24. MLX5 poll mode driver

24.1. Implementation details

Besides its dependency on libibverbs (that implies libmlx5 and associated kernel support), librte_pmd_mlx5 relies heavily on system calls for control operations such as querying/updating the MTU and flow control parameters.

For security reasons and robustness, this driver only deals with virtual memory addresses. The way resources allocations are handled by the kernel combined with hardware specifications that allow it to handle virtual memory addresses directly ensure that DPDK applications cannot access random physical memory (or memory that does not belong to the current process).

This capability allows the PMD to coexist with kernel network interfaces which remain functional, although they stop receiving unicast packets as long as they share the same MAC address. This means legacy linux control tools (for example: ethtool, ifconfig and more) can operate on the same network interfaces that owned by the DPDK application.

Enabling librte_pmd_mlx5 causes DPDK applications to be linked against libibverbs.

24.2. Features

• Multi arch support: x86_64, POWER8, ARMv8.
• Multiple TX and RX queues.
• Support for scattered TX and RX frames.
• IPv4, IPv6, TCPv4, TCPv6, UDPv4 and UDPv6 RSS on any number of queues.
• Several RSS hash keys, one for each flow type.
• Configurable RETA table.
• Support for multiple MAC addresses.
• VLAN filtering.
• RX VLAN stripping.
• TX VLAN insertion.
• RX CRC stripping configuration.
• Promiscuous mode.
• Multicast promiscuous mode.
• Hardware checksum offloads.
• Flow director (RTE_FDIR_MODE_PERFECT, RTE_FDIR_MODE_PERFECT_MAC_VLAN and RTE_ETH_FDIR_REJECT).
• Flow API.
• Multiple process.
• KVM and VMware ESX SR-IOV modes are supported.
• RSS hash result is supported.
• Hardware TSO for generic IP or UDP tunnel, including VXLAN and GRE.
• Hardware checksum Tx offload for generic IP or UDP tunnel, including VXLAN and GRE.
• RX interrupts.
• Statistics query including Basic, Extended and per queue.
• Rx HW timestamp.
• Tunnel types: VXLAN, L3 VXLAN, VXLAN-GPE, GRE, MPLSoGRE, MPLSoUDP.
• Tunnel HW offloads: packet type, inner/outer RSS, IP and UDP checksum verification.

24.3. Limitations

• For secondary process:

  • Forked secondary process not supported.
  • All mempools must be initialized before rte_eth_dev_start().

• Flow pattern without any specific vlan will match for vlan packets as well:

  When VLAN spec is not specified in the pattern, the matching rule will be created with VLAN as a wild card. Meaning, the flow rule:

  flow create 0 ingress pattern eth / vlan vid is 3 / ipv4 / end ...
  

  Will only match vlan packets with vid=3. and the flow rules:

  flow create 0 ingress pattern eth / ipv4 / end ...
  

  Or:

  flow create 0 ingress pattern eth / vlan / ipv4 / end ...
  

  Will match any ipv4 packet (VLAN included).

• A multi segment packet must have less than 6 segments in case the Tx burst function is set to multi-packet send or Enhanced multi-packet send. Otherwise it must have less than 50 segments.

• Count action for RTE flow is only supported in Mellanox OFED.

• Flows with a VXLAN Network Identifier equal (or ends to be equal) to 0 are not supported.

• VXLAN TSO and checksum offloads are not supported on VM.

• L3 VXLAN and VXLAN-GPE tunnels cannot be supported together with MPLSoGRE and MPLSoUDP.

• VF: flow rules created on VF devices can only match traffic targeted at the configured MAC addresses (see rte_eth_dev_mac_addr_add()).

• When Multi-Packet Rx queue is configured (mprq_en), a Rx packet can be externally attached to a user-provided mbuf with having EXT_ATTACHED_MBUF in ol_flags. As the mempool for the external buffer is managed by PMD, all the Rx mbufs must be freed before the device is closed. Otherwise, the mempool of the external buffers will be freed by PMD and the application which still holds the external buffers may be corrupted.

24.4. Statistics

MLX5 supports various of methods to report statistics:

Port statistics can be queried using rte_eth_stats_get(). The port statistics are through SW only and counts the number of packets received or sent successfully by the PMD.

Extended statistics can be queried using rte_eth_xstats_get(). The extended statistics expose a wider set of counters counted by the device. The extended port statistics counts the number of packets received or sent successfully by the port. As Mellanox NICs are using the Bifurcated Linux Driver those counters counts also packet received or sent by the Linux kernel. The counters with _phy suffix counts the total events on the physical port, therefore not valid for VF.

Finally per-flow statistics can by queried using rte_flow_query when attaching a count action for specific flow. The flow counter counts the number of packets received successfully by the port and match the specific flow.

24.5. Configuration

24.6. Prerequisites

This driver relies on external libraries and kernel drivers for resources allocations and initialization. The following dependencies are not part of DPDK and must be installed separately:

• libibverbs

  User space Verbs framework used by librte_pmd_mlx5. This library provides a generic interface between the kernel and low-level user space drivers such as libmlx5.

  It allows slow and privileged operations (context initialization, hardware resources allocations) to be managed by the kernel and fast operations to never leave user space.

• libmlx5

  Low-level user space driver library for Mellanox ConnectX-4/ConnectX-5/Bluefield devices, it is automatically loaded by libibverbs.

  This library basically implements send/receive calls to the hardware queues.

• Kernel modules

  They provide the kernel-side Verbs API and low level device drivers that manage actual hardware initialization and resources sharing with user space processes.

  Unlike most other PMDs, these modules must remain loaded and bound to their devices:

  • mlx5_core: hardware driver managing Mellanox ConnectX-4/ConnectX-5/Bluefield devices and related Ethernet kernel network devices.
  • mlx5_ib: InifiniBand device driver.
  • ib_uverbs: user space driver for Verbs (entry point for libibverbs).

• Firmware update

  Mellanox OFED releases include firmware updates for ConnectX-4/ConnectX-5/Bluefield adapters.

  Because each release provides new features, these updates must be applied to match the kernel modules and libraries they come with.

24.7. Supported NICs

• Mellanox(R) ConnectX(R)-4 10G MCX4111A-XCAT (1x10G)
• Mellanox(R) ConnectX(R)-4 10G MCX4121A-XCAT (2x10G)
• Mellanox(R) ConnectX(R)-4 25G MCX4111A-ACAT (1x25G)
• Mellanox(R) ConnectX(R)-4 25G MCX4121A-ACAT (2x25G)
• Mellanox(R) ConnectX(R)-4 40G MCX4131A-BCAT (1x40G)
• Mellanox(R) ConnectX(R)-4 40G MCX413A-BCAT (1x40G)
• Mellanox(R) ConnectX(R)-4 40G MCX415A-BCAT (1x40G)
• Mellanox(R) ConnectX(R)-4 50G MCX4131A-GCAT (1x50G)
• Mellanox(R) ConnectX(R)-4 50G MCX413A-GCAT (1x50G)
• Mellanox(R) ConnectX(R)-4 50G MCX414A-BCAT (2x50G)
• Mellanox(R) ConnectX(R)-4 50G MCX415A-GCAT (2x50G)
• Mellanox(R) ConnectX(R)-4 50G MCX416A-BCAT (2x50G)
• Mellanox(R) ConnectX(R)-4 50G MCX416A-GCAT (2x50G)
• Mellanox(R) ConnectX(R)-4 50G MCX415A-CCAT (1x100G)
• Mellanox(R) ConnectX(R)-4 100G MCX416A-CCAT (2x100G)
• Mellanox(R) ConnectX(R)-4 Lx 10G MCX4121A-XCAT (2x10G)
• Mellanox(R) ConnectX(R)-4 Lx 25G MCX4121A-ACAT (2x25G)
• Mellanox(R) ConnectX(R)-5 100G MCX556A-ECAT (2x100G)
• Mellanox(R) ConnectX(R)-5 Ex EN 100G MCX516A-CDAT (2x100G)

24.8. Quick Start Guide on OFED

1. Download latest Mellanox OFED. For more info check the prerequisites.

2. Install the required libraries and kernel modules either by installing only the required set, or by installing the entire Mellanox OFED:

   ./mlnxofedinstall --upstream-libs --dpdk
   

3. Verify the firmware is the correct one:

   ibv_devinfo
   

4. Verify all ports links are set to Ethernet:

   mlxconfig -d <mst device> query | grep LINK_TYPE
   LINK_TYPE_P1                        ETH(2)
   LINK_TYPE_P2                        ETH(2)
   

   Link types may have to be configured to Ethernet:

   mlxconfig -d <mst device> set LINK_TYPE_P1/2=1/2/3
   
   * LINK_TYPE_P1=<1|2|3> , 1=Infiniband 2=Ethernet 3=VPI(auto-sense)
   

   For hypervisors verify SR-IOV is enabled on the NIC:

   mlxconfig -d <mst device> query | grep SRIOV_EN
   SRIOV_EN                            True(1)
   

   If needed, set enable the set the relevant fields:

   mlxconfig -d <mst device> set SRIOV_EN=1 NUM_OF_VFS=16
   mlxfwreset -d <mst device> reset
   

5. Restart the driver:

   /etc/init.d/openibd restart
   

   or:

   service openibd restart
   

   If link type was changed, firmware must be reset as well:

   mlxfwreset -d <mst device> reset
   

   For hypervisors, after reset write the sysfs number of virtual functions needed for the PF.

   To dynamically instantiate a given number of virtual functions (VFs):

   echo [num_vfs] > /sys/class/infiniband/mlx5_0/device/sriov_numvfs
   

6. Compile DPDK and you are ready to go. See instructions on Development Kit Build System

24.9. Performance tuning

1. Configure aggressive CQE Zipping for maximum performance:

mlxconfig -d <mst device> s CQE_COMPRESSION=1

To set it back to the default CQE Zipping mode use:

mlxconfig -d <mst device> s CQE_COMPRESSION=0

2. In case of virtualization:

   • Make sure that hypervisor kernel is 3.16 or newer.
   • Configure boot with iommu=pt.
   • Use 1G huge pages.
   • Make sure to allocate a VM on huge pages.
   • Make sure to set CPU pinning.

3. Use the CPU near local NUMA node to which the PCIe adapter is connected, for better performance. For VMs, verify that the right CPU and NUMA node are pinned according to the above. Run:

   lstopo-no-graphics
   

   to identify the NUMA node to which the PCIe adapter is connected.

4. If more than one adapter is used, and root complex capabilities allow to put both adapters on the same NUMA node without PCI bandwidth degradation, it is recommended to locate both adapters on the same NUMA node. This in order to forward packets from one to the other without NUMA performance penalty.

5. Disable pause frames:

   ethtool -A <netdev> rx off tx off
   

6. Verify IO non-posted prefetch is disabled by default. This can be checked via the BIOS configuration. Please contact you server provider for more information about the settings.

setpci -s <NIC PCI address> 68.w

setpci -s <NIC PCI address> 68.w=3XXX

7. To minimize overhead of searching Memory Regions:
   • ‘–socket-mem’ is recommended to pin memory by predictable amount.
   • Configure per-lcore cache when creating Mempools for packet buffer.
   • Refrain from dynamically allocating/freeing memory in run-time.

24.10. Notes for testpmd

Compared to librte_pmd_mlx4 that implements a single RSS configuration per port, librte_pmd_mlx5 supports per-protocol RSS configuration.

Since testpmd defaults to IP RSS mode and there is currently no command-line parameter to enable additional protocols (UDP and TCP as well as IP), the following commands must be entered from its CLI to get the same behavior as librte_pmd_mlx4:

> port stop all
> port config all rss all
> port start all

24.11. Usage example

This section demonstrates how to launch testpmd with Mellanox ConnectX-4/ConnectX-5/Bluefield devices managed by librte_pmd_mlx5.

1. Load the kernel modules:

   modprobe -a ib_uverbs mlx5_core mlx5_ib
   

   Alternatively if MLNX_OFED is fully installed, the following script can be run:

   /etc/init.d/openibd restart
   

   Note

   User space I/O kernel modules (uio and igb_uio) are not used and do not have to be loaded.

2. Make sure Ethernet interfaces are in working order and linked to kernel verbs. Related sysfs entries should be present:

   ls -d /sys/class/net/*/device/infiniband_verbs/uverbs* | cut -d / -f 5
   

   Example output:

   eth30
   eth31
   eth32
   eth33
   

3. Optionally, retrieve their PCI bus addresses for whitelisting:

   {
       for intf in eth2 eth3 eth4 eth5;
       do
           (cd "/sys/class/net/${intf}/device/" && pwd -P);
       done;
   } |
   sed -n 's,.*/\(.*\),-w \1,p'
   

   Example output:

   -w 0000:05:00.1
   -w 0000:06:00.0
   -w 0000:06:00.1
   -w 0000:05:00.0
   

4. Request huge pages:

   echo 1024 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages/nr_hugepages
   

5. Start testpmd with basic parameters:

   testpmd -l 8-15 -n 4 -w 05:00.0 -w 05:00.1 -w 06:00.0 -w 06:00.1 -- --rxq=2 --txq=2 -i
   

   Example output:

   [...]
   EAL: PCI device 0000:05:00.0 on NUMA socket 0
   EAL:   probe driver: 15b3:1013 librte_pmd_mlx5
   PMD: librte_pmd_mlx5: PCI information matches, using device "mlx5_0" (VF: false)
   PMD: librte_pmd_mlx5: 1 port(s) detected
   PMD: librte_pmd_mlx5: port 1 MAC address is e4:1d:2d:e7:0c:fe
   EAL: PCI device 0000:05:00.1 on NUMA socket 0
   EAL:   probe driver: 15b3:1013 librte_pmd_mlx5
   PMD: librte_pmd_mlx5: PCI information matches, using device "mlx5_1" (VF: false)
   PMD: librte_pmd_mlx5: 1 port(s) detected
   PMD: librte_pmd_mlx5: port 1 MAC address is e4:1d:2d:e7:0c:ff
   EAL: PCI device 0000:06:00.0 on NUMA socket 0
   EAL:   probe driver: 15b3:1013 librte_pmd_mlx5
   PMD: librte_pmd_mlx5: PCI information matches, using device "mlx5_2" (VF: false)
   PMD: librte_pmd_mlx5: 1 port(s) detected
   PMD: librte_pmd_mlx5: port 1 MAC address is e4:1d:2d:e7:0c:fa
   EAL: PCI device 0000:06:00.1 on NUMA socket 0
   EAL:   probe driver: 15b3:1013 librte_pmd_mlx5
   PMD: librte_pmd_mlx5: PCI information matches, using device "mlx5_3" (VF: false)
   PMD: librte_pmd_mlx5: 1 port(s) detected
   PMD: librte_pmd_mlx5: port 1 MAC address is e4:1d:2d:e7:0c:fb
   Interactive-mode selected
   Configuring Port 0 (socket 0)
   PMD: librte_pmd_mlx5: 0x8cba80: TX queues number update: 0 -> 2
   PMD: librte_pmd_mlx5: 0x8cba80: RX queues number update: 0 -> 2
   Port 0: E4:1D:2D:E7:0C:FE
   Configuring Port 1 (socket 0)
   PMD: librte_pmd_mlx5: 0x8ccac8: TX queues number update: 0 -> 2
   PMD: librte_pmd_mlx5: 0x8ccac8: RX queues number update: 0 -> 2
   Port 1: E4:1D:2D:E7:0C:FF
   Configuring Port 2 (socket 0)
   PMD: librte_pmd_mlx5: 0x8cdb10: TX queues number update: 0 -> 2
   PMD: librte_pmd_mlx5: 0x8cdb10: RX queues number update: 0 -> 2
   Port 2: E4:1D:2D:E7:0C:FA
   Configuring Port 3 (socket 0)
   PMD: librte_pmd_mlx5: 0x8ceb58: TX queues number update: 0 -> 2
   PMD: librte_pmd_mlx5: 0x8ceb58: RX queues number update: 0 -> 2
   Port 3: E4:1D:2D:E7:0C:FB
   Checking link statuses...
   Port 0 Link Up - speed 40000 Mbps - full-duplex
   Port 1 Link Up - speed 40000 Mbps - full-duplex
   Port 2 Link Up - speed 10000 Mbps - full-duplex
   Port 3 Link Up - speed 10000 Mbps - full-duplex
   Done
   testpmd>