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

(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.

Considering that the list is short, I plan to rename 'supported-device-types' to 'always-available-buses', and document that it will include only the buses that are not disabled by -nodefaults. [1] I mean, the only ones from the set that don't crash with -nodefaults. The ones below could not be tested: > 2) A lot of machine-types won't start if using > "-nodefaults -machine <machine>" without any extra devices or > drives. > > Lots of machines require some drives or devices to be created > (especially ARM machines that require a SD drive to be > available). > > Some machines will make QEMU exit, some of them simply segfault. > I am looking for ways to work around it so we can still validate > -nodefaults-based info on the test code. The following machines won't work with -nodefaults: These make QEMU segfault: * cubieboard * petalogix-ml605 * or32-sim * virtex-ml507 * Niagara These exit with a "missing SecureDigital device" error: * akita * borzoi * cheetah * connex * mainstone * n800 * n810 * spitz * sx1 * sx1-v1 * terrier * tosa * verdex * z2