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>

1 files changed, 1 insertions, 1 deletions

diff --git a/docs/devel/migration.txt b/docs/devel/migration.txt
index 1b940a829b..4030703726 100644
--- a/docs/devel/migration.txt
+++ b/docs/devel/migration.txt
@@ -202,7 +202,7 @@ The functions to do that are inside a vmstate definition, and are called:
 
   This function is called after we load the state of one device.
 
-- void (*pre_save)(void *opaque);
+- int (*pre_save)(void *opaque);
 
   This function is called before we save the state of one device.