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

On Thu, 24 Nov 2016 12:51:19 +1100 David Gibson <david(a)gibson.dropbear.id.au&gt; wrote: > 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. I don't think it makes much sense for s390 either... is this a 'virtio' bus or a 'virtio-{pci,ccw}' bus? The transport bus should be present with -nodefaults; the virtio bus is basically a glue bus for virtio devices...