KVM: TDX: Add methods to ignore virtual apic related operation

TDX protects TDX guest APIC state from VMM.  Implement access methods of
TDX guest vAPIC state to ignore them or return zero.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Message-ID: <20250222014757.897978-13-binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: yamahata

arch/x86/kvm/vmx/main.c

@@ -240,6 +240,15 @@ static bool vt_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
 	return vmx_apic_init_signal_blocked(vcpu);
 }
 
+static void vt_set_virtual_apic_mode(struct kvm_vcpu *vcpu)
+{
+	/* Only x2APIC mode is supported for TD. */
+	if (is_td_vcpu(vcpu))
+		return;
+
+	return vmx_set_virtual_apic_mode(vcpu);
+}
+
 static void vt_apicv_pre_state_restore(struct kvm_vcpu *vcpu)
 {
 	struct pi_desc *pi = vcpu_to_pi_desc(vcpu);
@@ -248,6 +257,14 @@ static void vt_apicv_pre_state_restore(struct kvm_vcpu *vcpu)
 	memset(pi->pir, 0, sizeof(pi->pir));
 }
 
+static void vt_hwapic_isr_update(struct kvm_vcpu *vcpu, int max_isr)
+{
+	if (is_td_vcpu(vcpu))
+		return;
+
+	return vmx_hwapic_isr_update(vcpu, max_isr);
+}
+
 static int vt_sync_pir_to_irr(struct kvm_vcpu *vcpu)
 {
 	if (is_td_vcpu(vcpu))
@@ -437,6 +454,14 @@ static void vt_get_exit_info(struct kvm_vcpu *vcpu, u32 *reason,
 	vmx_get_exit_info(vcpu, reason, info1, info2, intr_info, error_code);
 }
 
+static void vt_set_apic_access_page_addr(struct kvm_vcpu *vcpu)
+{
+	if (is_td_vcpu(vcpu))
+		return;
+
+	vmx_set_apic_access_page_addr(vcpu);
+}
+
 static void vt_refresh_apicv_exec_ctrl(struct kvm_vcpu *vcpu)
 {
 	if (is_td_vcpu(vcpu)) {
@@ -561,13 +586,13 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.update_cr8_intercept = vmx_update_cr8_intercept,
 
 	.x2apic_icr_is_split = false,
-	.set_virtual_apic_mode = vmx_set_virtual_apic_mode,
-	.set_apic_access_page_addr = vmx_set_apic_access_page_addr,
+	.set_virtual_apic_mode = vt_set_virtual_apic_mode,
+	.set_apic_access_page_addr = vt_set_apic_access_page_addr,
 	.refresh_apicv_exec_ctrl = vt_refresh_apicv_exec_ctrl,
 	.load_eoi_exitmap = vmx_load_eoi_exitmap,
 	.apicv_pre_state_restore = vt_apicv_pre_state_restore,
 	.required_apicv_inhibits = VMX_REQUIRED_APICV_INHIBITS,
-	.hwapic_isr_update = vmx_hwapic_isr_update,
+	.hwapic_isr_update = vt_hwapic_isr_update,
 	.sync_pir_to_irr = vt_sync_pir_to_irr,
 	.deliver_interrupt = vt_deliver_interrupt,
 	.dy_apicv_has_pending_interrupt = pi_has_pending_interrupt,