Re: [PATCH v2 3/3] tun: Set num_buffers for virtio 1.0

Jason Wang
2025-01-13T03:04:41Z

On Fri, Jan 10, 2025 at 7:12 PM Akihiko Odaki <akihiko.odaki@daynix.com> wrote:
>
> On 2025/01/10 19:23, Michael S. Tsirkin wrote:
> > On Fri, Jan 10, 2025 at 11:27:13AM +0800, Jason Wang wrote:
> >> On Thu, Jan 9, 2025 at 2:59 PM Akihiko Odaki <akihiko.odaki@daynix.com> wrote:
> >>>
> >>> The specification says the device MUST set num_buffers to 1 if
> >>> VIRTIO_NET_F_MRG_RXBUF has not been negotiated.
> >>
> >> Have we agreed on how to fix the spec or not?
> >>
> >> As I replied in the spec patch, if we just remove this "MUST", it
> >> looks like we are all fine?
> >>
> >> Thanks
> >
> > We should replace MUST with SHOULD but it is not all fine,
> > ignoring SHOULD is a quality of implementation issue.
> >

So is this something that the driver should notice?

>
> Should we really replace it? It would mean that a driver conformant with
> the current specification may not be compatible with a device conformant
> with the future specification.

I don't get this. We are talking about devices and we want to relax so
it should compatibile.

>
> We are going to fix all implementations known to buggy (QEMU and Linux)
> anyway so I think it's just fine to leave that part of specification as is.

I don't think we can fix it all.

Thanks

>