Re: [PATCH 1/2] drm/ttm: further cleanup ttm_mem_reg handling

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 07.07.20 um 21:16 schrieb Chauhan, Madhav:
> [AMD Public Use]
>
> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@lists.freedesktop.org> On Behalf Of Christian König
> Sent: Monday, July 6, 2020 11:18 PM
> To: amd-gfx@lists.freedesktop.org; dri-devel@lists.freedesktop.org
> Subject: [PATCH 1/2] drm/ttm: further cleanup ttm_mem_reg handling
>
> Stop touching the backend private pointer alltogether and make sure we never put the same mem twice by.
>
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---
>   drivers/gpu/drm/ttm/ttm_bo.c    | 46 +++++++++++++++++++--------------
>   include/drm/ttm/ttm_bo_driver.h |  2 --
>   2 files changed, 26 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c index 0c13fe96c7e3..7be36b9996ed 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -312,7 +312,6 @@ static int ttm_bo_handle_move_mem(struct ttm_buffer_object *bo,
>   			if (bdev->driver->move_notify)
>   				bdev->driver->move_notify(bo, evict, mem);
>   			bo->mem = *mem;
> -			mem->mm_node = NULL;
>   			goto moved;
>   		}
>   	}
> @@ -616,7 +615,6 @@ static void ttm_bo_release(struct kref *kref)
>   	ttm_bo_cleanup_memtype_use(bo);
>   	dma_resv_unlock(bo->base.resv);
>   
> -	BUG_ON(bo->mem.mm_node != NULL);
>   	atomic_dec(&ttm_bo_glob.bo_count);
>   	dma_fence_put(bo->moving);
>   	if (!ttm_bo_uses_embedded_gem_object(bo))
> @@ -843,12 +841,29 @@ static int ttm_mem_evict_first(struct ttm_bo_device *bdev,
>   	return ret;
>   }
>   
> +static int ttm_bo_mem_get(struct ttm_buffer_object *bo,
> +			  const struct ttm_place *place,
> +			  struct ttm_mem_reg *mem)
> +{
> +	struct ttm_mem_type_manager *man = &bo->bdev->man[mem->mem_type];
> +
> +	mem->mm_node = NULL;
> +	if (!man->func || !man->func->get_node)
> +		return 0;
> +
> +	return man->func->get_node(man, bo, place, mem); }
> +
>
> Should not we export this as a symbol, so that it can be used similar to ttm_bo_mem_put in drm drivers??

No, it's a well known design problem of TTM that the exported counter 
part of ttm_bo_mem_put() is ttm_bo_mem_space().

I have it on my TODO list to fix this, but that needs a bigger change.

Regards,
Christian.

>
> Regards,
> Madhav
>
>   void ttm_bo_mem_put(struct ttm_buffer_object *bo, struct ttm_mem_reg *mem)  {
>   	struct ttm_mem_type_manager *man = &bo->bdev->man[mem->mem_type];
>   
> -	if (mem->mm_node)
> -		(*man->func->put_node)(man, mem);
> +	if (!man->func || !man->func->put_node)
> +		return;
> +
> +	man->func->put_node(man, mem);
> +	mem->mm_node = NULL;
> +	mem->mem_type = TTM_PL_SYSTEM;
>   }
>   EXPORT_SYMBOL(ttm_bo_mem_put);
>   
> @@ -902,7 +917,7 @@ static int ttm_bo_mem_force_space(struct ttm_buffer_object *bo,
>   
>   	ticket = dma_resv_locking_ctx(bo->base.resv);
>   	do {
> -		ret = (*man->func->get_node)(man, bo, place, mem);
> +		ret = ttm_bo_mem_get(bo, place, mem);
>   		if (likely(!ret))
>   			break;
>   		if (unlikely(ret != -ENOSPC))
> @@ -1032,7 +1047,6 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
>   	if (unlikely(ret))
>   		return ret;
>   
> -	mem->mm_node = NULL;
>   	for (i = 0; i < placement->num_placement; ++i) {
>   		const struct ttm_place *place = &placement->placement[i];
>   		struct ttm_mem_type_manager *man;
> @@ -1044,20 +1058,16 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
>   			goto error;
>   
>   		type_found = true;
> -		mem->mm_node = NULL;
> -		if (mem->mem_type == TTM_PL_SYSTEM)
> -			return 0;
> -
> -		man = &bdev->man[mem->mem_type];
> -		ret = (*man->func->get_node)(man, bo, place, mem);
> +		ret = ttm_bo_mem_get(bo, place, mem);
>   		if (ret == -ENOSPC)
>   			continue;
>   		if (unlikely(ret))
>   			goto error;
>   
> +		man = &bdev->man[mem->mem_type];
>   		ret = ttm_bo_add_move_fence(bo, man, mem, ctx->no_wait_gpu);
>   		if (unlikely(ret)) {
> -			(*man->func->put_node)(man, mem);
> +			ttm_bo_mem_put(bo, mem);
>   			if (ret == -EBUSY)
>   				continue;
>   
> @@ -1076,12 +1086,8 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
>   			goto error;
>   
>   		type_found = true;
> -		mem->mm_node = NULL;
> -		if (mem->mem_type == TTM_PL_SYSTEM)
> -			return 0;
> -
>   		ret = ttm_bo_mem_force_space(bo, place, mem, ctx);
> -		if (ret == 0 && mem->mm_node)
> +		if (likely(!ret))
>   			return 0;
>   
>   		if (ret && ret != -EBUSY)
> @@ -1129,7 +1135,7 @@ static int ttm_bo_move_buffer(struct ttm_buffer_object *bo,
>   		goto out_unlock;
>   	ret = ttm_bo_handle_move_mem(bo, &mem, false, ctx);
>   out_unlock:
> -	if (ret && mem.mm_node)
> +	if (ret)
>   		ttm_bo_mem_put(bo, &mem);
>   	return ret;
>   }
> @@ -1144,7 +1150,7 @@ static bool ttm_bo_places_compat(const struct ttm_place *places,
>   	for (i = 0; i < num_placement; i++) {
>   		const struct ttm_place *heap = &places[i];
>   
> -		if (mem->mm_node && (mem->start < heap->fpfn ||
> +		if ((mem->start < heap->fpfn ||
>   		     (heap->lpfn != 0 && (mem->start + mem->num_pages) > heap->lpfn)))
>   			continue;
>   
> diff --git a/include/drm/ttm/ttm_bo_driver.h b/include/drm/ttm/ttm_bo_driver.h index aa1f398c2ea7..732167cad130 100644
> --- a/include/drm/ttm/ttm_bo_driver.h
> +++ b/include/drm/ttm/ttm_bo_driver.h
> @@ -564,8 +564,6 @@ int ttm_bo_mem_space(struct ttm_buffer_object *bo,
>   		     struct ttm_operation_ctx *ctx);
>   
>   void ttm_bo_mem_put(struct ttm_buffer_object *bo, struct ttm_mem_reg *mem); -void ttm_bo_mem_put_locked(struct ttm_buffer_object *bo,
> -			   struct ttm_mem_reg *mem);
>   
>   int ttm_bo_device_release(struct ttm_bo_device *bdev);
>   
> --
> 2.17.1
>
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