genpool.c

  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(&err1->m, &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(&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
 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(&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(&x86_mce_decoder_chain, 0, mce);
 88		gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));
 89	}
 90}
 91
 92bool mce_gen_pool_empty(void)
 93{
 94	return llist_empty(&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(&err->m))
102		return false;
103
104	if (!mce_evt_pool)
105		return false;
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 false;
111	}
112
113	memcpy(&node->err, err, sizeof(*err));
114	llist_add(&node->llnode, &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(gpool, (unsigned long)mce_pool, mce_poolsz, -1)) {
139		gen_pool_destroy(gpool);
140		kfree(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}