Merge branch 'netdevsim-implement-rx-statistics-using-netdev_pcpu_stat_dstats'

Breno Leitao says:

====================
netdevsim: implement RX statistics using NETDEV_PCPU_STAT_DSTATS

The netdevsim driver previously lacked RX statistics support, which
prevented its use with the GenerateTraffic() test framework, as this
framework verifies traffic flow by checking RX byte counts.

This patch migrates netdevsim from its custom statistics collection to
the NETDEV_PCPU_STAT_DSTATS framework, as suggested by Jakub. This
change not only standardizes the statistics handling but also adds the
necessary RX statistics support required by the test framework.

v3: https://lore.kernel.org/20250617-netdevsim_stat-v3-0-afe4bdcbf237@debian.org
v2: https://lore.kernel.org/20250613-netdevsim_stat-v2-0-98fa38836c48@debian.org
v1: https://lore.kernel.org/20250611-netdevsim_stat-v1-0-c11b657d96bf@debian.org
====================

Link: https://patch.msgid.link/20250618-netdevsim_stat-v4-0-19fe0d35e28e@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

3 files changed, 33 insertions, 38 deletions

diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index fa5fbd97ad69..7f2809be5d48 100644
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -93,19 +93,14 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		hrtimer_start(&rq->napi_timer, us_to_ktime(5), HRTIMER_MODE_REL);
 
 	rcu_read_unlock();
-	u64_stats_update_begin(&ns->syncp);
-	ns->tx_packets++;
-	ns->tx_bytes += len;
-	u64_stats_update_end(&ns->syncp);
+	dev_dstats_tx_add(dev, skb->len);
 	return NETDEV_TX_OK;
 
 out_drop_free:
 	dev_kfree_skb(skb);
 out_drop_cnt:
 	rcu_read_unlock();
-	u64_stats_update_begin(&ns->syncp);
-	ns->tx_dropped++;
-	u64_stats_update_end(&ns->syncp);
+	dev_dstats_tx_dropped(dev);
 	return NETDEV_TX_OK;
 }
 
@@ -126,20 +121,6 @@ static int nsim_change_mtu(struct net_device *dev, int new_mtu)
 	return 0;
 }
 
-static void
-nsim_get_stats64(struct net_device *dev, struct rtnl_link_stats64 *stats)
-{
-	struct netdevsim *ns = netdev_priv(dev);
-	unsigned int start;
-
-	do {
-		start = u64_stats_fetch_begin(&ns->syncp);
-		stats->tx_bytes = ns->tx_bytes;
-		stats->tx_packets = ns->tx_packets;
-		stats->tx_dropped = ns->tx_dropped;
-	} while (u64_stats_fetch_retry(&ns->syncp, start));
-}
-
 static int
 nsim_setup_tc_block_cb(enum tc_setup_type type, void *type_data, void *cb_priv)
 {
@@ -350,16 +331,24 @@ static int nsim_get_iflink(const struct net_device *dev)
 
 static int nsim_rcv(struct nsim_rq *rq, int budget)
 {
+	struct net_device *dev = rq->napi.dev;
 	struct sk_buff *skb;
-	int i;
+	unsigned int skblen;
+	int i, ret;
 
 	for (i = 0; i < budget; i++) {
 		if (skb_queue_empty(&rq->skb_queue))
 			break;
 
 		skb = skb_dequeue(&rq->skb_queue);
+		/* skb might be discard at netif_receive_skb, save the len */
+		skblen = skb->len;
 		skb_mark_napi_id(skb, &rq->napi);
-		netif_receive_skb(skb);
+		ret = netif_receive_skb(skb);
+		if (ret == NET_RX_SUCCESS)
+			dev_dstats_rx_add(dev, skblen);
+		else
+			dev_dstats_rx_dropped(dev);
 	}
 
 	return i;
@@ -556,7 +545,6 @@ static const struct net_device_ops nsim_netdev_ops = {
 	.ndo_set_mac_address	= eth_mac_addr,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_change_mtu		= nsim_change_mtu,
-	.ndo_get_stats64	= nsim_get_stats64,
 	.ndo_set_vf_mac		= nsim_set_vf_mac,
 	.ndo_set_vf_vlan	= nsim_set_vf_vlan,
 	.ndo_set_vf_rate	= nsim_set_vf_rate,
@@ -580,7 +568,6 @@ static const struct net_device_ops nsim_vf_netdev_ops = {
 	.ndo_set_mac_address	= eth_mac_addr,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_change_mtu		= nsim_change_mtu,
-	.ndo_get_stats64	= nsim_get_stats64,
 	.ndo_setup_tc		= nsim_setup_tc,
 	.ndo_set_features	= nsim_set_features,
 };
@@ -594,7 +581,7 @@ static void nsim_get_queue_stats_rx(struct net_device *dev, int idx,
 	struct rtnl_link_stats64 rtstats = {};
 
 	if (!idx)
-		nsim_get_stats64(dev, &rtstats);
+		dev_get_stats(dev, &rtstats);
 
 	stats->packets = rtstats.rx_packets - !!rtstats.rx_packets;
 	stats->bytes = rtstats.rx_bytes;
@@ -606,7 +593,7 @@ static void nsim_get_queue_stats_tx(struct net_device *dev, int idx,
 	struct rtnl_link_stats64 rtstats = {};
 
 	if (!idx)
-		nsim_get_stats64(dev, &rtstats);
+		dev_get_stats(dev, &rtstats);
 
 	stats->packets = rtstats.tx_packets - !!rtstats.tx_packets;
 	stats->bytes = rtstats.tx_bytes;
@@ -618,7 +605,7 @@ static void nsim_get_base_stats(struct net_device *dev,
 {
 	struct rtnl_link_stats64 rtstats = {};
 
-	nsim_get_stats64(dev, &rtstats);
+	dev_get_stats(dev, &rtstats);
 
 	rx->packets = !!rtstats.rx_packets;
 	rx->bytes = 0;
@@ -645,9 +632,12 @@ static struct nsim_rq *nsim_queue_alloc(void)
 	return rq;
 }
 
-static void nsim_queue_free(struct nsim_rq *rq)
+static void nsim_queue_free(struct net_device *dev, struct nsim_rq *rq)
 {
 	hrtimer_cancel(&rq->napi_timer);
+	local_bh_disable();
+	dev_dstats_rx_dropped_add(dev, rq->skb_queue.qlen);
+	local_bh_enable();
 	skb_queue_purge_reason(&rq->skb_queue, SKB_DROP_REASON_QUEUE_PURGE);
 	kfree(rq);
 }
@@ -694,7 +684,7 @@ nsim_queue_mem_alloc(struct net_device *dev, void *per_queue_mem, int idx)
 	return 0;
 
 err_free:
-	nsim_queue_free(qmem->rq);
+	nsim_queue_free(dev, qmem->rq);
 	return err;
 }
 
@@ -708,7 +698,7 @@ static void nsim_queue_mem_free(struct net_device *dev, void *per_queue_mem)
 		if (!ns->rq_reset_mode)
 			netif_napi_del_locked(&qmem->rq->napi);
 		page_pool_destroy(qmem->rq->page_pool);
-		nsim_queue_free(qmem->rq);
+		nsim_queue_free(dev, qmem->rq);
 	}
 }
 
@@ -890,6 +880,7 @@ static void nsim_setup(struct net_device *dev)
 			    NETIF_F_HW_CSUM |
 			    NETIF_F_LRO |
 			    NETIF_F_TSO;
+	dev->pcpu_stat_type = NETDEV_PCPU_STAT_DSTATS;
 	dev->max_mtu = ETH_MAX_MTU;
 	dev->xdp_features = NETDEV_XDP_ACT_HW_OFFLOAD;
 }
@@ -925,7 +916,7 @@ static void nsim_queue_uninit(struct netdevsim *ns)
 	int i;
 
 	for (i = 0; i < dev->num_rx_queues; i++)
-		nsim_queue_free(ns->rq[i]);
+		nsim_queue_free(dev, ns->rq[i]);
 
 	kfree(ns->rq);
 	ns->rq = NULL;
@@ -1022,7 +1013,6 @@ nsim_create(struct nsim_dev *nsim_dev, struct nsim_dev_port *nsim_dev_port)
 	dev_net_set(dev, nsim_dev_net(nsim_dev));
 	ns = netdev_priv(dev);
 	ns->netdev = dev;
-	u64_stats_init(&ns->syncp);
 	ns->nsim_dev = nsim_dev;
 	ns->nsim_dev_port = nsim_dev_port;
 	ns->nsim_bus_dev = nsim_dev->nsim_bus_dev;
diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h
index 511ed72a93ce..4a0c48c7a384 100644
--- a/drivers/net/netdevsim/netdevsim.h
+++ b/drivers/net/netdevsim/netdevsim.h
@@ -108,11 +108,6 @@ struct netdevsim {
 
 	int rq_reset_mode;
 
-	u64 tx_packets;
-	u64 tx_bytes;
-	u64 tx_dropped;
-	struct u64_stats_sync syncp;
-
 	struct nsim_bus_dev *nsim_bus_dev;
 
 	struct bpf_prog	*bpf_offloaded;
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 9cbc4e54b7e4..03c26bb0fbbe 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3016,6 +3016,16 @@ static inline void dev_dstats_rx_dropped(struct net_device *dev)
 	u64_stats_update_end(&dstats->syncp);
 }
 
+static inline void dev_dstats_rx_dropped_add(struct net_device *dev,
+					     unsigned int packets)
+{
+	struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);
+
+	u64_stats_update_begin(&dstats->syncp);
+	u64_stats_add(&dstats->rx_drops, packets);
+	u64_stats_update_end(&dstats->syncp);
+}
+
 static inline void dev_dstats_tx_add(struct net_device *dev,
 				     unsigned int len)
 {