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

[Cornelia Huck <cohuck@redhat.com>]

On Thu, Jan 12 2023, 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 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.

Yes, 'communication domain' sounds better.

>
> 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).

Makes sense, I guess. But I haven't looked too much into the details of
ism yet.


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