Make the /sys/devices/system/cpu/smt/* files available on all arches, so
user space has a consistent way to detect whether SMT is enabled.
The 'control' file now shows 'notsupported' for architectures which
don't yet have CONFIG_HOTPLUG_SMT.
Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
---
.../ABI/testing/sysfs-devices-system-cpu | 3 +-
include/linux/cpu.h | 2 +-
kernel/cpu.c | 68 +++++++++++--------
3 files changed, 43 insertions(+), 30 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu
b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 9605dbd4b5b5..4a11cba73085 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -514,7 +514,8 @@ Description: Control Symetric Multi Threading (SMT)
"on" SMT is enabled
"off" SMT is disabled
"forceoff" SMT is force disabled. Cannot be
changed.
- "notsupported" SMT is not supported by the CPU
+ "notsupported" Runtime SMT toggling is not currently
+ supported 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..296753249343 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -182,7 +182,7 @@ 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_SUPPORTED)
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 025f419d16f6..517ab1803a22 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2017,19 +2017,6 @@ 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 +2087,10 @@ 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;
@@ -2118,9 +2106,6 @@ store_smt_control(struct device *dev, struct
device_attribute *attr,
if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
return -EPERM;
- if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
- return -ENODEV;
-
ret = lock_device_hotplug_sysfs();
if (ret)
return ret;
@@ -2140,14 +2125,45 @@ 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 0;
+}
+#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",
+};
+
+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 ssize_t
+store_smt_control(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+
+ if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
+ return -ENODEV;
+
+ 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 +2179,17 @@ 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 +2210,7 @@ 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
--
2.17.2
