drm/virtio: Use IDAs more efficiently

0-based IDAs are more efficient than any other base.  Convert the
1-based IDAs to be 0-based.
Signed-off-by: Matthew Wilcox <willy@infradead.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20181030165352.13065-2-willy@infradead.orgSigned-off-by: Gerd Hoffmann <kraxel@redhat.com>

drivers/gpu/drm/virtio/virtgpu_kms.c

@@ -55,10 +55,11 @@ static void virtio_gpu_config_changed_work_func(struct work_struct *work)
 static int virtio_gpu_context_create(struct virtio_gpu_device *vgdev,
 				      uint32_t nlen, const char *name)
 {
-	int handle = ida_alloc_min(&vgdev->ctx_id_ida, 1, GFP_KERNEL);
+	int handle = ida_alloc(&vgdev->ctx_id_ida, GFP_KERNEL);
 
 	if (handle < 0)
 		return handle;
+	handle += 1;
 	virtio_gpu_cmd_context_create(vgdev, handle, nlen, name);
 	return handle;
 }
@@ -67,7 +68,7 @@ static void virtio_gpu_context_destroy(struct virtio_gpu_device *vgdev,
 				      uint32_t ctx_id)
 {
 	virtio_gpu_cmd_context_destroy(vgdev, ctx_id);
-	ida_free(&vgdev->ctx_id_ida, ctx_id);
+	ida_free(&vgdev->ctx_id_ida, ctx_id - 1);
 }
 
 static void virtio_gpu_init_vq(struct virtio_gpu_queue *vgvq,

drivers/gpu/drm/virtio/virtgpu_object.c

@@ -28,18 +28,18 @@
 static int virtio_gpu_resource_id_get(struct virtio_gpu_device *vgdev,
 				       uint32_t *resid)
 {
-	int handle = ida_alloc_min(&vgdev->resource_ida, 1, GFP_KERNEL);
+	int handle = ida_alloc(&vgdev->resource_ida, GFP_KERNEL);
 
 	if (handle < 0)
 		return handle;
 
-	*resid = handle;
+	*resid = handle + 1;
 	return 0;
 }
 
 static void virtio_gpu_resource_id_put(struct virtio_gpu_device *vgdev, uint32_t id)
 {
-	ida_free(&vgdev->resource_ida, id);
+	ida_free(&vgdev->resource_ida, id - 1);
 }
 
 static void virtio_gpu_ttm_bo_destroy(struct ttm_buffer_object *tbo)