Commit 51beea88 authored by Giovanni Gherdovich's avatar Giovanni Gherdovich Committed by Peter Zijlstra

x86, sched: Bail out of frequency invariance if turbo frequency is unknown

There may be CPUs that support turbo boost but don't declare any turbo
ratio, i.e. their MSR_TURBO_RATIO_LIMIT is all zeroes. In that condition
scale-invariant calculations can't be performed.

Fixes: 1567c3e3 ("x86, sched: Add support for frequency invariance")
Suggested-by: default avatarRicardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: default avatarGiovanni Gherdovich <ggherdovich@suse.cz>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: default avatarRicardo Neri <ricardo.neri-calderon@linux.intel.com>
Link: https://lkml.kernel.org/r/20200531182453.15254-3-ggherdovich@suse.cz
parent e2b0d619
...@@ -2002,9 +2002,11 @@ static bool intel_set_max_freq_ratio(void) ...@@ -2002,9 +2002,11 @@ static bool intel_set_max_freq_ratio(void)
/* /*
* Some hypervisors advertise X86_FEATURE_APERFMPERF * Some hypervisors advertise X86_FEATURE_APERFMPERF
* but then fill all MSR's with zeroes. * but then fill all MSR's with zeroes.
* Some CPUs have turbo boost but don't declare any turbo ratio
* in MSR_TURBO_RATIO_LIMIT.
*/ */
if (!base_freq) { if (!base_freq || !turbo_freq) {
pr_debug("Couldn't determine cpu base frequency, necessary for scale-invariant accounting.\n"); pr_debug("Couldn't determine cpu base or turbo frequency, necessary for scale-invariant accounting.\n");
return false; return false;
} }
......
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