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@xxxxxxx>
AuthorDate: Sun, 31 May 2020 20:24:52 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Signed-off-by: Giovanni Gherdovich <ggherdovich@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Tested-by: Ricardo Neri <ricardo.neri-calderon@xxxxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200531182453.15254-3-ggherdovich@xxxxxxx
---
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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