Users of Intel's Skylake and Kaby Lake processors with HyperThreading capabilities are being warned to disable the feature pending firmware updates created to resolve an erratum in the chip which can hard-crash a system and result in data loss. This can only happen when both logical processors on the same physical processor are active.
However, the Debian developers uncovered what is called an errata flaw, an error in a CPUs hardwired logic, which has the potential to destabilise Intel's six and seventh generation processors and throw-up unpredictable behaviour.
Recently, Intel documented the defect in several specification updates for the affected processors and made microcode fixes available for some Skylake processors, according to Holschuh.
The issue came to light when Mark Shinwell, a developer working on the OCaml toolchain, contacted the Debian team to explain that the OCaml compiler triggered weird behavior on Intel processors.
Intel's Hyper-Threading is the term given to the process the chipmaker uses to run tasks across the multiple core found in modern processors at the same time. But, as HH points out, the "safest course of action is to disable HyperThreading for now". Although they state that Intel did not respond directly back to them, the chip giant issued microcode fixes since then. Find your motherboard manufacturer's BIOS update history and look for fixes that include "Intel processor errata KBL095, KBW095". Skylake CPUs have been in the wild since August 2015, and if this was a critical or easy-to-trigger bug, we'd likely have heard about it long before now.
If you're experiencing weird behavior since upgrading to Skylake or Kaby Lake, check your motherboard manufacturer for updated firmware. For now, it's best to disable hyperthreading if you handle sensitive data, particularly in business applications. In 2005, Canadian computer scientist Colin Percival also identified a hyper-threading-related security flaw that affected earlier Intel Pentium and Xeon processors.