I think the real problem is cache sharing and hyperthreading kind of depends on it, so it was only ever secure to run two threads from the same security domain in the same core
Newbie question, if the cores share an L3 cache, does that factor in the branch prediction vulnerabilities? Or is the data affected by the vulnerability stay in caches closer to the individual core? I assume so otherwise all cores would be impacted but I’m unclear where it does sit