powerpc/pseries: Initialise CPU hotplug callbacks earlier

As part of the generic HOTPLUG_SMT code, there is support for disabling secondary SMT threads at boot time, by passing "nosmt" on the kernel command line. The way that is implemented is the secondary threads are brought partly online, and then taken back offline again. That is done to support x86 CPUs needing certain initialisation done on all threads. However powerpc has similar needs, see commit d70a54e ("powerpc/powernv: Ignore smt-enabled on Power8 and later"). For that to work the powerpc CPU hotplug callbacks need to be registered before secondary CPUs are brought online, otherwise __cpu_disable() fails due to smp_ops->cpu_disable being NULL. So split the basic initialisation into pseries_cpu_hotplug_init() which can be called early from setup_arch(). The DLPAR related initialisation can still be done later, because it needs to do allocations. Signed-off-by: Michael Ellerman <[email protected]> Link: https://msgid.link/[email protected]
htbegin · Aug 2, 2023 · 3b3a4d0 · 3b3a4d0
1 parent d82e676
commit 3b3a4d0
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Showing 3 changed files with 17 additions and 9 deletions.
diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -845,15 +845,9 @@ static struct notifier_block pseries_smp_nb = {
 	.notifier_call = pseries_smp_notifier,
 };
 
-static int __init pseries_cpu_hotplug_init(void)
+void __init pseries_cpu_hotplug_init(void)
 {
 	int qcss_tok;
-	unsigned int node;
-
-#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
-	ppc_md.cpu_probe = dlpar_cpu_probe;
-	ppc_md.cpu_release = dlpar_cpu_release;
-#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 
 	rtas_stop_self_token = rtas_function_token(RTAS_FN_STOP_SELF);
 	qcss_tok = rtas_function_token(RTAS_FN_QUERY_CPU_STOPPED_STATE);
@@ -862,12 +856,22 @@ static int __init pseries_cpu_hotplug_init(void)
 			qcss_tok == RTAS_UNKNOWN_SERVICE) {
 		printk(KERN_INFO "CPU Hotplug not supported by firmware "
 				"- disabling.\n");
-		return 0;
+		return;
 	}
 
 	smp_ops->cpu_offline_self = pseries_cpu_offline_self;
 	smp_ops->cpu_disable = pseries_cpu_disable;
 	smp_ops->cpu_die = pseries_cpu_die;
+}
+
+static int __init pseries_dlpar_init(void)
+{
+	unsigned int node;
+
+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+	ppc_md.cpu_probe = dlpar_cpu_probe;
+	ppc_md.cpu_release = dlpar_cpu_release;
+#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 
 	/* Processors can be added/removed only on LPAR */
 	if (firmware_has_feature(FW_FEATURE_LPAR)) {
@@ -886,4 +890,4 @@ static int __init pseries_cpu_hotplug_init(void)
 
 	return 0;
 }
-machine_arch_initcall(pseries, pseries_cpu_hotplug_init);
+machine_arch_initcall(pseries, pseries_dlpar_init);
diff --git a/arch/powerpc/platforms/pseries/pseries.h b/arch/powerpc/platforms/pseries/pseries.h
@@ -75,11 +75,13 @@ static inline int dlpar_hp_pmem(struct pseries_hp_errorlog *hp_elog)
 
 #ifdef CONFIG_HOTPLUG_CPU
 int dlpar_cpu(struct pseries_hp_errorlog *hp_elog);
+void pseries_cpu_hotplug_init(void);
 #else
 static inline int dlpar_cpu(struct pseries_hp_errorlog *hp_elog)
 {
 	return -EOPNOTSUPP;
 }
+static inline void pseries_cpu_hotplug_init(void) { }
 #endif
 
 /* PCI root bridge prepare function override for pseries */

diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
@@ -816,6 +816,8 @@ static void __init pSeries_setup_arch(void)
 	/* Discover PIC type and setup ppc_md accordingly */
 	smp_init_pseries();
 
+	// Setup CPU hotplug callbacks
+	pseries_cpu_hotplug_init();
 
 	if (radix_enabled() && !mmu_has_feature(MMU_FTR_GTSE))
 		if (!firmware_has_feature(FW_FEATURE_RPT_INVALIDATE))