linux-kernel - Re: [PATCH v3 5/7] RISC-V: hwprobe: Support probing of misaligned access performance

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Message-ID: <2cf5852092ac5940b8bc6664f54bd6066fe03be2.camel@perches.com>
Date:   Wed, 22 Feb 2023 01:39:55 -0800
From:   Joe Perches <joe@...ches.com>
To:     Evan Green <evan@...osinc.com>,
        Palmer Dabbelt <palmer@...osinc.com>
Cc:     heiko@...ech.de, Conor Dooley <conor@...nel.org>,
        slewis@...osinc.com, vineetg@...osinc.com,
        Albert Ou <aou@...s.berkeley.edu>,
        Andrew Bresticker <abrestic@...osinc.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Atish Patra <atishp@...osinc.com>,
        Celeste Liu <coelacanthus@...look.com>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Guo Ren <guoren@...nel.org>,
        Jisheng Zhang <jszhang@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Ruizhe Pan <c141028@...il.com>,
        Sunil V L <sunilvl@...tanamicro.com>,
        Tsukasa OI <research_trasio@....a4lg.com>,
        Xianting Tian <xianting.tian@...ux.alibaba.com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v3 5/7] RISC-V: hwprobe: Support probing of misaligned
 access performance

On Tue, 2023-02-21 at 11:08 -0800, Evan Green wrote:
> This allows userspace to select various routines to use based on the
> performance of misaligned access on the target hardware.
[]
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
[]
> @@ -89,11 +94,11 @@ static bool riscv_isa_extension_check(int id)
>  void __init riscv_fill_hwcap(void)
>  {
>  	struct device_node *node;
> -	const char *isa;
> +	const char *isa, *misaligned;
>  	char print_str[NUM_ALPHA_EXTS + 1];
>  	int i, j, rc;
>  	unsigned long isa2hwcap[26] = {0};
> -	unsigned long hartid;
> +	unsigned long hartid, cpu;
>  
>  	isa2hwcap['i' - 'a'] = COMPAT_HWCAP_ISA_I;
>  	isa2hwcap['m' - 'a'] = COMPAT_HWCAP_ISA_M;
> @@ -246,6 +251,28 @@ void __init riscv_fill_hwcap(void)
>  			bitmap_copy(riscv_isa, this_isa, RISCV_ISA_EXT_MAX);
>  		else
>  			bitmap_and(riscv_isa, riscv_isa, this_isa, RISCV_ISA_EXT_MAX);
> +
> +		/*
> +		 * Check for the performance of misaligned accesses.
> +		 */
> +		cpu = hartid_to_cpuid_map(hartid);
> +		if (cpu < 0)
> +			continue;

unsigned long can't be less than 0
Likely cpu should be long not unsigned long
It seems cpu is rather randomly either int or long.
Perhaps standardizing on int would be better.