virtio: Rework virtio_gpu_object_kmap()

Currently, virtio_gpu_object_kmap() is only called by
virtio_gpufb_create(), when a DRM framebuffer is created.

Thus, instead of returning the vmap'ed address, emit a warning
if virtio_gpu_object_kmap is called on an already mapped
object. With this change, kmap/kunmap calls are now balanced.
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20180925161606.17980-3-ezequiel@collabora.comSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_drv.h

@@ -364,7 +364,7 @@ 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_kmap(struct virtio_gpu_object *bo);
 int virtio_gpu_object_get_sg_table(struct virtio_gpu_device *qdev,
 				   struct virtio_gpu_object *bo);
 void virtio_gpu_object_free_sg_table(struct virtio_gpu_object *bo);

drivers/gpu/drm/virtio/virtgpu_fb.c

@@ -203,12 +203,6 @@ static struct fb_ops virtio_gpufb_ops = {
 	.fb_imageblit = virtio_gpu_3d_imageblit,
 };
 
-static int virtio_gpu_vmap_fb(struct virtio_gpu_device *vgdev,
-			      struct virtio_gpu_object *obj)
-{
-	return virtio_gpu_object_kmap(obj, NULL);
-}
-
 static int virtio_gpufb_create(struct drm_fb_helper *helper,
 			       struct drm_fb_helper_surface_size *sizes)
 {
@@ -241,9 +235,9 @@ static int virtio_gpufb_create(struct drm_fb_helper *helper,
 	virtio_gpu_cmd_create_resource(vgdev, resid, format,
 				       mode_cmd.width, mode_cmd.height);
 
-	ret = virtio_gpu_vmap_fb(vgdev, obj);
+	ret = virtio_gpu_object_kmap(obj);
 	if (ret) {
-		DRM_ERROR("failed to vmap fb %d\n", ret);
+		DRM_ERROR("failed to kmap fb %d\n", ret);
 		goto err_obj_vmap;
 	}
 

drivers/gpu/drm/virtio/virtgpu_object.c

@@ -107,22 +107,17 @@ void virtio_gpu_object_kunmap(struct virtio_gpu_object *bo)
 	ttm_bo_kunmap(&bo->kmap);
 }
 
-int virtio_gpu_object_kmap(struct virtio_gpu_object *bo, void **ptr)
+int virtio_gpu_object_kmap(struct virtio_gpu_object *bo)
 {
 	bool is_iomem;
 	int r;
 
-	if (bo->vmap) {
-		if (ptr)
-			*ptr = bo->vmap;
-		return 0;
-	}
+	WARN_ON(bo->vmap);
+
 	r = ttm_bo_kmap(&bo->tbo, 0, bo->tbo.num_pages, &bo->kmap);
 	if (r)
 		return r;
 	bo->vmap = ttm_kmap_obj_virtual(&bo->kmap, &is_iomem);
-	if (ptr)
-		*ptr = bo->vmap;
 	return 0;
 }