[PATCH net 2/4] gve: Fix backward stats when interface goes down or configuration is adjusted

[Harshitha Ramamurthy <hramamurthy@google.com>]

From: Debarghya Kundu <debarghyak@google.com>

gve_get_base_stats() sets all the stats to 0, so the stats go backwards
when interface goes down or configuration is adjusted.

Fix this by persisting baseline stats across interface down.

This was discovered by drivers/net/stats.py selftest.

Cc: stable@vger.kernel.org
Fixes: 2e5e0932dff5 ("gve: add support for basic queue stats")
Signed-off-by: Debarghya Kundu <debarghyak@google.com>
Signed-off-by: Pin-yen Lin <treapking@google.com>
Signed-off-by: Harshitha Ramamurthy <hramamurthy@google.com>
---
 drivers/net/ethernet/google/gve/gve.h      |  6 ++
 drivers/net/ethernet/google/gve/gve_main.c | 64 +++++++++++++++++++---
 2 files changed, 63 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve.h b/drivers/net/ethernet/google/gve/gve.h
index cbdf3a842cfe..ff7797043908 100644
--- a/drivers/net/ethernet/google/gve/gve.h
+++ b/drivers/net/ethernet/google/gve/gve.h
@@ -794,6 +794,10 @@ struct gve_ptp {
 	struct gve_priv *priv;
 };
 
+struct gve_ring_err_stats {
+	u64 rx_alloc_fails;
+};
+
 struct gve_priv {
 	struct net_device *dev;
 	struct gve_tx_ring *tx; /* array of tx_cfg.num_queues */
@@ -882,6 +886,8 @@ struct gve_priv {
 	unsigned long service_task_flags;
 	unsigned long state_flags;
 
+	struct gve_ring_err_stats base_ring_err_stats;
+	struct rtnl_link_stats64 base_net_stats;
 	struct gve_stats_report *stats_report;
 	u64 stats_report_len;
 	dma_addr_t stats_report_bus; /* dma address for the stats report */
diff --git a/drivers/net/ethernet/google/gve/gve_main.c b/drivers/net/ethernet/google/gve/gve_main.c
index 675382e9756c..8617782791e0 100644
--- a/drivers/net/ethernet/google/gve/gve_main.c
+++ b/drivers/net/ethernet/google/gve/gve_main.c
@@ -105,9 +105,22 @@ static netdev_tx_t gve_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		return gve_tx_dqo(skb, dev);
 }
 
-static void gve_get_stats(struct net_device *dev, struct rtnl_link_stats64 *s)
+static void gve_add_base_stats(struct gve_priv *priv,
+			       struct rtnl_link_stats64 *s)
+{
+	struct rtnl_link_stats64 *base_stats = &priv->base_net_stats;
+
+	s->rx_packets += base_stats->rx_packets;
+	s->rx_bytes += base_stats->rx_bytes;
+	s->rx_dropped += base_stats->rx_dropped;
+	s->tx_packets += base_stats->tx_packets;
+	s->tx_bytes += base_stats->tx_bytes;
+	s->tx_dropped += base_stats->tx_dropped;
+}
+
+static void gve_get_ring_stats(struct gve_priv *priv,
+			       struct rtnl_link_stats64 *s)
 {
-	struct gve_priv *priv = netdev_priv(dev);
 	unsigned int start;
 	u64 packets, bytes;
 	int num_tx_queues;
@@ -142,6 +155,14 @@ static void gve_get_stats(struct net_device *dev, struct rtnl_link_stats64 *s)
 	}
 }
 
+static void gve_get_stats(struct net_device *dev, struct rtnl_link_stats64 *s)
+{
+	struct gve_priv *priv = netdev_priv(dev);
+
+	gve_get_ring_stats(priv, s);
+	gve_add_base_stats(priv, s);
+}
+
 static int gve_alloc_flow_rule_caches(struct gve_priv *priv)
 {
 	struct gve_flow_rules_cache *flow_rules_cache = &priv->flow_rules_cache;
@@ -1493,6 +1514,23 @@ static int gve_queues_stop(struct gve_priv *priv)
 	return gve_reset_recovery(priv, false);
 }
 
+static void gve_get_ring_err_stats(struct gve_priv *priv,
+				   struct gve_ring_err_stats *err_stats)
+{
+	int ring;
+
+	for (ring = 0; ring < priv->rx_cfg.num_queues; ring++) {
+		unsigned int start;
+		struct gve_rx_ring *rx = &priv->rx[ring];
+
+		do {
+			start = u64_stats_fetch_begin(&rx->statss);
+			err_stats->rx_alloc_fails +=
+				rx->rx_skb_alloc_fail + rx->rx_buf_alloc_fail;
+		} while (u64_stats_fetch_retry(&rx->statss, start));
+	}
+}
+
 static int gve_close(struct net_device *dev)
 {
 	struct gve_priv *priv = netdev_priv(dev);
@@ -1502,6 +1540,10 @@ static int gve_close(struct net_device *dev)
 	if (err)
 		return err;
 
+	/* Save ring queue and err stats before closing the interface */
+	gve_get_ring_stats(priv, &priv->base_net_stats);
+	gve_get_ring_err_stats(priv, &priv->base_ring_err_stats);
+
 	gve_queues_mem_remove(priv);
 	return 0;
 }
@@ -2743,12 +2785,20 @@ static void gve_get_base_stats(struct net_device *dev,
 			       struct netdev_queue_stats_rx *rx,
 			       struct netdev_queue_stats_tx *tx)
 {
-	rx->packets = 0;
-	rx->bytes = 0;
-	rx->alloc_fail = 0;
+	const struct gve_ring_err_stats *base_err_stats;
+	const struct rtnl_link_stats64 *base_stats;
+	struct gve_priv *priv;
+
+	priv = netdev_priv(dev);
+	base_stats = &priv->base_net_stats;
+	base_err_stats = &priv->base_ring_err_stats;
+
+	rx->packets = base_stats->rx_packets;
+	rx->bytes = base_stats->rx_bytes;
+	rx->alloc_fail = base_err_stats->rx_alloc_fails;
 
-	tx->packets = 0;
-	tx->bytes = 0;
+	tx->packets = base_stats->tx_packets;
+	tx->bytes = base_stats->tx_bytes;
 }
 
 static const struct netdev_stat_ops gve_stat_ops = {
-- 
2.54.0.rc0.605.g598a273b03-goog