Debian Project Warns: Turn off Hyperthreading with Skylake and Kaby Lake

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Demis
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Debian Project Warns: Turn off Hyperthreading with Skylake and Kaby Lake

Непрочитанное сообщение Demis » 2017-07-17 14:46:47

Народ, просто примите к сведению:

Суть истории (в кратце) такова, что нужно выключать гипертреадинг на этих процессорах, иначе бессонные ночи на этих процессорах с любой платформой гарантированы.

http://www.guru3d.com/news-story/debian-project-warns-turn-off-hyperthreading-with-skylake-and-kaby-lake.html

Debian developers have issued an advisory to disable hyper-threading with Intel and Skylake- Kaby Lake generation processors. The CPUs can cause problems under certain conditions, in fact on all operating systems.

They advside you to turn it off in the BIOS, and thus forfeit the extra performance you gain. It seems there is s defect for the CPUs in question that can cause compiler- and application crashes, unexpected behavior of programs and incorrect output software:

This warning advisory is relevant for users of systems with the Intel
processors code-named "Skylake" and "Kaby Lake". These are: the 6th and
7th generation Intel Core processors (desktop, embedded, mobile and
HEDT), their related server processors (such as Xeon v5 and Xeon v6), as
well as select Intel Pentium processor models.

TL;DR: unfixed Skylake and Kaby Lake processors could, in some
situations, dangerously misbehave when hyper-threading is enabled.
Disable hyper-threading immediately in BIOS/UEFI to work around the
problem. Read this advisory for instructions about an Intel-provided
fix.


SO, WHAT IS THIS ALL ABOUT?
---------------------------

This advisory is about a processor/microcode defect recently identified
on Intel Skylake and Intel Kaby Lake processors with hyper-threading
enabled. This defect can, when triggered, cause unpredictable system
behavior: it could cause spurious errors, such as application and system
misbehavior, data corruption, and data loss.

It was brought to the attention of the Debian project that this defect
is known to directly affect some Debian stable users (refer to the end
of this advisory for details), thus this advisory.

Please note that the defect can potentially affect any operating system
(it is not restricted to Debian, and it is not restricted to Linux-based
systems). It can be either avoided (by disabling hyper-threading), or
fixed (by updating the processor microcode).

Due to the difficult detection of potentially affected software, and the
unpredictable nature of the defect, all users of the affected Intel
processors are strongly urged to take action as recommended by this
advisory.

WHAT SHOULD I DO IF I DO HAVE SUCH PROCESSORS?
----------------------------------------------

Kaby Lake:

Users of systems with Intel Kaby Lake processors should immediately
*disable* hyper-threading in the BIOS/UEFI configuration. Please
consult your computer/motherboard's manual for instructions, or maybe
contact your system vendor's support line.

The Kaby Lake microcode updates that fix this issue are currently only
available to system vendors, so you will need a BIOS/UEFI update to get
it. Contact your system vendor: if you are lucky, such a BIOS/UEFI
update might already be available, or undergoing beta testing.

You want your system vendor to provide a BIOS/UEFI update that fixes
"Intel processor errata KBL095, KBW095 or the similar one for my Kaby
Lake processor".

We strongly recommend that you should not re-enable hyper-threading
until you install a BIOS/UEFI update with this fix.


Skylake:

Users of systems with Intel Skylake processors may have two choices:

1. If your processor model (listed in /proc/cpuinfo) is 78 or 94, and
the stepping is 3, install the non-free "intel-microcode" package
with base version 3.20170511.1, and reboot the system. THIS IS
THE RECOMMENDED SOLUTION FOR THESE SYSTEMS, AS IT FIXES OTHER
PROCESSOR ISSUES AS WELL.

Run this command in a command line shell (e.g. xterm) to know the
model numbers and steppings of your processor. All processors must
be either model 78 or 94, and stepping 3, for the intel-microcode fix
to work:

grep -E 'model|stepping' /proc/cpuinfo | sort -u

If you get any lines with a model number that is neither 78 or 94, or
the stepping is not 3, you will have to disable hyper-threading as
described on choice 2, below.

Refer to the section "INSTALLING THE MICROCODE UPDATES FROM NON-FREE"
for instructions on how to install the intel-microcode package.

2. For other processor models, disable hyper-threading in BIOS/UEFI
configuration. Please consult your computer/motherboard's manual for
instructions on how to do this. Contact your system vendor for a
BIOS/UEFI update that fixes "Intel erratum SKW144, SKL150, SKX150,
SKZ7, or the similar one for my Skylake processor".

NOTE: If you did not have the intel-microcode package installed on your
Skylake system before, it is best if you check for (and install) any
BIOS/UEFI updates *first*. Read the wiki page mentioned below.


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

Demis
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Debian Project Warns: Turn off Hyperthreading with Skylake and Kaby Lake

Непрочитанное сообщение Demis » 2017-07-19 19:31:54

И вот еще подсказали...
Ссылка на Интел https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/6th-gen-x-series-spec-update.pdf
http://www.tomshardware.co.uk/hyperthreading-kaby-lake-skylake-skylake-x,news-56085.html
Intel Hyperthreading Bug Unearthed In Kaby Lake And Skylake Processors
by Paul Alcorn June 26, 2017 at 5:06 PM

Hyperthreading, which schedules two logical threads on one physical core, has
been a boon to computing since its 2002 debut, but it hasn't been without its
headaches. After 15 years, we could logically expect the kinks to be ironed out,
but according to Henrique de Moraes Holschuh, a Debian Linux developer, Kaby
Lake and Skylake processors have a serious flaw in their hyperthreading
implementation.

This warning advisory is relevant for users of systems with the
Intel processors code-named "Skylake" and "Kaby Lake". These are:
the 6th and 7th generation Intel Core processors (desktop, embedded,
mobile and HEDT), their related server processors (such as Xeon v5
and Xeon v6), as well as select Intel Pentium processor models.
[...]
This advisory is about a processor/microcode defect recently
identified on Intel Skylake and Intel Kaby Lake processors with
hyper-threading enabled. This defect can, when triggered, cause
unpredictable system behavior: it could cause spurious errors, such
as application and system misbehavior, data corruption, and data
loss.

Intel's errata list for the recent Skylake-X processors (unearthed by Hot
Hardware), provide a bit more insight into the nuts and bolts of the issue.

Problem: 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 behaviour. This can only happen
when both logical processors on the same physical processor are
active.

Implication: Due to this erratum, the system may experience
unpredictable system behavior.
Workaround: It is possible for the BIOS to contain a workaround for
this erratum.

It appears the problem is confined to the sixth-generation Skylake and
seventh-generation Kaby Lake processors, but it spans from desktop and mobile
processors to Xeon models. The errata apply to any operating system, so it can
also impact Windows users. The defect can lead to data loss or corruption and
erratic system behavior. Unfortunately, the scope of the issue isn't
well-defined. Specific code patterns in applications will trigger the defect,
and as yet, there isn't a list of specific software to avoid.

For now, Holschuh recommends disabling hyperthreading to circumvent the issue,
but that isn't an acceptable long-term fix. There are microcode fixes available
for the Kaby Lake and Skylake processors through system vendors, which means you
might have to wait for a BIOS/UEFI update to rectify the issue. According to the
Debian post, for Kaby Lake processors that entails a BIOS/UEFI that fixes "Intel
processor errata KBL095, KBW095 or the similar one for Kaby Lake," and for
Skylake you'll need a fix for "Intel erratum SKW144, SKL150, SKX150, SKZ7."

Mark Shinwell, an OCaml toolchain developer, discovered the bug earlier this
year, but Intel hasn't responded to his queries. Intel did issue microcode
updates in the interim.

It's worth mentioning that we aren't aware of the extent of the issue and how
much it will impact everyday desktop users. Skylake debuted in August 2015, so
if there were a considerable number of mainstream desktop applications that
trigger the errata, it would have likely already been thrust into the spotlight.

We do recommend caution, though, until we learn how many motherboard vendors
have already issued the fix in BIOS/UEFI updates. For now, it's best to disable
hyperthreading if you handle sensitive data, particularly in business
applications. We've sent along the requisite request to Intel for more
information and will update accordingly.

Ну и так, до кучи:
https://hothardware.com/news/critical-flaw-in-intel-skylake-and-kaby-lake-hyperthreading-discovered-requiring-bios-microcode-fix

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BirdGovorun
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Debian Project Warns: Turn off Hyperthreading with Skylake and Kaby Lake

Непрочитанное сообщение BirdGovorun » 2017-07-21 15:51:42

Demis писал(а):Народ, просто примите к сведению:

Суть истории (в кратце) такова, что нужно выключать гипертреадинг на этих процессорах, иначе бессонные ночи на этих процессорах с любой платформой гарантированы.

Нашли где-то глючный процессор и пугают.

Код: Выделить всё

$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    2
Core(s) per socket:    2
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 158
Model name:            Intel(R) Pentium(R) CPU G4560 @ 3.50GHz
Stepping:              9
CPU MHz:               1499.847
CPU max MHz:           3500,0000
CPU min MHz:           800,0000
BogoMIPS:              7008.00
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              3072K
NUMA node0 CPU(s):     0-3


Код: Выделить всё

$ lsb_release -a
No LSB modules are available.
Distributor ID:   Debian
Description:   Debian GNU/Linux 9.0 (stretch)
Release:   9.0
Codename:   stretch

Работает без проблем, ни разу ничего не глючило.


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