Re: [PATCH] virtio-net: support reset queue

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Wed, 9 Feb 2022 04:23:17 -0500, "Michael S. Tsirkin" <mst@redhat.com> wrote:
> On Wed, Feb 09, 2022 at 05:01:58PM +0800, Xuan Zhuo wrote:
> > This patch defines some requirements for virtio-net to support reset
> > queues.
> >
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > ---
> >  conformance.tex |  2 ++
> >  content.tex     | 19 +++++++++++++++++++
> >  2 files changed, 21 insertions(+)
> >
> > diff --git a/conformance.tex b/conformance.tex
> > index 42f8537..52b4879 100644
> > --- a/conformance.tex
> > +++ b/conformance.tex
> > @@ -136,6 +136,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
> >  \item \ref{drivernormative:Device Types / Network Device / Device Operation / Packet Transmission}
> >  \item \ref{drivernormative:Device Types / Network Device / Device Operation / Setting Up Receive Buffers}
> >  \item \ref{drivernormative:Device Types / Network Device / Device Operation / Processing of Incoming Packets}
> > +\item \ref{drivernormative:Device Types / Network Device / Device Operation / Reset Virtqueue}
> >  \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Packet Receive Filtering}
> >  \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Setting MAC Address Filtering}
> >  \item \ref{drivernormative:Device Types / Network Device / Device Operation / Control Virtqueue / Gratuitous Packet Sending}
> > @@ -396,6 +397,7 @@ \section{Conformance Targets}\label{sec:Conformance / Conformance Targets}
> >  \item \ref{devicenormative:Device Types / Network Device / Device Operation / Packet Transmission}
> >  \item \ref{devicenormative:Device Types / Network Device / Device Operation / Setting Up Receive Buffers}
> >  \item \ref{devicenormative:Device Types / Network Device / Device Operation / Processing of Incoming Packets}
> > +\item \ref{devicenormative:Device Types / Network Device / Device Operation / Reset Virtqueue}
> >  \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Packet Receive Filtering}
> >  \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Setting MAC Address Filtering}
> >  \item \ref{devicenormative:Device Types / Network Device / Device Operation / Control Virtqueue / Gratuitous Packet Sending}
> > diff --git a/content.tex b/content.tex
> > index c6f116c..ce8e37a 100644
> > --- a/content.tex
> > +++ b/content.tex
> > @@ -4000,6 +4000,25 @@ \subsubsection{Processing of Incoming Packets}\label{sec:Device Types / Network
> >  #define VIRTIO_NET_HASH_REPORT_UDPv6_EX        9
> >  \end{lstlisting}
> >
> > +\subsubsection{Reset Virtqueue}\label{sec:Device Types / Network Device / Device Operation / Reset Virtqueue}
> > +
> > +The receive and transmission virtqueues can implement reset based on Virtqueue
> > +Reset (See \ref{sec:Basic Facilities of a Virtio Device / Virtqueues / Virtqueue Reset}).
> > +
> > +\drivernormative{\paragraph}{Gratuitous Packet Sending}{Device Types / Network Device / Device Operation / Reset Virtqueue}
> > +
> > +The driver MUST NOT reset the control virtqueue.
>
> Why not though? I am guessing if it does and command is in
> progress, it won't know if it completed. So it's safest to retry
> then? Reset as a way to recover from a VQ error seems useful for CVQ,
> I don't like disabling it like this.
> Besides, it's probably too late to make this change for 1.2 ...

I think there should be no need to reset cvq. So this setting is added.

I will remove this in the next version.


>
> > +
> > +\devicenormative{\paragraph}{Gratuitous Packet Sending}{Device Types / Network Device / Device Operation / Reset Virtqueue}
> > +
> > +After automatic receive steering or RSS receive steering has completed the
> > +selection of the queue, if the destination receive queue is in reset state,
> > +the device MUST re-select a different random queue. If all receive queues are in
> > +reset state, the device can drop the packet.
> > +
> > +A virtio-net device MUST support the above requirements in order to support
> > +VIRTIO_F_RING_RESET.
> > +
>
> This is more a quality of implementation issue, no? So I'd say SHOULD
> here.

OK.

Thanks.

>
> >  \subsubsection{Control Virtqueue}\label{sec:Device Types / Network Device / Device Operation / Control Virtqueue}
> >
> >  The driver uses the control virtqueue (if VIRTIO_NET_F_CTRL_VQ is
> > --
> > 2.31.0
>