vdpa_sim: switch to use __vdpa_alloc_device()

This allows us to control the allocation size of the structure.
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20221223055548.27810-2-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/vdpa/vdpa_sim/vdpa_sim.c

@@ -251,6 +251,7 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 			       const struct vdpa_dev_set_config *config)
 {
 	const struct vdpa_config_ops *ops;
+	struct vdpa_device *vdpa;
 	struct vdpasim *vdpasim;
 	struct device *dev;
 	int i, ret = -ENOMEM;
@@ -268,14 +269,16 @@ struct vdpasim *vdpasim_create(struct vdpasim_dev_attr *dev_attr,
 	else
 		ops = &vdpasim_config_ops;
 
-	vdpasim = vdpa_alloc_device(struct vdpasim, vdpa, NULL, ops,
+	vdpa = __vdpa_alloc_device(NULL, ops,
 				   dev_attr->ngroups, dev_attr->nas,
+				   sizeof(struct vdpasim),
 				   dev_attr->name, false);
-	if (IS_ERR(vdpasim)) {
-		ret = PTR_ERR(vdpasim);
+	if (IS_ERR(vdpa)) {
+		ret = PTR_ERR(vdpa);
 		goto err_alloc;
 	}
 
+	vdpasim = vdpa_to_sim(vdpa);
 	vdpasim->dev_attr = *dev_attr;
 	INIT_WORK(&vdpasim->work, dev_attr->work_fn);
 	spin_lock_init(&vdpasim->lock);