5. NTB Rawdev Driver

The ntb rawdev driver provides a non-transparent bridge between two separate hosts so that they can communicate with each other. Thus, many user cases can benefit from this, such as fault tolerance and visual acceleration.

This PMD allows two hosts to handshake for device start and stop, memory allocation for the peer to access and read/write allocated memory from peer. Also, the PMD allows to use doorbell registers to notify the peer and share some information by using scratchpad registers.

5.1. BIOS setting on Intel Skylake

Intel Non-transparent Bridge needs special BIOS setting. Since the PMD only supports Intel Skylake platform, introduce BIOS setting here. The referencce is https://www.intel.com/content/dam/support/us/en/documents/server-products/Intel_Xeon_Processor_Scalable_Family_BIOS_User_Guide.pdf

  • Set the needed PCIe port as NTB to NTB mode on both hosts.
  • Enable NTB bars and set bar size of bar 23 and bar 45 as 12-29 (2K-512M) on both hosts. Note that bar size on both hosts should be the same.
  • Disable split bars for both hosts.
  • Set crosslink control override as DSD/USP on one host, USD/DSP on another host.
  • Disable PCIe PII SSC (Spread Spectrum Clocking) for both hosts. This is a hardware requirement.

5.2. Build Options

  • CONFIG_RTE_LIBRTE_PMD_NTB_RAWDEV (default y)

    Toggle compilation of the ntb driver.

5.3. Device Setup

The Intel NTB devices need to be bound to a DPDK-supported kernel driver to use, i.e. igb_uio, vfio. The dpdk-devbind.py script can be used to show devices status and to bind them to a suitable kernel driver. They will appear under the category of “Misc (rawdev) devices”.

5.4. Limitation

  • The FIFO hasn’t been introduced and will come in 19.11 release.
  • This PMD only supports Intel Skylake platform.