Re: [Qemu-devel] [PATCH 0/3] arm/virt: refine virt.c code and implement hot_add_cpu interface

[Li Zhang]

On Fri, May 26, 2017 at 7:21 PM, Igor Mammedov <address@hidden> wrote:
> On Fri, 26 May 2017 17:21:05 +0800
> Li Zhang <address@hidden> wrote:
>
>> From: Li Zhang <address@hidden>
>>
>> virt machine doesn't support hot_add_cpu interface. This patchset is to 
>> implement
>> hot_add_cpu interface. A CPU can be added by QMP command with QEMU monitor.
>>
>> Here is command to add a CPU with QMP command.
>>
>> * qemu-system-aarch64 -machine virt -cpu cortex-a15 -smp 1,maxcpus=4 \
>>     -monitor telnet:127.0.0.1:4444,server,nowait -nographic
>> * connect monitor:      telnet 127.0.0.1 4444
>> * execute qmp command:  cpu-add 1
> cpu-add command shouldn't be used for new cpu hotplug,
> pls use generic device_add for that.

Ok,  I will drop this command and look at device_add.

>
> The last time I looked at it, virt machine needed quite a bit of
> re-factoring of the way it creates/wires up CPUs.

 Yes, I am looking into it and see if I can do something:)

>
> Pls see usage of following callbacks for example on how to implement
> device_add based cpu hotplug:
>
>   get_hotplug_handler
>   pc_cpu_pre_plug
>   pc_cpu_plug
>   pc_possible_cpu_arch_ids
>
> and pc_cpus_init() for initial cpu creation with above callbacks in use
>
Thanks, I will see it. :)

>>
>> Currently, when KVM is enabled and add a CPU with QMP command, QEMU
>> reports error "kvm_init_vcpu failed: Device or resourc busy". KVM can't
>> create a new CPU when vgic has been initialized and irqchip_in_kernel in
>> function kvm_arch_vcpu_create. It needs to change KVM code in the future.
> if KVM isn't capable do it yet, then qemu should refuse cpu hotplug if running
> with KVM accelarator and allow it only in TCG mode.

OK, I will add an assertion to allow hotplug only in TCG mode.

>
>>
>> Li Zhang (3):
>>   arm/virt: Refine fdt_add_cpu_nodes code
>>   arm/virt: Refine code of machvirt_init
>>   arm/virt: Implement hot_add_cpu interface
>>
>>  hw/arm/virt.c | 344 
>> ++++++++++++++++++++++++++++++++++------------------------
>>  1 file changed, 202 insertions(+), 142 deletions(-)
>>
>



-- 

Best Regards
-Li