diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index 77942eedf4f69055134a7c654b49acdfd02948c9..183a07c4f1916bf0a9e62a93d0747b76115c5994 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -556,6 +556,7 @@ 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/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst
index e6f5bc39cf5c632a220a7614d26e97f4ca57efe9..b9ae591d0b180e863f500c8511a1a3bfe1eafad9 100644
--- a/Documentation/core-api/cpu_hotplug.rst
+++ b/Documentation/core-api/cpu_hotplug.rst
@@ -395,8 +395,8 @@ multi-instance state the following function is available:
* cpuhp_setup_state_multi(state, name, startup, teardown)
The @state argument is either a statically allocated state or one of the
-constants for dynamically allocated states - CPUHP_PREPARE_DYN,
-CPUHP_ONLINE_DYN - depending on the state section (PREPARE, ONLINE) for
+constants for dynamically allocated states - CPUHP_BP_PREPARE_DYN,
+CPUHP_AP_ONLINE_DYN - depending on the state section (PREPARE, ONLINE) for
which a dynamic state should be allocated.
The @name argument is used for sysfs output and for instrumentation. The
@@ -588,7 +588,7 @@ notifications on online and offline operations::
Setup and teardown a dynamically allocated state in the ONLINE section
for notifications on offline operations::
- state = cpuhp_setup_state(CPUHP_ONLINE_DYN, "subsys:offline", NULL, subsys_cpu_offline);
+ state = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "subsys:offline", NULL, subsys_cpu_offline);
if (state < 0)
return state;
....
@@ -597,7 +597,7 @@ for notifications on offline operations::
Setup and teardown a dynamically allocated state in the ONLINE section
for notifications on online operations without invoking the callbacks::
- state = cpuhp_setup_state_nocalls(CPUHP_ONLINE_DYN, "subsys:online", subsys_cpu_online, NULL);
+ state = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "subsys:online", subsys_cpu_online, NULL);
if (state < 0)
return state;
....
@@ -606,7 +606,7 @@ for notifications on online operations without invoking the callbacks::
Setup, use and teardown a dynamically allocated multi-instance state in the
ONLINE section for notifications on online and offline operation::
- state = cpuhp_setup_state_multi(CPUHP_ONLINE_DYN, "subsys:online", subsys_cpu_online, subsys_cpu_offline);
+ state = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN, "subsys:online", subsys_cpu_online, subsys_cpu_offline);
if (state < 0)
return state;
....
diff --git a/arch/Kconfig b/arch/Kconfig
index aff2746c8af28b6ca56e3335e063936cbf911e33..63c5d6a2022bc3507e427a452cdd1d5d70121665 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -34,6 +34,9 @@ config ARCH_HAS_SUBPAGE_FAULTS
config HOTPLUG_SMT
bool
+config SMT_NUM_THREADS_DYNAMIC
+ bool
+
# Selected by HOTPLUG_CORE_SYNC_DEAD or HOTPLUG_CORE_SYNC_FULL
config HOTPLUG_CORE_SYNC
bool
diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h
index caf41c4869a0e470fc63a880d355460cbae02a2e..3235ba1e5b06d77f4f40962ef44888e62d30988c 100644
--- a/arch/x86/include/asm/topology.h
+++ b/arch/x86/include/asm/topology.h
@@ -136,10 +136,11 @@ static inline int topology_max_smt_threads(void)
return __max_smt_threads;
}
+#include <linux/cpu_smt.h>
+
int topology_update_package_map(unsigned int apicid, unsigned int cpu);
int topology_update_die_map(unsigned int dieid, unsigned int cpu);
int topology_phys_to_logical_pkg(unsigned int pkg);
-bool topology_smt_supported(void);
extern struct cpumask __cpu_primary_thread_mask;
#define cpu_primary_thread_mask ((const struct cpumask *)&__cpu_primary_thread_mask)
@@ -162,7 +163,6 @@ static inline int topology_phys_to_logical_pkg(unsigned int pkg) { return 0; }
static inline int topology_max_die_per_package(void) { return 1; }
static inline int topology_max_smt_threads(void) { return 1; }
static inline bool topology_is_primary_thread(unsigned int cpu) { return true; }
-static inline bool topology_smt_supported(void) { return false; }
#endif /* !CONFIG_SMP */
static inline void arch_fix_phys_package_id(int num, u32 slot)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index e3a65e9fc750db893798562a83ac0f5b1b0e9e0f..281fc3f6ea6bd61b2094b3e0ca6577e17593fdae 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2343,7 +2343,7 @@ void __init arch_cpu_finalize_init(void)
* identify_boot_cpu() initialized SMT support information, let the
* core code know.
*/
- cpu_smt_check_topology();
+ cpu_smt_set_num_threads(smp_num_siblings, smp_num_siblings);
if (!IS_ENABLED(CONFIG_SMP)) {
pr_info("CPU: ");
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index e1aa2cd7734ba40825f83ecfe01e25fd41b8e5a4..d4e897b820c416baeef7f0c02959069fdd7ed0d3 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -326,14 +326,6 @@ static void notrace start_secondary(void *unused)
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}
-/**
- * topology_smt_supported - Check whether SMT is supported by the CPUs
- */
-bool topology_smt_supported(void)
-{
- return smp_num_siblings > 1;
-}
-
/**
* topology_phys_to_logical_pkg - Map a physical package id to a logical
* @phys_pkg: The physical package id to map
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index e006c719182bac98901586d58d4dea4d6e351b61..0abd60a7987b6803db3e02c5571cf4a2f6c94b88 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -18,6 +18,7 @@
#include <linux/compiler.h>
#include <linux/cpumask.h>
#include <linux/cpuhotplug.h>
+#include <linux/cpu_smt.h>
struct device;
struct device_node;
@@ -194,7 +195,6 @@ void arch_cpu_finalize_init(void);
static inline void arch_cpu_finalize_init(void) { }
#endif
-void cpu_set_state_online(int cpu);
void play_idle_precise(u64 duration_ns, u64 latency_ns);
static inline void play_idle(unsigned long duration_us)
@@ -208,30 +208,6 @@ void cpuhp_report_idle_dead(void);
static inline void cpuhp_report_idle_dead(void) { }
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-enum cpuhp_smt_control {
- CPU_SMT_ENABLED,
- CPU_SMT_DISABLED,
- CPU_SMT_FORCE_DISABLED,
- CPU_SMT_NOT_SUPPORTED,
- CPU_SMT_NOT_IMPLEMENTED,
-};
-
-#if defined(CONFIG_SMP) && defined(CONFIG_HOTPLUG_SMT)
-extern enum cpuhp_smt_control cpu_smt_control;
-extern void cpu_smt_disable(bool force);
-extern void cpu_smt_check_topology(void);
-extern bool cpu_smt_possible(void);
-extern int cpuhp_smt_enable(void);
-extern int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval);
-#else
-# define cpu_smt_control (CPU_SMT_NOT_IMPLEMENTED)
-static inline void cpu_smt_disable(bool force) { }
-static inline void cpu_smt_check_topology(void) { }
-static inline bool cpu_smt_possible(void) { return false; }
-static inline int cpuhp_smt_enable(void) { return 0; }
-static inline int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) { return 0; }
-#endif
-
extern bool cpu_mitigations_off(void);
extern bool cpu_mitigations_auto_nosmt(void);
diff --git a/include/linux/cpu_smt.h b/include/linux/cpu_smt.h
new file mode 100644
index 0000000000000000000000000000000000000000..0c1664294b579529fbd9690abdfad4e64d43aa9d
--- /dev/null
+++ b/include/linux/cpu_smt.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_CPU_SMT_H_
+#define _LINUX_CPU_SMT_H_
+
+enum cpuhp_smt_control {
+ CPU_SMT_ENABLED,
+ CPU_SMT_DISABLED,
+ CPU_SMT_FORCE_DISABLED,
+ CPU_SMT_NOT_SUPPORTED,
+ CPU_SMT_NOT_IMPLEMENTED,
+};
+
+#if defined(CONFIG_SMP) && defined(CONFIG_HOTPLUG_SMT)
+extern enum cpuhp_smt_control cpu_smt_control;
+extern unsigned int cpu_smt_num_threads;
+extern void cpu_smt_disable(bool force);
+extern void cpu_smt_set_num_threads(unsigned int num_threads,
+ unsigned int max_threads);
+extern bool cpu_smt_possible(void);
+extern int cpuhp_smt_enable(void);
+extern int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval);
+#else
+# define cpu_smt_control (CPU_SMT_NOT_IMPLEMENTED)
+# define cpu_smt_num_threads 1
+static inline void cpu_smt_disable(bool force) { }
+static inline void cpu_smt_set_num_threads(unsigned int num_threads,
+ unsigned int max_threads) { }
+static inline bool cpu_smt_possible(void) { return false; }
+static inline int cpuhp_smt_enable(void) { return 0; }
+static inline int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval) { return 0; }
+#endif
+
+#endif /* _LINUX_CPU_SMT_H_ */
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 25b6e6e6ba6bc2c2dd2a7c6a6fea2c685382c5a7..06dda85f042445bb0d4b017b7e2aecd5b0587651 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -48,7 +48,7 @@
* same section.
*
* If neither #1 nor #2 apply, please use the dynamic state space when
- * setting up a state by using CPUHP_PREPARE_DYN or CPUHP_PREPARE_ONLINE
+ * setting up a state by using CPUHP_BP_PREPARE_DYN or CPUHP_AP_ONLINE_DYN
* for the @state argument of the setup function.
*
* See Documentation/core-api/cpu_hotplug.rst for further information and
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 88a7ede322bd5ebe940b459dc45be5e7469015e1..f6811c857102329c4f543f496a31e647b886ebb3 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -592,7 +592,10 @@ static void lockdep_release_cpus_lock(void)
void __weak arch_smt_update(void) { }
#ifdef CONFIG_HOTPLUG_SMT
+
enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
+static unsigned int cpu_smt_max_threads __ro_after_init;
+unsigned int cpu_smt_num_threads __read_mostly = UINT_MAX;
void __init cpu_smt_disable(bool force)
{
@@ -606,16 +609,33 @@ void __init cpu_smt_disable(bool force)
pr_info("SMT: disabled\n");
cpu_smt_control = CPU_SMT_DISABLED;
}
+ cpu_smt_num_threads = 1;
}
/*
* The decision whether SMT is supported can only be done after the full
* CPU identification. Called from architecture code.
*/
-void __init cpu_smt_check_topology(void)
+void __init cpu_smt_set_num_threads(unsigned int num_threads,
+ unsigned int max_threads)
{
- if (!topology_smt_supported())
+ WARN_ON(!num_threads || (num_threads > max_threads));
+
+ if (max_threads == 1)
cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
+
+ cpu_smt_max_threads = max_threads;
+
+ /*
+ * If SMT has been disabled via the kernel command line or SMT is
+ * not supported, set cpu_smt_num_threads to 1 for consistency.
+ * If enabled, take the architecture requested number of threads
+ * to bring up into account.
+ */
+ if (cpu_smt_control != CPU_SMT_ENABLED)
+ cpu_smt_num_threads = 1;
+ else if (num_threads < cpu_smt_num_threads)
+ cpu_smt_num_threads = num_threads;
}
static int __init smt_cmdline_disable(char *str)
@@ -625,9 +645,23 @@ static int __init smt_cmdline_disable(char *str)
}
early_param("nosmt", smt_cmdline_disable);
+/*
+ * For Archicture supporting partial SMT states check if the thread is allowed.
+ * Otherwise this has already been checked through cpu_smt_max_threads when
+ * setting the SMT level.
+ */
+static inline bool cpu_smt_thread_allowed(unsigned int cpu)
+{
+#ifdef CONFIG_SMT_NUM_THREADS_DYNAMIC
+ return topology_smt_thread_allowed(cpu);
+#else
+ return true;
+#endif
+}
+
static inline bool cpu_smt_allowed(unsigned int cpu)
{
- if (cpu_smt_control == CPU_SMT_ENABLED)
+ if (cpu_smt_control == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
return true;
if (topology_is_primary_thread(cpu))
@@ -642,7 +676,7 @@ static inline bool cpu_smt_allowed(unsigned int cpu)
return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
}
-/* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
+/* Returns true if SMT is supported and not forcefully (irreversibly) disabled */
bool cpu_smt_possible(void)
{
return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
@@ -650,22 +684,8 @@ bool cpu_smt_possible(void)
}
EXPORT_SYMBOL_GPL(cpu_smt_possible);
-static inline bool cpuhp_smt_aware(void)
-{
- return topology_smt_supported();
-}
-
-static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
-{
- return cpu_primary_thread_mask;
-}
#else
static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
-static inline bool cpuhp_smt_aware(void) { return false; }
-static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
-{
- return cpu_present_mask;
-}
#endif
static inline enum cpuhp_state
@@ -1793,6 +1813,16 @@ static int __init parallel_bringup_parse_param(char *arg)
}
early_param("cpuhp.parallel", parallel_bringup_parse_param);
+static inline bool cpuhp_smt_aware(void)
+{
+ return cpu_smt_max_threads > 1;
+}
+
+static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
+{
+ return cpu_primary_thread_mask;
+}
+
/*
* On architectures which have enabled parallel bringup this invokes all BP
* prepare states for each of the to be onlined APs first. The last state
@@ -2626,6 +2656,12 @@ int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
for_each_online_cpu(cpu) {
if (topology_is_primary_thread(cpu))
continue;
+ /*
+ * Disable can be called with CPU_SMT_ENABLED when changing
+ * from a higher to lower number of SMT threads per core.
+ */
+ if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
+ continue;
ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
if (ret)
break;
@@ -2660,6 +2696,8 @@ int cpuhp_smt_enable(void)
/* Skip online CPUs and CPUs on offline nodes */
if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
continue;
+ if (!cpu_smt_thread_allowed(cpu))
+ continue;
ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
if (ret)
break;
@@ -2838,20 +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;
-
- if (sysfs_streq(buf, "on"))
- ctrlval = CPU_SMT_ENABLED;
- else if (sysfs_streq(buf, "off"))
- ctrlval = CPU_SMT_DISABLED;
- else if (sysfs_streq(buf, "forceoff"))
- ctrlval = CPU_SMT_FORCE_DISABLED;
- else
- return -EINVAL;
+ int ctrlval, ret, num_threads, orig_threads;
+ bool force_off;
if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
return -EPERM;
@@ -2859,21 +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")) {
+ ctrlval = CPU_SMT_ENABLED;
+ num_threads = cpu_smt_max_threads;
+ } else if (sysfs_streq(buf, "off")) {
+ ctrlval = CPU_SMT_DISABLED;
+ num_threads = 1;
+ } else if (sysfs_streq(buf, "forceoff")) {
+ ctrlval = CPU_SMT_FORCE_DISABLED;
+ 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;
@@ -2901,6 +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);
}