netdev - [PATCH 2/2] xen-netfront: Update features after registering netdev

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Date:   Thu, 21 Jun 2018 14:00:21 +0100
From:   Ross Lagerwall <ross.lagerwall@...rix.com>
To:     <netdev@...r.kernel.org>
CC:     Ross Lagerwall <ross.lagerwall@...rix.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        "David S. Miller" <davem@...emloft.net>,
        <xen-devel@...ts.xenproject.org>, <linux-kernel@...r.kernel.org>,
        Liam Shepherd <liam@...cer.es>
Subject: [PATCH 2/2] xen-netfront: Update features after registering netdev

Update the features after calling register_netdev() otherwise the
device features are not set up correctly and it not possible to change
the MTU of the device. After this change, the features reported by
ethtool match the device's features before the commit which introduced
the issue and it is possible to change the device's MTU.

Fixes: f599c64fdf7d ("xen-netfront: Fix race between device setup and open")
Reported-by: Liam Shepherd <liam@...cer.es>
Signed-off-by: Ross Lagerwall <ross.lagerwall@...rix.com>
---
 drivers/net/xen-netfront.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index ee4cb6c..a57daec 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -1951,10 +1951,6 @@ static int xennet_connect(struct net_device *dev)
 	/* talk_to_netback() sets the correct number of queues */
 	num_queues = dev->real_num_tx_queues;
 
-	rtnl_lock();
-	netdev_update_features(dev);
-	rtnl_unlock();
-
 	if (dev->reg_state == NETREG_UNINITIALIZED) {
 		err = register_netdev(dev);
 		if (err) {
@@ -1964,6 +1960,10 @@ static int xennet_connect(struct net_device *dev)
 		}
 	}
 
+	rtnl_lock();
+	netdev_update_features(dev);
+	rtnl_unlock();
+
 	/*
 	 * All public and private state should now be sane.  Get
 	 * ready to start sending and receiving packets and give the driver
-- 
2.9.5