linux-kernel - Re: [PATCH v5 03/13] riscv: sbi: add FWFT extension interface

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Message-ID: <20250424-c85c9d2f189fe4470038b519@orel>
Date: Thu, 24 Apr 2025 13:00:50 +0200
From: Andrew Jones <ajones@...tanamicro.com>
To: Clément Léger <cleger@...osinc.com>
Cc: Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Anup Patel <anup@...infault.org>, 
	Atish Patra <atishp@...shpatra.org>, Shuah Khan <shuah@...nel.org>, Jonathan Corbet <corbet@....net>, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, 
	kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, linux-kselftest@...r.kernel.org, 
	Samuel Holland <samuel.holland@...ive.com>
Subject: Re: [PATCH v5 03/13] riscv: sbi: add FWFT extension interface

On Thu, Apr 17, 2025 at 02:19:50PM +0200, Clément Léger wrote:
> This SBI extensions enables supervisor mode to control feature that are
> under M-mode control (For instance, Svadu menvcfg ADUE bit, Ssdbltrp
> DTE, etc). Add an interface to set local features for a specific cpu
> mask as well as for the online cpu mask.
> 
> Signed-off-by: Clément Léger <cleger@...osinc.com>
> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>
> ---
>  arch/riscv/include/asm/sbi.h | 17 +++++++++++
>  arch/riscv/kernel/sbi.c      | 57 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 74 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 7ec249fea880..c8eab315c80e 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -503,6 +503,23 @@ int sbi_remote_hfence_vvma_asid(const struct cpumask *cpu_mask,
>  				unsigned long asid);
>  long sbi_probe_extension(int ext);
>  
> +int sbi_fwft_set(u32 feature, unsigned long value, unsigned long flags);
> +int sbi_fwft_local_set_cpumask(const cpumask_t *mask, u32 feature,
> +			       unsigned long value, unsigned long flags);

I'm confused by the naming that includes 'local' and 'cpumask' together
and...

> +/**
> + * sbi_fwft_local_set() - Set a feature on all online cpus
> + * @feature: The feature to be set
> + * @value: The feature value to be set
> + * @flags: FWFT feature set flags
> + *
> + * Return: 0 on success, appropriate linux error code otherwise.
> + */
> +static inline int sbi_fwft_local_set(u32 feature, unsigned long value,
> +				     unsigned long flags)
> +{
> +	return sbi_fwft_local_set_cpumask(cpu_online_mask, feature, value, flags);

...that something named with just 'local' is applied to all online cpus.
I've always considered 'local' functions to only affect the calling cpu.

Thanks,
drew