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

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Date:	Wed, 9 Sep 2015 02:15:00 +0000
From:	"Chen, Yu C" <yu.c.chen@...el.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"kristen@...ux.intel.com" <kristen@...ux.intel.com>
CC:	"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Zhang, Rui" <rui.zhang@...el.com>,
	"lenb@...nel.org" <lenb@...nel.org>,
	Seiichi Ikarashi <s.ikarashi@...fujitsu.com>
Subject: RE: [PATCH][rfc] intel_pstate: Fix user input of min/max to legal
 policy region

Hi ,Rafael

> -----Original Message-----
> From: Rafael J. Wysocki [mailto:rjw@...ysocki.net]
> Sent: Tuesday, September 08, 2015 5:47 AM
> To: Chen, Yu C; kristen@...ux.intel.com
> Cc: viresh.kumar@...aro.org; linux-pm@...r.kernel.org; linux-
> kernel@...r.kernel.org; Zhang, Rui; lenb@...nel.org
> Subject: Re: [PATCH][rfc] intel_pstate: Fix user input of min/max to legal
> policy region
> 
> On Wednesday, August 12, 2015 11:49:19 AM Chen Yu wrote:
> > In current code, if system is using performance policy, user can
> > modify the max_perf_pct to any values lower than 100:
> >
> > $ 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
> >
> > the max_perf_pct above is lower than min_perf_pct, which is not
> > reasonable.
> >
> > This patch solves this problem by clamping min_perf_pct and
> > max_perf_pct to be strictly inside [min_policy_pct,max_policy_pct].
> >
> > Signed-off-by: Chen Yu <yu.c.chen@...el.com>
> 
> Looks reasonable to me.
> 
> Kristen, any objections?
> 
Thanks for your reply! 
According to suggestion from  Seiichi, will re-send a V2 version patch,
to make some update.

Best Regards,
Yu