virtio — archive

[Stefan Hajnoczi <mgurtovoy@nvidia.com>]

On Thu, Mar 02, 2023 at 08:05:10AM -0500, Michael S. Tsirkin 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 | 35 +++++++++++++++++++++++++++++++++++ > 1 file changed, 35 insertions(+) > > diff --git a/content.tex b/content.tex > index c8647c9..1076125 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 +1035,20 @@ \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. > + This is a zero based value. 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). Why is this value zero-based? virtio_pci_common_cfg's num_queues field is le16 and not zero-based. It is not possible to have admin_queue_index=0 admin_queue_num=0xffff because num_queues=0x10000 cannot be represented. I suggest making this field behave the same as virtio_pci_common_cfg's num_queues. > + 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 +1135,14 @@ \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 s/less/fewer/ > +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 +7710,15 @@ \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 >