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 12:13:24 +0000
Wei Yang <richard.weiyang@gmail.com> wrote:

> On Mon, Feb 18, 2019 at 10:50:34AM +0100, Igor Mammedov wrote:
> >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
> > 
> 
> Ok, maybe different community has different convention.
> 
> Linux kernel mm subsystem maintainer suggest me to add above line.
> 
> >> 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)
> >     - ...
> >
> 
> 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.

see CODING_STYLE

> 
> >
> >> +{
> >> +    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,
> >
>