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linux/drivers/net/xen-netback
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Michael Brown 2afeec08ab 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>
History 2021-04-13 15:24:14 -07:00
..
common.h skbuff: Add skb parameter to the ubuf zerocopy callback 2021-01-07 16:06:37 -08:00
hash.c treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
interface.c xen/events: link interdomain events to associated xenbus device 2021-02-11 14:47:00 -08:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
netback.c Merge git://git.kernel.org:/pub/scm/linux/kernel/git/netdev/net 2021-03-09 17:15:56 -08:00
rx.c xen/netback: avoid race in xenvif_rx_ring_slots_available() 2021-02-04 10:54:37 -08:00
xenbus.c xen-netback: Check for hotplug-status existence before watching 2021-04-13 15:24:14 -07:00