13. I40E Poll Mode Driver

The I40E PMD (librte_pmd_i40e) provides poll mode driver support for the Intel X710/XL710/X722 10/40 Gbps family of adapters.

13.1. Features

Features of the I40E PMD are:

  • Multiple queues for TX and RX
  • Receiver Side Scaling (RSS)
  • MAC/VLAN filtering
  • Packet type information
  • Flow director
  • Cloud filter
  • Checksum offload
  • VLAN/QinQ stripping and inserting
  • TSO offload
  • Promiscuous mode
  • Multicast mode
  • Port hardware statistics
  • Jumbo frames
  • Link state information
  • Link flow control
  • Mirror on port, VLAN and VSI
  • Interrupt mode for RX
  • Scattered and gather for TX and RX
  • Vector Poll mode driver
  • DCB
  • VMDQ
  • SR-IOV VF
  • Hot plug
  • IEEE1588/802.1AS timestamping
  • VF Daemon (VFD) - EXPERIMENTAL

13.2. Prerequisites

13.3. Pre-Installation Configuration

13.3.1. Config File Options

The following options can be modified in the config file. Please note that enabling debugging options may affect system performance.

  • CONFIG_RTE_LIBRTE_I40E_PMD (default y)

    Toggle compilation of the librte_pmd_i40e driver.

  • CONFIG_RTE_LIBRTE_I40E_DEBUG_* (default n)

    Toggle display of generic debugging messages.

  • CONFIG_RTE_LIBRTE_I40E_RX_ALLOW_BULK_ALLOC (default y)

    Toggle bulk allocation for RX.

  • CONFIG_RTE_LIBRTE_I40E_INC_VECTOR (default n)

    Toggle the use of Vector PMD instead of normal RX/TX path. To enable vPMD for RX, bulk allocation for Rx must be allowed.

  • CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC (default n)

    Toggle to use a 16-byte RX descriptor, by default the RX descriptor is 32 byte.

  • CONFIG_RTE_LIBRTE_I40E_QUEUE_NUM_PER_PF (default 64)

    Number of queues reserved for PF.

  • CONFIG_RTE_LIBRTE_I40E_QUEUE_NUM_PER_VF (default 4)

    Number of queues reserved for each SR-IOV VF.

  • CONFIG_RTE_LIBRTE_I40E_QUEUE_NUM_PER_VM (default 4)

    Number of queues reserved for each VMDQ Pool.

  • CONFIG_RTE_LIBRTE_I40E_ITR_INTERVAL (default -1)

    Interrupt Throttling interval.

13.4. Driver compilation and testing

Refer to the document compiling and testing a PMD for a NIC for details.

13.5. SR-IOV: Prerequisites and sample Application Notes

  1. Load the kernel module:

    modprobe i40e
    

    Check the output in dmesg:

    i40e 0000:83:00.1 ens802f0: renamed from eth0
    
  2. Bring up the PF ports:

    ifconfig ens802f0 up
    
  3. Create VF device(s):

    Echo the number of VFs to be created into the sriov_numvfs sysfs entry of the parent PF.

    Example:

    echo 2 > /sys/devices/pci0000:00/0000:00:03.0/0000:81:00.0/sriov_numvfs
    
  4. Assign VF MAC address:

    Assign MAC address to the VF using iproute2 utility. The syntax is:

    ip link set <PF netdev id> vf <VF id> mac <macaddr>
    

    Example:

    ip link set ens802f0 vf 0 mac a0:b0:c0:d0:e0:f0
    
  5. Assign VF to VM, and bring up the VM. Please see the documentation for the I40E/IXGBE/IGB Virtual Function Driver.

  6. Running testpmd:

    Follow instructions available in the document compiling and testing a PMD for a NIC to run testpmd.

    Example output:

    ...
    EAL: PCI device 0000:83:00.0 on NUMA socket 1
    EAL: probe driver: 8086:1572 rte_i40e_pmd
    EAL: PCI memory mapped at 0x7f7f80000000
    EAL: PCI memory mapped at 0x7f7f80800000
    PMD: eth_i40e_dev_init(): FW 5.0 API 1.5 NVM 05.00.02 eetrack 8000208a
    Interactive-mode selected
    Configuring Port 0 (socket 0)
    ...
    
    PMD: i40e_dev_rx_queue_setup(): Rx Burst Bulk Alloc Preconditions are
    satisfied.Rx Burst Bulk Alloc function will be used on port=0, queue=0.
    
    ...
    Port 0: 68:05:CA:26:85:84
    Checking link statuses...
    Port 0 Link Up - speed 10000 Mbps - full-duplex
    Done
    
    testpmd>
    

13.6. Sample Application Notes

13.6.1. Vlan filter

Vlan filter only works when Promiscuous mode is off.

To start testpmd, and add vlan 10 to port 0:

./app/testpmd -l 0-15 -n 4 -- -i --forward-mode=mac
...

testpmd> set promisc 0 off
testpmd> rx_vlan add 10 0

13.6.2. Flow Director

The Flow Director works in receive mode to identify specific flows or sets of flows and route them to specific queues. The Flow Director filters can match the different fields for different type of packet: flow type, specific input set per flow type and the flexible payload.

The default input set of each flow type is:

ipv4-other : src_ip_address, dst_ip_address
ipv4-frag  : src_ip_address, dst_ip_address
ipv4-tcp   : src_ip_address, dst_ip_address, src_port, dst_port
ipv4-udp   : src_ip_address, dst_ip_address, src_port, dst_port
ipv4-sctp  : src_ip_address, dst_ip_address, src_port, dst_port,
             verification_tag
ipv6-other : src_ip_address, dst_ip_address
ipv6-frag  : src_ip_address, dst_ip_address
ipv6-tcp   : src_ip_address, dst_ip_address, src_port, dst_port
ipv6-udp   : src_ip_address, dst_ip_address, src_port, dst_port
ipv6-sctp  : src_ip_address, dst_ip_address, src_port, dst_port,
             verification_tag
l2_payload : ether_type

The flex payload is selected from offset 0 to 15 of packet’s payload by default, while it is masked out from matching.

Start testpmd with --disable-rss and --pkt-filter-mode=perfect:

./app/testpmd -l 0-15 -n 4 -- -i --disable-rss --pkt-filter-mode=perfect \
              --rxq=8 --txq=8 --nb-cores=8 --nb-ports=1

Add a rule to direct ipv4-udp packet whose dst_ip=2.2.2.5, src_ip=2.2.2.3, src_port=32, dst_port=32 to queue 1:

testpmd> flow_director_filter 0 mode IP add flow ipv4-udp  \
         src 2.2.2.3 32 dst 2.2.2.5 32 vlan 0 flexbytes () \
         fwd pf queue 1 fd_id 1

Check the flow director status:

testpmd> show port fdir 0

######################## FDIR infos for port 0      ####################
  MODE:   PERFECT
  SUPPORTED FLOW TYPE:  ipv4-frag ipv4-tcp ipv4-udp ipv4-sctp ipv4-other
                        ipv6-frag ipv6-tcp ipv6-udp ipv6-sctp ipv6-other
                        l2_payload
  FLEX PAYLOAD INFO:
  max_len:       16          payload_limit: 480
  payload_unit:  2           payload_seg:   3
  bitmask_unit:  2           bitmask_num:   2
  MASK:
    vlan_tci: 0x0000,
    src_ipv4: 0x00000000,
    dst_ipv4: 0x00000000,
    src_port: 0x0000,
    dst_port: 0x0000
    src_ipv6: 0x00000000,0x00000000,0x00000000,0x00000000,
    dst_ipv6: 0x00000000,0x00000000,0x00000000,0x00000000
  FLEX PAYLOAD SRC OFFSET:
    L2_PAYLOAD:    0      1      2      3      4      5      6  ...
    L3_PAYLOAD:    0      1      2      3      4      5      6  ...
    L4_PAYLOAD:    0      1      2      3      4      5      6  ...
  FLEX MASK CFG:
    ipv4-udp:    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ipv4-tcp:    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ipv4-sctp:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ipv4-other:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ipv4-frag:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ipv6-udp:    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ipv6-tcp:    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ipv6-sctp:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ipv6-other:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    ipv6-frag:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
    l2_payload:  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  guarant_count: 1           best_count:    0
  guarant_space: 512         best_space:    7168
  collision:     0           free:          0
  maxhash:       0           maxlen:        0
  add:           0           remove:        0
  f_add:         0           f_remove:      0

Delete all flow director rules on a port:

testpmd> flush_flow_director 0

13.6.3. Floating VEB

The IntelĀ® Ethernet Controller X710 and XL710 Family support a feature called “Floating VEB”.

A Virtual Ethernet Bridge (VEB) is an IEEE Edge Virtual Bridging (EVB) term for functionality that allows local switching between virtual endpoints within a physical endpoint and also with an external bridge/network.

A “Floating” VEB doesn’t have an uplink connection to the outside world so all switching is done internally and remains within the host. As such, this feature provides security benefits.

In addition, a Floating VEB overcomes a limitation of normal VEBs where they cannot forward packets when the physical link is down. Floating VEBs don’t need to connect to the NIC port so they can still forward traffic from VF to VF even when the physical link is down.

Therefore, with this feature enabled VFs can be limited to communicating with each other but not an outside network, and they can do so even when there is no physical uplink on the associated NIC port.

To enable this feature, the user should pass a devargs parameter to the EAL, for example:

-w 84:00.0,enable_floating_veb=1

In this configuration the PMD will use the floating VEB feature for all the VFs created by this PF device.

Alternatively, the user can specify which VFs need to connect to this floating VEB using the floating_veb_list argument:

-w 84:00.0,enable_floating_veb=1,floating_veb_list=1;3-4

In this example VF1, VF3 and VF4 connect to the floating VEB, while other VFs connect to the normal VEB.

The current implementation only supports one floating VEB and one regular VEB. VFs can connect to a floating VEB or a regular VEB according to the configuration passed on the EAL command line.

The floating VEB functionality requires a NIC firmware version of 5.0 or greater.

13.7. Limitations or Known issues

13.7.1. MPLS packet classification on X710/XL710

For firmware versions prior to 5.0, MPLS packets are not recognized by the NIC. The L2 Payload flow type in flow director can be used to classify MPLS packet by using a command in testpmd like:

testpmd> flow_director_filter 0 mode IP add flow l2_payload ether
0x8847 flexbytes () fwd pf queue <N> fd_id <M>

With the NIC firmware version 5.0 or greater, some limited MPLS support is added: Native MPLS (MPLS in Ethernet) skip is implemented, while no new packet type, no classification or offload are possible. With this change, L2 Payload flow type in flow director cannot be used to classify MPLS packet as with previous firmware versions. Meanwhile, the Ethertype filter can be used to classify MPLS packet by using a command in testpmd like:

testpmd> ethertype_filter 0 add mac_ignr 00:00:00:00:00:00 ethertype
0x8847 fwd queue <M>

13.7.2. 16 Byte Descriptor cannot be used on DPDK VF

If the Linux i40e kernel driver is used as host driver, while DPDK i40e PMD is used as the VF driver, DPDK cannot choose 16 byte receive descriptor. That is to say, user should keep CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n in config file.

13.7.4. Receive packets with Ethertype 0x88A8

Due to the FW limitation, PF can receive packets with Ethertype 0x88A8 only when floating VEB is disabled.

13.7.5. Incorrect Rx statistics when packet is oversize

When a packet is over maximum frame size, the packet is dropped. However the Rx statistics, when calling rte_eth_stats_get incorrectly shows it as received.

13.7.6. VF & TC max bandwidth setting

The per VF max bandwidth and per TC max bandwidth cannot be enabled in parallel. The dehavior is different when handling per VF and per TC max bandwidth setting. When enabling per VF max bandwidth, SW will check if per TC max bandwidth is enabled. If so, return failure. When enabling per TC max bandwidth, SW will check if per VF max bandwidth is enabled. If so, disable per VF max bandwidth and continue with per TC max bandwidth setting.

13.7.7. TC TX scheduling mode setting

There’re 2 TX scheduling modes for TCs, round robin and strict priority mode. If a TC is set to strict priority mode, it can consume unlimited bandwidth. It means if APP has set the max bandwidth for that TC, it comes to no effect. It’s suggested to set the strict priority mode for a TC that is latency sensitive but no consuming much bandwidth.

13.7.8. VF performance is impacted by PCI extended tag setting

To reach maximum NIC performance in the VF the PCI extended tag must be enabled. The DPDK I40E PF driver will set this feature during initialization, but the kernel PF driver does not. So when running traffic on a VF which is managed by the kernel PF driver, a significant NIC performance downgrade has been observed (for 64 byte packets, there is about 25% linerate downgrade for a 25G device and about 35% for a 40G device).

For kernel version >= 4.11, the kernel’s PCI driver will enable the extended tag if it detects that the device supports it. So by default, this is not an issue. For kernels <= 4.11 or when the PCI extended tag is disabled it can be enabled using the steps below.

  1. Get the current value of the PCI configure register:

    setpci -s <XX:XX.X> a8.w
    
  2. Set bit 8:

    value = value | 0x100
    
  3. Set the PCI configure register with new value:

    setpci -s <XX:XX.X> a8.w=<value>