libxc: provide notification of final checkpoint to restore end

When the restore code sees this notification it will restore the
currently in-progress checkpoint when it completes.

This allows the restore end to finish up without waiting for a
spurious timeout on the receive fd and thereby avoids unnecessary
error logging in the case of a successful migration or restore.

In the normal migration or restore case the first checkpoint is always
the last. For a rolling checkpoint (such as Remus) the notification is
currently unused but could be used in the future for example to
provide a controlled failover for reasons other than error

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Brendan Cully <brendan@cs.ubc.ca>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/tools/libxc/xc_domain_save.c b/tools/libxc/xc_domain_save.c
index ef33fa1134..15c4da3cba 100644
--- a/tools/libxc/xc_domain_save.c
+++ b/tools/libxc/xc_domain_save.c
@@ -1616,6 +1616,20 @@ int xc_domain_save(xc_interface *xch, int io_fd, uint32_t dom, uint32_t max_iter
         }
     }
 
+    if ( !callbacks->checkpoint )
+    {
+        /*
+         * If this is not a checkpointed save then this must be the first and
+         * last checkpoint.
+         */
+        i = XC_SAVE_ID_LAST_CHECKPOINT;
+        if ( wrexact(io_fd, &i, sizeof(int)) )
+        {
+            PERROR("Error when writing last checkpoint chunk");
+            goto out;
+        }
+    }
+
     /* Zero terminate */
     i = 0;
     if ( wrexact(io_fd, &i, sizeof(int)) )