KVM: x86: Add APIC_LVTx() macro.

An APIC_LVTx macro is introduced to calcualte the APIC_LVTx register
offset based on the index in the lapic_lvt_entry enum. Later patches
will extend the APIC_LVTx macro to support the APIC_LVTCMCI register
in order to implement Corrected Machine Check Interrupt signaling.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Jue Wang <juew@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220610171134.772566-4-juew@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -2093,9 +2093,8 @@ static int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
 			u32 lvt_val;
 
 			for (i = 0; i < KVM_APIC_MAX_NR_LVT_ENTRIES; i++) {
-				lvt_val = kvm_lapic_get_reg(apic,
-						       APIC_LVTT + 0x10 * i);
-				kvm_lapic_set_reg(apic, APIC_LVTT + 0x10 * i,
+				lvt_val = kvm_lapic_get_reg(apic, APIC_LVTx(i));
+				kvm_lapic_set_reg(apic, APIC_LVTx(i),
 					     lvt_val | APIC_LVT_MASKED);
 			}
 			apic_update_lvtt(apic);
@@ -2411,7 +2410,7 @@ void kvm_lapic_reset(struct kvm_vcpu *vcpu, bool init_event)
 	kvm_apic_set_version(apic->vcpu);
 
 	for (i = 0; i < KVM_APIC_MAX_NR_LVT_ENTRIES; i++)
-		kvm_lapic_set_reg(apic, APIC_LVTT + 0x10 * i, APIC_LVT_MASKED);
+		kvm_lapic_set_reg(apic, APIC_LVTx(i), APIC_LVT_MASKED);
 	apic_update_lvtt(apic);
 	if (kvm_vcpu_is_reset_bsp(vcpu) &&
 	    kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_LINT0_REENABLED))

arch/x86/kvm/lapic.h

@@ -39,6 +39,8 @@ enum lapic_lvt_entry {
 	KVM_APIC_MAX_NR_LVT_ENTRIES,
 };
 
+#define APIC_LVTx(x) (APIC_LVTT + 0x10 * (x))
+
 struct kvm_timer {
 	struct hrtimer timer;
 	s64 period; 				/* unit: ns */