RE: [PATCH v3 1/4] Add virtio Admin virtqueue

[Parav Pandit <parav@nvidia.com>]

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Tuesday, February 8, 2022 8:56 PM

> > I might have been a bit too vague about what I had been thinking
> > about. Let's do a sketch (intentionally without concrete sizes):
> >
> > +-------------------------------------------------------+
> > | command                                               |
> > +-------------------------------------------------------+
> > | target type (0 - self, 1 - dev id, 2 - group id, ...  |
> > +-------------------------------------------------------+
> > | dev id                                                |
> > +-------------------------------------------------------+
> > | group id                                              |
> > +-------------------------------------------------------+
> > | command-specific data                                 |
> > +-------------------------------------------------------+
> > | response part                                         |
> > +-------------------------------------------------------+
> >
> > 'dev id' would be valid for 'target type' == 1, 'group id' would be
> > valid for 'target type' == 2. Alternatively, 'dev id' and 'group id'
> > could be a single 'target id' field; if there's nothing better to use,
> > it can simply contain a uuid.
> 
> I am not sure why do we have both dev id and group id.
> They are never used together right?
> Maybe just have an id length field if we can't agree on how much space to
> reserve.
This is what I propose in a previous email.
A device id can be duplicate in different groups.
So to build hierarchy group id will be desired.

So id[] array can contain nested one or multiple fields.