On Mon, Apr 04, 2022 at 06:49:19PM +0300, Max Gurtovoy wrote:
>
> On 4/4/2022 4:02 PM, Michael S. Tsirkin wrote:
> > On Wed, Mar 02, 2022 at 05:56:07PM +0200, Max Gurtovoy wrote:
> > > In one of the many use cases a user wants to manipulate features and
> > > configuration of the virtio devices regardless of the device type
> > > (net/block/console). Some of this configuration is generic enough. i.e
> > > Number of MSI-X vectors of a virtio PCI VF device. There is a need to do
> > > such features query and manipulation by its parent PCI PF. For that the
> > > Admin Command Set introduced. The Admin virtqueue will be the first
> > > management interface to issue Admin commands.
> > >
> > > Currently virtio specification defines control virtqueue to manipulate
> > > features and configuration of the device it operates on. However,
> > > control virtqueue commands are device type specific, which makes it very
> > > difficult to extend for device agnostic commands.
> > >
> > > To support this requirement in elegant way, this patch introduces a new
> > > admin virtqueue interface.
> > >
> > > Manipulate features via admin virtqueue is asynchronous, scalable, easy
> > > to extend and doesn't require additional and expensive on-die resources
> > > to be allocated for every new feature that will be added in the future.
> > >
> > > Reviewed-by: Parav Pandit <[email protected]>
> > > Signed-off-by: Max Gurtovoy <[email protected]>
> > > ---
> > > admin.tex | 17 +++++++++++++++++
> > > conformance.tex | 1 +
> > > content.tex | 6 ++++--
> > > 3 files changed, 22 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/admin.tex b/admin.tex
> > > index 9a8969b..ed9f6bd 100644
> > > --- a/admin.tex
> > > +++ b/admin.tex
> > > @@ -158,3 +158,20 @@ \subsection{VIRTIO ADMIN DEVICE INFO
> > > command}\label{sec:Basic Facilities of a Vi
> > > specification and can't be equal to zero. If bit 0 is not set, the
> > > driver will ignore \field{vf_number}.}
> > > \end{note}
> > > +\section{Admin Virtqueues}\label{sec:Basic Facilities of a Virtio Device
> > > / Admin Virtqueues}
> > > +
> > > +An admin virtqueue is a management interface of a device that can be
> > > used to send administrative
> > > +commands to manipulate various features of the device and/or to
> > > manipulate
> > > +various features, if possible, of another device within the same virtio
> > > subsystem
> > > +(see \ref{sec:Introduction / Definitions / virtio subsystem}).
> > > +
> > > +An admin virtqueue exists for a certain device if VIRTIO_F_ADMIN_VQ is
> > > +negotiated. The index of the admin virtqueue is exposed by the device in
> > > a
> > > +transport specific manner.
> > > +
> > > +If VIRTIO_F_ADMIN_VQ has been negotiated, the driver will use the admin
> > > virtqueue to send all admin commands.
> > > +
> > Add links please, and explain how do commands map to VQ buffers.
>
> I added a link to the definitions section and I'll replace it with the new
> proposed terminology chapter.
That explains what a subsystem is.
> What other links should be added ?
A link to where it's explained how do admin commands look.
> > E.g. I guess device readable an output buffer and device writeable an input
> > buffer...
>
> The buffers transfer from/to device/driver are using existing mechanism.
> Nothing new here.
>
> It will just repeat existing chapters.
There could be some repetition but it's necessary to make things
explicit. Look at e.g.
subsection{Device Operation}\label{sec:Device Types / Block Device / Device
Operation}
as a lightweight example for how to explain it.
> >
> > > +\devicenormative{\subsection}{Admin Virtqueues}{Basic Facilities of a
> > > Virtio Device / Admin Virtqueues}
> > > +A device that advertises VIRTIO_F_ADMIN_VQ capability MUST support all
> > > the mandatory admin commands.
> > > +
> > > +A device that advertises VIRTIO_F_ADMIN_VQ capability MAY support one or
> > > more optional admin commands.
> > > diff --git a/conformance.tex b/conformance.tex
> > > index 42f8537..129831c 100644
> > > --- a/conformance.tex
> > > +++ b/conformance.tex
> > > @@ -341,6 +341,7 @@ \section{Conformance Targets}\label{sec:Conformance /
> > > Conformance Targets}
> > > \item \ref{devicenormative:Basic Facilities of a Virtio Device /
> > > Virtqueues / Available Buffer Notification Suppression}
> > > \item \ref{devicenormative:Basic Facilities of a Virtio Device / Shared
> > > Memory Regions}
> > > \item \ref{devicenormative:Reserved Feature Bits}
> > > +\item \ref{devicenormative:Basic Facilities of a Virtio Device / Admin
> > > Virtqueues}
> > > \end{itemize}
> > > \conformance{\subsection}{PCI Device Conformance}\label{sec:Conformance
> > > / Device Conformance / PCI Device Conformance}
> > > diff --git a/content.tex b/content.tex
> > > index 2e1df84..163cb34 100644
> > > --- a/content.tex
> > > +++ b/content.tex
> > > @@ -99,10 +99,10 @@ \section{Feature Bits}\label{sec:Basic Facilities of
> > > a Virtio Device / Feature B
> > > \begin{description}
> > > \item[0 to 23, and 50 to 127] Feature bits for the specific device type
> > > -\item[24 to 40] Feature bits reserved for extensions to the queue and
> > > +\item[24 to 41] Feature bits reserved for extensions to the queue and
> > > feature negotiation mechanisms
> > > -\item[41 to 49, and 128 and above] Feature bits reserved for future
> > > extensions.
> > > +\item[42 to 49, and 128 and above] Feature bits reserved for future
> > > extensions.
> > > \end{description}
> > > \begin{note}
> > > @@ -6849,6 +6849,8 @@ \chapter{Reserved Feature Bits}\label{sec:Reserved
> > > Feature Bits}
> > > that the driver can reset a queue individually.
> > > See \ref{sec:Basic Facilities of a Virtio Device / Virtqueues /
> > > Virtqueue Reset}.
> > > + \item[VIRTIO_F_ADMIN_VQ (41)] This feature indicates that an
> > > administration virtqueue is supported.
> > > +
> > > \end{description}
> > > \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits}
> > > --
> > > 2.21.0
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