[PATCH 5/7] net/gve: add DQO Tx descriptor limit

[Joshua Washington <joshwash@google.com>]

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: 4022f9999f56 ("net/gve: support basic Tx data path for DQO")
Cc: junfeng.guo@intel.com
Cc: stable@dpdk.org

Signed-off-by: Joshua Washington <joshwash@google.com>
Reviewed-by: Ankit Garg <nktgrg@google.com>
---
 drivers/net/gve/gve_ethdev.c | 1 +
 drivers/net/gve/gve_ethdev.h | 1 +
 drivers/net/gve/gve_tx_dqo.c | 6 ++++++
 3 files changed, 8 insertions(+)

diff --git a/drivers/net/gve/gve_ethdev.c b/drivers/net/gve/gve_ethdev.c
index bdb7f1d075..81325ba98c 100644
--- a/drivers/net/gve/gve_ethdev.c
+++ b/drivers/net/gve/gve_ethdev.c
@@ -603,6 +603,7 @@ gve_dev_info_get(struct rte_eth_dev *dev, struct rte_eth_dev_info *dev_info)
 		.nb_max = priv->max_tx_desc_cnt,
 		.nb_min = priv->min_tx_desc_cnt,
 		.nb_align = 1,
+		.nb_mtu_seg_max = GVE_TX_MAX_DATA_DESCS,
 	};
 
 	dev_info->flow_type_rss_offloads = GVE_RTE_RSS_OFFLOAD_ALL;
diff --git a/drivers/net/gve/gve_ethdev.h b/drivers/net/gve/gve_ethdev.h
index 35cb9062b1..195dadc4d4 100644
--- a/drivers/net/gve/gve_ethdev.h
+++ b/drivers/net/gve/gve_ethdev.h
@@ -102,6 +102,7 @@ struct gve_tx_stats {
 	uint64_t packets;
 	uint64_t bytes;
 	uint64_t errors;
+	uint64_t too_many_descs;
 };
 
 struct gve_rx_stats {
diff --git a/drivers/net/gve/gve_tx_dqo.c b/drivers/net/gve/gve_tx_dqo.c
index 7e03e75b20..27f98cdeb3 100644
--- a/drivers/net/gve/gve_tx_dqo.c
+++ b/drivers/net/gve/gve_tx_dqo.c
@@ -165,6 +165,12 @@ 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 (!tso && nb_descs > GVE_TX_MAX_DATA_DESCS) {
+			txq->stats.too_many_descs++;
+			break;
+		}
+
 		if (tso) {
 			txd = &txr[tx_id];
 			gve_tx_fill_seg_desc_dqo(txd, tx_pkt);
-- 
2.50.0.727.gbf7dc18ff4-goog