netdev - [PATCH net-next v2 2/5] net: Disable GRO_HW when generic XDP is installed on a device.

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Message-Id: <1512633815-25037-3-git-send-email-michael.chan@broadcom.com>
Date:   Thu,  7 Dec 2017 03:03:32 -0500
From:   Michael Chan <michael.chan@...adcom.com>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, andrew.gospodarek@...adcom.com,
        Ariel Elior <Ariel.Elior@...ium.com>,
        everest-linux-l2@...ium.com
Subject: [PATCH net-next v2 2/5] net: Disable GRO_HW when generic XDP is installed on a device.

Hardware should not aggregate any packets when generic XDP is installed.

Cc: Ariel Elior <Ariel.Elior@...ium.com>
Cc: everest-linux-l2@...ium.com
Signed-off-by: Michael Chan <michael.chan@...adcom.com>
---
 net/core/dev.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 7242e5e..7087f34 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1542,6 +1542,29 @@ void dev_disable_lro(struct net_device *dev)
 }
 EXPORT_SYMBOL(dev_disable_lro);
 
+/**
+ *	dev_disable_gro_hw - disable HW Generic Receive Offload on a device
+ *	@dev: device
+ *
+ *	Disable HW Generic Receive Offload (GRO_HW) on a net device.  Must be
+ *	called under RTNL.  This is needed if Generic XDP is installed on
+ *	the device.
+ */
+static void dev_disable_gro_hw(struct net_device *dev)
+{
+	struct net_device *lower_dev;
+	struct list_head *iter;
+
+	dev->wanted_features &= ~NETIF_F_GRO_HW;
+	netdev_update_features(dev);
+
+	if (unlikely(dev->features & NETIF_F_GRO_HW))
+		netdev_WARN(dev, "failed to disable GRO_HW!\n");
+
+	netdev_for_each_lower_dev(dev, lower_dev, iter)
+		dev_disable_gro_hw(lower_dev);
+}
+
 static int call_netdevice_notifier(struct notifier_block *nb, unsigned long val,
 				   struct net_device *dev)
 {
@@ -4545,6 +4568,7 @@ static int generic_xdp_install(struct net_device *dev, struct netdev_bpf *xdp)
 		} else if (new && !old) {
 			static_key_slow_inc(&generic_xdp_needed);
 			dev_disable_lro(dev);
+			dev_disable_gro_hw(dev);
 		}
 		break;
 
-- 
1.8.3.1