Add basic cpu hotplug interface framework, cpu hotplug interface is
stub function and only framework is added here.

Co-developed-by: Xianglai Li <lixianglai@loongson.cn>
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
---
 hw/loongarch/virt.c    | 29 +++++++++++++++++++++++++++++
 target/loongarch/cpu.c | 13 +++++++++++++
 target/loongarch/cpu.h |  1 +
 3 files changed, 43 insertions(+)

diff --git a/hw/loongarch/virt.c b/hw/loongarch/virt.c
index 2bbbbbfbcf..2b4b60f718 100644
--- a/hw/loongarch/virt.c
+++ b/hw/loongarch/virt.c
@@ -816,6 +816,26 @@ static int virt_get_arch_id_from_topo(MachineState *ms, LoongArchCPUTopo *topo)
     return arch_id;
 }
 
+static void virt_cpu_pre_plug(HotplugHandler *hotplug_dev,
+                              DeviceState *dev, Error **errp)
+{
+}
+
+static void virt_cpu_unplug_request(HotplugHandler *hotplug_dev,
+                                    DeviceState *dev, Error **errp)
+{
+}
+
+static void virt_cpu_unplug(HotplugHandler *hotplug_dev,
+                            DeviceState *dev, Error **errp)
+{
+}
+
+static void virt_cpu_plug(HotplugHandler *hotplug_dev,
+                          DeviceState *dev, Error **errp)
+{
+}
+
 static bool memhp_type_supported(DeviceState *dev)
 {
     /* we only support pc dimm now */
@@ -834,6 +854,8 @@ static void virt_device_pre_plug(HotplugHandler *hotplug_dev,
 {
     if (memhp_type_supported(dev)) {
         virt_mem_pre_plug(hotplug_dev, dev, errp);
+    } else if (object_dynamic_cast(OBJECT(dev), TYPE_LOONGARCH_CPU)) {
+        virt_cpu_pre_plug(hotplug_dev, dev, errp);
     }
 }
 
@@ -852,6 +874,8 @@ static void virt_device_unplug_request(HotplugHandler *hotplug_dev,
 {
     if (memhp_type_supported(dev)) {
         virt_mem_unplug_request(hotplug_dev, dev, errp);
+    } else if (object_dynamic_cast(OBJECT(dev), TYPE_LOONGARCH_CPU)) {
+        virt_cpu_unplug_request(hotplug_dev, dev, errp);
     }
 }
 
@@ -870,6 +894,8 @@ static void virt_device_unplug(HotplugHandler *hotplug_dev,
 {
     if (memhp_type_supported(dev)) {
         virt_mem_unplug(hotplug_dev, dev, errp);
+    } else if (object_dynamic_cast(OBJECT(dev), TYPE_LOONGARCH_CPU)) {
+        virt_cpu_unplug(hotplug_dev, dev, errp);
     }
 }
 
@@ -897,6 +923,8 @@ static void virt_device_plug_cb(HotplugHandler *hotplug_dev,
         }
     } else if (memhp_type_supported(dev)) {
         virt_mem_plug(hotplug_dev, dev, errp);
+    } else if (object_dynamic_cast(OBJECT(dev), TYPE_LOONGARCH_CPU)) {
+        virt_cpu_plug(hotplug_dev, dev, errp);
     }
 }
 
@@ -906,6 +934,7 @@ static HotplugHandler *virt_get_hotplug_handler(MachineState *machine,
     MachineClass *mc = MACHINE_GET_CLASS(machine);
 
     if (device_is_dynamic_sysbus(mc, dev) ||
+        object_dynamic_cast(OBJECT(dev), TYPE_LOONGARCH_CPU) ||
         object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_IOMMU_PCI) ||
         memhp_type_supported(dev)) {
         return HOTPLUG_HANDLER(machine);
diff --git a/target/loongarch/cpu.c b/target/loongarch/cpu.c
index df76ab66d5..8b99b8def4 100644
--- a/target/loongarch/cpu.c
+++ b/target/loongarch/cpu.c
@@ -647,6 +647,17 @@ static void loongarch_cpu_realizefn(DeviceState *dev, Error **errp)
     lacc->parent_realize(dev, errp);
 }
 
+static void loongarch_cpu_unrealizefn(DeviceState *dev)
+{
+    LoongArchCPUClass *lacc = LOONGARCH_CPU_GET_CLASS(dev);
+
+#ifndef CONFIG_USER_ONLY
+    cpu_remove_sync(CPU(dev));
+#endif
+
+    lacc->parent_unrealize(dev);
+}
+
 static bool loongarch_get_lsx(Object *obj, Error **errp)
 {
     return LOONGARCH_CPU(obj)->lsx != ON_OFF_AUTO_OFF;
@@ -897,6 +908,8 @@ static void loongarch_cpu_class_init(ObjectClass *c, void *data)
     device_class_set_props(dc, loongarch_cpu_properties);
     device_class_set_parent_realize(dc, loongarch_cpu_realizefn,
                                     &lacc->parent_realize);
+    device_class_set_parent_unrealize(dc, loongarch_cpu_unrealizefn,
+                                      &lacc->parent_unrealize);
     resettable_class_set_parent_phases(rc, NULL, loongarch_cpu_reset_hold, NULL,
                                        &lacc->parent_phases);
 
diff --git a/target/loongarch/cpu.h b/target/loongarch/cpu.h
index 677100bd42..eae874c67b 100644
--- a/target/loongarch/cpu.h
+++ b/target/loongarch/cpu.h
@@ -439,6 +439,7 @@ struct LoongArchCPUClass {
     CPUClass parent_class;
 
     DeviceRealize parent_realize;
+    DeviceUnrealize parent_unrealize;
     ResettablePhases parent_phases;
 };
 
-- 
2.43.5