From 7a4dcb4a5de1214c4a59448a759e2e264c2c4473 Mon Sep 17 00:00:00 2001 From: Laurent Dufour Date: Wed, 5 Jul 2023 16:51:34 +0200 Subject: [PATCH 01/10] cpu/hotplug: Remove dependancy against cpu_primary_thread_mask The commit 18415f33e2ac ("cpu/hotplug: Allow "parallel" bringup up to CPUHP_BP_KICK_AP_STATE") introduce a dependancy against a global variable cpu_primary_thread_mask exported by the X86 code. This variable is only used when CONFIG_HOTPLUG_PARALLEL is set. Since cpuhp_get_primary_thread_mask() and cpuhp_smt_aware() are only used when CONFIG_HOTPLUG_PARALLEL is set, don't define them when it is not set. No functional change. Signed-off-by: Laurent Dufour Signed-off-by: Thomas Gleixner Tested-by: Zhang Rui Link: https://lore.kernel.org/r/20230705145143.40545-2-ldufour@linux.ibm.com --- kernel/cpu.c | 24 ++++++++++-------------- 1 file changed, 10 insertions(+), 14 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 88a7ede322bd..03309f2f35a4 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -650,22 +650,8 @@ 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 +1779,16 @@ 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 topology_smt_supported(); +} + +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 From 3f9169196be55590a794b52f49637561ddd1ba4f Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 5 Jul 2023 16:51:35 +0200 Subject: [PATCH 02/10] cpu/SMT: Move SMT prototypes into cpu_smt.h In order to export the cpuhp_smt_control enum as part of the interface between generic and architecture code, the architecture code needs to include asm/topology.h. But that leads to circular header dependencies. So split the enum and related declarations into a separate header. [ ldufour: Reworded the commit's description ] Signed-off-by: Michael Ellerman Signed-off-by: Laurent Dufour Signed-off-by: Thomas Gleixner Tested-by: Zhang Rui Link: https://lore.kernel.org/r/20230705145143.40545-3-ldufour@linux.ibm.com --- arch/x86/include/asm/topology.h | 2 ++ include/linux/cpu.h | 25 +------------------------ include/linux/cpu_smt.h | 29 +++++++++++++++++++++++++++++ kernel/cpu.c | 1 + 4 files changed, 33 insertions(+), 24 deletions(-) create mode 100644 include/linux/cpu_smt.h diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h index caf41c4869a0..ae49ed4417d0 100644 --- a/arch/x86/include/asm/topology.h +++ b/arch/x86/include/asm/topology.h @@ -136,6 +136,8 @@ static inline int topology_max_smt_threads(void) return __max_smt_threads; } +#include + 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); diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 6e6e57ec69e8..6b326a9e8191 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -18,6 +18,7 @@ #include #include #include +#include struct device; struct device_node; @@ -204,30 +205,6 @@ 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 000000000000..722c2e306fef --- /dev/null +++ b/include/linux/cpu_smt.h @@ -0,0 +1,29 @@ +/* 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 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 + +#endif /* _LINUX_CPU_SMT_H_ */ diff --git a/kernel/cpu.c b/kernel/cpu.c index 03309f2f35a4..e02204c4675a 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -592,6 +592,7 @@ 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; void __init cpu_smt_disable(bool force) From c53361ce7d8771129c517dca529d2f2dc5bf04d1 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 5 Jul 2023 16:51:36 +0200 Subject: [PATCH 03/10] cpu/SMT: Move smt/control simple exit cases earlier Move the simple exit cases, i.e. those which don't depend on the value written, earlier in the function. That makes it clearer that regardless of the input those states cannot be transitioned out of. That does have a user-visible effect, in that the error returned will now always be EPERM/ENODEV for those states, regardless of the value written. Previously writing an invalid value would return EINVAL even when in those states. Signed-off-by: Michael Ellerman Signed-off-by: Thomas Gleixner Tested-by: Zhang Rui Link: https://lore.kernel.org/r/20230705145143.40545-4-ldufour@linux.ibm.com --- kernel/cpu.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index e02204c4675a..b6fe170c93e9 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -2841,6 +2841,12 @@ __store_smt_control(struct device *dev, struct device_attribute *attr, { int ctrlval, ret; + if (cpu_smt_control == CPU_SMT_FORCE_DISABLED) + return -EPERM; + + if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED) + return -ENODEV; + if (sysfs_streq(buf, "on")) ctrlval = CPU_SMT_ENABLED; else if (sysfs_streq(buf, "off")) @@ -2850,12 +2856,6 @@ __store_smt_control(struct device *dev, struct device_attribute *attr, else return -EINVAL; - 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; From 447ae4ac41130a7f127c2581a5e816bb0800b560 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 5 Jul 2023 16:51:37 +0200 Subject: [PATCH 04/10] cpu/SMT: Store the current/max number of threads Some architectures allow partial SMT states at boot time, ie. when not all SMT threads are brought online. To support that the SMT code needs to know the maximum number of SMT threads, and also the currently configured number. The architecture code knows the max number of threads, so have the architecture code pass that value to cpu_smt_set_num_threads(). Note that although topology_max_smt_threads() exists, it is not configured early enough to be used here. As architecture, like PowerPC, allows the threads number to be set through the kernel command line, also pass that value. [ ldufour: Slightly reword the commit message ] [ ldufour: Rename cpu_smt_check_topology and add a num_threads argument ] Signed-off-by: Michael Ellerman Signed-off-by: Laurent Dufour Signed-off-by: Thomas Gleixner Tested-by: Zhang Rui Link: https://lore.kernel.org/r/20230705145143.40545-5-ldufour@linux.ibm.com --- arch/x86/kernel/cpu/common.c | 2 +- include/linux/cpu_smt.h | 8 ++++++-- kernel/cpu.c | 21 ++++++++++++++++++++- 3 files changed, 27 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 52683fddafaf..12a48a85da3d 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2317,7 +2317,7 @@ 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/include/linux/cpu_smt.h b/include/linux/cpu_smt.h index 722c2e306fef..0c1664294b57 100644 --- a/include/linux/cpu_smt.h +++ b/include/linux/cpu_smt.h @@ -12,15 +12,19 @@ enum cpuhp_smt_control { #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_check_topology(void); +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_check_topology(void) { } +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; } diff --git a/kernel/cpu.c b/kernel/cpu.c index b6fe170c93e9..d7dd535cb5b5 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -594,6 +594,8 @@ 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) { @@ -607,16 +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) { + WARN_ON(!num_threads || (num_threads > max_threads)); + if (!topology_smt_supported()) 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) From 91b4a7dbfe05ddb6fd3cf78cc11fb5ed64d3af90 Mon Sep 17 00:00:00 2001 From: Laurent Dufour Date: Wed, 5 Jul 2023 16:51:38 +0200 Subject: [PATCH 05/10] cpu/SMT: Remove topology_smt_supported() Since the maximum number of threads is now passed to cpu_smt_set_num_threads(), checking that value is enough to know whether SMT is supported. Suggested-by: Thomas Gleixner Signed-off-by: Laurent Dufour Signed-off-by: Thomas Gleixner Tested-by: Zhang Rui Link: https://lore.kernel.org/r/20230705145143.40545-6-ldufour@linux.ibm.com --- arch/x86/include/asm/topology.h | 2 -- arch/x86/kernel/smpboot.c | 8 -------- kernel/cpu.c | 4 ++-- 3 files changed, 2 insertions(+), 12 deletions(-) diff --git a/arch/x86/include/asm/topology.h b/arch/x86/include/asm/topology.h index ae49ed4417d0..3235ba1e5b06 100644 --- a/arch/x86/include/asm/topology.h +++ b/arch/x86/include/asm/topology.h @@ -141,7 +141,6 @@ static inline int topology_max_smt_threads(void) 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) @@ -164,7 +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/smpboot.c b/arch/x86/kernel/smpboot.c index e1aa2cd7734b..d4e897b820c4 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/kernel/cpu.c b/kernel/cpu.c index d7dd535cb5b5..70add058e77b 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -621,7 +621,7 @@ void __init cpu_smt_set_num_threads(unsigned int num_threads, { WARN_ON(!num_threads || (num_threads > max_threads)); - if (!topology_smt_supported()) + if (max_threads == 1) cpu_smt_control = CPU_SMT_NOT_SUPPORTED; cpu_smt_max_threads = max_threads; @@ -1801,7 +1801,7 @@ early_param("cpuhp.parallel", parallel_bringup_parse_param); static inline bool cpuhp_smt_aware(void) { - return topology_smt_supported(); + return cpu_smt_max_threads > 1; } static inline const struct cpumask *cpuhp_get_primary_thread_mask(void) From 38253464bc821d6de6bba81bb1412ebb36f6cbd1 Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 5 Jul 2023 16:51:39 +0200 Subject: [PATCH 06/10] cpu/SMT: Create topology_smt_thread_allowed() Some architectures allows partial SMT states, i.e. when not all SMT threads are brought online. To support that, add an architecture helper which checks whether a given CPU is allowed to be brought online depending on how many SMT threads are currently enabled. Since this is only applicable to architecture supporting partial SMT, only these architectures should select the new configuration variable CONFIG_SMT_NUM_THREADS_DYNAMIC. For the other architectures, not supporting the partial SMT states, there is no need to define topology_cpu_smt_allowed(), the generic code assumed that all the threads are allowed or only the primary ones. Call the helper from cpu_smt_enable(), and cpu_smt_allowed() when SMT is enabled, to check if the particular thread should be onlined. Notably, also call it from cpu_smt_disable() if CPU_SMT_ENABLED, to allow offlining some threads to move from a higher to lower number of threads online. [ ldufour: Slightly reword the commit's description ] [ ldufour: Introduce CONFIG_SMT_NUM_THREADS_DYNAMIC ] Suggested-by: Thomas Gleixner Signed-off-by: Michael Ellerman Signed-off-by: Laurent Dufour Signed-off-by: Thomas Gleixner Tested-by: Zhang Rui Link: https://lore.kernel.org/r/20230705145143.40545-7-ldufour@linux.ibm.com --- arch/Kconfig | 3 +++ kernel/cpu.c | 24 +++++++++++++++++++++++- 2 files changed, 26 insertions(+), 1 deletion(-) diff --git a/arch/Kconfig b/arch/Kconfig index aff2746c8af2..63c5d6a2022b 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/kernel/cpu.c b/kernel/cpu.c index 70add058e77b..9a8d0685e055 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -645,9 +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)) @@ -2642,6 +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; @@ -2676,6 +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; From 7f48405c3c3437d578d0f1e4287aa0a3bfa5623f Mon Sep 17 00:00:00 2001 From: Michael Ellerman Date: Wed, 5 Jul 2023 16:51:40 +0200 Subject: [PATCH 07/10] cpu/SMT: Allow enabling partial SMT states via sysfs Add support to the /sys/devices/system/cpu/smt/control interface for enabling a specified number of SMT threads per core, including partial SMT states where not all threads are brought online. The current interface accepts "on" and "off", to enable either 1 or all SMT threads per core. This commit allows writing an integer, between 1 and the number of SMT threads supported by the machine. Writing 1 is a synonym for "off", 2 or more enables SMT with the specified number of threads. When reading the file, if all threads are online "on" is returned, to avoid changing behaviour for existing users. If some other number of threads is online then the integer value is returned. Architectures like x86 only supporting 1 thread or all threads, should not define CONFIG_SMT_NUM_THREADS_DYNAMIC. Architecture supporting partial SMT states, like PowerPC, should define it. [ ldufour: Slightly reword the commit's description ] [ ldufour: Remove switch() in __store_smt_control() ] [ ldufour: Rix build issue in control_show() ] Reported-by: kernel test robot Signed-off-by: Michael Ellerman Signed-off-by: Laurent Dufour Signed-off-by: Thomas Gleixner Tested-by: Zhang Rui Link: https://lore.kernel.org/r/20230705145143.40545-8-ldufour@linux.ibm.com --- .../ABI/testing/sysfs-devices-system-cpu | 1 + kernel/cpu.c | 60 ++++++++++++++----- 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 + "" 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); } From 52b38b7ad589c89a8c69272497bed20034f8e322 Mon Sep 17 00:00:00 2001 From: Zhang Rui Date: Fri, 28 Jul 2023 23:53:13 +0800 Subject: [PATCH 08/10] cpu/SMT: Fix cpu_smt_possible() comment Commit e1572f1d08be ("cpu/SMT: create and export cpu_smt_possible()") introduces cpu_smt_possible() to represent if SMT is theoretically possible. It returns true when SMT is supported and not forcefully disabled ('nosmt=force'). But the comment of it says "Returns true if SMT is not supported of forcefully (irreversibly) disabled", which is wrong. Fix that comment accordingly. Signed-off-by: Zhang Rui Signed-off-by: Thomas Gleixner Reviewed-by: Vitaly Kuznetsov Link: https://lore.kernel.org/r/20230728155313.44170-1-rui.zhang@intel.com --- kernel/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 7e8f1b044772..f6811c857102 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -676,7 +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 && From 33af38d85b5c9e8ffe26f9712319ed28c5ded64f Mon Sep 17 00:00:00 2001 From: Yue Haibing Date: Sat, 5 Aug 2023 19:04:06 +0800 Subject: [PATCH 09/10] cpu/hotplug: Remove unused function declaration cpu_set_state_online() Commit 5356297d12d9 ("cpu/hotplug: Remove cpu_report_state() and related unused cruft") removed function but leave the declaration. Signed-off-by: Yue Haibing Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20230805110406.45900-1-yuehaibing@huawei.com --- include/linux/cpu.h | 1 - 1 file changed, 1 deletion(-) diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 6b326a9e8191..ed56b2534500 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -191,7 +191,6 @@ 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) From e0a99a839f04c90bf9f16919997c4b34f9c8f1f0 Mon Sep 17 00:00:00 2001 From: Anna-Maria Behnsen Date: Mon, 15 May 2023 18:20:38 +0200 Subject: [PATCH 10/10] Documentation: core-api/cpuhotplug: Fix state names Dynamic allocated hotplug states in documentation and the comment above cpuhp_state enum do not match the code. To not get confused by wrong documentation, change to proper state names. Signed-off-by: Anna-Maria Behnsen Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20230515162038.62703-1-anna-maria@linutronix.de --- Documentation/core-api/cpu_hotplug.rst | 10 +++++----- include/linux/cpuhotplug.h | 2 +- 2 files changed, 6 insertions(+), 6 deletions(-) diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst index e6f5bc39cf5c..b9ae591d0b18 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/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h index 25b6e6e6ba6b..06dda85f0424 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