IPoIB: Only set Q_Key once: after joining broadcast group

The current code will set the Q_Key for any join of a non-sendonly
multicast group.  The operation involves a modify QP operation, which
is fairly heavyweight, and is only really required after the join of
the broadcast group.  Fix this by adding a parameter to ipoib_mcast_attach()
to control when the Q_Key is set.
Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -485,7 +485,7 @@ void ipoib_path_iter_read(struct ipoib_path_iter *iter,
 #endif
 
 int ipoib_mcast_attach(struct net_device *dev, u16 mlid,
-		       union ib_gid *mgid);
+		       union ib_gid *mgid, int set_qkey);
 int ipoib_mcast_detach(struct net_device *dev, u16 mlid,
 		       union ib_gid *mgid);
 

drivers/infiniband/ulp/ipoib/ipoib_multicast.c

@@ -186,6 +186,7 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 	struct ipoib_ah *ah;
 	int ret;
+	int set_qkey = 0;
 
 	mcast->mcmember = *mcmember;
 
@@ -200,6 +201,7 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
 		priv->qkey = be32_to_cpu(priv->broadcast->mcmember.qkey);
 		spin_unlock_irq(&priv->lock);
 		priv->tx_wr.wr.ud.remote_qkey = priv->qkey;
+		set_qkey = 1;
 	}
 
 	if (!test_bit(IPOIB_MCAST_FLAG_SENDONLY, &mcast->flags)) {
@@ -212,7 +214,7 @@ static int ipoib_mcast_join_finish(struct ipoib_mcast *mcast,
 		}
 
 		ret = ipoib_mcast_attach(dev, be16_to_cpu(mcast->mcmember.mlid),
-					 &mcast->mcmember.mgid);
+					 &mcast->mcmember.mgid, set_qkey);
 		if (ret < 0) {
 			ipoib_warn(priv, "couldn't attach QP to multicast group "
 				   IPOIB_GID_FMT "\n",

drivers/infiniband/ulp/ipoib/ipoib_verbs.c

@@ -33,18 +33,13 @@
 
 #include "ipoib.h"
 
-int ipoib_mcast_attach(struct net_device *dev, u16 mlid, union ib_gid *mgid)
+int ipoib_mcast_attach(struct net_device *dev, u16 mlid, union ib_gid *mgid, int set_qkey)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
-	struct ib_qp_attr *qp_attr;
+	struct ib_qp_attr *qp_attr = NULL;
 	int ret;
 	u16 pkey_index;
 
-	ret = -ENOMEM;
-	qp_attr = kmalloc(sizeof *qp_attr, GFP_KERNEL);
-	if (!qp_attr)
-		goto out;
-
 	if (ib_find_pkey(priv->ca, priv->port, priv->pkey, &pkey_index)) {
 		clear_bit(IPOIB_PKEY_ASSIGNED, &priv->flags);
 		ret = -ENXIO;
@@ -52,12 +47,19 @@ int ipoib_mcast_attach(struct net_device *dev, u16 mlid, union ib_gid *mgid)
 	}
 	set_bit(IPOIB_PKEY_ASSIGNED, &priv->flags);
 
-	/* set correct QKey for QP */
-	qp_attr->qkey = priv->qkey;
-	ret = ib_modify_qp(priv->qp, qp_attr, IB_QP_QKEY);
-	if (ret) {
-		ipoib_warn(priv, "failed to modify QP, ret = %d\n", ret);
-		goto out;
+	if (set_qkey) {
+		ret = -ENOMEM;
+		qp_attr = kmalloc(sizeof *qp_attr, GFP_KERNEL);
+		if (!qp_attr)
+			goto out;
+
+		/* set correct QKey for QP */
+		qp_attr->qkey = priv->qkey;
+		ret = ib_modify_qp(priv->qp, qp_attr, IB_QP_QKEY);
+		if (ret) {
+			ipoib_warn(priv, "failed to modify QP, ret = %d\n", ret);
+			goto out;
+		}
 	}
 
 	/* attach QP to multicast group */