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Date: Mon, 17 Aug 2020 17:10:58 +0200 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>, Giovanni Gherdovich <ggherdovich@...e.cz>, "Peter Zijlstra (Intel)" <peterz@...radead.org>, "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, Sasha Levin <sashal@...nel.org> Subject: [PATCH 5.7 008/393] x86, sched: Bail out of frequency invariance if turbo frequency is unknown From: Giovanni Gherdovich <ggherdovich@...e.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@...ux.intel.com> Signed-off-by: Giovanni Gherdovich <ggherdovich@...e.cz> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com> Tested-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com> Link: https://lkml.kernel.org/r/20200531182453.15254-3-ggherdovich@suse.cz Signed-off-by: Sasha Levin <sashal@...nel.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 2f24c334a938b..3917a2de1580c 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1999,9 +1999,11 @@ 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; } -- 2.25.1
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