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

.\" Copyright (c) 2009 Intel Corporation, Author Andi Kleen
.\" Some sentences copied from comments in arch/x86/kernel/msr.c
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" 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.\" manual page may be incorrect or out-of-date.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.
.\" %%%LICENSE_END
.\"
.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 .
.PP
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.
.PP
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:
.PP
.in +4n
.EX
$ modprobe msr
.EE
.in
.PP
.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
daad8dcd	1	.\" Copyright (c) 2009 Intel Corporation, Author Andi Kleen
027ac74c AK	2	.\" Some sentences copied from comments in arch/x86/kernel/msr.c
027ac74c AK	3	.\"
93015253	4	.\" %%%LICENSE_START(VERBATIM)
027ac74c AK	5	.\" Permission is granted to make and distribute verbatim copies of this
	6	.\" manual provided the copyright notice and this permission notice are
	7	.\" preserved on all copies.
	8	.\"
	9	.\" Permission is granted to copy and distribute modified versions of this
	10	.\" manual under the conditions for verbatim copying, provided that the
	11	.\" entire resulting derived work is distributed under the terms of a
	12	.\" permission notice identical to this one.
	13	.\"
	14	.\" Since the Linux kernel and libraries are constantly changing, this
	15	.\" manual page may be incorrect or out-of-date. The author(s) assume no
	16	.\" responsibility for errors or omissions, or for damages resulting from
	17	.\" the use of the information contained herein. The author(s) may not
	18	.\" have taken the same level of care in the production of this manual,
	19	.\" which is licensed free of charge, as they might when working
	20	.\" professionally.
	21	.\"
	22	.\" Formatted or processed versions of this manual, if unaccompanied by
	23	.\" the source, must acknowledge the copyright and authors of this work.
4b72fb64	24	.\" %%%LICENSE_END
027ac74c AK	25	.\"
	26	.TH MSR 4 2009-03-31 "Linux" "Linux Programmer's Manual"
	27	.SH NAME
	28	msr \- x86 CPU MSR access device
	29	.SH DESCRIPTION
	30	.I /dev/cpu/CPUNUM/msr
	31	provides an interface to read and write the model-specific
	32	registers (MSRs) of an x86 CPU.
7c63ca6c MK	33	.I CPUNUM
7c63ca6c MK	34	is the number of the CPU to access as listed in
027ac74c	35	.IR /proc/cpuinfo .
2dad4c59	36	.PP
027ac74c AK	37	The register access is done by opening the file and seeking
	38	to the MSR number as offset in the file, and then
	39	reading or writing in chunks of 8 bytes.
	40	An I/O transfer of more than 8 bytes means multiple reads or writes
	41	of the same register.
2dad4c59	42	.PP
33a0ccb2	43	This file is protected so that it can be read and written only by the user
027ac74c AK	44	.IR root ,
	45	or members of the group
	46	.IR root .
	47	.SH NOTES
7c63ca6c	48	The
027ac74c AK	49	.I msr
	50	driver is not auto-loaded.
	51	On modular kernels you might need to use the following command
	52	to load it explicitly before use:
019d9ee8 MK	53	.PP
	54	.in +4n
	55	.EX
54f011e7	56	$ modprobe msr
019d9ee8 MK	57	.EE
	58	.in
	59	.PP
027ac74c AK	60	.SH SEE ALSO
027ac74c AK	61	Intel Corporation Intel 64 and IA-32 Architectures
173fe7e7	62	Software Developer's Manual Volume 3B Appendix B,
027ac74c	63	for an overview of the Intel CPU MSRs.