[virtio-dev] Re: [PATCH v11 02/10] admin: introduce device group and related concepts

Parav Pandit
2023-04-06T03:42:39Z

On 4/3/2023 11:03 AM, Michael S. Tsirkin wrote:
> Each device group has a type. For now, define one initial group type:
>
> SR-IOV type - PCI SR-IOV virtual functions (VFs) of a given
> PCI SR-IOV physical function (PF). This group may contain zero or more
> virtio devices according to NumVFs configured.
>
> 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.
>
From this point onward you can add,
--- line. So that it doesnt go to the commit log.

> 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.
>
> There's a bit of duplication with 0x1 repeated twice and
> no special section for group type identifiers.
> I think it's ok to defer adding these until we have more group
> types.
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
> changes in v11:
> dropped Max's S.O.B.
> dropped an unmatched ) as reported by Parav
> document that member id is 1 to numvfs
> document that vf enable must be set (will also be reflected in
> the conformance section)
> document that we deferred generalizing text as requested by Parav -
> I think we can do it later
> minor wording fixes to address comments by David
> add concepts of owner and member driver. unused currently
> but will come in handy later, as suggested by Stefan
> ---
> admin.tex | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++
> content.tex | 2 ++
> 2 files changed, 65 insertions(+)
> create mode 100644 admin.tex
>
> diff --git a/admin.tex b/admin.tex
> new file mode 100644
> index 0000000..04d5498
> --- /dev/null
> +++ b/admin.tex
> @@ -0,0 +1,63 @@
> +\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:
> +
Only one case so, singular "such case:".

> +\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
is a device within a group.
So that the sentence completes like above two items.

> + 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.
to form the complete sentence like rest of the items writing it as below:

uniquely identifies a member within a group and is used to address it
through the owner device.

> +\item[Group type identifier]
> + specifies what kind of member devices there are in a
> + group, how the member identifier is interpreted
> + and what kind of control the owner has.
> + A given owner can control multiple groups
> + of different types but only 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.}
As as spec, better to avoid "we .."
How about,
too many new group types are not expected.?
> +\end{description}
> +
> +\begin{note}
> +Each device only has a single driver, thus for the purposes of
> +this section, "the driver" is usually unambiguous and refers to
> +the driver of the owner device. When there's ambiguity, "owner
> +driver" refers to the driver of the owner device, while "member
> +driver" refers to the driver of a member device.
> +\end{note}
> +
> +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 from 0x1 to
> +\field{NumVFs} as specified in the
> +SR-IOV Extended Capability of the owner device
> +and equals the SR-IOV VF number of the member device;
> +the group only exists when the \field{VF Enable} bit
> +in the SR-IOV Control Register within the
> +SR-IOV Extended Capability of the owner device is set
> +(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 8098988..04592fb 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -493,6 +493,8 @@ \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

Apart from above rewording,

Reviewed-by: Parav Pandit <parav@nvidia.com>