Linux Virtualization - Apr 2018 - [PATCH v7 net-next 4/4] netvsc: refactor notifier/event handling code to use the failover framework

On Fri, 20 Apr 2018 18:00:58 +0200
Jiri Pirko <jiri at resnulli.us> wrote:
> Fri, Apr 20, 2018 at 05:28:02PM CEST, stephen at networkplumber.org wrote:
> >On Thu, 19 Apr 2018 18:42:04 -0700
> >Sridhar Samudrala <sridhar.samudrala at intel.com> wrote:
> >  
> >> Use the registration/notification framework supported by the
generic
> >> failover infrastructure.
> >> 
> >> Signed-off-by: Sridhar Samudrala <sridhar.samudrala at
intel.com>
> >
> >Do what you want to other devices but leave netvsc alone.
> >Adding these failover ops does not reduce the code size, and really is
> >no benefit.  The netvsc device driver needs to be backported to several
> >other distributions and doing this makes that harder.  
> 
> We should not care about the backport burden when we are trying to make
> things right. And things are not right. The current netvsc approach is
> just plain wrong shortcut. It should have been done in a generic way
> from the very beginning. We are just trying to fix this situation.
> 
> Moreover, I believe that part of the fix is to convert netvsc to 3
> netdev solution too. 2 netdev model is wrong.
> 
> 
> >
> >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.
You can't go breaking userspace even if you don't like the application.

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.

-- 
MST

Mon, Apr 23, 2018 at 07:04:06PM CEST, stephen at networkplumber.org
wrote:
>On Fri, 20 Apr 2018 18:00:58 +0200
>Jiri Pirko <jiri at resnulli.us> wrote:
>
>> Fri, Apr 20, 2018 at 05:28:02PM CEST, stephen at networkplumber.org
wrote:
>> >On Thu, 19 Apr 2018 18:42:04 -0700
>> >Sridhar Samudrala <sridhar.samudrala at intel.com> wrote:
>> >  
>> >> Use the registration/notification framework supported by the
generic
>> >> failover infrastructure.
>> >> 
>> >> Signed-off-by: Sridhar Samudrala <sridhar.samudrala at
intel.com>
>> >
>> >Do what you want to other devices but leave netvsc alone.
>> >Adding these failover ops does not reduce the code size, and really
is
>> >no benefit.  The netvsc device driver needs to be backported to
several
>> >other distributions and doing this makes that harder.  
>> 
>> We should not care about the backport burden when we are trying to make
>> things right. And things are not right. The current netvsc approach is
>> just plain wrong shortcut. It should have been done in a generic way
>> from the very beginning. We are just trying to fix this situation.
>> 
>> Moreover, I believe that part of the fix is to convert netvsc to 3
>> netdev solution too. 2 netdev model is wrong.
>> 
>> 
>> >
>> >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.
>You can't go breaking userspace even if you don't like the
application.
I don't understand how you can break anything by exposing
just-another-netdevice. If you break it, it is already broken...

And how you can break anything in userspace by doing refactoring inside
the kernel is puzzling me even more...

On Mon, 23 Apr 2018 20:24:56 +0300
"Michael S. Tsirkin" <mst at redhat.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.