NUM_USER_VMIDS
vmid = find_next_zero_bit(vmid_map, NUM_USER_VMIDS, cur_idx);
if (vmid != NUM_USER_VMIDS)
vmid = find_next_zero_bit(vmid_map, NUM_USER_VMIDS, 1);
WARN_ON(NUM_USER_VMIDS - 1 <= num_possible_cpus());
vmid_map = bitmap_zalloc(NUM_USER_VMIDS, GFP_KERNEL);
bitmap_zero(vmid_map, NUM_USER_VMIDS);