// SPDX-License-Identifier: GPL-2.0-or-later /* * Intel SMP support routines. * * (c) 1995 Alan Cox, Building #3 * (c) 1998-99, 2000, 2009 Ingo Molnar * (c) 2002,2003 Andi Kleen, SuSE Labs. * * i386 and x86_64 integration by Glauber Costa */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Some notes on x86 processor bugs affecting SMP operation: * * Pentium, Pentium Pro, II, III (and all CPUs) have bugs. * The Linux implications for SMP are handled as follows: * * Pentium III / [Xeon] * None of the E1AP-E3AP errata are visible to the user. * * E1AP. see PII A1AP * E2AP. see PII A2AP * E3AP. see PII A3AP * * Pentium II / [Xeon] * None of the A1AP-A3AP errata are visible to the user. * * A1AP. see PPro 1AP * A2AP. see PPro 2AP * A3AP. see PPro 7AP * * Pentium Pro * None of 1AP-9AP errata are visible to the normal user, * except occasional delivery of 'spurious interrupt' as trap #15. * This is very rare and a non-problem. * * 1AP. Linux maps APIC as non-cacheable * 2AP. worked around in hardware * 3AP. fixed in C0 and above steppings microcode update. * Linux does not use excessive STARTUP_IPIs. * 4AP. worked around in hardware * 5AP. symmetric IO mode (normal Linux operation) not affected. * 'noapic' mode has vector 0xf filled out properly. * 6AP. 'noapic' mode might be affected - fixed in later steppings * 7AP. We do not assume writes to the LVT deasserting IRQs * 8AP. We do not enable low power mode (deep sleep) during MP bootup * 9AP. We do not use mixed mode * * Pentium * There is a marginal case where REP MOVS on 100MHz SMP * machines with B stepping processors can fail. XXX should provide * an L1cache=Writethrough or L1cache=off option. * * B stepping CPUs may hang. There are hardware work arounds * for this. We warn about it in case your board doesn't have the work * arounds. Basically that's so I can tell anyone with a B stepping * CPU and SMP problems "tough". * * Specific items [From Pentium Processor Specification Update] * * 1AP. Linux doesn't use remote read * 2AP. Linux doesn't trust APIC errors * 3AP. We work around this * 4AP. Linux never generated 3 interrupts of the same priority * to cause a lost local interrupt. * 5AP. Remote read is never used * 6AP. not affected - worked around in hardware * 7AP. not affected - worked around in hardware * 8AP. worked around in hardware - we get explicit CS errors if not * 9AP. only 'noapic' mode affected. Might generate spurious * interrupts, we log only the first one and count the * rest silently. * 10AP. not affected - worked around in hardware * 11AP. Linux reads the APIC between writes to avoid this, as per * the documentation. Make sure you preserve this as it affects * the C stepping chips too. * 12AP. not affected - worked around in hardware * 13AP. not affected - worked around in hardware * 14AP. we always deassert INIT during bootup * 15AP. not affected - worked around in hardware * 16AP. not affected - worked around in hardware * 17AP. not affected - worked around in hardware * 18AP. not affected - worked around in hardware * 19AP. not affected - worked around in BIOS * * If this sounds worrying believe me these bugs are either ___RARE___, * or are signal timing bugs worked around in hardware and there's * about nothing of note with C stepping upwards. */ static atomic_t stopping_cpu = ATOMIC_INIT(-1); static bool smp_no_nmi_ipi = false; static int smp_stop_nmi_callback(unsigned int val, struct pt_regs *regs) { /* We are registered on stopping cpu too, avoid spurious NMI */ if (raw_smp_processor_id() == atomic_read(&stopping_cpu)) return NMI_HANDLED; cpu_emergency_vmxoff(); stop_this_cpu(NULL); return NMI_HANDLED; } /* * this function calls the 'stop' function on all other CPUs in the system. */ DEFINE_IDTENTRY_SYSVEC(sysvec_reboot) { ack_APIC_irq(); cpu_emergency_vmxoff(); stop_this_cpu(NULL); } static int register_stop_handler(void) { return register_nmi_handler(NMI_LOCAL, smp_stop_nmi_callback, NMI_FLAG_FIRST, "smp_stop"); } static void native_stop_other_cpus(int wait) { unsigned long flags; unsigned long timeout; if (reboot_force) return; /* * Use an own vector here because smp_call_function * does lots of things not suitable in a panic situation. */ /* * We start by using the REBOOT_VECTOR irq. * The irq is treated as a sync point to allow critical * regions of code on other cpus to release their spin locks * and re-enable irqs. Jumping straight to an NMI might * accidentally cause deadlocks with further shutdown/panic * code. By syncing, we give the cpus up to one second to * finish their work before we force them off with the NMI. */ if (num_online_cpus() > 1) { /* did someone beat us here? */ if (atomic_cmpxchg(&stopping_cpu, -1, safe_smp_processor_id()) != -1) return; /* sync above data before sending IRQ */ wmb(); apic_send_IPI_allbutself(REBOOT_VECTOR); /* * Don't wait longer than a second for IPI completion. The * wait request is not checked here because that would * prevent an NMI shutdown attempt in case that not all * CPUs reach shutdown state. */ timeout = USEC_PER_SEC; while (num_online_cpus() > 1 && timeout--) udelay(1); } /* if the REBOOT_VECTOR didn't work, try with the NMI */ if (num_online_cpus() > 1) { /* * If NMI IPI is enabled, try to register the stop handler * and send the IPI. In any case try to wait for the other * CPUs to stop. */ if (!smp_no_nmi_ipi && !register_stop_handler()) { /* Sync above data before sending IRQ */ wmb(); pr_emerg("Shutting down cpus with NMI\n"); apic_send_IPI_allbutself(NMI_VECTOR); } /* * Don't wait longer than 10 ms if the caller didn't * reqeust it. If wait is true, the machine hangs here if * one or more CPUs do not reach shutdown state. */ timeout = USEC_PER_MSEC * 10; while (num_online_cpus() > 1 && (wait || timeout--)) udelay(1); } local_irq_save(flags); disable_local_APIC(); mcheck_cpu_clear(this_cpu_ptr(&cpu_info)); local_irq_restore(flags); } /* * Reschedule call back. KVM uses this interrupt to force a cpu out of * guest mode. */ DEFINE_IDTENTRY_SYSVEC_SIMPLE(sysvec_reschedule_ipi) { ack_APIC_irq(); trace_reschedule_entry(RESCHEDULE_VECTOR); inc_irq_stat(irq_resched_count); scheduler_ipi(); trace_reschedule_exit(RESCHEDULE_VECTOR); } DEFINE_IDTENTRY_SYSVEC(sysvec_call_function) { ack_APIC_irq(); trace_call_function_entry(CALL_FUNCTION_VECTOR); inc_irq_stat(irq_call_count); generic_smp_call_function_interrupt(); trace_call_function_exit(CALL_FUNCTION_VECTOR); } DEFINE_IDTENTRY_SYSVEC(sysvec_call_function_single) { ack_APIC_irq(); trace_call_function_single_entry(CALL_FUNCTION_SINGLE_VECTOR); inc_irq_stat(irq_call_count); generic_smp_call_function_single_interrupt(); trace_call_function_single_exit(CALL_FUNCTION_SINGLE_VECTOR); } static int __init nonmi_ipi_setup(char *str) { smp_no_nmi_ipi = true; return 1; } __setup("nonmi_ipi", nonmi_ipi_setup); struct smp_ops smp_ops = { .smp_prepare_boot_cpu = native_smp_prepare_boot_cpu, .smp_prepare_cpus = native_smp_prepare_cpus, .smp_cpus_done = native_smp_cpus_done, .stop_other_cpus = native_stop_other_cpus, #if defined(CONFIG_KEXEC_CORE) .crash_stop_other_cpus = kdump_nmi_shootdown_cpus, #endif .smp_send_reschedule = native_smp_send_reschedule, .cpu_up = native_cpu_up, .cpu_die = native_cpu_die, .cpu_disable = native_cpu_disable, .play_dead = native_play_dead, .send_call_func_ipi = native_send_call_func_ipi, .send_call_func_single_ipi = native_send_call_func_single_ipi, }; EXPORT_SYMBOL_GPL(smp_ops);