IB/mlx4: Configure QPs' max message size based on real device capability

ConnectX returns the max message size it supports through the
QUERY_DEV_CAP firmware command.  When modifying a QP to RTR, the max
message size for the QP must be specified.  This value must not exceed
the value declared through QUERY_DEV_CAP.  The current code ignores
the max allowed size and unconditionally sets the value to 2^31.  This
patch sets all QPs to the max value allowed as returned from firmware.
Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mlx4/qp.c

@@ -908,7 +908,8 @@ static int __mlx4_ib_modify_qp(struct ib_qp *ibqp,
 			       attr->path_mtu);
 			goto out;
 		}
-		context->mtu_msgmax = (attr->path_mtu << 5) | 31;
+		context->mtu_msgmax = (attr->path_mtu << 5) |
+			ilog2(dev->dev->caps.max_msg_sz);
 	}
 
 	if (qp->rq.wqe_cnt)