diff --git a/arch/s390/include/asm/mem_detect.h b/arch/s390/include/asm/mem_detect.h
index 058ac2647eb7..08798ddf5143 100644
--- a/arch/s390/include/asm/mem_detect.h
+++ b/arch/s390/include/asm/mem_detect.h
@@ -66,6 +66,17 @@ static inline int __get_mem_detect_block(u32 n, unsigned long *start,
 	     i < mem_detect.count;					\
 	     i++, __get_mem_detect_block(i, p_start, p_end))
 
+static inline unsigned long get_mem_detect_online_total(void)
+{
+	unsigned long start, end, total = 0;
+	int i;
+
+	for_each_mem_detect_block(i, &start, &end)
+		total += end - start;
+
+	return total;
+}
+
 static inline void get_mem_detect_reserved(unsigned long *start,
 					   unsigned long *size)
 {