Re: [PATCH v9 10/22] KVM: VMX: Add support for saving and restoring FRED MSRs

[Chao Gao]

>@@ -4316,6 +4374,12 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> #endif
> 	case MSR_IA32_U_CET:
> 	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
>+		if (!guest_cpu_cap_has(vcpu, X86_FEATURE_SHSTK)) {
>+			WARN_ON_ONCE(msr != MSR_IA32_FRED_SSP0);

This will be triggered if the guest only supports IBT and tries to write U_CET here.

>+			vcpu->arch.fred_ssp0_fallback = data;
>+			break;
>+		}
>+
> 		kvm_set_xstate_msr(vcpu, msr_info);
> 		break;
> 	default:
>@@ -4669,6 +4733,12 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> #endif
> 	case MSR_IA32_U_CET:
> 	case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP:
>+		if (!guest_cpu_cap_has(vcpu, X86_FEATURE_SHSTK)) {
>+			WARN_ON_ONCE(msr_info->index != MSR_IA32_FRED_SSP0);

ditto.

With this fixed,

Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>