This is a note to let you know that I've just added the patch titled

Revert "x86: CPU: Fix up "cpu MHz" in /proc/cpuinfo"

to the 4.13-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: revert-x86-cpu-fix-up-cpu-mhz-in-proc-cpuinfo.patch and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From ea0ee33988778fb73e4f45e7c73fb735787e2f32 Mon Sep 17 00:00:00 2001

From: Linus Torvalds torvalds@linux-foundation.org Date: Fri, 10 Nov 2017 11:19:11 -0800 Subject: Revert "x86: CPU: Fix up "cpu MHz" in /proc/cpuinfo"

From: Linus Torvalds torvalds@linux-foundation.org

commit ea0ee33988778fb73e4f45e7c73fb735787e2f32 upstream.

This reverts commit 941f5f0f6ef5338814145cf2b813cf1f98873e2f.

Sadly, it turns out that we really can't just do the cross-CPU IPI to all CPU's to get their proper frequencies, because it's much too expensive on systems with lots of cores.

So we'll have to revert this for now, and revisit it using a smarter model (probably doing one system-wide IPI at open time, and doing all the frequency calculations in parallel).

Reported-by: WANG Chao chao.wang@ucloud.cn Reported-by: Ingo Molnar mingo@kernel.org Cc: Rafael J Wysocki rafael.j.wysocki@intel.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- arch/x86/kernel/cpu/Makefile | 2 +- arch/x86/kernel/cpu/aperfmperf.c | 11 ++++------- arch/x86/kernel/cpu/proc.c | 4 +--- 3 files changed, 6 insertions(+), 11 deletions(-)

--- a/arch/x86/kernel/cpu/Makefile +++ b/arch/x86/kernel/cpu/Makefile @@ -21,7 +21,7 @@ obj-y += common.o obj-y += rdrand.o obj-y += match.o obj-y += bugs.o -obj-y += aperfmperf.o +obj-$(CONFIG_CPU_FREQ) += aperfmperf.o

obj-$(CONFIG_PROC_FS) += proc.o obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o --- a/arch/x86/kernel/cpu/aperfmperf.c +++ b/arch/x86/kernel/cpu/aperfmperf.c @@ -42,6 +42,10 @@ static void aperfmperf_snapshot_khz(void 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); @@ -70,7 +74,6 @@ static void aperfmperf_snapshot_khz(void

unsigned int arch_freq_get_on_cpu(int cpu) { - s64 time_delta; unsigned int khz;

if (!cpu_khz) @@ -79,12 +82,6 @@ unsigned int arch_freq_get_on_cpu(int cp if (!static_cpu_has(X86_FEATURE_APERFMPERF)) return 0;

- /* Don't bother re-computing within the cache threshold time. */ - time_delta = ktime_ms_delta(ktime_get(), per_cpu(samples.time, cpu)); - khz = per_cpu(samples.khz, cpu); - if (khz && time_delta < APERFMPERF_CACHE_THRESHOLD_MS) - return khz; - smp_call_function_single(cpu, aperfmperf_snapshot_khz, NULL, 1); khz = per_cpu(samples.khz, cpu); if (khz) --- a/arch/x86/kernel/cpu/proc.c +++ b/arch/x86/kernel/cpu/proc.c @@ -77,11 +77,9 @@ static int show_cpuinfo(struct seq_file seq_printf(m, "microcode\t: 0x%x\n", c->microcode);

if (cpu_has(c, X86_FEATURE_TSC)) { - unsigned int freq = arch_freq_get_on_cpu(cpu); + unsigned int freq = cpufreq_quick_get(cpu);

if (!freq) - freq = cpufreq_quick_get(cpu); - if (!freq) freq = cpu_khz; seq_printf(m, "cpu MHz\t\t: %u.%03u\n", freq / 1000, (freq % 1000));

Patches currently in stable-queue which might be from torvalds@linux-foundation.org are

queue-4.13/revert-x86-cpu-fix-up-cpu-mhz-in-proc-cpuinfo.patch