netdev - [PATCH net-next 1/2] net: typhoon: implement ndo_features

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Date:   Thu,  3 Feb 2022 10:02:26 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net-next 1/2] net: typhoon: implement ndo_features_check method

From: Eric Dumazet <edumazet@...gle.com>

Instead of disabling TSO if MAX_SKB_FRAGS > 32, implement
ndo_features_check() method for this driver.

If skb has more than 32 frags, use the following heuristic:

1) force GSO for gso packets.
2) Otherwise force linearization.

Most locally generated packets will use a small number
of fragments anyway.

For forwarding workloads, we can limit gro_max_size at ingress,
we might also implement gro_max_segs if needed.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 drivers/net/ethernet/3com/typhoon.c | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/3com/typhoon.c b/drivers/net/ethernet/3com/typhoon.c
index 8aec5d9fbfef2803c181387537300502a937caf0..67b1a1f439d841ed0ed0f620e9477607ac6e2fae 100644
--- a/drivers/net/ethernet/3com/typhoon.c
+++ b/drivers/net/ethernet/3com/typhoon.c
@@ -138,11 +138,6 @@ MODULE_PARM_DESC(use_mmio, "Use MMIO (1) or PIO(0) to access the NIC. "
 module_param(rx_copybreak, int, 0);
 module_param(use_mmio, int, 0);
 
-#if defined(NETIF_F_TSO) && MAX_SKB_FRAGS > 32
-#warning Typhoon only supports 32 entries in its SG list for TSO, disabling TSO
-#undef NETIF_F_TSO
-#endif
-
 #if TXLO_ENTRIES <= (2 * MAX_SKB_FRAGS)
 #error TX ring too small!
 #endif
@@ -2261,9 +2256,27 @@ typhoon_test_mmio(struct pci_dev *pdev)
 	return mode;
 }
 
+#if MAX_SKB_FRAGS > 32
+static netdev_features_t typhoon_features_check(struct sk_buff *skb,
+						struct net_device *dev,
+						netdev_features_t features)
+{
+	if (skb_shinfo(skb)->nr_frags > 32) {
+		if (skb_is_gso(skb))
+			features &= ~NETIF_F_GSO_MASK;
+		else
+			features &= ~NETIF_F_SG;
+	}
+	return features;
+}
+#endif
+
 static const struct net_device_ops typhoon_netdev_ops = {
 	.ndo_open		= typhoon_open,
 	.ndo_stop		= typhoon_close,
+#if MAX_SKB_FRAGS > 32
+	.ndo_features_check	= typhoon_features_check,
+#endif
 	.ndo_start_xmit		= typhoon_start_tx,
 	.ndo_set_rx_mode	= typhoon_set_rx_mode,
 	.ndo_tx_timeout		= typhoon_tx_timeout,
-- 
2.35.0.263.gb82422642f-goog