diff options
Diffstat (limited to 'Documentation/x86')
| -rw-r--r-- | Documentation/x86/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/x86/mtrr.rst | 354 | ||||
| -rw-r--r-- | Documentation/x86/mtrr.txt | 329 |
3 files changed, 355 insertions, 329 deletions
diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst index c4ea25350221..769c4491e9cb 100644 --- a/Documentation/x86/index.rst +++ b/Documentation/x86/index.rst @@ -16,3 +16,4 @@ x86-specific Documentation earlyprintk zero-page tlb + mtrr diff --git a/Documentation/x86/mtrr.rst b/Documentation/x86/mtrr.rst new file mode 100644 index 000000000000..c5b695d75349 --- /dev/null +++ b/Documentation/x86/mtrr.rst @@ -0,0 +1,354 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================================= +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 + + +Phasing out MTRR use +==================== + +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 +arch_phys_wc_add() in combination with ioremap_wc() to make MTRR effective on +non-PAT systems while a no-op but equally effective on PAT enabled systems. + +Even if Linux does not use MTRRs directly, some x86 platform firmware may still +set up MTRRs early before booting the OS. They do this as some platform +firmware may still have implemented access to MTRRs which would be controlled +and handled by the platform firmware directly. An example of platform use of +MTRRs is through the use of SMI handlers, one case could be for fan control, +the platform code would need uncachable access to some of its fan control +registers. Such platform access does not need any Operating System MTRR code in +place other than mtrr_type_lookup() to ensure any OS specific mapping requests +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 +requests mtrr_type_lookup() should always return MTRR_TYPE_INVALID. + +For details refer to :doc:`pat`. + +.. tip:: + On Intel P6 family processors (Pentium Pro, Pentium II and later) + the Memory Type Range Registers (MTRRs) may be used to control + processor access to memory ranges. This is most useful when you have + a video (VGA) card on a PCI or AGP bus. Enabling write-combining + allows bus write transfers to be combined into a larger transfer + before bursting over the PCI/AGP bus. This can increase performance + of image write operations 2.5 times or more. + + The Cyrix 6x86, 6x86MX and M II processors have Address Range + Registers (ARRs) which provide a similar functionality to MTRRs. For + these, the ARRs are used to emulate the MTRRs. + + The AMD K6-2 (stepping 8 and above) and K6-3 processors have two + MTRRs. These are supported. The AMD Athlon family provide 8 Intel + style MTRRs. + + The Centaur C6 (WinChip) has 8 MCRs, allowing write-combining. These + are supported. + + The VIA Cyrix III and VIA C3 CPUs offer 8 Intel style MTRRs. + + The CONFIG_MTRR option creates a /proc/mtrr file which may be used + to manipulate your MTRRs. Typically the X server should use + this. This should have a reasonably generic interface so that + similar control registers on other processors can be easily + supported. + +There are two interfaces to /proc/mtrr: one is an ASCII interface +which allows you to read and write. The other is an ioctl() +interface. The ASCII interface is meant for administration. The +ioctl() interface is meant for C programs (i.e. the X server). The +interfaces are described below, with sample commands and C code. + + +Reading MTRRs from the shell +============================ +:: + + % cat /proc/mtrr + 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:: + + # echo "base=0xf8000000 size=0x400000 type=write-combining" >! /proc/mtrr + +or if you use bash:: + + # 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 +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 +typical line that you may get is:: + + (--) S3: PCI: 968 rev 0, Linear FB @ 0xf8000000 + +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 +that reported by the X server. + +To find out the size of your framebuffer (what, you don't actually +know?), the following line will tell you:: + + (--) S3: videoram: 4096k + +That's 4 megabytes, which is 0x400000 bytes (in hexadecimal). +A patch is being written for XFree86 which will make this automatic: +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 +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 + 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 +excluded from the beginning of the region because it is used for +registers. + +NOTE: You can only create type=uncachable region, if the first +region that you created is type=write-combining. + + +Removing MTRRs from the C-shel +============================== +:: + + % echo "disable=2" >! /proc/mtrr + +or using bash:: + + % echo "disable=2" >| /proc/mtrr + + +Reading MTRRs from a C program using ioctl()'s +============================================== +:: + + /* mtrr-show.c + + Source file for mtrr-show (example program to show MTRRs using ioctl()'s) + + 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 program will use an ioctl() on /proc/mtrr to show the current MTRR + settings. This is an alternative to reading /proc/mtrr. + + + Written by Richard Gooch 17-DEC-1997 + + Last updated by Richard Gooch 2-MAY-1998 + + + */ + #include <stdio.h> + #include <stdlib.h> + #include <string.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 fd; + struct mtrr_gentry gentry; + + if ( ( fd = open ("/proc/mtrr", O_RDONLY, 0) ) == -1 ) + { + if (errno == ENOENT) + { + fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n", + stderr); + exit (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) + { + 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]); + exit (2); + } + if ( ( fd = open ("/proc/mtrr", O_WRONLY, 0) ) == -1 ) + { + if (errno == ENOENT) + { + 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, "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 */ diff --git a/Documentation/x86/mtrr.txt b/Documentation/x86/mtrr.txt deleted file mode 100644 index dc3e703913ac..000000000000 --- a/Documentation/x86/mtrr.txt +++ /dev/null @@ -1,329 +0,0 @@ -MTRR (Memory Type Range Register) control - -Richard Gooch <rgooch@atnf.csiro.au> - 3 Jun 1999 -Luis R. Rodriguez <mcgrof@do-not-panic.com> - April 9, 2015 - -=============================================================================== -Phasing out MTRR use - -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 -arch_phys_wc_add() in combination with ioremap_wc() to make MTRR effective on -non-PAT systems while a no-op but equally effective on PAT enabled systems. - -Even if Linux does not use MTRRs directly, some x86 platform firmware may still -set up MTRRs early before booting the OS. They do this as some platform -firmware may still have implemented access to MTRRs which would be controlled -and handled by the platform firmware directly. An example of platform use of -MTRRs is through the use of SMI handlers, one case could be for fan control, -the platform code would need uncachable access to some of its fan control -registers. Such platform access does not need any Operating System MTRR code in -place other than mtrr_type_lookup() to ensure any OS specific mapping requests -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 -requests mtrr_type_lookup() should always return MTRR_TYPE_INVALID. - -For details refer to Documentation/x86/pat.txt. - -=============================================================================== - - On Intel P6 family processors (Pentium Pro, Pentium II and later) - the Memory Type Range Registers (MTRRs) may be used to control - processor access to memory ranges. This is most useful when you have - a video (VGA) card on a PCI or AGP bus. Enabling write-combining - allows bus write transfers to be combined into a larger transfer - before bursting over the PCI/AGP bus. This can increase performance - of image write operations 2.5 times or more. - - The Cyrix 6x86, 6x86MX and M II processors have Address Range - Registers (ARRs) which provide a similar functionality to MTRRs. For - these, the ARRs are used to emulate the MTRRs. - - The AMD K6-2 (stepping 8 and above) and K6-3 processors have two - MTRRs. These are supported. The AMD Athlon family provide 8 Intel - style MTRRs. - - The Centaur C6 (WinChip) has 8 MCRs, allowing write-combining. These - are supported. - - The VIA Cyrix III and VIA C3 CPUs offer 8 Intel style MTRRs. - - The CONFIG_MTRR option creates a /proc/mtrr file which may be used - to manipulate your MTRRs. Typically the X server should use - this. This should have a reasonably generic interface so that - similar control registers on other processors can be easily - supported. - - -There are two interfaces to /proc/mtrr: one is an ASCII interface -which allows you to read and write. The other is an ioctl() -interface. The ASCII interface is meant for administration. The -ioctl() interface is meant for C programs (i.e. the X server). The -interfaces are described below, with sample commands and C code. - -=============================================================================== -Reading MTRRs from the shell: - -% cat /proc/mtrr -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: -# echo "base=0xf8000000 size=0x400000 type=write-combining" >! /proc/mtrr -or if you use bash: -# 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 -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 -typical line that you may get is: - -(--) S3: PCI: 968 rev 0, Linear FB @ 0xf8000000 - -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 -that reported by the X server. - -To find out the size of your framebuffer (what, you don't actually -know?), the following line will tell you: - -(--) S3: videoram: 4096k - -That's 4 megabytes, which is 0x400000 bytes (in hexadecimal). -A patch is being written for XFree86 which will make this automatic: -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 -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 -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 -excluded from the beginning of the region because it is used for -registers. - -NOTE: You can only create type=uncachable region, if the first -region that you created is type=write-combining. -=============================================================================== -Removing MTRRs from the C-shell: -% echo "disable=2" >! /proc/mtrr -or using bash: -% echo "disable=2" >| /proc/mtrr -=============================================================================== -Reading MTRRs from a C program using ioctl()'s: - -/* mtrr-show.c - - Source file for mtrr-show (example program to show MTRRs using ioctl()'s) - - 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 program will use an ioctl() on /proc/mtrr to show the current MTRR - settings. This is an alternative to reading /proc/mtrr. - - - Written by Richard Gooch 17-DEC-1997 - - Last updated by Richard Gooch 2-MAY-1998 - - -*/ -#include <stdio.h> -#include <stdlib.h> -#include <string.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 fd; - struct mtrr_gentry gentry; - - if ( ( fd = open ("/proc/mtrr", O_RDONLY, 0) ) == -1 ) - { - if (errno == ENOENT) - { - fputs ("/proc/mtrr not found: not supported or you don't have a PPro?\n", - stderr); - exit (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) - { - 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]); - exit (2); - } - if ( ( fd = open ("/proc/mtrr", O_WRONLY, 0) ) == -1 ) - { - if (errno == ENOENT) - { - 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, "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 */ -=============================================================================== |