Messages in this thread Patch in this message | | | From | Giovanni Gherdovich <> | Subject | [PATCH 2/2] x86, sched: Bail out of frequency invariance if turbo frequency is unknown | Date | Tue, 28 Apr 2020 15:24:50 +0200 |
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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.
Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz> Suggested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Fixes: 1567c3e3467c ("x86, sched: Add support for frequency invariance") --- arch/x86/kernel/smpboot.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 4718f29a3065..ab2a0df7d1fb 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1991,9 +1991,11 @@ static bool intel_set_max_freq_ratio(void) /* * Some hypervisors advertise X86_FEATURE_APERFMPERF * 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) { - pr_debug("Couldn't determine cpu base frequency, necessary for scale-invariant accounting.\n"); + if (!base_freq || !turbo_freq) { + pr_debug("Couldn't determine cpu base or turbo frequency, necessary for scale-invariant accounting.\n"); return false; } -- 2.16.4
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