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| author | Ard Biesheuvel <ard.biesheuvel@linaro.org> | 2016-02-22 20:46:04 +0300 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2016-02-23 20:43:25 +0300 |
| commit | 8439e62a15614e8fcd43835d57b7245cd9870dc5 (patch) | |
| tree | 8ace79af5dced3e6f18b5000d6ae4e9c5e6fa5c6 | |
| parent | a92405f082d43267575444a6927085e4c8a69e4e (diff) | |
| download | linux-8439e62a15614e8fcd43835d57b7245cd9870dc5.tar.xz | |
arm64: mm: use bit ops rather than arithmetic in pa/va translations
Since PAGE_OFFSET is chosen such that it cuts the kernel VA space right
in half, and since the size of the kernel VA space itself is always a
power of 2, we can treat PAGE_OFFSET as a bitmask and replace the
additions/subtractions with 'or' and 'and-not' operations.
For the comparison against PAGE_OFFSET, a mov/cmp/branch sequence ends
up getting replaced with a single tbz instruction. For the additions and
subtractions, we save a mov instruction since the mask is folded into the
instruction's immediate field.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
| -rw-r--r-- | arch/arm64/include/asm/memory.h | 7 |
1 files changed, 4 insertions, 3 deletions
diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index 460d09bf9442..eb798156cf56 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -88,10 +88,10 @@ */ #define __virt_to_phys(x) ({ \ phys_addr_t __x = (phys_addr_t)(x); \ - __x >= PAGE_OFFSET ? (__x - PAGE_OFFSET + PHYS_OFFSET) : \ - (__x - kimage_voffset); }) + __x & BIT(VA_BITS - 1) ? (__x & ~PAGE_OFFSET) + PHYS_OFFSET : \ + (__x - kimage_voffset); }) -#define __phys_to_virt(x) ((unsigned long)((x) - PHYS_OFFSET + PAGE_OFFSET)) +#define __phys_to_virt(x) ((unsigned long)((x) - PHYS_OFFSET) | PAGE_OFFSET) #define __phys_to_kimg(x) ((unsigned long)((x) + kimage_voffset)) /* @@ -132,6 +132,7 @@ #ifndef __ASSEMBLY__ +#include <linux/bitops.h> #include <linux/mmdebug.h> extern phys_addr_t memstart_addr; |