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mc146818rtc: fix timer interrupt reinjection

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commit 369b41359a broke timer interrupt
reinjection when there is no period change by the guest.

In that case, old_period is 0, which ends up zeroing irq_coalesced
(counter of reinjected interrupts).

The consequence is Windows 7 is unable to synchronize time via NTP.
Easily reproducible by playing a fullscreen video with cirrus and VNC.

Fix by not updating s->irq_coalesced when old_period is 0.

V2: reorganize code (Paolo Bonzini)

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Message-Id: <20191010123008.GA19158@amt.cnet>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Marcelo Tosatti 2019-10-10 09:30:08 -03:00 committed by Paolo Bonzini
parent 73284563dc
commit b429de7301
1 changed files with 27 additions and 26 deletions
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53
hw/timer/mc146818rtc.c
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@ -203,24 +203,28 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
period = rtc_periodic_clock_ticks(s);
if (period) {
/* compute 32 khz clock */
cur_clock =
muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
if (!period) {
s->irq_coalesced = 0;
timer_del(s->periodic_timer);
return;
}
/*
* if the periodic timer's update is due to period re-configuration,
* we should count the clock since last interrupt.
*/
if (old_period) {
int64_t last_periodic_clock, next_periodic_clock;
/* compute 32 khz clock */
cur_clock =
muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
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);
}
/*
* if the periodic timer's update is due to period re-configuration,
* we should count the clock since last interrupt.
*/
if (old_period) {
int64_t last_periodic_clock, next_periodic_clock;
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);
/*
* s->irq_coalesced can change for two reasons:
@ -251,22 +255,19 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
rtc_coalesced_timer_update(s);
}
} else {
/*
/*
* no way to compensate the interrupt if LOST_TICK_POLICY_SLEW
* is not used, we should make the time progress anyway.
*/
lost_clock = MIN(lost_clock, period);
}
assert(lost_clock >= 0 && lost_clock <= period);
next_irq_clock = cur_clock + period - lost_clock;
s->next_periodic_time = periodic_clock_to_ns(next_irq_clock) + 1;
timer_mod(s->periodic_timer, s->next_periodic_time);
} else {
s->irq_coalesced = 0;
timer_del(s->periodic_timer);
}
assert(lost_clock >= 0 && lost_clock <= period);
next_irq_clock = cur_clock + period - lost_clock;
s->next_periodic_time = periodic_clock_to_ns(next_irq_clock) + 1;
timer_mod(s->periodic_timer, s->next_periodic_time);
}
static void rtc_periodic_timer(void *opaque)