netdev-dpdk: don't enable scatter for jumbo RX support for nfp

Currently to RX jumbo packets fails for NICs not supporting scatter.
Scatter is not strictly needed for jumbo RX support. This change fixes
the issue by not enabling scatter only for the PMD/NIC known not to
need it to support jumbo RX.

Note: this change is temporary and not needed for later releases OVS/DPDK

Reported-by: Louis Peens <[email protected]>
Signed-off-by: Pablo Cascón <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Acked-by: Kevin Traynor <[email protected]>
Signed-off-by: Ian Stokes <[email protected]>

lib/netdev-dpdk.c

@@ -770,11 +770,19 @@ dpdk_eth_dev_queue_setup(struct netdev_dpdk *dev, int n_rxq, int n_txq)
     int diag = 0;
     int i;
     struct rte_eth_conf conf = port_conf;
+    struct rte_eth_dev_info info;
 
-    /* For some NICs (e.g. Niantic), scatter_rx mode needs to be explicitly
-     * enabled. */
+    /* As of DPDK 17.11.1 a few PMDs require to explicitly enable
+     * scatter to support jumbo RX. Checking the offload capabilities
+     * is not an option as PMDs are not required yet to report
+     * them. The only reliable info is the driver name and knowledge
+     * (testing or code review). Listing all such PMDs feels harder
+     * than highlighting the one known not to need scatter */
     if (dev->mtu > ETHER_MTU) {
-        conf.rxmode.enable_scatter = 1;
+        rte_eth_dev_info_get(dev->port_id, &info);
+        if (strncmp(info.driver_name, "net_nfp", 6)) {
+            conf.rxmode.enable_scatter = 1;
+        }
     }
 
     conf.rxmode.hw_ip_checksum = (dev->hw_ol_features &