User Manual

Rev 2.2-1.0.1
Mellanox Technologies
129
4.15.7.2 Granting SMP Capability to a Virtual Function
To enable SMP capability for a VF, one must enable the Subnet Management Interface (SMI) for
that
VF. By default, the SMI interface is disabled for VFs. To enable SMI mads for VFs, there are
two new sysfs entries per VF per on the Hypervisor (under
/sys/class/infiniband/mlx4_X/
iov/<b.d.f>/ports/<1 or 2>.
These entries are displayed only for VFs (not for the PF), and
only for IB ports (not ETH ports).
The first entry,
enable_smi_admin, is used to enable SMI on a VF. By default, the value of this
entry is zero (disabled). When set to
“1”, the SMI will be enabled for the VF on the next rebind
or openibd restart on the VM that the VF is bound to. If the VF is currently bound, it must be
unbound and then re-bound.
The second sysfs entry,
smi_enabled, indicates the current enablement state of the SMI. 0 indi-
cates disabled, and 1 indicates enabled. This entry is read-only.
When a VF is initialized (bound), during the initialization sequence, the driver copies the
requested
smi_state (enable_smi_admin) for that VF/port to the operational SMI state
(
smi_enabled) for that VF/port, and operate according to the operational state.
Thus, the sequence of operations on the hypevisor is:
Step 1. Enable SMI for any VF/port that you wish.
Step 2. Restart the VM that the VF is bound to (or just run /etc/init.d/openibd restart on that
VM)
The SMI will be enabled for the VF/port combinations that you set in step 2 above. You will then
be able to run network diagnostics from that
VF.
4.15.7.3 Installing MLNX_OFED with Network Diagnostics on a VM
 To install mlnx_ofed on a VF which will be enabled to run the tools, run the following on
the VM:
# mlnx_ofed_install
4.16 Quantized Congestion Control
Congestion control is used to reduce packet drops in lossy environments and mitigate congestion
spreading and resulting victim flows in lossless environments.
The Quantized Congestion Notification (QCN) IEEE standard (802.1Qau) provides congestion
control for long-lived flows in limited bandwidth-delay product Ethernet networks. It is part of
the IEEE Data Center Bridging (DCB) protocol suite, which also includes ETS, PFC, and
DCBX. QCN in conducted at L2, and is tar
geted for hardware implementations. QCN applies to
all Ethernet packets and all transports, and both the host and switch behavior is detailed in the
standard.
QCN user interface allows the user to configure QCN activity. QCN configuration and retrieval
of information is done by the
mlnx_qcn tool. The command interface provides the user with a set
of changeable attributes, and with information regarding QCN's counters and statistics. All
parameters and statistics are defined per port and priority. QCN command interface is available if
and only the hardware supports it.