linux_dsm_epyc7002/arch/arc/lib/memset-archs.S
Eugeniy Paltsev e6a72b7dae ARCv2: lib: memeset: fix doing prefetchw outside of buffer
ARCv2 optimized memset 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 issues in SMP config when next line was already owned by
other core. Fix the issue by avoiding the PREFETCHW

Some more details:

The current code has 3 logical loops (ignroing the unaligned part)
  (a) Big loop for doing aligned 64 bytes per iteration with PREALLOC
  (b) Loop for 32 x 2 bytes with PREFETCHW
  (c) any left over bytes

loop (a) was already eliding the last 64 bytes, so PREALLOC was
safe. The fix was removing PREFETCW from (b).

Another potential issue (applicable to configs with 32 or 128 byte L1
cache line) is that PREALLOC assumes 64 byte cache line and may not do
the right thing specially for 32b. While it would be easy to adapt,
there are no known configs with those lie sizes, so for now, just
compile out PREALLOC in such cases.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Cc: stable@vger.kernel.org #4.4+
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
[vgupta: rewrote changelog, used asm .macro vs. "C" macro]
2019-01-17 16:24:39 -08:00

147 lines
2.9 KiB
ArmAsm

/*
* Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <asm/cache.h>
/*
* The memset implementation below is optimized to use prefetchw and prealloc
* instruction in case of CPU with 64B L1 data cache line (L1_CACHE_SHIFT == 6)
* If you want to implement optimized memset for other possible L1 data cache
* line lengths (32B and 128B) you should rewrite code carefully checking
* we don't call any prefetchw/prealloc instruction for L1 cache lines which
* don't belongs to memset area.
*/
#if L1_CACHE_SHIFT == 6
.macro PREALLOC_INSTR reg, off
prealloc [\reg, \off]
.endm
.macro PREFETCHW_INSTR reg, off
prefetchw [\reg, \off]
.endm
#else
.macro PREALLOC_INSTR
.endm
.macro PREFETCHW_INSTR
.endm
#endif
ENTRY_CFI(memset)
PREFETCHW_INSTR r0, 0 ; Prefetch the first write location
mov.f 0, r2
;;; if size is zero
jz.d [blink]
mov r3, r0 ; don't clobber ret val
;;; if length < 8
brls.d.nt r2, 8, .Lsmallchunk
mov.f lp_count,r2
and.f r4, r0, 0x03
rsub lp_count, r4, 4
lpnz @.Laligndestination
;; LOOP BEGIN
stb.ab r1, [r3,1]
sub r2, r2, 1
.Laligndestination:
;;; Destination is aligned
and r1, r1, 0xFF
asl r4, r1, 8
or r4, r4, r1
asl r5, r4, 16
or r5, r5, r4
mov r4, r5
sub3 lp_count, r2, 8
cmp r2, 64
bmsk.hi r2, r2, 5
mov.ls lp_count, 0
add3.hi r2, r2, 8
;;; Convert len to Dwords, unfold x8
lsr.f lp_count, lp_count, 6
lpnz @.Lset64bytes
;; LOOP START
PREALLOC_INSTR r3, 64 ; alloc next line w/o fetching
#ifdef CONFIG_ARC_HAS_LL64
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
#else
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
#endif
.Lset64bytes:
lsr.f lp_count, r2, 5 ;Last remaining max 124 bytes
lpnz .Lset32bytes
;; LOOP START
#ifdef CONFIG_ARC_HAS_LL64
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
std.ab r4, [r3, 8]
#else
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
st.ab r4, [r3, 4]
#endif
.Lset32bytes:
and.f lp_count, r2, 0x1F ;Last remaining 31 bytes
.Lsmallchunk:
lpnz .Lcopy3bytes
;; LOOP START
stb.ab r1, [r3, 1]
.Lcopy3bytes:
j [blink]
END_CFI(memset)
ENTRY_CFI(memzero)
; adjust bzero args to memset args
mov r2, r1
b.d memset ;tail call so need to tinker with blink
mov r1, 0
END_CFI(memzero)