[PATCH v5 5/7] Add miscellaneous configuration structure for PCI

[Max Gurtovoy <mgurtovoy@nvidia.com>]

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     | 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.
+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 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