Re: [PATCH v2 04/20] drm/amdgpu: introduce amdgpu_ttm_buffer_entity

Felix Kuehling
2025-11-14T20:18:49Z

On 2025-11-14 07:57, Christian König wrote:
> On 11/13/25 17:05, Pierre-Eric Pelloux-Prayer wrote:
>> No functional change for now, but this struct will have more
>> fields added in the next commit.
>>
>> Technically the change introduces synchronisation issue, because
>> dependencies between successive jobs are not taken care of
>> properly. For instance, amdgpu_ttm_clear_buffer uses
>> amdgpu_ttm_map_buffer then amdgpu_ttm_fill_mem which use
>> different entities (default_entity then move/clear entity).
>> But it's all working as expected, because all entities use the
>> same sdma instance for now and default_entity has a higher prio
>> so its job always gets scheduler first.
>>
>> The next commits will deal with these dependencies correctly.
>>
>> ---
>> v2: renamed amdgpu_ttm_buffer_entity
>> ---
>>
>> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
> Reviewed-by: Christian König <christian.koenig@amd.com>
>
>> ---
>> drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c | 2 +-
>> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 30 +++++++++++++++++-------
>> drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h | 12 ++++++----
>> drivers/gpu/drm/amd/amdkfd/kfd_migrate.c | 13 ++++++----
>> 4 files changed, 39 insertions(+), 18 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
>> index 9dcf51991b5b..8e2d41c9c271 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c
>> @@ -687,7 +687,7 @@ void amdgpu_gmc_flush_gpu_tlb(struct amdgpu_device *adev, uint32_t vmid,
>> * itself at least for GART.
>> */
>> mutex_lock(&adev->mman.gtt_window_lock);
>> - r = amdgpu_job_alloc_with_ib(ring->adev, &adev->mman.high_pr,
>> + r = amdgpu_job_alloc_with_ib(ring->adev, &adev->mman.default_entity.base,
>> AMDGPU_FENCE_OWNER_UNDEFINED,
>> 16 * 4, AMDGPU_IB_POOL_IMMEDIATE,
>> &job, AMDGPU_KERNEL_JOB_ID_FLUSH_GPU_TLB);
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> index c985f57fa227..42d448cd6a6d 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
>> @@ -224,7 +224,7 @@ static int amdgpu_ttm_map_buffer(struct ttm_buffer_object *bo,
>> num_dw = ALIGN(adev->mman.buffer_funcs->copy_num_dw, 8);
>> num_bytes = num_pages * 8 * AMDGPU_GPU_PAGES_IN_CPU_PAGE;
>>
>> - r = amdgpu_job_alloc_with_ib(adev, &adev->mman.high_pr,
>> + r = amdgpu_job_alloc_with_ib(adev, &adev->mman.default_entity.base,
>> AMDGPU_FENCE_OWNER_UNDEFINED,
>> num_dw * 4 + num_bytes,
>> AMDGPU_IB_POOL_DELAYED, &job,
>> @@ -1486,7 +1486,7 @@ static int amdgpu_ttm_access_memory_sdma(struct ttm_buffer_object *bo,
>> memcpy(adev->mman.sdma_access_ptr, buf, len);
>>
>> num_dw = ALIGN(adev->mman.buffer_funcs->copy_num_dw, 8);
>> - r = amdgpu_job_alloc_with_ib(adev, &adev->mman.high_pr,
>> + r = amdgpu_job_alloc_with_ib(adev, &adev->mman.default_entity.base,
>> AMDGPU_FENCE_OWNER_UNDEFINED,
>> num_dw * 4, AMDGPU_IB_POOL_DELAYED,
>> &job,
>> @@ -2168,7 +2168,7 @@ void amdgpu_ttm_set_buffer_funcs_status(struct amdgpu_device *adev, bool enable)
>>
>> ring = adev->mman.buffer_funcs_ring;
>> sched = &ring->sched;
>> - r = drm_sched_entity_init(&adev->mman.high_pr,
>> + r = drm_sched_entity_init(&adev->mman.default_entity.base,
>> DRM_SCHED_PRIORITY_KERNEL, &sched,
>> 1, NULL);
>> if (r) {
>> @@ -2178,18 +2178,30 @@ void amdgpu_ttm_set_buffer_funcs_status(struct amdgpu_device *adev, bool enable)
>> return;
>> }
>>
>> - r = drm_sched_entity_init(&adev->mman.low_pr,
>> + r = drm_sched_entity_init(&adev->mman.clear_entity.base,
>> + DRM_SCHED_PRIORITY_NORMAL, &sched,
>> + 1, NULL);
>> + if (r) {
>> + dev_err(adev->dev,
>> + "Failed setting up TTM BO clear entity (%d)\n",
>> + r);
>> + goto error_free_entity;
>> + }
>> +
>> + r = drm_sched_entity_init(&adev->mman.move_entity.base,
>> DRM_SCHED_PRIORITY_NORMAL, &sched,
>> 1, NULL);
>> if (r) {
>> dev_err(adev->dev,
>> "Failed setting up TTM BO move entity (%d)\n",
>> r);
>> + drm_sched_entity_destroy(&adev->mman.clear_entity.base);
>> goto error_free_entity;
>> }
>> } else {
>> - drm_sched_entity_destroy(&adev->mman.high_pr);
>> - drm_sched_entity_destroy(&adev->mman.low_pr);
>> + drm_sched_entity_destroy(&adev->mman.default_entity.base);
>> + drm_sched_entity_destroy(&adev->mman.clear_entity.base);
>> + drm_sched_entity_destroy(&adev->mman.move_entity.base);
>> for (i = 0; i < TTM_NUM_MOVE_FENCES; i++) {
>> dma_fence_put(man->eviction_fences[i]);
>> man->eviction_fences[i] = NULL;
>> @@ -2207,7 +2219,7 @@ void amdgpu_ttm_set_buffer_funcs_status(struct amdgpu_device *adev, bool enable)
>> return;
>>
>> error_free_entity:
>> - drm_sched_entity_destroy(&adev->mman.high_pr);
>> + drm_sched_entity_destroy(&adev->mman.default_entity.base);
>> }
>>
>> static int amdgpu_ttm_prepare_job(struct amdgpu_device *adev,
>> @@ -2219,8 +2231,8 @@ static int amdgpu_ttm_prepare_job(struct amdgpu_device *adev,
>> {
>> enum amdgpu_ib_pool_type pool = AMDGPU_IB_POOL_DELAYED;
>> int r;
>> - struct drm_sched_entity *entity = delayed ? &adev->mman.low_pr :
>> - &adev->mman.high_pr;
>> + struct drm_sched_entity *entity = delayed ? &adev->mman.clear_entity.base :
>> + &adev->mman.move_entity.base;
>> r = amdgpu_job_alloc_with_ib(adev, entity,
>> AMDGPU_FENCE_OWNER_UNDEFINED,
>> num_dw * 4, pool, job, k_job_id);
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>> index 50e40380fe95..d2295d6c2b67 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h
>> @@ -52,6 +52,10 @@ struct amdgpu_gtt_mgr {
>> spinlock_t lock;
>> };
>>
>> +struct amdgpu_ttm_buffer_entity {
>> + struct drm_sched_entity base;
>> +};
>> +
>> struct amdgpu_mman {
>> struct ttm_device bdev;
>> struct ttm_pool *ttm_pools;
>> @@ -64,10 +68,10 @@ struct amdgpu_mman {
>> bool buffer_funcs_enabled;
>>
>> struct mutex gtt_window_lock;
>> - /* High priority scheduler entity for buffer moves */
>> - struct drm_sched_entity high_pr;
>> - /* Low priority scheduler entity for VRAM clearing */
>> - struct drm_sched_entity low_pr;
>> +
>> + struct amdgpu_ttm_buffer_entity default_entity;
>> + struct amdgpu_ttm_buffer_entity clear_entity;
>> + struct amdgpu_ttm_buffer_entity move_entity;
>>
>> struct amdgpu_vram_mgr vram_mgr;
>> struct amdgpu_gtt_mgr gtt_mgr;
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>> index 378af0b2aaa9..d74ff6e90590 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_migrate.c
>> @@ -45,7 +45,9 @@ svm_migrate_direct_mapping_addr(struct amdgpu_device *adev, u64 addr)
>> }
>>
>> static int
>> -svm_migrate_gart_map(struct amdgpu_ring *ring, u64 npages,
>> +svm_migrate_gart_map(struct amdgpu_ring *ring,
>> + struct amdgpu_ttm_buffer_entity *entity,

Do we still need the ring parameter, or is that implied by the entity?

Other than that, the patch is

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

>> + u64 npages,
>> dma_addr_t *addr, u64 *gart_addr, u64 flags)
>> {
>> struct amdgpu_device *adev = ring->adev;
>> @@ -63,7 +65,7 @@ svm_migrate_gart_map(struct amdgpu_ring *ring, u64 npages,
>> num_dw = ALIGN(adev->mman.buffer_funcs->copy_num_dw, 8);
>> num_bytes = npages * 8;
>>
>> - r = amdgpu_job_alloc_with_ib(adev, &adev->mman.high_pr,
>> + r = amdgpu_job_alloc_with_ib(adev, &entity->base,
>> AMDGPU_FENCE_OWNER_UNDEFINED,
>> num_dw * 4 + num_bytes,
>> AMDGPU_IB_POOL_DELAYED,
>> @@ -128,11 +130,14 @@ svm_migrate_copy_memory_gart(struct amdgpu_device *adev, dma_addr_t *sys,
>> {
>> const u64 GTT_MAX_PAGES = AMDGPU_GTT_MAX_TRANSFER_SIZE;
>> struct amdgpu_ring *ring = adev->mman.buffer_funcs_ring;
>> + struct amdgpu_ttm_buffer_entity *entity;
>> u64 gart_s, gart_d;
>> struct dma_fence *next;
>> u64 size;
>> int r;
>>
>> + entity = &adev->mman.move_entity;
>> +
>> mutex_lock(&adev->mman.gtt_window_lock);
>>
>> while (npages) {
>> @@ -140,10 +145,10 @@ svm_migrate_copy_memory_gart(struct amdgpu_device *adev, dma_addr_t *sys,
>>
>> if (direction == FROM_VRAM_TO_RAM) {
>> gart_s = svm_migrate_direct_mapping_addr(adev, *vram);
>> - r = svm_migrate_gart_map(ring, size, sys, &gart_d, 0);
>> + r = svm_migrate_gart_map(ring, entity, size, sys, &gart_d, 0);
>>
>> } else if (direction == FROM_RAM_TO_VRAM) {
>> - r = svm_migrate_gart_map(ring, size, sys, &gart_s,
>> + r = svm_migrate_gart_map(ring, entity, size, sys, &gart_s,
>> KFD_IOCTL_SVM_FLAG_GPU_RO);
>> gart_d = svm_migrate_direct_mapping_addr(adev, *vram);
>> }