1 files changed, 83 insertions, 28 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 025f419d16f6..f2ef10460698 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -9,6 +9,7 @@
 #include <linux/notifier.h>
 #include <linux/sched/signal.h>
 #include <linux/sched/hotplug.h>
+#include <linux/sched/isolation.h>
 #include <linux/sched/task.h>
 #include <linux/sched/smt.h>
 #include <linux/unistd.h>
@@ -564,6 +565,20 @@ static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
                 cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
 }
 
+static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
+{
+        if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
+                return true;
+        /*
+         * When CPU hotplug is disabled, then taking the CPU down is not
+         * possible because takedown_cpu() and the architecture and
+         * subsystem specific mechanisms are not available. So the CPU
+         * which would be completely unplugged again needs to stay around
+         * in the current state.
+         */
+        return st->state <= CPUHP_BRINGUP_CPU;
+}
+
 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
                               enum cpuhp_state target)
 {
@@ -574,8 +589,10 @@ static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
                 st->state++;
                 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
                 if (ret) {
-                        st->target = prev_state;
-                        undo_cpu_up(cpu, st);
+                        if (can_rollback_cpu(st)) {
+                                st->target = prev_state;
+                                undo_cpu_up(cpu, st);
+                        }
                         break;
                 }
         }
@@ -844,6 +861,8 @@ static int take_cpu_down(void *_param)
 
         /* Give up timekeeping duties */
         tick_handover_do_timer();
+        /* Remove CPU from timer broadcasting */
+        tick_offline_cpu(cpu);
         /* Park the stopper thread */
         stop_machine_park(cpu);
         return 0;
@@ -1183,8 +1202,15 @@ int freeze_secondary_cpus(int primary)
         int cpu, error = 0;
 
         cpu_maps_update_begin();
-        if (!cpu_online(primary))
+        if (primary == -1) {
                 primary = cpumask_first(cpu_online_mask);
+                if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
+                        primary = housekeeping_any_cpu(HK_FLAG_TIMER);
+        } else {
+                if (!cpu_online(primary))
+                        primary = cpumask_first(cpu_online_mask);
+        }
+
         /*
          * We take down all of the non-boot CPUs in one shot to avoid races
          * with the userspace trying to use the CPU hotplug at the same time
@@ -2017,19 +2043,6 @@ static const struct attribute_group cpuhp_cpu_root_attr_group = {
 
 #ifdef CONFIG_HOTPLUG_SMT
 
-static const char *smt_states[] = {
-        [CPU_SMT_ENABLED]               = "on",
-        [CPU_SMT_DISABLED]              = "off",
-        [CPU_SMT_FORCE_DISABLED]        = "forceoff",
-        [CPU_SMT_NOT_SUPPORTED]         = "notsupported",
-};
-
-static ssize_t
-show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
-{
-        return snprintf(buf, PAGE_SIZE - 2, "%s\n", smt_states[cpu_smt_control]);
-}
-
 static void cpuhp_offline_cpu_device(unsigned int cpu)
 {
         struct device *dev = get_cpu_device(cpu);
@@ -2100,9 +2113,10 @@ static int cpuhp_smt_enable(void)
         return ret;
 }
 
+
 static ssize_t
-store_smt_control(struct device *dev, struct device_attribute *attr,
-                  const char *buf, size_t count)
+__store_smt_control(struct device *dev, struct device_attribute *attr,
+                    const char *buf, size_t count)
 {
         int ctrlval, ret;
 
@@ -2140,14 +2154,44 @@ store_smt_control(struct device *dev, struct device_attribute *attr,
         unlock_device_hotplug();
         return ret ? ret : count;
 }
+
+#else /* !CONFIG_HOTPLUG_SMT */
+static ssize_t
+__store_smt_control(struct device *dev, struct device_attribute *attr,
+                    const char *buf, size_t count)
+{
+        return -ENODEV;
+}
+#endif /* CONFIG_HOTPLUG_SMT */
+
+static const char *smt_states[] = {
+        [CPU_SMT_ENABLED]               = "on",
+        [CPU_SMT_DISABLED]              = "off",
+        [CPU_SMT_FORCE_DISABLED]        = "forceoff",
+        [CPU_SMT_NOT_SUPPORTED]         = "notsupported",
+        [CPU_SMT_NOT_IMPLEMENTED]       = "notimplemented",
+};
+
+static ssize_t
+show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
+{
+        const char *state = smt_states[cpu_smt_control];
+
+        return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
+}
+
+static ssize_t
+store_smt_control(struct device *dev, struct device_attribute *attr,
+                  const char *buf, size_t count)
+{
+        return __store_smt_control(dev, attr, buf, count);
+}
 static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
 
 static ssize_t
 show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
 {
-        bool active = topology_max_smt_threads() > 1;
-
-        return snprintf(buf, PAGE_SIZE - 2, "%d\n", active);
+        return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
 }
 static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
 
@@ -2163,21 +2207,17 @@ static const struct attribute_group cpuhp_smt_attr_group = {
         NULL
 };
 
-static int __init cpu_smt_state_init(void)
+static int __init cpu_smt_sysfs_init(void)
 {
         return sysfs_create_group(&cpu_subsys.dev_root->kobj,
                                   &cpuhp_smt_attr_group);
 }
 
-#else
-static inline int cpu_smt_state_init(void) { return 0; }
-#endif
-
 static int __init cpuhp_sysfs_init(void)
 {
         int cpu, ret;
 
-        ret = cpu_smt_state_init();
+        ret = cpu_smt_sysfs_init();
         if (ret)
                 return ret;
 
@@ -2198,7 +2238,7 @@ static int __init cpuhp_sysfs_init(void)
         return 0;
 }
 device_initcall(cpuhp_sysfs_init);
-#endif
+#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
 
 /*
  * cpu_bit_bitmap[] is a special, "compressed" data structure that
@@ -2288,3 +2328,18 @@ void __init boot_cpu_hotplug_init(void)
 #endif
         this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
 }
+
+enum cpu_mitigations cpu_mitigations __ro_after_init = CPU_MITIGATIONS_AUTO;
+
+static int __init mitigations_parse_cmdline(char *arg)
+{
+        if (!strcmp(arg, "off"))
+                cpu_mitigations = CPU_MITIGATIONS_OFF;
+        else if (!strcmp(arg, "auto"))
+                cpu_mitigations = CPU_MITIGATIONS_AUTO;
+        else if (!strcmp(arg, "auto,nosmt"))
+                cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
+
+        return 0;
+}
+early_param("mitigations", mitigations_parse_cmdline);