xref: /qemu/hw/acpi/nvdimm.c (revision 1439f213)

/*
 * NVDIMM ACPI Implementation
 *
 * Copyright(C) 2015 Intel Corporation.
 *
 * Author:
 *  Xiao Guangrong <guangrong.xiao@linux.intel.com>
 *
 * NFIT is defined in ACPI 6.0: 5.2.25 NVDIMM Firmware Interface Table (NFIT)
 * and the DSM specification can be found at:
 *       http://pmem.io/documents/NVDIMM_DSM_Interface_Example.pdf
 *
 * Currently, it only supports PMEM Virtualization.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>
 */

#include "qemu/osdep.h"
#include "qemu/uuid.h"
#include "hw/acpi/acpi.h"
#include "hw/acpi/aml-build.h"
#include "hw/acpi/bios-linker-loader.h"
#include "hw/nvram/fw_cfg.h"
#include "hw/mem/nvdimm.h"
#include "qemu/nvdimm-utils.h"

/*
 * define Byte Addressable Persistent Memory (PM) Region according to
 * ACPI 6.0: 5.2.25.1 System Physical Address Range Structure.
 */
static const uint8_t nvdimm_nfit_spa_uuid[] =
      UUID_LE(0x66f0d379, 0xb4f3, 0x4074, 0xac, 0x43, 0x0d, 0x33,
              0x18, 0xb7, 0x8c, 0xdb);

/*
 * NVDIMM Firmware Interface Table
 * @signature: "NFIT"
 *
 * It provides information that allows OSPM to enumerate NVDIMM present in
 * the platform and associate system physical address ranges created by the
 * NVDIMMs.
 *
 * It is defined in ACPI 6.0: 5.2.25 NVDIMM Firmware Interface Table (NFIT)
 */
struct NvdimmNfitHeader {
    ACPI_TABLE_HEADER_DEF
    uint32_t reserved;
} QEMU_PACKED;
typedef struct NvdimmNfitHeader NvdimmNfitHeader;

/*
 * define NFIT structures according to ACPI 6.0: 5.2.25 NVDIMM Firmware
 * Interface Table (NFIT).
 */

/*
 * System Physical Address Range Structure
 *
 * It describes the system physical address ranges occupied by NVDIMMs and
 * the types of the regions.
 */
struct NvdimmNfitSpa {
    uint16_t type;
    uint16_t length;
    uint16_t spa_index;
    uint16_t flags;
    uint32_t reserved;
    uint32_t proximity_domain;
    uint8_t type_guid[16];
    uint64_t spa_base;
    uint64_t spa_length;
    uint64_t mem_attr;
} QEMU_PACKED;
typedef struct NvdimmNfitSpa NvdimmNfitSpa;

/*
 * Memory Device to System Physical Address Range Mapping Structure
 *
 * It enables identifying each NVDIMM region and the corresponding SPA
 * describing the memory interleave
 */
struct NvdimmNfitMemDev {
    uint16_t type;
    uint16_t length;
    uint32_t nfit_handle;
    uint16_t phys_id;
    uint16_t region_id;
    uint16_t spa_index;
    uint16_t dcr_index;
    uint64_t region_len;
    uint64_t region_offset;
    uint64_t region_dpa;
    uint16_t interleave_index;
    uint16_t interleave_ways;
    uint16_t flags;
    uint16_t reserved;
} QEMU_PACKED;
typedef struct NvdimmNfitMemDev NvdimmNfitMemDev;

#define ACPI_NFIT_MEM_NOT_ARMED     (1 << 3)

/*
 * NVDIMM Control Region Structure
 *
 * It describes the NVDIMM and if applicable, Block Control Window.
 */
struct NvdimmNfitControlRegion {
    uint16_t type;
    uint16_t length;
    uint16_t dcr_index;
    uint16_t vendor_id;
    uint16_t device_id;
    uint16_t revision_id;
    uint16_t sub_vendor_id;
    uint16_t sub_device_id;
    uint16_t sub_revision_id;
    uint8_t reserved[6];
    uint32_t serial_number;
    uint16_t fic;
    uint16_t num_bcw;
    uint64_t bcw_size;
    uint64_t cmd_offset;
    uint64_t cmd_size;
    uint64_t status_offset;
    uint64_t status_size;
    uint16_t flags;
    uint8_t reserved2[6];
} QEMU_PACKED;
typedef struct NvdimmNfitControlRegion NvdimmNfitControlRegion;

/*
 * NVDIMM Platform Capabilities Structure
 *
 * Defined in section 5.2.25.9 of ACPI 6.2 Errata A, September 2017
 */
struct NvdimmNfitPlatformCaps {
    uint16_t type;
    uint16_t length;
    uint8_t highest_cap;
    uint8_t reserved[3];
    uint32_t capabilities;
    uint8_t reserved2[4];
} QEMU_PACKED;
typedef struct NvdimmNfitPlatformCaps NvdimmNfitPlatformCaps;

/*
 * Module serial number is a unique number for each device. We use the
 * slot id of NVDIMM device to generate this number so that each device
 * associates with a different number.
 *
 * 0x123456 is a magic number we arbitrarily chose.
 */
static uint32_t nvdimm_slot_to_sn(int slot)
{
    return 0x123456 + slot;
}

/*
 * handle is used to uniquely associate nfit_memdev structure with NVDIMM
 * ACPI device - nfit_memdev.nfit_handle matches with the value returned
 * by ACPI device _ADR method.
 *
 * We generate the handle with the slot id of NVDIMM device and reserve
 * 0 for NVDIMM root device.
 */
static uint32_t nvdimm_slot_to_handle(int slot)
{
    return slot + 1;
}

/*
 * index uniquely identifies the structure, 0 is reserved which indicates
 * that the structure is not valid or the associated structure is not
 * present.
 *
 * Each NVDIMM device needs two indexes, one for nfit_spa and another for
 * nfit_dc which are generated by the slot id of NVDIMM device.
 */
static uint16_t nvdimm_slot_to_spa_index(int slot)
{
    return (slot + 1) << 1;
}

/* See the comments of nvdimm_slot_to_spa_index(). */
static uint32_t nvdimm_slot_to_dcr_index(int slot)
{
    return nvdimm_slot_to_spa_index(slot) + 1;
}

static NVDIMMDevice *nvdimm_get_device_by_handle(uint32_t handle)
{
    NVDIMMDevice *nvdimm = NULL;
    GSList *list, *device_list = nvdimm_get_device_list();

    for (list = device_list; list; list = list->next) {
        NVDIMMDevice *nvd = list->data;
        int slot = object_property_get_int(OBJECT(nvd), PC_DIMM_SLOT_PROP,
                                           NULL);

        if (nvdimm_slot_to_handle(slot) == handle) {
            nvdimm = nvd;
            break;
        }
    }

    g_slist_free(device_list);
    return nvdimm;
}

/* ACPI 6.0: 5.2.25.1 System Physical Address Range Structure */
static void
nvdimm_build_structure_spa(GArray *structures, DeviceState *dev)
{
    NvdimmNfitSpa *nfit_spa;
    uint64_t addr = object_property_get_uint(OBJECT(dev), PC_DIMM_ADDR_PROP,
                                             NULL);
    uint64_t size = object_property_get_uint(OBJECT(dev), PC_DIMM_SIZE_PROP,
                                             NULL);
    uint32_t node = object_property_get_uint(OBJECT(dev), PC_DIMM_NODE_PROP,
                                             NULL);
    int slot = object_property_get_int(OBJECT(dev), PC_DIMM_SLOT_PROP,
                                       NULL);

    nfit_spa = acpi_data_push(structures, sizeof(*nfit_spa));

    nfit_spa->type = cpu_to_le16(0 /* System Physical Address Range
                                      Structure */);
    nfit_spa->length = cpu_to_le16(sizeof(*nfit_spa));
    nfit_spa->spa_index = cpu_to_le16(nvdimm_slot_to_spa_index(slot));

    /*
     * Control region is strict as all the device info, such as SN, index,
     * is associated with slot id.
     */
    nfit_spa->flags = cpu_to_le16(1 /* Control region is strictly for
                                       management during hot add/online
                                       operation */ |
                                  2 /* Data in Proximity Domain field is
                                       valid*/);

    /* NUMA node. */
    nfit_spa->proximity_domain = cpu_to_le32(node);
    /* the region reported as PMEM. */
    memcpy(nfit_spa->type_guid, nvdimm_nfit_spa_uuid,
           sizeof(nvdimm_nfit_spa_uuid));

    nfit_spa->spa_base = cpu_to_le64(addr);
    nfit_spa->spa_length = cpu_to_le64(size);

    /* It is the PMEM and can be cached as writeback. */
    nfit_spa->mem_attr = cpu_to_le64(0x8ULL /* EFI_MEMORY_WB */ |
                                     0x8000ULL /* EFI_MEMORY_NV */);
}

/*
 * ACPI 6.0: 5.2.25.2 Memory Device to System Physical Address Range Mapping
 * Structure
 */
static void
nvdimm_build_structure_memdev(GArray *structures, DeviceState *dev)
{
    NvdimmNfitMemDev *nfit_memdev;
    NVDIMMDevice *nvdimm = NVDIMM(OBJECT(dev));
    uint64_t size = object_property_get_uint(OBJECT(dev), PC_DIMM_SIZE_PROP,
                                             NULL);
    int slot = object_property_get_int(OBJECT(dev), PC_DIMM_SLOT_PROP,
                                            NULL);
    uint32_t handle = nvdimm_slot_to_handle(slot);

    nfit_memdev = acpi_data_push(structures, sizeof(*nfit_memdev));

    nfit_memdev->type = cpu_to_le16(1 /* Memory Device to System Address
                                         Range Map Structure*/);
    nfit_memdev->length = cpu_to_le16(sizeof(*nfit_memdev));
    nfit_memdev->nfit_handle = cpu_to_le32(handle);

    /*
     * associate memory device with System Physical Address Range
     * Structure.
     */
    nfit_memdev->spa_index = cpu_to_le16(nvdimm_slot_to_spa_index(slot));
    /* associate memory device with Control Region Structure. */
    nfit_memdev->dcr_index = cpu_to_le16(nvdimm_slot_to_dcr_index(slot));

    /* The memory region on the device. */
    nfit_memdev->region_len = cpu_to_le64(size);
    /* The device address starts from 0. */
    nfit_memdev->region_dpa = cpu_to_le64(0);

    /* Only one interleave for PMEM. */
    nfit_memdev->interleave_ways = cpu_to_le16(1);

    if (nvdimm->unarmed) {
        nfit_memdev->flags |= cpu_to_le16(ACPI_NFIT_MEM_NOT_ARMED);
    }
}

/*
 * ACPI 6.0: 5.2.25.5 NVDIMM Control Region Structure.
 */
static void nvdimm_build_structure_dcr(GArray *structures, DeviceState *dev)
{
    NvdimmNfitControlRegion *nfit_dcr;
    int slot = object_property_get_int(OBJECT(dev), PC_DIMM_SLOT_PROP,
                                       NULL);
    uint32_t sn = nvdimm_slot_to_sn(slot);

    nfit_dcr = acpi_data_push(structures, sizeof(*nfit_dcr));

    nfit_dcr->type = cpu_to_le16(4 /* NVDIMM Control Region Structure */);
    nfit_dcr->length = cpu_to_le16(sizeof(*nfit_dcr));
    nfit_dcr->dcr_index = cpu_to_le16(nvdimm_slot_to_dcr_index(slot));

    /* vendor: Intel. */
    nfit_dcr->vendor_id = cpu_to_le16(0x8086);
    nfit_dcr->device_id = cpu_to_le16(1);

    /* The _DSM method is following Intel's DSM specification. */
    nfit_dcr->revision_id = cpu_to_le16(1 /* Current Revision supported
                                             in ACPI 6.0 is 1. */);
    nfit_dcr->serial_number = cpu_to_le32(sn);
    nfit_dcr->fic = cpu_to_le16(0x301 /* Format Interface Code:
                                         Byte addressable, no energy backed.
                                         See ACPI 6.2, sect 5.2.25.6 and
                                         JEDEC Annex L Release 3. */);
}

/*
 * ACPI 6.2 Errata A: 5.2.25.9 NVDIMM Platform Capabilities Structure
 */
static void
nvdimm_build_structure_caps(GArray *structures, uint32_t capabilities)
{
    NvdimmNfitPlatformCaps *nfit_caps;

    nfit_caps = acpi_data_push(structures, sizeof(*nfit_caps));

    nfit_caps->type = cpu_to_le16(7 /* NVDIMM Platform Capabilities */);
    nfit_caps->length = cpu_to_le16(sizeof(*nfit_caps));
    nfit_caps->highest_cap = 31 - clz32(capabilities);
    nfit_caps->capabilities = cpu_to_le32(capabilities);
}

static GArray *nvdimm_build_device_structure(NVDIMMState *state)
{
    GSList *device_list = nvdimm_get_device_list();
    GArray *structures = g_array_new(false, true /* clear */, 1);

    for (; device_list; device_list = device_list->next) {
        DeviceState *dev = device_list->data;

        /* build System Physical Address Range Structure. */
        nvdimm_build_structure_spa(structures, dev);

        /*
         * build Memory Device to System Physical Address Range Mapping
         * Structure.
         */
        nvdimm_build_structure_memdev(structures, dev);

        /* build NVDIMM Control Region Structure. */
        nvdimm_build_structure_dcr(structures, dev);
    }
    g_slist_free(device_list);

    if (state->persistence) {
        nvdimm_build_structure_caps(structures, state->persistence);
    }

    return structures;
}

static void nvdimm_init_fit_buffer(NvdimmFitBuffer *fit_buf)
{
    fit_buf->fit = g_array_new(false, true /* clear */, 1);
}

static void nvdimm_build_fit_buffer(NVDIMMState *state)
{
    NvdimmFitBuffer *fit_buf = &state->fit_buf;

    g_array_free(fit_buf->fit, true);
    fit_buf->fit = nvdimm_build_device_structure(state);
    fit_buf->dirty = true;
}

void nvdimm_plug(NVDIMMState *state)
{
    nvdimm_build_fit_buffer(state);
}

static void nvdimm_build_nfit(NVDIMMState *state, GArray *table_offsets,
                              GArray *table_data, BIOSLinker *linker)
{
    NvdimmFitBuffer *fit_buf = &state->fit_buf;
    unsigned int header;

    acpi_add_table(table_offsets, table_data);

    /* NFIT header. */
    header = table_data->len;
    acpi_data_push(table_data, sizeof(NvdimmNfitHeader));
    /* NVDIMM device structures. */
    g_array_append_vals(table_data, fit_buf->fit->data, fit_buf->fit->len);

    build_header(linker, table_data,
                 (void *)(table_data->data + header), "NFIT",
                 sizeof(NvdimmNfitHeader) + fit_buf->fit->len, 1, NULL, NULL);
}

#define NVDIMM_DSM_MEMORY_SIZE      4096

struct NvdimmDsmIn {
    uint32_t handle;
    uint32_t revision;
    uint32_t function;
    /* the remaining size in the page is used by arg3. */
    union {
        uint8_t arg3[4084];
    };
} QEMU_PACKED;
typedef struct NvdimmDsmIn NvdimmDsmIn;
QEMU_BUILD_BUG_ON(sizeof(NvdimmDsmIn) != NVDIMM_DSM_MEMORY_SIZE);

struct NvdimmDsmOut {
    /* the size of buffer filled by QEMU. */
    uint32_t len;
    uint8_t data[4092];
} QEMU_PACKED;
typedef struct NvdimmDsmOut NvdimmDsmOut;
QEMU_BUILD_BUG_ON(sizeof(NvdimmDsmOut) != NVDIMM_DSM_MEMORY_SIZE);

struct NvdimmDsmFunc0Out {
    /* the size of buffer filled by QEMU. */
     uint32_t len;
     uint32_t supported_func;
} QEMU_PACKED;
typedef struct NvdimmDsmFunc0Out NvdimmDsmFunc0Out;

struct NvdimmDsmFuncNoPayloadOut {
    /* the size of buffer filled by QEMU. */
     uint32_t len;
     uint32_t func_ret_status;
} QEMU_PACKED;
typedef struct NvdimmDsmFuncNoPayloadOut NvdimmDsmFuncNoPayloadOut;

struct NvdimmFuncGetLabelSizeOut {
    /* the size of buffer filled by QEMU. */
    uint32_t len;
    uint32_t func_ret_status; /* return status code. */
    uint32_t label_size; /* the size of label data area. */
    /*
     * Maximum size of the namespace label data length supported by
     * the platform in Get/Set Namespace Label Data functions.
     */
    uint32_t max_xfer;
} QEMU_PACKED;
typedef struct NvdimmFuncGetLabelSizeOut NvdimmFuncGetLabelSizeOut;
QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncGetLabelSizeOut) > NVDIMM_DSM_MEMORY_SIZE);

struct NvdimmFuncGetLabelDataIn {
    uint32_t offset; /* the offset in the namespace label data area. */
    uint32_t length; /* the size of data is to be read via the function. */
} QEMU_PACKED;
typedef struct NvdimmFuncGetLabelDataIn NvdimmFuncGetLabelDataIn;
QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncGetLabelDataIn) +
                  offsetof(NvdimmDsmIn, arg3) > NVDIMM_DSM_MEMORY_SIZE);

struct NvdimmFuncGetLabelDataOut {
    /* the size of buffer filled by QEMU. */
    uint32_t len;
    uint32_t func_ret_status; /* return status code. */
    uint8_t out_buf[]; /* the data got via Get Namesapce Label function. */
} QEMU_PACKED;
typedef struct NvdimmFuncGetLabelDataOut NvdimmFuncGetLabelDataOut;
QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncGetLabelDataOut) > NVDIMM_DSM_MEMORY_SIZE);

struct NvdimmFuncSetLabelDataIn {
    uint32_t offset; /* the offset in the namespace label data area. */
    uint32_t length; /* the size of data is to be written via the function. */
    uint8_t in_buf[]; /* the data written to label data area. */
} QEMU_PACKED;
typedef struct NvdimmFuncSetLabelDataIn NvdimmFuncSetLabelDataIn;
QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncSetLabelDataIn) +
                  offsetof(NvdimmDsmIn, arg3) > NVDIMM_DSM_MEMORY_SIZE);

struct NvdimmFuncReadFITIn {
    uint32_t offset; /* the offset into FIT buffer. */
} QEMU_PACKED;
typedef struct NvdimmFuncReadFITIn NvdimmFuncReadFITIn;
QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncReadFITIn) +
                  offsetof(NvdimmDsmIn, arg3) > NVDIMM_DSM_MEMORY_SIZE);

struct NvdimmFuncReadFITOut {
    /* the size of buffer filled by QEMU. */
    uint32_t len;
    uint32_t func_ret_status; /* return status code. */
    uint8_t fit[]; /* the FIT data. */
} QEMU_PACKED;
typedef struct NvdimmFuncReadFITOut NvdimmFuncReadFITOut;
QEMU_BUILD_BUG_ON(sizeof(NvdimmFuncReadFITOut) > NVDIMM_DSM_MEMORY_SIZE);

static void
nvdimm_dsm_function0(uint32_t supported_func, hwaddr dsm_mem_addr)
{
    NvdimmDsmFunc0Out func0 = {
        .len = cpu_to_le32(sizeof(func0)),
        .supported_func = cpu_to_le32(supported_func),
    };
    cpu_physical_memory_write(dsm_mem_addr, &func0, sizeof(func0));
}

static void
nvdimm_dsm_no_payload(uint32_t func_ret_status, hwaddr dsm_mem_addr)
{
    NvdimmDsmFuncNoPayloadOut out = {
        .len = cpu_to_le32(sizeof(out)),
        .func_ret_status = cpu_to_le32(func_ret_status),
    };
    cpu_physical_memory_write(dsm_mem_addr, &out, sizeof(out));
}

#define NVDIMM_DSM_RET_STATUS_SUCCESS        0 /* Success */
#define NVDIMM_DSM_RET_STATUS_UNSUPPORT      1 /* Not Supported */
#define NVDIMM_DSM_RET_STATUS_NOMEMDEV       2 /* Non-Existing Memory Device */
#define NVDIMM_DSM_RET_STATUS_INVALID        3 /* Invalid Input Parameters */
#define NVDIMM_DSM_RET_STATUS_FIT_CHANGED    0x100 /* FIT Changed */

#define NVDIMM_QEMU_RSVD_HANDLE_ROOT         0x10000

/* Read FIT data, defined in docs/specs/acpi_nvdimm.txt. */
static void nvdimm_dsm_func_read_fit(NVDIMMState *state, NvdimmDsmIn *in,
                                     hwaddr dsm_mem_addr)
{
    NvdimmFitBuffer *fit_buf = &state->fit_buf;
    NvdimmFuncReadFITIn *read_fit;
    NvdimmFuncReadFITOut *read_fit_out;
    GArray *fit;
    uint32_t read_len = 0, func_ret_status;
    int size;

    read_fit = (NvdimmFuncReadFITIn *)in->arg3;
    read_fit->offset = le32_to_cpu(read_fit->offset);

    fit = fit_buf->fit;

    nvdimm_debug("Read FIT: offset %#x FIT size %#x Dirty %s.\n",
                 read_fit->offset, fit->len, fit_buf->dirty ? "Yes" : "No");

    if (read_fit->offset > fit->len) {
        func_ret_status = NVDIMM_DSM_RET_STATUS_INVALID;
        goto exit;
    }

    /* It is the first time to read FIT. */
    if (!read_fit->offset) {
        fit_buf->dirty = false;
    } else if (fit_buf->dirty) { /* FIT has been changed during RFIT. */
        func_ret_status = NVDIMM_DSM_RET_STATUS_FIT_CHANGED;
        goto exit;
    }

    func_ret_status = NVDIMM_DSM_RET_STATUS_SUCCESS;
    read_len = MIN(fit->len - read_fit->offset,
                   NVDIMM_DSM_MEMORY_SIZE - sizeof(NvdimmFuncReadFITOut));

exit:
    size = sizeof(NvdimmFuncReadFITOut) + read_len;
    read_fit_out = g_malloc(size);

    read_fit_out->len = cpu_to_le32(size);
    read_fit_out->func_ret_status = cpu_to_le32(func_ret_status);
    memcpy(read_fit_out->fit, fit->data + read_fit->offset, read_len);

    cpu_physical_memory_write(dsm_mem_addr, read_fit_out, size);

    g_free(read_fit_out);
}

static void
nvdimm_dsm_handle_reserved_root_method(NVDIMMState *state,
                                       NvdimmDsmIn *in, hwaddr dsm_mem_addr)
{
    switch (in->function) {
    case 0x0:
        nvdimm_dsm_function0(0x1 | 1 << 1 /* Read FIT */, dsm_mem_addr);
        return;
    case 0x1 /* Read FIT */:
        nvdimm_dsm_func_read_fit(state, in, dsm_mem_addr);
        return;
    }

    nvdimm_dsm_no_payload(NVDIMM_DSM_RET_STATUS_UNSUPPORT, dsm_mem_addr);
}

static void nvdimm_dsm_root(NvdimmDsmIn *in, hwaddr dsm_mem_addr)
{
    /*
     * function 0 is called to inquire which functions are supported by
     * OSPM
     */
    if (!in->function) {
        nvdimm_dsm_function0(0 /* No function supported other than
                                  function 0 */, dsm_mem_addr);
        return;
    }

    /* No function except function 0 is supported yet. */
    nvdimm_dsm_no_payload(NVDIMM_DSM_RET_STATUS_UNSUPPORT, dsm_mem_addr);
}

/*
 * the max transfer size is the max size transferred by both a
 * 'Get Namespace Label Data' function and a 'Set Namespace Label Data'
 * function.
 */
static uint32_t nvdimm_get_max_xfer_label_size(void)
{
    uint32_t max_get_size, max_set_size, dsm_memory_size;

    dsm_memory_size = NVDIMM_DSM_MEMORY_SIZE;

    /*
     * the max data ACPI can read one time which is transferred by
     * the response of 'Get Namespace Label Data' function.
     */
    max_get_size = dsm_memory_size - sizeof(NvdimmFuncGetLabelDataOut);

    /*
     * the max data ACPI can write one time which is transferred by
     * 'Set Namespace Label Data' function.
     */
    max_set_size = dsm_memory_size - offsetof(NvdimmDsmIn, arg3) -
                   sizeof(NvdimmFuncSetLabelDataIn);

    return MIN(max_get_size, max_set_size);
}

/*
 * DSM Spec Rev1 4.4 Get Namespace Label Size (Function Index 4).
 *
 * It gets the size of Namespace Label data area and the max data size
 * that Get/Set Namespace Label Data functions can transfer.
 */
static void nvdimm_dsm_label_size(NVDIMMDevice *nvdimm, hwaddr dsm_mem_addr)
{
    NvdimmFuncGetLabelSizeOut label_size_out = {
        .len = cpu_to_le32(sizeof(label_size_out)),
    };
    uint32_t label_size, mxfer;

    label_size = nvdimm->label_size;
    mxfer = nvdimm_get_max_xfer_label_size();

    nvdimm_debug("label_size %#x, max_xfer %#x.\n", label_size, mxfer);

    label_size_out.func_ret_status = cpu_to_le32(NVDIMM_DSM_RET_STATUS_SUCCESS);
    label_size_out.label_size = cpu_to_le32(label_size);
    label_size_out.max_xfer = cpu_to_le32(mxfer);

    cpu_physical_memory_write(dsm_mem_addr, &label_size_out,
                              sizeof(label_size_out));
}

static uint32_t nvdimm_rw_label_data_check(NVDIMMDevice *nvdimm,
                                           uint32_t offset, uint32_t length)
{
    uint32_t ret = NVDIMM_DSM_RET_STATUS_INVALID;

    if (offset + length < offset) {
        nvdimm_debug("offset %#x + length %#x is overflow.\n", offset,
                     length);
        return ret;
    }

    if (nvdimm->label_size < offset + length) {
        nvdimm_debug("position %#x is beyond label data (len = %" PRIx64 ").\n",
                     offset + length, nvdimm->label_size);
        return ret;
    }

    if (length > nvdimm_get_max_xfer_label_size()) {
        nvdimm_debug("length (%#x) is larger than max_xfer (%#x).\n",
                     length, nvdimm_get_max_xfer_label_size());
        return ret;
    }

    return NVDIMM_DSM_RET_STATUS_SUCCESS;
}

/*
 * DSM Spec Rev1 4.5 Get Namespace Label Data (Function Index 5).
 */
static void nvdimm_dsm_get_label_data(NVDIMMDevice *nvdimm, NvdimmDsmIn *in,
                                      hwaddr dsm_mem_addr)
{
    NVDIMMClass *nvc = NVDIMM_GET_CLASS(nvdimm);
    NvdimmFuncGetLabelDataIn *get_label_data;
    NvdimmFuncGetLabelDataOut *get_label_data_out;
    uint32_t status;
    int size;

    get_label_data = (NvdimmFuncGetLabelDataIn *)in->arg3;
    get_label_data->offset = le32_to_cpu(get_label_data->offset);
    get_label_data->length = le32_to_cpu(get_label_data->length);

    nvdimm_debug("Read Label Data: offset %#x length %#x.\n",
                 get_label_data->offset, get_label_data->length);

    status = nvdimm_rw_label_data_check(nvdimm, get_label_data->offset,
                                        get_label_data->length);
    if (status != NVDIMM_DSM_RET_STATUS_SUCCESS) {
        nvdimm_dsm_no_payload(status, dsm_mem_addr);
        return;
    }

    size = sizeof(*get_label_data_out) + get_label_data->length;
    assert(size <= NVDIMM_DSM_MEMORY_SIZE);
    get_label_data_out = g_malloc(size);

    get_label_data_out->len = cpu_to_le32(size);
    get_label_data_out->func_ret_status =
                            cpu_to_le32(NVDIMM_DSM_RET_STATUS_SUCCESS);
    nvc->read_label_data(nvdimm, get_label_data_out->out_buf,
                         get_label_data->length, get_label_data->offset);

    cpu_physical_memory_write(dsm_mem_addr, get_label_data_out, size);
    g_free(get_label_data_out);
}

/*
 * DSM Spec Rev1 4.6 Set Namespace Label Data (Function Index 6).
 */
static void nvdimm_dsm_set_label_data(NVDIMMDevice *nvdimm, NvdimmDsmIn *in,
                                      hwaddr dsm_mem_addr)
{
    NVDIMMClass *nvc = NVDIMM_GET_CLASS(nvdimm);
    NvdimmFuncSetLabelDataIn *set_label_data;
    uint32_t status;

    set_label_data = (NvdimmFuncSetLabelDataIn *)in->arg3;

    set_label_data->offset = le32_to_cpu(set_label_data->offset);
    set_label_data->length = le32_to_cpu(set_label_data->length);

    nvdimm_debug("Write Label Data: offset %#x length %#x.\n",
                 set_label_data->offset, set_label_data->length);

    status = nvdimm_rw_label_data_check(nvdimm, set_label_data->offset,
                                        set_label_data->length);
    if (status != NVDIMM_DSM_RET_STATUS_SUCCESS) {
        nvdimm_dsm_no_payload(status, dsm_mem_addr);
        return;
    }

    assert(offsetof(NvdimmDsmIn, arg3) + sizeof(*set_label_data) +
                    set_label_data->length <= NVDIMM_DSM_MEMORY_SIZE);

    nvc->write_label_data(nvdimm, set_label_data->in_buf,
                          set_label_data->length, set_label_data->offset);
    nvdimm_dsm_no_payload(NVDIMM_DSM_RET_STATUS_SUCCESS, dsm_mem_addr);
}

static void nvdimm_dsm_device(NvdimmDsmIn *in, hwaddr dsm_mem_addr)
{
    NVDIMMDevice *nvdimm = nvdimm_get_device_by_handle(in->handle);

    /* See the comments in nvdimm_dsm_root(). */
    if (!in->function) {
        uint32_t supported_func = 0;

        if (nvdimm && nvdimm->label_size) {
            supported_func |= 0x1 /* Bit 0 indicates whether there is
                                     support for any functions other
                                     than function 0. */ |
                              1 << 4 /* Get Namespace Label Size */ |
                              1 << 5 /* Get Namespace Label Data */ |
                              1 << 6 /* Set Namespace Label Data */;
        }
        nvdimm_dsm_function0(supported_func, dsm_mem_addr);
        return;
    }

    if (!nvdimm) {
        nvdimm_dsm_no_payload(NVDIMM_DSM_RET_STATUS_NOMEMDEV,
                              dsm_mem_addr);
        return;
    }

    /* Encode DSM function according to DSM Spec Rev1. */
    switch (in->function) {
    case 4 /* Get Namespace Label Size */:
        if (nvdimm->label_size) {
            nvdimm_dsm_label_size(nvdimm, dsm_mem_addr);
            return;
        }
        break;
    case 5 /* Get Namespace Label Data */:
        if (nvdimm->label_size) {
            nvdimm_dsm_get_label_data(nvdimm, in, dsm_mem_addr);
            return;
        }
        break;
    case 0x6 /* Set Namespace Label Data */:
        if (nvdimm->label_size) {
            nvdimm_dsm_set_label_data(nvdimm, in, dsm_mem_addr);
            return;
        }
        break;
    }

    nvdimm_dsm_no_payload(NVDIMM_DSM_RET_STATUS_UNSUPPORT, dsm_mem_addr);
}

static uint64_t
nvdimm_dsm_read(void *opaque, hwaddr addr, unsigned size)
{
    nvdimm_debug("BUG: we never read _DSM IO Port.\n");
    return 0;
}

static void
nvdimm_dsm_write(void *opaque, hwaddr addr, uint64_t val, unsigned size)
{
    NVDIMMState *state = opaque;
    NvdimmDsmIn *in;
    hwaddr dsm_mem_addr = val;

    nvdimm_debug("dsm memory address %#" HWADDR_PRIx ".\n", dsm_mem_addr);

    /*
     * The DSM memory is mapped to guest address space so an evil guest
     * can change its content while we are doing DSM emulation. Avoid
     * this by copying DSM memory to QEMU local memory.
     */
    in = g_new(NvdimmDsmIn, 1);
    cpu_physical_memory_read(dsm_mem_addr, in, sizeof(*in));

    in->revision = le32_to_cpu(in->revision);
    in->function = le32_to_cpu(in->function);
    in->handle = le32_to_cpu(in->handle);

    nvdimm_debug("Revision %#x Handler %#x Function %#x.\n", in->revision,
                 in->handle, in->function);

    if (in->revision != 0x1 /* Currently we only support DSM Spec Rev1. */) {
        nvdimm_debug("Revision %#x is not supported, expect %#x.\n",
                     in->revision, 0x1);
        nvdimm_dsm_no_payload(NVDIMM_DSM_RET_STATUS_UNSUPPORT, dsm_mem_addr);
        goto exit;
    }

    if (in->handle == NVDIMM_QEMU_RSVD_HANDLE_ROOT) {
        nvdimm_dsm_handle_reserved_root_method(state, in, dsm_mem_addr);
        goto exit;
    }

     /* Handle 0 is reserved for NVDIMM Root Device. */
    if (!in->handle) {
        nvdimm_dsm_root(in, dsm_mem_addr);
        goto exit;
    }

    nvdimm_dsm_device(in, dsm_mem_addr);

exit:
    g_free(in);
}

static const MemoryRegionOps nvdimm_dsm_ops = {
    .read = nvdimm_dsm_read,
    .write = nvdimm_dsm_write,
    .endianness = DEVICE_LITTLE_ENDIAN,
    .valid = {
        .min_access_size = 4,
        .max_access_size = 4,
    },
};

void nvdimm_acpi_plug_cb(HotplugHandler *hotplug_dev, DeviceState *dev)
{
    if (dev->hotplugged) {
        acpi_send_event(DEVICE(hotplug_dev), ACPI_NVDIMM_HOTPLUG_STATUS);
    }
}

void nvdimm_init_acpi_state(NVDIMMState *state, MemoryRegion *io,
                            struct AcpiGenericAddress dsm_io,
                            FWCfgState *fw_cfg, Object *owner)
{
    state->dsm_io = dsm_io;
    memory_region_init_io(&state->io_mr, owner, &nvdimm_dsm_ops, state,
                          "nvdimm-acpi-io", dsm_io.bit_width >> 3);
    memory_region_add_subregion(io, dsm_io.address, &state->io_mr);

    state->dsm_mem = g_array_new(false, true /* clear */, 1);
    acpi_data_push(state->dsm_mem, sizeof(NvdimmDsmIn));
    fw_cfg_add_file(fw_cfg, NVDIMM_DSM_MEM_FILE, state->dsm_mem->data,
                    state->dsm_mem->len);

    nvdimm_init_fit_buffer(&state->fit_buf);
}

#define NVDIMM_COMMON_DSM       "NCAL"
#define NVDIMM_ACPI_MEM_ADDR    "MEMA"

#define NVDIMM_DSM_MEMORY       "NRAM"
#define NVDIMM_DSM_IOPORT       "NPIO"

#define NVDIMM_DSM_NOTIFY       "NTFI"
#define NVDIMM_DSM_HANDLE       "HDLE"
#define NVDIMM_DSM_REVISION     "REVS"
#define NVDIMM_DSM_FUNCTION     "FUNC"
#define NVDIMM_DSM_ARG3         "FARG"

#define NVDIMM_DSM_OUT_BUF_SIZE "RLEN"
#define NVDIMM_DSM_OUT_BUF      "ODAT"

#define NVDIMM_DSM_RFIT_STATUS  "RSTA"

#define NVDIMM_QEMU_RSVD_UUID   "648B9CF2-CDA1-4312-8AD9-49C4AF32BD62"

static void nvdimm_build_common_dsm(Aml *dev,
                                    NVDIMMState *nvdimm_state)
{
    Aml *method, *ifctx, *function, *handle, *uuid, *dsm_mem, *elsectx2;
    Aml *elsectx, *unsupport, *unpatched, *expected_uuid, *uuid_invalid;
    Aml *pckg, *pckg_index, *pckg_buf, *field, *dsm_out_buf, *dsm_out_buf_size;
    Aml *whilectx, *offset;
    uint8_t byte_list[1];
    AmlRegionSpace rs;

    method = aml_method(NVDIMM_COMMON_DSM, 5, AML_SERIALIZED);
    uuid = aml_arg(0);
    function = aml_arg(2);
    handle = aml_arg(4);
    dsm_mem = aml_local(6);
    dsm_out_buf = aml_local(7);

    aml_append(method, aml_store(aml_name(NVDIMM_ACPI_MEM_ADDR), dsm_mem));

    if (nvdimm_state->dsm_io.space_id == AML_AS_SYSTEM_IO) {
        rs = AML_SYSTEM_IO;
    } else {
        rs = AML_SYSTEM_MEMORY;
    }

    /* map DSM memory and IO into ACPI namespace. */
    aml_append(method, aml_operation_region(NVDIMM_DSM_IOPORT, rs,
               aml_int(nvdimm_state->dsm_io.address),
               nvdimm_state->dsm_io.bit_width >> 3));
    aml_append(method, aml_operation_region(NVDIMM_DSM_MEMORY,
               AML_SYSTEM_MEMORY, dsm_mem, sizeof(NvdimmDsmIn)));

    /*
     * DSM notifier:
     * NVDIMM_DSM_NOTIFY: write the address of DSM memory and notify QEMU to
     *                    emulate the access.
     *
     * It is the IO port so that accessing them will cause VM-exit, the
     * control will be transferred to QEMU.
     */
    field = aml_field(NVDIMM_DSM_IOPORT, AML_DWORD_ACC, AML_NOLOCK,
                      AML_PRESERVE);
    aml_append(field, aml_named_field(NVDIMM_DSM_NOTIFY,
               nvdimm_state->dsm_io.bit_width));
    aml_append(method, field);

    /*
     * DSM input:
     * NVDIMM_DSM_HANDLE: store device's handle, it's zero if the _DSM call
     *                    happens on NVDIMM Root Device.
     * NVDIMM_DSM_REVISION: store the Arg1 of _DSM call.
     * NVDIMM_DSM_FUNCTION: store the Arg2 of _DSM call.
     * NVDIMM_DSM_ARG3: store the Arg3 of _DSM call which is a Package
     *                  containing function-specific arguments.
     *
     * They are RAM mapping on host so that these accesses never cause
     * VM-EXIT.
     */
    field = aml_field(NVDIMM_DSM_MEMORY, AML_DWORD_ACC, AML_NOLOCK,
                      AML_PRESERVE);
    aml_append(field, aml_named_field(NVDIMM_DSM_HANDLE,
               sizeof(typeof_field(NvdimmDsmIn, handle)) * BITS_PER_BYTE));
    aml_append(field, aml_named_field(NVDIMM_DSM_REVISION,
               sizeof(typeof_field(NvdimmDsmIn, revision)) * BITS_PER_BYTE));
    aml_append(field, aml_named_field(NVDIMM_DSM_FUNCTION,
               sizeof(typeof_field(NvdimmDsmIn, function)) * BITS_PER_BYTE));
    aml_append(field, aml_named_field(NVDIMM_DSM_ARG3,
         (sizeof(NvdimmDsmIn) - offsetof(NvdimmDsmIn, arg3)) * BITS_PER_BYTE));
    aml_append(method, field);

    /*
     * DSM output:
     * NVDIMM_DSM_OUT_BUF_SIZE: the size of the buffer filled by QEMU.
     * NVDIMM_DSM_OUT_BUF: the buffer QEMU uses to store the result.
     *
     * Since the page is reused by both input and out, the input data
     * will be lost after storing new result into ODAT so we should fetch
     * all the input data before writing the result.
     */
    field = aml_field(NVDIMM_DSM_MEMORY, AML_DWORD_ACC, AML_NOLOCK,
                      AML_PRESERVE);
    aml_append(field, aml_named_field(NVDIMM_DSM_OUT_BUF_SIZE,
               sizeof(typeof_field(NvdimmDsmOut, len)) * BITS_PER_BYTE));
    aml_append(field, aml_named_field(NVDIMM_DSM_OUT_BUF,
       (sizeof(NvdimmDsmOut) - offsetof(NvdimmDsmOut, data)) * BITS_PER_BYTE));
    aml_append(method, field);

    /*
     * do not support any method if DSM memory address has not been
     * patched.
     */
    unpatched = aml_equal(dsm_mem, aml_int(0x0));

    expected_uuid = aml_local(0);

    ifctx = aml_if(aml_equal(handle, aml_int(0x0)));
    aml_append(ifctx, aml_store(
               aml_touuid("2F10E7A4-9E91-11E4-89D3-123B93F75CBA")
               /* UUID for NVDIMM Root Device */, expected_uuid));
    aml_append(method, ifctx);
    elsectx = aml_else();
    ifctx = aml_if(aml_equal(handle, aml_int(NVDIMM_QEMU_RSVD_HANDLE_ROOT)));
    aml_append(ifctx, aml_store(aml_touuid(NVDIMM_QEMU_RSVD_UUID
               /* UUID for QEMU internal use */), expected_uuid));
    aml_append(elsectx, ifctx);
    elsectx2 = aml_else();
    aml_append(elsectx2, aml_store(
               aml_touuid("4309AC30-0D11-11E4-9191-0800200C9A66")
               /* UUID for NVDIMM Devices */, expected_uuid));
    aml_append(elsectx, elsectx2);
    aml_append(method, elsectx);

    uuid_invalid = aml_lnot(aml_equal(uuid, expected_uuid));

    unsupport = aml_if(aml_or(unpatched, uuid_invalid, NULL));

    /*
     * function 0 is called to inquire what functions are supported by
     * OSPM
     */
    ifctx = aml_if(aml_equal(function, aml_int(0)));
    byte_list[0] = 0 /* No function Supported */;
    aml_append(ifctx, aml_return(aml_buffer(1, byte_list)));
    aml_append(unsupport, ifctx);

    /* No function is supported yet. */
    byte_list[0] = NVDIMM_DSM_RET_STATUS_UNSUPPORT;
    aml_append(unsupport, aml_return(aml_buffer(1, byte_list)));
    aml_append(method, unsupport);

    /*
     * The HDLE indicates the DSM function is issued from which device,
     * it reserves 0 for root device and is the handle for NVDIMM devices.
     * See the comments in nvdimm_slot_to_handle().
     */
    aml_append(method, aml_store(handle, aml_name(NVDIMM_DSM_HANDLE)));
    aml_append(method, aml_store(aml_arg(1), aml_name(NVDIMM_DSM_REVISION)));
    aml_append(method, aml_store(function, aml_name(NVDIMM_DSM_FUNCTION)));

    /*
     * The fourth parameter (Arg3) of _DSM is a package which contains
     * a buffer, the layout of the buffer is specified by UUID (Arg0),
     * Revision ID (Arg1) and Function Index (Arg2) which are documented
     * in the DSM Spec.
     */
    pckg = aml_arg(3);
    ifctx = aml_if(aml_and(aml_equal(aml_object_type(pckg),
                   aml_int(4 /* Package */)) /* It is a Package? */,
                   aml_equal(aml_sizeof(pckg), aml_int(1)) /* 1 element? */,
                   NULL));

    pckg_index = aml_local(2);
    pckg_buf = aml_local(3);
    aml_append(ifctx, aml_store(aml_index(pckg, aml_int(0)), pckg_index));
    aml_append(ifctx, aml_store(aml_derefof(pckg_index), pckg_buf));
    aml_append(ifctx, aml_store(pckg_buf, aml_name(NVDIMM_DSM_ARG3)));
    aml_append(method, ifctx);

    /*
     * tell QEMU about the real address of DSM memory, then QEMU
     * gets the control and fills the result in DSM memory.
     */
    aml_append(method, aml_store(dsm_mem, aml_name(NVDIMM_DSM_NOTIFY)));

    dsm_out_buf_size = aml_local(1);
    /* RLEN is not included in the payload returned to guest. */
    aml_append(method, aml_subtract(aml_name(NVDIMM_DSM_OUT_BUF_SIZE),
               aml_int(4), dsm_out_buf_size));

    /*
     * As per ACPI spec 6.3, Table 19-419 Object Conversion Rules, if
     * the Buffer Field <= to the size of an Integer (in bits), it will
     * be treated as an integer. Moreover, the integer size depends on
     * DSDT tables revision number. If revision number is < 2, integer
     * size is 32 bits, otherwise it is 64 bits.
     * Because of this CreateField() canot be used if RLEN < Integer Size.
     *
     * Also please note that APCI ASL operator SizeOf() doesn't support
     * Integer and there isn't any other way to figure out the Integer
     * size. Hence we assume 8 byte as Integer size and if RLEN < 8 bytes,
     * build dsm_out_buf byte by byte.
     */
    ifctx = aml_if(aml_lless(dsm_out_buf_size, aml_int(8)));
    offset = aml_local(2);
    aml_append(ifctx, aml_store(aml_int(0), offset));
    aml_append(ifctx, aml_name_decl("TBUF", aml_buffer(1, NULL)));
    aml_append(ifctx, aml_store(aml_buffer(0, NULL), dsm_out_buf));

    whilectx = aml_while(aml_lless(offset, dsm_out_buf_size));
    /* Copy 1 byte at offset from ODAT to temporary buffer(TBUF). */
    aml_append(whilectx, aml_store(aml_derefof(aml_index(
                                   aml_name(NVDIMM_DSM_OUT_BUF), offset)),
                                   aml_index(aml_name("TBUF"), aml_int(0))));
    aml_append(whilectx, aml_concatenate(dsm_out_buf, aml_name("TBUF"),
                                         dsm_out_buf));
    aml_append(whilectx, aml_increment(offset));
    aml_append(ifctx, whilectx);

    aml_append(ifctx, aml_return(dsm_out_buf));
    aml_append(method, ifctx);

    /* If RLEN >= Integer size, just use CreateField() operator */
    aml_append(method, aml_store(aml_shiftleft(dsm_out_buf_size, aml_int(3)),
                                 dsm_out_buf_size));
    aml_append(method, aml_create_field(aml_name(NVDIMM_DSM_OUT_BUF),
               aml_int(0), dsm_out_buf_size, "OBUF"));
    aml_append(method, aml_return(aml_name("OBUF")));

    aml_append(dev, method);
}

static void nvdimm_build_device_dsm(Aml *dev, uint32_t handle)
{
    Aml *method;

    method = aml_method("_DSM", 4, AML_NOTSERIALIZED);
    aml_append(method, aml_return(aml_call5(NVDIMM_COMMON_DSM, aml_arg(0),
                                  aml_arg(1), aml_arg(2), aml_arg(3),
                                  aml_int(handle))));
    aml_append(dev, method);
}

static void nvdimm_build_fit(Aml *dev)
{
    Aml *method, *pkg, *buf, *buf_size, *offset, *call_result;
    Aml *whilectx, *ifcond, *ifctx, *elsectx, *fit;

    buf = aml_local(0);
    buf_size = aml_local(1);
    fit = aml_local(2);

    aml_append(dev, aml_name_decl(NVDIMM_DSM_RFIT_STATUS, aml_int(0)));

    /* build helper function, RFIT. */
    method = aml_method("RFIT", 1, AML_SERIALIZED);
    aml_append(method, aml_name_decl("OFST", aml_int(0)));

    /* prepare input package. */
    pkg = aml_package(1);
    aml_append(method, aml_store(aml_arg(0), aml_name("OFST")));
    aml_append(pkg, aml_name("OFST"));

    /* call Read_FIT function. */
    call_result = aml_call5(NVDIMM_COMMON_DSM,
                            aml_touuid(NVDIMM_QEMU_RSVD_UUID),
                            aml_int(1) /* Revision 1 */,
                            aml_int(0x1) /* Read FIT */,
                            pkg, aml_int(NVDIMM_QEMU_RSVD_HANDLE_ROOT));
    aml_append(method, aml_store(call_result, buf));

    /* handle _DSM result. */
    aml_append(method, aml_create_dword_field(buf,
               aml_int(0) /* offset at byte 0 */, "STAU"));

    aml_append(method, aml_store(aml_name("STAU"),
                                 aml_name(NVDIMM_DSM_RFIT_STATUS)));

     /* if something is wrong during _DSM. */
    ifcond = aml_equal(aml_int(NVDIMM_DSM_RET_STATUS_SUCCESS),
                       aml_name("STAU"));
    ifctx = aml_if(aml_lnot(ifcond));
    aml_append(ifctx, aml_return(aml_buffer(0, NULL)));
    aml_append(method, ifctx);

    aml_append(method, aml_store(aml_sizeof(buf), buf_size));
    aml_append(method, aml_subtract(buf_size,
                                    aml_int(4) /* the size of "STAU" */,
                                    buf_size));

    /* if we read the end of fit. */
    ifctx = aml_if(aml_equal(buf_size, aml_int(0)));
    aml_append(ifctx, aml_return(aml_buffer(0, NULL)));
    aml_append(method, ifctx);

    aml_append(method, aml_create_field(buf,
                            aml_int(4 * BITS_PER_BYTE), /* offset at byte 4.*/
                            aml_shiftleft(buf_size, aml_int(3)), "BUFF"));
    aml_append(method, aml_return(aml_name("BUFF")));
    aml_append(dev, method);

    /* build _FIT. */
    method = aml_method("_FIT", 0, AML_SERIALIZED);
    offset = aml_local(3);

    aml_append(method, aml_store(aml_buffer(0, NULL), fit));
    aml_append(method, aml_store(aml_int(0), offset));

    whilectx = aml_while(aml_int(1));
    aml_append(whilectx, aml_store(aml_call1("RFIT", offset), buf));
    aml_append(whilectx, aml_store(aml_sizeof(buf), buf_size));

    /*
     * if fit buffer was changed during RFIT, read from the beginning
     * again.
     */
    ifctx = aml_if(aml_equal(aml_name(NVDIMM_DSM_RFIT_STATUS),
                             aml_int(NVDIMM_DSM_RET_STATUS_FIT_CHANGED)));
    aml_append(ifctx, aml_store(aml_buffer(0, NULL), fit));
    aml_append(ifctx, aml_store(aml_int(0), offset));
    aml_append(whilectx, ifctx);

    elsectx = aml_else();

    /* finish fit read if no data is read out. */
    ifctx = aml_if(aml_equal(buf_size, aml_int(0)));
    aml_append(ifctx, aml_return(fit));
    aml_append(elsectx, ifctx);

    /* update the offset. */
    aml_append(elsectx, aml_add(offset, buf_size, offset));
    /* append the data we read out to the fit buffer. */
    aml_append(elsectx, aml_concatenate(fit, buf, fit));
    aml_append(whilectx, elsectx);
    aml_append(method, whilectx);

    aml_append(dev, method);
}

static void nvdimm_build_nvdimm_devices(Aml *root_dev, uint32_t ram_slots)
{
    uint32_t slot;

    for (slot = 0; slot < ram_slots; slot++) {
        uint32_t handle = nvdimm_slot_to_handle(slot);
        Aml *nvdimm_dev;

        nvdimm_dev = aml_device("NV%02X", slot);

        /*
         * ACPI 6.0: 9.20 NVDIMM Devices:
         *
         * _ADR object that is used to supply OSPM with unique address
         * of the NVDIMM device. This is done by returning the NFIT Device
         * handle that is used to identify the associated entries in ACPI
         * table NFIT or _FIT.
         */
        aml_append(nvdimm_dev, aml_name_decl("_ADR", aml_int(handle)));

        nvdimm_build_device_dsm(nvdimm_dev, handle);
        aml_append(root_dev, nvdimm_dev);
    }
}

static void nvdimm_build_ssdt(GArray *table_offsets, GArray *table_data,
                              BIOSLinker *linker,
                              NVDIMMState *nvdimm_state,
                              uint32_t ram_slots)
{
    Aml *ssdt, *sb_scope, *dev;
    int mem_addr_offset, nvdimm_ssdt;

    acpi_add_table(table_offsets, table_data);

    ssdt = init_aml_allocator();
    acpi_data_push(ssdt->buf, sizeof(AcpiTableHeader));

    sb_scope = aml_scope("\\_SB");

    dev = aml_device("NVDR");

    /*
     * ACPI 6.0: 9.20 NVDIMM Devices:
     *
     * The ACPI Name Space device uses _HID of ACPI0012 to identify the root
     * NVDIMM interface device. Platform firmware is required to contain one
     * such device in _SB scope if NVDIMMs support is exposed by platform to
     * OSPM.
     * For each NVDIMM present or intended to be supported by platform,
     * platform firmware also exposes an ACPI Namespace Device under the
     * root device.
     */
    aml_append(dev, aml_name_decl("_HID", aml_string("ACPI0012")));

    nvdimm_build_common_dsm(dev, nvdimm_state);

    /* 0 is reserved for root device. */
    nvdimm_build_device_dsm(dev, 0);
    nvdimm_build_fit(dev);

    nvdimm_build_nvdimm_devices(dev, ram_slots);

    aml_append(sb_scope, dev);
    aml_append(ssdt, sb_scope);

    nvdimm_ssdt = table_data->len;

    /* copy AML table into ACPI tables blob and patch header there */
    g_array_append_vals(table_data, ssdt->buf->data, ssdt->buf->len);
    mem_addr_offset = build_append_named_dword(table_data,
                                               NVDIMM_ACPI_MEM_ADDR);

    bios_linker_loader_alloc(linker,
                             NVDIMM_DSM_MEM_FILE, nvdimm_state->dsm_mem,
                             sizeof(NvdimmDsmIn), false /* high memory */);
    bios_linker_loader_add_pointer(linker,
        ACPI_BUILD_TABLE_FILE, mem_addr_offset, sizeof(uint32_t),
        NVDIMM_DSM_MEM_FILE, 0);
    build_header(linker, table_data,
        (void *)(table_data->data + nvdimm_ssdt),
        "SSDT", table_data->len - nvdimm_ssdt, 1, NULL, "NVDIMM");
    free_aml_allocator();
}

void nvdimm_build_acpi(GArray *table_offsets, GArray *table_data,
                       BIOSLinker *linker, NVDIMMState *state,
                       uint32_t ram_slots)
{
    GSList *device_list;

    /* no nvdimm device can be plugged. */
    if (!ram_slots) {
        return;
    }

    nvdimm_build_ssdt(table_offsets, table_data, linker, state,
                      ram_slots);

    device_list = nvdimm_get_device_list();
    /* no NVDIMM device is plugged. */
    if (!device_list) {
        return;
    }

    nvdimm_build_nfit(state, table_offsets, table_data, linker);
    g_slist_free(device_list);
}