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authorEugeniy Paltsev <eugeniy.paltsev@synopsys.com>2019-01-30 19:32:40 +0300
committerVineet Gupta <vgupta@synopsys.com>2019-02-21 11:03:16 -0800
commitf8a15f97664178f27dfbf86a38f780a532cb6df0 (patch)
tree50efe7e5154fbbbc77f8c46b2a53c6773e2b6493 /arch/arc
parent252f6e8eae909bc075a1b1e3b9efb095ae4c0b56 (diff)
downloadlinux-f8a15f97664178f27dfbf86a38f780a532cb6df0.tar.bz2
ARCv2: lib: memcpy: fix doing prefetchw outside of buffer
ARCv2 optimized memcpy uses PREFETCHW instruction for prefetching the next cache line but doesn't ensure that the line is not past the end of the buffer. PRETECHW changes the line ownership and marks it dirty, which can cause data corruption if this area is used for DMA IO. Fix the issue by avoiding the PREFETCHW. This leads to performance degradation but it is OK as we'll introduce new memcpy implementation optimized for unaligned memory access using. We also cut off all PREFETCH instructions at they are quite useless here: * we call PREFETCH right before LOAD instruction call. * we copy 16 or 32 bytes of data (depending on CONFIG_ARC_HAS_LL64) in a main logical loop. so we call PREFETCH 4 times (or 2 times) for each L1 cache line (in case of 64B L1 cache Line which is default case). Obviously this is not optimal. Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com> Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc')
-rw-r--r--arch/arc/lib/memcpy-archs.S14
1 files changed, 0 insertions, 14 deletions
diff --git a/arch/arc/lib/memcpy-archs.S b/arch/arc/lib/memcpy-archs.S
index d61044dd8b58..ea14b0bf3116 100644
--- a/arch/arc/lib/memcpy-archs.S
+++ b/arch/arc/lib/memcpy-archs.S
@@ -25,15 +25,11 @@
#endif
#ifdef CONFIG_ARC_HAS_LL64
-# define PREFETCH_READ(RX) prefetch [RX, 56]
-# define PREFETCH_WRITE(RX) prefetchw [RX, 64]
# define LOADX(DST,RX) ldd.ab DST, [RX, 8]
# define STOREX(SRC,RX) std.ab SRC, [RX, 8]
# define ZOLSHFT 5
# define ZOLAND 0x1F
#else
-# define PREFETCH_READ(RX) prefetch [RX, 28]
-# define PREFETCH_WRITE(RX) prefetchw [RX, 32]
# define LOADX(DST,RX) ld.ab DST, [RX, 4]
# define STOREX(SRC,RX) st.ab SRC, [RX, 4]
# define ZOLSHFT 4
@@ -41,8 +37,6 @@
#endif
ENTRY_CFI(memcpy)
- prefetch [r1] ; Prefetch the read location
- prefetchw [r0] ; Prefetch the write location
mov.f 0, r2
;;; if size is zero
jz.d [blink]
@@ -72,8 +66,6 @@ ENTRY_CFI(memcpy)
lpnz @.Lcopy32_64bytes
;; LOOP START
LOADX (r6, r1)
- PREFETCH_READ (r1)
- PREFETCH_WRITE (r3)
LOADX (r8, r1)
LOADX (r10, r1)
LOADX (r4, r1)
@@ -117,9 +109,7 @@ ENTRY_CFI(memcpy)
lpnz @.Lcopy8bytes_1
;; LOOP START
ld.ab r6, [r1, 4]
- prefetch [r1, 28] ;Prefetch the next read location
ld.ab r8, [r1,4]
- prefetchw [r3, 32] ;Prefetch the next write location
SHIFT_1 (r7, r6, 24)
or r7, r7, r5
@@ -162,9 +152,7 @@ ENTRY_CFI(memcpy)
lpnz @.Lcopy8bytes_2
;; LOOP START
ld.ab r6, [r1, 4]
- prefetch [r1, 28] ;Prefetch the next read location
ld.ab r8, [r1,4]
- prefetchw [r3, 32] ;Prefetch the next write location
SHIFT_1 (r7, r6, 16)
or r7, r7, r5
@@ -204,9 +192,7 @@ ENTRY_CFI(memcpy)
lpnz @.Lcopy8bytes_3
;; LOOP START
ld.ab r6, [r1, 4]
- prefetch [r1, 28] ;Prefetch the next read location
ld.ab r8, [r1,4]
- prefetchw [r3, 32] ;Prefetch the next write location
SHIFT_1 (r7, r6, 8)
or r7, r7, r5