pc: Make device_del CPU work for x86 CPUs

ACPI subsystem already has all logic in place the only
thing left to eject CPU is destroy it and ammend
present CPUs counter in CMOS, do so.
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>
Reviewed-by: NMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

hw/i386/pc.c

@@ -1847,6 +1847,7 @@ static void pc_cpu_unplug_request_cb(HotplugHandler *hotplug_dev,
 static void pc_cpu_unplug_cb(HotplugHandler *hotplug_dev,
                              DeviceState *dev, Error **errp)
 {
+    CPUArchId *found_cpu;
     HotplugHandlerClass *hhc;
     Error *local_err = NULL;
     PCMachineState *pcms = PC_MACHINE(hotplug_dev);
@@ -1858,13 +1859,11 @@ static void pc_cpu_unplug_cb(HotplugHandler *hotplug_dev,
         goto out;
     }
 
-    /*
-     * TODO: enable unplug once generic CPU remove bits land
-     * for now guest will be able to eject CPU ACPI wise but
-     * it will come back again on machine reset.
-     */
-    /*  object_unparent(OBJECT(dev)); */
+    found_cpu = pc_find_cpu_slot(pcms, CPU(dev), NULL);
+    found_cpu->cpu = NULL;
+    object_unparent(OBJECT(dev));
 
+    rtc_set_memory(pcms->rtc, 0x5f, rtc_get_memory(pcms->rtc, 0x5f) - 1);
  out:
     error_propagate(errp, local_err);
 }