From 33572ac0ad5ba5016da72e6654e607726568f9c0 Mon Sep 17 00:00:00 2001 From: Chris Lalancette Date: Wed, 16 Jun 2010 17:11:11 -0400 Subject: [PATCH] KVM: x86: Introduce a workqueue to deliver PIT timer interrupts We really want to "kvm_set_irq" during the hrtimer callback, but that is risky because that is during interrupt context. Instead, offload the work to a workqueue, which is a bit safer and should provide most of the same functionality. Signed-off-by: Chris Lalancette Signed-off-by: Marcelo Tosatti --- arch/x86/kvm/i8254.c | 141 ++++++++++++++++++++++++++----------------- arch/x86/kvm/i8254.h | 4 +- arch/x86/kvm/irq.c | 1 - 3 files changed, 88 insertions(+), 58 deletions(-) diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c index 188d82762c1b..467cc47fb733 100644 --- a/arch/x86/kvm/i8254.c +++ b/arch/x86/kvm/i8254.c @@ -34,6 +34,7 @@ #include #include +#include #include "irq.h" #include "i8254.h" @@ -244,11 +245,22 @@ static 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); - raw_spin_lock(&ps->inject_lock); - if (atomic_dec_return(&ps->pit_timer.pending) < 0) + int value; + + spin_lock(&ps->inject_lock); + value = atomic_dec_return(&ps->pit_timer.pending); + if (value < 0) + /* spurious acks can be generated if, for example, the + * PIC is being reset. Handle it gracefully here + */ atomic_inc(&ps->pit_timer.pending); + else if (value > 0) + /* in this case, we had multiple outstanding pit interrupts + * that we needed to inject. Reinject + */ + queue_work(ps->pit->wq, &ps->pit->expired); ps->irq_ack = 1; - raw_spin_unlock(&ps->inject_lock); + spin_unlock(&ps->inject_lock); } void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu) @@ -264,10 +276,10 @@ void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu) hrtimer_start_expires(timer, HRTIMER_MODE_ABS); } -static void destroy_pit_timer(struct kvm_timer *pt) +static void destroy_pit_timer(struct kvm_pit *pit) { - pr_debug("execute del timer!\n"); - hrtimer_cancel(&pt->timer); + hrtimer_cancel(&pit->pit_state.pit_timer.timer); + cancel_work_sync(&pit->expired); } static bool kpit_is_periodic(struct kvm_timer *ktimer) @@ -281,6 +293,60 @@ static struct kvm_timer_ops kpit_ops = { .is_periodic = kpit_is_periodic, }; +static void pit_do_work(struct work_struct *work) +{ + struct kvm_pit *pit = container_of(work, struct kvm_pit, expired); + struct kvm *kvm = pit->kvm; + struct kvm_vcpu *vcpu; + int i; + struct kvm_kpit_state *ps = &pit->pit_state; + int inject = 0; + + /* Try to inject pending interrupts when + * last one has been acked. + */ + spin_lock(&ps->inject_lock); + if (ps->irq_ack) { + ps->irq_ack = 0; + inject = 1; + } + spin_unlock(&ps->inject_lock); + if (inject) { + kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 1); + kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 0); + + /* + * Provides NMI watchdog support via Virtual Wire mode. + * The route is: PIT -> PIC -> LVT0 in NMI mode. + * + * Note: Our Virtual Wire implementation is simplified, only + * propagating PIT interrupts to all VCPUs when they have set + * LVT0 to NMI delivery. Other PIC interrupts are just sent to + * VCPU0, and only if its LVT0 is in EXTINT mode. + */ + if (kvm->arch.vapics_in_nmi_mode > 0) + kvm_for_each_vcpu(i, vcpu, kvm) + kvm_apic_nmi_wd_deliver(vcpu); + } +} + +static enum hrtimer_restart pit_timer_fn(struct hrtimer *data) +{ + struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer); + struct kvm_pit *pt = ktimer->kvm->arch.vpit; + + if (ktimer->reinject || !atomic_read(&ktimer->pending)) { + atomic_inc(&ktimer->pending); + queue_work(pt->wq, &pt->expired); + } + + if (ktimer->t_ops->is_periodic(ktimer)) { + hrtimer_add_expires_ns(&ktimer->timer, ktimer->period); + return HRTIMER_RESTART; + } else + return HRTIMER_NORESTART; +} + static void create_pit_timer(struct kvm_kpit_state *ps, u32 val, int is_period) { struct kvm_timer *pt = &ps->pit_timer; @@ -292,13 +358,13 @@ static void create_pit_timer(struct kvm_kpit_state *ps, u32 val, int is_period) /* TODO The new value only affected after the retriggered */ hrtimer_cancel(&pt->timer); + cancel_work_sync(&ps->pit->expired); pt->period = interval; ps->is_periodic = is_period; - pt->timer.function = kvm_timer_fn; + pt->timer.function = pit_timer_fn; pt->t_ops = &kpit_ops; pt->kvm = ps->pit->kvm; - pt->vcpu = pt->kvm->bsp_vcpu; atomic_set(&pt->pending, 0); ps->irq_ack = 1; @@ -347,7 +413,7 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val) } break; default: - destroy_pit_timer(&ps->pit_timer); + destroy_pit_timer(kvm->arch.vpit); } } @@ -626,7 +692,14 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags) mutex_init(&pit->pit_state.lock); mutex_lock(&pit->pit_state.lock); - raw_spin_lock_init(&pit->pit_state.inject_lock); + spin_lock_init(&pit->pit_state.inject_lock); + + pit->wq = create_singlethread_workqueue("kvm-pit-wq"); + if (!pit->wq) { + kfree(pit); + return NULL; + } + INIT_WORK(&pit->expired, pit_do_work); kvm->arch.vpit = pit; pit->kvm = kvm; @@ -685,54 +758,10 @@ void kvm_free_pit(struct kvm *kvm) mutex_lock(&kvm->arch.vpit->pit_state.lock); timer = &kvm->arch.vpit->pit_state.pit_timer.timer; hrtimer_cancel(timer); + cancel_work_sync(&kvm->arch.vpit->expired); kvm_free_irq_source_id(kvm, kvm->arch.vpit->irq_source_id); mutex_unlock(&kvm->arch.vpit->pit_state.lock); + destroy_workqueue(kvm->arch.vpit->wq); kfree(kvm->arch.vpit); } } - -static void __inject_pit_timer_intr(struct kvm *kvm) -{ - struct kvm_vcpu *vcpu; - int i; - - kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 1); - kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 0); - - /* - * Provides NMI watchdog support via Virtual Wire mode. - * The route is: PIT -> PIC -> LVT0 in NMI mode. - * - * Note: Our Virtual Wire implementation is simplified, only - * propagating PIT interrupts to all VCPUs when they have set - * LVT0 to NMI delivery. Other PIC interrupts are just sent to - * VCPU0, and only if its LVT0 is in EXTINT mode. - */ - if (kvm->arch.vapics_in_nmi_mode > 0) - kvm_for_each_vcpu(i, vcpu, kvm) - kvm_apic_nmi_wd_deliver(vcpu); -} - -void kvm_inject_pit_timer_irqs(struct kvm_vcpu *vcpu) -{ - struct kvm_pit *pit = vcpu->kvm->arch.vpit; - struct kvm *kvm = vcpu->kvm; - struct kvm_kpit_state *ps; - - if (pit) { - int inject = 0; - ps = &pit->pit_state; - - /* Try to inject pending interrupts when - * last one has been acked. - */ - raw_spin_lock(&ps->inject_lock); - if (atomic_read(&ps->pit_timer.pending) && ps->irq_ack) { - ps->irq_ack = 0; - inject = 1; - } - raw_spin_unlock(&ps->inject_lock); - if (inject) - __inject_pit_timer_intr(kvm); - } -} diff --git a/arch/x86/kvm/i8254.h b/arch/x86/kvm/i8254.h index 900d6b0ba7c2..46d08ca0b48f 100644 --- a/arch/x86/kvm/i8254.h +++ b/arch/x86/kvm/i8254.h @@ -27,7 +27,7 @@ struct kvm_kpit_state { u32 speaker_data_on; struct mutex lock; struct kvm_pit *pit; - raw_spinlock_t inject_lock; + spinlock_t inject_lock; unsigned long irq_ack; struct kvm_irq_ack_notifier irq_ack_notifier; }; @@ -40,6 +40,8 @@ struct kvm_pit { struct kvm_kpit_state pit_state; int irq_source_id; struct kvm_irq_mask_notifier mask_notifier; + struct workqueue_struct *wq; + struct work_struct expired; }; #define KVM_PIT_BASE_ADDRESS 0x40 diff --git a/arch/x86/kvm/irq.c b/arch/x86/kvm/irq.c index 0f4e488331c7..2095a049835e 100644 --- a/arch/x86/kvm/irq.c +++ b/arch/x86/kvm/irq.c @@ -90,7 +90,6 @@ EXPORT_SYMBOL_GPL(kvm_cpu_get_interrupt); void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu) { kvm_inject_apic_timer_irqs(vcpu); - kvm_inject_pit_timer_irqs(vcpu); /* TODO: PIT, RTC etc. */ } EXPORT_SYMBOL_GPL(kvm_inject_pending_timer_irqs);