Re: [virtio-dev] [PATCH v2 1/1] virtio-ism: introduce new device virtio-ism

[Jason Wang <jasowang@redhat.com>]

On Fri, Jan 13, 2023 at 9:59 AM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>
> On Thu, 12 Jan 2023 16:41:32 +0100, Halil Pasic <pasic@linux.ibm.com> wrote:
> > On Thu, 12 Jan 2023 15:30:58 +0100
> > Cornelia Huck <cohuck@redhat.com> wrote:
> >
> > > >>
> > > >> I like that: we don't want to talk about hosts/VMMs/etc. as we
> > > >> fundamentally deal with devices and drivers, but sharing between guests
> > > >> is of course the obvious use case.
> > > >>
> > > >> I'm just wondering how best to express the uniqueness scope, is it per
> > > >> (ISM) device?
> > > >
> > > > No, each vm has at least one separate device. The devices in a host form
> > > > an uniqueness scope.
> > >
> > > Should we call it a 'group', then? A host would be an example of such a
> > > group.
> >
> > How about 'communication domain'? Devices within a single communication
> > domain may be able to speak to each other via SMC and may not have the
> > same device_id. Two devices from different communication domains can't
> > communicate via ISM, but may have the same device_id.
>
> I agree.
>
> >
> > I don't like group because it is very generic, and may sound like
> > the grouping can be done arbitrarily. E.g. with a shared memory based
> > implementation akin to the PoC putting devices on different hosts into
> > the same 'group' should be illegal.

Any reason why this is illegal?

> >
> > On the other hand there is also the following question. If we move away
> > form the one ID per host model ("The device MUST ensure that the gid on
> > the same entity i same and different from the gid on other entity.") then
> > we could also allow having more than one communication domains on a
> > single host (to limit what entities can use ISM to communicate).

Yes, but I think it might not be necessary to say how gid is actually
implemented, I can think most of the time it should be provisioned by
the the management stack which is probably out of the scope of the
spec.

Thanks

>
> Yes, this is a good idea.
>
> Thanks.
>
> >
> > Regards,
> > Halil
> >
>