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 void free_active_ring(struct sock_mapping *map)
 345 {
 346         free_pages((unsigned long)map->active.data.in,
 347                         map->active.ring->ring_order);
 348         free_page((unsigned long)map->active.ring);
 349 }
 350
 351 static int alloc_active_ring(struct sock_mapping *map)
 352 {
 353         void *bytes;
 354
 355         map->active.ring = (struct pvcalls_data_intf *)
 356                 get_zeroed_page(GFP_KERNEL);
 357         if (!map->active.ring)
 358                 goto out;
 359
 360         map->active.ring->ring_order = PVCALLS_RING_ORDER;
 361         bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 362                                         PVCALLS_RING_ORDER);
 363         if (!bytes)
 364                 goto out;
 365
 366         map->active.data.in = bytes;
 367         map->active.data.out = bytes +
 368                 XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 369
 370         return 0;
 371
 372 out:
 373         free_active_ring(map);
 374         return -ENOMEM;
 375 }
 376
 377 static int create_active(struct sock_mapping *map, int *evtchn)
 378 {
 379         void *bytes;
 380         int ret = -ENOMEM, irq = -1, i;
 381
 382         *evtchn = -1;
 383         init_waitqueue_head(&map->active.inflight_conn_req);
 384
 385         bytes = map->active.data.in;
 386         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 387                 map->active.ring->ref[i] = gnttab_grant_foreign_access(
 388                         pvcalls_front_dev->otherend_id,
 389                         pfn_to_gfn(virt_to_pfn(bytes) + i), 0);
 390
 391         map->active.ref = gnttab_grant_foreign_access(
 392                 pvcalls_front_dev->otherend_id,
 393                 pfn_to_gfn(virt_to_pfn((void *)map->active.ring)), 0);
 394
 395         ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
 396         if (ret)
 397                 goto out_error;
 398         irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
 399                                         0, "pvcalls-frontend", map);
 400         if (irq < 0) {
 401                 ret = irq;
 402                 goto out_error;
 403         }
 404
 405         map->active.irq = irq;
 406         map->active_socket = true;
 407         mutex_init(&map->active.in_mutex);
 408         mutex_init(&map->active.out_mutex);
 409
 410         return 0;
 411
 412 out_error:
 413         if (*evtchn >= 0)
 414                 xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
 415         return ret;
 416 }
 417
 418 int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 419                                 int addr_len, int flags)
 420 {
 421         struct pvcalls_bedata *bedata;
 422         struct sock_mapping *map = NULL;
 423         struct xen_pvcalls_request *req;
 424         int notify, req_id, ret, evtchn;
 425
 426         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 427                 return -EOPNOTSUPP;
 428
 429         map = pvcalls_enter_sock(sock);
 430         if (IS_ERR(map))
 431                 return PTR_ERR(map);
 432
 433         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 434         ret = alloc_active_ring(map);
 435         if (ret < 0) {
 436                 pvcalls_exit_sock(sock);
 437                 return ret;
 438         }
 439
 440         spin_lock(&bedata->socket_lock);
 441         ret = get_request(bedata, &req_id);
 442         if (ret < 0) {
 443                 spin_unlock(&bedata->socket_lock);
 444                 free_active_ring(map);
 445                 pvcalls_exit_sock(sock);
 446                 return ret;
 447         }
 448         ret = create_active(map, &evtchn);
 449         if (ret < 0) {
 450                 spin_unlock(&bedata->socket_lock);
 451                 free_active_ring(map);
 452                 pvcalls_exit_sock(sock);
 453                 return ret;
 454         }
 455
 456         req = RING_GET_REQUEST(&bedata->ring, req_id);
 457         req->req_id = req_id;
 458         req->cmd = PVCALLS_CONNECT;
 459         req->u.connect.id = (uintptr_t)map;
 460         req->u.connect.len = addr_len;
 461         req->u.connect.flags = flags;
 462         req->u.connect.ref = map->active.ref;
 463         req->u.connect.evtchn = evtchn;
 464         memcpy(req->u.connect.addr, addr, sizeof(*addr));
 465
 466         map->sock = sock;
 467
 468         bedata->ring.req_prod_pvt++;
 469         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 470         spin_unlock(&bedata->socket_lock);
 471
 472         if (notify)
 473                 notify_remote_via_irq(bedata->irq);
 474
 475         wait_event(bedata->inflight_req,
 476                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 477
 478         /* read req_id, then the content */
 479         smp_rmb();
 480         ret = bedata->rsp[req_id].ret;
 481         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 482         pvcalls_exit_sock(sock);
 483         return ret;
 484 }
 485
 486 static int __write_ring(struct pvcalls_data_intf *intf,
 487                         struct pvcalls_data *data,
 488                         struct iov_iter *msg_iter,
 489                         int len)
 490 {
 491         RING_IDX cons, prod, size, masked_prod, masked_cons;
 492         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 493         int32_t error;
 494
 495         error = intf->out_error;
 496         if (error < 0)
 497                 return error;
 498         cons = intf->out_cons;
 499         prod = intf->out_prod;
 500         /* read indexes before continuing */
 501         virt_mb();
 502
 503         size = pvcalls_queued(prod, cons, array_size);
 504         if (size > array_size)
 505                 return -EINVAL;
 506         if (size == array_size)
 507                 return 0;
 508         if (len > array_size - size)
 509                 len = array_size - size;
 510
 511         masked_prod = pvcalls_mask(prod, array_size);
 512         masked_cons = pvcalls_mask(cons, array_size);
 513
 514         if (masked_prod < masked_cons) {
 515                 len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 516         } else {
 517                 if (len > array_size - masked_prod) {
 518                         int ret = copy_from_iter(data->out + masked_prod,
 519                                        array_size - masked_prod, msg_iter);
 520                         if (ret != array_size - masked_prod) {
 521                                 len = ret;
 522                                 goto out;
 523                         }
 524                         len = ret + copy_from_iter(data->out, len - ret, msg_iter);
 525                 } else {
 526                         len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 527                 }
 528         }
 529 out:
 530         /* write to ring before updating pointer */
 531         virt_wmb();
 532         intf->out_prod += len;
 533
 534         return len;
 535 }
 536
 537 int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
 538                           size_t len)
 539 {
 540         struct pvcalls_bedata *bedata;
 541         struct sock_mapping *map;
 542         int sent, tot_sent = 0;
 543         int count = 0, flags;
 544
 545         flags = msg->msg_flags;
 546         if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
 547                 return -EOPNOTSUPP;
 548
 549         map = pvcalls_enter_sock(sock);
 550         if (IS_ERR(map))
 551                 return PTR_ERR(map);
 552         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 553
 554         mutex_lock(&map->active.out_mutex);
 555         if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
 556                 mutex_unlock(&map->active.out_mutex);
 557                 pvcalls_exit_sock(sock);
 558                 return -EAGAIN;
 559         }
 560         if (len > INT_MAX)
 561                 len = INT_MAX;
 562
 563 again:
 564         count++;
 565         sent = __write_ring(map->active.ring,
 566                             &map->active.data, &msg->msg_iter,
 567                             len);
 568         if (sent > 0) {
 569                 len -= sent;
 570                 tot_sent += sent;
 571                 notify_remote_via_irq(map->active.irq);
 572         }
 573         if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
 574                 goto again;
 575         if (sent < 0)
 576                 tot_sent = sent;
 577
 578         mutex_unlock(&map->active.out_mutex);
 579         pvcalls_exit_sock(sock);
 580         return tot_sent;
 581 }
 582
 583 static int __read_ring(struct pvcalls_data_intf *intf,
 584                        struct pvcalls_data *data,
 585                        struct iov_iter *msg_iter,
 586                        size_t len, int flags)
 587 {
 588         RING_IDX cons, prod, size, masked_prod, masked_cons;
 589         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 590         int32_t error;
 591
 592         cons = intf->in_cons;
 593         prod = intf->in_prod;
 594         error = intf->in_error;
 595         /* get pointers before reading from the ring */
 596         virt_rmb();
 597
 598         size = pvcalls_queued(prod, cons, array_size);
 599         masked_prod = pvcalls_mask(prod, array_size);
 600         masked_cons = pvcalls_mask(cons, array_size);
 601
 602         if (size == 0)
 603                 return error ?: size;
 604
 605         if (len > size)
 606                 len = size;
 607
 608         if (masked_prod > masked_cons) {
 609                 len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 610         } else {
 611                 if (len > (array_size - masked_cons)) {
 612                         int ret = copy_to_iter(data->in + masked_cons,
 613                                      array_size - masked_cons, msg_iter);
 614                         if (ret != array_size - masked_cons) {
 615                                 len = ret;
 616                                 goto out;
 617                         }
 618                         len = ret + copy_to_iter(data->in, len - ret, msg_iter);
 619                 } else {
 620                         len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 621                 }
 622         }
 623 out:
 624         /* read data from the ring before increasing the index */
 625         virt_mb();
 626         if (!(flags & MSG_PEEK))
 627                 intf->in_cons += len;
 628
 629         return len;
 630 }
 631
 632 int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 633                      int flags)
 634 {
 635         struct pvcalls_bedata *bedata;
 636         int ret;
 637         struct sock_mapping *map;
 638
 639         if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
 640                 return -EOPNOTSUPP;
 641
 642         map = pvcalls_enter_sock(sock);
 643         if (IS_ERR(map))
 644                 return PTR_ERR(map);
 645         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 646
 647         mutex_lock(&map->active.in_mutex);
 648         if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
 649                 len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 650
 651         while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
 652                 wait_event_interruptible(map->active.inflight_conn_req,
 653                                          pvcalls_front_read_todo(map));
 654         }
 655         ret = __read_ring(map->active.ring, &map->active.data,
 656                           &msg->msg_iter, len, flags);
 657
 658         if (ret > 0)
 659                 notify_remote_via_irq(map->active.irq);
 660         if (ret == 0)
 661                 ret = (flags & MSG_DONTWAIT) ? -EAGAIN : 0;
 662         if (ret == -ENOTCONN)
 663                 ret = 0;
 664
 665         mutex_unlock(&map->active.in_mutex);
 666         pvcalls_exit_sock(sock);
 667         return ret;
 668 }
 669
 670 int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 671 {
 672         struct pvcalls_bedata *bedata;
 673         struct sock_mapping *map = NULL;
 674         struct xen_pvcalls_request *req;
 675         int notify, req_id, ret;
 676
 677         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 678                 return -EOPNOTSUPP;
 679
 680         map = pvcalls_enter_sock(sock);
 681         if (IS_ERR(map))
 682                 return PTR_ERR(map);
 683         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 684
 685         spin_lock(&bedata->socket_lock);
 686         ret = get_request(bedata, &req_id);
 687         if (ret < 0) {
 688                 spin_unlock(&bedata->socket_lock);
 689                 pvcalls_exit_sock(sock);
 690                 return ret;
 691         }
 692         req = RING_GET_REQUEST(&bedata->ring, req_id);
 693         req->req_id = req_id;
 694         map->sock = sock;
 695         req->cmd = PVCALLS_BIND;
 696         req->u.bind.id = (uintptr_t)map;
 697         memcpy(req->u.bind.addr, addr, sizeof(*addr));
 698         req->u.bind.len = addr_len;
 699
 700         init_waitqueue_head(&map->passive.inflight_accept_req);
 701
 702         map->active_socket = false;
 703
 704         bedata->ring.req_prod_pvt++;
 705         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 706         spin_unlock(&bedata->socket_lock);
 707         if (notify)
 708                 notify_remote_via_irq(bedata->irq);
 709
 710         wait_event(bedata->inflight_req,
 711                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 712
 713         /* read req_id, then the content */
 714         smp_rmb();
 715         ret = bedata->rsp[req_id].ret;
 716         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 717
 718         map->passive.status = PVCALLS_STATUS_BIND;
 719         pvcalls_exit_sock(sock);
 720         return 0;
 721 }
 722
 723 int pvcalls_front_listen(struct socket *sock, int backlog)
 724 {
 725         struct pvcalls_bedata *bedata;
 726         struct sock_mapping *map;
 727         struct xen_pvcalls_request *req;
 728         int notify, req_id, ret;
 729
 730         map = pvcalls_enter_sock(sock);
 731         if (IS_ERR(map))
 732                 return PTR_ERR(map);
 733         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 734
 735         if (map->passive.status != PVCALLS_STATUS_BIND) {
 736                 pvcalls_exit_sock(sock);
 737                 return -EOPNOTSUPP;
 738         }
 739
 740         spin_lock(&bedata->socket_lock);
 741         ret = get_request(bedata, &req_id);
 742         if (ret < 0) {
 743                 spin_unlock(&bedata->socket_lock);
 744                 pvcalls_exit_sock(sock);
 745                 return ret;
 746         }
 747         req = RING_GET_REQUEST(&bedata->ring, req_id);
 748         req->req_id = req_id;
 749         req->cmd = PVCALLS_LISTEN;
 750         req->u.listen.id = (uintptr_t) map;
 751         req->u.listen.backlog = backlog;
 752
 753         bedata->ring.req_prod_pvt++;
 754         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 755         spin_unlock(&bedata->socket_lock);
 756         if (notify)
 757                 notify_remote_via_irq(bedata->irq);
 758
 759         wait_event(bedata->inflight_req,
 760                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 761
 762         /* read req_id, then the content */
 763         smp_rmb();
 764         ret = bedata->rsp[req_id].ret;
 765         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 766
 767         map->passive.status = PVCALLS_STATUS_LISTEN;
 768         pvcalls_exit_sock(sock);
 769         return ret;
 770 }
 771
 772 int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
 773 {
 774         struct pvcalls_bedata *bedata;
 775         struct sock_mapping *map;
 776         struct sock_mapping *map2 = NULL;
 777         struct xen_pvcalls_request *req;
 778         int notify, req_id, ret, evtchn, nonblock;
 779
 780         map = pvcalls_enter_sock(sock);
 781         if (IS_ERR(map))
 782                 return PTR_ERR(map);
 783         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 784
 785         if (map->passive.status != PVCALLS_STATUS_LISTEN) {
 786                 pvcalls_exit_sock(sock);
 787                 return -EINVAL;
 788         }
 789
 790         nonblock = flags & SOCK_NONBLOCK;
 791         /*
 792          * Backend only supports 1 inflight accept request, will return
 793          * errors for the others
 794          */
 795         if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 796                              (void *)&map->passive.flags)) {
 797                 req_id = READ_ONCE(map->passive.inflight_req_id);
 798                 if (req_id != PVCALLS_INVALID_ID &&
 799                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id) {
 800                         map2 = map->passive.accept_map;
 801                         goto received;
 802                 }
 803                 if (nonblock) {
 804                         pvcalls_exit_sock(sock);
 805                         return -EAGAIN;
 806                 }
 807                 if (wait_event_interruptible(map->passive.inflight_accept_req,
 808                         !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 809                                           (void *)&map->passive.flags))) {
 810                         pvcalls_exit_sock(sock);
 811                         return -EINTR;
 812                 }
 813         }
 814
 815         map2 = kzalloc(sizeof(*map2), GFP_KERNEL);
 816         if (map2 == NULL) {
 817                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 818                           (void *)&map->passive.flags);
 819                 pvcalls_exit_sock(sock);
 820                 return -ENOMEM;
 821         }
 822         ret = alloc_active_ring(map2);
 823         if (ret < 0) {
 824                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 825                                 (void *)&map->passive.flags);
 826                 kfree(map2);
 827                 pvcalls_exit_sock(sock);
 828                 return ret;
 829         }
 830         spin_lock(&bedata->socket_lock);
 831         ret = get_request(bedata, &req_id);
 832         if (ret < 0) {
 833                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 834                           (void *)&map->passive.flags);
 835                 spin_unlock(&bedata->socket_lock);
 836                 free_active_ring(map2);
 837                 kfree(map2);
 838                 pvcalls_exit_sock(sock);
 839                 return ret;
 840         }
 841
 842         ret = create_active(map2, &evtchn);
 843         if (ret < 0) {
 844                 free_active_ring(map2);
 845                 kfree(map2);
 846                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 847                           (void *)&map->passive.flags);
 848                 spin_unlock(&bedata->socket_lock);
 849                 pvcalls_exit_sock(sock);
 850                 return ret;
 851         }
 852         list_add_tail(&map2->list, &bedata->socket_mappings);
 853
 854         req = RING_GET_REQUEST(&bedata->ring, req_id);
 855         req->req_id = req_id;
 856         req->cmd = PVCALLS_ACCEPT;
 857         req->u.accept.id = (uintptr_t) map;
 858         req->u.accept.ref = map2->active.ref;
 859         req->u.accept.id_new = (uintptr_t) map2;
 860         req->u.accept.evtchn = evtchn;
 861         map->passive.accept_map = map2;
 862
 863         bedata->ring.req_prod_pvt++;
 864         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 865         spin_unlock(&bedata->socket_lock);
 866         if (notify)
 867                 notify_remote_via_irq(bedata->irq);
 868         /* We could check if we have received a response before returning. */
 869         if (nonblock) {
 870                 WRITE_ONCE(map->passive.inflight_req_id, req_id);
 871                 pvcalls_exit_sock(sock);
 872                 return -EAGAIN;
 873         }
 874
 875         if (wait_event_interruptible(bedata->inflight_req,
 876                 READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
 877                 pvcalls_exit_sock(sock);
 878                 return -EINTR;
 879         }
 880         /* read req_id, then the content */
 881         smp_rmb();
 882
 883 received:
 884         map2->sock = newsock;
 885         newsock->sk = sk_alloc(sock_net(sock->sk), PF_INET, GFP_KERNEL, &pvcalls_proto, false);
 886         if (!newsock->sk) {
 887                 bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 888                 map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 889                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 890                           (void *)&map->passive.flags);
 891                 pvcalls_front_free_map(bedata, map2);
 892                 pvcalls_exit_sock(sock);
 893                 return -ENOMEM;
 894         }
 895         newsock->sk->sk_send_head = (void *)map2;
 896
 897         ret = bedata->rsp[req_id].ret;
 898         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 899         map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 900
 901         clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
 902         wake_up(&map->passive.inflight_accept_req);
 903
 904         pvcalls_exit_sock(sock);
 905         return ret;
 906 }
 907
 908 static __poll_t pvcalls_front_poll_passive(struct file *file,
 909                                                struct pvcalls_bedata *bedata,
 910                                                struct sock_mapping *map,
 911                                                poll_table *wait)
 912 {
 913         int notify, req_id, ret;
 914         struct xen_pvcalls_request *req;
 915
 916         if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 917                      (void *)&map->passive.flags)) {
 918                 uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
 919
 920                 if (req_id != PVCALLS_INVALID_ID &&
 921                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
 922                         return EPOLLIN | EPOLLRDNORM;
 923
 924                 poll_wait(file, &map->passive.inflight_accept_req, wait);
 925                 return 0;
 926         }
 927
 928         if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
 929                                (void *)&map->passive.flags))
 930                 return EPOLLIN | EPOLLRDNORM;
 931
 932         /*
 933          * First check RET, then INFLIGHT. No barriers necessary to
 934          * ensure execution ordering because of the conditional
 935          * instructions creating control dependencies.
 936          */
 937
 938         if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 939                              (void *)&map->passive.flags)) {
 940                 poll_wait(file, &bedata->inflight_req, wait);
 941                 return 0;
 942         }
 943
 944         spin_lock(&bedata->socket_lock);
 945         ret = get_request(bedata, &req_id);
 946         if (ret < 0) {
 947                 spin_unlock(&bedata->socket_lock);
 948                 return ret;
 949         }
 950         req = RING_GET_REQUEST(&bedata->ring, req_id);
 951         req->req_id = req_id;
 952         req->cmd = PVCALLS_POLL;
 953         req->u.poll.id = (uintptr_t) map;
 954
 955         bedata->ring.req_prod_pvt++;
 956         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 957         spin_unlock(&bedata->socket_lock);
 958         if (notify)
 959                 notify_remote_via_irq(bedata->irq);
 960
 961         poll_wait(file, &bedata->inflight_req, wait);
 962         return 0;
 963 }
 964
 965 static __poll_t pvcalls_front_poll_active(struct file *file,
 966                                               struct pvcalls_bedata *bedata,
 967                                               struct sock_mapping *map,
 968                                               poll_table *wait)
 969 {
 970         __poll_t mask = 0;
 971         int32_t in_error, out_error;
 972         struct pvcalls_data_intf *intf = map->active.ring;
 973
 974         out_error = intf->out_error;
 975         in_error = intf->in_error;
 976
 977         poll_wait(file, &map->active.inflight_conn_req, wait);
 978         if (pvcalls_front_write_todo(map))
 979                 mask |= EPOLLOUT | EPOLLWRNORM;
 980         if (pvcalls_front_read_todo(map))
 981                 mask |= EPOLLIN | EPOLLRDNORM;
 982         if (in_error != 0 || out_error != 0)
 983                 mask |= EPOLLERR;
 984
 985         return mask;
 986 }
 987
 988 __poll_t pvcalls_front_poll(struct file *file, struct socket *sock,
 989                                poll_table *wait)
 990 {
 991         struct pvcalls_bedata *bedata;
 992         struct sock_mapping *map;
 993         __poll_t ret;
 994
 995         map = pvcalls_enter_sock(sock);
 996         if (IS_ERR(map))
 997                 return EPOLLNVAL;
 998         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 999
1000         if (map->active_socket)
1001                 ret = pvcalls_front_poll_active(file, bedata, map, wait);
1002         else
1003                 ret = pvcalls_front_poll_passive(file, bedata, map, wait);
1004         pvcalls_exit_sock(sock);
1005         return ret;
1006 }
1007
1008 int pvcalls_front_release(struct socket *sock)
1009 {
1010         struct pvcalls_bedata *bedata;
1011         struct sock_mapping *map;
1012         int req_id, notify, ret;
1013         struct xen_pvcalls_request *req;
1014
1015         if (sock->sk == NULL)
1016                 return 0;
1017
1018         map = pvcalls_enter_sock(sock);
1019         if (IS_ERR(map)) {
1020                 if (PTR_ERR(map) == -ENOTCONN)
1021                         return -EIO;
1022                 else
1023                         return 0;
1024         }
1025         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1026
1027         spin_lock(&bedata->socket_lock);
1028         ret = get_request(bedata, &req_id);
1029         if (ret < 0) {
1030                 spin_unlock(&bedata->socket_lock);
1031                 pvcalls_exit_sock(sock);
1032                 return ret;
1033         }
1034         sock->sk->sk_send_head = NULL;
1035
1036         req = RING_GET_REQUEST(&bedata->ring, req_id);
1037         req->req_id = req_id;
1038         req->cmd = PVCALLS_RELEASE;
1039         req->u.release.id = (uintptr_t)map;
1040
1041         bedata->ring.req_prod_pvt++;
1042         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
1043         spin_unlock(&bedata->socket_lock);
1044         if (notify)
1045                 notify_remote_via_irq(bedata->irq);
1046
1047         wait_event(bedata->inflight_req,
1048                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
1049
1050         if (map->active_socket) {
1051                 /*
1052                  * Set in_error and wake up inflight_conn_req to force
1053                  * recvmsg waiters to exit.
1054                  */
1055                 map->active.ring->in_error = -EBADF;
1056                 wake_up_interruptible(&map->active.inflight_conn_req);
1057
1058                 /*
1059                  * We need to make sure that sendmsg/recvmsg on this socket have
1060                  * not started before we've cleared sk_send_head here. The
1061                  * easiest way to guarantee this is to see that no pvcalls
1062                  * (other than us) is in progress on this socket.
1063                  */
1064                 while (atomic_read(&map->refcount) > 1)
1065                         cpu_relax();
1066
1067                 pvcalls_front_free_map(bedata, map);
1068         } else {
1069                 wake_up(&bedata->inflight_req);
1070                 wake_up(&map->passive.inflight_accept_req);
1071
1072                 while (atomic_read(&map->refcount) > 1)
1073                         cpu_relax();
1074
1075                 spin_lock(&bedata->socket_lock);
1076                 list_del(&map->list);
1077                 spin_unlock(&bedata->socket_lock);
1078                 if (READ_ONCE(map->passive.inflight_req_id) != PVCALLS_INVALID_ID &&
1079                         READ_ONCE(map->passive.inflight_req_id) != 0) {
1080                         pvcalls_front_free_map(bedata,
1081                                                map->passive.accept_map);
1082                 }
1083                 kfree(map);
1084         }
1085         WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
1086
1087         pvcalls_exit();
1088         return 0;
1089 }
1090
1091 static const struct xenbus_device_id pvcalls_front_ids[] = {
1092         { "pvcalls" },
1093         { "" }
1094 };
1095
1096 static int pvcalls_front_remove(struct xenbus_device *dev)
1097 {
1098         struct pvcalls_bedata *bedata;
1099         struct sock_mapping *map = NULL, *n;
1100
1101         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1102         dev_set_drvdata(&dev->dev, NULL);
1103         pvcalls_front_dev = NULL;
1104         if (bedata->irq >= 0)
1105                 unbind_from_irqhandler(bedata->irq, dev);
1106
1107         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1108                 map->sock->sk->sk_send_head = NULL;
1109                 if (map->active_socket) {
1110                         map->active.ring->in_error = -EBADF;
1111                         wake_up_interruptible(&map->active.inflight_conn_req);
1112                 }
1113         }
1114
1115         smp_mb();
1116         while (atomic_read(&pvcalls_refcount) > 0)
1117                 cpu_relax();
1118         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1119                 if (map->active_socket) {
1120                         /* No need to lock, refcount is 0 */
1121                         pvcalls_front_free_map(bedata, map);
1122                 } else {
1123                         list_del(&map->list);
1124                         kfree(map);
1125                 }
1126         }
1127         if (bedata->ref != -1)
1128                 gnttab_end_foreign_access(bedata->ref, 0, 0);
1129         kfree(bedata->ring.sring);
1130         kfree(bedata);
1131         xenbus_switch_state(dev, XenbusStateClosed);
1132         return 0;
1133 }
1134
1135 static int pvcalls_front_probe(struct xenbus_device *dev,
1136                           const struct xenbus_device_id *id)
1137 {
1138         int ret = -ENOMEM, evtchn, i;
1139         unsigned int max_page_order, function_calls, len;
1140         char *versions;
1141         grant_ref_t gref_head = 0;
1142         struct xenbus_transaction xbt;
1143         struct pvcalls_bedata *bedata = NULL;
1144         struct xen_pvcalls_sring *sring;
1145
1146         if (pvcalls_front_dev != NULL) {
1147                 dev_err(&dev->dev, "only one PV Calls connection supported\n");
1148                 return -EINVAL;
1149         }
1150
1151         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
1152         if (IS_ERR(versions))
1153                 return PTR_ERR(versions);
1154         if (!len)
1155                 return -EINVAL;
1156         if (strcmp(versions, "1")) {
1157                 kfree(versions);
1158                 return -EINVAL;
1159         }
1160         kfree(versions);
1161         max_page_order = xenbus_read_unsigned(dev->otherend,
1162                                               "max-page-order", 0);
1163         if (max_page_order < PVCALLS_RING_ORDER)
1164                 return -ENODEV;
1165         function_calls = xenbus_read_unsigned(dev->otherend,
1166                                               "function-calls", 0);
1167         /* See XENBUS_FUNCTIONS_CALLS in pvcalls.h */
1168         if (function_calls != 1)
1169                 return -ENODEV;
1170         pr_info("%s max-page-order is %u\n", __func__, max_page_order);
1171
1172         bedata = kzalloc(sizeof(struct pvcalls_bedata), GFP_KERNEL);
1173         if (!bedata)
1174                 return -ENOMEM;
1175
1176         dev_set_drvdata(&dev->dev, bedata);
1177         pvcalls_front_dev = dev;
1178         init_waitqueue_head(&bedata->inflight_req);
1179         INIT_LIST_HEAD(&bedata->socket_mappings);
1180         spin_lock_init(&bedata->socket_lock);
1181         bedata->irq = -1;
1182         bedata->ref = -1;
1183
1184         for (i = 0; i < PVCALLS_NR_RSP_PER_RING; i++)
1185                 bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
1186
1187         sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
1188                                                              __GFP_ZERO);
1189         if (!sring)
1190                 goto error;
1191         SHARED_RING_INIT(sring);
1192         FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
1193
1194         ret = xenbus_alloc_evtchn(dev, &evtchn);
1195         if (ret)
1196                 goto error;
1197
1198         bedata->irq = bind_evtchn_to_irqhandler(evtchn,
1199                                                 pvcalls_front_event_handler,
1200                                                 0, "pvcalls-frontend", dev);
1201         if (bedata->irq < 0) {
1202                 ret = bedata->irq;
1203                 goto error;
1204         }
1205
1206         ret = gnttab_alloc_grant_references(1, &gref_head);
1207         if (ret < 0)
1208                 goto error;
1209         ret = gnttab_claim_grant_reference(&gref_head);
1210         if (ret < 0)
1211                 goto error;
1212         bedata->ref = ret;
1213         gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
1214                                         virt_to_gfn((void *)sring), 0);
1215
1216  again:
1217         ret = xenbus_transaction_start(&xbt);
1218         if (ret) {
1219                 xenbus_dev_fatal(dev, ret, "starting transaction");
1220                 goto error;
1221         }
1222         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
1223         if (ret)
1224                 goto error_xenbus;
1225         ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
1226         if (ret)
1227                 goto error_xenbus;
1228         ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
1229                             evtchn);
1230         if (ret)
1231                 goto error_xenbus;
1232         ret = xenbus_transaction_end(xbt, 0);
1233         if (ret) {
1234                 if (ret == -EAGAIN)
1235                         goto again;
1236                 xenbus_dev_fatal(dev, ret, "completing transaction");
1237                 goto error;
1238         }
1239         xenbus_switch_state(dev, XenbusStateInitialised);
1240
1241         return 0;
1242
1243  error_xenbus:
1244         xenbus_transaction_end(xbt, 1);
1245         xenbus_dev_fatal(dev, ret, "writing xenstore");
1246  error:
1247         pvcalls_front_remove(dev);
1248         return ret;
1249 }
1250
1251 static void pvcalls_front_changed(struct xenbus_device *dev,
1252                             enum xenbus_state backend_state)
1253 {
1254         switch (backend_state) {
1255         case XenbusStateReconfiguring:
1256         case XenbusStateReconfigured:
1257         case XenbusStateInitialising:
1258         case XenbusStateInitialised:
1259         case XenbusStateUnknown:
1260                 break;
1261
1262         case XenbusStateInitWait:
1263                 break;
1264
1265         case XenbusStateConnected:
1266                 xenbus_switch_state(dev, XenbusStateConnected);
1267                 break;
1268
1269         case XenbusStateClosed:
1270                 if (dev->state == XenbusStateClosed)
1271                         break;
1272                 /* Missed the backend's CLOSING state */
1273                 /* fall through */
1274         case XenbusStateClosing:
1275                 xenbus_frontend_closed(dev);
1276                 break;
1277         }
1278 }
1279
1280 static struct xenbus_driver pvcalls_front_driver = {
1281         .ids = pvcalls_front_ids,
1282         .probe = pvcalls_front_probe,
1283         .remove = pvcalls_front_remove,
1284         .otherend_changed = pvcalls_front_changed,
1285 };
1286
1287 static int __init pvcalls_frontend_init(void)
1288 {
1289         if (!xen_domain())
1290                 return -ENODEV;
1291
1292         pr_info("Initialising Xen pvcalls frontend driver\n");
1293
1294         return xenbus_register_frontend(&pvcalls_front_driver);
1295 }
1296
1297 module_init(pvcalls_frontend_init);
1298
1299 MODULE_DESCRIPTION("Xen PV Calls frontend driver");
1300 MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
1301 MODULE_LICENSE("GPL");