Re: [PATCH v15 16/41] KVM: VMX: Set up interception for CET MSRs

[Xiaoyao Li]

On 9/13/2025 7:22 AM, Sean Christopherson wrote:
> From: Yang Weijiang <weijiang.yang@xxxxxxxxx>
>
> Enable/disable CET MSRs interception per associated feature configuration.
>
> Pass through CET MSRs that are managed by XSAVE, as they cannot be
> intercepted without also intercepting XSAVE. However, intercepting XSAVE
> would likely cause unacceptable performance overhead.
> MSR_IA32_INT_SSP_TAB is not managed by XSAVE, so it is intercepted.
>
> Note, this MSR design introduced an architectural limitation of SHSTK and
> IBT control for guest, i.e., when SHSTK is exposed, IBT is also available
> to guest from architectural perspective since IBT relies on subset of SHSTK
> relevant MSRs.
>
> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
> Tested-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
> Tested-by: John Allen <john.allen@xxxxxxx>
> Tested-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>

Reviewed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>