[PATCH 1/2] powerpc/cpu: raise DEVICE_ADD/REMOVE msg to usrspace

[Pingfan Liu]

Some user space tools such as kexec-tools resort to the event
add/remove to decide whether rebuilding dtb or not.
So if a new core added and a crash happens on one of its thread,
then kexec fails to bring up the 2nd kernel since lacking the info
of boot-cpu-hwid in dtb. This patch uses the interface
register_/unregister_cpu to fix the problem

Signed-off-by: Pingfan Liu <kernelfans at gmail.com>
Reported-by: Hari Bathini <hbathini at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/smp.h               |  1 +
 arch/powerpc/kernel/sysfs.c                  | 26 ++++++++++++++------------
 arch/powerpc/platforms/pseries/hotplug-cpu.c |  3 ++-
 3 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
index fac963e..3ef730d 100644
--- a/arch/powerpc/include/asm/smp.h
+++ b/arch/powerpc/include/asm/smp.h
@@ -35,6 +35,7 @@ extern int spinning_secondaries;
 extern void cpu_die(void);
 extern int cpu_to_chip_id(int cpu);
 
+DECLARE_PER_CPU(struct cpu, cpu_devices);
 #ifdef CONFIG_SMP
 
 struct smp_ops_t {
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index 04d0bbd..dbbcc96 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -26,7 +26,7 @@
 #include <asm/lppaca.h>
 #endif
 
-static DEFINE_PER_CPU(struct cpu, cpu_devices);
+DEFINE_PER_CPU(struct cpu, cpu_devices);
 
 /*
  * SMT snooze delay stuff, 64-bit only for now
@@ -716,6 +716,16 @@ static struct device_attribute pa6t_attrs[] = {
 #endif /* HAS_PPC_PMC_PA6T */
 #endif /* HAS_PPC_PMC_CLASSIC */
 
+/* Only valid if CPU is present. */
+static ssize_t show_physical_id(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct cpu *cpu = container_of(dev, struct cpu, dev);
+
+	return sprintf(buf, "%d\n", get_hard_smp_processor_id(cpu->dev.id));
+}
+static DEVICE_ATTR(physical_id, 0444, show_physical_id, NULL);
+
 static int register_cpu_online(unsigned int cpu)
 {
 	struct cpu *c = &per_cpu(cpu_devices, cpu);
@@ -723,6 +733,8 @@ static int register_cpu_online(unsigned int cpu)
 	struct device_attribute *attrs, *pmc_attrs;
 	int i, nattrs;
 
+	device_create_file(&c->dev, &dev_attr_physical_id);
+
 	/* For cpus present at boot a reference was already grabbed in register_cpu() */
 	if (!s->of_node)
 		s->of_node = of_get_cpu_node(cpu, NULL);
@@ -816,6 +828,7 @@ static int unregister_cpu_online(unsigned int cpu)
 
 	BUG_ON(!c->hotpluggable);
 
+	device_remove_file(s, &dev_attr_physical_id);
 #ifdef CONFIG_PPC64
 	if (cpu_has_feature(CPU_FTR_SMT))
 		device_remove_file(s, &dev_attr_smt_snooze_delay);
@@ -1017,16 +1030,6 @@ static void register_nodes(void)
 
 #endif
 
-/* Only valid if CPU is present. */
-static ssize_t show_physical_id(struct device *dev,
-				struct device_attribute *attr, char *buf)
-{
-	struct cpu *cpu = container_of(dev, struct cpu, dev);
-
-	return sprintf(buf, "%d\n", get_hard_smp_processor_id(cpu->dev.id));
-}
-static DEVICE_ATTR(physical_id, 0444, show_physical_id, NULL);
-
 static int __init topology_init(void)
 {
 	int cpu, r;
@@ -1049,7 +1052,6 @@ static int __init topology_init(void)
 		if (cpu_online(cpu) || c->hotpluggable) {
 			register_cpu(c, cpu);
 
-			device_create_file(&c->dev, &dev_attr_physical_id);
 		}
 	}
 	r = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "powerpc/topology:online",
diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index 652d3e96..697dfb7 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -367,6 +367,7 @@ static int dlpar_online_cpu(struct device_node *dn)
 			cpu_maps_update_done();
 			timed_topology_update(1);
 			find_and_online_cpu_nid(cpu);
+			register_cpu(&per_cpu(cpu_devices, cpu), cpu);
 			rc = device_online(get_cpu_device(cpu));
 			if (rc)
 				goto out;
@@ -541,6 +542,7 @@ static int dlpar_offline_cpu(struct device_node *dn)
 				rc = device_offline(get_cpu_device(cpu));
 				if (rc)
 					goto out;
+				unregister_cpu(container_of(get_cpu_device(cpu), struct cpu, dev));
 				cpu_maps_update_begin();
 				break;
 
@@ -599,7 +601,6 @@ static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index)
 
 		return saved_rc;
 	}
-
 	pr_debug("Successfully removed CPU, drc index: %x\n", drc_index);
 	return 0;
 }
-- 
2.7.4