Joel Hruska, 26 Jun 2017, ExtremeTech, Major Hyper-Threading Flaw Destabilizes Intel Kaby Lake, Skylake CPUs, here.
Here’s how Intel describes the errata in its own documentation.
Errata: SKZ7/SKW144/SKL150/SKX150/SKZ7/KBL095/KBW095 Short Loops Which Use AH/BH/CH/DH Registers May Cause Unpredictable System Behavior.
Problem: 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. This can only happen when both logical processors on the same physical processor are active.
Implication: Due to this erratum, the system may experience unpredictable system behavior.