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

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Date:   Mon, 23 Apr 2018 22:07:46 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Siwei Liu <loseweigh@...il.com>, Jiri Pirko <jiri@...nulli.us>,
        Sridhar Samudrala <sridhar.samudrala@...el.com>,
        David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        Jakub Kicinski <kubakici@...pl>,
        Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH v7 net-next 4/4] netvsc: refactor notifier/event
 handling code to use the failover framework

On Tue, 24 Apr 2018 04:42:22 +0300
"Michael S. Tsirkin" <mst@...hat.com> wrote:

> On Mon, Apr 23, 2018 at 06:25:03PM -0700, Stephen Hemminger wrote:
> > On Mon, 23 Apr 2018 12:44:39 -0700
> > Siwei Liu <loseweigh@...il.com> wrote:
> >   
> > > On Mon, Apr 23, 2018 at 10:56 AM, Michael S. Tsirkin <mst@...hat.com> wrote:  
> > > > On Mon, Apr 23, 2018 at 10:44:40AM -0700, Stephen Hemminger wrote:    
> > > >> 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.    
> > > >
> > > > Okay so how does the existing patch break that? IIUC does not go to
> > > > a 3 device model since netvsc calls failover_register directly.
> > > >    
> > > >> 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.    
> > > >
> > > > Maybe we should support same for virtio ...
> > > > Which serial do you mean? From vpd?
> > > >
> > > > I guess you will want to keep supporting MAC for old hypervisors?  
> > 
> > The serial number has always been in the hypervisor since original support of SR-IOV
> > in WS2008.  So no backward compatibility special cases would be needed.  
> 
> Is that a serial from real hardware or a hypervisor thing?
> 
> 

It is a hypervisor thing in the PCI hyperv code and the hyperv Netvsc interface.
It might also be in the PCI spec, but the value in Hyper-V is being generated by the host.