Linux 5.9 Bringing Mellanox VDPA Driver For Newer ConnectX Devices
Written by Michael Larabel in Virtualization on 11 August 2020 at 10:24 AM EDT. 5 Comments
VIRTUALIZATION --
There are a few changes worth mentioning out of the VirtIO updates submitted today for the Linux 5.9 kernel.

The latest Mellanox driver going mainline in the Linux kernel is a VDPA (Virtual Data Path Acceleration) for their ConnectX6 DX and newer devices.

The VDPA standard is an abstraction layer on top of SR-IOV and allows for a single VirtIO driver in the guest that isn't hardware specific while still allowing wire-speed performance on the data plane. VDPA is more versatile than the likes of VirtIO full hardware offloading. More details for those interested via this Red Hat post.

The Mellanox ConnectX VDPA support works with the ConnectX6 DX and newer devices. Currently just a single queue is supported while multi-queue support will come later along with a new block device driver (off a single queue with this VDPA driver the performance measured via iperf is around 12 Gbps). This VDPA driver builds off the existing Mellanox MLX5 driver code already in the mainline tree. For using this driver with QEMU and VirtIO networking, a currently branched version of QEMU is necessary at the moment although ultimately will work its way mainline.

This MLX5 VDPA code was sent in with the VirtIO updates for Linux 5.9. Also notable from the VirtIO updates is IRQ bypass support for VDPA and IFC. The IRQ offloading for VDPA is said to shave around 0.1ms in ping latency between two VFs.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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