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(I'm so sorry!) Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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#include <asm/mce.h>
#include "debugfs.h"
/* * RAS Correctable Errors Collector * * This is a simple gadget which collects correctable errors and counts their * occurrence per physical page address. * * We've opted for possibly the simplest data structure to collect those - an * array of the size of a memory page. It stores 512 u64's with the following * structure: * * [63 ... PFN ... 12 | 11 ... generation ... 10 | 9 ... count ... 0] * * The generation in the two highest order bits is two bits which are set to 11b * on every insertion. During the course of each entry's existence, the * generation field gets decremented during spring cleaning to 10b, then 01b and * then 00b. * * This way we're employing the natural numeric ordering to make sure that newly * inserted/touched elements have higher 12-bit counts (which we've manufactured) * and thus iterating over the array initially won't kick out those elements * which were inserted last. * * Spring cleaning is what we do when we reach a certain number CLEAN_ELEMS of * elements entered into the array, during which, we're decaying all elements. * If, after decay, an element gets inserted again, its generation is set to 11b * to make sure it has higher numerical count than other, older elements and * thus emulate an LRU-like behavior when deleting elements to free up space * in the page. * * When an element reaches it's max count of action_threshold, we try to poison * it by assuming that errors triggered action_threshold times in a single page * are excessive and that page shouldn't be used anymore. action_threshold is * initialized to COUNT_MASK which is the maximum. * * That error event entry causes cec_add_elem() to return !0 value and thus * signal to its callers to log the error. * * To the question why we've chosen a page and moving elements around with * memmove(), it is because it is a very simple structure to handle and max data * movement is 4K which on highly optimized modern CPUs is almost unnoticeable. * We wanted to avoid the pointer traversal of more complex structures like a * linked list or some sort of a balancing search tree. * * Deleting an element takes O(n) but since it is only a single page, it should * be fast enough and it shouldn't happen all too often depending on error * patterns. */
#undef pr_fmt#define pr_fmt(fmt) "RAS: " fmt
/* * We use DECAY_BITS bits of PAGE_SHIFT bits for counting decay, i.e., how long * elements have stayed in the array without having been accessed again. */#define DECAY_BITS 2#define DECAY_MASK ((1ULL << DECAY_BITS) - 1)#define MAX_ELEMS (PAGE_SIZE / sizeof(u64))
/* * Threshold amount of inserted elements after which we start spring * cleaning. */#define CLEAN_ELEMS (MAX_ELEMS >> DECAY_BITS)
/* Bits which count the number of errors happened in this 4K page. */#define COUNT_BITS (PAGE_SHIFT - DECAY_BITS)#define COUNT_MASK ((1ULL << COUNT_BITS) - 1)#define FULL_COUNT_MASK (PAGE_SIZE - 1)
/* * u64: [ 63 ... 12 | DECAY_BITS | COUNT_BITS ] */
#define PFN(e) ((e) >> PAGE_SHIFT)#define DECAY(e) (((e) >> COUNT_BITS) & DECAY_MASK)#define COUNT(e) ((unsigned int)(e) & COUNT_MASK)#define FULL_COUNT(e) ((e) & (PAGE_SIZE - 1))
static struct ce_array { u64 *array; /* container page */ unsigned int n; /* number of elements in the array */
unsigned int decay_count; /* * number of element insertions/increments * since the last spring cleaning. */
u64 pfns_poisoned; /* * number of PFNs which got poisoned. */
u64 ces_entered; /* * The number of correctable errors * entered into the collector. */
u64 decays_done; /* * Times we did spring cleaning. */
union { struct { __u32 disabled : 1, /* cmdline disabled */ __resv : 31; }; __u32 flags; };} ce_arr;
static DEFINE_MUTEX(ce_mutex);static u64 dfs_pfn;
/* Amount of errors after which we offline */static u64 action_threshold = COUNT_MASK;
/* Each element "decays" each decay_interval which is 24hrs by default. */#define CEC_DECAY_DEFAULT_INTERVAL 24 * 60 * 60 /* 24 hrs */#define CEC_DECAY_MIN_INTERVAL 1 * 60 * 60 /* 1h */#define CEC_DECAY_MAX_INTERVAL 30 * 24 * 60 * 60 /* one month */static struct delayed_work cec_work;static u64 decay_interval = CEC_DECAY_DEFAULT_INTERVAL;
/* * Decrement decay value. We're using DECAY_BITS bits to denote decay of an * element in the array. On insertion and any access, it gets reset to max. */static void do_spring_cleaning(struct ce_array *ca){ int i;
for (i = 0; i < ca->n; i++) { u8 decay = DECAY(ca->array[i]);
if (!decay) continue;
decay--;
ca->array[i] &= ~(DECAY_MASK << COUNT_BITS); ca->array[i] |= (decay << COUNT_BITS); } ca->decay_count = 0; ca->decays_done++;}
/* * @interval in seconds */static void cec_mod_work(unsigned long interval){ unsigned long iv;
iv = interval * HZ; mod_delayed_work(system_percpu_wq, &cec_work, round_jiffies(iv));}
static void cec_work_fn(struct work_struct *work){ mutex_lock(&ce_mutex); do_spring_cleaning(&ce_arr); mutex_unlock(&ce_mutex);
cec_mod_work(decay_interval);}
/* * @to: index of the smallest element which is >= then @pfn. * * Return the index of the pfn if found, otherwise negative value. */static int __find_elem(struct ce_array *ca, u64 pfn, unsigned int *to){ int min = 0, max = ca->n - 1; u64 this_pfn;
while (min <= max) { int i = (min + max) >> 1;
this_pfn = PFN(ca->array[i]);
if (this_pfn < pfn) min = i + 1; else if (this_pfn > pfn) max = i - 1; else if (this_pfn == pfn) { if (to) *to = i;
return i; } }
/* * When the loop terminates without finding @pfn, min has the index of * the element slot where the new @pfn should be inserted. The loop * terminates when min > max, which means the min index points to the * bigger element while the max index to the smaller element, in-between * which the new @pfn belongs to. * * For more details, see exercise 1, Section 6.2.1 in TAOCP, vol. 3. */ if (to) *to = min;
return -ENOKEY;}
static int find_elem(struct ce_array *ca, u64 pfn, unsigned int *to){ WARN_ON(!to);
if (!ca->n) { *to = 0; return -ENOKEY; } return __find_elem(ca, pfn, to);}
static void del_elem(struct ce_array *ca, int idx){ /* Save us a function call when deleting the last element. */ if (ca->n - (idx + 1)) memmove((void *)&ca->array[idx], (void *)&ca->array[idx + 1], (ca->n - (idx + 1)) * sizeof(u64));
ca->n--;}
static u64 del_lru_elem_unlocked(struct ce_array *ca){ unsigned int min = FULL_COUNT_MASK; int i, min_idx = 0;
for (i = 0; i < ca->n; i++) { unsigned int this = FULL_COUNT(ca->array[i]);
if (min > this) { min = this; min_idx = i; } }
del_elem(ca, min_idx);
return PFN(ca->array[min_idx]);}
/* * We return the 0th pfn in the error case under the assumption that it cannot * be poisoned and excessive CEs in there are a serious deal anyway. */static u64 __maybe_unused del_lru_elem(void){ struct ce_array *ca = &ce_arr; u64 pfn;
if (!ca->n) return 0;
mutex_lock(&ce_mutex); pfn = del_lru_elem_unlocked(ca); mutex_unlock(&ce_mutex);
return pfn;}
static bool sanity_check(struct ce_array *ca){ bool ret = false; u64 prev = 0; int i;
for (i = 0; i < ca->n; i++) { u64 this = PFN(ca->array[i]);
if (WARN(prev > this, "prev: 0x%016llx <-> this: 0x%016llx\n", prev, this)) ret = true;
prev = this; }
if (!ret) return ret;
pr_info("Sanity check dump:\n{ n: %d\n", ca->n); for (i = 0; i < ca->n; i++) { u64 this = PFN(ca->array[i]);
pr_info(" %03d: [%016llx|%03llx]\n", i, this, FULL_COUNT(ca->array[i])); } pr_info("}\n");
return ret;}
/** * cec_add_elem - Add an element to the CEC array. * @pfn: page frame number to insert * * Return values: * - <0: on error * - 0: on success * - >0: when the inserted pfn was offlined */static int cec_add_elem(u64 pfn){ struct ce_array *ca = &ce_arr; int count, err, ret = 0; unsigned int to = 0;
/* * We can be called very early on the identify_cpu() path where we are * not initialized yet. We ignore the error for simplicity. */ if (!ce_arr.array || ce_arr.disabled) return -ENODEV;
mutex_lock(&ce_mutex);
ca->ces_entered++;
/* Array full, free the LRU slot. */ if (ca->n == MAX_ELEMS) WARN_ON(!del_lru_elem_unlocked(ca));
err = find_elem(ca, pfn, &to); if (err < 0) { /* * Shift range [to-end] to make room for one more element. */ memmove((void *)&ca->array[to + 1], (void *)&ca->array[to], (ca->n - to) * sizeof(u64));
ca->array[to] = pfn << PAGE_SHIFT; ca->n++; }
/* Add/refresh element generation and increment count */ ca->array[to] |= DECAY_MASK << COUNT_BITS; ca->array[to]++;
/* Check action threshold and soft-offline, if reached. */ count = COUNT(ca->array[to]); if (count >= action_threshold) { u64 pfn = ca->array[to] >> PAGE_SHIFT;
if (!pfn_valid(pfn)) { pr_warn("CEC: Invalid pfn: 0x%llx\n", pfn); } else { /* We have reached max count for this page, soft-offline it. */ pr_err("Soft-offlining pfn: 0x%llx\n", pfn); memory_failure_queue(pfn, MF_SOFT_OFFLINE); ca->pfns_poisoned++; }
del_elem(ca, to);
/* * Return a >0 value to callers, to denote that we've reached * the offlining threshold. */ ret = 1;
goto unlock; }
ca->decay_count++;
if (ca->decay_count >= CLEAN_ELEMS) do_spring_cleaning(ca);
WARN_ON_ONCE(sanity_check(ca));
unlock: mutex_unlock(&ce_mutex);
return ret;}
static int u64_get(void *data, u64 *val){ *val = *(u64 *)data;
return 0;}
static int pfn_set(void *data, u64 val){ *(u64 *)data = val;
cec_add_elem(val);
return 0;}
DEFINE_DEBUGFS_ATTRIBUTE(pfn_ops, u64_get, pfn_set, "0x%llx\n");
static int decay_interval_set(void *data, u64 val){ if (val < CEC_DECAY_MIN_INTERVAL) return -EINVAL;
if (val > CEC_DECAY_MAX_INTERVAL) return -EINVAL;
*(u64 *)data = val; decay_interval = val;
cec_mod_work(decay_interval);
return 0;}DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, u64_get, decay_interval_set, "%lld\n");
static int action_threshold_set(void *data, u64 val){ *(u64 *)data = val;
if (val > COUNT_MASK) val = COUNT_MASK;
action_threshold = val;
return 0;}DEFINE_DEBUGFS_ATTRIBUTE(action_threshold_ops, u64_get, action_threshold_set, "%lld\n");
static const char * const bins[] = { "00", "01", "10", "11" };
static int array_show(struct seq_file *m, void *v){ struct ce_array *ca = &ce_arr; int i;
mutex_lock(&ce_mutex);
seq_printf(m, "{ n: %d\n", ca->n); for (i = 0; i < ca->n; i++) { u64 this = PFN(ca->array[i]);
seq_printf(m, " %3d: [%016llx|%s|%03llx]\n", i, this, bins[DECAY(ca->array[i])], COUNT(ca->array[i])); }
seq_printf(m, "}\n");
seq_printf(m, "Stats:\nCEs: %llu\nofflined pages: %llu\n", ca->ces_entered, ca->pfns_poisoned);
seq_printf(m, "Flags: 0x%x\n", ca->flags);
seq_printf(m, "Decay interval: %lld seconds\n", decay_interval); seq_printf(m, "Decays: %lld\n", ca->decays_done);
seq_printf(m, "Action threshold: %lld\n", action_threshold);
mutex_unlock(&ce_mutex);
return 0;}
DEFINE_SHOW_ATTRIBUTE(array);
static int __init create_debugfs_nodes(void){ struct dentry *d, *pfn, *decay, *count, *array, *dfs;
dfs = ras_get_debugfs_root(); if (!dfs) { pr_warn("Error getting RAS debugfs root!\n"); return -1; }
d = debugfs_create_dir("cec", dfs); if (!d) { pr_warn("Error creating cec debugfs node!\n"); return -1; }
decay = debugfs_create_file("decay_interval", S_IRUSR | S_IWUSR, d, &decay_interval, &decay_interval_ops); if (!decay) { pr_warn("Error creating decay_interval debugfs node!\n"); goto err; }
count = debugfs_create_file("action_threshold", S_IRUSR | S_IWUSR, d, &action_threshold, &action_threshold_ops); if (!count) { pr_warn("Error creating action_threshold debugfs node!\n"); goto err; }
if (!IS_ENABLED(CONFIG_RAS_CEC_DEBUG)) return 0;
pfn = debugfs_create_file("pfn", S_IRUSR | S_IWUSR, d, &dfs_pfn, &pfn_ops); if (!pfn) { pr_warn("Error creating pfn debugfs node!\n"); goto err; }
array = debugfs_create_file("array", S_IRUSR, d, NULL, &array_fops); if (!array) { pr_warn("Error creating array debugfs node!\n"); goto err; }
return 0;
err: debugfs_remove_recursive(d);
return 1;}
static int cec_notifier(struct notifier_block *nb, unsigned long val, void *data){ struct mce *m = (struct mce *)data;
if (!m) return NOTIFY_DONE;
/* We eat only correctable DRAM errors with usable addresses. */ if (mce_is_memory_error(m) && mce_is_correctable(m) && mce_usable_address(m)) { if (!cec_add_elem(m->addr >> PAGE_SHIFT)) { m->kflags |= MCE_HANDLED_CEC; return NOTIFY_OK; } }
return NOTIFY_DONE;}
static struct notifier_block cec_nb = { .notifier_call = cec_notifier, .priority = MCE_PRIO_CEC,};
static int __init cec_init(void){ if (ce_arr.disabled) return -ENODEV;
/* * Intel systems may avoid uncorrectable errors * if pages with corrected errors are aggressively * taken offline. */ if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) action_threshold = 2;
ce_arr.array = (void *)get_zeroed_page(GFP_KERNEL); if (!ce_arr.array) { pr_err("Error allocating CE array page!\n"); return -ENOMEM; }
if (create_debugfs_nodes()) { free_page((unsigned long)ce_arr.array); return -ENOMEM; }
INIT_DELAYED_WORK(&cec_work, cec_work_fn); schedule_delayed_work(&cec_work, CEC_DECAY_DEFAULT_INTERVAL);
mce_register_decode_chain(&cec_nb);
pr_info("Correctable Errors collector initialized.\n"); return 0;}late_initcall(cec_init);
int __init parse_cec_param(char *str){ if (!str) return 0;
if (*str == '=') str++;
if (!strcmp(str, "cec_disable")) ce_arr.disabled = 1; else return 0;
return 1;}