Re: [virtio-dev] [PATCH v4] content: Introduce VIRTIO_NET_F_STANDBY feature

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Sep 12, 2018 at 08:17:45AM -0700, Samudrala, Sridhar wrote:
> 
> 
> On 9/7/2018 2:34 PM, Michael S. Tsirkin wrote:
> > On Wed, Aug 15, 2018 at 11:49:15AM -0700, Sridhar Samudrala wrote:
> > > VIRTIO_NET_F_STANDBY feature enables hypervisor to indicate virtio_net
> > > device to act as a standby for another device with the same MAC address.
> > > 
> > > Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.com>
> > > Acked-by: Cornelia Huck <cohuck@redhat.com>
> > > Fixes: https://github.com/oasis-tcs/virtio-spec/issues/18
> > Applied but when do you plan to add documentation as pointed
> > out by Jan and Halil?
> 
> I thought additional documentation will be done as part of the Qemu enablement
> patches and i hope someone in RH is looking into it.
> 
> Does it make sense to add a link to to the kernel documentation of this feature in
> the spec
>  https://www.kernel.org/doc/html/latest/networking/net_failover.html


I do not think this will address the comments posted.  Specifically we
should probably include documentation for what is a standby and primary:
what is expected of driver (maintain configuration on standby, support
primary coming and going, transmit on standby only if there is no
primary) and of device (have same mac for standby as for standby).


> 
> > 
> > > ---
> > >   content.tex | 8 ++++++++
> > >   1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/content.tex b/content.tex
> > > index be18234..42a0e7e 100644
> > > --- a/content.tex
> > > +++ b/content.tex
> > > @@ -2525,6 +2525,9 @@ features.
> > >   \item[VIRTIO_NET_F_CTRL_MAC_ADDR(23)] Set MAC address through control
> > >       channel.
> > > +
> > > +\item[VIRTIO_NET_F_STANDBY(62)] Device may act as a standby for a primary
> > > +    device with the same MAC address.
> > >   \end{description}
> > >   \subsubsection{Feature bit requirements}\label{sec:Device Types / Network Device / Feature bits / Feature bit requirements}
> > > @@ -2614,6 +2617,9 @@ level ethernet header length) size with \field{gso_type} NONE or ECN, and do
> > >   so without fragmentation, after VIRTIO_NET_F_MTU has been successfully
> > >   negotiated.
> > > +If the driver negotiates the VIRTIO_NET_F_STANDBY feature, the device MAY act
> > > +as a standby device for a primary device with the same MAC address.
> > > +
> > >   \drivernormative{\subsubsection}{Device configuration layout}{Device Types / Network Device / Device configuration layout}
> > >   A driver SHOULD negotiate VIRTIO_NET_F_MAC if the device offers it.
> > > @@ -2636,6 +2642,8 @@ If the driver negotiates VIRTIO_NET_F_MTU, it MUST NOT transmit packets of
> > >   size exceeding the value of \field{mtu} (plus low level ethernet header length)
> > >   with \field{gso_type} NONE or ECN.
> > > +A driver SHOULD negotiate the VIRTIO_NET_F_STANDBY feature if the device offers it.
> > > +
> > >   \subsubsection{Legacy Interface: Device configuration layout}\label{sec:Device Types / Network Device / Device configuration layout / Legacy Interface: Device configuration layout}
> > >   \label{sec:Device Types / Block Device / Feature bits / Device configuration layout / Legacy Interface: Device configuration layout}
> > >   When using the legacy interface, transitional devices and drivers
> > > -- 
> > > 2.14.4
> > > 
> > > 
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