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-rw-r--r--Documentation/arm64/memory.txt98
1 files changed, 15 insertions, 83 deletions
diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt
index 4c720d698e8e..8845d0847a66 100644
--- a/Documentation/arm64/memory.txt
+++ b/Documentation/arm64/memory.txt
@@ -2,19 +2,18 @@
==============================
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 either 3 levels or 4 levels of translation tables with
-the 4KB page configuration, allowing 39-bit (512GB) or 48-bit (256TB)
-virtual addresses, respectively, for both user and kernel. With 64KB
-pages, only 2 levels of translation tables, allowing 42-bit (4TB)
+AArch64 Linux uses either 3 levels or 4 levels of translation tables
+with the 4KB page configuration, allowing 39-bit (512GB) or 48-bit
+(256TB) virtual addresses, respectively, for both user and kernel. With
+64KB pages, only 2 levels of translation tables, allowing 42-bit (4TB)
virtual address, are used but the memory layout is the same.
-User addresses have bits 63:39 set to 0 while the kernel addresses have
+User addresses have bits 63:48 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.
@@ -27,26 +26,7 @@ AArch64 Linux memory layout with 4KB pages + 3 levels:
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
+ffffff8000000000 ffffffffffffffff 512GB kernel
AArch64 Linux memory layout with 4KB pages + 4 levels:
@@ -54,26 +34,7 @@ AArch64 Linux memory layout with 4KB pages + 4 levels:
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 0000ffffffffffff 256TB user
-
-ffff000000000000 ffff7bfffffeffff ~124TB vmalloc
-
-ffff7bffffff0000 ffff7bffffffffff 64KB [guard page]
-
-ffff7c0000000000 ffff7dffffffffff 2TB vmemmap
-
-ffff7e0000000000 ffff7ffffbbfffff ~2TB [guard, future vmmemap]
-
-ffff7ffffa000000 ffff7ffffaffffff 16MB PCI I/O space
-
-ffff7ffffb000000 ffff7ffffbbfffff 12MB [guard]
-
-ffff7ffffbc00000 ffff7ffffbdfffff 2MB fixed mappings
-
-ffff7ffffbe00000 ffff7ffffbffffff 2MB [guard]
-
-ffff7ffffc000000 ffff7fffffffffff 64MB modules
-
-ffff800000000000 ffffffffffffffff 128TB kernel logical memory map
+ffff000000000000 ffffffffffffffff 256TB kernel
AArch64 Linux memory layout with 64KB pages + 2 levels:
@@ -81,44 +42,14 @@ AArch64 Linux memory layout with 64KB pages + 2 levels:
Start End Size Use
-----------------------------------------------------------------------
0000000000000000 000003ffffffffff 4TB user
+fffffc0000000000 ffffffffffffffff 4TB kernel
-fffffc0000000000 fffffdfbfffeffff ~2TB vmalloc
-
-fffffdfbffff0000 fffffdfbffffffff 64KB [guard page]
-fffffdfc00000000 fffffdfdffffffff 8GB vmemmap
+For details of the virtual kernel memory layout please see the kernel
+booting log.
-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 + 3 levels:
-
-+--------+--------+--------+--------+--------+--------+--------+--------+
-|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 4KB pages + 4 levels:
+Translation table lookup with 4KB pages:
+--------+--------+--------+--------+--------+--------+--------+--------+
|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
@@ -133,7 +64,7 @@ Translation table lookup with 4KB pages + 4 levels:
+-------------------------------------------------> [63] TTBR0/1
-Translation table lookup with 64KB pages + 2 levels:
+Translation table lookup with 64KB pages:
+--------+--------+--------+--------+--------+--------+--------+--------+
|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
@@ -142,10 +73,11 @@ Translation table lookup with 64KB pages + 2 levels:
| | | | v
| | | | [15:0] in-page offset
| | | +----------> [28:16] L3 index
- | | +--------------------------> [41:29] L2 index (only 38:29 used)
- | +-------------------------------> [47:42] L1 index (not used)
+ | | +--------------------------> [41:29] L2 index
+ | +-------------------------------> [47:42] L1 index
+-------------------------------------------------> [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):