/*
 * APEI Generic Hardware Error Source support
 *
 * Generic Hardware Error Source provides a way to report platform
 * hardware errors (such as that from chipset). It works in so called
 * "Firmware First" mode, that is, hardware errors are reported to
 * firmware firstly, then reported to Linux by firmware. This way,
 * some non-standard hardware error registers or non-standard hardware
 * link can be checked by firmware to produce more hardware error
 * information for Linux.
 *
 * For more information about Generic Hardware Error Source, please
 * refer to ACPI Specification version 4.0, section 17.3.2.6
 *
 * Copyright 2010,2011 Intel Corp.
 *   Author: Huang Ying <ying.huang@intel.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 as published by the Free Software Foundation;
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/kernel.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/acpi.h>
#include <linux/io.h>
#include <linux/interrupt.h>
#include <linux/timer.h>
#include <linux/cper.h>
#include <linux/kdebug.h>
#include <linux/platform_device.h>
#include <linux/mutex.h>
#include <linux/ratelimit.h>
#include <linux/vmalloc.h>
#include <linux/irq_work.h>
#include <linux/llist.h>
#include <linux/genalloc.h>
#include <linux/pci.h>
#include <linux/aer.h>
#include <linux/nmi.h>
#include <linux/sched/clock.h>
#include <linux/uuid.h>
#include <linux/ras.h>

#include <acpi/actbl1.h>
#include <acpi/ghes.h>
#include <acpi/apei.h>
#include <asm/fixmap.h>
#include <asm/tlbflush.h>
#include <ras/ras_event.h>

#include "apei-internal.h"

#define GHES_PFX        "GHES: "

#define GHES_ESTATUS_MAX_SIZE           65536
#define GHES_ESOURCE_PREALLOC_MAX_SIZE  65536

#define GHES_ESTATUS_POOL_MIN_ALLOC_ORDER 3

/* This is just an estimation for memory pool allocation */
#define GHES_ESTATUS_CACHE_AVG_SIZE     512

#define GHES_ESTATUS_CACHES_SIZE        4

#define GHES_ESTATUS_IN_CACHE_MAX_NSEC  10000000000ULL
/* Prevent too many caches are allocated because of RCU */
#define GHES_ESTATUS_CACHE_ALLOCED_MAX  (GHES_ESTATUS_CACHES_SIZE * 3 / 2)

#define GHES_ESTATUS_CACHE_LEN(estatus_len)                     \
        (sizeof(struct ghes_estatus_cache) + (estatus_len))
#define GHES_ESTATUS_FROM_CACHE(estatus_cache)                  \
        ((struct acpi_hest_generic_status *)                            \
         ((struct ghes_estatus_cache *)(estatus_cache) + 1))

#define GHES_ESTATUS_NODE_LEN(estatus_len)                      \
        (sizeof(struct ghes_estatus_node) + (estatus_len))
#define GHES_ESTATUS_FROM_NODE(estatus_node)                    \
        ((struct acpi_hest_generic_status *)                            \
         ((struct ghes_estatus_node *)(estatus_node) + 1))

static inline bool is_hest_type_generic_v2(struct ghes *ghes)
{
        return ghes->generic->header.type == ACPI_HEST_TYPE_GENERIC_ERROR_V2;
}

/*
 * This driver isn't really modular, however for the time being,
 * continuing to use module_param is the easiest way to remain
 * compatible with existing boot arg use cases.
 */
bool ghes_disable;
module_param_named(disable, ghes_disable, bool, 0);

/*
 * All error sources notified with HED (Hardware Error Device) share a
 * single notifier callback, so they need to be linked and checked one
 * by one. This holds true for NMI too.
 *
 * RCU is used for these lists, so ghes_list_mutex is only used for
 * list changing, not for traversing.
 */
static LIST_HEAD(ghes_hed);
static DEFINE_MUTEX(ghes_list_mutex);

/*
 * Because the memory area used to transfer hardware error information
 * from BIOS to Linux can be determined only in NMI, IRQ or timer
 * handler, but general ioremap can not be used in atomic context, so
 * the fixmap is used instead.
 *
 * These 2 spinlocks are used to prevent the fixmap entries from being used
 * simultaneously.
 */
static DEFINE_RAW_SPINLOCK(ghes_ioremap_lock_nmi);
static DEFINE_SPINLOCK(ghes_ioremap_lock_irq);

static struct gen_pool *ghes_estatus_pool;
static unsigned long ghes_estatus_pool_size_request;

static struct ghes_estatus_cache *ghes_estatus_caches[GHES_ESTATUS_CACHES_SIZE];
static atomic_t ghes_estatus_cache_alloced;

static int ghes_panic_timeout __read_mostly = 30;

static void __iomem *ghes_ioremap_pfn_nmi(u64 pfn)
{
        phys_addr_t paddr;
        pgprot_t prot;

        paddr = pfn << PAGE_SHIFT;
        prot = arch_apei_get_mem_attribute(paddr);
        __set_fixmap(FIX_APEI_GHES_NMI, paddr, prot);

        return (void __iomem *) fix_to_virt(FIX_APEI_GHES_NMI);
}

static void __iomem *ghes_ioremap_pfn_irq(u64 pfn)
{
        phys_addr_t paddr;
        pgprot_t prot;

        paddr = pfn << PAGE_SHIFT;
        prot = arch_apei_get_mem_attribute(paddr);
        __set_fixmap(FIX_APEI_GHES_IRQ, paddr, prot);

        return (void __iomem *) fix_to_virt(FIX_APEI_GHES_IRQ);
}

static void ghes_iounmap_nmi(void)
{
        clear_fixmap(FIX_APEI_GHES_NMI);
}

static void ghes_iounmap_irq(void)
{
        clear_fixmap(FIX_APEI_GHES_IRQ);
}

static int ghes_estatus_pool_init(void)
{
        ghes_estatus_pool = gen_pool_create(GHES_ESTATUS_POOL_MIN_ALLOC_ORDER, -1);
        if (!ghes_estatus_pool)
                return -ENOMEM;
        return 0;
}

static void ghes_estatus_pool_free_chunk_page(struct gen_pool *pool,
                                              struct gen_pool_chunk *chunk,
                                              void *data)
{
        free_page(chunk->start_addr);
}

static void ghes_estatus_pool_exit(void)
{
        gen_pool_for_each_chunk(ghes_estatus_pool,
                                ghes_estatus_pool_free_chunk_page, NULL);
        gen_pool_destroy(ghes_estatus_pool);
}

static int ghes_estatus_pool_expand(unsigned long len)
{
        unsigned long i, pages, size, addr;
        int ret;

        ghes_estatus_pool_size_request += PAGE_ALIGN(len);
        size = gen_pool_size(ghes_estatus_pool);
        if (size >= ghes_estatus_pool_size_request)
                return 0;
        pages = (ghes_estatus_pool_size_request - size) / PAGE_SIZE;
        for (i = 0; i < pages; i++) {
                addr = __get_free_page(GFP_KERNEL);
                if (!addr)
                        return -ENOMEM;
                ret = gen_pool_add(ghes_estatus_pool, addr, PAGE_SIZE, -1);
                if (ret)
                        return ret;
        }

        return 0;
}

static int map_gen_v2(struct ghes *ghes)
{
        return apei_map_generic_address(&ghes->generic_v2->read_ack_register);
}

static void unmap_gen_v2(struct ghes *ghes)
{
        apei_unmap_generic_address(&ghes->generic_v2->read_ack_register);
}

static struct ghes *ghes_new(struct acpi_hest_generic *generic)
{
        struct ghes *ghes;
        unsigned int error_block_length;
        int rc;

        ghes = kzalloc(sizeof(*ghes), GFP_KERNEL);
        if (!ghes)
                return ERR_PTR(-ENOMEM);

        ghes->generic = generic;
        if (is_hest_type_generic_v2(ghes)) {
                rc = map_gen_v2(ghes);
                if (rc)
                        goto err_free;
        }

        rc = apei_map_generic_address(&generic->error_status_address);
        if (rc)
                goto err_unmap_read_ack_addr;
        error_block_length = generic->error_block_length;
        if (error_block_length > GHES_ESTATUS_MAX_SIZE) {
                pr_warning(FW_WARN GHES_PFX
                           "Error status block length is too long: %u for "
                           "generic hardware error source: %d.\n",
                           error_block_length, generic->header.source_id);
                error_block_length = GHES_ESTATUS_MAX_SIZE;
        }
        ghes->estatus = kmalloc(error_block_length, GFP_KERNEL);
        if (!ghes->estatus) {
                rc = -ENOMEM;
                goto err_unmap_status_addr;
        }

        return ghes;

err_unmap_status_addr:
        apei_unmap_generic_address(&generic->error_status_address);
err_unmap_read_ack_addr:
        if (is_hest_type_generic_v2(ghes))
                unmap_gen_v2(ghes);
err_free:
        kfree(ghes);
        return ERR_PTR(rc);
}

static void ghes_fini(struct ghes *ghes)
{
        kfree(ghes->estatus);
        apei_unmap_generic_address(&ghes->generic->error_status_address);
        if (is_hest_type_generic_v2(ghes))
                unmap_gen_v2(ghes);
}

static inline int ghes_severity(int severity)
{
        switch (severity) {
        case CPER_SEV_INFORMATIONAL:
                return GHES_SEV_NO;
        case CPER_SEV_CORRECTED:
                return GHES_SEV_CORRECTED;
        case CPER_SEV_RECOVERABLE:
                return GHES_SEV_RECOVERABLE;
        case CPER_SEV_FATAL:
                return GHES_SEV_PANIC;
        default:
                /* Unknown, go panic */
                return GHES_SEV_PANIC;
        }
}

static void ghes_copy_tofrom_phys(void *buffer, u64 paddr, u32 len,
                                  int from_phys)
{
        void __iomem *vaddr;
        unsigned long flags = 0;
        int in_nmi = in_nmi();
        u64 offset;
        u32 trunk;

        while (len > 0) {
                offset = paddr - (paddr & PAGE_MASK);
                if (in_nmi) {
                        raw_spin_lock(&ghes_ioremap_lock_nmi);
                        vaddr = ghes_ioremap_pfn_nmi(paddr >> PAGE_SHIFT);
                } else {
                        spin_lock_irqsave(&ghes_ioremap_lock_irq, flags);
                        vaddr = ghes_ioremap_pfn_irq(paddr >> PAGE_SHIFT);
                }
                trunk = PAGE_SIZE - offset;
                trunk = min(trunk, len);
                if (from_phys)
                        memcpy_fromio(buffer, vaddr + offset, trunk);
                else
                        memcpy_toio(vaddr + offset, buffer, trunk);
                len -= trunk;
                paddr += trunk;
                buffer += trunk;
                if (in_nmi) {
                        ghes_iounmap_nmi();
                        raw_spin_unlock(&ghes_ioremap_lock_nmi);
                } else {
                        ghes_iounmap_irq();
                        spin_unlock_irqrestore(&ghes_ioremap_lock_irq, flags);
                }
        }
}

static int ghes_read_estatus(struct ghes *ghes, int silent)
{
        struct acpi_hest_generic *g = ghes->generic;
        u64 buf_paddr;
        u32 len;
        int rc;

        rc = apei_read(&buf_paddr, &g->error_status_address);
        if (rc) {
                if (!silent && printk_ratelimit())
                        pr_warning(FW_WARN GHES_PFX
"Failed to read error status block address for hardware error source: %d.\n",
                                   g->header.source_id);
                return -EIO;
        }
        if (!buf_paddr)
                return -ENOENT;

        ghes_copy_tofrom_phys(ghes->estatus, buf_paddr,
                              sizeof(*ghes->estatus), 1);
        if (!ghes->estatus->block_status)
                return -ENOENT;

        ghes->buffer_paddr = buf_paddr;
        ghes->flags |= GHES_TO_CLEAR;

        rc = -EIO;
        len = cper_estatus_len(ghes->estatus);
        if (len < sizeof(*ghes->estatus))
                goto err_read_block;
        if (len > ghes->generic->error_block_length)
                goto err_read_block;
        if (cper_estatus_check_header(ghes->estatus))
                goto err_read_block;
        ghes_copy_tofrom_phys(ghes->estatus + 1,
                              buf_paddr + sizeof(*ghes->estatus),
                              len - sizeof(*ghes->estatus), 1);
        if (cper_estatus_check(ghes->estatus))
                goto err_read_block;
        rc = 0;

err_read_block:
        if (rc && !silent && printk_ratelimit())
                pr_warning(FW_WARN GHES_PFX
                           "Failed to read error status block!\n");
        return rc;
}

static void ghes_clear_estatus(struct ghes *ghes)
{
        ghes->estatus->block_status = 0;
        if (!(ghes->flags & GHES_TO_CLEAR))
                return;
        ghes_copy_tofrom_phys(ghes->estatus, ghes->buffer_paddr,
                              sizeof(ghes->estatus->block_status), 0);
        ghes->flags &= ~GHES_TO_CLEAR;
}

static void ghes_handle_memory_failure(struct acpi_hest_generic_data *gdata, int sev)
{
#ifdef CONFIG_ACPI_APEI_MEMORY_FAILURE
        unsigned long pfn;
        int flags = -1;
        int sec_sev = ghes_severity(gdata->error_severity);
        struct cper_sec_mem_err *mem_err = acpi_hest_get_payload(gdata);

        if (!(mem_err->validation_bits & CPER_MEM_VALID_PA))
                return;

        pfn = mem_err->physical_addr >> PAGE_SHIFT;
        if (!pfn_valid(pfn)) {
                pr_warn_ratelimited(FW_WARN GHES_PFX
                "Invalid address in generic error data: %#llx\n",
                mem_err->physical_addr);
                return;
        }

        /* iff following two events can be handled properly by now */
        if (sec_sev == GHES_SEV_CORRECTED &&
            (gdata->flags & CPER_SEC_ERROR_THRESHOLD_EXCEEDED))
                flags = MF_SOFT_OFFLINE;
        if (sev == GHES_SEV_RECOVERABLE && sec_sev == GHES_SEV_RECOVERABLE)
                flags = 0;

        if (flags != -1)
                memory_failure_queue(pfn, flags);
#endif
}

/*
 * PCIe AER errors need to be sent to the AER driver for reporting and
 * recovery. The GHES severities map to the following AER severities and
 * require the following handling:
 *
 * GHES_SEV_CORRECTABLE -> AER_CORRECTABLE
 *     These need to be reported by the AER driver but no recovery is
 *     necessary.
 * GHES_SEV_RECOVERABLE -> AER_NONFATAL
 * GHES_SEV_RECOVERABLE && CPER_SEC_RESET -> AER_FATAL
 *     These both need to be reported and recovered from by the AER driver.
 * GHES_SEV_PANIC does not make it to this handling since the kernel must
 *     panic.
 */
static void ghes_handle_aer(struct acpi_hest_generic_data *gdata)
{
#ifdef CONFIG_ACPI_APEI_PCIEAER
        struct cper_sec_pcie *pcie_err = acpi_hest_get_payload(gdata);

        if (pcie_err->validation_bits & CPER_PCIE_VALID_DEVICE_ID &&
            pcie_err->validation_bits & CPER_PCIE_VALID_AER_INFO) {
                unsigned int devfn;
                int aer_severity;

                devfn = PCI_DEVFN(pcie_err->device_id.device,
                                  pcie_err->device_id.function);
                aer_severity = cper_severity_to_aer(gdata->error_severity);

                /*
                 * If firmware reset the component to contain
                 * the error, we must reinitialize it before
                 * use, so treat it as a fatal AER error.
                 */
                if (gdata->flags & CPER_SEC_RESET)
                        aer_severity = AER_FATAL;

                aer_recover_queue(pcie_err->device_id.segment,
                                  pcie_err->device_id.bus,
                                  devfn, aer_severity,
                                  (struct aer_capability_regs *)
                                  pcie_err->aer_info);
        }
#endif
}

static void ghes_do_proc(struct ghes *ghes,
                         const struct acpi_hest_generic_status *estatus)
{
        int sev, sec_sev;
        struct acpi_hest_generic_data *gdata;
        guid_t *sec_type;
        guid_t *fru_id = &NULL_UUID_LE;
        char *fru_text = "";

        sev = ghes_severity(estatus->error_severity);
        apei_estatus_for_each_section(estatus, gdata) {
                sec_type = (guid_t *)gdata->section_type;
                sec_sev = ghes_severity(gdata->error_severity);
                if (gdata->validation_bits & CPER_SEC_VALID_FRU_ID)
                        fru_id = (guid_t *)gdata->fru_id;

                if (gdata->validation_bits & CPER_SEC_VALID_FRU_TEXT)
                        fru_text = gdata->fru_text;

                if (guid_equal(sec_type, &CPER_SEC_PLATFORM_MEM)) {
                        struct cper_sec_mem_err *mem_err = acpi_hest_get_payload(gdata);

                        ghes_edac_report_mem_error(ghes, sev, mem_err);

                        arch_apei_report_mem_error(sev, mem_err);
                        ghes_handle_memory_failure(gdata, sev);
                }
                else if (guid_equal(sec_type, &CPER_SEC_PCIE)) {
                        ghes_handle_aer(gdata);
                }
                else if (guid_equal(sec_type, &CPER_SEC_PROC_ARM)) {
                        struct cper_sec_proc_arm *err = acpi_hest_get_payload(gdata);

                        log_arm_hw_error(err);
                } else {
                        void *err = acpi_hest_get_payload(gdata);

                        log_non_standard_event(sec_type, fru_id, fru_text,
                                               sec_sev, err,
                                               gdata->error_data_length);
                }
        }
}

static void __ghes_print_estatus(const char *pfx,
                                 const struct acpi_hest_generic *generic,
                                 const struct acpi_hest_generic_status *estatus)
{
        static atomic_t seqno;
        unsigned int curr_seqno;
        char pfx_seq[64];

        if (pfx == NULL) {
                if (ghes_severity(estatus->error_severity) <=
                    GHES_SEV_CORRECTED)
                        pfx = KERN_WARNING;
                else
                        pfx = KERN_ERR;
        }
        curr_seqno = atomic_inc_return(&seqno);
        snprintf(pfx_seq, sizeof(pfx_seq), "%s{%u}" HW_ERR, pfx, curr_seqno);
        printk("%s""Hardware error from APEI Generic Hardware Error Source: %d\n",
               pfx_seq, generic->header.source_id);
        cper_estatus_print(pfx_seq, estatus);
}

static int ghes_print_estatus(const char *pfx,
                              const struct acpi_hest_generic *generic,
                              const struct acpi_hest_generic_status *estatus)
{
        /* Not more than 2 messages every 5 seconds */
        static DEFINE_RATELIMIT_STATE(ratelimit_corrected, 5*HZ, 2);
        static DEFINE_RATELIMIT_STATE(ratelimit_uncorrected, 5*HZ, 2);
        struct ratelimit_state *ratelimit;

        if (ghes_severity(estatus->error_severity) <= GHES_SEV_CORRECTED)
                ratelimit = &ratelimit_corrected;
        else
                ratelimit = &ratelimit_uncorrected;
        if (__ratelimit(ratelimit)) {
                __ghes_print_estatus(pfx, generic, estatus);
                return 1;
        }
        return 0;
}

/*
 * GHES error status reporting throttle, to report more kinds of
 * errors, instead of just most frequently occurred errors.
 */
static int ghes_estatus_cached(struct acpi_hest_generic_status *estatus)
{
        u32 len;
        int i, cached = 0;
        unsigned long long now;
        struct ghes_estatus_cache *cache;
        struct acpi_hest_generic_status *cache_estatus;

        len = cper_estatus_len(estatus);
        rcu_read_lock();
        for (i = 0; i < GHES_ESTATUS_CACHES_SIZE; i++) {
                cache = rcu_dereference(ghes_estatus_caches[i]);
                if (cache == NULL)
                        continue;
                if (len != cache->estatus_len)
                        continue;
                cache_estatus = GHES_ESTATUS_FROM_CACHE(cache);
                if (memcmp(estatus, cache_estatus, len))
                        continue;
                atomic_inc(&cache->count);
                now = sched_clock();
                if (now - cache->time_in < GHES_ESTATUS_IN_CACHE_MAX_NSEC)
                        cached = 1;
                break;
        }
        rcu_read_unlock();
        return cached;
}

static struct ghes_estatus_cache *ghes_estatus_cache_alloc(
        struct acpi_hest_generic *generic,
        struct acpi_hest_generic_status *estatus)
{
        int alloced;
        u32 len, cache_len;
        struct ghes_estatus_cache *cache;
        struct acpi_hest_generic_status *cache_estatus;

        alloced = atomic_add_return(1, &ghes_estatus_cache_alloced);
        if (alloced > GHES_ESTATUS_CACHE_ALLOCED_MAX) {
                atomic_dec(&ghes_estatus_cache_alloced);
                return NULL;
        }
        len = cper_estatus_len(estatus);
        cache_len = GHES_ESTATUS_CACHE_LEN(len);
        cache = (void *)gen_pool_alloc(ghes_estatus_pool, cache_len);
        if (!cache) {
                atomic_dec(&ghes_estatus_cache_alloced);
                return NULL;
        }
        cache_estatus = GHES_ESTATUS_FROM_CACHE(cache);
        memcpy(cache_estatus, estatus, len);
        cache->estatus_len = len;
        atomic_set(&cache->count, 0);
        cache->generic = generic;
        cache->time_in = sched_clock();
        return cache;
}

static void ghes_estatus_cache_free(struct ghes_estatus_cache *cache)
{
        u32 len;

        len = cper_estatus_len(GHES_ESTATUS_FROM_CACHE(cache));
        len = GHES_ESTATUS_CACHE_LEN(len);
        gen_pool_free(ghes_estatus_pool, (unsigned long)cache, len);
        atomic_dec(&ghes_estatus_cache_alloced);
}

static void ghes_estatus_cache_rcu_free(struct rcu_head *head)
{
        struct ghes_estatus_cache *cache;

        cache = container_of(head, struct ghes_estatus_cache, rcu);
        ghes_estatus_cache_free(cache);
}

static void ghes_estatus_cache_add(
        struct acpi_hest_generic *generic,
        struct acpi_hest_generic_status *estatus)
{
        int i, slot = -1, count;
        unsigned long long now, duration, period, max_period = 0;
        struct ghes_estatus_cache *cache, *slot_cache = NULL, *new_cache;

        new_cache = ghes_estatus_cache_alloc(generic, estatus);
        if (new_cache == NULL)
                return;
        rcu_read_lock();
        now = sched_clock();
        for (i = 0; i < GHES_ESTATUS_CACHES_SIZE; i++) {
                cache = rcu_dereference(ghes_estatus_caches[i]);
                if (cache == NULL) {
                        slot = i;
                        slot_cache = NULL;
                        break;
                }
                duration = now - cache->time_in;
                if (duration >= GHES_ESTATUS_IN_CACHE_MAX_NSEC) {
                        slot = i;
                        slot_cache = cache;
                        break;
                }
                count = atomic_read(&cache->count);
                period = duration;
                do_div(period, (count + 1));
                if (period > max_period) {
                        max_period = period;
                        slot = i;
                        slot_cache = cache;
                }
        }
        /* new_cache must be put into array after its contents are written */
        smp_wmb();
        if (slot != -1 && cmpxchg(ghes_estatus_caches + slot,
                                  slot_cache, new_cache) == slot_cache) {
                if (slot_cache)
                        call_rcu(&slot_cache->rcu, ghes_estatus_cache_rcu_free);
        } else
                ghes_estatus_cache_free(new_cache);
        rcu_read_unlock();
}

static int ghes_ack_error(struct acpi_hest_generic_v2 *gv2)
{
        int rc;
        u64 val = 0;

        rc = apei_read(&val, &gv2->read_ack_register);
        if (rc)
                return rc;

        val &= gv2->read_ack_preserve << gv2->read_ack_register.bit_offset;
        val |= gv2->read_ack_write    << gv2->read_ack_register.bit_offset;

        return apei_write(val, &gv2->read_ack_register);
}

static void __ghes_panic(struct ghes *ghes)
{
        __ghes_print_estatus(KERN_EMERG, ghes->generic, ghes->estatus);

        /* reboot to log the error! */
        if (!panic_timeout)
                panic_timeout = ghes_panic_timeout;
        panic("Fatal hardware error!");
}

static int ghes_proc(struct ghes *ghes)
{
        int rc;

        rc = ghes_read_estatus(ghes, 0);
        if (rc)
                goto out;

        if (ghes_severity(ghes->estatus->error_severity) >= GHES_SEV_PANIC) {
                __ghes_panic(ghes);
        }

        if (!ghes_estatus_cached(ghes->estatus)) {
                if (ghes_print_estatus(NULL, ghes->generic, ghes->estatus))
                        ghes_estatus_cache_add(ghes->generic, ghes->estatus);
        }
        ghes_do_proc(ghes, ghes->estatus);

out:
        ghes_clear_estatus(ghes);

        if (rc == -ENOENT)
                return rc;

        /*
         * GHESv2 type HEST entries introduce support for error acknowledgment,
         * so only acknowledge the error if this support is present.
         */
        if (is_hest_type_generic_v2(ghes))
                return ghes_ack_error(ghes->generic_v2);

        return rc;
}

static void ghes_add_timer(struct ghes *ghes)
{
        struct acpi_hest_generic *g = ghes->generic;
        unsigned long expire;

        if (!g->notify.poll_interval) {
                pr_warning(FW_WARN GHES_PFX "Poll interval is 0 for generic hardware error source: %d, disabled.\n",
                           g->header.source_id);
                return;
        }
        expire = jiffies + msecs_to_jiffies(g->notify.poll_interval);
        ghes->timer.expires = round_jiffies_relative(expire);
        add_timer(&ghes->timer);
}

static void ghes_poll_func(struct timer_list *t)
{
        struct ghes *ghes = from_timer(ghes, t, timer);

        ghes_proc(ghes);
        if (!(ghes->flags & GHES_EXITING))
                ghes_add_timer(ghes);
}

static irqreturn_t ghes_irq_func(int irq, void *data)
{
        struct ghes *ghes = data;
        int rc;

        rc = ghes_proc(ghes);
        if (rc)
                return IRQ_NONE;

        return IRQ_HANDLED;
}

static int ghes_notify_hed(struct notifier_block *this, unsigned long event,
                           void *data)
{
        struct ghes *ghes;
        int ret = NOTIFY_DONE;

        rcu_read_lock();
        list_for_each_entry_rcu(ghes, &ghes_hed, list) {
                if (!ghes_proc(ghes))
                        ret = NOTIFY_OK;
        }
        rcu_read_unlock();

        return ret;
}

static struct notifier_block ghes_notifier_hed = {
        .notifier_call = ghes_notify_hed,
};

#ifdef CONFIG_ACPI_APEI_SEA
static LIST_HEAD(ghes_sea);

/*
 * Return 0 only if one of the SEA error sources successfully reported an error
 * record sent from the firmware.
 */
int ghes_notify_sea(void)
{
        struct ghes *ghes;
        int ret = -ENOENT;

        rcu_read_lock();
        list_for_each_entry_rcu(ghes, &ghes_sea, list) {
                if (!ghes_proc(ghes))
                        ret = 0;
        }
        rcu_read_unlock();
        return ret;
}

static void ghes_sea_add(struct ghes *ghes)
{
        mutex_lock(&ghes_list_mutex);
        list_add_rcu(&ghes->list, &ghes_sea);
        mutex_unlock(&ghes_list_mutex);
}

static void ghes_sea_remove(struct ghes *ghes)
{
        mutex_lock(&ghes_list_mutex);
        list_del_rcu(&ghes->list);
        mutex_unlock(&ghes_list_mutex);
        synchronize_rcu();
}
#else /* CONFIG_ACPI_APEI_SEA */
static inline void ghes_sea_add(struct ghes *ghes) { }
static inline void ghes_sea_remove(struct ghes *ghes) { }
#endif /* CONFIG_ACPI_APEI_SEA */

#ifdef CONFIG_HAVE_ACPI_APEI_NMI
/*
 * printk is not safe in NMI context.  So in NMI handler, we allocate
 * required memory from lock-less memory allocator
 * (ghes_estatus_pool), save estatus into it, put them into lock-less
 * list (ghes_estatus_llist), then delay printk into IRQ context via
 * irq_work (ghes_proc_irq_work).  ghes_estatus_size_request record
 * required pool size by all NMI error source.
 */
static struct llist_head ghes_estatus_llist;
static struct irq_work ghes_proc_irq_work;

/*
 * NMI may be triggered on any CPU, so ghes_in_nmi is used for
 * having only one concurrent reader.
 */
static atomic_t ghes_in_nmi = ATOMIC_INIT(0);

static LIST_HEAD(ghes_nmi);

static void ghes_proc_in_irq(struct irq_work *irq_work)
{
        struct llist_node *llnode, *next;
        struct ghes_estatus_node *estatus_node;
        struct acpi_hest_generic *generic;
        struct acpi_hest_generic_status *estatus;
        u32 len, node_len;

        llnode = llist_del_all(&ghes_estatus_llist);
        /*
         * Because the time order of estatus in list is reversed,
         * revert it back to proper order.
         */
        llnode = llist_reverse_order(llnode);
        while (llnode) {
                next = llnode->next;
                estatus_node = llist_entry(llnode, struct ghes_estatus_node,
                                           llnode);
                estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
                len = cper_estatus_len(estatus);
                node_len = GHES_ESTATUS_NODE_LEN(len);
                ghes_do_proc(estatus_node->ghes, estatus);
                if (!ghes_estatus_cached(estatus)) {
                        generic = estatus_node->generic;
                        if (ghes_print_estatus(NULL, generic, estatus))
                                ghes_estatus_cache_add(generic, estatus);
                }
                gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node,
                              node_len);
                llnode = next;
        }
}

static void ghes_print_queued_estatus(void)
{
        struct llist_node *llnode;
        struct ghes_estatus_node *estatus_node;
        struct acpi_hest_generic *generic;
        struct acpi_hest_generic_status *estatus;

        llnode = llist_del_all(&ghes_estatus_llist);
        /*
         * Because the time order of estatus in list is reversed,
         * revert it back to proper order.
         */
        llnode = llist_reverse_order(llnode);
        while (llnode) {
                estatus_node = llist_entry(llnode, struct ghes_estatus_node,
                                           llnode);
                estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
                generic = estatus_node->generic;
                ghes_print_estatus(NULL, generic, estatus);
                llnode = llnode->next;
        }
}

/* Save estatus for further processing in IRQ context */
static void __process_error(struct ghes *ghes)
{
#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
        u32 len, node_len;
        struct ghes_estatus_node *estatus_node;
        struct acpi_hest_generic_status *estatus;

        if (ghes_estatus_cached(ghes->estatus))
                return;

        len = cper_estatus_len(ghes->estatus);
        node_len = GHES_ESTATUS_NODE_LEN(len);

        estatus_node = (void *)gen_pool_alloc(ghes_estatus_pool, node_len);
        if (!estatus_node)
                return;

        estatus_node->ghes = ghes;
        estatus_node->generic = ghes->generic;
        estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
        memcpy(estatus, ghes->estatus, len);
        llist_add(&estatus_node->llnode, &ghes_estatus_llist);
#endif
}

static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
{
        struct ghes *ghes;
        int sev, ret = NMI_DONE;

        if (!atomic_add_unless(&ghes_in_nmi, 1, 1))
                return ret;

        list_for_each_entry_rcu(ghes, &ghes_nmi, list) {
                if (ghes_read_estatus(ghes, 1)) {
                        ghes_clear_estatus(ghes);
                        continue;
                } else {
                        ret = NMI_HANDLED;
                }

                sev = ghes_severity(ghes->estatus->error_severity);
                if (sev >= GHES_SEV_PANIC) {
                        oops_begin();
                        ghes_print_queued_estatus();
                        __ghes_panic(ghes);
                }

                if (!(ghes->flags & GHES_TO_CLEAR))
                        continue;

                __process_error(ghes);
                ghes_clear_estatus(ghes);
        }

#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
        if (ret == NMI_HANDLED)
                irq_work_queue(&ghes_proc_irq_work);
#endif
        atomic_dec(&ghes_in_nmi);
        return ret;
}

static unsigned long ghes_esource_prealloc_size(
        const struct acpi_hest_generic *generic)
{
        unsigned long block_length, prealloc_records, prealloc_size;

        block_length = min_t(unsigned long, generic->error_block_length,
                             GHES_ESTATUS_MAX_SIZE);
        prealloc_records = max_t(unsigned long,
                                 generic->records_to_preallocate, 1);
        prealloc_size = min_t(unsigned long, block_length * prealloc_records,
                              GHES_ESOURCE_PREALLOC_MAX_SIZE);

        return prealloc_size;
}

static void ghes_estatus_pool_shrink(unsigned long len)
{
        ghes_estatus_pool_size_request -= PAGE_ALIGN(len);
}

static void ghes_nmi_add(struct ghes *ghes)
{
        unsigned long len;

        len = ghes_esource_prealloc_size(ghes->generic);
        ghes_estatus_pool_expand(len);
        mutex_lock(&ghes_list_mutex);
        if (list_empty(&ghes_nmi))
                register_nmi_handler(NMI_LOCAL, ghes_notify_nmi, 0, "ghes");
        list_add_rcu(&ghes->list, &ghes_nmi);
        mutex_unlock(&ghes_list_mutex);

}

static void ghes_nmi_remove(struct ghes *ghes)
{
        unsigned long len;

        mutex_lock(&ghes_list_mutex);
        list_del_rcu(&ghes->list);
        if (list_empty(&ghes_nmi))
                unregister_nmi_handler(NMI_LOCAL, "ghes");
        mutex_unlock(&ghes_list_mutex);
        /*
         * To synchronize with NMI handler, ghes can only be
         * freed after NMI handler finishes.
         */
        synchronize_rcu();
        len = ghes_esource_prealloc_size(ghes->generic);
        ghes_estatus_pool_shrink(len);
}

static void ghes_nmi_init_cxt(void)
{
        init_irq_work(&ghes_proc_irq_work, ghes_proc_in_irq);
}
#else /* CONFIG_HAVE_ACPI_APEI_NMI */
static inline void ghes_nmi_add(struct ghes *ghes) { }
static inline void ghes_nmi_remove(struct ghes *ghes) { }
static inline void ghes_nmi_init_cxt(void) { }
#endif /* CONFIG_HAVE_ACPI_APEI_NMI */

static int ghes_probe(struct platform_device *ghes_dev)
{
        struct acpi_hest_generic *generic;
        struct ghes *ghes = NULL;

        int rc = -EINVAL;

        generic = *(struct acpi_hest_generic **)ghes_dev->dev.platform_data;
        if (!generic->enabled)
                return -ENODEV;

        switch (generic->notify.type) {
        case ACPI_HEST_NOTIFY_POLLED:
        case ACPI_HEST_NOTIFY_EXTERNAL:
        case ACPI_HEST_NOTIFY_SCI:
        case ACPI_HEST_NOTIFY_GSIV:
        case ACPI_HEST_NOTIFY_GPIO:
                break;

        case ACPI_HEST_NOTIFY_SEA:
                if (!IS_ENABLED(CONFIG_ACPI_APEI_SEA)) {
                        pr_warn(GHES_PFX "Generic hardware error source: %d notified via SEA is not supported\n",
                                generic->header.source_id);
                        rc = -ENOTSUPP;
                        goto err;
                }
                break;
        case ACPI_HEST_NOTIFY_NMI:
                if (!IS_ENABLED(CONFIG_HAVE_ACPI_APEI_NMI)) {
                        pr_warn(GHES_PFX "Generic hardware error source: %d notified via NMI interrupt is not supported!\n",
                                generic->header.source_id);
                        goto err;
                }
                break;
        case ACPI_HEST_NOTIFY_LOCAL:
                pr_warning(GHES_PFX "Generic hardware error source: %d notified via local interrupt is not supported!\n",
                           generic->header.source_id);
                goto err;
        default:
                pr_warning(FW_WARN GHES_PFX "Unknown notification type: %u for generic hardware error source: %d\n",
                           generic->notify.type, generic->header.source_id);
                goto err;
        }

        rc = -EIO;
        if (generic->error_block_length <
            sizeof(struct acpi_hest_generic_status)) {
                pr_warning(FW_BUG GHES_PFX "Invalid error block length: %u for generic hardware error source: %d\n",
                           generic->error_block_length,
                           generic->header.source_id);
                goto err;
        }
        ghes = ghes_new(generic);
        if (IS_ERR(ghes)) {
                rc = PTR_ERR(ghes);
                ghes = NULL;
                goto err;
        }

        rc = ghes_edac_register(ghes, &ghes_dev->dev);
        if (rc < 0)
                goto err;

        switch (generic->notify.type) {
        case ACPI_HEST_NOTIFY_POLLED:
                timer_setup(&ghes->timer, ghes_poll_func, TIMER_DEFERRABLE);
                ghes_add_timer(ghes);
                break;
        case ACPI_HEST_NOTIFY_EXTERNAL:
                /* External interrupt vector is GSI */
                rc = acpi_gsi_to_irq(generic->notify.vector, &ghes->irq);
                if (rc) {
                        pr_err(GHES_PFX "Failed to map GSI to IRQ for generic hardware error source: %d\n",
                               generic->header.source_id);
                        goto err_edac_unreg;
                }
                rc = request_irq(ghes->irq, ghes_irq_func, IRQF_SHARED,
                                 "GHES IRQ", ghes);
                if (rc) {
                        pr_err(GHES_PFX "Failed to register IRQ for generic hardware error source: %d\n",
                               generic->header.source_id);
                        goto err_edac_unreg;
                }
                break;

        case ACPI_HEST_NOTIFY_SCI:
        case ACPI_HEST_NOTIFY_GSIV:
        case ACPI_HEST_NOTIFY_GPIO:
                mutex_lock(&ghes_list_mutex);
                if (list_empty(&ghes_hed))
                        register_acpi_hed_notifier(&ghes_notifier_hed);
                list_add_rcu(&ghes->list, &ghes_hed);
                mutex_unlock(&ghes_list_mutex);
                break;

        case ACPI_HEST_NOTIFY_SEA:
                ghes_sea_add(ghes);
                break;
        case ACPI_HEST_NOTIFY_NMI:
                ghes_nmi_add(ghes);
                break;
        default:
                BUG();
        }
        platform_set_drvdata(ghes_dev, ghes);

        /* Handle any pending errors right away */
        ghes_proc(ghes);

        return 0;
err_edac_unreg:
        ghes_edac_unregister(ghes);
err:
        if (ghes) {
                ghes_fini(ghes);
                kfree(ghes);
        }
        return rc;
}

static int ghes_remove(struct platform_device *ghes_dev)
{
        struct ghes *ghes;
        struct acpi_hest_generic *generic;

        ghes = platform_get_drvdata(ghes_dev);
        generic = ghes->generic;

        ghes->flags |= GHES_EXITING;
        switch (generic->notify.type) {
        case ACPI_HEST_NOTIFY_POLLED:
                del_timer_sync(&ghes->timer);
                break;
        case ACPI_HEST_NOTIFY_EXTERNAL:
                free_irq(ghes->irq, ghes);
                break;

        case ACPI_HEST_NOTIFY_SCI:
        case ACPI_HEST_NOTIFY_GSIV:
        case ACPI_HEST_NOTIFY_GPIO:
                mutex_lock(&ghes_list_mutex);
                list_del_rcu(&ghes->list);
                if (list_empty(&ghes_hed))
                        unregister_acpi_hed_notifier(&ghes_notifier_hed);
                mutex_unlock(&ghes_list_mutex);
                synchronize_rcu();
                break;

        case ACPI_HEST_NOTIFY_SEA:
                ghes_sea_remove(ghes);
                break;
        case ACPI_HEST_NOTIFY_NMI:
                ghes_nmi_remove(ghes);
                break;
        default:
                BUG();
                break;
        }

        ghes_fini(ghes);

        ghes_edac_unregister(ghes);

        kfree(ghes);

        platform_set_drvdata(ghes_dev, NULL);

        return 0;
}

static struct platform_driver ghes_platform_driver = {
        .driver         = {
                .name   = "GHES",
        },
        .probe          = ghes_probe,
        .remove         = ghes_remove,
};

static int __init ghes_init(void)
{
        int rc;

        if (acpi_disabled)
                return -ENODEV;

        switch (hest_disable) {
        case HEST_NOT_FOUND:
                return -ENODEV;
        case HEST_DISABLED:
                pr_info(GHES_PFX "HEST is not enabled!\n");
                return -EINVAL;
        default:
                break;
        }

        if (ghes_disable) {
                pr_info(GHES_PFX "GHES is not enabled!\n");
                return -EINVAL;
        }

        ghes_nmi_init_cxt();

        rc = ghes_estatus_pool_init();
        if (rc)
                goto err;

        rc = ghes_estatus_pool_expand(GHES_ESTATUS_CACHE_AVG_SIZE *
                                      GHES_ESTATUS_CACHE_ALLOCED_MAX);
        if (rc)
                goto err_pool_exit;

        rc = platform_driver_register(&ghes_platform_driver);
        if (rc)
                goto err_pool_exit;

        rc = apei_osc_setup();
        if (rc == 0 && osc_sb_apei_support_acked)
                pr_info(GHES_PFX "APEI firmware first mode is enabled by APEI bit and WHEA _OSC.\n");
        else if (rc == 0 && !osc_sb_apei_support_acked)
                pr_info(GHES_PFX "APEI firmware first mode is enabled by WHEA _OSC.\n");
        else if (rc && osc_sb_apei_support_acked)
                pr_info(GHES_PFX "APEI firmware first mode is enabled by APEI bit.\n");
        else
                pr_info(GHES_PFX "Failed to enable APEI firmware first mode.\n");

        return 0;
err_pool_exit:
        ghes_estatus_pool_exit();
err:
        return rc;
}
device_initcall(ghes_init);