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Commit 33572ac0 authored by Chris Lalancette's avatar Chris Lalancette Committed by Avi Kivity
Browse files

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: default avatarChris Lalancette <clalance@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent c37eda13

arch/x86/kvm/i8254.c

+85 −56
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 


#include <linux/kvm_host.h>

#include <linux/slab.h>

#include <linux/workqueue.h>



#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);

	}

}

arch/x86/kvm/i8254.h

+3 −1
Original line number Diff line number Diff line
@@ -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

arch/x86/kvm/irq.c

+0 −1
Original line number Diff line number Diff line
@@ -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);