linux-kernel - [PATCH 0/2] More frequency invariance fixes for x86

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Date:   Tue, 28 Apr 2020 15:24:48 +0200
From:   Giovanni Gherdovich <ggherdovich@...e.cz>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>, Len Brown <lenb@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>
Cc:     x86@...nel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Giovanni Gherdovich <ggherdovich@...e.cz>
Subject: [PATCH 0/2] More frequency invariance fixes for x86

Patch 1/2 prevents a division by zero in case the product
"delta_MPERF * arch_max_freq_ratio" overflows u64, as suggested by Linus at [1].
This patch supersedes the version at [2], as it also disables frequency
invariance when that overflow happens.

Patch 2/2 implements the recommendation by Ricardo Neri to check for an all
zero MSR_TURBO_RATIO_LIMIT and disable freq invariance in that case too.

[1] https://lore.kernel.org/lkml/CAHk-=wiX+NT2yxtdPszH9U_S96MCNQA56GJFXY45mZc47yG5KQ@mail.gmail.com/
[2] https://lore.kernel.org/lkml/20200422144055.18171-1-ggherdovich@suse.cz/
[3] https://lore.kernel.org/lkml/20200424013222.GA26355@ranerica-svr.sc.intel.com/

Giovanni Gherdovich (2):
  x86, sched: Prevent divisions by zero in frequency invariant
    accounting
  x86, sched: Bail out of frequency invariance if turbo frequency is
    unknown

 arch/x86/kernel/smpboot.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

-- 
2.16.4