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 static struct proto pvcalls_proto = {
  35         .name   = "PVCalls",
  36         .owner  = THIS_MODULE,
  37         .obj_size = sizeof(struct sock),
  38 };
  39
  40 struct pvcalls_bedata {
  41         struct xen_pvcalls_front_ring ring;
  42         grant_ref_t ref;
  43         int irq;
  44
  45         struct list_head socket_mappings;
  46         spinlock_t socket_lock;
  47
  48         wait_queue_head_t inflight_req;
  49         struct xen_pvcalls_response rsp[PVCALLS_NR_RSP_PER_RING];
  50 };
  51 /* Only one front/back connection supported. */
  52 static struct xenbus_device *pvcalls_front_dev;
  53 static atomic_t pvcalls_refcount;
  54
  55 /* first increment refcount, then proceed */
  56 #define pvcalls_enter() {               \
  57         atomic_inc(&pvcalls_refcount);      \
  58 }
  59
  60 /* first complete other operations, then decrement refcount */
  61 #define pvcalls_exit() {                \
  62         atomic_dec(&pvcalls_refcount);      \
  63 }
  64
  65 struct sock_mapping {
  66         bool active_socket;
  67         struct list_head list;
  68         struct socket *sock;
  69         atomic_t refcount;
  70         union {
  71                 struct {
  72                         int irq;
  73                         grant_ref_t ref;
  74                         struct pvcalls_data_intf *ring;
  75                         struct pvcalls_data data;
  76                         struct mutex in_mutex;
  77                         struct mutex out_mutex;
  78
  79                         wait_queue_head_t inflight_conn_req;
  80                 } active;
  81                 struct {
  82                 /*
  83                  * Socket status, needs to be 64-bit aligned due to the
  84                  * test_and_* functions which have this requirement on arm64.
  85                  */
  86 #define PVCALLS_STATUS_UNINITALIZED  0
  87 #define PVCALLS_STATUS_BIND          1
  88 #define PVCALLS_STATUS_LISTEN        2
  89                         uint8_t status __attribute__((aligned(8)));
  90                 /*
  91                  * Internal state-machine flags.
  92                  * Only one accept operation can be inflight for a socket.
  93                  * Only one poll operation can be inflight for a given socket.
  94                  * flags needs to be 64-bit aligned due to the test_and_*
  95                  * functions which have this requirement on arm64.
  96                  */
  97 #define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
  98 #define PVCALLS_FLAG_POLL_INFLIGHT   1
  99 #define PVCALLS_FLAG_POLL_RET        2
 100                         uint8_t flags __attribute__((aligned(8)));
 101                         uint32_t inflight_req_id;
 102                         struct sock_mapping *accept_map;
 103                         wait_queue_head_t inflight_accept_req;
 104                 } passive;
 105         };
 106 };
 107
 108 static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
 109 {
 110         struct sock_mapping *map;
 111
 112         if (!pvcalls_front_dev ||
 113                 dev_get_drvdata(&pvcalls_front_dev->dev) == NULL)
 114                 return ERR_PTR(-ENOTCONN);
 115
 116         map = (struct sock_mapping *)sock->sk->sk_send_head;
 117         if (map == NULL)
 118                 return ERR_PTR(-ENOTSOCK);
 119
 120         pvcalls_enter();
 121         atomic_inc(&map->refcount);
 122         return map;
 123 }
 124
 125 static inline void pvcalls_exit_sock(struct socket *sock)
 126 {
 127         struct sock_mapping *map;
 128
 129         map = (struct sock_mapping *)sock->sk->sk_send_head;
 130         atomic_dec(&map->refcount);
 131         pvcalls_exit();
 132 }
 133
 134 static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
 135 {
 136         *req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
 137         if (RING_FULL(&bedata->ring) ||
 138             bedata->rsp[*req_id].req_id != PVCALLS_INVALID_ID)
 139                 return -EAGAIN;
 140         return 0;
 141 }
 142
 143 static bool pvcalls_front_write_todo(struct sock_mapping *map)
 144 {
 145         struct pvcalls_data_intf *intf = map->active.ring;
 146         RING_IDX cons, prod, size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 147         int32_t error;
 148
 149         error = intf->out_error;
 150         if (error == -ENOTCONN)
 151                 return false;
 152         if (error != 0)
 153                 return true;
 154
 155         cons = intf->out_cons;
 156         prod = intf->out_prod;
 157         return !!(size - pvcalls_queued(prod, cons, size));
 158 }
 159
 160 static bool pvcalls_front_read_todo(struct sock_mapping *map)
 161 {
 162         struct pvcalls_data_intf *intf = map->active.ring;
 163         RING_IDX cons, prod;
 164         int32_t error;
 165
 166         cons = intf->in_cons;
 167         prod = intf->in_prod;
 168         error = intf->in_error;
 169         return (error != 0 ||
 170                 pvcalls_queued(prod, cons,
 171                                XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER)) != 0);
 172 }
 173
 174 static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
 175 {
 176         struct xenbus_device *dev = dev_id;
 177         struct pvcalls_bedata *bedata;
 178         struct xen_pvcalls_response *rsp;
 179         uint8_t *src, *dst;
 180         int req_id = 0, more = 0, done = 0;
 181
 182         if (dev == NULL)
 183                 return IRQ_HANDLED;
 184
 185         pvcalls_enter();
 186         bedata = dev_get_drvdata(&dev->dev);
 187         if (bedata == NULL) {
 188                 pvcalls_exit();
 189                 return IRQ_HANDLED;
 190         }
 191
 192 again:
 193         while (RING_HAS_UNCONSUMED_RESPONSES(&bedata->ring)) {
 194                 rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);
 195
 196                 req_id = rsp->req_id;
 197                 if (rsp->cmd == PVCALLS_POLL) {
 198                         struct sock_mapping *map = (struct sock_mapping *)(uintptr_t)
 199                                                    rsp->u.poll.id;
 200
 201                         clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 202                                   (void *)&map->passive.flags);
 203                         /*
 204                          * clear INFLIGHT, then set RET. It pairs with
 205                          * the checks at the beginning of
 206                          * pvcalls_front_poll_passive.
 207                          */
 208                         smp_wmb();
 209                         set_bit(PVCALLS_FLAG_POLL_RET,
 210                                 (void *)&map->passive.flags);
 211                 } else {
 212                         dst = (uint8_t *)&bedata->rsp[req_id] +
 213                               sizeof(rsp->req_id);
 214                         src = (uint8_t *)rsp + sizeof(rsp->req_id);
 215                         memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
 216                         /*
 217                          * First copy the rest of the data, then req_id. It is
 218                          * paired with the barrier when accessing bedata->rsp.
 219                          */
 220                         smp_wmb();
 221                         bedata->rsp[req_id].req_id = req_id;
 222                 }
 223
 224                 done = 1;
 225                 bedata->ring.rsp_cons++;
 226         }
 227
 228         RING_FINAL_CHECK_FOR_RESPONSES(&bedata->ring, more);
 229         if (more)
 230                 goto again;
 231         if (done)
 232                 wake_up(&bedata->inflight_req);
 233         pvcalls_exit();
 234         return IRQ_HANDLED;
 235 }
 236
 237 static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
 238                                    struct sock_mapping *map)
 239 {
 240         int i;
 241
 242         unbind_from_irqhandler(map->active.irq, map);
 243
 244         spin_lock(&bedata->socket_lock);
 245         if (!list_empty(&map->list))
 246                 list_del_init(&map->list);
 247         spin_unlock(&bedata->socket_lock);
 248
 249         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 250                 gnttab_end_foreign_access(map->active.ring->ref[i], 0, 0);
 251         gnttab_end_foreign_access(map->active.ref, 0, 0);
 252         free_page((unsigned long)map->active.ring);
 253
 254         kfree(map);
 255 }
 256
 257 static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
 258 {
 259         struct sock_mapping *map = sock_map;
 260
 261         if (map == NULL)
 262                 return IRQ_HANDLED;
 263
 264         wake_up_interruptible(&map->active.inflight_conn_req);
 265
 266         return IRQ_HANDLED;
 267 }
 268
 269 int pvcalls_front_socket(struct socket *sock)
 270 {
 271         struct pvcalls_bedata *bedata;
 272         struct sock_mapping *map = NULL;
 273         struct xen_pvcalls_request *req;
 274         int notify, req_id, ret;
 275
 276         /*
 277          * PVCalls only supports domain AF_INET,
 278          * type SOCK_STREAM and protocol 0 sockets for now.
 279          *
 280          * Check socket type here, AF_INET and protocol checks are done
 281          * by the caller.
 282          */
 283         if (sock->type != SOCK_STREAM)
 284                 return -EOPNOTSUPP;
 285
 286         pvcalls_enter();
 287         if (!pvcalls_front_dev) {
 288                 pvcalls_exit();
 289                 return -EACCES;
 290         }
 291         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 292
 293         map = kzalloc(sizeof(*map), GFP_KERNEL);
 294         if (map == NULL) {
 295                 pvcalls_exit();
 296                 return -ENOMEM;
 297         }
 298
 299         spin_lock(&bedata->socket_lock);
 300
 301         ret = get_request(bedata, &req_id);
 302         if (ret < 0) {
 303                 kfree(map);
 304                 spin_unlock(&bedata->socket_lock);
 305                 pvcalls_exit();
 306                 return ret;
 307         }
 308
 309         /*
 310          * sock->sk->sk_send_head is not used for ip sockets: reuse the
 311          * field to store a pointer to the struct sock_mapping
 312          * corresponding to the socket. This way, we can easily get the
 313          * struct sock_mapping from the struct socket.
 314          */
 315         sock->sk->sk_send_head = (void *)map;
 316         list_add_tail(&map->list, &bedata->socket_mappings);
 317
 318         req = RING_GET_REQUEST(&bedata->ring, req_id);
 319         req->req_id = req_id;
 320         req->cmd = PVCALLS_SOCKET;
 321         req->u.socket.id = (uintptr_t) map;
 322         req->u.socket.domain = AF_INET;
 323         req->u.socket.type = SOCK_STREAM;
 324         req->u.socket.protocol = IPPROTO_IP;
 325
 326         bedata->ring.req_prod_pvt++;
 327         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 328         spin_unlock(&bedata->socket_lock);
 329         if (notify)
 330                 notify_remote_via_irq(bedata->irq);
 331
 332         wait_event(bedata->inflight_req,
 333                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 334
 335         /* read req_id, then the content */
 336         smp_rmb();
 337         ret = bedata->rsp[req_id].ret;
 338         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 339
 340         pvcalls_exit();
 341         return ret;
 342 }
 343
 344 static int create_active(struct sock_mapping *map, int *evtchn)
 345 {
 346         void *bytes;
 347         int ret = -ENOMEM, irq = -1, i;
 348
 349         *evtchn = -1;
 350         init_waitqueue_head(&map->active.inflight_conn_req);
 351
 352         map->active.ring = (struct pvcalls_data_intf *)
 353                 __get_free_page(GFP_KERNEL | __GFP_ZERO);
 354         if (map->active.ring == NULL)
 355                 goto out_error;
 356         map->active.ring->ring_order = PVCALLS_RING_ORDER;
 357         bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 358                                         PVCALLS_RING_ORDER);
 359         if (bytes == NULL)
 360                 goto out_error;
 361         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 362                 map->active.ring->ref[i] = gnttab_grant_foreign_access(
 363                         pvcalls_front_dev->otherend_id,
 364                         pfn_to_gfn(virt_to_pfn(bytes) + i), 0);
 365
 366         map->active.ref = gnttab_grant_foreign_access(
 367                 pvcalls_front_dev->otherend_id,
 368                 pfn_to_gfn(virt_to_pfn((void *)map->active.ring)), 0);
 369
 370         map->active.data.in = bytes;
 371         map->active.data.out = bytes +
 372                 XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 373
 374         ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
 375         if (ret)
 376                 goto out_error;
 377         irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
 378                                         0, "pvcalls-frontend", map);
 379         if (irq < 0) {
 380                 ret = irq;
 381                 goto out_error;
 382         }
 383
 384         map->active.irq = irq;
 385         map->active_socket = true;
 386         mutex_init(&map->active.in_mutex);
 387         mutex_init(&map->active.out_mutex);
 388
 389         return 0;
 390
 391 out_error:
 392         if (*evtchn >= 0)
 393                 xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
 394         free_pages((unsigned long)map->active.data.in, PVCALLS_RING_ORDER);
 395         free_page((unsigned long)map->active.ring);
 396         return ret;
 397 }
 398
 399 int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 400                                 int addr_len, int flags)
 401 {
 402         struct pvcalls_bedata *bedata;
 403         struct sock_mapping *map = NULL;
 404         struct xen_pvcalls_request *req;
 405         int notify, req_id, ret, evtchn;
 406
 407         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 408                 return -EOPNOTSUPP;
 409
 410         map = pvcalls_enter_sock(sock);
 411         if (IS_ERR(map))
 412                 return PTR_ERR(map);
 413
 414         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 415
 416         spin_lock(&bedata->socket_lock);
 417         ret = get_request(bedata, &req_id);
 418         if (ret < 0) {
 419                 spin_unlock(&bedata->socket_lock);
 420                 pvcalls_exit_sock(sock);
 421                 return ret;
 422         }
 423         ret = create_active(map, &evtchn);
 424         if (ret < 0) {
 425                 spin_unlock(&bedata->socket_lock);
 426                 pvcalls_exit_sock(sock);
 427                 return ret;
 428         }
 429
 430         req = RING_GET_REQUEST(&bedata->ring, req_id);
 431         req->req_id = req_id;
 432         req->cmd = PVCALLS_CONNECT;
 433         req->u.connect.id = (uintptr_t)map;
 434         req->u.connect.len = addr_len;
 435         req->u.connect.flags = flags;
 436         req->u.connect.ref = map->active.ref;
 437         req->u.connect.evtchn = evtchn;
 438         memcpy(req->u.connect.addr, addr, sizeof(*addr));
 439
 440         map->sock = sock;
 441
 442         bedata->ring.req_prod_pvt++;
 443         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 444         spin_unlock(&bedata->socket_lock);
 445
 446         if (notify)
 447                 notify_remote_via_irq(bedata->irq);
 448
 449         wait_event(bedata->inflight_req,
 450                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 451
 452         /* read req_id, then the content */
 453         smp_rmb();
 454         ret = bedata->rsp[req_id].ret;
 455         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 456         pvcalls_exit_sock(sock);
 457         return ret;
 458 }
 459
 460 static int __write_ring(struct pvcalls_data_intf *intf,
 461                         struct pvcalls_data *data,
 462                         struct iov_iter *msg_iter,
 463                         int len)
 464 {
 465         RING_IDX cons, prod, size, masked_prod, masked_cons;
 466         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 467         int32_t error;
 468
 469         error = intf->out_error;
 470         if (error < 0)
 471                 return error;
 472         cons = intf->out_cons;
 473         prod = intf->out_prod;
 474         /* read indexes before continuing */
 475         virt_mb();
 476
 477         size = pvcalls_queued(prod, cons, array_size);
 478         if (size >= array_size)
 479                 return -EINVAL;
 480         if (len > array_size - size)
 481                 len = array_size - size;
 482
 483         masked_prod = pvcalls_mask(prod, array_size);
 484         masked_cons = pvcalls_mask(cons, array_size);
 485
 486         if (masked_prod < masked_cons) {
 487                 len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 488         } else {
 489                 if (len > array_size - masked_prod) {
 490                         int ret = copy_from_iter(data->out + masked_prod,
 491                                        array_size - masked_prod, msg_iter);
 492                         if (ret != array_size - masked_prod) {
 493                                 len = ret;
 494                                 goto out;
 495                         }
 496                         len = ret + copy_from_iter(data->out, len - ret, msg_iter);
 497                 } else {
 498                         len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 499                 }
 500         }
 501 out:
 502         /* write to ring before updating pointer */
 503         virt_wmb();
 504         intf->out_prod += len;
 505
 506         return len;
 507 }
 508
 509 int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
 510                           size_t len)
 511 {
 512         struct pvcalls_bedata *bedata;
 513         struct sock_mapping *map;
 514         int sent, tot_sent = 0;
 515         int count = 0, flags;
 516
 517         flags = msg->msg_flags;
 518         if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
 519                 return -EOPNOTSUPP;
 520
 521         map = pvcalls_enter_sock(sock);
 522         if (IS_ERR(map))
 523                 return PTR_ERR(map);
 524         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 525
 526         mutex_lock(&map->active.out_mutex);
 527         if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
 528                 mutex_unlock(&map->active.out_mutex);
 529                 pvcalls_exit_sock(sock);
 530                 return -EAGAIN;
 531         }
 532         if (len > INT_MAX)
 533                 len = INT_MAX;
 534
 535 again:
 536         count++;
 537         sent = __write_ring(map->active.ring,
 538                             &map->active.data, &msg->msg_iter,
 539                             len);
 540         if (sent > 0) {
 541                 len -= sent;
 542                 tot_sent += sent;
 543                 notify_remote_via_irq(map->active.irq);
 544         }
 545         if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
 546                 goto again;
 547         if (sent < 0)
 548                 tot_sent = sent;
 549
 550         mutex_unlock(&map->active.out_mutex);
 551         pvcalls_exit_sock(sock);
 552         return tot_sent;
 553 }
 554
 555 static int __read_ring(struct pvcalls_data_intf *intf,
 556                        struct pvcalls_data *data,
 557                        struct iov_iter *msg_iter,
 558                        size_t len, int flags)
 559 {
 560         RING_IDX cons, prod, size, masked_prod, masked_cons;
 561         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 562         int32_t error;
 563
 564         cons = intf->in_cons;
 565         prod = intf->in_prod;
 566         error = intf->in_error;
 567         /* get pointers before reading from the ring */
 568         virt_rmb();
 569
 570         size = pvcalls_queued(prod, cons, array_size);
 571         masked_prod = pvcalls_mask(prod, array_size);
 572         masked_cons = pvcalls_mask(cons, array_size);
 573
 574         if (size == 0)
 575                 return error ?: size;
 576
 577         if (len > size)
 578                 len = size;
 579
 580         if (masked_prod > masked_cons) {
 581                 len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 582         } else {
 583                 if (len > (array_size - masked_cons)) {
 584                         int ret = copy_to_iter(data->in + masked_cons,
 585                                      array_size - masked_cons, msg_iter);
 586                         if (ret != array_size - masked_cons) {
 587                                 len = ret;
 588                                 goto out;
 589                         }
 590                         len = ret + copy_to_iter(data->in, len - ret, msg_iter);
 591                 } else {
 592                         len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 593                 }
 594         }
 595 out:
 596         /* read data from the ring before increasing the index */
 597         virt_mb();
 598         if (!(flags & MSG_PEEK))
 599                 intf->in_cons += len;
 600
 601         return len;
 602 }
 603
 604 int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 605                      int flags)
 606 {
 607         struct pvcalls_bedata *bedata;
 608         int ret;
 609         struct sock_mapping *map;
 610
 611         if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
 612                 return -EOPNOTSUPP;
 613
 614         map = pvcalls_enter_sock(sock);
 615         if (IS_ERR(map))
 616                 return PTR_ERR(map);
 617         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 618
 619         mutex_lock(&map->active.in_mutex);
 620         if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
 621                 len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 622
 623         while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
 624                 wait_event_interruptible(map->active.inflight_conn_req,
 625                                          pvcalls_front_read_todo(map));
 626         }
 627         ret = __read_ring(map->active.ring, &map->active.data,
 628                           &msg->msg_iter, len, flags);
 629
 630         if (ret > 0)
 631                 notify_remote_via_irq(map->active.irq);
 632         if (ret == 0)
 633                 ret = (flags & MSG_DONTWAIT) ? -EAGAIN : 0;
 634         if (ret == -ENOTCONN)
 635                 ret = 0;
 636
 637         mutex_unlock(&map->active.in_mutex);
 638         pvcalls_exit_sock(sock);
 639         return ret;
 640 }
 641
 642 int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 643 {
 644         struct pvcalls_bedata *bedata;
 645         struct sock_mapping *map = NULL;
 646         struct xen_pvcalls_request *req;
 647         int notify, req_id, ret;
 648
 649         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 650                 return -EOPNOTSUPP;
 651
 652         map = pvcalls_enter_sock(sock);
 653         if (IS_ERR(map))
 654                 return PTR_ERR(map);
 655         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 656
 657         spin_lock(&bedata->socket_lock);
 658         ret = get_request(bedata, &req_id);
 659         if (ret < 0) {
 660                 spin_unlock(&bedata->socket_lock);
 661                 pvcalls_exit_sock(sock);
 662                 return ret;
 663         }
 664         req = RING_GET_REQUEST(&bedata->ring, req_id);
 665         req->req_id = req_id;
 666         map->sock = sock;
 667         req->cmd = PVCALLS_BIND;
 668         req->u.bind.id = (uintptr_t)map;
 669         memcpy(req->u.bind.addr, addr, sizeof(*addr));
 670         req->u.bind.len = addr_len;
 671
 672         init_waitqueue_head(&map->passive.inflight_accept_req);
 673
 674         map->active_socket = false;
 675
 676         bedata->ring.req_prod_pvt++;
 677         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 678         spin_unlock(&bedata->socket_lock);
 679         if (notify)
 680                 notify_remote_via_irq(bedata->irq);
 681
 682         wait_event(bedata->inflight_req,
 683                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 684
 685         /* read req_id, then the content */
 686         smp_rmb();
 687         ret = bedata->rsp[req_id].ret;
 688         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 689
 690         map->passive.status = PVCALLS_STATUS_BIND;
 691         pvcalls_exit_sock(sock);
 692         return 0;
 693 }
 694
 695 int pvcalls_front_listen(struct socket *sock, int backlog)
 696 {
 697         struct pvcalls_bedata *bedata;
 698         struct sock_mapping *map;
 699         struct xen_pvcalls_request *req;
 700         int notify, req_id, ret;
 701
 702         map = pvcalls_enter_sock(sock);
 703         if (IS_ERR(map))
 704                 return PTR_ERR(map);
 705         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 706
 707         if (map->passive.status != PVCALLS_STATUS_BIND) {
 708                 pvcalls_exit_sock(sock);
 709                 return -EOPNOTSUPP;
 710         }
 711
 712         spin_lock(&bedata->socket_lock);
 713         ret = get_request(bedata, &req_id);
 714         if (ret < 0) {
 715                 spin_unlock(&bedata->socket_lock);
 716                 pvcalls_exit_sock(sock);
 717                 return ret;
 718         }
 719         req = RING_GET_REQUEST(&bedata->ring, req_id);
 720         req->req_id = req_id;
 721         req->cmd = PVCALLS_LISTEN;
 722         req->u.listen.id = (uintptr_t) map;
 723         req->u.listen.backlog = backlog;
 724
 725         bedata->ring.req_prod_pvt++;
 726         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 727         spin_unlock(&bedata->socket_lock);
 728         if (notify)
 729                 notify_remote_via_irq(bedata->irq);
 730
 731         wait_event(bedata->inflight_req,
 732                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 733
 734         /* read req_id, then the content */
 735         smp_rmb();
 736         ret = bedata->rsp[req_id].ret;
 737         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 738
 739         map->passive.status = PVCALLS_STATUS_LISTEN;
 740         pvcalls_exit_sock(sock);
 741         return ret;
 742 }
 743
 744 int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
 745 {
 746         struct pvcalls_bedata *bedata;
 747         struct sock_mapping *map;
 748         struct sock_mapping *map2 = NULL;
 749         struct xen_pvcalls_request *req;
 750         int notify, req_id, ret, evtchn, nonblock;
 751
 752         map = pvcalls_enter_sock(sock);
 753         if (IS_ERR(map))
 754                 return PTR_ERR(map);
 755         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 756
 757         if (map->passive.status != PVCALLS_STATUS_LISTEN) {
 758                 pvcalls_exit_sock(sock);
 759                 return -EINVAL;
 760         }
 761
 762         nonblock = flags & SOCK_NONBLOCK;
 763         /*
 764          * Backend only supports 1 inflight accept request, will return
 765          * errors for the others
 766          */
 767         if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 768                              (void *)&map->passive.flags)) {
 769                 req_id = READ_ONCE(map->passive.inflight_req_id);
 770                 if (req_id != PVCALLS_INVALID_ID &&
 771                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id) {
 772                         map2 = map->passive.accept_map;
 773                         goto received;
 774                 }
 775                 if (nonblock) {
 776                         pvcalls_exit_sock(sock);
 777                         return -EAGAIN;
 778                 }
 779                 if (wait_event_interruptible(map->passive.inflight_accept_req,
 780                         !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 781                                           (void *)&map->passive.flags))) {
 782                         pvcalls_exit_sock(sock);
 783                         return -EINTR;
 784                 }
 785         }
 786
 787         spin_lock(&bedata->socket_lock);
 788         ret = get_request(bedata, &req_id);
 789         if (ret < 0) {
 790                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 791                           (void *)&map->passive.flags);
 792                 spin_unlock(&bedata->socket_lock);
 793                 pvcalls_exit_sock(sock);
 794                 return ret;
 795         }
 796         map2 = kzalloc(sizeof(*map2), GFP_ATOMIC);
 797         if (map2 == NULL) {
 798                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 799                           (void *)&map->passive.flags);
 800                 spin_unlock(&bedata->socket_lock);
 801                 pvcalls_exit_sock(sock);
 802                 return -ENOMEM;
 803         }
 804         ret = create_active(map2, &evtchn);
 805         if (ret < 0) {
 806                 kfree(map2);
 807                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 808                           (void *)&map->passive.flags);
 809                 spin_unlock(&bedata->socket_lock);
 810                 pvcalls_exit_sock(sock);
 811                 return ret;
 812         }
 813         list_add_tail(&map2->list, &bedata->socket_mappings);
 814
 815         req = RING_GET_REQUEST(&bedata->ring, req_id);
 816         req->req_id = req_id;
 817         req->cmd = PVCALLS_ACCEPT;
 818         req->u.accept.id = (uintptr_t) map;
 819         req->u.accept.ref = map2->active.ref;
 820         req->u.accept.id_new = (uintptr_t) map2;
 821         req->u.accept.evtchn = evtchn;
 822         map->passive.accept_map = map2;
 823
 824         bedata->ring.req_prod_pvt++;
 825         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 826         spin_unlock(&bedata->socket_lock);
 827         if (notify)
 828                 notify_remote_via_irq(bedata->irq);
 829         /* We could check if we have received a response before returning. */
 830         if (nonblock) {
 831                 WRITE_ONCE(map->passive.inflight_req_id, req_id);
 832                 pvcalls_exit_sock(sock);
 833                 return -EAGAIN;
 834         }
 835
 836         if (wait_event_interruptible(bedata->inflight_req,
 837                 READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
 838                 pvcalls_exit_sock(sock);
 839                 return -EINTR;
 840         }
 841         /* read req_id, then the content */
 842         smp_rmb();
 843
 844 received:
 845         map2->sock = newsock;
 846         newsock->sk = sk_alloc(sock_net(sock->sk), PF_INET, GFP_KERNEL, &pvcalls_proto, false);
 847         if (!newsock->sk) {
 848                 bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 849                 map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 850                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 851                           (void *)&map->passive.flags);
 852                 pvcalls_front_free_map(bedata, map2);
 853                 pvcalls_exit_sock(sock);
 854                 return -ENOMEM;
 855         }
 856         newsock->sk->sk_send_head = (void *)map2;
 857
 858         ret = bedata->rsp[req_id].ret;
 859         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 860         map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 861
 862         clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
 863         wake_up(&map->passive.inflight_accept_req);
 864
 865         pvcalls_exit_sock(sock);
 866         return ret;
 867 }
 868
 869 static __poll_t pvcalls_front_poll_passive(struct file *file,
 870                                                struct pvcalls_bedata *bedata,
 871                                                struct sock_mapping *map,
 872                                                poll_table *wait)
 873 {
 874         int notify, req_id, ret;
 875         struct xen_pvcalls_request *req;
 876
 877         if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 878                      (void *)&map->passive.flags)) {
 879                 uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
 880
 881                 if (req_id != PVCALLS_INVALID_ID &&
 882                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
 883                         return EPOLLIN | EPOLLRDNORM;
 884
 885                 poll_wait(file, &map->passive.inflight_accept_req, wait);
 886                 return 0;
 887         }
 888
 889         if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
 890                                (void *)&map->passive.flags))
 891                 return EPOLLIN | EPOLLRDNORM;
 892
 893         /*
 894          * First check RET, then INFLIGHT. No barriers necessary to
 895          * ensure execution ordering because of the conditional
 896          * instructions creating control dependencies.
 897          */
 898
 899         if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 900                              (void *)&map->passive.flags)) {
 901                 poll_wait(file, &bedata->inflight_req, wait);
 902                 return 0;
 903         }
 904
 905         spin_lock(&bedata->socket_lock);
 906         ret = get_request(bedata, &req_id);
 907         if (ret < 0) {
 908                 spin_unlock(&bedata->socket_lock);
 909                 return ret;
 910         }
 911         req = RING_GET_REQUEST(&bedata->ring, req_id);
 912         req->req_id = req_id;
 913         req->cmd = PVCALLS_POLL;
 914         req->u.poll.id = (uintptr_t) map;
 915
 916         bedata->ring.req_prod_pvt++;
 917         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 918         spin_unlock(&bedata->socket_lock);
 919         if (notify)
 920                 notify_remote_via_irq(bedata->irq);
 921
 922         poll_wait(file, &bedata->inflight_req, wait);
 923         return 0;
 924 }
 925
 926 static __poll_t pvcalls_front_poll_active(struct file *file,
 927                                               struct pvcalls_bedata *bedata,
 928                                               struct sock_mapping *map,
 929                                               poll_table *wait)
 930 {
 931         __poll_t mask = 0;
 932         int32_t in_error, out_error;
 933         struct pvcalls_data_intf *intf = map->active.ring;
 934
 935         out_error = intf->out_error;
 936         in_error = intf->in_error;
 937
 938         poll_wait(file, &map->active.inflight_conn_req, wait);
 939         if (pvcalls_front_write_todo(map))
 940                 mask |= EPOLLOUT | EPOLLWRNORM;
 941         if (pvcalls_front_read_todo(map))
 942                 mask |= EPOLLIN | EPOLLRDNORM;
 943         if (in_error != 0 || out_error != 0)
 944                 mask |= EPOLLERR;
 945
 946         return mask;
 947 }
 948
 949 __poll_t pvcalls_front_poll(struct file *file, struct socket *sock,
 950                                poll_table *wait)
 951 {
 952         struct pvcalls_bedata *bedata;
 953         struct sock_mapping *map;
 954         __poll_t ret;
 955
 956         map = pvcalls_enter_sock(sock);
 957         if (IS_ERR(map))
 958                 return EPOLLNVAL;
 959         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 960
 961         if (map->active_socket)
 962                 ret = pvcalls_front_poll_active(file, bedata, map, wait);
 963         else
 964                 ret = pvcalls_front_poll_passive(file, bedata, map, wait);
 965         pvcalls_exit_sock(sock);
 966         return ret;
 967 }
 968
 969 int pvcalls_front_release(struct socket *sock)
 970 {
 971         struct pvcalls_bedata *bedata;
 972         struct sock_mapping *map;
 973         int req_id, notify, ret;
 974         struct xen_pvcalls_request *req;
 975
 976         if (sock->sk == NULL)
 977                 return 0;
 978
 979         map = pvcalls_enter_sock(sock);
 980         if (IS_ERR(map)) {
 981                 if (PTR_ERR(map) == -ENOTCONN)
 982                         return -EIO;
 983                 else
 984                         return 0;
 985         }
 986         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 987
 988         spin_lock(&bedata->socket_lock);
 989         ret = get_request(bedata, &req_id);
 990         if (ret < 0) {
 991                 spin_unlock(&bedata->socket_lock);
 992                 pvcalls_exit_sock(sock);
 993                 return ret;
 994         }
 995         sock->sk->sk_send_head = NULL;
 996
 997         req = RING_GET_REQUEST(&bedata->ring, req_id);
 998         req->req_id = req_id;
 999         req->cmd = PVCALLS_RELEASE;
1000         req->u.release.id = (uintptr_t)map;
1001
1002         bedata->ring.req_prod_pvt++;
1003         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
1004         spin_unlock(&bedata->socket_lock);
1005         if (notify)
1006                 notify_remote_via_irq(bedata->irq);
1007
1008         wait_event(bedata->inflight_req,
1009                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
1010
1011         if (map->active_socket) {
1012                 /*
1013                  * Set in_error and wake up inflight_conn_req to force
1014                  * recvmsg waiters to exit.
1015                  */
1016                 map->active.ring->in_error = -EBADF;
1017                 wake_up_interruptible(&map->active.inflight_conn_req);
1018
1019                 /*
1020                  * We need to make sure that sendmsg/recvmsg on this socket have
1021                  * not started before we've cleared sk_send_head here. The
1022                  * easiest way to guarantee this is to see that no pvcalls
1023                  * (other than us) is in progress on this socket.
1024                  */
1025                 while (atomic_read(&map->refcount) > 1)
1026                         cpu_relax();
1027
1028                 pvcalls_front_free_map(bedata, map);
1029         } else {
1030                 wake_up(&bedata->inflight_req);
1031                 wake_up(&map->passive.inflight_accept_req);
1032
1033                 while (atomic_read(&map->refcount) > 1)
1034                         cpu_relax();
1035
1036                 spin_lock(&bedata->socket_lock);
1037                 list_del(&map->list);
1038                 spin_unlock(&bedata->socket_lock);
1039                 if (READ_ONCE(map->passive.inflight_req_id) != PVCALLS_INVALID_ID &&
1040                         READ_ONCE(map->passive.inflight_req_id) != 0) {
1041                         pvcalls_front_free_map(bedata,
1042                                                map->passive.accept_map);
1043                 }
1044                 kfree(map);
1045         }
1046         WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
1047
1048         pvcalls_exit();
1049         return 0;
1050 }
1051
1052 static const struct xenbus_device_id pvcalls_front_ids[] = {
1053         { "pvcalls" },
1054         { "" }
1055 };
1056
1057 static int pvcalls_front_remove(struct xenbus_device *dev)
1058 {
1059         struct pvcalls_bedata *bedata;
1060         struct sock_mapping *map = NULL, *n;
1061
1062         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1063         dev_set_drvdata(&dev->dev, NULL);
1064         pvcalls_front_dev = NULL;
1065         if (bedata->irq >= 0)
1066                 unbind_from_irqhandler(bedata->irq, dev);
1067
1068         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1069                 map->sock->sk->sk_send_head = NULL;
1070                 if (map->active_socket) {
1071                         map->active.ring->in_error = -EBADF;
1072                         wake_up_interruptible(&map->active.inflight_conn_req);
1073                 }
1074         }
1075
1076         smp_mb();
1077         while (atomic_read(&pvcalls_refcount) > 0)
1078                 cpu_relax();
1079         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1080                 if (map->active_socket) {
1081                         /* No need to lock, refcount is 0 */
1082                         pvcalls_front_free_map(bedata, map);
1083                 } else {
1084                         list_del(&map->list);
1085                         kfree(map);
1086                 }
1087         }
1088         if (bedata->ref != -1)
1089                 gnttab_end_foreign_access(bedata->ref, 0, 0);
1090         kfree(bedata->ring.sring);
1091         kfree(bedata);
1092         xenbus_switch_state(dev, XenbusStateClosed);
1093         return 0;
1094 }
1095
1096 static int pvcalls_front_probe(struct xenbus_device *dev,
1097                           const struct xenbus_device_id *id)
1098 {
1099         int ret = -ENOMEM, evtchn, i;
1100         unsigned int max_page_order, function_calls, len;
1101         char *versions;
1102         grant_ref_t gref_head = 0;
1103         struct xenbus_transaction xbt;
1104         struct pvcalls_bedata *bedata = NULL;
1105         struct xen_pvcalls_sring *sring;
1106
1107         if (pvcalls_front_dev != NULL) {
1108                 dev_err(&dev->dev, "only one PV Calls connection supported\n");
1109                 return -EINVAL;
1110         }
1111
1112         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
1113         if (IS_ERR(versions))
1114                 return PTR_ERR(versions);
1115         if (!len)
1116                 return -EINVAL;
1117         if (strcmp(versions, "1")) {
1118                 kfree(versions);
1119                 return -EINVAL;
1120         }
1121         kfree(versions);
1122         max_page_order = xenbus_read_unsigned(dev->otherend,
1123                                               "max-page-order", 0);
1124         if (max_page_order < PVCALLS_RING_ORDER)
1125                 return -ENODEV;
1126         function_calls = xenbus_read_unsigned(dev->otherend,
1127                                               "function-calls", 0);
1128         /* See XENBUS_FUNCTIONS_CALLS in pvcalls.h */
1129         if (function_calls != 1)
1130                 return -ENODEV;
1131         pr_info("%s max-page-order is %u\n", __func__, max_page_order);
1132
1133         bedata = kzalloc(sizeof(struct pvcalls_bedata), GFP_KERNEL);
1134         if (!bedata)
1135                 return -ENOMEM;
1136
1137         dev_set_drvdata(&dev->dev, bedata);
1138         pvcalls_front_dev = dev;
1139         init_waitqueue_head(&bedata->inflight_req);
1140         INIT_LIST_HEAD(&bedata->socket_mappings);
1141         spin_lock_init(&bedata->socket_lock);
1142         bedata->irq = -1;
1143         bedata->ref = -1;
1144
1145         for (i = 0; i < PVCALLS_NR_RSP_PER_RING; i++)
1146                 bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
1147
1148         sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
1149                                                              __GFP_ZERO);
1150         if (!sring)
1151                 goto error;
1152         SHARED_RING_INIT(sring);
1153         FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
1154
1155         ret = xenbus_alloc_evtchn(dev, &evtchn);
1156         if (ret)
1157                 goto error;
1158
1159         bedata->irq = bind_evtchn_to_irqhandler(evtchn,
1160                                                 pvcalls_front_event_handler,
1161                                                 0, "pvcalls-frontend", dev);
1162         if (bedata->irq < 0) {
1163                 ret = bedata->irq;
1164                 goto error;
1165         }
1166
1167         ret = gnttab_alloc_grant_references(1, &gref_head);
1168         if (ret < 0)
1169                 goto error;
1170         ret = gnttab_claim_grant_reference(&gref_head);
1171         if (ret < 0)
1172                 goto error;
1173         bedata->ref = ret;
1174         gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
1175                                         virt_to_gfn((void *)sring), 0);
1176
1177  again:
1178         ret = xenbus_transaction_start(&xbt);
1179         if (ret) {
1180                 xenbus_dev_fatal(dev, ret, "starting transaction");
1181                 goto error;
1182         }
1183         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
1184         if (ret)
1185                 goto error_xenbus;
1186         ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
1187         if (ret)
1188                 goto error_xenbus;
1189         ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
1190                             evtchn);
1191         if (ret)
1192                 goto error_xenbus;
1193         ret = xenbus_transaction_end(xbt, 0);
1194         if (ret) {
1195                 if (ret == -EAGAIN)
1196                         goto again;
1197                 xenbus_dev_fatal(dev, ret, "completing transaction");
1198                 goto error;
1199         }
1200         xenbus_switch_state(dev, XenbusStateInitialised);
1201
1202         return 0;
1203
1204  error_xenbus:
1205         xenbus_transaction_end(xbt, 1);
1206         xenbus_dev_fatal(dev, ret, "writing xenstore");
1207  error:
1208         pvcalls_front_remove(dev);
1209         return ret;
1210 }
1211
1212 static void pvcalls_front_changed(struct xenbus_device *dev,
1213                             enum xenbus_state backend_state)
1214 {
1215         switch (backend_state) {
1216         case XenbusStateReconfiguring:
1217         case XenbusStateReconfigured:
1218         case XenbusStateInitialising:
1219         case XenbusStateInitialised:
1220         case XenbusStateUnknown:
1221                 break;
1222
1223         case XenbusStateInitWait:
1224                 break;
1225
1226         case XenbusStateConnected:
1227                 xenbus_switch_state(dev, XenbusStateConnected);
1228                 break;
1229
1230         case XenbusStateClosed:
1231                 if (dev->state == XenbusStateClosed)
1232                         break;
1233                 /* Missed the backend's CLOSING state */
1234                 /* fall through */
1235         case XenbusStateClosing:
1236                 xenbus_frontend_closed(dev);
1237                 break;
1238         }
1239 }
1240
1241 static struct xenbus_driver pvcalls_front_driver = {
1242         .ids = pvcalls_front_ids,
1243         .probe = pvcalls_front_probe,
1244         .remove = pvcalls_front_remove,
1245         .otherend_changed = pvcalls_front_changed,
1246 };
1247
1248 static int __init pvcalls_frontend_init(void)
1249 {
1250         if (!xen_domain())
1251                 return -ENODEV;
1252
1253         pr_info("Initialising Xen pvcalls frontend driver\n");
1254
1255         return xenbus_register_frontend(&pvcalls_front_driver);
1256 }
1257
1258 module_init(pvcalls_frontend_init);
1259
1260 MODULE_DESCRIPTION("Xen PV Calls frontend driver");
1261 MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
1262 MODULE_LICENSE("GPL");