Re: [Qemu-devel] [PATCH v5] i386, acpi: check acpi_memory_hotplug capacity in pre_plug

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

On Mon, Feb 25, 2019 at 09:15:34AM +0800, Wei Yang wrote:
>On Mon, Feb 25, 2019 at 09:07:08AM +0800, Wei Yang 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 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>
>>Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
>>
>>---
>>v5:
>>   * rebase on latest upstream
>>   * remove a comment before hotplug_handler_pre_plug
>>   * fix alignment for ich9_pm_device_pre_plug_cb
>>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        | 13 ++++++++++---
>> hw/i386/pc.c           |  2 ++
>> hw/isa/lpc_ich9.c      |  1 +
>> include/hw/acpi/ich9.h |  2 ++
>> 5 files changed, 28 insertions(+), 5 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 df8c0db909..8b9654e437 100644
>>--- a/hw/acpi/piix4.c
>>+++ b/hw/acpi/piix4.c
>>@@ -374,9 +374,16 @@ static void piix4_pm_powerdown_req(Notifier *n, void *opaque)
>> static void piix4_device_pre_plug_cb(HotplugHandler *hotplug_dev,
>>                                     DeviceState *dev, Error **errp)
>

Where will we invoke this check for pci devices?

pc_machine_device_pre_plug_cb() seems has no connection with this function. So
how this pre_plug handler takes effect?

Do I miss something?


-- 
Wei Yang
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