Re: [RFC PATCH 22/23] x86/hreset: Configure history reset

[Peter Zijlstra]

On Fri, Sep 09, 2022 at 04:12:04PM -0700, Ricardo Neri wrote:

> +static u32 hardware_history_features __read_mostly;

__ro_after_init ?

> +static __always_inline void setup_hreset(struct cpuinfo_x86 *c)
> +{
> +	if (!cpu_feature_enabled(X86_FEATURE_HRESET))
> +		return;
> +
> +	/*
> +	 * Use on all CPUs the hardware history features that the boot
> +	 * CPU supports.
> +	 */
> +	if (c == &boot_cpu_data)
> +		hardware_history_features = cpuid_ebx(0x20);
> +
> +	if (!hardware_history_features)
> +		return;
> +
> +	wrmsrl(MSR_IA32_HW_HRESET_ENABLE, hardware_history_features);
> +
> +	pr_info_once("x86/cpu: Intel History Reset (HRESET) activated\n");
> +}
> +
>  /* These bits should not change their value after CPU init is finished. */
>  static const unsigned long cr4_pinned_mask =
>  	X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |