3 ms·
Speculative execution modifies observable state. What you call it is imaterial.
by pdpi 9y ago
Speculative execution modifies observable state. What you call it is imaterial.
- rayiner 9y agoWords have meaning. The “result” of a computation is different from side effects. The distinction is important. Speculative execution will always modify “observable state.” E.g. power usage.
- dfox 9y agoThe point there is that what spectre/meltdown exploits are sideffects that are not part of the architectural state as it is specified by any manufacturer. The whole issue points to the fact that security-wise the typical approach used for descriptions of CPU's architectural behavior is insufficient as there can be implementation-specific observable sideeffects that have security ramifications.
- mannykannot 9y ago'Results' and 'side-effects' are useful modifiers of 'modifies observable state', and the long-overlooked fact that the latter falls into the category is an important insight. I think you would find it very difficult to explain the problem or discuss possible solutions without making additional distinctions, beyond 'modifies observable state', with regard to what speculative execution does.