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>
This commit is contained in:
Chris Lalancette 2010-06-16 17:11:11 -04:00 committed by Avi Kivity
parent c37eda1384
commit 33572ac0ad
3 changed files with 88 additions and 58 deletions

View File

@ -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);
}
}

View File

@ -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

View File

@ -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);