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Diffstat (limited to 'Documentation/arm64/memory.txt')
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diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt deleted file mode 100644 index c5dab30d3389..000000000000 --- a/Documentation/arm64/memory.txt +++ /dev/null @@ -1,97 +0,0 @@ - Memory Layout on AArch64 Linux - ============================== - -Author: Catalin Marinas <catalin.marinas@arm.com> - -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) -virtual address, are used but the memory layout is the same. - -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. -The swapper_pg_dir address is written to TTBR1 and never written to -TTBR0. - - -AArch64 Linux memory layout with 4KB pages + 3 levels: - -Start End Size Use ------------------------------------------------------------------------ -0000000000000000 0000007fffffffff 512GB user -ffffff8000000000 ffffffffffffffff 512GB kernel - - -AArch64 Linux memory layout with 4KB pages + 4 levels: - -Start End Size Use ------------------------------------------------------------------------ -0000000000000000 0000ffffffffffff 256TB user -ffff000000000000 ffffffffffffffff 256TB kernel - - -AArch64 Linux memory layout with 64KB pages + 2 levels: - -Start End Size Use ------------------------------------------------------------------------ -0000000000000000 000003ffffffffff 4TB user -fffffc0000000000 ffffffffffffffff 4TB kernel - - -AArch64 Linux memory layout with 64KB pages + 3 levels: - -Start End Size Use ------------------------------------------------------------------------ -0000000000000000 0000ffffffffffff 256TB user -ffff000000000000 ffffffffffffffff 256TB kernel - - -For details of the virtual kernel memory layout please see the kernel -booting log. - - -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 - +-------------------------------------------------> [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 - | +-------------------------------> [47:42] L1 index - +-------------------------------------------------> [63] TTBR0/1 - - -When using KVM without the Virtualization Host Extensions, the -hypervisor maps kernel pages in EL2 at a fixed (and potentially -random) offset from the linear mapping. See the kern_hyp_va macro and -kvm_update_va_mask function for more details. MMIO devices such as -GICv2 gets mapped next to the HYP idmap page, as do vectors when -ARM64_HARDEN_EL2_VECTORS is selected for particular CPUs. - -When using KVM with the Virtualization Host Extensions, no additional -mappings are created, since the host kernel runs directly in EL2. |