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    SubjectRe: [PATCH 19/19] KVM: x86: Enable supervisor IBT support for guest
    On Thu, Jun 16, 2022 at 04:46:43AM -0400, Yang Weijiang wrote:
    > Mainline kernel now supports supervisor IBT for kernel code,
    > to make s-IBT work in guest(nested guest), pass through
    > MSR_IA32_S_CET to guest(nested guest) if host kernel and KVM
    > enabled IBT. Note, s-IBT can work independent to host xsaves
    > support because guest MSR_IA32_S_CET can be stored/loaded from
    > specific VMCS field.
    >
    > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
    > ---
    > arch/x86/kvm/cpuid.h | 5 +++++
    > arch/x86/kvm/vmx/nested.c | 3 +++
    > arch/x86/kvm/vmx/vmx.c | 27 ++++++++++++++++++++++++---
    > arch/x86/kvm/x86.c | 13 ++++++++++++-
    > 4 files changed, 44 insertions(+), 4 deletions(-)
    >
    > diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
    > index ac72aabba981..c67c1e2fc11a 100644
    > --- a/arch/x86/kvm/cpuid.h
    > +++ b/arch/x86/kvm/cpuid.h
    > @@ -230,4 +230,9 @@ static __always_inline bool guest_pv_has(struct kvm_vcpu *vcpu,
    > return vcpu->arch.pv_cpuid.features & (1u << kvm_feature);
    > }
    >
    > +static __always_inline bool cet_kernel_ibt_supported(void)
    > +{
    > + return HAS_KERNEL_IBT && kvm_cpu_cap_has(X86_FEATURE_IBT);
    > +}

    As stated before; I would much rather it expose S_CET unconditional of
    host kernel config.

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