![Borislav Petkov](/assets/img/avatar_default.png)
Introduce a simple data structure for collecting correctable errors along with accessors. More detailed description in the code itself. The error decoding is done with the decoding chain now and mce_first_notifier() gets to see the error first and the CEC decides whether to log it and then the rest of the chain doesn't hear about it - basically the main reason for the CE collector - or to continue running the notifiers. When the CEC hits the action threshold, it will try to soft-offine the page containing the ECC and then the whole decoding chain gets to see the error. Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-edac <linux-edac@vger.kernel.org> Link: http://lkml.kernel.org/r/20170327093304.10683-5-bp@alien8.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
533 lines
12 KiB
C
533 lines
12 KiB
C
#include <linux/mm.h>
|
|
#include <linux/gfp.h>
|
|
#include <linux/kernel.h>
|
|
|
|
#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 an LRU-like behavior when deleting elements to free up space
|
|
* in the page.
|
|
*
|
|
* When an element reaches it's max count of count_threshold, we try to poison
|
|
* it by assuming that errors triggered count_threshold times in a single page
|
|
* are excessive and that page shouldn't be used anymore. count_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 unsigned int count_threshold = COUNT_MASK;
|
|
|
|
/*
|
|
* The timer "decays" element count each timer_interval which is 24hrs by
|
|
* default.
|
|
*/
|
|
|
|
#define CEC_TIMER_DEFAULT_INTERVAL 24 * 60 * 60 /* 24 hrs */
|
|
#define CEC_TIMER_MIN_INTERVAL 1 * 60 * 60 /* 1h */
|
|
#define CEC_TIMER_MAX_INTERVAL 30 * 24 * 60 * 60 /* one month */
|
|
static struct timer_list cec_timer;
|
|
static u64 timer_interval = CEC_TIMER_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_timer(struct timer_list *t, unsigned long interval)
|
|
{
|
|
unsigned long iv;
|
|
|
|
iv = interval * HZ + jiffies;
|
|
|
|
mod_timer(t, round_jiffies(iv));
|
|
}
|
|
|
|
static void cec_timer_fn(unsigned long data)
|
|
{
|
|
struct ce_array *ca = (struct ce_array *)data;
|
|
|
|
do_spring_cleaning(ca);
|
|
|
|
cec_mod_timer(&cec_timer, timer_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)
|
|
{
|
|
u64 this_pfn;
|
|
int min = 0, max = ca->n;
|
|
|
|
while (min < max) {
|
|
int tmp = (max + min) >> 1;
|
|
|
|
this_pfn = PFN(ca->array[tmp]);
|
|
|
|
if (this_pfn < pfn)
|
|
min = tmp + 1;
|
|
else if (this_pfn > pfn)
|
|
max = tmp;
|
|
else {
|
|
min = tmp;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (to)
|
|
*to = min;
|
|
|
|
this_pfn = PFN(ca->array[min]);
|
|
|
|
if (this_pfn == pfn)
|
|
return 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;
|
|
}
|
|
|
|
|
|
int cec_add_elem(u64 pfn)
|
|
{
|
|
struct ce_array *ca = &ce_arr;
|
|
unsigned int to;
|
|
int count, ret = 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;
|
|
|
|
ca->ces_entered++;
|
|
|
|
mutex_lock(&ce_mutex);
|
|
|
|
if (ca->n == MAX_ELEMS)
|
|
WARN_ON(!del_lru_elem_unlocked(ca));
|
|
|
|
ret = find_elem(ca, pfn, &to);
|
|
if (ret < 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) |
|
|
(DECAY_MASK << COUNT_BITS) | 1;
|
|
|
|
ca->n++;
|
|
|
|
ret = 0;
|
|
|
|
goto decay;
|
|
}
|
|
|
|
count = COUNT(ca->array[to]);
|
|
|
|
if (count < count_threshold) {
|
|
ca->array[to] |= (DECAY_MASK << COUNT_BITS);
|
|
ca->array[to]++;
|
|
|
|
ret = 0;
|
|
} else {
|
|
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, 0, MF_SOFT_OFFLINE);
|
|
ca->pfns_poisoned++;
|
|
}
|
|
|
|
del_elem(ca, to);
|
|
|
|
/*
|
|
* Return a >0 value to denote that we've reached the offlining
|
|
* threshold.
|
|
*/
|
|
ret = 1;
|
|
|
|
goto unlock;
|
|
}
|
|
|
|
decay:
|
|
ca->decay_count++;
|
|
|
|
if (ca->decay_count >= CLEAN_ELEMS)
|
|
do_spring_cleaning(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;
|
|
|
|
return cec_add_elem(val);
|
|
}
|
|
|
|
DEFINE_DEBUGFS_ATTRIBUTE(pfn_ops, u64_get, pfn_set, "0x%llx\n");
|
|
|
|
static int decay_interval_set(void *data, u64 val)
|
|
{
|
|
*(u64 *)data = val;
|
|
|
|
if (val < CEC_TIMER_MIN_INTERVAL)
|
|
return -EINVAL;
|
|
|
|
if (val > CEC_TIMER_MAX_INTERVAL)
|
|
return -EINVAL;
|
|
|
|
timer_interval = val;
|
|
|
|
cec_mod_timer(&cec_timer, timer_interval);
|
|
return 0;
|
|
}
|
|
DEFINE_DEBUGFS_ATTRIBUTE(decay_interval_ops, u64_get, decay_interval_set, "%lld\n");
|
|
|
|
static int count_threshold_set(void *data, u64 val)
|
|
{
|
|
*(u64 *)data = val;
|
|
|
|
if (val > COUNT_MASK)
|
|
val = COUNT_MASK;
|
|
|
|
count_threshold = val;
|
|
|
|
return 0;
|
|
}
|
|
DEFINE_DEBUGFS_ATTRIBUTE(count_threshold_ops, u64_get, count_threshold_set, "%lld\n");
|
|
|
|
static int array_dump(struct seq_file *m, void *v)
|
|
{
|
|
struct ce_array *ca = &ce_arr;
|
|
u64 prev = 0;
|
|
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, " %03d: [%016llx|%03llx]\n", i, this, FULL_COUNT(ca->array[i]));
|
|
|
|
WARN_ON(prev > this);
|
|
|
|
prev = this;
|
|
}
|
|
|
|
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, "Timer interval: %lld seconds\n", timer_interval);
|
|
seq_printf(m, "Decays: %lld\n", ca->decays_done);
|
|
|
|
seq_printf(m, "Action threshold: %d\n", count_threshold);
|
|
|
|
mutex_unlock(&ce_mutex);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int array_open(struct inode *inode, struct file *filp)
|
|
{
|
|
return single_open(filp, array_dump, NULL);
|
|
}
|
|
|
|
static const struct file_operations array_ops = {
|
|
.owner = THIS_MODULE,
|
|
.open = array_open,
|
|
.read = seq_read,
|
|
.llseek = seq_lseek,
|
|
.release = single_release,
|
|
};
|
|
|
|
static int __init create_debugfs_nodes(void)
|
|
{
|
|
struct dentry *d, *pfn, *decay, *count, *array;
|
|
|
|
d = debugfs_create_dir("cec", ras_debugfs_dir);
|
|
if (!d) {
|
|
pr_warn("Error creating cec debugfs node!\n");
|
|
return -1;
|
|
}
|
|
|
|
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_ops);
|
|
if (!array) {
|
|
pr_warn("Error creating array debugfs node!\n");
|
|
goto err;
|
|
}
|
|
|
|
decay = debugfs_create_file("decay_interval", S_IRUSR | S_IWUSR, d,
|
|
&timer_interval, &decay_interval_ops);
|
|
if (!decay) {
|
|
pr_warn("Error creating decay_interval debugfs node!\n");
|
|
goto err;
|
|
}
|
|
|
|
count = debugfs_create_file("count_threshold", S_IRUSR | S_IWUSR, d,
|
|
&count_threshold, &count_threshold_ops);
|
|
if (!decay) {
|
|
pr_warn("Error creating count_threshold debugfs node!\n");
|
|
goto err;
|
|
}
|
|
|
|
|
|
return 0;
|
|
|
|
err:
|
|
debugfs_remove_recursive(d);
|
|
|
|
return 1;
|
|
}
|
|
|
|
void __init cec_init(void)
|
|
{
|
|
if (ce_arr.disabled)
|
|
return;
|
|
|
|
ce_arr.array = (void *)get_zeroed_page(GFP_KERNEL);
|
|
if (!ce_arr.array) {
|
|
pr_err("Error allocating CE array page!\n");
|
|
return;
|
|
}
|
|
|
|
if (create_debugfs_nodes())
|
|
return;
|
|
|
|
setup_timer(&cec_timer, cec_timer_fn, (unsigned long)&ce_arr);
|
|
cec_mod_timer(&cec_timer, CEC_TIMER_DEFAULT_INTERVAL);
|
|
|
|
pr_info("Correctable Errors collector initialized.\n");
|
|
}
|
|
|
|
int __init parse_cec_param(char *str)
|
|
{
|
|
if (!str)
|
|
return 0;
|
|
|
|
if (*str == '=')
|
|
str++;
|
|
|
|
if (!strncmp(str, "cec_disable", 7))
|
|
ce_arr.disabled = 1;
|
|
else
|
|
return 0;
|
|
|
|
return 1;
|
|
}
|