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@xxxxxxxxxx>
---
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 188d827..467cc47 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -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);
- }
-}
diff --git a/arch/x86/kvm/i8254.h b/arch/x86/kvm/i8254.h
index 900d6b0..46d08ca 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 0f4e488..2095a04 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);
--
1.6.6.1
--
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