1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * MCE event pool management in MCE context
4 *
5 * Copyright (C) 2015 Intel Corp.
6 * Author: Chen, Gong <gong.chen@linux.intel.com>
7 */
8 #include <linux/smp.h>
9 #include <linux/mm.h>
10 #include <linux/genalloc.h>
11 #include <linux/llist.h>
12 #include "internal.h"
13
14 /*
15 * printk() is not safe in MCE context. This is a lock-less memory allocator
16 * used to save error information organized in a lock-less list.
17 *
18 * This memory pool is only to be used to save MCE records in MCE context.
19 * MCE events are rare, so a fixed size memory pool should be enough.
20 * Allocate on a sliding scale based on number of CPUs.
21 */
22 #define MCE_MIN_ENTRIES 80
23 #define MCE_PER_CPU 2
24
25 static struct gen_pool *mce_evt_pool;
26 static LLIST_HEAD(mce_event_llist);
27
28 /*
29 * Compare the record "t" with each of the records on list "l" to see if
30 * an equivalent one is present in the list.
31 */
32 static bool is_duplicate_mce_record(struct mce_evt_llist *t, struct mce_evt_llist *l)
33 {
34 struct mce_evt_llist *node;
35 struct mce *m1, *m2;
36
37 m1 = &t->mce;
38
39 llist_for_each_entry(node, &l->llnode, llnode) {
40 m2 = &node->mce;
41
42 if (!mce_cmp(m1, m2))
43 return true;
44 }
45 return false;
46 }
47
48 /*
49 * The system has panicked - we'd like to peruse the list of MCE records
50 * that have been queued, but not seen by anyone yet. The list is in
51 * reverse time order, so we need to reverse it. While doing that we can
52 * also drop duplicate records (these were logged because some banks are
53 * shared between cores or by all threads on a socket).
54 */
55 struct llist_node *mce_gen_pool_prepare_records(void)
56 {
57 struct llist_node *head;
58 LLIST_HEAD(new_head);
59 struct mce_evt_llist *node, *t;
60
61 head = llist_del_all(&mce_event_llist);
62 if (!head)
63 return NULL;
64
65 /* squeeze out duplicates while reversing order */
66 llist_for_each_entry_safe(node, t, head, llnode) {
67 if (!is_duplicate_mce_record(node, t))
68 llist_add(&node->llnode, &new_head);
69 }
70
71 return new_head.first;
72 }
73
74 void mce_gen_pool_process(struct work_struct *__unused)
75 {
76 struct llist_node *head;
77 struct mce_evt_llist *node, *tmp;
78 struct mce *mce;
79
80 head = llist_del_all(&mce_event_llist);
81 if (!head)
82 return;
83
84 head = llist_reverse_order(head);
85 llist_for_each_entry_safe(node, tmp, head, llnode) {
86 mce = &node->mce;
87 blocking_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
88 gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));
89 }
90 }
91
92 bool mce_gen_pool_empty(void)
93 {
94 return llist_empty(&mce_event_llist);
95 }
96
97 int mce_gen_pool_add(struct mce *mce)
98 {
99 struct mce_evt_llist *node;
100
101 if (filter_mce(mce))
102 return -EINVAL;
103
104 if (!mce_evt_pool)
105 return -EINVAL;
106
107 node = (void *)gen_pool_alloc(mce_evt_pool, sizeof(*node));
108 if (!node) {
109 pr_warn_ratelimited("MCE records pool full!\n");
110 return -ENOMEM;
111 }
112
113 memcpy(&node->mce, mce, sizeof(*mce));
114 llist_add(&node->llnode, &mce_event_llist);
115
116 return 0;
117 }
118
119 static int mce_gen_pool_create(void)
120 {
121 int mce_numrecords, mce_poolsz, order;
122 struct gen_pool *gpool;
123 int ret = -ENOMEM;
124 void *mce_pool;
125
126 order = order_base_2(sizeof(struct mce_evt_llist));
127 gpool = gen_pool_create(order, -1);
128 if (!gpool)
129 return ret;
130
131 mce_numrecords = max(MCE_MIN_ENTRIES, num_possible_cpus() * MCE_PER_CPU);
132 mce_poolsz = mce_numrecords * (1 << order);
133 mce_pool = kmalloc(mce_poolsz, GFP_KERNEL);
134 if (!mce_pool) {
135 gen_pool_destroy(gpool);
136 return ret;
137 }
138 ret = gen_pool_add(gpool, (unsigned long)mce_pool, mce_poolsz, -1);
139 if (ret) {
140 gen_pool_destroy(gpool);
141 kfree(mce_pool);
142 return ret;
143 }
144
145 mce_evt_pool = gpool;
146
147 return ret;
148 }
149
150 int mce_gen_pool_init(void)
151 {
152 /* Just init mce_gen_pool once. */
153 if (mce_evt_pool)
154 return 0;
155
156 return mce_gen_pool_create();
157 }
158
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