drm/cma-helper: Add DRM_GEM_CMA_VMAP_DRIVER_OPS

This adds functionality to the CMA helper which ensures that the kernel
virtual address is set on the CMA GEM object also for imported buffers.

The drivers have been audited to ensure that none set ->vaddr on imported
buffers, making the conditional dma_buf_vunmap() call in
drm_gem_cma_free_object() safe.
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20181110145647.17580-5-noralf@tronnes.org

drivers/gpu/drm/drm_gem_cma_helper.c

@@ -176,6 +176,7 @@ drm_gem_cma_create_with_handle(struct drm_file *file_priv,
  *
  * This function frees the backing memory of the CMA GEM object, cleans up the
  * GEM object state and frees the memory used to store the object itself.
+ * If the buffer is imported and the virtual address is set, it is released.
  * Drivers using the CMA helpers should set this as their
  * &drm_driver.gem_free_object_unlocked callback.
  */
@@ -189,6 +190,8 @@ void drm_gem_cma_free_object(struct drm_gem_object *gem_obj)
 		dma_free_wc(gem_obj->dev->dev, cma_obj->base.size,
 			    cma_obj->vaddr, cma_obj->paddr);
 	} else if (gem_obj->import_attach) {
+		if (cma_obj->vaddr)
+			dma_buf_vunmap(gem_obj->import_attach->dmabuf, cma_obj->vaddr);
 		drm_prime_gem_destroy(gem_obj, cma_obj->sgt);
 	}
 
@@ -575,3 +578,86 @@ void drm_gem_cma_prime_vunmap(struct drm_gem_object *obj, void *vaddr)
 	/* Nothing to do */
 }
 EXPORT_SYMBOL_GPL(drm_gem_cma_prime_vunmap);
+
+static const struct drm_gem_object_funcs drm_cma_gem_default_funcs = {
+	.free = drm_gem_cma_free_object,
+	.print_info = drm_gem_cma_print_info,
+	.get_sg_table = drm_gem_cma_prime_get_sg_table,
+	.vmap = drm_gem_cma_prime_vmap,
+	.vm_ops = &drm_gem_cma_vm_ops,
+};
+
+/**
+ * drm_cma_gem_create_object_default_funcs - Create a CMA GEM object with a
+ *                                           default function table
+ * @dev: DRM device
+ * @size: Size of the object to allocate
+ *
+ * This sets the GEM object functions to the default CMA helper functions.
+ * This function can be used as the &drm_driver.gem_create_object callback.
+ *
+ * Returns:
+ * A pointer to a allocated GEM object or an error pointer on failure.
+ */
+struct drm_gem_object *
+drm_cma_gem_create_object_default_funcs(struct drm_device *dev, size_t size)
+{
+	struct drm_gem_cma_object *cma_obj;
+
+	cma_obj = kzalloc(sizeof(*cma_obj), GFP_KERNEL);
+	if (!cma_obj)
+		return NULL;
+
+	cma_obj->base.funcs = &drm_cma_gem_default_funcs;
+
+	return &cma_obj->base;
+}
+EXPORT_SYMBOL(drm_cma_gem_create_object_default_funcs);
+
+/**
+ * drm_gem_cma_prime_import_sg_table_vmap - PRIME import another driver's
+ *	scatter/gather table and get the virtual address of the buffer
+ * @dev: DRM device
+ * @attach: DMA-BUF attachment
+ * @sgt: Scatter/gather table of pinned pages
+ *
+ * This function imports a scatter/gather table using
+ * drm_gem_cma_prime_import_sg_table() and uses dma_buf_vmap() to get the kernel
+ * virtual address. This ensures that a CMA GEM object always has its virtual
+ * address set. This address is released when the object is freed.
+ *
+ * This function can be used as the &drm_driver.gem_prime_import_sg_table
+ * callback. The DRM_GEM_CMA_VMAP_DRIVER_OPS() macro provides a shortcut to set
+ * the necessary DRM driver operations.
+ *
+ * Returns:
+ * A pointer to a newly created GEM object or an ERR_PTR-encoded negative
+ * error code on failure.
+ */
+struct drm_gem_object *
+drm_gem_cma_prime_import_sg_table_vmap(struct drm_device *dev,
+				       struct dma_buf_attachment *attach,
+				       struct sg_table *sgt)
+{
+	struct drm_gem_cma_object *cma_obj;
+	struct drm_gem_object *obj;
+	void *vaddr;
+
+	vaddr = dma_buf_vmap(attach->dmabuf);
+	if (!vaddr) {
+		DRM_ERROR("Failed to vmap PRIME buffer\n");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	obj = drm_gem_cma_prime_import_sg_table(dev, attach, sgt);
+	if (IS_ERR(obj)) {
+		dma_buf_vunmap(attach->dmabuf, vaddr);
+		return obj;
+	}
+
+	cma_obj = to_drm_gem_cma_obj(obj);
+	cma_obj->vaddr = vaddr;
+
+	return obj;
+}
+EXPORT_SYMBOL(drm_gem_cma_prime_import_sg_table_vmap);

include/drm/drm_gem_cma_helper.h

@@ -103,4 +103,28 @@ int drm_gem_cma_prime_mmap(struct drm_gem_object *obj,
 void *drm_gem_cma_prime_vmap(struct drm_gem_object *obj);
 void drm_gem_cma_prime_vunmap(struct drm_gem_object *obj, void *vaddr);
 
+struct drm_gem_object *
+drm_cma_gem_create_object_default_funcs(struct drm_device *dev, size_t size);
+
+/**
+ * DRM_GEM_CMA_VMAP_DRIVER_OPS - CMA GEM driver operations ensuring a virtual
+ *                               address on the buffer
+ *
+ * This macro provides a shortcut for setting the default GEM operations in the
+ * &drm_driver structure for drivers that need the virtual address also on
+ * imported buffers.
+ */
+#define DRM_GEM_CMA_VMAP_DRIVER_OPS \
+	.gem_create_object	= drm_cma_gem_create_object_default_funcs, \
+	.dumb_create		= drm_gem_cma_dumb_create, \
+	.prime_handle_to_fd	= drm_gem_prime_handle_to_fd, \
+	.prime_fd_to_handle	= drm_gem_prime_fd_to_handle, \
+	.gem_prime_import_sg_table = drm_gem_cma_prime_import_sg_table_vmap, \
+	.gem_prime_mmap		= drm_gem_prime_mmap
+
+struct drm_gem_object *
+drm_gem_cma_prime_import_sg_table_vmap(struct drm_device *drm,
+				       struct dma_buf_attachment *attach,
+				       struct sg_table *sgt);
+
 #endif /* __DRM_GEM_CMA_HELPER_H__ */