/*
 * Migration support for VFIO devices
 *
 * Copyright NVIDIA, Inc. 2020
 *
 * 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 "qemu/main-loop.h"
#include "qemu/cutils.h"
#include "qemu/units.h"
#include "qemu/error-report.h"
#include <linux/vfio.h>
#include <sys/ioctl.h>

#include "system/runstate.h"
#include "hw/core/boards.h"
#include "hw/vfio/vfio-device.h"
#include "hw/vfio/vfio-migration.h"
#include "migration/misc.h"
#include "migration/savevm.h"
#include "migration/vmstate.h"
#include "migration/qemu-file.h"
#include "migration/register.h"
#include "migration/blocker.h"
#include "migration-multifd.h"
#include "qapi/error.h"
#include "qapi/qapi-events-vfio.h"
#include "system/ramlist.h"
#include "pci.h"
#include "trace.h"
#include "hw/core/hw-error.h"
#include "vfio-migration-internal.h"

/*
 * This is an arbitrary size based on migration of mlx5 devices, where typically
 * total device migration size is on the order of 100s of MB. Testing with
 * larger values, e.g. 128MB and 1GB, did not show a performance improvement.
 */
#define VFIO_MIG_DEFAULT_DATA_BUFFER_SIZE (1 * MiB)

/*
 * Migration size of VFIO devices can be as little as a few KBs or as big as
 * many GBs. This value should be big enough to cover the worst case.
 */
#define VFIO_MIG_STOP_COPY_SIZE (100 * GiB)

static unsigned long bytes_transferred;

static const char *mig_state_to_str(enum vfio_device_mig_state state)
{
    switch (state) {
    case VFIO_DEVICE_STATE_ERROR:
        return "ERROR";
    case VFIO_DEVICE_STATE_STOP:
        return "STOP";
    case VFIO_DEVICE_STATE_RUNNING:
        return "RUNNING";
    case VFIO_DEVICE_STATE_STOP_COPY:
        return "STOP_COPY";
    case VFIO_DEVICE_STATE_RESUMING:
        return "RESUMING";
    case VFIO_DEVICE_STATE_RUNNING_P2P:
        return "RUNNING_P2P";
    case VFIO_DEVICE_STATE_PRE_COPY:
        return "PRE_COPY";
    case VFIO_DEVICE_STATE_PRE_COPY_P2P:
        return "PRE_COPY_P2P";
    default:
        return "UNKNOWN STATE";
    }
}

static QapiVfioMigrationState
mig_state_to_qapi_state(enum vfio_device_mig_state state, bool prepare)
{
    switch (state) {
    case VFIO_DEVICE_STATE_STOP:
        return QAPI_VFIO_MIGRATION_STATE_STOP;
    case VFIO_DEVICE_STATE_RUNNING:
        return QAPI_VFIO_MIGRATION_STATE_RUNNING;
    case VFIO_DEVICE_STATE_STOP_COPY:
        return QAPI_VFIO_MIGRATION_STATE_STOP_COPY;
    case VFIO_DEVICE_STATE_RESUMING:
        return QAPI_VFIO_MIGRATION_STATE_RESUMING;
    case VFIO_DEVICE_STATE_RUNNING_P2P:
        return QAPI_VFIO_MIGRATION_STATE_RUNNING_P2P;
    case VFIO_DEVICE_STATE_PRE_COPY:
        return QAPI_VFIO_MIGRATION_STATE_PRE_COPY;
    case VFIO_DEVICE_STATE_PRE_COPY_P2P:
        return prepare ? QAPI_VFIO_MIGRATION_STATE_PRE_COPY_P2P_PREPARE :
                         QAPI_VFIO_MIGRATION_STATE_PRE_COPY_P2P;
    default:
        g_assert_not_reached();
    }
}

static void vfio_migration_send_event(VFIODevice *vbasedev,
                                      enum vfio_device_mig_state state,
                                      bool prepare)
{
    DeviceState *dev = vbasedev->dev;
    g_autofree char *qom_path = NULL;
    Object *obj;

    if (!vbasedev->migration_events) {
        return;
    }

    g_assert(vbasedev->ops->vfio_get_object);
    obj = vbasedev->ops->vfio_get_object(vbasedev);
    g_assert(obj);
    qom_path = object_get_canonical_path(obj);

    qapi_event_send_vfio_migration(dev->id, qom_path,
                                   mig_state_to_qapi_state(state, prepare));
}

static void vfio_migration_set_device_state(VFIODevice *vbasedev,
                                            enum vfio_device_mig_state state)
{
    VFIOMigration *migration = vbasedev->migration;

    trace_vfio_migration_set_device_state(vbasedev->name,
                                          mig_state_to_str(state));

    migration->device_state = state;
    vfio_migration_send_event(vbasedev, state, false);
}

int vfio_migration_set_state(VFIODevice *vbasedev,
                             enum vfio_device_mig_state new_state,
                             enum vfio_device_mig_state recover_state,
                             Error **errp)
{
    VFIOMigration *migration = vbasedev->migration;
    uint64_t buf[DIV_ROUND_UP(sizeof(struct vfio_device_feature) +
                              sizeof(struct vfio_device_feature_mig_state),
                              sizeof(uint64_t))] = {};
    struct vfio_device_feature *feature = (struct vfio_device_feature *)buf;
    struct vfio_device_feature_mig_state *mig_state =
        (struct vfio_device_feature_mig_state *)feature->data;
    int ret;
    g_autofree char *error_prefix =
        g_strdup_printf("%s: Failed setting device state to %s.",
                        vbasedev->name, mig_state_to_str(new_state));

    trace_vfio_migration_set_state(vbasedev->name, mig_state_to_str(new_state),
                                   mig_state_to_str(recover_state));

    if (new_state == migration->device_state) {
        return 0;
    }

    /*
     * Send a prepare event before initiating the PRE_COPY_P2P transition to
     * ensure timely event delivery regardless of how long the state transition
     * takes.
     */
    if (new_state == VFIO_DEVICE_STATE_PRE_COPY_P2P) {
        vfio_migration_send_event(vbasedev, VFIO_DEVICE_STATE_PRE_COPY_P2P,
                                  true);
    }

    feature->argsz = sizeof(buf);
    feature->flags =
        VFIO_DEVICE_FEATURE_SET | VFIO_DEVICE_FEATURE_MIG_DEVICE_STATE;
    mig_state->device_state = new_state;
    if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
        /* Try to set the device in some good state */
        ret = -errno;

        if (recover_state == VFIO_DEVICE_STATE_ERROR) {
            error_setg_errno(errp, errno,
                             "%s Recover state is ERROR. Resetting device",
                             error_prefix);

            goto reset_device;
        }

        error_setg_errno(errp, errno,
                         "%s Setting device in recover state %s",
                         error_prefix, mig_state_to_str(recover_state));

        mig_state->device_state = recover_state;
        if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
            ret = -errno;
            /*
             * If setting the device in recover state fails, report
             * the error here and propagate the first error.
             */
            error_report(
                "%s: Failed setting device in recover state, err: %s. Resetting device",
                         vbasedev->name, strerror(errno));

            goto reset_device;
        }

        vfio_migration_set_device_state(vbasedev, recover_state);

        return ret;
    }

    vfio_migration_set_device_state(vbasedev, new_state);
    if (mig_state->data_fd != -1) {
        if (migration->data_fd != -1) {
            /*
             * This can happen if the device is asynchronously reset and
             * terminates a data transfer.
             */
            error_setg(errp, "%s: data_fd out of sync", vbasedev->name);
            close(mig_state->data_fd);

            return -EBADF;
        }

        migration->data_fd = mig_state->data_fd;
    }

    return 0;

reset_device:
    if (ioctl(vbasedev->fd, VFIO_DEVICE_RESET)) {
        hw_error("%s: Failed resetting device, err: %s", vbasedev->name,
                 strerror(errno));
    }

    vfio_migration_set_device_state(vbasedev, VFIO_DEVICE_STATE_RUNNING);

    return ret;
}

/*
 * Some device state transitions require resetting the device if they fail.
 * This function sets the device in new_state and resets the device if that
 * fails. Reset is done by using ERROR as the recover state.
 */
static int
vfio_migration_set_state_or_reset(VFIODevice *vbasedev,
                                  enum vfio_device_mig_state new_state,
                                  Error **errp)
{
    return vfio_migration_set_state(vbasedev, new_state,
                                    VFIO_DEVICE_STATE_ERROR, errp);
}

static int vfio_load_buffer(QEMUFile *f, VFIODevice *vbasedev,
                            uint64_t data_size)
{
    VFIOMigration *migration = vbasedev->migration;
    int ret;

    ret = qemu_file_get_to_fd(f, migration->data_fd, data_size);
    trace_vfio_load_state_device_data(vbasedev->name, data_size, ret);

    return ret;
}

int vfio_save_device_config_state(QEMUFile *f, void *opaque, Error **errp)
{
    VFIODevice *vbasedev = opaque;
    int ret;

    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_CONFIG_STATE);

    if (vbasedev->ops && vbasedev->ops->vfio_save_config) {
        ret = vbasedev->ops->vfio_save_config(vbasedev, f, errp);
        if (ret) {
            return ret;
        }
    }

    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);

    trace_vfio_save_device_config_state(vbasedev->name);

    ret = qemu_file_get_error(f);
    if (ret < 0) {
        error_setg_errno(errp, -ret, "Failed to save state");
    }
    return ret;
}

int vfio_load_device_config_state(QEMUFile *f, void *opaque)
{
    VFIODevice *vbasedev = opaque;
    uint64_t data;

    trace_vfio_load_device_config_state_start(vbasedev->name);

    if (vbasedev->ops && vbasedev->ops->vfio_load_config) {
        int ret;

        ret = vbasedev->ops->vfio_load_config(vbasedev, f);
        if (ret) {
            error_report("%s: Failed to load device config space",
                         vbasedev->name);
            return ret;
        }
    }

    data = qemu_get_be64(f);
    if (data != VFIO_MIG_FLAG_END_OF_STATE) {
        error_report("%s: Failed loading device config space, "
                     "end flag incorrect 0x%"PRIx64, vbasedev->name, data);
        return -EINVAL;
    }

    trace_vfio_load_device_config_state_end(vbasedev->name);
    return qemu_file_get_error(f);
}

static void vfio_migration_cleanup(VFIODevice *vbasedev)
{
    VFIOMigration *migration = vbasedev->migration;

    close(migration->data_fd);
    migration->data_fd = -1;
}

static bool vfio_migration_check_overflow(VFIODevice *vbasedev, uint64_t size,
                                          const char *name)
{
    if (size > INT64_MAX) {
        error_report("%s: Estimated %s size overflow: 0x%"PRIx64,
                     vbasedev->name, name, size);
        return true;
    }

    return false;
}

static int vfio_query_stop_copy_size(VFIODevice *vbasedev)
{
    uint64_t buf[DIV_ROUND_UP(sizeof(struct vfio_device_feature) +
                              sizeof(struct vfio_device_feature_mig_data_size),
                              sizeof(uint64_t))] = {};
    struct vfio_device_feature *feature = (struct vfio_device_feature *)buf;
    struct vfio_device_feature_mig_data_size *mig_data_size =
        (struct vfio_device_feature_mig_data_size *)feature->data;
    VFIOMigration *migration = vbasedev->migration;
    int ret = 0;

    feature->argsz = sizeof(buf);
    feature->flags =
        VFIO_DEVICE_FEATURE_GET | VFIO_DEVICE_FEATURE_MIG_DATA_SIZE;

    if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
        /*
         * If getting pending migration size fails, VFIO_MIG_STOP_COPY_SIZE
         * is reported so downtime limit won't be violated.
         */
        migration->stopcopy_size = VFIO_MIG_STOP_COPY_SIZE;
        ret = -errno;
        warn_report_once("VFIO device %s ioctl(VFIO_DEVICE_FEATURE) on "
                         "VFIO_DEVICE_FEATURE_MIG_DATA_SIZE failed (%d)",
                         vbasedev->name, ret);
    } else {
        migration->stopcopy_size = mig_data_size->stop_copy_length;
        if (vfio_migration_check_overflow(vbasedev, migration->stopcopy_size,
                                          "stop copy size")) {
            ret = -ERANGE;
        }
    }

    trace_vfio_query_stop_copy_size(vbasedev->name,
                                    migration->stopcopy_size, ret);

    return ret;
}

static int vfio_query_precopy_size(VFIOMigration *migration)
{
    struct vfio_precopy_info precopy = {
        .argsz = sizeof(precopy),
    };
    int ret = 0;

    if (ioctl(migration->data_fd, VFIO_MIG_GET_PRECOPY_INFO, &precopy)) {
        migration->precopy_init_size = 0;
        migration->precopy_dirty_size = 0;
        ret = -errno;
        warn_report_once("VFIO device %s ioctl(VFIO_MIG_GET_PRECOPY_INFO) "
                         "failed (%d)", migration->vbasedev->name, ret);
    } else {
        bool overflow;

        migration->precopy_init_size = precopy.initial_bytes;
        migration->precopy_dirty_size = precopy.dirty_bytes;

        overflow  = vfio_migration_check_overflow(migration->vbasedev,
                         migration->precopy_init_size,  "precopy init size");
        overflow |= vfio_migration_check_overflow(migration->vbasedev,
                         migration->precopy_dirty_size, "precopy dirty size");
        if (overflow) {
            ret = -ERANGE;
        }
    }

    trace_vfio_query_precopy_size(migration->vbasedev->name,
                                  migration->precopy_init_size,
                                  migration->precopy_dirty_size, ret);

    return ret;
}

/* Returns the size of saved data on success and -errno on error */
static ssize_t vfio_save_block(QEMUFile *f, VFIOMigration *migration)
{
    ssize_t data_size;

    data_size = read(migration->data_fd, migration->data_buffer,
                     migration->data_buffer_size);
    if (data_size < 0) {
        /*
         * Pre-copy emptied all the device state for now. For more information,
         * please refer to the Linux kernel VFIO uAPI.
         */
        if (errno == ENOMSG) {
            if (!migration->event_precopy_empty_hit) {
                trace_vfio_save_block_precopy_empty_hit(migration->vbasedev->name);
                migration->event_precopy_empty_hit = true;
            }
            return 0;
        }

        return -errno;
    }
    if (data_size == 0) {
        return 0;
    }

    /* Non-empty read: re-arm the trace event */
    migration->event_precopy_empty_hit = false;

    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_DATA_STATE);
    qemu_put_be64(f, data_size);
    qemu_put_buffer(f, migration->data_buffer, data_size);
    vfio_migration_add_bytes_transferred(data_size);

    trace_vfio_save_block(migration->vbasedev->name, data_size);

    return qemu_file_get_error(f) ?: data_size;
}

static void vfio_update_estimated_pending_data(VFIOMigration *migration,
                                               uint64_t data_size)
{
    if (!data_size) {
        /*
         * Pre-copy emptied all the device state for now, update estimated sizes
         * accordingly.
         */
        migration->precopy_init_size = 0;
        migration->precopy_dirty_size = 0;

        return;
    }

    /*
     * The total size remaining requires separate accounting.  Do not trust
     * the counter, so what we have read() may be more than what reported.
     */
    if (migration->stopcopy_size > data_size) {
        migration->stopcopy_size -= data_size;
    } else {
        migration->stopcopy_size = 0;
    }

    if (migration->precopy_init_size) {
        uint64_t init_size = MIN(migration->precopy_init_size, data_size);

        migration->precopy_init_size -= init_size;
        data_size -= init_size;
    }

    migration->precopy_dirty_size -= MIN(migration->precopy_dirty_size,
                                         data_size);
}

static bool vfio_precopy_supported(VFIODevice *vbasedev)
{
    VFIOMigration *migration = vbasedev->migration;

    return migration->mig_flags & VFIO_MIGRATION_PRE_COPY;
}

/* ---------------------------------------------------------------------- */

static int vfio_save_prepare(void *opaque, Error **errp)
{
    VFIODevice *vbasedev = opaque;

    /*
     * Snapshot doesn't use postcopy nor background snapshot, so allow snapshot
     * even if they are on.
     */
    if (runstate_check(RUN_STATE_SAVE_VM)) {
        return 0;
    }

    if (migrate_postcopy_ram()) {
        error_setg(
            errp, "%s: VFIO migration is not supported with postcopy migration",
            vbasedev->name);
        return -EOPNOTSUPP;
    }

    if (migrate_background_snapshot()) {
        error_setg(
            errp,
            "%s: VFIO migration is not supported with background snapshot",
            vbasedev->name);
        return -EOPNOTSUPP;
    }

    return 0;
}

static int vfio_save_setup(QEMUFile *f, void *opaque, Error **errp)
{
    VFIODevice *vbasedev = opaque;
    VFIOMigration *migration = vbasedev->migration;
    int ret;

    if (!vfio_multifd_setup(vbasedev, false, errp)) {
        return -EINVAL;
    }

    qemu_put_be64(f, VFIO_MIG_FLAG_DEV_SETUP_STATE);

    vfio_query_stop_copy_size(vbasedev);
    migration->data_buffer_size = MIN(VFIO_MIG_DEFAULT_DATA_BUFFER_SIZE,
                                      migration->stopcopy_size);
    migration->data_buffer = g_try_malloc0(migration->data_buffer_size);
    if (!migration->data_buffer) {
        error_setg(errp, "%s: Failed to allocate migration data buffer",
                   vbasedev->name);
        return -ENOMEM;
    }

    migration->event_save_iterate_started = false;
    migration->event_precopy_empty_hit = false;

    if (vfio_precopy_supported(vbasedev)) {
        switch (migration->device_state) {
        case VFIO_DEVICE_STATE_RUNNING:
            ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_PRE_COPY,
                                           VFIO_DEVICE_STATE_RUNNING, errp);
            if (ret) {
                return ret;
            }

            vfio_query_precopy_size(migration);

            break;
        case VFIO_DEVICE_STATE_STOP:
            /* vfio_save_complete_precopy() will go to STOP_COPY */
            break;
        default:
            error_setg(errp, "%s: Invalid device state %d", vbasedev->name,
                       migration->device_state);
            return -EINVAL;
        }
    }

    trace_vfio_save_setup(vbasedev->name, migration->data_buffer_size);

    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);

    ret = qemu_file_get_error(f);
    if (ret < 0) {
        error_setg_errno(errp, -ret, "%s: save setup failed", vbasedev->name);
    }

    return ret;
}

static void vfio_save_cleanup(void *opaque)
{
    VFIODevice *vbasedev = opaque;
    VFIOMigration *migration = vbasedev->migration;
    Error *local_err = NULL;
    int ret;

    /* Currently a NOP, done for symmetry with load_cleanup() */
    vfio_multifd_cleanup(vbasedev);

    /*
     * Changing device state from STOP_COPY to STOP can take time. Do it here,
     * after migration has completed, so it won't increase downtime.
     */
    if (migration->device_state == VFIO_DEVICE_STATE_STOP_COPY) {
        ret = vfio_migration_set_state_or_reset(vbasedev,
                                                VFIO_DEVICE_STATE_STOP,
                                                &local_err);
        if (ret) {
            error_report_err(local_err);
        }
    }

    g_free(migration->data_buffer);
    migration->data_buffer = NULL;
    migration->precopy_init_size = 0;
    migration->precopy_dirty_size = 0;
    migration->initial_data_sent = false;
    vfio_migration_cleanup(vbasedev);
    trace_vfio_save_cleanup(vbasedev->name);
}

static void vfio_state_pending_sync(VFIODevice *vbasedev)
{
    VFIOMigration *migration = vbasedev->migration;

    vfio_query_stop_copy_size(vbasedev);

    if (vfio_device_state_is_precopy(vbasedev)) {
        vfio_query_precopy_size(migration);
    }
}

static void vfio_state_pending(void *opaque, MigPendingData *pending,
                               bool exact)
{
    VFIODevice *vbasedev = opaque;
    VFIOMigration *migration = vbasedev->migration;
    uint64_t precopy_size, stopcopy_size;

    if (exact) {
        vfio_state_pending_sync(vbasedev);
    }

    precopy_size =
        migration->precopy_init_size + migration->precopy_dirty_size;

    if (migration->stopcopy_size > precopy_size) {
        stopcopy_size = migration->stopcopy_size - precopy_size;
    } else {
        stopcopy_size = 0;
    }

    pending->precopy_bytes += precopy_size;
    pending->stopcopy_bytes += stopcopy_size;

    trace_vfio_state_pending(vbasedev->name, migration->stopcopy_size,
                             migration->precopy_init_size,
                             migration->precopy_dirty_size, exact);
}

static bool vfio_is_active_iterate(void *opaque)
{
    VFIODevice *vbasedev = opaque;

    return vfio_device_state_is_precopy(vbasedev);
}

/*
 * Note about migration rate limiting: VFIO migration buffer size is currently
 * limited to 1MB, so there is no need to check if migration rate exceeded (as
 * in the worst case it will exceed by 1MB). However, if the buffer size is
 * later changed to a bigger value, migration rate should be enforced here.
 */
static int vfio_save_iterate(QEMUFile *f, void *opaque)
{
    VFIODevice *vbasedev = opaque;
    VFIOMigration *migration = vbasedev->migration;
    ssize_t data_size;

    if (!migration->event_save_iterate_started) {
        trace_vfio_save_iterate_start(vbasedev->name);
        migration->event_save_iterate_started = true;
    }

    data_size = vfio_save_block(f, migration);
    if (data_size < 0) {
        return data_size;
    }

    vfio_update_estimated_pending_data(migration, data_size);

    if (migrate_switchover_ack() && !migration->precopy_init_size &&
        !migration->initial_data_sent) {
        qemu_put_be64(f, VFIO_MIG_FLAG_DEV_INIT_DATA_SENT);
        migration->initial_data_sent = true;
    } else {
        qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
    }

    trace_vfio_save_iterate(vbasedev->name, migration->precopy_init_size,
                            migration->precopy_dirty_size);

    return !migration->precopy_init_size && !migration->precopy_dirty_size;
}

static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
{
    VFIODevice *vbasedev = opaque;
    ssize_t data_size;
    int ret;
    Error *local_err = NULL;

    if (vfio_multifd_transfer_enabled(vbasedev)) {
        vfio_multifd_emit_dummy_eos(vbasedev, f);
        return 0;
    }

    trace_vfio_save_complete_precopy_start(vbasedev->name);

    /* We reach here with device state STOP or STOP_COPY only */
    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP_COPY,
                                   VFIO_DEVICE_STATE_STOP, &local_err);
    if (ret) {
        error_report_err(local_err);
        return ret;
    }

    do {
        data_size = vfio_save_block(f, vbasedev->migration);
        if (data_size < 0) {
            return data_size;
        }
    } while (data_size);

    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
    ret = qemu_file_get_error(f);

    trace_vfio_save_complete_precopy(vbasedev->name, ret);

    return ret;
}

static void vfio_save_state(QEMUFile *f, void *opaque)
{
    VFIODevice *vbasedev = opaque;
    Error *local_err = NULL;
    int ret;

    if (vfio_multifd_transfer_enabled(vbasedev)) {
        if (vfio_load_config_after_iter(vbasedev)) {
            qemu_put_be64(f, VFIO_MIG_FLAG_DEV_CONFIG_LOAD_READY);
        } else {
            vfio_multifd_emit_dummy_eos(vbasedev, f);
        }
        return;
    }

    ret = vfio_save_device_config_state(f, opaque, &local_err);
    if (ret) {
        error_prepend(&local_err,
                      "vfio: Failed to save device config space of %s - ",
                      vbasedev->name);
        qemu_file_set_error_obj(f, ret, local_err);
    }
}

static int vfio_load_setup(QEMUFile *f, void *opaque, Error **errp)
{
    VFIODevice *vbasedev = opaque;
    VFIOMigration *migration = vbasedev->migration;
    int ret;

    if (!vfio_multifd_setup(vbasedev, true, errp)) {
        return -EINVAL;
    }

    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RESUMING,
                                   migration->device_state, errp);
    if (ret) {
        return ret;
    }

    return 0;
}

static int vfio_load_cleanup(void *opaque)
{
    VFIODevice *vbasedev = opaque;

    vfio_multifd_cleanup(vbasedev);

    vfio_migration_cleanup(vbasedev);
    trace_vfio_load_cleanup(vbasedev->name);

    return 0;
}

static int vfio_load_state(QEMUFile *f, void *opaque, int version_id)
{
    VFIODevice *vbasedev = opaque;
    int ret = 0;
    uint64_t data;

    data = qemu_get_be64(f);
    while (data != VFIO_MIG_FLAG_END_OF_STATE) {

        trace_vfio_load_state(vbasedev->name, data);

        switch (data) {
        case VFIO_MIG_FLAG_DEV_CONFIG_STATE:
        {
            if (vfio_multifd_transfer_enabled(vbasedev)) {
                error_report("%s: got DEV_CONFIG_STATE in main migration "
                             "channel but doing multifd transfer",
                             vbasedev->name);
                return -EINVAL;
            }

            return vfio_load_device_config_state(f, opaque);
        }
        case VFIO_MIG_FLAG_DEV_SETUP_STATE:
        {
            data = qemu_get_be64(f);
            if (data == VFIO_MIG_FLAG_END_OF_STATE) {
                return ret;
            } else {
                error_report("%s: SETUP STATE: EOS not found 0x%"PRIx64,
                             vbasedev->name, data);
                return -EINVAL;
            }
            break;
        }
        case VFIO_MIG_FLAG_DEV_DATA_STATE:
        {
            uint64_t data_size = qemu_get_be64(f);

            if (data_size) {
                ret = vfio_load_buffer(f, vbasedev, data_size);
                if (ret < 0) {
                    return ret;
                }
            }
            break;
        }
        case VFIO_MIG_FLAG_DEV_INIT_DATA_SENT:
        {
            if (!vfio_precopy_supported(vbasedev) ||
                !migrate_switchover_ack()) {
                error_report("%s: Received INIT_DATA_SENT but switchover ack "
                             "is not used", vbasedev->name);
                return -EINVAL;
            }

            ret = qemu_loadvm_approve_switchover();
            if (ret) {
                error_report(
                    "%s: qemu_loadvm_approve_switchover failed, err=%d (%s)",
                    vbasedev->name, ret, strerror(-ret));
            }

            return ret;
        }
        case VFIO_MIG_FLAG_DEV_CONFIG_LOAD_READY:
        {
            return vfio_load_state_config_load_ready(vbasedev);
        }
        default:
            error_report("%s: Unknown tag 0x%"PRIx64, vbasedev->name, data);
            return -EINVAL;
        }

        data = qemu_get_be64(f);
        ret = qemu_file_get_error(f);
        if (ret) {
            return ret;
        }
    }
    return ret;
}

static bool vfio_switchover_ack_needed(void *opaque)
{
    VFIODevice *vbasedev = opaque;

    return vfio_precopy_supported(vbasedev);
}

static int vfio_switchover_start(void *opaque)
{
    VFIODevice *vbasedev = opaque;

    if (vfio_multifd_transfer_enabled(vbasedev)) {
        return vfio_multifd_switchover_start(vbasedev);
    }

    return 0;
}

static const SaveVMHandlers savevm_vfio_handlers = {
    .save_prepare = vfio_save_prepare,
    .save_setup = vfio_save_setup,
    .save_cleanup = vfio_save_cleanup,
    .save_query_pending = vfio_state_pending,
    .is_active_iterate = vfio_is_active_iterate,
    .save_live_iterate = vfio_save_iterate,
    .save_complete = vfio_save_complete_precopy,
    .save_state = vfio_save_state,
    .load_setup = vfio_load_setup,
    .load_cleanup = vfio_load_cleanup,
    .load_state = vfio_load_state,
    .switchover_ack_needed = vfio_switchover_ack_needed,
    /*
     * Multifd support
     */
    .load_state_buffer = vfio_multifd_load_state_buffer,
    .switchover_start = vfio_switchover_start,
    .save_complete_precopy_thread = vfio_multifd_save_complete_precopy_thread,
};

/* ---------------------------------------------------------------------- */

static void vfio_vmstate_change_prepare(void *opaque, bool running,
                                        RunState state)
{
    VFIODevice *vbasedev = opaque;
    VFIOMigration *migration = vbasedev->migration;
    enum vfio_device_mig_state new_state;
    Error *local_err = NULL;
    int ret;

    new_state = migration->device_state == VFIO_DEVICE_STATE_PRE_COPY ?
                    VFIO_DEVICE_STATE_PRE_COPY_P2P :
                    VFIO_DEVICE_STATE_RUNNING_P2P;

    ret = vfio_migration_set_state_or_reset(vbasedev, new_state, &local_err);
    if (ret) {
        /*
         * Migration should be aborted in this case, but vm_state_notify()
         * currently does not support reporting failures.
         */
        migration_file_set_error(ret, local_err);
    }

    trace_vfio_vmstate_change_prepare(vbasedev->name, running,
                                      RunState_str(state),
                                      mig_state_to_str(new_state));
}

static void vfio_vmstate_change(void *opaque, bool running, RunState state)
{
    VFIODevice *vbasedev = opaque;
    enum vfio_device_mig_state new_state;
    Error *local_err = NULL;
    int ret;

    if (running) {
        new_state = VFIO_DEVICE_STATE_RUNNING;
    } else {
        new_state =
            (vfio_device_state_is_precopy(vbasedev) &&
             (state == RUN_STATE_FINISH_MIGRATE || state == RUN_STATE_PAUSED)) ?
                VFIO_DEVICE_STATE_STOP_COPY :
                VFIO_DEVICE_STATE_STOP;
    }

    ret = vfio_migration_set_state_or_reset(vbasedev, new_state, &local_err);
    if (ret) {
        /*
         * Migration should be aborted in this case, but vm_state_notify()
         * currently does not support reporting failures.
         */
        migration_file_set_error(ret, local_err);
    }

    trace_vfio_vmstate_change(vbasedev->name, running, RunState_str(state),
                              mig_state_to_str(new_state));
}

static int vfio_migration_state_notifier(NotifierWithReturn *notifier,
                                         MigrationEvent *e, Error **errp)
{
    VFIOMigration *migration = container_of(notifier, VFIOMigration,
                                            migration_state);
    VFIODevice *vbasedev = migration->vbasedev;
    Error *local_err = NULL;
    int ret;

    trace_vfio_migration_state_notifier(vbasedev->name, e->type);

    if (e->type == MIG_EVENT_FAILED) {
        /*
         * MigrationNotifyFunc may not return an error code and an Error
         * object for MIG_EVENT_FAILED. Hence, report the error
         * locally and ignore the errp argument.
         */
        ret = vfio_migration_set_state_or_reset(vbasedev,
                                                VFIO_DEVICE_STATE_RUNNING,
                                                &local_err);
        if (ret) {
            error_report_err(local_err);
        }
    }
    return 0;
}

static void vfio_migration_free(VFIODevice *vbasedev)
{
    g_free(vbasedev->migration);
    vbasedev->migration = NULL;
}

static int vfio_migration_query_flags(VFIODevice *vbasedev, uint64_t *mig_flags)
{
    uint64_t buf[DIV_ROUND_UP(sizeof(struct vfio_device_feature) +
                                  sizeof(struct vfio_device_feature_migration),
                              sizeof(uint64_t))] = {};
    struct vfio_device_feature *feature = (struct vfio_device_feature *)buf;
    struct vfio_device_feature_migration *mig =
        (struct vfio_device_feature_migration *)feature->data;

    feature->argsz = sizeof(buf);
    feature->flags = VFIO_DEVICE_FEATURE_GET | VFIO_DEVICE_FEATURE_MIGRATION;
    if (ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature)) {
        return -errno;
    }

    *mig_flags = mig->flags;

    return 0;
}

static bool vfio_dma_logging_supported(VFIODevice *vbasedev)
{
    uint64_t buf[DIV_ROUND_UP(sizeof(struct vfio_device_feature),
                              sizeof(uint64_t))] = {};
    struct vfio_device_feature *feature = (struct vfio_device_feature *)buf;

    feature->argsz = sizeof(buf);
    feature->flags = VFIO_DEVICE_FEATURE_PROBE |
                     VFIO_DEVICE_FEATURE_DMA_LOGGING_START;

    return !ioctl(vbasedev->fd, VFIO_DEVICE_FEATURE, feature);
}

static int vfio_migration_init(VFIODevice *vbasedev)
{
    int ret;
    Object *obj;
    VFIOMigration *migration;
    char id[256] = "";
    g_autofree char *path = NULL, *oid = NULL;
    uint64_t mig_flags = 0;
    VMChangeStateHandler *prepare_cb;

    if (!vbasedev->ops->vfio_get_object) {
        return -EINVAL;
    }

    obj = vbasedev->ops->vfio_get_object(vbasedev);
    if (!obj) {
        return -EINVAL;
    }

    ret = vfio_migration_query_flags(vbasedev, &mig_flags);
    if (ret) {
        return ret;
    }

    /* Basic migration functionality must be supported */
    if (!(mig_flags & VFIO_MIGRATION_STOP_COPY)) {
        return -EOPNOTSUPP;
    }

    vbasedev->migration = g_new0(VFIOMigration, 1);
    migration = vbasedev->migration;
    migration->vbasedev = vbasedev;
    migration->device_state = VFIO_DEVICE_STATE_RUNNING;
    migration->data_fd = -1;
    migration->mig_flags = mig_flags;

    vbasedev->dirty_pages_supported = vfio_dma_logging_supported(vbasedev);

    oid = vmstate_if_get_id(VMSTATE_IF(DEVICE(obj)));
    if (oid) {
        path = g_strdup_printf("%s/vfio", oid);
    } else {
        path = g_strdup("vfio");
    }
    strpadcpy(id, sizeof(id), path, '\0');

    register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1, &savevm_vfio_handlers,
                         vbasedev);

    prepare_cb = migration->mig_flags & VFIO_MIGRATION_P2P ?
                     vfio_vmstate_change_prepare :
                     NULL;
    migration->vm_state = qdev_add_vm_change_state_handler_full(
        vbasedev->dev, vfio_vmstate_change, prepare_cb, NULL, vbasedev);
    migration_add_notifier(&migration->migration_state,
                           vfio_migration_state_notifier);

    return 0;
}

static Error *multiple_devices_migration_blocker;

/*
 * Multiple devices migration is allowed only if all devices support P2P
 * migration. Single device migration is allowed regardless of P2P migration
 * support.
 */
static bool vfio_multiple_devices_migration_is_supported(void)
{
    VFIODevice *vbasedev;
    unsigned int device_num = 0;
    bool all_support_p2p = true;

    QLIST_FOREACH(vbasedev, &vfio_device_list, global_next) {
        if (vbasedev->migration) {
            device_num++;

            if (!(vbasedev->migration->mig_flags & VFIO_MIGRATION_P2P)) {
                all_support_p2p = false;
            }
        }
    }

    return all_support_p2p || device_num <= 1;
}

static int vfio_block_multiple_devices_migration(VFIODevice *vbasedev, Error **errp)
{
    if (vfio_multiple_devices_migration_is_supported()) {
        return 0;
    }

    if (vbasedev->enable_migration == ON_OFF_AUTO_ON) {
        error_setg(errp, "Multiple VFIO devices migration is supported only if "
                         "all of them support P2P migration");
        return -EINVAL;
    }

    if (multiple_devices_migration_blocker) {
        return 0;
    }

    error_setg(&multiple_devices_migration_blocker,
               "Multiple VFIO devices migration is supported only if all of "
               "them support P2P migration");
    return migrate_add_blocker_normal(&multiple_devices_migration_blocker,
                                      errp);
}

static void vfio_unblock_multiple_devices_migration(void)
{
    if (!multiple_devices_migration_blocker ||
        !vfio_multiple_devices_migration_is_supported()) {
        return;
    }

    migrate_del_blocker(&multiple_devices_migration_blocker);
}

static void vfio_migration_deinit(VFIODevice *vbasedev)
{
    VFIOMigration *migration = vbasedev->migration;

    migration_remove_notifier(&migration->migration_state);
    qemu_del_vm_change_state_handler(migration->vm_state);
    unregister_savevm(VMSTATE_IF(vbasedev->dev), "vfio", vbasedev);
    vfio_migration_free(vbasedev);
    vfio_unblock_multiple_devices_migration();
}

static int vfio_block_migration(VFIODevice *vbasedev, Error *err, Error **errp)
{
    if (vbasedev->enable_migration == ON_OFF_AUTO_ON) {
        error_propagate(errp, err);
        return -EINVAL;
    }

    vbasedev->migration_blocker = error_copy(err);
    error_free(err);

    return migrate_add_blocker_normal(&vbasedev->migration_blocker, errp);
}

/* ---------------------------------------------------------------------- */

int64_t vfio_migration_bytes_transferred(void)
{
    return MIN(qatomic_read(&bytes_transferred), INT64_MAX);
}

void vfio_migration_reset_bytes_transferred(void)
{
    qatomic_set(&bytes_transferred, 0);
}

void vfio_migration_add_bytes_transferred(unsigned long val)
{
    qatomic_add(&bytes_transferred, val);
}

bool vfio_migration_active(void)
{
    VFIODevice *vbasedev;

    if (QLIST_EMPTY(&vfio_device_list)) {
        return false;
    }

    QLIST_FOREACH(vbasedev, &vfio_device_list, global_next) {
        if (vbasedev->migration_blocker) {
            return false;
        }
    }
    return true;
}

static bool vfio_viommu_preset(VFIODevice *vbasedev)
{
    return vbasedev->bcontainer->space->as != &address_space_memory;
}

static bool vfio_dirty_tracking_exceed_limit(VFIODevice *vbasedev)
{
    VFIOContainer *bcontainer = vbasedev->bcontainer;
    uint64_t max_size, page_size;

    if (!bcontainer->dirty_pages_supported) {
        return false;
    }

    /*
     * VFIO IOMMU type1 driver has limitation of bitmap size on unmap_bitmap
     * ioctl(), calculate the limit and compare with guest memory size to
     * catch dirty tracking failure early.
     *
     * This limit is 8TB with default kernel and QEMU config, we are a bit
     * conservative here as VM memory layout may be nonconsecutive or VM
     * can run with vIOMMU enabled so the limitation could be relaxed. One
     * can also switch to use IOMMUFD backend if there is a need to migrate
     * large VM.
     */
    page_size = 1ULL << ctz64(bcontainer->dirty_pgsizes);
    max_size = bcontainer->max_dirty_bitmap_size * BITS_PER_BYTE * page_size;

    return current_machine->ram_size > max_size;
}

/*
 * Return true when either migration initialized or blocker registered.
 * Currently only return false when adding blocker fails which will
 * de-register vfio device.
 */
bool vfio_migration_realize(VFIODevice *vbasedev, Error **errp)
{
    Error *err = NULL;
    int ret;

    if (vbasedev->enable_migration == ON_OFF_AUTO_OFF) {
        error_setg(&err, "%s: Migration is disabled for VFIO device",
                   vbasedev->name);
        return !vfio_block_migration(vbasedev, err, errp);
    }

    ret = vfio_migration_init(vbasedev);
    if (ret) {
        if (ret == -ENOTTY) {
            error_setg(&err, "%s: VFIO migration is not supported in kernel",
                       vbasedev->name);
        } else {
            error_setg(&err,
                       "%s: Migration couldn't be initialized for VFIO device, "
                       "err: %d (%s)",
                       vbasedev->name, ret, strerror(-ret));
        }

        return !vfio_block_migration(vbasedev, err, errp);
    }

    if (vfio_device_dirty_pages_disabled(vbasedev) &&
        !vbasedev->iommu_dirty_tracking) {
        if (vbasedev->enable_migration == ON_OFF_AUTO_AUTO) {
            error_setg(&err,
                       "%s: VFIO device doesn't support device and "
                       "IOMMU dirty tracking", vbasedev->name);
            goto add_blocker;
        }

        if (vfio_dirty_tracking_exceed_limit(vbasedev)) {
            error_setg(&err, "%s: Migration is currently not supported with "
                       "large memory VM due to dirty tracking limitation in "
                       "backend", vbasedev->name);
            goto add_blocker;
        }

        warn_report("%s: VFIO device doesn't support device and "
                    "IOMMU dirty tracking", vbasedev->name);
    }

    ret = vfio_block_multiple_devices_migration(vbasedev, errp);
    if (ret) {
        goto out_deinit;
    }

    if (!vfio_device_dirty_pages_disabled(vbasedev) &&
        vfio_viommu_preset(vbasedev)) {
        error_setg(&err, "%s: Migration is currently not supported "
                   "with vIOMMU enabled", vbasedev->name);
        goto add_blocker;
    }

    trace_vfio_migration_realize(vbasedev->name);
    return true;

add_blocker:
    ret = vfio_block_migration(vbasedev, err, errp);
out_deinit:
    if (ret) {
        vfio_migration_deinit(vbasedev);
    }
    return !ret;
}

void vfio_migration_exit(VFIODevice *vbasedev)
{
    if (vbasedev->migration) {
        vfio_migration_deinit(vbasedev);
    }

    migrate_del_blocker(&vbasedev->migration_blocker);
}

bool vfio_device_state_is_running(VFIODevice *vbasedev)
{
    VFIOMigration *migration = vbasedev->migration;

    return migration->device_state == VFIO_DEVICE_STATE_RUNNING ||
           migration->device_state == VFIO_DEVICE_STATE_RUNNING_P2P;
}

bool vfio_device_state_is_precopy(VFIODevice *vbasedev)
{
    VFIOMigration *migration = vbasedev->migration;

    return migration->device_state == VFIO_DEVICE_STATE_PRE_COPY ||
           migration->device_state == VFIO_DEVICE_STATE_PRE_COPY_P2P;
}
