lib/librte_eal/linuxapp/kni/kni_misc.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright(c) 2010-2014 Intel Corporation.
   4  */
   5
   6 #include <linux/version.h>
   7 #include <linux/module.h>
   8 #include <linux/miscdevice.h>
   9 #include <linux/netdevice.h>
  10 #include <linux/etherdevice.h>
  11 #include <linux/pci.h>
  12 #include <linux/kthread.h>
  13 #include <linux/rwsem.h>
  14 #include <linux/mutex.h>
  15 #include <linux/nsproxy.h>
  16 #include <net/net_namespace.h>
  17 #include <net/netns/generic.h>
  18
  19 #include <exec-env/rte_kni_common.h>
  20
  21 #include "compat.h"
  22 #include "kni_dev.h"
  23
  24 MODULE_LICENSE("Dual BSD/GPL");
  25 MODULE_AUTHOR("Intel Corporation");
  26 MODULE_DESCRIPTION("Kernel Module for managing kni devices");
  27
  28 #define KNI_RX_LOOP_NUM 1000
  29
  30 #define KNI_MAX_DEVICES 32
  31
  32 extern const struct pci_device_id ixgbe_pci_tbl[];
  33 extern const struct pci_device_id igb_pci_tbl[];
  34
  35 /* loopback mode */
  36 static char *lo_mode;
  37
  38 /* Kernel thread mode */
  39 static char *kthread_mode;
  40 static uint32_t multiple_kthread_on;
  41
  42 #define KNI_DEV_IN_USE_BIT_NUM 0 /* Bit number for device in use */
  43
  44 static int kni_net_id;
  45
  46 struct kni_net {
  47         unsigned long device_in_use; /* device in use flag */
  48         struct mutex kni_kthread_lock;
  49         struct task_struct *kni_kthread;
  50         struct rw_semaphore kni_list_lock;
  51         struct list_head kni_list_head;
  52 };
  53
  54 static int __net_init
  55 kni_init_net(struct net *net)
  56 {
  57 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
  58         struct kni_net *knet = net_generic(net, kni_net_id);
  59
  60         memset(knet, 0, sizeof(*knet));
  61 #else
  62         struct kni_net *knet;
  63         int ret;
  64
  65         knet = kzalloc(sizeof(struct kni_net), GFP_KERNEL);
  66         if (!knet) {
  67                 ret = -ENOMEM;
  68                 return ret;
  69         }
  70 #endif
  71
  72         /* Clear the bit of device in use */
  73         clear_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use);
  74
  75         mutex_init(&knet->kni_kthread_lock);
  76
  77         init_rwsem(&knet->kni_list_lock);
  78         INIT_LIST_HEAD(&knet->kni_list_head);
  79
  80 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
  81         return 0;
  82 #else
  83         ret = net_assign_generic(net, kni_net_id, knet);
  84         if (ret < 0)
  85                 kfree(knet);
  86
  87         return ret;
  88 #endif
  89 }
  90
  91 static void __net_exit
  92 kni_exit_net(struct net *net)
  93 {
  94         struct kni_net *knet __maybe_unused;
  95
  96         knet = net_generic(net, kni_net_id);
  97         mutex_destroy(&knet->kni_kthread_lock);
  98
  99 #ifndef HAVE_SIMPLIFIED_PERNET_OPERATIONS
 100         kfree(knet);
 101 #endif
 102 }
 103
 104 static struct pernet_operations kni_net_ops = {
 105         .init = kni_init_net,
 106         .exit = kni_exit_net,
 107 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
 108         .id   = &kni_net_id,
 109         .size = sizeof(struct kni_net),
 110 #endif
 111 };
 112
 113 static int
 114 kni_thread_single(void *data)
 115 {
 116         struct kni_net *knet = data;
 117         int j;
 118         struct kni_dev *dev;
 119
 120         while (!kthread_should_stop()) {
 121                 down_read(&knet->kni_list_lock);
 122                 for (j = 0; j < KNI_RX_LOOP_NUM; j++) {
 123                         list_for_each_entry(dev, &knet->kni_list_head, list) {
 124                                 kni_net_rx(dev);
 125                                 kni_net_poll_resp(dev);
 126                         }
 127                 }
 128                 up_read(&knet->kni_list_lock);
 129 #ifdef RTE_KNI_PREEMPT_DEFAULT
 130                 /* reschedule out for a while */
 131                 schedule_timeout_interruptible(
 132                         usecs_to_jiffies(KNI_KTHREAD_RESCHEDULE_INTERVAL));
 133 #endif
 134         }
 135
 136         return 0;
 137 }
 138
 139 static int
 140 kni_thread_multiple(void *param)
 141 {
 142         int j;
 143         struct kni_dev *dev = param;
 144
 145         while (!kthread_should_stop()) {
 146                 for (j = 0; j < KNI_RX_LOOP_NUM; j++) {
 147                         kni_net_rx(dev);
 148                         kni_net_poll_resp(dev);
 149                 }
 150 #ifdef RTE_KNI_PREEMPT_DEFAULT
 151                 schedule_timeout_interruptible(
 152                         usecs_to_jiffies(KNI_KTHREAD_RESCHEDULE_INTERVAL));
 153 #endif
 154         }
 155
 156         return 0;
 157 }
 158
 159 static int
 160 kni_open(struct inode *inode, struct file *file)
 161 {
 162         struct net *net = current->nsproxy->net_ns;
 163         struct kni_net *knet = net_generic(net, kni_net_id);
 164
 165         /* kni device can be opened by one user only per netns */
 166         if (test_and_set_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use))
 167                 return -EBUSY;
 168
 169         file->private_data = get_net(net);
 170         pr_debug("/dev/kni opened\n");
 171
 172         return 0;
 173 }
 174
 175 static int
 176 kni_dev_remove(struct kni_dev *dev)
 177 {
 178         if (!dev)
 179                 return -ENODEV;
 180
 181 #ifdef RTE_KNI_KMOD_ETHTOOL
 182         if (dev->pci_dev) {
 183                 if (pci_match_id(ixgbe_pci_tbl, dev->pci_dev))
 184                         ixgbe_kni_remove(dev->pci_dev);
 185                 else if (pci_match_id(igb_pci_tbl, dev->pci_dev))
 186                         igb_kni_remove(dev->pci_dev);
 187         }
 188 #endif
 189
 190         if (dev->net_dev) {
 191                 unregister_netdev(dev->net_dev);
 192                 free_netdev(dev->net_dev);
 193         }
 194
 195         return 0;
 196 }
 197
 198 static int
 199 kni_release(struct inode *inode, struct file *file)
 200 {
 201         struct net *net = file->private_data;
 202         struct kni_net *knet = net_generic(net, kni_net_id);
 203         struct kni_dev *dev, *n;
 204
 205         /* Stop kernel thread for single mode */
 206         if (multiple_kthread_on == 0) {
 207                 mutex_lock(&knet->kni_kthread_lock);
 208                 /* Stop kernel thread */
 209                 if (knet->kni_kthread != NULL) {
 210                         kthread_stop(knet->kni_kthread);
 211                         knet->kni_kthread = NULL;
 212                 }
 213                 mutex_unlock(&knet->kni_kthread_lock);
 214         }
 215
 216         down_write(&knet->kni_list_lock);
 217         list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
 218                 /* Stop kernel thread for multiple mode */
 219                 if (multiple_kthread_on && dev->pthread != NULL) {
 220                         kthread_stop(dev->pthread);
 221                         dev->pthread = NULL;
 222                 }
 223
 224                 kni_dev_remove(dev);
 225                 list_del(&dev->list);
 226         }
 227         up_write(&knet->kni_list_lock);
 228
 229         /* Clear the bit of device in use */
 230         clear_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use);
 231
 232         put_net(net);
 233         pr_debug("/dev/kni closed\n");
 234
 235         return 0;
 236 }
 237
 238 static int
 239 kni_check_param(struct kni_dev *kni, struct rte_kni_device_info *dev)
 240 {
 241         if (!kni || !dev)
 242                 return -1;
 243
 244         /* Check if network name has been used */
 245         if (!strncmp(kni->name, dev->name, RTE_KNI_NAMESIZE)) {
 246                 pr_err("KNI name %s duplicated\n", dev->name);
 247                 return -1;
 248         }
 249
 250         return 0;
 251 }
 252
 253 static int
 254 kni_run_thread(struct kni_net *knet, struct kni_dev *kni, uint8_t force_bind)
 255 {
 256         /**
 257          * Create a new kernel thread for multiple mode, set its core affinity,
 258          * and finally wake it up.
 259          */
 260         if (multiple_kthread_on) {
 261                 kni->pthread = kthread_create(kni_thread_multiple,
 262                         (void *)kni, "kni_%s", kni->name);
 263                 if (IS_ERR(kni->pthread)) {
 264                         kni_dev_remove(kni);
 265                         return -ECANCELED;
 266                 }
 267
 268                 if (force_bind)
 269                         kthread_bind(kni->pthread, kni->core_id);
 270                 wake_up_process(kni->pthread);
 271         } else {
 272                 mutex_lock(&knet->kni_kthread_lock);
 273
 274                 if (knet->kni_kthread == NULL) {
 275                         knet->kni_kthread = kthread_create(kni_thread_single,
 276                                 (void *)knet, "kni_single");
 277                         if (IS_ERR(knet->kni_kthread)) {
 278                                 mutex_unlock(&knet->kni_kthread_lock);
 279                                 kni_dev_remove(kni);
 280                                 return -ECANCELED;
 281                         }
 282
 283                         if (force_bind)
 284                                 kthread_bind(knet->kni_kthread, kni->core_id);
 285                         wake_up_process(knet->kni_kthread);
 286                 }
 287
 288                 mutex_unlock(&knet->kni_kthread_lock);
 289         }
 290
 291         return 0;
 292 }
 293
 294 static int
 295 kni_ioctl_create(struct net *net, uint32_t ioctl_num,
 296                 unsigned long ioctl_param)
 297 {
 298         struct kni_net *knet = net_generic(net, kni_net_id);
 299         int ret;
 300         struct rte_kni_device_info dev_info;
 301         struct net_device *net_dev = NULL;
 302         struct kni_dev *kni, *dev, *n;
 303 #ifdef RTE_KNI_KMOD_ETHTOOL
 304         struct pci_dev *found_pci = NULL;
 305         struct net_device *lad_dev = NULL;
 306         struct pci_dev *pci = NULL;
 307 #endif
 308
 309         pr_info("Creating kni...\n");
 310         /* Check the buffer size, to avoid warning */
 311         if (_IOC_SIZE(ioctl_num) > sizeof(dev_info))
 312                 return -EINVAL;
 313
 314         /* Copy kni info from user space */
 315         ret = copy_from_user(&dev_info, (void *)ioctl_param, sizeof(dev_info));
 316         if (ret) {
 317                 pr_err("copy_from_user in kni_ioctl_create");
 318                 return -EIO;
 319         }
 320
 321         /* Check if name is zero-ended */
 322         if (strnlen(dev_info.name, sizeof(dev_info.name)) == sizeof(dev_info.name)) {
 323                 pr_err("kni.name not zero-terminated");
 324                 return -EINVAL;
 325         }
 326
 327         /**
 328          * Check if the cpu core id is valid for binding.
 329          */
 330         if (dev_info.force_bind && !cpu_online(dev_info.core_id)) {
 331                 pr_err("cpu %u is not online\n", dev_info.core_id);
 332                 return -EINVAL;
 333         }
 334
 335         /* Check if it has been created */
 336         down_read(&knet->kni_list_lock);
 337         list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
 338                 if (kni_check_param(dev, &dev_info) < 0) {
 339                         up_read(&knet->kni_list_lock);
 340                         return -EINVAL;
 341                 }
 342         }
 343         up_read(&knet->kni_list_lock);
 344
 345         net_dev = alloc_netdev(sizeof(struct kni_dev), dev_info.name,
 346 #ifdef NET_NAME_USER
 347                                                         NET_NAME_USER,
 348 #endif
 349                                                         kni_net_init);
 350         if (net_dev == NULL) {
 351                 pr_err("error allocating device \"%s\"\n", dev_info.name);
 352                 return -EBUSY;
 353         }
 354
 355         dev_net_set(net_dev, net);
 356
 357         kni = netdev_priv(net_dev);
 358
 359         kni->net_dev = net_dev;
 360         kni->group_id = dev_info.group_id;
 361         kni->core_id = dev_info.core_id;
 362         strncpy(kni->name, dev_info.name, RTE_KNI_NAMESIZE);
 363
 364         /* Translate user space info into kernel space info */
 365         kni->tx_q = phys_to_virt(dev_info.tx_phys);
 366         kni->rx_q = phys_to_virt(dev_info.rx_phys);
 367         kni->alloc_q = phys_to_virt(dev_info.alloc_phys);
 368         kni->free_q = phys_to_virt(dev_info.free_phys);
 369
 370         kni->req_q = phys_to_virt(dev_info.req_phys);
 371         kni->resp_q = phys_to_virt(dev_info.resp_phys);
 372         kni->sync_va = dev_info.sync_va;
 373         kni->sync_kva = phys_to_virt(dev_info.sync_phys);
 374
 375         kni->mbuf_size = dev_info.mbuf_size;
 376
 377         pr_debug("tx_phys:      0x%016llx, tx_q addr:      0x%p\n",
 378                 (unsigned long long) dev_info.tx_phys, kni->tx_q);
 379         pr_debug("rx_phys:      0x%016llx, rx_q addr:      0x%p\n",
 380                 (unsigned long long) dev_info.rx_phys, kni->rx_q);
 381         pr_debug("alloc_phys:   0x%016llx, alloc_q addr:   0x%p\n",
 382                 (unsigned long long) dev_info.alloc_phys, kni->alloc_q);
 383         pr_debug("free_phys:    0x%016llx, free_q addr:    0x%p\n",
 384                 (unsigned long long) dev_info.free_phys, kni->free_q);
 385         pr_debug("req_phys:     0x%016llx, req_q addr:     0x%p\n",
 386                 (unsigned long long) dev_info.req_phys, kni->req_q);
 387         pr_debug("resp_phys:    0x%016llx, resp_q addr:    0x%p\n",
 388                 (unsigned long long) dev_info.resp_phys, kni->resp_q);
 389         pr_debug("mbuf_size:    %u\n", kni->mbuf_size);
 390
 391         pr_debug("PCI: %02x:%02x.%02x %04x:%04x\n",
 392                                         dev_info.bus,
 393                                         dev_info.devid,
 394                                         dev_info.function,
 395                                         dev_info.vendor_id,
 396                                         dev_info.device_id);
 397 #ifdef RTE_KNI_KMOD_ETHTOOL
 398         pci = pci_get_device(dev_info.vendor_id, dev_info.device_id, NULL);
 399
 400         /* Support Ethtool */
 401         while (pci) {
 402                 pr_debug("pci_bus: %02x:%02x:%02x\n",
 403                                         pci->bus->number,
 404                                         PCI_SLOT(pci->devfn),
 405                                         PCI_FUNC(pci->devfn));
 406
 407                 if ((pci->bus->number == dev_info.bus) &&
 408                         (PCI_SLOT(pci->devfn) == dev_info.devid) &&
 409                         (PCI_FUNC(pci->devfn) == dev_info.function)) {
 410                         found_pci = pci;
 411
 412                         if (pci_match_id(ixgbe_pci_tbl, found_pci))
 413                                 ret = ixgbe_kni_probe(found_pci, &lad_dev);
 414                         else if (pci_match_id(igb_pci_tbl, found_pci))
 415                                 ret = igb_kni_probe(found_pci, &lad_dev);
 416                         else
 417                                 ret = -1;
 418
 419                         pr_debug("PCI found: pci=0x%p, lad_dev=0x%p\n",
 420                                                         pci, lad_dev);
 421                         if (ret == 0) {
 422                                 kni->lad_dev = lad_dev;
 423                                 kni_set_ethtool_ops(kni->net_dev);
 424                         } else {
 425                                 pr_err("Device not supported by ethtool");
 426                                 kni->lad_dev = NULL;
 427                         }
 428
 429                         kni->pci_dev = found_pci;
 430                         kni->device_id = dev_info.device_id;
 431                         break;
 432                 }
 433                 pci = pci_get_device(dev_info.vendor_id,
 434                                 dev_info.device_id, pci);
 435         }
 436         if (pci)
 437                 pci_dev_put(pci);
 438 #endif
 439
 440         if (kni->lad_dev)
 441                 ether_addr_copy(net_dev->dev_addr, kni->lad_dev->dev_addr);
 442         else {
 443                 /* if user has provided a valid mac address */
 444                 if (is_valid_ether_addr((unsigned char *)(dev_info.mac_addr)))
 445                         memcpy(net_dev->dev_addr, dev_info.mac_addr, ETH_ALEN);
 446                 else
 447                         /*
 448                          * Generate random mac address. eth_random_addr() is the
 449                          * newer version of generating mac address in kernel.
 450                          */
 451                         random_ether_addr(net_dev->dev_addr);
 452         }
 453
 454         if (dev_info.mtu)
 455                 net_dev->mtu = dev_info.mtu;
 456
 457         ret = register_netdev(net_dev);
 458         if (ret) {
 459                 pr_err("error %i registering device \"%s\"\n",
 460                                         ret, dev_info.name);
 461                 kni->net_dev = NULL;
 462                 kni_dev_remove(kni);
 463                 free_netdev(net_dev);
 464                 return -ENODEV;
 465         }
 466
 467         ret = kni_run_thread(knet, kni, dev_info.force_bind);
 468         if (ret != 0)
 469                 return ret;
 470
 471         down_write(&knet->kni_list_lock);
 472         list_add(&kni->list, &knet->kni_list_head);
 473         up_write(&knet->kni_list_lock);
 474
 475         return 0;
 476 }
 477
 478 static int
 479 kni_ioctl_release(struct net *net, uint32_t ioctl_num,
 480                 unsigned long ioctl_param)
 481 {
 482         struct kni_net *knet = net_generic(net, kni_net_id);
 483         int ret = -EINVAL;
 484         struct kni_dev *dev, *n;
 485         struct rte_kni_device_info dev_info;
 486
 487         if (_IOC_SIZE(ioctl_num) > sizeof(dev_info))
 488                 return -EINVAL;
 489
 490         ret = copy_from_user(&dev_info, (void *)ioctl_param, sizeof(dev_info));
 491         if (ret) {
 492                 pr_err("copy_from_user in kni_ioctl_release");
 493                 return -EIO;
 494         }
 495
 496         /* Release the network device according to its name */
 497         if (strlen(dev_info.name) == 0)
 498                 return ret;
 499
 500         down_write(&knet->kni_list_lock);
 501         list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
 502                 if (strncmp(dev->name, dev_info.name, RTE_KNI_NAMESIZE) != 0)
 503                         continue;
 504
 505                 if (multiple_kthread_on && dev->pthread != NULL) {
 506                         kthread_stop(dev->pthread);
 507                         dev->pthread = NULL;
 508                 }
 509
 510                 kni_dev_remove(dev);
 511                 list_del(&dev->list);
 512                 ret = 0;
 513                 break;
 514         }
 515         up_write(&knet->kni_list_lock);
 516         pr_info("%s release kni named %s\n",
 517                 (ret == 0 ? "Successfully" : "Unsuccessfully"), dev_info.name);
 518
 519         return ret;
 520 }
 521
 522 static int
 523 kni_ioctl(struct inode *inode, uint32_t ioctl_num, unsigned long ioctl_param)
 524 {
 525         int ret = -EINVAL;
 526         struct net *net = current->nsproxy->net_ns;
 527
 528         pr_debug("IOCTL num=0x%0x param=0x%0lx\n", ioctl_num, ioctl_param);
 529
 530         /*
 531          * Switch according to the ioctl called
 532          */
 533         switch (_IOC_NR(ioctl_num)) {
 534         case _IOC_NR(RTE_KNI_IOCTL_TEST):
 535                 /* For test only, not used */
 536                 break;
 537         case _IOC_NR(RTE_KNI_IOCTL_CREATE):
 538                 ret = kni_ioctl_create(net, ioctl_num, ioctl_param);
 539                 break;
 540         case _IOC_NR(RTE_KNI_IOCTL_RELEASE):
 541                 ret = kni_ioctl_release(net, ioctl_num, ioctl_param);
 542                 break;
 543         default:
 544                 pr_debug("IOCTL default\n");
 545                 break;
 546         }
 547
 548         return ret;
 549 }
 550
 551 static int
 552 kni_compat_ioctl(struct inode *inode, uint32_t ioctl_num,
 553                 unsigned long ioctl_param)
 554 {
 555         /* 32 bits app on 64 bits OS to be supported later */
 556         pr_debug("Not implemented.\n");
 557
 558         return -EINVAL;
 559 }
 560
 561 static const struct file_operations kni_fops = {
 562         .owner = THIS_MODULE,
 563         .open = kni_open,
 564         .release = kni_release,
 565         .unlocked_ioctl = (void *)kni_ioctl,
 566         .compat_ioctl = (void *)kni_compat_ioctl,
 567 };
 568
 569 static struct miscdevice kni_misc = {
 570         .minor = MISC_DYNAMIC_MINOR,
 571         .name = KNI_DEVICE,
 572         .fops = &kni_fops,
 573 };
 574
 575 static int __init
 576 kni_parse_kthread_mode(void)
 577 {
 578         if (!kthread_mode)
 579                 return 0;
 580
 581         if (strcmp(kthread_mode, "single") == 0)
 582                 return 0;
 583         else if (strcmp(kthread_mode, "multiple") == 0)
 584                 multiple_kthread_on = 1;
 585         else
 586                 return -1;
 587
 588         return 0;
 589 }
 590
 591 static int __init
 592 kni_init(void)
 593 {
 594         int rc;
 595
 596         if (kni_parse_kthread_mode() < 0) {
 597                 pr_err("Invalid parameter for kthread_mode\n");
 598                 return -EINVAL;
 599         }
 600
 601         if (multiple_kthread_on == 0)
 602                 pr_debug("Single kernel thread for all KNI devices\n");
 603         else
 604                 pr_debug("Multiple kernel thread mode enabled\n");
 605
 606 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
 607         rc = register_pernet_subsys(&kni_net_ops);
 608 #else
 609         rc = register_pernet_gen_subsys(&kni_net_id, &kni_net_ops);
 610 #endif
 611         if (rc)
 612                 return -EPERM;
 613
 614         rc = misc_register(&kni_misc);
 615         if (rc != 0) {
 616                 pr_err("Misc registration failed\n");
 617                 goto out;
 618         }
 619
 620         /* Configure the lo mode according to the input parameter */
 621         kni_net_config_lo_mode(lo_mode);
 622
 623         return 0;
 624
 625 out:
 626 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
 627         unregister_pernet_subsys(&kni_net_ops);
 628 #else
 629         unregister_pernet_gen_subsys(kni_net_id, &kni_net_ops);
 630 #endif
 631         return rc;
 632 }
 633
 634 static void __exit
 635 kni_exit(void)
 636 {
 637         misc_deregister(&kni_misc);
 638 #ifdef HAVE_SIMPLIFIED_PERNET_OPERATIONS
 639         unregister_pernet_subsys(&kni_net_ops);
 640 #else
 641         unregister_pernet_gen_subsys(kni_net_id, &kni_net_ops);
 642 #endif
 643 }
 644
 645 module_init(kni_init);
 646 module_exit(kni_exit);
 647
 648 module_param(lo_mode, charp, S_IRUGO | S_IWUSR);
 649 MODULE_PARM_DESC(lo_mode,
 650 "KNI loopback mode (default=lo_mode_none):\n"
 651 "    lo_mode_none        Kernel loopback disabled\n"
 652 "    lo_mode_fifo        Enable kernel loopback with fifo\n"
 653 "    lo_mode_fifo_skb    Enable kernel loopback with fifo and skb buffer\n"
 654 "\n"
 655 );
 656
 657 module_param(kthread_mode, charp, S_IRUGO);
 658 MODULE_PARM_DESC(kthread_mode,
 659 "Kernel thread mode (default=single):\n"
 660 "    single    Single kernel thread mode enabled.\n"
 661 "    multiple  Multiple kernel thread mode enabled.\n"
 662 "\n"
 663 );