| Message ID | 1500921322-36875-1-git-send-email-peng.hao2@zte.com.cn (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 24/07/2017 20:35, Peng Hao wrote: > When a windows vm starts, periodic timer of rtc will stop several times. > windows kernel will check whether REG_A_UIP is changed. REG_C's interrupt > flags will not be cleared when periodic timer stops and the update timer > will switch to alarm timer. So the expiration time of alarm timer is very > long and REG_A_UIP will not vary.At last windows kernel will repeat to > check REG_A_UIP all the time. This should not happen. REG_A_UIP is set and cleared in register A every second, like this: case RTC_REG_A: if (update_in_progress(s)) { s->cmos_data[s->cmos_index] |= REG_A_UIP; } else { s->cmos_data[s->cmos_index] &= ~REG_A_UIP; } ret = s->cmos_data[s->cmos_index]; break; where update_in_progress does: guest_nsec = get_guest_rtc_ns(s); /* UIP bit will be set at last 244us of every second. */ if ((guest_nsec % NANOSECONDS_PER_SECOND) >= (NANOSECONDS_PER_SECOND - UIP_HOLD_LENGTH)) { return 1; } return 0; This is done even if the timer is not pending. How can the bug be reproduced? Paolo > Signed-off-by: Peng Hao <peng.hao2@zte.com.cn> > Signed-off-by: Liu Yi <liu.yi24@zte.com.cn> > --- > hw/timer/mc146818rtc.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c > index 1b8d3d7..aa55fae 100644 > --- a/hw/timer/mc146818rtc.c > +++ b/hw/timer/mc146818rtc.c > @@ -457,6 +457,8 @@ static void rtc_update_timer(void *opaque) > if ((new_irqs & s->cmos_data[RTC_REG_B]) != 0) { > s->cmos_data[RTC_REG_C] |= REG_C_IRQF; > qemu_irq_raise(s->irq); > + } else if ((s->cmos_data[RTC_REG_B] & REG_B_UIE) == 0) { > + s->cmos_data[RTC_REG_C] &= ~REG_C_UF; > } > check_update_timer(s); > } > @@ -559,7 +561,7 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, > s->cmos_data[RTC_REG_C] |= REG_C_IRQF; > qemu_irq_raise(s->irq); > } else { > - s->cmos_data[RTC_REG_C] &= ~REG_C_IRQF; > + s->cmos_data[RTC_REG_C] &= ~(REG_C_UF | REG_C_IRQF); > qemu_irq_lower(s->irq); > } > s->cmos_data[RTC_REG_B] = data; >
On 07/24/2017 01:35 PM, Peng Hao wrote: > When a windows vm starts, periodic timer of rtc will stop several times. > windows kernel will check whether REG_A_UIP is changed. REG_C's interrupt > flags will not be cleared when periodic timer stops and the update timer > will switch to alarm timer. So the expiration time of alarm timer is very > long and REG_A_UIP will not vary.At last windows kernel will repeat to > check REG_A_UIP all the time. > > Signed-off-by: Peng Hao <peng.hao2@zte.com.cn> > Signed-off-by: Liu Yi <liu.yi24@zte.com.cn> > --- When posting a v3, it's useful to tell us (after the --- separator) what changed from v2, to help us focus on why a v3 was needed.
diff --git a/hw/timer/mc146818rtc.c b/hw/timer/mc146818rtc.c index 1b8d3d7..aa55fae 100644 --- a/hw/timer/mc146818rtc.c +++ b/hw/timer/mc146818rtc.c @@ -457,6 +457,8 @@ static void rtc_update_timer(void *opaque) if ((new_irqs & s->cmos_data[RTC_REG_B]) != 0) { s->cmos_data[RTC_REG_C] |= REG_C_IRQF; qemu_irq_raise(s->irq); + } else if ((s->cmos_data[RTC_REG_B] & REG_B_UIE) == 0) { + s->cmos_data[RTC_REG_C] &= ~REG_C_UF; } check_update_timer(s); } @@ -559,7 +561,7 @@ static void cmos_ioport_write(void *opaque, hwaddr addr, s->cmos_data[RTC_REG_C] |= REG_C_IRQF; qemu_irq_raise(s->irq); } else { - s->cmos_data[RTC_REG_C] &= ~REG_C_IRQF; + s->cmos_data[RTC_REG_C] &= ~(REG_C_UF | REG_C_IRQF); qemu_irq_lower(s->irq); } s->cmos_data[RTC_REG_B] = data;