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Subject: Re: [virtio-dev] Re: [PATCH v9 02/10] admin: introduce device group and related concepts
On Thu, Nov 24, 2022 at 03:37:42PM +0800, Jason Wang wrote: > On Thu, Nov 24, 2022 at 3:08 PM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > 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? > > Because it is transport specific. The basic facility should be > transport independent. I tried this but the result is spread all over the spec and does not result in a readable cohesive whole. So we give up on the transport independent purity a bit and it seems worth it. Also explained this in the cover letter - have you seen that? > > And I think we might find a use for this with MMIO > > down the road with some kind of passthrough. Who knows. > > Probably, but can it be modeled exactly as what SR-IOV looks like? Or > anyhow, it's not too late to define this for MMIO at that time. For > example, we know MSI-X may work for MMIO but we define it only for PCI > now. > > Thanks Right. So if we reserve the id for all transports then it will be easy to do. > > > > > > > > > > + > > > > +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 > > > > > > > > > > --------------------------------------------------------------------- > > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org > >
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