Re: [PATCH 1/2] drm: allow limiting the scatter list size.

Christian König <christian.koenig@xxxxxxx> · Tue, 18 Aug 2020 09:57:59 +0200

Am 18.08.20 um 09:48 schrieb Gerd Hoffmann:
Add max_segment argument to drm_prime_pages_to_sg().  When set pass it
through to the __sg_alloc_table_from_pages() call, otherwise use
SCATTERLIST_MAX_SEGMENT.

Also add max_segment field to gem objects and pass it to
drm_prime_pages_to_sg() calls in drivers and helpers.

Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>

I'm missing an explanation why this should be useful (it certainly is).

And the maximum segment size seems misplaced in the GEM object. This is 
usually a property of the device or even completely constant.

Christian.

---
  include/drm/drm_gem.h                       |  8 ++++++++
  include/drm/drm_prime.h                     |  3 ++-
  drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c |  3 ++-
  drivers/gpu/drm/drm_gem_shmem_helper.c      |  3 ++-
  drivers/gpu/drm/drm_prime.c                 | 10 +++++++---
  drivers/gpu/drm/etnaviv/etnaviv_gem.c       |  3 ++-
  drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c |  3 ++-
  drivers/gpu/drm/msm/msm_gem.c               |  3 ++-
  drivers/gpu/drm/msm/msm_gem_prime.c         |  3 ++-
  drivers/gpu/drm/nouveau/nouveau_prime.c     |  3 ++-
  drivers/gpu/drm/radeon/radeon_prime.c       |  3 ++-
  drivers/gpu/drm/rockchip/rockchip_drm_gem.c |  6 ++++--
  drivers/gpu/drm/tegra/gem.c                 |  3 ++-
  drivers/gpu/drm/vgem/vgem_drv.c             |  3 ++-
  drivers/gpu/drm/xen/xen_drm_front_gem.c     |  3 ++-
  15 files changed, 43 insertions(+), 17 deletions(-)

diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 337a48321705..dea5e92e745b 100644
--- a/include/drm/drm_gem.h
+++ b/include/drm/drm_gem.h
@@ -241,6 +241,14 @@ struct drm_gem_object {
  	 */
  	size_t size;
  
+	/**
+	 * @max_segment:
+	 *
+	 * Max size for scatter list segments.  When unset the default
+	 * (SCATTERLIST_MAX_SEGMENT) is used.
+	 */
+	size_t max_segment;
+
  	/**
  	 * @name:
  	 *
diff --git a/include/drm/drm_prime.h b/include/drm/drm_prime.h
index 9af7422b44cf..2c3689435cb4 100644
--- a/include/drm/drm_prime.h
+++ b/include/drm/drm_prime.h
@@ -88,7 +88,8 @@ void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, void *vaddr);
  int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma);
  int drm_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *vma);
  
-struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_pages);
+struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_pages,
+				       size_t max_segment);
  struct dma_buf *drm_gem_prime_export(struct drm_gem_object *obj,
  				     int flags);
  
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
index 519ce4427fce..5e8a9760b33f 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
@@ -303,7 +303,8 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
  	switch (bo->tbo.mem.mem_type) {
  	case TTM_PL_TT:
  		sgt = drm_prime_pages_to_sg(bo->tbo.ttm->pages,
-					    bo->tbo.num_pages);
+					    bo->tbo.num_pages,
+					    obj->max_segment);
  		if (IS_ERR(sgt))
  			return sgt;
  
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 4b7cfbac4daa..cfb979d808fd 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -656,7 +656,8 @@ struct sg_table *drm_gem_shmem_get_sg_table(struct drm_gem_object *obj)
  
  	WARN_ON(shmem->base.import_attach);
  
-	return drm_prime_pages_to_sg(shmem->pages, obj->size >> PAGE_SHIFT);
+	return drm_prime_pages_to_sg(shmem->pages, obj->size >> PAGE_SHIFT,
+				     obj->max_segment);
  }
  EXPORT_SYMBOL_GPL(drm_gem_shmem_get_sg_table);
  
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 1693aa7c14b5..27c783fd6633 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -802,7 +802,8 @@ static const struct dma_buf_ops drm_gem_prime_dmabuf_ops =  {
   *
   * This is useful for implementing &drm_gem_object_funcs.get_sg_table.
   */
-struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_pages)
+struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_pages,
+				       size_t max_segment)
  {
  	struct sg_table *sg = NULL;
  	int ret;
@@ -813,8 +814,11 @@ struct sg_table *drm_prime_pages_to_sg(struct page **pages, unsigned int nr_page
  		goto out;
  	}
  
-	ret = sg_alloc_table_from_pages(sg, pages, nr_pages, 0,
-				nr_pages << PAGE_SHIFT, GFP_KERNEL);
+	if (max_segment == 0 || max_segment > SCATTERLIST_MAX_SEGMENT)
+		max_segment = SCATTERLIST_MAX_SEGMENT;
+	ret = __sg_alloc_table_from_pages(sg, pages, nr_pages, 0,
+					  nr_pages << PAGE_SHIFT,
+					  max_segment, GFP_KERNEL);
  	if (ret)
  		goto out;
  
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
index f06e19e7be04..e5b6e7996f80 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
@@ -103,7 +103,8 @@ struct page **etnaviv_gem_get_pages(struct etnaviv_gem_object *etnaviv_obj)
  		int npages = etnaviv_obj->base.size >> PAGE_SHIFT;
  		struct sg_table *sgt;
  
-		sgt = drm_prime_pages_to_sg(etnaviv_obj->pages, npages);
+		sgt = drm_prime_pages_to_sg(etnaviv_obj->pages, npages,
+					    etnaviv_obj->base.max_segment);
  		if (IS_ERR(sgt)) {
  			dev_err(dev->dev, "failed to allocate sgt: %ld\n",
  				PTR_ERR(sgt));
diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
index 6d9e5c3c4dd5..f327676450bd 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_prime.c
@@ -19,7 +19,8 @@ struct sg_table *etnaviv_gem_prime_get_sg_table(struct drm_gem_object *obj)
  	if (WARN_ON(!etnaviv_obj->pages))  /* should have already pinned! */
  		return ERR_PTR(-EINVAL);
  
-	return drm_prime_pages_to_sg(etnaviv_obj->pages, npages);
+	return drm_prime_pages_to_sg(etnaviv_obj->pages, npages,
+				     obj->max_segment);
  }
  
  void *etnaviv_gem_prime_vmap(struct drm_gem_object *obj)
diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c
index b2f49152b4d4..f805419bb84a 100644
--- a/drivers/gpu/drm/msm/msm_gem.c
+++ b/drivers/gpu/drm/msm/msm_gem.c
@@ -126,7 +126,8 @@ static struct page **get_pages(struct drm_gem_object *obj)
  
  		msm_obj->pages = p;
  
-		msm_obj->sgt = drm_prime_pages_to_sg(p, npages);
+		msm_obj->sgt = drm_prime_pages_to_sg(p, npages,
+						     obj->max_segment);
  		if (IS_ERR(msm_obj->sgt)) {
  			void *ptr = ERR_CAST(msm_obj->sgt);
  
diff --git a/drivers/gpu/drm/msm/msm_gem_prime.c b/drivers/gpu/drm/msm/msm_gem_prime.c
index d7c8948427fe..a5a412564c7f 100644
--- a/drivers/gpu/drm/msm/msm_gem_prime.c
+++ b/drivers/gpu/drm/msm/msm_gem_prime.c
@@ -19,7 +19,8 @@ struct sg_table *msm_gem_prime_get_sg_table(struct drm_gem_object *obj)
  	if (WARN_ON(!msm_obj->pages))  /* should have already pinned! */
  		return NULL;
  
-	return drm_prime_pages_to_sg(msm_obj->pages, npages);
+	return drm_prime_pages_to_sg(msm_obj->pages, npages,
+				     obj->max_segment);
  }
  
  void *msm_gem_prime_vmap(struct drm_gem_object *obj)
diff --git a/drivers/gpu/drm/nouveau/nouveau_prime.c b/drivers/gpu/drm/nouveau/nouveau_prime.c
index bae6a3eccee0..56a2e916d51a 100644
--- a/drivers/gpu/drm/nouveau/nouveau_prime.c
+++ b/drivers/gpu/drm/nouveau/nouveau_prime.c
@@ -32,7 +32,8 @@ struct sg_table *nouveau_gem_prime_get_sg_table(struct drm_gem_object *obj)
  	struct nouveau_bo *nvbo = nouveau_gem_object(obj);
  	int npages = nvbo->bo.num_pages;
  
-	return drm_prime_pages_to_sg(nvbo->bo.ttm->pages, npages);
+	return drm_prime_pages_to_sg(nvbo->bo.ttm->pages, npages,
+				     obj->max_segment);
  }
  
  void *nouveau_gem_prime_vmap(struct drm_gem_object *obj)
diff --git a/drivers/gpu/drm/radeon/radeon_prime.c b/drivers/gpu/drm/radeon/radeon_prime.c
index b906e8fbd5f3..503e35625045 100644
--- a/drivers/gpu/drm/radeon/radeon_prime.c
+++ b/drivers/gpu/drm/radeon/radeon_prime.c
@@ -36,7 +36,8 @@ struct sg_table *radeon_gem_prime_get_sg_table(struct drm_gem_object *obj)
  	struct radeon_bo *bo = gem_to_radeon_bo(obj);
  	int npages = bo->tbo.num_pages;
  
-	return drm_prime_pages_to_sg(bo->tbo.ttm->pages, npages);
+	return drm_prime_pages_to_sg(bo->tbo.ttm->pages, npages,
+				     obj->max_segment);
  }
  
  void *radeon_gem_prime_vmap(struct drm_gem_object *obj)
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
index b9275ba7c5a5..444657e03c16 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
@@ -85,7 +85,8 @@ static int rockchip_gem_get_pages(struct rockchip_gem_object *rk_obj)
  
  	rk_obj->num_pages = rk_obj->base.size >> PAGE_SHIFT;
  
-	rk_obj->sgt = drm_prime_pages_to_sg(rk_obj->pages, rk_obj->num_pages);
+	rk_obj->sgt = drm_prime_pages_to_sg(rk_obj->pages, rk_obj->num_pages,
+					    rk_obj->base.max_segment);
  	if (IS_ERR(rk_obj->sgt)) {
  		ret = PTR_ERR(rk_obj->sgt);
  		goto err_put_pages;
@@ -442,7 +443,8 @@ struct sg_table *rockchip_gem_prime_get_sg_table(struct drm_gem_object *obj)
  	int ret;
  
  	if (rk_obj->pages)
-		return drm_prime_pages_to_sg(rk_obj->pages, rk_obj->num_pages);
+		return drm_prime_pages_to_sg(rk_obj->pages, rk_obj->num_pages,
+					     obj->max_segment);
  
  	sgt = kzalloc(sizeof(*sgt), GFP_KERNEL);
  	if (!sgt)
diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
index 723df142a981..8d98b02a8d21 100644
--- a/drivers/gpu/drm/tegra/gem.c
+++ b/drivers/gpu/drm/tegra/gem.c
@@ -284,7 +284,8 @@ static int tegra_bo_get_pages(struct drm_device *drm, struct tegra_bo *bo)
  
  	bo->num_pages = bo->gem.size >> PAGE_SHIFT;
  
-	bo->sgt = drm_prime_pages_to_sg(bo->pages, bo->num_pages);
+	bo->sgt = drm_prime_pages_to_sg(bo->pages, bo->num_pages,
+					bo->gem.max_segment);
  	if (IS_ERR(bo->sgt)) {
  		err = PTR_ERR(bo->sgt);
  		goto put_pages;
diff --git a/drivers/gpu/drm/vgem/vgem_drv.c b/drivers/gpu/drm/vgem/vgem_drv.c
index 313339bbff90..d25c93b5a2c1 100644
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -321,7 +321,8 @@ static struct sg_table *vgem_prime_get_sg_table(struct drm_gem_object *obj)
  {
  	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);
  
-	return drm_prime_pages_to_sg(bo->pages, bo->base.size >> PAGE_SHIFT);
+	return drm_prime_pages_to_sg(bo->pages, bo->base.size >> PAGE_SHIFT,
+				     obj->max_segment);
  }
  
  static struct drm_gem_object* vgem_prime_import(struct drm_device *dev,
diff --git a/drivers/gpu/drm/xen/xen_drm_front_gem.c b/drivers/gpu/drm/xen/xen_drm_front_gem.c
index f0b85e094111..362fe5311b1b 100644
--- a/drivers/gpu/drm/xen/xen_drm_front_gem.c
+++ b/drivers/gpu/drm/xen/xen_drm_front_gem.c
@@ -179,7 +179,8 @@ struct sg_table *xen_drm_front_gem_get_sg_table(struct drm_gem_object *gem_obj)
  	if (!xen_obj->pages)
  		return ERR_PTR(-ENOMEM);
  
-	return drm_prime_pages_to_sg(xen_obj->pages, xen_obj->num_pages);
+	return drm_prime_pages_to_sg(xen_obj->pages, xen_obj->num_pages,
+				     gem_obj->max_segment);
  }
  
  struct drm_gem_object *

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