From 8439e62a15614e8fcd43835d57b7245cd9870dc5 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Mon, 22 Feb 2016 18:46:04 +0100 Subject: [PATCH] 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 Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/memory.h | 7 ++++--- 1 file 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 #include extern phys_addr_t memstart_addr; -- 2.11.0