KVM: x86: add tracepoint to wait_lapic_expire

Add tracepoint to wait_lapic_expire.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
[Remind reader if early or late. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -1134,6 +1134,7 @@ void wait_lapic_expire(struct kvm_vcpu *vcpu)
 	tsc_deadline = apic->lapic_timer.expired_tscdeadline;
 	apic->lapic_timer.expired_tscdeadline = 0;
 	guest_tsc = kvm_x86_ops->read_l1_tsc(vcpu, native_read_tsc());
+	trace_kvm_wait_lapic_expire(vcpu->vcpu_id, guest_tsc - tsc_deadline);
 
 	/* __delay is delay_tsc whenever the hardware has TSC, thus always.  */
 	if (guest_tsc < tsc_deadline)

arch/x86/kvm/trace.h

@@ -914,6 +914,26 @@ TRACE_EVENT(kvm_pvclock_update,
 		  __entry->flags)
 );
 
+TRACE_EVENT(kvm_wait_lapic_expire,
+	TP_PROTO(unsigned int vcpu_id, s64 delta),
+	TP_ARGS(vcpu_id, delta),
+
+	TP_STRUCT__entry(
+		__field(	unsigned int,	vcpu_id		)
+		__field(	s64,		delta		)
+	),
+
+	TP_fast_assign(
+		__entry->vcpu_id	   = vcpu_id;
+		__entry->delta             = delta;
+	),
+
+	TP_printk("vcpu %u: delta %lld (%s)",
+		  __entry->vcpu_id,
+		  __entry->delta,
+		  __entry->delta < 0 ? "early" : "late")
+);
+
 #endif /* _TRACE_KVM_H */
 
 #undef TRACE_INCLUDE_PATH