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Commit 26d14a20 authored by Changbin Du's avatar Changbin Du Committed by Jonathan Corbet
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Documentation: x86: convert mtrr.txt to reST 

This converts the plain text documentation to reStructuredText format and
add it to Sphinx TOC tree. No essential content change.
Signed-off-by: default avatarChangbin Du <changbin.du@gmail.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 17156044
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Documentation/x86/index.rst
View file @ 26d14a20
...@@ -16,3 +16,4 @@ x86-specific Documentation ...@@ -16,3 +16,4 @@ x86-specific Documentation
earlyprintk earlyprintk
zero-page zero-page
tlb tlb
mtrr
Documentation/x86/mtrr.txt → Documentation/x86/mtrr.rst
View file @ 26d14a20
.. SPDX-License-Identifier: GPL-2.0
=========================================
MTRR (Memory Type Range Register) control MTRR (Memory Type Range Register) control
=========================================
:Authors: - Richard Gooch <rgooch@atnf.csiro.au> - 3 Jun 1999
- Luis R. Rodriguez <mcgrof@do-not-panic.com> - April 9, 2015
Richard Gooch <rgooch@atnf.csiro.au> - 3 Jun 1999
Luis R. Rodriguez <mcgrof@do-not-panic.com> - April 9, 2015
===============================================================================
Phasing out MTRR use Phasing out MTRR use
====================
MTRR use is replaced on modern x86 hardware with PAT. Direct MTRR use by MTRR use is replaced on modern x86 hardware with PAT. Direct MTRR use by
drivers on Linux is now completely phased out, device drivers should use drivers on Linux is now completely phased out, device drivers should use
...@@ -23,10 +28,9 @@ are aligned with platform MTRR setup. If MTRRs are only set up by the platform ...@@ -23,10 +28,9 @@ are aligned with platform MTRR setup. If MTRRs are only set up by the platform
firmware code though and the OS does not make any specific MTRR mapping firmware code though and the OS does not make any specific MTRR mapping
requests mtrr_type_lookup() should always return MTRR_TYPE_INVALID. requests mtrr_type_lookup() should always return MTRR_TYPE_INVALID.
For details refer to Documentation/x86/pat.txt. For details refer to :doc:`pat`.
===============================================================================
.. tip::
On Intel P6 family processors (Pentium Pro, Pentium II and later) On Intel P6 family processors (Pentium Pro, Pentium II and later)
the Memory Type Range Registers (MTRRs) may be used to control the Memory Type Range Registers (MTRRs) may be used to control
processor access to memory ranges. This is most useful when you have processor access to memory ranges. This is most useful when you have
...@@ -54,62 +58,72 @@ For details refer to Documentation/x86/pat.txt. ...@@ -54,62 +58,72 @@ For details refer to Documentation/x86/pat.txt.
similar control registers on other processors can be easily similar control registers on other processors can be easily
supported. supported.
There are two interfaces to /proc/mtrr: one is an ASCII interface There are two interfaces to /proc/mtrr: one is an ASCII interface
which allows you to read and write. The other is an ioctl() which allows you to read and write. The other is an ioctl()
interface. The ASCII interface is meant for administration. The interface. The ASCII interface is meant for administration. The
ioctl() interface is meant for C programs (i.e. the X server). The ioctl() interface is meant for C programs (i.e. the X server). The
interfaces are described below, with sample commands and C code. interfaces are described below, with sample commands and C code.
===============================================================================
Reading MTRRs from the shell:
% cat /proc/mtrr Reading MTRRs from the shell
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1 ============================
reg01: base=0x08000000 ( 128MB), size= 64MB: write-back, count=1 ::
===============================================================================
Creating MTRRs from the C-shell: % cat /proc/mtrr
# echo "base=0xf8000000 size=0x400000 type=write-combining" >! /proc/mtrr reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
or if you use bash: reg01: base=0x08000000 ( 128MB), size= 64MB: write-back, count=1
# echo "base=0xf8000000 size=0x400000 type=write-combining" >| /proc/mtrr
Creating MTRRs from the C-shell::
And the result thereof: # echo "base=0xf8000000 size=0x400000 type=write-combining" >! /proc/mtrr
% cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1 or if you use bash::
reg01: base=0x08000000 ( 128MB), size= 64MB: write-back, count=1
reg02: base=0xf8000000 (3968MB), size= 4MB: write-combining, count=1 # echo "base=0xf8000000 size=0x400000 type=write-combining" >| /proc/mtrr
And the result thereof::
% cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 128MB: write-back, count=1
reg01: base=0x08000000 ( 128MB), size= 64MB: write-back, count=1
reg02: base=0xf8000000 (3968MB), size= 4MB: write-combining, count=1
This is for video RAM at base address 0xf8000000 and size 4 megabytes. To This is for video RAM at base address 0xf8000000 and size 4 megabytes. To
find out your base address, you need to look at the output of your X find out your base address, you need to look at the output of your X
server, which tells you where the linear framebuffer address is. A server, which tells you where the linear framebuffer address is. A
typical line that you may get is: typical line that you may get is::
(--) S3: PCI: 968 rev 0, Linear FB @ 0xf8000000 (--) S3: PCI: 968 rev 0, Linear FB @ 0xf8000000
Note that you should only use the value from the X server, as it may Note that you should only use the value from the X server, as it may
move the framebuffer base address, so the only value you can trust is move the framebuffer base address, so the only value you can trust is
that reported by the X server. that reported by the X server.
To find out the size of your framebuffer (what, you don't actually To find out the size of your framebuffer (what, you don't actually
know?), the following line will tell you: know?), the following line will tell you::
(--) S3: videoram: 4096k (--) S3: videoram: 4096k
That's 4 megabytes, which is 0x400000 bytes (in hexadecimal). That's 4 megabytes, which is 0x400000 bytes (in hexadecimal).
A patch is being written for XFree86 which will make this automatic: A patch is being written for XFree86 which will make this automatic:
in other words the X server will manipulate /proc/mtrr using the in other words the X server will manipulate /proc/mtrr using the
ioctl() interface, so users won't have to do anything. If you use a ioctl() interface, so users won't have to do anything. If you use a
commercial X server, lobby your vendor to add support for MTRRs. commercial X server, lobby your vendor to add support for MTRRs.
===============================================================================
Creating overlapping MTRRs:
%echo "base=0xfb000000 size=0x1000000 type=write-combining" >/proc/mtrr
%echo "base=0xfb000000 size=0x1000 type=uncachable" >/proc/mtrr
And the results: cat /proc/mtrr Creating overlapping MTRRs
reg00: base=0x00000000 ( 0MB), size= 64MB: write-back, count=1 ==========================
reg01: base=0xfb000000 (4016MB), size= 16MB: write-combining, count=1 ::
reg02: base=0xfb000000 (4016MB), size= 4kB: uncachable, count=1
%echo "base=0xfb000000 size=0x1000000 type=write-combining" >/proc/mtrr
%echo "base=0xfb000000 size=0x1000 type=uncachable" >/proc/mtrr
And the results::
% cat /proc/mtrr
reg00: base=0x00000000 ( 0MB), size= 64MB: write-back, count=1
reg01: base=0xfb000000 (4016MB), size= 16MB: write-combining, count=1
reg02: base=0xfb000000 (4016MB), size= 4kB: uncachable, count=1
Some cards (especially Voodoo Graphics boards) need this 4 kB area Some cards (especially Voodoo Graphics boards) need this 4 kB area
excluded from the beginning of the region because it is used for excluded from the beginning of the region because it is used for
...@@ -117,213 +131,224 @@ registers. ...@@ -117,213 +131,224 @@ registers.
NOTE: You can only create type=uncachable region, if the first NOTE: You can only create type=uncachable region, if the first
region that you created is type=write-combining. region that you created is type=write-combining.
===============================================================================
Removing MTRRs from the C-shell:
% echo "disable=2" >! /proc/mtrr Removing MTRRs from the C-shel
or using bash: ==============================
% echo "disable=2" >| /proc/mtrr ::
===============================================================================
Reading MTRRs from a C program using ioctl()'s: % echo "disable=2" >! /proc/mtrr
/* mtrr-show.c or using bash::
Source file for mtrr-show (example program to show MTRRs using ioctl()'s) % echo "disable=2" >| /proc/mtrr
Copyright (C) 1997-1998 Richard Gooch
Reading MTRRs from a C program using ioctl()'s
This program is free software; you can redistribute it and/or modify ==============================================
it under the terms of the GNU General Public License as published by ::
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version. /* mtrr-show.c
This program is distributed in the hope that it will be useful, Source file for mtrr-show (example program to show MTRRs using ioctl()'s)
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the Copyright (C) 1997-1998 Richard Gooch
GNU General Public License for more details.
This program is free software; you can redistribute it and/or modify
You should have received a copy of the GNU General Public License it under the terms of the GNU General Public License as published by
along with this program; if not, write to the Free Software the Free Software Foundation; either version 2 of the License, or
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. (at your option) any later version.
Richard Gooch may be reached by email at rgooch@atnf.csiro.au This program is distributed in the hope that it will be useful,
The postal address is: but WITHOUT ANY WARRANTY; without even the implied warranty of
Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
*/ GNU General Public License for more details.
/* You should have received a copy of the GNU General Public License
This program will use an ioctl() on /proc/mtrr to show the current MTRR along with this program; if not, write to the Free Software
settings. This is an alternative to reading /proc/mtrr. Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Richard Gooch may be reached by email at rgooch@atnf.csiro.au
Written by Richard Gooch 17-DEC-1997 The postal address is:
Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
Last updated by Richard Gooch 2-MAY-1998 */
/*
*/ This program will use an ioctl() on /proc/mtrr to show the current MTRR
#include <stdio.h> settings. This is an alternative to reading /proc/mtrr.
#include <stdlib.h>
#include <string.h>
#include <sys/types.h> Written by Richard Gooch 17-DEC-1997
#include <sys/stat.h>
#include <fcntl.h> Last updated by Richard Gooch 2-MAY-1998
#include <sys/ioctl.h>
#include <errno.h>
#include <asm/mtrr.h> */
#include <stdio.h>
#define TRUE 1 #include <stdlib.h>
#define FALSE 0 #include <string.h>
#define ERRSTRING strerror (errno) #include <sys/types.h>
#include <sys/stat.h>
static char *mtrr_strings[MTRR_NUM_TYPES] = #include <fcntl.h>
{ #include <sys/ioctl.h>
"uncachable", /* 0 */ #include <errno.h>
"write-combining", /* 1 */ #include <asm/mtrr.h>
"?", /* 2 */
"?", /* 3 */ #define TRUE 1
"write-through", /* 4 */ #define FALSE 0
"write-protect", /* 5 */ #define ERRSTRING strerror (errno)
"write-back", /* 6 */
}; static char *mtrr_strings[MTRR_NUM_TYPES] =
{
int main () "uncachable", /* 0 */
{ "write-combining", /* 1 */
int fd; "?", /* 2 */
struct mtrr_gentry gentry; "?", /* 3 */
"write-through", /* 4 */
if ( ( fd = open ("/proc/mtrr", O_RDONLY, 0) ) == -1 ) "write-protect", /* 5 */
{ "write-back", /* 6 */
if (errno == ENOENT) };
{
fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n", int main ()
stderr); {
exit (1); int fd;
} struct mtrr_gentry gentry;
fprintf (stderr, "Error opening /proc/mtrr\t%s\n", ERRSTRING);
exit (2); if ( ( fd = open ("/proc/mtrr", O_RDONLY, 0) ) == -1 )
} {
for (gentry.regnum = 0; ioctl (fd, MTRRIOC_GET_ENTRY, &gentry) == 0; if (errno == ENOENT)
++gentry.regnum)
{
if (gentry.size < 1)
{
fprintf (stderr, "Register: %u disabled\n", gentry.regnum);
continue;
}
fprintf (stderr, "Register: %u base: 0x%lx size: 0x%lx type: %s\n",
gentry.regnum, gentry.base, gentry.size,
mtrr_strings[gentry.type]);
}
if (errno == EINVAL) exit (0);
fprintf (stderr, "Error doing ioctl(2) on /dev/mtrr\t%s\n", ERRSTRING);
exit (3);
} /* End Function main */
===============================================================================
Creating MTRRs from a C programme using ioctl()'s:
/* mtrr-add.c
Source file for mtrr-add (example programme to add an MTRRs using ioctl())
Copyright (C) 1997-1998 Richard Gooch
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Richard Gooch may be reached by email at rgooch@atnf.csiro.au
The postal address is:
Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
*/
/*
This programme will use an ioctl() on /proc/mtrr to add an entry. The first
available mtrr is used. This is an alternative to writing /proc/mtrr.
Written by Richard Gooch 17-DEC-1997
Last updated by Richard Gooch 2-MAY-1998
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <asm/mtrr.h>
#define TRUE 1
#define FALSE 0
#define ERRSTRING strerror (errno)
static char *mtrr_strings[MTRR_NUM_TYPES] =
{
"uncachable", /* 0 */
"write-combining", /* 1 */
"?", /* 2 */
"?", /* 3 */
"write-through", /* 4 */
"write-protect", /* 5 */
"write-back", /* 6 */
};
int main (int argc, char **argv)
{
int fd;
struct mtrr_sentry sentry;
if (argc != 4)
{
fprintf (stderr, "Usage:\tmtrr-add base size type\n");
exit (1);
}
sentry.base = strtoul (argv[1], NULL, 0);
sentry.size = strtoul (argv[2], NULL, 0);
for (sentry.type = 0; sentry.type < MTRR_NUM_TYPES; ++sentry.type)
{
if (strcmp (argv[3], mtrr_strings[sentry.type]) == 0) break;
}
if (sentry.type >= MTRR_NUM_TYPES)
{ {
fprintf (stderr, "Illegal type: \"%s\"\n", argv[3]); fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n",
exit (2); stderr);
exit (1);
} }
if ( ( fd = open ("/proc/mtrr", O_WRONLY, 0) ) == -1 ) fprintf (stderr, "Error opening /proc/mtrr\t%s\n", ERRSTRING);
exit (2);
}
for (gentry.regnum = 0; ioctl (fd, MTRRIOC_GET_ENTRY, &gentry) == 0;
++gentry.regnum)
{
if (gentry.size < 1)
{ {
if (errno == ENOENT) fprintf (stderr, "Register: %u disabled\n", gentry.regnum);
{ continue;
fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n",
stderr);
exit (3);
}
fprintf (stderr, "Error opening /proc/mtrr\t%s\n", ERRSTRING);
exit (4);
} }
if (ioctl (fd, MTRRIOC_ADD_ENTRY, &sentry) == -1) fprintf (stderr, "Register: %u base: 0x%lx size: 0x%lx type: %s\n",
gentry.regnum, gentry.base, gentry.size,
mtrr_strings[gentry.type]);
}
if (errno == EINVAL) exit (0);
fprintf (stderr, "Error doing ioctl(2) on /dev/mtrr\t%s\n", ERRSTRING);
exit (3);
} /* End Function main */
Creating MTRRs from a C programme using ioctl()'s
=================================================
::
/* mtrr-add.c
Source file for mtrr-add (example programme to add an MTRRs using ioctl())
Copyright (C) 1997-1998 Richard Gooch
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
Richard Gooch may be reached by email at rgooch@atnf.csiro.au
The postal address is:
Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.
*/
/*
This programme will use an ioctl() on /proc/mtrr to add an entry. The first
available mtrr is used. This is an alternative to writing /proc/mtrr.
Written by Richard Gooch 17-DEC-1997
Last updated by Richard Gooch 2-MAY-1998
*/
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <asm/mtrr.h>
#define TRUE 1
#define FALSE 0
#define ERRSTRING strerror (errno)
static char *mtrr_strings[MTRR_NUM_TYPES] =
{
"uncachable", /* 0 */
"write-combining", /* 1 */
"?", /* 2 */
"?", /* 3 */
"write-through", /* 4 */
"write-protect", /* 5 */
"write-back", /* 6 */
};
int main (int argc, char **argv)
{
int fd;
struct mtrr_sentry sentry;
if (argc != 4)
{
fprintf (stderr, "Usage:\tmtrr-add base size type\n");
exit (1);
}
sentry.base = strtoul (argv[1], NULL, 0);
sentry.size = strtoul (argv[2], NULL, 0);
for (sentry.type = 0; sentry.type < MTRR_NUM_TYPES; ++sentry.type)
{
if (strcmp (argv[3], mtrr_strings[sentry.type]) == 0) break;
}
if (sentry.type >= MTRR_NUM_TYPES)
{
fprintf (stderr, "Illegal type: \"%s\"\n", argv[3]);
exit (2);
}
if ( ( fd = open ("/proc/mtrr", O_WRONLY, 0) ) == -1 )
{
if (errno == ENOENT)
{ {
fprintf (stderr, "Error doing ioctl(2) on /dev/mtrr\t%s\n", ERRSTRING); fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n",
exit (5); stderr);
exit (3);
} }
fprintf (stderr, "Sleeping for 5 seconds so you can see the new entry\n"); fprintf (stderr, "Error opening /proc/mtrr\t%s\n", ERRSTRING);
sleep (5); exit (4);
close (fd); }
fputs ("I've just closed /proc/mtrr so now the new entry should be gone\n", if (ioctl (fd, MTRRIOC_ADD_ENTRY, &sentry) == -1)
stderr); {
} /* End Function main */ fprintf (stderr, "Error doing ioctl(2) on /dev/mtrr\t%s\n", ERRSTRING);
=============================================================================== exit (5);
}
fprintf (stderr, "Sleeping for 5 seconds so you can see the new entry\n");
sleep (5);
close (fd);
fputs ("I've just closed /proc/mtrr so now the new entry should be gone\n",
stderr);
} /* End Function main */
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