[v2,3/3] x86, sched: Bail out of frequency invariance if turbo_freq/base_freq gives 0
diff mbox series

Message ID 20200531182453.15254-4-ggherdovich@suse.cz
State New, archived
Headers show
Series
  • More frequency invariance fixes for x86
Related show

Commit Message

Giovanni Gherdovich May 31, 2020, 6:24 p.m. UTC
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")
---
 arch/x86/kernel/smpboot.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

Comments

Rafael J. Wysocki June 3, 2020, 2:51 p.m. UTC | #1
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
>

Patch
diff mbox series

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;
 }