Re: [PATCH v9 03/22] KVM: VMX: Disable FRED if FRED consistency checks fail

[Sean Christopherson]

On Sun, Oct 26, 2025, Xin Li (Intel) wrote:
> diff --git a/arch/x86/kvm/vmx/capabilities.h b/arch/x86/kvm/vmx/capabilities.h
> index 6bd67c40ca3b..651507627ef3 100644
> --- a/arch/x86/kvm/vmx/capabilities.h
> +++ b/arch/x86/kvm/vmx/capabilities.h
> @@ -405,6 +405,16 @@ static inline bool vmx_pebs_supported(void)
>  	return boot_cpu_has(X86_FEATURE_PEBS) && kvm_pmu_cap.pebs_ept;
>  }
>  
> +static inline bool cpu_has_vmx_fred(void)
> +{
> +	/*
> +	 * setup_vmcs_config() guarantees FRED VM-entry/exit controls
> +	 * are either all set or none.  So, no need to check FRED VM-exit
> +	 * controls.
> +	 */

Eh, omit the comment, there are at least six other control pairs that use this
logic.

> +	return (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_FRED);

Unnecessary parentheses.

> +}
> +
>  static inline bool cpu_has_notify_vmexit(void)
>  {
>  	return vmcs_config.cpu_based_2nd_exec_ctrl &
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index be48ba2d70e1..fcfa99160018 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -8020,6 +8020,9 @@ static __init void vmx_set_cpu_caps(void)
>  		kvm_cpu_cap_check_and_set(X86_FEATURE_DTES64);
>  	}
>  
> +	if (!cpu_has_vmx_fred())
> +		kvm_cpu_cap_clear(X86_FEATURE_FRED);
> +
>  	if (!enable_pmu)
>  		kvm_cpu_cap_clear(X86_FEATURE_PDCM);
>  	kvm_caps.supported_perf_cap = vmx_get_perf_capabilities();
> -- 
> 2.51.0
>