vdpa/mlx5: Fix tracking of current number of VQs

Modify the code such that ndev->cur_num_vqs better reflects the actual
number of data virtqueues. The value can be accurately realized after
features have been negotiated.

This is to prevent possible failures when modifying the RQT object if
the cur_num_vqs bears invalid value.

No issue was actually encountered but this also makes the code more
readable.

Fixes: c5a5cd3d3217 ("vdpa/mlx5: Support configuring max data virtqueue")
Signed-off-by: Eli Cohen <elic@nvidia.com>
Link: https://lore.kernel.org/r/20220111183400.38418-5-elic@nvidia.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Si-Wei Liu<si-wei.liu@oracle.com>
Acked-by: Jason Wang <jasowang@redhat.com>

drivers/vdpa/mlx5/net/mlx5_vnet.c

@@ -1246,8 +1246,7 @@ static int create_rqt(struct mlx5_vdpa_net *ndev)
 	if (!(ndev->mvdev.actual_features & BIT_ULL(VIRTIO_NET_F_MQ)))
 		num = 1;
 	else
-		num = mlx5vdpa16_to_cpu(&ndev->mvdev,
-					ndev->config.max_virtqueue_pairs);
+		num = ndev->cur_num_vqs / 2;
 
 	max_rqt = min_t(int, roundup_pow_of_two(num),
 			1 << MLX5_CAP_GEN(ndev->mvdev.mdev, log_max_rqt_size));
@@ -1983,6 +1982,11 @@ static int mlx5_vdpa_set_driver_features(struct vdpa_device *vdev, u64 features)
 		return err;
 
 	ndev->mvdev.actual_features = features & ndev->mvdev.mlx_features;
+	if (ndev->mvdev.actual_features & BIT_ULL(VIRTIO_NET_F_MQ))
+		ndev->cur_num_vqs = 2 * mlx5vdpa16_to_cpu(mvdev, ndev->config.max_virtqueue_pairs);
+	else
+		ndev->cur_num_vqs = 2;
+
 	update_cvq_info(mvdev);
 	return err;
 }
@@ -2233,6 +2237,7 @@ static int mlx5_vdpa_reset(struct vdpa_device *vdev)
 	clear_vqs_ready(ndev);
 	mlx5_vdpa_destroy_mr(&ndev->mvdev);
 	ndev->mvdev.status = 0;
+	ndev->cur_num_vqs = 0;
 	memset(ndev->event_cbs, 0, sizeof(*ndev->event_cbs) * (mvdev->max_vqs + 1));
 	ndev->mvdev.actual_features = 0;
 	++mvdev->generation;
@@ -2641,9 +2646,8 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev *v_mdev, const char *name,
 
 	ndev->nb.notifier_call = event_handler;
 	mlx5_notifier_register(mdev, &ndev->nb);
-	ndev->cur_num_vqs = 2 * mlx5_vdpa_max_qps(max_vqs);
 	mvdev->vdev.mdev = &mgtdev->mgtdev;
-	err = _vdpa_register_device(&mvdev->vdev, ndev->cur_num_vqs + 1);
+	err = _vdpa_register_device(&mvdev->vdev, 2 * mlx5_vdpa_max_qps(max_vqs) + 1);
 	if (err)
 		goto err_reg;