Merge remote-tracking branch 'vfio/next'

[deliverable/linux.git] / drivers / acpi / tables.c

/*
 *  acpi_tables.c - ACPI Boot-Time Table Parsing
 *
 *  Copyright (C) 2001 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  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.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 */

/* Uncomment next line to get verbose printout */
/* #define DEBUG */
#define pr_fmt(fmt) "ACPI: " fmt

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/irq.h>
#include <linux/errno.h>
#include <linux/acpi.h>
#include <linux/bootmem.h>
#include <linux/earlycpio.h>
#include <linux/memblock.h>
#include <linux/initrd.h>
#include <linux/acpi.h>
#include "internal.h"

#ifdef CONFIG_ACPI_CUSTOM_DSDT
#include CONFIG_ACPI_CUSTOM_DSDT_FILE
#endif

#define ACPI_MAX_TABLES         128

static char *mps_inti_flags_polarity[] = { "dfl", "high", "res", "low" };
static char *mps_inti_flags_trigger[] = { "dfl", "edge", "res", "level" };

static struct acpi_table_desc initial_tables[ACPI_MAX_TABLES] __initdata;

static int acpi_apic_instance __initdata;

/*
 * Disable table checksum verification for the early stage due to the size
 * limitation of the current x86 early mapping implementation.
 */
static bool acpi_verify_table_checksum __initdata = false;

void acpi_table_print_madt_entry(struct acpi_subtable_header *header)
{
        if (!header)
                return;

        switch (header->type) {

        case ACPI_MADT_TYPE_LOCAL_APIC:
                {
                        struct acpi_madt_local_apic *p =
                            (struct acpi_madt_local_apic *)header;
                        pr_debug("LAPIC (acpi_id[0x%02x] lapic_id[0x%02x] %s)\n",
                                 p->processor_id, p->id,
                                 (p->lapic_flags & ACPI_MADT_ENABLED) ? "enabled" : "disabled");
                }
                break;

        case ACPI_MADT_TYPE_LOCAL_X2APIC:
                {
                        struct acpi_madt_local_x2apic *p =
                            (struct acpi_madt_local_x2apic *)header;
                        pr_debug("X2APIC (apic_id[0x%02x] uid[0x%02x] %s)\n",
                                 p->local_apic_id, p->uid,
                                 (p->lapic_flags & ACPI_MADT_ENABLED) ? "enabled" : "disabled");
                }
                break;

        case ACPI_MADT_TYPE_IO_APIC:
                {
                        struct acpi_madt_io_apic *p =
                            (struct acpi_madt_io_apic *)header;
                        pr_debug("IOAPIC (id[0x%02x] address[0x%08x] gsi_base[%d])\n",
                                 p->id, p->address, p->global_irq_base);
                }
                break;

        case ACPI_MADT_TYPE_INTERRUPT_OVERRIDE:
                {
                        struct acpi_madt_interrupt_override *p =
                            (struct acpi_madt_interrupt_override *)header;
                        pr_info("INT_SRC_OVR (bus %d bus_irq %d global_irq %d %s %s)\n",
                                p->bus, p->source_irq, p->global_irq,
                                mps_inti_flags_polarity[p->inti_flags & ACPI_MADT_POLARITY_MASK],
                                mps_inti_flags_trigger[(p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2]);
                        if (p->inti_flags  &
                            ~(ACPI_MADT_POLARITY_MASK | ACPI_MADT_TRIGGER_MASK))
                                pr_info("INT_SRC_OVR unexpected reserved flags: 0x%x\n",
                                        p->inti_flags  &
                                        ~(ACPI_MADT_POLARITY_MASK | ACPI_MADT_TRIGGER_MASK));
                }
                break;

        case ACPI_MADT_TYPE_NMI_SOURCE:
                {
                        struct acpi_madt_nmi_source *p =
                            (struct acpi_madt_nmi_source *)header;
                        pr_info("NMI_SRC (%s %s global_irq %d)\n",
                                mps_inti_flags_polarity[p->inti_flags & ACPI_MADT_POLARITY_MASK],
                                mps_inti_flags_trigger[(p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2],
                                p->global_irq);
                }
                break;

        case ACPI_MADT_TYPE_LOCAL_APIC_NMI:
                {
                        struct acpi_madt_local_apic_nmi *p =
                            (struct acpi_madt_local_apic_nmi *)header;
                        pr_info("LAPIC_NMI (acpi_id[0x%02x] %s %s lint[0x%x])\n",
                                p->processor_id,
                                mps_inti_flags_polarity[p->inti_flags & ACPI_MADT_POLARITY_MASK ],
                                mps_inti_flags_trigger[(p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2],
                                p->lint);
                }
                break;

        case ACPI_MADT_TYPE_LOCAL_X2APIC_NMI:
                {
                        u16 polarity, trigger;
                        struct acpi_madt_local_x2apic_nmi *p =
                            (struct acpi_madt_local_x2apic_nmi *)header;

                        polarity = p->inti_flags & ACPI_MADT_POLARITY_MASK;
                        trigger = (p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2;

                        pr_info("X2APIC_NMI (uid[0x%02x] %s %s lint[0x%x])\n",
                                p->uid,
                                mps_inti_flags_polarity[polarity],
                                mps_inti_flags_trigger[trigger],
                                p->lint);
                }
                break;

        case ACPI_MADT_TYPE_LOCAL_APIC_OVERRIDE:
                {
                        struct acpi_madt_local_apic_override *p =
                            (struct acpi_madt_local_apic_override *)header;
                        pr_info("LAPIC_ADDR_OVR (address[%p])\n",
                                (void *)(unsigned long)p->address);
                }
                break;

        case ACPI_MADT_TYPE_IO_SAPIC:
                {
                        struct acpi_madt_io_sapic *p =
                            (struct acpi_madt_io_sapic *)header;
                        pr_debug("IOSAPIC (id[0x%x] address[%p] gsi_base[%d])\n",
                                 p->id, (void *)(unsigned long)p->address,
                                 p->global_irq_base);
                }
                break;

        case ACPI_MADT_TYPE_LOCAL_SAPIC:
                {
                        struct acpi_madt_local_sapic *p =
                            (struct acpi_madt_local_sapic *)header;
                        pr_debug("LSAPIC (acpi_id[0x%02x] lsapic_id[0x%02x] lsapic_eid[0x%02x] %s)\n",
                                 p->processor_id, p->id, p->eid,
                                 (p->lapic_flags & ACPI_MADT_ENABLED) ? "enabled" : "disabled");
                }
                break;

        case ACPI_MADT_TYPE_INTERRUPT_SOURCE:
                {
                        struct acpi_madt_interrupt_source *p =
                            (struct acpi_madt_interrupt_source *)header;
                        pr_info("PLAT_INT_SRC (%s %s type[0x%x] id[0x%04x] eid[0x%x] iosapic_vector[0x%x] global_irq[0x%x]\n",
                                mps_inti_flags_polarity[p->inti_flags & ACPI_MADT_POLARITY_MASK],
                                mps_inti_flags_trigger[(p->inti_flags & ACPI_MADT_TRIGGER_MASK) >> 2],
                                p->type, p->id, p->eid, p->io_sapic_vector,
                                p->global_irq);
                }
                break;

        case ACPI_MADT_TYPE_GENERIC_INTERRUPT:
                {
                        struct acpi_madt_generic_interrupt *p =
                                (struct acpi_madt_generic_interrupt *)header;
                        pr_debug("GICC (acpi_id[0x%04x] address[%llx] MPIDR[0x%llx] %s)\n",
                                 p->uid, p->base_address,
                                 p->arm_mpidr,
                                 (p->flags & ACPI_MADT_ENABLED) ? "enabled" : "disabled");

                }
                break;

        case ACPI_MADT_TYPE_GENERIC_DISTRIBUTOR:
                {
                        struct acpi_madt_generic_distributor *p =
                                (struct acpi_madt_generic_distributor *)header;
                        pr_debug("GIC Distributor (gic_id[0x%04x] address[%llx] gsi_base[%d])\n",
                                 p->gic_id, p->base_address,
                                 p->global_irq_base);
                }
                break;

        default:
                pr_warn("Found unsupported MADT entry (type = 0x%x)\n",
                        header->type);
                break;
        }
}

/**
 * acpi_parse_entries_array - for each proc_num find a suitable subtable
 *
 * @id: table id (for debugging purposes)
 * @table_size: single entry size
 * @table_header: where does the table start?
 * @proc: array of acpi_subtable_proc struct containing entry id
 *        and associated handler with it
 * @proc_num: how big proc is?
 * @max_entries: how many entries can we process?
 *
 * For each proc_num find a subtable with proc->id and run proc->handler
 * on it. Assumption is that there's only single handler for particular
 * entry id.
 *
 * On success returns sum of all matching entries for all proc handlers.
 * Otherwise, -ENODEV or -EINVAL is returned.
 */
static int __init
acpi_parse_entries_array(char *id, unsigned long table_size,
                struct acpi_table_header *table_header,
                struct acpi_subtable_proc *proc, int proc_num,
                unsigned int max_entries)
{
        struct acpi_subtable_header *entry;
        unsigned long table_end;
        int count = 0;
        int errs = 0;
        int i;

        if (acpi_disabled)
                return -ENODEV;

        if (!id)
                return -EINVAL;

        if (!table_size)
                return -EINVAL;

        if (!table_header) {
                pr_warn("%4.4s not present\n", id);
                return -ENODEV;
        }

        table_end = (unsigned long)table_header + table_header->length;

        /* Parse all entries looking for a match. */

        entry = (struct acpi_subtable_header *)
            ((unsigned long)table_header + table_size);

        while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) <
               table_end) {
                if (max_entries && count >= max_entries)
                        break;

                for (i = 0; i < proc_num; i++) {
                        if (entry->type != proc[i].id)
                                continue;
                        if (!proc[i].handler ||
                             (!errs && proc[i].handler(entry, table_end))) {
                                errs++;
                                continue;
                        }

                        proc[i].count++;
                        break;
                }
                if (i != proc_num)
                        count++;

                /*
                 * If entry->length is 0, break from this loop to avoid
                 * infinite loop.
                 */
                if (entry->length == 0) {
                        pr_err("[%4.4s:0x%02x] Invalid zero length\n", id, proc->id);
                        return -EINVAL;
                }

                entry = (struct acpi_subtable_header *)
                    ((unsigned long)entry + entry->length);
        }

        if (max_entries && count > max_entries) {
                pr_warn("[%4.4s:0x%02x] found the maximum %i entries\n",
                        id, proc->id, count);
        }

        return errs ? -EINVAL : count;
}

int __init
acpi_parse_entries(char *id,
                        unsigned long table_size,
                        acpi_tbl_entry_handler handler,
                        struct acpi_table_header *table_header,
                        int entry_id, unsigned int max_entries)
{
        struct acpi_subtable_proc proc = {
                .id             = entry_id,
                .handler        = handler,
        };

        return acpi_parse_entries_array(id, table_size, table_header,
                        &proc, 1, max_entries);
}

int __init
acpi_table_parse_entries_array(char *id,
                         unsigned long table_size,
                         struct acpi_subtable_proc *proc, int proc_num,
                         unsigned int max_entries)
{
        struct acpi_table_header *table_header = NULL;
        acpi_size tbl_size;
        int count;
        u32 instance = 0;

        if (acpi_disabled)
                return -ENODEV;

        if (!id)
                return -EINVAL;

        if (!strncmp(id, ACPI_SIG_MADT, 4))
                instance = acpi_apic_instance;

        acpi_get_table_with_size(id, instance, &table_header, &tbl_size);
        if (!table_header) {
                pr_warn("%4.4s not present\n", id);
                return -ENODEV;
        }

        count = acpi_parse_entries_array(id, table_size, table_header,
                        proc, proc_num, max_entries);

        early_acpi_os_unmap_memory((char *)table_header, tbl_size);
        return count;
}

int __init
acpi_table_parse_entries(char *id,
                        unsigned long table_size,
                        int entry_id,
                        acpi_tbl_entry_handler handler,
                        unsigned int max_entries)
{
        struct acpi_subtable_proc proc = {
                .id             = entry_id,
                .handler        = handler,
        };

        return acpi_table_parse_entries_array(id, table_size, &proc, 1,
                                                max_entries);
}

int __init
acpi_table_parse_madt(enum acpi_madt_type id,
                      acpi_tbl_entry_handler handler, unsigned int max_entries)
{
        return acpi_table_parse_entries(ACPI_SIG_MADT,
                                            sizeof(struct acpi_table_madt), id,
                                            handler, max_entries);
}

/**
 * acpi_table_parse - find table with @id, run @handler on it
 * @id: table id to find
 * @handler: handler to run
 *
 * Scan the ACPI System Descriptor Table (STD) for a table matching @id,
 * run @handler on it.
 *
 * Return 0 if table found, -errno if not.
 */
int __init acpi_table_parse(char *id, acpi_tbl_table_handler handler)
{
        struct acpi_table_header *table = NULL;
        acpi_size tbl_size;

        if (acpi_disabled)
                return -ENODEV;

        if (!id || !handler)
                return -EINVAL;

        if (strncmp(id, ACPI_SIG_MADT, 4) == 0)
                acpi_get_table_with_size(id, acpi_apic_instance, &table, &tbl_size);
        else
                acpi_get_table_with_size(id, 0, &table, &tbl_size);

        if (table) {
                handler(table);
                early_acpi_os_unmap_memory(table, tbl_size);
                return 0;
        } else
                return -ENODEV;
}

/* 
 * The BIOS is supposed to supply a single APIC/MADT,
 * but some report two.  Provide a knob to use either.
 * (don't you wish instance 0 and 1 were not the same?)
 */
static void __init check_multiple_madt(void)
{
        struct acpi_table_header *table = NULL;
        acpi_size tbl_size;

        acpi_get_table_with_size(ACPI_SIG_MADT, 2, &table, &tbl_size);
        if (table) {
                pr_warn("BIOS bug: multiple APIC/MADT found, using %d\n",
                        acpi_apic_instance);
                pr_warn("If \"acpi_apic_instance=%d\" works better, "
                        "notify linux-acpi@vger.kernel.org\n",
                        acpi_apic_instance ? 0 : 2);
                early_acpi_os_unmap_memory(table, tbl_size);

        } else
                acpi_apic_instance = 0;

        return;
}

static void acpi_table_taint(struct acpi_table_header *table)
{
        pr_warn("Override [%4.4s-%8.8s], this is unsafe: tainting kernel\n",
                table->signature, table->oem_table_id);
        add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
}

#ifdef CONFIG_ACPI_TABLE_UPGRADE
static u64 acpi_tables_addr;
static int all_tables_size;

/* Copied from acpica/tbutils.c:acpi_tb_checksum() */
static u8 __init acpi_table_checksum(u8 *buffer, u32 length)
{
        u8 sum = 0;
        u8 *end = buffer + length;

        while (buffer < end)
                sum = (u8) (sum + *(buffer++));
        return sum;
}

/* All but ACPI_SIG_RSDP and ACPI_SIG_FACS: */
static const char * const table_sigs[] = {
        ACPI_SIG_BERT, ACPI_SIG_CPEP, ACPI_SIG_ECDT, ACPI_SIG_EINJ,
        ACPI_SIG_ERST, ACPI_SIG_HEST, ACPI_SIG_MADT, ACPI_SIG_MSCT,
        ACPI_SIG_SBST, ACPI_SIG_SLIT, ACPI_SIG_SRAT, ACPI_SIG_ASF,
        ACPI_SIG_BOOT, ACPI_SIG_DBGP, ACPI_SIG_DMAR, ACPI_SIG_HPET,
        ACPI_SIG_IBFT, ACPI_SIG_IVRS, ACPI_SIG_MCFG, ACPI_SIG_MCHI,
        ACPI_SIG_SLIC, ACPI_SIG_SPCR, ACPI_SIG_SPMI, ACPI_SIG_TCPA,
        ACPI_SIG_UEFI, ACPI_SIG_WAET, ACPI_SIG_WDAT, ACPI_SIG_WDDT,
        ACPI_SIG_WDRT, ACPI_SIG_DSDT, ACPI_SIG_FADT, ACPI_SIG_PSDT,
        ACPI_SIG_RSDT, ACPI_SIG_XSDT, ACPI_SIG_SSDT, NULL };

#define ACPI_HEADER_SIZE sizeof(struct acpi_table_header)

#define NR_ACPI_INITRD_TABLES 64
static struct cpio_data __initdata acpi_initrd_files[NR_ACPI_INITRD_TABLES];
static DECLARE_BITMAP(acpi_initrd_installed, NR_ACPI_INITRD_TABLES);

#define MAP_CHUNK_SIZE   (NR_FIX_BTMAPS << PAGE_SHIFT)

void __init acpi_table_upgrade(void)
{
        void *data = (void *)initrd_start;
        size_t size = initrd_end - initrd_start;
        int sig, no, table_nr = 0, total_offset = 0;
        long offset = 0;
        struct acpi_table_header *table;
        char cpio_path[32] = "kernel/firmware/acpi/";
        struct cpio_data file;

        if (data == NULL || size == 0)
                return;

        for (no = 0; no < NR_ACPI_INITRD_TABLES; no++) {
                file = find_cpio_data(cpio_path, data, size, &offset);
                if (!file.data)
                        break;

                data += offset;
                size -= offset;

                if (file.size < sizeof(struct acpi_table_header)) {
                        pr_err("ACPI OVERRIDE: Table smaller than ACPI header [%s%s]\n",
                                cpio_path, file.name);
                        continue;
                }

                table = file.data;

                for (sig = 0; table_sigs[sig]; sig++)
                        if (!memcmp(table->signature, table_sigs[sig], 4))
                                break;

                if (!table_sigs[sig]) {
                        pr_err("ACPI OVERRIDE: Unknown signature [%s%s]\n",
                                cpio_path, file.name);
                        continue;
                }
                if (file.size != table->length) {
                        pr_err("ACPI OVERRIDE: File length does not match table length [%s%s]\n",
                                cpio_path, file.name);
                        continue;
                }
                if (acpi_table_checksum(file.data, table->length)) {
                        pr_err("ACPI OVERRIDE: Bad table checksum [%s%s]\n",
                                cpio_path, file.name);
                        continue;
                }

                pr_info("%4.4s ACPI table found in initrd [%s%s][0x%x]\n",
                        table->signature, cpio_path, file.name, table->length);

                all_tables_size += table->length;
                acpi_initrd_files[table_nr].data = file.data;
                acpi_initrd_files[table_nr].size = file.size;
                table_nr++;
        }
        if (table_nr == 0)
                return;

        acpi_tables_addr =
                memblock_find_in_range(0, ACPI_TABLE_UPGRADE_MAX_PHYS,
                                       all_tables_size, PAGE_SIZE);
        if (!acpi_tables_addr) {
                WARN_ON(1);
                return;
        }
        /*
         * Only calling e820_add_reserve does not work and the
         * tables are invalid (memory got used) later.
         * memblock_reserve works as expected and the tables won't get modified.
         * But it's not enough on X86 because ioremap will
         * complain later (used by acpi_os_map_memory) that the pages
         * that should get mapped are not marked "reserved".
         * Both memblock_reserve and e820_add_region (via arch_reserve_mem_area)
         * works fine.
         */
        memblock_reserve(acpi_tables_addr, all_tables_size);
        arch_reserve_mem_area(acpi_tables_addr, all_tables_size);

        /*
         * early_ioremap only can remap 256k one time. If we map all
         * tables one time, we will hit the limit. Need to map chunks
         * one by one during copying the same as that in relocate_initrd().
         */
        for (no = 0; no < table_nr; no++) {
                unsigned char *src_p = acpi_initrd_files[no].data;
                phys_addr_t size = acpi_initrd_files[no].size;
                phys_addr_t dest_addr = acpi_tables_addr + total_offset;
                phys_addr_t slop, clen;
                char *dest_p;

                total_offset += size;

                while (size) {
                        slop = dest_addr & ~PAGE_MASK;
                        clen = size;
                        if (clen > MAP_CHUNK_SIZE - slop)
                                clen = MAP_CHUNK_SIZE - slop;
                        dest_p = early_memremap(dest_addr & PAGE_MASK,
                                                clen + slop);
                        memcpy(dest_p + slop, src_p, clen);
                        early_memunmap(dest_p, clen + slop);
                        src_p += clen;
                        dest_addr += clen;
                        size -= clen;
                }
        }
}

static acpi_status
acpi_table_initrd_override(struct acpi_table_header *existing_table,
                           acpi_physical_address *address, u32 *length)
{
        int table_offset = 0;
        int table_index = 0;
        struct acpi_table_header *table;
        u32 table_length;

        *length = 0;
        *address = 0;
        if (!acpi_tables_addr)
                return AE_OK;

        while (table_offset + ACPI_HEADER_SIZE <= all_tables_size) {
                table = acpi_os_map_memory(acpi_tables_addr + table_offset,
                                           ACPI_HEADER_SIZE);
                if (table_offset + table->length > all_tables_size) {
                        acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
                        WARN_ON(1);
                        return AE_OK;
                }

                table_length = table->length;

                /* Only override tables matched */
                if (memcmp(existing_table->signature, table->signature, 4) ||
                    memcmp(table->oem_id, existing_table->oem_id,
                           ACPI_OEM_ID_SIZE) ||
                    memcmp(table->oem_table_id, existing_table->oem_table_id,
                           ACPI_OEM_TABLE_ID_SIZE)) {
                        acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
                        goto next_table;
                }
                /*
                 * Mark the table to avoid being used in
                 * acpi_table_initrd_scan() and check the revision.
                 */
                if (test_and_set_bit(table_index, acpi_initrd_installed) ||
                    existing_table->oem_revision >= table->oem_revision) {
                        acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
                        goto next_table;
                }

                *length = table_length;
                *address = acpi_tables_addr + table_offset;
                pr_info("Table Upgrade: override [%4.4s-%6.6s-%8.8s]\n",
                        table->signature, table->oem_id,
                        table->oem_table_id);
                acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
                break;

next_table:
                table_offset += table_length;
                table_index++;
        }
        return AE_OK;
}

static void __init acpi_table_initrd_scan(void)
{
        int table_offset = 0;
        int table_index = 0;
        u32 table_length;
        struct acpi_table_header *table;

        if (!acpi_tables_addr)
                return;

        while (table_offset + ACPI_HEADER_SIZE <= all_tables_size) {
                table = acpi_os_map_memory(acpi_tables_addr + table_offset,
                                           ACPI_HEADER_SIZE);
                if (table_offset + table->length > all_tables_size) {
                        acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
                        WARN_ON(1);
                        return;
                }

                table_length = table->length;

                /* Skip RSDT/XSDT which should only be used for override */
                if (ACPI_COMPARE_NAME(table->signature, ACPI_SIG_RSDT) ||
                    ACPI_COMPARE_NAME(table->signature, ACPI_SIG_XSDT)) {
                        acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
                        goto next_table;
                }
                /*
                 * Mark the table to avoid being used in
                 * acpi_table_initrd_override(). Though this is not possible
                 * because override is disabled in acpi_install_table().
                 */
                if (test_and_set_bit(table_index, acpi_initrd_installed)) {
                        acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
                        goto next_table;
                }

                pr_info("Table Upgrade: install [%4.4s-%6.6s-%8.8s]\n",
                        table->signature, table->oem_id,
                        table->oem_table_id);
                acpi_os_unmap_memory(table, ACPI_HEADER_SIZE);
                acpi_install_table(acpi_tables_addr + table_offset, TRUE);
next_table:
                table_offset += table_length;
                table_index++;
        }
}
#else
static acpi_status
acpi_table_initrd_override(struct acpi_table_header *existing_table,
                           acpi_physical_address *address,
                           u32 *table_length)
{
        *table_length = 0;
        *address = 0;
        return AE_OK;
}

static void __init acpi_table_initrd_scan(void)
{
}
#endif /* CONFIG_ACPI_TABLE_UPGRADE */

acpi_status
acpi_os_physical_table_override(struct acpi_table_header *existing_table,
                                acpi_physical_address *address,
                                u32 *table_length)
{
        return acpi_table_initrd_override(existing_table, address,
                                          table_length);
}

acpi_status
acpi_os_table_override(struct acpi_table_header *existing_table,
                       struct acpi_table_header **new_table)
{
        if (!existing_table || !new_table)
                return AE_BAD_PARAMETER;

        *new_table = NULL;

#ifdef CONFIG_ACPI_CUSTOM_DSDT
        if (strncmp(existing_table->signature, "DSDT", 4) == 0)
                *new_table = (struct acpi_table_header *)AmlCode;
#endif
        if (*new_table != NULL)
                acpi_table_taint(existing_table);
        return AE_OK;
}

/*
 * acpi_table_init()
 *
 * find RSDP, find and checksum SDT/XSDT.
 * checksum all tables, print SDT/XSDT
 *
 * result: sdt_entry[] is initialized
 */

int __init acpi_table_init(void)
{
        acpi_status status;

        if (acpi_verify_table_checksum) {
                pr_info("Early table checksum verification enabled\n");
                acpi_gbl_verify_table_checksum = TRUE;
        } else {
                pr_info("Early table checksum verification disabled\n");
                acpi_gbl_verify_table_checksum = FALSE;
        }

        status = acpi_initialize_tables(initial_tables, ACPI_MAX_TABLES, 0);
        if (ACPI_FAILURE(status))
                return -EINVAL;
        acpi_table_initrd_scan();

        check_multiple_madt();
        return 0;
}

static int __init acpi_parse_apic_instance(char *str)
{
        if (!str)
                return -EINVAL;

        if (kstrtoint(str, 0, &acpi_apic_instance))
                return -EINVAL;

        pr_notice("Shall use APIC/MADT table %d\n", acpi_apic_instance);

        return 0;
}

early_param("acpi_apic_instance", acpi_parse_apic_instance);

static int __init acpi_force_table_verification_setup(char *s)
{
        acpi_verify_table_checksum = true;

        return 0;
}

early_param("acpi_force_table_verification", acpi_force_table_verification_setup);

static int __init acpi_force_32bit_fadt_addr(char *s)
{
        pr_info("Forcing 32 Bit FADT addresses\n");
        acpi_gbl_use32_bit_fadt_addresses = TRUE;

        return 0;
}

early_param("acpi_force_32bit_fadt_addr", acpi_force_32bit_fadt_addr);