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New HyperThreading Flaw Affects Intel 6th And 7th Generation Skylake and Kaby Lake-Based Processors (hothardware.com)
MojoKid writes: A new flaw has been discovered that impacts Intel 6th and 7th Generation Skylake and Kaby Lake-based processors that support HyperThreading. The issue affects all OS types and is detailed by Intel errata documentation and points out that 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 (e.g. RAX, EAX or AX for AH), may cause unpredictable system behavior, including crashes and potential data loss. The OCaml toolchain community first began investigating processors with these malfunctions back in January and found reports stemming back to at least the first half of 2016.
The OCaml team was able pinpoint the issue to Skylake's HyperThreading implementation and notified Intel. While Intel reportedly did not respond directly, it has issued some microcode fixes since then. That's not the end of the story, however, as the microcode fixes need to be implemented into BIOS/UEFI updates as well and it is not clear at this time if all major vendors have included these changes in their latest revisions.
The OCaml team was able pinpoint the issue to Skylake's HyperThreading implementation and notified Intel. While Intel reportedly did not respond directly, it has issued some microcode fixes since then. That's not the end of the story, however, as the microcode fixes need to be implemented into BIOS/UEFI updates as well and it is not clear at this time if all major vendors have included these changes in their latest revisions.
The fix doesn't disable hyperthreading, the fix fixes the bug.
The fix works only for some models of Skylake (models 78 and 94, stepping 3). On any other Skylakes and all Kaby Lakes there's no way other than disabling hyperthreading entirely.
A fix might or might not be released in the future, Intel doesn't say a word about the issue.
The creatures outside looked from Alt-Right to Antifa; but already it was impossible to say which was which.
There are a lot of inaccurate comments here. First of all, reloading a new BIOS/system firmware may be the best solution for most users, however it is not the only solution. If you know how you can do a hotfix load of firmware in Linux and I suspect other OSes.
For example, I downloaded the latest firmware from Intel (dated 10 May) and placed it in /lib/firmware. Then running:
echo 1 > /sys/devices/system/cpu/microcode/reload
was enough. In the log is an entry:
[2246029.695843] microcode: updated to revision 0xba, date = 2017-04-09
In addition, the article points to a message on the debian-devel (not users) mailing list. This indicates that i3/5/7 processors with hyperthreading are affected. AFAIK, no i5 processors have hyperthreading, even though the family/model/stepping on my system is indicated in the message as vulnerable.
CPU(s): 4
On-line CPU(s) list: 0-3
Thread(s) per core: 1
Core(s) per socket: 4
Socket(s): 1
Well what is it? Hyperthreading or all skylake/kaby lake? Curious minds want to know.
One last thing. The current firmware package is dated May 10. Seven weeks ago, The firmware itself was produced April 9 -- 11 weeks ago. Unless Intel has not updated yet for this, many posters here are running around with their hair on fire about something already fixed.
But I guess that is normal for slashdot.