diff --git a/docs/devel/migration/main.rst b/docs/devel/migration/main.rst
index 784c899dca..c2857fc244 100644
--- a/docs/devel/migration/main.rst
+++ b/docs/devel/migration/main.rst
@@ -465,6 +465,12 @@ Examples of such API functions are:
   - portio_list_set_address()
   - portio_list_set_enabled()
 
+Since the order of device save/restore is not defined, you must
+avoid accessing or changing any other device's state in one of these
+callbacks. (For instance, don't do anything that calls ``update_irq()``
+in a ``post_load`` hook.) Otherwise, restore will not be deterministic,
+and this will break execution record/replay.
+
 Iterative device migration
 --------------------------
 
diff --git a/docs/devel/replay.rst b/docs/devel/replay.rst
index effd856f0c..40f58d9d4f 100644
--- a/docs/devel/replay.rst
+++ b/docs/devel/replay.rst
@@ -202,6 +202,9 @@ into the log.
 Saving/restoring the VM state
 -----------------------------
 
+Record/replay relies on VM state save and restore being complete and
+deterministic.
+
 All fields in the device state structure (including virtual timers)
 should be restored by loadvm to the same values they had before savevm.