Re: [PATCH RFC v7 4/8] Add admin_queue_index register to PCI common configuration structure

[Jason Wang <jasowang@redhat.com>]

On Thu, Aug 18, 2022 at 4:55 PM Max Gurtovoy <mgurtovoy@nvidia.com> wrote:
>
>
> On 8/18/2022 11:49 AM, Jason Wang wrote:
> > On Sat, Aug 13, 2022 at 1:19 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >> From: Max Gurtovoy <mgurtovoy@nvidia.com>
> >>
> >> This new register will be used for querying the index of the admin
> >> virtqueue of a virtio device. To configure, reset or enable the admin
> >> virtqueue, 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 | 14 ++++++++++++++
> >>   1 file changed, 14 insertions(+)
> >>
> >> diff --git a/content.tex b/content.tex
> >> index 6ce1c07..297cb4a 100644
> >> --- a/content.tex
> >> +++ b/content.tex
> >> @@ -904,6 +904,9 @@ \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 */
> > Is there a chance that we may have multiple admin virtqueues?
>
> No, same as we probably can't have multiple ctrl virtqueues..

For control virtqueue, it's technically possible but doesn't have too
much value.

But for admin virtqueue we can:

admin vq 1: group 1
admin vq 2: group 2

?

Thanks

>
>
> >
> > Thanks
> >
> >
> >>   };
> >>   \end{lstlisting}
> >>
> >> @@ -989,6 +992,10 @@ \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 administration virtqueue.
> >> +        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}
> >> @@ -1075,6 +1082,9 @@ \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, the driver MUST
> >> +configure the administration virtqueue using the value of \field{admin_queue_index}.
> >> +
> >>   \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
> >> @@ -6947,6 +6957,10 @@ \chapter{Reserved Feature Bits}\label{sec:Reserved Feature Bits}
> >>     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.
> >> +  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.
> >>
> >>   \end{description}
> >>
> >> --
> >> MST
> >>
>