[PATCH v2 4/6] powerpc/pseries: Add CPU dlpar remove functionality

Nathan Fontenot nfont at linux.vnet.ibm.com
Wed Oct 28 05:26:48 AEDT 2015


Add the ability to dlpar remove CPUs via hotplug rtas events, either by
specifying the drc-index of the CPU to remove or providing a count of cpus
to remove.

To remove multiple cpus in a single request we create a list of possible
DR (Dynamic Reconfiguration) cpus and their drc indexes that can be
removed.  We can then traverse the list remove each cpu and easily clean
up in any cases of failure.

Signed-off-by: Nathan Fontenot <nfont at linux.vnet.ibm.com>
---

Updates for v2:
- use for_each_node_by_type() instead of for_each_child_of_node
- updated how the list of cpus to remove is generated
- change to remove all cpus requested or none at all
- put function declarations under CONFIG_HOTPLUG_CPU

 arch/powerpc/platforms/pseries/hotplug-cpu.c |  138 ++++++++++++++++++++++++++
 arch/powerpc/platforms/pseries/pseries.h     |    9 ++
 2 files changed, 147 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index f080e81..635f0ba 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -26,6 +26,7 @@
 #include <linux/sched.h>	/* for idle_task_exit */
 #include <linux/cpu.h>
 #include <linux/of.h>
+#include <linux/slab.h>
 #include <asm/prom.h>
 #include <asm/rtas.h>
 #include <asm/firmware.h>
@@ -570,6 +571,143 @@ static ssize_t dlpar_cpu_remove(struct device_node *dn, u32 drc_index)
 	return 0;
 }
 
+static struct device_node *cpu_drc_index_to_dn(u32 drc_index)
+{
+	struct device_node *dn;
+	u32 my_index;
+	int rc;
+
+	for_each_node_by_type(dn, "cpu") {
+		rc = of_property_read_u32(dn, "ibm,my-drc-index", &my_index);
+		if (rc)
+			continue;
+
+		if (my_index == drc_index)
+			break;
+	}
+
+	return dn;
+}
+
+static int dlpar_cpu_remove_by_index(u32 drc_index)
+{
+	struct device_node *dn;
+	int rc;
+
+	dn = cpu_drc_index_to_dn(drc_index);
+	if (!dn)
+		return -ENODEV;
+
+	rc = dlpar_cpu_remove(dn, drc_index);
+	of_node_put(dn);
+	return rc;
+}
+
+static u32 *dlpar_cpus_to_remove(int cpus_to_remove)
+{
+	struct device_node *dn;
+	u32 *cpu_drcs;
+	int cpus_found = 0;
+	int i, rc;
+
+	cpu_drcs = kcalloc(cpus_to_remove, sizeof(*cpu_drcs), GFP_KERNEL);
+	if (!cpu_drcs)
+		return NULL;
+
+	i = 0;
+	for_each_node_by_type(dn, "cpu") {
+		cpus_found++;
+
+		if (cpus_found > cpus_to_remove) {
+			of_node_put(dn);
+			break;
+		}
+
+		rc = of_property_read_u32(dn, "ibm,my-drc-index",
+					  &cpu_drcs[i++]);
+		if (rc) {
+			of_node_put(dn);
+			break;
+		}
+	}
+
+	/* We want to find cpus_to_remove + 1 CPUs to ensure we do not
+	 * remove the last CPU.
+	 */
+	if (cpus_found <= cpus_to_remove) {
+		pr_warn("Failed to find enough CPUs (%d of %d) to remove\n",
+			cpus_found, cpus_to_remove);
+		kfree(cpu_drcs);
+		cpu_drcs = NULL;
+	}
+
+	return cpu_drcs;
+}
+
+static int dlpar_cpu_remove_by_count(u32 cpus_to_remove)
+{
+	u32 *cpu_drcs;
+	int cpus_removed = 0;
+	int i, rc;
+
+	pr_debug("Attempting to hot-remove %d CPUs\n", cpus_to_remove);
+
+	cpu_drcs = dlpar_cpus_to_remove(cpus_to_remove);
+	if (!cpu_drcs)
+		return -EINVAL;
+
+	for (i = 0; i < cpus_to_remove; i++) {
+		rc = dlpar_cpu_remove_by_index(cpu_drcs[i]);
+		if (rc)
+			break;
+
+		cpus_removed++;
+	}
+
+	if (cpus_removed != cpus_to_remove) {
+		pr_warn("CPU hot-remove failed, adding back removed CPUs\n");
+
+		for (i = 0; i < cpus_removed; i++)
+			dlpar_cpu_add(cpu_drcs[i]);
+
+		rc = -EINVAL;
+	} else {
+		rc = 0;
+	}
+
+	kfree(cpu_drcs);
+	return rc;
+}
+
+int dlpar_cpu(struct pseries_hp_errorlog *hp_elog)
+{
+	u32 count, drc_index;
+	int rc;
+
+	count = hp_elog->_drc_u.drc_count;
+	drc_index = hp_elog->_drc_u.drc_index;
+
+	lock_device_hotplug();
+
+	switch (hp_elog->action) {
+	case PSERIES_HP_ELOG_ACTION_REMOVE:
+		if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_COUNT)
+			rc = dlpar_cpu_remove_by_count(count);
+		else if (hp_elog->id_type == PSERIES_HP_ELOG_ID_DRC_INDEX)
+			rc = dlpar_cpu_remove_by_index(drc_index);
+		else
+			rc = -EINVAL;
+		break;
+	default:
+		pr_err("Invalid action (%d) specified\n", hp_elog->action);
+		rc = -EINVAL;
+		break;
+	}
+
+	unlock_device_hotplug();
+	return rc;
+}
+
 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 
 static ssize_t dlpar_cpu_probe(const char *buf, size_t count)
diff --git a/arch/powerpc/platforms/pseries/pseries.h b/arch/powerpc/platforms/pseries/pseries.h
index 8411c27..7aa83f0 100644
--- a/arch/powerpc/platforms/pseries/pseries.h
+++ b/arch/powerpc/platforms/pseries/pseries.h
@@ -73,6 +73,15 @@ static inline int dlpar_memory(struct pseries_hp_errorlog *hp_elog)
 }
 #endif
 
+#ifdef CONFIG_HOTPLUG_CPU
+int dlpar_cpu(struct pseries_hp_errorlog *hp_elog);
+#else
+static inline int dlpar_cpu(struct pseries_hp_errorlog *hp_elog)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
 /* PCI root bridge prepare function override for pseries */
 struct pci_host_bridge;
 int pseries_root_bridge_prepare(struct pci_host_bridge *bridge);



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