Re: [libvirt] [RFC 0/7] Warn at runtime when deprecated features are used

On Fri, Oct 05, 2018 at 12:33:57PM +0200, Jiri Denemark wrote: > OK, but if it's us choosing some default which QEMU considers > deprecated, it's us who should dealt with it. That is, change the > default IMHO. Sure apps could just stop relying on defaults and choose > something specific which is not deprecated, but that doesn't mean we as > a user of QEMU should continue using default values which got deprecated > and are likely to be removed. > > If it's something which is not user/guest visible, we are already trying > to move to more modern interfaces. That is easy since it doesn't change > anything for libvirt users, but I feel like we need to have a plan for > stuff which actually is visible to our users. If some user visible feature is actually removed, then our hand is forced - we have to pick something else to replace it. This is what happened with the default NIC with RHEL stopped building rtl8139, so we had to have a default fallback. That change is/was not seemless since there exist OS which supported rtl8139 but which lacked e1000 / virtio-net drivers. Fortunately apps already use libosinfo to explicitly set NIC model so the breakage was not so visible. If 'i440fx' is ever actually deleted we would have todo something similar - prefer i440fx for best historical compat, but fallback to q35 despite knowing it could break.