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

[David Edmondson <david.edmondson@oracle.com>]

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.

> +	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}
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