virtio: Add virtio_gpu_object_kunmap()

Implement a virtio_gpu_object_kunmap() to unmap the kernel
mapping, and use it in the TTM object destroy path.
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20180925161606.17980-2-ezequiel@collabora.comSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_drv.h

@@ -363,6 +363,7 @@ void virtio_gpu_fence_event_process(struct virtio_gpu_device *vdev,
 int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
 			     unsigned long size, bool kernel, bool pinned,
 			     struct virtio_gpu_object **bo_ptr);
+void virtio_gpu_object_kunmap(struct virtio_gpu_object *bo);
 int virtio_gpu_object_kmap(struct virtio_gpu_object *bo, void **ptr);
 int virtio_gpu_object_get_sg_table(struct virtio_gpu_device *qdev,
 				   struct virtio_gpu_object *bo);

drivers/gpu/drm/virtio/virtgpu_object.c

@@ -37,6 +37,8 @@ static void virtio_gpu_ttm_bo_destroy(struct ttm_buffer_object *tbo)
 		virtio_gpu_cmd_unref_resource(vgdev, bo->hw_res_handle);
 	if (bo->pages)
 		virtio_gpu_object_free_sg_table(bo);
+	if (bo->vmap)
+		virtio_gpu_object_kunmap(bo);
 	drm_gem_object_release(&bo->gem_base);
 	kfree(bo);
 }
@@ -99,6 +101,12 @@ int virtio_gpu_object_create(struct virtio_gpu_device *vgdev,
 	return 0;
 }
 
+void virtio_gpu_object_kunmap(struct virtio_gpu_object *bo)
+{
+	bo->vmap = NULL;
+	ttm_bo_kunmap(&bo->kmap);
+}
+
 int virtio_gpu_object_kmap(struct virtio_gpu_object *bo, void **ptr)
 {
 	bool is_iomem;