linux-kernel - Re: [PATCH v2 6/8] x86: Add hardware prefetch control support for x86

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Date:   Mon, 14 Mar 2022 14:05:56 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Kohei Tarumizu <tarumizu.kohei@...itsu.com>,
        catalin.marinas@....com, will@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, hpa@...or.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 6/8] x86: Add hardware prefetch control support for x86

On 3/11/22 02:19, Kohei Tarumizu wrote:
> +static int broadwell_write_pfreg(enum pfctl_attr pattr, unsigned int cpu,
> +				 unsigned int level, u64 val)
> +{
> +	int ret;
> +	u64 reg;
> +
> +	ret = rdmsrl_on_cpu(cpu, MSR_MISC_FEATURE_CONTROL, &reg);
> +	if (ret)
> +		return ret;
> +
> +	ret = broadwell_modify_pfreg(pattr, &reg, level, val);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = wrmsrl_on_cpu(cpu, MSR_MISC_FEATURE_CONTROL, reg);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
> +}

This needs to integrate _somehow_ with the pseudo_lock.c code.  Right
now, I suspect that code would just overwrite any MSR changes made by
this code.