
10 Year Old Bug Crushed by Hacker on a Mission - szczys
https://hackaday.com/2017/10/31/10-year-old-bug-crushed-by-hacker-on-a-mission/
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kenning
Was hoping this would be about a very old insect

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Multicomp
Good job gnif!

I'll admit my thoughts from reading just the headline were that a hacker spent
10 years working on trying to fix the same bug over and over again.

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monochromatic
Zero details, nice.

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shakna
> The reason turned out to be that SVM is discarding the guest PAT setting and
> uses the default (PA0=PA4=WB, PA1=PA5=WT, PA2=PA6=UC-, PA3=UC). The guest
> might be using a different setting, and especially might want write
> combining but isn't getting it (instead getting slow UC or UC- accesses).
> [0]

That's all it is. Not a big complicated bug, the patch is seven simple lines.

[0]
[https://patchwork.kernel.org/patch/10027523/](https://patchwork.kernel.org/patch/10027523/)

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danschuller
That patch might be small but I imagine the path to the patch had more details
than mentioned in the article. It would be nice to hear that side of it to.

For someone benefiting from the patch it's a great story, from a developer
viewpoint there aren't enough details for it to be satisfying.

~~~
shakna
Not much of a story [0] either. A quick benchmark or three, an assumption that
something was missing... And it was, it was just stubbed.

This isn't a heisenbug, it was just never high enough priority for someone to
notice.

[0]
[https://lists.linuxfoundation.org/pipermail/iommu/2017-Octob...](https://lists.linuxfoundation.org/pipermail/iommu/2017-October/024823.html)

