[PATCH v4 17/32] system/qtest: properly feedback results of clock_[step|set]

[Alex Bennée]

Time will not advance if the system is paused or there are no timer
events set for the future. In absence of pending timer events
advancing time would make no difference the system state. Attempting
to do so would be a bug and the test or device under test would need
fixing.

Tighten up the result reporting to `FAIL` if time was not advanced.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2687
---
 system/qtest.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/system/qtest.c b/system/qtest.c
index 99ef2042f6..e68ed0f2a8 100644
--- a/system/qtest.c
+++ b/system/qtest.c
@@ -78,6 +78,11 @@ static void *qtest_server_send_opaque;
  * let you adjust the value of the clock (monotonically).  All the commands
  * return the current value of the clock in nanoseconds.
  *
+ * If the commands FAIL then time wasn't advanced which is likely
+ * because the machine was in a paused state or no timer events exist
+ * in the future. This will cause qtest to abort and the test will
+ * need to check its assumptions.
+ *
  * .. code-block:: none
  *
  *  > clock_step
@@ -710,7 +715,8 @@ static void qtest_process_command(CharBackend *chr, gchar 
**words)
             qtest_sendf(chr, "OK little\n");
         }
     } else if (qtest_enabled() && strcmp(words[0], "clock_step") == 0) {
-        int64_t ns;
+        int64_t old_ns = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+        int64_t ns, new_ns;
 
         if (words[1]) {
             int ret = qemu_strtoi64(words[1], NULL, 0, &ns);
@@ -719,11 +725,10 @@ static void qtest_process_command(CharBackend *chr, gchar 
**words)
             ns = qemu_clock_deadline_ns_all(QEMU_CLOCK_VIRTUAL,
                                             QEMU_TIMER_ATTR_ALL);
         }
-        qemu_clock_advance_virtual_time(
-            qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + ns);
+        new_ns = qemu_clock_advance_virtual_time(old_ns + ns);
         qtest_send_prefix(chr);
-        qtest_sendf(chr, "OK %"PRIi64"\n",
-                    (int64_t)qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
+        qtest_sendf(chr, "%s %"PRIi64"\n",
+                    new_ns > old_ns ? "OK" : "FAIL", new_ns);
     } else if (strcmp(words[0], "module_load") == 0) {
         Error *local_err = NULL;
         int rv;
@@ -740,16 +745,16 @@ static void qtest_process_command(CharBackend *chr, gchar 
**words)
             qtest_sendf(chr, "FAIL\n");
         }
     } else if (qtest_enabled() && strcmp(words[0], "clock_set") == 0) {
-        int64_t ns;
+        int64_t ns, new_ns;
         int ret;
 
         g_assert(words[1]);
         ret = qemu_strtoi64(words[1], NULL, 0, &ns);
         g_assert(ret == 0);
-        qemu_clock_advance_virtual_time(ns);
+        new_ns = qemu_clock_advance_virtual_time(ns);
         qtest_send_prefix(chr);
-        qtest_sendf(chr, "OK %"PRIi64"\n",
-                    (int64_t)qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL));
+        qtest_sendf(chr, "%s %"PRIi64"\n",
+                    new_ns == ns ? "OK" : "FAIL", new_ns);
     } else if (process_command_cb && process_command_cb(chr, words)) {
         /* Command got consumed by the callback handler */
     } else {
-- 
2.39.5