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         if (!map->active.ring)
 347                 return;
 348
 349         free_pages((unsigned long)map->active.data.in,
 350                         map->active.ring->ring_order);
 351         free_page((unsigned long)map->active.ring);
 352 }
 353
 354 static int alloc_active_ring(struct sock_mapping *map)
 355 {
 356         void *bytes;
 357
 358         map->active.ring = (struct pvcalls_data_intf *)
 359                 get_zeroed_page(GFP_KERNEL);
 360         if (!map->active.ring)
 361                 goto out;
 362
 363         map->active.ring->ring_order = PVCALLS_RING_ORDER;
 364         bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 365                                         PVCALLS_RING_ORDER);
 366         if (!bytes)
 367                 goto out;
 368
 369         map->active.data.in = bytes;
 370         map->active.data.out = bytes +
 371                 XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 372
 373         return 0;
 374
 375 out:
 376         free_active_ring(map);
 377         return -ENOMEM;
 378 }
 379
 380 static int create_active(struct sock_mapping *map, int *evtchn)
 381 {
 382         void *bytes;
 383         int ret = -ENOMEM, irq = -1, i;
 384
 385         *evtchn = -1;
 386         init_waitqueue_head(&map->active.inflight_conn_req);
 387
 388         bytes = map->active.data.in;
 389         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 390                 map->active.ring->ref[i] = gnttab_grant_foreign_access(
 391                         pvcalls_front_dev->otherend_id,
 392                         pfn_to_gfn(virt_to_pfn(bytes) + i), 0);
 393
 394         map->active.ref = gnttab_grant_foreign_access(
 395                 pvcalls_front_dev->otherend_id,
 396                 pfn_to_gfn(virt_to_pfn((void *)map->active.ring)), 0);
 397
 398         ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
 399         if (ret)
 400                 goto out_error;
 401         irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
 402                                         0, "pvcalls-frontend", map);
 403         if (irq < 0) {
 404                 ret = irq;
 405                 goto out_error;
 406         }
 407
 408         map->active.irq = irq;
 409         map->active_socket = true;
 410         mutex_init(&map->active.in_mutex);
 411         mutex_init(&map->active.out_mutex);
 412
 413         return 0;
 414
 415 out_error:
 416         if (*evtchn >= 0)
 417                 xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
 418         return ret;
 419 }
 420
 421 int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 422                                 int addr_len, int flags)
 423 {
 424         struct pvcalls_bedata *bedata;
 425         struct sock_mapping *map = NULL;
 426         struct xen_pvcalls_request *req;
 427         int notify, req_id, ret, evtchn;
 428
 429         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 430                 return -EOPNOTSUPP;
 431
 432         map = pvcalls_enter_sock(sock);
 433         if (IS_ERR(map))
 434                 return PTR_ERR(map);
 435
 436         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 437         ret = alloc_active_ring(map);
 438         if (ret < 0) {
 439                 pvcalls_exit_sock(sock);
 440                 return ret;
 441         }
 442
 443         spin_lock(&bedata->socket_lock);
 444         ret = get_request(bedata, &req_id);
 445         if (ret < 0) {
 446                 spin_unlock(&bedata->socket_lock);
 447                 free_active_ring(map);
 448                 pvcalls_exit_sock(sock);
 449                 return ret;
 450         }
 451         ret = create_active(map, &evtchn);
 452         if (ret < 0) {
 453                 spin_unlock(&bedata->socket_lock);
 454                 free_active_ring(map);
 455                 pvcalls_exit_sock(sock);
 456                 return ret;
 457         }
 458
 459         req = RING_GET_REQUEST(&bedata->ring, req_id);
 460         req->req_id = req_id;
 461         req->cmd = PVCALLS_CONNECT;
 462         req->u.connect.id = (uintptr_t)map;
 463         req->u.connect.len = addr_len;
 464         req->u.connect.flags = flags;
 465         req->u.connect.ref = map->active.ref;
 466         req->u.connect.evtchn = evtchn;
 467         memcpy(req->u.connect.addr, addr, sizeof(*addr));
 468
 469         map->sock = sock;
 470
 471         bedata->ring.req_prod_pvt++;
 472         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 473         spin_unlock(&bedata->socket_lock);
 474
 475         if (notify)
 476                 notify_remote_via_irq(bedata->irq);
 477
 478         wait_event(bedata->inflight_req,
 479                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 480
 481         /* read req_id, then the content */
 482         smp_rmb();
 483         ret = bedata->rsp[req_id].ret;
 484         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 485         pvcalls_exit_sock(sock);
 486         return ret;
 487 }
 488
 489 static int __write_ring(struct pvcalls_data_intf *intf,
 490                         struct pvcalls_data *data,
 491                         struct iov_iter *msg_iter,
 492                         int len)
 493 {
 494         RING_IDX cons, prod, size, masked_prod, masked_cons;
 495         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 496         int32_t error;
 497
 498         error = intf->out_error;
 499         if (error < 0)
 500                 return error;
 501         cons = intf->out_cons;
 502         prod = intf->out_prod;
 503         /* read indexes before continuing */
 504         virt_mb();
 505
 506         size = pvcalls_queued(prod, cons, array_size);
 507         if (size > array_size)
 508                 return -EINVAL;
 509         if (size == array_size)
 510                 return 0;
 511         if (len > array_size - size)
 512                 len = array_size - size;
 513
 514         masked_prod = pvcalls_mask(prod, array_size);
 515         masked_cons = pvcalls_mask(cons, array_size);
 516
 517         if (masked_prod < masked_cons) {
 518                 len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 519         } else {
 520                 if (len > array_size - masked_prod) {
 521                         int ret = copy_from_iter(data->out + masked_prod,
 522                                        array_size - masked_prod, msg_iter);
 523                         if (ret != array_size - masked_prod) {
 524                                 len = ret;
 525                                 goto out;
 526                         }
 527                         len = ret + copy_from_iter(data->out, len - ret, msg_iter);
 528                 } else {
 529                         len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 530                 }
 531         }
 532 out:
 533         /* write to ring before updating pointer */
 534         virt_wmb();
 535         intf->out_prod += len;
 536
 537         return len;
 538 }
 539
 540 int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
 541                           size_t len)
 542 {
 543         struct pvcalls_bedata *bedata;
 544         struct sock_mapping *map;
 545         int sent, tot_sent = 0;
 546         int count = 0, flags;
 547
 548         flags = msg->msg_flags;
 549         if (flags & (MSG_CONFIRM|MSG_DONTROUTE|MSG_EOR|MSG_OOB))
 550                 return -EOPNOTSUPP;
 551
 552         map = pvcalls_enter_sock(sock);
 553         if (IS_ERR(map))
 554                 return PTR_ERR(map);
 555         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 556
 557         mutex_lock(&map->active.out_mutex);
 558         if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
 559                 mutex_unlock(&map->active.out_mutex);
 560                 pvcalls_exit_sock(sock);
 561                 return -EAGAIN;
 562         }
 563         if (len > INT_MAX)
 564                 len = INT_MAX;
 565
 566 again:
 567         count++;
 568         sent = __write_ring(map->active.ring,
 569                             &map->active.data, &msg->msg_iter,
 570                             len);
 571         if (sent > 0) {
 572                 len -= sent;
 573                 tot_sent += sent;
 574                 notify_remote_via_irq(map->active.irq);
 575         }
 576         if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
 577                 goto again;
 578         if (sent < 0)
 579                 tot_sent = sent;
 580
 581         mutex_unlock(&map->active.out_mutex);
 582         pvcalls_exit_sock(sock);
 583         return tot_sent;
 584 }
 585
 586 static int __read_ring(struct pvcalls_data_intf *intf,
 587                        struct pvcalls_data *data,
 588                        struct iov_iter *msg_iter,
 589                        size_t len, int flags)
 590 {
 591         RING_IDX cons, prod, size, masked_prod, masked_cons;
 592         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 593         int32_t error;
 594
 595         cons = intf->in_cons;
 596         prod = intf->in_prod;
 597         error = intf->in_error;
 598         /* get pointers before reading from the ring */
 599         virt_rmb();
 600
 601         size = pvcalls_queued(prod, cons, array_size);
 602         masked_prod = pvcalls_mask(prod, array_size);
 603         masked_cons = pvcalls_mask(cons, array_size);
 604
 605         if (size == 0)
 606                 return error ?: size;
 607
 608         if (len > size)
 609                 len = size;
 610
 611         if (masked_prod > masked_cons) {
 612                 len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 613         } else {
 614                 if (len > (array_size - masked_cons)) {
 615                         int ret = copy_to_iter(data->in + masked_cons,
 616                                      array_size - masked_cons, msg_iter);
 617                         if (ret != array_size - masked_cons) {
 618                                 len = ret;
 619                                 goto out;
 620                         }
 621                         len = ret + copy_to_iter(data->in, len - ret, msg_iter);
 622                 } else {
 623                         len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 624                 }
 625         }
 626 out:
 627         /* read data from the ring before increasing the index */
 628         virt_mb();
 629         if (!(flags & MSG_PEEK))
 630                 intf->in_cons += len;
 631
 632         return len;
 633 }
 634
 635 int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 636                      int flags)
 637 {
 638         struct pvcalls_bedata *bedata;
 639         int ret;
 640         struct sock_mapping *map;
 641
 642         if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
 643                 return -EOPNOTSUPP;
 644
 645         map = pvcalls_enter_sock(sock);
 646         if (IS_ERR(map))
 647                 return PTR_ERR(map);
 648         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 649
 650         mutex_lock(&map->active.in_mutex);
 651         if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
 652                 len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 653
 654         while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
 655                 wait_event_interruptible(map->active.inflight_conn_req,
 656                                          pvcalls_front_read_todo(map));
 657         }
 658         ret = __read_ring(map->active.ring, &map->active.data,
 659                           &msg->msg_iter, len, flags);
 660
 661         if (ret > 0)
 662                 notify_remote_via_irq(map->active.irq);
 663         if (ret == 0)
 664                 ret = (flags & MSG_DONTWAIT) ? -EAGAIN : 0;
 665         if (ret == -ENOTCONN)
 666                 ret = 0;
 667
 668         mutex_unlock(&map->active.in_mutex);
 669         pvcalls_exit_sock(sock);
 670         return ret;
 671 }
 672
 673 int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 674 {
 675         struct pvcalls_bedata *bedata;
 676         struct sock_mapping *map = NULL;
 677         struct xen_pvcalls_request *req;
 678         int notify, req_id, ret;
 679
 680         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 681                 return -EOPNOTSUPP;
 682
 683         map = pvcalls_enter_sock(sock);
 684         if (IS_ERR(map))
 685                 return PTR_ERR(map);
 686         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 687
 688         spin_lock(&bedata->socket_lock);
 689         ret = get_request(bedata, &req_id);
 690         if (ret < 0) {
 691                 spin_unlock(&bedata->socket_lock);
 692                 pvcalls_exit_sock(sock);
 693                 return ret;
 694         }
 695         req = RING_GET_REQUEST(&bedata->ring, req_id);
 696         req->req_id = req_id;
 697         map->sock = sock;
 698         req->cmd = PVCALLS_BIND;
 699         req->u.bind.id = (uintptr_t)map;
 700         memcpy(req->u.bind.addr, addr, sizeof(*addr));
 701         req->u.bind.len = addr_len;
 702
 703         init_waitqueue_head(&map->passive.inflight_accept_req);
 704
 705         map->active_socket = false;
 706
 707         bedata->ring.req_prod_pvt++;
 708         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 709         spin_unlock(&bedata->socket_lock);
 710         if (notify)
 711                 notify_remote_via_irq(bedata->irq);
 712
 713         wait_event(bedata->inflight_req,
 714                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 715
 716         /* read req_id, then the content */
 717         smp_rmb();
 718         ret = bedata->rsp[req_id].ret;
 719         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 720
 721         map->passive.status = PVCALLS_STATUS_BIND;
 722         pvcalls_exit_sock(sock);
 723         return 0;
 724 }
 725
 726 int pvcalls_front_listen(struct socket *sock, int backlog)
 727 {
 728         struct pvcalls_bedata *bedata;
 729         struct sock_mapping *map;
 730         struct xen_pvcalls_request *req;
 731         int notify, req_id, ret;
 732
 733         map = pvcalls_enter_sock(sock);
 734         if (IS_ERR(map))
 735                 return PTR_ERR(map);
 736         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 737
 738         if (map->passive.status != PVCALLS_STATUS_BIND) {
 739                 pvcalls_exit_sock(sock);
 740                 return -EOPNOTSUPP;
 741         }
 742
 743         spin_lock(&bedata->socket_lock);
 744         ret = get_request(bedata, &req_id);
 745         if (ret < 0) {
 746                 spin_unlock(&bedata->socket_lock);
 747                 pvcalls_exit_sock(sock);
 748                 return ret;
 749         }
 750         req = RING_GET_REQUEST(&bedata->ring, req_id);
 751         req->req_id = req_id;
 752         req->cmd = PVCALLS_LISTEN;
 753         req->u.listen.id = (uintptr_t) map;
 754         req->u.listen.backlog = backlog;
 755
 756         bedata->ring.req_prod_pvt++;
 757         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 758         spin_unlock(&bedata->socket_lock);
 759         if (notify)
 760                 notify_remote_via_irq(bedata->irq);
 761
 762         wait_event(bedata->inflight_req,
 763                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 764
 765         /* read req_id, then the content */
 766         smp_rmb();
 767         ret = bedata->rsp[req_id].ret;
 768         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 769
 770         map->passive.status = PVCALLS_STATUS_LISTEN;
 771         pvcalls_exit_sock(sock);
 772         return ret;
 773 }
 774
 775 int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
 776 {
 777         struct pvcalls_bedata *bedata;
 778         struct sock_mapping *map;
 779         struct sock_mapping *map2 = NULL;
 780         struct xen_pvcalls_request *req;
 781         int notify, req_id, ret, evtchn, nonblock;
 782
 783         map = pvcalls_enter_sock(sock);
 784         if (IS_ERR(map))
 785                 return PTR_ERR(map);
 786         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 787
 788         if (map->passive.status != PVCALLS_STATUS_LISTEN) {
 789                 pvcalls_exit_sock(sock);
 790                 return -EINVAL;
 791         }
 792
 793         nonblock = flags & SOCK_NONBLOCK;
 794         /*
 795          * Backend only supports 1 inflight accept request, will return
 796          * errors for the others
 797          */
 798         if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 799                              (void *)&map->passive.flags)) {
 800                 req_id = READ_ONCE(map->passive.inflight_req_id);
 801                 if (req_id != PVCALLS_INVALID_ID &&
 802                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id) {
 803                         map2 = map->passive.accept_map;
 804                         goto received;
 805                 }
 806                 if (nonblock) {
 807                         pvcalls_exit_sock(sock);
 808                         return -EAGAIN;
 809                 }
 810                 if (wait_event_interruptible(map->passive.inflight_accept_req,
 811                         !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 812                                           (void *)&map->passive.flags))) {
 813                         pvcalls_exit_sock(sock);
 814                         return -EINTR;
 815                 }
 816         }
 817
 818         map2 = kzalloc(sizeof(*map2), GFP_KERNEL);
 819         if (map2 == NULL) {
 820                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 821                           (void *)&map->passive.flags);
 822                 pvcalls_exit_sock(sock);
 823                 return -ENOMEM;
 824         }
 825         ret = alloc_active_ring(map2);
 826         if (ret < 0) {
 827                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 828                                 (void *)&map->passive.flags);
 829                 kfree(map2);
 830                 pvcalls_exit_sock(sock);
 831                 return ret;
 832         }
 833         spin_lock(&bedata->socket_lock);
 834         ret = get_request(bedata, &req_id);
 835         if (ret < 0) {
 836                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 837                           (void *)&map->passive.flags);
 838                 spin_unlock(&bedata->socket_lock);
 839                 free_active_ring(map2);
 840                 kfree(map2);
 841                 pvcalls_exit_sock(sock);
 842                 return ret;
 843         }
 844
 845         ret = create_active(map2, &evtchn);
 846         if (ret < 0) {
 847                 free_active_ring(map2);
 848                 kfree(map2);
 849                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 850                           (void *)&map->passive.flags);
 851                 spin_unlock(&bedata->socket_lock);
 852                 pvcalls_exit_sock(sock);
 853                 return ret;
 854         }
 855         list_add_tail(&map2->list, &bedata->socket_mappings);
 856
 857         req = RING_GET_REQUEST(&bedata->ring, req_id);
 858         req->req_id = req_id;
 859         req->cmd = PVCALLS_ACCEPT;
 860         req->u.accept.id = (uintptr_t) map;
 861         req->u.accept.ref = map2->active.ref;
 862         req->u.accept.id_new = (uintptr_t) map2;
 863         req->u.accept.evtchn = evtchn;
 864         map->passive.accept_map = map2;
 865
 866         bedata->ring.req_prod_pvt++;
 867         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 868         spin_unlock(&bedata->socket_lock);
 869         if (notify)
 870                 notify_remote_via_irq(bedata->irq);
 871         /* We could check if we have received a response before returning. */
 872         if (nonblock) {
 873                 WRITE_ONCE(map->passive.inflight_req_id, req_id);
 874                 pvcalls_exit_sock(sock);
 875                 return -EAGAIN;
 876         }
 877
 878         if (wait_event_interruptible(bedata->inflight_req,
 879                 READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
 880                 pvcalls_exit_sock(sock);
 881                 return -EINTR;
 882         }
 883         /* read req_id, then the content */
 884         smp_rmb();
 885
 886 received:
 887         map2->sock = newsock;
 888         newsock->sk = sk_alloc(sock_net(sock->sk), PF_INET, GFP_KERNEL, &pvcalls_proto, false);
 889         if (!newsock->sk) {
 890                 bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 891                 map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 892                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 893                           (void *)&map->passive.flags);
 894                 pvcalls_front_free_map(bedata, map2);
 895                 pvcalls_exit_sock(sock);
 896                 return -ENOMEM;
 897         }
 898         newsock->sk->sk_send_head = (void *)map2;
 899
 900         ret = bedata->rsp[req_id].ret;
 901         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 902         map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 903
 904         clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
 905         wake_up(&map->passive.inflight_accept_req);
 906
 907         pvcalls_exit_sock(sock);
 908         return ret;
 909 }
 910
 911 static __poll_t pvcalls_front_poll_passive(struct file *file,
 912                                                struct pvcalls_bedata *bedata,
 913                                                struct sock_mapping *map,
 914                                                poll_table *wait)
 915 {
 916         int notify, req_id, ret;
 917         struct xen_pvcalls_request *req;
 918
 919         if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 920                      (void *)&map->passive.flags)) {
 921                 uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
 922
 923                 if (req_id != PVCALLS_INVALID_ID &&
 924                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
 925                         return EPOLLIN | EPOLLRDNORM;
 926
 927                 poll_wait(file, &map->passive.inflight_accept_req, wait);
 928                 return 0;
 929         }
 930
 931         if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
 932                                (void *)&map->passive.flags))
 933                 return EPOLLIN | EPOLLRDNORM;
 934
 935         /*
 936          * First check RET, then INFLIGHT. No barriers necessary to
 937          * ensure execution ordering because of the conditional
 938          * instructions creating control dependencies.
 939          */
 940
 941         if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 942                              (void *)&map->passive.flags)) {
 943                 poll_wait(file, &bedata->inflight_req, wait);
 944                 return 0;
 945         }
 946
 947         spin_lock(&bedata->socket_lock);
 948         ret = get_request(bedata, &req_id);
 949         if (ret < 0) {
 950                 spin_unlock(&bedata->socket_lock);
 951                 return ret;
 952         }
 953         req = RING_GET_REQUEST(&bedata->ring, req_id);
 954         req->req_id = req_id;
 955         req->cmd = PVCALLS_POLL;
 956         req->u.poll.id = (uintptr_t) map;
 957
 958         bedata->ring.req_prod_pvt++;
 959         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 960         spin_unlock(&bedata->socket_lock);
 961         if (notify)
 962                 notify_remote_via_irq(bedata->irq);
 963
 964         poll_wait(file, &bedata->inflight_req, wait);
 965         return 0;
 966 }
 967
 968 static __poll_t pvcalls_front_poll_active(struct file *file,
 969                                               struct pvcalls_bedata *bedata,
 970                                               struct sock_mapping *map,
 971                                               poll_table *wait)
 972 {
 973         __poll_t mask = 0;
 974         int32_t in_error, out_error;
 975         struct pvcalls_data_intf *intf = map->active.ring;
 976
 977         out_error = intf->out_error;
 978         in_error = intf->in_error;
 979
 980         poll_wait(file, &map->active.inflight_conn_req, wait);
 981         if (pvcalls_front_write_todo(map))
 982                 mask |= EPOLLOUT | EPOLLWRNORM;
 983         if (pvcalls_front_read_todo(map))
 984                 mask |= EPOLLIN | EPOLLRDNORM;
 985         if (in_error != 0 || out_error != 0)
 986                 mask |= EPOLLERR;
 987
 988         return mask;
 989 }
 990
 991 __poll_t pvcalls_front_poll(struct file *file, struct socket *sock,
 992                                poll_table *wait)
 993 {
 994         struct pvcalls_bedata *bedata;
 995         struct sock_mapping *map;
 996         __poll_t ret;
 997
 998         map = pvcalls_enter_sock(sock);
 999         if (IS_ERR(map))
1000                 return EPOLLNVAL;
1001         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1002
1003         if (map->active_socket)
1004                 ret = pvcalls_front_poll_active(file, bedata, map, wait);
1005         else
1006                 ret = pvcalls_front_poll_passive(file, bedata, map, wait);
1007         pvcalls_exit_sock(sock);
1008         return ret;
1009 }
1010
1011 int pvcalls_front_release(struct socket *sock)
1012 {
1013         struct pvcalls_bedata *bedata;
1014         struct sock_mapping *map;
1015         int req_id, notify, ret;
1016         struct xen_pvcalls_request *req;
1017
1018         if (sock->sk == NULL)
1019                 return 0;
1020
1021         map = pvcalls_enter_sock(sock);
1022         if (IS_ERR(map)) {
1023                 if (PTR_ERR(map) == -ENOTCONN)
1024                         return -EIO;
1025                 else
1026                         return 0;
1027         }
1028         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1029
1030         spin_lock(&bedata->socket_lock);
1031         ret = get_request(bedata, &req_id);
1032         if (ret < 0) {
1033                 spin_unlock(&bedata->socket_lock);
1034                 pvcalls_exit_sock(sock);
1035                 return ret;
1036         }
1037         sock->sk->sk_send_head = NULL;
1038
1039         req = RING_GET_REQUEST(&bedata->ring, req_id);
1040         req->req_id = req_id;
1041         req->cmd = PVCALLS_RELEASE;
1042         req->u.release.id = (uintptr_t)map;
1043
1044         bedata->ring.req_prod_pvt++;
1045         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
1046         spin_unlock(&bedata->socket_lock);
1047         if (notify)
1048                 notify_remote_via_irq(bedata->irq);
1049
1050         wait_event(bedata->inflight_req,
1051                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
1052
1053         if (map->active_socket) {
1054                 /*
1055                  * Set in_error and wake up inflight_conn_req to force
1056                  * recvmsg waiters to exit.
1057                  */
1058                 map->active.ring->in_error = -EBADF;
1059                 wake_up_interruptible(&map->active.inflight_conn_req);
1060
1061                 /*
1062                  * We need to make sure that sendmsg/recvmsg on this socket have
1063                  * not started before we've cleared sk_send_head here. The
1064                  * easiest way to guarantee this is to see that no pvcalls
1065                  * (other than us) is in progress on this socket.
1066                  */
1067                 while (atomic_read(&map->refcount) > 1)
1068                         cpu_relax();
1069
1070                 pvcalls_front_free_map(bedata, map);
1071         } else {
1072                 wake_up(&bedata->inflight_req);
1073                 wake_up(&map->passive.inflight_accept_req);
1074
1075                 while (atomic_read(&map->refcount) > 1)
1076                         cpu_relax();
1077
1078                 spin_lock(&bedata->socket_lock);
1079                 list_del(&map->list);
1080                 spin_unlock(&bedata->socket_lock);
1081                 if (READ_ONCE(map->passive.inflight_req_id) != PVCALLS_INVALID_ID &&
1082                         READ_ONCE(map->passive.inflight_req_id) != 0) {
1083                         pvcalls_front_free_map(bedata,
1084                                                map->passive.accept_map);
1085                 }
1086                 kfree(map);
1087         }
1088         WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
1089
1090         pvcalls_exit();
1091         return 0;
1092 }
1093
1094 static const struct xenbus_device_id pvcalls_front_ids[] = {
1095         { "pvcalls" },
1096         { "" }
1097 };
1098
1099 static int pvcalls_front_remove(struct xenbus_device *dev)
1100 {
1101         struct pvcalls_bedata *bedata;
1102         struct sock_mapping *map = NULL, *n;
1103
1104         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1105         dev_set_drvdata(&dev->dev, NULL);
1106         pvcalls_front_dev = NULL;
1107         if (bedata->irq >= 0)
1108                 unbind_from_irqhandler(bedata->irq, dev);
1109
1110         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1111                 map->sock->sk->sk_send_head = NULL;
1112                 if (map->active_socket) {
1113                         map->active.ring->in_error = -EBADF;
1114                         wake_up_interruptible(&map->active.inflight_conn_req);
1115                 }
1116         }
1117
1118         smp_mb();
1119         while (atomic_read(&pvcalls_refcount) > 0)
1120                 cpu_relax();
1121         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1122                 if (map->active_socket) {
1123                         /* No need to lock, refcount is 0 */
1124                         pvcalls_front_free_map(bedata, map);
1125                 } else {
1126                         list_del(&map->list);
1127                         kfree(map);
1128                 }
1129         }
1130         if (bedata->ref != -1)
1131                 gnttab_end_foreign_access(bedata->ref, 0, 0);
1132         kfree(bedata->ring.sring);
1133         kfree(bedata);
1134         xenbus_switch_state(dev, XenbusStateClosed);
1135         return 0;
1136 }
1137
1138 static int pvcalls_front_probe(struct xenbus_device *dev,
1139                           const struct xenbus_device_id *id)
1140 {
1141         int ret = -ENOMEM, evtchn, i;
1142         unsigned int max_page_order, function_calls, len;
1143         char *versions;
1144         grant_ref_t gref_head = 0;
1145         struct xenbus_transaction xbt;
1146         struct pvcalls_bedata *bedata = NULL;
1147         struct xen_pvcalls_sring *sring;
1148
1149         if (pvcalls_front_dev != NULL) {
1150                 dev_err(&dev->dev, "only one PV Calls connection supported\n");
1151                 return -EINVAL;
1152         }
1153
1154         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
1155         if (IS_ERR(versions))
1156                 return PTR_ERR(versions);
1157         if (!len)
1158                 return -EINVAL;
1159         if (strcmp(versions, "1")) {
1160                 kfree(versions);
1161                 return -EINVAL;
1162         }
1163         kfree(versions);
1164         max_page_order = xenbus_read_unsigned(dev->otherend,
1165                                               "max-page-order", 0);
1166         if (max_page_order < PVCALLS_RING_ORDER)
1167                 return -ENODEV;
1168         function_calls = xenbus_read_unsigned(dev->otherend,
1169                                               "function-calls", 0);
1170         /* See XENBUS_FUNCTIONS_CALLS in pvcalls.h */
1171         if (function_calls != 1)
1172                 return -ENODEV;
1173         pr_info("%s max-page-order is %u\n", __func__, max_page_order);
1174
1175         bedata = kzalloc(sizeof(struct pvcalls_bedata), GFP_KERNEL);
1176         if (!bedata)
1177                 return -ENOMEM;
1178
1179         dev_set_drvdata(&dev->dev, bedata);
1180         pvcalls_front_dev = dev;
1181         init_waitqueue_head(&bedata->inflight_req);
1182         INIT_LIST_HEAD(&bedata->socket_mappings);
1183         spin_lock_init(&bedata->socket_lock);
1184         bedata->irq = -1;
1185         bedata->ref = -1;
1186
1187         for (i = 0; i < PVCALLS_NR_RSP_PER_RING; i++)
1188                 bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
1189
1190         sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
1191                                                              __GFP_ZERO);
1192         if (!sring)
1193                 goto error;
1194         SHARED_RING_INIT(sring);
1195         FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
1196
1197         ret = xenbus_alloc_evtchn(dev, &evtchn);
1198         if (ret)
1199                 goto error;
1200
1201         bedata->irq = bind_evtchn_to_irqhandler(evtchn,
1202                                                 pvcalls_front_event_handler,
1203                                                 0, "pvcalls-frontend", dev);
1204         if (bedata->irq < 0) {
1205                 ret = bedata->irq;
1206                 goto error;
1207         }
1208
1209         ret = gnttab_alloc_grant_references(1, &gref_head);
1210         if (ret < 0)
1211                 goto error;
1212         ret = gnttab_claim_grant_reference(&gref_head);
1213         if (ret < 0)
1214                 goto error;
1215         bedata->ref = ret;
1216         gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
1217                                         virt_to_gfn((void *)sring), 0);
1218
1219  again:
1220         ret = xenbus_transaction_start(&xbt);
1221         if (ret) {
1222                 xenbus_dev_fatal(dev, ret, "starting transaction");
1223                 goto error;
1224         }
1225         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
1226         if (ret)
1227                 goto error_xenbus;
1228         ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
1229         if (ret)
1230                 goto error_xenbus;
1231         ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
1232                             evtchn);
1233         if (ret)
1234                 goto error_xenbus;
1235         ret = xenbus_transaction_end(xbt, 0);
1236         if (ret) {
1237                 if (ret == -EAGAIN)
1238                         goto again;
1239                 xenbus_dev_fatal(dev, ret, "completing transaction");
1240                 goto error;
1241         }
1242         xenbus_switch_state(dev, XenbusStateInitialised);
1243
1244         return 0;
1245
1246  error_xenbus:
1247         xenbus_transaction_end(xbt, 1);
1248         xenbus_dev_fatal(dev, ret, "writing xenstore");
1249  error:
1250         pvcalls_front_remove(dev);
1251         return ret;
1252 }
1253
1254 static void pvcalls_front_changed(struct xenbus_device *dev,
1255                             enum xenbus_state backend_state)
1256 {
1257         switch (backend_state) {
1258         case XenbusStateReconfiguring:
1259         case XenbusStateReconfigured:
1260         case XenbusStateInitialising:
1261         case XenbusStateInitialised:
1262         case XenbusStateUnknown:
1263                 break;
1264
1265         case XenbusStateInitWait:
1266                 break;
1267
1268         case XenbusStateConnected:
1269                 xenbus_switch_state(dev, XenbusStateConnected);
1270                 break;
1271
1272         case XenbusStateClosed:
1273                 if (dev->state == XenbusStateClosed)
1274                         break;
1275                 /* Missed the backend's CLOSING state */
1276                 /* fall through */
1277         case XenbusStateClosing:
1278                 xenbus_frontend_closed(dev);
1279                 break;
1280         }
1281 }
1282
1283 static struct xenbus_driver pvcalls_front_driver = {
1284         .ids = pvcalls_front_ids,
1285         .probe = pvcalls_front_probe,
1286         .remove = pvcalls_front_remove,
1287         .otherend_changed = pvcalls_front_changed,
1288 };
1289
1290 static int __init pvcalls_frontend_init(void)
1291 {
1292         if (!xen_domain())
1293                 return -ENODEV;
1294
1295         pr_info("Initialising Xen pvcalls frontend driver\n");
1296
1297         return xenbus_register_frontend(&pvcalls_front_driver);
1298 }
1299
1300 module_init(pvcalls_frontend_init);
1301
1302 MODULE_DESCRIPTION("Xen PV Calls frontend driver");
1303 MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
1304 MODULE_LICENSE("GPL");