bf4b558eba
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>
112 lines
4.3 KiB
Plaintext
112 lines
4.3 KiB
Plaintext
Memory Layout on AArch64 Linux
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==============================
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Author: Catalin Marinas <catalin.marinas@arm.com>
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Date : 20 February 2012
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This document describes the virtual memory layout used by the AArch64
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Linux kernel. The architecture allows up to 4 levels of translation
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tables with a 4KB page size and up to 3 levels with a 64KB page size.
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AArch64 Linux uses 3 levels of translation tables with the 4KB page
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configuration, allowing 39-bit (512GB) virtual addresses for both user
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and kernel. With 64KB pages, only 2 levels of translation tables are
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used but the memory layout is the same.
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User addresses have bits 63:39 set to 0 while the kernel addresses have
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the same bits set to 1. TTBRx selection is given by bit 63 of the
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virtual address. The swapper_pg_dir contains only kernel (global)
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mappings while the user pgd contains only user (non-global) mappings.
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The swapper_pgd_dir address is written to TTBR1 and never written to
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TTBR0.
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AArch64 Linux memory layout with 4KB pages:
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Start End Size Use
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-----------------------------------------------------------------------
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0000000000000000 0000007fffffffff 512GB user
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ffffff8000000000 ffffffbbfffeffff ~240GB vmalloc
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ffffffbbffff0000 ffffffbbffffffff 64KB [guard page]
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ffffffbc00000000 ffffffbdffffffff 8GB vmemmap
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ffffffbe00000000 ffffffbffbbfffff ~8GB [guard, future vmmemap]
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ffffffbffa000000 ffffffbffaffffff 16MB PCI I/O space
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ffffffbffb000000 ffffffbffbbfffff 12MB [guard]
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ffffffbffbc00000 ffffffbffbdfffff 2MB fixed mappings
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ffffffbffbe00000 ffffffbffbffffff 2MB [guard]
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ffffffbffc000000 ffffffbfffffffff 64MB modules
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ffffffc000000000 ffffffffffffffff 256GB kernel logical memory map
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AArch64 Linux memory layout with 64KB pages:
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Start End Size Use
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-----------------------------------------------------------------------
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0000000000000000 000003ffffffffff 4TB user
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fffffc0000000000 fffffdfbfffeffff ~2TB vmalloc
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fffffdfbffff0000 fffffdfbffffffff 64KB [guard page]
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fffffdfc00000000 fffffdfdffffffff 8GB vmemmap
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fffffdfe00000000 fffffdfffbbfffff ~8GB [guard, future vmmemap]
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fffffdfffa000000 fffffdfffaffffff 16MB PCI I/O space
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fffffdfffb000000 fffffdfffbbfffff 12MB [guard]
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fffffdfffbc00000 fffffdfffbdfffff 2MB fixed mappings
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fffffdfffbe00000 fffffdfffbffffff 2MB [guard]
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fffffdfffc000000 fffffdffffffffff 64MB modules
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fffffe0000000000 ffffffffffffffff 2TB kernel logical memory map
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Translation table lookup with 4KB pages:
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+--------+--------+--------+--------+--------+--------+--------+--------+
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|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
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+--------+--------+--------+--------+--------+--------+--------+--------+
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| | | | | |
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| | | | | v
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| | | | | [11:0] in-page offset
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| | | | +-> [20:12] L3 index
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| | | +-----------> [29:21] L2 index
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| | +---------------------> [38:30] L1 index
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| +-------------------------------> [47:39] L0 index (not used)
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+-------------------------------------------------> [63] TTBR0/1
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Translation table lookup with 64KB pages:
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+--------+--------+--------+--------+--------+--------+--------+--------+
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|63 56|55 48|47 40|39 32|31 24|23 16|15 8|7 0|
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+--------+--------+--------+--------+--------+--------+--------+--------+
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| | | | |
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| | | | v
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| | | | [15:0] in-page offset
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| | | +----------> [28:16] L3 index
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| | +--------------------------> [41:29] L2 index (only 38:29 used)
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| +-------------------------------> [47:42] L1 index (not used)
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+-------------------------------------------------> [63] TTBR0/1
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When using KVM, the hypervisor maps kernel pages in EL2, at a fixed
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offset from the kernel VA (top 24bits of the kernel VA set to zero):
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Start End Size Use
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-----------------------------------------------------------------------
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0000004000000000 0000007fffffffff 256GB kernel objects mapped in HYP
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