// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *      Intel SMP support routines.
 *
 *      (c) 1995 Alan Cox, Building #3 <alan@lxorguk.ukuu.org.uk>
 *      (c) 1998-99, 2000, 2009 Ingo Molnar <mingo@redhat.com>
 *      (c) 2002,2003 Andi Kleen, SuSE Labs.
 *
 *      i386 and x86_64 integration by Glauber Costa <gcosta@redhat.com>
 */

#include <linux/init.h>

#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/spinlock.h>
#include <linux/export.h>
#include <linux/kernel_stat.h>
#include <linux/mc146818rtc.h>
#include <linux/cache.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/gfp.h>

#include <asm/mtrr.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/proto.h>
#include <asm/apic.h>
#include <asm/idtentry.h>
#include <asm/nmi.h>
#include <asm/mce.h>
#include <asm/trace/irq_vectors.h>
#include <asm/kexec.h>
#include <asm/virtext.h>

/*
 *      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
                 * request 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);