IB/mlx4: Fix incorrectly releasing steerable UD QPs when have only ETH ports

commit 852f6927 upstream.

Allocating steerable UD QPs depends on having at least one IB port,
while releasing those QPs does not.

As a result, when there are only ETH ports, the IB (RoCE) driver
requests releasing a qp range whose base qp is zero, with
qp count zero.

When SR-IOV is enabled, and the VF driver is running on a VM over
a hypervisor which treats such qp release calls as errors
(rather than NOPs), we see lines in the VM message log like:

 mlx4_core 0002:00:02.0: Failed to release qp range base:0 cnt:0

Fix this by adding a check for a zero count in mlx4_release_qp_range()
(which thus treats releasing 0 qps as a nop), and eliminating the
check for device managed flow steering when releasing steerable UD QPs.
(Freeing ib_uc_qpns_bitmap unconditionally is also OK, since it
remains NULL when steerable UD QPs are not allocated).

Fixes: 4196670b ("IB/mlx4: Don't allocate range of steerable UD QPs for Ethernet-only device")
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/infiniband/hw/mlx4/main.c

@@ -2483,7 +2483,6 @@ static void *mlx4_ib_add(struct mlx4_dev *dev)
 	kfree(ibdev->ib_uc_qpns_bitmap);
 
 err_steer_qp_release:
-	if (ibdev->steering_support == MLX4_STEERING_MODE_DEVICE_MANAGED)
 	mlx4_qp_release_range(dev, ibdev->steer_qpn_base,
 			      ibdev->steer_qpn_count);
 err_counter:
@@ -2586,11 +2585,9 @@ static void mlx4_ib_remove(struct mlx4_dev *dev, void *ibdev_ptr)
 		ibdev->iboe.nb.notifier_call = NULL;
 	}
 
-	if (ibdev->steering_support == MLX4_STEERING_MODE_DEVICE_MANAGED) {
 	mlx4_qp_release_range(dev, ibdev->steer_qpn_base,
 			      ibdev->steer_qpn_count);
 	kfree(ibdev->ib_uc_qpns_bitmap);
-	}
 
 	iounmap(ibdev->uar_map);
 	for (p = 0; p < ibdev->num_ports; ++p)

drivers/net/ethernet/mellanox/mlx4/qp.c

@@ -280,6 +280,9 @@ void mlx4_qp_release_range(struct mlx4_dev *dev, int base_qpn, int cnt)
 	u64 in_param = 0;
 	int err;
 
+	if (!cnt)
+		return;
+
 	if (mlx4_is_mfunc(dev)) {
 		set_param_l(&in_param, base_qpn);
 		set_param_h(&in_param, cnt);