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

> 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.

No. The spec, however, is designed for a single device, and lacks some
specifications for multiple devices.

For example, we should have a mechanism to select a device from all to
communicate with a peer.

This patch introduces a new feature bit "VIRTIO_VSOCK_F_MULTI_DEVICES", and
involves some modifications to the config space, device & driver norms.

> > 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.
> 
> Thanks

Yes, indeed. As we discussed before, I marked this as a side gain. And
@Stefano said that the community has a plan to implement multiqueue for
vsock. The foundational goal of this patch is to enable vsock to support
multiple backends.

Thanks,
Xuewei