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Subject: Re: [PATCH v5 5/7] Add miscellaneous configuration structure for PCI
On Wed, Apr 27, 2022 at 01:58:22AM +0300, 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> I guess we discussed this but I forgot. Why do we have this new structure as opposed to just adding the value at the end of config structure? I was kind of hoping that the structure can be reused for CCW/MMIO and then we can add more use-cases with new transport and device independent structures. If we keep it transport specific I don't really understand why is it useful ... > --- > conformance.tex | 2 ++ > content.tex | 29 +++++++++++++++++++++++++++++ > 2 files changed, 31 insertions(+) > > diff --git a/conformance.tex b/conformance.tex > index 3c7b7bc..c183581 100644 > --- a/conformance.tex > +++ b/conformance.tex > @@ -103,6 +103,7 @@ \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} > @@ -364,6 +365,7 @@ \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..0c1d44f 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 +1355,32 @@ \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. If this is all there is going to be there, maybe just stick the value in the capability directly. > +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} > + we need to explain that we will add more fields and drivers must not make assumptions that this structure is 2 bytes in size. look for a language like this in device specific and common structures. > +\devicenormative{\paragraph}{Miscellaneous configuration structure layout}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Layout / Miscellaneous configuration structure layout} > +The device MUST present VIRTIO_PCI_CAP_MISC_CFG capability when VIRTIO_F_ADMIN_VQ is set. > + > +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 NOT proceed with configuring the admin virtqueue in case VIRTIO_F_ADMIN_VQ is set and VIRTIO_PCI_CAP_MISC_CFG capability is not present. > + > +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 > -- > 2.21.0
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