[RFC] dropping network hotplug support from network service

[Bill Nottingham]

Don Dutile (ddutile at redhat.com) said: 
> > Essentially, hot-adding a virtual device would not bring the device
> > up automatically if you're using the old network service; you'd have
> > to run 'ifup' by hand.
> >
> hot-adding a VF-nic to a Linux kvm guest brings up the hot-added (VF) 
> nic in the guest today.... am I missing what you mean?

It depends on the network system in use - if NetworkManager is running,
the guest will bring it up. If the old /etc/init.d/network service is
running, it will only bring it up if there's an ifcfg file for that
device (which is usually tied to the hardware address, but is sometimes
just tied to the device name.) 

> >>> For #4, bringing up the device automatically can cause more issues
> >>> than it solves. (We've seen this happen for vlans, for example.)
> >> This is done all the time (on KVM hosts) to take down PF driver&  load
> >> PF+VF drivers for SRIOV-capable devices.
> >
> > This would be a different device with a different hardware address,
> > correct?
> >
> Nope; typically start up an SRIOV device in PF-only mode (igb, for 
> example), then do an rmmod igb; modprobe igb max_vfs=7;  same PF mac;
> new VF mac's.
> 
> and as VF's are added & removed from guests, they may be removed & added
> back to host.

The MAC addresses in the VF are still pseudo-random, correct?

Bill