qemu/hw/cxl/cxl-mailbox-utils.c

/*
 * CXL Utility library for mailbox interface
 *
 * Copyright(C) 2020 Intel Corporation.
 *
 * This work is licensed under the terms of the GNU GPL, version 2. See the
 * COPYING file in the top-level directory.
 */

#include "qemu/osdep.h"
#include "hw/cxl/cxl.h"
#include "hw/pci/pci.h"
#include "qemu/cutils.h"
#include "qemu/log.h"
#include "qemu/units.h"
#include "qemu/uuid.h"

#define CXL_CAPACITY_MULTIPLIER   (256 * MiB)

/*
 * How to add a new command, example. The command set FOO, with cmd BAR.
 *  1. Add the command set and cmd to the enum.
 *     FOO    = 0x7f,
 *          #define BAR 0
 *  2. Implement the handler
 *    static CXLRetCode cmd_foo_bar(struct cxl_cmd *cmd,
 *                                  CXLDeviceState *cxl_dstate, uint16_t *len)
 *  3. Add the command to the cxl_cmd_set[][]
 *    [FOO][BAR] = { "FOO_BAR", cmd_foo_bar, x, y },
 *  4. Implement your handler
 *     define_mailbox_handler(FOO_BAR) { ... return CXL_MBOX_SUCCESS; }
 *
 *
 *  Writing the handler:
 *    The handler will provide the &struct cxl_cmd, the &CXLDeviceState, and the
 *    in/out length of the payload. The handler is responsible for consuming the
 *    payload from cmd->payload and operating upon it as necessary. It must then
 *    fill the output data into cmd->payload (overwriting what was there),
 *    setting the length, and returning a valid return code.
 *
 *  XXX: The handler need not worry about endianess. The payload is read out of
 *  a register interface that already deals with it.
 */

enum {
    EVENTS      = 0x01,
        #define GET_RECORDS   0x0
        #define CLEAR_RECORDS   0x1
        #define GET_INTERRUPT_POLICY   0x2
        #define SET_INTERRUPT_POLICY   0x3
    FIRMWARE_UPDATE = 0x02,
        #define GET_INFO      0x0
    TIMESTAMP   = 0x03,
        #define GET           0x0
        #define SET           0x1
    LOGS        = 0x04,
        #define GET_SUPPORTED 0x0
        #define GET_LOG       0x1
    IDENTIFY    = 0x40,
        #define MEMORY_DEVICE 0x0
    CCLS        = 0x41,
        #define GET_PARTITION_INFO     0x0
        #define GET_LSA       0x2
        #define SET_LSA       0x3
    MEDIA_AND_POISON = 0x43,
        #define GET_POISON_LIST        0x0
        #define INJECT_POISON          0x1
        #define CLEAR_POISON           0x2
};

struct cxl_cmd;
typedef CXLRetCode (*opcode_handler)(struct cxl_cmd *cmd,
                                   CXLDeviceState *cxl_dstate, uint16_t *len);
struct cxl_cmd {
    const char *name;
    opcode_handler handler;
    ssize_t in;
    uint16_t effect; /* Reported in CEL */
    uint8_t *payload;
};

#define DEFINE_MAILBOX_HANDLER_ZEROED(name, size)                         \
    uint16_t __zero##name = size;                                         \
    static CXLRetCode cmd_##name(struct cxl_cmd *cmd,                       \
                                 CXLDeviceState *cxl_dstate, uint16_t *len) \
    {                                                                     \
        *len = __zero##name;                                              \
        memset(cmd->payload, 0, *len);                                    \
        return CXL_MBOX_SUCCESS;                                          \
    }
#define DEFINE_MAILBOX_HANDLER_NOP(name)                                  \
    static CXLRetCode cmd_##name(struct cxl_cmd *cmd,                       \
                                 CXLDeviceState *cxl_dstate, uint16_t *len) \
    {                                                                     \
        return CXL_MBOX_SUCCESS;                                          \
    }

DEFINE_MAILBOX_HANDLER_ZEROED(events_get_records, 0x20);
DEFINE_MAILBOX_HANDLER_NOP(events_clear_records);
DEFINE_MAILBOX_HANDLER_ZEROED(events_get_interrupt_policy, 4);
DEFINE_MAILBOX_HANDLER_NOP(events_set_interrupt_policy);

/* 8.2.9.2.1 */
static CXLRetCode cmd_firmware_update_get_info(struct cxl_cmd *cmd,
                                               CXLDeviceState *cxl_dstate,
                                               uint16_t *len)
{
    struct {
        uint8_t slots_supported;
        uint8_t slot_info;
        uint8_t caps;
        uint8_t rsvd[0xd];
        char fw_rev1[0x10];
        char fw_rev2[0x10];
        char fw_rev3[0x10];
        char fw_rev4[0x10];
    } QEMU_PACKED *fw_info;
    QEMU_BUILD_BUG_ON(sizeof(*fw_info) != 0x50);

    if ((cxl_dstate->vmem_size < CXL_CAPACITY_MULTIPLIER) ||
        (cxl_dstate->pmem_size < CXL_CAPACITY_MULTIPLIER)) {
        return CXL_MBOX_INTERNAL_ERROR;
    }

    fw_info = (void *)cmd->payload;
    memset(fw_info, 0, sizeof(*fw_info));

    fw_info->slots_supported = 2;
    fw_info->slot_info = BIT(0) | BIT(3);
    fw_info->caps = 0;
    pstrcpy(fw_info->fw_rev1, sizeof(fw_info->fw_rev1), "BWFW VERSION 0");

    *len = sizeof(*fw_info);
    return CXL_MBOX_SUCCESS;
}

/* 8.2.9.3.1 */
static CXLRetCode cmd_timestamp_get(struct cxl_cmd *cmd,
                                    CXLDeviceState *cxl_dstate,
                                    uint16_t *len)
{
    uint64_t final_time = cxl_device_get_timestamp(cxl_dstate);

    stq_le_p(cmd->payload, final_time);
    *len = 8;

    return CXL_MBOX_SUCCESS;
}

/* 8.2.9.3.2 */
static CXLRetCode cmd_timestamp_set(struct cxl_cmd *cmd,
                                  CXLDeviceState *cxl_dstate,
                                  uint16_t *len)
{
    cxl_dstate->timestamp.set = true;
    cxl_dstate->timestamp.last_set = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);

    cxl_dstate->timestamp.host_set = le64_to_cpu(*(uint64_t *)cmd->payload);

    *len = 0;
    return CXL_MBOX_SUCCESS;
}

/* CXL 3.0 8.2.9.5.2.1 Command Effects Log (CEL) */
static const QemuUUID cel_uuid = {
    .data = UUID(0x0da9c0b5, 0xbf41, 0x4b78, 0x8f, 0x79,
                 0x96, 0xb1, 0x62, 0x3b, 0x3f, 0x17)
};

/* 8.2.9.4.1 */
static CXLRetCode cmd_logs_get_supported(struct cxl_cmd *cmd,
                                         CXLDeviceState *cxl_dstate,
                                         uint16_t *len)
{
    struct {
        uint16_t entries;
        uint8_t rsvd[6];
        struct {
            QemuUUID uuid;
            uint32_t size;
        } log_entries[1];
    } QEMU_PACKED *supported_logs = (void *)cmd->payload;
    QEMU_BUILD_BUG_ON(sizeof(*supported_logs) != 0x1c);

    supported_logs->entries = 1;
    supported_logs->log_entries[0].uuid = cel_uuid;
    supported_logs->log_entries[0].size = 4 * cxl_dstate->cel_size;

    *len = sizeof(*supported_logs);
    return CXL_MBOX_SUCCESS;
}

/* 8.2.9.4.2 */
static CXLRetCode cmd_logs_get_log(struct cxl_cmd *cmd,
                                   CXLDeviceState *cxl_dstate,
                                   uint16_t *len)
{
    struct {
        QemuUUID uuid;
        uint32_t offset;
        uint32_t length;
    } QEMU_PACKED QEMU_ALIGNED(16) *get_log = (void *)cmd->payload;

    /*
     * 8.2.9.4.2
     *   The device shall return Invalid Parameter if the Offset or Length
     *   fields attempt to access beyond the size of the log as reported by Get
     *   Supported Logs.
     *
     * XXX: Spec is wrong, "Invalid Parameter" isn't a thing.
     * XXX: Spec doesn't address incorrect UUID incorrectness.
     *
     * The CEL buffer is large enough to fit all commands in the emulation, so
     * the only possible failure would be if the mailbox itself isn't big
     * enough.
     */
    if (get_log->offset + get_log->length > cxl_dstate->payload_size) {
        return CXL_MBOX_INVALID_INPUT;
    }

    if (!qemu_uuid_is_equal(&get_log->uuid, &cel_uuid)) {
        return CXL_MBOX_UNSUPPORTED;
    }

    /* Store off everything to local variables so we can wipe out the payload */
    *len = get_log->length;

    memmove(cmd->payload, cxl_dstate->cel_log + get_log->offset,
           get_log->length);

    return CXL_MBOX_SUCCESS;
}

/* 8.2.9.5.1.1 */
static CXLRetCode cmd_identify_memory_device(struct cxl_cmd *cmd,
                                             CXLDeviceState *cxl_dstate,
                                             uint16_t *len)
{
    struct {
        char fw_revision[0x10];
        uint64_t total_capacity;
        uint64_t volatile_capacity;
        uint64_t persistent_capacity;
        uint64_t partition_align;
        uint16_t info_event_log_size;
        uint16_t warning_event_log_size;
        uint16_t failure_event_log_size;
        uint16_t fatal_event_log_size;
        uint32_t lsa_size;
        uint8_t poison_list_max_mer[3];
        uint16_t inject_poison_limit;
        uint8_t poison_caps;
        uint8_t qos_telemetry_caps;
    } QEMU_PACKED *id;
    QEMU_BUILD_BUG_ON(sizeof(*id) != 0x43);

    CXLType3Dev *ct3d = container_of(cxl_dstate, CXLType3Dev, cxl_dstate);
    CXLType3Class *cvc = CXL_TYPE3_GET_CLASS(ct3d);

    if ((!QEMU_IS_ALIGNED(cxl_dstate->vmem_size, CXL_CAPACITY_MULTIPLIER)) ||
        (!QEMU_IS_ALIGNED(cxl_dstate->pmem_size, CXL_CAPACITY_MULTIPLIER))) {
        return CXL_MBOX_INTERNAL_ERROR;
    }

    id = (void *)cmd->payload;
    memset(id, 0, sizeof(*id));

    snprintf(id->fw_revision, 0x10, "BWFW VERSION %02d", 0);

    stq_le_p(&id->total_capacity, cxl_dstate->mem_size / CXL_CAPACITY_MULTIPLIER);
    stq_le_p(&id->persistent_capacity, cxl_dstate->pmem_size / CXL_CAPACITY_MULTIPLIER);
    stq_le_p(&id->volatile_capacity, cxl_dstate->vmem_size / CXL_CAPACITY_MULTIPLIER);
    stl_le_p(&id->lsa_size, cvc->get_lsa_size(ct3d));
    /* 256 poison records */
    st24_le_p(id->poison_list_max_mer, 256);
    /* No limit - so limited by main poison record limit */
    stw_le_p(&id->inject_poison_limit, 0);

    *len = sizeof(*id);
    return CXL_MBOX_SUCCESS;
}

static CXLRetCode cmd_ccls_get_partition_info(struct cxl_cmd *cmd,
                                              CXLDeviceState *cxl_dstate,
                                              uint16_t *len)
{
    struct {
        uint64_t active_vmem;
        uint64_t active_pmem;
        uint64_t next_vmem;
        uint64_t next_pmem;
    } QEMU_PACKED *part_info = (void *)cmd->payload;
    QEMU_BUILD_BUG_ON(sizeof(*part_info) != 0x20);

    if ((!QEMU_IS_ALIGNED(cxl_dstate->vmem_size, CXL_CAPACITY_MULTIPLIER)) ||
        (!QEMU_IS_ALIGNED(cxl_dstate->pmem_size, CXL_CAPACITY_MULTIPLIER))) {
        return CXL_MBOX_INTERNAL_ERROR;
    }

    stq_le_p(&part_info->active_vmem, cxl_dstate->vmem_size / CXL_CAPACITY_MULTIPLIER);
    /*
     * When both next_vmem and next_pmem are 0, there is no pending change to
     * partitioning.
     */
    stq_le_p(&part_info->next_vmem, 0);
    stq_le_p(&part_info->active_pmem, cxl_dstate->pmem_size / CXL_CAPACITY_MULTIPLIER);
    stq_le_p(&part_info->next_pmem, 0);

    *len = sizeof(*part_info);
    return CXL_MBOX_SUCCESS;
}

static CXLRetCode cmd_ccls_get_lsa(struct cxl_cmd *cmd,
                                   CXLDeviceState *cxl_dstate,
                                   uint16_t *len)
{
    struct {
        uint32_t offset;
        uint32_t length;
    } QEMU_PACKED *get_lsa;
    CXLType3Dev *ct3d = container_of(cxl_dstate, CXLType3Dev, cxl_dstate);
    CXLType3Class *cvc = CXL_TYPE3_GET_CLASS(ct3d);
    uint32_t offset, length;

    get_lsa = (void *)cmd->payload;
    offset = get_lsa->offset;
    length = get_lsa->length;

    if (offset + length > cvc->get_lsa_size(ct3d)) {
        *len = 0;
        return CXL_MBOX_INVALID_INPUT;
    }

    *len = cvc->get_lsa(ct3d, get_lsa, length, offset);
    return CXL_MBOX_SUCCESS;
}

static CXLRetCode cmd_ccls_set_lsa(struct cxl_cmd *cmd,
                                   CXLDeviceState *cxl_dstate,
                                   uint16_t *len)
{
    struct set_lsa_pl {
        uint32_t offset;
        uint32_t rsvd;
        uint8_t data[];
    } QEMU_PACKED;
    struct set_lsa_pl *set_lsa_payload = (void *)cmd->payload;
    CXLType3Dev *ct3d = container_of(cxl_dstate, CXLType3Dev, cxl_dstate);
    CXLType3Class *cvc = CXL_TYPE3_GET_CLASS(ct3d);
    const size_t hdr_len = offsetof(struct set_lsa_pl, data);
    uint16_t plen = *len;

    *len = 0;
    if (!plen) {
        return CXL_MBOX_SUCCESS;
    }

    if (set_lsa_payload->offset + plen > cvc->get_lsa_size(ct3d) + hdr_len) {
        return CXL_MBOX_INVALID_INPUT;
    }
    plen -= hdr_len;

    cvc->set_lsa(ct3d, set_lsa_payload->data, plen, set_lsa_payload->offset);
    return CXL_MBOX_SUCCESS;
}

/*
 * This is very inefficient, but good enough for now!
 * Also the payload will always fit, so no need to handle the MORE flag and
 * make this stateful. We may want to allow longer poison lists to aid
 * testing that kernel functionality.
 */
static CXLRetCode cmd_media_get_poison_list(struct cxl_cmd *cmd,
                                            CXLDeviceState *cxl_dstate,
                                            uint16_t *len)
{
    struct get_poison_list_pl {
        uint64_t pa;
        uint64_t length;
    } QEMU_PACKED;

    struct get_poison_list_out_pl {
        uint8_t flags;
        uint8_t rsvd1;
        uint64_t overflow_timestamp;
        uint16_t count;
        uint8_t rsvd2[0x14];
        struct {
            uint64_t addr;
            uint32_t length;
            uint32_t resv;
        } QEMU_PACKED records[];
    } QEMU_PACKED;

    struct get_poison_list_pl *in = (void *)cmd->payload;
    struct get_poison_list_out_pl *out = (void *)cmd->payload;
    CXLType3Dev *ct3d = container_of(cxl_dstate, CXLType3Dev, cxl_dstate);
    uint16_t record_count = 0, i = 0;
    uint64_t query_start, query_length;
    CXLPoisonList *poison_list = &ct3d->poison_list;
    CXLPoison *ent;
    uint16_t out_pl_len;

    query_start = ldq_le_p(&in->pa);
    /* 64 byte alignemnt required */
    if (query_start & 0x3f) {
        return CXL_MBOX_INVALID_INPUT;
    }
    query_length = ldq_le_p(&in->length) * CXL_CACHE_LINE_SIZE;

    QLIST_FOREACH(ent, poison_list, node) {
        /* Check for no overlap */
        if (ent->start >= query_start + query_length ||
            ent->start + ent->length <= query_start) {
            continue;
        }
        record_count++;
    }
    out_pl_len = sizeof(*out) + record_count * sizeof(out->records[0]);
    assert(out_pl_len <= CXL_MAILBOX_MAX_PAYLOAD_SIZE);

    memset(out, 0, out_pl_len);
    QLIST_FOREACH(ent, poison_list, node) {
        uint64_t start, stop;

        /* Check for no overlap */
        if (ent->start >= query_start + query_length ||
            ent->start + ent->length <= query_start) {
            continue;
        }

        /* Deal with overlap */
        start = MAX(ROUND_DOWN(ent->start, 64ull), query_start);
        stop = MIN(ROUND_DOWN(ent->start, 64ull) + ent->length,
                   query_start + query_length);
        stq_le_p(&out->records[i].addr, start | (ent->type & 0x7));
        stl_le_p(&out->records[i].length, (stop - start) / CXL_CACHE_LINE_SIZE);
        i++;
    }
    if (ct3d->poison_list_overflowed) {
        out->flags = (1 << 1);
        stq_le_p(&out->overflow_timestamp, ct3d->poison_list_overflow_ts);
    }
    stw_le_p(&out->count, record_count);
    *len = out_pl_len;
    return CXL_MBOX_SUCCESS;
}

static CXLRetCode cmd_media_inject_poison(struct cxl_cmd *cmd,
                                          CXLDeviceState *cxl_dstate,
                                          uint16_t *len_unused)
{
    CXLType3Dev *ct3d = container_of(cxl_dstate, CXLType3Dev, cxl_dstate);
    CXLPoisonList *poison_list = &ct3d->poison_list;
    CXLPoison *ent;
    struct inject_poison_pl {
        uint64_t dpa;
    };
    struct inject_poison_pl *in = (void *)cmd->payload;
    uint64_t dpa = ldq_le_p(&in->dpa);
    CXLPoison *p;

    QLIST_FOREACH(ent, poison_list, node) {
        if (dpa >= ent->start &&
            dpa + CXL_CACHE_LINE_SIZE <= ent->start + ent->length) {
            return CXL_MBOX_SUCCESS;
        }
    }

    if (ct3d->poison_list_cnt == CXL_POISON_LIST_LIMIT) {
        return CXL_MBOX_INJECT_POISON_LIMIT;
    }
    p = g_new0(CXLPoison, 1);

    p->length = CXL_CACHE_LINE_SIZE;
    p->start = dpa;
    p->type = CXL_POISON_TYPE_INJECTED;

    /*
     * Possible todo: Merge with existing entry if next to it and if same type
     */
    QLIST_INSERT_HEAD(poison_list, p, node);
    ct3d->poison_list_cnt++;

    return CXL_MBOX_SUCCESS;
}

static CXLRetCode cmd_media_clear_poison(struct cxl_cmd *cmd,
                                         CXLDeviceState *cxl_dstate,
                                         uint16_t *len_unused)
{
    CXLType3Dev *ct3d = container_of(cxl_dstate, CXLType3Dev, cxl_dstate);
    CXLPoisonList *poison_list = &ct3d->poison_list;
    CXLType3Class *cvc = CXL_TYPE3_GET_CLASS(ct3d);
    struct clear_poison_pl {
        uint64_t dpa;
        uint8_t data[64];
    };
    CXLPoison *ent;
    uint64_t dpa;

    struct clear_poison_pl *in = (void *)cmd->payload;

    dpa = ldq_le_p(&in->dpa);
    if (dpa + CXL_CACHE_LINE_SIZE > cxl_dstate->mem_size) {
        return CXL_MBOX_INVALID_PA;
    }

    /* Clearing a region with no poison is not an error so always do so */
    if (cvc->set_cacheline) {
        if (!cvc->set_cacheline(ct3d, dpa, in->data)) {
            return CXL_MBOX_INTERNAL_ERROR;
        }
    }

    QLIST_FOREACH(ent, poison_list, node) {
        /*
         * Test for contained in entry. Simpler than general case
         * as clearing 64 bytes and entries 64 byte aligned
         */
        if ((dpa >= ent->start) && (dpa < ent->start + ent->length)) {
            break;
        }
    }
    if (!ent) {
        return CXL_MBOX_SUCCESS;
    }

    QLIST_REMOVE(ent, node);
    ct3d->poison_list_cnt--;

    if (dpa > ent->start) {
        CXLPoison *frag;
        /* Cannot overflow as replacing existing entry */

        frag = g_new0(CXLPoison, 1);

        frag->start = ent->start;
        frag->length = dpa - ent->start;
        frag->type = ent->type;

        QLIST_INSERT_HEAD(poison_list, frag, node);
        ct3d->poison_list_cnt++;
    }

    if (dpa + CXL_CACHE_LINE_SIZE < ent->start + ent->length) {
        CXLPoison *frag;

        if (ct3d->poison_list_cnt == CXL_POISON_LIST_LIMIT) {
            cxl_set_poison_list_overflowed(ct3d);
        } else {
            frag = g_new0(CXLPoison, 1);

            frag->start = dpa + CXL_CACHE_LINE_SIZE;
            frag->length = ent->start + ent->length - frag->start;
            frag->type = ent->type;
            QLIST_INSERT_HEAD(poison_list, frag, node);
            ct3d->poison_list_cnt++;
        }
    }
    /* Any fragments have been added, free original entry */
    g_free(ent);

    return CXL_MBOX_SUCCESS;
}

#define IMMEDIATE_CONFIG_CHANGE (1 << 1)
#define IMMEDIATE_DATA_CHANGE (1 << 2)
#define IMMEDIATE_POLICY_CHANGE (1 << 3)
#define IMMEDIATE_LOG_CHANGE (1 << 4)

static struct cxl_cmd cxl_cmd_set[256][256] = {
    [EVENTS][GET_RECORDS] = { "EVENTS_GET_RECORDS",
        cmd_events_get_records, 1, 0 },
    [EVENTS][CLEAR_RECORDS] = { "EVENTS_CLEAR_RECORDS",
        cmd_events_clear_records, ~0, IMMEDIATE_LOG_CHANGE },
    [EVENTS][GET_INTERRUPT_POLICY] = { "EVENTS_GET_INTERRUPT_POLICY",
        cmd_events_get_interrupt_policy, 0, 0 },
    [EVENTS][SET_INTERRUPT_POLICY] = { "EVENTS_SET_INTERRUPT_POLICY",
        cmd_events_set_interrupt_policy, 4, IMMEDIATE_CONFIG_CHANGE },
    [FIRMWARE_UPDATE][GET_INFO] = { "FIRMWARE_UPDATE_GET_INFO",
        cmd_firmware_update_get_info, 0, 0 },
    [TIMESTAMP][GET] = { "TIMESTAMP_GET", cmd_timestamp_get, 0, 0 },
    [TIMESTAMP][SET] = { "TIMESTAMP_SET", cmd_timestamp_set, 8, IMMEDIATE_POLICY_CHANGE },
    [LOGS][GET_SUPPORTED] = { "LOGS_GET_SUPPORTED", cmd_logs_get_supported, 0, 0 },
    [LOGS][GET_LOG] = { "LOGS_GET_LOG", cmd_logs_get_log, 0x18, 0 },
    [IDENTIFY][MEMORY_DEVICE] = { "IDENTIFY_MEMORY_DEVICE",
        cmd_identify_memory_device, 0, 0 },
    [CCLS][GET_PARTITION_INFO] = { "CCLS_GET_PARTITION_INFO",
        cmd_ccls_get_partition_info, 0, 0 },
    [CCLS][GET_LSA] = { "CCLS_GET_LSA", cmd_ccls_get_lsa, 8, 0 },
    [CCLS][SET_LSA] = { "CCLS_SET_LSA", cmd_ccls_set_lsa,
        ~0, IMMEDIATE_CONFIG_CHANGE | IMMEDIATE_DATA_CHANGE },
    [MEDIA_AND_POISON][GET_POISON_LIST] = { "MEDIA_AND_POISON_GET_POISON_LIST",
        cmd_media_get_poison_list, 16, 0 },
    [MEDIA_AND_POISON][INJECT_POISON] = { "MEDIA_AND_POISON_INJECT_POISON",
        cmd_media_inject_poison, 8, 0 },
    [MEDIA_AND_POISON][CLEAR_POISON] = { "MEDIA_AND_POISON_CLEAR_POISON",
        cmd_media_clear_poison, 72, 0 },
};

void cxl_process_mailbox(CXLDeviceState *cxl_dstate)
{
    uint16_t ret = CXL_MBOX_SUCCESS;
    struct cxl_cmd *cxl_cmd;
    uint64_t status_reg;
    opcode_handler h;
    uint64_t command_reg = cxl_dstate->mbox_reg_state64[R_CXL_DEV_MAILBOX_CMD];

    uint8_t set = FIELD_EX64(command_reg, CXL_DEV_MAILBOX_CMD, COMMAND_SET);
    uint8_t cmd = FIELD_EX64(command_reg, CXL_DEV_MAILBOX_CMD, COMMAND);
    uint16_t len = FIELD_EX64(command_reg, CXL_DEV_MAILBOX_CMD, LENGTH);
    cxl_cmd = &cxl_cmd_set[set][cmd];
    h = cxl_cmd->handler;
    if (h) {
        if (len == cxl_cmd->in || cxl_cmd->in == ~0) {
            cxl_cmd->payload = cxl_dstate->mbox_reg_state +
                A_CXL_DEV_CMD_PAYLOAD;
            ret = (*h)(cxl_cmd, cxl_dstate, &len);
            assert(len <= cxl_dstate->payload_size);
        } else {
            ret = CXL_MBOX_INVALID_PAYLOAD_LENGTH;
        }
    } else {
        qemu_log_mask(LOG_UNIMP, "Command %04xh not implemented\n",
                      set << 8 | cmd);
        ret = CXL_MBOX_UNSUPPORTED;
    }

    /* Set the return code */
    status_reg = FIELD_DP64(0, CXL_DEV_MAILBOX_STS, ERRNO, ret);

    /* Set the return length */
    command_reg = FIELD_DP64(command_reg, CXL_DEV_MAILBOX_CMD, COMMAND_SET, 0);
    command_reg = FIELD_DP64(command_reg, CXL_DEV_MAILBOX_CMD, COMMAND, 0);
    command_reg = FIELD_DP64(command_reg, CXL_DEV_MAILBOX_CMD, LENGTH, len);

    cxl_dstate->mbox_reg_state64[R_CXL_DEV_MAILBOX_CMD] = command_reg;
    cxl_dstate->mbox_reg_state64[R_CXL_DEV_MAILBOX_STS] = status_reg;

    /* Tell the host we're done */
    ARRAY_FIELD_DP32(cxl_dstate->mbox_reg_state32, CXL_DEV_MAILBOX_CTRL,
                     DOORBELL, 0);
}

void cxl_initialize_mailbox(CXLDeviceState *cxl_dstate)
{
    for (int set = 0; set < 256; set++) {
        for (int cmd = 0; cmd < 256; cmd++) {
            if (cxl_cmd_set[set][cmd].handler) {
                struct cxl_cmd *c = &cxl_cmd_set[set][cmd];
                struct cel_log *log =
                    &cxl_dstate->cel_log[cxl_dstate->cel_size];

                log->opcode = (set << 8) | cmd;
                log->effect = c->effect;
                cxl_dstate->cel_size++;
            }
        }
    }
}