[v5,05/10] migration: move global_state.optional out

diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index 46a2bc4..3b51297 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -318,7 +318,6 @@  static void pc_compat_2_3(MachineState *machine)
     if (kvm_enabled()) {
         pcms->smm = ON_OFF_AUTO_OFF;
     }
-    global_state_set_optional();
     savevm_skip_configuration();
 }
 
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index e877d45..edbdbfd 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -3580,7 +3580,6 @@  static void spapr_machine_2_3_instance_options(MachineState *machine)
 {
     spapr_machine_2_4_instance_options(machine);
     savevm_skip_section_footers();
-    global_state_set_optional();
     savevm_skip_configuration();
 }
 
diff --git a/hw/xen/xen-common.c b/hw/xen/xen-common.c
index d3fa705..9163a0a 100644
--- a/hw/xen/xen-common.c
+++ b/hw/xen/xen-common.c
@@ -139,19 +139,28 @@  static int xen_init(MachineState *ms)
     }
     qemu_add_vm_change_state_handler(xen_change_state_handler, NULL);
 
-    global_state_set_optional();
     savevm_skip_configuration();
     savevm_skip_section_footers();
 
     return 0;
 }
 
+GlobalProperty xen_compat_props[] = {
+    {
+        .driver = "migration",
+        .property = "store-global-state",
+        .value = "off",
+    },
+    { .driver = NULL, .property = NULL, .value = NULL },
+};
+
 static void xen_accel_class_init(ObjectClass *oc, void *data)
 {
     AccelClass *ac = ACCEL_CLASS(oc);
     ac->name = "Xen";
     ac->init_machine = xen_init;
     ac->allowed = &xen_allowed;
+    ac->global_props = xen_compat_props;
 }
 
 #define TYPE_XEN_ACCEL ACCEL_CLASS_NAME("xen")
diff --git a/include/hw/compat.h b/include/hw/compat.h
index 26cd585..a506a74 100644
--- a/include/hw/compat.h
+++ b/include/hw/compat.h
@@ -181,6 +181,10 @@ 
         .driver   = TYPE_PCI_DEVICE,\
         .property = "x-pcie-lnksta-dllla",\
         .value    = "off",\
+    },{\
+        .driver   = "migration",\
+        .property = "store-global-state",\
+        .value    = "off",\
     },
 
 #define HW_COMPAT_2_2 \
diff --git a/include/migration/global_state.h b/include/migration/global_state.h
index 90faea7..d307de8 100644
--- a/include/migration/global_state.h
+++ b/include/migration/global_state.h
@@ -16,7 +16,6 @@ 
 #include "sysemu/sysemu.h"
 
 void register_global_state(void);
-void global_state_set_optional(void);
 int global_state_store(void);
 void global_state_store_running(void);
 bool global_state_received(void);
diff --git a/migration/global_state.c b/migration/global_state.c
index f792cf5..dcbbcb2 100644
--- a/migration/global_state.c
+++ b/migration/global_state.c
@@ -15,12 +15,12 @@ 
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "qapi/util.h"
+#include "migration.h"
 #include "migration/global_state.h"
 #include "migration/vmstate.h"
 #include "trace.h"
 
 typedef struct {
-    bool optional;
     uint32_t size;
     uint8_t runstate[100];
     RunState state;
@@ -57,11 +57,6 @@  RunState global_state_get_runstate(void)
     return global_state.state;
 }
 
-void global_state_set_optional(void)
-{
-    global_state.optional = true;
-}
-
 static bool global_state_needed(void *opaque)
 {
     GlobalState *s = opaque;
@@ -69,7 +64,7 @@  static bool global_state_needed(void *opaque)
 
     /* If it is not optional, it is mandatory */
 
-    if (s->optional == false) {
+    if (migrate_get_current()->store_global_state) {
         return true;
     }
 
diff --git a/migration/migration.c b/migration/migration.c
index 2c25927..221b22c 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1976,11 +1976,18 @@  void migrate_fd_connect(MigrationState *s)
     s->migration_thread_running = true;
 }
 
+static Property migration_properties[] = {
+    DEFINE_PROP_BOOL("store-global-state", MigrationState,
+                     store_global_state, true),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
 static void migration_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
 
     dc->user_creatable = false;
+    dc->props = migration_properties;
 }
 
 static void migration_instance_init(Object *obj)
diff --git a/migration/migration.h b/migration/migration.h
index 3fca364..4b898e9 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -133,6 +133,12 @@  struct MigrationState
     /* Do we have to clean up -b/-i from old migrate parameters */
     /* This feature is deprecated and will be removed */
     bool must_remove_block_options;
+
+    /*
+     * Global switch on whether we need to store the global state
+     * during migration.
+     */
+    bool store_global_state;
 };
 
 void migrate_set_state(int *state, int old_state, int new_state);