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