Downfall Attacks
What I find odd is that after the initial Spectre attacks, there have been a long string of these attacks discovered by outside researchers and then patched by the chipmakers.In principle it seems like the chipmakers should hold all the cards when it comes to discovery: they are experts in speculative execution, know exactly how their chips work and have massive existing validation suites, simulators and internal machine-readable specifications for the low-level operations of these chips.Outside researches need to reverse all this by probing a black box (plus a few much-worse-than-insider sources like patents).Yet years after the initial disclosures it's still random individuals or groups who are discovering these? Perhaps pre-Spectre this attack vector wasn't even considered, but once the general mechanism was obvious did the chip-makers not simply set their biggest brains down and say "go through this with a fine-toothed comb looking for other Spectre attacks"?Maybe they did and are well aware of all these attacks but to save face and performance hits they simply hold on to them hoping nobody makes them public?