root/drivers/base/cpu.c

DEFINITIONS

1. cpu_subsys_match
2. change_cpu_under_node
3. cpu_subsys_online
4. cpu_subsys_offline
5. unregister_cpu
6. cpu_probe_store
7. cpu_release_store
8. show_crash_notes
9. show_crash_notes_size
10. show_cpus_attr
11. print_cpus_kernel_max
12. print_cpus_offline
13. print_cpus_isolated
14. print_cpus_nohz_full
15. cpu_device_release
16. print_cpu_modalias
17. cpu_uevent
18. register_cpu
19. get_cpu_device
20. device_create_release
21. __printf
22. cpu_device_create
23. cpu_is_hotpluggable
24. cpu_dev_register_generic
25. cpu_show_meltdown
26. cpu_show_spectre_v1
27. cpu_show_spectre_v2
28. cpu_show_spec_store_bypass
29. cpu_show_l1tf
30. cpu_show_mds
31. cpu_show_tsx_async_abort
32. cpu_show_itlb_multihit
33. cpu_show_srbds
34. cpu_register_vulnerabilities
35. cpu_register_vulnerabilities
36. cpu_dev_init

   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                 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 
 398 struct 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 }
 405 EXPORT_SYMBOL_GPL(get_cpu_device);
 406 
 407 static void device_create_release(struct device *dev)
 408 {
 409         kfree(dev);
 410 }
 411 
 412 __printf(4, 0)
 413 static struct device *
 414 __cpu_device_create(struct device *parent, void *drvdata,
 415                     const struct attribute_group **groups,
 416                     const char *fmt, va_list args)
 417 {
 418         struct device *dev = NULL;
 419         int retval = -ENODEV;
 420 
 421         dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 422         if (!dev) {
 423                 retval = -ENOMEM;
 424                 goto error;
 425         }
 426 
 427         device_initialize(dev);
 428         dev->parent = parent;
 429         dev->groups = groups;
 430         dev->release = device_create_release;
 431         device_set_pm_not_required(dev);
 432         dev_set_drvdata(dev, drvdata);
 433 
 434         retval = kobject_set_name_vargs(&dev->kobj, fmt, args);
 435         if (retval)
 436                 goto error;
 437 
 438         retval = device_add(dev);
 439         if (retval)
 440                 goto error;
 441 
 442         return dev;
 443 
 444 error:
 445         put_device(dev);
 446         return ERR_PTR(retval);
 447 }
 448 
 449 struct device *cpu_device_create(struct device *parent, void *drvdata,
 450                                  const struct attribute_group **groups,
 451                                  const char *fmt, ...)
 452 {
 453         va_list vargs;
 454         struct device *dev;
 455 
 456         va_start(vargs, fmt);
 457         dev = __cpu_device_create(parent, drvdata, groups, fmt, vargs);
 458         va_end(vargs);
 459         return dev;
 460 }
 461 EXPORT_SYMBOL_GPL(cpu_device_create);
 462 
 463 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 464 static DEVICE_ATTR(modalias, 0444, print_cpu_modalias, NULL);
 465 #endif
 466 
 467 static struct attribute *cpu_root_attrs[] = {
 468 #ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
 469         &dev_attr_probe.attr,
 470         &dev_attr_release.attr,
 471 #endif
 472         &cpu_attrs[0].attr.attr,
 473         &cpu_attrs[1].attr.attr,
 474         &cpu_attrs[2].attr.attr,
 475         &dev_attr_kernel_max.attr,
 476         &dev_attr_offline.attr,
 477         &dev_attr_isolated.attr,
 478 #ifdef CONFIG_NO_HZ_FULL
 479         &dev_attr_nohz_full.attr,
 480 #endif
 481 #ifdef CONFIG_GENERIC_CPU_AUTOPROBE
 482         &dev_attr_modalias.attr,
 483 #endif
 484         NULL
 485 };
 486 
 487 static struct attribute_group cpu_root_attr_group = {
 488         .attrs = cpu_root_attrs,
 489 };
 490 
 491 static const struct attribute_group *cpu_root_attr_groups[] = {
 492         &cpu_root_attr_group,
 493         NULL,
 494 };
 495 
 496 bool cpu_is_hotpluggable(unsigned cpu)
 497 {
 498         struct device *dev = get_cpu_device(cpu);
 499         return dev && container_of(dev, struct cpu, dev)->hotpluggable;
 500 }
 501 EXPORT_SYMBOL_GPL(cpu_is_hotpluggable);
 502 
 503 #ifdef CONFIG_GENERIC_CPU_DEVICES
 504 static DEFINE_PER_CPU(struct cpu, cpu_devices);
 505 #endif
 506 
 507 static void __init cpu_dev_register_generic(void)
 508 {
 509 #ifdef CONFIG_GENERIC_CPU_DEVICES
 510         int i;
 511 
 512         for_each_possible_cpu(i) {
 513                 if (register_cpu(&per_cpu(cpu_devices, i), i))
 514                         panic("Failed to register CPU device");
 515         }
 516 #endif
 517 }
 518 
 519 #ifdef CONFIG_GENERIC_CPU_VULNERABILITIES
 520 
 521 ssize_t __weak cpu_show_meltdown(struct device *dev,
 522                                  struct device_attribute *attr, char *buf)
 523 {
 524         return sprintf(buf, "Not affected\n");
 525 }
 526 
 527 ssize_t __weak cpu_show_spectre_v1(struct device *dev,
 528                                    struct device_attribute *attr, char *buf)
 529 {
 530         return sprintf(buf, "Not affected\n");
 531 }
 532 
 533 ssize_t __weak cpu_show_spectre_v2(struct device *dev,
 534                                    struct device_attribute *attr, char *buf)
 535 {
 536         return sprintf(buf, "Not affected\n");
 537 }
 538 
 539 ssize_t __weak cpu_show_spec_store_bypass(struct device *dev,
 540                                           struct device_attribute *attr, char *buf)
 541 {
 542         return sprintf(buf, "Not affected\n");
 543 }
 544 
 545 ssize_t __weak cpu_show_l1tf(struct device *dev,
 546                              struct device_attribute *attr, char *buf)
 547 {
 548         return sprintf(buf, "Not affected\n");
 549 }
 550 
 551 ssize_t __weak cpu_show_mds(struct device *dev,
 552                             struct device_attribute *attr, char *buf)
 553 {
 554         return sprintf(buf, "Not affected\n");
 555 }
 556 
 557 ssize_t __weak cpu_show_tsx_async_abort(struct device *dev,
 558                                         struct device_attribute *attr,
 559                                         char *buf)
 560 {
 561         return sprintf(buf, "Not affected\n");
 562 }
 563 
 564 ssize_t __weak cpu_show_itlb_multihit(struct device *dev,
 565                             struct device_attribute *attr, char *buf)
 566 {
 567         return sprintf(buf, "Not affected\n");
 568 }
 569 
 570 ssize_t __weak cpu_show_srbds(struct device *dev,
 571                               struct device_attribute *attr, char *buf)
 572 {
 573         return sprintf(buf, "Not affected\n");
 574 }
 575 
 576 static DEVICE_ATTR(meltdown, 0444, cpu_show_meltdown, NULL);
 577 static DEVICE_ATTR(spectre_v1, 0444, cpu_show_spectre_v1, NULL);
 578 static DEVICE_ATTR(spectre_v2, 0444, cpu_show_spectre_v2, NULL);
 579 static DEVICE_ATTR(spec_store_bypass, 0444, cpu_show_spec_store_bypass, NULL);
 580 static DEVICE_ATTR(l1tf, 0444, cpu_show_l1tf, NULL);
 581 static DEVICE_ATTR(mds, 0444, cpu_show_mds, NULL);
 582 static DEVICE_ATTR(tsx_async_abort, 0444, cpu_show_tsx_async_abort, NULL);
 583 static DEVICE_ATTR(itlb_multihit, 0444, cpu_show_itlb_multihit, NULL);
 584 static DEVICE_ATTR(srbds, 0444, cpu_show_srbds, NULL);
 585 
 586 static struct attribute *cpu_root_vulnerabilities_attrs[] = {
 587         &dev_attr_meltdown.attr,
 588         &dev_attr_spectre_v1.attr,
 589         &dev_attr_spectre_v2.attr,
 590         &dev_attr_spec_store_bypass.attr,
 591         &dev_attr_l1tf.attr,
 592         &dev_attr_mds.attr,
 593         &dev_attr_tsx_async_abort.attr,
 594         &dev_attr_itlb_multihit.attr,
 595         &dev_attr_srbds.attr,
 596         NULL
 597 };
 598 
 599 static const struct attribute_group cpu_root_vulnerabilities_group = {
 600         .name  = "vulnerabilities",
 601         .attrs = cpu_root_vulnerabilities_attrs,
 602 };
 603 
 604 static void __init cpu_register_vulnerabilities(void)
 605 {
 606         if (sysfs_create_group(&cpu_subsys.dev_root->kobj,
 607                                &cpu_root_vulnerabilities_group))
 608                 pr_err("Unable to register CPU vulnerabilities\n");
 609 }
 610 
 611 #else
 612 static inline void cpu_register_vulnerabilities(void) { }
 613 #endif
 614 
 615 void __init cpu_dev_init(void)
 616 {
 617         if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
 618                 panic("Failed to register CPU subsystem");
 619 
 620         cpu_dev_register_generic();
 621         cpu_register_vulnerabilities();
 622 }