linux/Documentation/arm64/memory.txt
Mark Salter bf4b558eba arm64: add early_ioremap support
Add support for early IO or memory mappings which are needed before the
normal ioremap() is usable.  This also adds fixmap support for permanent
fixed mappings such as that used by the earlyprintk device register
region.

Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Borislav Petkov <borislav.petkov@amd.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-04-07 16:36:15 -07:00

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Memory Layout on AArch64 Linux
==============================
Author: Catalin Marinas <catalin.marinas@arm.com>
Date : 20 February 2012
This document describes the virtual memory layout used by the AArch64
Linux kernel. The architecture allows up to 4 levels of translation
tables with a 4KB page size and up to 3 levels with a 64KB page size.
AArch64 Linux uses 3 levels of translation tables with the 4KB page
configuration, allowing 39-bit (512GB) virtual addresses for both user
and kernel. With 64KB pages, only 2 levels of translation tables are
used but the memory layout is the same.
User addresses have bits 63:39 set to 0 while the kernel addresses have
the same bits set to 1. TTBRx selection is given by bit 63 of the
virtual address. The swapper_pg_dir contains only kernel (global)
mappings while the user pgd contains only user (non-global) mappings.
The swapper_pgd_dir address is written to TTBR1 and never written to
TTBR0.
AArch64 Linux memory layout with 4KB pages:
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 0000007fffffffff 512GB user
ffffff8000000000 ffffffbbfffeffff ~240GB vmalloc
ffffffbbffff0000 ffffffbbffffffff 64KB [guard page]
ffffffbc00000000 ffffffbdffffffff 8GB vmemmap
ffffffbe00000000 ffffffbffbbfffff ~8GB [guard, future vmmemap]
ffffffbffa000000 ffffffbffaffffff 16MB PCI I/O space
ffffffbffb000000 ffffffbffbbfffff 12MB [guard]
ffffffbffbc00000 ffffffbffbdfffff 2MB fixed mappings
ffffffbffbe00000 ffffffbffbffffff 2MB [guard]
ffffffbffc000000 ffffffbfffffffff 64MB modules
ffffffc000000000 ffffffffffffffff 256GB kernel logical memory map
AArch64 Linux memory layout with 64KB pages:
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 000003ffffffffff 4TB user
fffffc0000000000 fffffdfbfffeffff ~2TB vmalloc
fffffdfbffff0000 fffffdfbffffffff 64KB [guard page]
fffffdfc00000000 fffffdfdffffffff 8GB vmemmap
fffffdfe00000000 fffffdfffbbfffff ~8GB [guard, future vmmemap]
fffffdfffa000000 fffffdfffaffffff 16MB PCI I/O space
fffffdfffb000000 fffffdfffbbfffff 12MB [guard]
fffffdfffbc00000 fffffdfffbdfffff 2MB fixed mappings
fffffdfffbe00000 fffffdfffbffffff 2MB [guard]
fffffdfffc000000 fffffdffffffffff 64MB modules
fffffe0000000000 ffffffffffffffff 2TB kernel logical memory map
Translation table lookup with 4KB pages:
+--------+--------+--------+--------+--------+--------+--------+--------+
|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
+--------+--------+--------+--------+--------+--------+--------+--------+
| | | | | |
| | | | | v
| | | | | [11:0] in-page offset
| | | | +-> [20:12] L3 index
| | | +-----------> [29:21] L2 index
| | +---------------------> [38:30] L1 index
| +-------------------------------> [47:39] L0 index (not used)
+-------------------------------------------------> [63] TTBR0/1
Translation table lookup with 64KB pages:
+--------+--------+--------+--------+--------+--------+--------+--------+
|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
+--------+--------+--------+--------+--------+--------+--------+--------+
| | | | |
| | | | v
| | | | [15:0] in-page offset
| | | +----------> [28:16] L3 index
| | +--------------------------> [41:29] L2 index (only 38:29 used)
| +-------------------------------> [47:42] L1 index (not used)
+-------------------------------------------------> [63] TTBR0/1
When using KVM, the hypervisor maps kernel pages in EL2, at a fixed
offset from the kernel VA (top 24bits of the kernel VA set to zero):
Start End Size Use
-----------------------------------------------------------------------
0000004000000000 0000007fffffffff 256GB kernel objects mapped in HYP