Re: [Qemu-devel] [PATCH] i386, acpi: check acpi_memory_hotplug capacity in pre_plug

[Wei Yang]

On Thu, Feb 14, 2019 at 12:25:27PM +0100, Igor Mammedov wrote:
>On Thu, 14 Feb 2019 08:52:25 +0800
>Wei Yang <address@hidden> wrote:
>
>> Currently we do device realization like below:
>> 
>>    hotplug_handler_pre_plug()
>>    dc->realize()
>>    hotplug_handler_plug()
>> 
>> Before we do device realization and plug, we would allocate necessary
>> resources and check the capacity.
>'capacity' probably is not right word to use here
>maybe s/the capacity/if 'memory-hotplug-support' property is enabled/
>
>> 
>> While we leave acpi_memory_hotplug capacity check in the last step. This
>wouldn't use 'leave' and 'capacity' here either, pls rephrase.
>
>> looks not comply with current architecture and does some unnecessary
>s/looks not/doesn't/
>> work.
>add more explanation about 'unnecessary work'.
>problem as I see it, is that after successful pc_dimm_plug()
>we get into piix4_device_plug_cb() and since
> s->acpi_memory_hotplug.is_enabled == false
>and all other 'if' conditions also false we would endup
>at g_assert_not_reached() causing QEMU crash in piix4 case
>and with error_abort up the call chain in case of ich9.
>

Thanks Igor, I rephrase above change log like this. Does this look
better to you now?

    Before we do device realization and plug, we would allocate
    necessary resources and check if memory-hotplug-support property is
    enabled.
    
    In piix4 and ich9, the acpi_memory_hotplug property is checked in
    plug stage, this doesn't comply with current architecture. This
    means we have prepared everything and even do pc_dimm_plug()
    successfuly, but failed at last because
    acpi_memory_hotplug.is_enabled == false. Which is worse is in piix4,
    this endup at g_assert_not_reached() and cause QEMU crash.


>> This patch abstract the check on acpi_memory_hotplug capacity in
>> pre_plug stage.
>> 
>> Signed-off-by: Wei Yang <address@hidden>
>> ---
>>  hw/acpi/piix4.c | 14 ++++++++++++--
>>  hw/i386/pc.c    |  8 ++++++++
>doesn't look complete, why did you skip on similar code in ich9
>(Q35 machine)?
>

You are right, I missed this part.

>>  2 files changed, 20 insertions(+), 2 deletions(-)
>> 
>> diff --git a/hw/acpi/piix4.c b/hw/acpi/piix4.c
>> index e330f24c71..c97b747496 100644
>> --- a/hw/acpi/piix4.c
>> +++ b/hw/acpi/piix4.c
>> @@ -370,13 +370,22 @@ static void piix4_pm_powerdown_req(Notifier *n, void 
>> *opaque)
>>      acpi_pm1_evt_power_down(&s->ar);
>>  }
>>  
>> +static void piix4_device_pre_plug_cb(HotplugHandler *hotplug_dev,
>> +                                 DeviceState *dev, Error **errp)
>> +{
>> +    PIIX4PMState *s = PIIX4_PM(hotplug_dev);
>> +
>> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) &&
>> +        !s->acpi_memory_hotplug.is_enabled)
>> +        error_setg(errp,
>> +            "memory hotplug is not enabled: PIIX4 memory hotplug disabled");
>> +}
>>  static void piix4_device_plug_cb(HotplugHandler *hotplug_dev,
>>                                   DeviceState *dev, Error **errp)
>>  {
>>      PIIX4PMState *s = PIIX4_PM(hotplug_dev);
>>  
>> -    if (s->acpi_memory_hotplug.is_enabled &&
>> -        object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>>          if (object_dynamic_cast(OBJECT(dev), TYPE_NVDIMM)) {
>>              nvdimm_acpi_plug_cb(hotplug_dev, dev);
>>          } else {
>> @@ -702,6 +711,7 @@ static void piix4_pm_class_init(ObjectClass *klass, void 
>> *data)
>>       */
>>      dc->user_creatable = false;
>>      dc->hotpluggable = false;
>> +    hc->pre_plug = piix4_device_pre_plug_cb;
>>      hc->plug = piix4_device_plug_cb;
>>      hc->unplug_request = piix4_device_unplug_request_cb;
>>      hc->unplug = piix4_device_unplug_cb;
>> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> index 734d3268fa..3c6eed0cd3 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -1662,6 +1662,7 @@ static void pc_memory_pre_plug(HotplugHandler 
>> *hotplug_dev, DeviceState *dev,
>>      const PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms);
>>      const bool is_nvdimm = object_dynamic_cast(OBJECT(dev), TYPE_NVDIMM);
>>      const uint64_t legacy_align = TARGET_PAGE_SIZE;
>> +    HotplugHandlerClass *hhc;
>>  
>>      /*
>>       * When -no-acpi is used with Q35 machine type, no ACPI is built,
>> @@ -1674,6 +1675,13 @@ static void pc_memory_pre_plug(HotplugHandler 
>> *hotplug_dev, DeviceState *dev,
>>          return;
>>      }
>>  
>> +    /*
>> +     * Check acpi_dev memory hotplug capacity
>> +     */
>> +    hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
>> +    if (hcc->pre_plug)
>> +        hhc->pre_plug(HOTPLUG_HANDLER(pcms->acpi_dev), dev, errp);
>use hotplug_handler_pre_plug() instead of open-coding check
>

Thanks, will fix this.

>>      if (is_nvdimm && !pcms->acpi_nvdimm_state.is_enabled) {
>>          error_setg(errp, "nvdimm is not enabled: missing 'nvdimm' in '-M'");
>>          return;
>

-- 
Wei Yang
Help you, Help me