linux/drivers/base/cpu.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * CPU subsystem support
   4 */
   5
   6#include <linux/kernel.h>
   7#include <linux/module.h>
   8#include <linux/init.h>
   9#include <linux/sched.h>
  10#include <linux/cpu.h>
  11#include <linux/topology.h>
  12#include <linux/device.h>
  13#include <linux/node.h>
  14#include <linux/gfp.h>
  15#include <linux/slab.h>
  16#include <linux/percpu.h>
  17#include <linux/acpi.h>
  18#include <linux/of.h>
  19#include <linux/cpufeature.h>
  20#include <linux/tick.h>
  21#include <linux/pm_qos.h>
  22#include <linux/sched/isolation.h>
  23
  24#include "base.h"
  25
  26static DEFINE_PER_CPU(struct device *, cpu_sys_devices);
  27
  28static int cpu_subsys_match(struct device *dev, struct device_driver *drv)
  29{
  30        /* ACPI style match is the only one that may succeed. */
  31        if (acpi_driver_match_device(dev, drv))
  32                return 1;
  33
  34        return 0;
  35}
  36
  37#ifdef CONFIG_HOTPLUG_CPU
  38static void change_cpu_under_node(struct cpu *cpu,
  39                        unsigned int from_nid, unsigned int to_nid)
  40{
  41        int cpuid = cpu->dev.id;
  42        unregister_cpu_under_node(cpuid, from_nid);
  43        register_cpu_under_node(cpuid, to_nid);
  44        cpu->node_id = to_nid;
  45}
  46
  47static int cpu_subsys_online(struct device *dev)
  48{
  49        struct cpu *cpu = container_of(dev, struct cpu, dev);
  50        int cpuid = dev->id;
  51        int from_nid, to_nid;
  52        int ret;
  53
  54        from_nid = cpu_to_node(cpuid);
  55        if (from_nid == NUMA_NO_NODE)
  56                return -ENODEV;
  57
  58        ret = cpu_up(cpuid);
  59        /*
  60         * When hot adding memory to memoryless node and enabling a cpu
  61         * on the node, node number of the cpu may internally change.
  62         */
  63        to_nid = cpu_to_node(cpuid);
  64        if (from_nid != to_nid)
  65                change_cpu_under_node(cpu, from_nid, to_nid);
  66
  67        return ret;
  68}
  69
  70static int cpu_subsys_offline(struct device *dev)
  71{
  72        return cpu_down(dev->id);
  73}
  74
  75void unregister_cpu(struct cpu *cpu)
  76{
  77        int logical_cpu = cpu->dev.id;
  78
  79        unregister_cpu_under_node(logical_cpu, cpu_to_node(logical_cpu));
  80
  81        device_unregister(&cpu->dev);
  82        per_cpu(cpu_sys_devices, logical_cpu) = NULL;
  83        return;
  84}
  85
  86#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
  87static ssize_t cpu_probe_store(struct device *dev,
  88                               struct device_attribute *attr,
  89                               const char *buf,
  90                               size_t count)
  91{
  92        ssize_t cnt;
  93        int ret;
  94
  95        ret = lock_device_hotplug_sysfs();
  96        if (ret)
  97                return ret;
  98
  99        cnt = arch_cpu_probe(buf, count);
 100
 101        unlock_device_hotplug();
 102        return cnt;
 103}
 104
 105static ssize_t cpu_release_store(struct device *dev,
 106                                 struct device_attribute *attr,
 107                                 const char *buf,
 108                                 size_t count)
 109{
 110        ssize_t cnt;
 111        int ret;
 112
 113        ret = lock_device_hotplug_sysfs();
 114        if (ret)
 115                return ret;
 116
 117        cnt = arch_cpu_release(buf, count);
 118
 119        unlock_device_hotplug();
 120        return cnt;
 121}
 122
 123static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
 124static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
 125#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 126#endif /* CONFIG_HOTPLUG_CPU */
 127
 128struct bus_type cpu_subsys = {
 129        .name = "cpu",
 130        .dev_name = "cpu",
 131        .match = cpu_subsys_match,
 132#ifdef CONFIG_HOTPLUG_CPU
 133        .online = cpu_subsys_online,
 134        .offline = cpu_subsys_offline,
 135#endif
 136};
 137EXPORT_SYMBOL_GPL(cpu_subsys);
 138
 139#ifdef CONFIG_KEXEC
 140#include <linux/kexec.h>
 141
 142static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
 143                                char *buf)
 144{
 145        struct cpu *cpu = container_of(dev, struct cpu, dev);
 146        ssize_t rc;
 147        unsigned long long addr;
 148        int cpunum;
 149
 150        cpunum = cpu->dev.id;
 151
 152        /*
 153         * Might be reading other cpu's data based on which cpu read thread
 154         * has been scheduled. But cpu data (memory) is allocated once during
 155         * boot up and this data does not change there after. Hence this
 156         * operation should be safe. No locking required.
 157         */
 158        addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum));
 159        rc = sprintf(buf, "%Lx\n", addr);
 160        return rc;
 161}
 162static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
 163
 164static ssize_t show_crash_notes_size(struct device *dev,
 165                                     struct device_attribute *attr,
 166                                     char *buf)
 167{
 168        ssize_t rc;
 169
 170        rc = sprintf(buf, "%zu\n", sizeof(note_buf_t));
 171        return rc;
 172}
 173static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);
 174
 175static struct attribute *crash_note_cpu_attrs[] = {
 176        &dev_attr_crash_notes.attr,
 177        &dev_attr_crash_notes_size.attr,
 178        NULL
 179};
 180
 181static struct attribute_group crash_note_cpu_attr_group = {
 182        .attrs = crash_note_cpu_attrs,
 183};
 184#endif
 185
 186static const struct attribute_group *common_cpu_attr_groups[] = {
 187#ifdef CONFIG_KEXEC
 188        &crash_note_cpu_attr_group,
 189#endif
 190        NULL
 191};
 192
 193static const struct attribute_group *hotplugable_cpu_attr_groups[] = {
 194#ifdef CONFIG_KEXEC
 195        &crash_note_cpu_attr_group,
 196#endif
 197        NULL
 198};
 199
 200/*
 201 * Print cpu online, possible, present, and system maps
 202 */
 203
 204struct cpu_attr {
 205        struct device_attribute attr;
 206        const struct cpumask *const map;
 207};
 208
 209static ssize_t show_cpus_attr(struct device *dev,
 210                              struct device_attribute *attr,
 211                              char *buf)
 212{
 213        struct cpu_attr *ca = container_of(attr, struct cpu_attr, attr);
 214
 215        return cpumap_print_to_pagebuf(true, buf, ca->map);
 216}
 217
 218#define _CPU_ATTR(name, map) \
 219        { __ATTR(name, 0444, show_cpus_attr, NULL), map }
 220
 221/* Keep in sync with cpu_subsys_attrs */
 222static struct cpu_attr cpu_attrs[] = {
 223        _CPU_ATTR(online, &__cpu_online_mask),
 224        _CPU_ATTR(possible, &__cpu_possible_mask),
 225        _CPU_ATTR(present, &__cpu_present_mask),
 226};
 227
 228/*
 229 * Print values for NR_CPUS and offlined cpus
 230 */
 231static ssize_t print_cpus_kernel_max(struct device *dev,
 232                                     struct device_attribute *attr, char *buf)
 233{
 234        int n = snprintf(buf, PAGE_SIZE-2, "%d\n", NR_CPUS - 1);
 235        return n;
 236}
 237static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 238
 239/* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 240unsigned int total_cpus;
 241
 242static ssize_t print_cpus_offline(struct device *dev,
 243                                  struct device_attribute *attr, char *buf)
 244{
 245        int n = 0, len = PAGE_SIZE-2;
 246        cpumask_var_t offline;
 247
 248        /* display offline cpus < nr_cpu_ids */
 249        if (!alloc_cpumask_var(&offline, GFP_KERNEL))
 250                return -ENOMEM;
 251        cpumask_andnot(offline, cpu_possible_mask, cpu_online_mask);
 252        n = scnprintf(buf, len, "%*pbl", cpumask_pr_args(offline));
 253        free_cpumask_var(offline);
 254
 255        /* display offline cpus >= nr_cpu_ids */
 256        if (total_cpus && nr_cpu_ids < total_cpus) {
 257                if (n && n < len)
 258                        buf[n++] = ',';
 259
 260                if (nr_cpu_ids == total_cpus-1)
 261                        n += snprintf(&buf[n], len - n, "%u", nr_cpu_ids);
 262                else
 263                        n += snprintf(&buf[n], len - n, "%u-%d",
 264                                                      nr_cpu_ids, total_cpus-1);
 265        }
 266
 267        n += snprintf(&buf[n], len - n, "\n");
 268        return n;
 269}
 270static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 271
 272static ssize_t print_cpus_isolated(struct device *dev,
 273                                  struct device_attribute *attr, char *buf)
 274{
 275        int n = 0, len = PAGE_SIZE-2;
 276        cpumask_var_t isolated;
 277
 278        if (!alloc_cpumask_var(&isolated, GFP_KERNEL))
 279                return -ENOMEM;
 280
 281        cpumask_andnot(isolated, cpu_possible_mask,
 282                       housekeeping_cpumask(HK_FLAG_DOMAIN));
 283        n = scnprintf(buf, len, "%*pbl\n", cpumask_pr_args(isolated));
 284
 285        free_cpumask_var(isolated);
 286
 287        return n;
 288}
 289static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL);
 290
 291#ifdef CONFIG_NO_HZ_FULL
 292static ssize_t print_cpus_nohz_full(struct device *dev,
 293                                  struct device_attribute *attr, char *buf)
 294{
 295        int n = 0, len = PAGE_SIZE-2;
 296
 297        n = scnprintf(buf, len, "%*pbl\n", cpumask_pr_args(tick_nohz_full_mask));
 298
 299        return n;
 300}
 301static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
 302#endif
 303
 304static void cpu_device_release(struct device *dev)
 305{
 306        /*
 307         * This is an empty function to prevent the driver core from spitting a
 308         * warning at us.  Yes, I know this is directly opposite of what the
 309         * documentation for the driver core and kobjects say, and the author
 310         * of this code has already been publically ridiculed for doing
 311         * something as foolish as this.  However, at this point in time, it is
 312         * the only way to handle the issue of statically allocated cpu
 313         * devices.  The different architectures will have their cpu device
 314         * code reworked to properly handle this in the near future, so this
 315         * function will then be changed to correctly free up the memory held
 316         * by the cpu device.
 317         *
 318         * Never copy this way of doing things, or you too will be made fun of
 319         * on the linux-kernel list, you have been warned.
 320         */
 321}
 322
 323#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 324static ssize_t print_cpu_modalias(struct device *dev,
 325                                  struct device_attribute *attr,
 326                                  char *buf)
 327{
 328        ssize_t n;
 329        u32 i;
 330
 331        n = sprintf(buf, "cpu:type:" CPU_FEATURE_TYPEFMT ":feature:",
 332                    CPU_FEATURE_TYPEVAL);
 333
 334        for (i = 0; i < MAX_CPU_FEATURES; i++)
 335                if (cpu_have_feature(i)) {
 336                        if (PAGE_SIZE < n + sizeof(",XXXX\n")) {
 337                                WARN(1, "CPU features overflow page\n");
 338                                break;
 339                        }
 340                        n += sprintf(&buf[n], ",%04X", i);
 341                }
 342        buf[n++] = '\n';
 343        return n;
 344}
 345
 346static int cpu_uevent(struct device *dev, struct kobj_uevent_env *env)
 347{
 348        char *buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
 349        if (buf) {
 350                print_cpu_modalias(NULL, NULL, buf);
 351                add_uevent_var(env, "MODALIAS=%s", buf);
 352                kfree(buf);
 353        }
 354        return 0;
 355}
 356#endif
 357
 358/*
 359 * register_cpu - Setup a sysfs device for a CPU.
 360 * @cpu - cpu->hotpluggable field set to 1 will generate a control file in
 361 *        sysfs for this CPU.
 362 * @num - CPU number to use when creating the device.
 363 *
 364 * Initialize and register the CPU device.
 365 */
 366int register_cpu(struct cpu *cpu, int num)
 367{
 368        int error;
 369
 370        cpu->node_id = cpu_to_node(num);
 371        memset(&cpu->dev, 0x00, sizeof(struct device));
 372        cpu->dev.id = num;
 373        cpu->dev.bus = &cpu_subsys;
 374        cpu->dev.release = cpu_device_release;
 375        cpu->dev.offline_disabled = !cpu->hotpluggable;
 376        cpu->dev.offline = !cpu_online(num);
 377        cpu->dev.of_node = of_get_cpu_node(num, NULL);
 378#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 379        cpu->dev.bus->uevent = cpu_uevent;
 380#endif
 381        cpu->dev.groups = common_cpu_attr_groups;
 382        if (cpu->hotpluggable)
 383                cpu->dev.groups = hotplugable_cpu_attr_groups;
 384        error = device_register(&cpu->dev);
 385        if (error) {
 386                put_device(&cpu->dev);
 387                return error;
 388        }
 389
 390        per_cpu(cpu_sys_devices, num) = &cpu->dev;
 391        register_cpu_under_node(num, cpu_to_node(num));
 392        dev_pm_qos_expose_latency_limit(&cpu->dev,
 393                                        PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
 394
 395        return 0;
 396}
 397
 398struct device *get_cpu_device(unsigned cpu)
 399{
 400        if (cpu < nr_cpu_ids && cpu_possible(cpu))
 401                return per_cpu(cpu_sys_devices, cpu);
 402        else
 403                return NULL;
 404}
 405EXPORT_SYMBOL_GPL(get_cpu_device);
 406
 407static void device_create_release(struct device *dev)
 408{
 409        kfree(dev);
 410}
 411
 412static struct device *
 413__cpu_device_create(struct device *parent, void *drvdata,
 414                    const struct attribute_group **groups,
 415                    const char *fmt, va_list args)
 416{
 417        struct device *dev = NULL;
 418        int retval = -ENODEV;
 419
 420        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 421        if (!dev) {
 422                retval = -ENOMEM;
 423                goto error;
 424        }
 425
 426        device_initialize(dev);
 427        dev->parent = parent;
 428        dev->groups = groups;
 429        dev->release = device_create_release;
 430        dev_set_drvdata(dev, drvdata);
 431
 432        retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
 433        if (retval)
 434                goto error;
 435
 436        retval = device_add(dev);
 437        if (retval)
 438                goto error;
 439
 440        return dev;
 441
 442error:
 443        put_device(dev);
 444        return ERR_PTR(retval);
 445}
 446
 447struct device *cpu_device_create(struct device *parent, void *drvdata,
 448                                 const struct attribute_group **groups,
 449                                 const char *fmt, ...)
 450{
 451        va_list vargs;
 452        struct device *dev;
 453
 454        va_start(vargs, fmt);
 455        dev = __cpu_device_create(parent, drvdata, groups, fmt, vargs);
 456        va_end(vargs);
 457        return dev;
 458}
 459EXPORT_SYMBOL_GPL(cpu_device_create);
 460
 461#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 462static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
 463#endif
 464
 465static struct attribute *cpu_root_attrs[] = {
 466#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 467        &dev_attr_probe.attr,
 468        &dev_attr_release.attr,
 469#endif
 470        &cpu_attrs[0].attr.attr,
 471        &cpu_attrs[1].attr.attr,
 472        &cpu_attrs[2].attr.attr,
 473        &dev_attr_kernel_max.attr,
 474        &dev_attr_offline.attr,
 475        &dev_attr_isolated.attr,
 476#ifdef CONFIG_NO_HZ_FULL
 477        &dev_attr_nohz_full.attr,
 478#endif
 479#ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 480        &dev_attr_modalias.attr,
 481#endif
 482        NULL
 483};
 484
 485static struct attribute_group cpu_root_attr_group = {
 486        .attrs = cpu_root_attrs,
 487};
 488
 489static const struct attribute_group *cpu_root_attr_groups[] = {
 490        &cpu_root_attr_group,
 491        NULL,
 492};
 493
 494bool cpu_is_hotpluggable(unsigned cpu)
 495{
 496        struct device *dev = get_cpu_device(cpu);
 497        return dev && container_of(dev, struct cpu, dev)->hotpluggable;
 498}
 499EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 500
 501#ifdef CONFIG_GENERIC_CPU_DEVICES
 502static DEFINE_PER_CPU(struct cpu, cpu_devices);
 503#endif
 504
 505static void __init cpu_dev_register_generic(void)
 506{
 507#ifdef CONFIG_GENERIC_CPU_DEVICES
 508        int i;
 509
 510        for_each_possible_cpu(i) {
 511                if (register_cpu(&per_cpu(cpu_devices, i), i))
 512                        panic("Failed to register CPU device");
 513        }
 514#endif
 515}
 516
 517#ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
 518
 519ssize_t __weak cpu_show_meltdown(struct device *dev,
 520                                 struct device_attribute *attr, char *buf)
 521{
 522        return sprintf(buf, "Not affected\n");
 523}
 524
 525ssize_t __weak cpu_show_spectre_v1(struct device *dev,
 526                                   struct device_attribute *attr, char *buf)
 527{
 528        return sprintf(buf, "Not affected\n");
 529}
 530
 531ssize_t __weak cpu_show_spectre_v2(struct device *dev,
 532                                   struct device_attribute *attr, char *buf)
 533{
 534        return sprintf(buf, "Not affected\n");
 535}
 536
 537ssize_t __weak cpu_show_spec_store_bypass(struct device *dev,
 538                                          struct device_attribute *attr, char *buf)
 539{
 540        return sprintf(buf, "Not affected\n");
 541}
 542
 543ssize_t __weak cpu_show_l1tf(struct device *dev,
 544                             struct device_attribute *attr, char *buf)
 545{
 546        return sprintf(buf, "Not affected\n");
 547}
 548
 549static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
 550static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
 551static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
 552static DEVICE_ATTR(spec_store_bypass, 0444, cpu_show_spec_store_bypass, NULL);
 553static DEVICE_ATTR(l1tf, 0444, cpu_show_l1tf, NULL);
 554
 555static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 556        &dev_attr_meltdown.attr,
 557        &dev_attr_spectre_v1.attr,
 558        &dev_attr_spectre_v2.attr,
 559        &dev_attr_spec_store_bypass.attr,
 560        &dev_attr_l1tf.attr,
 561        NULL
 562};
 563
 564static const struct attribute_group cpu_root_vulnerabilities_group = {
 565        .name  = "vulnerabilities",
 566        .attrs = cpu_root_vulnerabilities_attrs,
 567};
 568
 569static void __init cpu_register_vulnerabilities(void)
 570{
 571        if (sysfs_create_group(&cpu_subsys.dev_root->kobj,
 572                               &cpu_root_vulnerabilities_group))
 573                pr_err("Unable to register CPU vulnerabilities\n");
 574}
 575
 576#else
 577static inline void cpu_register_vulnerabilities(void) { }
 578#endif
 579
 580void __init cpu_dev_init(void)
 581{
 582        if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 583                panic("Failed to register CPU subsystem");
 584
 585        cpu_dev_register_generic();
 586        cpu_register_vulnerabilities();
 587}
 588