15. I40E Poll Mode Driver

15.3.1. 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_VM (default 4)

  Number of queues reserved for each VMDQ Pool.

• CONFIG_RTE_LIBRTE_I40E_ITR_INTERVAL (default -1)

  Interrupt Throttling interval.

15.3.2. Runtime Config Options

• Number of Queues per VF (default 4)

  The number of queue per VF is determined by its host PF. If the PCI address of an i40e PF is aaaa:bb.cc, the number of queues per VF can be configured with EAL parameter like -w aaaa:bb.cc,queue-num-per-vf=n. The value n can be 1, 2, 4, 8 or 16. If no such parameter is configured, the number of queues per VF is 4 by default.

• Support multiple driver (default disable)

  There was a multiple driver support issue during use of 700 series Ethernet Adapter with both Linux kernel and DPDK PMD. To fix this issue, devargs parameter support-multi-driver is introduced, for example:

  -w 84:00.0,support-multi-driver=1
  

  With the above configuration, DPDK PMD will not change global registers, and will switch PF interrupt from IntN to Int0 to avoid interrupt conflict between DPDK and Linux Kernel.

15.6.1. 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

15.6.2. 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

15.6.3. Floating VEB

The Intel® 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.

15.6.4. Dynamic Device Personalization (DDP)

The Intel® Ethernet Controller X*710 support a feature called “Dynamic Device Personalization (DDP)”, which is used to configure hardware by downloading a profile to support protocols/filters which are not supported by default. The DDP functionality requires a NIC firmware version of 6.0 or greater.

Current implementation supports MPLSoUDP/MPLSoGRE/GTP-C/GTP-U/PPPoE/PPPoL2TP, steering can be used with rte_flow API.

Load a profile which supports MPLSoUDP/MPLSoGRE and store backup profile:

testpmd> ddp add 0 ./mpls.pkgo,./backup.pkgo

Delete a MPLS profile and restore backup profile:

testpmd> ddp del 0 ./backup.pkgo

Get loaded DDP package info list:

testpmd> ddp get list 0

Display information about a MPLS profile:

testpmd> ddp get info ./mpls.pkgo

15.6.5. Input set configuration

Input set for any PCTYPE can be configured with user defined configuration, For example, to use only 48bit prefix for IPv6 src address for IPv6 TCP RSS:

testpmd> port config 0 pctype 43 hash_inset clear all
testpmd> port config 0 pctype 43 hash_inset set field 13
testpmd> port config 0 pctype 43 hash_inset set field 14
testpmd> port config 0 pctype 43 hash_inset set field 15

15.6.6. Queue region configuration

The Ethernet Controller X710/XL710 supports a feature of queue regions configuration for RSS in the PF, so that different traffic classes or different packet classification types can be separated to different queues in different queue regions. There is an API for configuration of queue regions in RSS with a command line. It can parse the parameters of the region index, queue number, queue start index, user priority, traffic classes and so on. Depending on commands from the command line, it will call i40e private APIs and start the process of setting or flushing the queue region configuration. As this feature is specific for i40e only private APIs are used. These new test_pmd commands are as shown below. For details please refer to Testpmd Application User Guide.

testpmd> set port (port_id) queue-region region_id (value) \
             queue_start_index (value) queue_num (value)
testpmd> set port (port_id) queue-region region_id (value) flowtype (value)
testpmd> set port (port_id) queue-region UP (value) region_id (value)
testpmd> set port (port_id) queue-region flush (on|off)
testpmd> show port (port_id) queue-region

15.7.1. 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>

15.7.2. 16 Byte RX Descriptor setting on DPDK VF

Currently the VF’s RX descriptor mode is decided by PF. There’s no PF-VF interface for VF to request the RX descriptor mode, also no interface to notify VF its own RX descriptor mode. For all available versions of the i40e driver, these drivers don’t support 16 byte RX descriptor. 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. The reason is that the RX descriptor is already set to 32 byte by the i40e kernel driver. That is to say, user should keep CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n in config file. In the future, if the Linux i40e driver supports 16 byte RX descriptor, user should make sure the DPDK VF uses the same RX descriptor mode, 16 byte or 32 byte, as the PF driver.

The same rule for DPDK PF + DPDK VF. The PF and VF should use the same RX descriptor mode. Or the VF RX will not work.

15.7.3. Receive packets with Ethertype 0x88A8

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

15.7.4. 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.

15.7.5. 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.

15.7.6. 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.

15.7.7. 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>
   

15.7.8. Vlan strip of VF

The VF vlan strip function is only supported in the i40e kernel driver >= 2.1.26.

15.7.9. DCB function

DCB works only when RSS is enabled.

15.7.10. Global configuration warning

I40E PMD will set some global registers to enable some function or set some configure. Then when using different ports of the same NIC with Linux kernel and DPDK, the port with Linux kernel will be impacted by the port with DPDK. For example, register I40E_GL_SWT_L2TAGCTRL is used to control L2 tag, i40e PMD uses I40E_GL_SWT_L2TAGCTRL to set vlan TPID. If setting TPID in port A with DPDK, then the configuration will also impact port B in the NIC with kernel driver, which don’t want to use the TPID. So PMD reports warning to clarify what is changed by writing global register.

15.8.1. Use 16 Bytes RX Descriptor Size

As i40e PMD supports both 16 and 32 bytes RX descriptor sizes, and 16 bytes size can provide helps to high performance of small packets. Configuration of CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC in config files can be changed to use 16 bytes size RX descriptors.

15.8.2. High Performance and per Packet Latency Tradeoff

Due to the hardware design, the interrupt signal inside NIC is needed for per packet descriptor write-back. The minimum interval of interrupts could be set at compile time by CONFIG_RTE_LIBRTE_I40E_ITR_INTERVAL in configuration files. Though there is a default configuration, the interval could be tuned by the users with that configuration item depends on what the user cares about more, performance or per packet latency.