migration: pre_save return int

Modify the pre_save method on VMStateDescription to return an int
rather than void so that it potentially can fail.

Changed zillions of devices to make them return 0; the only
case I've made it return non-0 is hw/intc/s390_flic_kvm.c that already
had an error_report/return case.

Note: If you add an error exit in your pre_save you must emit
an error_report to say why.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <20170925112917.21340-2-dgilbert@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

3 files changed, 9 insertions, 3 deletions

diff --git a/migration/colo-comm.c b/migration/colo-comm.c
index b61aa19..df26e4d 100644
--- a/migration/colo-comm.c
+++ b/migration/colo-comm.c
@@ -34,11 +34,13 @@ COLOMode get_colo_mode(void)
     }
 }
 
-static void colo_info_pre_save(void *opaque)
+static int colo_info_pre_save(void *opaque)
 {
     COLOInfo *s = opaque;
 
     s->colo_requested = migrate_colo_enabled();
+
+    return 0;
 }
 
 static bool colo_info_need(void *opaque)
diff --git a/migration/global_state.c b/migration/global_state.c
index dfdaf63..8e8ab5c 100644
--- a/migration/global_state.c
+++ b/migration/global_state.c
@@ -101,12 +101,14 @@ static int global_state_post_load(void *opaque, int version_id)
     return 0;
 }
 
-static void global_state_pre_save(void *opaque)
+static int global_state_pre_save(void *opaque)
 {
     GlobalState *s = opaque;
 
     trace_migrate_global_state_pre_save((char *)s->runstate);
     s->size = strlen((char *)s->runstate) + 1;
+
+    return 0;
 }
 
 static const VMStateDescription vmstate_globalstate = {
diff --git a/migration/savevm.c b/migration/savevm.c
index 2478352..e9feade 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -312,7 +312,7 @@ static SaveState savevm_state = {
     .global_section_id = 0,
 };
 
-static void configuration_pre_save(void *opaque)
+static int configuration_pre_save(void *opaque)
 {
     SaveState *state = opaque;
     const char *current_name = MACHINE_GET_CLASS(current_machine)->name;
@@ -320,6 +320,8 @@ static void configuration_pre_save(void *opaque)
     state->len = strlen(current_name);
     state->name = current_name;
     state->target_page_bits = qemu_target_page_bits();
+
+    return 0;
 }
 
 static int configuration_pre_load(void *opaque)