From ae11a1ea30f43abebd96a22988619eb9f52e6a4e Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Wed, 4 Dec 2019 15:21:07 +0100 Subject: [PATCH 1/3] mc146818rtc: fix timer interrupt reinjection RH-Author: Marcelo Tosatti Message-id: <20191204152436.680299856@amt.cnet> Patchwork-id: 92889 O-Subject: [RHEL-7.8 qemu-kvm-rhev PATCH 1/3] mc146818rtc: fix timer interrupt reinjection Bugzilla: 1639098 RH-Acked-by: Laszlo Ersek RH-Acked-by: Paolo Bonzini RH-Acked-by: Vitaly Kuznetsov BZ: 1639098 Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=24854309 BRANCH: rhv7/master-2.12.0 Upstream: b429de730174b388ea5760e3debb0d542ea3c261 of pbonzini's for-upstream tree. 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. V2: reorganize code (Paolo Bonzini) Signed-off-by: Marcelo Tosatti Message-Id: <20191010123008.GA19158@amt.cnet> Signed-off-by: Paolo Bonzini Signed-off-by: Miroslav Rezanina --- hw/timer/mc146818rtc.c | 53 +++++++++++++++++++++++++------------------------- 1 file changed, 27 insertions(+), 26 deletions(-) diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c index 68c353f..296d974 100644 --- a/hw/timer/mc146818rtc.c +++ b/hw/timer/mc146818rtc.c @@ -197,24 +197,28 @@ 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; - - 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: @@ -245,22 +249,19 @@ 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); + 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) -- 1.8.3.1