Re: [PATCH 3/3 v8] s390/pai: Support CPU hotplug for PMU PAI

[Heiko Carstens <hca@linux.ibm.com>]

On Tue, Sep 01, 2026 at 10:54:48AM +0200, Thomas Richter wrote:
> +static int pai_online_cpu(unsigned int cpu)
> +{
> +	int rc;
> +
> +	mutex_lock(&pai_reserve_mutex);
> +	rc = pai_alloc_cpu(PAI_PMU_CRYPTO, cpu, true);
> +	if (!rc) {
> +		rc = pai_alloc_cpu(PAI_PMU_EXT, cpu, true);
> +		if (rc)
> +			pai_event_destroy_cpu(PAI_PMU_CRYPTO, cpu, true);
> +	}
> +	mutex_unlock(&pai_reserve_mutex);
> +	return rc;
> +}

This unusual coding style. Please change to something like:

	mutex_lock(&pai_reserve_mutex);
	rc = pai_alloc_cpu(PAI_PMU_CRYPTO, cpu, true);
	if (rc)
		goto out;
	rc = pai_alloc_cpu(PAI_PMU_EXT, cpu, true);
	if (rc)
		pai_event_destroy_cpu(PAI_PMU_CRYPTO, cpu, true);
out:
	mutex_unlock(&pai_reserve_mutex);
> +	/* CPUHP_BP_PREPARE_DYN --> before CPU is brought online */
> +	rc = cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "perf/pai:prepare",
> +			       pai_online_cpu, pai_offline_cpu);
> +	if (rc < 0) {
> +		debug_unregister_view(paidbg, &debug_sprintf_view);
> +		debug_unregister(paidbg);
> +		return rc;
> +	}
> +
>  	if (!paipmu_setup()) {
> +		cpuhp_remove_state(rc);
>  		/* No PMU registration, no need for debug buffer */
>  		debug_unregister_view(paidbg, &debug_sprintf_view);
>  		debug_unregister(paidbg);

Code duplication. Can't we have _something_ like:

diff --git a/arch/s390/kernel/perf_pai.c b/arch/s390/kernel/perf_pai.c
index 72023b35e70f..e1134e50f3e9 100644
--- a/arch/s390/kernel/perf_pai.c
+++ b/arch/s390/kernel/perf_pai.c
@@ -1316,20 +1316,19 @@ static int __init pai_init(void)
 	/* CPUHP_BP_PREPARE_DYN --> before CPU is brought online */
 	rc = cpuhp_setup_state(CPUHP_BP_PREPARE_DYN, "perf/pai:prepare",
 			       pai_online_cpu, pai_offline_cpu);
-	if (rc < 0) {
-		debug_unregister_view(paidbg, &debug_sprintf_view);
-		debug_unregister(paidbg);
-		return rc;
-	}
-
-	if (!paipmu_setup()) {
-		cpuhp_remove_state(rc);
-		/* No PMU registration, no need for debug buffer */
-		debug_unregister_view(paidbg, &debug_sprintf_view);
-		debug_unregister(paidbg);
-		return -ENODEV;
-	}
+	if (rc < 0)
+		goto out_debug;
+	rc = -ENODEV;
+	if (!paipmu_setup())
+		goto out_cpuhp;
 	return 0;
+
+out_cpuhp:
+	cpuhp_remove_state(rc);
+out_debug:
+	debug_unregister_view(paidbg, &debug_sprintf_view);
+	debug_unregister(paidbg);
+	return rc;
 }
 
 device_initcall(pai_init);