i386, acpi: check acpi_memory_hotplug capacity in pre_plug

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.

While we leave acpi_memory_hotplug capacity check in the last step. This
looks not comply with current architecture and does some unnecessary
work.

This patch abstract the check on acpi_memory_hotplug capacity in
pre_plug stage.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
---
 hw/acpi/piix4.c | 14 ++++++++++++--
 hw/i386/pc.c    |  8 ++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

On Thu, 14 Feb 2019 08:52:25 +0800
Wei Yang <richardw.yang@linux.intel.com> 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.

> This patch abstract the check on acpi_memory_hotplug capacity in
> pre_plug stage.
> 
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> ---
>  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)?

>  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

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

On Thu, Feb 14, 2019 at 12:25:27PM +0100, Igor Mammedov wrote:
>On Thu, 14 Feb 2019 08:52:25 +0800
>Wei Yang <richardw.yang@linux.intel.com> 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 <richardw.yang@linux.intel.com>
>> ---
>>  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;
>

On Thu, 14 Feb 2019 20:53:31 +0000
Wei Yang <richard.weiyang@gmail.com> wrote:

> On Thu, Feb 14, 2019 at 12:25:27PM +0100, Igor Mammedov wrote:
> >On Thu, 14 Feb 2019 08:52:25 +0800
> >Wei Yang <richardw.yang@linux.intel.com> 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
s/would/should/

>     necessary resources and check if memory-hotplug-support property is
>     enabled.
>     
>     In piix4 and ich9, the acpi_memory_hotplug property is checked in
s/in/at the/
>     plug stage, this doesn't comply with current architecture. This
drop              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>     means we have prepared everything and even do pc_dimm_plug()
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
that device has been realized and mapped into guest address space
'pc_dimm_plug()' by the time acpi plug handler is called, where it might
fail and crash QEMU due to reaching  g_assert_not_reached() (piix4) or
error_abort (ich9).

or something like this, I'm not native speaker either so CC Eric Blake
on next respin so he could check commit message.

>     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 <richardw.yang@linux.intel.com>
> >> ---
> >>  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;
> >
>

On Fri, Feb 15, 2019 at 12:14:32PM +0100, Igor Mammedov wrote:
>On Thu, 14 Feb 2019 20:53:31 +0000
>Wei Yang <richard.weiyang@gmail.com> wrote:
>
>> On Thu, Feb 14, 2019 at 12:25:27PM +0100, Igor Mammedov wrote:
>> >On Thu, 14 Feb 2019 08:52:25 +0800
>> >Wei Yang <richardw.yang@linux.intel.com> 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
>s/would/should/
>
>>     necessary resources and check if memory-hotplug-support property is
>>     enabled.
>>     
>>     In piix4 and ich9, the acpi_memory_hotplug property is checked in
>s/in/at the/
>>     plug stage, this doesn't comply with current architecture. This
>drop              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>     means we have prepared everything and even do pc_dimm_plug()
>            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>that device has been realized and mapped into guest address space
>'pc_dimm_plug()' by the time acpi plug handler is called, where it might
>fail and crash QEMU due to reaching  g_assert_not_reached() (piix4) or
>error_abort (ich9).
>
>or something like this, I'm not native speaker either so CC Eric Blake
>on next respin so he could check commit message.
>

Thanks for your patience and detailed suggestion :-)

>>     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 <richardw.yang@linux.intel.com>
>> >> ---
>> >>  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;
>> >
>>