Re: [PATCH v5 11/19] KVM:VMX: Emulate read and write to CET MSRs

Yang, Weijiang
2023-08-09T03:05:25Z

On 8/5/2023 5:40 AM, Paolo Bonzini wrote:
> On 8/3/23 06:27, Yang Weijiang wrote:
>> +        if (msr_info->index == MSR_KVM_GUEST_SSP)
>> +            msr_info->data = vmcs_readl(GUEST_SSP);
>
> Accesses to MSR_KVM_(GUEST_)SSP must be rejected unless host-initiated.
Yes, it's kept, in v5 it's folded in:

+static bool kvm_cet_is_msr_accessible(struct kvm_vcpu *vcpu,

+struct msr_data *msr)

+{

+if (is_shadow_stack_msr(msr->index)) {

+if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK))

+return false;

+

+if (msr->index == MSR_KVM_GUEST_SSP)

+return msr->host_initiated;

+

+return msr->host_initiated ||

+guest_cpuid_has(vcpu, X86_FEATURE_SHSTK);

+}

+

+if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK) &&

+!kvm_cpu_cap_has(X86_FEATURE_IBT))

+return false;

+

+return msr->host_initiated ||

+guest_cpuid_has(vcpu, X86_FEATURE_IBT) ||

+guest_cpuid_has(vcpu, X86_FEATURE_SHSTK); }

+

> Paolo
>