From 9ca255bf041ddc7698b6906dbd846c0ba64b1fe1 Mon Sep 17 00:00:00 2001 From: Mark Salyzyn Date: Tue, 24 Oct 2017 07:47:14 -0700 Subject: arm64: Avoid aligning normal memory pointers in __memcpy_{to,from}io __memcpy_{to,from}io fall back to byte-at-a-time copying if both the source and destination pointers are not 8-byte aligned. Since one of the pointers always points at normal memory, this is unnecessary and detrimental to performance, so only do byte copying until we hit an 8-byte boundary for the device pointer. This change was motivated by performance issues in the pstore driver. On a test platform, measuring probe time for pstore, console buffer size of 1/4MB and pmsg of 1/2MB, was in the 90-107ms region. Change managed to reduce it to 10-25ms, an improvement in boot time. Cc: Kees Cook Cc: Anton Vorontsov Cc: Tony Luck Cc: Catalin Marinas Cc: Will Deacon Cc: Anton Vorontsov Cc: Robin Murphy Signed-off-by: Mark Salyzyn Signed-off-by: Will Deacon --- arch/arm64/kernel/io.c | 12 +++++------- 1 file changed, 5 insertions(+), 7 deletions(-) (limited to 'arch/arm64/kernel') diff --git a/arch/arm64/kernel/io.c b/arch/arm64/kernel/io.c index 354be2a872ae..79b17384effa 100644 --- a/arch/arm64/kernel/io.c +++ b/arch/arm64/kernel/io.c @@ -25,8 +25,7 @@ */ void __memcpy_fromio(void *to, const volatile void __iomem *from, size_t count) { - while (count && (!IS_ALIGNED((unsigned long)from, 8) || - !IS_ALIGNED((unsigned long)to, 8))) { + while (count && !IS_ALIGNED((unsigned long)from, 8)) { *(u8 *)to = __raw_readb(from); from++; to++; @@ -54,23 +53,22 @@ EXPORT_SYMBOL(__memcpy_fromio); */ void __memcpy_toio(volatile void __iomem *to, const void *from, size_t count) { - while (count && (!IS_ALIGNED((unsigned long)to, 8) || - !IS_ALIGNED((unsigned long)from, 8))) { - __raw_writeb(*(volatile u8 *)from, to); + while (count && !IS_ALIGNED((unsigned long)to, 8)) { + __raw_writeb(*(u8 *)from, to); from++; to++; count--; } while (count >= 8) { - __raw_writeq(*(volatile u64 *)from, to); + __raw_writeq(*(u64 *)from, to); from += 8; to += 8; count -= 8; } while (count) { - __raw_writeb(*(volatile u8 *)from, to); + __raw_writeb(*(u8 *)from, to); from++; to++; count--; -- cgit