5 ms·
> Thus they decided to do permissions checking in parallel with other operations, leading to Spectre No. Leading to Meltdown. Spectre is fundamental to the way
by wilun 9y ago
> Thus they decided to do permissions checking in parallel with other operations, leading to Spectre
No. Leading to Meltdown. Spectre is fundamental to the way we approached any speculative execution until now.
- amelius 9y agoAny idea what will be the solution? Keep more speculative data in the pipeline? Performance penalties on security faults? Complex rollback?
- convolvatron 9y agoyou could certainly extend the unused transactional support to do a chandy-lamport thing, with the difference that when you run out of space isolated cache versions, you just can't speculate any more. it would be a lot of machinery you could also do latency hiding with smt instead of trying to fight it head-on with speculation. ultimately probably more productive, but either the compiler or the programming model or the user has to expose that concurrency.
- jnwatson 9y agoIf all speculation used a separate cache that is only committed on retirement, that should keep the side channels at bay.
- bonzini 9y agoSpectre variant 2 is not fundamental to speculative execution. It can be fixed by tagging the indirect branch predictions with the full virtual address and the ASID, and flushing it together with the TLB.