On Wed, Jan 06, 2016 at 01:30:16PM +0000, Peter Maydell wrote: > On 6 January 2016 at 12:49, Andrea Bolognani <abologna@xxxxxxxxxx> wrote: > > That's correct, having a QMP command that lists the values gic-version > > can have on the current host would be just great. > > > > If we had that, we could validate the GIC version chosen for a guest, > > and expose it in the capabilities XML so that higher-level tools can > > provide a list of choices to the user. > > > > Please note that this QMP command would have to work regardless of the > > machine type selected on QEMU's command line, because libvirt always > > runs a QEMU binary with '-M none' when probing its capabilities. > > On the other hand, if you don't tell us the machine type you care > about then we can't tell you: > (a) "this machine type doesn't support setting this property at all" > (which applies to machines like vexpress-a15 which you can use with > KVM on 32-bit hosts, and of course also to all the non-KVM models) > (b) "this machine type only supports GIC versions X and Y even if the > host supports more" (this is currently only hypothetical, though, > since we only have the property on 'virt'. it would only happen > if in the future we needed something other than '2' or '3' or > 'host' I think.) > > If you use -M none then we can only tell you information you > could have got yourself by directly asking the kernel about it. > So where does this leave us? Do we need a QMP command or not? It sounds to me like we should implement one, and the answer depends on the machine option chosen, where -M none gives you the generic capabilities of the kernel and for other machines it tells you what's possible? Thanks, -Christoffer -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list