From 9476654bd5e8ad42abe8ee9f9e90069ff8e60c17 Mon Sep 17 00:00:00 2001 From: Paul Durrant Date: Mon, 23 Dec 2019 09:59:23 +0000 Subject: xen-netback: support dynamic unbind/bind By re-attaching RX, TX, and CTL rings during connect() rather than assuming they are freshly allocated (i.e. assuming the counters are zero), and avoiding forcing state to Closed in netback_remove() it is possible for vif instances to be unbound and re-bound from and to (respectively) a running guest. Dynamic unbind/bind is a highly useful feature for a backend module as it allows it to be unloaded and re-loaded (i.e. updated) without requiring domUs to be halted. This has been tested by running iperf as a server in the test VM and then running a client against it in a continuous loop, whilst also running: while true; do echo vif-$DOMID-$VIF >unbind; echo down; rmmod xen-netback; echo unloaded; modprobe xen-netback; cd $(pwd); brctl addif xenbr0 vif$DOMID.$VIF; ip link set vif$DOMID.$VIF up; echo up; sleep 5; done in dom0 from /sys/bus/xen-backend/drivers/vif to continuously unbind, unload, re-load, re-bind and re-plumb the backend. Clearly a performance drop was seen but no TCP connection resets were observed during this test and moreover a parallel SSH connection into the guest remained perfectly usable throughout. Signed-off-by: Paul Durrant Reviewed-by: Wei Liu Signed-off-by: David S. Miller --- drivers/net/xen-netback/xenbus.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'drivers/net/xen-netback/xenbus.c') diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-netback/xenbus.c index 17b4950ec051..286054b60d47 100644 --- a/drivers/net/xen-netback/xenbus.c +++ b/drivers/net/xen-netback/xenbus.c @@ -954,12 +954,10 @@ static int netback_remove(struct xenbus_device *dev) { struct backend_info *be = dev_get_drvdata(&dev->dev); - set_backend_state(be, XenbusStateClosed); - unregister_hotplug_status_watch(be); if (be->vif) { kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE); - xen_unregister_watchers(be->vif); + backend_disconnect(be); xenvif_free(be->vif); be->vif = NULL; } @@ -1131,6 +1129,7 @@ static struct xenbus_driver netback_driver = { .remove = netback_remove, .uevent = netback_uevent, .otherend_changed = frontend_changed, + .allow_rebind = true, }; int xenvif_xenbus_init(void) -- cgit