The Debian project is warning Intel Skylake and Kaby Lake users to disable Hyper Threading (HT) on their CPUs due to a possible issue affecting those with out-of-date microcode. Intel Skylake and Kabylake (6th and 7th gen CPUs) could “dangerously misbehave” when Hyper Threading is enabled. Users are advised to get an updated BIOS/UEFI while for some Skylake CPUs the updated Intel microcode packages available on Linux have a fix.
— source phoronix.com