Re: [PATCH] riscv: Report error when repeatedly recording CPU hardware ID

From: Conor Dooley <conor@kernel.org>
To: Zhe Qiao <qiaozhe@iscas.ac.cn>
Cc: paul.walmsley@sifive.com, palmer@dabbelt.com,
	aou@eecs.berkeley.edu, conor.dooley@microchip.com,
	samuel.holland@sifive.com, evan@rivosinc.com, tglx@linutronix.de,
	andy.chiu@sifive.com, cleger@rivosinc.com,
	ajones@ventanamicro.com, linux-riscv@lists.infradead.org
Subject: Re: [PATCH] riscv: Report error when repeatedly recording CPU hardware ID
Date: Fri, 23 Aug 2024 13:57:01 +0100	[thread overview]
Message-ID: <20240823-circulate-underarm-13406fd8cc44@spud> (raw)
In-Reply-To: <20240823091100.598162-1-qiaozhe@iscas.ac.cn>

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On Fri, Aug 23, 2024 at 05:11:00PM +0800, Zhe Qiao wrote:
> In the of_parse_and_init_cpus() function, when the __cpuid_to_hartid_map[]
> array records the CPU hardware ID, if the same CPU hardware attribute has 
> been recorded, an error report is issued, thereby ensuring the uniqueness
> of the CPU hardware ID recorded in the __cpuid_to_hartid_map[] array.

Why is this actually required? On what system did you encounter this?

> Signed-off-by: Zhe Qiao <qiaozhe@iscas.ac.cn>
> ---
>  arch/riscv/kernel/smpboot.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
> index 0f8f1c95ac38..698f9fe791f7 100644
> --- a/arch/riscv/kernel/smpboot.c
> +++ b/arch/riscv/kernel/smpboot.c
> @@ -118,6 +118,16 @@ static void __init acpi_parse_and_init_cpus(void)
>  #define acpi_parse_and_init_cpus(...)	do { } while (0)
>  #endif
>  
> +static bool __init is_mpidr_duplicate(unsigned int cpuid, u64 hart)
> +{
> +	unsigned int i;
> +
> +	for (i = 1; (i < cpuid) && (i < NR_CPUS); i++)
> +		if (cpuid_to_hartid_map(i) == hart)
> +			return true;
> +	return false;
> +}
> +
>  static void __init of_parse_and_init_cpus(void)
>  {
>  	struct device_node *dn;
> @@ -131,6 +141,12 @@ static void __init of_parse_and_init_cpus(void)
>  		if (rc < 0)
>  			continue;
>  
> +		if (is_mpidr_duplicate(cpuid, hart)) {
> +			pr_err("%pOF: duplicate cpu reg properties in the DT\n",
> +				dn);
> +			continue;

Why would we continue in this case? If the devicetree is this broken,
why shouldn't we just BUG() and abort immediately?

> +		}
> +
>  		if (hart == cpuid_to_hartid_map(0)) {
>  			BUG_ON(found_boot_cpu);
>  			found_boot_cpu = 1;
> -- 
> 2.43.0
> 
> 
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv

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