2009-03-31 19:32:21 +00:00
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.\" Copyright (c) 2009 Intel Corporation, Author Andi Kleen
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2009-03-30 19:33:25 +00:00
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.\" Some sentences copied from comments in arch/x86/kernel/msr.c
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.\"
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.\" Permission is granted to make and distribute verbatim copies of this
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.\" preserved on all copies.
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.\" permission notice identical to this one.
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.TH MSR 4 2009-03-31 "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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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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This file is protected so that it can only be read and written 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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$ \fImodprobe msr\fP
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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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