Re: [virtio-comment] [PATCH v3] clarify device reset

[Cornelia Huck <cohuck@redhat.com>]

On Wed, 27 Jan 2021 11:07:53 +0800
Jason Wang <jasowang@redhat.com> wrote:

> On 2021/1/25 äå7:08, 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>
> > ---
> >
> > 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     | 19 +++++++++++++++++++
> >   2 files changed, 21 insertions(+)
> >
> > diff --git a/conformance.tex b/conformance.tex
> > index eb3324053080..21fe89ccd937 100644
> > --- a/conformance.tex
> > +++ b/conformance.tex
> > @@ -60,6 +60,7 @@ \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}
> > @@ -271,6 +272,7 @@ \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 620c0e28c9a7..9cdefe16509e 100644
> > --- a/content.tex
> > +++ b/content.tex
> > @@ -193,6 +193,25 @@ \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 initiate a device reset at various times; notably, 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 device status to 0 after receiving a reset.
> > +  
> 
> 
> We had similar description in "2.1.2 Device Requirements: Device Status 
> Field":
> 
> "The device MUST initialize device status to 0 upon reset."
> 
> Consider we had a dedicated part for reset, maybe we can remove that one.

Maybe we can replace the normative statement with an informal
description in the device status section? I.e. something like

"The device status field starts out as 0, and is reinitialized to 0 by
the device during reset."

> 
> Thanks
> 
> 
> > +A device MUST NOT send notifications after indicating completion of
> > +the reset by reinitializing the device status to 0.
> > +
> > +\drivernormative{\subsection}{Device Reset}{Basic Facilities of a Virtio Device / Device Reset}
> > +
> > +The driver SHOULD consider a driver-initiated reset complete when it
> > +reads the 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