On Thu, Nov 24, 2022 at 03:46:00PM +0800, Jason Wang wrote:
> On Thu, Nov 24, 2022 at 3:14 PM Michael S. Tsirkin <[email protected]> wrote:
> >
> > 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 <[email protected]>
> > > 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 <[email protected]>
> > > > Signed-off-by: Michael S. Tsirkin <[email protected]>
> > > > ---
> > > > 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.
>
> I may miss something but it should be a part of ABI. How could we
> refactor it without breaking ABI?
>
> Thanks
/* About the administration virtqueue. */
- le16 admin_queue_index; /* read-only for driver */
- le16 admin_queue_num; /* read-only for driver */
+ struct { /* read-only for driver */
+ le16 index;
+ le16 num;
+ } admin_queue;
does not affect the ABI. But the order of things makes it less readable.
We would also have to change references to admin_queue_index with
admin_queue.index and explain the "." notation in introduction.
All doable but this patchset is large enough as it is.
> > 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
> > > >
> >
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