linux/drivers/ras/cec.c
Linus Torvalds 2bcc673101 Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
 "Yet another big pile of changes:

   - More year 2038 work from Arnd slowly reaching the point where we
     need to think about the syscalls themself.

   - A new timer function which allows to conditionally (re)arm a timer
     only when it's either not running or the new expiry time is sooner
     than the armed expiry time. This allows to use a single timer for
     multiple timeout requirements w/o caring about the first expiry
     time at the call site.

   - A new NMI safe accessor to clock real time for the printk timestamp
     work. Can be used by tracing, perf as well if required.

   - A large number of timer setup conversions from Kees which got
     collected here because either maintainers requested so or they
     simply got ignored. As Kees pointed out already there are a few
     trivial merge conflicts and some redundant commits which was
     unavoidable due to the size of this conversion effort.

   - Avoid a redundant iteration in the timer wheel softirq processing.

   - Provide a mechanism to treat RTC implementations depending on their
     hardware properties, i.e. don't inflict the write at the 0.5
     seconds boundary which originates from the PC CMOS RTC to all RTCs.
     No functional change as drivers need to be updated separately.

   - The usual small updates to core code clocksource drivers. Nothing
     really exciting"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (111 commits)
  timers: Add a function to start/reduce a timer
  pstore: Use ktime_get_real_fast_ns() instead of __getnstimeofday()
  timer: Prepare to change all DEFINE_TIMER() callbacks
  netfilter: ipvs: Convert timers to use timer_setup()
  scsi: qla2xxx: Convert timers to use timer_setup()
  block/aoe: discover_timer: Convert timers to use timer_setup()
  ide: Convert timers to use timer_setup()
  drbd: Convert timers to use timer_setup()
  mailbox: Convert timers to use timer_setup()
  crypto: Convert timers to use timer_setup()
  drivers/pcmcia: omap1: Fix error in automated timer conversion
  ARM: footbridge: Fix typo in timer conversion
  drivers/sgi-xp: Convert timers to use timer_setup()
  drivers/pcmcia: Convert timers to use timer_setup()
  drivers/memstick: Convert timers to use timer_setup()
  drivers/macintosh: Convert timers to use timer_setup()
  hwrng/xgene-rng: Convert timers to use timer_setup()
  auxdisplay: Convert timers to use timer_setup()
  sparc/led: Convert timers to use timer_setup()
  mips: ip22/32: Convert timers to use timer_setup()
  ...
2017-11-13 17:56:58 -08:00

532 lines
12 KiB
C

// SPDX-License-Identifier: GPL-2.0
#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(struct timer_list *unused)
{
do_spring_cleaning(&ce_arr);
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 (!count) {
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;
timer_setup(&cec_timer, cec_timer_fn, 0);
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 (!strcmp(str, "cec_disable"))
ce_arr.disabled = 1;
else
return 0;
return 1;
}