linux-kernel - Re: [PATCH v4 1/5] arch_topology: validate input frequencies to arch_set_freq

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Message-ID: <20200901205757.GA31302@arm.com>
Date:   Tue, 1 Sep 2020 21:57:57 +0100
From:   Ionela Voinescu <ionela.voinescu@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     rjw@...ysocki.net, dietmar.eggemann@....com,
        catalin.marinas@....com, sudeep.holla@....com, will@...nel.org,
        valentin.schneider@....com, linux-pm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/5] arch_topology: validate input frequencies to
 arch_set_freq_scale()

Hi Viresh,

On Monday 31 Aug 2020 at 16:43:08 (+0530), Viresh Kumar wrote:
> On 28-08-20, 18:32, Ionela Voinescu wrote:
> > The current frequency passed to arch_set_freq_scale() could end up
> > being 0, signaling an error in setting a new frequency. Also, if the
> > maximum frequency in 0, this will result in a division by 0 error.
> > 
> > Therefore, validate these input values before using them for the
> > setting of the frequency scale factor.
> > 
> > Signed-off-by: Ionela Voinescu <ionela.voinescu@....com>
> > Cc: Sudeep Holla <sudeep.holla@....com>
> > Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> > ---
> >  drivers/base/arch_topology.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> > 
> > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> > index 75f72d684294..5708eb724790 100644
> > --- a/drivers/base/arch_topology.c
> > +++ b/drivers/base/arch_topology.c
> > @@ -33,6 +33,11 @@ void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
> >  	unsigned long scale;
> >  	int i;
> >  
> > +	if (unlikely(!cur_freq || !max_freq)) {
> > +		WARN_ON_ONCE(1);
> > +		return;
> > +	}
> 
> This can be written as:
> 
>         if (WARN_ON_ONCE(!cur_freq || !max_freq))
>                 return;

Yes, that's better.

I've pushed v5 with this and your Acked-by.

Thanks for all your reviews,
Ionela.

> 
> With that.
> 
> Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
> 
> > +
> >  	/*
> >  	 * If the use of counters for FIE is enabled, just return as we don't
> >  	 * want to update the scale factor with information from CPUFREQ.
> > -- 
> > 2.17.1
> 
> -- 
> viresh