diff options
Diffstat (limited to 'arch/x86/kernel/apic/ipi.c')
| -rw-r--r-- | arch/x86/kernel/apic/ipi.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/arch/x86/kernel/apic/ipi.c b/arch/x86/kernel/apic/ipi.c index ca3bcdb7c4a8..5bd8a001a887 100644 --- a/arch/x86/kernel/apic/ipi.c +++ b/arch/x86/kernel/apic/ipi.c @@ -5,6 +5,8 @@ #include "local.h" +DEFINE_STATIC_KEY_FALSE(apic_use_ipi_shorthand); + #ifdef CONFIG_SMP #ifdef CONFIG_HOTPLUG_CPU #define DEFAULT_SEND_IPI (1) @@ -28,7 +30,27 @@ static int __init print_ipi_mode(void) return 0; } late_initcall(print_ipi_mode); -#endif + +void apic_smt_update(void) +{ + /* + * Do not switch to broadcast mode if: + * - Disabled on the command line + * - Only a single CPU is online + * - Not all present CPUs have been at least booted once + * + * The latter is important as the local APIC might be in some + * random state and a broadcast might cause havoc. That's + * especially true for NMI broadcasting. + */ + if (apic_ipi_shorthand_off || num_online_cpus() == 1 || + !cpumask_equal(cpu_present_mask, &cpus_booted_once_mask)) { + static_branch_disable(&apic_use_ipi_shorthand); + } else { + static_branch_enable(&apic_use_ipi_shorthand); + } +} +#endif /* CONFIG_SMP */ static inline int __prepare_ICR2(unsigned int mask) { |