msr(4) — Linux manual page


MSR(4)                    Linux Programmer's 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 use:

           $ 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.

COLOPHON         top

       This page is part of release 5.09 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

Linux                            2009-03-31                           MSR(4)

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