The clearcpuid= kernel parameter can be used to disable specific CPUID features for the kernel by specifying the targeted bit numbers of the feature(s) to disable or their flags from the /proc/cpuinfo output. The clearcpuid parameter, for example, has been useful for carrying out AVX-512 comparison benchmarks for apps that check for the presence of the AVX-512 extensions via /proc/cpuinfo. But moving forward the documentation on clearcpuid is being removed to discourage its use...
The decision to remove documentation suggests an intent by kernel developers to deprecate or disincentivize the use of clearcpuid due to potential misuse or instability.
A strategic reader should care because this change in kernel behavior, even subtle, can impact performance tuning, security research, and the perceived stability of specific CPU features like AVX-512.
While the feature itself isn't immediately removed, the hidden documentation makes it harder for developers and researchers to predictably interact with or disable specific CPU features.
- · Performance benchmarkers
- · Security researchers
It becomes significantly harder for users to intentionally disable CPU features for testing or compatibility purposes without internal knowledge.
This could lead to less controlled testing environments for certain CPU features, potentially obscuring performance bottlenecks or security vulnerabilities.
The Linux kernel community might be signaling a broader move towards tighter control over CPU feature exposure, impacting hardware abstraction layers and virtualized environments in the long run.
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Read at Phoronix