drivers/xen/pvcalls-front.c

   1 /*
   2  * (c) 2017 Stefano Stabellini <stefano@aporeto.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/net.h>
  17 #include <linux/socket.h>
  18
  19 #include <net/sock.h>
  20
  21 #include <xen/events.h>
  22 #include <xen/grant_table.h>
  23 #include <xen/xen.h>
  24 #include <xen/xenbus.h>
  25 #include <xen/interface/io/pvcalls.h>
  26
  27 #include "pvcalls-front.h"
  28
  29 #define PVCALLS_INVALID_ID UINT_MAX
  30 #define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
  31 #define PVCALLS_NR_RSP_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
  32 #define PVCALLS_FRONT_MAX_SPIN 5000
  33
  34 struct pvcalls_bedata {
  35         struct xen_pvcalls_front_ring ring;
  36         grant_ref_t ref;
  37         int irq;
  38
  39         struct list_head socket_mappings;
  40         spinlock_t socket_lock;
  41
  42         wait_queue_head_t inflight_req;
  43         struct xen_pvcalls_response rsp[PVCALLS_NR_RSP_PER_RING];
  44 };
  45 /* Only one front/back connection supported. */
  46 static struct xenbus_device *pvcalls_front_dev;
  47 static atomic_t pvcalls_refcount;
  48
  49 /* first increment refcount, then proceed */
  50 #define pvcalls_enter() {               \
  51         atomic_inc(&pvcalls_refcount);      \
  52 }
  53
  54 /* first complete other operations, then decrement refcount */
  55 #define pvcalls_exit() {                \
  56         atomic_dec(&pvcalls_refcount);      \
  57 }
  58
  59 struct sock_mapping {
  60         bool active_socket;
  61         struct list_head list;
  62         struct socket *sock;
  63         atomic_t refcount;
  64         union {
  65                 struct {
  66                         int irq;
  67                         grant_ref_t ref;
  68                         struct pvcalls_data_intf *ring;
  69                         struct pvcalls_data data;
  70                         struct mutex in_mutex;
  71                         struct mutex out_mutex;
  72
  73                         wait_queue_head_t inflight_conn_req;
  74                 } active;
  75                 struct {
  76                 /*
  77                  * Socket status, needs to be 64-bit aligned due to the
  78                  * test_and_* functions which have this requirement on arm64.
  79                  */
  80 #define PVCALLS_STATUS_UNINITALIZED  0
  81 #define PVCALLS_STATUS_BIND          1
  82 #define PVCALLS_STATUS_LISTEN        2
  83                         uint8_t status __attribute__((aligned(8)));
  84                 /*
  85                  * Internal state-machine flags.
  86                  * Only one accept operation can be inflight for a socket.
  87                  * Only one poll operation can be inflight for a given socket.
  88                  * flags needs to be 64-bit aligned due to the test_and_*
  89                  * functions which have this requirement on arm64.
  90                  */
  91 #define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
  92 #define PVCALLS_FLAG_POLL_INFLIGHT   1
  93 #define PVCALLS_FLAG_POLL_RET        2
  94                         uint8_t flags __attribute__((aligned(8)));
  95                         uint32_t inflight_req_id;
  96                         struct sock_mapping *accept_map;
  97                         wait_queue_head_t inflight_accept_req;
  98                 } passive;
  99         };
 100 };
 101
 102 static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
 103 {
 104         struct sock_mapping *map;
 105
 106         if (!pvcalls_front_dev ||
 107                 dev_get_drvdata(&pvcalls_front_dev->dev) == NULL)
 108                 return ERR_PTR(-ENOTCONN);
 109
 110         map = (struct sock_mapping *)sock->sk->sk_send_head;
 111         if (map == NULL)
 112                 return ERR_PTR(-ENOTSOCK);
 113
 114         pvcalls_enter();
 115         atomic_inc(&map->refcount);
 116         return map;
 117 }
 118
 119 static inline void pvcalls_exit_sock(struct socket *sock)
 120 {
 121         struct sock_mapping *map;
 122
 123         map = (struct sock_mapping *)sock->sk->sk_send_head;
 124         atomic_dec(&map->refcount);
 125         pvcalls_exit();
 126 }
 127
 128 static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
 129 {
 130         *req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
 131         if (RING_FULL(&bedata->ring) ||
 132             bedata->rsp[*req_id].req_id != PVCALLS_INVALID_ID)
 133                 return -EAGAIN;
 134         return 0;
 135 }
 136
 137 static bool pvcalls_front_write_todo(struct sock_mapping *map)
 138 {
 139         struct pvcalls_data_intf *intf = map->active.ring;
 140         RING_IDX cons, prod, size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 141         int32_t error;
 142
 143         error = intf->out_error;
 144         if (error == -ENOTCONN)
 145                 return false;
 146         if (error != 0)
 147                 return true;
 148
 149         cons = intf->out_cons;
 150         prod = intf->out_prod;
 151         return !!(size - pvcalls_queued(prod, cons, size));
 152 }
 153
 154 static bool pvcalls_front_read_todo(struct sock_mapping *map)
 155 {
 156         struct pvcalls_data_intf *intf = map->active.ring;
 157         RING_IDX cons, prod;
 158         int32_t error;
 159
 160         cons = intf->in_cons;
 161         prod = intf->in_prod;
 162         error = intf->in_error;
 163         return (error != 0 ||
 164                 pvcalls_queued(prod, cons,
 165                                XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER)) != 0);
 166 }
 167
 168 static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
 169 {
 170         struct xenbus_device *dev = dev_id;
 171         struct pvcalls_bedata *bedata;
 172         struct xen_pvcalls_response *rsp;
 173         uint8_t *src, *dst;
 174         int req_id = 0, more = 0, done = 0;
 175
 176         if (dev == NULL)
 177                 return IRQ_HANDLED;
 178
 179         pvcalls_enter();
 180         bedata = dev_get_drvdata(&dev->dev);
 181         if (bedata == NULL) {
 182                 pvcalls_exit();
 183                 return IRQ_HANDLED;
 184         }
 185
 186 again:
 187         while (RING_HAS_UNCONSUMED_RESPONSES(&bedata->ring)) {
 188                 rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);
 189
 190                 req_id = rsp->req_id;
 191                 if (rsp->cmd == PVCALLS_POLL) {
 192                         struct sock_mapping *map = (struct sock_mapping *)(uintptr_t)
 193                                                    rsp->u.poll.id;
 194
 195                         clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 196                                   (void *)&map->passive.flags);
 197                         /*
 198                          * clear INFLIGHT, then set RET. It pairs with
 199                          * the checks at the beginning of
 200                          * pvcalls_front_poll_passive.
 201                          */
 202                         smp_wmb();
 203                         set_bit(PVCALLS_FLAG_POLL_RET,
 204                                 (void *)&map->passive.flags);
 205                 } else {
 206                         dst = (uint8_t *)&bedata->rsp[req_id] +
 207                               sizeof(rsp->req_id);
 208                         src = (uint8_t *)rsp + sizeof(rsp->req_id);
 209                         memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
 210                         /*
 211                          * First copy the rest of the data, then req_id. It is
 212                          * paired with the barrier when accessing bedata->rsp.
 213                          */
 214                         smp_wmb();
 215                         bedata->rsp[req_id].req_id = req_id;
 216                 }
 217
 218                 done = 1;
 219                 bedata->ring.rsp_cons++;
 220         }
 221
 222         RING_FINAL_CHECK_FOR_RESPONSES(&bedata->ring, more);
 223         if (more)
 224                 goto again;
 225         if (done)
 226                 wake_up(&bedata->inflight_req);
 227         pvcalls_exit();
 228         return IRQ_HANDLED;
 229 }
 230
 231 static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
 232                                    struct sock_mapping *map)
 233 {
 234         int i;
 235
 236         unbind_from_irqhandler(map->active.irq, map);
 237
 238         spin_lock(&bedata->socket_lock);
 239         if (!list_empty(&map->list))
 240                 list_del_init(&map->list);
 241         spin_unlock(&bedata->socket_lock);
 242
 243         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 244                 gnttab_end_foreign_access(map->active.ring->ref[i], 0, 0);
 245         gnttab_end_foreign_access(map->active.ref, 0, 0);
 246         free_page((unsigned long)map->active.ring);
 247
 248         kfree(map);
 249 }
 250
 251 static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
 252 {
 253         struct sock_mapping *map = sock_map;
 254
 255         if (map == NULL)
 256                 return IRQ_HANDLED;
 257
 258         wake_up_interruptible(&map->active.inflight_conn_req);
 259
 260         return IRQ_HANDLED;
 261 }
 262
 263 int pvcalls_front_socket(struct socket *sock)
 264 {
 265         struct pvcalls_bedata *bedata;
 266         struct sock_mapping *map = NULL;
 267         struct xen_pvcalls_request *req;
 268         int notify, req_id, ret;
 269
 270         /*
 271          * PVCalls only supports domain AF_INET,
 272          * type SOCK_STREAM and protocol 0 sockets for now.
 273          *
 274          * Check socket type here, AF_INET and protocol checks are done
 275          * by the caller.
 276          */
 277         if (sock->type != SOCK_STREAM)
 278                 return -EOPNOTSUPP;
 279
 280         pvcalls_enter();
 281         if (!pvcalls_front_dev) {
 282                 pvcalls_exit();
 283                 return -EACCES;
 284         }
 285         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 286
 287         map = kzalloc(sizeof(*map), GFP_KERNEL);
 288         if (map == NULL) {
 289                 pvcalls_exit();
 290                 return -ENOMEM;
 291         }
 292
 293         spin_lock(&bedata->socket_lock);
 294
 295         ret = get_request(bedata, &req_id);
 296         if (ret < 0) {
 297                 kfree(map);
 298                 spin_unlock(&bedata->socket_lock);
 299                 pvcalls_exit();
 300                 return ret;
 301         }
 302
 303         /*
 304          * sock->sk->sk_send_head is not used for ip sockets: reuse the
 305          * field to store a pointer to the struct sock_mapping
 306          * corresponding to the socket. This way, we can easily get the
 307          * struct sock_mapping from the struct socket.
 308          */
 309         sock->sk->sk_send_head = (void *)map;
 310         list_add_tail(&map->list, &bedata->socket_mappings);
 311
 312         req = RING_GET_REQUEST(&bedata->ring, req_id);
 313         req->req_id = req_id;
 314         req->cmd = PVCALLS_SOCKET;
 315         req->u.socket.id = (uintptr_t) map;
 316         req->u.socket.domain = AF_INET;
 317         req->u.socket.type = SOCK_STREAM;
 318         req->u.socket.protocol = IPPROTO_IP;
 319
 320         bedata->ring.req_prod_pvt++;
 321         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 322         spin_unlock(&bedata->socket_lock);
 323         if (notify)
 324                 notify_remote_via_irq(bedata->irq);
 325
 326         wait_event(bedata->inflight_req,
 327                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 328
 329         /* read req_id, then the content */
 330         smp_rmb();
 331         ret = bedata->rsp[req_id].ret;
 332         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 333
 334         pvcalls_exit();
 335         return ret;
 336 }
 337
 338 static int create_active(struct sock_mapping *map, int *evtchn)
 339 {
 340         void *bytes;
 341         int ret = -ENOMEM, irq = -1, i;
 342
 343         *evtchn = -1;
 344         init_waitqueue_head(&map->active.inflight_conn_req);
 345
 346         map->active.ring = (struct pvcalls_data_intf *)
 347                 __get_free_page(GFP_KERNEL | __GFP_ZERO);
 348         if (map->active.ring == NULL)
 349                 goto out_error;
 350         map->active.ring->ring_order = PVCALLS_RING_ORDER;
 351         bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 352                                         PVCALLS_RING_ORDER);
 353         if (bytes == NULL)
 354                 goto out_error;
 355         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 356                 map->active.ring->ref[i] = gnttab_grant_foreign_access(
 357                         pvcalls_front_dev->otherend_id,
 358                         pfn_to_gfn(virt_to_pfn(bytes) + i), 0);
 359
 360         map->active.ref = gnttab_grant_foreign_access(
 361                 pvcalls_front_dev->otherend_id,
 362                 pfn_to_gfn(virt_to_pfn((void *)map->active.ring)), 0);
 363
 364         map->active.data.in = bytes;
 365         map->active.data.out = bytes +
 366                 XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 367
 368         ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
 369         if (ret)
 370                 goto out_error;
 371         irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
 372                                         0, "pvcalls-frontend", map);
 373         if (irq < 0) {
 374                 ret = irq;
 375                 goto out_error;
 376         }
 377
 378         map->active.irq = irq;
 379         map->active_socket = true;
 380         mutex_init(&map->active.in_mutex);
 381         mutex_init(&map->active.out_mutex);
 382
 383         return 0;
 384
 385 out_error:
 386         if (*evtchn >= 0)
 387                 xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
 388         free_pages((unsigned long)map->active.data.in, PVCALLS_RING_ORDER);
 389         free_page((unsigned long)map->active.ring);
 390         return ret;
 391 }
 392
 393 int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 394                                 int addr_len, int flags)
 395 {
 396         struct pvcalls_bedata *bedata;
 397         struct sock_mapping *map = NULL;
 398         struct xen_pvcalls_request *req;
 399         int notify, req_id, ret, evtchn;
 400
 401         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 402                 return -EOPNOTSUPP;
 403
 404         map = pvcalls_enter_sock(sock);
 405         if (IS_ERR(map))
 406                 return PTR_ERR(map);
 407
 408         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 409
 410         spin_lock(&bedata->socket_lock);
 411         ret = get_request(bedata, &req_id);
 412         if (ret < 0) {
 413                 spin_unlock(&bedata->socket_lock);
 414                 pvcalls_exit_sock(sock);
 415                 return ret;
 416         }
 417         ret = create_active(map, &evtchn);
 418         if (ret < 0) {
 419                 spin_unlock(&bedata->socket_lock);
 420                 pvcalls_exit_sock(sock);
 421                 return ret;
 422         }
 423
 424         req = RING_GET_REQUEST(&bedata->ring, req_id);
 425         req->req_id = req_id;
 426         req->cmd = PVCALLS_CONNECT;
 427         req->u.connect.id = (uintptr_t)map;
 428         req->u.connect.len = addr_len;
 429         req->u.connect.flags = flags;
 430         req->u.connect.ref = map->active.ref;
 431         req->u.connect.evtchn = evtchn;
 432         memcpy(req->u.connect.addr, addr, sizeof(*addr));
 433
 434         map->sock = sock;
 435
 436         bedata->ring.req_prod_pvt++;
 437         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 438         spin_unlock(&bedata->socket_lock);
 439
 440         if (notify)
 441                 notify_remote_via_irq(bedata->irq);
 442
 443         wait_event(bedata->inflight_req,
 444                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 445
 446         /* read req_id, then the content */
 447         smp_rmb();
 448         ret = bedata->rsp[req_id].ret;
 449         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 450         pvcalls_exit_sock(sock);
 451         return ret;
 452 }
 453
 454 static int __write_ring(struct pvcalls_data_intf *intf,
 455                         struct pvcalls_data *data,
 456                         struct iov_iter *msg_iter,
 457                         int len)
 458 {
 459         RING_IDX cons, prod, size, masked_prod, masked_cons;
 460         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 461         int32_t error;
 462
 463         error = intf->out_error;
 464         if (error < 0)
 465                 return error;
 466         cons = intf->out_cons;
 467         prod = intf->out_prod;
 468         /* read indexes before continuing */
 469         virt_mb();
 470
 471         size = pvcalls_queued(prod, cons, array_size);
 472         if (size >= array_size)
 473                 return -EINVAL;
 474         if (len > array_size - size)
 475                 len = array_size - size;
 476
 477         masked_prod = pvcalls_mask(prod, array_size);
 478         masked_cons = pvcalls_mask(cons, array_size);
 479
 480         if (masked_prod < masked_cons) {
 481                 len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 482         } else {
 483                 if (len > array_size - masked_prod) {
 484                         int ret = copy_from_iter(data->out + masked_prod,
 485                                        array_size - masked_prod, msg_iter);
 486                         if (ret != array_size - masked_prod) {
 487                                 len = ret;
 488                                 goto out;
 489                         }
 490                         len = ret + copy_from_iter(data->out, len - ret, msg_iter);
 491                 } else {
 492                         len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 493                 }
 494         }
 495 out:
 496         /* write to ring before updating pointer */
 497         virt_wmb();
 498         intf->out_prod += len;
 499
 500         return len;
 501 }
 502
 503 int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
 504                           size_t len)
 505 {
 506         struct pvcalls_bedata *bedata;
 507         struct sock_mapping *map;
 508         int sent, tot_sent = 0;
 509         int count = 0, flags;
 510
 511         flags = msg->msg_flags;
 512         if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
 513                 return -EOPNOTSUPP;
 514
 515         map = pvcalls_enter_sock(sock);
 516         if (IS_ERR(map))
 517                 return PTR_ERR(map);
 518         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 519
 520         mutex_lock(&map->active.out_mutex);
 521         if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
 522                 mutex_unlock(&map->active.out_mutex);
 523                 pvcalls_exit_sock(sock);
 524                 return -EAGAIN;
 525         }
 526         if (len > INT_MAX)
 527                 len = INT_MAX;
 528
 529 again:
 530         count++;
 531         sent = __write_ring(map->active.ring,
 532                             &map->active.data, &msg->msg_iter,
 533                             len);
 534         if (sent > 0) {
 535                 len -= sent;
 536                 tot_sent += sent;
 537                 notify_remote_via_irq(map->active.irq);
 538         }
 539         if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
 540                 goto again;
 541         if (sent < 0)
 542                 tot_sent = sent;
 543
 544         mutex_unlock(&map->active.out_mutex);
 545         pvcalls_exit_sock(sock);
 546         return tot_sent;
 547 }
 548
 549 static int __read_ring(struct pvcalls_data_intf *intf,
 550                        struct pvcalls_data *data,
 551                        struct iov_iter *msg_iter,
 552                        size_t len, int flags)
 553 {
 554         RING_IDX cons, prod, size, masked_prod, masked_cons;
 555         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 556         int32_t error;
 557
 558         cons = intf->in_cons;
 559         prod = intf->in_prod;
 560         error = intf->in_error;
 561         /* get pointers before reading from the ring */
 562         virt_rmb();
 563         if (error < 0)
 564                 return error;
 565
 566         size = pvcalls_queued(prod, cons, array_size);
 567         masked_prod = pvcalls_mask(prod, array_size);
 568         masked_cons = pvcalls_mask(cons, array_size);
 569
 570         if (size == 0)
 571                 return 0;
 572
 573         if (len > size)
 574                 len = size;
 575
 576         if (masked_prod > masked_cons) {
 577                 len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 578         } else {
 579                 if (len > (array_size - masked_cons)) {
 580                         int ret = copy_to_iter(data->in + masked_cons,
 581                                      array_size - masked_cons, msg_iter);
 582                         if (ret != array_size - masked_cons) {
 583                                 len = ret;
 584                                 goto out;
 585                         }
 586                         len = ret + copy_to_iter(data->in, len - ret, msg_iter);
 587                 } else {
 588                         len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 589                 }
 590         }
 591 out:
 592         /* read data from the ring before increasing the index */
 593         virt_mb();
 594         if (!(flags & MSG_PEEK))
 595                 intf->in_cons += len;
 596
 597         return len;
 598 }
 599
 600 int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 601                      int flags)
 602 {
 603         struct pvcalls_bedata *bedata;
 604         int ret;
 605         struct sock_mapping *map;
 606
 607         if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
 608                 return -EOPNOTSUPP;
 609
 610         map = pvcalls_enter_sock(sock);
 611         if (IS_ERR(map))
 612                 return PTR_ERR(map);
 613         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 614
 615         mutex_lock(&map->active.in_mutex);
 616         if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
 617                 len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 618
 619         while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
 620                 wait_event_interruptible(map->active.inflight_conn_req,
 621                                          pvcalls_front_read_todo(map));
 622         }
 623         ret = __read_ring(map->active.ring, &map->active.data,
 624                           &msg->msg_iter, len, flags);
 625
 626         if (ret > 0)
 627                 notify_remote_via_irq(map->active.irq);
 628         if (ret == 0)
 629                 ret = (flags & MSG_DONTWAIT) ? -EAGAIN : 0;
 630         if (ret == -ENOTCONN)
 631                 ret = 0;
 632
 633         mutex_unlock(&map->active.in_mutex);
 634         pvcalls_exit_sock(sock);
 635         return ret;
 636 }
 637
 638 int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 639 {
 640         struct pvcalls_bedata *bedata;
 641         struct sock_mapping *map = NULL;
 642         struct xen_pvcalls_request *req;
 643         int notify, req_id, ret;
 644
 645         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 646                 return -EOPNOTSUPP;
 647
 648         map = pvcalls_enter_sock(sock);
 649         if (IS_ERR(map))
 650                 return PTR_ERR(map);
 651         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 652
 653         spin_lock(&bedata->socket_lock);
 654         ret = get_request(bedata, &req_id);
 655         if (ret < 0) {
 656                 spin_unlock(&bedata->socket_lock);
 657                 pvcalls_exit_sock(sock);
 658                 return ret;
 659         }
 660         req = RING_GET_REQUEST(&bedata->ring, req_id);
 661         req->req_id = req_id;
 662         map->sock = sock;
 663         req->cmd = PVCALLS_BIND;
 664         req->u.bind.id = (uintptr_t)map;
 665         memcpy(req->u.bind.addr, addr, sizeof(*addr));
 666         req->u.bind.len = addr_len;
 667
 668         init_waitqueue_head(&map->passive.inflight_accept_req);
 669
 670         map->active_socket = false;
 671
 672         bedata->ring.req_prod_pvt++;
 673         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 674         spin_unlock(&bedata->socket_lock);
 675         if (notify)
 676                 notify_remote_via_irq(bedata->irq);
 677
 678         wait_event(bedata->inflight_req,
 679                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 680
 681         /* read req_id, then the content */
 682         smp_rmb();
 683         ret = bedata->rsp[req_id].ret;
 684         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 685
 686         map->passive.status = PVCALLS_STATUS_BIND;
 687         pvcalls_exit_sock(sock);
 688         return 0;
 689 }
 690
 691 int pvcalls_front_listen(struct socket *sock, int backlog)
 692 {
 693         struct pvcalls_bedata *bedata;
 694         struct sock_mapping *map;
 695         struct xen_pvcalls_request *req;
 696         int notify, req_id, ret;
 697
 698         map = pvcalls_enter_sock(sock);
 699         if (IS_ERR(map))
 700                 return PTR_ERR(map);
 701         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 702
 703         if (map->passive.status != PVCALLS_STATUS_BIND) {
 704                 pvcalls_exit_sock(sock);
 705                 return -EOPNOTSUPP;
 706         }
 707
 708         spin_lock(&bedata->socket_lock);
 709         ret = get_request(bedata, &req_id);
 710         if (ret < 0) {
 711                 spin_unlock(&bedata->socket_lock);
 712                 pvcalls_exit_sock(sock);
 713                 return ret;
 714         }
 715         req = RING_GET_REQUEST(&bedata->ring, req_id);
 716         req->req_id = req_id;
 717         req->cmd = PVCALLS_LISTEN;
 718         req->u.listen.id = (uintptr_t) map;
 719         req->u.listen.backlog = backlog;
 720
 721         bedata->ring.req_prod_pvt++;
 722         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 723         spin_unlock(&bedata->socket_lock);
 724         if (notify)
 725                 notify_remote_via_irq(bedata->irq);
 726
 727         wait_event(bedata->inflight_req,
 728                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 729
 730         /* read req_id, then the content */
 731         smp_rmb();
 732         ret = bedata->rsp[req_id].ret;
 733         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 734
 735         map->passive.status = PVCALLS_STATUS_LISTEN;
 736         pvcalls_exit_sock(sock);
 737         return ret;
 738 }
 739
 740 int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
 741 {
 742         struct pvcalls_bedata *bedata;
 743         struct sock_mapping *map;
 744         struct sock_mapping *map2 = NULL;
 745         struct xen_pvcalls_request *req;
 746         int notify, req_id, ret, evtchn, nonblock;
 747
 748         map = pvcalls_enter_sock(sock);
 749         if (IS_ERR(map))
 750                 return PTR_ERR(map);
 751         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 752
 753         if (map->passive.status != PVCALLS_STATUS_LISTEN) {
 754                 pvcalls_exit_sock(sock);
 755                 return -EINVAL;
 756         }
 757
 758         nonblock = flags & SOCK_NONBLOCK;
 759         /*
 760          * Backend only supports 1 inflight accept request, will return
 761          * errors for the others
 762          */
 763         if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 764                              (void *)&map->passive.flags)) {
 765                 req_id = READ_ONCE(map->passive.inflight_req_id);
 766                 if (req_id != PVCALLS_INVALID_ID &&
 767                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id) {
 768                         map2 = map->passive.accept_map;
 769                         goto received;
 770                 }
 771                 if (nonblock) {
 772                         pvcalls_exit_sock(sock);
 773                         return -EAGAIN;
 774                 }
 775                 if (wait_event_interruptible(map->passive.inflight_accept_req,
 776                         !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 777                                           (void *)&map->passive.flags))) {
 778                         pvcalls_exit_sock(sock);
 779                         return -EINTR;
 780                 }
 781         }
 782
 783         spin_lock(&bedata->socket_lock);
 784         ret = get_request(bedata, &req_id);
 785         if (ret < 0) {
 786                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 787                           (void *)&map->passive.flags);
 788                 spin_unlock(&bedata->socket_lock);
 789                 pvcalls_exit_sock(sock);
 790                 return ret;
 791         }
 792         map2 = kzalloc(sizeof(*map2), GFP_ATOMIC);
 793         if (map2 == NULL) {
 794                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 795                           (void *)&map->passive.flags);
 796                 spin_unlock(&bedata->socket_lock);
 797                 pvcalls_exit_sock(sock);
 798                 return -ENOMEM;
 799         }
 800         ret = create_active(map2, &evtchn);
 801         if (ret < 0) {
 802                 kfree(map2);
 803                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 804                           (void *)&map->passive.flags);
 805                 spin_unlock(&bedata->socket_lock);
 806                 pvcalls_exit_sock(sock);
 807                 return ret;
 808         }
 809         list_add_tail(&map2->list, &bedata->socket_mappings);
 810
 811         req = RING_GET_REQUEST(&bedata->ring, req_id);
 812         req->req_id = req_id;
 813         req->cmd = PVCALLS_ACCEPT;
 814         req->u.accept.id = (uintptr_t) map;
 815         req->u.accept.ref = map2->active.ref;
 816         req->u.accept.id_new = (uintptr_t) map2;
 817         req->u.accept.evtchn = evtchn;
 818         map->passive.accept_map = map2;
 819
 820         bedata->ring.req_prod_pvt++;
 821         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 822         spin_unlock(&bedata->socket_lock);
 823         if (notify)
 824                 notify_remote_via_irq(bedata->irq);
 825         /* We could check if we have received a response before returning. */
 826         if (nonblock) {
 827                 WRITE_ONCE(map->passive.inflight_req_id, req_id);
 828                 pvcalls_exit_sock(sock);
 829                 return -EAGAIN;
 830         }
 831
 832         if (wait_event_interruptible(bedata->inflight_req,
 833                 READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
 834                 pvcalls_exit_sock(sock);
 835                 return -EINTR;
 836         }
 837         /* read req_id, then the content */
 838         smp_rmb();
 839
 840 received:
 841         map2->sock = newsock;
 842         newsock->sk = kzalloc(sizeof(*newsock->sk), GFP_KERNEL);
 843         if (!newsock->sk) {
 844                 bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 845                 map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 846                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 847                           (void *)&map->passive.flags);
 848                 pvcalls_front_free_map(bedata, map2);
 849                 pvcalls_exit_sock(sock);
 850                 return -ENOMEM;
 851         }
 852         newsock->sk->sk_send_head = (void *)map2;
 853
 854         ret = bedata->rsp[req_id].ret;
 855         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 856         map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 857
 858         clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
 859         wake_up(&map->passive.inflight_accept_req);
 860
 861         pvcalls_exit_sock(sock);
 862         return ret;
 863 }
 864
 865 static __poll_t pvcalls_front_poll_passive(struct file *file,
 866                                                struct pvcalls_bedata *bedata,
 867                                                struct sock_mapping *map,
 868                                                poll_table *wait)
 869 {
 870         int notify, req_id, ret;
 871         struct xen_pvcalls_request *req;
 872
 873         if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 874                      (void *)&map->passive.flags)) {
 875                 uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
 876
 877                 if (req_id != PVCALLS_INVALID_ID &&
 878                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
 879                         return EPOLLIN | EPOLLRDNORM;
 880
 881                 poll_wait(file, &map->passive.inflight_accept_req, wait);
 882                 return 0;
 883         }
 884
 885         if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
 886                                (void *)&map->passive.flags))
 887                 return EPOLLIN | EPOLLRDNORM;
 888
 889         /*
 890          * First check RET, then INFLIGHT. No barriers necessary to
 891          * ensure execution ordering because of the conditional
 892          * instructions creating control dependencies.
 893          */
 894
 895         if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 896                              (void *)&map->passive.flags)) {
 897                 poll_wait(file, &bedata->inflight_req, wait);
 898                 return 0;
 899         }
 900
 901         spin_lock(&bedata->socket_lock);
 902         ret = get_request(bedata, &req_id);
 903         if (ret < 0) {
 904                 spin_unlock(&bedata->socket_lock);
 905                 return ret;
 906         }
 907         req = RING_GET_REQUEST(&bedata->ring, req_id);
 908         req->req_id = req_id;
 909         req->cmd = PVCALLS_POLL;
 910         req->u.poll.id = (uintptr_t) map;
 911
 912         bedata->ring.req_prod_pvt++;
 913         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 914         spin_unlock(&bedata->socket_lock);
 915         if (notify)
 916                 notify_remote_via_irq(bedata->irq);
 917
 918         poll_wait(file, &bedata->inflight_req, wait);
 919         return 0;
 920 }
 921
 922 static __poll_t pvcalls_front_poll_active(struct file *file,
 923                                               struct pvcalls_bedata *bedata,
 924                                               struct sock_mapping *map,
 925                                               poll_table *wait)
 926 {
 927         __poll_t mask = 0;
 928         int32_t in_error, out_error;
 929         struct pvcalls_data_intf *intf = map->active.ring;
 930
 931         out_error = intf->out_error;
 932         in_error = intf->in_error;
 933
 934         poll_wait(file, &map->active.inflight_conn_req, wait);
 935         if (pvcalls_front_write_todo(map))
 936                 mask |= EPOLLOUT | EPOLLWRNORM;
 937         if (pvcalls_front_read_todo(map))
 938                 mask |= EPOLLIN | EPOLLRDNORM;
 939         if (in_error != 0 || out_error != 0)
 940                 mask |= EPOLLERR;
 941
 942         return mask;
 943 }
 944
 945 __poll_t pvcalls_front_poll(struct file *file, struct socket *sock,
 946                                poll_table *wait)
 947 {
 948         struct pvcalls_bedata *bedata;
 949         struct sock_mapping *map;
 950         __poll_t ret;
 951
 952         map = pvcalls_enter_sock(sock);
 953         if (IS_ERR(map))
 954                 return EPOLLNVAL;
 955         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 956
 957         if (map->active_socket)
 958                 ret = pvcalls_front_poll_active(file, bedata, map, wait);
 959         else
 960                 ret = pvcalls_front_poll_passive(file, bedata, map, wait);
 961         pvcalls_exit_sock(sock);
 962         return ret;
 963 }
 964
 965 int pvcalls_front_release(struct socket *sock)
 966 {
 967         struct pvcalls_bedata *bedata;
 968         struct sock_mapping *map;
 969         int req_id, notify, ret;
 970         struct xen_pvcalls_request *req;
 971
 972         if (sock->sk == NULL)
 973                 return 0;
 974
 975         map = pvcalls_enter_sock(sock);
 976         if (IS_ERR(map)) {
 977                 if (PTR_ERR(map) == -ENOTCONN)
 978                         return -EIO;
 979                 else
 980                         return 0;
 981         }
 982         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 983
 984         spin_lock(&bedata->socket_lock);
 985         ret = get_request(bedata, &req_id);
 986         if (ret < 0) {
 987                 spin_unlock(&bedata->socket_lock);
 988                 pvcalls_exit_sock(sock);
 989                 return ret;
 990         }
 991         sock->sk->sk_send_head = NULL;
 992
 993         req = RING_GET_REQUEST(&bedata->ring, req_id);
 994         req->req_id = req_id;
 995         req->cmd = PVCALLS_RELEASE;
 996         req->u.release.id = (uintptr_t)map;
 997
 998         bedata->ring.req_prod_pvt++;
 999         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
1000         spin_unlock(&bedata->socket_lock);
1001         if (notify)
1002                 notify_remote_via_irq(bedata->irq);
1003
1004         wait_event(bedata->inflight_req,
1005                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
1006
1007         if (map->active_socket) {
1008                 /*
1009                  * Set in_error and wake up inflight_conn_req to force
1010                  * recvmsg waiters to exit.
1011                  */
1012                 map->active.ring->in_error = -EBADF;
1013                 wake_up_interruptible(&map->active.inflight_conn_req);
1014
1015                 /*
1016                  * We need to make sure that sendmsg/recvmsg on this socket have
1017                  * not started before we've cleared sk_send_head here. The
1018                  * easiest way to guarantee this is to see that no pvcalls
1019                  * (other than us) is in progress on this socket.
1020                  */
1021                 while (atomic_read(&map->refcount) > 1)
1022                         cpu_relax();
1023
1024                 pvcalls_front_free_map(bedata, map);
1025         } else {
1026                 wake_up(&bedata->inflight_req);
1027                 wake_up(&map->passive.inflight_accept_req);
1028
1029                 while (atomic_read(&map->refcount) > 1)
1030                         cpu_relax();
1031
1032                 spin_lock(&bedata->socket_lock);
1033                 list_del(&map->list);
1034                 spin_unlock(&bedata->socket_lock);
1035                 if (READ_ONCE(map->passive.inflight_req_id) !=
1036                     PVCALLS_INVALID_ID) {
1037                         pvcalls_front_free_map(bedata,
1038                                                map->passive.accept_map);
1039                 }
1040                 kfree(map);
1041         }
1042         WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
1043
1044         pvcalls_exit();
1045         return 0;
1046 }
1047
1048 static const struct xenbus_device_id pvcalls_front_ids[] = {
1049         { "pvcalls" },
1050         { "" }
1051 };
1052
1053 static int pvcalls_front_remove(struct xenbus_device *dev)
1054 {
1055         struct pvcalls_bedata *bedata;
1056         struct sock_mapping *map = NULL, *n;
1057
1058         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1059         dev_set_drvdata(&dev->dev, NULL);
1060         pvcalls_front_dev = NULL;
1061         if (bedata->irq >= 0)
1062                 unbind_from_irqhandler(bedata->irq, dev);
1063
1064         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1065                 map->sock->sk->sk_send_head = NULL;
1066                 if (map->active_socket) {
1067                         map->active.ring->in_error = -EBADF;
1068                         wake_up_interruptible(&map->active.inflight_conn_req);
1069                 }
1070         }
1071
1072         smp_mb();
1073         while (atomic_read(&pvcalls_refcount) > 0)
1074                 cpu_relax();
1075         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1076                 if (map->active_socket) {
1077                         /* No need to lock, refcount is 0 */
1078                         pvcalls_front_free_map(bedata, map);
1079                 } else {
1080                         list_del(&map->list);
1081                         kfree(map);
1082                 }
1083         }
1084         if (bedata->ref != -1)
1085                 gnttab_end_foreign_access(bedata->ref, 0, 0);
1086         kfree(bedata->ring.sring);
1087         kfree(bedata);
1088         xenbus_switch_state(dev, XenbusStateClosed);
1089         return 0;
1090 }
1091
1092 static int pvcalls_front_probe(struct xenbus_device *dev,
1093                           const struct xenbus_device_id *id)
1094 {
1095         int ret = -ENOMEM, evtchn, i;
1096         unsigned int max_page_order, function_calls, len;
1097         char *versions;
1098         grant_ref_t gref_head = 0;
1099         struct xenbus_transaction xbt;
1100         struct pvcalls_bedata *bedata = NULL;
1101         struct xen_pvcalls_sring *sring;
1102
1103         if (pvcalls_front_dev != NULL) {
1104                 dev_err(&dev->dev, "only one PV Calls connection supported\n");
1105                 return -EINVAL;
1106         }
1107
1108         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
1109         if (IS_ERR(versions))
1110                 return PTR_ERR(versions);
1111         if (!len)
1112                 return -EINVAL;
1113         if (strcmp(versions, "1")) {
1114                 kfree(versions);
1115                 return -EINVAL;
1116         }
1117         kfree(versions);
1118         max_page_order = xenbus_read_unsigned(dev->otherend,
1119                                               "max-page-order", 0);
1120         if (max_page_order < PVCALLS_RING_ORDER)
1121                 return -ENODEV;
1122         function_calls = xenbus_read_unsigned(dev->otherend,
1123                                               "function-calls", 0);
1124         /* See XENBUS_FUNCTIONS_CALLS in pvcalls.h */
1125         if (function_calls != 1)
1126                 return -ENODEV;
1127         pr_info("%s max-page-order is %u\n", __func__, max_page_order);
1128
1129         bedata = kzalloc(sizeof(struct pvcalls_bedata), GFP_KERNEL);
1130         if (!bedata)
1131                 return -ENOMEM;
1132
1133         dev_set_drvdata(&dev->dev, bedata);
1134         pvcalls_front_dev = dev;
1135         init_waitqueue_head(&bedata->inflight_req);
1136         INIT_LIST_HEAD(&bedata->socket_mappings);
1137         spin_lock_init(&bedata->socket_lock);
1138         bedata->irq = -1;
1139         bedata->ref = -1;
1140
1141         for (i = 0; i < PVCALLS_NR_RSP_PER_RING; i++)
1142                 bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
1143
1144         sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
1145                                                              __GFP_ZERO);
1146         if (!sring)
1147                 goto error;
1148         SHARED_RING_INIT(sring);
1149         FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
1150
1151         ret = xenbus_alloc_evtchn(dev, &evtchn);
1152         if (ret)
1153                 goto error;
1154
1155         bedata->irq = bind_evtchn_to_irqhandler(evtchn,
1156                                                 pvcalls_front_event_handler,
1157                                                 0, "pvcalls-frontend", dev);
1158         if (bedata->irq < 0) {
1159                 ret = bedata->irq;
1160                 goto error;
1161         }
1162
1163         ret = gnttab_alloc_grant_references(1, &gref_head);
1164         if (ret < 0)
1165                 goto error;
1166         ret = gnttab_claim_grant_reference(&gref_head);
1167         if (ret < 0)
1168                 goto error;
1169         bedata->ref = ret;
1170         gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
1171                                         virt_to_gfn((void *)sring), 0);
1172
1173  again:
1174         ret = xenbus_transaction_start(&xbt);
1175         if (ret) {
1176                 xenbus_dev_fatal(dev, ret, "starting transaction");
1177                 goto error;
1178         }
1179         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
1180         if (ret)
1181                 goto error_xenbus;
1182         ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
1183         if (ret)
1184                 goto error_xenbus;
1185         ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
1186                             evtchn);
1187         if (ret)
1188                 goto error_xenbus;
1189         ret = xenbus_transaction_end(xbt, 0);
1190         if (ret) {
1191                 if (ret == -EAGAIN)
1192                         goto again;
1193                 xenbus_dev_fatal(dev, ret, "completing transaction");
1194                 goto error;
1195         }
1196         xenbus_switch_state(dev, XenbusStateInitialised);
1197
1198         return 0;
1199
1200  error_xenbus:
1201         xenbus_transaction_end(xbt, 1);
1202         xenbus_dev_fatal(dev, ret, "writing xenstore");
1203  error:
1204         pvcalls_front_remove(dev);
1205         return ret;
1206 }
1207
1208 static void pvcalls_front_changed(struct xenbus_device *dev,
1209                             enum xenbus_state backend_state)
1210 {
1211         switch (backend_state) {
1212         case XenbusStateReconfiguring:
1213         case XenbusStateReconfigured:
1214         case XenbusStateInitialising:
1215         case XenbusStateInitialised:
1216         case XenbusStateUnknown:
1217                 break;
1218
1219         case XenbusStateInitWait:
1220                 break;
1221
1222         case XenbusStateConnected:
1223                 xenbus_switch_state(dev, XenbusStateConnected);
1224                 break;
1225
1226         case XenbusStateClosed:
1227                 if (dev->state == XenbusStateClosed)
1228                         break;
1229                 /* Missed the backend's CLOSING state */
1230                 /* fall through */
1231         case XenbusStateClosing:
1232                 xenbus_frontend_closed(dev);
1233                 break;
1234         }
1235 }
1236
1237 static struct xenbus_driver pvcalls_front_driver = {
1238         .ids = pvcalls_front_ids,
1239         .probe = pvcalls_front_probe,
1240         .remove = pvcalls_front_remove,
1241         .otherend_changed = pvcalls_front_changed,
1242 };
1243
1244 static int __init pvcalls_frontend_init(void)
1245 {
1246         if (!xen_domain())
1247                 return -ENODEV;
1248
1249         pr_info("Initialising Xen pvcalls frontend driver\n");
1250
1251         return xenbus_register_frontend(&pvcalls_front_driver);
1252 }
1253
1254 module_init(pvcalls_frontend_init);
1255
1256 MODULE_DESCRIPTION("Xen PV Calls frontend driver");
1257 MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
1258 MODULE_LICENSE("GPL");