xen-netback: Check for hotplug-status existence before watching
[ Upstream commit 2afeec08 ] 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 1f256578 ("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>
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78687d6a
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