Re: [PATCH v2 21/21] KVM:x86: Support CET supervisor shadow stack MSR access

[Edgecombe, Rick P]

On Fri, 2023-04-21 at 09:46 -0400, Yang Weijiang wrote:
> +
> +       incpt = !is_cet_state_supported(vcpu,
> XFEATURE_MASK_CET_KERNEL);
> +       incpt |= !guest_cpuid_has(vcpu, X86_FEATURE_SHSTK);
> +
> +       vmx_set_intercept_for_msr(vcpu, MSR_IA32_INT_SSP_TAB,
> MSR_TYPE_RW, incpt);
> +       vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL0_SSP,
> MSR_TYPE_RW, incpt);
> +       vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL1_SSP,
> MSR_TYPE_RW, incpt);
> +       vmx_set_intercept_for_msr(vcpu, MSR_IA32_PL2_SSP,
> MSR_TYPE_RW, incpt);
>  }

Why is this tied to XFEATURE_MASK_CET_KERNEL? I don't know how the SVM
side works, but the host kernel doesn't use this xfeature. Just not
clear on what the intention is. Why not use
kvm_cet_kernel_shstk_supported() again?