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

[Halil Pasic <pasic@linux.ibm.com>]

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 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.

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).

Regards,
Halil