Re: [Qemu-devel] net: Next steps to deprecate -net

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

On Wed, Jul 22, 2015 at 03:40:55PM +0200, Markus Armbruster wrote:
> Copying Andreas just in case.
> 
> Thomas Huth <thuth@redhat.com> writes:
> 
> > On 07/17/2015 09:25 AM, Peter Maydell wrote:
> >> On 17 July 2015 at 07:53, Thomas Huth <thuth@redhat.com> wrote:
> >>> Ok, assuming that my "Network traffic dumping for -netdev devices" patch
> >>> series is going to solve the dumping-for-netdev problem, how do we
> >>> tackle the remaining problems that we have to solve before we can
> >>> deprecate -net? Does anybody have a survey of the (onboard) NICs that
> >>> can only be configured with -net but not with -device? Could they
> >>> nowadays be changed to work with -device, too, or are there still major
> >>> obstacles to solve first?
> >> 
> >> The problem is that "-device" says "create a new device and
> >> configure it like this". But onboard NICs are created by
> >> the board, so we want let the user say how to configure
> >> those devices, not create new ones...
> 
> The more general problem is lack of a uniform way to configure onboard
> devices.
> 
> We have a bunch of ways to configure onboard devices: -net nic, -serial,
> -parallel, -drive, ...  These all deposit configuration requests in
> well-known places for the board code to pick up.  A request can apply
> 
> (a) to a mandatory onboard device, modifying its configuration, or
> 
> (b) to an optional onboard device, triggering its creation, or
> 
> (c) to nothing in particular.
> 
> It all depends on the board code.
> 
> For qdevified devices, you can replace (b) with -device, but not (a), as
> Peter points out.
> 
> To likewise replace (a), we'd need means to change an *existing*
> device's properties.  Complication: how to address the device.  Onboard
> devices don't have a qdev ID...  QOM path?
> 
> Aside: you can sometimes use -global to replace (a), but it's not
> general, because -global applies to all devices of a certain type, not
> just the one you're actually targeting.
> 
> > Ok, I see ... maybe it makes sense to simply keep "-net nic" to be able
> > to configure the default/onboard NIC, and only to remove all the other
> > -net options instead ("-net user" etc.). The disliked vlan/hub concept
> > could then be removed, too, since "-net nic" can be used together with
> > "-netdev" nowadays by using something like "-net nic,netdev=xxx" as far
> > as I know. That would clean up most points of confusion, I think, and
> > would not cause too much code churn for the onboard NICs. Does that
> > sound feasible?
> 
> Deprecating -net except for -net nic sounds like a fine step forward to
> me.

-net dump is also useful, we'll need some solution for that if we
want to deprecate vlans.

-- 
MST