diff --git a/migration/ram.c b/migration/ram.c
index d9336d8a09..ce28328141 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -3036,6 +3036,31 @@ static int ram_save_setup(QEMUFile *f, void *opaque, Error **errp)
         migration_ops->ram_save_target_page = ram_save_target_page_legacy;
     }
 
+    /*
+     * This operation is unfortunate..
+     *
+     * For legacy QEMUs using per-section sync
+     * =======================================
+     *
+     * This must exist because the EOS below requires the SYNC messages
+     * per-channel to work.
+     *
+     * For modern QEMUs using per-round sync
+     * =====================================
+     *
+     * Logically such sync is not needed, and recv threads should not run
+     * until setup ready (using things like channels_ready on src).  Then
+     * we should be all fine.
+     *
+     * However even if we add channels_ready to recv side in new QEMUs, old
+     * QEMU won't have them so this sync will still be needed to make sure
+     * multifd recv threads won't start processing guest pages early before
+     * ram_load_setup() is properly done.
+     *
+     * Let's stick with this.  Fortunately the overhead is low to sync
+     * during setup because the VM is running, so at least it's not
+     * accounted as part of downtime.
+     */
     bql_unlock();
     ret = multifd_ram_flush_and_sync(f);
     bql_lock();