arch/x86/kernel/setup_percpu.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   3
   4 #include <linux/kernel.h>
   5 #include <linux/export.h>
   6 #include <linux/init.h>
   7 #include <linux/memblock.h>
   8 #include <linux/percpu.h>
   9 #include <linux/kexec.h>
  10 #include <linux/crash_dump.h>
  11 #include <linux/smp.h>
  12 #include <linux/topology.h>
  13 #include <linux/pfn.h>
  14 #include <linux/stackprotector.h>
  15 #include <asm/sections.h>
  16 #include <asm/processor.h>
  17 #include <asm/desc.h>
  18 #include <asm/setup.h>
  19 #include <asm/mpspec.h>
  20 #include <asm/apicdef.h>
  21 #include <asm/highmem.h>
  22 #include <asm/proto.h>
  23 #include <asm/cpumask.h>
  24 #include <asm/cpu.h>
  25
  26 #ifdef CONFIG_X86_64
  27 #define BOOT_PERCPU_OFFSET ((unsigned long)__per_cpu_load)
  28 #else
  29 #define BOOT_PERCPU_OFFSET 0
  30 #endif
  31
  32 DEFINE_PER_CPU_READ_MOSTLY(unsigned long, this_cpu_off) = BOOT_PERCPU_OFFSET;
  33 EXPORT_PER_CPU_SYMBOL(this_cpu_off);
  34
  35 unsigned long __per_cpu_offset[NR_CPUS] __ro_after_init = {
  36         [0 ... NR_CPUS-1] = BOOT_PERCPU_OFFSET,
  37 };
  38 EXPORT_SYMBOL(__per_cpu_offset);
  39
  40 /*
  41  * On x86_64 symbols referenced from code should be reachable using
  42  * 32bit relocations.  Reserve space for static percpu variables in
  43  * modules so that they are always served from the first chunk which
  44  * is located at the percpu segment base.  On x86_32, anything can
  45  * address anywhere.  No need to reserve space in the first chunk.
  46  */
  47 #ifdef CONFIG_X86_64
  48 #define PERCPU_FIRST_CHUNK_RESERVE      PERCPU_MODULE_RESERVE
  49 #else
  50 #define PERCPU_FIRST_CHUNK_RESERVE      0
  51 #endif
  52
  53 #ifdef CONFIG_X86_32
  54 /**
  55  * pcpu_need_numa - determine percpu allocation needs to consider NUMA
  56  *
  57  * If NUMA is not configured or there is only one NUMA node available,
  58  * there is no reason to consider NUMA.  This function determines
  59  * whether percpu allocation should consider NUMA or not.
  60  *
  61  * RETURNS:
  62  * true if NUMA should be considered; otherwise, false.
  63  */
  64 static bool __init pcpu_need_numa(void)
  65 {
  66 #ifdef CONFIG_NUMA
  67         pg_data_t *last = NULL;
  68         unsigned int cpu;
  69
  70         for_each_possible_cpu(cpu) {
  71                 int node = early_cpu_to_node(cpu);
  72
  73                 if (node_online(node) && NODE_DATA(node) &&
  74                     last && last != NODE_DATA(node))
  75                         return true;
  76
  77                 last = NODE_DATA(node);
  78         }
  79 #endif
  80         return false;
  81 }
  82 #endif
  83
  84 static int __init pcpu_cpu_distance(unsigned int from, unsigned int to)
  85 {
  86 #ifdef CONFIG_NUMA
  87         if (early_cpu_to_node(from) == early_cpu_to_node(to))
  88                 return LOCAL_DISTANCE;
  89         else
  90                 return REMOTE_DISTANCE;
  91 #else
  92         return LOCAL_DISTANCE;
  93 #endif
  94 }
  95
  96 static int __init pcpu_cpu_to_node(int cpu)
  97 {
  98         return early_cpu_to_node(cpu);
  99 }
 100
 101 void __init pcpu_populate_pte(unsigned long addr)
 102 {
 103         populate_extra_pte(addr);
 104 }
 105
 106 static inline void setup_percpu_segment(int cpu)
 107 {
 108 #ifdef CONFIG_X86_32
 109         struct desc_struct d = GDT_ENTRY_INIT(DESC_DATA32,
 110                                               per_cpu_offset(cpu), 0xFFFFF);
 111
 112         write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_PERCPU, &d, DESCTYPE_S);
 113 #endif
 114 }
 115
 116 void __init setup_per_cpu_areas(void)
 117 {
 118         unsigned int cpu;
 119         unsigned long delta;
 120         int rc;
 121
 122         pr_info("NR_CPUS:%d nr_cpumask_bits:%d nr_cpu_ids:%u nr_node_ids:%u\n",
 123                 NR_CPUS, nr_cpumask_bits, nr_cpu_ids, nr_node_ids);
 124
 125         /*
 126          * Allocate percpu area.  Embedding allocator is our favorite;
 127          * however, on NUMA configurations, it can result in very
 128          * sparse unit mapping and vmalloc area isn't spacious enough
 129          * on 32bit.  Use page in that case.
 130          */
 131 #ifdef CONFIG_X86_32
 132         if (pcpu_chosen_fc == PCPU_FC_AUTO && pcpu_need_numa())
 133                 pcpu_chosen_fc = PCPU_FC_PAGE;
 134 #endif
 135         rc = -EINVAL;
 136         if (pcpu_chosen_fc != PCPU_FC_PAGE) {
 137                 const size_t dyn_size = PERCPU_MODULE_RESERVE +
 138                         PERCPU_DYNAMIC_RESERVE - PERCPU_FIRST_CHUNK_RESERVE;
 139                 size_t atom_size;
 140
 141                 /*
 142                  * On 64bit, use PMD_SIZE for atom_size so that embedded
 143                  * percpu areas are aligned to PMD.  This, in the future,
 144                  * can also allow using PMD mappings in vmalloc area.  Use
 145                  * PAGE_SIZE on 32bit as vmalloc space is highly contended
 146                  * and large vmalloc area allocs can easily fail.
 147                  */
 148 #ifdef CONFIG_X86_64
 149                 atom_size = PMD_SIZE;
 150 #else
 151                 atom_size = PAGE_SIZE;
 152 #endif
 153                 rc = pcpu_embed_first_chunk(PERCPU_FIRST_CHUNK_RESERVE,
 154                                             dyn_size, atom_size,
 155                                             pcpu_cpu_distance,
 156                                             pcpu_cpu_to_node);
 157                 if (rc < 0)
 158                         pr_warn("%s allocator failed (%d), falling back to page size\n",
 159                                 pcpu_fc_names[pcpu_chosen_fc], rc);
 160         }
 161         if (rc < 0)
 162                 rc = pcpu_page_first_chunk(PERCPU_FIRST_CHUNK_RESERVE,
 163                                            pcpu_cpu_to_node);
 164         if (rc < 0)
 165                 panic("cannot initialize percpu area (err=%d)", rc);
 166
 167         /* alrighty, percpu areas up and running */
 168         delta = (unsigned long)pcpu_base_addr - (unsigned long)__per_cpu_start;
 169         for_each_possible_cpu(cpu) {
 170                 per_cpu_offset(cpu) = delta + pcpu_unit_offsets[cpu];
 171                 per_cpu(this_cpu_off, cpu) = per_cpu_offset(cpu);
 172                 per_cpu(pcpu_hot.cpu_number, cpu) = cpu;
 173                 setup_percpu_segment(cpu);
 174                 /*
 175                  * Copy data used in early init routines from the
 176                  * initial arrays to the per cpu data areas.  These
 177                  * arrays then become expendable and the *_early_ptr's
 178                  * are zeroed indicating that the static arrays are
 179                  * gone.
 180                  */
 181 #ifdef CONFIG_X86_LOCAL_APIC
 182                 per_cpu(x86_cpu_to_apicid, cpu) =
 183                         early_per_cpu_map(x86_cpu_to_apicid, cpu);
 184                 per_cpu(x86_cpu_to_acpiid, cpu) =
 185                         early_per_cpu_map(x86_cpu_to_acpiid, cpu);
 186 #endif
 187 #ifdef CONFIG_NUMA
 188                 per_cpu(x86_cpu_to_node_map, cpu) =
 189                         early_per_cpu_map(x86_cpu_to_node_map, cpu);
 190                 /*
 191                  * Ensure that the boot cpu numa_node is correct when the boot
 192                  * cpu is on a node that doesn't have memory installed.
 193                  * Also cpu_up() will call cpu_to_node() for APs when
 194                  * MEMORY_HOTPLUG is defined, before per_cpu(numa_node) is set
 195                  * up later with c_init aka intel_init/amd_init.
 196                  * So set them all (boot cpu and all APs).
 197                  */
 198                 set_cpu_numa_node(cpu, early_cpu_to_node(cpu));
 199 #endif
 200                 /*
 201                  * Up to this point, the boot CPU has been using .init.data
 202                  * area.  Reload any changed state for the boot CPU.
 203                  */
 204                 if (!cpu)
 205                         switch_gdt_and_percpu_base(cpu);
 206         }
 207
 208         /* indicate the early static arrays will soon be gone */
 209 #ifdef CONFIG_X86_LOCAL_APIC
 210         early_per_cpu_ptr(x86_cpu_to_apicid) = NULL;
 211         early_per_cpu_ptr(x86_cpu_to_acpiid) = NULL;
 212 #endif
 213 #ifdef CONFIG_NUMA
 214         early_per_cpu_ptr(x86_cpu_to_node_map) = NULL;
 215 #endif
 216
 217         /* Setup node to cpumask map */
 218         setup_node_to_cpumask_map();
 219
 220         /* Setup cpu initialized, callin, callout masks */
 221         setup_cpu_local_masks();
 222
 223         /*
 224          * Sync back kernel address range again.  We already did this in
 225          * setup_arch(), but percpu data also needs to be available in
 226          * the smpboot asm and arch_sync_kernel_mappings() doesn't sync to
 227          * swapper_pg_dir on 32-bit. The per-cpu mappings need to be available
 228          * there too.
 229          *
 230          * FIXME: Can the later sync in setup_cpu_entry_areas() replace
 231          * this call?
 232          */
 233         sync_initial_page_table();
 234 }