contrib/plugins: avoid hanging program

Although we asks for instructions per second we work in quanta and
that cannot be 0. Fail to load the plugin instead and report the
minimum IPS we can handle.

Reported-by: Elisha Hollander <just4now666666@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-Id: <20240916085400.1046925-19-alex.bennee@linaro.org>

contrib/plugins/ips.c

@@ -152,6 +152,12 @@ QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
     vcpus = qemu_plugin_scoreboard_new(sizeof(vCPUTime));
     max_insn_per_quantum = max_insn_per_second / NUM_TIME_UPDATE_PER_SEC;
 
+    if (max_insn_per_quantum == 0) {
+        fprintf(stderr, "minimum of %d instructions per second needed\n",
+                NUM_TIME_UPDATE_PER_SEC);
+        return -1;
+    }
+
     time_handle = qemu_plugin_request_time_control();
     g_assert(time_handle);