netdev - [PATCH] net: xen-netback: correctly restart Tx after a VM restore/migrate

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Date:	Fri, 30 Sep 2011 17:37:51 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	"David S. Miller" <davem@...emloft.net>
CC:	netdev@...r.kernel.org, xen-devel@...ts.xensource.com,
	David Vrabel <david.vrabel@...rix.com>,
	Ian Campbell <ian.campbell@...rix.com>
Subject: [PATCH] net: xen-netback: correctly restart Tx after a VM restore/migrate

If a VM is saved and restored (or migrated) the netback driver will no
longer process any Tx packets from the frontend.  xenvif_up() does not
schedule the processing of any pending Tx requests from the front end
because the carrier is off.  Without this initial kick the frontend
just adds Tx requests to the ring without raising an event (until the
ring is full).

This was caused by 47103041e91794acdbc6165da0ae288d844c820b (net:
xen-netback: convert to hw_features) which reordered the calls to
xenvif_up() and netif_carrier_on() in xenvif_connect().

Signed-off-by: David Vrabel <david.vrabel@...rix.com>
Cc: Ian Campbell <ian.campbell@...rix.com>
---
 drivers/net/xen-netback/interface.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index 0ca86f9..1825629 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -327,12 +327,12 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
 	xenvif_get(vif);
 
 	rtnl_lock();
-	if (netif_running(vif->dev))
-		xenvif_up(vif);
 	if (!vif->can_sg && vif->dev->mtu > ETH_DATA_LEN)
 		dev_set_mtu(vif->dev, ETH_DATA_LEN);
 	netdev_update_features(vif->dev);
 	netif_carrier_on(vif->dev);
+	if (netif_running(vif->dev))
+		xenvif_up(vif);
 	rtnl_unlock();
 
 	return 0;
-- 
1.7.2.5

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