drivers/base/cpu.c

   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
  26 static DEFINE_PER_CPU(struct device *, cpu_sys_devices);
  27
  28 static 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
  38 static 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
  47 static 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
  70 static int cpu_subsys_offline(struct device *dev)
  71 {
  72         return cpu_down(dev->id);
  73 }
  74
  75 void 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
  87 static 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
 105 static 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
 123 static DEVICE_ATTR(probe, S_IWUSR, NULL, cpu_probe_store);
 124 static DEVICE_ATTR(release, S_IWUSR, NULL, cpu_release_store);
 125 #endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
 126 #endif /* CONFIG_HOTPLUG_CPU */
 127
 128 struct 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 };
 137 EXPORT_SYMBOL_GPL(cpu_subsys);
 138
 139 #ifdef CONFIG_KEXEC
 140 #include <linux/kexec.h>
 141
 142 static 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 }
 162 static DEVICE_ATTR(crash_notes, 0400, show_crash_notes, NULL);
 163
 164 static 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 }
 173 static DEVICE_ATTR(crash_notes_size, 0400, show_crash_notes_size, NULL);
 174
 175 static struct attribute *crash_note_cpu_attrs[] = {
 176         &dev_attr_crash_notes.attr,
 177         &dev_attr_crash_notes_size.attr,
 178         NULL
 179 };
 180
 181 static struct attribute_group crash_note_cpu_attr_group = {
 182         .attrs = crash_note_cpu_attrs,
 183 };
 184 #endif
 185
 186 static const struct attribute_group *common_cpu_attr_groups[] = {
 187 #ifdef CONFIG_KEXEC
 188         &crash_note_cpu_attr_group,
 189 #endif
 190         NULL
 191 };
 192
 193 static 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
 204 struct cpu_attr {
 205         struct device_attribute attr;
 206         const struct cpumask *const map;
 207 };
 208
 209 static 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 */
 222 static 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  */
 231 static 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 }
 237 static DEVICE_ATTR(kernel_max, 0444, print_cpus_kernel_max, NULL);
 238
 239 /* arch-optional setting to enable display of offline cpus >= nr_cpu_ids */
 240 unsigned int total_cpus;
 241
 242 static 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 }
 270 static DEVICE_ATTR(offline, 0444, print_cpus_offline, NULL);
 271
 272 static 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 }
 289 static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL);
 290
 291 #ifdef CONFIG_NO_HZ_FULL
 292 static 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 }
 301 static DEVICE_ATTR(nohz_full, 0444, print_cpus_nohz_full, NULL);
 302 #endif
 303
 304 static 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
 324 static 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
 346 static 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  */
 366 int 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                 return error;
 387
 388         per_cpu(cpu_sys_devices, num) = &cpu->dev;
 389         register_cpu_under_node(num, cpu_to_node(num));
 390         dev_pm_qos_expose_latency_limit(&cpu->dev,
 391                                         PM_QOS_RESUME_LATENCY_NO_CONSTRAINT);
 392
 393         return 0;
 394 }
 395
 396 struct device *get_cpu_device(unsigned cpu)
 397 {
 398         if (cpu < nr_cpu_ids && cpu_possible(cpu))
 399                 return per_cpu(cpu_sys_devices, cpu);
 400         else
 401                 return NULL;
 402 }
 403 EXPORT_SYMBOL_GPL(get_cpu_device);
 404
 405 static void device_create_release(struct device *dev)
 406 {
 407         kfree(dev);
 408 }
 409
 410 static struct device *
 411 __cpu_device_create(struct device *parent, void *drvdata,
 412                     const struct attribute_group **groups,
 413                     const char *fmt, va_list args)
 414 {
 415         struct device *dev = NULL;
 416         int retval = -ENODEV;
 417
 418         dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 419         if (!dev) {
 420                 retval = -ENOMEM;
 421                 goto error;
 422         }
 423
 424         device_initialize(dev);
 425         dev->parent = parent;
 426         dev->groups = groups;
 427         dev->release = device_create_release;
 428         dev_set_drvdata(dev, drvdata);
 429
 430         retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
 431         if (retval)
 432                 goto error;
 433
 434         retval = device_add(dev);
 435         if (retval)
 436                 goto error;
 437
 438         return dev;
 439
 440 error:
 441         put_device(dev);
 442         return ERR_PTR(retval);
 443 }
 444
 445 struct device *cpu_device_create(struct device *parent, void *drvdata,
 446                                  const struct attribute_group **groups,
 447                                  const char *fmt, ...)
 448 {
 449         va_list vargs;
 450         struct device *dev;
 451
 452         va_start(vargs, fmt);
 453         dev = __cpu_device_create(parent, drvdata, groups, fmt, vargs);
 454         va_end(vargs);
 455         return dev;
 456 }
 457 EXPORT_SYMBOL_GPL(cpu_device_create);
 458
 459 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 460 static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
 461 #endif
 462
 463 static struct attribute *cpu_root_attrs[] = {
 464 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 465         &dev_attr_probe.attr,
 466         &dev_attr_release.attr,
 467 #endif
 468         &cpu_attrs[0].attr.attr,
 469         &cpu_attrs[1].attr.attr,
 470         &cpu_attrs[2].attr.attr,
 471         &dev_attr_kernel_max.attr,
 472         &dev_attr_offline.attr,
 473         &dev_attr_isolated.attr,
 474 #ifdef CONFIG_NO_HZ_FULL
 475         &dev_attr_nohz_full.attr,
 476 #endif
 477 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 478         &dev_attr_modalias.attr,
 479 #endif
 480         NULL
 481 };
 482
 483 static struct attribute_group cpu_root_attr_group = {
 484         .attrs = cpu_root_attrs,
 485 };
 486
 487 static const struct attribute_group *cpu_root_attr_groups[] = {
 488         &cpu_root_attr_group,
 489         NULL,
 490 };
 491
 492 bool cpu_is_hotpluggable(unsigned cpu)
 493 {
 494         struct device *dev = get_cpu_device(cpu);
 495         return dev && container_of(dev, struct cpu, dev)->hotpluggable;
 496 }
 497 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 498
 499 #ifdef CONFIG_GENERIC_CPU_DEVICES
 500 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 501 #endif
 502
 503 static void __init cpu_dev_register_generic(void)
 504 {
 505 #ifdef CONFIG_GENERIC_CPU_DEVICES
 506         int i;
 507
 508         for_each_possible_cpu(i) {
 509                 if (register_cpu(&per_cpu(cpu_devices, i), i))
 510                         panic("Failed to register CPU device");
 511         }
 512 #endif
 513 }
 514
 515 #ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
 516
 517 ssize_t __weak cpu_show_meltdown(struct device *dev,
 518                                  struct device_attribute *attr, char *buf)
 519 {
 520         return sprintf(buf, "Not affected\n");
 521 }
 522
 523 ssize_t __weak cpu_show_spectre_v1(struct device *dev,
 524                                    struct device_attribute *attr, char *buf)
 525 {
 526         return sprintf(buf, "Not affected\n");
 527 }
 528
 529 ssize_t __weak cpu_show_spectre_v2(struct device *dev,
 530                                    struct device_attribute *attr, char *buf)
 531 {
 532         return sprintf(buf, "Not affected\n");
 533 }
 534
 535 static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
 536 static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
 537 static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
 538
 539 static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 540         &dev_attr_meltdown.attr,
 541         &dev_attr_spectre_v1.attr,
 542         &dev_attr_spectre_v2.attr,
 543         NULL
 544 };
 545
 546 static const struct attribute_group cpu_root_vulnerabilities_group = {
 547         .name  = "vulnerabilities",
 548         .attrs = cpu_root_vulnerabilities_attrs,
 549 };
 550
 551 static void __init cpu_register_vulnerabilities(void)
 552 {
 553         if (sysfs_create_group(&cpu_subsys.dev_root->kobj,
 554                                &cpu_root_vulnerabilities_group))
 555                 pr_err("Unable to register CPU vulnerabilities\n");
 556 }
 557
 558 #else
 559 static inline void cpu_register_vulnerabilities(void) { }
 560 #endif
 561
 562 void __init cpu_dev_init(void)
 563 {
 564         if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 565                 panic("Failed to register CPU subsystem");
 566
 567         cpu_dev_register_generic();
 568         cpu_register_vulnerabilities();
 569 }