void memory_region_add_eventfd(MemoryRegion *mr,
                               hwaddr addr,
                               unsigned size,
                               bool match_data,
                               uint64_t data,
                               EventNotifier *e)
{
    MemoryRegionIoeventfd mrfd = {
        .addr.start = int128_make64(addr),
        .addr.size = int128_make64(size),
        .match_data = match_data,
        .data = data,
        .e = e,
    };
    unsigned i;
    if (size) {
        adjust_endianness(mr, &mrfd.data, size);
    memory_region_transaction_begin();
    for (i = 0; i < mr->ioeventfd_nb; ++i) {
        if (memory_region_ioeventfd_before(mrfd, mr->ioeventfds[i])) {
            break;
    ++mr->ioeventfd_nb;
    mr->ioeventfds = g_realloc(mr->ioeventfds,
                                  sizeof(*mr->ioeventfds) * mr->ioeventfd_nb);
    memmove(&mr->ioeventfds[i+1], &mr->ioeventfds[i],
            sizeof(*mr->ioeventfds) * (mr->ioeventfd_nb-1 - i));
    mr->ioeventfds[i] = mrfd;
    ioeventfd_update_pending |= mr->enabled;
    memory_region_transaction_commit();