Re: [PATCH V2 1/3] riscv: Add Zicbop instruction definitions & cpufeature

Clément Léger
2024-01-03T09:31:41Z

On 31/12/2023 09:29, guoren@kernel.org wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
>
> Cache-block prefetch instructions are HINTs to the hardware to
> indicate that software intends to perform a particular type of
> memory access in the near future. This patch adds prefetch.i,
> prefetch.r and prefetch.w instruction definitions by
> RISCV_ISA_EXT_ZICBOP cpufeature.
>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> ---
> arch/riscv/Kconfig | 15 ++++++++
> arch/riscv/include/asm/hwcap.h | 1 +
> arch/riscv/include/asm/insn-def.h | 60 +++++++++++++++++++++++++++++++
> arch/riscv/kernel/cpufeature.c | 1 +
> 4 files changed, 77 insertions(+)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 24c1799e2ec4..fcbd417d65ea 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -579,6 +579,21 @@ config RISCV_ISA_ZICBOZ
>
> If you don't know what to do here, say Y.
>
> +config RISCV_ISA_ZICBOP
> + bool "Zicbop extension support for cache block prefetch"
> + depends on MMU
> + depends on RISCV_ALTERNATIVE
> + default y
> + help
> + Adds support to dynamically detect the presence of the ZICBOP
> + extension (Cache Block Prefetch Operations) and enable its
> + usage.
> +
> + The Zicbop extension can be used to prefetch cache block for
> + read/write fetch.
> +
> + If you don't know what to do here, say Y.
> +
> config TOOLCHAIN_HAS_ZIHINTPAUSE
> bool
> default y
> diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
> index 06d30526ef3b..77d3b6ee25ab 100644
> --- a/arch/riscv/include/asm/hwcap.h
> +++ b/arch/riscv/include/asm/hwcap.h
> @@ -57,6 +57,7 @@
> #define RISCV_ISA_EXT_ZIHPM 42
> #define RISCV_ISA_EXT_SMSTATEEN 43
> #define RISCV_ISA_EXT_ZICOND 44
> +#define RISCV_ISA_EXT_ZICBOP 45

Hi Guo,

Since you are adding support for the Zicbop extension, you could
probably also allow to probe it from userspace using hwprobe. Add a few
definitions to sys_riscv.c/hwprobe.h and it will be fine.

Thanks,

Clément

>
> #define RISCV_ISA_EXT_MAX 64
>
> diff --git a/arch/riscv/include/asm/insn-def.h b/arch/riscv/include/asm/insn-def.h
> index e27179b26086..bbda350a63bf 100644
> --- a/arch/riscv/include/asm/insn-def.h
> +++ b/arch/riscv/include/asm/insn-def.h
> @@ -18,6 +18,13 @@
> #define INSN_I_RD_SHIFT 7
> #define INSN_I_OPCODE_SHIFT 0
>
> +#define INSN_S_SIMM7_SHIFT 25
> +#define INSN_S_RS2_SHIFT 20
> +#define INSN_S_RS1_SHIFT 15
> +#define INSN_S_FUNC3_SHIFT 12
> +#define INSN_S_SIMM5_SHIFT 7
> +#define INSN_S_OPCODE_SHIFT 0
> +
> #ifdef __ASSEMBLY__
>
> #ifdef CONFIG_AS_HAS_INSN
> @@ -30,6 +37,10 @@
> .insn i \opcode, \func3, \rd, \rs1, \simm12
> .endm
>
> + .macro insn_s, opcode, func3, rs2, simm12, rs1
> + .insn s \opcode, \func3, \rs2, \simm12(\rs1)
> + .endm
> +
> #else
>
> #include <asm/gpr-num.h>
> @@ -51,10 +62,20 @@
> (\simm12 << INSN_I_SIMM12_SHIFT))
> .endm
>
> + .macro insn_s, opcode, func3, rs2, simm12, rs1
> + .4byte ((\opcode << INSN_S_OPCODE_SHIFT) | \
> + (\func3 << INSN_S_FUNC3_SHIFT) | \
> + (.L__gpr_num_\rs2 << INSN_S_RS2_SHIFT) | \
> + (.L__gpr_num_\rs1 << INSN_S_RS1_SHIFT) | \
> + ((\simm12 & 0x1f) << INSN_S_SIMM5_SHIFT) | \
> + (((\simm12 >> 5) & 0x7f) << INSN_S_SIMM7_SHIFT))
> + .endm
> +
> #endif
>
> #define __INSN_R(...) insn_r __VA_ARGS__
> #define __INSN_I(...) insn_i __VA_ARGS__
> +#define __INSN_S(...) insn_s __VA_ARGS__
>
> #else /* ! __ASSEMBLY__ */
>
> @@ -66,6 +87,9 @@
> #define __INSN_I(opcode, func3, rd, rs1, simm12) \
> ".insn i " opcode ", " func3 ", " rd ", " rs1 ", " simm12 "\n"
>
> +#define __INSN_S(opcode, func3, rs2, simm12, rs1) \
> + ".insn s " opcode ", " func3 ", " rs2 ", " simm12 "(" rs1 ")\n"
> +
> #else
>
> #include <linux/stringify.h>
> @@ -92,12 +116,26 @@
> " (\\simm12 << " __stringify(INSN_I_SIMM12_SHIFT) "))\n" \
> " .endm\n"
>
> +#define DEFINE_INSN_S \
> + __DEFINE_ASM_GPR_NUMS \
> +" .macro insn_s, opcode, func3, rs2, simm12, rs1\n" \
> +" .4byte ((\\opcode << " __stringify(INSN_S_OPCODE_SHIFT) ") |" \
> +" (\\func3 << " __stringify(INSN_S_FUNC3_SHIFT) ") |" \
> +" (.L__gpr_num_\\rs2 << " __stringify(INSN_S_RS2_SHIFT) ") |" \
> +" (.L__gpr_num_\\rs1 << " __stringify(INSN_S_RS1_SHIFT) ") |" \
> +" ((\\simm12 & 0x1f) << " __stringify(INSN_S_SIMM5_SHIFT) ") |" \
> +" (((\\simm12 >> 5) & 0x7f) << " __stringify(INSN_S_SIMM7_SHIFT) "))\n" \
> +" .endm\n"
> +
> #define UNDEFINE_INSN_R \
> " .purgem insn_r\n"
>
> #define UNDEFINE_INSN_I \
> " .purgem insn_i\n"
>
> +#define UNDEFINE_INSN_S \
> +" .purgem insn_s\n"
> +
> #define __INSN_R(opcode, func3, func7, rd, rs1, rs2) \
> DEFINE_INSN_R \
> "insn_r " opcode ", " func3 ", " func7 ", " rd ", " rs1 ", " rs2 "\n" \
> @@ -108,6 +146,11 @@
> "insn_i " opcode ", " func3 ", " rd ", " rs1 ", " simm12 "\n" \
> UNDEFINE_INSN_I
>
> +#define __INSN_S(opcode, func3, rs2, simm12, rs1) \
> + DEFINE_INSN_S \
> + "insn_s " opcode ", " func3 ", " rs2 ", " simm12 ", " rs1 "\n" \
> + UNDEFINE_INSN_S
> +
> #endif
>
> #endif /* ! __ASSEMBLY__ */
> @@ -120,6 +163,10 @@
> __INSN_I(RV_##opcode, RV_##func3, RV_##rd, \
> RV_##rs1, RV_##simm12)
>
> +#define INSN_S(opcode, func3, rs2, simm12, rs1) \
> + __INSN_S(RV_##opcode, RV_##func3, RV_##rs2, \
> + RV_##simm12, RV_##rs1)
> +
> #define RV_OPCODE(v) __ASM_STR(v)
> #define RV_FUNC3(v) __ASM_STR(v)
> #define RV_FUNC7(v) __ASM_STR(v)
> @@ -133,6 +180,7 @@
> #define RV___RS2(v) __RV_REG(v)
>
> #define RV_OPCODE_MISC_MEM RV_OPCODE(15)
> +#define RV_OPCODE_OP_IMM RV_OPCODE(19)
> #define RV_OPCODE_SYSTEM RV_OPCODE(115)
>
> #define HFENCE_VVMA(vaddr, asid) \
> @@ -196,4 +244,16 @@
> INSN_I(OPCODE_MISC_MEM, FUNC3(2), __RD(0), \
> RS1(base), SIMM12(4))
>
> +#define CBO_PREFETCH_I(base, offset) \
> + INSN_S(OPCODE_OP_IMM, FUNC3(6), __RS2(0), \
> + SIMM12(offset), RS1(base))
> +
> +#define CBO_PREFETCH_R(base, offset) \
> + INSN_S(OPCODE_OP_IMM, FUNC3(6), __RS2(1), \
> + SIMM12(offset), RS1(base))
> +
> +#define CBO_PREFETCH_W(base, offset) \
> + INSN_S(OPCODE_OP_IMM, FUNC3(6), __RS2(3), \
> + SIMM12(offset), RS1(base))
> +
> #endif /* __ASM_INSN_DEF_H */
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index b3785ffc1570..bdb02b066041 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -168,6 +168,7 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
> __RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_h),
> __RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
> __RISCV_ISA_EXT_DATA(zicboz, RISCV_ISA_EXT_ZICBOZ),
> + __RISCV_ISA_EXT_DATA(zicbop, RISCV_ISA_EXT_ZICBOP),
> __RISCV_ISA_EXT_DATA(zicntr, RISCV_ISA_EXT_ZICNTR),
> __RISCV_ISA_EXT_DATA(zicond, RISCV_ISA_EXT_ZICOND),
> __RISCV_ISA_EXT_DATA(zicsr, RISCV_ISA_EXT_ZICSR),