On Tue, 24 Jul 2018 11:35:31 -0700 Maran Wilson <maran.wilson@xxxxxxxxxx> wrote: > It's been a few months since this email thread died off. Has anyone > started working on a potential solution that would allow VCPU hotplug on > KVM/ARM ? Or is this a project that is still waiting for an owner who > has the time and inclination to get started? I'm working on QEMU side of it as time allows. I can guide or share task if are you interested in helping out with it? > Thanks, > -Maran > > On 2/27/2018 5:21 AM, Andrew Jones wrote: > > On Tue, Feb 27, 2018 at 01:46:04PM +0100, Christoffer Dall wrote: > >> On Tue, Feb 27, 2018 at 05:34:28PM +0530, bthakur@xxxxxxxxxxxxxx wrote: > >>> Hi Christoffer, > >>> > >>> Thanks for your reply. > >>> > >>> On 2018-02-27 16:17, Christoffer Dall wrote: > >>>> Hi Bhupinder, > >>>> > >>>> On Tue, Feb 27, 2018 at 03:01:17PM +0530, bthakur@xxxxxxxxxxxxxx wrote: > >>>>> I hope it is the right forum to post my query. > >>>>> > >>>>> > >>>>> > >>>>> I am currently looking at the possibility of adding a new VCPU to a > >>>>> running > >>>>> guest VM in KVM/ARM. I see that currently, it is not allowed to add a > >>>>> new > >>>>> VCPU to a guest VM, if it is already initialized. The first check in > >>>>> kvm_arch_vcpu_create() returns failure if it is already initialized. > >>>>> > >>>> This would require a major rework of a lot of logic surrounding the GIC > >>>> and other parts of KVM initialization. > >>>> > >>>>> > >>>>> There was some work done in QEMU to add support for VCPU hotplug: > >>>>> https://lists.gnu.org/archive/html/qemu-arm/2017-05/msg00404.html > >>>>> > >>>>> > >>>>> > >>>>> But I am looking at the KVM side for enabling adding a new VCPU. If you > >>>>> can > >>>>> point me to any relevant work/resources, which I can refer to then it > >>>>> will > >>>>> help me. > >>>>> > >>>> I don't have any specific pointers, but I was always told that the way > >>>> we were going to do CPU hotplug would be to instantiate a large number > >>>> of VCPUs, and hotplug would be equivalent to turning on a VCPU which was > >>>> previously powered off. > >>>> > >>>> Is this not still a feasible solution? > >>> It should be a feasible solution provided the guest VM is not able to > >>> control the onlining/offlining of VCPUs. It should be controlled by the > >>> Host. > >>> > >> KVM could simply refuse to turn on some of the CPUs unless given > >> permission from host userspace. > >> > >>>> How does VCPU hotplug work on x86? > >>> On x86, you can add a vcpu through libvirt setvcpu command and it shows up > >>> in the guest VM as a new CPU if you do lscpu. > >>> > >> Sure, but what is the mechanism, does x86 qemu actually call > >> KVM_CREATE_VCPU, or is this also a question of turning on already > >> created vcpus ? > >> > > CC'ing Igor and qemu-devel > > > > drew > > _______________________________________________ > > kvmarm mailing list > > kvmarm@xxxxxxxxxxxxxxxxxxxxx > > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm > > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
