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1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright (c) 2017-2019 Borislav Petkov, SUSE Labs.4 */5#include <linux/mm.h>6#include <linux/gfp.h>7#include <linux/ras.h>8#include <linux/kernel.h>9#include <linux/workqueue.h>10 11#include <asm/mce.h>12 13#include "debugfs.h"14 15/*16 * RAS Correctable Errors Collector17 *18 * This is a simple gadget which collects correctable errors and counts their19 * occurrence per physical page address.20 *21 * We've opted for possibly the simplest data structure to collect those - an22 * array of the size of a memory page. It stores 512 u64's with the following23 * structure:24 *25 * [63 ... PFN ... 12 | 11 ... generation ... 10 | 9 ... count ... 0]26 *27 * The generation in the two highest order bits is two bits which are set to 11b28 * on every insertion. During the course of each entry's existence, the29 * generation field gets decremented during spring cleaning to 10b, then 01b and30 * then 00b.31 *32 * This way we're employing the natural numeric ordering to make sure that newly33 * inserted/touched elements have higher 12-bit counts (which we've manufactured)34 * and thus iterating over the array initially won't kick out those elements35 * which were inserted last.36 *37 * Spring cleaning is what we do when we reach a certain number CLEAN_ELEMS of38 * elements entered into the array, during which, we're decaying all elements.39 * If, after decay, an element gets inserted again, its generation is set to 11b40 * to make sure it has higher numerical count than other, older elements and41 * thus emulate an LRU-like behavior when deleting elements to free up space42 * in the page.43 *44 * When an element reaches it's max count of action_threshold, we try to poison45 * it by assuming that errors triggered action_threshold times in a single page46 * are excessive and that page shouldn't be used anymore. action_threshold is47 * initialized to COUNT_MASK which is the maximum.48 *49 * That error event entry causes cec_add_elem() to return !0 value and thus50 * signal to its callers to log the error.51 *52 * To the question why we've chosen a page and moving elements around with53 * memmove(), it is because it is a very simple structure to handle and max data54 * movement is 4K which on highly optimized modern CPUs is almost unnoticeable.55 * We wanted to avoid the pointer traversal of more complex structures like a56 * linked list or some sort of a balancing search tree.57 *58 * Deleting an element takes O(n) but since it is only a single page, it should59 * be fast enough and it shouldn't happen all too often depending on error60 * patterns.61 */62 63#undef pr_fmt64#define pr_fmt(fmt) "RAS: " fmt65 66/*67 * We use DECAY_BITS bits of PAGE_SHIFT bits for counting decay, i.e., how long68 * elements have stayed in the array without having been accessed again.69 */70#define DECAY_BITS 271#define DECAY_MASK ((1ULL << DECAY_BITS) - 1)72#define MAX_ELEMS (PAGE_SIZE / sizeof(u64))73 74/*75 * Threshold amount of inserted elements after which we start spring76 * cleaning.77 */78#define CLEAN_ELEMS (MAX_ELEMS >> DECAY_BITS)79 80/* Bits which count the number of errors happened in this 4K page. */81#define COUNT_BITS (PAGE_SHIFT - DECAY_BITS)82#define COUNT_MASK ((1ULL << COUNT_BITS) - 1)83#define FULL_COUNT_MASK (PAGE_SIZE - 1)84 85/*86 * u64: [ 63 ... 12 | DECAY_BITS | COUNT_BITS ]87 */88 89#define PFN(e) ((e) >> PAGE_SHIFT)90#define DECAY(e) (((e) >> COUNT_BITS) & DECAY_MASK)91#define COUNT(e) ((unsigned int)(e) & COUNT_MASK)92#define FULL_COUNT(e) ((e) & (PAGE_SIZE - 1))93 94static struct ce_array {95 u64 *array; /* container page */96 unsigned int n; /* number of elements in the array */97 98 unsigned int decay_count; /*99 * number of element insertions/increments100 * since the last spring cleaning.101 */102 103 u64 pfns_poisoned; /*104 * number of PFNs which got poisoned.105 */106 107 u64 ces_entered; /*108 * The number of correctable errors109 * entered into the collector.110 */111 112 u64 decays_done; /*113 * Times we did spring cleaning.114 */115 116 union {117 struct {118 __u32 disabled : 1, /* cmdline disabled */119 __resv : 31;120 };121 __u32 flags;122 };123} ce_arr;124 125static DEFINE_MUTEX(ce_mutex);126static u64 dfs_pfn;127 128/* Amount of errors after which we offline */129static u64 action_threshold = COUNT_MASK;130 131/* Each element "decays" each decay_interval which is 24hrs by default. */132#define CEC_DECAY_DEFAULT_INTERVAL 24 * 60 * 60 /* 24 hrs */133#define CEC_DECAY_MIN_INTERVAL 1 * 60 * 60 /* 1h */134#define CEC_DECAY_MAX_INTERVAL 30 * 24 * 60 * 60 /* one month */135static struct delayed_work cec_work;136static u64 decay_interval = CEC_DECAY_DEFAULT_INTERVAL;137 138/*139 * Decrement decay value. We're using DECAY_BITS bits to denote decay of an140 * element in the array. On insertion and any access, it gets reset to max.141 */142static void do_spring_cleaning(struct ce_array *ca)143{144 int i;145 146 for (i = 0; i < ca->n; i++) {147 u8 decay = DECAY(ca->array[i]);148 149 if (!decay)150 continue;151 152 decay--;153 154 ca->array[i] &= ~(DECAY_MASK << COUNT_BITS);155 ca->array[i] |= (decay << COUNT_BITS);156 }157 ca->decay_count = 0;158 ca->decays_done++;159}160 161/*162 * @interval in seconds163 */164static void cec_mod_work(unsigned long interval)165{166 unsigned long iv;167 168 iv = interval * HZ;169 mod_delayed_work(system_wq, &cec_work, round_jiffies(iv));170}171 172static void cec_work_fn(struct work_struct *work)173{174 mutex_lock(&ce_mutex);175 do_spring_cleaning(&ce_arr);176 mutex_unlock(&ce_mutex);177 178 cec_mod_work(decay_interval);179}180 181/*182 * @to: index of the smallest element which is >= then @pfn.183 *184 * Return the index of the pfn if found, otherwise negative value.185 */186static int __find_elem(struct ce_array *ca, u64 pfn, unsigned int *to)187{188 int min = 0, max = ca->n - 1;189 u64 this_pfn;190 191 while (min <= max) {192 int i = (min + max) >> 1;193 194 this_pfn = PFN(ca->array[i]);195 196 if (this_pfn < pfn)197 min = i + 1;198 else if (this_pfn > pfn)199 max = i - 1;200 else if (this_pfn == pfn) {201 if (to)202 *to = i;203 204 return i;205 }206 }207 208 /*209 * When the loop terminates without finding @pfn, min has the index of210 * the element slot where the new @pfn should be inserted. The loop211 * terminates when min > max, which means the min index points to the212 * bigger element while the max index to the smaller element, in-between213 * which the new @pfn belongs to.214 *215 * For more details, see exercise 1, Section 6.2.1 in TAOCP, vol. 3.216 */217 if (to)218 *to = min;219 220 return -ENOKEY;221}222 223static int find_elem(struct ce_array *ca, u64 pfn, unsigned int *to)224{225 WARN_ON(!to);226 227 if (!ca->n) {228 *to = 0;229 return -ENOKEY;230 }231 return __find_elem(ca, pfn, to);232}233 234static void del_elem(struct ce_array *ca, int idx)235{236 /* Save us a function call when deleting the last element. */237 if (ca->n - (idx + 1))238 memmove((void *)&ca->array[idx],239 (void *)&ca->array[idx + 1],240 (ca->n - (idx + 1)) * sizeof(u64));241 242 ca->n--;243}244 245static u64 del_lru_elem_unlocked(struct ce_array *ca)246{247 unsigned int min = FULL_COUNT_MASK;248 int i, min_idx = 0;249 250 for (i = 0; i < ca->n; i++) {251 unsigned int this = FULL_COUNT(ca->array[i]);252 253 if (min > this) {254 min = this;255 min_idx = i;256 }257 }258 259 del_elem(ca, min_idx);260 261 return PFN(ca->array[min_idx]);262}263 264/*265 * We return the 0th pfn in the error case under the assumption that it cannot266 * be poisoned and excessive CEs in there are a serious deal anyway.267 */268static u64 __maybe_unused del_lru_elem(void)269{270 struct ce_array *ca = &ce_arr;271 u64 pfn;272 273 if (!ca->n)274 return 0;275 276 mutex_lock(&ce_mutex);277 pfn = del_lru_elem_unlocked(ca);278 mutex_unlock(&ce_mutex);279 280 return pfn;281}282 283static bool sanity_check(struct ce_array *ca)284{285 bool ret = false;286 u64 prev = 0;287 int i;288 289 for (i = 0; i < ca->n; i++) {290 u64 this = PFN(ca->array[i]);291 292 if (WARN(prev > this, "prev: 0x%016llx <-> this: 0x%016llx\n", prev, this))293 ret = true;294 295 prev = this;296 }297 298 if (!ret)299 return ret;300 301 pr_info("Sanity check dump:\n{ n: %d\n", ca->n);302 for (i = 0; i < ca->n; i++) {303 u64 this = PFN(ca->array[i]);304 305 pr_info(" %03d: [%016llx|%03llx]\n", i, this, FULL_COUNT(ca->array[i]));306 }307 pr_info("}\n");308 309 return ret;310}311 312/**313 * cec_add_elem - Add an element to the CEC array.314 * @pfn: page frame number to insert315 *316 * Return values:317 * - <0: on error318 * - 0: on success319 * - >0: when the inserted pfn was offlined320 */321static int cec_add_elem(u64 pfn)322{323 struct ce_array *ca = &ce_arr;324 int count, err, ret = 0;325 unsigned int to = 0;326 327 /*328 * We can be called very early on the identify_cpu() path where we are329 * not initialized yet. We ignore the error for simplicity.330 */331 if (!ce_arr.array || ce_arr.disabled)332 return -ENODEV;333 334 mutex_lock(&ce_mutex);335 336 ca->ces_entered++;337 338 /* Array full, free the LRU slot. */339 if (ca->n == MAX_ELEMS)340 WARN_ON(!del_lru_elem_unlocked(ca));341 342 err = find_elem(ca, pfn, &to);343 if (err < 0) {344 /*345 * Shift range [to-end] to make room for one more element.346 */347 memmove((void *)&ca->array[to + 1],348 (void *)&ca->array[to],349 (ca->n - to) * sizeof(u64));350 351 ca->array[to] = pfn << PAGE_SHIFT;352 ca->n++;353 }354 355 /* Add/refresh element generation and increment count */356 ca->array[to] |= DECAY_MASK << COUNT_BITS;357 ca->array[to]++;358 359 /* Check action threshold and soft-offline, if reached. */360 count = COUNT(ca->array[to]);361 if (count >= action_threshold) {362 u64 pfn = ca->array[to] >> PAGE_SHIFT;363 364 if (!pfn_valid(pfn)) {365 pr_warn("CEC: Invalid pfn: 0x%llx\n", pfn);366 } else {367 /* We have reached max count for this page, soft-offline it. */368 pr_err("Soft-offlining pfn: 0x%llx\n", pfn);369 memory_failure_queue(pfn, MF_SOFT_OFFLINE);370 ca->pfns_poisoned++;371 }372 373 del_elem(ca, to);374 375 /*376 * Return a >0 value to callers, to denote that we've reached377 * the offlining threshold.378 */379 ret = 1;380 381 goto unlock;382 }383 384 ca->decay_count++;385 386 if (ca->decay_count >= CLEAN_ELEMS)387 do_spring_cleaning(ca);388 389 WARN_ON_ONCE(sanity_check(ca));390 391unlock:392 mutex_unlock(&ce_mutex);393 394 return ret;395}396 397static int u64_get(void *data, u64 *val)398{399 *val = *(u64 *)data;400 401 return 0;402}403 404static int pfn_set(void *data, u64 val)405{406 *(u64 *)data = val;407 408 cec_add_elem(val);409 410 return 0;411}412 413DEFINE_DEBUGFS_ATTRIBUTE(pfn_ops, u64_get, pfn_set, "0x%llx\n");414 415static int decay_interval_set(void *data, u64 val)416{417 if (val < CEC_DECAY_MIN_INTERVAL)418 return -EINVAL;419 420 if (val > CEC_DECAY_MAX_INTERVAL)421 return -EINVAL;422 423 *(u64 *)data = val;424 decay_interval = val;425 426 cec_mod_work(decay_interval);427 428 return 0;429}430DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, u64_get, decay_interval_set, "%lld\n");431 432static int action_threshold_set(void *data, u64 val)433{434 *(u64 *)data = val;435 436 if (val > COUNT_MASK)437 val = COUNT_MASK;438 439 action_threshold = val;440 441 return 0;442}443DEFINE_DEBUGFS_ATTRIBUTE(action_threshold_ops, u64_get, action_threshold_set, "%lld\n");444 445static const char * const bins[] = { "00", "01", "10", "11" };446 447static int array_show(struct seq_file *m, void *v)448{449 struct ce_array *ca = &ce_arr;450 int i;451 452 mutex_lock(&ce_mutex);453 454 seq_printf(m, "{ n: %d\n", ca->n);455 for (i = 0; i < ca->n; i++) {456 u64 this = PFN(ca->array[i]);457 458 seq_printf(m, " %3d: [%016llx|%s|%03llx]\n",459 i, this, bins[DECAY(ca->array[i])], COUNT(ca->array[i]));460 }461 462 seq_printf(m, "}\n");463 464 seq_printf(m, "Stats:\nCEs: %llu\nofflined pages: %llu\n",465 ca->ces_entered, ca->pfns_poisoned);466 467 seq_printf(m, "Flags: 0x%x\n", ca->flags);468 469 seq_printf(m, "Decay interval: %lld seconds\n", decay_interval);470 seq_printf(m, "Decays: %lld\n", ca->decays_done);471 472 seq_printf(m, "Action threshold: %lld\n", action_threshold);473 474 mutex_unlock(&ce_mutex);475 476 return 0;477}478 479DEFINE_SHOW_ATTRIBUTE(array);480 481static int __init create_debugfs_nodes(void)482{483 struct dentry *d, *pfn, *decay, *count, *array, *dfs;484 485 dfs = ras_get_debugfs_root();486 if (!dfs) {487 pr_warn("Error getting RAS debugfs root!\n");488 return -1;489 }490 491 d = debugfs_create_dir("cec", dfs);492 if (!d) {493 pr_warn("Error creating cec debugfs node!\n");494 return -1;495 }496 497 decay = debugfs_create_file("decay_interval", S_IRUSR | S_IWUSR, d,498 &decay_interval, &decay_interval_ops);499 if (!decay) {500 pr_warn("Error creating decay_interval debugfs node!\n");501 goto err;502 }503 504 count = debugfs_create_file("action_threshold", S_IRUSR | S_IWUSR, d,505 &action_threshold, &action_threshold_ops);506 if (!count) {507 pr_warn("Error creating action_threshold debugfs node!\n");508 goto err;509 }510 511 if (!IS_ENABLED(CONFIG_RAS_CEC_DEBUG))512 return 0;513 514 pfn = debugfs_create_file("pfn", S_IRUSR | S_IWUSR, d, &dfs_pfn, &pfn_ops);515 if (!pfn) {516 pr_warn("Error creating pfn debugfs node!\n");517 goto err;518 }519 520 array = debugfs_create_file("array", S_IRUSR, d, NULL, &array_fops);521 if (!array) {522 pr_warn("Error creating array debugfs node!\n");523 goto err;524 }525 526 return 0;527 528err:529 debugfs_remove_recursive(d);530 531 return 1;532}533 534static int cec_notifier(struct notifier_block *nb, unsigned long val,535 void *data)536{537 struct mce *m = (struct mce *)data;538 539 if (!m)540 return NOTIFY_DONE;541 542 /* We eat only correctable DRAM errors with usable addresses. */543 if (mce_is_memory_error(m) &&544 mce_is_correctable(m) &&545 mce_usable_address(m)) {546 if (!cec_add_elem(m->addr >> PAGE_SHIFT)) {547 m->kflags |= MCE_HANDLED_CEC;548 return NOTIFY_OK;549 }550 }551 552 return NOTIFY_DONE;553}554 555static struct notifier_block cec_nb = {556 .notifier_call = cec_notifier,557 .priority = MCE_PRIO_CEC,558};559 560static int __init cec_init(void)561{562 if (ce_arr.disabled)563 return -ENODEV;564 565 /*566 * Intel systems may avoid uncorrectable errors567 * if pages with corrected errors are aggressively568 * taken offline.569 */570 if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)571 action_threshold = 2;572 573 ce_arr.array = (void *)get_zeroed_page(GFP_KERNEL);574 if (!ce_arr.array) {575 pr_err("Error allocating CE array page!\n");576 return -ENOMEM;577 }578 579 if (create_debugfs_nodes()) {580 free_page((unsigned long)ce_arr.array);581 return -ENOMEM;582 }583 584 INIT_DELAYED_WORK(&cec_work, cec_work_fn);585 schedule_delayed_work(&cec_work, CEC_DECAY_DEFAULT_INTERVAL);586 587 mce_register_decode_chain(&cec_nb);588 589 pr_info("Correctable Errors collector initialized.\n");590 return 0;591}592late_initcall(cec_init);593 594int __init parse_cec_param(char *str)595{596 if (!str)597 return 0;598 599 if (*str == '=')600 str++;601 602 if (!strcmp(str, "cec_disable"))603 ce_arr.disabled = 1;604 else605 return 0;606 607 return 1;608}609