Re: [PATCH v8 2/9] admin: introduce device group and related concepts

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Nov 22, 2022 at 01:11:19PM +0100, Cornelia Huck wrote:
> On Sun, Nov 20 2022, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> 
> > Each device group has a type. For now, define one initial group:
> >
> > SR-IOV type - PCI SR-IOV virtual functions (VFs) of a given
> > PCI SR-IOV physical function (PF). This group may contain one or more
> > virtio devices.
> >
> > Each device within a group has a unique identifier. This identifier
> > is the group member identifier.
> >
> > Note: one can argue both ways whether the new device group handling
> > functionality (this and following patches) is closer
> > to a new device type or a new transport type.
> >
> > However, I expect that we will add more features in the near future. To
> > facilitate this as much as possible of the text is located in the new
> > admin chapter.
> >
> > I did my best to minimize transport-specific text.
> >
> > Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  admin.tex   | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  content.tex |  2 ++
> >  2 files changed, 52 insertions(+)
> >  create mode 100644 admin.tex
> >
> > diff --git a/admin.tex b/admin.tex
> > new file mode 100644
> > index 0000000..4337db0
> > --- /dev/null
> > +++ b/admin.tex
> > @@ -0,0 +1,50 @@
> > +\section{Device groups}\label{sec:Basic Facilities of a Virtio Device / Device groups}
> > +
> > +It is occasionally useful to have a device control a group of
> > +other devices. Terminology used in such cases:
> > +
> > +\begin{description}
> > +\item[Device group]
> > +        or just group, includes zero or more devices.
> > +\item[Owner device]
> > +        or owner, the device controlling the group.
> > +\item[Member device]
> > +        a device within a group. Owner device itself is not
> 
> s/Owner/The owner/
> 
> > +	a member of the group. In the future it is envisoned that
> > +	new group types may be introduced where the owner
> > +	device is a member of the group.
> 
> So, shouldn't it rather be: "Whether the owner device itself is a member
> of the group depends on the type of the group." ?
> Or do we want to
> prefer the owner _not_ being a member of the group?

Maybe I will drop this "In the future" thing. We'll cross that bridge
when we get to it.

> > +\item[Member identifier]
> > +        each member has this identifier, unique within the group
> > +	and used to address it through the owner device.
> > +\item[Group type identifier]
> > +	specifies what kind of member devices there are in a
> > +	group, how is the member identifier interpreted
> 
> "how the member indentifier is interpreted, ..."
> 
> > +	and what kind of control does the owner have.
> 
> s/does the owner have/the owner has/
> 
> > +	At the moment, a given owner can control
> > +	a single group of a given type, thus the type and
> > +	the owner together identify the group.
> > +	It is envisioned that this last restriction might be relaxed in the future,
> > +	with multiple groups of the same type for a given owner.
> 
> Hm...
> 
> "A given owner may control a single group of a given type (which means
> that the type and the owner together identify the group), or multiple
> groups of the same type. Currently, only a single group per owner is
> supported." ?
> 
> Basically, I'd prefer if we spelled out what is possible in general, and
> then add a comment that only a subset of the possibilities is currently
> implemented.

I feel I went too broad here. Let's just drop the "It is envisioned"
for now.


> > +\end{description}
> > +
> > +A single group type is currently specified:
> 
> "The following group types are currently specified:" ?
> 
> Less editing once we add a second one :)
> 
> > +\begin{description}
> > +\item[SR-IOV group type]
> 
> Maybe \item[SR-IOV group type (1)] ? It's nice to have the identifier in
> the title already (like we do for features.)
> 
> > +This device group has a PCI Single Root I/O Virtualization
> > +(SR-IOV) physical function (PF) device as the owner and includes
> > +all its SR-IOV virtual functions (VFs) as members (see
> > +\hyperref[intro:PCIe]{[PCIe]}).
> > +
> > +The PF device itself is not a member of the group.
> > +
> > +The group type identifier for this group is 0x1.
> > +
> > +A member identifier for this group can have a value 0x1 to 0xFFFF
> > +and equals the SR-IOV VF number of the member device (see
> > +\hyperref[intro:PCIe]{[PCIe]}).
> > +
> > +Both owner and member devices for this group type use the Virtio
> > +PCI transport (see \ref{sec:Virtio Transport Options / Virtio Over PCI Bus}).
> > +\end{description}


Others look good to me, will use, thanks!

-- 
MST