> I do wonder to what degree we could hard-partition caches, such that speculative prefetches go straight into CPU-specific caches, and doesn't get to go into s

> I do wonder to what degree we could hard-partition caches, such that speculative prefetches go straight into CPU-specific caches, and doesn't get to go into shared caches (e.g. L3) until it stops being speculative. This is already sort of possible. The TLB flushing can take advantage of the PCID to determine, based on the process, whether the cache must be flushed - this provides process level isolation of the TLB. I believe recent CPUs are increasing the size of some PCID related components since it's becoming increasingly important post-kPTI.