Re: [PATCH v6 3/5] Introduce virtio admin virtqueue

[Max Gurtovoy <mgurtovoy@nvidia.com>]

On 8/1/2022 12:00 AM, Michael S. Tsirkin wrote:
> On Sun, Jul 31, 2022 at 06:43:52PM +0300, 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). 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 <parav@nvidia.com>
> > Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
> > ---
> >   admin.tex   | 12 ++++++++++++
> >   content.tex |  6 ++++--
> >   2 files changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/admin.tex b/admin.tex
> > index d14f8f7..26ac60e 100644
> > --- a/admin.tex
> > +++ b/admin.tex
> > @@ -80,3 +80,15 @@ \section{Administration command set}\label{sec:Basic Facilities of a Virtio Devi
> >   8000h - FFFFh   & Reserved    \\
> >   \hline
> >   \end{tabular}
> > +
> > +\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 (see \ref{sec:Basic Facilities of a Virtio Device / Administration command set}) to manipulate
> > +various features of the device and/or to manipulate various features, if possible, of another device.
> > +
> > +An admin virtqueue exists for a certain device if VIRTIO_F_ADMIN_VQ feature 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.
> > diff --git a/content.tex b/content.tex
> > index caab298..c15423e 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}
> > @@ -6841,6 +6841,8 @@ \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.
> mention here that index is in transport specific manner too?

is this ok ?

+Â \item[VIRTIO_F_ADMIN_VQ (41)] This feature indicates that an 
administration virtqueue is supported.
+Â The index of the administration virtqueue exposed in a transport 
specific manner.


> > +
> >   \end{description}
> >   
> >   \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits}
> > --
> > 2.21.0