From c587c79f90632df59c61383c6abebb2e07a81911 Mon Sep 17 00:00:00 2001 From: Doug Smythies Date: Tue, 8 Aug 2017 14:05:12 -0700 Subject: [PATCH 1/2] cpufreq: intel_pstate: report correct CPU frequencies during trace The intel_pstate CPU frequency scaling driver has always calculated CPU frequency incorrectly. Recent changes have eliminted most of the issues, however the frequency reported in the trace buffer, if used, is incorrect. It remains desireable that cpu->pstate.scaling still be a nice round number for things such as when setting max and min frequencies. So the proposal is to just fix the reported frequency in the trace data. Fixes what remains of [1]. Link: https://bugzilla.kernel.org/show_bug.cgi?id=96521 # [1] Signed-off-by: Doug Smythies Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/intel_pstate.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 0566455f233e..65ee4fcace1f 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -1613,8 +1613,7 @@ static inline bool intel_pstate_sample(struct cpudata *cpu, u64 time) static inline int32_t get_avg_frequency(struct cpudata *cpu) { - return mul_ext_fp(cpu->sample.core_avg_perf, - cpu->pstate.max_pstate_physical * cpu->pstate.scaling); + return mul_ext_fp(cpu->sample.core_avg_perf, cpu_khz); } static inline int32_t get_avg_pstate(struct cpudata *cpu) From 8e2f3bce05e056575c2c84a344a8291fdabb5f21 Mon Sep 17 00:00:00 2001 From: Doug Smythies Date: Tue, 8 Aug 2017 14:12:49 -0700 Subject: [PATCH 2/2] cpufreq: x86: Disable interrupts during MSRs reading According to Intel 64 and IA-32 Architectures SDM, Volume 3, Chapter 14.2, "Software needs to exercise care to avoid delays between the two RDMSRs (for example interrupts)". So, disable interrupts during reading MSRs IA32_APERF and IA32_MPERF. See also: commit 4ab60c3f32c7 (cpufreq: intel_pstate: Disable interrupts during MSRs reading). Signed-off-by: Doug Smythies Reviewed-by: Len Brown Signed-off-by: Rafael J. Wysocki --- arch/x86/kernel/cpu/aperfmperf.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c index 7cf7c70b6ef2..0ee83321a313 100644 --- a/arch/x86/kernel/cpu/aperfmperf.c +++ b/arch/x86/kernel/cpu/aperfmperf.c @@ -40,13 +40,16 @@ static void aperfmperf_snapshot_khz(void *dummy) struct aperfmperf_sample *s = this_cpu_ptr(&samples); ktime_t now = ktime_get(); s64 time_delta = ktime_ms_delta(now, s->time); + unsigned long flags; /* Don't bother re-computing within the cache threshold time. */ if (time_delta < APERFMPERF_CACHE_THRESHOLD_MS) return; + local_irq_save(flags); rdmsrl(MSR_IA32_APERF, aperf); rdmsrl(MSR_IA32_MPERF, mperf); + local_irq_restore(flags); aperf_delta = aperf - s->aperf; mperf_delta = mperf - s->mperf;