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Comment by jtokoph | Hacker News Reader

I’m going to predict that they release a new version for macOS that includes a bug fix for the latest generation of processors. It will fix inaccurate readings. The new version will “correctly” show the flat line instead of the spikes.

Then again it could also just be related to reports of it causing some macs not to be able to reboot after install. The only fix was booting safe mode and manually removing the kernel extension.

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I believe that was fixed in the most recent Mac version already - see the devs comments on the page. I have it installed on my MBP and have had no issues.

bizarrely though they have pulled it for some reason.

> Then again it could also just be related to reports of it causing some macs not to be able to reboot after install. The only fix was booting safe mode and manually removing the kernel extension.

Yikes, If that's true I'd bet that's the case. A bad kext that prevents booting would be a horrible experience.

Why does this need to be a kernel extension? Is there really no access to MSRs in macos as shipped by Apple?

Generally no, the instructions that get access to many MSRs are privileged since they can affect the way things execute.

I understand they are privileged but the way Linux handles this feature seems acceptable.

Why? MSR are not userspace registers. You don't want the userspace messing around with them either because they won't know 100% what they do. But more importantly for security.

Even Linux requires this be done in kernel space, it's a requirement set by the architecture that the instructions that access them are run as part of the kernel. This is just like OSX, no different at all.

In Linux root can open, read, and write /dev/msr.

I haven't seen a /dev/msr before, but there is /dev/cpu/*/msr [1] provided by a kernel module. So there is a generic interface for them, but it's still all happening in kernel space. It's also not loaded by default either because it can cause system panics and corruption.

[1] http://man7.org/linux/man-pages/man4/msr.4.html

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