Re: [PATCH v4] clarify device reset

[Jason Wang <jasowang@redhat.com>]

On 2021/1/28 äå9:52, Cornelia Huck wrote:
> Properly specify that the method for the driver to request a
> device reset is transport specific, and some action the device
> has to take.
>
> Signed-off-by: Cornelia Huck <cohuck@redhat.com>
> ---
>
> Stefan, Halil: I did not apply your R-b due to the amount of changes.
>
> v3 -> v4:
>    - moved device status 're-initialize to 0' clause that is now duplicated
>      to an informal description
>    - more clarifications on when reset may be used and device requirements
>    - use \field{device status} consistently
> RFC v2 -> v3:
>    - re-worded the "must not send notifications" clause to avoid guessing
>    - added a driver conformance clause on how a driver should find out
>      when reset is complete
> RFC -> RFC v2:
>    - moved reset spec to basic facilities
>
> ---
>   conformance.tex |  2 ++
>   content.tex     | 24 +++++++++++++++++++++++-
>   2 files changed, 25 insertions(+), 1 deletion(-)


Reviewed-by: Jason Wang <jasowang@redhat.com>


> diff --git a/conformance.tex b/conformance.tex
> index e78adfdbd283..17c390d249db 100644
> --- a/conformance.tex
> +++ b/conformance.tex
> @@ -64,6 +64,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
>   \begin{itemize}
>   \item \ref{drivernormative:Basic Facilities of a Virtio Device / Device Status Field}
>   \item \ref{drivernormative:Basic Facilities of a Virtio Device / Feature Bits}
> +\item \ref{drivernormative:Basic Facilities of a Virtio Device / Device Reset}
>   \item \ref{drivernormative:Basic Facilities of a Virtio Device / Device Configuration Space}
>   \item \ref{drivernormative:Basic Facilities of a Virtio Device / Virtqueues}
>   \item \ref{drivernormative:Basic Facilities of a Virtio Device / Message Framing}
> @@ -283,6 +284,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
>   \begin{itemize}
>   \item \ref{devicenormative:Basic Facilities of a Virtio Device / Device Status Field}
>   \item \ref{devicenormative:Basic Facilities of a Virtio Device / Feature Bits}
> +\item \ref{devicenormative:Basic Facilities of a Virtio Device / Device Reset}
>   \item \ref{devicenormative:Basic Facilities of a Virtio Device / Device Configuration Space}
>   \item \ref{devicenormative:Basic Facilities of a Virtio Device / Message Framing}
>   \item \ref{devicenormative:Basic Facilities of a Virtio Device / Virtqueues / The Virtqueue Descriptor Table}
> diff --git a/content.tex b/content.tex
> index 1ca24c13f2d0..47239b877c6c 100644
> --- a/content.tex
> +++ b/content.tex
> @@ -51,6 +51,9 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev
>     an error from which it can't recover.
>   \end{description}
>   
> +The \field{device status} field starts out as 0, and is reinitialized to 0 by
> +the device during reset.
> +
>   \drivernormative{\subsection}{Device Status Field}{Basic Facilities of a Virtio Device / Device Status Field}
>   The driver MUST update \field{device status},
>   setting bits to indicate the completed steps of the driver
> @@ -71,7 +74,6 @@ \section{\field{Device Status} Field}\label{sec:Basic Facilities of a Virtio Dev
>   \end{note}
>   
>   \devicenormative{\subsection}{Device Status Field}{Basic Facilities of a Virtio Device / Device Status Field}
> -The device MUST initialize \field{device status} to 0 upon reset.
>   
>   The device MUST NOT consume buffers or send any used buffer
>   notifications to the driver before DRIVER_OK.
> @@ -193,6 +195,26 @@ \section{Notifications}\label{sec:Basic Facilities of a Virtio Device
>   terminology. Occasionally, the term event is used to refer to
>   a notification or a receipt of a notification.
>   
> +\section{Device Reset}\label{sec:Basic Facilities of a Virtio Device / Device Reset}
> +
> +The driver may want to initiate a device reset at various times; notably,
> +it is required to do so during device initialization and device cleanup.
> +
> +The mechanism used by the driver to initiate the reset is transport specific.
> +
> +\devicenormative{\subsection}{Device Reset}{Basic Facilities of a Virtio Device / Device Reset}
> +
> +A device MUST reinitialize \field{device status} to 0 after receiving a reset.
> +
> +A device MUST NOT send notifications or interact with the queues after
> +indicating completion of the reset by reinitializing \field{device status}
> +to 0, until the driver re-initializes the device.
> +
> +\drivernormative{\subsection}{Device Reset}{Basic Facilities of a Virtio Device / Device Reset}
> +
> +The driver SHOULD consider a driver-initiated reset complete when it
> +reads \field{device status} as 0.
> +
>   \section{Device Configuration Space}\label{sec:Basic Facilities of a Virtio Device / Device Configuration Space}
>   
>   Device configuration space is generally used for rarely-changing or