From 3cf57fed216e2c1b6fdfeccb792650bab72a350a Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Sat, 26 Jul 2008 17:01:01 -0300 Subject: KVM: PIT: fix injection logic and count The PIT injection logic is problematic under the following cases: 1) If there is a higher priority vector to be delivered by the time kvm_pit_timer_intr_post is invoked ps->inject_pending won't be set. This opens the possibility for missing many PIT event injections (say if guest executes hlt at this point). 2) ps->inject_pending is racy with more than two vcpus. Since there's no locking around read/dec of pt->pending, two vcpu's can inject two interrupts for a single pt->pending count. Fix 1 by using an irq ack notifier: only reinject when the previous irq has been acked. Fix 2 with appropriate locking around manipulation of pending count and irq_ack by the injection / ack paths. Signed-off-by: Marcelo Tosatti Signed-off-by: Avi Kivity --- arch/x86/kvm/i8254.c | 70 ++++++++++++++++++++++++++-------------------------- 1 file changed, 35 insertions(+), 35 deletions(-) (limited to 'arch/x86/kvm/i8254.c') diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c index c0f7872a9124..7d04dd3ef857 100644 --- a/arch/x86/kvm/i8254.c +++ b/arch/x86/kvm/i8254.c @@ -207,6 +207,8 @@ static int __pit_timer_fn(struct kvm_kpit_state *ps) pt->timer.expires = ktime_add_ns(pt->timer.expires, pt->period); pt->scheduled = ktime_to_ns(pt->timer.expires); + if (pt->period) + ps->channels[0].count_load_time = pt->timer.expires; return (pt->period == 0 ? 0 : 1); } @@ -215,12 +217,22 @@ int pit_has_pending_timer(struct kvm_vcpu *vcpu) { struct kvm_pit *pit = vcpu->kvm->arch.vpit; - if (pit && vcpu->vcpu_id == 0 && pit->pit_state.inject_pending) + if (pit && vcpu->vcpu_id == 0 && pit->pit_state.irq_ack) return atomic_read(&pit->pit_state.pit_timer.pending); - return 0; } +void kvm_pit_ack_irq(struct kvm_irq_ack_notifier *kian) +{ + struct kvm_kpit_state *ps = container_of(kian, struct kvm_kpit_state, + irq_ack_notifier); + spin_lock(&ps->inject_lock); + if (atomic_dec_return(&ps->pit_timer.pending) < 0) + WARN_ON(1); + ps->irq_ack = 1; + spin_unlock(&ps->inject_lock); +} + static enum hrtimer_restart pit_timer_fn(struct hrtimer *data) { struct kvm_kpit_state *ps; @@ -255,8 +267,9 @@ static void destroy_pit_timer(struct kvm_kpit_timer *pt) hrtimer_cancel(&pt->timer); } -static void create_pit_timer(struct kvm_kpit_timer *pt, u32 val, int is_period) +static void create_pit_timer(struct kvm_kpit_state *ps, u32 val, int is_period) { + struct kvm_kpit_timer *pt = &ps->pit_timer; s64 interval; interval = muldiv64(val, NSEC_PER_SEC, KVM_PIT_FREQ); @@ -268,6 +281,7 @@ static void create_pit_timer(struct kvm_kpit_timer *pt, u32 val, int is_period) pt->period = (is_period == 0) ? 0 : interval; pt->timer.function = pit_timer_fn; atomic_set(&pt->pending, 0); + ps->irq_ack = 1; hrtimer_start(&pt->timer, ktime_add_ns(ktime_get(), interval), HRTIMER_MODE_ABS); @@ -302,11 +316,11 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val) case 1: /* FIXME: enhance mode 4 precision */ case 4: - create_pit_timer(&ps->pit_timer, val, 0); + create_pit_timer(ps, val, 0); break; case 2: case 3: - create_pit_timer(&ps->pit_timer, val, 1); + create_pit_timer(ps, val, 1); break; default: destroy_pit_timer(&ps->pit_timer); @@ -520,7 +534,7 @@ void kvm_pit_reset(struct kvm_pit *pit) mutex_unlock(&pit->pit_state.lock); atomic_set(&pit->pit_state.pit_timer.pending, 0); - pit->pit_state.inject_pending = 1; + pit->pit_state.irq_ack = 1; } struct kvm_pit *kvm_create_pit(struct kvm *kvm) @@ -534,6 +548,7 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm) mutex_init(&pit->pit_state.lock); mutex_lock(&pit->pit_state.lock); + spin_lock_init(&pit->pit_state.inject_lock); /* Initialize PIO device */ pit->dev.read = pit_ioport_read; @@ -555,6 +570,9 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm) pit_state->pit = pit; hrtimer_init(&pit_state->pit_timer.timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); + pit_state->irq_ack_notifier.gsi = 0; + pit_state->irq_ack_notifier.irq_acked = kvm_pit_ack_irq; + kvm_register_irq_ack_notifier(kvm, &pit_state->irq_ack_notifier); mutex_unlock(&pit->pit_state.lock); kvm_pit_reset(pit); @@ -592,37 +610,19 @@ void kvm_inject_pit_timer_irqs(struct kvm_vcpu *vcpu) struct kvm_kpit_state *ps; if (vcpu && pit) { + int inject = 0; ps = &pit->pit_state; - /* Try to inject pending interrupts when: - * 1. Pending exists - * 2. Last interrupt was accepted or waited for too long time*/ - if (atomic_read(&ps->pit_timer.pending) && - (ps->inject_pending || - (jiffies - ps->last_injected_time - >= KVM_MAX_PIT_INTR_INTERVAL))) { - ps->inject_pending = 0; - __inject_pit_timer_intr(kvm); - ps->last_injected_time = jiffies; - } - } -} - -void kvm_pit_timer_intr_post(struct kvm_vcpu *vcpu, int vec) -{ - struct kvm_arch *arch = &vcpu->kvm->arch; - struct kvm_kpit_state *ps; - - if (vcpu && arch->vpit) { - ps = &arch->vpit->pit_state; - if (atomic_read(&ps->pit_timer.pending) && - (((arch->vpic->pics[0].imr & 1) == 0 && - arch->vpic->pics[0].irq_base == vec) || - (arch->vioapic->redirtbl[0].fields.vector == vec && - arch->vioapic->redirtbl[0].fields.mask != 1))) { - ps->inject_pending = 1; - atomic_dec(&ps->pit_timer.pending); - ps->channels[0].count_load_time = ktime_get(); + /* Try to inject pending interrupts when + * last one has been acked. + */ + spin_lock(&ps->inject_lock); + if (atomic_read(&ps->pit_timer.pending) && ps->irq_ack) { + ps->irq_ack = 0; + inject = 1; } + spin_unlock(&ps->inject_lock); + if (inject) + __inject_pit_timer_intr(kvm); } } -- cgit v1.2.3