Re: [PATCH] vhost-user.rst: Explicitly allow front-end to write to kick FDs

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Tue, Apr 21, 2026 at 06:49:32PM +0200, Stefano Garzarella wrote:
> On Tue, 21 Apr 2026 at 18:06, Jorge Moreira <jemoreira@google.com> wrote:
> >
> > > Do you know other backends we should check?
> >
> > CrosVm's: https://github.com/google/crosvm/tree/main/devices/src/virtio/vhost_user_backend
> 
> Which do exactly the same
> https://github.com/google/crosvm/blob/b49e336de56d6353ae06245de0c7fabec3db2d5e/devices/src/virtio/vhost_user_backend/handler.rs#L596
> 
> No?

To round this out, I looked at DPDK, one of the most popular vhost-user
back-end implementations.

The DPDK back-end starts/stops the rings in the vhost-user message
handler rather than upon reading the kick fd:
https://github.com/DPDK/dpdk/blob/main/lib/vhost/vhost_user.c#L3274

I think it would be nice to update the spec since it seems
implementations aren't actually waiting for the kick fd. However, it is
not central to the original discussion, so feel free to skip it if you
want.

Stefan

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