Re: [PATCH v3 23/28] drm/amdgpu: use TTM_NUM_MOVE_FENCES when reserving fences

["Christian König" <christian.koenig@amd.com>]

On 11/21/25 11:12, Pierre-Eric Pelloux-Prayer wrote:
> Use TTM_NUM_MOVE_FENCES as an upperbound of how many fences
> ttm might need to deal with moves/evictions.
> 
> ---
> v2: removed drm_err calls
> ---
> 
> Signed-off-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
> Acked-by: Felix Kuehling <felix.kuehling@amd.com>
> Reviewed-by: Christian König <christian.koenig@amd.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c                  | 5 ++---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c                 | 2 +-
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vkms.c                | 6 ++----
>  drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c                  | 3 ++-
>  drivers/gpu/drm/amd/amdkfd/kfd_svm.c                    | 3 +--
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c | 6 ++----
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_wb.c    | 6 ++----
>  7 files changed, 12 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> index d591dce0f3b3..5215238f8fc9 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> @@ -916,9 +916,8 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
>  			goto out_free_user_pages;
>  
>  		amdgpu_bo_list_for_each_entry(e, p->bo_list) {
> -			/* One fence for TTM and one for each CS job */
>  			r = drm_exec_prepare_obj(&p->exec, &e->bo->tbo.base,
> -						 1 + p->gang_size);
> +						 TTM_NUM_MOVE_FENCES + p->gang_size);
>  			drm_exec_retry_on_contention(&p->exec);
>  			if (unlikely(r))
>  				goto out_free_user_pages;
> @@ -928,7 +927,7 @@ static int amdgpu_cs_parser_bos(struct amdgpu_cs_parser *p,
>  
>  		if (p->uf_bo) {
>  			r = drm_exec_prepare_obj(&p->exec, &p->uf_bo->tbo.base,
> -						 1 + p->gang_size);
> +						 TTM_NUM_MOVE_FENCES + p->gang_size);
>  			drm_exec_retry_on_contention(&p->exec);
>  			if (unlikely(r))
>  				goto out_free_user_pages;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index f2505ae5fd65..41fd84a19d66 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -354,7 +354,7 @@ static void amdgpu_gem_object_close(struct drm_gem_object *obj,
>  
>  	drm_exec_init(&exec, DRM_EXEC_IGNORE_DUPLICATES, 0);
>  	drm_exec_until_all_locked(&exec) {
> -		r = drm_exec_prepare_obj(&exec, &bo->tbo.base, 1);
> +		r = drm_exec_prepare_obj(&exec, &bo->tbo.base, TTM_NUM_MOVE_FENCES);

This here can stay 1, we just need a single slot for the VM update fence.

>  		drm_exec_retry_on_contention(&exec);
>  		if (unlikely(r))
>  			goto out_unlock;
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vkms.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vkms.c
> index 79bad9cbe2ab..b92561eea3da 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vkms.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vkms.c
> @@ -326,11 +326,9 @@ static int amdgpu_vkms_prepare_fb(struct drm_plane *plane,
>  		return r;
>  	}
>  
> -	r = dma_resv_reserve_fences(rbo->tbo.base.resv, 1);
> -	if (r) {
> -		dev_err(adev->dev, "allocating fence slot failed (%d)\n", r);
> +	r = dma_resv_reserve_fences(rbo->tbo.base.resv, TTM_NUM_MOVE_FENCES);
> +	if (r)
>  		goto error_unlock;
> -	}
>  
>  	if (plane->type != DRM_PLANE_TYPE_CURSOR)
>  		domain = amdgpu_display_supported_domains(adev, rbo->flags);
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 5061d5b0f875..62f37a9ca966 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -2656,7 +2656,8 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>  	}
>  
>  	amdgpu_vm_bo_base_init(&vm->root, vm, root_bo);
> -	r = dma_resv_reserve_fences(root_bo->tbo.base.resv, 1);
> +	r = dma_resv_reserve_fences(root_bo->tbo.base.resv,
> +				    TTM_NUM_MOVE_FENCES);

Here we only need a single slot to clear the root PD during init.

With those two removed the patch is Reviewed-by: Christian König <christian.koenig@amd.com>.

Fingers crossed that we haven't missed any.

Regards,
Christian.

>  	if (r)
>  		goto error_free_root;
>  
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> index 97c2270f278f..0f8d85ee97fc 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> @@ -627,9 +627,8 @@ svm_range_vram_node_new(struct kfd_node *node, struct svm_range *prange,
>  		}
>  	}
>  
> -	r = dma_resv_reserve_fences(bo->tbo.base.resv, 1);
> +	r = dma_resv_reserve_fences(bo->tbo.base.resv, TTM_NUM_MOVE_FENCES);
>  	if (r) {
> -		pr_debug("failed %d to reserve bo\n", r);
>  		amdgpu_bo_unreserve(bo);
>  		goto reserve_bo_failed;
>  	}
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
> index 56cb866ac6f8..ceb55dd183ed 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_plane.c
> @@ -952,11 +952,9 @@ static int amdgpu_dm_plane_helper_prepare_fb(struct drm_plane *plane,
>  		return r;
>  	}
>  
> -	r = dma_resv_reserve_fences(rbo->tbo.base.resv, 1);
> -	if (r) {
> -		drm_err(adev_to_drm(adev), "reserving fence slot failed (%d)\n", r);
> +	r = dma_resv_reserve_fences(rbo->tbo.base.resv, TTM_NUM_MOVE_FENCES);
> +	if (r)
>  		goto error_unlock;
> -	}
>  
>  	if (plane->type != DRM_PLANE_TYPE_CURSOR)
>  		domain = amdgpu_display_supported_domains(adev, rbo->flags);
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_wb.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_wb.c
> index d9527c05fc87..110f0173eee6 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_wb.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_wb.c
> @@ -106,11 +106,9 @@ static int amdgpu_dm_wb_prepare_job(struct drm_writeback_connector *wb_connector
>  		return r;
>  	}
>  
> -	r = dma_resv_reserve_fences(rbo->tbo.base.resv, 1);
> -	if (r) {
> -		drm_err(adev_to_drm(adev), "reserving fence slot failed (%d)\n", r);
> +	r = dma_resv_reserve_fences(rbo->tbo.base.resv, TTM_NUM_MOVE_FENCES);
> +	if (r)
>  		goto error_unlock;
> -	}
>  
>  	domain = amdgpu_display_supported_domains(adev, rbo->flags);
>