[PATCH] RISC-V: cpu-hotplug fix

[Andrew Jones]

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 at cloudbear.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 at ventanamicro.com>