MSR(4)                              Linux Programmer's Manual                              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 mem‐
       bers 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 explicitly 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 3.74 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 http://www.kernel.org/doc/man-pages/.



Linux                                       2009-03-31                                     MSR(4)