netdev - [PATCH net 2/2] bnxt_en: Linearize TX SKB if the fragments exceed the max

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Message-ID: <20250321211639.3812992-3-michael.chan@broadcom.com>
Date: Fri, 21 Mar 2025 14:16:39 -0700
From: Michael Chan <michael.chan@...adcom.com>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	andrew+netdev@...n.ch,
	pavan.chebbi@...adcom.com,
	andrew.gospodarek@...adcom.com,
	osk@...gle.com,
	Somnath Kotur <somnath.kotur@...adcom.com>,
	Kalesh AP <kalesh-anakkur.purayil@...adcom.com>
Subject: [PATCH net 2/2] bnxt_en: Linearize TX SKB if the fragments exceed the max

If skb_shinfo(skb)->nr_frags excceds what the chip can support,
linearize the SKB and warn once to let the user know.
net.core.max_skb_frags can be lowered, for example, to avoid the
issue.

Fixes: 3948b05950fd ("net: introduce a config option to tweak MAX_SKB_FRAGS")
Reviewed-by: Somnath Kotur <somnath.kotur@...adcom.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@...adcom.com>
Reviewed-by: Andy Gospodarek <andrew.gospodarek@...adcom.com>
Signed-off-by: Michael Chan <michael.chan@...adcom.com>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 11 +++++++++++
 drivers/net/ethernet/broadcom/bnxt/bnxt.h |  4 ++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 158e9789c1f4..2cd79b59cf00 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -485,6 +485,17 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	txr = &bp->tx_ring[bp->tx_ring_map[i]];
 	prod = txr->tx_prod;
 
+#if (MAX_SKB_FRAGS > TX_MAX_FRAGS)
+	if (skb_shinfo(skb)->nr_frags > TX_MAX_FRAGS) {
+		netdev_warn_once(dev, "SKB has too many (%d) fragments, max supported is %d.  SKB will be linearized.\n",
+				 skb_shinfo(skb)->nr_frags, TX_MAX_FRAGS);
+		if (skb_linearize(skb)) {
+			dev_kfree_skb_any(skb);
+			dev_core_stats_tx_dropped_inc(dev);
+			return NETDEV_TX_OK;
+		}
+	}
+#endif
 	free_size = bnxt_tx_avail(bp, txr);
 	if (unlikely(free_size < skb_shinfo(skb)->nr_frags + 2)) {
 		/* We must have raced with NAPI cleanup */
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index 3b4a044db73e..d621fb621f30 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -84,6 +84,10 @@ struct tx_bd {
 
 #define TX_BD_CNT(n)	(((n) << TX_BD_FLAGS_BD_CNT_SHIFT) & TX_BD_FLAGS_BD_CNT)
 
+#define TX_MAX_BD_CNT	32
+
+#define TX_MAX_FRAGS		(TX_MAX_BD_CNT - 2)
+
 struct tx_bd_ext {
 	__le32 tx_bd_hsize_lflags;
 	#define TX_BD_FLAGS_TCP_UDP_CHKSUM			(1 << 0)
-- 
2.30.1