 iavf FreeBSD* Base Driver for Adaptive Virtual Functions
========================================================
March 14, 2022

Contents
========

- Overview
- Identifying Your Adapter
- The VF Driver
- Building and Installation
- Configuration and Tuning
- Known Issues/Troubleshooting


Overview
========
This file describes the FreeBSD* driver for Intel(R) Ethernet. This driver has
been developed for use with all community-supported versions of FreeBSD.

For questions related to hardware requirements, refer to the documentation
supplied with your Intel Ethernet Adapter. All hardware requirements listed
apply to use with FreeBSD.

The associated Physical Function (PF) drivers for this VF driver are:
- ice
- ixl


Identifying Your Adapter
========================
This driver is compatible with virtual functions bound to devices based on the
following:
  * Intel(R) Ethernet Controller E810-C
  * Intel(R) Ethernet Controller E810-XXV
  * Intel(R) Ethernet Connection E822-C
  * Intel(R) Ethernet Connection E822-L
  * Intel(R) Ethernet Connection E823-C
  * Intel(R) Ethernet Connection E823-L
  * Intel(R) Ethernet Controller X710
  * Intel(R) Ethernet Controller XL710
  * Intel(R) Ethernet Network Connection X722
  * Intel(R) Ethernet Controller XXV710
  * Intel(R) Ethernet Controller V710

For information on how to identify your adapter, and for the latest Intel
network drivers, refer to the Intel Support website:
http://www.intel.com/support


The VF Driver
=============
The VF driver is normally used in a virtualized environment where a host driver
manages SRIOV, and provides a VF device to the guest.

In the FreeBSD guest, the iavf driver would be loaded and will function using
the VF device assigned to it.

The VF driver provides most of the same functionality as the core driver, but
is actually a subordinate to the host. Access to many controls is accomplished
by a request to the host via what is called the "Admin queue." These are
startup and initialization events, however; once in operation, the device is
self-contained and should achieve near native performance.

Some notable limitations of the VF environment:
  * The PF can configure the VF to allow promiscuous mode, when using iovctl.
  * Media info is not available from the PF, so it will always appear as auto.


Adaptive Virtual Function
-------------------------
Adaptive Virtual Function (AVF) allows the virtual function driver, or VF, to
adapt to changing feature sets of the physical function driver (PF) with which
it is associated. This allows system administrators to update a PF without
having to update all the VFs associated with it. All AVFs have a single common
device ID and branding string.

AVFs have a minimum set of features known as "base mode," but may provide
additional features depending on what features are available in the PF with
which the AVF is associated. The following are base mode features:

- 4 Queue Pairs (QP) and associated Configuration Status Registers (CSRs)
  for Tx/Rx
- iavf descriptors and ring format
- Descriptor write-back completion
- 1 control queue, with iavf descriptors, CSRs and ring format
- 5 MSI-X interrupt vectors and corresponding iavf CSRs
- 1 Interrupt Throttle Rate (ITR) index
- 1 Virtual Station Interface (VSI) per VF
- 1 Traffic Class (TC), TC0
- Receive Side Scaling (RSS) with 64 entry indirection table and key,
  configured through the PF
- 1 unicast MAC address reserved per VF
- 16 MAC address filters for each VF
- Stateless offloads - non-tunneled checksums
- AVF device ID
- HW mailbox is used for VF to PF communications (including on Windows)


Building and Installation
=========================
NOTE: This driver package is to be used only as a standalone archive and the
user should not attempt to incorporate it into the kernel source tree.

In the instructions below, x.x.x is the driver version as indicated in the name
of the driver tar file.

1. Move the base driver tar file to the directory of your choice. For
   example, use /home/username/iavf or /usr/local/src/iavf.

2. Untar/unzip the archive:

   # tar xzf iavf-x.x.x.tar.gz

This will create the iavf-x.x.x directory.

3. To install man page:

   # cd iavf-x.x.x
   # gzip -c iavf.4 > /usr/share/man/man4/iavf.4.gz

4. To load the driver onto a running system:

   # cd iavf-x.x.x/src
   # make
   # kldload ./if_iavf.ko

To install the driver without using iflib:
   # cd iavf-x.x.x/src
   # make legacy
   # kldload ./if_iavf.ko

5. To assign an IP address to the interface, enter the following,
   where X is the interface number for the device:

   # ifconfig iavfX <IP_address>

6. Verify that the interface works. Enter the following, where <IP_address>
   is the IP address for another machine on the same subnet as the interface
   that is being tested:

   # ping <IP_address>

7. If you want the driver to load automatically when the system is booted:

   # cd iavf-x.x.x/src
   # make
   # make install

Edit /boot/loader.conf, and add the following line:
   if_iavf_load="YES"

Edit /etc/rc.conf, and create the appropriate ifconfig_iavfX entry:

   ifconfig_iavfX="<ifconfig_settings>"

Example usage:
   ifconfig_iavf0="inet 192.168.10.1 netmask 255.255.255.0"

    NOTE: For assistance, see the ifconfig man page.


Configuration and Tuning
========================

Important System Configuration Changes
--------------------------------------
- Change the file /etc/sysctl.conf, and add the line:

  hw.intr_storm_threshold: 0 (the default is 1000)

- Best throughput results are seen with a large MTU; use 9706 if possible.
  The default number of descriptors per ring is 1024. Increasing this may
  improve performance, depending on your use case.


Configuring for iflib
---------------------
Iflib is a common framework for network interface drivers for FreeBSD that uses
a shared set of sysctl names. The iflib driver works best in FreeBSD 11.3 and
later.

See the iflib man page for more information.


Jumbo Frames
------------
Jumbo Frames support is enabled by changing the Maximum Transmission Unit (MTU)
to a value larger than the default value of 1500.

Use the ifconfig command to increase the MTU size. For example, enter the
following where X is the interface number:

# ifconfig iavfX mtu 9000

To confirm an interface's MTU value, use the ifconfig command.

To confirm the MTU used between two specific devices, use:

# route get <destination_IP_address>

NOTE: The maximum MTU setting for jumbo frames is 9706. This corresponds to the
maximum jumbo frame size of 9728 bytes.

NOTE: This driver will attempt to use multiple page sized buffers to receive
each jumbo packet. This should help to avoid buffer starvation issues when
allocating receive packets.

NOTE: Packet loss may have a greater impact on throughput when you use jumbo
frames. If you observe a drop in performance after enabling jumbo frames,
enabling flow control may mitigate the issue.


VLANS
-----
To create a new VLAN interface:

# ifconfig <vlan_name> create

To associate the VLAN interface with a physical interface and assign a VLAN ID,
IP address, and netmask:

# ifconfig <vlan_name> <ip_address> netmask <subnet_mask> vlan <vlan_id>
vlandev <physical_interface>

Example:

# ifconfig vlan10 10.0.0.1 netmask 255.255.255.0 vlan 10 vlandev iavf0

In this example, all packets will be marked on egress with 802.1Q VLAN tags,
specifying a VLAN ID of 10.

To remove a VLAN interface:

# ifconfig <vlan_name> destroy


Checksum Offload
----------------
Checksum offloading supports both TCP and UDP packets and is supported for both
transmit and receive.

Checksum offloading can be enabled or disabled using ifconfig.

To enable checksum offloading:

# ifconfig iavfX rxcsum rxcsum6
# ifconfig iavfX txcsum txcsum6

To disable checksum offloading:

# ifconfig iavfX -rxcsum -rxcsum6
# ifconfig iavfX -txcsum -txcsum6

To confirm the current setting:

# ifconfig iavfX

Look for the presence or absence of the following line:
  options=3 <RXCSUM,TXCSUM,RXCSUM6,TXCSUM6>

See the ifconfig man page for further information.


TSO
---
TSO (TCP Segmentation Offload) supports both IPv4 and IPv6. TSO can be disabled
and enabled using the ifconfig utility or sysctl.

NOTE: TSO requires Tx checksum, if Tx checksum is disabled, TSO will also be
disabled.

To enable/disable TSO in the stack:

# sysctl net.inet.tcp.tso=0 (or 1 to enable it)

Doing this disables/enables TSO in the stack and affects all installed adapters.

To disable BOTH TSO IPv4 and IPv6, where X is the number of the interface in
use:

# ifconfig iavfX -tso

To enable BOTH TSO IPv4 and IPv6:

# ifconfig iavfX tso

You can also enable/disable IPv4 TSO or IPv6 TSO individually. Simply replace
tso|-tso in the above command with tso4 or tso6. For example, to disable
TSO IPv4:

# ifconfig iavfX -tso4

To disable TSO IPv6:

# ifconfig iavfX -tso6


LRO
---
LRO (Large Receive Offload) may provide Rx performance improvement. However, it
is incompatible with packet-forwarding workloads. You should carefully evaluate
the environment and enable LRO when possible.

To enable:

# ifconfig iavfX lro

It can be disabled by using:

# ifconfig iavfX -lro


Rx and Tx Descriptor Rings
--------------------------
Allows you to set the Rx and Tx descriptor rings independently. The tunables
are:
  hw.iavf.rx_ring_size
  hw.iavf.tx_ring_size

The valid range is 32-4096 in increments of 32. Use kenv to configure the
descriptor rings. Changes will take effect on the next driver reload.
For example:

# kenv hw.iavf.rx_ring_size=1024
# kenv hw.iavf.rx_ring_size=1280

NOTE: When you are handling a large number of connections in a VF, we recommend
setting the number of Rx descriptors to 1024 or above.

You can verify the descriptor ring size by using the following sysctls:

# sysctl dev.iavf.<interface_num>.rx_ring_size
# sysctl dev.iavf.<interface_num>.tx_ring_size

If you are using iflib, use the following sysctls instead:

# sysctl dev.iavf.<interface_num>.iflib.override_nrxds
# sysctl dev.iavf.<interface_num>.iflib.override_ntxds


Link-Level Flow Control (LFC)
-----------------------------
The VF driver does not have access to flow control. It must be managed from the
host side.


Known Issues/Troubleshooting
============================

Driver Buffer Overflow Fix
--------------------------
The fix to resolve CVE-2016-8105, referenced in Intel SA-00069
<https://security-center.intel.com/advisory.aspx?intelid=INTEL-SA-00069&language
id=en-fr>, is included in this and future versions of the driver.


Network Memory Buffer Allocation
--------------------------------
FreeBSD may have a low number of network memory buffers (mbufs) by default. If
your mbuf value is too low, it may cause the driver to fail to initialize
and/or cause the system to become unresponsive. You can check to see if the
system is mbuf-starved by running 'netstat -m'. Increase the number of mbufs by
editing the lines below in /etc/sysctl.conf:

  kern.ipc.nmbclusters
  kern.ipc.nmbjumbop
  kern.ipc.nmbjumbo9
  kern.ipc.nmbjumbo16
  kern.ipc.nmbufs

The amount of memory that you allocate is system specific, and may require some
trial and error. Also, increasing the following in /etc/sysctl.conf could help
increase network performance:

  kern.ipc.maxsockbuf
  net.inet.tcp.sendspace
  net.inet.tcp.recvspace
  net.inet.udp.maxdgram
  net.inet.udp.recvspace


UDP Stress Test Dropped Packet Issue
------------------------------------
Under small packet UDP stress with the iavf driver, the system may drop UDP
packets due to socket buffers being full. Setting the driver Intel Ethernet
Flow Control variables to the minimum may resolve the issue. You may also try
increasing the kernel's default buffer sizes by changing the values in

  /proc/sys/net/core/rmem_default and rmem_max


Disable LRO when routing/bridging
---------------------------------
LRO must be turned off when forwarding traffic.


Throughput lower than expected
------------------------------
In FreeBSD 11.3, you may observe lower than expected throughput. This is due to
an underlying OS limitation in FreeBSD 11.3. Using FreeBSD 12.0 or newer should
resolve the issue.

If your Rx throughput is lower than expected in FreeBSD 11.3 or 12.1, you can
also adjust the iflib sysctl variable 'rx_budget.' We have seen performance
benefits by increasing that value to at least 85. For example:

# sysctl dev.iavf.0.iflib.rx_budget=85


Support
=======
For general information, go to the Intel support website at:
http://www.intel.com/support/

If an issue is identified with the released source code on a supported kernel
with a supported adapter, email the specific information related to the issue
to freebsd@intel.com


Copyright(c) 2018 - 2022 Intel Corporation.


Trademarks
==========
Intel is a trademark or registered trademark of Intel Corporation or its
subsidiaries in the United States and/or other countries.

* Other names and brands may be claimed as the property of others.


