Messages in this thread Patch in this message | | | Date | Tue, 16 Jun 2020 12:21:54 -0000 | From | "tip-bot2 for Giovanni Gherdovich" <> | Subject | [tip: sched/core] x86, sched: Bail out of frequency invariance if turbo frequency is unknown |
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The following commit has been merged into the sched/core branch of tip:
Commit-ID: 51beea8862a3095559862df39554f05042e1195b Gitweb: https://git.kernel.org/tip/51beea8862a3095559862df39554f05042e1195b Author: Giovanni Gherdovich <ggherdovich@suse.cz> AuthorDate: Sun, 31 May 2020 20:24:52 +02:00 Committer: Peter Zijlstra <peterz@infradead.org> CommitterDate: Mon, 15 Jun 2020 14:10:02 +02:00
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: 1567c3e3467c ("x86, sched: Add support for frequency invariance") Suggested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Signed-off-by: Giovanni Gherdovich <ggherdovich@suse.cz> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Tested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Link: https://lkml.kernel.org/r/20200531182453.15254-3-ggherdovich@suse.cz --- 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 18d292f..20e1cea 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -2002,9 +2002,11 @@ out: /* * 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; }
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