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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>
> ---
> 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.
not very clear what is within what.
Simplify the sentence:
The VIRTIO_PCI_CAP_MISC_CFG specifies the location of The miscellaneous
configuration structure.
> +Its layout is below.
who's layout? and try to avoid using "below".
better:
The miscellaneous configuration structure has the following layout
> +\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.
> +
set meaning "offered"?
> +\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.
"set" is vague. do you mean "negotiated"?
also then let's mandate not negotiating VIRTIO_F_ADMIN_VQ.
also if you are addressing this, address the reverse case
what to do without VIRTIO_F_ADMIN_VQ but with the capability.
> +
> +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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