cpu: Introduce CPU hot-plug notifier

Hot-add CPU event will be distributed to acpi_piix4 and rtc_cmos.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
diff --git a/qom/cpu.c b/qom/cpu.c
index b91213e..34fa805 100644
--- a/qom/cpu.c
+++ b/qom/cpu.c
@@ -21,6 +21,17 @@
 #include "qom/cpu.h"
 #include "qemu-common.h"
 #include "sysemu/kvm.h"
+#include "qemu/notify.h"
+#include "sysemu/sysemu.h"
+
+/* CPU hot-plug notifiers */
+static NotifierList cpu_added_notifiers =
+    NOTIFIER_LIST_INITIALIZER(cpu_add_notifiers);
+
+void qemu_register_cpu_added_notifier(Notifier *notifier)
+{
+    notifier_list_add(&cpu_added_notifiers, notifier);
+}
 
 void cpu_reset_interrupt(CPUState *cpu, int mask)
 {
@@ -62,6 +73,7 @@
 
     if (dev->hotplugged) {
         cpu_synchronize_post_init(cpu);
+        notifier_list_notify(&cpu_added_notifiers, dev);
         cpu_resume(cpu);
     }
 }