Re: [RFC PATCH v2 11/31] kvx: Add atomic/locking headers

[Guo Ren <guoren@kernel.org>]

On Fri, Jan 20, 2023 at 10:13 PM Yann Sionneau <ysionneau@kalray.eu> wrote:
>
> Add common headers (atomic, bitops, barrier and locking) for basic
> kvx support.
>
> Co-developed-by: Clement Leger <clement@clement-leger.fr>
> Signed-off-by: Clement Leger <clement@clement-leger.fr>
> Co-developed-by: Jules Maselbas <jmaselbas@kalray.eu>
> Signed-off-by: Jules Maselbas <jmaselbas@kalray.eu>
> Co-developed-by: Julian Vetter <jvetter@kalray.eu>
> Signed-off-by: Julian Vetter <jvetter@kalray.eu>
> Co-developed-by: Julien Villette <jvillette@kalray.eu>
> Signed-off-by: Julien Villette <jvillette@kalray.eu>
> Co-developed-by: Yann Sionneau <ysionneau@kalray.eu>
> Signed-off-by: Yann Sionneau <ysionneau@kalray.eu>
> ---
>
> Notes:
>     V1 -> V2:
>      - use {READ,WRITE}_ONCE for arch_atomic64_{read,set}
>      - use asm-generic/bitops/atomic.h instead of __test_and_*_bit
>      - removed duplicated includes
>      - rewrite xchg and cmpxchg in C using builtins for acswap insn
>
>  arch/kvx/include/asm/atomic.h  | 104 ++++++++++++++++++++
>  arch/kvx/include/asm/barrier.h |  15 +++
>  arch/kvx/include/asm/bitops.h  | 115 ++++++++++++++++++++++
>  arch/kvx/include/asm/bitrev.h  |  32 +++++++
>  arch/kvx/include/asm/cmpxchg.h | 170 +++++++++++++++++++++++++++++++++
>  5 files changed, 436 insertions(+)
>  create mode 100644 arch/kvx/include/asm/atomic.h
>  create mode 100644 arch/kvx/include/asm/barrier.h
>  create mode 100644 arch/kvx/include/asm/bitops.h
>  create mode 100644 arch/kvx/include/asm/bitrev.h
>  create mode 100644 arch/kvx/include/asm/cmpxchg.h
>
> diff --git a/arch/kvx/include/asm/atomic.h b/arch/kvx/include/asm/atomic.h
> new file mode 100644
> index 000000000000..bea3d70785b1
> --- /dev/null
> +++ b/arch/kvx/include/asm/atomic.h
> @@ -0,0 +1,104 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2017-2023 Kalray Inc.
> + * Author(s): Clement Leger
> + */
> +
> +#ifndef _ASM_KVX_ATOMIC_H
> +#define _ASM_KVX_ATOMIC_H
> +
> +#include <linux/types.h>
> +
> +#include <asm/cmpxchg.h>
> +
> +#define ATOMIC64_INIT(i)     { (i) }
> +
> +#define arch_atomic64_cmpxchg(v, old, new) (arch_cmpxchg(&((v)->counter), old, new))
> +#define arch_atomic64_xchg(v, new) (arch_xchg(&((v)->counter), new))
> +
> +static inline long arch_atomic64_read(const atomic64_t *v)
> +{
> +       return READ_ONCE(v->counter);
> +}
> +
> +static inline void arch_atomic64_set(atomic64_t *v, long i)
> +{
> +       WRITE_ONCE(v->counter, i);
> +}
> +
> +#define ATOMIC64_RETURN_OP(op, c_op)                                   \
> +static inline long arch_atomic64_##op##_return(long i, atomic64_t *v)  \
> +{                                                                      \
> +       long new, old, ret;                                             \
> +                                                                       \
> +       do {                                                            \
> +               old = v->counter;                                       \
> +               new = old c_op i;                                       \
> +               ret = arch_cmpxchg(&v->counter, old, new);              \
> +       } while (ret != old);                                           \
> +                                                                       \
> +       return new;                                                     \
> +}
> +
> +#define ATOMIC64_OP(op, c_op)                                          \
> +static inline void arch_atomic64_##op(long i, atomic64_t *v)           \
> +{                                                                      \
> +       long new, old, ret;                                             \
> +                                                                       \
> +       do {                                                            \
> +               old = v->counter;                                       \
> +               new = old c_op i;                                       \
> +               ret = arch_cmpxchg(&v->counter, old, new);              \
> +       } while (ret != old);                                           \
> +}
> +
> +#define ATOMIC64_FETCH_OP(op, c_op)                                    \
> +static inline long arch_atomic64_fetch_##op(long i, atomic64_t *v)     \
> +{                                                                      \
> +       long new, old, ret;                                             \
> +                                                                       \
> +       do {                                                            \
> +               old = v->counter;                                       \
> +               new = old c_op i;                                       \
> +               ret = arch_cmpxchg(&v->counter, old, new);              \
> +       } while (ret != old);                                           \
> +                                                                       \
> +       return old;                                                     \
> +}
> +
> +#define ATOMIC64_OPS(op, c_op)                                         \
> +       ATOMIC64_OP(op, c_op)                                           \
> +       ATOMIC64_RETURN_OP(op, c_op)                                    \
> +       ATOMIC64_FETCH_OP(op, c_op)
> +
> +ATOMIC64_OPS(and, &)
> +ATOMIC64_OPS(or, |)
> +ATOMIC64_OPS(xor, ^)
> +ATOMIC64_OPS(add, +)
> +ATOMIC64_OPS(sub, -)
> +
> +#undef ATOMIC64_OPS
> +#undef ATOMIC64_FETCH_OP
> +#undef ATOMIC64_OP
> +
> +static inline int arch_atomic_add_return(int i, atomic_t *v)
> +{
> +       int new, old, ret;
> +
> +       do {
> +               old = v->counter;
> +               new = old + i;
> +               ret = arch_cmpxchg(&v->counter, old, new);
> +       } while (ret != old);
> +
> +       return new;
> +}
> +
> +static inline int arch_atomic_sub_return(int i, atomic_t *v)
> +{
> +       return arch_atomic_add_return(-i, v);
> +}
> +
> +#include <asm-generic/atomic.h>
> +
> +#endif /* _ASM_KVX_ATOMIC_H */
> diff --git a/arch/kvx/include/asm/barrier.h b/arch/kvx/include/asm/barrier.h
> new file mode 100644
> index 000000000000..371f1c70746d
> --- /dev/null
> +++ b/arch/kvx/include/asm/barrier.h
> @@ -0,0 +1,15 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2017-2023 Kalray Inc.
> + * Author(s): Clement Leger
> + */
> +
> +#ifndef _ASM_KVX_BARRIER_H
> +#define _ASM_KVX_BARRIER_H
> +
> +/* fence is sufficient to guarantee write ordering */
> +#define mb()   __builtin_kvx_fence()
> +
> +#include <asm-generic/barrier.h>
> +
> +#endif /* _ASM_KVX_BARRIER_H */
> diff --git a/arch/kvx/include/asm/bitops.h b/arch/kvx/include/asm/bitops.h
> new file mode 100644
> index 000000000000..c643f4765059
> --- /dev/null
> +++ b/arch/kvx/include/asm/bitops.h
> @@ -0,0 +1,115 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2017-2023 Kalray Inc.
> + * Author(s): Clement Leger
> + *            Yann Sionneau
> + */
> +
> +#ifndef _ASM_KVX_BITOPS_H
> +#define _ASM_KVX_BITOPS_H
> +
> +#ifdef __KERNEL__
> +
> +#ifndef _LINUX_BITOPS_H
> +#error only <linux/bitops.h> can be included directly
> +#endif
> +
> +#include <asm/cmpxchg.h>
> +
> +static inline int fls(int x)
> +{
> +       return 32 - __builtin_kvx_clzw(x);
> +}
> +
> +static inline int fls64(__u64 x)
> +{
> +       return 64 - __builtin_kvx_clzd(x);
> +}
> +
> +/**
> + * __ffs - find first set bit in word
> + * @word: The word to search
> + *
> + * Undefined if no set bit exists, so code should check against 0 first.
> + */
> +static inline unsigned long __ffs(unsigned long word)
> +{
> +       return __builtin_kvx_ctzd(word);
> +}
> +
> +/**
> + * __fls - find last set bit in word
> + * @word: The word to search
> + *
> + * Undefined if no set bit exists, so code should check against 0 first.
> + */
> +static inline unsigned long __fls(unsigned long word)
> +{
> +       return 63 - __builtin_kvx_clzd(word);
> +}
> +
> +
> +/**
> + * ffs - find first set bit in word
> + * @x: the word to search
> + *
> + * This is defined the same way as the libc and compiler builtin ffs
> + * routines, therefore differs in spirit from the other bitops.
> + *
> + * ffs(value) returns 0 if value is 0 or the position of the first
> + * set bit if value is nonzero. The first (least significant) bit
> + * is at position 1.
> + */
> +static inline int ffs(int x)
> +{
> +       if (!x)
> +               return 0;
> +       return __builtin_kvx_ctzw(x) + 1;
> +}
> +
> +static inline unsigned int __arch_hweight32(unsigned int w)
> +{
> +       unsigned int count;
> +
> +       asm volatile ("cbsw %0 = %1\n\t;;"
> +       : "=r" (count)
> +       : "r" (w));
> +
> +       return count;
> +}
> +
> +static inline unsigned int __arch_hweight64(__u64 w)
> +{
> +       unsigned int count;
> +
> +       asm volatile ("cbsd %0 = %1\n\t;;"
> +       : "=r" (count)
> +       : "r" (w));
> +
> +       return count;
> +}
> +
> +static inline unsigned int __arch_hweight16(unsigned int w)
> +{
> +       return __arch_hweight32(w & 0xffff);
> +}
> +
> +static inline unsigned int __arch_hweight8(unsigned int w)
> +{
> +       return __arch_hweight32(w & 0xff);
> +}
> +
> +#include <asm-generic/bitops/ffz.h>
> +
> +#include <asm-generic/bitops/sched.h>
> +#include <asm-generic/bitops/const_hweight.h>
> +
> +#include <asm-generic/bitops/atomic.h>
> +#include <asm-generic/bitops/non-atomic.h>
> +#include <asm-generic/bitops/lock.h>
> +#include <asm-generic/bitops/le.h>
> +#include <asm-generic/bitops/ext2-atomic.h>
> +
> +#endif
> +
> +#endif
> diff --git a/arch/kvx/include/asm/bitrev.h b/arch/kvx/include/asm/bitrev.h
> new file mode 100644
> index 000000000000..79865081905a
> --- /dev/null
> +++ b/arch/kvx/include/asm/bitrev.h
> @@ -0,0 +1,32 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2017-2023 Kalray Inc.
> + * Author(s): Clement Leger
> + */
> +
> +#ifndef _ASM_KVX_BITREV_H
> +#define _ASM_KVX_BITREV_H
> +
> +#include <linux/swab.h>
> +
> +/* Bit reversal constant for matrix multiply */
> +#define BIT_REVERSE 0x0102040810204080ULL
> +
> +static __always_inline __attribute_const__ u32 __arch_bitrev32(u32 x)
> +{
> +       /* Reverse all bits for each bytes and then byte-reverse the 32 LSB */
> +       return swab32(__builtin_kvx_sbmm8(BIT_REVERSE, x));
> +}
> +
> +static __always_inline __attribute_const__ u16 __arch_bitrev16(u16 x)
> +{
> +       /* Reverse all bits for each bytes and then byte-reverse the 16 LSB */
> +       return swab16(__builtin_kvx_sbmm8(BIT_REVERSE, x));
> +}
> +
> +static __always_inline __attribute_const__ u8 __arch_bitrev8(u8 x)
> +{
> +       return __builtin_kvx_sbmm8(BIT_REVERSE, x);
> +}
> +
> +#endif
> diff --git a/arch/kvx/include/asm/cmpxchg.h b/arch/kvx/include/asm/cmpxchg.h
> new file mode 100644
> index 000000000000..51ccb83757cc
> --- /dev/null
> +++ b/arch/kvx/include/asm/cmpxchg.h
> @@ -0,0 +1,170 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2017-2023 Kalray Inc.
> + * Author(s): Clement Leger
> + *            Yann Sionneau
> + *            Jules Maselbas
> + */
> +
> +#ifndef _ASM_KVX_CMPXCHG_H
> +#define _ASM_KVX_CMPXCHG_H
> +
> +#include <linux/bits.h>
> +#include <linux/types.h>
> +#include <linux/align.h>
> +#include <linux/build_bug.h>
> +
> +/*
> + * On kvx, we have a boolean compare and swap which means that the operation
> + * returns only the success of operation.
> + * If operation succeed, this is simple, we just need to return the provided
> + * old value. However, if it fails, we need to load the value to return it for
> + * the caller. If the loaded value is different from the "old" provided by the
> + * caller, we can return it since it will means it failed.
> + * However, if for some reason the value we read is equal to the old value
> + * provided by the caller, we can't simply return it or the caller will think it
> + * succeeded. So if the value we read is the same as the "old" provided by
> + * the caller, we try again until either we succeed or we fail with a different
> + * value than the provided one.
> + */
> +
> +static inline unsigned int __cmpxchg_u32(unsigned int old, unsigned int new,
> +                                        volatile unsigned int *ptr)
> +{
> +       unsigned int exp = old;
> +
> +       __builtin_kvx_fence();
> +       while (exp == old) {
> +               if (__builtin_kvx_acswapw((void *)ptr, new, exp))
What's the acswapw/d machine code? Seems all RMW-atomic operations are
based on it.

> +                       break; /* acswap succeed */
> +               exp = *ptr;
> +       }
> +
> +       return exp;
> +}
> +
> +static inline unsigned long __cmpxchg_u64(unsigned long old, unsigned long new,
> +                                         volatile unsigned long *ptr)
> +{
> +       unsigned long exp = old;
> +
> +       __builtin_kvx_fence();
> +       while (exp == old) {
> +               if (__builtin_kvx_acswapd((void *)ptr, new, exp))
> +                       break; /* acswap succeed */
> +               exp = *ptr;
> +       }
> +
> +       return exp;
> +}
> +
> +extern unsigned long __cmpxchg_called_with_bad_pointer(void)
> +       __compiletime_error("Bad argument size for cmpxchg");
> +
> +static __always_inline unsigned long __cmpxchg(unsigned long old,
> +                                              unsigned long new,
> +                                              volatile void *ptr, int size)
> +{
> +       switch (size) {
> +       case 4:
> +               return __cmpxchg_u32(old, new, ptr);
> +       case 8:
> +               return __cmpxchg_u64(old, new, ptr);
> +       default:
> +               return __cmpxchg_called_with_bad_pointer();
> +       }
> +}
> +
> +#define arch_cmpxchg(ptr, old, new)                                    \
> +       ((__typeof__(*(ptr))) __cmpxchg(                                \
> +               (unsigned long)(old), (unsigned long)(new),             \
> +               (ptr), sizeof(*(ptr))))
> +
> +/*
> + * In order to optimize xchg for 16 byte, we can use insf/extfs if we know the
> + * bounds. This way, we only take one more bundle than standard xchg.
> + * We simply do a read modify acswap on a 32 bit word.
> + */
> +
> +#define __kvx_insf(org, val, start, stop) __asm__ __volatile__(        \
> +               "insf %[_org] = %[_val], %[_stop], %[_start]\n\t;;"     \
> +               : [_org]"+r"(org)                                       \
> +               : [_val]"r"(val), [_stop]"i"(stop), [_start]"i"(start))
> +
> +#define __kvx_extfz(out, val, start, stop) __asm__ __volatile__(       \
> +               "extfz %[_out] = %[_val], %[_stop], %[_start]\n\t;;"    \
> +               : [_out]"=r"(out)                                       \
> +               : [_val]"r"(val), [_stop]"i"(stop), [_start]"i"(start))
> +
> +/* Needed for generic qspinlock implementation */
> +static inline unsigned int __xchg_u16(unsigned int old, unsigned int new,
> +                                     volatile unsigned int *ptr)
> +{
> +       unsigned int off = ((unsigned long)ptr) % sizeof(unsigned int);
> +       unsigned int val;
> +
> +       ptr = PTR_ALIGN_DOWN(ptr, sizeof(unsigned int));
> +       __builtin_kvx_fence();
> +       do {
> +               old = *ptr;
> +               val = old;
> +               if (off == 0)
> +                       __kvx_insf(val, new, 0, 15);
> +               else
> +                       __kvx_insf(val, new, 16, 31);
> +       } while (!__builtin_kvx_acswapw((void *)ptr, val, old));
> +
> +       if (off == 0)
> +               __kvx_extfz(old, old, 0, 15);
> +       else
> +               __kvx_extfz(old, old, 16, 31);
> +
> +       return old;
> +}
> +
> +static inline unsigned int __xchg_u32(unsigned int old, unsigned int new,
> +                                     volatile unsigned int *ptr)
> +{
> +       __builtin_kvx_fence();
> +       do
> +               old = *ptr;
> +       while (!__builtin_kvx_acswapw((void *)ptr, new, old));
> +
> +       return old;
> +}
> +
> +static inline unsigned long __xchg_u64(unsigned long old, unsigned long new,
> +                                      volatile unsigned long *ptr)
> +{
> +       __builtin_kvx_fence();
> +       do
> +               old = *ptr;
> +       while (!__builtin_kvx_acswapd((void *)ptr, new, old));
> +
> +       return old;
> +}
> +
> +extern unsigned long __xchg_called_with_bad_pointer(void)
> +       __compiletime_error("Bad argument size for xchg");
> +
> +static __always_inline unsigned long __xchg(unsigned long val,
> +                                           volatile void *ptr, int size)
> +{
> +       switch (size) {
> +       case 2:
> +               return __xchg_u16(0, val, ptr);
> +       case 4:
> +               return __xchg_u32(0, val, ptr);
> +       case 8:
> +               return __xchg_u64(0, val, ptr);
> +       default:
> +               return __xchg_called_with_bad_pointer();
> +       }
> +}
> +
> +#define arch_xchg(ptr, val)                                            \
> +       ((__typeof__(*(ptr))) __xchg(                                   \
> +               (unsigned long)(val),                                   \
> +               (ptr), sizeof(*(ptr))))
> +
> +#endif
> --
> 2.37.2
>
>
>
>
>


-- 
Best Regards
 Guo Ren