nfp: allow apps to request larger MTU on control vNIC

Some apps may want to have higher MTU on the control vNIC/queue.
Allow them to set the requested MTU at init time.
Signed-off-by: NJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>

drivers/net/ethernet/netronome/nfp/nfp_app.h

@@ -40,6 +40,8 @@
 
 #include "nfp_net_repr.h"
 
+#define NFP_APP_CTRL_MTU_MAX	U32_MAX
+
 struct bpf_prog;
 struct net_device;
 struct netdev_bpf;
@@ -178,6 +180,7 @@ struct nfp_app_type {
  * @ctrl:	pointer to ctrl vNIC struct
  * @reprs:	array of pointers to representors
  * @type:	pointer to const application ops and info
+ * @ctrl_mtu:	MTU to set on the control vNIC (set in .init())
  * @priv:	app-specific priv data
  */
 struct nfp_app {
@@ -189,6 +192,7 @@ struct nfp_app {
 	struct nfp_reprs __rcu *reprs[NFP_REPR_TYPE_MAX + 1];
 
 	const struct nfp_app_type *type;
+	unsigned int ctrl_mtu;
 	void *priv;
 };
 

drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -3877,10 +3877,20 @@ int nfp_net_init(struct nfp_net *nn)
 		return err;
 
 	/* Set default MTU and Freelist buffer size */
-	if (nn->max_mtu < NFP_NET_DEFAULT_MTU)
+	if (!nfp_net_is_data_vnic(nn) && nn->app->ctrl_mtu) {
+		if (nn->app->ctrl_mtu <= nn->max_mtu) {
+			nn->dp.mtu = nn->app->ctrl_mtu;
+		} else {
+			if (nn->app->ctrl_mtu != NFP_APP_CTRL_MTU_MAX)
+				nn_warn(nn, "app requested MTU above max supported %u > %u\n",
+					nn->app->ctrl_mtu, nn->max_mtu);
+			nn->dp.mtu = nn->max_mtu;
+		}
+	} else if (nn->max_mtu < NFP_NET_DEFAULT_MTU) {
 		nn->dp.mtu = nn->max_mtu;
-	else
+	} else {
 		nn->dp.mtu = NFP_NET_DEFAULT_MTU;
+	}
 	nn->dp.fl_bufsz = nfp_net_calc_fl_bufsz(&nn->dp);
 
 	if (nfp_app_ctrl_uses_data_vnics(nn->app))