netdev-dpdk: Avoid reconfiguration on VIRTIO_NET_F_MQ changes.

At the moment, a malicious guest might negotiate VIRTIO_NET_F_MQ and !VIRTIO_NET_F_MQ in a loop which would be seen as qp_num going from 1 to n and n to 1 continuously, triggering datapath reconfigurations at each transition. Limit this by only reconfiguring on increased qp_num. The previous patch reduced the observed cost of polling disabled queues, so the only cost is memory. Co-authored-by: Ilya Maximets <[email protected]> Signed-off-by: Ilya Maximets <[email protected]> Signed-off-by: David Marchand <[email protected]> Acked-by: Kevin Traynor <[email protected]> Signed-off-by: Ian Stokes <[email protected]>
jotak · Jun 26, 2019 · 7235cd2 · 7235cd2
1 parent 35c9156
commit 7235cd2
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/lib/netdev-dpdk.c b/lib/netdev-dpdk.c
@@ -3512,8 +3512,8 @@ new_device(int vid)
                 newnode = dev->socket_id;
             }
 
-            if (dev->requested_n_txq != qp_num
-                || dev->requested_n_rxq != qp_num
+            if (dev->requested_n_txq < qp_num
+                || dev->requested_n_rxq < qp_num
                 || dev->requested_socket_id != newnode) {
                 dev->requested_socket_id = newnode;
                 dev->requested_n_rxq = qp_num;