linux-kernel - Re: [PATCH] [v2] intel_pstate: Fix user input of min/max to legal policy region

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Date:	Wed, 9 Sep 2015 20:12:01 +0900
From:	Seiichi Ikarashi <s.ikarashi@...fujitsu.com>
To:	Chen Yu <yu.c.chen@...el.com>
CC:	<kristen@...ux.intel.com>, <rjw@...ysocki.net>,
	<viresh.kumar@...aro.org>, <rui.zhang@...el.com>,
	<linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] [v2] intel_pstate: Fix user input of min/max to legal
 policy region

Hi, Yu

On 2015-09-09 19:27, Chen Yu wrote:
> In current code, max_perf_pct might be smaller than min_perf_pct
> by improper user input:
> 
> $ grep . /sys/devices/system/cpu/intel_pstate/m*_perf_pct
> /sys/devices/system/cpu/intel_pstate/max_perf_pct:100
> /sys/devices/system/cpu/intel_pstate/min_perf_pct:100
> 
> $ echo 80 > /sys/devices/system/cpu/intel_pstate/max_perf_pct
> 
> $ grep . /sys/devices/system/cpu/intel_pstate/m*_perf_pct
> /sys/devices/system/cpu/intel_pstate/max_perf_pct:80
> /sys/devices/system/cpu/intel_pstate/min_perf_pct:100
> 
> Fix this problem by 2 steps:
> 1.Normalize the user input to [min_policy, max_policy].
> 2.Make sure max_perf_pct>=min_perf_pct, suggested by Seiichi Ikarashi.
> 
> Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> ---
> v2:
>  - Add logic to ensure max_perf_pct>=min_perf_pct.
> ---
>  drivers/cpufreq/intel_pstate.c | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
> index fcb929e..a0b935f 100644
> --- a/drivers/cpufreq/intel_pstate.c
> +++ b/drivers/cpufreq/intel_pstate.c
> @@ -423,6 +423,8 @@ static ssize_t store_max_perf_pct(struct kobject *a, struct attribute *b,
>  
>  	limits.max_sysfs_pct = clamp_t(int, input, 0 , 100);
>  	limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct);
> +	limits.max_perf_pct = max(limits.min_policy_pct, limits.max_perf_pct);
> +	limits.max_perf_pct = max(limits.min_perf_pct, limits.max_perf_pct);
>  	limits.max_perf = div_fp(int_tofp(limits.max_perf_pct), int_tofp(100));
>  
>  	if (hwp_active)
> @@ -442,6 +444,8 @@ static ssize_t store_min_perf_pct(struct kobject *a, struct attribute *b,
>  
>  	limits.min_sysfs_pct = clamp_t(int, input, 0 , 100);
>  	limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct);
> +	limits.min_perf_pct = min(limits.max_policy_pct, limits.min_perf_pct);
> +	limits.min_perf_pct = min(limits.max_perf_pct, limits.min_perf_pct);
>  	limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
>  
>  	if (hwp_active)
> @@ -985,12 +989,19 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
>  
>  	limits.min_policy_pct = (policy->min * 100) / policy->cpuinfo.max_freq;
>  	limits.min_policy_pct = clamp_t(int, limits.min_policy_pct, 0 , 100);
> -	limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct);
> -	limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
> -
>  	limits.max_policy_pct = (policy->max * 100) / policy->cpuinfo.max_freq;
>  	limits.max_policy_pct = clamp_t(int, limits.max_policy_pct, 0 , 100);
> +
> +	/* Normalize user input to [min_policy_pct, max_policy_pct] */
> +	limits.min_perf_pct = max(limits.min_policy_pct, limits.min_sysfs_pct);
> +	limits.min_perf_pct = min(limits.max_policy_pct, limits.min_perf_pct);
>  	limits.max_perf_pct = min(limits.max_policy_pct, limits.max_sysfs_pct);
> +	limits.max_perf_pct = max(limits.min_policy_pct, limits.max_perf_pct);
> +
> +	/* Make sure min_perf_pct <= max_perf_pct */
> +	limits.min_perf_pct = min(limits.max_perf_pct, limits.min_perf_pct);

You chose max_perf_pct prior to min_perf_pct here.
I agree.

> +
> +	limits.min_perf = div_fp(int_tofp(limits.min_perf_pct), int_tofp(100));
>  	limits.max_perf = div_fp(int_tofp(limits.max_perf_pct), int_tofp(100));
>  
>  	if (hwp_active)
> 

I think this patch is what it should be. Good job.

Regards,
Seiichi

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