L1d Cache Flushing On Context Switch Trying Again But More Conservative In 2021

[phoronix]

Phoronix: L1d Cache Flushing On Context Switch Trying Again But More Conservative In 2021

Coming out in early 2020 were patches by an Amazon engineer to implement flushing the L1 data cache on context switching in the name of security given the various data sampling vulnerabilities. That work so far has been rejected from the mainline kernel but today was updated and makes it harder to enable and thus moving forward could stand chances to finally see the opt-in functionality merged to mainline...

http://www.phoronix.com/scan.php?page=news_item&px=L1d-Flush-2021-Patches

[chuckula]

I think having it as an option that can be turned on if you really REALLY want to is OK, but I also agree with Torvalds that it's not a particularly good idea for the vast vast majority of systems.

[CochainComplex]

Applyng it by default would set the (digital) world back 5 years...not even talking about power efficiency....Serverfarms needing x amount of energy to achieve the same - wasn't the penalty up to 50%?

[Caffarius]

Applyng it by default would set the (digital) world back 5 years...not even talking about power efficiency....Serverfarms needing x amount of energy to achieve the same - wasn't the penalty up to 50%?

They'd just raise the cloud pricing by 100% and pitch it as a security feature. Some organizations go well out of their way to claim they tried everything to lock their infrastructure down.

[Alex/AT]

"most significant is the functionality is disabled by default"
Nice, that's the practical way to implement those.
Leaving it all as that and adding some heavy boot warnings about hardware being crap is a way to go, for some other mitigations like Meltdown as well.