Re: Call for GSoC internship project ideas

[John Levon <john.levon@nutanix.com>]

On Wed, Jan 14, 2026 at 02:26:48PM -0500, Stefan Hajnoczi wrote:

> I have some thoughts about the vfio-user project idea:

https://wiki.qemu.org/Internships/ProjectIdeas/VFIOUSER
> 
> > === First-Class vfio-user Device Support ===
> >
> > '''Summary:''' Promote QEMU's experimental vfio-user device support to production-ready status by adding comprehensive testing, documentation, migration support, and seamless CLI integration.
> >
> > Since 2022, QEMU has included `x-vfio-user-server` for running emulated PCI devices in standalone processes using the vfio-user protocol. This enables security isolation, modular device development, and flexible deployment architectures.
> >
> > However, adoption has been limited due to:
> > * '''Experimental status''' - All components use `x-` prefix indicating unstable API
> 
> This is a question of whether the command-line interface is stable.
> John Levon, Thanos Makatos, and Cédric Le Goater are the maintainers
> for vfio-user. I wonder what their thoughts on removing the "x-" are?

Just remembered I hadn't replied here in public. Actually, Jag and Elena are the
maintainers of the server portion of this, so would be interested in their
opinions.

As a maintainer of the client side, I think this is a great project, though, and
would love to see vfio-user-server brought back into a good working state and
the legacy protocol dropped! And we would be happy to support where we can.

> The vfio-user protocol has adopted the kernel VFIO interface's device
> state migration features. In theory the protocol supports migration,
> but I don't see QEMU code that implements the protocol features. If my
> understanding is correct, then there is a (sub-)project here to
> implement live migration protocol features in --device vfio-user-pci
> (the proxy) as well as in --object x-vfio-user-server (QEMU's server)?

Correct; we dropped all the live migration stuff as part of integrating. We have
protocol definitions and library server support for this. There is also somebody
who has some draft qemu patches around!

regards
john