arm64: MMU definitions

The virtual memory layout is described in
Documentation/arm64/memory.txt. This patch adds the MMU definitions for
the 4KB and 64KB translation table configurations. The SECTION_SIZE is
2MB with 4KB page and 512MB with 64KB page configuration.

PHYS_OFFSET is calculated at run-time and stored in a variable (no
run-time code patching at this stage).

On the current implementation, both user and kernel address spaces are
512G (39-bit) each with a maximum of 256G for the RAM linear mapping.
Linux uses 3 levels of translation tables with the 4K page configuration
and 2 levels with the 64K configuration. Extending the memory space
beyond 39-bit with the 4K pages or 42-bit with 64K pages requires an
additional level of translation tables.

The SPARSEMEM configuration is global to all AArch64 platforms and
allows for 1GB sections with SPARSEMEM_VMEMMAP enabled by default.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 73 insertions, 0 deletions

diff --git a/Documentation/arm64/memory.txt b/Documentation/arm64/memory.txt
new file mode 100644
index 000000000000..dbbdcbba75a3
--- /dev/null
+++ b/Documentation/arm64/memory.txt
@@ -0,0 +1,73 @@
+                     Memory Layout on AArch64 Linux
+                     ==============================
+
+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.
+
+User addresses have bits 63:39 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_pgd_dir address is written to TTBR1 and never written to
+TTBR0.
+
+
+AArch64 Linux memory layout:
+
+Start                   End                     Size            Use
+-----------------------------------------------------------------------
+0000000000000000        0000007fffffffff         512GB          user
+
+ffffff8000000000        ffffffbbfffcffff        ~240GB          vmalloc
+
+ffffffbbfffd0000        ffffffbcfffdffff          64KB          [guard page]
+
+ffffffbbfffe0000        ffffffbcfffeffff          64KB          PCI I/O space
+
+ffffffbbffff0000        ffffffbcffffffff          64KB          [guard page]
+
+ffffffbc00000000        ffffffbdffffffff           8GB          vmemmap
+
+ffffffbe00000000        ffffffbffbffffff          ~8GB          [guard, future vmmemap]
+
+ffffffbffc000000        ffffffbfffffffff          64MB          modules
+
+ffffffc000000000        ffffffffffffffff         256GB          memory
+
+
+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 (not used)
+ +-------------------------------------------------> [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 (only 38:29 used)
+ |                 +-------------------------------> [47:42] L1 index (not used)
+ +-------------------------------------------------> [63] TTBR0/1