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Mitigations=off considered harmful or spurious SIGILL on AMD Zen4

forum.level1techs.com

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Re: Mitigations=off considered harmful or spurious SIGILL on AMD Zen4

#2

Post by 2bluesc »

Interesting walk through in the linked video as he tried to troubleshoot this:

https://www.youtube.com/live/1UnoBfw6soI

Pretty shocking to see (extremely unlikely) non-malicious code work / not-work depending on a security mitigation setting.

Curious to see where this goes as to whether it's a kernel bug and nobody is paying attention to `mitigations=off` now or the unlikely outcome that it's an actual hardware bug where mitigations work around it and nobody has noticed.

Seems he had overclocked and maybe disabling the migation has revealed an instability in his setup that's otherwise stable (or at best marginal).

Re: Mitigations=off considered harmful or spurious SIGILL on AMD Zen4

#3

Post by yellow_lead »

2bluesc wrote: post #2

Interesting walk through in the linked video as he tried to troubleshoot this: https://www.youtube.com/live/1UnoBfw6soI Pretty shocking to see (extremely unlikely) non-malicious code work / not-work depending on a security mitigation setting. Curious to see where this goes as to whether it's a kernel bug and nobody is paying attention to `mitigations=off` now or the unlikely outcome that it's an actual hardware bug w…

He says that he tried stock voltage for everything, and even undervolted/underclocked CPU/memory and still had the bug.

Re: Mitigations=off considered harmful or spurious SIGILL on AMD Zen4

#4

Post by tux3 »

2bluesc wrote: post #2

Interesting walk through in the linked video as he tried to troubleshoot this: https://www.youtube.com/live/1UnoBfw6soI Pretty shocking to see (extremely unlikely) non-malicious code work / not-work depending on a security mitigation setting. Curious to see where this goes as to whether it's a kernel bug and nobody is paying attention to `mitigations=off` now or the unlikely outcome that it's an actual hardware bug w…

mitigations=off does a lot of things, it's a bundle of options

Perhaps the next step is trying to figure out which mitigation exactly causes it to fail. Then kernel peeps should have a fighting chance of tracking this down

Re: Mitigations=off considered harmful or spurious SIGILL on AMD Zen4

#6

Post by simcop2387 »

tux3 wrote: post #4
2bluesc wrote: post #2

Interesting walk through in the linked video as he tried to troubleshoot this: https://www.youtube.com/live/1UnoBfw6soI Pretty shocking to see (extremely unlikely) non-malicious code work / not-work depending on a security mitigation setting. Curious to see where this goes as to whether it's a kernel bug and nobody is paying attention to `mitigations=off` now or the unlikely outcome that it's an actual hardware bug w…

mitigations=off does a lot of things, it's a bundle of options Perhaps the next step is trying to figure out which mitigation exactly causes it to fail. Then kernel peeps should have a fighting chance of tracking this down

In the video comments it looks like he's done some of that and it's one of the spectre v2 mitigations. Makes me wonder if there's now less QA happening on the oem side without mitigations=on.

Re: Mitigations=off considered harmful or spurious SIGILL on AMD Zen4

#8

Post by fabianhjr »

secondcoming wrote: post #5

Isn't there a rule about titles containing 'considered harmful'? Either way, this is pretty interesting and the guy is pretty excited about finding it.

There is a rule on mostly not editorializing titles and in this case that is the title of the source article.

> Otherwise please use the original title, unless it is misleading or linkbait; don't editorialize.

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