CHROMIUM: drm/virtio: Add virtio specific dma_buf_ops.

BUG=chromium:892342
TEST=xeyes repeatedly does not fail

Change-Id: Ic4ed0b2bd3a6cc3afe1bb563e7474f407f1de0ec
Signed-off-by: David Riley <davidriley@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1351814
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Reviewed-by: Zach Reizner <zachr@chromium.org>

drivers/gpu/drm/virtio/virtgpu_drv.c

@@ -128,8 +128,8 @@ static struct drm_driver driver = {
 #endif
 	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,
 	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,
-	.gem_prime_export = drm_gem_prime_export,
-	.gem_prime_import = drm_gem_prime_import,
+	.gem_prime_export = virtgpu_gem_prime_export,
+	.gem_prime_import = virtgpu_gem_prime_import,
 	.gem_prime_pin = virtgpu_gem_prime_pin,
 	.gem_prime_unpin = virtgpu_gem_prime_unpin,
 	.gem_prime_get_sg_table = virtgpu_gem_prime_get_sg_table,

drivers/gpu/drm/virtio/virtgpu_drv.h

@@ -379,6 +379,13 @@ void virtio_gpu_object_free_sg_table(struct virtio_gpu_object *bo);
 int virtio_gpu_object_wait(struct virtio_gpu_object *bo, bool no_wait);
 
 /* virtgpu_prime.c */
+struct dma_buf_ops;
+extern const struct dma_buf_ops virtgpu_dmabuf_ops;
+struct dma_buf *virtgpu_gem_prime_export(struct drm_device *dev,
+					 struct drm_gem_object *obj,
+					 int flags);
+struct drm_gem_object *virtgpu_gem_prime_import(struct drm_device *dev,
+						struct dma_buf *buf);
 int virtgpu_gem_prime_pin(struct drm_gem_object *obj);
 void virtgpu_gem_prime_unpin(struct drm_gem_object *obj);
 struct sg_table *virtgpu_gem_prime_get_sg_table(struct drm_gem_object *obj);

drivers/gpu/drm/virtio/virtgpu_prime.c

@@ -22,12 +22,59 @@
  * Authors: Andreas Pokorny
  */
 
+#include <linux/dma-buf.h>
 #include "virtgpu_drv.h"
 
 /* Empty Implementations as there should not be any other driver for a virtual
  * device that might share buffers with virtgpu
  */
 
+const struct dma_buf_ops virtgpu_dmabuf_ops =  {
+	.attach = drm_gem_map_attach,
+	.detach = drm_gem_map_detach,
+	.map_dma_buf = drm_gem_map_dma_buf,
+	.unmap_dma_buf = drm_gem_unmap_dma_buf,
+	.release = drm_gem_dmabuf_release,
+	.map = drm_gem_dmabuf_kmap,
+	.unmap = drm_gem_dmabuf_kunmap,
+	.mmap = drm_gem_dmabuf_mmap,
+	.vmap = drm_gem_dmabuf_vmap,
+	.vunmap = drm_gem_dmabuf_vunmap,
+};
+
+struct dma_buf *virtgpu_gem_prime_export(struct drm_device *dev,
+					 struct drm_gem_object *obj,
+					 int flags)
+{
+	struct dma_buf *buf;
+
+	buf = drm_gem_prime_export(dev, obj, flags);
+	if (!IS_ERR(buf))
+		buf->ops = &virtgpu_dmabuf_ops;
+
+	return buf;
+}
+
+struct drm_gem_object *virtgpu_gem_prime_import(struct drm_device *dev,
+						struct dma_buf *buf)
+{
+	struct drm_gem_object *obj;
+
+	if (buf->ops == &virtgpu_dmabuf_ops) {
+		obj = buf->priv;
+		if (obj->dev == dev) {
+			/*
+			 * Importing dmabuf exported from our own gem increases
+			 * refcount on gem itself instead of f_count of dmabuf.
+			 */
+			drm_gem_object_get(obj);
+			return obj;
+		}
+	}
+
+	return drm_gem_prime_import(dev, buf);
+}
+
 int virtgpu_gem_prime_pin(struct drm_gem_object *obj)
 {
 	WARN_ONCE(1, "not implemented");