global_state: Make section optional

This section would be sent:

a- for all new machine types
b- for old machine types if section state is different form {running,paused}
   that were the only giving us troubles.

So, in new qemus: it is alwasy there.  In old qemus: they are only
there if it an error has happened, basically stoping on target.
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Reviewed-by: NDr. David Alan Gilbert <dgilbert@redhat.com>

hw/i386/pc_piix.c

@@ -312,6 +312,7 @@ static void pc_compat_2_3(MachineState *machine)
     if (kvm_enabled()) {
         pcms->smm = ON_OFF_AUTO_OFF;
     }
+    global_state_set_optional();
 }
 
 static void pc_compat_2_2(MachineState *machine)

hw/i386/pc_q35.c

@@ -295,6 +295,7 @@ static void pc_compat_2_3(MachineState *machine)
     if (kvm_enabled()) {
         pcms->smm = ON_OFF_AUTO_OFF;
     }
+    global_state_set_optional();
 }
 
 static void pc_compat_2_2(MachineState *machine)

hw/ppc/spapr.c

@@ -1853,6 +1853,7 @@ static const TypeInfo spapr_machine_info = {
 static void spapr_compat_2_3(Object *obj)
 {
     savevm_skip_section_footers();
+    global_state_set_optional();
 }
 
 static void spapr_compat_2_2(Object *obj)

include/migration/migration.h

@@ -198,4 +198,5 @@ size_t ram_control_save_page(QEMUFile *f, ram_addr_t block_offset,
 void ram_mig_init(void);
 void savevm_skip_section_footers(void);
 void register_global_state(void);
+void global_state_set_optional(void);
 #endif

migration/migration.c

@@ -100,6 +100,7 @@ void migration_incoming_state_destroy(void)
 
 
 typedef struct {
+    bool optional;
     uint32_t size;
     uint8_t runstate[100];
 } GlobalState;
@@ -122,6 +123,33 @@ static char *global_state_get_runstate(void)
     return (char *)global_state.runstate;
 }
 
+void global_state_set_optional(void)
+{
+    global_state.optional = true;
+}
+
+static bool global_state_needed(void *opaque)
+{
+    GlobalState *s = opaque;
+    char *runstate = (char *)s->runstate;
+
+    /* If it is not optional, it is mandatory */
+
+    if (s->optional == false) {
+        return true;
+    }
+
+    /* If state is running or paused, it is not needed */
+
+    if (strcmp(runstate, "running") == 0 ||
+        strcmp(runstate, "paused") == 0) {
+        return false;
+    }
+
+    /* for any other state it is needed */
+    return true;
+}
+
 static int global_state_post_load(void *opaque, int version_id)
 {
     GlobalState *s = opaque;
@@ -161,6 +189,7 @@ static const VMStateDescription vmstate_globalstate = {
     .minimum_version_id = 1,
     .post_load = global_state_post_load,
     .pre_save = global_state_pre_save,
+    .needed = global_state_needed,
     .fields = (VMStateField[]) {
         VMSTATE_UINT32(size, GlobalState),
         VMSTATE_BUFFER(runstate, GlobalState),