netdev - Re: [PATCH v7 net-next 4/4] netvsc: refactor notifier/event handling code to use the failover framework

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Message-ID: <20180423104440.2fe6cfd2@xeon-e3>
Date:   Mon, 23 Apr 2018 10:44:40 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Jiri Pirko <jiri@...nulli.us>,
        Sridhar Samudrala <sridhar.samudrala@...el.com>,
        davem@...emloft.net, netdev@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, jesse.brandeburg@...el.com,
        alexander.h.duyck@...el.com, kubakici@...pl, jasowang@...hat.com,
        loseweigh@...il.com
Subject: Re: [PATCH v7 net-next 4/4] netvsc: refactor notifier/event
 handling code to use the failover framework

On Mon, 23 Apr 2018 20:24:56 +0300
"Michael S. Tsirkin" <mst@...hat.com> wrote:

> On Mon, Apr 23, 2018 at 10:04:06AM -0700, Stephen Hemminger wrote:
> > > >
> > > >I will NAK patches to change to common code for netvsc especially the
> > > >three device model.  MS worked hard with distro vendors to support transparent
> > > >mode, ans we really can't have a new model; or do backport.
> > > >
> > > >Plus, DPDK is now dependent on existing model.    
> > > 
> > > Sorry, but nobody here cares about dpdk or other similar oddities.  
> > 
> > The network device model is a userspace API, and DPDK is a userspace application.  
> 
> It is userspace but are you sure dpdk is actually poking at netdevs?
> AFAIK it's normally banging device registers directly.
> 
> > You can't go breaking userspace even if you don't like the application.  
> 
> Could you please explain how is the proposed patchset breaking
> userspace? Ignoring DPDK for now, I don't think it changes the userspace
> API at all.
> 

The DPDK has a device driver vdev_netvsc which scans the Linux network devices
to look for Linux netvsc device and the paired VF device and setup the
DPDK environment.  This setup creates a DPDK failsafe (bondingish) instance
and sets up TAP support over the Linux netvsc device as well as the Mellanox
VF device.

So it depends on existing 2 device model. You can't go to a 3 device model
or start hiding devices from userspace.

Also, I am working on associating netvsc and VF device based on serial number
rather than MAC address. The serial number is how Windows works now, and it makes
sense for Linux and Windows to use the same mechanism if possible.