Re: [PATCH v12 20/24] KVM: x86: Enable CET virtualization for VMX and advertise to userspace

[Sean Christopherson]

On Mon, Aug 11, 2025, Chao Gao wrote:
> diff --git a/arch/x86/include/asm/vmx.h b/arch/x86/include/asm/vmx.h
> index ce10a7e2d3d9..c85c50019523 100644
> --- a/arch/x86/include/asm/vmx.h
> +++ b/arch/x86/include/asm/vmx.h
> @@ -134,6 +134,7 @@
>  #define VMX_BASIC_DUAL_MONITOR_TREATMENT	BIT_ULL(49)
>  #define VMX_BASIC_INOUT				BIT_ULL(54)
>  #define VMX_BASIC_TRUE_CTLS			BIT_ULL(55)
> +#define VMX_BASIC_NO_HW_ERROR_CODE_CC		BIT_ULL(56)
>  
>  static inline u32 vmx_basic_vmcs_revision_id(u64 vmx_basic)
>  {
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index 85079caaf507..2515b2623fb1 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -944,6 +944,7 @@ void kvm_set_cpu_caps(void)
>  		VENDOR_F(WAITPKG),
>  		F(SGX_LC),
>  		F(BUS_LOCK_DETECT),
> +		F(SHSTK),

I think we should limit this to 64-bit kernels with X86_64_F().  It probably
won't change anything in practice, but we mitigate the virtualization holes related
to 32-bit vCPUs at least a little bit.

>  	);
>  
>  	/*
> @@ -970,6 +971,7 @@ void kvm_set_cpu_caps(void)
>  		F(AMX_INT8),
>  		F(AMX_BF16),
>  		F(FLUSH_L1D),
> +		F(IBT),
>  	);
>