diff --git a/target-xtensa/cpu.h b/target-xtensa/cpu.h
index beb5486..ac463f2 100644
--- a/target-xtensa/cpu.h
+++ b/target-xtensa/cpu.h
@@ -472,6 +472,12 @@
         env->itlb[wi] + ei;
 }
 
+static inline uint32_t xtensa_replicate_windowstart(CPUXtensaState *env)
+{
+    return env->sregs[WINDOW_START] |
+        (env->sregs[WINDOW_START] << env->config->nareg / 4);
+}
+
 /* MMU modes definitions */
 #define MMU_MODE0_SUFFIX _ring0
 #define MMU_MODE1_SUFFIX _ring1