MSR(4)                    (2009-03-31)                     MSR(4)

     NAME
          msr - x86 CPU MSR access device

     DESCRIPTION
          /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
          The msr driver is not auto-loaded.  On modular kernels you
          might need to use the following command to load it explic-
          itly before use:

              $ modprobe msr

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

     COLOPHON
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

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