* [PATCH] mc146818rtc: fix timer interrupt reinjection
@ 2019-10-09 18:40 Marcelo Tosatti
2019-10-09 21:13 ` Paolo Bonzini
0 siblings, 1 reply; 3+ messages in thread
From: Marcelo Tosatti @ 2019-10-09 18:40 UTC (permalink / raw)
To: qemu-devel; +Cc: Tai Yunfang, Xiao Guangrong, Vadim Rozenfeld, Paolo Bonzini
commit 369b41359af46bded5799c9ef8be2b641d92e043 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.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c
index 6cb378751b..aabffa8c67 100644
--- a/hw/timer/mc146818rtc.c
+++ b/hw/timer/mc146818rtc.c
@@ -241,7 +241,10 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
s->period = period;
lost_clock += old_irq_coalesced * old_period;
- s->irq_coalesced = lost_clock / s->period;
+ if (old_period) {
+ s->irq_coalesced = lost_clock / s->period;
+ }
+
lost_clock %= s->period;
if (old_irq_coalesced != s->irq_coalesced ||
old_period != s->period) {
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mc146818rtc: fix timer interrupt reinjection
2019-10-09 18:40 [PATCH] mc146818rtc: fix timer interrupt reinjection Marcelo Tosatti
@ 2019-10-09 21:13 ` Paolo Bonzini
2019-10-10 12:28 ` Marcelo Tosatti
0 siblings, 1 reply; 3+ messages in thread
From: Paolo Bonzini @ 2019-10-09 21:13 UTC (permalink / raw)
To: Marcelo Tosatti, qemu-devel; +Cc: Tai Yunfang, Xiao Guangrong, Vadim Rozenfeld
On 09/10/19 20:40, Marcelo Tosatti wrote:
> s->period = period;
> lost_clock += old_irq_coalesced * old_period;
> - s->irq_coalesced = lost_clock / s->period;
> + if (old_period) {
> + s->irq_coalesced = lost_clock / s->period;
> + }
> +
> lost_clock %= s->period;
> if (old_irq_coalesced != s->irq_coalesced ||
> old_period != s->period) {
I think none of the code in the "if (s->lost_tick_policy ==
LOST_TICK_POLICY_SLEW) {" matters if old_period == 0 (and lost_clock
will always be 0). So perhaps we should place all that big "if" under
the existing "if (old_period)"?
Or even something like:
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c
index 6cb378751b..3337a8da98 100644
--- a/hw/timer/mc146818rtc.c
+++ b/hw/timer/mc146818rtc.c
@@ -202,25 +202,33 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
int64_t cur_clock, next_irq_clock, lost_clock = 0;
period = rtc_periodic_clock_ticks(s);
+ if (old_period && old_period == period) {
+ return;
+ }
- 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;
-
- 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);
- }
+ }
+
+ /* compute 32 khz clock */
+ cur_clock =
+ muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
+
+ /*
+ * 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:
@@ -243,13 +251,10 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
lost_clock += old_irq_coalesced * old_period;
s->irq_coalesced = lost_clock / s->period;
lost_clock %= s->period;
- if (old_irq_coalesced != s->irq_coalesced ||
- old_period != s->period) {
- DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, "
- "period scaled from %d to %d\n", old_irq_coalesced,
- s->irq_coalesced, old_period, s->period);
- rtc_coalesced_timer_update(s);
- }
+ DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, "
+ "period scaled from %d to %d\n", old_irq_coalesced,
+ s->irq_coalesced, old_period, s->period);
+ rtc_coalesced_timer_update(s);
} else {
/*
* no way to compensate the interrupt if LOST_TICK_POLICY_SLEW
@@ -257,16 +262,12 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
*/
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);
}
+
+ 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)
Best read with "diff -b".
Paolo
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mc146818rtc: fix timer interrupt reinjection
2019-10-09 21:13 ` Paolo Bonzini
@ 2019-10-10 12:28 ` Marcelo Tosatti
0 siblings, 0 replies; 3+ messages in thread
From: Marcelo Tosatti @ 2019-10-10 12:28 UTC (permalink / raw)
To: Paolo Bonzini; +Cc: Tai Yunfang, Xiao Guangrong, qemu-devel, Vadim Rozenfeld
On Wed, Oct 09, 2019 at 11:13:16PM +0200, Paolo Bonzini wrote:
> On 09/10/19 20:40, Marcelo Tosatti wrote:
> > s->period = period;
> > lost_clock += old_irq_coalesced * old_period;
> > - s->irq_coalesced = lost_clock / s->period;
> > + if (old_period) {
> > + s->irq_coalesced = lost_clock / s->period;
> > + }
> > +
> > lost_clock %= s->period;
> > if (old_irq_coalesced != s->irq_coalesced ||
> > old_period != s->period) {
>
> I think none of the code in the "if (s->lost_tick_policy ==
> LOST_TICK_POLICY_SLEW) {" matters if old_period == 0 (and lost_clock
> will always be 0). So perhaps we should place all that big "if" under
> the existing "if (old_period)"?
>
> Or even something like:
This skips reprogramming the timer if the period is equal.
Sending v2 based on your suggestions and patch below.
>
> diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c
> index 6cb378751b..3337a8da98 100644
> --- a/hw/timer/mc146818rtc.c
> +++ b/hw/timer/mc146818rtc.c
> @@ -202,25 +202,33 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
> int64_t cur_clock, next_irq_clock, lost_clock = 0;
>
> period = rtc_periodic_clock_ticks(s);
> + if (old_period && old_period == period) {
> + return;
> + }
>
> - 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;
> -
> - 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);
> - }
> + }
> +
> + /* compute 32 khz clock */
> + cur_clock =
> + muldiv64(current_time, RTC_CLOCK_RATE, NANOSECONDS_PER_SECOND);
> +
> + /*
> + * 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:
> @@ -243,13 +251,10 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
> lost_clock += old_irq_coalesced * old_period;
> s->irq_coalesced = lost_clock / s->period;
> lost_clock %= s->period;
> - if (old_irq_coalesced != s->irq_coalesced ||
> - old_period != s->period) {
> - DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, "
> - "period scaled from %d to %d\n", old_irq_coalesced,
> - s->irq_coalesced, old_period, s->period);
> - rtc_coalesced_timer_update(s);
> - }
> + DPRINTF_C("cmos: coalesced irqs scaled from %d to %d, "
> + "period scaled from %d to %d\n", old_irq_coalesced,
> + s->irq_coalesced, old_period, s->period);
> + rtc_coalesced_timer_update(s);
> } else {
> /*
> * no way to compensate the interrupt if LOST_TICK_POLICY_SLEW
> @@ -257,16 +262,12 @@ periodic_timer_update(RTCState *s, int64_t current_time, uint32_t old_period)
> */
> 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);
> }
> +
> + 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)
>
>
> Best read with "diff -b".
>
> Paolo
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2019-10-10 12:56 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-10-09 18:40 [PATCH] mc146818rtc: fix timer interrupt reinjection Marcelo Tosatti
2019-10-09 21:13 ` Paolo Bonzini
2019-10-10 12:28 ` Marcelo Tosatti
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).