[RFC PATCH v2 135/137] tests/qtest/qom-test: Add smp-max init-time ceiling test

Add a slow-mode subtest that boots aarch64/virt and ppc64/pseries at
their maximum -smp count and asserts that qtest_init() returns within
15 seconds.  This guards against quadratic-time init regressions when
many child objects are created under a single parent, such as the
"[*]" auto-index property scan that made pseries take ~10 s to launch
before qemu_extend_irqs() switched to explicit indices.

AI-used-for: code (refactoring)
Signed-off-by: Alexander Graf <[email protected]>
---
 tests/qtest/qom-test.c | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/tests/qtest/qom-test.c b/tests/qtest/qom-test.c
index cf4c6b5add..0bfb3233ac 100644
--- a/tests/qtest/qom-test.c
+++ b/tests/qtest/qom-test.c
@@ -238,8 +238,32 @@ static void test_qom_qtests(void)
     qtest_quit(qts);
 }
 
+/*
+ * Guard against O(n^2) init-time regressions when many child objects are
+ * created under one parent (e.g. board-created CPUs).  Launch the machine
+ * at its maximum SMP count and assert an upper bound on time-to-monitor.
+ * The bound is generous (15 s) so this only fires when init cost blows up
+ * quadratically, not on ordinary CI jitter.
+ */
+static void test_smp_max(gconstpointer data)
+{
+    const char *args = data;
+    gint64 t0, dt;
+    QTestState *qts;
+
+    t0 = g_get_monotonic_time();
+    qts = qtest_initf("%s", args);
+    dt = g_get_monotonic_time() - t0;
+
+    g_test_message("smp-max init time: %" G_GINT64_FORMAT " ms", dt / 1000);
+    g_assert_cmpint(dt, <, 15 * G_USEC_PER_SEC);
+
+    qtest_quit(qts);
+}
+
 int main(int argc, char **argv)
 {
+    const char *arch = qtest_get_arch();
     char *v_env = getenv("V");
 
     if (v_env) {
@@ -251,5 +275,16 @@ int main(int argc, char **argv)
     qtest_cb_for_every_machine(add_machine_test_case, g_test_quick());
     qtest_add_func("qom/qom-qtests", test_qom_qtests);
 
+    if (g_test_slow()) {
+        if (g_str_equal(arch, "aarch64")) {
+            qtest_add_data_func("qom/smp-max/virt",
+                                "-M virt,gic-version=max -smp 512",
+                                test_smp_max);
+        } else if (g_str_equal(arch, "ppc64")) {
+            qtest_add_data_func("qom/smp-max/pseries",
+                                "-M pseries -smp 512", test_smp_max);
+        }
+    }
+
     return g_test_run();
 }
-- 
2.47.1