KVM: Add irq ack notifier list

This can be used by kvm subsystems that are interested in when
interrupts are acked, for example time drift compensation.
Signed-off-by: Avi Kivity <avi@qumranet.com>

arch/x86/kvm/irq.c

@@ -111,3 +111,25 @@ void kvm_set_irq(struct kvm *kvm, int irq, int level)
 	kvm_ioapic_set_irq(kvm->arch.vioapic, irq, level);
 	kvm_pic_set_irq(pic_irqchip(kvm), irq, level);
 }
+
+void kvm_notify_acked_irq(struct kvm *kvm, unsigned gsi)
+{
+	struct kvm_irq_ack_notifier *kian;
+	struct hlist_node *n;
+
+	hlist_for_each_entry(kian, n, &kvm->arch.irq_ack_notifier_list, link)
+		if (kian->gsi == gsi)
+			kian->irq_acked(kian);
+}
+
+void kvm_register_irq_ack_notifier(struct kvm *kvm,
+				   struct kvm_irq_ack_notifier *kian)
+{
+	hlist_add_head(&kian->link, &kvm->arch.irq_ack_notifier_list);
+}
+
+void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
+				     struct kvm_irq_ack_notifier *kian)
+{
+	hlist_del(&kian->link);
+}

arch/x86/kvm/irq.h

@@ -83,6 +83,11 @@ static inline int irqchip_in_kernel(struct kvm *kvm)
 void kvm_pic_reset(struct kvm_kpic_state *s);
 
 void kvm_set_irq(struct kvm *kvm, int irq, int level);
+void kvm_notify_acked_irq(struct kvm *kvm, unsigned gsi);
+void kvm_register_irq_ack_notifier(struct kvm *kvm,
+				   struct kvm_irq_ack_notifier *kian);
+void kvm_unregister_irq_ack_notifier(struct kvm *kvm,
+				     struct kvm_irq_ack_notifier *kian);
 
 void kvm_timer_intr_post(struct kvm_vcpu *vcpu, int vec);
 void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu);

include/asm-x86/kvm_host.h

@@ -321,6 +321,12 @@ struct kvm_mem_alias {
 	gfn_t target_gfn;
 };
 
+struct kvm_irq_ack_notifier {
+	struct hlist_node link;
+	unsigned gsi;
+	void (*irq_acked)(struct kvm_irq_ack_notifier *kian);
+};
+
 struct kvm_arch{
 	int naliases;
 	struct kvm_mem_alias aliases[KVM_ALIAS_SLOTS];
@@ -336,6 +342,7 @@ struct kvm_arch{
 	struct kvm_pic *vpic;
 	struct kvm_ioapic *vioapic;
 	struct kvm_pit *vpit;
+	struct hlist_head irq_ack_notifier_list;
 
 	int round_robin_prev_vcpu;
 	unsigned int tss_addr;