Model-specific registers (MSR) are control registers provided by the processor implementation so that system software can interact with a variety of features, including performance monitoring, checking processor status, debugging, program tracing or toggling specific CPU features.

/dev/cpu/CPUNUM/msr provides an interface to read and write the model-specific registers (MSRs) of an x86 CPU. CPUNUM is the number of the CPU to access as listed in /proc/cpuinfo. The register access is done by opening the file and seeking to the MSR number as offset in the file, and then reading or writing in chunks of 8 bytes.

/dev/cpu/CPUNUM/msr provides an interface to read and write the model-specific registers (MSRs) of an x86 CPU. CPUNUM is the number of the CPU to access as listed in /proc/cpuinfo. The register access is done by opening the file and seeking to the MSR number as offset in the file, and then reading or writing in chunks of 8 bytes.