[andreiw]

Depends on how you define hardware and software. There are global workarounds that amount to crippling CPU behavior, to provide guarantees for code not written to be spectre safe. I guess that’s what you mean by “hardware”. But “software” approaches are localized mitigations to code written to avoid spectre attacks - and these localized mitigations use arch specific sequences to do so.

[microcolonel]

Another major problem with the software level mitigations is that they cost considerably more. Speculation fences cut performance to a small integer fraction of prior performance.

[andreiw]

Then tell your SiP to do better.

On Arm the conditional speculation barrier couldn’t be more lightweight (CSDB).