vDPA: support for block devices in Linux and QEMU

Using libblkio, QEMU Storage Daemon, and VDUSE

A vDPA device is a type of device that follows the virtio specification for its datapath but has a vendor-specific control path.

vDPA devices can be both physically located on the hardware or emulated by software.

vDPA overview

A small vDPA parent driver in the host kernel is required only for the control path. The main advantage is the unified software stack for all vDPA devices:

  • vhost interface (vhost-vdpa) for userspace or guest virtio driver, like a VM running in QEMU
  • virtio interface (virtio-vdpa) for bare-metal or containerized applications running in the host
  • management interface (vdpa netlink) for instantiating devices and configuring virtio parameters
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SOCAT now supports AF_VSOCK

SOCAT is a CLI utility which enables the concatenation of two sockets together. It establishes two bidirectional byte streams and transfers data between them.

socat supports several address types (e.g. TCP, UDP, UNIX domain sockets, etc.) to construct the streams. The latest version 1.7.4, released earlier this year [2021-01-04], supports also AF_VSOCK addresses:

  • VSOCK-LISTEN:<port>

    • Listen on port and accepts a VSOCK connection.
  • VSOCK-CONNECT:<cid>:<port>

    • Establishes a VSOCK stream connection to the specified cid and port.


If you are interested on VSOCK, I’ll talk witn Andra Paraschiv (AWS) about it at FOSDEM 2021. The talk is titled Leveraging virtio-vsock in the cloud and containers and it’s scheduled for Saturday, February 6th 2021 at 11:30 AM (CET).

We will show cool VSOCK use cases and some demos about developing, debugging, and measuring the VSOCK performance, including socat demos.

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AF_VSOCK: nested VMs and loopback support available

Recent updates in Linux 5.5 and Linux 5.6

During the last KVM Forum 2019, we discussed some next steps and several requests came from the audience.

In the last months, we worked on that and recent Linux releases contain interesting new features that we will describe in this blog post:

DevConf.CZ 2020

These updates and an introduction to AF_VSOCK were presented at DevConf.CZ 2020 during the “VSOCK: VM↔host socket with minimal configuration” talk. Slides and recording are available.

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KVM Forum 2019: virtio-vsock in QEMU, Firecracker and Linux

Status, Performance and Challenges

Slides and recording are available for the “virtio-vsock in QEMU, Firecracker and Linux: Status, Performance and Challenges” talk that Andra Paraschiv and I presented at KVM Forum 2019. This was the 13th edition of the KVM Forum conference. It took place in Lyon, France in October 2019.

We talked about the current status and future works of VSOCK drivers in Linux and how Firecracker and QEMU provides the virtio-vsock device.

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