arm64: Determine the vmalloc/vmemmap space at build time based on VA_BITS

[cascardo/linux.git] / Documentation / arm64 / memory.txt

diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt
index d50fa61..8845d08 100644 (file)
--- a/Documentation/arm64/memory.txt
+++ b/Documentation/arm64/memory.txt
@@ -2,18 +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 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.
+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.
@@ -21,58 +21,32 @@ The swapper_pgd_dir address is written to TTBR1 and never written to
 TTBR0.
 
 
-AArch64 Linux memory layout with 4KB pages:
+AArch64 Linux memory layout with 4KB pages + 3 levels:
 
 Start                  End                     Size            Use
 -----------------------------------------------------------------------
 0000000000000000       0000007fffffffff         512GB          user
+ffffff8000000000       ffffffffffffffff         512GB          kernel
 
-ffffff8000000000       ffffffbbfffeffff        ~240GB          vmalloc
 
-ffffffbbffff0000       ffffffbbffffffff          64KB          [guard page]
+AArch64 Linux memory layout with 4KB pages + 4 levels:
 
-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
+Start                  End                     Size            Use
+-----------------------------------------------------------------------
+0000000000000000       0000ffffffffffff         256TB          user
+ffff000000000000       ffffffffffffffff         256TB          kernel
 
 
-AArch64 Linux memory layout with 64KB pages:
+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
-
-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
+For details of the virtual kernel memory layout please see the kernel
+booting log.
 
 
 Translation table lookup with 4KB pages:
@@ -86,7 +60,7 @@ Translation table lookup with 4KB pages:
  |                 |         |         |         +-> [20:12] L3 index
  |                 |         |         +-----------> [29:21] L2 index
  |                 |         +---------------------> [38:30] L1 index
- |                 +-------------------------------> [47:39] L0 index (not used)
+ |                 +-------------------------------> [47:39] L0 index
  +-------------------------------------------------> [63] TTBR0/1
 
 
@@ -99,10 +73,11 @@ Translation table lookup with 64KB pages:
  |                 |    |               |              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):