1 files changed, 173 insertions, 9 deletions

diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index ebff6d9a4e39..6ea4698d9176 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -30,6 +30,7 @@
 #include <asm/pSeries_reconfig.h>
 #include "xics.h"
 #include "plpar_wrappers.h"
+#include "offline_states.h"
 
 /* This version can't take the spinlock, because it never returns */
 static struct rtas_args rtas_stop_self_args = {
@@ -39,6 +40,55 @@ static struct rtas_args rtas_stop_self_args = {
         .rets = &rtas_stop_self_args.args[0],
 };
 
+static DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) =
+                                                        CPU_STATE_OFFLINE;
+static DEFINE_PER_CPU(enum cpu_state_vals, current_state) = CPU_STATE_OFFLINE;
+
+static enum cpu_state_vals default_offline_state = CPU_STATE_OFFLINE;
+
+static int cede_offline_enabled __read_mostly = 1;
+
+/*
+ * Enable/disable cede_offline when available.
+ */
+static int __init setup_cede_offline(char *str)
+{
+        if (!strcmp(str, "off"))
+                cede_offline_enabled = 0;
+        else if (!strcmp(str, "on"))
+                cede_offline_enabled = 1;
+        else
+                return 0;
+        return 1;
+}
+
+__setup("cede_offline=", setup_cede_offline);
+
+enum cpu_state_vals get_cpu_current_state(int cpu)
+{
+        return per_cpu(current_state, cpu);
+}
+
+void set_cpu_current_state(int cpu, enum cpu_state_vals state)
+{
+        per_cpu(current_state, cpu) = state;
+}
+
+enum cpu_state_vals get_preferred_offline_state(int cpu)
+{
+        return per_cpu(preferred_offline_state, cpu);
+}
+
+void set_preferred_offline_state(int cpu, enum cpu_state_vals state)
+{
+        per_cpu(preferred_offline_state, cpu) = state;
+}
+
+void set_default_offline_state(int cpu)
+{
+        per_cpu(preferred_offline_state, cpu) = default_offline_state;
+}
+
 static void rtas_stop_self(void)
 {
         struct rtas_args *args = &rtas_stop_self_args;
@@ -56,11 +106,61 @@ static void rtas_stop_self(void)
 
 static void pseries_mach_cpu_die(void)
 {
+        unsigned int cpu = smp_processor_id();
+        unsigned int hwcpu = hard_smp_processor_id();
+        u8 cede_latency_hint = 0;
+
         local_irq_disable();
         idle_task_exit();
         xics_teardown_cpu();
-        unregister_slb_shadow(hard_smp_processor_id(), __pa(get_slb_shadow()));
-        rtas_stop_self();
+
+        if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
+                set_cpu_current_state(cpu, CPU_STATE_INACTIVE);
+                cede_latency_hint = 2;
+
+                get_lppaca()->idle = 1;
+                if (!get_lppaca()->shared_proc)
+                        get_lppaca()->donate_dedicated_cpu = 1;
+
+                printk(KERN_INFO
+                        "cpu %u (hwid %u) ceding for offline with hint %d\n",
+                        cpu, hwcpu, cede_latency_hint);
+                while (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
+                        extended_cede_processor(cede_latency_hint);
+                        printk(KERN_INFO "cpu %u (hwid %u) returned from cede.\n",
+                                cpu, hwcpu);
+                        printk(KERN_INFO
+                        "Decrementer value = %x Timebase value = %llx\n",
+                        get_dec(), get_tb());
+                }
+
+                printk(KERN_INFO "cpu %u (hwid %u) got prodded to go online\n",
+                        cpu, hwcpu);
+
+                if (!get_lppaca()->shared_proc)
+                        get_lppaca()->donate_dedicated_cpu = 0;
+                get_lppaca()->idle = 0;
+        }
+
+        if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
+                unregister_slb_shadow(hwcpu, __pa(get_slb_shadow()));
+
+                /*
+                 * NOTE: Calling start_secondary() here for now to
+                 * start new context.
+                 * However, need to do it cleanly by resetting the
+                 * stack pointer.
+                 */
+                start_secondary();
+
+        } else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
+
+                set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
+                unregister_slb_shadow(hard_smp_processor_id(),
+                                        __pa(get_slb_shadow()));
+                rtas_stop_self();
+        }
+
         /* Should never get here... */
         BUG();
         for(;;);
@@ -106,18 +206,43 @@ static int pseries_cpu_disable(void)
         return 0;
 }
 
+/*
+ * pseries_cpu_die: Wait for the cpu to die.
+ * @cpu: logical processor id of the CPU whose death we're awaiting.
+ *
+ * This function is called from the context of the thread which is performing
+ * the cpu-offline. Here we wait for long enough to allow the cpu in question
+ * to self-destroy so that the cpu-offline thread can send the CPU_DEAD
+ * notifications.
+ *
+ * OTOH, pseries_mach_cpu_die() is called by the @cpu when it wants to
+ * self-destruct.
+ */
 static void pseries_cpu_die(unsigned int cpu)
 {
         int tries;
-        int cpu_status;
+        int cpu_status = 1;
         unsigned int pcpu = get_hard_smp_processor_id(cpu);
 
-        for (tries = 0; tries < 25; tries++) {
-                cpu_status = query_cpu_stopped(pcpu);
-                if (cpu_status == 0 || cpu_status == -1)
-                        break;
-                cpu_relax();
+        if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
+                cpu_status = 1;
+                for (tries = 0; tries < 1000; tries++) {
+                        if (get_cpu_current_state(cpu) == CPU_STATE_INACTIVE) {
+                                cpu_status = 0;
+                                break;
+                        }
+                        cpu_relax();
+                }
+        } else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
+
+                for (tries = 0; tries < 25; tries++) {
+                        cpu_status = query_cpu_stopped(pcpu);
+                        if (cpu_status == 0 || cpu_status == -1)
+                                break;
+                        cpu_relax();
+                }
         }
+
         if (cpu_status != 0) {
                 printk("Querying DEAD? cpu %i (%i) shows %i\n",
                        cpu, pcpu, cpu_status);
@@ -252,10 +377,41 @@ static struct notifier_block pseries_smp_nb = {
         .notifier_call = pseries_smp_notifier,
 };
 
+#define MAX_CEDE_LATENCY_LEVELS         4
+#define CEDE_LATENCY_PARAM_LENGTH       10
+#define CEDE_LATENCY_PARAM_MAX_LENGTH   \
+        (MAX_CEDE_LATENCY_LEVELS * CEDE_LATENCY_PARAM_LENGTH * sizeof(char))
+#define CEDE_LATENCY_TOKEN              45
+
+static char cede_parameters[CEDE_LATENCY_PARAM_MAX_LENGTH];
+
+static int parse_cede_parameters(void)
+{
+        int call_status;
+
+        memset(cede_parameters, 0, CEDE_LATENCY_PARAM_MAX_LENGTH);
+        call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
+                                NULL,
+                                CEDE_LATENCY_TOKEN,
+                                __pa(cede_parameters),
+                                CEDE_LATENCY_PARAM_MAX_LENGTH);
+
+        if (call_status != 0)
+                printk(KERN_INFO "CEDE_LATENCY: \
+                        %s %s Error calling get-system-parameter(0x%x)\n",
+                        __FILE__, __func__, call_status);
+        else
+                printk(KERN_INFO "CEDE_LATENCY: \
+                        get-system-parameter successful.\n");
+
+        return call_status;
+}
+
 static int __init pseries_cpu_hotplug_init(void)
 {
         struct device_node *np;
         const char *typep;
+        int cpu;
 
         for_each_node_by_name(np, "interrupt-controller") {
                 typep = of_get_property(np, "compatible", NULL);
@@ -283,8 +439,16 @@ static int __init pseries_cpu_hotplug_init(void)
         smp_ops->cpu_die = pseries_cpu_die;
 
         /* Processors can be added/removed only on LPAR */
-        if (firmware_has_feature(FW_FEATURE_LPAR))
+        if (firmware_has_feature(FW_FEATURE_LPAR)) {
                 pSeries_reconfig_notifier_register(&pseries_smp_nb);
+                cpu_maps_update_begin();
+                if (cede_offline_enabled && parse_cede_parameters() == 0) {
+                        default_offline_state = CPU_STATE_INACTIVE;
+                        for_each_online_cpu(cpu)
+                                set_default_offline_state(cpu);
+                }
+                cpu_maps_update_done();
+        }
 
         return 0;
 }