Re: [PATCH v7] virtio-vsock: Add support for multi devices

On Fri, 13 Jun 2025 at 06:23, Jason Wang <[email protected]> wrote:
>
> On Sat, Apr 12, 2025 at 10:39 PM Xuewei Niu <[email protected]> wrote:
> >
> > This patch brings a new feature, called "multi devices", to the virtio
> > vsock. It introduces a "VIRTIO_VSOCK_F_MULTI_DEVICES" feature bit, and a
> > "device_order" field to the config for the virtio vsock.
> >
> > == Motivition ==
> >
> > Vsock is a lightweight and widely used data exchange mechanism between host
> > and guest. Currently, the virtio-vsock only supports one device, resulting
> > in the inability to enable more than one backend.
>
> I wonder which part of the spec forbids more than one device.

I don't think there isn't anything that forbid it, but what we don't
have is a kind of default gateway/interface to use when sending
messages.
So, this proposal is mostly to chose the default device to use, when
the user don't bind any CID on the source socket.

>
> > For instance, two devices
> > are required: one to transfer data to the VMM via virtio-vsock, and another
> > to a user process via vhost-user-vsock.
> >
> > Apart from that, a side gain is that theoretically the performance might be
> > improved since each device has its own queue. But it varies depending on
> > the implementation.
>
> It could implement multiqueue anyhow.

Yeah, I pointed out multiple times to skip this as justification,
since multi-queue has more much sense for that.
IMHO it's confusing to still talk about it in this proposal.

Stefano

>
> Thanks
>