New x86 micro-op vulnerability breaks all known Spectre defenses • Hacker News Board

Re: New x86 micro-op vulnerability breaks all known Spectre defenses

#201

Post by mondoshawan » Tue, May 04, 2021, 5:16 PM UTC

salawat wrote: post #190

mondoshawan wrote: post #132

Earlier quoted context omitted.

Isn't that Von Neumann architecture vs. Harvard?

That's not what the poster is talking about though. They're talking Von Neumann with a special "blessed" tooling written to not produce behaviors that would let users do nefarious things. They want to reduce the space of possible computations from arbitrary to "only these patterns which are provably safe". Essentially, they want to hobble the user (malicious or not) and force good behavior by giving them tools that a…

Ookay. Not sure how you can glean all that from a statement like the one I was responding to...

Re: New x86 micro-op vulnerability breaks all known Spectre defenses

#202

Post by samus » Tue, May 04, 2021, 7:23 PM UTC

mikewarot wrote: post #37

baybal2 wrote: post #30

Earlier quoted context omitted.

You are completely correct. The safe execution of any untrusted Turing complete code is a pipe dream. You, at least, need a clean sheet CPU design starting from ISA, and basic logic operations formally validated against instruction level analysis to have a fighting chance. But even such chip do get pwned, as shown by key recovery from credit cards in the wild.

>The safe execution of any untrusted Turing complete code is a pipe dream. The safe execution of any code requires an operating environment that never trusts the code with more than the least privilege required to complete a task. It has worked in mainframes that way for decades. The IT zeitgeist these days makes me sad. Things can be better, but almost everyone is pushing in counterproductive directions, or has give…

The people operating mainframes have a vastly diffrerent mindset and skills from the average computer/smartphone user. The former can and do dedicate 40h/week and more to studying documentation and tweaking the sandboxes of the stuff they run.

Re: New x86 micro-op vulnerability breaks all known Spectre defenses

#203

Post by SG2000 » Fri, May 14, 2021, 8:05 PM UTC

A close reading of the paper “I see dead uOps” would seem to indicate that Intel’s static thread partitioning of their micro-op cache would confer some inherent protection against uOp cache information leakage between threads - as compared to AMD’s dynamic thread partitioning scheme which could theoretically allow threads to spy on each other using the described techniques.

If true, wouldn’t this also imply that an Intel Skylake CPU mitigates against such attempted attacks by one user against another in a shared CPU/ISP/cloud environment, whereas an AMD CPU theoretically would not? If true, this would be a key point that the authors failed to mention in their concluding remarks.

Anyone else read it this way? Or am I missing something?