Re: [virtio-comment] [PATCH v10 05/10] pci: add admin vq registers to virtio over pci

[Max Gurtovoy <mgurtovoy@nvidia.com>]

On 13/02/2023 14:21, David Edmondson wrote:
> On Thursday, 2023-02-09 at 07:13:48 -05, Michael S. Tsirkin wrote:
> > @@ -1031,6 +1035,19 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
> >           This field exists only if VIRTIO_F_RING_RESET has been
> >           negotiated. (see \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset}).
> >   
> > +\item[\field{admin_queue_index}]
> > +        The device uses this to report the index of the first administration virtqueue.
> > +        This field is valid only if VIRTIO_F_ADMIN_VQ has been negotiated.
> > +\item[\field{admin_queue_num}]
> > +	The device uses this to report the number of the
> > +	supported administration virtqueues.  Virtqueues with index
> > +	between \field{admin_queue_index} and (\field{admin_queue_index} +
> > +	\field{admin_queue_num}) inclusive serve as administration
> > +	virtqueues.
> > +	Thus the number of administration virtqueues equals
> > +	(\field{admin_queue_num} + 1).
>
> Really the number of queues is "admin_queue_num + 1"?
>
> That seems ... odd.

It's not odd if we'll mention that this is a zero based value.
MST, can you add it please for the next version ?


> > +	This field is valid only if VIRTIO_F_ADMIN_VQ has been
> > +	negotiated.
> >   \end{description}
> >   
> >   \devicenormative{\paragraph}{Common configuration structure layout}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Common configuration structure layout}
> > @@ -1117,6 +1134,14 @@ \subsubsection{Common configuration structure layout}\label{sec:Virtio Transport
> >   were used before the queue reset.
> >   (see \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset}).
> >   
> > +If VIRTIO_F_ADMIN_VQ has been negotiated, and if the driver
> > +configures any administration virtqueues, the driver MUST
> > +configure the administration virtqueues using the index
> > +in the range \field{admin_queue_index} to
> > +\field{admin_queue_index} + \field{admin_queue_num} inclusive.
> > +The driver MAY configure less administration virtqueues than
> > +supported by the device.
> > +
> >   \subsubsection{Notification structure layout}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Notification capability}
> >   
> >   The notification location is found using the VIRTIO_PCI_CAP_NOTIFY_CFG
> > @@ -7684,6 +7709,15 @@ \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits}
> >   
> >     \item[VIRTIO_F_ADMIN_VQ(41)] This feature indicates that the device exposes one or more
> >     administration virtqueues.
> > +  At the moment this feature is only supported for devices using
> > +  \ref{sec:Virtio Transport Options / Virtio Over PCI
> > +	  Bus}~\nameref{sec:Virtio Transport Options / Virtio Over PCI Bus}
> > +	  as the transport and is reserved for future use for
> > +	  devices using other transports (see
> > +	  \ref{drivernormative:Basic Facilities of a Virtio Device / Feature Bits}
> > +	and
> > +	\ref{devicenormative:Basic Facilities of a Virtio Device / Feature Bits} for
> > +	handling features reserved for future use.
> >   
> >   \end{description}