7. ENIC Poll Mode Driver

ENIC PMD is the DPDK poll-mode driver for the Cisco System Inc. VIC Ethernet NICs. These adapters are also referred to as vNICs below. If you are running or would like to run DPDK software applications on Cisco UCS servers using Cisco VIC adapters the following documentation is relevant.

7.1. How to obtain ENIC PMD integrated DPDK

ENIC PMD support is integrated into the DPDK suite. dpdk-<version>.tar.gz should be downloaded from http://core.dpdk.org/download/

7.2. Configuration information

  • DPDK Configuration Parameters

    The following configuration options are available for the ENIC PMD:

    • CONFIG_RTE_LIBRTE_ENIC_PMD (default y): Enables or disables inclusion of the ENIC PMD driver in the DPDK compilation.
    • CONFIG_RTE_LIBRTE_ENIC_DEBUG (default n): Enables or disables debug logging within the ENIC PMD driver.

  • vNIC Configuration Parameters

    • Number of Queues

      The maximum number of receive queues (RQs), work queues (WQs) and completion queues (CQs) are configurable on a per vNIC basis through the Cisco UCS Manager (CIMC or UCSM).

      These values should be configured as follows:

      • The number of WQs should be greater or equal to the value of the expected nb_tx_q parameter in the call to the rte_eth_dev_configure()
      • The number of RQs configured in the vNIC should be greater or equal to twice the value of the expected nb_rx_q parameter in the call to rte_eth_dev_configure(). With the addition of rx scatter, a pair of RQs on the vnic is needed for each receive queue used by DPDK, even if rx scatter is not being used. Having a vNIC with only 1 RQ is not a valid configuration, and will fail with an error message.
      • The number of CQs should set so that there is one CQ for each WQ, and one CQ for each pair of RQs.

      For example: If the application requires 3 Rx queues, and 3 Tx queues, the vNIC should be configured to have at least 3 WQs, 6 RQs (3 pairs), and 6 CQs (3 for use by WQs + 3 for use by the 3 pairs of RQs).

    • Size of Queues

      Likewise, the number of receive and transmit descriptors are configurable on a per vNIC bases via the UCS Manager and should be greater than or equal to the nb_rx_desc and nb_tx_desc parameters expected to be used in the calls to rte_eth_rx_queue_setup() and rte_eth_tx_queue_setup() respectively. An application requesting more than the set size will be limited to that size.

      Unless there is a lack of resources due to creating many vNICs, it is recommended that the WQ and RQ sizes be set to the maximum. This gives the application the greatest amount of flexibility in its queue configuration.

      • Note: Since the introduction of rx scatter, for performance reasons, this PMD uses two RQs on the vNIC per receive queue in DPDK. One RQ holds descriptors for the start of a packet the second RQ holds the descriptors for the rest of the fragments of a packet. This means that the nb_rx_desc parameter to rte_eth_rx_queue_setup() can be a greater than 4096. The exact amount will depend on the size of the mbufs being used for receives, and the MTU size.

        For example: If the mbuf size is 2048, and the MTU is 9000, then receiving a full size packet will take 5 descriptors, 1 from the start of packet queue, and 4 from the second queue. Assuming that the RQ size was set to the maximum of 4096, then the application can specify up to 1024 + 4096 as the nb_rx_desc parameter to rte_eth_rx_queue_setup().

    • Interrupts

      Only one interrupt per vNIC interface should be configured in the UCS manager regardless of the number receive/transmit queues. The ENIC PMD uses this interrupt to get information about link status and errors in the fast path.

7.3. Flow director support

Advanced filtering support was added to 1300 series VIC firmware starting with version 2.0.13 for C-series UCS servers and version 3.1.2 for UCSM managed blade servers. In order to enable advanced filtering the ‘Advanced filter’ radio button should be enabled via CIMC or UCSM followed by a reboot of the server.

With advanced filters, perfect matching of all fields of IPv4, IPv6 headers as well as TCP, UDP and SCTP L4 headers is available through flow director. Masking of these feilds for partial match is also supported.

Without advanced filter support, the flow director is limited to IPv4 perfect filtering of the 5-tuple with no masking of fields supported.

7.4. Ingress VLAN Rewrite

VIC adapters can tag, untag, or modify the VLAN headers of ingress packets. The ingress VLAN rewrite mode controls this behavior. By default, it is set to pass-through, where the NIC does not modify the VLAN header in any way so that the application can see the original header. This mode is sufficient for many applications, but may not be suitable for others. Such applications may change the mode by setting devargs parameter ig-vlan-rewrite to one of the following.

  • pass: Pass-through mode. The NIC does not modify the VLAN header. This is the default mode.
  • priority: Priority-tag default VLAN mode. If the ingress packet is tagged with the default VLAN, the NIC replaces its VLAN header with the priority tag (VLAN ID 0).
  • trunk: Default trunk mode. The NIC tags untagged ingress packets with the default VLAN. Tagged ingress packets are not modified. To the application, every packet appears as tagged.
  • untag: Untag default VLAN mode. If the ingress packet is tagged with the default VLAN, the NIC removes or untags its VLAN header so that the application sees an untagged packet. As a result, the default VLAN becomes untagged. This mode can be useful for applications such as OVS-DPDK performance benchmarks that utilize only the default VLAN and want to see only untagged packets.

7.5. Limitations

  • VLAN 0 Priority Tagging

    If a vNIC is configured in TRUNK mode by the UCS manager, the adapter will priority tag egress packets according to 802.1Q if they were not already VLAN tagged by software. If the adapter is connected to a properly configured switch, there will be no unexpected behavior.

    In test setups where an Ethernet port of a Cisco adapter in TRUNK mode is connected point-to-point to another adapter port or connected though a router instead of a switch, all ingress packets will be VLAN tagged. Programs such as l3fwd may not account for VLAN tags in packets and may misbehave. One solution is to enable VLAN stripping on ingress so the VLAN tag is removed from the packet and put into the mbuf->vlan_tci field. Here is an example of how to accomplish this:

vlan_offload = rte_eth_dev_get_vlan_offload(port);
vlan_offload |= ETH_VLAN_STRIP_OFFLOAD;
rte_eth_dev_set_vlan_offload(port, vlan_offload);

Another alternative is modify the adapter’s ingress VLAN rewrite mode so that packets with the default VLAN tag are stripped by the adapter and presented to DPDK as untagged packets. In this case mbuf->vlan_tci and the PKT_RX_VLAN and PKT_RX_VLAN_STRIPPED mbuf flags would not be set. This mode is enabled with the devargs parameter ig-vlan-rewrite=untag. For example:

-w 12:00.0,ig-vlan-rewrite=untag
  • Limited flow director support on 1200 series and 1300 series Cisco VIC adapters with old firmware. Please see Flow director support.
  • Flow director features are not supported on generation 1 Cisco VIC adapters (M81KR and P81E)

7.6. How to build the suite?

The build instructions for the DPDK suite should be followed. By default the ENIC PMD library will be built into the DPDK library.

For configuring and using UIO and VFIO frameworks, please refer the documentation that comes with DPDK suite.

7.7. Supported Cisco VIC adapters

ENIC PMD supports all recent generations of Cisco VIC adapters including:

  • VIC 1280
  • VIC 1240
  • VIC 1225
  • VIC 1285
  • VIC 1225T
  • VIC 1227
  • VIC 1227T
  • VIC 1380
  • VIC 1340
  • VIC 1385
  • VIC 1387

7.8. Supported Operating Systems

Any Linux distribution fulfilling the conditions described in Dependencies section of DPDK documentation.

7.9. Supported features

  • Unicast, multicast and broadcast transmission and reception
  • Receive queue polling
  • Port Hardware Statistics
  • Hardware VLAN acceleration
  • IP checksum offload
  • Receive side VLAN stripping
  • Multiple receive and transmit queues
  • Flow Director ADD, UPDATE, DELETE, STATS operation support IPv4 and IPv6
  • Promiscuous mode
  • Setting RX VLAN (supported via UCSM/CIMC only)
  • VLAN filtering (supported via UCSM/CIMC only)
  • Execution of application by unprivileged system users
  • IPV4, IPV6 and TCP RSS hashing
  • Scattered Rx
  • MTU update

7.10. Known bugs and Unsupported features in this release

  • Signature or flex byte based flow direction
  • Drop feature of flow direction
  • VLAN based flow direction
  • non-IPV4 flow direction
  • Setting of extended VLAN
  • UDP RSS hashing
  • MTU update only works if Scattered Rx mode is disabled

7.11. Prerequisites

  • Prepare the system as recommended by DPDK suite. This includes environment variables, hugepages configuration, tool-chains and configuration
  • Insert vfio-pci kernel module using the command ‘modprobe vfio-pci’ if the user wants to use VFIO framework
  • Insert uio kernel module using the command ‘modprobe uio’ if the user wants to use UIO framework
  • DPDK suite should be configured based on the user’s decision to use VFIO or UIO framework
  • If the vNIC device(s) to be used is bound to the kernel mode Ethernet driver (enic), use ‘ifconfig’ to bring the interface down. The dpdk-devbind.py tool can then be used to unbind the device’s bus id from the enic kernel mode driver.
  • Bind the intended vNIC to vfio-pci in case the user wants ENIC PMD to use VFIO framework using dpdk-devbind.py.
  • Bind the intended vNIC to igb_uio in case the user wants ENIC PMD to use UIO framework using dpdk-devbind.py.

At this point the system should be ready to run DPDK applications. Once the application runs to completion, the vNIC can be detached from vfio-pci or igb_uio if necessary.

Root privilege is required to bind and unbind vNICs to/from VFIO/UIO. VFIO framework helps an unprivileged user to run the applications. For an unprivileged user to run the applications on DPDK and ENIC PMD, it may be necessary to increase the maximum locked memory of the user. The following command could be used to do this.

sudo sh -c "ulimit -l <value in Kilo Bytes>"

The value depends on the memory configuration of the application, DPDK and PMD. Typically, the limit has to be raised to higher than 2GB. e.g., 2621440

The compilation of any unused drivers can be disabled using the configuration file in config/ directory (e.g., config/common_linuxapp). This would help in bringing down the time taken for building the libraries and the initialization time of the application.

7.13. Contact Information

Any questions or bugs should be reported to DPDK community and to the ENIC PMD maintainers: