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Intel Skylake/Kaby Lake processors: broken hyper-threading (update BIOS asap)

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

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.

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).

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:
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"
.

The post goes into further detail about the problem itself and how Intel fixed it months after it was reported and didn't bother contacting the open source project that reported it (OCaml), so they didn't even know a fix was available.
 
May explain why my new laptop with an i5 7200u can't handle external video through the hdmi port (audio/video will not stay synced). Gonna test out turning off HT later this week.
 

Mohasus

Member
i7 7700 + Asus ROG STRIX B250F here.

Looking at their website, a BIOS update was released two days ago

STRIX B250F GAMING BIOS 0807
1.Update RC code to 1.8
2.Improve system stability and performance

Hope that's what they mean by system stability. Thanks for the warning.
 

Steel

Banned

Core i3s are 2/4 thread hyperthreaded. Most 5s are 4/4, but it seems I was wrong for mobile I5s, they're 2/4.

Mobile i3, i5 , and i7 skylake/Kaby lake CPUs all have HT.

I missed them adding hyperthreading to mobile i5s. learn something new.
 
Is the new MacBook pro that just released effected?

If the system contains a skylake or kaby lake processor with hyper threading, then yes. And I believe all new apple machines will contain either. This is a hardware issue and not OS exclusive. What I'm not too sure of is whether or not Apple/MacOS let's you shut off HT in it's bios.

Either way, make sure you update your bios/firmware immediately (but that's assuming laptop manufacturers have fixed the issue).
 

Xyphie

Member
Skylake has been out so long. How is this now a thing?

All complex silicon has bugs. It's likely an extreme edge case which 99% of users will never encounter.

Anyway should be fixed for months if you're on Windows via microcode updates.
 

mrklaw

MrArseFace
So my surface pro 4 i5, and my desktop 6700k both apparently ticking time bombs the the last 12 months. For the surface pro I'm stuck waiting for MS i suppose. For my desktop I need to check

Guessing this is very unlikely to happen otherwise we'd have had examples all over the internet by now.
 

jstripes

Banned
If the system contains a skylake or kaby lake processor with hyper threading, then yes. And I believe all new apple machines will contain either. This is a hardware issue and not OS exclusive. What I'm not too sure of is whether or not Apple/MacOS let's you shut off HT in it's bios.

Either way, make sure you update your bios/firmware immediately (but that's assuming laptop manufacturers have fixed the issue).

If any Apple products contain the flawed chips Apple will have a firmware update out in no time.
 

Guess Who

Banned
Is the new MacBook pro that just released effected?

Theoretically, all, 2016 and 2017 MacBooks and MacBook Pros, 2015 and 2017 27" iMacs with i7 processors (but not i5), and all 2017 21.5" iMacs with mobile i5 or desktop i7 processors (but not desktop i5) could be affected.
 
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