linux-kernel - Re: [PATCH v5 04/13] riscv: sbi: add SBI FWFT extension calls

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Message-ID: <20250424-c0700f89bcd29438d6d8d65c@orel>
Date: Thu, 24 Apr 2025 13:06:30 +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 04/13] riscv: sbi: add SBI FWFT extension calls

On Thu, Apr 17, 2025 at 02:19:51PM +0200, Clément Léger wrote:
> Add FWFT extension calls. This will be ratified in SBI V3.0 hence, it is
> provided as a separate commit that can be left out if needed.
> 
> Signed-off-by: Clément Léger <cleger@...osinc.com>
> ---
>  arch/riscv/kernel/sbi.c | 20 +++++++++++++++++++-
>  1 file changed, 19 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/sbi.c b/arch/riscv/kernel/sbi.c
> index 379981c2bb21..7b062189b184 100644
> --- a/arch/riscv/kernel/sbi.c
> +++ b/arch/riscv/kernel/sbi.c
> @@ -299,6 +299,8 @@ static int __sbi_rfence_v02(int fid, const struct cpumask *cpu_mask,
>  	return 0;
>  }
>  
> +static bool sbi_fwft_supported;

At some point we may want an SBI extension bitmap, but this is only the
second SBI extension supported boolean that I'm aware of, so I guess we're
still OK for now.

> +
>  /**
>   * sbi_fwft_set() - Set a feature on the local hart
>   * @feature: The feature ID to be set
> @@ -309,7 +311,15 @@ static int __sbi_rfence_v02(int fid, const struct cpumask *cpu_mask,
>   */
>  int sbi_fwft_set(u32 feature, unsigned long value, unsigned long flags)
>  {
> -	return -EOPNOTSUPP;
> +	struct sbiret ret;
> +
> +	if (!sbi_fwft_supported)
> +		return -EOPNOTSUPP;
> +
> +	ret = sbi_ecall(SBI_EXT_FWFT, SBI_EXT_FWFT_SET,
> +			feature, value, flags, 0, 0, 0);
> +
> +	return sbi_err_map_linux_errno(ret.error);
>  }
>  
>  struct fwft_set_req {
> @@ -348,6 +358,9 @@ int sbi_fwft_local_set_cpumask(const cpumask_t *mask, u32 feature,
>  		.error = ATOMIC_INIT(0),
>  	};
>  
> +	if (!sbi_fwft_supported)
> +		return -EOPNOTSUPP;
> +
>  	if (feature & SBI_FWFT_GLOBAL_FEATURE_BIT)
>  		return -EINVAL;
>  
> @@ -679,6 +692,11 @@ void __init sbi_init(void)
>  			pr_info("SBI DBCN extension detected\n");
>  			sbi_debug_console_available = true;
>  		}
> +		if ((sbi_spec_version >= sbi_mk_version(3, 0)) &&
> +		    (sbi_probe_extension(SBI_EXT_FWFT) > 0)) {

Unnecessary (), but I see it's consistent with the expressions above.

> +			pr_info("SBI FWFT extension detected\n");
> +			sbi_fwft_supported = true;
> +		}
>  	} else {
>  		__sbi_set_timer = __sbi_set_timer_v01;
>  		__sbi_send_ipi	= __sbi_send_ipi_v01;
> -- 
> 2.49.0
>

Besides the () nit

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