Return zero for success for now. Prepare for non-zero return
in the next few patches.

Signed-off-by: Si-Wei Liu <si-wei.liu@oracle.com>
---
 hw/virtio/vhost-vdpa.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 2db2832..e0137f0 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -187,16 +187,18 @@ static bool vhost_vdpa_map_batch_begin(VhostVDPAShared *s, uint32_t asid)
     return true;
 }
 
-static void vhost_vdpa_dma_batch_begin_once(VhostVDPAShared *s)
+static int vhost_vdpa_dma_batch_begin_once(VhostVDPAShared *s)
 {
     if (!(s->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH)) ||
         s->iotlb_batch_begin_sent) {
-        return;
+        return 0;
     }
 
     if (vhost_vdpa_map_batch_begin(s, 0)) {
         s->iotlb_batch_begin_sent = true;
     }
+
+    return 0;
 }
 
 static bool vhost_vdpa_dma_batch_end(VhostVDPAShared *s, uint32_t asid)
@@ -225,19 +227,21 @@ static bool vhost_vdpa_dma_batch_end(VhostVDPAShared *s, uint32_t asid)
     return true;
 }
 
-static void vhost_vdpa_dma_batch_end_once(VhostVDPAShared *s)
+static int vhost_vdpa_dma_batch_end_once(VhostVDPAShared *s)
 {
     if (!(s->backend_cap & (0x1ULL << VHOST_BACKEND_F_IOTLB_BATCH))) {
-        return;
+        return 0;
     }
 
     if (!s->iotlb_batch_begin_sent) {
-        return;
+        return 0;
     }
 
     if (vhost_vdpa_dma_batch_end(s, 0)) {
         s->iotlb_batch_begin_sent = false;
     }
+
+    return 0;
 }
 
 static void vhost_vdpa_listener_commit(MemoryListener *listener)
-- 
1.8.3.1