lib/librte_eal/linuxapp/kni/kni_misc.c

   1 /*-
   2  * GPL LICENSE SUMMARY
   3  *
   4  *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
   5  *
   6  *   This program is free software; you can redistribute it and/or modify
   7  *   it under the terms of version 2 of the GNU General Public License as
   8  *   published by the Free Software Foundation.
   9  *
  10  *   This program is distributed in the hope that it will be useful, but
  11  *   WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  *   General Public License for more details.
  14  *
  15  *   You should have received a copy of the GNU General Public License
  16  *   along with this program; if not, write to the Free Software
  17  *   Foundation, Inc., 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
  18  *   The full GNU General Public License is included in this distribution
  19  *   in the file called LICENSE.GPL.
  20  *
  21  *   Contact Information:
  22  *   Intel Corporation
  23  */
  24
  25 #include <linux/module.h>
  26 #include <linux/miscdevice.h>
  27 #include <linux/netdevice.h>
  28 #include <linux/pci.h>
  29 #include <linux/kthread.h>
  30 #include <linux/rwsem.h>
  31 #include <linux/nsproxy.h>
  32 #include <net/net_namespace.h>
  33 #include <net/netns/generic.h>
  34
  35 #include <exec-env/rte_kni_common.h>
  36 #include "kni_dev.h"
  37 #include <rte_config.h>
  38
  39 MODULE_LICENSE("Dual BSD/GPL");
  40 MODULE_AUTHOR("Intel Corporation");
  41 MODULE_DESCRIPTION("Kernel Module for managing kni devices");
  42
  43 #define KNI_RX_LOOP_NUM 1000
  44
  45 #define KNI_MAX_DEVICES 32
  46
  47 extern void kni_net_rx(struct kni_dev *kni);
  48 extern void kni_net_init(struct net_device *dev);
  49 extern void kni_net_config_lo_mode(char *lo_str);
  50 extern void kni_net_poll_resp(struct kni_dev *kni);
  51 extern void kni_set_ethtool_ops(struct net_device *netdev);
  52
  53 extern int ixgbe_kni_probe(struct pci_dev *pdev, struct net_device **lad_dev);
  54 extern void ixgbe_kni_remove(struct pci_dev *pdev);
  55 extern int igb_kni_probe(struct pci_dev *pdev, struct net_device **lad_dev);
  56 extern void igb_kni_remove(struct pci_dev *pdev);
  57
  58 static int kni_open(struct inode *inode, struct file *file);
  59 static int kni_release(struct inode *inode, struct file *file);
  60 static int kni_ioctl(struct inode *inode, unsigned int ioctl_num,
  61                                         unsigned long ioctl_param);
  62 static int kni_compat_ioctl(struct inode *inode, unsigned int ioctl_num,
  63                                                 unsigned long ioctl_param);
  64 static int kni_dev_remove(struct kni_dev *dev);
  65
  66 static int __init kni_parse_kthread_mode(void);
  67
  68 /* KNI processing for single kernel thread mode */
  69 static int kni_thread_single(void *unused);
  70 /* KNI processing for multiple kernel thread mode */
  71 static int kni_thread_multiple(void *param);
  72
  73 static struct file_operations kni_fops = {
  74         .owner = THIS_MODULE,
  75         .open = kni_open,
  76         .release = kni_release,
  77         .unlocked_ioctl = (void *)kni_ioctl,
  78         .compat_ioctl = (void *)kni_compat_ioctl,
  79 };
  80
  81 static struct miscdevice kni_misc = {
  82         .minor = MISC_DYNAMIC_MINOR,
  83         .name = KNI_DEVICE,
  84         .fops = &kni_fops,
  85 };
  86
  87 /* loopback mode */
  88 static char *lo_mode = NULL;
  89
  90 /* Kernel thread mode */
  91 static char *kthread_mode = NULL;
  92 static unsigned multiple_kthread_on = 0;
  93
  94 #define KNI_DEV_IN_USE_BIT_NUM 0 /* Bit number for device in use */
  95
  96 static int kni_net_id;
  97
  98 struct kni_net {
  99         unsigned long device_in_use; /* device in use flag */
 100         struct task_struct *kni_kthread;
 101         struct rw_semaphore kni_list_lock;
 102         struct list_head kni_list_head;
 103 };
 104
 105 static __net_init int kni_init_net(struct net *net)
 106 {
 107         struct kni_net *knet = net_generic(net, kni_net_id);
 108
 109         /* Clear the bit of device in use */
 110         clear_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use);
 111
 112         init_rwsem(&knet->kni_list_lock);
 113         INIT_LIST_HEAD(&knet->kni_list_head);
 114
 115         return 0;
 116 }
 117
 118 static struct pernet_operations kni_net_ops = {
 119         .init = kni_init_net,
 120         .exit = NULL,
 121         .id   = &kni_net_id,
 122         .size = sizeof(struct kni_net),
 123 };
 124
 125 static int __init
 126 kni_init(void)
 127 {
 128         int rc;
 129
 130         KNI_PRINT("######## DPDK kni module loading ########\n");
 131
 132         if (kni_parse_kthread_mode() < 0) {
 133                 KNI_ERR("Invalid parameter for kthread_mode\n");
 134                 return -EINVAL;
 135         }
 136
 137         rc = register_pernet_subsys(&kni_net_ops);
 138         if (rc)
 139                 return -EPERM;
 140
 141         rc = misc_register(&kni_misc);
 142         if (rc != 0) {
 143                 KNI_ERR("Misc registration failed\n");
 144                 goto out;
 145         }
 146
 147         /* Configure the lo mode according to the input parameter */
 148         kni_net_config_lo_mode(lo_mode);
 149
 150         KNI_PRINT("######## DPDK kni module loaded  ########\n");
 151
 152         return 0;
 153
 154 out:
 155         unregister_pernet_subsys(&kni_net_ops);
 156         return rc;
 157 }
 158
 159 static void __exit
 160 kni_exit(void)
 161 {
 162         misc_deregister(&kni_misc);
 163         unregister_pernet_subsys(&kni_net_ops);
 164         KNI_PRINT("####### DPDK kni module unloaded  #######\n");
 165 }
 166
 167 static int __init
 168 kni_parse_kthread_mode(void)
 169 {
 170         if (!kthread_mode)
 171                 return 0;
 172
 173         if (strcmp(kthread_mode, "single") == 0)
 174                 return 0;
 175         else if (strcmp(kthread_mode, "multiple") == 0)
 176                 multiple_kthread_on = 1;
 177         else
 178                 return -1;
 179
 180         return 0;
 181 }
 182
 183 static int
 184 kni_open(struct inode *inode, struct file *file)
 185 {
 186         struct net *net = current->nsproxy->net_ns;
 187         struct kni_net *knet = net_generic(net, kni_net_id);
 188
 189         /* kni device can be opened by one user only per netns */
 190         if (test_and_set_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use))
 191                 return -EBUSY;
 192
 193         /* Create kernel thread for single mode */
 194         if (multiple_kthread_on == 0) {
 195                 KNI_PRINT("Single kernel thread for all KNI devices\n");
 196                 /* Create kernel thread for RX */
 197                 knet->kni_kthread = kthread_run(kni_thread_single, (void *)knet,
 198                                                 "kni_single");
 199                 if (IS_ERR(knet->kni_kthread)) {
 200                         KNI_ERR("Unable to create kernel threaed\n");
 201                         return PTR_ERR(knet->kni_kthread);
 202                 }
 203         } else
 204                 KNI_PRINT("Multiple kernel thread mode enabled\n");
 205
 206         file->private_data = get_net(net);
 207         KNI_PRINT("/dev/kni opened\n");
 208
 209         return 0;
 210 }
 211
 212 static int
 213 kni_release(struct inode *inode, struct file *file)
 214 {
 215         struct net *net = file->private_data;
 216         struct kni_net *knet = net_generic(net, kni_net_id);
 217         struct kni_dev *dev, *n;
 218
 219         /* Stop kernel thread for single mode */
 220         if (multiple_kthread_on == 0) {
 221                 /* Stop kernel thread */
 222                 kthread_stop(knet->kni_kthread);
 223                 knet->kni_kthread = NULL;
 224         }
 225
 226         down_write(&knet->kni_list_lock);
 227         list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
 228                 /* Stop kernel thread for multiple mode */
 229                 if (multiple_kthread_on && dev->pthread != NULL) {
 230                         kthread_stop(dev->pthread);
 231                         dev->pthread = NULL;
 232                 }
 233
 234 #ifdef RTE_KNI_VHOST
 235                 kni_vhost_backend_release(dev);
 236 #endif
 237                 kni_dev_remove(dev);
 238                 list_del(&dev->list);
 239         }
 240         up_write(&knet->kni_list_lock);
 241
 242         /* Clear the bit of device in use */
 243         clear_bit(KNI_DEV_IN_USE_BIT_NUM, &knet->device_in_use);
 244
 245         put_net(net);
 246         KNI_PRINT("/dev/kni closed\n");
 247
 248         return 0;
 249 }
 250
 251 static int
 252 kni_thread_single(void *data)
 253 {
 254         struct kni_net *knet = data;
 255         int j;
 256         struct kni_dev *dev;
 257
 258         while (!kthread_should_stop()) {
 259                 down_read(&knet->kni_list_lock);
 260                 for (j = 0; j < KNI_RX_LOOP_NUM; j++) {
 261                         list_for_each_entry(dev, &knet->kni_list_head, list) {
 262 #ifdef RTE_KNI_VHOST
 263                                 kni_chk_vhost_rx(dev);
 264 #else
 265                                 kni_net_rx(dev);
 266 #endif
 267                                 kni_net_poll_resp(dev);
 268                         }
 269                 }
 270                 up_read(&knet->kni_list_lock);
 271 #ifdef RTE_KNI_PREEMPT_DEFAULT
 272                 /* reschedule out for a while */
 273                 schedule_timeout_interruptible(usecs_to_jiffies( \
 274                                 KNI_KTHREAD_RESCHEDULE_INTERVAL));
 275 #endif
 276         }
 277
 278         return 0;
 279 }
 280
 281 static int
 282 kni_thread_multiple(void *param)
 283 {
 284         int j;
 285         struct kni_dev *dev = (struct kni_dev *)param;
 286
 287         while (!kthread_should_stop()) {
 288                 for (j = 0; j < KNI_RX_LOOP_NUM; j++) {
 289 #ifdef RTE_KNI_VHOST
 290                         kni_chk_vhost_rx(dev);
 291 #else
 292                         kni_net_rx(dev);
 293 #endif
 294                         kni_net_poll_resp(dev);
 295                 }
 296 #ifdef RTE_KNI_PREEMPT_DEFAULT
 297                 schedule_timeout_interruptible(usecs_to_jiffies( \
 298                                 KNI_KTHREAD_RESCHEDULE_INTERVAL));
 299 #endif
 300         }
 301
 302         return 0;
 303 }
 304
 305 static int
 306 kni_dev_remove(struct kni_dev *dev)
 307 {
 308         if (!dev)
 309                 return -ENODEV;
 310
 311         switch (dev->device_id) {
 312         #define RTE_PCI_DEV_ID_DECL_IGB(vend, dev) case (dev):
 313         #include <rte_pci_dev_ids.h>
 314                 igb_kni_remove(dev->pci_dev);
 315                 break;
 316         #define RTE_PCI_DEV_ID_DECL_IXGBE(vend, dev) case (dev):
 317         #include <rte_pci_dev_ids.h>
 318                 ixgbe_kni_remove(dev->pci_dev);
 319                 break;
 320         default:
 321                 break;
 322         }
 323
 324         if (dev->net_dev) {
 325                 unregister_netdev(dev->net_dev);
 326                 free_netdev(dev->net_dev);
 327         }
 328
 329         return 0;
 330 }
 331
 332 static int
 333 kni_check_param(struct kni_dev *kni, struct rte_kni_device_info *dev)
 334 {
 335         if (!kni || !dev)
 336                 return -1;
 337
 338         /* Check if network name has been used */
 339         if (!strncmp(kni->name, dev->name, RTE_KNI_NAMESIZE)) {
 340                 KNI_ERR("KNI name %s duplicated\n", dev->name);
 341                 return -1;
 342         }
 343
 344         return 0;
 345 }
 346
 347 static int
 348 kni_ioctl_create(struct net *net,
 349                 unsigned int ioctl_num, unsigned long ioctl_param)
 350 {
 351         struct kni_net *knet = net_generic(net, kni_net_id);
 352         int ret;
 353         struct rte_kni_device_info dev_info;
 354         struct pci_dev *pci = NULL;
 355         struct pci_dev *found_pci = NULL;
 356         struct net_device *net_dev = NULL;
 357         struct net_device *lad_dev = NULL;
 358         struct kni_dev *kni, *dev, *n;
 359
 360         printk(KERN_INFO "KNI: Creating kni...\n");
 361         /* Check the buffer size, to avoid warning */
 362         if (_IOC_SIZE(ioctl_num) > sizeof(dev_info))
 363                 return -EINVAL;
 364
 365         /* Copy kni info from user space */
 366         ret = copy_from_user(&dev_info, (void *)ioctl_param, sizeof(dev_info));
 367         if (ret) {
 368                 KNI_ERR("copy_from_user in kni_ioctl_create");
 369                 return -EIO;
 370         }
 371
 372         /**
 373          * Check if the cpu core id is valid for binding,
 374          * for multiple kernel thread mode.
 375          */
 376         if (multiple_kthread_on && dev_info.force_bind &&
 377                                 !cpu_online(dev_info.core_id)) {
 378                 KNI_ERR("cpu %u is not online\n", dev_info.core_id);
 379                 return -EINVAL;
 380         }
 381
 382         /* Check if it has been created */
 383         down_read(&knet->kni_list_lock);
 384         list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
 385                 if (kni_check_param(dev, &dev_info) < 0) {
 386                         up_read(&knet->kni_list_lock);
 387                         return -EINVAL;
 388                 }
 389         }
 390         up_read(&knet->kni_list_lock);
 391
 392         net_dev = alloc_netdev(sizeof(struct kni_dev), dev_info.name,
 393 #ifdef NET_NAME_UNKNOWN
 394                                                         NET_NAME_UNKNOWN,
 395 #endif
 396                                                         kni_net_init);
 397         if (net_dev == NULL) {
 398                 KNI_ERR("error allocating device \"%s\"\n", dev_info.name);
 399                 return -EBUSY;
 400         }
 401
 402         dev_net_set(net_dev, net);
 403
 404         kni = netdev_priv(net_dev);
 405
 406         kni->net_dev = net_dev;
 407         kni->group_id = dev_info.group_id;
 408         kni->core_id = dev_info.core_id;
 409         strncpy(kni->name, dev_info.name, RTE_KNI_NAMESIZE);
 410
 411         /* Translate user space info into kernel space info */
 412         kni->tx_q = phys_to_virt(dev_info.tx_phys);
 413         kni->rx_q = phys_to_virt(dev_info.rx_phys);
 414         kni->alloc_q = phys_to_virt(dev_info.alloc_phys);
 415         kni->free_q = phys_to_virt(dev_info.free_phys);
 416
 417         kni->req_q = phys_to_virt(dev_info.req_phys);
 418         kni->resp_q = phys_to_virt(dev_info.resp_phys);
 419         kni->sync_va = dev_info.sync_va;
 420         kni->sync_kva = phys_to_virt(dev_info.sync_phys);
 421
 422         kni->mbuf_kva = phys_to_virt(dev_info.mbuf_phys);
 423         kni->mbuf_va = dev_info.mbuf_va;
 424
 425 #ifdef RTE_KNI_VHOST
 426         kni->vhost_queue = NULL;
 427         kni->vq_status = BE_STOP;
 428 #endif
 429         kni->mbuf_size = dev_info.mbuf_size;
 430
 431         KNI_PRINT("tx_phys:      0x%016llx, tx_q addr:      0x%p\n",
 432                 (unsigned long long) dev_info.tx_phys, kni->tx_q);
 433         KNI_PRINT("rx_phys:      0x%016llx, rx_q addr:      0x%p\n",
 434                 (unsigned long long) dev_info.rx_phys, kni->rx_q);
 435         KNI_PRINT("alloc_phys:   0x%016llx, alloc_q addr:   0x%p\n",
 436                 (unsigned long long) dev_info.alloc_phys, kni->alloc_q);
 437         KNI_PRINT("free_phys:    0x%016llx, free_q addr:    0x%p\n",
 438                 (unsigned long long) dev_info.free_phys, kni->free_q);
 439         KNI_PRINT("req_phys:     0x%016llx, req_q addr:     0x%p\n",
 440                 (unsigned long long) dev_info.req_phys, kni->req_q);
 441         KNI_PRINT("resp_phys:    0x%016llx, resp_q addr:    0x%p\n",
 442                 (unsigned long long) dev_info.resp_phys, kni->resp_q);
 443         KNI_PRINT("mbuf_phys:    0x%016llx, mbuf_kva:       0x%p\n",
 444                 (unsigned long long) dev_info.mbuf_phys, kni->mbuf_kva);
 445         KNI_PRINT("mbuf_va:      0x%p\n", dev_info.mbuf_va);
 446         KNI_PRINT("mbuf_size:    %u\n", kni->mbuf_size);
 447
 448         KNI_DBG("PCI: %02x:%02x.%02x %04x:%04x\n",
 449                                         dev_info.bus,
 450                                         dev_info.devid,
 451                                         dev_info.function,
 452                                         dev_info.vendor_id,
 453                                         dev_info.device_id);
 454
 455         pci = pci_get_device(dev_info.vendor_id, dev_info.device_id, NULL);
 456
 457         /* Support Ethtool */
 458         while (pci) {
 459                 KNI_PRINT("pci_bus: %02x:%02x:%02x \n",
 460                                         pci->bus->number,
 461                                         PCI_SLOT(pci->devfn),
 462                                         PCI_FUNC(pci->devfn));
 463
 464                 if ((pci->bus->number == dev_info.bus) &&
 465                         (PCI_SLOT(pci->devfn) == dev_info.devid) &&
 466                         (PCI_FUNC(pci->devfn) == dev_info.function)) {
 467                         found_pci = pci;
 468                         switch (dev_info.device_id) {
 469                         #define RTE_PCI_DEV_ID_DECL_IGB(vend, dev) case (dev):
 470                         #include <rte_pci_dev_ids.h>
 471                                 ret = igb_kni_probe(found_pci, &lad_dev);
 472                                 break;
 473                         #define RTE_PCI_DEV_ID_DECL_IXGBE(vend, dev) \
 474                                                         case (dev):
 475                         #include <rte_pci_dev_ids.h>
 476                                 ret = ixgbe_kni_probe(found_pci, &lad_dev);
 477                                 break;
 478                         default:
 479                                 ret = -1;
 480                                 break;
 481                         }
 482
 483                         KNI_DBG("PCI found: pci=0x%p, lad_dev=0x%p\n",
 484                                                         pci, lad_dev);
 485                         if (ret == 0) {
 486                                 kni->lad_dev = lad_dev;
 487                                 kni_set_ethtool_ops(kni->net_dev);
 488                         } else {
 489                                 KNI_ERR("Device not supported by ethtool");
 490                                 kni->lad_dev = NULL;
 491                         }
 492
 493                         kni->pci_dev = found_pci;
 494                         kni->device_id = dev_info.device_id;
 495                         break;
 496                 }
 497                 pci = pci_get_device(dev_info.vendor_id,
 498                                 dev_info.device_id, pci);
 499         }
 500         if (pci)
 501                 pci_dev_put(pci);
 502
 503         ret = register_netdev(net_dev);
 504         if (ret) {
 505                 KNI_ERR("error %i registering device \"%s\"\n",
 506                                         ret, dev_info.name);
 507                 kni_dev_remove(kni);
 508                 return -ENODEV;
 509         }
 510
 511 #ifdef RTE_KNI_VHOST
 512         kni_vhost_init(kni);
 513 #endif
 514
 515         /**
 516          * Create a new kernel thread for multiple mode, set its core affinity,
 517          * and finally wake it up.
 518          */
 519         if (multiple_kthread_on) {
 520                 kni->pthread = kthread_create(kni_thread_multiple,
 521                                               (void *)kni,
 522                                               "kni_%s", kni->name);
 523                 if (IS_ERR(kni->pthread)) {
 524                         kni_dev_remove(kni);
 525                         return -ECANCELED;
 526                 }
 527                 if (dev_info.force_bind)
 528                         kthread_bind(kni->pthread, kni->core_id);
 529                 wake_up_process(kni->pthread);
 530         }
 531
 532         down_write(&knet->kni_list_lock);
 533         list_add(&kni->list, &knet->kni_list_head);
 534         up_write(&knet->kni_list_lock);
 535
 536         return 0;
 537 }
 538
 539 static int
 540 kni_ioctl_release(struct net *net,
 541                 unsigned int ioctl_num, unsigned long ioctl_param)
 542 {
 543         struct kni_net *knet = net_generic(net, kni_net_id);
 544         int ret = -EINVAL;
 545         struct kni_dev *dev, *n;
 546         struct rte_kni_device_info dev_info;
 547
 548         if (_IOC_SIZE(ioctl_num) > sizeof(dev_info))
 549                         return -EINVAL;
 550
 551         ret = copy_from_user(&dev_info, (void *)ioctl_param, sizeof(dev_info));
 552         if (ret) {
 553                 KNI_ERR("copy_from_user in kni_ioctl_release");
 554                 return -EIO;
 555         }
 556
 557         /* Release the network device according to its name */
 558         if (strlen(dev_info.name) == 0)
 559                 return ret;
 560
 561         down_write(&knet->kni_list_lock);
 562         list_for_each_entry_safe(dev, n, &knet->kni_list_head, list) {
 563                 if (strncmp(dev->name, dev_info.name, RTE_KNI_NAMESIZE) != 0)
 564                         continue;
 565
 566                 if (multiple_kthread_on && dev->pthread != NULL) {
 567                         kthread_stop(dev->pthread);
 568                         dev->pthread = NULL;
 569                 }
 570
 571 #ifdef RTE_KNI_VHOST
 572                 kni_vhost_backend_release(dev);
 573 #endif
 574                 kni_dev_remove(dev);
 575                 list_del(&dev->list);
 576                 ret = 0;
 577                 break;
 578         }
 579         up_write(&knet->kni_list_lock);
 580         printk(KERN_INFO "KNI: %s release kni named %s\n",
 581                 (ret == 0 ? "Successfully" : "Unsuccessfully"), dev_info.name);
 582
 583         return ret;
 584 }
 585
 586 static int
 587 kni_ioctl(struct inode *inode,
 588         unsigned int ioctl_num,
 589         unsigned long ioctl_param)
 590 {
 591         int ret = -EINVAL;
 592         struct net *net = current->nsproxy->net_ns;
 593
 594         KNI_DBG("IOCTL num=0x%0x param=0x%0lx\n", ioctl_num, ioctl_param);
 595
 596         /*
 597          * Switch according to the ioctl called
 598          */
 599         switch (_IOC_NR(ioctl_num)) {
 600         case _IOC_NR(RTE_KNI_IOCTL_TEST):
 601                 /* For test only, not used */
 602                 break;
 603         case _IOC_NR(RTE_KNI_IOCTL_CREATE):
 604                 ret = kni_ioctl_create(net, ioctl_num, ioctl_param);
 605                 break;
 606         case _IOC_NR(RTE_KNI_IOCTL_RELEASE):
 607                 ret = kni_ioctl_release(net, ioctl_num, ioctl_param);
 608                 break;
 609         default:
 610                 KNI_DBG("IOCTL default\n");
 611                 break;
 612         }
 613
 614         return ret;
 615 }
 616
 617 static int
 618 kni_compat_ioctl(struct inode *inode,
 619                 unsigned int ioctl_num,
 620                 unsigned long ioctl_param)
 621 {
 622         /* 32 bits app on 64 bits OS to be supported later */
 623         KNI_PRINT("Not implemented.\n");
 624
 625         return -EINVAL;
 626 }
 627
 628 module_init(kni_init);
 629 module_exit(kni_exit);
 630
 631 module_param(lo_mode, charp, S_IRUGO | S_IWUSR);
 632 MODULE_PARM_DESC(lo_mode,
 633 "KNI loopback mode (default=lo_mode_none):\n"
 634 "    lo_mode_none        Kernel loopback disabled\n"
 635 "    lo_mode_fifo        Enable kernel loopback with fifo\n"
 636 "    lo_mode_fifo_skb    Enable kernel loopback with fifo and skb buffer\n"
 637 "\n"
 638 );
 639
 640 module_param(kthread_mode, charp, S_IRUGO);
 641 MODULE_PARM_DESC(kthread_mode,
 642 "Kernel thread mode (default=single):\n"
 643 "    single    Single kernel thread mode enabled.\n"
 644 "    multiple  Multiple kernel thread mode enabled.\n"
 645 "\n"
 646 );