msr(4) — Linux manual page


msr(4)                  Kernel Interfaces Manual                  msr(4)

NAME         top

       msr - x86 CPU MSR access device

DESCRIPTION         top

       /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.  An I/O transfer of more than 8 bytes means
       multiple reads or writes of the same register.

       This file is protected so that it can be read and written only by
       the user root, or members of the group root.

NOTES         top

       The msr driver is not auto-loaded.  On modular kernels you might
       need to use the following command to load it explicitly before

           $ modprobe msr

SEE ALSO         top

       Intel Corporation Intel 64 and IA-32 Architectures Software
       Developer's Manual Volume 3B Appendix B, for an overview of the
       Intel CPU MSRs.

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