softmmu/rtc: Emit warning when using driftfix=slew on systems without mc146818

The 'slew' lost tick policy is only available on systems with a mc146818
RTC. On other systems, "-rtc driftfix=slew" is currently silently ignored.
Let's emit at least a warning in this case to make the users aware that
there is something wrong in their command line settings.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <20230110095351.611724-5-thuth@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

diff --git a/softmmu/rtc.c b/softmmu/rtc.c
index 7e2956f81e99d67d6ef071758eb65acb909c8c4b..f7114bed7d51985f94ff6c8ed8ddfd9c8cf04b5e 100644 (file)
--- a/softmmu/rtc.c
+++ b/softmmu/rtc.c
@@ -33,6 +33,7 @@
 #include "sysemu/replay.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/rtc.h"
+#include "hw/rtc/mc146818rtc.h"
 
 static enum {
     RTC_BASE_UTC,
@@ -177,10 +178,13 @@ void configure_rtc(QemuOpts *opts)
     value = qemu_opt_get(opts, "driftfix");
     if (value) {
         if (!strcmp(value, "slew")) {
-            object_register_sugar_prop("mc146818rtc",
+            object_register_sugar_prop(TYPE_MC146818_RTC,
                                        "lost_tick_policy",
                                        "slew",
                                        false);
+            if (!object_class_by_name(TYPE_MC146818_RTC)) {
+                warn_report("driftfix 'slew' is not available with this machine");
+            }
         } else if (!strcmp(value, "none")) {
             /* discard is default */
         } else {