On Wed, 2015-01-21 at 09:49 +0100, Peter Krempa wrote: > On Wed, Jan 21, 2015 at 16:00:52 +0800, Zhu Guihua wrote: > > If you apply the folowing patchset > > [PATCH v3 0/7] cpu: add device_add foo-x86_64-cpu support > > https://lists.nongnu.org/archive/html/qemu-devel/2015-01/msg01552.html, > > and [PATCH v2 00/11] cpu: add i386 cpu hot remove support > > https://lists.nongnu.org/archive/html/qemu-devel/2015-01/msg01557.html, > > qemu can support hotplug and hot-unplug cpu device. > > > > So this patch series will make libvirt support hotplug and hot-unplug cpu > > device for qemu driver, and now only supports one cpu driver which is > > 'qemu64-x86_64-cpu'. > > > > The cpu device's xml like this: > > <cpu driver='qemu64-x86_64-cpu' apic_id='3'> > > > > Libvirt already implements vCPU hotplug and unplug via > virDomainSetVcpusFlags() API and implements this API also for the qemu > driver. Granted that the existing code uses older comands but that can > be tweaked to support the new stuff too. > Now Libvirt only supported vCPU hotplug by qemu command 'cpu-add', but vCPU hot-unplug has not been implemented for qemu driver. > Additionally the new <cpu> subelement of <devices> doesn't seem > necessary: > > - There's only one model that can be plugged there are more model will be plugged in next version. > - Configuring the APIC id doesn't make much sense for users I agree. I will not consider the APIC id in future. > - nothing else can be configured > Yes, only cpu model shoud be configured. > I have following questions though: > > Is there a difference in specifying the cpu via the -device option and > via the legacy -cpu argument? > Of course, -device has more functions than -cpu. > Is there a plan to have more than one cpu "model" that can be plugged? > Yes, all x86 cpu model will be supported. This is an RFC patchset, so the feature is realized in a simple way. > Can more than one cpu model be plugged to the same VM at the same time? > Yes, it can. > In general I don't think it's necessary to add the new device type and > we should rather improve the existing API to support the new device > type. > I think it's necessary to support more cpu model. When user hotplug a cpu, it is essential to point the cpu model. And I think improve the existing API would change too much. The feature is implemented by command 'device_add', so I think it should also keep consistent with the other devices' hotplug. Regards, Zhu > More comments will be inline in the patches. > > Peter -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list