Dell Mellanox Family of Adapters - Manual (Page 38)

Driver Installation and Configuration Rev 1.1
Mellanox Technologies 38
4.2.5.4 Querying the Hardware Time
Querying the hardware for time is done via the ibv_query_values_ex verb.
For example:
To change the queried time in nanoseconds resolution, use the IBV_VALUES_HW_CLOCK_NS flag
along with the hwclock_ns field.
4.2.6 Flow Steering
Flow steering is a new model which steers network flows based on flow specifications to specific
QPs. Those flows can be either unicast or multicast network flows. In order to maintain flexibil-
ity, domains and priorities are used. Flow steering uses a methodology of flow attribute, which is
a combination of L2-L4 flow specifications, a destination QP and a priority. Flow steering rules
may be inserted either by using ethtool or by using InfiniBand verbs. The verbs abstraction uses a
different terminology from the flow attribute (ibv_flow_attr), defined by a combination of speci-
fications (struct ibv_flow_spec_*).
4.2.6.1 Enable/Disable Flow Steering
Flow Steering is disabled by default and regular L2 steering is performed instead (B0 Steering).
When using SR-IOV, flow steering is enabled if there is an adequate amount of space to store the
flow steering table for the guest/master.
 To enable Flow Steering:
Step 1. Open the /etc/modprobe.d/mlnx.conf file.
Step 2. Set the parameter log_num_mgm_entry_size to -1 by writing the option mlx4_core
log_num_mgm_entry_size=-1 .
Step 3. Restart the driver
 To disable Flow Steering:
Step 1. Open the /etc/modprobe.d/mlnx.conf file.
Step 2. Remove the options mlx4_core log_num_mgm_entry_size= -1 .
Step 3. Restart the driver
ret = ibv_query_values_ex(context, IBV_VALUES_HW_CLOCK, &queried_values);
if (!ret && queried_values.comp_mask & IBV_VALUES_HW_CLOCK)
queried_time = queried_values.hwclock;
ret = ibv_query_values_ex(context, IBV_VALUES_HW_CLOCK_NS, &queried_values);
if (!ret && queried_values.comp_mask & IBV_VALUES_HW_CLOCK_NS)
queried_time_ns = queried_values.hwclock_ns;
Querying the Hardware Time is available only on physical functions / native machines.
Flow Steering is applicable to the mlx4 driver only.