Re: [PATCH v2 06/10] riscv: Implement xchg8/16() using Zabha

Alexandre Ghiti
2024-07-04T17:26:00Z

On 27/06/2024 15:45, Andrea Parri wrote:
>> -#define __arch_xchg_masked(sc_sfx, prepend, append, r, p, n) \
>> +#define __arch_xchg_masked(sc_sfx, swap_sfx, prepend, sc_append, \
>> + swap_append, r, p, n) \
>> ({ \
>> + __label__ zabha, end; \
>> + \
>> + if (IS_ENABLED(CONFIG_RISCV_ISA_ZABHA)) { \
>> + asm goto(ALTERNATIVE("nop", "j %[zabha]", 0, \
>> + RISCV_ISA_EXT_ZABHA, 1) \
>> + : : : : zabha); \
>> + } \
>> + \
>> u32 *__ptr32b = (u32 *)((ulong)(p) & ~0x3); \
>> ulong __s = ((ulong)(p) & (0x4 - sizeof(*p))) * BITS_PER_BYTE; \
>> ulong __mask = GENMASK(((sizeof(*p)) * BITS_PER_BYTE) - 1, 0) \
>> @@ -28,12 +37,25 @@
>> " or %1, %1, %z3\n" \
>> " sc.w" sc_sfx " %1, %1, %2\n" \
>> " bnez %1, 0b\n" \
>> - append \
>> + sc_append \
>> : "=&r" (__retx), "=&r" (__rc), "+A" (*(__ptr32b)) \
>> : "rJ" (__newx), "rJ" (~__mask) \
>> : "memory"); \
>> \
>> r = (__typeof__(*(p)))((__retx & __mask) >> __s); \
>> + goto end; \
>> + \
>> +zabha: \
>> + if (IS_ENABLED(CONFIG_RISCV_ISA_ZABHA)) { \
>> + __asm__ __volatile__ ( \
>> + prepend \
>> + " amoswap" swap_sfx " %0, %z2, %1\n" \
>> + swap_append \
>> + : "=&r" (r), "+A" (*(p)) \
>> + : "rJ" (n) \
>> + : "memory"); \
>> + } \
>> +end:; \
>> })
> As for patch #1: why the semicolon? and should the second IS_ENABLED()
> be kept?
>
>
>> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
>> index e17d0078a651..f71ddd2ca163 100644
>> --- a/arch/riscv/include/asm/hwcap.h
>> +++ b/arch/riscv/include/asm/hwcap.h
>> @@ -81,6 +81,7 @@
>> #define RISCV_ISA_EXT_ZTSO 72
>> #define RISCV_ISA_EXT_ZACAS 73
>> #define RISCV_ISA_EXT_XANDESPMU 74
>> +#define RISCV_ISA_EXT_ZABHA 75
>>
>> #define RISCV_ISA_EXT_XLINUXENVCFG 127
>>
>> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
>> index 5ef48cb20ee1..c125d82c894b 100644
>> --- a/arch/riscv/kernel/cpufeature.c
>> +++ b/arch/riscv/kernel/cpufeature.c
>> @@ -257,6 +257,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
>> __RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
>> __RISCV_ISA_EXT_DATA(zihpm, RISCV_ISA_EXT_ZIHPM),
>> __RISCV_ISA_EXT_DATA(zacas, RISCV_ISA_EXT_ZACAS),
>> + __RISCV_ISA_EXT_DATA(zabha, RISCV_ISA_EXT_ZABHA),
>> __RISCV_ISA_EXT_DATA(zfa, RISCV_ISA_EXT_ZFA),
>> __RISCV_ISA_EXT_DATA(zfh, RISCV_ISA_EXT_ZFH),
>> __RISCV_ISA_EXT_DATA(zfhmin, RISCV_ISA_EXT_ZFHMIN),
> To be squashed into patch #3?

Yep, done, thanks.

>
> Andrea
>
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