// SPDX-License-Identifier: GPL-2.0-only
/*
 * MCE event pool management in MCE context
 *
 * Copyright (C) 2015 Intel Corp.
 * Author: Chen, Gong <gong.chen@linux.intel.com>
 */
#include <linux/smp.h>
#include <linux/mm.h>
#include <linux/genalloc.h>
#include <linux/llist.h>
#include "internal.h"

/*
 * printk() is not safe in MCE context. This is a lock-less memory allocator
 * used to save error information organized in a lock-less list.
 *
 * This memory pool is only to be used to save MCE records in MCE context.
 * MCE events are rare, so a fixed size memory pool should be enough.
 * Allocate on a sliding scale based on number of CPUs.
 */
#define MCE_MIN_ENTRIES 80
#define MCE_PER_CPU     2

static struct gen_pool *mce_evt_pool;
static LLIST_HEAD(mce_event_llist);

/*
 * Compare the record "t" with each of the records on list "l" to see if
 * an equivalent one is present in the list.
 */
static bool is_duplicate_mce_record(struct mce_evt_llist *t, struct mce_evt_llist *l)
{
        struct mce_hw_err *err1, *err2;
        struct mce_evt_llist *node;

        err1 = &t->err;

        llist_for_each_entry(node, &l->llnode, llnode) {
                err2 = &node->err;

                if (!mce_cmp(&err1->m, &err2->m))
                        return true;
        }
        return false;
}

/*
 * The system has panicked - we'd like to peruse the list of MCE records
 * that have been queued, but not seen by anyone yet.  The list is in
 * reverse time order, so we need to reverse it. While doing that we can
 * also drop duplicate records (these were logged because some banks are
 * shared between cores or by all threads on a socket).
 */
struct llist_node *mce_gen_pool_prepare_records(void)
{
        struct llist_node *head;
        LLIST_HEAD(new_head);
        struct mce_evt_llist *node, *t;

        head = llist_del_all(&mce_event_llist);
        if (!head)
                return NULL;

        /* squeeze out duplicates while reversing order */
        llist_for_each_entry_safe(node, t, head, llnode) {
                if (!is_duplicate_mce_record(node, t))
                        llist_add(&node->llnode, &new_head);
        }

        return new_head.first;
}

void mce_gen_pool_process(struct work_struct *__unused)
{
        struct mce_evt_llist *node, *tmp;
        struct llist_node *head;
        struct mce *mce;

        head = llist_del_all(&mce_event_llist);
        if (!head)
                return;

        head = llist_reverse_order(head);
        llist_for_each_entry_safe(node, tmp, head, llnode) {
                mce = &node->err.m;
                blocking_notifier_call_chain(&x86_mce_decoder_chain, 0, mce);
                gen_pool_free(mce_evt_pool, (unsigned long)node, sizeof(*node));
        }
}

bool mce_gen_pool_empty(void)
{
        return llist_empty(&mce_event_llist);
}

bool mce_gen_pool_add(struct mce_hw_err *err)
{
        struct mce_evt_llist *node;

        if (filter_mce(&err->m))
                return false;

        if (!mce_evt_pool)
                return false;

        node = (void *)gen_pool_alloc(mce_evt_pool, sizeof(*node));
        if (!node) {
                pr_warn_ratelimited("MCE records pool full!\n");
                return false;
        }

        memcpy(&node->err, err, sizeof(*err));
        llist_add(&node->llnode, &mce_event_llist);

        return true;
}

static bool mce_gen_pool_create(void)
{
        int mce_numrecords, mce_poolsz, order;
        struct gen_pool *gpool;
        void *mce_pool;

        order = order_base_2(sizeof(struct mce_evt_llist));
        gpool = gen_pool_create(order, -1);
        if (!gpool)
                return false;

        mce_numrecords = max(MCE_MIN_ENTRIES, num_possible_cpus() * MCE_PER_CPU);
        mce_poolsz = mce_numrecords * (1 << order);
        mce_pool = kmalloc(mce_poolsz, GFP_KERNEL);
        if (!mce_pool) {
                gen_pool_destroy(gpool);
                return false;
        }

        if (gen_pool_add(gpool, (unsigned long)mce_pool, mce_poolsz, -1)) {
                gen_pool_destroy(gpool);
                kfree(mce_pool);
                return false;
        }

        mce_evt_pool = gpool;

        return true;
}

bool mce_gen_pool_init(void)
{
        /* Just init mce_gen_pool once. */
        if (mce_evt_pool)
                return true;

        return mce_gen_pool_create();
}