Discovered by the developers of the OCaml language, an issue that door, under specific conditions, a behavior not consistent system when enabled HyperThreading Skylake and Kaby Lake processors.
A flaw in the implementation of the technology Hyper-Threading Processor Intel Skylake and Kaby Lake was discovered by some developers of the OCaml language, who reported the fact to the developers of the Debian project. Intel partners and manufacturers of motherboards are working on a solution, but for now it is advisable to disable the feature on which processors are equipped with it.
The problem, which involves all facets of Skylake and Kaby Lake processors including Xeon lines, is described from an incorrect SKZ7 / SKW144 / SKL150 / SKX150 / KBL095 / KBW095, which says (as reported on the Debian mailing list ):
Errata: SKZ7 / SKW144 / SKL150 / SKX150 / KBL095 / KBW095 – Short cycles that use AH / BH / CH / DH registers can cause unpredictable behavior of the system.
Problem: in micro-complex architectural conditions, short cycles of less than 64 instructions that use the AH registers, BH, CH, or DH as well as their wider equivalents (eg. RAX, EAX or AX for AH) can cause a behavior unpredictable system. This can only happen when both logical processors on the same physical processor are active.
Implication: because of this erratum, the system may give rise to unpredictable behavior.
Assuming that the computer is (or should be) a deterministic science and introduce non-determinism can lead to problems of varying severity, including the loss of data, at the moment there are still no universal and permanent solutions to the problem. The suggestion is to completely disable the HyperThreading functionality , so as to avoid in toto that we can verify the situation described from an incorrect.
If, in fact, Intel has released a microcode update that fixes the problem for some Skylake processors (specifically, the models 78 and 94 with stepping 3), there are currently no solutions for other models. To get a solution you must wait to be released by the manufacturer of an updated BIOS / UEFI motherboard that solves the wrong KBL095 KBW095 and in the case of processors Kaby Lake and SKW144, SKL150, SKX150 and SK27 for Skylake processors. Some updates are already being released, while others will be released in the future.
It is recommended for anyone with a processor with Hyper-Threading architecture or Skylake Kaby Lake, follow actively updates the BIOS / UEFI own mother and install patches board as soon as they are released.