KVM: nVMX: Sync L2 guest CET states between L1/L2

When L2 guest status has been changed by L1 QEMU/KVM, sync the change back
to L2 guest before the later's next vm-entry. On the other hand, if it's
changed due to L2 guest, sync it back so as to let L1 guest see the change.

Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>

arch/x86/kvm/vmx/nested.c

@@ -2572,6 +2572,12 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	/* Note: may modify VM_ENTRY/EXIT_CONTROLS and GUEST/HOST_IA32_EFER */
 	vmx_set_efer(vcpu, vcpu->arch.efer);
 
+	if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE) {
+		vmcs_writel(GUEST_SSP, vmcs12->guest_ssp);
+		vmcs_writel(GUEST_INTR_SSP_TABLE, vmcs12->guest_ssp_tbl);
+		vmcs_writel(GUEST_S_CET, vmcs12->guest_s_cet);
+	}
+
 	/*
 	 * Guest state is invalid and unrestricted guest is disabled,
 	 * which means L1 attempted VMEntry to L2 with invalid state.
@@ -4103,6 +4109,12 @@ static void sync_vmcs02_to_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 
 	if (vmcs12->vm_exit_controls & VM_EXIT_SAVE_IA32_EFER)
 		vmcs12->guest_ia32_efer = vcpu->arch.efer;
+
+	if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_CET_STATE) {
+		vmcs12->guest_ssp = vmcs_readl(GUEST_SSP);
+		vmcs12->guest_ssp_tbl = vmcs_readl(GUEST_INTR_SSP_TABLE);
+		vmcs12->guest_s_cet = vmcs_readl(GUEST_S_CET);
+	}
 }
 
 /*