Re: [RFC PATCH 00/32] ACPI/arm64: add support for virtual cpuhotplug

[Gavin Shan <gshan@redhat.com>]

Hi James,

On 9/13/23 03:01, James Morse wrote:
> On 29/03/2023 03:35, Gavin Shan wrote:
>> On 2/3/23 9:50 PM, James Morse wrote:
> 
>>> If folk want to play along at home, you'll need a copy of Qemu that supports this.
>>> https://github.com/salil-mehta/qemu.git
>>> salil/virt-cpuhp-armv8/rfc-v1-port29092022.psci.present
>>>
>>> You'll need to fix the numbers of KVM_CAP_ARM_HVC_TO_USER and KVM_CAP_ARM_PSCI_TO_USER
>>> to match your host kernel. Replace your '-smp' argument with something like:
>>> | -smp cpus=1,maxcpus=3,cores=3,threads=1,sockets=1
>>>
>>> then feed the following to the Qemu montior;
>>> | (qemu) device_add driver=host-arm-cpu,core-id=1,id=cpu1
>>> | (qemu) device_del cpu1
>>>
>>>
>>> This series is based on v6.2-rc3, and can be retrieved from:
>>> https://git.kernel.org/pub/scm/linux/kernel/git/morse/linux.git/ virtual_cpu_hotplug/rfc/v1
> 
>> I give it a try, but the hot-added CPU needs to be put into online
>> state manually. I'm not sure if it's expected or not.
> 
> This is expected. If you want the CPUs to be brought online automatically, you can add
> udev rules to do that.
> 

Yeah, I usually execute the following command to bring the CPU into online state,
after the vCPU is hot added by QMP command.

(qemu) device_add driver=host-arm-cpu,core-id=1,id=cpu1
guest# echo 1 > /sys/devices/system/cpu/cpux/online

James, the series was posted a while ago and do you have plan to respin
and post RFCv2 in near future? :)

Thanks,
Gavin