Re: [PATCH v1 5/5] Add miscellaneous configuration structure for PCI

[Max Gurtovoy <mgurtovoy@nvidia.com>]

On 4/4/2022 4:04 PM, Michael S. Tsirkin wrote:
> On Wed, Mar 02, 2022 at 05:56:08PM +0200, Max Gurtovoy wrote:
> > This new structure will be used for adding new miscellaneous registers
> > for a virtio device configuration layout.
> >
> > For now, only admin_queue_index register is added. Admin virtqueue index
> > does not depend on the device type. Hence, add a PCI capability to read
> > the admin virtqueue index.
> >
> > Reviewed-by: Parav Pandit <parav@nvidia.com>
> > Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
> > ---
> >   conformance.tex |  2 ++
> >   content.tex     | 25 +++++++++++++++++++++++++
> >   2 files changed, 27 insertions(+)
> >
> > diff --git a/conformance.tex b/conformance.tex
> > index 129831c..e31645e 100644
> > --- a/conformance.tex
> > +++ b/conformance.tex
> > @@ -102,6 +102,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
> >   \item \ref{drivernormative:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / PCI configuration access capability}
> >   \item \ref{drivernormative:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / MSI-X Vector Configuration}
> >   \item \ref{drivernormative:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Notification of Device Configuration Changes}
> > +\item \ref{drivernormative:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Miscellaneous configuration structure layout}
> >   \end{itemize}
> >   
> >   \conformance{\subsection}{MMIO Driver Conformance}\label{sec:Conformance / Driver Conformance / MMIO Driver Conformance}
> > @@ -363,6 +364,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
> >   \item \ref{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / MSI-X Vector Configuration}
> >   \item \ref{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Used Buffer Notifications}
> >   \item \ref{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Notification of Device Configuration Changes}
> > +\item \ref{devicenormative:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Miscellaneous configuration structure layout}
> >   \end{itemize}
> >   
> >   \conformance{\subsection}{MMIO Device Conformance}\label{sec:Conformance / Device Conformance / MMIO Device Conformance}
> > diff --git a/content.tex b/content.tex
> > index 163cb34..bf46192 100644
> > --- a/content.tex
> > +++ b/content.tex
> > @@ -712,6 +712,7 @@ \subsection{Virtio Structure PCI Capabilities}\label{sec:Virtio Transport Option
> >   \item ISR Status
> >   \item Device-specific configuration (optional)
> >   \item PCI configuration access
> > +\item Miscellaneous configuration
> >   \end{itemize}
> >   
> >   Each structure can be mapped by a Base Address register (BAR) belonging to
> > @@ -771,6 +772,8 @@ \subsection{Virtio Structure PCI Capabilities}\label{sec:Virtio Transport Option
> >   #define VIRTIO_PCI_CAP_SHARED_MEMORY_CFG 8
> >   /* Vendor-specific data */
> >   #define VIRTIO_PCI_CAP_VENDOR_CFG        9
> > +/* Miscellaneous configuration */
> > +#define VIRTIO_PCI_CAP_MISC_CFG          10
> >   \end{lstlisting}
> >   
> >           Any other value is reserved for future use.
> > @@ -1352,6 +1355,28 @@ \subsubsection{PCI configuration access capability}\label{sec:Virtio Transport O
> >   specified by some other Virtio Structure PCI Capability
> >   of type other than \field{VIRTIO_PCI_CAP_PCI_CFG}.
> >   
> > +\subsubsection{Miscellaneous configuration structure layout}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Miscellaneous configuration structure layout}
> > +
> > +The miscellaneous configuration structure is found at the bar and offset within the VIRTIO_PCI_CAP_MISC_CFG capability.
> > +Its layout is below.
> > +\begin{lstlisting}
> > +struct virtio_pci_misc_cfg {
> > +        le16 admin_queue_index;         /* read-only for driver */
> > +};
> > +\end{lstlisting}
> > +
> > +\begin{description}
> > +\item[\field{admin_queue_index}]
> > +        The device uses this to report the index of the admin virtqueue.
> > +        This field is valid only if VIRTIO_F_ADMIN_VQ is set.
> > +\end{description}
> > +
> > +\devicenormative{\paragraph}{Miscellaneous configuration structure layout}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Miscellaneous configuration structure layout}
> > +The device MUST present a valid \field{admin_queue_index} when VIRTIO_F_ADMIN_VQ is set.
> > +
> > +\drivernormative{\paragraph}{Miscellaneous configuration structure layout}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Miscellaneous configuration structure layout}
> > +The driver MUST use the value of \field{admin_queue_index} to configure the admin virtqueue. For more details on virtqueue configuration see section \ref{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI-specific Initialization And Device Operation / Device Initialization / Virtqueue Configuration}.
> > +
> >   \subsubsection{Legacy Interfaces: A Note on PCI Device Layout}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Legacy Interfaces: A Note on PCI Device Layout}
> >   
> >   Transitional devices MUST present part of configuration
> This is useful, but I think we'll want this for all transports then.

I think that adding more transports can be incremental and should be a 
no-go for merging this patch set.

We discussed this in the previous version and nobody had a conclusion on 
the right approach for other transports.

> > --
> > 2.21.0