Re: [libvirt] [RFC PATCH 0/2] ARM: add QMP command to query GIC version

On Sun, Feb 14, 2016 at 01:41:41PM +0800, Peter Xu wrote: This looks nice. I have some questions, but I'm not an expert in this area, so excuse me if they are stupid. So hardware itself supports some GIC version, let's say 3 for our case. Does that mean it can be triggered to do v2 as well? I mean is it possible that HW supports multiple versions? If yes, then I suspect there is (will be) HW that does *not* do it and that's where QEMU (or KVM) must emulate that version. If all I'm having in mind is true, then you are trying to reply with two orthogonal types of information. A) versions kernel/HW supports and B) qemu/kvm can emulate. That is fine if libvirt can choose all the versions specified (e.g. gicv2-kvm, gicv2), but if we can only select a version, then it might be worth just returning those two types of information separately, e.g.: ["v2": {"emulated": true, "kvm":true}, "v3": {"emulated": false, "kvm": true}] But as I said, I don't know the pre-requisites for this and mainly I'm not dealing with arm support now in libvirt, I'm just curious about it. As mentioned in the other thread, making it available everywhere and just returning a proper error message (so we can parse the class and not the error message itself) is the best choice, IMHO.