On Wed, Jun 13, 2018 at 02:53:37PM +0100, Daniel P. Berrangé wrote: > On Wed, Jun 13, 2018 at 10:47:45AM -0300, Eduardo Habkost wrote: > > On Tue, Jun 12, 2018 at 09:49:14AM +0100, Dr. David Alan Gilbert wrote: > > [...] > > > > > People have been trying to add qom-get etc for quite a while (I tried > > > > > a > > > > > couple of years ago); it gets stuck in type display issues. I've not > > > > > directly seen a need for those other variants, but qom-get is > > > > > something > > > > > I'd love to have, still that's a job for another patch. > > > > > > > > Yes. > > > > > > > > > 'info qom-tree' is very very useful when debugging qemu to see what > > > > > the > > > > > basic state we're building is; it's primarily for debugging. > > > > > > > > I'm not at all opposed to enabling qom-tree, but I want its QMP building > > > > blocks enabled as well then. I think enabling their HMP buddies as well > > > > would only make sense. > > > > > > Hmm; OK, enabling qom-list, qom-get, qom-set, qom-list-types, > > > qom-list-properties for qmp. > > > qom-list and qom-set enabled in HMP. > > > > I would prefer to avoid enabling qom-set in preconfig mode unless > > we have a good reason for that. I don't trust all existing > > property setters to not crash or break if the machine is not > > initialized yet. > > If we're in early startup, the impact of a crash is pretty minor - QEMU > will simply exit, which is not significantly differnt from if a setter > handled it "correctly" by setting an Error **errp. A mgmt app that uses > this and finds a setter which crashes will detect the problem pretty > quickly & report bugs. > > QEMU is complex enough that we're unlikely to ever find broken setters > by code inspection. So if we don't allow it in preconfig mode, then > I doubt we'll ever find & fix the problems. > > So, IMHO, we should allow qom-set and just fix problems as they come > to light, as we would for any other part of QEMU which has plenty of > scope for crashers in rarely tested codepaths.
Good points. I'm still worried about making qom-set confused with a supported configuration API, and have applications starting to rely on it. But I guess this problem could be solved by properly documenting qom-set as a debugging aid, not a supported API. -- Eduardo
