From: Giovanni Gherdovich ggherdovich@suse.cz
[ Upstream commit 51beea8862a3095559862df39554f05042e1195b ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- 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 18d292fc466cb..20e1cea262e4b 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -2002,9 +2002,11 @@ 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; }