To indicate to the destination whether or not emulational SCSI
requests are sent, introduce the migrate_emulate_scsi_request
in struct SCSIDiskState. It seeks to achieve migration backend
compatibility.

This commit sets the stage for the next one, which addresses
the crash of a VM configured with a CDROM during live migration.

Signed-off-by: Hyman Huang <yong.huang@smartx.com>
---
 hw/scsi/scsi-disk.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
index 4bd7af9d0c..0985676f73 100644
--- a/hw/scsi/scsi-disk.c
+++ b/hw/scsi/scsi-disk.c
@@ -111,6 +111,7 @@ struct SCSIDiskState {
      * 0xffff        - reserved
      */
     uint16_t rotation_rate;
+    bool migrate_emulate_scsi_request;
 };
 
 static void scsi_free_request(SCSIRequest *req)
@@ -3133,11 +3134,21 @@ static Property scsi_hd_properties[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+static int scsi_disk_pre_save(void *opaque)
+{
+    SCSIDiskState *dev = opaque;
+    dev->migrate_emulate_scsi_request = false;
+
+    return 0;
+}
+
 static const VMStateDescription vmstate_scsi_disk_state = {
     .name = "scsi-disk",
-    .version_id = 1,
+    .version_id = 2,
     .minimum_version_id = 1,
+    .pre_save = scsi_disk_pre_save,
     .fields = (const VMStateField[]) {
+        VMSTATE_BOOL_V(migrate_emulate_scsi_request, SCSIDiskState, 2),
         VMSTATE_SCSI_DEVICE(qdev, SCSIDiskState),
         VMSTATE_BOOL(media_changed, SCSIDiskState),
         VMSTATE_BOOL(media_event, SCSIDiskState),
-- 
2.39.3