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, 3 insertions, 1 deletions

diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
index 49e0022533..5ec1c6a2a2 100644
--- a/hw/virtio/vhost-vsock.c
+++ b/hw/virtio/vhost-vsock.c
@@ -254,13 +254,15 @@ static void vhost_vsock_post_load_timer_cb(void *opaque)
     vhost_vsock_send_transport_reset(vsock);
 }
 
-static void vhost_vsock_pre_save(void *opaque)
+static int vhost_vsock_pre_save(void *opaque)
 {
     VHostVSock *vsock = opaque;
 
     /* At this point, backend must be stopped, otherwise
      * it might keep writing to memory. */
     assert(!vsock->vhost_dev.started);
+
+    return 0;
 }
 
 static int vhost_vsock_post_load(void *opaque, int version_id)