On 5 January 2016 at 17:58, Andrea Bolognani <abologna@xxxxxxxxxx> wrote: > On Tue, 2016-01-05 at 14:47 +0100, Christoffer Dall wrote: >> Why can libvirt not just run the tool and parse its output? That's what >> I understood was done for other things, but perhaps I misunderstood. > > It's the other way around: the tool uses libvirt to implement its > checks. Running a command and parsing its output makes sense when the > binary (as is the case for QEMU) is developed by a third party; if > you control both pieces, it's usually better to stick to C and avoid > spawning extra processes. That argument suggests libvirt should just go ahead and do the ioctls to check for GICv2/v3 support, rather than spawning a separate QEMU binary to do the check for it ? > I realized the information is already sort of exposed by QEMU: > > $ qemu-system-aarch64 -machine virt,? > ... > virt.gic-version=string (Set GIC version. Valid values are 2, 3 and host) > ... > > Not the best format to parse, but the information is there. And we > already have some code to extract such parameters from QEMU using QMP's > query-command-line-options command![1] Note that helpstring will tell you whether the qemu you have supports the machine parameter, but not whether the host CPU supports GICv2 or 3 (or both) -- it's just a fixed string. thanks -- PMM -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list