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From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Giovanni Gherdovich <ggherdovich@suse.cz>
Cc: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Borislav Petkov <bp@suse.de>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	"the arch/x86 maintainers" <x86@kernel.org>,
	Linux PM <linux-pm@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Subject: Re: [PATCH v2 3/3] x86, sched: Bail out of frequency invariance if turbo_freq/base_freq gives 0
Date: Wed, 3 Jun 2020 16:51:21 +0200	[thread overview]
Message-ID: <CAJZ5v0iNFDjt6rqXfiwn_UwiKgJDgAUshChVh5YoOCXF9hy=_A@mail.gmail.com> (raw)
In-Reply-To: <20200531182453.15254-4-ggherdovich@suse.cz>

On Sun, May 31, 2020 at 8:26 PM Giovanni Gherdovich <ggherdovich@suse.cz> wrote:
>
> Be defensive against the case where the processor reports a base_freq
> larger than turbo_freq (the ratio would be zero).
>
> Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Fixes: 1567c3e3467c ("x86, sched: Add support for frequency invariance")

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

> ---
>  arch/x86/kernel/smpboot.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index fe154c8226ba..f619007f46cf 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -1976,6 +1976,7 @@ static bool core_set_max_freq_ratio(u64 *base_freq, u64 *turbo_freq)
>  static bool intel_set_max_freq_ratio(void)
>  {
>         u64 base_freq, turbo_freq;
> +       u64 turbo_ratio;
>
>         if (slv_set_max_freq_ratio(&base_freq, &turbo_freq))
>                 goto out;
> @@ -2009,9 +2010,15 @@ static bool intel_set_max_freq_ratio(void)
>                 return false;
>         }
>
> -       arch_turbo_freq_ratio = div_u64(turbo_freq * SCHED_CAPACITY_SCALE,
> -                                       base_freq);
> +       turbo_ratio = div_u64(turbo_freq * SCHED_CAPACITY_SCALE, base_freq);
> +       if (!turbo_ratio) {
> +               pr_debug("Non-zero turbo and base frequencies led to a 0 ratio.\n");
> +               return false;
> +       }
> +
> +       arch_turbo_freq_ratio = turbo_ratio;
>         arch_set_max_freq_ratio(turbo_disabled());
> +
>         return true;
>  }
>
> --
> 2.16.4
>

  reply	other threads:[~2020-06-03 14:51 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-31 18:24 [PATCH v2 0/3] More frequency invariance fixes for x86 Giovanni Gherdovich
2020-05-31 18:24 ` [PATCH v2 1/3] x86, sched: check for counters overflow in frequency invariant accounting Giovanni Gherdovich
2020-06-03 14:22   ` Rafael J. Wysocki
2020-06-16 12:21   ` [tip: sched/core] " tip-bot2 for Giovanni Gherdovich
2020-10-22  8:46   ` [PATCH v2 1/3] " Peter Zijlstra
2020-10-22 12:21     ` Giovanni Gherdovich
2020-10-22 12:30       ` Peter Zijlstra
2020-05-31 18:24 ` [PATCH v2 2/3] x86, sched: Bail out of frequency invariance if turbo frequency is unknown Giovanni Gherdovich
2020-06-01 23:34   ` Ricardo Neri
2020-07-06 20:19     ` Ira Weiny
2020-06-03 14:23   ` Rafael J. Wysocki
2020-06-16 12:21   ` [tip: sched/core] " tip-bot2 for Giovanni Gherdovich
2020-05-31 18:24 ` [PATCH v2 3/3] x86, sched: Bail out of frequency invariance if turbo_freq/base_freq gives 0 Giovanni Gherdovich
2020-06-03 14:51   ` Rafael J. Wysocki [this message]
2020-06-16 12:21   ` [tip: sched/core] " tip-bot2 for Giovanni Gherdovich
2020-06-03 12:31 ` [PATCH v2 0/3] More frequency invariance fixes for x86 Peter Zijlstra

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