| .\" Copyright (c) 2009 Intel Corporation, Author Andi Kleen |
| .\" Some sentences copied from comments in arch/x86/kernel/msr.c |
| .\" |
| .\" SPDX-License-Identifier: Linux-man-pages-copyleft |
| .\" |
| .TH msr 4 (date) "Linux man-pages (unreleased)" |
| .SH NAME |
| msr \- x86 CPU MSR access device |
| .SH DESCRIPTION |
| .I /dev/cpu/CPUNUM/msr |
| provides an interface to read and write the model-specific |
| registers (MSRs) of an x86 CPU. |
| .I CPUNUM |
| is the number of the CPU to access as listed in |
| .IR /proc/cpuinfo . |
| .P |
| 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. |
| .P |
| This file is protected so that it can be read and written only by the user |
| .IR root , |
| or members of the group |
| .IR root . |
| .SH NOTES |
| The |
| .I msr |
| driver is not auto-loaded. |
| On modular kernels you might need to use the following command |
| to load it explicitly before use: |
| .P |
| .in +4n |
| .EX |
| $ modprobe msr |
| .EE |
| .in |
| .SH 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. |
