arch/x86/kernel/cpu/mcheck/mce-genpool.c

   1 /*
   2  * MCE event pool management in MCE context
   3  *
   4  * Copyright (C) 2015 Intel Corp.
   5  * Author: Chen, Gong <gong.chen@linux.intel.com>
   6  *
   7  * This file is licensed under GPLv2.
   8  */
   9 #include <linux/smp.h>
  10 #include <linux/mm.h>
  11 #include <linux/genalloc.h>
  12 #include <linux/llist.h>
  13 #include "mce-internal.h"
  14
  15 /*
  16  * printk() is not safe in MCE context. This is a lock-less memory allocator
  17  * used to save error information organized in a lock-less list.
  18  *
  19  * This memory pool is only to be used to save MCE records in MCE context.
  20  * MCE events are rare, so a fixed size memory pool should be enough. Use
  21  * 2 pages to save MCE events for now (~80 MCE records at most).
  22  */
  23 #define MCE_POOLSZ      (2 * PAGE_SIZE)
  24
  25 static struct gen_pool *mce_evt_pool;
  26 static LLIST_HEAD(mce_event_llist);
  27 static char gen_pool_buf[MCE_POOLSZ];
  28
  29 /*
  30  * Compare the record "t" with each of the records on list "l" to see if
  31  * an equivalent one is present in the list.
  32  */
  33 static bool is_duplicate_mce_record(struct mce_evt_llist *t, struct mce_evt_llist *l)
  34 {
  35         struct mce_evt_llist *node;
  36         struct mce *m1, *m2;
  37
  38         m1 = &t->mce;
  39
  40         llist_for_each_entry(node, &l->llnode, llnode) {
  41                 m2 = &node->mce;
  42
  43                 if (!mce_cmp(m1, m2))
  44                         return true;
  45         }
  46         return false;
  47 }
  48
  49 /*
  50  * The system has panicked - we'd like to peruse the list of MCE records
  51  * that have been queued, but not seen by anyone yet.  The list is in
  52  * reverse time order, so we need to reverse it. While doing that we can
  53  * also drop duplicate records (these were logged because some banks are
  54  * shared between cores or by all threads on a socket).
  55  */
  56 struct llist_node *mce_gen_pool_prepare_records(void)
  57 {
  58         struct llist_node *head;
  59         LLIST_HEAD(new_head);
  60         struct mce_evt_llist *node, *t;
  61
  62         head = llist_del_all(&mce_event_llist);
  63         if (!head)
  64                 return NULL;
  65
  66         /* squeeze out duplicates while reversing order */
  67         llist_for_each_entry_safe(node, t, head, llnode) {
  68                 if (!is_duplicate_mce_record(node, t))
  69                         llist_add(&node->llnode, &new_head);
  70         }
  71
  72         return new_head.first;
  73 }
  74
  75 void mce_gen_pool_process(struct work_struct *__unused)
  76 {
  77         struct llist_node *head;
  78         struct mce_evt_llist *node, *tmp;
  79         struct mce *mce;
  80
  81         head = llist_del_all(&mce_event_llist);
  82         if (!head)
  83                 return;
  84
  85         head = llist_reverse_order(head);
  86         llist_for_each_entry_safe(node, tmp, head, llnode) {
  87                 mce = &node->mce;
  88                 blocking_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
  89                 gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));
  90         }
  91 }
  92
  93 bool mce_gen_pool_empty(void)
  94 {
  95         return llist_empty(&mce_event_llist);
  96 }
  97
  98 int mce_gen_pool_add(struct mce *mce)
  99 {
 100         struct mce_evt_llist *node;
 101
 102         if (!mce_evt_pool)
 103                 return -EINVAL;
 104
 105         node = (void *)gen_pool_alloc(mce_evt_pool, sizeof(*node));
 106         if (!node) {
 107                 pr_warn_ratelimited("MCE records pool full!\n");
 108                 return -ENOMEM;
 109         }
 110
 111         memcpy(&node->mce, mce, sizeof(*mce));
 112         llist_add(&node->llnode, &mce_event_llist);
 113
 114         return 0;
 115 }
 116
 117 static int mce_gen_pool_create(void)
 118 {
 119         struct gen_pool *tmpp;
 120         int ret = -ENOMEM;
 121
 122         tmpp = gen_pool_create(ilog2(sizeof(struct mce_evt_llist)), -1);
 123         if (!tmpp)
 124                 goto out;
 125
 126         ret = gen_pool_add(tmpp, (unsigned long)gen_pool_buf, MCE_POOLSZ, -1);
 127         if (ret) {
 128                 gen_pool_destroy(tmpp);
 129                 goto out;
 130         }
 131
 132         mce_evt_pool = tmpp;
 133
 134 out:
 135         return ret;
 136 }
 137
 138 int mce_gen_pool_init(void)
 139 {
 140         /* Just init mce_gen_pool once. */
 141         if (mce_evt_pool)
 142                 return 0;
 143
 144         return mce_gen_pool_create();
 145 }