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Comment by causi | Hacker News Reader

I wonder if eventually we'll have to have a "secure mode" operational setting where all speculation is disabled along with other extreme security measures any time a computer needs to handle credentials.

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You can speculate all you want, just dont Fking share the state between cores/threads/processes.

My understanding is that flushing all cache and other state on every thread/process context switch has a big performance impact.

You don't need to flush predictor state on every task switch, only when entering a less private context from a more private one. Systems with a feature known as multiple-level security (or "multiple levels of security") can be designed to track these privacy/information requirements automatically.

I'm not familiar with this concept of a "less private context" in computing.

Could you please link me to something I can read about it?

It's not something that's currently reified or supported as a feature in mainstream OS's, but multilevel security has been studied for a long time in an academic context.

Bell-LaPadula?

No need to flush cache if we could have all the caches tagged per process.

But then shared libraries would have to be duplicated in the I-cache.

Space-privacy tradeoff, sounds fair.

All the cool kids statically link everything now anyways.

No, you can't. Many speculation vulnerabilities have been single-threaded.

dedicating a single core to the task and interfacing with existing secure enclave / smart card like protocols would get you pretty far.

Cores can share cache. Cache leaks from speculation are a thing. So dedicating a single core might not be strong enough countermeasure.

There's of course little other recourse without a secure processor. I will be very saddened when a secure processor becomes required standard hardware because it will, no doubt, contain only phantom blobs that hinder ownership and promote corporate bullshit.

Apple's maniacal control of their hardware is what makes my phone an excellent appliance but a terrible general purpose computer.

My MacBook and Mac studio make pretty good general purpose computers.

Isn't MS Pluton already standard in all new processors?

>"secure mode" operational setting where all speculation is disabled

We have that, it's called OpenBSD. :)

On SPARC64 or POWER.

IIRC, SPARC actually is affected by speculative vulnerabilities.

I think you’re confusing hyperthreading (disabled on amd64 in OpenBSD) with speculation (neither disabled nor afaik disableable on amd64).

Yeah, in this mode the CPU will just work 10 times slower.

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