mirror of https://github.com/mkerrisk/man-pages
63 lines
2.2 KiB
Groff
63 lines
2.2 KiB
Groff
.\" Copyright (c) 2009 Intel Corporation, Author Andi Kleen
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.\" Some sentences copied from comments in arch/x86/kernel/msr.c
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.\"
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.\" %%%LICENSE_START(VERBATIM)
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" manual provided the copyright notice and this permission notice are
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.\" preserved on all copies.
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.\"
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.\" Permission is granted to copy and distribute modified versions of this
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.\" manual under the conditions for verbatim copying, provided that the
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.\" entire resulting derived work is distributed under the terms of a
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.\" permission notice identical to this one.
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.\"
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" manual page may be incorrect or out-of-date. The author(s) assume no
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.\" responsibility for errors or omissions, or for damages resulting from
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.\" the use of the information contained herein. The author(s) may not
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.\" have taken the same level of care in the production of this manual,
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.\" which is licensed free of charge, as they might when working
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.\" professionally.
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.\"
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.\" Formatted or processed versions of this manual, if unaccompanied by
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.\" the source, must acknowledge the copyright and authors of this work.
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.\" %%%LICENSE_END
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.\"
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.TH MSR 4 2021-03-22 "Linux" "Linux Programmer's Manual"
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.SH NAME
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msr \- x86 CPU MSR access device
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.SH DESCRIPTION
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.I /dev/cpu/CPUNUM/msr
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provides an interface to read and write the model-specific
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registers (MSRs) of an x86 CPU.
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.I CPUNUM
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is the number of the CPU to access as listed in
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.IR /proc/cpuinfo .
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.PP
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The register access is done by opening the file and seeking
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to the MSR number as offset in the file, and then
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reading or writing in chunks of 8 bytes.
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An I/O transfer of more than 8 bytes means multiple reads or writes
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of the same register.
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.PP
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This file is protected so that it can be read and written only by the user
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.IR root ,
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or members of the group
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.IR root .
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.SH NOTES
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The
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.I msr
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driver is not auto-loaded.
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On modular kernels you might need to use the following command
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to load it explicitly before use:
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.PP
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.in +4n
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.EX
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$ modprobe msr
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.EE
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.in
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.SH SEE ALSO
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Intel Corporation Intel 64 and IA-32 Architectures
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Software Developer's Manual Volume 3B Appendix B,
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for an overview of the Intel CPU MSRs.
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