3 files changed, 47 insertions, 30 deletions

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 9605dbd4b5b5..5eea46fefcb2 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -511,10 +511,12 @@ Description:	Control Symetric Multi Threading (SMT)
                 control: Read/write interface to control SMT. Possible
                          values:
 
-                         "on"           SMT is enabled
-                         "off"          SMT is disabled
-                         "forceoff"     SMT is force disabled. Cannot be changed.
-                         "notsupported" SMT is not supported by the CPU
+                         "on"             SMT is enabled
+                         "off"            SMT is disabled
+                         "forceoff"       SMT is force disabled. Cannot be changed.
+                         "notsupported"   SMT is not supported by the CPU
+                         "notimplemented" SMT runtime toggling is not
+                                          implemented for the architecture
 
                          If control status is "forceoff" or "notsupported" writes
                          are rejected.
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 5041357d0297..ae99dde02320 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -175,6 +175,7 @@ enum cpuhp_smt_control {
         CPU_SMT_DISABLED,
         CPU_SMT_FORCE_DISABLED,
         CPU_SMT_NOT_SUPPORTED,
+        CPU_SMT_NOT_IMPLEMENTED,
 };
 
 #if defined(CONFIG_SMP) && defined(CONFIG_HOTPLUG_SMT)
@@ -182,7 +183,7 @@ extern enum cpuhp_smt_control cpu_smt_control;
 extern void cpu_smt_disable(bool force);
 extern void cpu_smt_check_topology(void);
 #else
-# define cpu_smt_control                (CPU_SMT_ENABLED)
+# define cpu_smt_control                (CPU_SMT_NOT_IMPLEMENTED)
 static inline void cpu_smt_disable(bool force) { }
 static inline void cpu_smt_check_topology(void) { }
 #endif
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 6754f3ecfd94..b8bf3f93e39b 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2033,19 +2033,6 @@ 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);
@@ -2116,9 +2103,10 @@ 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;
 
@@ -2156,14 +2144,44 @@ 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);
 
@@ -2179,21 +2197,17 @@ 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;
 
@@ -2214,7 +2228,7 @@ 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