Re: [Xen-devel] [PATCH RESEND] netif.h: Document xen-net{back, front} multi-queue feature

[Andrew Bennieston <andrew.bennieston@xxxxxxxxxx>]

On 29/04/14 17:19, Ian Campbell wrote:
> On Tue, 2014-04-29 at 17:15 +0100, Andrew J. Bennieston wrote:
> > From: "Andrew J. Bennieston" <andrew.bennieston@xxxxxxxxxx>
> >
> > Document the multi-queue feature in terms of XenStore keys to be written
> > by the backend and by the frontend.
> You seem to have missed my comments on v2 in
> <1394714132.25873.56.camel@xxxxxxxxxxxxxxxxxxxxxx>, dated "Thu, 13 Mar
> 2014 12:35:32 +0000".
You're right; that one must have slipped through the net. I'll fix this 
up and repost.
Andrew

> Ian.
>
> > Signed-off-by: Andrew J. Bennieston <andrew.bennieston@xxxxxxxxxx>
> > ---
> >   xen/include/public/io/netif.h |   29 +++++++++++++++++++++++++++++
> >   1 file changed, 29 insertions(+)
> >
> > diff --git a/xen/include/public/io/netif.h b/xen/include/public/io/netif.h
> > index d7fb771..5d98734 100644
> > --- a/xen/include/public/io/netif.h
> > +++ b/xen/include/public/io/netif.h
> > @@ -69,6 +69,35 @@
> >    */
> >
> >   /*
> > + * Multiple transmit and receive queues:
> > + * If supported, the backend will write "multi-queue-max-queues" and set its
> > + * value to the maximum supported number of queues.
> > + * Frontends that are aware of this feature and wish to use it can write the
> > + * key "multi-queue-num-queues", set to the number they wish to use.
> > + *
> > + * Queues replicate the shared rings and event channels, and
> > + * "feature-split-event-channels" may be used when using multiple queues.
> > + * Each queue consists of one shared ring pair, i.e. there must be the same
> > + * number of tx and rx rings.
> > + *
> > + * For frontends requesting just one queue, the usual event-channel and
> > + * ring-ref keys are written as before, simplifying the backend processing
> > + * to avoid distinguishing between a frontend that doesn't understand the
> > + * multi-queue feature, and one that does, but requested only one queue.
> > + *
> > + * Frontends requesting two or more queues must not write the toplevel
> > + * event-channel (or event-channel-{tx,rx}) and {tx,rx}-ring-ref keys,
> > + * instead writing them under sub-keys having the name "queue-N" where
> > + * N is the integer ID of the queue for which those keys belong. Queues
> > + * are indexed from zero.
> > + *
> > + * Mapping of packets to queues is considered to be a function of the
> > + * transmitting system (backend or frontend) and is not negotiated
> > + * between the two. Guests are free to transmit packets on any queue
> > + * they choose, provided it has been set up correctly.
> > + */
> > +
> > +/*
> >    * "feature-no-csum-offload" should be used to turn IPv4 TCP/UDP checksum
> >    * offload off or on. If it is missing then the feature is assumed to be on.
> >    * "feature-ipv6-csum-offload" should be used to turn IPv6 TCP/UDP checksum

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