9. MLX5 poll mode driver

9.1. 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.

Enabling librte_pmd_mlx5 causes DPDK applications to be linked against libibverbs.

9.2. Features

• 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.
• Promiscuous mode.
• Multicast promiscuous mode.
• Hardware checksum offloads.

9.3. Limitations

• KVM and VMware ESX SR-IOV modes are not supported yet.
• Inner RSS for VXLAN frames is not supported yet.
• Port statistics through software counters only.
• Hardware checksum offloads for VXLAN inner header are not supported yet.
• Secondary processes are not supported yet.

9.4. Configuration

9.5. 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 devices, it is automatically loaded by libibverbs.

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

• Kernel modules (mlnx-ofed-kernel)

  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 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 adapters.

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

Currently supported by DPDK:

• Mellanox OFED 3.1-1.0.3 or 3.1-1.5.7.1 depending on usage.

  The following features are supported with version 3.1-1.5.7.1 and above only:

  • IPv6, UPDv6, TCPv6 RSS.
  • RX checksum offloads.
  • IBM POWER8.

• Minimum firmware version:

  With MLNX_OFED 3.1-1.0.3:

  • ConnectX-4: 12.12.1240
  • ConnectX-4 Lx: 14.12.1100

  With MLNX_OFED 3.1-1.5.7.1:

  • ConnectX-4: 12.13.0144
  • ConnectX-4 Lx: 14.13.0144

9.6. 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

9.7. Usage example

This section demonstrates how to launch testpmd with Mellanox ConnectX-4 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 -c 0xff00 -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>