[thirdparty/man-pages.git] / man4 / msr.4

.\" Copyright (c) 2009 by Andi Kleen <andi@firstfloor.org>
.\" Some sentences copied from comments in arch/x86/kernel/msr.c
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.TH MSR 4 2009-03-31 "Linux" "Linux Programmer's Manual"
.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 .

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 only be read and written 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:

    $ \fImodprobe msr\fP
.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.
Commit	Line	Data
027ac74c AK	1	.\" Copyright (c) 2009 by Andi Kleen <andi@firstfloor.org>
	2	.\" Some sentences copied from comments in arch/x86/kernel/msr.c
	3	.\"
	4	.\" Permission is granted to make and distribute verbatim copies of this
	5	.\" manual provided the copyright notice and this permission notice are
	6	.\" preserved on all copies.
	7	.\"
	8	.\" Permission is granted to copy and distribute modified versions of this
	9	.\" manual under the conditions for verbatim copying, provided that the
	10	.\" entire resulting derived work is distributed under the terms of a
	11	.\" permission notice identical to this one.
	12	.\"
	13	.\" Since the Linux kernel and libraries are constantly changing, this
	14	.\" manual page may be incorrect or out-of-date. The author(s) assume no
	15	.\" responsibility for errors or omissions, or for damages resulting from
	16	.\" the use of the information contained herein. The author(s) may not
	17	.\" have taken the same level of care in the production of this manual,
	18	.\" which is licensed free of charge, as they might when working
	19	.\" professionally.
	20	.\"
	21	.\" Formatted or processed versions of this manual, if unaccompanied by
	22	.\" the source, must acknowledge the copyright and authors of this work.
	23	.\"
	24	.TH MSR 4 2009-03-31 "Linux" "Linux Programmer's Manual"
	25	.SH NAME
	26	msr \- x86 CPU MSR access device
	27	.SH DESCRIPTION
	28	.I /dev/cpu/CPUNUM/msr
	29	provides an interface to read and write the model-specific
	30	registers (MSRs) of an x86 CPU.
	31	.I CPUNUM
	32	is the number of the CPU to access as listed in
	33	.IR /proc/cpuinfo .
	34
	35	The register access is done by opening the file and seeking
	36	to the MSR number as offset in the file, and then
	37	reading or writing in chunks of 8 bytes.
	38	An I/O transfer of more than 8 bytes means multiple reads or writes
	39	of the same register.
	40
	41	This file is protected so that it can only be read and written by the user
	42	.IR root ,
	43	or members of the group
	44	.IR root .
	45	.SH NOTES
	46	The
	47	.I msr
	48	driver is not auto-loaded.
	49	On modular kernels you might need to use the following command
	50	to load it explicitly before use:
	51
	52	$ \fImodprobe msr\fP
	53	.SH SEE ALSO
	54	Intel Corporation Intel 64 and IA-32 Architectures
	55	Software Developer's Manual Volume 3B Appendix B
	56	for an overview of the Intel CPU MSRs.