Re: [PATCH 1/6] riscv: hwprobe: Report FP extensions only when available

[Andy Chiu <tchiu@tenstorrent.com>]

On Tue, Oct 06, 2026 at 09:52:58AM +0200, Radim Krcmár wrote:
> User-mode use of Zcd, Zcf, Zfa, Zfbfmin, Zfh and Zfhmin requires
> non-Off sstatus.FS, which we set only when has_fpu() (CONFIG_FPU and D
> on all harts).  The vector floating-point extensions Zve32f, Zve64f,
> Zve64d, Zvfbfmin, Zvfbfwma, Zvfh and Zvfhmin require it as well, but
> hwprobe gates them only on has_vector().  hwprobe otherwise reports the
> extensions from the per-hart ISA bitmaps alone, so it can advertise
> extensions that are always disabled in user-mode.
> 
> Report correct environment to user-mode.
> 
> Fixes: 2e2cf5581fcc ("riscv: cpufeature: add validation for zfa, zfh and zfhmin")
> Fixes: de8f8282a969 ("riscv: hwprobe: add zve Vector subextensions into hwprobe interface")
> Fixes: 5dadda5e6a59 ("riscv: hwprobe: export Zvfh[min] ISA extensions")
> Signed-off-by: Radim Krcmár <radim.krcmar@oss.qualcomm.com>

Reviewed-by: Andy Chiu <tchiu@tenstorrent.com>

> ---
>  arch/riscv/kernel/sys_hwprobe.c | 31 ++++++++++++++++++-------------
>  1 file changed, 18 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
> index 7818e1d32622..b57ccd116bb1 100644
> --- a/arch/riscv/kernel/sys_hwprobe.c
> +++ b/arch/riscv/kernel/sys_hwprobe.c
> @@ -146,15 +146,8 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
>  		if (has_vector()) {
>  			EXT_KEY(isainfo->isa, ZVBB, pair->value, missing);
>  			EXT_KEY(isainfo->isa, ZVBC, pair->value, missing);
> -			EXT_KEY(isainfo->isa, ZVE32F, pair->value, missing);
>  			EXT_KEY(isainfo->isa, ZVE32X, pair->value, missing);
> -			EXT_KEY(isainfo->isa, ZVE64D, pair->value, missing);
> -			EXT_KEY(isainfo->isa, ZVE64F, pair->value, missing);
>  			EXT_KEY(isainfo->isa, ZVE64X, pair->value, missing);
> -			EXT_KEY(isainfo->isa, ZVFBFMIN, pair->value, missing);
> -			EXT_KEY(isainfo->isa, ZVFBFWMA, pair->value, missing);
> -			EXT_KEY(isainfo->isa, ZVFH, pair->value, missing);
> -			EXT_KEY(isainfo->isa, ZVFHMIN, pair->value, missing);
>  			EXT_KEY(isainfo->isa, ZVKB, pair->value, missing);
>  			EXT_KEY(isainfo->isa, ZVKG, pair->value, missing);
>  			EXT_KEY(isainfo->isa, ZVKNED, pair->value, missing);
> @@ -163,14 +156,26 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
>  			EXT_KEY(isainfo->isa, ZVKSED, pair->value, missing);
>  			EXT_KEY(isainfo->isa, ZVKSH, pair->value, missing);
>  			EXT_KEY(isainfo->isa, ZVKT, pair->value, missing);
> +
> +			if (has_fpu()) {
> +				EXT_KEY(isainfo->isa, ZVE32F, pair->value, missing);
> +				EXT_KEY(isainfo->isa, ZVE64D, pair->value, missing);
> +				EXT_KEY(isainfo->isa, ZVE64F, pair->value, missing);
> +				EXT_KEY(isainfo->isa, ZVFBFMIN, pair->value, missing);
> +				EXT_KEY(isainfo->isa, ZVFBFWMA, pair->value, missing);
> +				EXT_KEY(isainfo->isa, ZVFH, pair->value, missing);
> +				EXT_KEY(isainfo->isa, ZVFHMIN, pair->value, missing);
> +			}
>  		}
>  
> -		EXT_KEY(isainfo->isa, ZCD, pair->value, missing);
> -		EXT_KEY(isainfo->isa, ZCF, pair->value, missing);
> -		EXT_KEY(isainfo->isa, ZFA, pair->value, missing);
> -		EXT_KEY(isainfo->isa, ZFBFMIN, pair->value, missing);
> -		EXT_KEY(isainfo->isa, ZFH, pair->value, missing);
> -		EXT_KEY(isainfo->isa, ZFHMIN, pair->value, missing);
> +		if (has_fpu()) {
> +			EXT_KEY(isainfo->isa, ZCD, pair->value, missing);
> +			EXT_KEY(isainfo->isa, ZCF, pair->value, missing);
> +			EXT_KEY(isainfo->isa, ZFA, pair->value, missing);
> +			EXT_KEY(isainfo->isa, ZFBFMIN, pair->value, missing);
> +			EXT_KEY(isainfo->isa, ZFH, pair->value, missing);
> +			EXT_KEY(isainfo->isa, ZFHMIN, pair->value, missing);
> +		}
>  
>  		if (IS_ENABLED(CONFIG_RISCV_ISA_SUPM))
>  			EXT_KEY(isainfo->isa, SUPM, pair->value, missing);
> -- 
> 2.55.0
>