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