// SPDX-License-Identifier: GPL-2.0
#include <linux/threads.h>
#include <linux/cpumask.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/ctype.h>
#include <linux/dmar.h>
#include <linux/irq.h>
#include <linux/cpu.h>

#include <asm/smp.h>
#include <asm/x2apic.h>

static DEFINE_PER_CPU(u32, x86_cpu_to_logical_apicid);
static DEFINE_PER_CPU(cpumask_var_t, cpus_in_cluster);
static DEFINE_PER_CPU(cpumask_var_t, ipi_mask);

static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
{
        return x2apic_enabled();
}

static inline u32 x2apic_cluster(int cpu)
{
        return per_cpu(x86_cpu_to_logical_apicid, cpu) >> 16;
}

static void x2apic_send_IPI(int cpu, int vector)
{
        u32 dest = per_cpu(x86_cpu_to_logical_apicid, cpu);

        x2apic_wrmsr_fence();
        __x2apic_send_IPI_dest(dest, vector, APIC_DEST_LOGICAL);
}

static void
__x2apic_send_IPI_mask(const struct cpumask *mask, int vector, int apic_dest)
{
        struct cpumask *cpus_in_cluster_ptr;
        struct cpumask *ipi_mask_ptr;
        unsigned int cpu, this_cpu;
        unsigned long flags;
        u32 dest;

        x2apic_wrmsr_fence();

        local_irq_save(flags);

        this_cpu = smp_processor_id();

        /*
         * We are to modify mask, so we need an own copy
         * and be sure it's manipulated with irq off.
         */
        ipi_mask_ptr = this_cpu_cpumask_var_ptr(ipi_mask);
        cpumask_copy(ipi_mask_ptr, mask);

        /*
         * The idea is to send one IPI per cluster.
         */
        for_each_cpu(cpu, ipi_mask_ptr) {
                unsigned long i;

                cpus_in_cluster_ptr = per_cpu(cpus_in_cluster, cpu);
                dest = 0;

                /* Collect cpus in cluster. */
                for_each_cpu_and(i, ipi_mask_ptr, cpus_in_cluster_ptr) {
                        if (apic_dest == APIC_DEST_ALLINC || i != this_cpu)
                                dest |= per_cpu(x86_cpu_to_logical_apicid, i);
                }

                if (!dest)
                        continue;

                __x2apic_send_IPI_dest(dest, vector, apic->dest_logical);
                /*
                 * Cluster sibling cpus should be discared now so
                 * we would not send IPI them second time.
                 */
                cpumask_andnot(ipi_mask_ptr, ipi_mask_ptr, cpus_in_cluster_ptr);
        }

        local_irq_restore(flags);
}

static void x2apic_send_IPI_mask(const struct cpumask *mask, int vector)
{
        __x2apic_send_IPI_mask(mask, vector, APIC_DEST_ALLINC);
}

static void
x2apic_send_IPI_mask_allbutself(const struct cpumask *mask, int vector)
{
        __x2apic_send_IPI_mask(mask, vector, APIC_DEST_ALLBUT);
}

static void x2apic_send_IPI_allbutself(int vector)
{
        __x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLBUT);
}

static void x2apic_send_IPI_all(int vector)
{
        __x2apic_send_IPI_mask(cpu_online_mask, vector, APIC_DEST_ALLINC);
}

static int
x2apic_cpu_mask_to_apicid(const struct cpumask *mask, struct irq_data *irqdata,
                          unsigned int *apicid)
{
        struct cpumask *effmsk = irq_data_get_effective_affinity_mask(irqdata);
        unsigned int cpu;
        u32 dest = 0;
        u16 cluster;

        cpu = cpumask_first(mask);
        if (cpu >= nr_cpu_ids)
                return -EINVAL;

        dest = per_cpu(x86_cpu_to_logical_apicid, cpu);
        cluster = x2apic_cluster(cpu);

        cpumask_clear(effmsk);
        for_each_cpu(cpu, mask) {
                if (cluster != x2apic_cluster(cpu))
                        continue;
                dest |= per_cpu(x86_cpu_to_logical_apicid, cpu);
                cpumask_set_cpu(cpu, effmsk);
        }

        *apicid = dest;
        return 0;
}

static void init_x2apic_ldr(void)
{
        unsigned int this_cpu = smp_processor_id();
        unsigned int cpu;

        per_cpu(x86_cpu_to_logical_apicid, this_cpu) = apic_read(APIC_LDR);

        cpumask_set_cpu(this_cpu, per_cpu(cpus_in_cluster, this_cpu));
        for_each_online_cpu(cpu) {
                if (x2apic_cluster(this_cpu) != x2apic_cluster(cpu))
                        continue;
                cpumask_set_cpu(this_cpu, per_cpu(cpus_in_cluster, cpu));
                cpumask_set_cpu(cpu, per_cpu(cpus_in_cluster, this_cpu));
        }
}

/*
 * At CPU state changes, update the x2apic cluster sibling info.
 */
static int x2apic_prepare_cpu(unsigned int cpu)
{
        if (!zalloc_cpumask_var(&per_cpu(cpus_in_cluster, cpu), GFP_KERNEL))
                return -ENOMEM;

        if (!zalloc_cpumask_var(&per_cpu(ipi_mask, cpu), GFP_KERNEL)) {
                free_cpumask_var(per_cpu(cpus_in_cluster, cpu));
                return -ENOMEM;
        }

        return 0;
}

static int x2apic_dead_cpu(unsigned int this_cpu)
{
        int cpu;

        for_each_online_cpu(cpu) {
                if (x2apic_cluster(this_cpu) != x2apic_cluster(cpu))
                        continue;
                cpumask_clear_cpu(this_cpu, per_cpu(cpus_in_cluster, cpu));
                cpumask_clear_cpu(cpu, per_cpu(cpus_in_cluster, this_cpu));
        }
        free_cpumask_var(per_cpu(cpus_in_cluster, this_cpu));
        free_cpumask_var(per_cpu(ipi_mask, this_cpu));
        return 0;
}

static int x2apic_cluster_probe(void)
{
        int cpu = smp_processor_id();
        int ret;

        if (!x2apic_mode)
                return 0;

        ret = cpuhp_setup_state(CPUHP_X2APIC_PREPARE, "x86/x2apic:prepare",
                                x2apic_prepare_cpu, x2apic_dead_cpu);
        if (ret < 0) {
                pr_err("Failed to register X2APIC_PREPARE\n");
                return 0;
        }
        cpumask_set_cpu(cpu, per_cpu(cpus_in_cluster, cpu));
        return 1;
}

static const struct cpumask *x2apic_cluster_target_cpus(void)
{
        return cpu_all_mask;
}

/*
 * Each x2apic cluster is an allocation domain.
 */
static void cluster_vector_allocation_domain(int cpu, struct cpumask *retmask,
                                             const struct cpumask *mask)
{
        /*
         * To minimize vector pressure, default case of boot, device bringup
         * etc will use a single cpu for the interrupt destination.
         *
         * On explicit migration requests coming from irqbalance etc,
         * interrupts will be routed to the x2apic cluster (cluster-id
         * derived from the first cpu in the mask) members specified
         * in the mask.
         */
        if (mask == x2apic_cluster_target_cpus())
                cpumask_copy(retmask, cpumask_of(cpu));
        else
                cpumask_and(retmask, mask, per_cpu(cpus_in_cluster, cpu));
}

static struct apic apic_x2apic_cluster __ro_after_init = {

        .name                           = "cluster x2apic",
        .probe                          = x2apic_cluster_probe,
        .acpi_madt_oem_check            = x2apic_acpi_madt_oem_check,
        .apic_id_valid                  = x2apic_apic_id_valid,
        .apic_id_registered             = x2apic_apic_id_registered,

        .irq_delivery_mode              = dest_LowestPrio,
        .irq_dest_mode                  = 1, /* logical */

        .target_cpus                    = x2apic_cluster_target_cpus,
        .disable_esr                    = 0,
        .dest_logical                   = APIC_DEST_LOGICAL,
        .check_apicid_used              = NULL,

        .vector_allocation_domain       = cluster_vector_allocation_domain,
        .init_apic_ldr                  = init_x2apic_ldr,

        .ioapic_phys_id_map             = NULL,
        .setup_apic_routing             = NULL,
        .cpu_present_to_apicid          = default_cpu_present_to_apicid,
        .apicid_to_cpu_present          = NULL,
        .check_phys_apicid_present      = default_check_phys_apicid_present,
        .phys_pkg_id                    = x2apic_phys_pkg_id,

        .get_apic_id                    = x2apic_get_apic_id,
        .set_apic_id                    = x2apic_set_apic_id,

        .cpu_mask_to_apicid             = x2apic_cpu_mask_to_apicid,

        .send_IPI                       = x2apic_send_IPI,
        .send_IPI_mask                  = x2apic_send_IPI_mask,
        .send_IPI_mask_allbutself       = x2apic_send_IPI_mask_allbutself,
        .send_IPI_allbutself            = x2apic_send_IPI_allbutself,
        .send_IPI_all                   = x2apic_send_IPI_all,
        .send_IPI_self                  = x2apic_send_IPI_self,

        .inquire_remote_apic            = NULL,

        .read                           = native_apic_msr_read,
        .write                          = native_apic_msr_write,
        .eoi_write                      = native_apic_msr_eoi_write,
        .icr_read                       = native_x2apic_icr_read,
        .icr_write                      = native_x2apic_icr_write,
        .wait_icr_idle                  = native_x2apic_wait_icr_idle,
        .safe_wait_icr_idle             = native_safe_x2apic_wait_icr_idle,
};

apic_driver(apic_x2apic_cluster);