Re: [virtio-comment] [PATCH v10 02/10] admin: introduce device group and related concepts

[David Edmondson <david.edmondson@oracle.com>]

On Thursday, 2023-02-09 at 10:13:46 -05, Michael S. Tsirkin wrote:
> On Thu, Feb 09, 2023 at 03:00:58PM +0000, David Edmondson wrote:
>> 
>> On Thursday, 2023-02-09 at 07:13:36 -05, Michael S. Tsirkin 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.
>> 
>> The specification says zero or more generally and nothing to refine that
>> for SR-IOV groups.
>
> Well it says:
>
> 	(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]}).
>
> how can that be zero?

If I remove all of the VFs of a PF, does the group implicitly disappear?
How about the converse?

>
>> >
>> > 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   | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
>> >  content.tex |  2 ++
>> >  2 files changed, 51 insertions(+)
>> >  create mode 100644 admin.tex
>> >
>> > diff --git a/admin.tex b/admin.tex
>> > new file mode 100644
>> > index 0000000..2bc7322
>> > --- /dev/null
>> > +++ b/admin.tex
>> > @@ -0,0 +1,49 @@
>> > +\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. The owner device itself is not
>> > +	a member of the group.
>> > +\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 is interpreted
>> > +	and what kind of control the owner has.
>> > +	A given owner can control a single group of a given type,
>> > +	thus the type and the owner together identify the group.
>> > +	\footnote{Even though some group types only support
>> > +			specific transports, group type identifiers
>> > +			are global rather than transport-specific -
>> > +			we don't expect a flood of new group types.}
>> > +\end{description}
>> > +
>> > +The following group types, and their identifiers, are currently specified):
>> > +\begin{description}
>> > +\item[SR-IOV group type (0x1)]
>> > +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}
>> > +
>> > +
>> > diff --git a/content.tex b/content.tex
>> > index 0c2d917..ffe45c4 100644
>> > --- a/content.tex
>> > +++ b/content.tex
>> > @@ -491,6 +491,8 @@ \section{Exporting Objects}\label{sec:Basic Facilities of a Virtio Device / Expo
>> >  types. It is RECOMMENDED that devices generate version 4
>> >  UUIDs as specified by \hyperref[intro:rfc4122]{[RFC4122]}.
>> >  
>> > +\input{admin.tex}
>> > +
>> >  \chapter{General Initialization And Device Operation}\label{sec:General Initialization And Device Operation}
>> >  
>> >  We start with an overview of device initialization, then expand on the
>> -- 
>> Tell her I'll be waiting, in the usual place.
-- 
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