Re: [Qemu-ppc] [PATCH v4 04/14] pc: prepare for multi stage hotplug handlers

[David Hildenbrand]

On 30.05.2018 15:08, Igor Mammedov wrote:
> On Thu, 17 May 2018 10:15:17 +0200
> David Hildenbrand <address@hidden> wrote:
> 
>> For multi stage hotplug handlers, we'll have to do some error handling
>> in some hotplug functions, so let's use a local error variable (except
>> for unplug requests).
> I'd split out introducing local error into separate patch
> so patch would do a single thing.
> 
>> Also, add code to pass control to the final stage hotplug handler at the
>> parent bus.
> But I don't agree with generic
>  "} else if (dev->parent_bus && dev->parent_bus->hotplug_handler) {"
> forwarding, it's done by 3/14 for generic case and in case of
> special device that needs bus handler called from machine one,
> I'd suggest to do forwarding explicitly for that device only
> like we do with acpi_dev.

I decided to do it that way because it is generic and results in nicer
recovery handling (e.g. in case pc_dimm plug fails, we can simply
rollback all (for now MemoryDevice) previous plug operations).

IMHO, the resulting code is easier to read.

>From this handling it is clear that
"if we reach the hotplug handler, and it is not some special device
plugged by the machine (CPU, PC_DIMM), pass it on to the actual hotplug
handler if any exists"

> 
> 
>> Signed-off-by: David Hildenbrand <address@hidden>
>> ---
>>  hw/i386/pc.c | 39 +++++++++++++++++++++++++++++++--------
>>  1 file changed, 31 insertions(+), 8 deletions(-)
>>
>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> index d768930d02..510076e156 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -2007,19 +2007,32 @@ static void pc_cpu_pre_plug(HotplugHandler 
>> *hotplug_dev,
>>  static void pc_machine_device_pre_plug_cb(HotplugHandler *hotplug_dev,
>>                                            DeviceState *dev, Error **errp)
>>  {
>> +    Error *local_err = NULL;
>> +
>> +    /* final stage hotplug handler */
>>      if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>> -        pc_cpu_pre_plug(hotplug_dev, dev, errp);
>> +        pc_cpu_pre_plug(hotplug_dev, dev, &local_err);
>> +    } else if (dev->parent_bus && dev->parent_bus->hotplug_handler) {
>> +        hotplug_handler_pre_plug(dev->parent_bus->hotplug_handler, dev,
>> +                                 &local_err);
>>      }
>> +    error_propagate(errp, local_err);
>>  }
>>  
>>  static void pc_machine_device_plug_cb(HotplugHandler *hotplug_dev,
>>                                        DeviceState *dev, Error **errp)
>>  {
>> +    Error *local_err = NULL;
>> +
>> +    /* final stage hotplug handler */
>>      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>> -        pc_dimm_plug(hotplug_dev, dev, errp);
>> +        pc_dimm_plug(hotplug_dev, dev, &local_err);
>>      } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>> -        pc_cpu_plug(hotplug_dev, dev, errp);
>> +        pc_cpu_plug(hotplug_dev, dev, &local_err);
>> +    } else if (dev->parent_bus && dev->parent_bus->hotplug_handler) {
>> +        hotplug_handler_plug(dev->parent_bus->hotplug_handler, dev, 
>> &local_err);
>>      }
>> +    error_propagate(errp, local_err);
>>  }
>>  
>>  static void pc_machine_device_unplug_request_cb(HotplugHandler *hotplug_dev,
>> @@ -2029,7 +2042,10 @@ static void 
>> pc_machine_device_unplug_request_cb(HotplugHandler *hotplug_dev,
>>          pc_dimm_unplug_request(hotplug_dev, dev, errp);
>>      } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>>          pc_cpu_unplug_request_cb(hotplug_dev, dev, errp);
>> -    } else {
>> +    } else if (dev->parent_bus && dev->parent_bus->hotplug_handler) {
>> +        hotplug_handler_unplug_request(dev->parent_bus->hotplug_handler, 
>> dev,
>> +                                       errp);
>> +    } else if (!dev->parent_bus) {
>>          error_setg(errp, "acpi: device unplug request for not supported 
>> device"
>>                     " type: %s", object_get_typename(OBJECT(dev)));
>>      }
>> @@ -2038,14 +2054,21 @@ static void 
>> pc_machine_device_unplug_request_cb(HotplugHandler *hotplug_dev,
>>  static void pc_machine_device_unplug_cb(HotplugHandler *hotplug_dev,
>>                                          DeviceState *dev, Error **errp)
>>  {
>> +    Error *local_err = NULL;
>> +
>> +    /* final stage hotplug handler */
>>      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>> -        pc_dimm_unplug(hotplug_dev, dev, errp);
>> +        pc_dimm_unplug(hotplug_dev, dev, &local_err);
>>      } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>> -        pc_cpu_unplug_cb(hotplug_dev, dev, errp);
>> -    } else {
>> -        error_setg(errp, "acpi: device unplug for not supported device"
>> +        pc_cpu_unplug_cb(hotplug_dev, dev, &local_err);
>> +    } else if (dev->parent_bus && dev->parent_bus->hotplug_handler) {
>> +        hotplug_handler_unplug(dev->parent_bus->hotplug_handler, dev,
>> +                               &local_err);
>> +    } else if (!dev->parent_bus) {
>> +        error_setg(&local_err, "acpi: device unplug for not supported 
>> device"
>>                     " type: %s", object_get_typename(OBJECT(dev)));
>>      }
>> +    error_propagate(errp, local_err);
>>  }
>>  
>>  static HotplugHandler *pc_get_hotpug_handler(MachineState *machine,
> 


-- 

Thanks,

David / dhildenb