// SPDX-License-Identifier: GPL-2.0-or-later
 /*
 *      x86 SMP booting functions
 *
 *      (c) 1995 Alan Cox, Building #3 <alan@lxorguk.ukuu.org.uk>
 *      (c) 1998, 1999, 2000, 2009 Ingo Molnar <mingo@redhat.com>
 *      Copyright 2001 Andi Kleen, SuSE Labs.
 *
 *      Much of the core SMP work is based on previous work by Thomas Radke, to
 *      whom a great many thanks are extended.
 *
 *      Thanks to Intel for making available several different Pentium,
 *      Pentium Pro and Pentium-II/Xeon MP machines.
 *      Original development of Linux SMP code supported by Caldera.
 *
 *      Fixes
 *              Felix Koop      :       NR_CPUS used properly
 *              Jose Renau      :       Handle single CPU case.
 *              Alan Cox        :       By repeated request 8) - Total BogoMIPS report.
 *              Greg Wright     :       Fix for kernel stacks panic.
 *              Erich Boleyn    :       MP v1.4 and additional changes.
 *      Matthias Sattler        :       Changes for 2.1 kernel map.
 *      Michel Lespinasse       :       Changes for 2.1 kernel map.
 *      Michael Chastain        :       Change trampoline.S to gnu as.
 *              Alan Cox        :       Dumb bug: 'B' step PPro's are fine
 *              Ingo Molnar     :       Added APIC timers, based on code
 *                                      from Jose Renau
 *              Ingo Molnar     :       various cleanups and rewrites
 *              Tigran Aivazian :       fixed "0.00 in /proc/uptime on SMP" bug.
 *      Maciej W. Rozycki       :       Bits for genuine 82489DX APICs
 *      Andi Kleen              :       Changed for SMP boot into long mode.
 *              Martin J. Bligh :       Added support for multi-quad systems
 *              Dave Jones      :       Report invalid combinations of Athlon CPUs.
 *              Rusty Russell   :       Hacked into shape for new "hotplug" boot process.
 *      Andi Kleen              :       Converted to new state machine.
 *      Ashok Raj               :       CPU hotplug support
 *      Glauber Costa           :       i386 and x86_64 integration
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/init.h>
#include <linux/smp.h>
#include <linux/export.h>
#include <linux/sched.h>
#include <linux/sched/topology.h>
#include <linux/sched/hotplug.h>
#include <linux/sched/task_stack.h>
#include <linux/percpu.h>
#include <linux/memblock.h>
#include <linux/err.h>
#include <linux/nmi.h>
#include <linux/tboot.h>
#include <linux/gfp.h>
#include <linux/cpuidle.h>
#include <linux/kexec.h>
#include <linux/numa.h>
#include <linux/pgtable.h>
#include <linux/overflow.h>
#include <linux/stackprotector.h>
#include <linux/cpuhotplug.h>
#include <linux/mc146818rtc.h>
#include <linux/acpi.h>

#include <asm/acpi.h>
#include <asm/cacheinfo.h>
#include <asm/cpuid/api.h>
#include <asm/desc.h>
#include <asm/nmi.h>
#include <asm/irq.h>
#include <asm/realmode.h>
#include <asm/cpu.h>
#include <asm/numa.h>
#include <asm/tlbflush.h>
#include <asm/mtrr.h>
#include <asm/mwait.h>
#include <asm/apic.h>
#include <asm/io_apic.h>
#include <asm/fpu/api.h>
#include <asm/setup.h>
#include <asm/uv/uv.h>
#include <asm/microcode.h>
#include <asm/i8259.h>
#include <asm/misc.h>
#include <asm/qspinlock.h>
#include <asm/intel-family.h>
#include <asm/cpu_device_id.h>
#include <asm/spec-ctrl.h>
#include <asm/hw_irq.h>
#include <asm/stackprotector.h>
#include <asm/sev.h>
#include <asm/spec-ctrl.h>

/* representing HT siblings of each logical CPU */
DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_map);
EXPORT_PER_CPU_SYMBOL(cpu_sibling_map);

/* representing HT and core siblings of each logical CPU */
DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_core_map);
EXPORT_PER_CPU_SYMBOL(cpu_core_map);

/* representing HT, core, and die siblings of each logical CPU */
DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_die_map);
EXPORT_PER_CPU_SYMBOL(cpu_die_map);

/* Representing CPUs for which sibling maps can be computed */
static cpumask_var_t cpu_sibling_setup_mask;

struct mwait_cpu_dead {
        unsigned int    control;
        unsigned int    status;
};

#define CPUDEAD_MWAIT_WAIT      0xDEADBEEF
#define CPUDEAD_MWAIT_KEXEC_HLT 0x4A17DEAD

/*
 * Cache line aligned data for mwait_play_dead(). Separate on purpose so
 * that it's unlikely to be touched by other CPUs.
 */
static DEFINE_PER_CPU_ALIGNED(struct mwait_cpu_dead, mwait_cpu_dead);

/* Maximum number of SMT threads on any online core */
int __read_mostly __max_smt_threads = 1;

/* Flag to indicate if a complete sched domain rebuild is required */
bool x86_topology_update;

int arch_update_cpu_topology(void)
{
        int retval = x86_topology_update;

        x86_topology_update = false;
        return retval;
}

static unsigned int smpboot_warm_reset_vector_count;

static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)
{
        unsigned long flags;

        spin_lock_irqsave(&rtc_lock, flags);
        if (!smpboot_warm_reset_vector_count++) {
                CMOS_WRITE(0xa, 0xf);
                *((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_HIGH)) = start_eip >> 4;
                *((volatile unsigned short *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) = start_eip & 0xf;
        }
        spin_unlock_irqrestore(&rtc_lock, flags);
}

static inline void smpboot_restore_warm_reset_vector(void)
{
        unsigned long flags;

        /*
         * Paranoid:  Set warm reset code and vector here back
         * to default values.
         */
        spin_lock_irqsave(&rtc_lock, flags);
        if (!--smpboot_warm_reset_vector_count) {
                CMOS_WRITE(0, 0xf);
                *((volatile u32 *)phys_to_virt(TRAMPOLINE_PHYS_LOW)) = 0;
        }
        spin_unlock_irqrestore(&rtc_lock, flags);

}

/* Run the next set of setup steps for the upcoming CPU */
static void ap_starting(void)
{
        int cpuid = smp_processor_id();

        /* Mop up eventual mwait_play_dead() wreckage */
        this_cpu_write(mwait_cpu_dead.status, 0);
        this_cpu_write(mwait_cpu_dead.control, 0);

        /*
         * If woken up by an INIT in an 82489DX configuration the alive
         * synchronization guarantees that the CPU does not reach this
         * point before an INIT_deassert IPI reaches the local APIC, so it
         * is now safe to touch the local APIC.
         *
         * Set up this CPU, first the APIC, which is probably redundant on
         * most boards.
         */
        apic_ap_setup();

        /* Save the processor parameters. */
        identify_secondary_cpu(cpuid);

        /*
         * The topology information must be up to date before
         * notify_cpu_starting().
         */
        set_cpu_sibling_map(cpuid);

        ap_init_aperfmperf();

        pr_debug("Stack at about %p\n", &cpuid);

        wmb();

        /*
         * This runs the AP through all the cpuhp states to its target
         * state CPUHP_ONLINE.
         */
        notify_cpu_starting(cpuid);
}

static void ap_calibrate_delay(void)
{
        /*
         * Calibrate the delay loop and update loops_per_jiffy in cpu_data.
         * identify_secondary_cpu() stored a value that is close but not as
         * accurate as the value just calculated.
         *
         * As this is invoked after the TSC synchronization check,
         * calibrate_delay_is_known() will skip the calibration routine
         * when TSC is synchronized across sockets.
         */
        calibrate_delay();
        cpu_data(smp_processor_id()).loops_per_jiffy = loops_per_jiffy;
}

/*
 * Activate a secondary processor.
 */
static void notrace __noendbr start_secondary(void *unused)
{
        /*
         * Don't put *anything* except direct CPU state initialization
         * before cpu_init(), SMP booting is too fragile that we want to
         * limit the things done here to the most necessary things.
         */
        cr4_init();

        /*
         * 32-bit specific. 64-bit reaches this code with the correct page
         * table established. Yet another historical divergence.
         */
        if (IS_ENABLED(CONFIG_X86_32)) {
                /* switch away from the initial page table */
                load_cr3(swapper_pg_dir);
                __flush_tlb_all();
        }

        cpu_init_exception_handling(false);

        /*
         * Load the microcode before reaching the AP alive synchronization
         * point below so it is not part of the full per CPU serialized
         * bringup part when "parallel" bringup is enabled.
         *
         * That's even safe when hyperthreading is enabled in the CPU as
         * the core code starts the primary threads first and leaves the
         * secondary threads waiting for SIPI. Loading microcode on
         * physical cores concurrently is a safe operation.
         *
         * This covers both the Intel specific issue that concurrent
         * microcode loading on SMT siblings must be prohibited and the
         * vendor independent issue`that microcode loading which changes
         * CPUID, MSRs etc. must be strictly serialized to maintain
         * software state correctness.
         */
        load_ucode_ap();

        /*
         * Synchronization point with the hotplug core. Sets this CPUs
         * synchronization state to ALIVE and spin-waits for the control CPU to
         * release this CPU for further bringup.
         */
        cpuhp_ap_sync_alive();

        cpu_init();
        fpu__init_cpu();
        rcutree_report_cpu_starting(raw_smp_processor_id());
        x86_cpuinit.early_percpu_clock_init();

        ap_starting();

        /* Check TSC synchronization with the control CPU. */
        check_tsc_sync_target();

        /*
         * Calibrate the delay loop after the TSC synchronization check.
         * This allows to skip the calibration when TSC is synchronized
         * across sockets.
         */
        ap_calibrate_delay();

        speculative_store_bypass_ht_init();

        /*
         * Lock vector_lock, set CPU online and bring the vector
         * allocator online. Online must be set with vector_lock held
         * to prevent a concurrent irq setup/teardown from seeing a
         * half valid vector space.
         */
        lock_vector_lock();
        set_cpu_online(smp_processor_id(), true);
        lapic_online();
        unlock_vector_lock();
        x86_platform.nmi_init();

        /* enable local interrupts */
        local_irq_enable();

        x86_cpuinit.setup_percpu_clockev();

        wmb();
        cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}
ANNOTATE_NOENDBR_SYM(start_secondary);

static bool
topology_same_node(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
{
        int cpu1 = c->cpu_index, cpu2 = o->cpu_index;

        return (cpu_to_node(cpu1) == cpu_to_node(cpu2));
}

static bool
topology_sane(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o, const char *name)
{
        int cpu1 = c->cpu_index, cpu2 = o->cpu_index;

        return !WARN_ONCE(!topology_same_node(c, o),
                "sched: CPU #%d's %s-sibling CPU #%d is not on the same node! "
                "[node: %d != %d]. Ignoring dependency.\n",
                cpu1, name, cpu2, cpu_to_node(cpu1), cpu_to_node(cpu2));
}

#define link_mask(mfunc, c1, c2)                                        \
do {                                                                    \
        cpumask_set_cpu((c1), mfunc(c2));                               \
        cpumask_set_cpu((c2), mfunc(c1));                               \
} while (0)

static bool match_smt(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
{
        if (boot_cpu_has(X86_FEATURE_TOPOEXT)) {
                int cpu1 = c->cpu_index, cpu2 = o->cpu_index;

                if (c->topo.pkg_id == o->topo.pkg_id &&
                    c->topo.die_id == o->topo.die_id &&
                    c->topo.amd_node_id == o->topo.amd_node_id &&
                    per_cpu_llc_id(cpu1) == per_cpu_llc_id(cpu2)) {
                        if (c->topo.core_id == o->topo.core_id)
                                return topology_sane(c, o, "smt");

                        if ((c->topo.cu_id != 0xff) &&
                            (o->topo.cu_id != 0xff) &&
                            (c->topo.cu_id == o->topo.cu_id))
                                return topology_sane(c, o, "smt");
                }

        } else if (c->topo.pkg_id == o->topo.pkg_id &&
                   c->topo.die_id == o->topo.die_id &&
                   c->topo.core_id == o->topo.core_id) {
                return topology_sane(c, o, "smt");
        }

        return false;
}

static bool match_die(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
{
        if (c->topo.pkg_id != o->topo.pkg_id || c->topo.die_id != o->topo.die_id)
                return false;

        if (cpu_feature_enabled(X86_FEATURE_TOPOEXT) && topology_amd_nodes_per_pkg() > 1)
                return c->topo.amd_node_id == o->topo.amd_node_id;

        return true;
}

static bool match_l2c(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
{
        int cpu1 = c->cpu_index, cpu2 = o->cpu_index;

        /* If the arch didn't set up l2c_id, fall back to SMT */
        if (per_cpu_l2c_id(cpu1) == BAD_APICID)
                return match_smt(c, o);

        /* Do not match if L2 cache id does not match: */
        if (per_cpu_l2c_id(cpu1) != per_cpu_l2c_id(cpu2))
                return false;

        return topology_sane(c, o, "l2c");
}

/*
 * Unlike the other levels, we do not enforce keeping a
 * multicore group inside a NUMA node.  If this happens, we will
 * discard the MC level of the topology later.
 */
static bool match_pkg(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
{
        if (c->topo.pkg_id == o->topo.pkg_id)
                return true;
        return false;
}

/*
 * Define intel_cod_cpu[] for Intel COD (Cluster-on-Die) CPUs.
 *
 * Any Intel CPU that has multiple nodes per package and does not
 * match intel_cod_cpu[] has the SNC (Sub-NUMA Cluster) topology.
 *
 * When in SNC mode, these CPUs enumerate an LLC that is shared
 * by multiple NUMA nodes. The LLC is shared for off-package data
 * access but private to the NUMA node (half of the package) for
 * on-package access. CPUID (the source of the information about
 * the LLC) can only enumerate the cache as shared or unshared,
 * but not this particular configuration.
 */

static const struct x86_cpu_id intel_cod_cpu[] = {
        X86_MATCH_VFM(INTEL_HASWELL_X,   0),    /* COD */
        X86_MATCH_VFM(INTEL_BROADWELL_X, 0),    /* COD */
        X86_MATCH_VFM(INTEL_ANY,         1),    /* SNC */
        {}
};

static bool match_llc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
{
        const struct x86_cpu_id *id = x86_match_cpu(intel_cod_cpu);
        int cpu1 = c->cpu_index, cpu2 = o->cpu_index;
        bool intel_snc = id && id->driver_data;

        /* Do not match if we do not have a valid APICID for cpu: */
        if (per_cpu_llc_id(cpu1) == BAD_APICID)
                return false;

        /* Do not match if LLC id does not match: */
        if (per_cpu_llc_id(cpu1) != per_cpu_llc_id(cpu2))
                return false;

        /*
         * Allow the SNC topology without warning. Return of false
         * means 'c' does not share the LLC of 'o'. This will be
         * reflected to userspace.
         */
        if (match_pkg(c, o) && !topology_same_node(c, o) && intel_snc)
                return false;

        return topology_sane(c, o, "llc");
}


static inline int x86_sched_itmt_flags(void)
{
        return sysctl_sched_itmt_enabled ? SD_ASYM_PACKING : 0;
}

#ifdef CONFIG_SCHED_MC
static int x86_core_flags(void)
{
        return cpu_core_flags() | x86_sched_itmt_flags();
}
#endif
#ifdef CONFIG_SCHED_CLUSTER
static int x86_cluster_flags(void)
{
        return cpu_cluster_flags() | x86_sched_itmt_flags();
}
#endif

static struct sched_domain_topology_level x86_topology[] = {
        SDTL_INIT(tl_smt_mask, cpu_smt_flags, SMT),
#ifdef CONFIG_SCHED_CLUSTER
        SDTL_INIT(tl_cls_mask, x86_cluster_flags, CLS),
#endif
#ifdef CONFIG_SCHED_MC
        SDTL_INIT(tl_mc_mask, x86_core_flags, MC),
#endif
        SDTL_INIT(tl_pkg_mask, x86_sched_itmt_flags, PKG),
        { NULL },
};

static void __init build_sched_topology(void)
{
        struct sched_domain_topology_level *topology = x86_topology;

        /*
         * When there is NUMA topology inside the package invalidate the
         * PKG domain since the NUMA domains will auto-magically create the
         * right spanning domains based on the SLIT.
         */
        if (topology_num_nodes_per_package() > 1) {
                unsigned int pkgdom = ARRAY_SIZE(x86_topology) - 2;

                memset(&x86_topology[pkgdom], 0, sizeof(x86_topology[pkgdom]));
        }

        /*
         * Drop the SMT domains if there is only one thread per-core
         * since it'll get degenerated by the scheduler anyways.
         */
        if (cpu_smt_num_threads <= 1)
                ++topology;

        set_sched_topology(topology);
}

#ifdef CONFIG_NUMA
/*
 * Test if the on-trace cluster at (N,N) is symmetric.
 * Uses upper triangle iteration to avoid obvious duplicates.
 */
static bool slit_cluster_symmetric(int N)
{
        int u = topology_num_nodes_per_package();

        for (int k = 0; k < u; k++) {
                for (int l = k; l < u; l++) {
                        if (node_distance(N + k, N + l) !=
                            node_distance(N + l, N + k))
                                return false;
                }
        }

        return true;
}

/*
 * Return the package-id of the cluster, or ~0 if indeterminate.
 * Each node in the on-trace cluster should have the same package-id.
 */
static u32 slit_cluster_package(int N)
{
        int u = topology_num_nodes_per_package();
        u32 pkg_id = ~0;

        for (int n = 0; n < u; n++) {
                const struct cpumask *cpus = cpumask_of_node(N + n);
                int cpu;

                for_each_cpu(cpu, cpus) {
                        u32 id = topology_logical_package_id(cpu);

                        if (pkg_id == ~0)
                                pkg_id = id;
                        if (pkg_id != id)
                                return ~0;
                }
        }

        return pkg_id;
}

/*
 * Validate the SLIT table is of the form expected for SNC, specifically:
 *
 *  - each on-trace cluster should be symmetric,
 *  - each on-trace cluster should have a unique package-id.
 *
 * If you NUMA_EMU on top of SNC, you get to keep the pieces.
 */
static bool slit_validate(void)
{
        int u = topology_num_nodes_per_package();
        u32 pkg_id, prev_pkg_id = ~0;

        for (int pkg = 0; pkg < topology_max_packages(); pkg++) {
                int n = pkg * u;

                /*
                 * Ensure the on-trace cluster is symmetric and each cluster
                 * has a different package id.
                 */
                if (!slit_cluster_symmetric(n))
                        return false;
                pkg_id = slit_cluster_package(n);
                if (pkg_id == ~0)
                        return false;
                if (pkg && pkg_id == prev_pkg_id)
                        return false;

                prev_pkg_id = pkg_id;
        }

        return true;
}

/*
 * Compute a sanitized SLIT table for SNC; notably SNC-3 can end up with
 * asymmetric off-trace clusters, reflecting physical assymmetries. However
 * this leads to 'unfortunate' sched_domain configurations.
 *
 * For example dual socket GNR with SNC-3:
 *
 * node distances:
 * node     0    1    2    3    4    5
 *     0:   10   15   17   21   28   26
 *     1:   15   10   15   23   26   23
 *     2:   17   15   10   26   23   21
 *     3:   21   28   26   10   15   17
 *     4:   23   26   23   15   10   15
 *     5:   26   23   21   17   15   10
 *
 * Fix things up by averaging out the off-trace clusters; resulting in:
 *
 * node     0    1    2    3    4    5
 *     0:   10   15   17   24   24   24
 *     1:   15   10   15   24   24   24
 *     2:   17   15   10   24   24   24
 *     3:   24   24   24   10   15   17
 *     4:   24   24   24   15   10   15
 *     5:   24   24   24   17   15   10
 */
static int slit_cluster_distance(int i, int j)
{
        static int slit_valid = -1;
        int u = topology_num_nodes_per_package();
        long d = 0;
        int x, y;

        if (slit_valid < 0) {
                slit_valid = slit_validate();
                if (!slit_valid)
                        pr_err(FW_BUG "SLIT table doesn't have the expected form for SNC -- fixup disabled!\n");
                else
                        pr_info("Fixing up SNC SLIT table.\n");
        }

        /*
         * Is this a unit cluster on the trace?
         */
        if ((i / u) == (j / u) || !slit_valid)
                return node_distance(i, j);

        /*
         * Off-trace cluster.
         *
         * Notably average out the symmetric pair of off-trace clusters to
         * ensure the resulting SLIT table is symmetric.
         */
        x = i - (i % u);
        y = j - (j % u);

        for (i = x; i < x + u; i++) {
                for (j = y; j < y + u; j++) {
                        d += node_distance(i, j);
                        d += node_distance(j, i);
                }
        }

        return d / (2*u*u);
}

int arch_sched_node_distance(int from, int to)
{
        int d = node_distance(from, to);

        switch (boot_cpu_data.x86_vfm) {
        case INTEL_GRANITERAPIDS_X:
        case INTEL_ATOM_DARKMONT_X:
                if (topology_max_packages() == 1 ||
                    topology_num_nodes_per_package() < 3)
                        return d;

                /*
                 * Handle SNC-3 asymmetries.
                 */
                return slit_cluster_distance(from, to);
        }
        return d;
}
#endif /* CONFIG_NUMA */

void set_cpu_sibling_map(int cpu)
{
        bool has_smt = __max_threads_per_core > 1;
        bool has_mp = has_smt || topology_num_cores_per_package() > 1;
        struct cpuinfo_x86 *c = &cpu_data(cpu);
        struct cpuinfo_x86 *o;
        int i, threads;

        cpumask_set_cpu(cpu, cpu_sibling_setup_mask);

        if (!has_mp) {
                cpumask_set_cpu(cpu, topology_sibling_cpumask(cpu));
                cpumask_set_cpu(cpu, cpu_llc_shared_mask(cpu));
                cpumask_set_cpu(cpu, cpu_l2c_shared_mask(cpu));
                cpumask_set_cpu(cpu, topology_core_cpumask(cpu));
                cpumask_set_cpu(cpu, topology_die_cpumask(cpu));
                c->booted_cores = 1;
                return;
        }

        for_each_cpu(i, cpu_sibling_setup_mask) {
                o = &cpu_data(i);

                if (match_pkg(c, o) && !topology_same_node(c, o))
                        WARN_ON_ONCE(topology_num_nodes_per_package() == 1);

                if ((i == cpu) || (has_smt && match_smt(c, o)))
                        link_mask(topology_sibling_cpumask, cpu, i);

                if ((i == cpu) || (has_mp && match_llc(c, o)))
                        link_mask(cpu_llc_shared_mask, cpu, i);

                if ((i == cpu) || (has_mp && match_l2c(c, o)))
                        link_mask(cpu_l2c_shared_mask, cpu, i);

                if ((i == cpu) || (has_mp && match_die(c, o)))
                        link_mask(topology_die_cpumask, cpu, i);
        }

        threads = cpumask_weight(topology_sibling_cpumask(cpu));
        if (threads > __max_smt_threads)
                __max_smt_threads = threads;

        for_each_cpu(i, topology_sibling_cpumask(cpu))
                cpu_data(i).smt_active = threads > 1;

        /*
         * This needs a separate iteration over the cpus because we rely on all
         * topology_sibling_cpumask links to be set-up.
         */
        for_each_cpu(i, cpu_sibling_setup_mask) {
                o = &cpu_data(i);

                if ((i == cpu) || (has_mp && match_pkg(c, o))) {
                        link_mask(topology_core_cpumask, cpu, i);

                        /*
                         *  Does this new cpu bringup a new core?
                         */
                        if (threads == 1) {
                                /*
                                 * for each core in package, increment
                                 * the booted_cores for this new cpu
                                 */
                                if (cpumask_first(
                                    topology_sibling_cpumask(i)) == i)
                                        c->booted_cores++;
                                /*
                                 * increment the core count for all
                                 * the other cpus in this package
                                 */
                                if (i != cpu)
                                        cpu_data(i).booted_cores++;
                        } else if (i != cpu && !c->booted_cores)
                                c->booted_cores = cpu_data(i).booted_cores;
                }
        }
}

/* maps the cpu to the sched domain representing multi-core */
const struct cpumask *cpu_coregroup_mask(int cpu)
{
        return cpu_llc_shared_mask(cpu);
}

const struct cpumask *cpu_clustergroup_mask(int cpu)
{
        return cpu_l2c_shared_mask(cpu);
}
EXPORT_SYMBOL_GPL(cpu_clustergroup_mask);

static void impress_friends(void)
{
        int cpu;
        unsigned long bogosum = 0;
        /*
         * Allow the user to impress friends.
         */
        pr_debug("Before bogomips\n");
        for_each_online_cpu(cpu)
                bogosum += cpu_data(cpu).loops_per_jiffy;

        pr_info("Total of %d processors activated (%lu.%02lu BogoMIPS)\n",
                num_online_cpus(),
                bogosum/(500000/HZ),
                (bogosum/(5000/HZ))%100);

        pr_debug("Before bogocount - setting activated=1\n");
}

/*
 * The Multiprocessor Specification 1.4 (1997) example code suggests
 * that there should be a 10ms delay between the BSP asserting INIT
 * and de-asserting INIT, when starting a remote processor.
 * But that slows boot and resume on modern processors, which include
 * many cores and don't require that delay.
 *
 * Cmdline "cpu_init_udelay=" is available to override this delay.
 */
#define UDELAY_10MS_LEGACY 10000

static unsigned int init_udelay = UINT_MAX;

static int __init cpu_init_udelay(char *str)
{
        get_option(&str, &init_udelay);

        return 0;
}
early_param("cpu_init_udelay", cpu_init_udelay);

static void __init smp_set_init_udelay(void)
{
        /* if cmdline changed it from default, leave it alone */
        if (init_udelay != UINT_MAX)
                return;

        /* if modern processor, use no delay */
        if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL && boot_cpu_data.x86_vfm >= INTEL_PENTIUM_PRO) ||
            (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON && boot_cpu_data.x86 >= 0x18) ||
            (boot_cpu_data.x86_vendor == X86_VENDOR_AMD   && boot_cpu_data.x86 >= 0xF)) {
                init_udelay = 0;
                return;
        }
        /* else, use legacy delay */
        init_udelay = UDELAY_10MS_LEGACY;
}

/*
 * Wake up AP by INIT, INIT, STARTUP sequence.
 */
static void send_init_sequence(u32 phys_apicid)
{
        int maxlvt = lapic_get_maxlvt();

        /* Be paranoid about clearing APIC errors. */
        if (APIC_INTEGRATED(boot_cpu_apic_version)) {
                /* Due to the Pentium erratum 3AP.  */
                if (maxlvt > 3)
                        apic_write(APIC_ESR, 0);
                apic_read(APIC_ESR);
        }

        /* Assert INIT on the target CPU */
        apic_icr_write(APIC_INT_LEVELTRIG | APIC_INT_ASSERT | APIC_DM_INIT, phys_apicid);
        safe_apic_wait_icr_idle();

        udelay(init_udelay);

        /* Deassert INIT on the target CPU */
        apic_icr_write(APIC_INT_LEVELTRIG | APIC_DM_INIT, phys_apicid);
        safe_apic_wait_icr_idle();
}

/*
 * Wake up AP by INIT, INIT, STARTUP sequence.
 */
static int wakeup_secondary_cpu_via_init(u32 phys_apicid, unsigned long start_eip, unsigned int cpu)
{
        unsigned long send_status = 0, accept_status = 0;
        int num_starts, j, maxlvt;

        preempt_disable();
        maxlvt = lapic_get_maxlvt();
        send_init_sequence(phys_apicid);

        mb();

        /*
         * Should we send STARTUP IPIs ?
         *
         * Determine this based on the APIC version.
         * If we don't have an integrated APIC, don't send the STARTUP IPIs.
         */
        if (APIC_INTEGRATED(boot_cpu_apic_version))
                num_starts = 2;
        else
                num_starts = 0;

        /*
         * Run STARTUP IPI loop.
         */
        pr_debug("#startup loops: %d\n", num_starts);

        for (j = 1; j <= num_starts; j++) {
                pr_debug("Sending STARTUP #%d\n", j);
                if (maxlvt > 3)         /* Due to the Pentium erratum 3AP.  */
                        apic_write(APIC_ESR, 0);
                apic_read(APIC_ESR);
                pr_debug("After apic_write\n");

                /*
                 * STARTUP IPI
                 */

                /* Target chip */
                /* Boot on the stack */
                /* Kick the second */
                apic_icr_write(APIC_DM_STARTUP | (start_eip >> 12),
                               phys_apicid);

                /*
                 * Give the other CPU some time to accept the IPI.
                 */
                if (init_udelay == 0)
                        udelay(10);
                else
                        udelay(300);

                pr_debug("Startup point 1\n");

                pr_debug("Waiting for send to finish...\n");
                send_status = safe_apic_wait_icr_idle();

                /*
                 * Give the other CPU some time to accept the IPI.
                 */
                if (init_udelay == 0)
                        udelay(10);
                else
                        udelay(200);

                if (maxlvt > 3)         /* Due to the Pentium erratum 3AP.  */
                        apic_write(APIC_ESR, 0);
                accept_status = (apic_read(APIC_ESR) & 0xEF);
                if (send_status || accept_status)
                        break;
        }
        pr_debug("After Startup\n");

        if (send_status)
                pr_err("APIC never delivered???\n");
        if (accept_status)
                pr_err("APIC delivery error (%lx)\n", accept_status);

        preempt_enable();
        return (send_status | accept_status);
}

/* reduce the number of lines printed when booting a large cpu count system */
static void announce_cpu(int cpu, int apicid)
{
        static int width, node_width, first = 1;
        static int current_node = NUMA_NO_NODE;
        int node = early_cpu_to_node(cpu);

        if (!width)
                width = num_digits(num_possible_cpus()) + 1; /* + '#' sign */

        if (!node_width)
                node_width = num_digits(num_possible_nodes()) + 1; /* + '#' */

        if (system_state < SYSTEM_RUNNING) {
                if (first)
                        pr_info("x86: Booting SMP configuration:\n");

                if (node != current_node) {
                        if (current_node > (-1))
                                pr_cont("\n");
                        current_node = node;

                        printk(KERN_INFO ".... node %*s#%d, CPUs:  ",
                               node_width - num_digits(node), " ", node);
                }

                /* Add padding for the BSP */
                if (first)
                        pr_cont("%*s", width + 1, " ");
                first = 0;

                pr_cont("%*s#%d", width - num_digits(cpu), " ", cpu);
        } else
                pr_info("Booting Node %d Processor %d APIC 0x%x\n",
                        node, cpu, apicid);
}

int common_cpu_up(unsigned int cpu, struct task_struct *idle)
{
        int ret;

        /* Just in case we booted with a single CPU. */
        alternatives_enable_smp();

        per_cpu(current_task, cpu) = idle;
        cpu_init_stack_canary(cpu, idle);

        /* Initialize the interrupt stack(s) */
        ret = irq_init_percpu_irqstack(cpu);
        if (ret)
                return ret;

#ifdef CONFIG_X86_32
        /* Stack for startup_32 can be just as for start_secondary onwards */
        per_cpu(cpu_current_top_of_stack, cpu) = task_top_of_stack(idle);
#endif
        return 0;
}

/*
 * NOTE - on most systems this is a PHYSICAL apic ID, but on multiquad
 * (ie clustered apic addressing mode), this is a LOGICAL apic ID.
 * Returns zero if startup was successfully sent, else error code from
 * ->wakeup_secondary_cpu.
 */
static int do_boot_cpu(u32 apicid, unsigned int cpu, struct task_struct *idle)
{
        unsigned long start_ip = real_mode_header->trampoline_start;
        int ret;

#ifdef CONFIG_X86_64
        /* If 64-bit wakeup method exists, use the 64-bit mode trampoline IP */
        if (apic->wakeup_secondary_cpu_64)
                start_ip = real_mode_header->trampoline_start64;
#endif
        idle->thread.sp = (unsigned long)task_pt_regs(idle);
        initial_code = (unsigned long)start_secondary;

        if (IS_ENABLED(CONFIG_X86_32)) {
                early_gdt_descr.address = (unsigned long)get_cpu_gdt_rw(cpu);
                initial_stack  = idle->thread.sp;
        } else if (!(smpboot_control & STARTUP_PARALLEL_MASK)) {
                smpboot_control = cpu;
        }

        /* Enable the espfix hack for this CPU */
        init_espfix_ap(cpu);

        /* So we see what's up */
        announce_cpu(cpu, apicid);

        /*
         * This grunge runs the startup process for
         * the targeted processor.
         */
        if (x86_platform.legacy.warm_reset) {

                pr_debug("Setting warm reset code and vector.\n");

                smpboot_setup_warm_reset_vector(start_ip);
                /*
                 * Be paranoid about clearing APIC errors.
                */
                if (APIC_INTEGRATED(boot_cpu_apic_version)) {
                        apic_write(APIC_ESR, 0);
                        apic_read(APIC_ESR);
                }
        }

        smp_mb();

        /*
         * Wake up a CPU in difference cases:
         * - Use a method from the APIC driver if one defined, with wakeup
         *   straight to 64-bit mode preferred over wakeup to RM.
         * Otherwise,
         * - Use an INIT boot APIC message
         */
        if (apic->wakeup_secondary_cpu_64)
                ret = apic->wakeup_secondary_cpu_64(apicid, start_ip, cpu);
        else if (apic->wakeup_secondary_cpu)
                ret = apic->wakeup_secondary_cpu(apicid, start_ip, cpu);
        else
                ret = wakeup_secondary_cpu_via_init(apicid, start_ip, cpu);

        /* If the wakeup mechanism failed, cleanup the warm reset vector */
        if (ret)
                arch_cpuhp_cleanup_kick_cpu(cpu);
        return ret;
}

int native_kick_ap(unsigned int cpu, struct task_struct *tidle)
{
        u32 apicid = apic->cpu_present_to_apicid(cpu);
        int err;

        lockdep_assert_irqs_enabled();

        pr_debug("++++++++++++++++++++=_---CPU UP  %u\n", cpu);

        if (apicid == BAD_APICID || !apic_id_valid(apicid)) {
                pr_err("CPU %u has invalid APIC ID %x. Aborting bringup\n", cpu, apicid);
                return -EINVAL;
        }

        if (!test_bit(apicid, phys_cpu_present_map)) {
                pr_err("CPU %u APIC ID %x is not present. Aborting bringup\n", cpu, apicid);
                return -EINVAL;
        }

        /*
         * Save current MTRR state in case it was changed since early boot
         * (e.g. by the ACPI SMI) to initialize new CPUs with MTRRs in sync:
         */
        mtrr_save_state();

        /* the FPU context is blank, nobody can own it */
        per_cpu(fpu_fpregs_owner_ctx, cpu) = NULL;

        err = common_cpu_up(cpu, tidle);
        if (err)
                return err;

        err = do_boot_cpu(apicid, cpu, tidle);
        if (err)
                pr_err("do_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu);

        return err;
}

int arch_cpuhp_kick_ap_alive(unsigned int cpu, struct task_struct *tidle)
{
        return smp_ops.kick_ap_alive(cpu, tidle);
}

void arch_cpuhp_cleanup_kick_cpu(unsigned int cpu)
{
        /* Cleanup possible dangling ends... */
        if (smp_ops.kick_ap_alive == native_kick_ap && x86_platform.legacy.warm_reset)
                smpboot_restore_warm_reset_vector();
}

void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu)
{
        if (smp_ops.cleanup_dead_cpu)
                smp_ops.cleanup_dead_cpu(cpu);

        if (system_state == SYSTEM_RUNNING)
                pr_info("CPU %u is now offline\n", cpu);
}

void arch_cpuhp_sync_state_poll(void)
{
        if (smp_ops.poll_sync_state)
                smp_ops.poll_sync_state();
}

/**
 * arch_disable_smp_support() - Disables SMP support for x86 at boottime
 */
void __init arch_disable_smp_support(void)
{
        disable_ioapic_support();
}

/*
 * Fall back to non SMP mode after errors.
 *
 * RED-PEN audit/test this more. I bet there is more state messed up here.
 */
static __init void disable_smp(void)
{
        pr_info("SMP disabled\n");

        disable_ioapic_support();
        topology_reset_possible_cpus_up();

        cpumask_set_cpu(0, topology_sibling_cpumask(0));
        cpumask_set_cpu(0, topology_core_cpumask(0));
        cpumask_set_cpu(0, topology_die_cpumask(0));
}

void __init smp_prepare_cpus_common(void)
{
        unsigned int cpu, node;

        /* Mark all except the boot CPU as hotpluggable */
        for_each_possible_cpu(cpu) {
                if (cpu)
                        per_cpu(cpu_info.cpu_index, cpu) = nr_cpu_ids;
        }

        for_each_possible_cpu(cpu) {
                node = cpu_to_node(cpu);

                zalloc_cpumask_var_node(&per_cpu(cpu_sibling_map,    cpu), GFP_KERNEL, node);
                zalloc_cpumask_var_node(&per_cpu(cpu_core_map,       cpu), GFP_KERNEL, node);
                zalloc_cpumask_var_node(&per_cpu(cpu_die_map,        cpu), GFP_KERNEL, node);
                zalloc_cpumask_var_node(&per_cpu(cpu_llc_shared_map, cpu), GFP_KERNEL, node);
                zalloc_cpumask_var_node(&per_cpu(cpu_l2c_shared_map, cpu), GFP_KERNEL, node);
        }

        set_cpu_sibling_map(0);
}

void __init smp_prepare_boot_cpu(void)
{
        smp_ops.smp_prepare_boot_cpu();
}

#ifdef CONFIG_X86_64
/* Establish whether parallel bringup can be supported. */
bool __init arch_cpuhp_init_parallel_bringup(void)
{
        if (!x86_cpuinit.parallel_bringup) {
                pr_info("Parallel CPU startup disabled by the platform\n");
                return false;
        }

        smpboot_control = STARTUP_READ_APICID;
        pr_debug("Parallel CPU startup enabled: 0x%08x\n", smpboot_control);
        return true;
}
#endif

/*
 * Prepare for SMP bootup.
 * @max_cpus: configured maximum number of CPUs, It is a legacy parameter
 *            for common interface support.
 */
void __init native_smp_prepare_cpus(unsigned int max_cpus)
{
        smp_prepare_cpus_common();

        switch (apic_intr_mode) {
        case APIC_PIC:
        case APIC_VIRTUAL_WIRE_NO_CONFIG:
                disable_smp();
                return;
        case APIC_SYMMETRIC_IO_NO_ROUTING:
                disable_smp();
                /* Setup local timer */
                x86_init.timers.setup_percpu_clockev();
                return;
        case APIC_VIRTUAL_WIRE:
        case APIC_SYMMETRIC_IO:
                break;
        }

        /* Setup local timer */
        x86_init.timers.setup_percpu_clockev();

        pr_info("CPU0: ");
        print_cpu_info(&cpu_data(0));

        uv_system_init();

        smp_set_init_udelay();

        speculative_store_bypass_ht_init();

        snp_set_wakeup_secondary_cpu();
}

void arch_thaw_secondary_cpus_begin(void)
{
        set_cache_aps_delayed_init(true);
}

void arch_thaw_secondary_cpus_end(void)
{
        cache_aps_init();
}

/*
 * Early setup to make printk work.
 */
void __init native_smp_prepare_boot_cpu(void)
{
        int me = smp_processor_id();

        /* SMP handles this from setup_per_cpu_areas() */
        if (!IS_ENABLED(CONFIG_SMP))
                switch_gdt_and_percpu_base(me);

        native_pv_lock_init();
}

void __init native_smp_cpus_done(unsigned int max_cpus)
{
        pr_debug("Boot done\n");

        build_sched_topology();
        nmi_selftest();
        impress_friends();
        cache_aps_init();
}

/* correctly size the local cpu masks */
void __init setup_cpu_local_masks(void)
{
        alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);
}

#ifdef CONFIG_HOTPLUG_CPU

/* Recompute SMT state for all CPUs on offline */
static void recompute_smt_state(void)
{
        int max_threads, cpu;

        max_threads = 0;
        for_each_online_cpu (cpu) {
                int threads = cpumask_weight(topology_sibling_cpumask(cpu));

                if (threads > max_threads)
                        max_threads = threads;
        }
        __max_smt_threads = max_threads;
}

static void remove_siblinginfo(int cpu)
{
        int sibling;
        struct cpuinfo_x86 *c = &cpu_data(cpu);

        for_each_cpu(sibling, topology_core_cpumask(cpu)) {
                cpumask_clear_cpu(cpu, topology_core_cpumask(sibling));
                /*/
                 * last thread sibling in this cpu core going down
                 */
                if (cpumask_weight(topology_sibling_cpumask(cpu)) == 1)
                        cpu_data(sibling).booted_cores--;
        }

        for_each_cpu(sibling, topology_die_cpumask(cpu))
                cpumask_clear_cpu(cpu, topology_die_cpumask(sibling));

        for_each_cpu(sibling, topology_sibling_cpumask(cpu)) {
                cpumask_clear_cpu(cpu, topology_sibling_cpumask(sibling));
                if (cpumask_weight(topology_sibling_cpumask(sibling)) == 1)
                        cpu_data(sibling).smt_active = false;
        }

        for_each_cpu(sibling, cpu_llc_shared_mask(cpu))
                cpumask_clear_cpu(cpu, cpu_llc_shared_mask(sibling));
        for_each_cpu(sibling, cpu_l2c_shared_mask(cpu))
                cpumask_clear_cpu(cpu, cpu_l2c_shared_mask(sibling));
        cpumask_clear(cpu_llc_shared_mask(cpu));
        cpumask_clear(cpu_l2c_shared_mask(cpu));
        cpumask_clear(topology_sibling_cpumask(cpu));
        cpumask_clear(topology_core_cpumask(cpu));
        cpumask_clear(topology_die_cpumask(cpu));
        c->topo.core_id = 0;
        c->booted_cores = 0;
        cpumask_clear_cpu(cpu, cpu_sibling_setup_mask);
        recompute_smt_state();
}

static void remove_cpu_from_maps(int cpu)
{
        set_cpu_online(cpu, false);
        numa_remove_cpu(cpu);
}

void cpu_disable_common(void)
{
        int cpu = smp_processor_id();

        remove_siblinginfo(cpu);

        /*
         * Stop allowing kernel-mode FPU. This is needed so that if the CPU is
         * brought online again, the initial state is not allowed:
         */
        this_cpu_write(kernel_fpu_allowed, false);

        /* It's now safe to remove this processor from the online map */
        lock_vector_lock();
        remove_cpu_from_maps(cpu);
        unlock_vector_lock();
        fixup_irqs();
        lapic_offline();
}

int native_cpu_disable(void)
{
        int ret;

        ret = lapic_can_unplug_cpu();
        if (ret)
                return ret;

        cpu_disable_common();

        /*
         * Disable the local APIC. Otherwise IPI broadcasts will reach
         * it. It still responds normally to INIT, NMI, SMI, and SIPI
         * messages.
         *
         * Disabling the APIC must happen after cpu_disable_common()
         * which invokes fixup_irqs().
         *
         * Disabling the APIC preserves already set bits in IRR, but
         * an interrupt arriving after disabling the local APIC does not
         * set the corresponding IRR bit.
         *
         * fixup_irqs() scans IRR for set bits so it can raise a not
         * yet handled interrupt on the new destination CPU via an IPI
         * but obviously it can't do so for IRR bits which are not set.
         * IOW, interrupts arriving after disabling the local APIC will
         * be lost.
         */
        apic_soft_disable();

        return 0;
}

void play_dead_common(void)
{
        idle_task_exit();

        cpuhp_ap_report_dead();

        local_irq_disable();
}

/*
 * We need to flush the caches before going to sleep, lest we have
 * dirty data in our caches when we come back up.
 */
void __noreturn mwait_play_dead(unsigned int eax_hint)
{
        struct mwait_cpu_dead *md = this_cpu_ptr(&mwait_cpu_dead);

        /* Set up state for the kexec() hack below */
        md->status = CPUDEAD_MWAIT_WAIT;
        md->control = CPUDEAD_MWAIT_WAIT;

        wbinvd();

        while (1) {
                /*
                 * The CLFLUSH is a workaround for erratum AAI65 for
                 * the Xeon 7400 series.  It's not clear it is actually
                 * needed, but it should be harmless in either case.
                 * The WBINVD is insufficient due to the spurious-wakeup
                 * case where we return around the loop.
                 */
                mb();
                clflush(md);
                mb();
                __monitor(md, 0, 0);
                mb();
                __mwait(eax_hint, 0);

                if (READ_ONCE(md->control) == CPUDEAD_MWAIT_KEXEC_HLT) {
                        /*
                         * Kexec is about to happen. Don't go back into mwait() as
                         * the kexec kernel might overwrite text and data including
                         * page tables and stack. So mwait() would resume when the
                         * monitor cache line is written to and then the CPU goes
                         * south due to overwritten text, page tables and stack.
                         *
                         * Note: This does _NOT_ protect against a stray MCE, NMI,
                         * SMI. They will resume execution at the instruction
                         * following the HLT instruction and run into the problem
                         * which this is trying to prevent.
                         */
                        WRITE_ONCE(md->status, CPUDEAD_MWAIT_KEXEC_HLT);
                        while(1)
                                native_halt();
                }
        }
}

/*
 * Kick all "offline" CPUs out of mwait on kexec(). See comment in
 * mwait_play_dead().
 */
void smp_kick_mwait_play_dead(void)
{
        u32 newstate = CPUDEAD_MWAIT_KEXEC_HLT;
        struct mwait_cpu_dead *md;
        unsigned int cpu, i;

        for_each_cpu_andnot(cpu, cpu_present_mask, cpu_online_mask) {
                md = per_cpu_ptr(&mwait_cpu_dead, cpu);

                /* Does it sit in mwait_play_dead() ? */
                if (READ_ONCE(md->status) != CPUDEAD_MWAIT_WAIT)
                        continue;

                /* Wait up to 5ms */
                for (i = 0; READ_ONCE(md->status) != newstate && i < 1000; i++) {
                        /* Bring it out of mwait */
                        WRITE_ONCE(md->control, newstate);
                        udelay(5);
                }

                if (READ_ONCE(md->status) != newstate)
                        pr_err_once("CPU%u is stuck in mwait_play_dead()\n", cpu);
        }
}

void __noreturn hlt_play_dead(void)
{
        if (__this_cpu_read(cpu_info.x86) >= 4)
                wbinvd();

        while (1)
                native_halt();
}

void __noreturn native_play_dead(void)
{
        if (cpu_feature_enabled(X86_FEATURE_KERNEL_IBRS))
                __update_spec_ctrl(0);

        play_dead_common();
        tboot_shutdown(TB_SHUTDOWN_WFS);

        /* Below returns only on error. */
        cpuidle_play_dead();
        hlt_play_dead();
}

#else /* ... !CONFIG_HOTPLUG_CPU */
int native_cpu_disable(void)
{
        return -ENOSYS;
}

void __noreturn native_play_dead(void)
{
        BUG();
}

#endif