It's just been one security disaster after another for Intel the last few years. Meltdown, Spectre variant after variant and this week the "Microarchitectural Data Sampling" aka Zombieload attack have all required performance-degrading fixes and workarounds. There is no way around turning hyperthreading off to be safe from MDS/Zombieload and this is a rather high performance-price to pay. So what if you don't want to?

Disabling SMT/HyperThreading to get full protection against MDS/Zombieload on top of the mitigation code for "meltdown", several "spectre" variants and other security-issues discovered on Intel CPUs is a high price to pay for security on Intel CPUs. The total performance-penalty in many workloads is adding up. Unfortunately there is no safe and secure way around the performance-penalties - so you may want to..