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

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Message-ID: <67e81f13-5e5e-4630-9a3f-73856b952e6e@rivosinc.com>
Date: Thu, 24 Apr 2025 14:32:01 +0200
From: Clément Léger <cleger@...osinc.com>
To: Andrew Jones <ajones@...tanamicro.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 24/04/2025 13:00, Andrew Jones wrote:
> 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.

Yeah I thought of that as well, local here refers to the fact that this
function applies for a local feature (as described in the SBI
documentation) but agreed that it's really missleading. Any idea for a
better naming ?

Thanks,

Clément

> 
> Thanks,
> drew