[Qemu-devel] [PATCH v4] i386, acpi: check acpi_memory_hotplug capacity in pre_plug

[Wei Yang <richardw.yang@linux.intel.com>]

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 memory-hotplug-support property is checked 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).

Fix it by checking if memory hotplug is enabled at pre_plug stage
where we can gracefully abort hotplug request.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
CC: Igor Mammedov <imammedo@redhat.com>
CC: Eric Blake <eblake@redhat.com>

---
v4:
   * fix code alignment of piix4_device_pre_plug_cb
v3:
   * replace acpi_memory_hotplug with memory-hotplug-support in changelog
   * fix code alignment of ich9_pm_device_pre_plug_cb
   * print which device type memory-hotplug-support is disabled in
     ich9_pm_device_pre_plug_cb and piix4_device_pre_plug_cb
v2:
   * (imammedo@redhat.com)
     - Almost the whole third paragraph
   * apply this change to ich9
   * use hotplug_handler_pre_plug() instead of open-coding check
---
 hw/acpi/ich9.c         | 15 +++++++++++++--
 hw/acpi/piix4.c        | 15 +++++++++++++--
 hw/i386/pc.c           |  5 +++++
 hw/isa/lpc_ich9.c      |  1 +
 include/hw/acpi/ich9.h |  2 ++
 5 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/hw/acpi/ich9.c b/hw/acpi/ich9.c
index c5d8646abc..e53dfe1ee3 100644
--- a/hw/acpi/ich9.c
+++ b/hw/acpi/ich9.c
@@ -483,13 +483,24 @@ 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)
+{
+    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: %s.memory-hotplug-support "
+                   "is not set", object_get_typename(OBJECT(lpc)));
+}
+
 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..699aca630e 100644
--- a/hw/acpi/piix4.c
+++ b/hw/acpi/piix4.c
@@ -370,13 +370,23 @@ 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: %s.memory-hotplug-support "
+                   "is not set", object_get_typename(OBJECT(s)));
+}
 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 +712,7 @@ 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 0f61314b79..0b11ebe2c9 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,
-- 
2.19.1