linux-kernel - Re: [PATCH v2 3/7] arch_topology: disable frequency invariance for CONFIG_BL

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 30 Jul 2020 09:54:23 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ionela Voinescu <ionela.voinescu@....com>
Cc:     rjw@...ysocki.net, dietmar.eggemann@....com,
        catalin.marinas@....com, sudeep.holla@....com, will@...nel.org,
        linux@...linux.org.uk, mingo@...hat.com, peterz@...radead.org,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/7] arch_topology: disable frequency invariance for
 CONFIG_BL_SWITCHER

On 22-07-20, 10:37, Ionela Voinescu wrote:
> +++ b/drivers/base/arch_topology.c
> @@ -27,6 +27,7 @@ __weak bool arch_freq_counters_available(struct cpumask *cpus)
>  }
>  DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
>  
> +#ifndef CONFIG_BL_SWITCHER
>  void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
>  			 unsigned long max_freq)
>  {
> @@ -46,6 +47,7 @@ void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
>  	for_each_cpu(i, cpus)
>  		per_cpu(freq_scale, i) = scale;
>  }
> +#endif

I don't really like this change, the ifdef hackery is disgusting and
then we are putting that in a completely different part of the kernel.

There are at least these two ways of solving this, maybe more:

- Fix the bl switcher driver and add the complexity in it (which you
  tried to do earlier).

- Add a cpufreq flag to skip arch-set-freq-scale call.

Rafael ?

-- 
viresh