Intel Skylake, Kaby Lake users warned of HT flaw

The bug affects all Kaby Lake and Skylake chips with Hyperthreading

The bug affects all Kaby Lake and Skylake chips with Hyperthreading

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". This can only happen when both logical processors on the same physical processor are active. What this means is that "application and system misbehavior, data corruption, and data loss" are all real possibilities.

Implication: "Due to this erratum, the system may experience unpredictable system behavior". However, it's not clear whether the updates made to date will address the issue in Kaby Lake processors, he noted.

"We do not have enough information at this time to know how much software out there will trigger this specific defect", Holschuh said yesterday.

This advisory is about a processor/microcode defect recently identified on Intel Skylake and Intel Kaby Lake processors with hyper-threading enabled.

Henrique de Moraes Holschuh warned that all operating systems, not only Linux, were subject to the bug.

It is not known how common these conditions are, but that they can occur in the wild is confirmed: The erratum was brought to the attention of the Debian team by OCaml toolchain developer Mark Shinwell following crashes in the OCaml compiler traced back to the bug.

The second option is to wait for the vendor of the motherboard being used with the CPU to roll out a new version of the Unified Extensible Firmware Interface (UEFI) or BIOS that provides a fix for the errata.

Intel has fixed the issue for certain processors, but users will have to install a microcode package or BIOS update to apply the fix. Those with other Skylake model numbers should disable hyper-threading and then contact their vendors for a BIOS/UEFI fix, he added.

The message recommended users of Kaby Lake processors "immediately disable hyper-threading in the BIOS/UEFI configuration".

Computing has requested comment on this issue from Intel.

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