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| author | Michael Brown <mbrown@fensystems.co.uk> | 2021-04-13 16:25:12 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2021-04-13 15:24:14 -0700 |
| commit | 2afeec08ab5c86ae21952151f726bfe184f6b23d (patch) | |
| tree | 68d755c22e5a1ebea73397b4e1d958f88adb16a2 | |
| parent | 38ec4944b593fd90c5ef42aaaa53e66ae5769d04 (diff) | |
| download | tpmdd-2afeec08ab5c86ae21952151f726bfe184f6b23d.tar.gz | |
xen-netback: Check for hotplug-status existence before watching
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>
| -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 a5439c130130f8..d24b7a7993aa05 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); |