>   Felix
>
>
>>
>> Signed-off-by: Philip Yang <Philip.Yang@amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c      | 3 ++-
>>   drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c | 2 +-
>>   2 files changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
>> index 9cd1660b8f60..c11e37915365 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c
>> @@ -329,7 +329,8 @@ int amdgpu_amdkfd_alloc_gtt_mem(struct 
>> amdgpu_device *adev, size_t size,
>>       bp.size = size;
>>       bp.byte_align = PAGE_SIZE;
>>       bp.domain = domain;
>> -    bp.flags = AMDGPU_GEM_CREATE_CPU_GTT_USWC;
>> +    bp.flags = AMDGPU_GEM_CREATE_VRAM_CONTIGUOUS |
>> +           AMDGPU_GEM_CREATE_CPU_GTT_USWC;
>>       bp.type = ttm_bo_type_kernel;
>>       bp.resv = NULL;
>>       bp.bo_ptr_size = sizeof(struct amdgpu_bo);
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c 
>> b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
>> index a489d43d5f64..c6945c842267 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_mqd_manager_v9.c
>> @@ -139,7 +139,7 @@ static struct kfd_mem_obj *allocate_mqd(struct 
>> kfd_node *node,
>>               (ALIGN(q->ctl_stack_size, PAGE_SIZE) +
>>               ALIGN(sizeof(struct v9_mqd), PAGE_SIZE)) *
>>               NUM_XCC(node->xcc_mask),
>> -            AMDGPU_GEM_DOMAIN_GTT,
>> +            AMDGPU_GEM_DOMAIN_VRAM,
>>               &(mqd_mem_obj->gtt_mem),
>>               &(mqd_mem_obj->gpu_addr),
>>               (void *)&(mqd_mem_obj->cpu_ptr), true);