RDMA/qedr: fix QP's ack timeout configuration

BugLink: http://bugs.launchpad.net/bugs/1786352
[ Upstream commit c3594f22302cca5e924e47ec1cc8edd265708f41 ]

QPs that were configured with ack timeout value lower than 1
msec will not implement re-transmission timeout.
This means that if a packet / ACK were dropped, the QP
will not retransmit this packet.

This can lead to an application hang.

Fixes: cecbcddf6 ("qedr: Add support for QP verbs")
Signed-off-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Signed-off-by: Ariel Elior <Ariel.Elior@cavium.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/infiniband/hw/qedr/verbs.c b/drivers/infiniband/hw/qedr/verbs.c
index e5dc0115192d17b207368e1b3e25b4ae38f806ac..f76ef8dfcda41e72c7a09fb7384beb221b416a17 100644 (file)
--- a/drivers/infiniband/hw/qedr/verbs.c
+++ b/drivers/infiniband/hw/qedr/verbs.c
@@ -2087,18 +2087,23 @@ int qedr_modify_qp(struct ib_qp *ibqp, struct ib_qp_attr *attr,
                SET_FIELD(qp_params.modify_flags,
                          QED_ROCE_MODIFY_QP_VALID_ACK_TIMEOUT, 1);
 
-               qp_params.ack_timeout = attr->timeout;
-               if (attr->timeout) {
-                       u32 temp;
-
-                       temp = 4096 * (1UL << attr->timeout) / 1000 / 1000;
-                       /* FW requires [msec] */
-                       qp_params.ack_timeout = temp;
-               } else {
-                       /* Infinite */
+               /* The received timeout value is an exponent used like this:
+                *    "12.7.34 LOCAL ACK TIMEOUT
+                *    Value representing the transport (ACK) timeout for use by
+                *    the remote, expressed as: 4.096 * 2^timeout [usec]"
+                * The FW expects timeout in msec so we need to divide the usec
+                * result by 1000. We'll approximate 1000~2^10, and 4.096 ~ 2^2,
+                * so we get: 2^2 * 2^timeout / 2^10 = 2^(timeout - 8).
+                * The value of zero means infinite so we use a 'max_t' to make
+                * sure that sub 1 msec values will be configured as 1 msec.
+                */
+               if (attr->timeout)
+                       qp_params.ack_timeout =
+                                       1 << max_t(int, attr->timeout - 8, 0);
+               else
                        qp_params.ack_timeout = 0;
-               }
        }
+
        if (attr_mask & IB_QP_RETRY_CNT) {
                SET_FIELD(qp_params.modify_flags,
                          QED_ROCE_MODIFY_QP_VALID_RETRY_CNT, 1);