Re: [Qemu-devel] [PATCH v2] i386, acpi: check acpi_memory_hotplug capacity in pre_plug

[Wei Yang]

On Mon, Feb 18, 2019 at 10:50:34AM +0100, Igor Mammedov wrote:
>On Mon, 18 Feb 2019 09:13:33 +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 should allocate necessary
>> resources and check if memory-hotplug-support property is enabled.
>> 
>> At the piix4 and ich9, the acpi_memory_hotplug property is checked in
>                             ^^^^^^^ is field name and not a property so
>s/acpi_memory_hotplug/memory-hotplug-support/
>s/in/at/
>
>> plug stage. This means 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).
>
>
>> This patch abstract the check on acpi_memory_hotplug capacity in
>> pre_plug stage.
>maybe better would be:
>"Fix it by checking if memory hotplug is enabled at pre_plug stage
>where we can gracefully abort hotplug request."
>
>> [changelog rephrase from address@hidden
>this provides zero information for a commit reader,
>it should go under --- to chagelog
> 

Ok, maybe different community has different convention.

Linux kernel mm subsystem maintainer suggest me to add above line.

>> Signed-off-by: Wei Yang <address@hidden>
>> CC: Igor Mammedov <address@hidden>
>> CC: Eric Blake <address@hidden>
>> 
>> ---
>> v2:
>>    * rephrase change log
>one usually adds commenter's name here
>   * like this (address@hidden)
>or
>   * (address@hidden)
>     - entry 1
>     - entry 2
>   * (address@hidden)
>     - ...
>

Well, I would change to this style.

>>    * apply this change to ich9
>>    * use hotplug_handler_pre_plug() instead of open-coding check
>> ---
>>  hw/acpi/ich9.c         | 14 ++++++++++++--
>>  hw/acpi/piix4.c        | 14 ++++++++++++--
>>  hw/i386/pc.c           |  5 +++++
>>  hw/isa/lpc_ich9.c      |  1 +
>>  include/hw/acpi/ich9.h |  2 ++
>>  5 files changed, 32 insertions(+), 4 deletions(-)
>> 
>> diff --git a/hw/acpi/ich9.c b/hw/acpi/ich9.c
>> index c5d8646abc..906a10f09a 100644
>> --- a/hw/acpi/ich9.c
>> +++ b/hw/acpi/ich9.c
>> @@ -483,13 +483,23 @@ void ich9_pm_add_properties(Object *obj, ICH9LPCPMRegs 
>> *pm, Error **errp)
>>                               NULL);
>>  }
>>  
>> +void ich9_pm_device_pre_plug_cb(HotplugHandler *hotplug_dev, DeviceState 
>> *dev,
>> +                            Error **errp)
>broken alignment?
>
>run /scripts/checkpatch.pl on patches before submitting them

I copied this from ich9_pm_device_plug_cb(), so thought this is the
correct style.

Will adjust this according to checkpatch.pl.

>
>> +{
>> +    ICH9LPCState *lpc = ICH9_LPC_DEVICE(hotplug_dev);
>> +
>> +    if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) &&
>> +        !lpc->pm.acpi_memory_hotplug.is_enabled)
>> +        error_setg(errp,
>> +            "memory hotplug is not enabled: ICH9 memory hotplug disabled");
>I'd give a hint where it's disabled, something like
>
>"memory hotplug is not enabled: %s.memory-hotplug-support is not set", 
>object_get_typename(lpc)
>
>the same for piix4
>
>> +}
>> +
>>  void ich9_pm_device_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
>>                              Error **errp)
>>  {
>>      ICH9LPCState *lpc = ICH9_LPC_DEVICE(hotplug_dev);
>>  
>> -    if (lpc->pm.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 {
>> 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..59c8ccf0ff 100644
>> --- a/hw/i386/pc.c
>> +++ b/hw/i386/pc.c
>> @@ -1674,6 +1674,11 @@ static void pc_memory_pre_plug(HotplugHandler 
>> *hotplug_dev, DeviceState *dev,
>>          return;
>>      }
>>  
>> +    /*
>> +     * Check acpi_dev memory-hotplug-support property
>> +     */
>> +    hotplug_handler_pre_plug(pcms->acpi_dev, dev, errp);
>> +
>>      if (is_nvdimm && !pcms->acpi_nvdimm_state.is_enabled) {
>>          error_setg(errp, "nvdimm is not enabled: missing 'nvdimm' in '-M'");
>>          return;
>> diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
>> index e692b9fdc1..ac44aa53be 100644
>> --- a/hw/isa/lpc_ich9.c
>> +++ b/hw/isa/lpc_ich9.c
>> @@ -805,6 +805,7 @@ static void ich9_lpc_class_init(ObjectClass *klass, void 
>> *data)
>>       * pc_q35_init()
>>       */
>>      dc->user_creatable = false;
>> +    hc->pre_plug = ich9_pm_device_pre_plug_cb;
>>      hc->plug = ich9_pm_device_plug_cb;
>>      hc->unplug_request = ich9_pm_device_unplug_request_cb;
>>      hc->unplug = ich9_pm_device_unplug_cb;
>> diff --git a/include/hw/acpi/ich9.h b/include/hw/acpi/ich9.h
>> index 59aeb06393..428af0b0be 100644
>> --- a/include/hw/acpi/ich9.h
>> +++ b/include/hw/acpi/ich9.h
>> @@ -74,6 +74,8 @@ extern const VMStateDescription vmstate_ich9_pm;
>>  
>>  void ich9_pm_add_properties(Object *obj, ICH9LPCPMRegs *pm, Error **errp);
>>  
>> +void ich9_pm_device_pre_plug_cb(HotplugHandler *hotplug_dev, DeviceState 
>> *dev,
>> +                            Error **errp);
>>  void ich9_pm_device_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev,
>>                              Error **errp);
>>  void ich9_pm_device_unplug_request_cb(HotplugHandler *hotplug_dev,
>

-- 
Wei Yang
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