IB/mlx4: Do not allow APM under RoCE

Automatic Path Migration is not supported under RoCE. Therefore,
return a "not-supported" error if the caller attempts to set an
alternate path in a QP context.

In addition, if there are no IB ports configured, do not report
APM capability in the device flags returned by mlx4_ib_query_device.

Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c
index 25e0208..393423c 100644
--- a/drivers/infiniband/hw/mlx4/qp.c
+++ b/drivers/infiniband/hw/mlx4/qp.c
@@ -1424,6 +1424,12 @@
 	int steer_qp = 0;
 	int err = -EINVAL;
 
+	/* APM is not supported under RoCE */
+	if (attr_mask & IB_QP_ALT_PATH &&
+	    rdma_port_get_link_layer(&dev->ib_dev, qp->port) ==
+	    IB_LINK_LAYER_ETHERNET)
+		return -ENOTSUPP;
+
 	context = kzalloc(sizeof *context, GFP_KERNEL);
 	if (!context)
 		return -ENOMEM;