RE: [RFC 00/27] Add VDUSE support to Vhost library

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Maxime Coquelin [mailto:maxime.coquelin@redhat.com]
> Sent: Wednesday, 12 April 2023 17.28
> 
> Hi Ferruh,
> 
> On 4/12/23 13:33, Ferruh Yigit wrote:
> > On 3/31/2023 4:42 PM, Maxime Coquelin wrote:
> >> This series introduces a new type of backend, VDUSE,
> >> to the Vhost library.
> >>
> >> VDUSE stands for vDPA device in Userspace, it enables
> >> implementing a Virtio device in userspace and have it
> >> attached to the Kernel vDPA bus.
> >>
> >> Once attached to the vDPA bus, it can be used either by
> >> Kernel Virtio drivers, like virtio-net in our case, via
> >> the virtio-vdpa driver. Doing that, the device is visible
> >> to the Kernel networking stack and is exposed to userspace
> >> as a regular netdev.
> >>
> >> It can also be exposed to userspace thanks to the
> >> vhost-vdpa driver, via a vhost-vdpa chardev that can be
> >> passed to QEMU or Virtio-user PMD.
> >>
> >> While VDUSE support is already available in upstream
> >> Kernel, a couple of patches are required to support
> >> network device type:
> >>
> >> https://gitlab.com/mcoquelin/linux/-/tree/vduse_networking_poc
> >>
> >> In order to attach the created VDUSE device to the vDPA
> >> bus, a recent iproute2 version containing the vdpa tool is
> >> required.
> >
> > Hi Maxime,
> >
> > Is this a replacement to the existing DPDK vDPA framework? What is the
> > plan for long term?
> >
> 
> No, this is not a replacement for DPDK vDPA framework.
> 
> We (Red Hat) don't have plans to support DPDK vDPA framework in our
> products, but there are still contribution to DPDK vDPA by several vDPA
> hardware vendors (Intel, Nvidia, Xilinx), so I don't think it is going
> to be deprecated soon.

Ferruh's question made me curious...

I don't know anything about VDUSE or vDPA, and don't use any of it, so consider me ignorant in this area.

Is VDUSE an alternative to the existing DPDK vDPA framework? What are the differences, e.g. in which cases would an application developer (or user) choose one or the other?

And if it is a better alternative, perhaps the documentation should mention that it is recommended over DPDK vDPA. Just like we started recommending alternatives to the KNI driver, so we could phase it out and eventually get rid of it.

> 
> Regards,
> Maxime