KVM: LAPIC: introduce kvm_get_lapic_target_expiration_tsc()

Introdce kvm_get_lapic_target_expiration_tsc() to get APIC Timer target
deadline tsc.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index dce6c0b..531fc28 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1706,6 +1706,15 @@ void kvm_free_lapic(struct kvm_vcpu *vcpu)
  * LAPIC interface
  *----------------------------------------------------------------------
  */
+u64 kvm_get_lapic_target_expiration_tsc(struct kvm_vcpu *vcpu)
+{
+	struct kvm_lapic *apic = vcpu->arch.apic;
+
+	if (!lapic_in_kernel(vcpu))
+		return 0;
+
+	return apic->lapic_timer.tscdeadline;
+}
 
 u64 kvm_get_lapic_tscdeadline_msr(struct kvm_vcpu *vcpu)
 {