Loosen restriction on computed lost_tick. When QEMU's rtc_clock is set
to host, the walltime is used for mc146818rtc which requires computed
lost_tick to be strictly non-negative. But host walltime could possibly
run backwards, for example, configured by NTP service. Under such
circumstances QEMU process could crash unexpectly. This situation is
easy to reproduce for Windows 2012/2016 guests.
---
hw/rtc/mc146818rtc.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/hw/rtc/mc146818rtc.c b/hw/rtc/mc146818rtc.c
index 8631386b9f..04185eb6e9 100644
--- a/hw/rtc/mc146818rtc.c
+++ b/hw/rtc/mc146818rtc.c
@@ -173,8 +173,7 @@ static void periodic_timer_update(MC146818RtcState *s,
int64_t current_time,
next_periodic_clock = muldiv64(s->next_periodic_time,
RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
last_periodic_clock = next_periodic_clock - old_period;
- lost_clock = cur_clock - last_periodic_clock;
- assert(lost_clock >= 0);
+ lost_clock = MAX(cur_clock - last_periodic_clock, 0);
}
/*
--
2.34.1
