KVM: x86: reset APIC ID when enabling LAPIC

APIC ID should be set to the initial APIC ID when enabling LAPIC.
This only matters if the guest changes APIC ID.  No sane OS does that.
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -1720,9 +1720,10 @@ void kvm_lapic_set_base(struct kvm_vcpu *vcpu, u64 value)
 
 	/* update jump label if enable bit changes */
 	if ((old_value ^ value) & MSR_IA32_APICBASE_ENABLE) {
-		if (value & MSR_IA32_APICBASE_ENABLE)
+		if (value & MSR_IA32_APICBASE_ENABLE) {
+			kvm_apic_set_xapic_id(apic, vcpu->vcpu_id);
 			static_key_slow_dec_deferred(&apic_hw_disabled);
-		else
+		} else
 			static_key_slow_inc(&apic_hw_disabled.key);
 		recalculate_apic_map(vcpu->kvm);
 	}