linux-kernel - Re: [PATCH] RISC-V: cpu-hotplug fix

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Message-ID: <20250924-6e273138195103ca5b7912f6@orel>
Date: Wed, 24 Sep 2025 11:56:40 -0500
From: Andrew Jones <ajones@...tanamicro.com>
To: Danil Skrebenkov <danil.skrebenkov@...udbear.ru>
Cc: pjw@...nel.org, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Alexandre Ghiti <alex@...ti.fr>, Charlie Jenkins <charlie@...osinc.com>, 
	WangYuli <wangyuli@...ontech.com>, linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RISC-V: cpu-hotplug fix

On Fri, Sep 19, 2025 at 04:28:46PM +0300, Danil Skrebenkov wrote:
> openSBI v1.7 adds harts checks for ipi operations. Especially it
> adds comparison between hmask passed as an argument from linux
> and mask of online harts (from openSBI side). If they don't
> fit each other the error occurs.
> 
> When cpu is offline, cpu_online_mask is explicitly cleared in
> __cpu_disable. However, there is no explicit clearing of
> mm_cpumask. mm_cpumask is used for rfence operations that
> call openSBI RFENCE extension which uses ipi to remote harts.
> If hart is offline there may be error if mask of linux is not
> as mask of online harts in openSBI.
> 
> this patch adds explicit clearing of mm_cpumask for offline hart.
> 
> Signed-off-by: Danil Skrebenkov <danil.skrebenkov@...udbear.ru>
> ---
>  arch/riscv/kernel/cpu-hotplug.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/riscv/kernel/cpu-hotplug.c b/arch/riscv/kernel/cpu-hotplug.c
> index a1e38ecfc8be..3f50d3dd76c6 100644
> --- a/arch/riscv/kernel/cpu-hotplug.c
> +++ b/arch/riscv/kernel/cpu-hotplug.c
> @@ -54,6 +54,7 @@ void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu)
>  
>  	pr_notice("CPU%u: off\n", cpu);
>  
> +	clear_tasks_mm_cpumask(cpu);
>  	/* Verify from the firmware if the cpu is really stopped*/
>  	if (cpu_ops->cpu_is_stopped)
>  		ret = cpu_ops->cpu_is_stopped(cpu);
> -- 
> 2.43.0
>

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