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

Paolo Bonzini
2023-08-04T21:46:11Z

On 8/4/23 23:27, Sean Christopherson wrote:
>>> +
>>> + 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);
>
> Similar to my suggestsion for XSS, I think we drop the waiver for host_initiated
> accesses, i.e. require the feature to be enabled and exposed to the guest, even
> for the host.

No, please don't. Allowing host-initiated accesses is what makes it
possible to take the list of MSR indices and pass it blindly to
KVM_GET_MSR and KVM_SET_MSR. This should be documented, will send a patch.

Paolo