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

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 18 Feb 2019 09:13:33 +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 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 imammedo@redhat.com]
this provides zero information for a commit reader,
it should go under --- to chagelog
 
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> CC: Igor Mammedov <imammedo@redhat.com>
> CC: Eric Blake <eblake@redhat.com>
> 
> ---
> v2:
>    * rephrase change log
one usually adds commenter's name here
   * like this (someone@foo.bar)
or
   * (someone@foo.bar)
     - entry 1
     - entry 2
   * (someone-else@foo.bar)
     - ...

>    * 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

> +{
> +    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,