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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 2/3] x86/hvm/rtc: Inject RTC periodic interupts from the vpt code.
From: Tim Deegan <tim@xxxxxxx>
Let the vpt code drive the RTC's timer interrupts directly, as it does
for other periodic time sources, and fix up the register state in a
vpt callback when the interrupt is injected.
This fixes a hang seen on Windows 2003 in no-missed-ticks mode, where
when a tick was pending, the early callback from the VPT code would
always set REG_C.PF on every VMENTER; meanwhile the guest was in its
interrupt handler reading REG_C in a loop and waiting to see it clear.
One drawback is that a guest that attempts to suppress RTC periodic
interrupts by failing to read REG_C will receive up to 10 spurious
interrupts, even in 'strict' mode. However:
- since all previous RTC models have had this property (including
the current one, since 'no-ack' mode is hard-coded on) we're
pretty sure that all guests can handle this; and
- we're already playing some other interesting games with this
interrupt in the vpt code.
One other corner case: a guest that enables the PF timer interrupt,
masks the interupt in the APIC and then polls REG_C looking for PF
will not see PF getting set. The more likely case of enabling the
timers and masking the interrupt with REG_B.PIE is already handled
correctly.
Signed-off-by: Tim Deegan <tim@xxxxxxx>
---
xen/arch/x86/hvm/rtc.c | 25 +++++++++++--------------
xen/arch/x86/hvm/vpt.c | 40 ----------------------------------------
xen/include/asm-x86/hvm/vpt.h | 1 -
3 files changed, 11 insertions(+), 55 deletions(-)
diff --git a/xen/arch/x86/hvm/rtc.c b/xen/arch/x86/hvm/rtc.c
index 1a731f7..d641d95 100644
--- a/xen/arch/x86/hvm/rtc.c
+++ b/xen/arch/x86/hvm/rtc.c
@@ -78,29 +78,26 @@ static void rtc_update_irq(RTCState *s)
hvm_isa_irq_assert(vrtc_domain(s), RTC_IRQ);
}
-bool_t rtc_periodic_interrupt(void *opaque)
+/* Called by the VPT code after it's injected a PF interrupt for us.
+ * Fix up the register state to reflect what happened. */
+static void rtc_pf_callback(struct vcpu *v, void *opaque)
{
RTCState *s = opaque;
- bool_t ret;
spin_lock(&s->lock);
- ret = rtc_mode_is(s, no_ack) || !(s->hw.cmos_data[RTC_REG_C] & RTC_IRQF);
- if ( rtc_mode_is(s, no_ack) || !(s->hw.cmos_data[RTC_REG_C] & RTC_PF) )
- {
- s->hw.cmos_data[RTC_REG_C] |= RTC_PF;
- rtc_update_irq(s);
- }
- else if ( ++(s->pt_dead_ticks) >= 10 )
+
+ if ( !rtc_mode_is(s, no_ack)
+ && (s->hw.cmos_data[RTC_REG_C] & RTC_IRQF)
+ && ++(s->pt_dead_ticks) >= 10 )
{
/* VM is ignoring its RTC; no point in running the timer */
destroy_periodic_time(&s->pt);
s->period = 0;
}
- if ( !(s->hw.cmos_data[RTC_REG_C] & RTC_IRQF) )
- ret = 0;
- spin_unlock(&s->lock);
- return ret;
+ s->hw.cmos_data[RTC_REG_C] |= RTC_PF|RTC_IRQF;
+
+ spin_unlock(&s->lock);
}
/* Check whether the REG_C.PF bit should have been set by a tick since
@@ -156,7 +153,7 @@ static void rtc_timer_update(RTCState *s)
delta = period - ((now - s->start_time) % period);
if ( s->hw.cmos_data[RTC_REG_B] & RTC_PIE )
create_periodic_time(v, &s->pt, delta, period,
- RTC_IRQ, NULL, s);
+ RTC_IRQ, rtc_pf_callback, s);
else
s->check_ticks_since = now;
}
diff --git a/xen/arch/x86/hvm/vpt.c b/xen/arch/x86/hvm/vpt.c
index 1961bda..f7af688 100644
--- a/xen/arch/x86/hvm/vpt.c
+++ b/xen/arch/x86/hvm/vpt.c
@@ -231,12 +231,9 @@ int pt_update_irq(struct vcpu *v)
struct periodic_time *pt, *temp, *earliest_pt;
uint64_t max_lag;
int irq, is_lapic;
- void *pt_priv;
- rescan:
spin_lock(&v->arch.hvm_vcpu.tm_lock);
- rescan_locked:
earliest_pt = NULL;
max_lag = -1ULL;
list_for_each_entry_safe ( pt, temp, head, list )
@@ -270,48 +267,11 @@ int pt_update_irq(struct vcpu *v)
earliest_pt->irq_issued = 1;
irq = earliest_pt->irq;
is_lapic = (earliest_pt->source == PTSRC_lapic);
- pt_priv = earliest_pt->priv;
spin_unlock(&v->arch.hvm_vcpu.tm_lock);
if ( is_lapic )
vlapic_set_irq(vcpu_vlapic(v), irq, 0);
- else if ( irq == RTC_IRQ && pt_priv )
- {
- if ( !rtc_periodic_interrupt(pt_priv) )
- irq = -1;
-
- pt_lock(earliest_pt);
-
- if ( irq < 0 && earliest_pt->pending_intr_nr )
- {
- /*
- * RTC periodic timer runs without the corresponding interrupt
- * being enabled - need to mimic enough of pt_intr_post() to keep
- * things going.
- */
- earliest_pt->pending_intr_nr = 0;
- earliest_pt->irq_issued = 0;
- set_timer(&earliest_pt->timer, earliest_pt->scheduled);
- }
- else if ( irq >= 0 && pt_irq_masked(earliest_pt) )
- {
- if ( earliest_pt->on_list )
- {
- /* suspend timer emulation */
- list_del(&earliest_pt->list);
- earliest_pt->on_list = 0;
- }
- irq = -1;
- }
-
- /* Avoid dropping the lock if we can. */
- if ( irq < 0 && v == earliest_pt->vcpu )
- goto rescan_locked;
- pt_unlock(earliest_pt);
- if ( irq < 0 )
- goto rescan;
- }
else
{
hvm_isa_irq_deassert(v->domain, irq);
diff --git a/xen/include/asm-x86/hvm/vpt.h b/xen/include/asm-x86/hvm/vpt.h
index 9f48635..7d62653 100644
--- a/xen/include/asm-x86/hvm/vpt.h
+++ b/xen/include/asm-x86/hvm/vpt.h
@@ -184,7 +184,6 @@ void rtc_migrate_timers(struct vcpu *v);
void rtc_deinit(struct domain *d);
void rtc_reset(struct domain *d);
void rtc_update_clock(struct domain *d);
-bool_t rtc_periodic_interrupt(void *);
void pmtimer_init(struct vcpu *v);
void pmtimer_deinit(struct domain *d);
--
1.7.10.4
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