| From e90e263376391e94e01ab5820a47dc29026cbc51 Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Sun, 31 May 2020 20:24:52 +0200 |
| Subject: x86, sched: Bail out of frequency invariance if turbo frequency is |
| unknown |
| |
| 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 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 |
| |
