Re: [Qemu-devel] [PATCH 4/5] pc: add cpu hotplug handler to PC_MACHINE

[Gu Zheng <guz.fnst@cn.fujitsu.com>]

Hi Igor,
On 09/10/2014 09:55 PM, Igor Mammedov wrote:

> On Wed,  3 Sep 2014 17:06:16 +0800
> Gu Zheng <guz.fnst@cn.fujitsu.com> wrote:
> 
>> Add cpu hotplug handler to PC_MACHINE, which will perform the acpi
>> cpu hotplug callback via hotplug_handler API.
>>
>> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
>> ---
>>  hw/i386/pc.c |   26 +++++++++++++++++++++++++-
>>  qom/cpu.c    |    1 -
>>  2 files changed, 25 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> index 8fa8d2f..c2956f9 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -1607,11 +1607,34 @@ 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 (dev->hotplugged) {
> for startup CPUs we set gpe_cpu status bits in AcpiCpuHotplug_init()
> and for hotpluged in AcpiCpuHotplug_add() which is duplicating
> essentially the same code.
> 
> Could you drop above check and make AcpiCpuHotplug_init() take care
> about startup CPUs as well, keeping bit setting in one place.

Yeah, with the above change, code will be more neat, but I think it is not
a serious problem.:)
And pcms->acpi_dev is set when PC hardware initialisation (e.g. pc_init1),
for start up cpus, the plug handler is not valid, so the check is needed
here to avoid trigger error by start cpu.

> 
>> +        if (!pcms->acpi_dev) {
>> +            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);
>> +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);
>>      }
>>  }
>>  
>> @@ -1620,7 +1643,8 @@ 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);
>>      }
>>  
>> diff --git a/qom/cpu.c b/qom/cpu.c
>> index b32dd0a..af8e83f 100644
>> --- a/qom/cpu.c
>> +++ b/qom/cpu.c
>> @@ -304,7 +304,6 @@ static void cpu_common_realizefn(DeviceState *dev, Error **errp)
>>      if (dev->hotplugged) {
>>          cpu_synchronize_post_init(cpu);
>>          notifier_list_notify(&cpu_added_notifiers, dev);
>> -        cpu_resume(cpu);
>>      }
>>  }
>>  
> 
> I don't see what sets PCMachine as hotplug_handler for CPU,
> maybe series is missing a patch?

Previous memory hotplug has built the frame work, here just adding the case
to handle CPU.

 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);
     }

Thanks,
Gu

> 
> .
>