drm/amdgpu: add support for exporting VRAM using DMA-buf v3

We should be able to do this now after checking all the prerequisites.

v2: fix entrie count in the sgt
v3: manually construct the sg

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://patchwork.freedesktop.org/patch/359295

drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c

@@ -276,14 +276,21 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
 	struct dma_buf *dma_buf = attach->dmabuf;
 	struct drm_gem_object *obj = dma_buf->priv;
 	struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
+	struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
 	struct sg_table *sgt;
 	long r;
 
 	if (!bo->pin_count) {
-		/* move buffer into GTT */
+		/* move buffer into GTT or VRAM */
 		struct ttm_operation_ctx ctx = { false, false };
+		unsigned domains = AMDGPU_GEM_DOMAIN_GTT;
 
-		amdgpu_bo_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_GTT);
+		if (bo->preferred_domains & AMDGPU_GEM_DOMAIN_VRAM &&
+		    attach->peer2peer) {
+			bo->flags |= AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
+			domains |= AMDGPU_GEM_DOMAIN_VRAM;
+		}
+		amdgpu_bo_placement_from_domain(bo, domains);
 		r = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
 		if (r)
 			return ERR_PTR(r);
@@ -293,20 +300,34 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
 		return ERR_PTR(-EBUSY);
 	}
 
-	sgt = drm_prime_pages_to_sg(bo->tbo.ttm->pages, bo->tbo.num_pages);
-	if (IS_ERR(sgt))
-		return sgt;
+	switch (bo->tbo.mem.mem_type) {
+	case TTM_PL_TT:
+		sgt = drm_prime_pages_to_sg(bo->tbo.ttm->pages,
+					    bo->tbo.num_pages);
+		if (IS_ERR(sgt))
+			return sgt;
 
-	if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
-			      DMA_ATTR_SKIP_CPU_SYNC))
-		goto error_free;
+		if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
+				      DMA_ATTR_SKIP_CPU_SYNC))
+			goto error_free;
+		break;
+
+	case TTM_PL_VRAM:
+		r = amdgpu_vram_mgr_alloc_sgt(adev, &bo->tbo.mem, attach->dev,
+					      dir, &sgt);
+		if (r)
+			return ERR_PTR(r);
+		break;
+	default:
+		return ERR_PTR(-EINVAL);
+	}
 
 	return sgt;
 
 error_free:
 	sg_free_table(sgt);
 	kfree(sgt);
-	return ERR_PTR(-ENOMEM);
+	return ERR_PTR(-EBUSY);
 }
 
 /**
@@ -322,9 +343,18 @@ static void amdgpu_dma_buf_unmap(struct dma_buf_attachment *attach,
 				 struct sg_table *sgt,
 				 enum dma_data_direction dir)
 {
-	dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
-	sg_free_table(sgt);
-	kfree(sgt);
+	struct dma_buf *dma_buf = attach->dmabuf;
+	struct drm_gem_object *obj = dma_buf->priv;
+	struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
+	struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
+
+	if (sgt->sgl->page_link) {
+		dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
+		sg_free_table(sgt);
+		kfree(sgt);
+	} else {
+		amdgpu_vram_mgr_free_sgt(adev, attach->dev, dir, sgt);
+	}
 }
 
 /**

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.h

@@ -24,8 +24,9 @@
 #ifndef __AMDGPU_TTM_H__
 #define __AMDGPU_TTM_H__
 
-#include "amdgpu.h"
+#include <linux/dma-direction.h>
 #include <drm/gpu_scheduler.h>
+#include "amdgpu.h"
 
 #define AMDGPU_PL_GDS		(TTM_PL_PRIV + 0)
 #define AMDGPU_PL_GWS		(TTM_PL_PRIV + 1)
@@ -74,6 +75,15 @@ uint64_t amdgpu_gtt_mgr_usage(struct ttm_mem_type_manager *man);
 int amdgpu_gtt_mgr_recover(struct ttm_mem_type_manager *man);
 
 u64 amdgpu_vram_mgr_bo_visible_size(struct amdgpu_bo *bo);
+int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
+			      struct ttm_mem_reg *mem,
+			      struct device *dev,
+			      enum dma_data_direction dir,
+			      struct sg_table **sgt);
+void amdgpu_vram_mgr_free_sgt(struct amdgpu_device *adev,
+			      struct device *dev,
+			      enum dma_data_direction dir,
+			      struct sg_table *sgt);
 uint64_t amdgpu_vram_mgr_usage(struct ttm_mem_type_manager *man);
 uint64_t amdgpu_vram_mgr_vis_usage(struct ttm_mem_type_manager *man);
 

drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c

@@ -22,6 +22,7 @@
  * Authors: Christian König
  */
 
+#include <linux/dma-mapping.h>
 #include "amdgpu.h"
 #include "amdgpu_vm.h"
 #include "amdgpu_atomfirmware.h"
@@ -458,6 +459,104 @@ static void amdgpu_vram_mgr_del(struct ttm_mem_type_manager *man,
 	mem->mm_node = NULL;
 }
 
+/**
+ * amdgpu_vram_mgr_alloc_sgt - allocate and fill a sg table
+ *
+ * @adev: amdgpu device pointer
+ * @mem: TTM memory object
+ * @dev: the other device
+ * @dir: dma direction
+ * @sgt: resulting sg table
+ *
+ * Allocate and fill a sg table from a VRAM allocation.
+ */
+int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
+			      struct ttm_mem_reg *mem,
+			      struct device *dev,
+			      enum dma_data_direction dir,
+			      struct sg_table **sgt)
+{
+	struct drm_mm_node *node;
+	struct scatterlist *sg;
+	int num_entries = 0;
+	unsigned int pages;
+	int i, r;
+
+	*sgt = kmalloc(sizeof(*sg), GFP_KERNEL);
+	if (!*sgt)
+		return -ENOMEM;
+
+	for (pages = mem->num_pages, node = mem->mm_node;
+	     pages; pages -= node->size, ++node)
+		++num_entries;
+
+	r = sg_alloc_table(*sgt, num_entries, GFP_KERNEL);
+	if (r)
+		goto error_free;
+
+	for_each_sg((*sgt)->sgl, sg, num_entries, i)
+		sg->length = 0;
+
+	node = mem->mm_node;
+	for_each_sg((*sgt)->sgl, sg, num_entries, i) {
+		phys_addr_t phys = (node->start << PAGE_SHIFT) +
+			adev->gmc.aper_base;
+		size_t size = node->size << PAGE_SHIFT;
+		dma_addr_t addr;
+
+		++node;
+		addr = dma_map_resource(dev, phys, size, dir,
+					DMA_ATTR_SKIP_CPU_SYNC);
+		r = dma_mapping_error(dev, addr);
+		if (r)
+			goto error_unmap;
+
+		sg_set_page(sg, NULL, size, 0);
+		sg_dma_address(sg) = addr;
+		sg_dma_len(sg) = size;
+	}
+	return 0;
+
+error_unmap:
+	for_each_sg((*sgt)->sgl, sg, num_entries, i) {
+		if (!sg->length)
+			continue;
+
+		dma_unmap_resource(dev, sg->dma_address,
+				   sg->length, dir,
+				   DMA_ATTR_SKIP_CPU_SYNC);
+	}
+	sg_free_table(*sgt);
+
+error_free:
+	kfree(*sgt);
+	return r;
+}
+
+/**
+ * amdgpu_vram_mgr_alloc_sgt - allocate and fill a sg table
+ *
+ * @adev: amdgpu device pointer
+ * @sgt: sg table to free
+ *
+ * Free a previously allocate sg table.
+ */
+void amdgpu_vram_mgr_free_sgt(struct amdgpu_device *adev,
+			      struct device *dev,
+			      enum dma_data_direction dir,
+			      struct sg_table *sgt)
+{
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgt->sgl, sg, sgt->nents, i)
+		dma_unmap_resource(dev, sg->dma_address,
+				   sg->length, dir,
+				   DMA_ATTR_SKIP_CPU_SYNC);
+	sg_free_table(sgt);
+	kfree(sgt);
+}
+
 /**
  * amdgpu_vram_mgr_usage - how many bytes are used in this domain
  *