[Qemu-devel] [PATCH] register_savevm etc.: make save function optional

[Ian Jackson]

    register_savevm etc.: make save function optional
    
    This allows a device to provide only a loading function, not a saving
    function.
    
    This is useful if a later version of an emulation restores its state
    in some other way (eg by having a different device name, or by
    exploiting invariants in the state); when this happens it is still
    necessary to load or skip the information when it is found in old
    savefiles.
    
    Signed-off-by: Ian Jackson <address@hidden>

diff --git a/vl.c b/vl.c
index 67712f0..3a9135c 100644
--- a/vl.c
+++ b/vl.c
@@ -5988,6 +5988,10 @@ static int qemu_savevm_state(QEMUFile *f)
     qemu_put_be64(f, 0); /* total size */
 
     for(se = first_se; se != NULL; se = se->next) {
+       if (se->save_state == NULL)
+           /* this one has a loader only, for backwards compatibility */
+           continue;
+
         /* ID string */
         len = strlen(se->idstr);
         qemu_put_byte(f, len);