linux-kernel - Re: [PATCH 2/5] riscv: cpu_ops_spinwait: Support for 64bit hartid

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Message-ID: <a7910ff4-0bce-befa-f961-a82a8a1025a1@canonical.com>
Date:   Wed, 25 May 2022 17:27:51 +0200
From:   Heinrich Schuchardt <heinrich.schuchardt@...onical.com>
To:     Sunil V L <sunilvl@...tanamicro.com>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-efi@...r.kernel.org, Sunil V L <sunil.vl@...il.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Anup Patel <apatel@...tanamicro.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Ard Biesheuvel <ardb@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Atish Patra <atishp@...osinc.com>
Subject: Re: [PATCH 2/5] riscv: cpu_ops_spinwait: Support for 64bit hartid

On 5/25/22 17:11, Sunil V L wrote:
> The hartid can be a 64bit value on RV64 platforms. This patch modifies
> the hartid variable type to unsigned long so that it can hold 64bit
> value on RV64 platforms.
> 
> Signed-off-by: Sunil V L <sunilvl@...tanamicro.com>
> ---
>   arch/riscv/kernel/cpu_ops_spinwait.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/riscv/kernel/cpu_ops_spinwait.c b/arch/riscv/kernel/cpu_ops_spinwait.c
> index 346847f6c41c..51ac07514a62 100644
> --- a/arch/riscv/kernel/cpu_ops_spinwait.c
> +++ b/arch/riscv/kernel/cpu_ops_spinwait.c
> @@ -18,7 +18,7 @@ void *__cpu_spinwait_task_pointer[NR_CPUS] __section(".data");
>   static void cpu_update_secondary_bootdata(unsigned int cpuid,
>   				   struct task_struct *tidle)
>   {
> -	int hartid = cpuid_to_hartid_map(cpuid);
> +	unsigned long hartid = cpuid_to_hartid_map(cpuid);
>   
>   	/*
>   	 * The hartid must be less than NR_CPUS to avoid out-of-bound access

This line follows:

if (hartid == INVALID_HARTID || hartid >= NR_CPUS)

INVALID_HARTID is defined as ULONG_MAX. Please, mention that you are 
fixing a bug:

Fixes: c78f94f35cf648 ("RISC-V: Use __cpu_up_stack/task_pointer only for 
spinwait method")

NR_CPUS alias CONFIG_NR_CPUS is an int. You should convert it to 
unsigned before comparing it to hartid to avoid build warnings.

Best regards

Heinrich