On 29-05-24, 12:42, Stefano Garzarella wrote:
> mmm, I had interpreted this statement as if we could:
>
> The transport MAY provide a mechanism for the driver to initiate a
> reset of the virtqueues and device.
>
> IIUC device reset is always supported (see `\section{Device Reset}` in
> content.txt) and it's transport specific. While single virtqueue reset
> depends on VIRTIO_F_RING_RESET.
Done, thanks.
--
viresh
On 29-05-24, 13:12, Matias Ezequiel Vara Larsen wrote:
> > +The driver doesn't 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.
> > +
>
> I think last sentence could be rewritten as:
> - The driver accesses queued buffers after the device has processed them
> and notified the driver of their availability. This mechanism is
> transport defined.
>
>
> > +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.
> >
>
> I would rewrite last sentence as:
> - The driver asks 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.
>
>
> With that, LGTM!
Done. Thanks.
--
viresh
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(a)linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar(a)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
Dropped virtio-dev list.
On 20-05-24, 12:20, Stefano Garzarella wrote:
> I haven't followed v1 and v2, so apologies in advance if my comments have
> already been discussed.
No issues.
> On Mon, May 20, 2024 at 02:59:40PM GMT, Viresh Kumar wrote:
> > +\transportnormative{\subsection}{Virtio Transport Requirements}{Virtio Transport Options / Virtio Transport Requirements}
> > +The transport MUST provide a mechanism for the driver to discover the
> > +device.
>
> This seems a little too stringent. For example, does MMIO offer a discovery
> mechanism? IIRC we have to pass the address via device tree or kernel
> command line.
Right. Is converting this to SHOULD okay or do you suggest some other
change ?
> > +The transport MUST provide a mechanism to implement config space
>
> "configuration space"
Sure.
> > 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
>
> Should we also talk about the possibility of resetting the entire device?
Do we support that today ? Maybe we can if the maintainers agree.
--
viresh
On Mon, May 20, 2024 at 09:42:02AM +0000, Parav Pandit wrote:
> Michael,
>
> > From: Viresh Kumar <viresh.kumar(a)linaro.org>
> > Sent: Monday, May 20, 2024 3:00 PM
> > To: virtio-comment(a)lists.linux.dev; virtio-dev(a)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(a)linaro.org>; Vincent Guittot
> > <vincent.guittot(a)linaro.org>; Alex Bennée <alex.bennee(a)linaro.org>; stratos-
> > dev(a)op-lists.linaro.org; Manos Pitsidianakis
> > <manos.pitsidianakis(a)linaro.org>; Cornelia Huck <cohuck(a)redhat.com>;
> > Michael S. Tsirkin <mst(a)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(a)linaro.org>
> > Signed-off-by: Viresh Kumar <viresh.kumar(a)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
> >
>
On Mon, May 20, 2024 at 12:29:35PM +0000, Parav Pandit wrote:
>
> > From: Michael S. Tsirkin <mst(a)redhat.com>
> > Sent: Monday, May 20, 2024 5:55 PM
> >
> > On Mon, May 20, 2024 at 09:42:02AM +0000, Parav Pandit wrote:
> > > Michael,
> > >
> > > > From: Viresh Kumar <viresh.kumar(a)linaro.org>
> > > > Sent: Monday, May 20, 2024 3:00 PM
> > > > To: virtio-comment(a)lists.linux.dev; virtio-dev(a)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.
> >
> True. I meant to ask that do contributors need to wait for patch [1] to be merged before posting patches here?
> You indicated there might be voting in [2], so trying to find what is next for contributors?
>
> [1] https://lore.kernel.org/virtio-comment/te6tzbegqky7uz4skrag3yowet3phtq6nn7t…
> [2] https://lore.kernel.org/virtio-comment/te6tzbegqky7uz4skrag3yowet3phtq6nn7t…
I think we can assume existing contributors are aware of the process and
we do not need to vote. I spent a day on it but could not fix the voting
scripts yet.
> > > 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(a)linaro.org>; Vincent Guittot
> > > > <vincent.guittot(a)linaro.org>; Alex Bennée <alex.bennee(a)linaro.org>;
> > > > stratos- dev(a)op-lists.linaro.org; Manos Pitsidianakis
> > > > <manos.pitsidianakis(a)linaro.org>; Cornelia Huck <cohuck(a)redhat.com>;
> > > > Michael S. Tsirkin <mst(a)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(a)linaro.org>
> > > > Signed-off-by: Viresh Kumar <viresh.kumar(a)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
> > > >
> > >
