Re: [libvirt] [Qemu-devel] -nodefaults and available buses (was Re: [RFC 00/15] qmp: Report supported device types on 'query-machines')

On Wed, Nov 23, 2016 at 03:10:47PM -0200, Eduardo Habkost wrote: > (CCing the maintainers of the machines that crash when using > -nodefaults) > > On Tue, Nov 22, 2016 at 08:34:50PM -0200, Eduardo Habkost wrote: > [...] > > "default defaults" vs "-nodefault defaults" > > ------------------------------------------- > > > > Two bad news: > > > > 1) We need to differentiate buses created by the machine with > > "-nodefaults" and buses that are created only without > > "-nodefaults". > > > > libvirt use -nodefaults when starting QEMU, so knowing which > > buses are available when using -nodefaults is more interesting > > for them. > > > > Other software, on the other hand, might be interested in the > > results without -nodefaults. > > > > We need to be able model both cases in the new interface. > > Suggestions are welcome. > > The good news is that the list is short. The only[1] machines > where the list of buses seem to change when using -nodefaults > are: > > * mpc8544ds > * ppce500 > * mpc8544ds > * ppce500 > * s390-ccw-virtio-* > > On all cases above, the only difference is that a virtio bus is > available if not using -nodefaults. Hrm.. that's odd. Well, it makes sense for the s390 which has special virtio arrangements.

However, the others are all embedded ppc machines, whose virtio should be bog-standard virtio-pci. I'm wondering if the addition of the virtio "bus" is a side-effect of the NIC or storage device created without -nodefaults being virtio.