Re: [PATCH v9 05/10] pci: add admin vq registers to virtio over pci

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Nov 24, 2022 at 02:00:54PM +0800, Jason Wang wrote:
> On Thu, Nov 24, 2022 at 5:08 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >
> > Add new registers to the PCI common configuration structure.
> >
> > These registers will be used for querying the indices of the admin
> > virtqueues of the owner device. To configure, reset or enable the admin
> > virtqueues, the driver should follow existing queue configuration/setup
> > sequence.
> >
> > Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >  content.tex | 34 ++++++++++++++++++++++++++++++++++
> >  1 file changed, 34 insertions(+)
> >
> > diff --git a/content.tex b/content.tex
> > index 04235da..aa68926 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 */
> 
> If we are adding more queue related functionality, it would be placed
> under the above two fields which seems not elegant. I wonder if a new
> structure is needed here.
> 
> Thanks

I don't expect more, if that happens we can always refactor it.
Generally this is not C, no one compiles this directly.
So we do not need to add structures unless
they are referred to in spec text.

> >  };
> >  \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.  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
> > @@ -6992,6 +7017,15 @@ \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
> >