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Subject: Re: [virtio-dev] [PATCH 2/2] virtio-net: add default_mtu configuration field
On Wed, Aug 12, 2015 at 06:37:24PM +0300, Victor Kaplansky wrote: > Sometimes it is essential for libvirt to be able to configure MTU > on guest's NICs to a value different from 1500. > > The change adds a new field to configuration area of network > devices. It will be used to pass initial MTU from the device to > the driver, and to pass modified MTU from driver to the device > when a new MTU is assigned by the guest OS. > > In addition, in order to support backward and forward > compatibility, we introduce a new feature bit called > VIRTIO_NET_F_DEFAULT_MTU. > > Signed-off-by: Victor Kaplansky <victork@redhat.com> > --- > content.tex | 18 ++++++++++++++++++ > 1 file changed, 18 insertions(+) > > diff --git a/content.tex b/content.tex > index 37e6a18..5aba1de 100644 > --- a/content.tex > +++ b/content.tex > @@ -3078,6 +3078,13 @@ features. > > \item[VIRTIO_NET_F_CTRL_MAC_ADDR(23)] Set MAC address through control > channel. > + > +\item[VIRTIO_NET_F_DEFAULT_MTU(24)] Default MTU is supported. If > + set by the device, device is able to advise driver about initial > + MTU to be used. If it remains set after negotiation, the driver > + can use \field{default_mtu} as initial value, and will report MTU > + changes to the device. > + > \end{description} > > \subsubsection{Feature bit requirements}\label{sec:Device Types / Network Device / Feature bits / Feature bit requirements} > @@ -3128,6 +3135,7 @@ struct virtio_net_config { > u8 mac[6]; > le16 status; > le16 max_virtqueue_pairs; > + le16 default_mtu; > }; > \end{lstlisting} > > @@ -3148,6 +3156,16 @@ struct virtio_net_config { > \field{max_virtqueue_pairs} is valid only if VIRTIO_NET_F_MQ is > set and should not be modified by the driver. > > +\item [\field{default_mtu}] is a hint to the driver set by > + the device. It is valid during feature negotiation only if > + VIRTIO_NET_F_DEFAULT_MTU is set simply say "if VIRTIO_NET_F_DEFAULT_MTU is offered" > and holds the initial value of > + MTU to be used by the driver. > If VIRTIO_NET_F_DEFAULT_MTU remains > + set after negotiation, simply "is negotiated". > the driver should use the > + \field{default_mtu} as initial value, and also should report MTU Looks like we need a conformance statement. Also, pls don't write should/must/may outside conformance statements. You can say e.g. "uses", "reports". Applies to previous patch as well. > + changes to the device by \field{default_mtu} writes. Such > + reporting will be used for debugging purposes. Can it be useful for tuning? > + > + Pls avoid double empty lines, here and elsewhere. > \end{description} > > > -- > --Victor > > --------------------------------------------------------------------- > To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org > For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
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