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Subject: Re: [virtio-comment] [PATCH v4] clarify device reset
On Wed, 5 May 2021 09:20:45 -0400 "Michael S. Tsirkin" <mst@redhat.com> wrote: > On Thu, Jan 28, 2021 at 02:52:35PM +0100, 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(-) > > (...) > > 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. > > Do we want to keep the part where it starts out as 0 here? Wouldn't that duplicate the statement in the 'Device Reset' normative section below? > > > @@ -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
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