xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Merge branch 'x86/setup' into x86/devel

Browse Source
This commit is contained in:
Ingo Molnar
2008-07-08 09:43:01 +02:00
parent 6924d1ab8b 6bcb13b35a
commit 3c1ca43faf
20 changed files with 210 additions and 148 deletions
Download Patch File Download Diff File Expand all files Collapse all files

119
Documentation/x86/i386/IO-APIC.txt Normal file
View File

@@ -0,0 +1,119 @@
Most (all) Intel-MP compliant SMP boards have the so-called 'IO-APIC',
which is an enhanced interrupt controller. It enables us to route
hardware interrupts to multiple CPUs, or to CPU groups. Without an
IO-APIC, interrupts from hardware will be delivered only to the
CPU which boots the operating system (usually CPU#0).
Linux supports all variants of compliant SMP boards, including ones with
multiple IO-APICs. Multiple IO-APICs are used in high-end servers to
distribute IRQ load further.
There are (a few) known breakages in certain older boards, such bugs are
usually worked around by the kernel. If your MP-compliant SMP board does
not boot Linux, then consult the linux-smp mailing list archives first.
If your box boots fine with enabled IO-APIC IRQs, then your
/proc/interrupts will look like this one:
---------------------------->
hell:~> cat /proc/interrupts
CPU0
0: 1360293 IO-APIC-edge timer
1: 4 IO-APIC-edge keyboard
2: 0 XT-PIC cascade
13: 1 XT-PIC fpu
14: 1448 IO-APIC-edge ide0
16: 28232 IO-APIC-level Intel EtherExpress Pro 10/100 Ethernet
17: 51304 IO-APIC-level eth0
NMI: 0
ERR: 0
hell:~>
<----------------------------
Some interrupts are still listed as 'XT PIC', but this is not a problem;
none of those IRQ sources is performance-critical.
In the unlikely case that your board does not create a working mp-table,
you can use the pirq= boot parameter to 'hand-construct' IRQ entries. This
is non-trivial though and cannot be automated. One sample /etc/lilo.conf
entry:
append="pirq=15,11,10"
The actual numbers depend on your system, on your PCI cards and on their
PCI slot position. Usually PCI slots are 'daisy chained' before they are
connected to the PCI chipset IRQ routing facility (the incoming PIRQ1-4
lines):
,-. ,-. ,-. ,-. ,-.
PIRQ4 ----| |-. ,-| |-. ,-| |-. ,-| |--------| |
|S| \ / |S| \ / |S| \ / |S| |S|
PIRQ3 ----|l|-. `/---|l|-. `/---|l|-. `/---|l|--------|l|
|o| \/ |o| \/ |o| \/ |o| |o|
PIRQ2 ----|t|-./`----|t|-./`----|t|-./`----|t|--------|t|
|1| /\ |2| /\ |3| /\ |4| |5|
PIRQ1 ----| |- `----| |- `----| |- `----| |--------| |
`-' `-' `-' `-' `-'
Every PCI card emits a PCI IRQ, which can be INTA, INTB, INTC or INTD:
,-.
INTD--| |
|S|
INTC--|l|
|o|
INTB--|t|
|x|
INTA--| |
`-'
These INTA-D PCI IRQs are always 'local to the card', their real meaning
depends on which slot they are in. If you look at the daisy chaining diagram,
a card in slot4, issuing INTA IRQ, it will end up as a signal on PIRQ4 of
the PCI chipset. Most cards issue INTA, this creates optimal distribution
between the PIRQ lines. (distributing IRQ sources properly is not a
necessity, PCI IRQs can be shared at will, but it's a good for performance
to have non shared interrupts). Slot5 should be used for videocards, they
do not use interrupts normally, thus they are not daisy chained either.
so if you have your SCSI card (IRQ11) in Slot1, Tulip card (IRQ9) in
Slot2, then you'll have to specify this pirq= line:
append="pirq=11,9"
the following script tries to figure out such a default pirq= line from
your PCI configuration:
echo -n pirq=; echo `scanpci | grep T_L | cut -c56-` | sed 's/ /,/g'
note that this script wont work if you have skipped a few slots or if your
board does not do default daisy-chaining. (or the IO-APIC has the PIRQ pins
connected in some strange way). E.g. if in the above case you have your SCSI
card (IRQ11) in Slot3, and have Slot1 empty:
append="pirq=0,9,11"
[value '0' is a generic 'placeholder', reserved for empty (or non-IRQ emitting)
slots.]
Generally, it's always possible to find out the correct pirq= settings, just
permute all IRQ numbers properly ... it will take some time though. An
'incorrect' pirq line will cause the booting process to hang, or a device
won't function properly (e.g. if it's inserted as a module).
If you have 2 PCI buses, then you can use up to 8 pirq values, although such
boards tend to have a good configuration.
Be prepared that it might happen that you need some strange pirq line:
append="pirq=0,0,0,0,0,0,9,11"
Use smart trial-and-error techniques to find out the correct pirq line ...
Good luck and mail to linux-smp@vger.kernel.org or
linux-kernel@vger.kernel.org if you have any problems that are not covered
by this document.
-- mingo

900
Documentation/x86/i386/boot.txt Normal file
View File

@@ -0,0 +1,900 @@
THE LINUX/x86 BOOT PROTOCOL
---------------------------
On the x86 platform, the Linux kernel uses a rather complicated boot
convention. This has evolved partially due to historical aspects, as
well as the desire in the early days to have the kernel itself be a
bootable image, the complicated PC memory model and due to changed
expectations in the PC industry caused by the effective demise of
real-mode DOS as a mainstream operating system.
Currently, the following versions of the Linux/x86 boot protocol exist.
Old kernels: zImage/Image support only. Some very early kernels
may not even support a command line.
Protocol 2.00: (Kernel 1.3.73) Added bzImage and initrd support, as
well as a formalized way to communicate between the
boot loader and the kernel. setup.S made relocatable,
although the traditional setup area still assumed
writable.
Protocol 2.01: (Kernel 1.3.76) Added a heap overrun warning.
Protocol 2.02: (Kernel 2.4.0-test3-pre3) New command line protocol.
Lower the conventional memory ceiling. No overwrite
of the traditional setup area, thus making booting
safe for systems which use the EBDA from SMM or 32-bit
BIOS entry points. zImage deprecated but still
supported.
Protocol 2.03: (Kernel 2.4.18-pre1) Explicitly makes the highest possible
initrd address available to the bootloader.
Protocol 2.04: (Kernel 2.6.14) Extend the syssize field to four bytes.
Protocol 2.05: (Kernel 2.6.20) Make protected mode kernel relocatable.
Introduce relocatable_kernel and kernel_alignment fields.
Protocol 2.06: (Kernel 2.6.22) Added a field that contains the size of
the boot command line.
Protocol 2.07: (Kernel 2.6.24) Added paravirtualised boot protocol.
Introduced hardware_subarch and hardware_subarch_data
and KEEP_SEGMENTS flag in load_flags.
Protocol 2.08: (Kernel 2.6.26) Added crc32 checksum and ELF format
payload. Introduced payload_offset and payload length
fields to aid in locating the payload.
Protocol 2.09: (Kernel 2.6.26) Added a field of 64-bit physical
pointer to single linked list of struct setup_data.
**** MEMORY LAYOUT
The traditional memory map for the kernel loader, used for Image or
zImage kernels, typically looks like:
| |
0A0000 +------------------------+
| Reserved for BIOS | Do not use. Reserved for BIOS EBDA.
09A000 +------------------------+
| Command line |
| Stack/heap | For use by the kernel real-mode code.
098000 +------------------------+
| Kernel setup | The kernel real-mode code.
090200 +------------------------+
| Kernel boot sector | The kernel legacy boot sector.
090000 +------------------------+
| Protected-mode kernel | The bulk of the kernel image.
010000 +------------------------+
| Boot loader | <- Boot sector entry point 0000:7C00
001000 +------------------------+
| Reserved for MBR/BIOS |
000800 +------------------------+
| Typically used by MBR |
000600 +------------------------+
| BIOS use only |
000000 +------------------------+
When using bzImage, the protected-mode kernel was relocated to
0x100000 ("high memory"), and the kernel real-mode block (boot sector,
setup, and stack/heap) was made relocatable to any address between
0x10000 and end of low memory. Unfortunately, in protocols 2.00 and
2.01 the 0x90000+ memory range is still used internally by the kernel;
the 2.02 protocol resolves that problem.
It is desirable to keep the "memory ceiling" -- the highest point in
low memory touched by the boot loader -- as low as possible, since
some newer BIOSes have begun to allocate some rather large amounts of
memory, called the Extended BIOS Data Area, near the top of low
memory. The boot loader should use the "INT 12h" BIOS call to verify
how much low memory is available.
Unfortunately, if INT 12h reports that the amount of memory is too
low, there is usually nothing the boot loader can do but to report an
error to the user. The boot loader should therefore be designed to
take up as little space in low memory as it reasonably can. For
zImage or old bzImage kernels, which need data written into the
0x90000 segment, the boot loader should make sure not to use memory
above the 0x9A000 point; too many BIOSes will break above that point.
For a modern bzImage kernel with boot protocol version >= 2.02, a
memory layout like the following is suggested:
~ ~
| Protected-mode kernel |
100000 +------------------------+
| I/O memory hole |
0A0000 +------------------------+
| Reserved for BIOS | Leave as much as possible unused
~ ~
| Command line | (Can also be below the X+10000 mark)
X+10000 +------------------------+
| Stack/heap | For use by the kernel real-mode code.
X+08000 +------------------------+
| Kernel setup | The kernel real-mode code.
| Kernel boot sector | The kernel legacy boot sector.
X +------------------------+
| Boot loader | <- Boot sector entry point 0000:7C00
001000 +------------------------+
| Reserved for MBR/BIOS |
000800 +------------------------+
| Typically used by MBR |
000600 +------------------------+
| BIOS use only |
000000 +------------------------+
... where the address X is as low as the design of the boot loader
permits.
**** THE REAL-MODE KERNEL HEADER
In the following text, and anywhere in the kernel boot sequence, "a
sector" refers to 512 bytes. It is independent of the actual sector
size of the underlying medium.
The first step in loading a Linux kernel should be to load the
real-mode code (boot sector and setup code) and then examine the
following header at offset 0x01f1. The real-mode code can total up to
32K, although the boot loader may choose to load only the first two
sectors (1K) and then examine the bootup sector size.
The header looks like:
Offset Proto Name Meaning
/Size
01F1/1 ALL(1 setup_sects The size of the setup in sectors
01F2/2 ALL root_flags If set, the root is mounted readonly
01F4/4 2.04+(2 syssize The size of the 32-bit code in 16-byte paras
01F8/2 ALL ram_size DO NOT USE - for bootsect.S use only
01FA/2 ALL vid_mode Video mode control
01FC/2 ALL root_dev Default root device number
01FE/2 ALL boot_flag 0xAA55 magic number
0200/2 2.00+ jump Jump instruction
0202/4 2.00+ header Magic signature "HdrS"
0206/2 2.00+ version Boot protocol version supported
0208/4 2.00+ realmode_swtch Boot loader hook (see below)
020C/2 2.00+ start_sys The load-low segment (0x1000) (obsolete)
020E/2 2.00+ kernel_version Pointer to kernel version string
0210/1 2.00+ type_of_loader Boot loader identifier
0211/1 2.00+ loadflags Boot protocol option flags
0212/2 2.00+ setup_move_size Move to high memory size (used with hooks)
0214/4 2.00+ code32_start Boot loader hook (see below)
0218/4 2.00+ ramdisk_image initrd load address (set by boot loader)
021C/4 2.00+ ramdisk_size initrd size (set by boot loader)
0220/4 2.00+ bootsect_kludge DO NOT USE - for bootsect.S use only
0224/2 2.01+ heap_end_ptr Free memory after setup end
0226/2 N/A pad1 Unused
0228/4 2.02+ cmd_line_ptr 32-bit pointer to the kernel command line
022C/4 2.03+ initrd_addr_max Highest legal initrd address
0230/4 2.05+ kernel_alignment Physical addr alignment required for kernel
0234/1 2.05+ relocatable_kernel Whether kernel is relocatable or not
0235/3 N/A pad2 Unused
0238/4 2.06+ cmdline_size Maximum size of the kernel command line
023C/4 2.07+ hardware_subarch Hardware subarchitecture
0240/8 2.07+ hardware_subarch_data Subarchitecture-specific data
0248/4 2.08+ payload_offset Offset of kernel payload
024C/4 2.08+ payload_length Length of kernel payload
0250/8 2.09+ setup_data 64-bit physical pointer to linked list
of struct setup_data
(1) For backwards compatibility, if the setup_sects field contains 0, the
real value is 4.
(2) For boot protocol prior to 2.04, the upper two bytes of the syssize
field are unusable, which means the size of a bzImage kernel
cannot be determined.
If the "HdrS" (0x53726448) magic number is not found at offset 0x202,
the boot protocol version is "old". Loading an old kernel, the
following parameters should be assumed:
Image type = zImage
initrd not supported
Real-mode kernel must be located at 0x90000.
Otherwise, the "version" field contains the protocol version,
e.g. protocol version 2.01 will contain 0x0201 in this field. When
setting fields in the header, you must make sure only to set fields
supported by the protocol version in use.
**** DETAILS OF HEADER FIELDS
For each field, some are information from the kernel to the bootloader
("read"), some are expected to be filled out by the bootloader
("write"), and some are expected to be read and modified by the
bootloader ("modify").
All general purpose boot loaders should write the fields marked
(obligatory). Boot loaders who want to load the kernel at a
nonstandard address should fill in the fields marked (reloc); other
boot loaders can ignore those fields.
The byte order of all fields is littleendian (this is x86, after all.)
Field name: setup_sects
Type: read
Offset/size: 0x1f1/1
Protocol: ALL
The size of the setup code in 512-byte sectors. If this field is
0, the real value is 4. The real-mode code consists of the boot
sector (always one 512-byte sector) plus the setup code.
Field name: root_flags
Type: modify (optional)
Offset/size: 0x1f2/2
Protocol: ALL
If this field is nonzero, the root defaults to readonly. The use of
this field is deprecated; use the "ro" or "rw" options on the
command line instead.
Field name: syssize
Type: read
Offset/size: 0x1f4/4 (protocol 2.04+) 0x1f4/2 (protocol ALL)
Protocol: 2.04+
The size of the protected-mode code in units of 16-byte paragraphs.
For protocol versions older than 2.04 this field is only two bytes
wide, and therefore cannot be trusted for the size of a kernel if
the LOAD_HIGH flag is set.
Field name: ram_size
Type: kernel internal
Offset/size: 0x1f8/2
Protocol: ALL
This field is obsolete.
Field name: vid_mode
Type: modify (obligatory)
Offset/size: 0x1fa/2
Please see the section on SPECIAL COMMAND LINE OPTIONS.
Field name: root_dev
Type: modify (optional)
Offset/size: 0x1fc/2
Protocol: ALL
The default root device device number. The use of this field is
deprecated, use the "root=" option on the command line instead.
Field name: boot_flag
Type: read
Offset/size: 0x1fe/2
Protocol: ALL
Contains 0xAA55. This is the closest thing old Linux kernels have
to a magic number.
Field name: jump
Type: read
Offset/size: 0x200/2
Protocol: 2.00+
Contains an x86 jump instruction, 0xEB followed by a signed offset
relative to byte 0x202. This can be used to determine the size of
the header.
Field name: header
Type: read
Offset/size: 0x202/4
Protocol: 2.00+
Contains the magic number "HdrS" (0x53726448).
Field name: version
Type: read
Offset/size: 0x206/2
Protocol: 2.00+
Contains the boot protocol version, in (major << 8)+minor format,
e.g. 0x0204 for version 2.04, and 0x0a11 for a hypothetical version
10.17.
Field name: readmode_swtch
Type: modify (optional)
Offset/size: 0x208/4
Protocol: 2.00+
Boot loader hook (see ADVANCED BOOT LOADER HOOKS below.)
Field name: start_sys
Type: read
Offset/size: 0x20c/4
Protocol: 2.00+
The load low segment (0x1000). Obsolete.
Field name: kernel_version
Type: read
Offset/size: 0x20e/2
Protocol: 2.00+
If set to a nonzero value, contains a pointer to a NUL-terminated
human-readable kernel version number string, less 0x200. This can
be used to display the kernel version to the user. This value
should be less than (0x200*setup_sects).
For example, if this value is set to 0x1c00, the kernel version
number string can be found at offset 0x1e00 in the kernel file.
This is a valid value if and only if the "setup_sects" field
contains the value 15 or higher, as:
0x1c00 < 15*0x200 (= 0x1e00) but
0x1c00 >= 14*0x200 (= 0x1c00)
0x1c00 >> 9 = 14, so the minimum value for setup_secs is 15.
Field name: type_of_loader
Type: write (obligatory)
Offset/size: 0x210/1
Protocol: 2.00+
If your boot loader has an assigned id (see table below), enter
0xTV here, where T is an identifier for the boot loader and V is
a version number. Otherwise, enter 0xFF here.
Assigned boot loader ids:
0 LILO (0x00 reserved for pre-2.00 bootloader)
1 Loadlin
2 bootsect-loader (0x20, all other values reserved)
3 SYSLINUX
4 EtherBoot
5 ELILO
7 GRuB
8 U-BOOT
9 Xen
A Gujin
B Qemu
Please contact <hpa@zytor.com> if you need a bootloader ID
value assigned.
Field name: loadflags
Type: modify (obligatory)
Offset/size: 0x211/1
Protocol: 2.00+
This field is a bitmask.
Bit 0 (read): LOADED_HIGH
- If 0, the protected-mode code is loaded at 0x10000.
- If 1, the protected-mode code is loaded at 0x100000.
Bit 5 (write): QUIET_FLAG
- If 0, print early messages.
- If 1, suppress early messages.
This requests to the kernel (decompressor and early
kernel) to not write early messages that require
accessing the display hardware directly.
Bit 6 (write): KEEP_SEGMENTS
Protocol: 2.07+
- If 0, reload the segment registers in the 32bit entry point.
- If 1, do not reload the segment registers in the 32bit entry point.
Assume that %cs %ds %ss %es are all set to flat segments with
a base of 0 (or the equivalent for their environment).
Bit 7 (write): CAN_USE_HEAP
Set this bit to 1 to indicate that the value entered in the
heap_end_ptr is valid. If this field is clear, some setup code
functionality will be disabled.
Field name: setup_move_size
Type: modify (obligatory)
Offset/size: 0x212/2
Protocol: 2.00-2.01
When using protocol 2.00 or 2.01, if the real mode kernel is not
loaded at 0x90000, it gets moved there later in the loading
sequence. Fill in this field if you want additional data (such as
the kernel command line) moved in addition to the real-mode kernel
itself.
The unit is bytes starting with the beginning of the boot sector.
This field is can be ignored when the protocol is 2.02 or higher, or
if the real-mode code is loaded at 0x90000.
Field name: code32_start
Type: modify (optional, reloc)
Offset/size: 0x214/4
Protocol: 2.00+
The address to jump to in protected mode. This defaults to the load
address of the kernel, and can be used by the boot loader to
determine the proper load address.
This field can be modified for two purposes:
1. as a boot loader hook (see ADVANCED BOOT LOADER HOOKS below.)
2. if a bootloader which does not install a hook loads a
relocatable kernel at a nonstandard address it will have to modify
this field to point to the load address.
Field name: ramdisk_image
Type: write (obligatory)
Offset/size: 0x218/4
Protocol: 2.00+
The 32-bit linear address of the initial ramdisk or ramfs. Leave at
zero if there is no initial ramdisk/ramfs.
Field name: ramdisk_size
Type: write (obligatory)
Offset/size: 0x21c/4
Protocol: 2.00+
Size of the initial ramdisk or ramfs. Leave at zero if there is no
initial ramdisk/ramfs.
Field name: bootsect_kludge
Type: kernel internal
Offset/size: 0x220/4
Protocol: 2.00+
This field is obsolete.
Field name: heap_end_ptr
Type: write (obligatory)
Offset/size: 0x224/2
Protocol: 2.01+
Set this field to the offset (from the beginning of the real-mode
code) of the end of the setup stack/heap, minus 0x0200.
Field name: cmd_line_ptr
Type: write (obligatory)
Offset/size: 0x228/4
Protocol: 2.02+
Set this field to the linear address of the kernel command line.
The kernel command line can be located anywhere between the end of
the setup heap and 0xA0000; it does not have to be located in the
same 64K segment as the real-mode code itself.
Fill in this field even if your boot loader does not support a
command line, in which case you can point this to an empty string
(or better yet, to the string "auto".) If this field is left at
zero, the kernel will assume that your boot loader does not support
the 2.02+ protocol.
Field name: initrd_addr_max
Type: read
Offset/size: 0x22c/4
Protocol: 2.03+
The maximum address that may be occupied by the initial
ramdisk/ramfs contents. For boot protocols 2.02 or earlier, this
field is not present, and the maximum address is 0x37FFFFFF. (This
address is defined as the address of the highest safe byte, so if
your ramdisk is exactly 131072 bytes long and this field is
0x37FFFFFF, you can start your ramdisk at 0x37FE0000.)
Field name: kernel_alignment
Type: read (reloc)
Offset/size: 0x230/4
Protocol: 2.05+
Alignment unit required by the kernel (if relocatable_kernel is true.)
Field name: relocatable_kernel
Type: read (reloc)
Offset/size: 0x234/1
Protocol: 2.05+
If this field is nonzero, the protected-mode part of the kernel can
be loaded at any address that satisfies the kernel_alignment field.
After loading, the boot loader must set the code32_start field to
point to the loaded code, or to a boot loader hook.
Field name: cmdline_size
Type: read
Offset/size: 0x238/4
Protocol: 2.06+
The maximum size of the command line without the terminating
zero. This means that the command line can contain at most
cmdline_size characters. With protocol version 2.05 and earlier, the
maximum size was 255.
Field name: hardware_subarch
Type: write (optional, defaults to x86/PC)
Offset/size: 0x23c/4
Protocol: 2.07+
In a paravirtualized environment the hardware low level architectural
pieces such as interrupt handling, page table handling, and
accessing process control registers needs to be done differently.
This field allows the bootloader to inform the kernel we are in one
one of those environments.
0x00000000 The default x86/PC environment
0x00000001 lguest
0x00000002 Xen
Field name: hardware_subarch_data
Type: write (subarch-dependent)
Offset/size: 0x240/8
Protocol: 2.07+
A pointer to data that is specific to hardware subarch
This field is currently unused for the default x86/PC environment,
do not modify.
Field name: payload_offset
Type: read
Offset/size: 0x248/4
Protocol: 2.08+
If non-zero then this field contains the offset from the end of the
real-mode code to the payload.
The payload may be compressed. The format of both the compressed and
uncompressed data should be determined using the standard magic
numbers. Currently only gzip compressed ELF is used.
Field name: payload_length
Type: read
Offset/size: 0x24c/4
Protocol: 2.08+
The length of the payload.
Field name: setup_data
Type: write (special)
Offset/size: 0x250/8
Protocol: 2.09+
The 64-bit physical pointer to NULL terminated single linked list of
struct setup_data. This is used to define a more extensible boot
parameters passing mechanism. The definition of struct setup_data is
as follow:
struct setup_data {
u64 next;
u32 type;
u32 len;
u8 data[0];
};
Where, the next is a 64-bit physical pointer to the next node of
linked list, the next field of the last node is 0; the type is used
to identify the contents of data; the len is the length of data
field; the data holds the real payload.
This list may be modified at a number of points during the bootup
process. Therefore, when modifying this list one should always make
sure to consider the case where the linked list already contains
entries.
**** THE IMAGE CHECKSUM
From boot protocol version 2.08 onwards the CRC-32 is calculated over
the entire file using the characteristic polynomial 0x04C11DB7 and an
initial remainder of 0xffffffff. The checksum is appended to the
file; therefore the CRC of the file up to the limit specified in the
syssize field of the header is always 0.
**** THE KERNEL COMMAND LINE
The kernel command line has become an important way for the boot
loader to communicate with the kernel. Some of its options are also
relevant to the boot loader itself, see "special command line options"
below.
The kernel command line is a null-terminated string. The maximum
length can be retrieved from the field cmdline_size. Before protocol
version 2.06, the maximum was 255 characters. A string that is too
long will be automatically truncated by the kernel.
If the boot protocol version is 2.02 or later, the address of the
kernel command line is given by the header field cmd_line_ptr (see
above.) This address can be anywhere between the end of the setup
heap and 0xA0000.
If the protocol version is *not* 2.02 or higher, the kernel
command line is entered using the following protocol:
At offset 0x0020 (word), "cmd_line_magic", enter the magic
number 0xA33F.
At offset 0x0022 (word), "cmd_line_offset", enter the offset
of the kernel command line (relative to the start of the
real-mode kernel).
The kernel command line *must* be within the memory region
covered by setup_move_size, so you may need to adjust this
field.
**** MEMORY LAYOUT OF THE REAL-MODE CODE
The real-mode code requires a stack/heap to be set up, as well as
memory allocated for the kernel command line. This needs to be done
in the real-mode accessible memory in bottom megabyte.
It should be noted that modern machines often have a sizable Extended
BIOS Data Area (EBDA). As a result, it is advisable to use as little
of the low megabyte as possible.
Unfortunately, under the following circumstances the 0x90000 memory
segment has to be used:
- When loading a zImage kernel ((loadflags & 0x01) == 0).
- When loading a 2.01 or earlier boot protocol kernel.
-> For the 2.00 and 2.01 boot protocols, the real-mode code
can be loaded at another address, but it is internally
relocated to 0x90000. For the "old" protocol, the
real-mode code must be loaded at 0x90000.
When loading at 0x90000, avoid using memory above 0x9a000.
For boot protocol 2.02 or higher, the command line does not have to be
located in the same 64K segment as the real-mode setup code; it is
thus permitted to give the stack/heap the full 64K segment and locate
the command line above it.
The kernel command line should not be located below the real-mode
code, nor should it be located in high memory.
**** SAMPLE BOOT CONFIGURATION
As a sample configuration, assume the following layout of the real
mode segment:
When loading below 0x90000, use the entire segment:
0x0000-0x7fff Real mode kernel
0x8000-0xdfff Stack and heap
0xe000-0xffff Kernel command line
When loading at 0x90000 OR the protocol version is 2.01 or earlier:
0x0000-0x7fff Real mode kernel
0x8000-0x97ff Stack and heap
0x9800-0x9fff Kernel command line
Such a boot loader should enter the following fields in the header:
unsigned long base_ptr; /* base address for real-mode segment */
if ( setup_sects == 0 ) {
setup_sects = 4;
}
if ( protocol >= 0x0200 ) {
type_of_loader = <type code>;
if ( loading_initrd ) {
ramdisk_image = <initrd_address>;
ramdisk_size = <initrd_size>;
}
if ( protocol >= 0x0202 && loadflags & 0x01 )
heap_end = 0xe000;
else
heap_end = 0x9800;
if ( protocol >= 0x0201 ) {
heap_end_ptr = heap_end - 0x200;
loadflags |= 0x80; /* CAN_USE_HEAP */
}
if ( protocol >= 0x0202 ) {
cmd_line_ptr = base_ptr + heap_end;
strcpy(cmd_line_ptr, cmdline);
} else {
cmd_line_magic = 0xA33F;
cmd_line_offset = heap_end;
setup_move_size = heap_end + strlen(cmdline)+1;
strcpy(base_ptr+cmd_line_offset, cmdline);
}
} else {
/* Very old kernel */
heap_end = 0x9800;
cmd_line_magic = 0xA33F;
cmd_line_offset = heap_end;
/* A very old kernel MUST have its real-mode code
loaded at 0x90000 */
if ( base_ptr != 0x90000 ) {
/* Copy the real-mode kernel */
memcpy(0x90000, base_ptr, (setup_sects+1)*512);
base_ptr = 0x90000; /* Relocated */
}
strcpy(0x90000+cmd_line_offset, cmdline);
/* It is recommended to clear memory up to the 32K mark */
memset(0x90000 + (setup_sects+1)*512, 0,
(64-(setup_sects+1))*512);
}
**** LOADING THE REST OF THE KERNEL
The 32-bit (non-real-mode) kernel starts at offset (setup_sects+1)*512
in the kernel file (again, if setup_sects == 0 the real value is 4.)
It should be loaded at address 0x10000 for Image/zImage kernels and
0x100000 for bzImage kernels.
The kernel is a bzImage kernel if the protocol >= 2.00 and the 0x01
bit (LOAD_HIGH) in the loadflags field is set:
is_bzImage = (protocol >= 0x0200) && (loadflags & 0x01);
load_address = is_bzImage ? 0x100000 : 0x10000;
Note that Image/zImage kernels can be up to 512K in size, and thus use
the entire 0x10000-0x90000 range of memory. This means it is pretty
much a requirement for these kernels to load the real-mode part at
0x90000. bzImage kernels allow much more flexibility.
**** SPECIAL COMMAND LINE OPTIONS
If the command line provided by the boot loader is entered by the
user, the user may expect the following command line options to work.
They should normally not be deleted from the kernel command line even
though not all of them are actually meaningful to the kernel. Boot
loader authors who need additional command line options for the boot
loader itself should get them registered in
Documentation/kernel-parameters.txt to make sure they will not
conflict with actual kernel options now or in the future.
vga=<mode>
<mode> here is either an integer (in C notation, either
decimal, octal, or hexadecimal) or one of the strings
"normal" (meaning 0xFFFF), "ext" (meaning 0xFFFE) or "ask"
(meaning 0xFFFD). This value should be entered into the
vid_mode field, as it is used by the kernel before the command
line is parsed.
mem=<size>
<size> is an integer in C notation optionally followed by
(case insensitive) K, M, G, T, P or E (meaning << 10, << 20,
<< 30, << 40, << 50 or << 60). This specifies the end of
memory to the kernel. This affects the possible placement of
an initrd, since an initrd should be placed near end of
memory. Note that this is an option to *both* the kernel and
the bootloader!
initrd=<file>
An initrd should be loaded. The meaning of <file> is
obviously bootloader-dependent, and some boot loaders
(e.g. LILO) do not have such a command.
In addition, some boot loaders add the following options to the
user-specified command line:
BOOT_IMAGE=<file>
The boot image which was loaded. Again, the meaning of <file>
is obviously bootloader-dependent.
auto
The kernel was booted without explicit user intervention.
If these options are added by the boot loader, it is highly
recommended that they are located *first*, before the user-specified
or configuration-specified command line. Otherwise, "init=/bin/sh"
gets confused by the "auto" option.
**** RUNNING THE KERNEL
The kernel is started by jumping to the kernel entry point, which is
located at *segment* offset 0x20 from the start of the real mode
kernel. This means that if you loaded your real-mode kernel code at
0x90000, the kernel entry point is 9020:0000.
At entry, ds = es = ss should point to the start of the real-mode
kernel code (0x9000 if the code is loaded at 0x90000), sp should be
set up properly, normally pointing to the top of the heap, and
interrupts should be disabled. Furthermore, to guard against bugs in
the kernel, it is recommended that the boot loader sets fs = gs = ds =
es = ss.
In our example from above, we would do:
/* Note: in the case of the "old" kernel protocol, base_ptr must
be == 0x90000 at this point; see the previous sample code */
seg = base_ptr >> 4;
cli(); /* Enter with interrupts disabled! */
/* Set up the real-mode kernel stack */
_SS = seg;
_SP = heap_end;
_DS = _ES = _FS = _GS = seg;
jmp_far(seg+0x20, 0); /* Run the kernel */
If your boot sector accesses a floppy drive, it is recommended to
switch off the floppy motor before running the kernel, since the
kernel boot leaves interrupts off and thus the motor will not be
switched off, especially if the loaded kernel has the floppy driver as
a demand-loaded module!
**** ADVANCED BOOT LOADER HOOKS
If the boot loader runs in a particularly hostile environment (such as
LOADLIN, which runs under DOS) it may be impossible to follow the
standard memory location requirements. Such a boot loader may use the
following hooks that, if set, are invoked by the kernel at the
appropriate time. The use of these hooks should probably be
considered an absolutely last resort!
IMPORTANT: All the hooks are required to preserve %esp, %ebp, %esi and
%edi across invocation.
realmode_swtch:
A 16-bit real mode far subroutine invoked immediately before
entering protected mode. The default routine disables NMI, so
your routine should probably do so, too.
code32_start:
A 32-bit flat-mode routine *jumped* to immediately after the
transition to protected mode, but before the kernel is
uncompressed. No segments, except CS, are guaranteed to be
set up (current kernels do, but older ones do not); you should
set them up to BOOT_DS (0x18) yourself.
After completing your hook, you should jump to the address
that was in this field before your boot loader overwrote it
(relocated, if appropriate.)
**** 32-bit BOOT PROTOCOL
For machine with some new BIOS other than legacy BIOS, such as EFI,
LinuxBIOS, etc, and kexec, the 16-bit real mode setup code in kernel
based on legacy BIOS can not be used, so a 32-bit boot protocol needs
to be defined.
In 32-bit boot protocol, the first step in loading a Linux kernel
should be to setup the boot parameters (struct boot_params,
traditionally known as "zero page"). The memory for struct boot_params
should be allocated and initialized to all zero. Then the setup header
from offset 0x01f1 of kernel image on should be loaded into struct
boot_params and examined. The end of setup header can be calculated as
follow:
0x0202 + byte value at offset 0x0201
In addition to read/modify/write the setup header of the struct
boot_params as that of 16-bit boot protocol, the boot loader should
also fill the additional fields of the struct boot_params as that
described in zero-page.txt.
After setupping the struct boot_params, the boot loader can load the
32/64-bit kernel in the same way as that of 16-bit boot protocol.
In 32-bit boot protocol, the kernel is started by jumping to the
32-bit kernel entry point, which is the start address of loaded
32/64-bit kernel.
At entry, the CPU must be in 32-bit protected mode with paging
disabled; a GDT must be loaded with the descriptors for selectors
__BOOT_CS(0x10) and __BOOT_DS(0x18); both descriptors must be 4G flat
segment; __BOOS_CS must have execute/read permission, and __BOOT_DS
must have read/write permission; CS must be __BOOT_CS and DS, ES, SS
must be __BOOT_DS; interrupt must be disabled; %esi must hold the base
address of the struct boot_params; %ebp, %edi and %ebx must be zero.

44
Documentation/x86/i386/usb-legacy-support.txt Normal file
View File

@@ -0,0 +1,44 @@
USB Legacy support
~~~~~~~~~~~~~~~~~~
Vojtech Pavlik <vojtech@suse.cz>, January 2004
Also known as "USB Keyboard" or "USB Mouse support" in the BIOS Setup is a
feature that allows one to use the USB mouse and keyboard as if they were
their classic PS/2 counterparts. This means one can use an USB keyboard to
type in LILO for example.
It has several drawbacks, though:
1) On some machines, the emulated PS/2 mouse takes over even when no USB
mouse is present and a real PS/2 mouse is present. In that case the extra
features (wheel, extra buttons, touchpad mode) of the real PS/2 mouse may
not be available.
2) If CONFIG_HIGHMEM64G is enabled, the PS/2 mouse emulation can cause
system crashes, because the SMM BIOS is not expecting to be in PAE mode.
The Intel E7505 is a typical machine where this happens.
3) If AMD64 64-bit mode is enabled, again system crashes often happen,
because the SMM BIOS isn't expecting the CPU to be in 64-bit mode. The
BIOS manufacturers only test with Windows, and Windows doesn't do 64-bit
yet.
Solutions:
Problem 1) can be solved by loading the USB drivers prior to loading the
PS/2 mouse driver. Since the PS/2 mouse driver is in 2.6 compiled into
the kernel unconditionally, this means the USB drivers need to be
compiled-in, too.
Problem 2) can currently only be solved by either disabling HIGHMEM64G
in the kernel config or USB Legacy support in the BIOS. A BIOS update
could help, but so far no such update exists.
Problem 3) is usually fixed by a BIOS update. Check the board
manufacturers web site. If an update is not available, disable USB
Legacy support in the BIOS. If this alone doesn't help, try also adding
idle=poll on the kernel command line. The BIOS may be entering the SMM
on the HLT instruction as well.

31
Documentation/x86/i386/zero-page.txt Normal file
View File

@@ -0,0 +1,31 @@
The additional fields in struct boot_params as a part of 32-bit boot
protocol of kernel. These should be filled by bootloader or 16-bit
real-mode setup code of the kernel. References/settings to it mainly
are in:
include/asm-x86/bootparam.h
Offset Proto Name Meaning
/Size
000/040 ALL screen_info Text mode or frame buffer information
(struct screen_info)
040/014 ALL apm_bios_info APM BIOS information (struct apm_bios_info)
060/010 ALL ist_info Intel SpeedStep (IST) BIOS support information
(struct ist_info)
080/010 ALL hd0_info hd0 disk parameter, OBSOLETE!!
090/010 ALL hd1_info hd1 disk parameter, OBSOLETE!!
0A0/010 ALL sys_desc_table System description table (struct sys_desc_table)
140/080 ALL edid_info Video mode setup (struct edid_info)
1C0/020 ALL efi_info EFI 32 information (struct efi_info)
1E0/004 ALL alk_mem_k Alternative mem check, in KB
1E4/004 ALL scratch Scratch field for the kernel setup code
1E8/001 ALL e820_entries Number of entries in e820_map (below)
1E9/001 ALL eddbuf_entries Number of entries in eddbuf (below)
1EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer
(below)
290/040 ALL edd_mbr_sig_buffer EDD MBR signatures
2D0/A00 ALL e820_map E820 memory map table
(array of struct e820entry)
D00/1EC ALL eddbuf EDD data (array of struct edd_info)

16
Documentation/x86/x86_64/00-INDEX Normal file
View File

@@ -0,0 +1,16 @@
00-INDEX
- This file
boot-options.txt
- AMD64-specific boot options.
cpu-hotplug-spec
- Firmware support for CPU hotplug under Linux/x86-64
fake-numa-for-cpusets
- Using numa=fake and CPUSets for Resource Management
kernel-stacks
- Context-specific per-processor interrupt stacks.
machinecheck
- Configurable sysfs parameters for the x86-64 machine check code.
mm.txt
- Memory layout of x86-64 (4 level page tables, 46 bits physical).
uefi.txt
- Booting Linux via Unified Extensible Firmware Interface.

314
Documentation/x86/x86_64/boot-options.txt Normal file
View File

@@ -0,0 +1,314 @@
AMD64 specific boot options
There are many others (usually documented in driver documentation), but
only the AMD64 specific ones are listed here.
Machine check
mce=off disable machine check
mce=bootlog Enable logging of machine checks left over from booting.
Disabled by default on AMD because some BIOS leave bogus ones.
If your BIOS doesn't do that it's a good idea to enable though
to make sure you log even machine check events that result
in a reboot. On Intel systems it is enabled by default.
mce=nobootlog
Disable boot machine check logging.
mce=tolerancelevel (number)
0: always panic on uncorrected errors, log corrected errors
1: panic or SIGBUS on uncorrected errors, log corrected errors
2: SIGBUS or log uncorrected errors, log corrected errors
3: never panic or SIGBUS, log all errors (for testing only)
Default is 1
Can be also set using sysfs which is preferable.
nomce (for compatibility with i386): same as mce=off
Everything else is in sysfs now.
APICs
apic Use IO-APIC. Default
noapic Don't use the IO-APIC.
disableapic Don't use the local APIC
nolapic Don't use the local APIC (alias for i386 compatibility)
pirq=... See Documentation/i386/IO-APIC.txt
noapictimer Don't set up the APIC timer
no_timer_check Don't check the IO-APIC timer. This can work around
problems with incorrect timer initialization on some boards.
apicmaintimer Run time keeping from the local APIC timer instead
of using the PIT/HPET interrupt for this. This is useful
when the PIT/HPET interrupts are unreliable.
noapicmaintimer Don't do time keeping using the APIC timer.
Useful when this option was auto selected, but doesn't work.
apicpmtimer
Do APIC timer calibration using the pmtimer. Implies
apicmaintimer. Useful when your PIT timer is totally
broken.
disable_8254_timer / enable_8254_timer
Enable interrupt 0 timer routing over the 8254 in addition to over
the IO-APIC. The kernel tries to set a sensible default.
Early Console
syntax: earlyprintk=vga
earlyprintk=serial[,ttySn[,baudrate]]
The early console is useful when the kernel crashes before the
normal console is initialized. It is not enabled by
default because it has some cosmetic problems.
Append ,keep to not disable it when the real console takes over.
Only vga or serial at a time, not both.
Currently only ttyS0 and ttyS1 are supported.
Interaction with the standard serial driver is not very good.
The VGA output is eventually overwritten by the real console.
Timing
notsc
Don't use the CPU time stamp counter to read the wall time.
This can be used to work around timing problems on multiprocessor systems
with not properly synchronized CPUs.
report_lost_ticks
Report when timer interrupts are lost because some code turned off
interrupts for too long.
nmi_watchdog=NUMBER[,panic]
NUMBER can be:
0 don't use an NMI watchdog
1 use the IO-APIC timer for the NMI watchdog
2 use the local APIC for the NMI watchdog using a performance counter. Note
This will use one performance counter and the local APIC's performance
vector.
When panic is specified panic when an NMI watchdog timeout occurs.
This is useful when you use a panic=... timeout and need the box
quickly up again.
nohpet
Don't use the HPET timer.
Idle loop
idle=poll
Don't do power saving in the idle loop using HLT, but poll for rescheduling
event. This will make the CPUs eat a lot more power, but may be useful
to get slightly better performance in multiprocessor benchmarks. It also
makes some profiling using performance counters more accurate.
Please note that on systems with MONITOR/MWAIT support (like Intel EM64T
CPUs) this option has no performance advantage over the normal idle loop.
It may also interact badly with hyperthreading.
Rebooting
reboot=b[ios] | t[riple] | k[bd] | a[cpi] | e[fi] [, [w]arm | [c]old]
bios Use the CPU reboot vector for warm reset
warm Don't set the cold reboot flag
cold Set the cold reboot flag
triple Force a triple fault (init)
kbd Use the keyboard controller. cold reset (default)
acpi Use the ACPI RESET_REG in the FADT. If ACPI is not configured or the
ACPI reset does not work, the reboot path attempts the reset using
the keyboard controller.
efi Use efi reset_system runtime service. If EFI is not configured or the
EFI reset does not work, the reboot path attempts the reset using
the keyboard controller.
Using warm reset will be much faster especially on big memory
systems because the BIOS will not go through the memory check.
Disadvantage is that not all hardware will be completely reinitialized
on reboot so there may be boot problems on some systems.
reboot=force
Don't stop other CPUs on reboot. This can make reboot more reliable
in some cases.
Non Executable Mappings
noexec=on|off
on Enable(default)
off Disable
SMP
additional_cpus=NUM Allow NUM more CPUs for hotplug
(defaults are specified by the BIOS, see Documentation/x86_64/cpu-hotplug-spec)
NUMA
numa=off Only set up a single NUMA node spanning all memory.
numa=noacpi Don't parse the SRAT table for NUMA setup
numa=fake=CMDLINE
If a number, fakes CMDLINE nodes and ignores NUMA setup of the
actual machine. Otherwise, system memory is configured
depending on the sizes and coefficients listed. For example:
numa=fake=2*512,1024,4*256,*128
gives two 512M nodes, a 1024M node, four 256M nodes, and the
rest split into 128M chunks. If the last character of CMDLINE
is a *, the remaining memory is divided up equally among its
coefficient:
numa=fake=2*512,2*
gives two 512M nodes and the rest split into two nodes.
Otherwise, the remaining system RAM is allocated to an
additional node.
numa=hotadd=percent
Only allow hotadd memory to preallocate page structures upto
percent of already available memory.
numa=hotadd=0 will disable hotadd memory.
ACPI
acpi=off Don't enable ACPI
acpi=ht Use ACPI boot table parsing, but don't enable ACPI
interpreter
acpi=force Force ACPI on (currently not needed)
acpi=strict Disable out of spec ACPI workarounds.
acpi_sci={edge,level,high,low} Set up ACPI SCI interrupt.
acpi=noirq Don't route interrupts
PCI
pci=off Don't use PCI
pci=conf1 Use conf1 access.
pci=conf2 Use conf2 access.
pci=rom Assign ROMs.
pci=assign-busses Assign busses
pci=irqmask=MASK Set PCI interrupt mask to MASK
pci=lastbus=NUMBER Scan upto NUMBER busses, no matter what the mptable says.
pci=noacpi Don't use ACPI to set up PCI interrupt routing.
IOMMU (input/output memory management unit)
Currently four x86-64 PCI-DMA mapping implementations exist:
1. <arch/x86_64/kernel/pci-nommu.c>: use no hardware/software IOMMU at all
(e.g. because you have < 3 GB memory).
Kernel boot message: "PCI-DMA: Disabling IOMMU"
2. <arch/x86_64/kernel/pci-gart.c>: AMD GART based hardware IOMMU.
Kernel boot message: "PCI-DMA: using GART IOMMU"
3. <arch/x86_64/kernel/pci-swiotlb.c> : Software IOMMU implementation. Used
e.g. if there is no hardware IOMMU in the system and it is need because
you have >3GB memory or told the kernel to us it (iommu=soft))
Kernel boot message: "PCI-DMA: Using software bounce buffering
for IO (SWIOTLB)"
4. <arch/x86_64/pci-calgary.c> : IBM Calgary hardware IOMMU. Used in IBM
pSeries and xSeries servers. This hardware IOMMU supports DMA address
mapping with memory protection, etc.
Kernel boot message: "PCI-DMA: Using Calgary IOMMU"
iommu=[<size>][,noagp][,off][,force][,noforce][,leak[=<nr_of_leak_pages>]
[,memaper[=<order>]][,merge][,forcesac][,fullflush][,nomerge]
[,noaperture][,calgary]
General iommu options:
off Don't initialize and use any kind of IOMMU.
noforce Don't force hardware IOMMU usage when it is not needed.
(default).
force Force the use of the hardware IOMMU even when it is
not actually needed (e.g. because < 3 GB memory).
soft Use software bounce buffering (SWIOTLB) (default for
Intel machines). This can be used to prevent the usage
of an available hardware IOMMU.
iommu options only relevant to the AMD GART hardware IOMMU:
<size> Set the size of the remapping area in bytes.
allowed Overwrite iommu off workarounds for specific chipsets.
fullflush Flush IOMMU on each allocation (default).
nofullflush Don't use IOMMU fullflush.
leak Turn on simple iommu leak tracing (only when
CONFIG_IOMMU_LEAK is on). Default number of leak pages
is 20.
memaper[=<order>] Allocate an own aperture over RAM with size 32MB<<order.
(default: order=1, i.e. 64MB)
merge Do scatter-gather (SG) merging. Implies "force"
(experimental).
nomerge Don't do scatter-gather (SG) merging.
noaperture Ask the IOMMU not to touch the aperture for AGP.
forcesac Force single-address cycle (SAC) mode for masks <40bits
(experimental).
noagp Don't initialize the AGP driver and use full aperture.
allowdac Allow double-address cycle (DAC) mode, i.e. DMA >4GB.
DAC is used with 32-bit PCI to push a 64-bit address in
two cycles. When off all DMA over >4GB is forced through
an IOMMU or software bounce buffering.
nodac Forbid DAC mode, i.e. DMA >4GB.
panic Always panic when IOMMU overflows.
calgary Use the Calgary IOMMU if it is available
iommu options only relevant to the software bounce buffering (SWIOTLB) IOMMU
implementation:
swiotlb=<pages>[,force]
<pages> Prereserve that many 128K pages for the software IO
bounce buffering.
force Force all IO through the software TLB.
Settings for the IBM Calgary hardware IOMMU currently found in IBM
pSeries and xSeries machines:
calgary=[64k,128k,256k,512k,1M,2M,4M,8M]
calgary=[translate_empty_slots]
calgary=[disable=<PCI bus number>]
panic Always panic when IOMMU overflows
64k,...,8M - Set the size of each PCI slot's translation table
when using the Calgary IOMMU. This is the size of the translation
table itself in main memory. The smallest table, 64k, covers an IO
space of 32MB; the largest, 8MB table, can cover an IO space of
4GB. Normally the kernel will make the right choice by itself.
translate_empty_slots - Enable translation even on slots that have
no devices attached to them, in case a device will be hotplugged
in the future.
disable=<PCI bus number> - Disable translation on a given PHB. For
example, the built-in graphics adapter resides on the first bridge
(PCI bus number 0); if translation (isolation) is enabled on this
bridge, X servers that access the hardware directly from user
space might stop working. Use this option if you have devices that
are accessed from userspace directly on some PCI host bridge.
Debugging
oops=panic Always panic on oopses. Default is to just kill the process,
but there is a small probability of deadlocking the machine.
This will also cause panics on machine check exceptions.
Useful together with panic=30 to trigger a reboot.
kstack=N Print N words from the kernel stack in oops dumps.
pagefaulttrace Dump all page faults. Only useful for extreme debugging
and will create a lot of output.
call_trace=[old|both|newfallback|new]
old: use old inexact backtracer
new: use new exact dwarf2 unwinder
both: print entries from both
newfallback: use new unwinder but fall back to old if it gets
stuck (default)
Miscellaneous
nogbpages
Do not use GB pages for kernel direct mappings.
gbpages
Use GB pages for kernel direct mappings.

21
Documentation/x86/x86_64/cpu-hotplug-spec Normal file
View File

@@ -0,0 +1,21 @@
Firmware support for CPU hotplug under Linux/x86-64
---------------------------------------------------
Linux/x86-64 supports CPU hotplug now. For various reasons Linux wants to
know in advance of boot time the maximum number of CPUs that could be plugged
into the system. ACPI 3.0 currently has no official way to supply
this information from the firmware to the operating system.
In ACPI each CPU needs an LAPIC object in the MADT table (5.2.11.5 in the
ACPI 3.0 specification). ACPI already has the concept of disabled LAPIC
objects by setting the Enabled bit in the LAPIC object to zero.
For CPU hotplug Linux/x86-64 expects now that any possible future hotpluggable
CPU is already available in the MADT. If the CPU is not available yet
it should have its LAPIC Enabled bit set to 0. Linux will use the number
of disabled LAPICs to compute the maximum number of future CPUs.
In the worst case the user can overwrite this choice using a command line
option (additional_cpus=...), but it is recommended to supply the correct
number (or a reasonable approximation of it, with erring towards more not less)
in the MADT to avoid manual configuration.

66
Documentation/x86/x86_64/fake-numa-for-cpusets Normal file
View File

@@ -0,0 +1,66 @@
Using numa=fake and CPUSets for Resource Management
Written by David Rientjes <rientjes@cs.washington.edu>
This document describes how the numa=fake x86_64 command-line option can be used
in conjunction with cpusets for coarse memory management. Using this feature,
you can create fake NUMA nodes that represent contiguous chunks of memory and
assign them to cpusets and their attached tasks. This is a way of limiting the
amount of system memory that are available to a certain class of tasks.
For more information on the features of cpusets, see Documentation/cpusets.txt.
There are a number of different configurations you can use for your needs. For
more information on the numa=fake command line option and its various ways of
configuring fake nodes, see Documentation/x86_64/boot-options.txt.
For the purposes of this introduction, we'll assume a very primitive NUMA
emulation setup of "numa=fake=4*512,". This will split our system memory into
four equal chunks of 512M each that we can now use to assign to cpusets. As
you become more familiar with using this combination for resource control,
you'll determine a better setup to minimize the number of nodes you have to deal
with.
A machine may be split as follows with "numa=fake=4*512," as reported by dmesg:
Faking node 0 at 0000000000000000-0000000020000000 (512MB)
Faking node 1 at 0000000020000000-0000000040000000 (512MB)
Faking node 2 at 0000000040000000-0000000060000000 (512MB)
Faking node 3 at 0000000060000000-0000000080000000 (512MB)
...
On node 0 totalpages: 130975
On node 1 totalpages: 131072
On node 2 totalpages: 131072
On node 3 totalpages: 131072
Now following the instructions for mounting the cpusets filesystem from
Documentation/cpusets.txt, you can assign fake nodes (i.e. contiguous memory
address spaces) to individual cpusets:
[root@xroads /]# mkdir exampleset
[root@xroads /]# mount -t cpuset none exampleset
[root@xroads /]# mkdir exampleset/ddset
[root@xroads /]# cd exampleset/ddset
[root@xroads /exampleset/ddset]# echo 0-1 > cpus
[root@xroads /exampleset/ddset]# echo 0-1 > mems
Now this cpuset, 'ddset', will only allowed access to fake nodes 0 and 1 for
memory allocations (1G).
You can now assign tasks to these cpusets to limit the memory resources
available to them according to the fake nodes assigned as mems:
[root@xroads /exampleset/ddset]# echo $$ > tasks
[root@xroads /exampleset/ddset]# dd if=/dev/zero of=tmp bs=1024 count=1G
[1] 13425
Notice the difference between the system memory usage as reported by
/proc/meminfo between the restricted cpuset case above and the unrestricted
case (i.e. running the same 'dd' command without assigning it to a fake NUMA
cpuset):
Unrestricted Restricted
MemTotal: 3091900 kB 3091900 kB
MemFree: 42113 kB 1513236 kB
This allows for coarse memory management for the tasks you assign to particular
cpusets. Since cpusets can form a hierarchy, you can create some pretty
interesting combinations of use-cases for various classes of tasks for your
memory management needs.

99
Documentation/x86/x86_64/kernel-stacks Normal file
View File

@@ -0,0 +1,99 @@
Most of the text from Keith Owens, hacked by AK
x86_64 page size (PAGE_SIZE) is 4K.
Like all other architectures, x86_64 has a kernel stack for every
active thread. These thread stacks are THREAD_SIZE (2*PAGE_SIZE) big.
These stacks contain useful data as long as a thread is alive or a
zombie. While the thread is in user space the kernel stack is empty
except for the thread_info structure at the bottom.
In addition to the per thread stacks, there are specialized stacks
associated with each CPU. These stacks are only used while the kernel
is in control on that CPU; when a CPU returns to user space the
specialized stacks contain no useful data. The main CPU stacks are:
* Interrupt stack. IRQSTACKSIZE
Used for external hardware interrupts. If this is the first external
hardware interrupt (i.e. not a nested hardware interrupt) then the
kernel switches from the current task to the interrupt stack. Like
the split thread and interrupt stacks on i386 (with CONFIG_4KSTACKS),
this gives more room for kernel interrupt processing without having
to increase the size of every per thread stack.
The interrupt stack is also used when processing a softirq.
Switching to the kernel interrupt stack is done by software based on a
per CPU interrupt nest counter. This is needed because x86-64 "IST"
hardware stacks cannot nest without races.
x86_64 also has a feature which is not available on i386, the ability
to automatically switch to a new stack for designated events such as
double fault or NMI, which makes it easier to handle these unusual
events on x86_64. This feature is called the Interrupt Stack Table
(IST). There can be up to 7 IST entries per CPU. The IST code is an
index into the Task State Segment (TSS). The IST entries in the TSS
point to dedicated stacks; each stack can be a different size.
An IST is selected by a non-zero value in the IST field of an
interrupt-gate descriptor. When an interrupt occurs and the hardware
loads such a descriptor, the hardware automatically sets the new stack
pointer based on the IST value, then invokes the interrupt handler. If
software wants to allow nested IST interrupts then the handler must
adjust the IST values on entry to and exit from the interrupt handler.
(This is occasionally done, e.g. for debug exceptions.)
Events with different IST codes (i.e. with different stacks) can be
nested. For example, a debug interrupt can safely be interrupted by an
NMI. arch/x86_64/kernel/entry.S::paranoidentry adjusts the stack
pointers on entry to and exit from all IST events, in theory allowing
IST events with the same code to be nested. However in most cases, the
stack size allocated to an IST assumes no nesting for the same code.
If that assumption is ever broken then the stacks will become corrupt.
The currently assigned IST stacks are :-
* STACKFAULT_STACK. EXCEPTION_STKSZ (PAGE_SIZE).
Used for interrupt 12 - Stack Fault Exception (#SS).
This allows the CPU to recover from invalid stack segments. Rarely
happens.
* DOUBLEFAULT_STACK. EXCEPTION_STKSZ (PAGE_SIZE).
Used for interrupt 8 - Double Fault Exception (#DF).
Invoked when handling one exception causes another exception. Happens
when the kernel is very confused (e.g. kernel stack pointer corrupt).
Using a separate stack allows the kernel to recover from it well enough
in many cases to still output an oops.
* NMI_STACK. EXCEPTION_STKSZ (PAGE_SIZE).
Used for non-maskable interrupts (NMI).
NMI can be delivered at any time, including when the kernel is in the
middle of switching stacks. Using IST for NMI events avoids making
assumptions about the previous state of the kernel stack.
* DEBUG_STACK. DEBUG_STKSZ
Used for hardware debug interrupts (interrupt 1) and for software
debug interrupts (INT3).
When debugging a kernel, debug interrupts (both hardware and
software) can occur at any time. Using IST for these interrupts
avoids making assumptions about the previous state of the kernel
stack.
* MCE_STACK. EXCEPTION_STKSZ (PAGE_SIZE).
Used for interrupt 18 - Machine Check Exception (#MC).
MCE can be delivered at any time, including when the kernel is in the
middle of switching stacks. Using IST for MCE events avoids making
assumptions about the previous state of the kernel stack.
For more details see the Intel IA32 or AMD AMD64 architecture manuals.

77
Documentation/x86/x86_64/machinecheck Normal file
View File

@@ -0,0 +1,77 @@
Configurable sysfs parameters for the x86-64 machine check code.
Machine checks report internal hardware error conditions detected
by the CPU. Uncorrected errors typically cause a machine check
(often with panic), corrected ones cause a machine check log entry.
Machine checks are organized in banks (normally associated with
a hardware subsystem) and subevents in a bank. The exact meaning
of the banks and subevent is CPU specific.
mcelog knows how to decode them.
When you see the "Machine check errors logged" message in the system
log then mcelog should run to collect and decode machine check entries
from /dev/mcelog. Normally mcelog should be run regularly from a cronjob.
Each CPU has a directory in /sys/devices/system/machinecheck/machinecheckN
(N = CPU number)
The directory contains some configurable entries:
Entries:
bankNctl
(N bank number)
64bit Hex bitmask enabling/disabling specific subevents for bank N
When a bit in the bitmask is zero then the respective
subevent will not be reported.
By default all events are enabled.
Note that BIOS maintain another mask to disable specific events
per bank. This is not visible here
The following entries appear for each CPU, but they are truly shared
between all CPUs.
check_interval
How often to poll for corrected machine check errors, in seconds
(Note output is hexademical). Default 5 minutes. When the poller
finds MCEs it triggers an exponential speedup (poll more often) on
the polling interval. When the poller stops finding MCEs, it
triggers an exponential backoff (poll less often) on the polling
interval. The check_interval variable is both the initial and
maximum polling interval.
tolerant
Tolerance level. When a machine check exception occurs for a non
corrected machine check the kernel can take different actions.
Since machine check exceptions can happen any time it is sometimes
risky for the kernel to kill a process because it defies
normal kernel locking rules. The tolerance level configures
how hard the kernel tries to recover even at some risk of
deadlock. Higher tolerant values trade potentially better uptime
with the risk of a crash or even corruption (for tolerant >= 3).
0: always panic on uncorrected errors, log corrected errors
1: panic or SIGBUS on uncorrected errors, log corrected errors
2: SIGBUS or log uncorrected errors, log corrected errors
3: never panic or SIGBUS, log all errors (for testing only)
Default: 1
Note this only makes a difference if the CPU allows recovery
from a machine check exception. Current x86 CPUs generally do not.
trigger
Program to run when a machine check event is detected.
This is an alternative to running mcelog regularly from cron
and allows to detect events faster.
TBD document entries for AMD threshold interrupt configuration
For more details about the x86 machine check architecture
see the Intel and AMD architecture manuals from their developer websites.
For more details about the architecture see
see http://one.firstfloor.org/~andi/mce.pdf

28
Documentation/x86/x86_64/mm.txt Normal file
View File

@@ -0,0 +1,28 @@
<previous description obsolete, deleted>
Virtual memory map with 4 level page tables:
0000000000000000 - 00007fffffffffff (=47 bits) user space, different per mm
hole caused by [48:63] sign extension
ffff800000000000 - ffff80ffffffffff (=40 bits) guard hole
ffff810000000000 - ffffc0ffffffffff (=46 bits) direct mapping of all phys. memory
ffffc10000000000 - ffffc1ffffffffff (=40 bits) hole
ffffc20000000000 - ffffe1ffffffffff (=45 bits) vmalloc/ioremap space
ffffe20000000000 - ffffe2ffffffffff (=40 bits) virtual memory map (1TB)
... unused hole ...
ffffffff80000000 - ffffffffa0000000 (=512 MB) kernel text mapping, from phys 0
ffffffffa0000000 - fffffffffff00000 (=1536 MB) module mapping space
The direct mapping covers all memory in the system up to the highest
memory address (this means in some cases it can also include PCI memory
holes).
vmalloc space is lazily synchronized into the different PML4 pages of
the processes using the page fault handler, with init_level4_pgt as
reference.
Current X86-64 implementations only support 40 bits of address space,
but we support up to 46 bits. This expands into MBZ space in the page tables.
-Andi Kleen, Jul 2004

38
Documentation/x86/x86_64/uefi.txt Normal file
View File

@@ -0,0 +1,38 @@
General note on [U]EFI x86_64 support
-------------------------------------
The nomenclature EFI and UEFI are used interchangeably in this document.
Although the tools below are _not_ needed for building the kernel,
the needed bootloader support and associated tools for x86_64 platforms
with EFI firmware and specifications are listed below.
1. UEFI specification: http://www.uefi.org
2. Booting Linux kernel on UEFI x86_64 platform requires bootloader
support. Elilo with x86_64 support can be used.
3. x86_64 platform with EFI/UEFI firmware.
Mechanics:
---------
- Build the kernel with the following configuration.
CONFIG_FB_EFI=y
CONFIG_FRAMEBUFFER_CONSOLE=y
If EFI runtime services are expected, the following configuration should
be selected.
CONFIG_EFI=y
CONFIG_EFI_VARS=y or m # optional
- Create a VFAT partition on the disk
- Copy the following to the VFAT partition:
elilo bootloader with x86_64 support, elilo configuration file,
kernel image built in first step and corresponding
initrd. Instructions on building elilo and its dependencies
can be found in the elilo sourceforge project.
- Boot to EFI shell and invoke elilo choosing the kernel image built
in first step.
- If some or all EFI runtime services don't work, you can try following
kernel command line parameters to turn off some or all EFI runtime
services.
noefi turn off all EFI runtime services
reboot_type=k turn off EFI reboot runtime service