Small constant-sized flushcache copies currently fall back to __memcpy_flushcache() unless they are exactly 4, 8, or 16 bytes.
Factor the existing inline movnti sequences into small helpers and extend the fixed-size fastpath coverage to 24..96 bytes for naturally aligned transfers. This keeps common struct-page-sized copies on the inline path for the upcoming memcpy_streaming() user, while still falling back to __memcpy_flushcache() for unaligned or uncommon sizes. Zero-length copies return immediately. Issue the fixed-size stores in ascending address order so write-combining sees a forward stream. Signed-off-by: Li Zhe <[email protected]> --- arch/x86/include/asm/string_64.h | 125 ++++++++++++++++++++++++++----- 1 file changed, 107 insertions(+), 18 deletions(-) diff --git a/arch/x86/include/asm/string_64.h b/arch/x86/include/asm/string_64.h index 0b57e9e6f3db..8e6fca0185ee 100644 --- a/arch/x86/include/asm/string_64.h +++ b/arch/x86/include/asm/string_64.h @@ -82,24 +82,6 @@ int strcmp(const char *cs, const char *ct); #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE #define __HAVE_ARCH_MEMCPY_FLUSHCACHE 1 void __memcpy_flushcache(void *dst, const void *src, size_t cnt); -static __always_inline void memcpy_flushcache(void *dst, const void *src, size_t cnt) -{ - if (__builtin_constant_p(cnt)) { - switch (cnt) { - case 4: - asm ("movntil %1, %0" : "=m"(*(u32 *)dst) : "r"(*(u32 *)src)); - return; - case 8: - asm ("movntiq %1, %0" : "=m"(*(u64 *)dst) : "r"(*(u64 *)src)); - return; - case 16: - asm ("movntiq %1, %0" : "=m"(*(u64 *)dst) : "r"(*(u64 *)src)); - asm ("movntiq %1, %0" : "=m"(*(u64 *)(dst + 8)) : "r"(*(u64 *)(src + 8))); - return; - } - } - __memcpy_flushcache(dst, src, cnt); -} /* * Only reuse memcpy_flushcache() for transfers that can stay entirely @@ -123,6 +105,113 @@ static __always_inline int memcpy_flushcache_nt_safe(const void *dst, return cnt == 4 && !(d & 3) && !(s & 3); } +static __always_inline void memcpy_flushcache_4(void *dst, const void *src) +{ + asm volatile("movntil %1, %0" + : "=m"(*(u32 *)dst) + : "r"(*(const u32 *)src) + : "memory"); +} + +static __always_inline void memcpy_flushcache_8(void *dst, const void *src) +{ + asm volatile("movntiq %1, %0" + : "=m"(*(u64 *)dst) + : "r"(*(const u64 *)src) + : "memory"); +} + +static __always_inline void memcpy_flushcache_16(void *dst, + const void *src) +{ + memcpy_flushcache_8(dst, src); + memcpy_flushcache_8(dst + 8, src + 8); +} + +static __always_inline void memcpy_flushcache_32(void *dst, + const void *src) +{ + memcpy_flushcache_16(dst, src); + memcpy_flushcache_16(dst + 16, src + 16); +} + +static __always_inline void memcpy_flushcache_64(void *dst, + const void *src) +{ + memcpy_flushcache_32(dst, src); + memcpy_flushcache_32(dst + 32, src + 32); +} + +/* + * Keep common fixed-size copies on the inline movnti path when they can + * stay entirely on aligned non-temporal stores. Issue the stores in + * ascending address order so write-combining sees a forward stream. + */ +static __always_inline int memcpy_flushcache_small(void *dst, + const void *src, + size_t cnt) +{ + char *d = dst; + const char *s = src; + + if (!memcpy_flushcache_nt_safe(dst, src, cnt)) + return 0; + + switch (cnt) { + case 4: + memcpy_flushcache_4(d, s); + return 1; + case 8: + memcpy_flushcache_8(d, s); + return 1; + } + + if (cnt & 8) { + memcpy_flushcache_8(d, s); + d += 8; + s += 8; + cnt -= 8; + } + + switch (cnt) { + case 16: + memcpy_flushcache_16(d, s); + return 1; + case 32: + memcpy_flushcache_32(d, s); + return 1; + case 48: + memcpy_flushcache_32(d, s); + memcpy_flushcache_16(d + 32, s + 32); + return 1; + case 64: + memcpy_flushcache_64(d, s); + return 1; + case 80: + memcpy_flushcache_64(d, s); + memcpy_flushcache_16(d + 64, s + 64); + return 1; + case 96: + memcpy_flushcache_64(d, s); + memcpy_flushcache_32(d + 64, s + 64); + return 1; + } + + return 0; +} + +static __always_inline void memcpy_flushcache(void *dst, const void *src, + size_t cnt) +{ + if (!cnt) + return; + + if (__builtin_constant_p(cnt) && memcpy_flushcache_small(dst, src, cnt)) + return; + + __memcpy_flushcache(dst, src, cnt); +} + #define __HAVE_ARCH_MEMCPY_STREAMING 1 static __always_inline void memcpy_streaming(void *dst, const void *src, size_t cnt) -- 2.20.1
