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.
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.
Thanks,
-Christoffer
Regards,
Bhupinder
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