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 <clalance@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
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@ -34,6 +34,7 @@
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#include <linux/kvm_host.h>
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#include <linux/slab.h>
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#include <linux/workqueue.h>
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#include "irq.h"
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#include "i8254.h"
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@ -244,11 +245,22 @@ static void kvm_pit_ack_irq(struct kvm_irq_ack_notifier *kian)
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{
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struct kvm_kpit_state *ps = container_of(kian, struct kvm_kpit_state,
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irq_ack_notifier);
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raw_spin_lock(&ps->inject_lock);
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if (atomic_dec_return(&ps->pit_timer.pending) < 0)
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int value;
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spin_lock(&ps->inject_lock);
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value = atomic_dec_return(&ps->pit_timer.pending);
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if (value < 0)
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/* spurious acks can be generated if, for example, the
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* PIC is being reset. Handle it gracefully here
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*/
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atomic_inc(&ps->pit_timer.pending);
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else if (value > 0)
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/* in this case, we had multiple outstanding pit interrupts
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* that we needed to inject. Reinject
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*/
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queue_work(ps->pit->wq, &ps->pit->expired);
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ps->irq_ack = 1;
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raw_spin_unlock(&ps->inject_lock);
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spin_unlock(&ps->inject_lock);
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}
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void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu)
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@ -264,10 +276,10 @@ void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu)
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hrtimer_start_expires(timer, HRTIMER_MODE_ABS);
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}
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static void destroy_pit_timer(struct kvm_timer *pt)
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static void destroy_pit_timer(struct kvm_pit *pit)
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{
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pr_debug("execute del timer!\n");
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hrtimer_cancel(&pt->timer);
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hrtimer_cancel(&pit->pit_state.pit_timer.timer);
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cancel_work_sync(&pit->expired);
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}
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static bool kpit_is_periodic(struct kvm_timer *ktimer)
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@ -281,6 +293,60 @@ static struct kvm_timer_ops kpit_ops = {
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.is_periodic = kpit_is_periodic,
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};
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static void pit_do_work(struct work_struct *work)
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{
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struct kvm_pit *pit = container_of(work, struct kvm_pit, expired);
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struct kvm *kvm = pit->kvm;
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struct kvm_vcpu *vcpu;
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int i;
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struct kvm_kpit_state *ps = &pit->pit_state;
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int inject = 0;
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/* Try to inject pending interrupts when
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* last one has been acked.
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*/
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spin_lock(&ps->inject_lock);
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if (ps->irq_ack) {
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ps->irq_ack = 0;
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inject = 1;
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}
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spin_unlock(&ps->inject_lock);
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if (inject) {
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kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 1);
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kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 0);
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/*
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* Provides NMI watchdog support via Virtual Wire mode.
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* The route is: PIT -> PIC -> LVT0 in NMI mode.
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*
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* Note: Our Virtual Wire implementation is simplified, only
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* propagating PIT interrupts to all VCPUs when they have set
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* LVT0 to NMI delivery. Other PIC interrupts are just sent to
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* VCPU0, and only if its LVT0 is in EXTINT mode.
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*/
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if (kvm->arch.vapics_in_nmi_mode > 0)
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kvm_for_each_vcpu(i, vcpu, kvm)
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kvm_apic_nmi_wd_deliver(vcpu);
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}
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}
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static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
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{
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struct kvm_timer *ktimer = container_of(data, struct kvm_timer, timer);
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struct kvm_pit *pt = ktimer->kvm->arch.vpit;
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if (ktimer->reinject || !atomic_read(&ktimer->pending)) {
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atomic_inc(&ktimer->pending);
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queue_work(pt->wq, &pt->expired);
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}
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if (ktimer->t_ops->is_periodic(ktimer)) {
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hrtimer_add_expires_ns(&ktimer->timer, ktimer->period);
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return HRTIMER_RESTART;
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} else
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return HRTIMER_NORESTART;
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}
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static void create_pit_timer(struct kvm_kpit_state *ps, u32 val, int is_period)
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{
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struct kvm_timer *pt = &ps->pit_timer;
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@ -292,13 +358,13 @@ static void create_pit_timer(struct kvm_kpit_state *ps, u32 val, int is_period)
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/* TODO The new value only affected after the retriggered */
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hrtimer_cancel(&pt->timer);
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cancel_work_sync(&ps->pit->expired);
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pt->period = interval;
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ps->is_periodic = is_period;
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pt->timer.function = kvm_timer_fn;
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pt->timer.function = pit_timer_fn;
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pt->t_ops = &kpit_ops;
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pt->kvm = ps->pit->kvm;
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pt->vcpu = pt->kvm->bsp_vcpu;
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atomic_set(&pt->pending, 0);
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ps->irq_ack = 1;
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@ -347,7 +413,7 @@ static void pit_load_count(struct kvm *kvm, int channel, u32 val)
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}
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break;
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default:
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destroy_pit_timer(&ps->pit_timer);
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destroy_pit_timer(kvm->arch.vpit);
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}
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}
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@ -626,7 +692,14 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
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mutex_init(&pit->pit_state.lock);
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mutex_lock(&pit->pit_state.lock);
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raw_spin_lock_init(&pit->pit_state.inject_lock);
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spin_lock_init(&pit->pit_state.inject_lock);
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pit->wq = create_singlethread_workqueue("kvm-pit-wq");
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if (!pit->wq) {
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kfree(pit);
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return NULL;
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}
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INIT_WORK(&pit->expired, pit_do_work);
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kvm->arch.vpit = pit;
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pit->kvm = kvm;
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@ -685,54 +758,10 @@ void kvm_free_pit(struct kvm *kvm)
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mutex_lock(&kvm->arch.vpit->pit_state.lock);
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timer = &kvm->arch.vpit->pit_state.pit_timer.timer;
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hrtimer_cancel(timer);
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cancel_work_sync(&kvm->arch.vpit->expired);
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kvm_free_irq_source_id(kvm, kvm->arch.vpit->irq_source_id);
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mutex_unlock(&kvm->arch.vpit->pit_state.lock);
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destroy_workqueue(kvm->arch.vpit->wq);
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kfree(kvm->arch.vpit);
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}
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}
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static void __inject_pit_timer_intr(struct kvm *kvm)
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{
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struct kvm_vcpu *vcpu;
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int i;
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kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 1);
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kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 0);
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/*
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* Provides NMI watchdog support via Virtual Wire mode.
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* The route is: PIT -> PIC -> LVT0 in NMI mode.
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*
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* Note: Our Virtual Wire implementation is simplified, only
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* propagating PIT interrupts to all VCPUs when they have set
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* LVT0 to NMI delivery. Other PIC interrupts are just sent to
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* VCPU0, and only if its LVT0 is in EXTINT mode.
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*/
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if (kvm->arch.vapics_in_nmi_mode > 0)
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kvm_for_each_vcpu(i, vcpu, kvm)
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kvm_apic_nmi_wd_deliver(vcpu);
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}
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void kvm_inject_pit_timer_irqs(struct kvm_vcpu *vcpu)
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{
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struct kvm_pit *pit = vcpu->kvm->arch.vpit;
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struct kvm *kvm = vcpu->kvm;
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struct kvm_kpit_state *ps;
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if (pit) {
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int inject = 0;
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ps = &pit->pit_state;
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/* Try to inject pending interrupts when
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* last one has been acked.
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*/
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raw_spin_lock(&ps->inject_lock);
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if (atomic_read(&ps->pit_timer.pending) && ps->irq_ack) {
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ps->irq_ack = 0;
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inject = 1;
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}
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raw_spin_unlock(&ps->inject_lock);
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if (inject)
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__inject_pit_timer_intr(kvm);
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}
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}
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@ -27,7 +27,7 @@ struct kvm_kpit_state {
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u32 speaker_data_on;
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struct mutex lock;
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struct kvm_pit *pit;
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raw_spinlock_t inject_lock;
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spinlock_t inject_lock;
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unsigned long irq_ack;
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struct kvm_irq_ack_notifier irq_ack_notifier;
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};
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@ -40,6 +40,8 @@ struct kvm_pit {
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struct kvm_kpit_state pit_state;
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int irq_source_id;
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struct kvm_irq_mask_notifier mask_notifier;
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struct workqueue_struct *wq;
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struct work_struct expired;
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};
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#define KVM_PIT_BASE_ADDRESS 0x40
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@ -90,7 +90,6 @@ EXPORT_SYMBOL_GPL(kvm_cpu_get_interrupt);
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void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu)
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{
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kvm_inject_apic_timer_irqs(vcpu);
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kvm_inject_pit_timer_irqs(vcpu);
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/* TODO: PIT, RTC etc. */
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}
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EXPORT_SYMBOL_GPL(kvm_inject_pending_timer_irqs);
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