On Mon, May 20, 2024 at 09:42:02AM +0000, Parav Pandit wrote:

Michael,

...

From: Viresh Kumar viresh.kumar@linaro.org Sent: Monday, May 20, 2024 3:00 PM To: virtio-comment@lists.linux.dev; virtio-dev@lists.linux.dev

There is still cross posting to virtio-dev.

Well we say "do not do this" in the list subscription form. Viresh, what gives?

Is the list open to community now?

It's been open for a week. I think it's fair to say whoever wanted to subscribe, has subscribed.

If not, can you please send out the guidance and timeline to open it on virtio-comment list?

This way contributors can avoid resending it multiple times.

...

Cc: Viresh Kumar viresh.kumar@linaro.org; Vincent Guittot vincent.guittot@linaro.org; Alex Bennée alex.bennee@linaro.org; stratos- dev@op-lists.linaro.org; Manos Pitsidianakis manos.pitsidianakis@linaro.org; Cornelia Huck cohuck@redhat.com; Michael S. Tsirkin mst@redhat.com Subject: [PATCH V3 Resend] virtio-transport: Clarify requirements

The virtio documentation currently doesn't define any generic requirements that are applicable to all transports. They can be useful while adding support for a new transport.

This commit tries to define the same.

Reviewed-by: Alex Bennée alex.bennee@linaro.org Signed-off-by: Viresh Kumar viresh.kumar@linaro.org

---

V2->V3:

• Minor fixes.
• Added Reviewed by from Alex.

V1->V2:

• Lot of changes after discussions with Alex and Cornelia.
• Almost a rewrite of the first commit.
• Add Transport normative sections.

commands.tex | 3 +- conformance.tex | 14 +++++++++ content.tex | 78 +++++++++++++++++++++++++++++++++++++++++++++++-- 3 files changed, 92 insertions(+), 3 deletions(-)

diff --git a/commands.tex b/commands.tex index 25ea8ee3bc78..b64b14424bd2 100644 --- a/commands.tex +++ b/commands.tex @@ -7,7 +7,8 @@ % How we format a field name \newcommand{\field}[1]{\emph{#1}}

-% Mark a normative section (driver or device) +% Mark a normative section (driver or device, or transport) +\newcommand{\transportnormative}[3]{#1{Transport Requirements: +#2}\label{transportnormative:#3}} \newcommand{\drivernormative}[3]{#1{Driver Requirements: #2}\label{drivernormative:#3}} \newcommand{\devicenormative}[3]{#1{Device Requirements: #2}\label{devicenormative:#3}} \newcounter{clausecounter} diff --git a/conformance.tex b/conformance.tex index dc00e84e75ae..4a873169ce63 100644 --- a/conformance.tex +++ b/conformance.tex @@ -11,6 +11,10 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}

Conformance targets: \begin{description} +\item[Transport] A transport MUST conform to one conformance clauses:

• \begin{itemize}
• \item Clause \ref{sec:Conformance / Transport Conformance}.
• \end{itemize}

\item[Driver] A driver MUST conform to four conformance clauses: \begin{itemize} \item Clause \ref{sec:Conformance / Driver Conformance}. @@ -66,6 +70,14 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \end{itemize} \end{description}

+\conformance{\section}{Transport Conformance}\label{sec:Conformance / +Transport Conformance}

+A transport MUST conform to the following normative statements:

+\begin{itemize} +\item \ref{transportnormative:Virtio Transport Options / Virtio +Transport Requirements} \end{itemize}

\conformance{\section}{Driver Conformance}\label{sec:Conformance / Driver Conformance}

A driver MUST conform to the following normative statements: @@ -93,6 +105,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \item \ref{drivernormative:Basic Facilities of a Virtio Device / Packed Virtqueues / Supplying Buffers to The Device / Sending Available Buffer Notifications} \item \ref{drivernormative:General Initialization And Device Operation / Device Initialization} \item \ref{drivernormative:General Initialization And Device Operation / Device Cleanup} +\item \ref{drivernormative:Virtio Transport Options / Virtio Transport +Requirements} \item \ref{drivernormative:Reserved Feature Bits} \end{itemize}

@@ -172,6 +185,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets} \item \ref{devicenormative:Basic Facilities of a Virtio Device / Packed Virtqueues / The Virtqueue Descriptor Table} \item \ref{devicenormative:Basic Facilities of a Virtio Device / Packed Virtqueues / Scatter-Gather Support} \item \ref{devicenormative:Basic Facilities of a Virtio Device / Shared Memory Regions} +\item \ref{devicenormative:Virtio Transport Options / Virtio Transport +Requirements} \item \ref{devicenormative:Reserved Feature Bits} \end{itemize}

diff --git a/content.tex b/content.tex index 0a62dce5f65f..a79993b5ed69 100644 --- a/content.tex +++ b/content.tex @@ -631,8 +631,82 @@ \section{Device Cleanup}\label{sec:General Initialization And Device Operation /

\chapter{Virtio Transport Options}\label{sec:Virtio Transport Options}

-Virtio can use various different buses, thus the standard is split -into virtio general and bus-specific sections. +Devices and drivers can use different transport methods to enable +interaction, for example PCI, MMIO, or Channel I/O. The transport +methods define various aspects of the communication between the device +and the driver, like device discovery, exchanging capabilities, +interrupt handling, data transfer, etc. For example, in a host/guest +architecture, the host might expose a device to the guest on a PCI bus, +and the guest will use a PCI-specific driver to interact with it.

+The standard is split into sections describing general virtio +implementation and transport-specific sections.

+\section{Virtio Transport Requirements}\label{sec:Virtio Transport +Options / Virtio Transport Requirements}

+\transportnormative{\subsection}{Virtio Transport Requirements}{Virtio +Transport Options / Virtio Transport Requirements} The transport MUST +provide a mechanism for the driver to discover the device.

+The transport MUST provide a mechanism for the driver to identify the +device type.

+The transport MUST provide a mechanism for communicating virtqueue +configurations between the device and the driver.

+The transport MUST allow multiple virtqueues per device. The number of +virtqueues for a pair of device-driver are governed by the individual +device protocol.

+The transport MUST provide a mechanism that the device and the driver +use to access memory for implementing virtqueues.

+The transport MUST provide a mechanism for the device to notify the +driver and a mechanism for the driver to notify the device, for example +regarding availability of a buffer on the virtqueue.

+The transport MAY provide a mechanism for the driver to initiate a +reset of the virtqueues and device.

+The transport SHOULD provide a mechanism for the driver to read the +device status. The transport MUST provide a mechanism for the driver to +change the device status.

+The transport MUST provide a mechanism to implement config space +between the device and the driver.

+\devicenormative{\subsection}{Virtio Transport Requirements}{Virtio +Transport Options / Virtio Transport Requirements}

+The device MUST keep any data associated with a device-initiated +transaction accessible to the driver until the driver acknowledges the +transaction to be complete.

+The device MUST NOT access the contents of a virtqueue before the +driver notifies, in a transport defined way, the device that the +virtqueue is ready to be accessed.

+The device MUST NOT access or modify buffers on a virtqueue after it +has notified the driver about their availability.

+The device MUST reset the virtqueues if requested by the driver, in a +transport defined way, if the transport provides such a method.

+\drivernormative{\subsection}{Virtio Transport Requirements}{Virtio +Transport Options / Virtio Transport Requirements}

+The driver MUST acknowledge device notifications, as mandated by the +transport.

+The driver MUST NOT access virtqueue contents before the device +notifies about the readiness of the same.

+The driver MUST NOT access buffers, after it has added them to the +virtqueue and notified the device about their availability. The driver +MAY access them after the device has processed them and notified the +driver of their availability, in a transport defined way.

+The driver MAY ask the device to reset the virtqueues if, for example, +the driver times out waiting for a notification from the device for a +previously queued request.

\input{transport-pci.tex} \input{transport-mmio.tex} -- 2.31.1.272.g89b43f80a514