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Date: Wed, 3 Feb 2016 17:23:03 +0100
From: Radim Krčmář <rkrcmar@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
Yuki Shibuya <shibuya.yk@...s.nec.co.jp>
Subject: [PATCH 2/4] KVM: x86: refactor PIT state inject_lock
Following patches would be even uglier if inject_lock didn't go away.
Patch changes the virtual wire comment to better describe our situation.
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
arch/x86/kvm/i8254.c | 67 ++++++++++++++++++++++------------------------------
arch/x86/kvm/i8254.h | 3 +--
2 files changed, 29 insertions(+), 41 deletions(-)
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index de5f5018026f..a137eb381012 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -236,16 +236,13 @@ 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);
- int value;
- spin_lock(&ps->inject_lock);
+ atomic_set(&ps->irq_ack, 1);
if (atomic_add_unless(&ps->pending, -1, 0))
/* in this case, we had multiple outstanding pit interrupts
* that we needed to inject. Reinject
*/
queue_kthread_work(&ps->pit->worker, &ps->pit->expired);
- ps->irq_ack = 1;
- spin_unlock(&ps->inject_lock);
}
void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu)
@@ -276,34 +273,25 @@ static void pit_do_work(struct kthread_work *work)
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.
+ if (!atomic_xchg(&ps->irq_ack, 0))
+ return;
+
+ kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 1, false);
+ kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 0, false);
+
+ /*
+ * Provides NMI watchdog support via Virtual Wire mode.
+ * The route is: PIT -> LVT0 in NMI mode.
+ *
+ * Note: Our Virtual Wire implementation does not follow
+ * the MP specification. We propagate a PIT interrupt to all
+ * VCPUs and only when LVT0 is in NMI mode. The interrupt can
+ * also be simultaneously delivered through PIC and IOAPIC.
*/
- 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, false);
- kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 0, false);
-
- /*
- * 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 (atomic_read(&kvm->arch.vapics_in_nmi_mode) > 0)
- kvm_for_each_vcpu(i, vcpu, kvm)
- kvm_apic_nmi_wd_deliver(vcpu);
- }
+ if (atomic_read(&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)
@@ -323,6 +311,12 @@ static enum hrtimer_restart pit_timer_fn(struct hrtimer *data)
return HRTIMER_NORESTART;
}
+static void kvm_pit_reset_reinject(struct kvm_pit *pit)
+{
+ atomic_set(&pit->pit_state.pending, 0);
+ atomic_set(&pit->pit_state.irq_ack, 1);
+}
+
static void create_pit_timer(struct kvm *kvm, u32 val, int is_period)
{
struct kvm_kpit_state *ps = &kvm->arch.vpit->pit_state;
@@ -345,8 +339,7 @@ static void create_pit_timer(struct kvm *kvm, u32 val, int is_period)
ps->timer.function = pit_timer_fn;
ps->kvm = ps->pit->kvm;
- atomic_set(&ps->pending, 0);
- ps->irq_ack = 1;
+ kvm_pit_reset_reinject(ps->pit);
/*
* Do not allow the guest to program periodic timers with small
@@ -646,18 +639,15 @@ void kvm_pit_reset(struct kvm_pit *pit)
}
mutex_unlock(&pit->pit_state.lock);
- atomic_set(&pit->pit_state.pending, 0);
- pit->pit_state.irq_ack = 1;
+ kvm_pit_reset_reinject(pit);
}
static void pit_mask_notifer(struct kvm_irq_mask_notifier *kimn, bool mask)
{
struct kvm_pit *pit = container_of(kimn, struct kvm_pit, mask_notifier);
- if (!mask) {
- atomic_set(&pit->pit_state.pending, 0);
- pit->pit_state.irq_ack = 1;
- }
+ if (!mask)
+ kvm_pit_reset_reinject(pit);
}
static const struct kvm_io_device_ops pit_dev_ops = {
@@ -691,7 +681,6 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
mutex_init(&pit->pit_state.lock);
mutex_lock(&pit->pit_state.lock);
- spin_lock_init(&pit->pit_state.inject_lock);
pid = get_pid(task_tgid(current));
pid_nr = pid_vnr(pid);
diff --git a/arch/x86/kvm/i8254.h b/arch/x86/kvm/i8254.h
index c84990b42b5b..f8cf4b84f435 100644
--- a/arch/x86/kvm/i8254.h
+++ b/arch/x86/kvm/i8254.h
@@ -33,8 +33,7 @@ struct kvm_kpit_state {
u32 speaker_data_on;
struct mutex lock;
struct kvm_pit *pit;
- spinlock_t inject_lock;
- unsigned long irq_ack;
+ atomic_t irq_ack;
struct kvm_irq_ack_notifier irq_ack_notifier;
};
--
2.7.0
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