forked from Minki/linux
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>
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@ -88,10 +88,10 @@
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*/
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#define __virt_to_phys(x) ({ \
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phys_addr_t __x = (phys_addr_t)(x); \
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__x >= PAGE_OFFSET ? (__x - PAGE_OFFSET + PHYS_OFFSET) : \
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(__x - kimage_voffset); })
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__x & BIT(VA_BITS - 1) ? (__x & ~PAGE_OFFSET) + PHYS_OFFSET : \
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(__x - kimage_voffset); })
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#define __phys_to_virt(x) ((unsigned long)((x) - PHYS_OFFSET + PAGE_OFFSET))
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#define __phys_to_virt(x) ((unsigned long)((x) - PHYS_OFFSET) | PAGE_OFFSET)
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#define __phys_to_kimg(x) ((unsigned long)((x) + kimage_voffset))
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/*
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@ -132,6 +132,7 @@
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#ifndef __ASSEMBLY__
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#include <linux/bitops.h>
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#include <linux/mmdebug.h>
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extern phys_addr_t memstart_addr;
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