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Comment by rzzzt | Hacker News Reader

The answer is yes, if the processor supports PCID: https://news.ycombinator.com/item?id=16094349

  Simplistically, it allows TLB-cached page table contents to be tagged with a 
  context identifier, and limits the lookups in the TLB to only match within 
  the currently allowed context. TLB cached entires with a different PCID will 
  be ignored.

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I think you are confusing the TLB and processor data caches.

PCIDs exist for virtual addresses and are implemented in the TLB, not the processor caches. The processor caches are physically indexed, not virtually indexed.

So, does the processor cache have a mechanism to tell which "process" to which a given line belongs? Nope. Two processes (or a process and the kernel) that share memory can be in two PCIDs, but share the processor caches.

You are correct. My assumption was that the original question is not focused on the data cache itself, and so the DTLB does qualify for "knowing" what belongs to which context.

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