RDMA/cma: Use ACK timeout for RoCE packetLifeTime

The cma is currently using a hard-coded value, CMA_IBOE_PACKET_LIFETIME,
for the PacketLifeTime, as it can not be determined from the network.
This value might not be optimal for all networks.

The cma module supports the function rdma_set_ack_timeout to set the ACK
timeout for a QP associated with a connection. As per IBTA 12.7.34 local
ACK timeout = (2 * PacketLifeTime + Local CA’s ACK delay).  Assuming a
negligible local ACK delay, we can use PacketLifeTime = local ACK
timeout/2 as a reasonable approximation for RoCE networks.

Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Dag Moxnes <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: Dag Moxnes

drivers/infiniband/core/cma.c

@@ -2504,7 +2504,9 @@ EXPORT_SYMBOL(rdma_set_service_type);
  * This function should be called before rdma_connect() on active side,
  * and on passive side before rdma_accept(). It is applicable to primary
  * path only. The timeout will affect the local side of the QP, it is not
- * negotiated with remote side and zero disables the timer.
+ * negotiated with remote side and zero disables the timer. In case it is
+ * set before rdma_resolve_route, the value will also be used to determine
+ * PacketLifeTime for RoCE.
  *
  * Return: 0 for success
  */
@@ -2913,7 +2915,16 @@ static int cma_resolve_iboe_route(struct rdma_id_private *id_priv)
 	route->path_rec->rate = iboe_get_rate(ndev);
 	dev_put(ndev);
 	route->path_rec->packet_life_time_selector = IB_SA_EQ;
-	route->path_rec->packet_life_time = CMA_IBOE_PACKET_LIFETIME;
+	/* In case ACK timeout is set, use this value to calculate
+	 * PacketLifeTime.  As per IBTA 12.7.34,
+	 * local ACK timeout = (2 * PacketLifeTime + Local CA’s ACK delay).
+	 * Assuming a negligible local ACK delay, we can use
+	 * PacketLifeTime = local ACK timeout/2
+	 * as a reasonable approximation for RoCE networks.
+	 */
+	route->path_rec->packet_life_time = id_priv->timeout_set ?
+		id_priv->timeout - 1 : CMA_IBOE_PACKET_LIFETIME;
+
 	if (!route->path_rec->mtu) {
 		ret = -EINVAL;
 		goto err2;