path: root/drivers/net/xen-netback/netback.c
diff options
authorPaul Durrant <pdurrant@amazon.com>2019-12-23 09:59:23 +0000
committerDavid S. Miller <davem@davemloft.net>2019-12-26 15:16:26 -0800
commit9476654bd5e8ad42abe8ee9f9e90069ff8e60c17 (patch)
treed063572a1f27c26bb642e0fb30a5afe50ba5afb4 /drivers/net/xen-netback/netback.c
parentMerge branch 'RTL8211F-RGMII-RX-TX-delay-configuration-improvements' (diff)
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 <pdurrant@amazon.com> Reviewed-by: Wei Liu <wei.liu@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'drivers/net/xen-netback/netback.c')
1 files changed, 17 insertions, 3 deletions
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;