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

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Message-ID: <YzLmr/vmYZozeUKm@hirez.programming.kicks-ass.net>
Date:   Tue, 27 Sep 2022 14:03:59 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc:     Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Ricardo Neri <ricardo.neri@...el.com>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Ben Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Len Brown <len.brown@...el.com>, Mel Gorman <mgorman@...e.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Valentin Schneider <vschneid@...hat.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, "Tim C . Chen" <tim.c.chen@...el.com>
Subject: Re: [RFC PATCH 22/23] x86/hreset: Configure history reset

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 |