diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index aa1bc4f88f82..5229eaf73828 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -61,7 +61,7 @@ void __init check_bugs(void) * identify_boot_cpu() initialized SMT support information, let the * core code know. */ - cpu_smt_check_topology(); + cpu_smt_check_topology_early(); if (!IS_ENABLED(CONFIG_SMP)) { pr_info("CPU: "); diff --git a/include/linux/cpu.h b/include/linux/cpu.h index d059c67e4658..ae5ac89324df 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -267,10 +267,12 @@ enum cpuhp_smt_control { #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_early(void); extern void cpu_smt_check_topology(void); #else # define cpu_smt_control (CPU_SMT_ENABLED) static inline void cpu_smt_disable(bool force) { } +static inline void cpu_smt_check_topology_early(void) { } static inline void cpu_smt_check_topology(void) { } #endif diff --git a/kernel/cpu.c b/kernel/cpu.c index 3b3a3d782c0f..58f55c2815cd 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -360,6 +360,8 @@ EXPORT_SYMBOL_GPL(cpu_hotplug_enable); enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED; EXPORT_SYMBOL_GPL(cpu_smt_control); +static bool cpu_smt_available __read_mostly; + void __init cpu_smt_disable(bool force) { if (cpu_smt_control == CPU_SMT_FORCE_DISABLED || @@ -376,11 +378,25 @@ void __init cpu_smt_disable(bool force) /* * The decision whether SMT is supported can only be done after the full - * CPU identification. Called from architecture code. + * CPU identification. Called from architecture code before non boot CPUs + * are brought up. + */ +void __init cpu_smt_check_topology_early(void) +{ + if (!topology_smt_supported()) + cpu_smt_control = CPU_SMT_NOT_SUPPORTED; +} + +/* + * If SMT was disabled by BIOS, detect it here, after the CPUs have been + * brought online. This ensures the smt/l1tf sysfs entries are consistent + * with reality. cpu_smt_available is set to true during the bringup of non + * boot CPUs when a SMT sibling is detected. Note, this may overwrite + * cpu_smt_control's previous setting. */ void __init cpu_smt_check_topology(void) { - if (!topology_smt_supported()) + if (!cpu_smt_available) cpu_smt_control = CPU_SMT_NOT_SUPPORTED; } @@ -393,10 +409,18 @@ early_param("nosmt", smt_cmdline_disable); static inline bool cpu_smt_allowed(unsigned int cpu) { - if (cpu_smt_control == CPU_SMT_ENABLED) + if (topology_is_primary_thread(cpu)) return true; - if (topology_is_primary_thread(cpu)) + /* + * If the CPU is not a 'primary' thread and the booted_once bit is + * set then the processor has SMT support. Store this information + * for the late check of SMT support in cpu_smt_check_topology(). + */ + if (per_cpu(cpuhp_state, cpu).booted_once) + cpu_smt_available = true; + + if (cpu_smt_control == CPU_SMT_ENABLED) return true; /* @@ -2063,15 +2087,6 @@ static const struct attribute_group cpuhp_smt_attr_group = { static int __init cpu_smt_state_init(void) { - /* - * If SMT was disabled by BIOS, detect it here, after the CPUs have - * been brought online. This ensures the smt/l1tf sysfs entries are - * consistent with reality. Note this may overwrite cpu_smt_control's - * previous setting. - */ - if (topology_max_smt_threads() == 1) - cpu_smt_control = CPU_SMT_NOT_SUPPORTED; - return sysfs_create_group(&cpu_subsys.dev_root->kobj, &cpuhp_smt_attr_group); } diff --git a/kernel/smp.c b/kernel/smp.c index bba3b201668d..399905fdfa3f 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -564,6 +564,8 @@ void __init smp_init(void) cpu_up(cpu); } + /* Final decision about SMT support */ + cpu_smt_check_topology(); /* Any cleanup work */ smp_announce(); smp_cpus_done(setup_max_cpus);