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A comment on Google developing own CPUs for Chromebook laptops. Parent comment

Re:Google developing own CPUs for Chromebook laptops by ithkuil on Saturday October 02, 2021 @04:43PM (#28731910)
If the extra instructions also operate in extra state (e.g. extra registers) a kernel needs to know about their existence so it can correctly save and restore state on context switches
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Re:Google developing own CPUs for Chromebook laptops by my123 on Saturday October 02, 2021 @04:56PM (#28732004)
Not necessarily/really, the custom extensions still need to be enabled by the kernel before they can be used.

As such, it isn’t actually an issue.

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Re:Google developing own CPUs for Chromebook laptops by ndesaulniers on Saturday October 02, 2021 @09:18PM (#28733713)
You're confusing MSRs (which don't have to be saved/restored on context switch) with GPRs (which do).
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Re:Google developing own CPUs for Chromebook laptops by ithkuil on Sunday October 03, 2021 @08:16AM (#28736584)
Well if there is a truly undocumented extension, how do I know it doesn't come with it's own registers (e.g. like a floating point unit does)
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Re:Google developing own CPUs for Chromebook laptops by saagarjha on Saturday October 02, 2021 @09:58PM (#28733900)
Apple reserves certain MSRs that apply on a per-process basis, and thus must be applied on context switch.
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