Re: [PATCH fixes] riscv: Fix CONFIG_AS_HAS_INSN for new .insn usage

From: Andrew Jones <ajones@ventanamicro.com>
To: Nathan Chancellor <nathan@kernel.org>
Cc: Paul Walmsley <pjw@kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	 Alexandre Ghiti <alex@ghiti.fr>,
	Nick Desaulniers <nick.desaulniers+lkml@gmail.com>,
	 Bill Wendling <morbo@google.com>,
	Justin Stitt <justinstitt@google.com>,
	 Ben Dooks <ben.dooks@codethink.co.uk>,
	linux-riscv@lists.infradead.org, llvm@lists.linux.dev,
	 patches@lists.linux.dev
Subject: Re: [PATCH fixes] riscv: Fix CONFIG_AS_HAS_INSN for new .insn usage
Date: Fri, 7 Nov 2025 16:35:07 -0600	[thread overview]
Message-ID: <20251107-e4e324e725ddf47b9aafa0b4@orel> (raw)
In-Reply-To: <20251107-riscv-fix-new-insn-usage-v1-1-9a186c5928a0@kernel.org>

On Fri, Nov 07, 2025 at 02:56:59PM -0700, Nathan Chancellor wrote:
> After commit 44aa25c000b4 ("riscv: asm: use .insn for making custom
> instructions"), builds using LLVM older that 19 or binutils older than
> 2.38 fail with:
> 
>   arch/riscv/include/asm/vdso/processor.h: Assembler messages:
>   arch/riscv/include/asm/vdso/processor.h:27: Error: unrecognized opcode `0x100000f'
>   arch/riscv/include/asm/vdso/processor.h:27: Error: unrecognized opcode `0x100000f'
>   arch/riscv/include/asm/vdso/processor.h:27: Error: unrecognized opcode `0x100000f'
>   arch/riscv/include/asm/vdso/processor.h:27: Error: unrecognized opcode `0x100000f'
>   make[4]: *** [scripts/Makefile.build:287: arch/riscv/kernel/vdso/vgettimeofday.o] Error 1
> 
>   In file included from <built-in>:4:
>   In file included from lib/vdso/gettimeofday.c:6:
>   In file included from include/vdso/datapage.h:21:
>   In file included from include/vdso/processor.h:10:
>   arch/riscv/include/asm/vdso/processor.h:23:2: error: expected instruction format
>      23 |         ALT_RISCV_PAUSE();
>         |         ^
>   arch/riscv/include/asm/errata_list.h:47:3: note: expanded from macro 'ALT_RISCV_PAUSE'
>      47 |                 RISCV_PAUSE, /* Original RISC‑V pause insn */ \
>         |                 ^
>   arch/riscv/include/asm/insn-def.h:259:21: note: expanded from macro 'RISCV_PAUSE'
>     259 | #define RISCV_PAUSE     ASM_INSN_I("0x100000f")
>         |                         ^
>   arch/riscv/include/asm/asm.h:16:26: note: expanded from macro 'ASM_INSN_I'
>      16 | #define ASM_INSN_I(__x) ".insn " __x
>         |                          ^
>   <inline asm>:5:7: note: instantiated into assembly here
>       5 | .insn 0x100000f
>         |       ^
> 
> binutils gained support for '.insn <value>' in 2.38 [1] and LLVM gained
> support in 19 [2]. Adjust the test for CONFIG_AS_HAS_INSN to ensure that
> all versions of .insn are supported before being used.
> 
> Fixes: 44aa25c000b4 ("riscv: asm: use .insn for making custom instructions")
> Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=a262b82fdbf4cda3b0648b1adc32245ca3f78b7a [1]
> Link: https://github.com/llvm/llvm-project/commit/2a086dce691e3cc34a2fc27f4fb255bb2cbbfac9 [2]
> Suggested-by: Andrew Jones <ajones@ventanamicro.com>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
>  arch/riscv/Kconfig | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 22cda9c452d2..fadec20b87a8 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -367,7 +367,7 @@ config RISCV_NONSTANDARD_CACHE_OPS
>  	  systems to handle cache management.
>  
>  config AS_HAS_INSN
> -	def_bool $(as-instr,.insn r 51$(comma) 0$(comma) 0$(comma) t0$(comma) t0$(comma) zero)
> +	def_bool $(as-instr,.insn 0x100000f)
>  
>  config AS_HAS_OPTION_ARCH
>  	# https://github.com/llvm/llvm-project/commit/9e8ed3403c191ab9c4903e8eeb8f732ff8a43cb4
> 
> ---
> base-commit: a882126c42fc53275ac91969d460d939191db7b0
> change-id: 20251107-riscv-fix-new-insn-usage-2261377c2d38
> 
> Best regards,
> --  
> Nathan Chancellor <nathan@kernel.org>
>

Thanks for posting this Nathan.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>