s390x/flic: fail migration on source already

Current code puts a 'FLIC_FAILED' marker into the migration stream
to indicate something went wrong while saving flic state and fails
load if it encounters that marker. VMState's put routine recently
gained the ability to return error codes (but did not wire it up
yet).

In order to be able to reap the benefits of returning an error and
failing migration on the source already once this gets wired up
in core, return an error in addition to storing 'FLIC_FAILED'.
Suggested-by: NDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: NJens Freimann <jfrei@linux.vnet.ibm.com>
Reviewed-by: NChristian Borntraeger <borntraeger@de.ibm.com>

hw/intc/s390_flic_kvm.c

@@ -293,6 +293,7 @@ static int kvm_flic_save(QEMUFile *f, void *opaque, size_t size,
     int len = FLIC_SAVE_INITIAL_SIZE;
     void *buf;
     int count;
+    int r = 0;
 
     flic_disable_wait_pfault((struct KVMS390FLICState *) opaque);
 
@@ -303,7 +304,7 @@ static int kvm_flic_save(QEMUFile *f, void *opaque, size_t size,
          * migration state */
         error_report("flic: couldn't allocate memory");
         qemu_put_be64(f, FLIC_FAILED);
-        return 0;
+        return -ENOMEM;
     }
 
     count = __get_all_irqs(flic, &buf, len);
@@ -314,6 +315,7 @@ static int kvm_flic_save(QEMUFile *f, void *opaque, size_t size,
          * target system to fail when attempting to load irqs from the
          * migration state */
         qemu_put_be64(f, FLIC_FAILED);
+        r = count;
     } else {
         qemu_put_be64(f, count);
         qemu_put_buffer(f, (uint8_t *) buf,
@@ -321,7 +323,7 @@ static int kvm_flic_save(QEMUFile *f, void *opaque, size_t size,
     }
     g_free(buf);
 
-    return 0;
+    return r;
 }
 
 /**