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
25static struct gen_pool *mce_evt_pool;
26static 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 */
32static bool is_duplicate_mce_record(struct mce_evt_llist *t, struct mce_evt_llist *l)
33{
34 struct mce_hw_err *err1, *err2;
35 struct mce_evt_llist *node;
36
37 err1 = &t->err;
38
39 llist_for_each_entry(node, &l->llnode, llnode) {
40 err2 = &node->err;
41
42 if (!mce_cmp(m1: &err1->m, m2: &err2->m))
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 */
55struct 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(head: &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(t: node, l: t))
68 llist_add(new: &node->llnode, head: &new_head);
69 }
70
71 return new_head.first;
72}
73
74void mce_gen_pool_process(struct work_struct *__unused)
75{
76 struct mce_evt_llist *node, *tmp;
77 struct llist_node *head;
78 struct mce *mce;
79
80 head = llist_del_all(head: &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->err.m;
87 blocking_notifier_call_chain(nh: &x86_mce_decoder_chain, val: 0, v: mce);
88 gen_pool_free(pool: mce_evt_pool, addr: (unsigned long)node, size: sizeof(*node));
89 }
90}
91
92bool mce_gen_pool_empty(void)
93{
94 return llist_empty(head: &mce_event_llist);
95}
96
97bool mce_gen_pool_add(struct mce_hw_err *err)
98{
99 struct mce_evt_llist *node;
100
101 if (filter_mce(m: &err->m))
102 return false;
103
104 if (!mce_evt_pool)
105 return false;
106
107 node = (void *)gen_pool_alloc(pool: mce_evt_pool, size: sizeof(*node));
108 if (!node) {
109 pr_warn_ratelimited("MCE records pool full!\n");
110 return false;
111 }
112
113 memcpy(&node->err, err, sizeof(*err));
114 llist_add(new: &node->llnode, head: &mce_event_llist);
115
116 return true;
117}
118
119static bool mce_gen_pool_create(void)
120{
121 int mce_numrecords, mce_poolsz, order;
122 struct gen_pool *gpool;
123 void *mce_pool;
124
125 order = order_base_2(sizeof(struct mce_evt_llist));
126 gpool = gen_pool_create(order, -1);
127 if (!gpool)
128 return false;
129
130 mce_numrecords = max(MCE_MIN_ENTRIES, num_possible_cpus() * MCE_PER_CPU);
131 mce_poolsz = mce_numrecords * (1 << order);
132 mce_pool = kmalloc(mce_poolsz, GFP_KERNEL);
133 if (!mce_pool) {
134 gen_pool_destroy(gpool);
135 return false;
136 }
137
138 if (gen_pool_add(pool: gpool, addr: (unsigned long)mce_pool, size: mce_poolsz, nid: -1)) {
139 gen_pool_destroy(gpool);
140 kfree(objp: mce_pool);
141 return false;
142 }
143
144 mce_evt_pool = gpool;
145
146 return true;
147}
148
149bool mce_gen_pool_init(void)
150{
151 /* Just init mce_gen_pool once. */
152 if (mce_evt_pool)
153 return true;
154
155 return mce_gen_pool_create();
156}
157

source code of linux/arch/x86/kernel/cpu/mce/genpool.c