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Subject: Re: [PATCH v9 02/10] admin: introduce device group and related concepts
On Thu, Nov 24, 2022 at 01:41:41PM +0800, Jason Wang wrote: > On Thu, Nov 24, 2022 at 5:08 AM 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 | 45 +++++++++++++++++++++++++++++++++++++++++++++ > > content.tex | 2 ++ > > 2 files changed, 47 insertions(+) > > create mode 100644 admin.tex > > > > diff --git a/admin.tex b/admin.tex > > new file mode 100644 > > index 0000000..6ebdd05 > > --- /dev/null > > +++ b/admin.tex > > @@ -0,0 +1,45 @@ > > +\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. > > +\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]}). > > So I wonder what's the advantage of using a global identifier over the > transport specific one. There's almost no way for CCW/MMIO to use > SR-IOV. Limiting it to PCI seems much easier and avoids layer > violation. > > Thanks So we burn up an identifier, ccw and mmio won't be able to use it. Big deal? Why? And I think we might find a use for this with MMIO down the road with some kind of passthrough. Who knows. > > + > > +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 e3203be..3f3585d 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 > > -- > > MST > >
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