diff --git a/cutils.c b/cutils.c
index 28089aa3e4..7984bc1ca4 100644
--- a/cutils.c
+++ b/cutils.c
@@ -291,10 +291,10 @@ int fcntl_setfl(int fd, int flag)
  * value must be terminated by whitespace, ',' or '\0'. Return -1 on
  * error.
  */
-ssize_t strtosz(const char *nptr, char **end)
+ssize_t strtosz_suffix(const char *nptr, char **end, const char default_suffix)
 {
     ssize_t retval = -1;
-    char *endptr, c;
+    char *endptr, c, d;
     int mul_required = 0;
     double val, mul, integral, fraction;
 
@@ -313,10 +313,16 @@ ssize_t strtosz(const char *nptr, char **end)
      * part of a multi token argument.
      */
     c = *endptr;
+    d = c;
     if (isspace(c) || c == '\0' || c == ',') {
         c = 0;
+        if (default_suffix) {
+            d = default_suffix;
+        } else {
+            d = c;
+        }
     }
-    switch (c) {
+    switch (d) {
     case 'B':
     case 'b':
         mul = 1;
@@ -371,3 +377,8 @@ fail:
 
     return retval;
 }
+
+ssize_t strtosz(const char *nptr, char **end)
+{
+    return strtosz_suffix(nptr, end, STRTOSZ_DEFSUFFIX_MB);
+}
diff --git a/qemu-common.h b/qemu-common.h
index de82c2ea13..1ed32e5b2c 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -149,7 +149,14 @@ time_t mktimegm(struct tm *tm);
 int qemu_fls(int i);
 int qemu_fdatasync(int fd);
 int fcntl_setfl(int fd, int flag);
+
+#define STRTOSZ_DEFSUFFIX_TB	'T'
+#define STRTOSZ_DEFSUFFIX_GB	'G'
+#define STRTOSZ_DEFSUFFIX_MB	'M'
+#define STRTOSZ_DEFSUFFIX_KB	'K'
+#define STRTOSZ_DEFSUFFIX_B	'B'
 ssize_t strtosz(const char *nptr, char **end);
+ssize_t strtosz_suffix(const char *nptr, char **end, const char default_suffix);
 
 /* path.c */
 void init_paths(const char *prefix);