net/hns3: fix unchecked Rx free threshold

[ upstream commit c1f0cd3a4c834c2e550370b6d31b6bcd456a15f9 ]

To reduce the frequency of updating the head pointer of Rx queue,
driver just updates this pointer when the number of processed
descriptors is greater than the Rx free threshold. If the Rx free
threshold is set to a value greater than or equal to the number of
descriptors in Rx queue, the driver does not update this pointer.
As a result, the hardware cannot receive more packets.

This patch fix it by adding Rx free threshold check.

Fixes: bba6366 ("net/hns3: support Rx/Tx and related operations")

Signed-off-by: Dengdui Huang <huangdengdui@huawei.com>

drivers/net/hns3/hns3_rxtx.c

@@ -1796,6 +1796,12 @@ hns3_rx_queue_conf_check(struct hns3_hw *hw, const struct rte_eth_rxconf *conf,
 		return -EINVAL;
 	}
 
+	if (conf->rx_free_thresh >= nb_desc) {
+		hns3_err(hw, "rx_free_thresh (%u) must be less than %u",
+			 conf->rx_free_thresh, nb_desc);
+		return -EINVAL;
+	}
+
 	if (conf->rx_drop_en == 0)
 		hns3_warn(hw, "if no descriptors available, packets are always "
 			  "dropped and rx_drop_en (1) is fixed on");