On Sun, May 31, 2020 at 8:26 PM Giovanni Gherdovich <ggherdov...@suse.cz> wrote:
>
> 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.
>
> Signed-off-by: Giovanni Gherdovich <ggherdov...@suse.cz>
> Suggested-by: Ricardo Neri <ricardo.neri-calde...@linux.intel.com>
> Fixes: 1567c3e3467c ("x86, sched: Add support for frequency invariance")
Reviewed-by: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
> ---
> 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 d660966d7de7..fe154c8226ba 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -2001,9 +2001,11 @@ 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;
> }
>
> --
> 2.16.4
>
