net/gve: add DQO Tx descriptor limit

The hardware supports at most 10 data descriptors per MTU-sized segment.
GVE_TX_MAX_DATA_DESCS was defined in the initial implmenentation, but
the descriptor limit was never actually enforced.

Fixes: 4022f99 ("net/gve: support basic Tx data path for DQO")
Cc: [email protected]

Signed-off-by: Joshua Washington <[email protected]>
Reviewed-by: Ankit Garg <[email protected]>

Author: josh8551021

drivers/net/gve/gve_ethdev.c

@@ -450,6 +450,7 @@ gve_dev_info_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
 		.nb_max = gve_is_gqi(priv) ? priv->tx_desc_cnt : GVE_MAX_QUEUE_SIZE_DQO,
 		.nb_min = priv->tx_desc_cnt,
 		.nb_align = 1,
+		.nb_mtu_seg_max = GVE_TX_MAX_DATA_DESCS,
 	};
 
 	return 0;

drivers/net/gve/gve_ethdev.h

@@ -82,6 +82,7 @@ struct gve_tx_stats {
 	uint64_t packets;
 	uint64_t bytes;
 	uint64_t errors;
+	uint64_t too_many_descs;
 };
 
 struct gve_rx_stats {

drivers/net/gve/gve_tx_dqo.c

@@ -154,6 +154,12 @@ gve_tx_burst_dqo(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
 				break;
 		}
 
+		/* Drop packet if it doesn't adhere to hardware limits. */
+		if (nb_descs > GVE_TX_MAX_DATA_DESCS) {
+			txq->stats.too_many_descs++;
+			break;
+		}
+
 		do {
 			if (sw_ring[sw_id] != NULL)
 				PMD_DRV_LOG(DEBUG, "Overwriting an entry in sw_ring");