qtest: Adding qtest_memset and qmemset.

Currently, libqtest allows for memread and memwrite, but
does not offer a simple way to zero out regions of memory.
This patch adds a simple function to do so.
Signed-off-by: NJohn Snow <jsnow@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

tests/libqtest.c

@@ -659,6 +659,18 @@ void qtest_memwrite(QTestState *s, uint64_t addr, const void *data, size_t size)
     qtest_rsp(s, 0);
 }
 
+void qtest_memset(QTestState *s, uint64_t addr, uint8_t pattern, size_t size)
+{
+    size_t i;
+
+    qtest_sendf(s, "write 0x%" PRIx64 " 0x%zx 0x", addr, size);
+    for (i = 0; i < size; i++) {
+        qtest_sendf(s, "%02x", pattern);
+    }
+    qtest_sendf(s, "\n");
+    qtest_rsp(s, 0);
+}
+
 QDict *qmp(const char *fmt, ...)
 {
     va_list ap;

tests/libqtest.h

@@ -282,6 +282,17 @@ void qtest_memread(QTestState *s, uint64_t addr, void *data, size_t size);
  */
 void qtest_memwrite(QTestState *s, uint64_t addr, const void *data, size_t size);
 
+/**
+ * qtest_memset:
+ * @s: #QTestState instance to operate on.
+ * @addr: Guest address to write to.
+ * @patt: Byte pattern to fill the guest memory region with.
+ * @size: Number of bytes to write.
+ *
+ * Write a pattern to guest memory.
+ */
+void qtest_memset(QTestState *s, uint64_t addr, uint8_t patt, size_t size);
+
 /**
  * qtest_clock_step_next:
  * @s: #QTestState instance to operate on.
@@ -620,6 +631,19 @@ static inline void memwrite(uint64_t addr, const void *data, size_t size)
     qtest_memwrite(global_qtest, addr, data, size);
 }
 
+/**
+ * qmemset:
+ * @addr: Guest address to write to.
+ * @patt: Byte pattern to fill the guest memory region with.
+ * @size: Number of bytes to write.
+ *
+ * Write a pattern to guest memory.
+ */
+static inline void qmemset(uint64_t addr, uint8_t patt, size_t size)
+{
+    qtest_memset(global_qtest, addr, patt, size);
+}
+
 /**
  * clock_step_next:
  *