Re: [PATCH 33/44] KVM: x86: Do VMX/SVM support checks directly in vendor code

[Paolo Bonzini]

On 11/3/22 19:35, Sean Christopherson wrote:
> It's technically required.  IA32_FEAT_CTL and thus KVM_INTEL depends on any of
> CPU_SUP_{INTEL,CENATUR,ZHAOXIN}, but init_ia32_feat_ctl() is invoked if and only
> if the actual CPU type matches one of the aforementioned CPU_SUP_*.
>
> E.g. running a kernel built with
>
>    CONFIG_CPU_SUP_INTEL=y
>    CONFIG_CPU_SUP_AMD=y
>    # CONFIG_CPU_SUP_HYGON is not set
>    # CONFIG_CPU_SUP_CENTAUR is not set
>    # CONFIG_CPU_SUP_ZHAOXIN is not set
>
> on a Cenatur or Zhaoxin CPU will leave X86_FEATURE_VMX set but not set
> X86_FEATURE_MSR_IA32_FEAT_CTL.  If VMX isn't enabled in MSR_IA32_FEAT_CTL, KVM
> will get unexpected #UDs when trying to enable VMX.

Oh, I see.  Perhaps X86_FEATURE_VMX and X86_FEATURE_SGX should be moved 
to one of the software words instead of using cpuid.  Nothing that you 
should care about for this series though.

Paolo