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

[Parav Pandit <parav@nvidia.com>]

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Thursday, February 9, 2023 7:14 AM

> diff --git a/content.tex b/content.tex
> index c8647c9..2d9b903 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -946,6 +946,10 @@ \subsubsection{Common configuration structure
> layout}\label{sec:Virtio Transport
>          le64 queue_device;              /* read-write */
>          le16 queue_notify_data;         /* read-only for driver */
>          le16 queue_reset;               /* read-write */
> +
> +        /* About the administration virtqueue. */
> +        le16 admin_queue_index;         /* read-only for driver */
> +        le16 admin_queue_num;         /* read-only for driver */
>  };
>  \end{lstlisting}
> 
> @@ -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.  
admin_queue_count reads more intuitive to me to indicate how many aqs.
It may be even simpler to have start and end vq numbers rather than complication of index + inclusive sum of number.

> 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).
> +	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}
> 
> --
> MST
Reviewed-by: Parav Pandit <parav@nvidia.com>