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Diffstat (limited to 'Documentation/arm64/memory.txt')
| -rw-r--r-- | Documentation/arm64/memory.txt | 98 |
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): |