Re: [Qemu-devel] [PATCH V3 4/7] pc: add cpu hotplug handler to PC_MACHINE

[Gu Zheng]

Hi Igor,
On 09/26/2014 09:06 PM, Igor Mammedov wrote:

> On Wed, 17 Sep 2014 09:24:00 +0800
> Gu Zheng <address@hidden> wrote:
> 
>> Add cpu hotplug handler to PC_MACHINE, which will perform the acpi
>> cpu hotplug callback via hotplug_handler API.
>>
>> v3:
>>  -deal with start up cpus in a more neat way as Igor suggested.
>> v2:
>>  -just rebase.
>>
>> Signed-off-by: Gu Zheng <address@hidden>
>> ---
>>  hw/i386/pc.c |   26 +++++++++++++++++++++++++-
>>  1 files changed, 25 insertions(+), 1 deletions(-)
>>
>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> index b6c9b61..e25e71b 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -1613,11 +1613,34 @@ out:
>>      error_propagate(errp, local_err);
>>  }
>>  
>> +static void pc_cpu_plug(HotplugHandler *hotplug_dev,
>> +                        DeviceState *dev, Error **errp)
>> +{
>> +    HotplugHandlerClass *hhc;
>> +    Error *local_err = NULL;
>> +    PCMachineState *pcms = PC_MACHINE(hotplug_dev);
>> +
>> +    if (!pcms->acpi_dev) {
>> +        if (dev->hotplugged) {
>> +            error_setg(&local_err,
>> +                       "cpu hotplug is not enabled: missing acpi device");
>> +        }
>> +        goto out;
>> +    }
>> +
>> +    hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
>> +    hhc->plug(HOTPLUG_HANDLER(pcms->acpi_dev), dev, &local_err);
> above call this would rise SCI unconditionally whether CPU is hotplugged or 
> not.

Above precheck can avoid this, startup CPUs won't run into this: 
    if (!pcms->acpi_dev) {
        if (dev->hotplugged) {
            error_setg(&local_err,
                       "cpu hotplug is not enabled: missing acpi device");
        }
        goto out;
    }

Thanks,
Gu

> perhaps checking for this in acpi_cpu_plug_cb() and rising IRQ only for 
> hotplugged
> CPUs would be better.
> 
>> +out:
>> +    error_propagate(errp, local_err);
>> +}
>> +
>>  static void pc_machine_device_plug_cb(HotplugHandler *hotplug_dev,
>>                                        DeviceState *dev, Error **errp)
>>  {
>>      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>>          pc_dimm_plug(hotplug_dev, dev, errp);
>> +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>> +        pc_cpu_plug(hotplug_dev, dev, errp);
>>      }
>>  }
>>  
>> @@ -1626,7 +1649,8 @@ static HotplugHandler 
>> *pc_get_hotpug_handler(MachineState *machine,
>>  {
>>      PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(machine);
>>  
>> -    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) ||
>> +        object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>>          return HOTPLUG_HANDLER(machine);
>>      }
>>  
> 
> .
>