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-rw-r--r--Documentation/ABI/testing/sysfs-devices-system-cpu1
-rw-r--r--kernel/cpu.c60
2 files changed, 45 insertions, 16 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index ecd585ca2d50..6dba65fb1956 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -555,6 +555,7 @@ Description: Control Symmetric Multi Threading (SMT)
================ =========================================
"on" SMT is enabled
"off" SMT is disabled
+ "<N>" SMT is enabled with N threads per core.
"forceoff" SMT is force disabled. Cannot be changed.
"notsupported" SMT is not supported by the CPU
"notimplemented" SMT runtime toggling is not
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 9a8d0685e055..7e8f1b044772 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2876,11 +2876,19 @@ static const struct attribute_group cpuhp_cpu_root_attr_group = {
#ifdef CONFIG_HOTPLUG_SMT
+static bool cpu_smt_num_threads_valid(unsigned int threads)
+{
+ if (IS_ENABLED(CONFIG_SMT_NUM_THREADS_DYNAMIC))
+ return threads >= 1 && threads <= cpu_smt_max_threads;
+ return threads == 1 || threads == cpu_smt_max_threads;
+}
+
static ssize_t
__store_smt_control(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
- int ctrlval, ret;
+ int ctrlval, ret, num_threads, orig_threads;
+ bool force_off;
if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
return -EPERM;
@@ -2888,30 +2896,39 @@ __store_smt_control(struct device *dev, struct device_attribute *attr,
if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
return -ENODEV;
- if (sysfs_streq(buf, "on"))
+ if (sysfs_streq(buf, "on")) {
ctrlval = CPU_SMT_ENABLED;
- else if (sysfs_streq(buf, "off"))
+ num_threads = cpu_smt_max_threads;
+ } else if (sysfs_streq(buf, "off")) {
ctrlval = CPU_SMT_DISABLED;
- else if (sysfs_streq(buf, "forceoff"))
+ num_threads = 1;
+ } else if (sysfs_streq(buf, "forceoff")) {
ctrlval = CPU_SMT_FORCE_DISABLED;
- else
+ num_threads = 1;
+ } else if (kstrtoint(buf, 10, &num_threads) == 0) {
+ if (num_threads == 1)
+ ctrlval = CPU_SMT_DISABLED;
+ else if (cpu_smt_num_threads_valid(num_threads))
+ ctrlval = CPU_SMT_ENABLED;
+ else
+ return -EINVAL;
+ } else {
return -EINVAL;
+ }
ret = lock_device_hotplug_sysfs();
if (ret)
return ret;
- if (ctrlval != cpu_smt_control) {
- switch (ctrlval) {
- case CPU_SMT_ENABLED:
- ret = cpuhp_smt_enable();
- break;
- case CPU_SMT_DISABLED:
- case CPU_SMT_FORCE_DISABLED:
- ret = cpuhp_smt_disable(ctrlval);
- break;
- }
- }
+ orig_threads = cpu_smt_num_threads;
+ cpu_smt_num_threads = num_threads;
+
+ force_off = ctrlval != cpu_smt_control && ctrlval == CPU_SMT_FORCE_DISABLED;
+
+ if (num_threads > orig_threads)
+ ret = cpuhp_smt_enable();
+ else if (num_threads < orig_threads || force_off)
+ ret = cpuhp_smt_disable(ctrlval);
unlock_device_hotplug();
return ret ? ret : count;
@@ -2939,6 +2956,17 @@ static ssize_t control_show(struct device *dev,
{
const char *state = smt_states[cpu_smt_control];
+#ifdef CONFIG_HOTPLUG_SMT
+ /*
+ * If SMT is enabled but not all threads are enabled then show the
+ * number of threads. If all threads are enabled show "on". Otherwise
+ * show the state name.
+ */
+ if (cpu_smt_control == CPU_SMT_ENABLED &&
+ cpu_smt_num_threads != cpu_smt_max_threads)
+ return sysfs_emit(buf, "%d\n", cpu_smt_num_threads);
+#endif
+
return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
}