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/netback.c | 20 +++++++++++++++++--- 1 file changed, 17 insertions(+), 3 deletions(-) (limited to 'drivers/net/xen-netback/netback.c') diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 0020b2e8c279..315dfc6ea297 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -1453,7 +1453,7 @@ int xenvif_map_frontend_data_rings(struct xenvif_queue *queue, void *addr; struct xen_netif_tx_sring *txs; struct xen_netif_rx_sring *rxs; - + RING_IDX rsp_prod, req_prod; int err = -ENOMEM; err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(queue->vif), @@ -1462,7 +1462,14 @@ int xenvif_map_frontend_data_rings(struct xenvif_queue *queue, goto err; txs = (struct xen_netif_tx_sring *)addr; - BACK_RING_INIT(&queue->tx, txs, XEN_PAGE_SIZE); + rsp_prod = READ_ONCE(txs->rsp_prod); + req_prod = READ_ONCE(txs->req_prod); + + BACK_RING_ATTACH(&queue->tx, txs, rsp_prod, XEN_PAGE_SIZE); + + err = -EIO; + if (req_prod - rsp_prod > RING_SIZE(&queue->tx)) + goto err; err = xenbus_map_ring_valloc(xenvif_to_xenbus_device(queue->vif), &rx_ring_ref, 1, &addr); @@ -1470,7 +1477,14 @@ int xenvif_map_frontend_data_rings(struct xenvif_queue *queue, goto err; rxs = (struct xen_netif_rx_sring *)addr; - BACK_RING_INIT(&queue->rx, rxs, XEN_PAGE_SIZE); + rsp_prod = READ_ONCE(rxs->rsp_prod); + req_prod = READ_ONCE(rxs->req_prod); + + BACK_RING_ATTACH(&queue->rx, rxs, rsp_prod, XEN_PAGE_SIZE); + + err = -EIO; + if (req_prod - rsp_prod > RING_SIZE(&queue->rx)) + goto err; return 0; -- cgit v1.2.3-59-g8ed1b