drivers/xen/pvcalls-front.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * (c) 2017 Stefano Stabellini <stefano@aporeto.com>
   4  */
   5
   6 #include <linux/module.h>
   7 #include <linux/net.h>
   8 #include <linux/socket.h>
   9
  10 #include <net/sock.h>
  11
  12 #include <xen/events.h>
  13 #include <xen/grant_table.h>
  14 #include <xen/xen.h>
  15 #include <xen/xenbus.h>
  16 #include <xen/interface/io/pvcalls.h>
  17
  18 #include "pvcalls-front.h"
  19
  20 #define PVCALLS_INVALID_ID UINT_MAX
  21 #define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
  22 #define PVCALLS_NR_RSP_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
  23 #define PVCALLS_FRONT_MAX_SPIN 5000
  24
  25 static struct proto pvcalls_proto = {
  26         .name   = "PVCalls",
  27         .owner  = THIS_MODULE,
  28         .obj_size = sizeof(struct sock),
  29 };
  30
  31 struct pvcalls_bedata {
  32         struct xen_pvcalls_front_ring ring;
  33         grant_ref_t ref;
  34         int irq;
  35
  36         struct list_head socket_mappings;
  37         spinlock_t socket_lock;
  38
  39         wait_queue_head_t inflight_req;
  40         struct xen_pvcalls_response rsp[PVCALLS_NR_RSP_PER_RING];
  41 };
  42 /* Only one front/back connection supported. */
  43 static struct xenbus_device *pvcalls_front_dev;
  44 static atomic_t pvcalls_refcount;
  45
  46 /* first increment refcount, then proceed */
  47 #define pvcalls_enter() {               \
  48         atomic_inc(&pvcalls_refcount);      \
  49 }
  50
  51 /* first complete other operations, then decrement refcount */
  52 #define pvcalls_exit() {                \
  53         atomic_dec(&pvcalls_refcount);      \
  54 }
  55
  56 struct sock_mapping {
  57         bool active_socket;
  58         struct list_head list;
  59         struct socket *sock;
  60         atomic_t refcount;
  61         union {
  62                 struct {
  63                         int irq;
  64                         grant_ref_t ref;
  65                         struct pvcalls_data_intf *ring;
  66                         struct pvcalls_data data;
  67                         struct mutex in_mutex;
  68                         struct mutex out_mutex;
  69
  70                         wait_queue_head_t inflight_conn_req;
  71                 } active;
  72                 struct {
  73                 /*
  74                  * Socket status, needs to be 64-bit aligned due to the
  75                  * test_and_* functions which have this requirement on arm64.
  76                  */
  77 #define PVCALLS_STATUS_UNINITALIZED  0
  78 #define PVCALLS_STATUS_BIND          1
  79 #define PVCALLS_STATUS_LISTEN        2
  80                         uint8_t status __attribute__((aligned(8)));
  81                 /*
  82                  * Internal state-machine flags.
  83                  * Only one accept operation can be inflight for a socket.
  84                  * Only one poll operation can be inflight for a given socket.
  85                  * flags needs to be 64-bit aligned due to the test_and_*
  86                  * functions which have this requirement on arm64.
  87                  */
  88 #define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
  89 #define PVCALLS_FLAG_POLL_INFLIGHT   1
  90 #define PVCALLS_FLAG_POLL_RET        2
  91                         uint8_t flags __attribute__((aligned(8)));
  92                         uint32_t inflight_req_id;
  93                         struct sock_mapping *accept_map;
  94                         wait_queue_head_t inflight_accept_req;
  95                 } passive;
  96         };
  97 };
  98
  99 static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
 100 {
 101         struct sock_mapping *map;
 102
 103         if (!pvcalls_front_dev ||
 104                 dev_get_drvdata(&pvcalls_front_dev->dev) == NULL)
 105                 return ERR_PTR(-ENOTCONN);
 106
 107         map = (struct sock_mapping *)sock->sk->sk_send_head;
 108         if (map == NULL)
 109                 return ERR_PTR(-ENOTSOCK);
 110
 111         pvcalls_enter();
 112         atomic_inc(&map->refcount);
 113         return map;
 114 }
 115
 116 static inline void pvcalls_exit_sock(struct socket *sock)
 117 {
 118         struct sock_mapping *map;
 119
 120         map = (struct sock_mapping *)sock->sk->sk_send_head;
 121         atomic_dec(&map->refcount);
 122         pvcalls_exit();
 123 }
 124
 125 static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
 126 {
 127         *req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
 128         if (RING_FULL(&bedata->ring) ||
 129             bedata->rsp[*req_id].req_id != PVCALLS_INVALID_ID)
 130                 return -EAGAIN;
 131         return 0;
 132 }
 133
 134 static bool pvcalls_front_write_todo(struct sock_mapping *map)
 135 {
 136         struct pvcalls_data_intf *intf = map->active.ring;
 137         RING_IDX cons, prod, size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 138         int32_t error;
 139
 140         error = intf->out_error;
 141         if (error == -ENOTCONN)
 142                 return false;
 143         if (error != 0)
 144                 return true;
 145
 146         cons = intf->out_cons;
 147         prod = intf->out_prod;
 148         return !!(size - pvcalls_queued(prod, cons, size));
 149 }
 150
 151 static bool pvcalls_front_read_todo(struct sock_mapping *map)
 152 {
 153         struct pvcalls_data_intf *intf = map->active.ring;
 154         RING_IDX cons, prod;
 155         int32_t error;
 156
 157         cons = intf->in_cons;
 158         prod = intf->in_prod;
 159         error = intf->in_error;
 160         return (error != 0 ||
 161                 pvcalls_queued(prod, cons,
 162                                XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER)) != 0);
 163 }
 164
 165 static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
 166 {
 167         struct xenbus_device *dev = dev_id;
 168         struct pvcalls_bedata *bedata;
 169         struct xen_pvcalls_response *rsp;
 170         uint8_t *src, *dst;
 171         int req_id = 0, more = 0, done = 0;
 172
 173         if (dev == NULL)
 174                 return IRQ_HANDLED;
 175
 176         pvcalls_enter();
 177         bedata = dev_get_drvdata(&dev->dev);
 178         if (bedata == NULL) {
 179                 pvcalls_exit();
 180                 return IRQ_HANDLED;
 181         }
 182
 183 again:
 184         while (RING_HAS_UNCONSUMED_RESPONSES(&bedata->ring)) {
 185                 rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);
 186
 187                 req_id = rsp->req_id;
 188                 if (rsp->cmd == PVCALLS_POLL) {
 189                         struct sock_mapping *map = (struct sock_mapping *)(uintptr_t)
 190                                                    rsp->u.poll.id;
 191
 192                         clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 193                                   (void *)&map->passive.flags);
 194                         /*
 195                          * clear INFLIGHT, then set RET. It pairs with
 196                          * the checks at the beginning of
 197                          * pvcalls_front_poll_passive.
 198                          */
 199                         smp_wmb();
 200                         set_bit(PVCALLS_FLAG_POLL_RET,
 201                                 (void *)&map->passive.flags);
 202                 } else {
 203                         dst = (uint8_t *)&bedata->rsp[req_id] +
 204                               sizeof(rsp->req_id);
 205                         src = (uint8_t *)rsp + sizeof(rsp->req_id);
 206                         memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
 207                         /*
 208                          * First copy the rest of the data, then req_id. It is
 209                          * paired with the barrier when accessing bedata->rsp.
 210                          */
 211                         smp_wmb();
 212                         bedata->rsp[req_id].req_id = req_id;
 213                 }
 214
 215                 done = 1;
 216                 bedata->ring.rsp_cons++;
 217         }
 218
 219         RING_FINAL_CHECK_FOR_RESPONSES(&bedata->ring, more);
 220         if (more)
 221                 goto again;
 222         if (done)
 223                 wake_up(&bedata->inflight_req);
 224         pvcalls_exit();
 225         return IRQ_HANDLED;
 226 }
 227
 228 static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
 229                                    struct sock_mapping *map)
 230 {
 231         int i;
 232
 233         unbind_from_irqhandler(map->active.irq, map);
 234
 235         spin_lock(&bedata->socket_lock);
 236         if (!list_empty(&map->list))
 237                 list_del_init(&map->list);
 238         spin_unlock(&bedata->socket_lock);
 239
 240         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 241                 gnttab_end_foreign_access(map->active.ring->ref[i], 0, 0);
 242         gnttab_end_foreign_access(map->active.ref, 0, 0);
 243         free_page((unsigned long)map->active.ring);
 244
 245         kfree(map);
 246 }
 247
 248 static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
 249 {
 250         struct sock_mapping *map = sock_map;
 251
 252         if (map == NULL)
 253                 return IRQ_HANDLED;
 254
 255         wake_up_interruptible(&map->active.inflight_conn_req);
 256
 257         return IRQ_HANDLED;
 258 }
 259
 260 int pvcalls_front_socket(struct socket *sock)
 261 {
 262         struct pvcalls_bedata *bedata;
 263         struct sock_mapping *map = NULL;
 264         struct xen_pvcalls_request *req;
 265         int notify, req_id, ret;
 266
 267         /*
 268          * PVCalls only supports domain AF_INET,
 269          * type SOCK_STREAM and protocol 0 sockets for now.
 270          *
 271          * Check socket type here, AF_INET and protocol checks are done
 272          * by the caller.
 273          */
 274         if (sock->type != SOCK_STREAM)
 275                 return -EOPNOTSUPP;
 276
 277         pvcalls_enter();
 278         if (!pvcalls_front_dev) {
 279                 pvcalls_exit();
 280                 return -EACCES;
 281         }
 282         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 283
 284         map = kzalloc(sizeof(*map), GFP_KERNEL);
 285         if (map == NULL) {
 286                 pvcalls_exit();
 287                 return -ENOMEM;
 288         }
 289
 290         spin_lock(&bedata->socket_lock);
 291
 292         ret = get_request(bedata, &req_id);
 293         if (ret < 0) {
 294                 kfree(map);
 295                 spin_unlock(&bedata->socket_lock);
 296                 pvcalls_exit();
 297                 return ret;
 298         }
 299
 300         /*
 301          * sock->sk->sk_send_head is not used for ip sockets: reuse the
 302          * field to store a pointer to the struct sock_mapping
 303          * corresponding to the socket. This way, we can easily get the
 304          * struct sock_mapping from the struct socket.
 305          */
 306         sock->sk->sk_send_head = (void *)map;
 307         list_add_tail(&map->list, &bedata->socket_mappings);
 308
 309         req = RING_GET_REQUEST(&bedata->ring, req_id);
 310         req->req_id = req_id;
 311         req->cmd = PVCALLS_SOCKET;
 312         req->u.socket.id = (uintptr_t) map;
 313         req->u.socket.domain = AF_INET;
 314         req->u.socket.type = SOCK_STREAM;
 315         req->u.socket.protocol = IPPROTO_IP;
 316
 317         bedata->ring.req_prod_pvt++;
 318         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 319         spin_unlock(&bedata->socket_lock);
 320         if (notify)
 321                 notify_remote_via_irq(bedata->irq);
 322
 323         wait_event(bedata->inflight_req,
 324                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 325
 326         /* read req_id, then the content */
 327         smp_rmb();
 328         ret = bedata->rsp[req_id].ret;
 329         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 330
 331         pvcalls_exit();
 332         return ret;
 333 }
 334
 335 static void free_active_ring(struct sock_mapping *map)
 336 {
 337         if (!map->active.ring)
 338                 return;
 339
 340         free_pages((unsigned long)map->active.data.in,
 341                         map->active.ring->ring_order);
 342         free_page((unsigned long)map->active.ring);
 343 }
 344
 345 static int alloc_active_ring(struct sock_mapping *map)
 346 {
 347         void *bytes;
 348
 349         map->active.ring = (struct pvcalls_data_intf *)
 350                 get_zeroed_page(GFP_KERNEL);
 351         if (!map->active.ring)
 352                 goto out;
 353
 354         map->active.ring->ring_order = PVCALLS_RING_ORDER;
 355         bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 356                                         PVCALLS_RING_ORDER);
 357         if (!bytes)
 358                 goto out;
 359
 360         map->active.data.in = bytes;
 361         map->active.data.out = bytes +
 362                 XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 363
 364         return 0;
 365
 366 out:
 367         free_active_ring(map);
 368         return -ENOMEM;
 369 }
 370
 371 static int create_active(struct sock_mapping *map, evtchn_port_t *evtchn)
 372 {
 373         void *bytes;
 374         int ret, irq = -1, i;
 375
 376         *evtchn = 0;
 377         init_waitqueue_head(&map->active.inflight_conn_req);
 378
 379         bytes = map->active.data.in;
 380         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 381                 map->active.ring->ref[i] = gnttab_grant_foreign_access(
 382                         pvcalls_front_dev->otherend_id,
 383                         pfn_to_gfn(virt_to_pfn(bytes) + i), 0);
 384
 385         map->active.ref = gnttab_grant_foreign_access(
 386                 pvcalls_front_dev->otherend_id,
 387                 pfn_to_gfn(virt_to_pfn((void *)map->active.ring)), 0);
 388
 389         ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
 390         if (ret)
 391                 goto out_error;
 392         irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
 393                                         0, "pvcalls-frontend", map);
 394         if (irq < 0) {
 395                 ret = irq;
 396                 goto out_error;
 397         }
 398
 399         map->active.irq = irq;
 400         map->active_socket = true;
 401         mutex_init(&map->active.in_mutex);
 402         mutex_init(&map->active.out_mutex);
 403
 404         return 0;
 405
 406 out_error:
 407         if (*evtchn > 0)
 408                 xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
 409         return ret;
 410 }
 411
 412 int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 413                                 int addr_len, int flags)
 414 {
 415         struct pvcalls_bedata *bedata;
 416         struct sock_mapping *map = NULL;
 417         struct xen_pvcalls_request *req;
 418         int notify, req_id, ret;
 419         evtchn_port_t evtchn;
 420
 421         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 422                 return -EOPNOTSUPP;
 423
 424         map = pvcalls_enter_sock(sock);
 425         if (IS_ERR(map))
 426                 return PTR_ERR(map);
 427
 428         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 429         ret = alloc_active_ring(map);
 430         if (ret < 0) {
 431                 pvcalls_exit_sock(sock);
 432                 return ret;
 433         }
 434
 435         spin_lock(&bedata->socket_lock);
 436         ret = get_request(bedata, &req_id);
 437         if (ret < 0) {
 438                 spin_unlock(&bedata->socket_lock);
 439                 free_active_ring(map);
 440                 pvcalls_exit_sock(sock);
 441                 return ret;
 442         }
 443         ret = create_active(map, &evtchn);
 444         if (ret < 0) {
 445                 spin_unlock(&bedata->socket_lock);
 446                 free_active_ring(map);
 447                 pvcalls_exit_sock(sock);
 448                 return ret;
 449         }
 450
 451         req = RING_GET_REQUEST(&bedata->ring, req_id);
 452         req->req_id = req_id;
 453         req->cmd = PVCALLS_CONNECT;
 454         req->u.connect.id = (uintptr_t)map;
 455         req->u.connect.len = addr_len;
 456         req->u.connect.flags = flags;
 457         req->u.connect.ref = map->active.ref;
 458         req->u.connect.evtchn = evtchn;
 459         memcpy(req->u.connect.addr, addr, sizeof(*addr));
 460
 461         map->sock = sock;
 462
 463         bedata->ring.req_prod_pvt++;
 464         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 465         spin_unlock(&bedata->socket_lock);
 466
 467         if (notify)
 468                 notify_remote_via_irq(bedata->irq);
 469
 470         wait_event(bedata->inflight_req,
 471                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 472
 473         /* read req_id, then the content */
 474         smp_rmb();
 475         ret = bedata->rsp[req_id].ret;
 476         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 477         pvcalls_exit_sock(sock);
 478         return ret;
 479 }
 480
 481 static int __write_ring(struct pvcalls_data_intf *intf,
 482                         struct pvcalls_data *data,
 483                         struct iov_iter *msg_iter,
 484                         int len)
 485 {
 486         RING_IDX cons, prod, size, masked_prod, masked_cons;
 487         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 488         int32_t error;
 489
 490         error = intf->out_error;
 491         if (error < 0)
 492                 return error;
 493         cons = intf->out_cons;
 494         prod = intf->out_prod;
 495         /* read indexes before continuing */
 496         virt_mb();
 497
 498         size = pvcalls_queued(prod, cons, array_size);
 499         if (size > array_size)
 500                 return -EINVAL;
 501         if (size == array_size)
 502                 return 0;
 503         if (len > array_size - size)
 504                 len = array_size - size;
 505
 506         masked_prod = pvcalls_mask(prod, array_size);
 507         masked_cons = pvcalls_mask(cons, array_size);
 508
 509         if (masked_prod < masked_cons) {
 510                 len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 511         } else {
 512                 if (len > array_size - masked_prod) {
 513                         int ret = copy_from_iter(data->out + masked_prod,
 514                                        array_size - masked_prod, msg_iter);
 515                         if (ret != array_size - masked_prod) {
 516                                 len = ret;
 517                                 goto out;
 518                         }
 519                         len = ret + copy_from_iter(data->out, len - ret, msg_iter);
 520                 } else {
 521                         len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 522                 }
 523         }
 524 out:
 525         /* write to ring before updating pointer */
 526         virt_wmb();
 527         intf->out_prod += len;
 528
 529         return len;
 530 }
 531
 532 int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
 533                           size_t len)
 534 {
 535         struct sock_mapping *map;
 536         int sent, tot_sent = 0;
 537         int count = 0, flags;
 538
 539         flags = msg->msg_flags;
 540         if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
 541                 return -EOPNOTSUPP;
 542
 543         map = pvcalls_enter_sock(sock);
 544         if (IS_ERR(map))
 545                 return PTR_ERR(map);
 546
 547         mutex_lock(&map->active.out_mutex);
 548         if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
 549                 mutex_unlock(&map->active.out_mutex);
 550                 pvcalls_exit_sock(sock);
 551                 return -EAGAIN;
 552         }
 553         if (len > INT_MAX)
 554                 len = INT_MAX;
 555
 556 again:
 557         count++;
 558         sent = __write_ring(map->active.ring,
 559                             &map->active.data, &msg->msg_iter,
 560                             len);
 561         if (sent > 0) {
 562                 len -= sent;
 563                 tot_sent += sent;
 564                 notify_remote_via_irq(map->active.irq);
 565         }
 566         if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
 567                 goto again;
 568         if (sent < 0)
 569                 tot_sent = sent;
 570
 571         mutex_unlock(&map->active.out_mutex);
 572         pvcalls_exit_sock(sock);
 573         return tot_sent;
 574 }
 575
 576 static int __read_ring(struct pvcalls_data_intf *intf,
 577                        struct pvcalls_data *data,
 578                        struct iov_iter *msg_iter,
 579                        size_t len, int flags)
 580 {
 581         RING_IDX cons, prod, size, masked_prod, masked_cons;
 582         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 583         int32_t error;
 584
 585         cons = intf->in_cons;
 586         prod = intf->in_prod;
 587         error = intf->in_error;
 588         /* get pointers before reading from the ring */
 589         virt_rmb();
 590
 591         size = pvcalls_queued(prod, cons, array_size);
 592         masked_prod = pvcalls_mask(prod, array_size);
 593         masked_cons = pvcalls_mask(cons, array_size);
 594
 595         if (size == 0)
 596                 return error ?: size;
 597
 598         if (len > size)
 599                 len = size;
 600
 601         if (masked_prod > masked_cons) {
 602                 len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 603         } else {
 604                 if (len > (array_size - masked_cons)) {
 605                         int ret = copy_to_iter(data->in + masked_cons,
 606                                      array_size - masked_cons, msg_iter);
 607                         if (ret != array_size - masked_cons) {
 608                                 len = ret;
 609                                 goto out;
 610                         }
 611                         len = ret + copy_to_iter(data->in, len - ret, msg_iter);
 612                 } else {
 613                         len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 614                 }
 615         }
 616 out:
 617         /* read data from the ring before increasing the index */
 618         virt_mb();
 619         if (!(flags & MSG_PEEK))
 620                 intf->in_cons += len;
 621
 622         return len;
 623 }
 624
 625 int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 626                      int flags)
 627 {
 628         int ret;
 629         struct sock_mapping *map;
 630
 631         if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
 632                 return -EOPNOTSUPP;
 633
 634         map = pvcalls_enter_sock(sock);
 635         if (IS_ERR(map))
 636                 return PTR_ERR(map);
 637
 638         mutex_lock(&map->active.in_mutex);
 639         if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
 640                 len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 641
 642         while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
 643                 wait_event_interruptible(map->active.inflight_conn_req,
 644                                          pvcalls_front_read_todo(map));
 645         }
 646         ret = __read_ring(map->active.ring, &map->active.data,
 647                           &msg->msg_iter, len, flags);
 648
 649         if (ret > 0)
 650                 notify_remote_via_irq(map->active.irq);
 651         if (ret == 0)
 652                 ret = (flags & MSG_DONTWAIT) ? -EAGAIN : 0;
 653         if (ret == -ENOTCONN)
 654                 ret = 0;
 655
 656         mutex_unlock(&map->active.in_mutex);
 657         pvcalls_exit_sock(sock);
 658         return ret;
 659 }
 660
 661 int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 662 {
 663         struct pvcalls_bedata *bedata;
 664         struct sock_mapping *map = NULL;
 665         struct xen_pvcalls_request *req;
 666         int notify, req_id, ret;
 667
 668         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 669                 return -EOPNOTSUPP;
 670
 671         map = pvcalls_enter_sock(sock);
 672         if (IS_ERR(map))
 673                 return PTR_ERR(map);
 674         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 675
 676         spin_lock(&bedata->socket_lock);
 677         ret = get_request(bedata, &req_id);
 678         if (ret < 0) {
 679                 spin_unlock(&bedata->socket_lock);
 680                 pvcalls_exit_sock(sock);
 681                 return ret;
 682         }
 683         req = RING_GET_REQUEST(&bedata->ring, req_id);
 684         req->req_id = req_id;
 685         map->sock = sock;
 686         req->cmd = PVCALLS_BIND;
 687         req->u.bind.id = (uintptr_t)map;
 688         memcpy(req->u.bind.addr, addr, sizeof(*addr));
 689         req->u.bind.len = addr_len;
 690
 691         init_waitqueue_head(&map->passive.inflight_accept_req);
 692
 693         map->active_socket = false;
 694
 695         bedata->ring.req_prod_pvt++;
 696         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 697         spin_unlock(&bedata->socket_lock);
 698         if (notify)
 699                 notify_remote_via_irq(bedata->irq);
 700
 701         wait_event(bedata->inflight_req,
 702                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 703
 704         /* read req_id, then the content */
 705         smp_rmb();
 706         ret = bedata->rsp[req_id].ret;
 707         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 708
 709         map->passive.status = PVCALLS_STATUS_BIND;
 710         pvcalls_exit_sock(sock);
 711         return 0;
 712 }
 713
 714 int pvcalls_front_listen(struct socket *sock, int backlog)
 715 {
 716         struct pvcalls_bedata *bedata;
 717         struct sock_mapping *map;
 718         struct xen_pvcalls_request *req;
 719         int notify, req_id, ret;
 720
 721         map = pvcalls_enter_sock(sock);
 722         if (IS_ERR(map))
 723                 return PTR_ERR(map);
 724         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 725
 726         if (map->passive.status != PVCALLS_STATUS_BIND) {
 727                 pvcalls_exit_sock(sock);
 728                 return -EOPNOTSUPP;
 729         }
 730
 731         spin_lock(&bedata->socket_lock);
 732         ret = get_request(bedata, &req_id);
 733         if (ret < 0) {
 734                 spin_unlock(&bedata->socket_lock);
 735                 pvcalls_exit_sock(sock);
 736                 return ret;
 737         }
 738         req = RING_GET_REQUEST(&bedata->ring, req_id);
 739         req->req_id = req_id;
 740         req->cmd = PVCALLS_LISTEN;
 741         req->u.listen.id = (uintptr_t) map;
 742         req->u.listen.backlog = backlog;
 743
 744         bedata->ring.req_prod_pvt++;
 745         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 746         spin_unlock(&bedata->socket_lock);
 747         if (notify)
 748                 notify_remote_via_irq(bedata->irq);
 749
 750         wait_event(bedata->inflight_req,
 751                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 752
 753         /* read req_id, then the content */
 754         smp_rmb();
 755         ret = bedata->rsp[req_id].ret;
 756         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 757
 758         map->passive.status = PVCALLS_STATUS_LISTEN;
 759         pvcalls_exit_sock(sock);
 760         return ret;
 761 }
 762
 763 int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
 764 {
 765         struct pvcalls_bedata *bedata;
 766         struct sock_mapping *map;
 767         struct sock_mapping *map2 = NULL;
 768         struct xen_pvcalls_request *req;
 769         int notify, req_id, ret, nonblock;
 770         evtchn_port_t evtchn;
 771
 772         map = pvcalls_enter_sock(sock);
 773         if (IS_ERR(map))
 774                 return PTR_ERR(map);
 775         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 776
 777         if (map->passive.status != PVCALLS_STATUS_LISTEN) {
 778                 pvcalls_exit_sock(sock);
 779                 return -EINVAL;
 780         }
 781
 782         nonblock = flags & SOCK_NONBLOCK;
 783         /*
 784          * Backend only supports 1 inflight accept request, will return
 785          * errors for the others
 786          */
 787         if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 788                              (void *)&map->passive.flags)) {
 789                 req_id = READ_ONCE(map->passive.inflight_req_id);
 790                 if (req_id != PVCALLS_INVALID_ID &&
 791                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id) {
 792                         map2 = map->passive.accept_map;
 793                         goto received;
 794                 }
 795                 if (nonblock) {
 796                         pvcalls_exit_sock(sock);
 797                         return -EAGAIN;
 798                 }
 799                 if (wait_event_interruptible(map->passive.inflight_accept_req,
 800                         !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 801                                           (void *)&map->passive.flags))) {
 802                         pvcalls_exit_sock(sock);
 803                         return -EINTR;
 804                 }
 805         }
 806
 807         map2 = kzalloc(sizeof(*map2), GFP_KERNEL);
 808         if (map2 == NULL) {
 809                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 810                           (void *)&map->passive.flags);
 811                 pvcalls_exit_sock(sock);
 812                 return -ENOMEM;
 813         }
 814         ret = alloc_active_ring(map2);
 815         if (ret < 0) {
 816                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 817                                 (void *)&map->passive.flags);
 818                 kfree(map2);
 819                 pvcalls_exit_sock(sock);
 820                 return ret;
 821         }
 822         spin_lock(&bedata->socket_lock);
 823         ret = get_request(bedata, &req_id);
 824         if (ret < 0) {
 825                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 826                           (void *)&map->passive.flags);
 827                 spin_unlock(&bedata->socket_lock);
 828                 free_active_ring(map2);
 829                 kfree(map2);
 830                 pvcalls_exit_sock(sock);
 831                 return ret;
 832         }
 833
 834         ret = create_active(map2, &evtchn);
 835         if (ret < 0) {
 836                 free_active_ring(map2);
 837                 kfree(map2);
 838                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 839                           (void *)&map->passive.flags);
 840                 spin_unlock(&bedata->socket_lock);
 841                 pvcalls_exit_sock(sock);
 842                 return ret;
 843         }
 844         list_add_tail(&map2->list, &bedata->socket_mappings);
 845
 846         req = RING_GET_REQUEST(&bedata->ring, req_id);
 847         req->req_id = req_id;
 848         req->cmd = PVCALLS_ACCEPT;
 849         req->u.accept.id = (uintptr_t) map;
 850         req->u.accept.ref = map2->active.ref;
 851         req->u.accept.id_new = (uintptr_t) map2;
 852         req->u.accept.evtchn = evtchn;
 853         map->passive.accept_map = map2;
 854
 855         bedata->ring.req_prod_pvt++;
 856         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 857         spin_unlock(&bedata->socket_lock);
 858         if (notify)
 859                 notify_remote_via_irq(bedata->irq);
 860         /* We could check if we have received a response before returning. */
 861         if (nonblock) {
 862                 WRITE_ONCE(map->passive.inflight_req_id, req_id);
 863                 pvcalls_exit_sock(sock);
 864                 return -EAGAIN;
 865         }
 866
 867         if (wait_event_interruptible(bedata->inflight_req,
 868                 READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
 869                 pvcalls_exit_sock(sock);
 870                 return -EINTR;
 871         }
 872         /* read req_id, then the content */
 873         smp_rmb();
 874
 875 received:
 876         map2->sock = newsock;
 877         newsock->sk = sk_alloc(sock_net(sock->sk), PF_INET, GFP_KERNEL, &pvcalls_proto, false);
 878         if (!newsock->sk) {
 879                 bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 880                 map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 881                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 882                           (void *)&map->passive.flags);
 883                 pvcalls_front_free_map(bedata, map2);
 884                 pvcalls_exit_sock(sock);
 885                 return -ENOMEM;
 886         }
 887         newsock->sk->sk_send_head = (void *)map2;
 888
 889         ret = bedata->rsp[req_id].ret;
 890         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 891         map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 892
 893         clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
 894         wake_up(&map->passive.inflight_accept_req);
 895
 896         pvcalls_exit_sock(sock);
 897         return ret;
 898 }
 899
 900 static __poll_t pvcalls_front_poll_passive(struct file *file,
 901                                                struct pvcalls_bedata *bedata,
 902                                                struct sock_mapping *map,
 903                                                poll_table *wait)
 904 {
 905         int notify, req_id, ret;
 906         struct xen_pvcalls_request *req;
 907
 908         if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 909                      (void *)&map->passive.flags)) {
 910                 uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
 911
 912                 if (req_id != PVCALLS_INVALID_ID &&
 913                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
 914                         return EPOLLIN | EPOLLRDNORM;
 915
 916                 poll_wait(file, &map->passive.inflight_accept_req, wait);
 917                 return 0;
 918         }
 919
 920         if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
 921                                (void *)&map->passive.flags))
 922                 return EPOLLIN | EPOLLRDNORM;
 923
 924         /*
 925          * First check RET, then INFLIGHT. No barriers necessary to
 926          * ensure execution ordering because of the conditional
 927          * instructions creating control dependencies.
 928          */
 929
 930         if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 931                              (void *)&map->passive.flags)) {
 932                 poll_wait(file, &bedata->inflight_req, wait);
 933                 return 0;
 934         }
 935
 936         spin_lock(&bedata->socket_lock);
 937         ret = get_request(bedata, &req_id);
 938         if (ret < 0) {
 939                 spin_unlock(&bedata->socket_lock);
 940                 return ret;
 941         }
 942         req = RING_GET_REQUEST(&bedata->ring, req_id);
 943         req->req_id = req_id;
 944         req->cmd = PVCALLS_POLL;
 945         req->u.poll.id = (uintptr_t) map;
 946
 947         bedata->ring.req_prod_pvt++;
 948         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 949         spin_unlock(&bedata->socket_lock);
 950         if (notify)
 951                 notify_remote_via_irq(bedata->irq);
 952
 953         poll_wait(file, &bedata->inflight_req, wait);
 954         return 0;
 955 }
 956
 957 static __poll_t pvcalls_front_poll_active(struct file *file,
 958                                               struct pvcalls_bedata *bedata,
 959                                               struct sock_mapping *map,
 960                                               poll_table *wait)
 961 {
 962         __poll_t mask = 0;
 963         int32_t in_error, out_error;
 964         struct pvcalls_data_intf *intf = map->active.ring;
 965
 966         out_error = intf->out_error;
 967         in_error = intf->in_error;
 968
 969         poll_wait(file, &map->active.inflight_conn_req, wait);
 970         if (pvcalls_front_write_todo(map))
 971                 mask |= EPOLLOUT | EPOLLWRNORM;
 972         if (pvcalls_front_read_todo(map))
 973                 mask |= EPOLLIN | EPOLLRDNORM;
 974         if (in_error != 0 || out_error != 0)
 975                 mask |= EPOLLERR;
 976
 977         return mask;
 978 }
 979
 980 __poll_t pvcalls_front_poll(struct file *file, struct socket *sock,
 981                                poll_table *wait)
 982 {
 983         struct pvcalls_bedata *bedata;
 984         struct sock_mapping *map;
 985         __poll_t ret;
 986
 987         map = pvcalls_enter_sock(sock);
 988         if (IS_ERR(map))
 989                 return EPOLLNVAL;
 990         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 991
 992         if (map->active_socket)
 993                 ret = pvcalls_front_poll_active(file, bedata, map, wait);
 994         else
 995                 ret = pvcalls_front_poll_passive(file, bedata, map, wait);
 996         pvcalls_exit_sock(sock);
 997         return ret;
 998 }
 999
1000 int pvcalls_front_release(struct socket *sock)
1001 {
1002         struct pvcalls_bedata *bedata;
1003         struct sock_mapping *map;
1004         int req_id, notify, ret;
1005         struct xen_pvcalls_request *req;
1006
1007         if (sock->sk == NULL)
1008                 return 0;
1009
1010         map = pvcalls_enter_sock(sock);
1011         if (IS_ERR(map)) {
1012                 if (PTR_ERR(map) == -ENOTCONN)
1013                         return -EIO;
1014                 else
1015                         return 0;
1016         }
1017         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1018
1019         spin_lock(&bedata->socket_lock);
1020         ret = get_request(bedata, &req_id);
1021         if (ret < 0) {
1022                 spin_unlock(&bedata->socket_lock);
1023                 pvcalls_exit_sock(sock);
1024                 return ret;
1025         }
1026         sock->sk->sk_send_head = NULL;
1027
1028         req = RING_GET_REQUEST(&bedata->ring, req_id);
1029         req->req_id = req_id;
1030         req->cmd = PVCALLS_RELEASE;
1031         req->u.release.id = (uintptr_t)map;
1032
1033         bedata->ring.req_prod_pvt++;
1034         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
1035         spin_unlock(&bedata->socket_lock);
1036         if (notify)
1037                 notify_remote_via_irq(bedata->irq);
1038
1039         wait_event(bedata->inflight_req,
1040                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
1041
1042         if (map->active_socket) {
1043                 /*
1044                  * Set in_error and wake up inflight_conn_req to force
1045                  * recvmsg waiters to exit.
1046                  */
1047                 map->active.ring->in_error = -EBADF;
1048                 wake_up_interruptible(&map->active.inflight_conn_req);
1049
1050                 /*
1051                  * We need to make sure that sendmsg/recvmsg on this socket have
1052                  * not started before we've cleared sk_send_head here. The
1053                  * easiest way to guarantee this is to see that no pvcalls
1054                  * (other than us) is in progress on this socket.
1055                  */
1056                 while (atomic_read(&map->refcount) > 1)
1057                         cpu_relax();
1058
1059                 pvcalls_front_free_map(bedata, map);
1060         } else {
1061                 wake_up(&bedata->inflight_req);
1062                 wake_up(&map->passive.inflight_accept_req);
1063
1064                 while (atomic_read(&map->refcount) > 1)
1065                         cpu_relax();
1066
1067                 spin_lock(&bedata->socket_lock);
1068                 list_del(&map->list);
1069                 spin_unlock(&bedata->socket_lock);
1070                 if (READ_ONCE(map->passive.inflight_req_id) != PVCALLS_INVALID_ID &&
1071                         READ_ONCE(map->passive.inflight_req_id) != 0) {
1072                         pvcalls_front_free_map(bedata,
1073                                                map->passive.accept_map);
1074                 }
1075                 kfree(map);
1076         }
1077         WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
1078
1079         pvcalls_exit();
1080         return 0;
1081 }
1082
1083 static const struct xenbus_device_id pvcalls_front_ids[] = {
1084         { "pvcalls" },
1085         { "" }
1086 };
1087
1088 static int pvcalls_front_remove(struct xenbus_device *dev)
1089 {
1090         struct pvcalls_bedata *bedata;
1091         struct sock_mapping *map = NULL, *n;
1092
1093         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1094         dev_set_drvdata(&dev->dev, NULL);
1095         pvcalls_front_dev = NULL;
1096         if (bedata->irq >= 0)
1097                 unbind_from_irqhandler(bedata->irq, dev);
1098
1099         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1100                 map->sock->sk->sk_send_head = NULL;
1101                 if (map->active_socket) {
1102                         map->active.ring->in_error = -EBADF;
1103                         wake_up_interruptible(&map->active.inflight_conn_req);
1104                 }
1105         }
1106
1107         smp_mb();
1108         while (atomic_read(&pvcalls_refcount) > 0)
1109                 cpu_relax();
1110         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1111                 if (map->active_socket) {
1112                         /* No need to lock, refcount is 0 */
1113                         pvcalls_front_free_map(bedata, map);
1114                 } else {
1115                         list_del(&map->list);
1116                         kfree(map);
1117                 }
1118         }
1119         if (bedata->ref != -1)
1120                 gnttab_end_foreign_access(bedata->ref, 0, 0);
1121         kfree(bedata->ring.sring);
1122         kfree(bedata);
1123         xenbus_switch_state(dev, XenbusStateClosed);
1124         return 0;
1125 }
1126
1127 static int pvcalls_front_probe(struct xenbus_device *dev,
1128                           const struct xenbus_device_id *id)
1129 {
1130         int ret = -ENOMEM, i;
1131         evtchn_port_t evtchn;
1132         unsigned int max_page_order, function_calls, len;
1133         char *versions;
1134         grant_ref_t gref_head = 0;
1135         struct xenbus_transaction xbt;
1136         struct pvcalls_bedata *bedata = NULL;
1137         struct xen_pvcalls_sring *sring;
1138
1139         if (pvcalls_front_dev != NULL) {
1140                 dev_err(&dev->dev, "only one PV Calls connection supported\n");
1141                 return -EINVAL;
1142         }
1143
1144         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
1145         if (IS_ERR(versions))
1146                 return PTR_ERR(versions);
1147         if (!len)
1148                 return -EINVAL;
1149         if (strcmp(versions, "1")) {
1150                 kfree(versions);
1151                 return -EINVAL;
1152         }
1153         kfree(versions);
1154         max_page_order = xenbus_read_unsigned(dev->otherend,
1155                                               "max-page-order", 0);
1156         if (max_page_order < PVCALLS_RING_ORDER)
1157                 return -ENODEV;
1158         function_calls = xenbus_read_unsigned(dev->otherend,
1159                                               "function-calls", 0);
1160         /* See XENBUS_FUNCTIONS_CALLS in pvcalls.h */
1161         if (function_calls != 1)
1162                 return -ENODEV;
1163         pr_info("%s max-page-order is %u\n", __func__, max_page_order);
1164
1165         bedata = kzalloc(sizeof(struct pvcalls_bedata), GFP_KERNEL);
1166         if (!bedata)
1167                 return -ENOMEM;
1168
1169         dev_set_drvdata(&dev->dev, bedata);
1170         pvcalls_front_dev = dev;
1171         init_waitqueue_head(&bedata->inflight_req);
1172         INIT_LIST_HEAD(&bedata->socket_mappings);
1173         spin_lock_init(&bedata->socket_lock);
1174         bedata->irq = -1;
1175         bedata->ref = -1;
1176
1177         for (i = 0; i < PVCALLS_NR_RSP_PER_RING; i++)
1178                 bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
1179
1180         sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
1181                                                              __GFP_ZERO);
1182         if (!sring)
1183                 goto error;
1184         SHARED_RING_INIT(sring);
1185         FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
1186
1187         ret = xenbus_alloc_evtchn(dev, &evtchn);
1188         if (ret)
1189                 goto error;
1190
1191         bedata->irq = bind_evtchn_to_irqhandler(evtchn,
1192                                                 pvcalls_front_event_handler,
1193                                                 0, "pvcalls-frontend", dev);
1194         if (bedata->irq < 0) {
1195                 ret = bedata->irq;
1196                 goto error;
1197         }
1198
1199         ret = gnttab_alloc_grant_references(1, &gref_head);
1200         if (ret < 0)
1201                 goto error;
1202         ret = gnttab_claim_grant_reference(&gref_head);
1203         if (ret < 0)
1204                 goto error;
1205         bedata->ref = ret;
1206         gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
1207                                         virt_to_gfn((void *)sring), 0);
1208
1209  again:
1210         ret = xenbus_transaction_start(&xbt);
1211         if (ret) {
1212                 xenbus_dev_fatal(dev, ret, "starting transaction");
1213                 goto error;
1214         }
1215         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
1216         if (ret)
1217                 goto error_xenbus;
1218         ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
1219         if (ret)
1220                 goto error_xenbus;
1221         ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
1222                             evtchn);
1223         if (ret)
1224                 goto error_xenbus;
1225         ret = xenbus_transaction_end(xbt, 0);
1226         if (ret) {
1227                 if (ret == -EAGAIN)
1228                         goto again;
1229                 xenbus_dev_fatal(dev, ret, "completing transaction");
1230                 goto error;
1231         }
1232         xenbus_switch_state(dev, XenbusStateInitialised);
1233
1234         return 0;
1235
1236  error_xenbus:
1237         xenbus_transaction_end(xbt, 1);
1238         xenbus_dev_fatal(dev, ret, "writing xenstore");
1239  error:
1240         pvcalls_front_remove(dev);
1241         return ret;
1242 }
1243
1244 static void pvcalls_front_changed(struct xenbus_device *dev,
1245                             enum xenbus_state backend_state)
1246 {
1247         switch (backend_state) {
1248         case XenbusStateReconfiguring:
1249         case XenbusStateReconfigured:
1250         case XenbusStateInitialising:
1251         case XenbusStateInitialised:
1252         case XenbusStateUnknown:
1253                 break;
1254
1255         case XenbusStateInitWait:
1256                 break;
1257
1258         case XenbusStateConnected:
1259                 xenbus_switch_state(dev, XenbusStateConnected);
1260                 break;
1261
1262         case XenbusStateClosed:
1263                 if (dev->state == XenbusStateClosed)
1264                         break;
1265                 /* Missed the backend's CLOSING state */
1266                 fallthrough;
1267         case XenbusStateClosing:
1268                 xenbus_frontend_closed(dev);
1269                 break;
1270         }
1271 }
1272
1273 static struct xenbus_driver pvcalls_front_driver = {
1274         .ids = pvcalls_front_ids,
1275         .probe = pvcalls_front_probe,
1276         .remove = pvcalls_front_remove,
1277         .otherend_changed = pvcalls_front_changed,
1278 };
1279
1280 static int __init pvcalls_frontend_init(void)
1281 {
1282         if (!xen_domain())
1283                 return -ENODEV;
1284
1285         pr_info("Initialising Xen pvcalls frontend driver\n");
1286
1287         return xenbus_register_frontend(&pvcalls_front_driver);
1288 }
1289
1290 module_init(pvcalls_frontend_init);
1291
1292 MODULE_DESCRIPTION("Xen PV Calls frontend driver");
1293 MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
1294 MODULE_LICENSE("GPL");