exec: Do vmstate unregistration from cpu_exec_exit()

cpu_exec_init() does vmstate_register for the CPU device. This needs to be
undone from cpu_exec_exit(). This change is needed to support CPU hot
removal.
Signed-off-by: NBharata B Rao <bharata@linux.vnet.ibm.com>
Reviewed-by: NThomas Huth <thuth@redhat.com>
Reviewed-by: NDavid Gibson <david@gibson.dropbear.id.au>
Acked-by: NPaolo Bonzini <pbonzini@redhat.com>
[dwg: added missing include to fix compile on some archs]
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>

exec.c

@@ -57,6 +57,8 @@
 #include "exec/ram_addr.h"
 #include "exec/log.h"
 
+#include "migration/vmstate.h"
+
 #include "qemu/range.h"
 #ifndef _WIN32
 #include "qemu/mmap-alloc.h"
@@ -637,6 +639,8 @@ static void cpu_release_index(CPUState *cpu)
 
 void cpu_exec_exit(CPUState *cpu)
 {
+    CPUClass *cc = CPU_GET_CLASS(cpu);
+
 #if defined(CONFIG_USER_ONLY)
     cpu_list_lock();
 #endif
@@ -654,6 +658,13 @@ void cpu_exec_exit(CPUState *cpu)
 #if defined(CONFIG_USER_ONLY)
     cpu_list_unlock();
 #endif
+
+    if (cc->vmsd != NULL) {
+        vmstate_unregister(NULL, cc->vmsd, cpu);
+    }
+    if (qdev_get_vmsd(DEVICE(cpu)) == NULL) {
+        vmstate_unregister(NULL, &vmstate_cpu_common, cpu);
+    }
 }
 
 void cpu_exec_init(CPUState *cpu, Error **errp)