diff --git a/qtest.c b/qtest.c
index 73b7a0f..04412dd 100644
--- a/qtest.c
+++ b/qtest.c
@@ -125,6 +125,9 @@
  *  > b64write ADDR SIZE B64_DATA
  *  < OK
  *
+ *  > memset ADDR SIZE VALUE
+ *  < OK
+ *
  * ADDR, SIZE, VALUE are all integers parsed with strtoul() with a base of 0.
  *
  * DATA is an arbitrarily long hex number prefixed with '0x'.  If it's smaller
@@ -473,6 +476,23 @@
 
         qtest_send_prefix(chr);
         qtest_send(chr, "OK\n");
+    } else if (strcmp(words[0], "memset") == 0) {
+        uint64_t addr, len;
+        uint8_t *data;
+        uint8_t pattern;
+
+        g_assert(words[1] && words[2] && words[3]);
+        addr = strtoull(words[1], NULL, 0);
+        len = strtoull(words[2], NULL, 0);
+        pattern = strtoull(words[3], NULL, 0);
+
+        data = g_malloc(len);
+        memset(data, pattern, len);
+        cpu_physical_memory_write(addr, data, len);
+        g_free(data);
+
+        qtest_send_prefix(chr);
+        qtest_send(chr, "OK\n");
     }  else if (strcmp(words[0], "b64write") == 0) {
         uint64_t addr, len;
         uint8_t *data;