Intel Hyperthreading bug...

[Rhinox]

It seems all Intel Skylake/Kabylake CPUs (i3, i5, i7, xeon e3) have bug in hyperthreading affecting every OS. Solution is to disable HT in bios, or update to the latest microcode...

 

[PigLover]

This one could be bad...

Sent from my SM-G950U using Tapatalk

 

[zir_blazer]

Technically it is already fixed in Microcode. AMD had a similar issue with SMT in Ryzen, also patched with Microcode.

 

[Evan]

This one could be bad...

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But I guess not very common or everybody would be screaming already.

 

[Tom5051]

The issue only occurs under very specific circumstances like running prime95. Pretty unlikely the average punter will run into this.

 

[Rhinox]

It is triggered by specific code sequence rather than some specific application, as Intel writes in documentation:

"...short loops of less than 64 instructions that use AH, BH, CH or DH registers as well as their corresponding wider register (e.g. RAX, EAX or AX for AH) may cause unpredictable system behavior..."

BTW, if anyone wants to know why high-end xeon cpus never use the latest architecture, here is the answer...

 

[nthu9280]

Is this different issue than the one discovered back in Dec 2015 timeframe?

Simple instructions for freezing a Skylake Processor.

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[gigatexal]

How does a chip’s microcode get updated? I doubt I’ve ever had to do it.

 

[anoother]

How does a chip’s microcode get updated? I doubt I’ve ever had to do it.

Usually included in new BIOS/UEFI releases.

Can also be applied during OS boot (see Microcode - Debian Wiki for a good overview)

 

[gigatexal]

Ahh thanks.

 

[niekbergboer]

Usually included in new BIOS/UEFI releases.

Can also be applied during OS boot (see Microcode - Debian Wiki for a good overview)

Indeed, two of my Proxmox VE / Ceph nodes run a Core i3-6100T (model 94, stepping 3), and these can be updated using the intel-microcode package and a reboot:

[ 0.000000] microcode: microcode updated early to revision 0xba, date = 2017-04-09
[ 0.000000] Linux version 4.10.15-1-pve (root@stretchbuild) (gcc version 6.3.0 20170516 (Debian 6.3.0-18) ) #1 SMP PVE 4.10.15-12 (Mon, 12 Jun 2017 11:18:07 +0200) ()
...
[ 0.093802] smpboot: CPU0: Intel(R) Core(TM) i3-6100T CPU @ 3.20GHz (family: 0x6, model: 0x5e, stepping: 0x3
...
[ 1.275300] microcode: sig=0x506e3, pf=0x2, revision=0xba
[ 1.282128] microcode: Microcode Update Driver: v2.2.

The update 0xba, with signature 0x506e3 is the fix.