diff options
| author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2016-03-30 16:46:00 +0200 |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2016-04-14 16:31:49 +0100 |
| commit | 3e1907d5bf5a1e0b182ee599f92586f0165029e2 (patch) | |
| tree | 1882d1a6d4532815ebe3090d12d3920f0cef3243 /arch/arm64/include/asm/memory.h | |
| parent | e44308e62e19b42810207780a2a32148af0cb5d9 (diff) | |
arm64: mm: move vmemmap region right below the linear region
This moves the vmemmap region right below PAGE_OFFSET, aka the start
of the linear region, and redefines its size to be a power of two.
Due to the placement of PAGE_OFFSET in the middle of the address space,
whose size is a power of two as well, this guarantees that virt to
page conversions and vice versa can be implemented efficiently, by
masking and shifting rather than ordinary arithmetic.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/memory.h')
| -rw-r--r-- | arch/arm64/include/asm/memory.h | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index 12f8a00fb3f1..8a2ab195ca77 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -40,6 +40,21 @@ #define PCI_IO_SIZE SZ_16M /* + * Log2 of the upper bound of the size of a struct page. Used for sizing + * the vmemmap region only, does not affect actual memory footprint. + * We don't use sizeof(struct page) directly since taking its size here + * requires its definition to be available at this point in the inclusion + * chain, and it may not be a power of 2 in the first place. + */ +#define STRUCT_PAGE_MAX_SHIFT 6 + +/* + * VMEMMAP_SIZE - allows the whole linear region to be covered by + * a struct page array + */ +#define VMEMMAP_SIZE (UL(1) << (VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)) + +/* * PAGE_OFFSET - the virtual address of the start of the kernel image (top * (VA_BITS - 1)) * VA_BITS - the maximum number of bits for virtual addresses. @@ -54,7 +69,8 @@ #define MODULES_END (MODULES_VADDR + MODULES_VSIZE) #define MODULES_VADDR (VA_START + KASAN_SHADOW_SIZE) #define MODULES_VSIZE (SZ_128M) -#define PCI_IO_END (PAGE_OFFSET - SZ_2M) +#define VMEMMAP_START (PAGE_OFFSET - VMEMMAP_SIZE) +#define PCI_IO_END (VMEMMAP_START - SZ_2M) #define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE) #define FIXADDR_TOP (PCI_IO_START - SZ_2M) #define TASK_SIZE_64 (UL(1) << VA_BITS) |