Re: [PATCH v3 3/5] powerpc/xive: propagate IPI init errors to prevent use-after-free

[Srikar Dronamraju <srikar@linux.ibm.com>]

* Gou Hao <gouhao@uniontech.com> [2026-07-27 18:42:13]:

>  
>  static void __init pnv_smp_probe(void)
>  {
> -	if (xive_enabled())
> -		xive_smp_probe();
> -	else
> +	if (xive_enabled()) {
> +		if (xive_smp_probe() < 0)
> +			return;
> +	} else {

If xive_smp_probe() fails and we return from here, what is the IPI mechanism
that is going to be used?

Before the patch, we were not configured for IPI and we would fail.
Now we have not configured IPI mechanism, so what are the consequences?

Should we try disable xive_enabled() and try xics_smp_probe() instead?

>  		xics_smp_probe();
> +	}
>  
>  	if (cpu_has_feature(CPU_FTR_DBELL)) {
>  		ic_cause_ipi = smp_ops->cause_ipi;
> diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
> index db99725e752b..14cd0634eeca 100644
> --- a/arch/powerpc/platforms/pseries/smp.c
> +++ b/arch/powerpc/platforms/pseries/smp.c
> @@ -194,10 +194,12 @@ static int pseries_cause_nmi_ipi(int cpu)
>  
>  static __init void pSeries_smp_probe(void)
>  {
> -	if (xive_enabled())
> -		xive_smp_probe();
> -	else
> +	if (xive_enabled()) {
> +		if (xive_smp_probe() < 0)
> +			return;
> +	} else {
>  		xics_smp_probe();
> +	}
>  
>  	/* No doorbell facility, must use the interrupt controller for IPIs */
>  	if (!cpu_has_feature(CPU_FTR_DBELL))
> diff --git a/arch/powerpc/sysdev/xive/common.c b/arch/powerpc/sysdev/xive/common.c
> index 9f80c16be23f..bbe7c85274ea 100644
> --- a/arch/powerpc/sysdev/xive/common.c
> +++ b/arch/powerpc/sysdev/xive/common.c
> @@ -1267,15 +1267,17 @@ noinstr static void xive_cleanup_cpu_ipi(unsigned int cpu, struct xive_cpu *xc)
>  
>  int __init xive_smp_probe(void)
>  {
> +	int ret;
> +
>  	smp_ops->cause_ipi = xive_cause_ipi;
>  
>  	/* Register the IPI */
> -	xive_init_ipis();
> +	ret = xive_init_ipis();
> +	if (ret < 0)
> +		return ret;
>  
>  	/* Allocate and setup IPI for the boot CPU */
> -	xive_setup_cpu_ipi(smp_processor_id());
> -
> -	return 0;
> +	return xive_setup_cpu_ipi(smp_processor_id());
>  }
>  
>  #endif /* CONFIG_SMP */
> -- 
> 2.20.1
> 

-- 
Thanks and Regards
Srikar Dronamraju