setup_percpu.c

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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/bootmem.h>
#include <linux/percpu.h>
#include <linux/kexec.h>
#include <linux/crash_dump.h>
#include <linux/smp.h>
#include <linux/topology.h>
#include <linux/pfn.h>
#include <asm/sections.h>
#include <asm/processor.h>
#include <asm/setup.h>
#include <asm/mpspec.h>
#include <asm/apicdef.h>
#include <asm/highmem.h>
#include <asm/proto.h>
#include <asm/cpumask.h>
#include <asm/cpu.h>
#include <asm/stackprotector.h>

DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number);
EXPORT_PER_CPU_SYMBOL(cpu_number);

#ifdef CONFIG_X86_64
#define BOOT_PERCPU_OFFSET ((unsigned long)__per_cpu_load)
#else
#define BOOT_PERCPU_OFFSET 0
#endif

DEFINE_PER_CPU(unsigned long, this_cpu_off) = BOOT_PERCPU_OFFSET;
EXPORT_PER_CPU_SYMBOL(this_cpu_off);

unsigned long __per_cpu_offset[NR_CPUS] __read_mostly = {
    [0 ... NR_CPUS-1] = BOOT_PERCPU_OFFSET,
};
EXPORT_SYMBOL(__per_cpu_offset);

/*
 * On x86_64 symbols referenced from code should be reachable using
 * 32bit relocations.  Reserve space for static percpu variables in
 * modules so that they are always served from the first chunk which
 * is located at the percpu segment base.  On x86_32, anything can
 * address anywhere.  No need to reserve space in the first chunk.
 */
#ifdef CONFIG_X86_64
#define PERCPU_FIRST_CHUNK_RESERVE  PERCPU_MODULE_RESERVE
#else
#define PERCPU_FIRST_CHUNK_RESERVE  0
#endif

#ifdef CONFIG_X86_32

static bool __init pcpu_need_numa(void)
{
#ifdef CONFIG_NEED_MULTIPLE_NODES
    pg_data_t *last = NULL;
    unsigned int cpu;

    for_each_possible_cpu(cpu) {
        int node = early_cpu_to_node(cpu);

        if (node_online(node) && NODE_DATA(node) &&
            last && last != NODE_DATA(node))
            return true;

        last = NODE_DATA(node);
    }
#endif
    return false;
}
#endif

static void * __init pcpu_alloc_bootmem(unsigned int cpu, unsigned long size,
                    unsigned long align)
{
    const unsigned long goal = __pa(MAX_DMA_ADDRESS);
#ifdef CONFIG_NEED_MULTIPLE_NODES
    int node = early_cpu_to_node(cpu);
    void *ptr;

    if (!node_online(node) || !NODE_DATA(node)) {
        ptr = __alloc_bootmem_nopanic(size, align, goal);
        pr_info("cpu %d has no node %d or node-local memory\n",
            cpu, node);
        pr_debug("per cpu data for cpu%d %lu bytes at %016lx\n",
             cpu, size, __pa(ptr));
    } else {
        ptr = __alloc_bootmem_node_nopanic(NODE_DATA(node),
                           size, align, goal);
        pr_debug("per cpu data for cpu%d %lu bytes on node%d at %016lx\n",
             cpu, size, node, __pa(ptr));
    }
    return ptr;
#else
    return __alloc_bootmem_nopanic(size, align, goal);
#endif
}

/*
 * Helpers for first chunk memory allocation
 */
static void * __init pcpu_fc_alloc(unsigned int cpu, size_t size, size_t align)
{
    return pcpu_alloc_bootmem(cpu, size, align);
}

static void __init pcpu_fc_free(void *ptr, size_t size)
{
    free_bootmem(__pa(ptr), size);
}

static int __init pcpu_cpu_distance(unsigned int from, unsigned int to)
{
#ifdef CONFIG_NEED_MULTIPLE_NODES
    if (early_cpu_to_node(from) == early_cpu_to_node(to))
        return LOCAL_DISTANCE;
    else
        return REMOTE_DISTANCE;
#else
    return LOCAL_DISTANCE;
#endif
}

static void __init pcpup_populate_pte(unsigned long addr)
{
    populate_extra_pte(addr);
}

static inline void setup_percpu_segment(int cpu)
{
#ifdef CONFIG_X86_32
    struct desc_struct gdt;

    pack_descriptor(&gdt, per_cpu_offset(cpu), 0xFFFFF,
            0x2 | DESCTYPE_S, 0x8);
    gdt.s = 1;
    write_gdt_entry(get_cpu_gdt_table(cpu),
            GDT_ENTRY_PERCPU, &gdt, DESCTYPE_S);
#endif
}

void __init setup_per_cpu_areas(void)
{
    unsigned int cpu;
    unsigned long delta;
    int rc;

    pr_info("NR_CPUS:%d nr_cpumask_bits:%d nr_cpu_ids:%d nr_node_ids:%d\n",
        NR_CPUS, nr_cpumask_bits, nr_cpu_ids, nr_node_ids);

    /*
     * Allocate percpu area.  Embedding allocator is our favorite;
     * however, on NUMA configurations, it can result in very
     * sparse unit mapping and vmalloc area isn't spacious enough
     * on 32bit.  Use page in that case.
     */
#ifdef CONFIG_X86_32
    if (pcpu_chosen_fc == PCPU_FC_AUTO && pcpu_need_numa())
        pcpu_chosen_fc = PCPU_FC_PAGE;
#endif
    rc = -EINVAL;
    if (pcpu_chosen_fc != PCPU_FC_PAGE) {
        const size_t dyn_size = PERCPU_MODULE_RESERVE +
            PERCPU_DYNAMIC_RESERVE - PERCPU_FIRST_CHUNK_RESERVE;
        size_t atom_size;

        /*
         * On 64bit, use PMD_SIZE for atom_size so that embedded
         * percpu areas are aligned to PMD.  This, in the future,
         * can also allow using PMD mappings in vmalloc area.  Use
         * PAGE_SIZE on 32bit as vmalloc space is highly contended
         * and large vmalloc area allocs can easily fail.
         */
#ifdef CONFIG_X86_64
        atom_size = PMD_SIZE;
#else
        atom_size = PAGE_SIZE;
#endif
        rc = pcpu_embed_first_chunk(PERCPU_FIRST_CHUNK_RESERVE,
                        dyn_size, atom_size,
                        pcpu_cpu_distance,
                        pcpu_fc_alloc, pcpu_fc_free);
        if (rc < 0)
            pr_warning("%s allocator failed (%d), falling back to page size\n",
                   pcpu_fc_names[pcpu_chosen_fc], rc);
    }
    if (rc < 0)
        rc = pcpu_page_first_chunk(PERCPU_FIRST_CHUNK_RESERVE,
                       pcpu_fc_alloc, pcpu_fc_free,
                       pcpup_populate_pte);
    if (rc < 0)
        panic("cannot initialize percpu area (err=%d)", rc);

    /* alrighty, percpu areas up and running */
    delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
    for_each_possible_cpu(cpu) {
        per_cpu_offset(cpu) = delta + pcpu_unit_offsets[cpu];
        per_cpu(this_cpu_off, cpu) = per_cpu_offset(cpu);
        per_cpu(cpu_number, cpu) = cpu;
        setup_percpu_segment(cpu);
        setup_stack_canary_segment(cpu);
        /*
         * Copy data used in early init routines from the
         * initial arrays to the per cpu data areas.  These
         * arrays then become expendable and the *_early_ptr's
         * are zeroed indicating that the static arrays are
         * gone.
         */
#ifdef CONFIG_X86_LOCAL_APIC
        per_cpu(x86_cpu_to_apicid, cpu) =
            early_per_cpu_map(x86_cpu_to_apicid, cpu);
        per_cpu(x86_bios_cpu_apicid, cpu) =
            early_per_cpu_map(x86_bios_cpu_apicid, cpu);
#endif
#ifdef CONFIG_X86_32
        per_cpu(x86_cpu_to_logical_apicid, cpu) =
            early_per_cpu_map(x86_cpu_to_logical_apicid, cpu);
#endif
#ifdef CONFIG_X86_64
        per_cpu(irq_stack_ptr, cpu) =
            per_cpu(irq_stack_union.irq_stack, cpu) +
            IRQ_STACK_SIZE - 64;
#endif
#ifdef CONFIG_NUMA
        per_cpu(x86_cpu_to_node_map, cpu) =
            early_per_cpu_map(x86_cpu_to_node_map, cpu);
        /*
         * Ensure that the boot cpu numa_node is correct when the boot
         * cpu is on a node that doesn't have memory installed.
         * Also cpu_up() will call cpu_to_node() for APs when
         * MEMORY_HOTPLUG is defined, before per_cpu(numa_node) is set
         * up later with c_init aka intel_init/amd_init.
         * So set them all (boot cpu and all APs).
         */
        set_cpu_numa_node(cpu, early_cpu_to_node(cpu));
#endif
        /*
         * Up to this point, the boot CPU has been using .init.data
         * area.  Reload any changed state for the boot CPU.
         */
        if (!cpu)
            switch_to_new_gdt(cpu);
    }

    /* indicate the early static arrays will soon be gone */
#ifdef CONFIG_X86_LOCAL_APIC
    early_per_cpu_ptr(x86_cpu_to_apicid) = NULL;
    early_per_cpu_ptr(x86_bios_cpu_apicid) = NULL;
#endif
#ifdef CONFIG_X86_32
    early_per_cpu_ptr(x86_cpu_to_logical_apicid) = NULL;
#endif
#ifdef CONFIG_NUMA
    early_per_cpu_ptr(x86_cpu_to_node_map) = NULL;
#endif

    /* Setup node to cpumask map */
    setup_node_to_cpumask_map();

    /* Setup cpu initialized, callin, callout masks */
    setup_cpu_local_masks();
}