[dpdk-dev] [PATCH 12/17] net/hns3: fix stats flip overflow

[Lijun Ou <oulijun@huawei.com>]

From: Chengchang Tang <tangchengchang@huawei.com>

Currently, statistics may overflow in some scenarios.

For example, if HW statistics are reset by stats reset operation,
but there are still a lot of residual packets exist in the HW
queues and these packets are error packets, flip may occurred
because the ipacket is obtained by substracting the number of
software error packets from the number of HW received packets.

This patch verifies the calculation and returns 0 when overflow
may occur.

Fixes: 8839c5e202f3 ("net/hns3: support device stats")
Cc: stable@dpdk.org

Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>
Signed-off-by: Lijun Ou <oulijun@huawei.com>
---
 drivers/net/hns3/hns3_stats.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/net/hns3/hns3_stats.c b/drivers/net/hns3/hns3_stats.c
index e58ebea..58cce35 100644
--- a/drivers/net/hns3/hns3_stats.c
+++ b/drivers/net/hns3/hns3_stats.c
@@ -637,8 +637,14 @@ hns3_stats_get(struct rte_eth_dev *eth_dev, struct rte_eth_stats *rte_stats)
 #endif
 
 	rte_stats->oerrors = 0;
-	rte_stats->ipackets = stats->rcb_rx_ring_pktnum_rcd -
-		rte_stats->ierrors;
+	/*
+	 * If HW statistics are reset by stats_reset, but a lot of residual
+	 * packets exist in the hardware queue and these packets are error
+	 * packets, flip overflow may occurred. So return 0 in this case.
+	 */
+	rte_stats->ipackets =
+		stats->rcb_rx_ring_pktnum_rcd > rte_stats->ierrors ?
+		stats->rcb_rx_ring_pktnum_rcd - rte_stats->ierrors : 0;
 	rte_stats->opackets  = stats->rcb_tx_ring_pktnum_rcd -
 		rte_stats->oerrors;
 	rte_stats->rx_nombuf = eth_dev->data->rx_mbuf_alloc_failed;
@@ -889,8 +895,15 @@ hns3_rxq_basic_stats_get(struct rte_eth_dev *dev, struct rte_eth_xstat *xstats,
 		rxq_stats = &rxq->basic_stats;
 		rxq_stats->errors = rxq->err_stats.l2_errors +
 					rxq->err_stats.pkt_len_errors;
-		rxq_stats->packets = stats->rcb_rx_ring_pktnum[i] -
-			rxq_stats->errors;
+		/*
+		 * If HW statistics are reset by stats_reset, but a lot of
+		 * residual packets exist in the hardware queue and these
+		 * packets are error packets, flip overflow may occurred.
+		 * So return 0 in this case.
+		 */
+		rxq_stats->packets =
+			stats->rcb_rx_ring_pktnum[i] > rxq_stats->errors ?
+			stats->rcb_rx_ring_pktnum[i] - rxq_stats->errors : 0;
 
 		for (j = 0; j < HNS3_NUM_RXQ_BASIC_STATS; j++) {
 			val = (char *)rxq_stats +
-- 
2.7.4