diff options
Diffstat (limited to 'kernel/cpu.c')
| -rw-r--r-- | kernel/cpu.c | 41 |
1 files changed, 28 insertions, 13 deletions
diff --git a/kernel/cpu.c b/kernel/cpu.c index 2bc3d2f5b2a5..9d2512dd263c 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -347,6 +347,8 @@ 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 || @@ -363,14 +365,28 @@ 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(void) +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 (!cpu_smt_available) + cpu_smt_control = CPU_SMT_NOT_SUPPORTED; +} + static int __init smt_cmdline_disable(char *str) { cpu_smt_disable(str && !strcmp(str, "force")); @@ -380,10 +396,18 @@ 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; /* @@ -2125,15 +2149,6 @@ 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); } |