diff options
author | Michael Brown <mbrown@fensystems.co.uk> | 2021-04-13 16:25:12 +0100 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-04-28 13:40:02 +0200 |
commit | 1bfefd866195987ded82605dc417c1a2ba523bf7 (patch) | |
tree | 3355357583b464d66604b46ccd24062288dc9be5 | |
parent | 509ae27a1874389182b3709de0940a8f8d4dfb8b (diff) |
xen-netback: Check for hotplug-status existence before watching
[ Upstream commit 2afeec08ab5c86ae21952151f726bfe184f6b23d ]
The logic in connect() is currently written with the assumption that
xenbus_watch_pathfmt() will return an error for a node that does not
exist. This assumption is incorrect: xenstore does allow a watch to
be registered for a nonexistent node (and will send notifications
should the node be subsequently created).
As of commit 1f2565780 ("xen-netback: remove 'hotplug-status' once it
has served its purpose"), this leads to a failure when a domU
transitions into XenbusStateConnected more than once. On the first
domU transition into Connected state, the "hotplug-status" node will
be deleted by the hotplug_status_changed() callback in dom0. On the
second or subsequent domU transition into Connected state, the
hotplug_status_changed() callback will therefore never be invoked, and
so the backend will remain stuck in InitWait.
This failure prevents scenarios such as reloading the xen-netfront
module within a domU, or booting a domU via iPXE. There is
unfortunately no way for the domU to work around this dom0 bug.
Fix by explicitly checking for existence of the "hotplug-status" node,
thereby creating the behaviour that was previously assumed to exist.
Signed-off-by: Michael Brown <mbrown@fensystems.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
-rw-r--r-- | drivers/net/xen-netback/xenbus.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c index 6f10e0998f1c..94d19158efc1 100644 --- a/drivers/net/xen-netback/xenbus.c +++ b/drivers/net/xen-netback/xenbus.c @@ -824,11 +824,15 @@ static void connect(struct backend_info *be) xenvif_carrier_on(be->vif); unregister_hotplug_status_watch(be); - err = xenbus_watch_pathfmt(dev, &be->hotplug_status_watch, NULL, - hotplug_status_changed, - "%s/%s", dev->nodename, "hotplug-status"); - if (!err) + if (xenbus_exists(XBT_NIL, dev->nodename, "hotplug-status")) { + err = xenbus_watch_pathfmt(dev, &be->hotplug_status_watch, + NULL, hotplug_status_changed, + "%s/%s", dev->nodename, + "hotplug-status"); + if (err) + goto err; be->have_hotplug_status_watch = 1; + } netif_tx_wake_all_queues(be->vif->dev); |