linux-kernel - [PATCH] net: stmmac: fix ethtool per-queue statistics

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Date: Fri,  5 Jan 2024 19:10:24 +0100
From: Petr Tesarik <petr@...arici.cz>
To: Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Jisheng Zhang <jszhang@...nel.org>,
	netdev@...r.kernel.org (open list:STMMAC ETHERNET DRIVER),
	linux-stm32@...md-mailman.stormreply.com (moderated list:ARM/STM32 ARCHITECTURE),
	linux-arm-kernel@...ts.infradead.org (moderated list:ARM/STM32 ARCHITECTURE),
	linux-kernel@...r.kernel.org (open list)
Cc: Petr Tesarik <petr@...arici.cz>
Subject: [PATCH] net: stmmac: fix ethtool per-queue  statistics

Fix per-queue statistics for devices with more than one queue.

The output data pointer is currently reset in each loop iteration,
effectively summing all queue statistics in the first four u64 values.

The summary values are not even labeled correctly. For example, if eth0 has
2 queues, ethtool -S eth0 shows:

     q0_tx_pkt_n: 374 (actually tx_pkt_n over all queues)
     q0_tx_irq_n: 23  (actually tx_normal_irq_n over all queues)
     q1_tx_pkt_n: 462 (actually rx_pkt_n over all queues)
     q1_tx_irq_n: 446 (actually rx_normal_irq_n over all queues)
     q0_rx_pkt_n: 0
     q0_rx_irq_n: 0
     q1_rx_pkt_n: 0
     q1_rx_irq_n: 0

While touching this code, change the pointer type to u64 and get rid of the
weird pointer arithmetic.

Signed-off-by: Petr Tesarik <petr@...arici.cz>
Fixes: 133466c3bbe1 ("net: stmmac: use per-queue 64 bit statistics where necessary")
---
 .../ethernet/stmicro/stmmac/stmmac_ethtool.c  | 23 ++++++-------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
index f628411ae4ae..023876fc4da7 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_ethtool.c
@@ -543,43 +543,34 @@ static void stmmac_get_per_qstats(struct stmmac_priv *priv, u64 *data)
 	u32 rx_cnt = priv->plat->rx_queues_to_use;
 	unsigned int start;
 	int q, stat;
-	u64 *pos;
-	char *p;
+	u64 *p;
 
-	pos = data;
 	for (q = 0; q < tx_cnt; q++) {
 		struct stmmac_txq_stats *txq_stats = &priv->xstats.txq_stats[q];
 		struct stmmac_txq_stats snapshot;
 
-		data = pos;
 		do {
 			start = u64_stats_fetch_begin(&txq_stats->syncp);
 			snapshot = *txq_stats;
 		} while (u64_stats_fetch_retry(&txq_stats->syncp, start));
 
-		p = (char *)&snapshot + offsetof(struct stmmac_txq_stats, tx_pkt_n);
-		for (stat = 0; stat < STMMAC_TXQ_STATS; stat++) {
-			*data++ += (*(u64 *)p);
-			p += sizeof(u64);
-		}
+		p = &snapshot.tx_pkt_n;
+		for (stat = 0; stat < STMMAC_TXQ_STATS; stat++)
+			*data++ = *p++;
 	}
 
-	pos = data;
 	for (q = 0; q < rx_cnt; q++) {
 		struct stmmac_rxq_stats *rxq_stats = &priv->xstats.rxq_stats[q];
 		struct stmmac_rxq_stats snapshot;
 
-		data = pos;
 		do {
 			start = u64_stats_fetch_begin(&rxq_stats->syncp);
 			snapshot = *rxq_stats;
 		} while (u64_stats_fetch_retry(&rxq_stats->syncp, start));
 
-		p = (char *)&snapshot + offsetof(struct stmmac_rxq_stats, rx_pkt_n);
-		for (stat = 0; stat < STMMAC_RXQ_STATS; stat++) {
-			*data++ += (*(u64 *)p);
-			p += sizeof(u64);
-		}
+		p = &snapshot.rx_pkt_n;
+		for (stat = 0; stat < STMMAC_RXQ_STATS; stat++)
+			*data++ = *p++;
 	}
 }
 
-- 
2.43.0