Skylake / Kaby Lake Hyper-threading bug

Discussion in 'Hardware Components and Aftermarket Upgrades' started by Assembler, Jun 26, 2017.

  1. Assembler

    Assembler Notebook Geek

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    According to some debian developers, all Skylake and Kaby Lake (Desktop and mobile) processors are affected by a bug related to Intel's HT technology. It can cause "unpredictable system behavior", which means everything from simple calculation errors to system erros and even data loss. It does only occur on certain instructions and cases and has to be fixed by a microcode (BIOS) update.

    https://lists.debian.org/debian-devel/2017/06/msg00308.html

    As such errors are very common, it is still a drawback for all notebook users, because some machines might never receive an update for this bug.

    * First reported by @ajc9988 @TANWare in the Intel Core-X thread !

    * There is a way to update the CPU microcode to fix this issue without the need of a new BIOS version. Check post #51 for details !
     
    Last edited: Jul 1, 2017
  2. hmscott

    hmscott Notebook Nobel Laureate

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    Update: @Dufus has instructions for using the "VMware CPU Microcode Update Driver" that can be used to apply the latest Microcode updates for your CPU until a new BIOS with the Intel HT microcode patches is released for your computer:

    [How to] Update microcode from Windows
    ---------------------------------------------
    This might explain a lot of the "unexplainable" inconsistent behavior reported here from users... wow.

    In short, disable hyperthreading in the BIOS until you can get a BIOS / microcode update to fix the errata.

    @Phoenix @Papusan@Diversion @Shehary @HTWingNut @iunlock @Mr. Fox @mason2smart @Prema @TBoneSan @unclewebb@Rage Set @dspboys @ThePerfectStorm @DukeCLR@Coolane @Johnksss@iBUYPOWER@saturnotaku @iDave@Falkentyne @Coruscator @HardCoreGamer4Life @Arestavo @BanditBuzz @Atma

    @every-one-with-a-Skylake-Kabylake-CPU...sorry to those I skipped, it's a long list :)

    Intel's Skylake and Kaby Lake CPUs have nasty microcode bug
    Debian devs noticed errata to deep docs and now the fit's hitting the shan
    https://www.theregister.co.uk/2017/06/25/intel_skylake_kaby_lake_microcode_bug/

    "During April and May, Intel started updating processor documentation with a new errata note, and over the weekend we learned why: Skylake and Kaby Lake silicon has a microcode bug."

    "The errata is described in detail on the Debian mailing list, and affects Skylake and Kaby Lake Intel Core processors (in desktop, high-end desktop, embedded and mobile platforms), Xeon v5 and v6 server processors, and some Pentium models."

    "The Debian advisory says affected users need to disable hyper-threading “immediately” in their BIOS or UEFI settings, because the processors can “dangerously misbehave when hyper-threading is enabled.”

    Symptoms can include “application and system misbehavior, data corruption, and data loss”.

    Henrique de Moraes Holschuh, who authored the Debian post, notes that all operating systems, not only Linux, are subject to the bug.

    Intel's errata note (for example in this document), describes the issue like this:

    Under complex micro-architectural conditions, short loops of less than 64 instructions that use AH, BH, CH or DH registers as well as their corresponding wider register (eg RAX, EAX or AX for AH) may cause unpredictable system behavior. This can only happen when both logical processors on the same physical processor are active.

    The issue went rose above obscurity when Mark Shinwell, a developer working on the OCamlL toolchain, contacted the Debian team to explain that the OCaml compiler triggered an Intel microcode issue.

    Fixes
    Debian's post notes that Intel has documented the bug and its microcode fixes for Core 6th generation, Core 7th generation, Xeon v5 and v6, and Core 6th generation X series.

    For Debian users:
    • Kaby Lake – contact system vendors for BIOS/UEFI updates, and in the meantime disable hyper-threading;
    • Skylake – Depending on model, an intel-hyperthreading package is available; otherwise disable hyper-threading and wait for a BIOS/UEFI fix.
    Other users will need platform-specific fixes, or for BIOS/UEFI upgrades to land from their system vendors."
     
    Last edited: Jun 29, 2017
  3. hmscott

    hmscott Notebook Nobel Laureate

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    Serious Intel Skylake and Kaby Lake microcode bug unearthed
    http://hexus.net/tech/news/cpu/107293-serious-intel-skylake-kaby-lake-microcode-bug-unearthed/

    "Over the weekend an Intel processor microcode bug was highlighted with a warning advisory via the Debian.org mailing lists. Henrique de Moraes Holschuh warned that systems equipped with Intel Skylake and Kaby Lake processors could "in some situations, dangerously misbehave when hyper-threading is enabled." The errant behaviour could include"application and system misbehavior, data corruption, and data loss," all of which are serious for practical computer use."

    Lots more news outlets have checked-in articles on this...
     
  4. TANWare

    TANWare Just This Side of Senile, I think. Moderator

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    This was covered under the Intel thread at first too. by @ajc9988 .
     
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  5. hmscott

    hmscott Notebook Nobel Laureate

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    @ALLurGroceries please sticky this thread, it's an important problem with a temporary fix (disable hyperthreading in UEFI / BIOS) that all Skylake / Kabylake owners need to know about.

    Agreed, This thread for now needs a sticky. (added by @TANWare ?)

    Edit: How can this sticky be promoted to each vendor's forum that uses Skylake / Kabylake CPU's? In other words, what is the best way to get notice to everyone that reads NBR that is affected?
     
    Last edited: Jun 26, 2017
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  6. Assembler

    Assembler Notebook Geek

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    I honeslty didn't saw that and a quick forum search gave me no results on that topic, I will link to that in the first post.
     
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  7. ThatOldGuy

    ThatOldGuy Notebook Deity

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    Unless you don't backup your important Data; disabling Hyper-threading is an Overreaction.

    You got about the same chance of getting hit by lightning as causing a critical error with this bug. Light erratic system behavior is ok to live with until fix
     
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  8. JKnows

    JKnows Notebook Consultant

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    I was using using Skylake for overs a year and never had any problem, so i won't turn off hyper threading or wait bios update.
     
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  9. saturnotaku

    saturnotaku Notebook Prophet

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    We just have to hope that notebook manufacturers release the fix, rather than dismissing it as "light erratic system behavior." I think the large OEMs (HP, Dell, Lenovo) will come through, but I'm less certain about Asus, MSI, Clevo, since they don't have nearly the market share.
     
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  10. Tinderbox (UK)

    Tinderbox (UK) Sir Pumpkin Longshanks

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    I hope Intel does not provide the CPU for the mission to mars or some robotic surgery machine.

    John.
     
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