"Daniel P. Berrange" <berra...@redhat.com> writes: > On Tue, Dec 04, 2012 at 03:44:54PM -0600, Anthony Liguori wrote: >> "Daniel P. Berrange" <berra...@redhat.com> writes: >> >> > On Tue, Dec 04, 2012 at 01:13:46PM -0600, Anthony Liguori wrote: >> >> "Daniel P. Berrange" <berra...@redhat.com> writes: >> >> >> >> > >> >> > In the absence of any way to detect it via QMP, libvirt should fallback >> >> > to hardcoding it based on the version number. This presumes that QEMU >> >> > was >> >> > built with it enabled in configure, but we've no other option for >> >> > current >> >> > released 1.2/1.3 versions. >> >> >> >> echo quit | qemu -machine none -S -monitor stdio -vnc none -sandbox on >> >> >> >> A non-zero execute means QEMU doesn't support the option. This will >> >> work for any new command line option introduction and can be considered >> >> a "supported" way of probing for whether options are supported. >> > >> > One of the significant benefits to libvirt of the QMP based feature >> > detection, was that we no longer have to invoke QEMU multiple times >> > to query different data. I don't want to regress in this regard, >> > because invoking QEMU many times has a noticable performance impact >> > for some applications eg virt-sandbox were even 100ms delays are >> > relevant. So while what you describe does work, I don't think it >> > is a satisfactory approach for libvirt. >> >> Okay, so in terms of what exists today, I don't have a better option. >> But we could add: >> >> { 'enum': 'ConfigEntryType', >> 'data': [ 'number', 'string', 'bool', 'size' ] } >> >> { 'type': 'ConfigEntry', >> 'data': { 'name': 'str', 'type': 'ConfigEntryType' } } >> >> { 'type': 'ConfigSection', >> 'data': { 'name': 'str', 'fields': [ 'ConfigEntry' ] } } >> >> { 'command': 'query-config-schema', >> 'returns': [ 'ConfigSection' ] }
>> >> This technically introspects config sections but obviously could be used >> to detect the availability of -sandbox. >> >> If it's useful, I can take a quick swing at implementing (or someone >> else certainly could). > > I'm not sure I entirely understand what information a 'ConfigSection' > would represent. By config here, do you mean any command line argument > or something else ? We no longer should be adding command line arguments that don't use QemuOpts and have a equivalent -readconfig syntax. We could even eliminate new options and do something like: qemu -conf sandbox:enable=on But that's not user friendly so we'll stick with adding higher level options like -sandbox. So what I'm proposing is to introspection on what -readconfig supports and then from that, you can infer when new higher level command line arguments are added. > Could you give a short example of the actual JSON > you envisage returning for this schema. Your suggestion sounds good, > but I want to make sure I'm not mis-understanding things :-) [ { 'name': 'sandbox', 'fields': [ { 'name': 'enable', 'type': 'bool' } ] }, { 'name': 'add-fd', 'fields': [ { 'name': 'fd', 'type': 'number' }, { 'name': 'set', 'type': 'number' }, { 'name': 'opaque', 'type': 'str' } ] }, ... ] Regards, Anthony Liguori > > Regards, > Daniel > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :|