drivers/xen/pvcalls-front.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * (c) 2017 Stefano Stabellini <stefano@aporeto.com>
   4  */
   5
   6 #include <linux/module.h>
   7 #include <linux/net.h>
   8 #include <linux/socket.h>
   9
  10 #include <net/sock.h>
  11
  12 #include <xen/events.h>
  13 #include <xen/grant_table.h>
  14 #include <xen/xen.h>
  15 #include <xen/xenbus.h>
  16 #include <xen/interface/io/pvcalls.h>
  17
  18 #include "pvcalls-front.h"
  19
  20 #define PVCALLS_INVALID_ID UINT_MAX
  21 #define PVCALLS_RING_ORDER XENBUS_MAX_RING_GRANT_ORDER
  22 #define PVCALLS_NR_RSP_PER_RING __CONST_RING_SIZE(xen_pvcalls, XEN_PAGE_SIZE)
  23 #define PVCALLS_FRONT_MAX_SPIN 5000
  24
  25 static struct proto pvcalls_proto = {
  26         .name   = "PVCalls",
  27         .owner  = THIS_MODULE,
  28         .obj_size = sizeof(struct sock),
  29 };
  30
  31 struct pvcalls_bedata {
  32         struct xen_pvcalls_front_ring ring;
  33         grant_ref_t ref;
  34         int irq;
  35
  36         struct list_head socket_mappings;
  37         spinlock_t socket_lock;
  38
  39         wait_queue_head_t inflight_req;
  40         struct xen_pvcalls_response rsp[PVCALLS_NR_RSP_PER_RING];
  41 };
  42 /* Only one front/back connection supported. */
  43 static struct xenbus_device *pvcalls_front_dev;
  44 static atomic_t pvcalls_refcount;
  45
  46 /* first increment refcount, then proceed */
  47 #define pvcalls_enter() {               \
  48         atomic_inc(&pvcalls_refcount);      \
  49 }
  50
  51 /* first complete other operations, then decrement refcount */
  52 #define pvcalls_exit() {                \
  53         atomic_dec(&pvcalls_refcount);      \
  54 }
  55
  56 struct sock_mapping {
  57         bool active_socket;
  58         struct list_head list;
  59         struct socket *sock;
  60         atomic_t refcount;
  61         union {
  62                 struct {
  63                         int irq;
  64                         grant_ref_t ref;
  65                         struct pvcalls_data_intf *ring;
  66                         struct pvcalls_data data;
  67                         struct mutex in_mutex;
  68                         struct mutex out_mutex;
  69
  70                         wait_queue_head_t inflight_conn_req;
  71                 } active;
  72                 struct {
  73                 /*
  74                  * Socket status, needs to be 64-bit aligned due to the
  75                  * test_and_* functions which have this requirement on arm64.
  76                  */
  77 #define PVCALLS_STATUS_UNINITALIZED  0
  78 #define PVCALLS_STATUS_BIND          1
  79 #define PVCALLS_STATUS_LISTEN        2
  80                         uint8_t status __attribute__((aligned(8)));
  81                 /*
  82                  * Internal state-machine flags.
  83                  * Only one accept operation can be inflight for a socket.
  84                  * Only one poll operation can be inflight for a given socket.
  85                  * flags needs to be 64-bit aligned due to the test_and_*
  86                  * functions which have this requirement on arm64.
  87                  */
  88 #define PVCALLS_FLAG_ACCEPT_INFLIGHT 0
  89 #define PVCALLS_FLAG_POLL_INFLIGHT   1
  90 #define PVCALLS_FLAG_POLL_RET        2
  91                         uint8_t flags __attribute__((aligned(8)));
  92                         uint32_t inflight_req_id;
  93                         struct sock_mapping *accept_map;
  94                         wait_queue_head_t inflight_accept_req;
  95                 } passive;
  96         };
  97 };
  98
  99 static inline struct sock_mapping *pvcalls_enter_sock(struct socket *sock)
 100 {
 101         struct sock_mapping *map;
 102
 103         if (!pvcalls_front_dev ||
 104                 dev_get_drvdata(&pvcalls_front_dev->dev) == NULL)
 105                 return ERR_PTR(-ENOTCONN);
 106
 107         map = (struct sock_mapping *)sock->sk->sk_send_head;
 108         if (map == NULL)
 109                 return ERR_PTR(-ENOTSOCK);
 110
 111         pvcalls_enter();
 112         atomic_inc(&map->refcount);
 113         return map;
 114 }
 115
 116 static inline void pvcalls_exit_sock(struct socket *sock)
 117 {
 118         struct sock_mapping *map;
 119
 120         map = (struct sock_mapping *)sock->sk->sk_send_head;
 121         atomic_dec(&map->refcount);
 122         pvcalls_exit();
 123 }
 124
 125 static inline int get_request(struct pvcalls_bedata *bedata, int *req_id)
 126 {
 127         *req_id = bedata->ring.req_prod_pvt & (RING_SIZE(&bedata->ring) - 1);
 128         if (RING_FULL(&bedata->ring) ||
 129             bedata->rsp[*req_id].req_id != PVCALLS_INVALID_ID)
 130                 return -EAGAIN;
 131         return 0;
 132 }
 133
 134 static bool pvcalls_front_write_todo(struct sock_mapping *map)
 135 {
 136         struct pvcalls_data_intf *intf = map->active.ring;
 137         RING_IDX cons, prod, size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 138         int32_t error;
 139
 140         error = intf->out_error;
 141         if (error == -ENOTCONN)
 142                 return false;
 143         if (error != 0)
 144                 return true;
 145
 146         cons = intf->out_cons;
 147         prod = intf->out_prod;
 148         return !!(size - pvcalls_queued(prod, cons, size));
 149 }
 150
 151 static bool pvcalls_front_read_todo(struct sock_mapping *map)
 152 {
 153         struct pvcalls_data_intf *intf = map->active.ring;
 154         RING_IDX cons, prod;
 155         int32_t error;
 156
 157         cons = intf->in_cons;
 158         prod = intf->in_prod;
 159         error = intf->in_error;
 160         return (error != 0 ||
 161                 pvcalls_queued(prod, cons,
 162                                XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER)) != 0);
 163 }
 164
 165 static irqreturn_t pvcalls_front_event_handler(int irq, void *dev_id)
 166 {
 167         struct xenbus_device *dev = dev_id;
 168         struct pvcalls_bedata *bedata;
 169         struct xen_pvcalls_response *rsp;
 170         uint8_t *src, *dst;
 171         int req_id = 0, more = 0, done = 0;
 172
 173         if (dev == NULL)
 174                 return IRQ_HANDLED;
 175
 176         pvcalls_enter();
 177         bedata = dev_get_drvdata(&dev->dev);
 178         if (bedata == NULL) {
 179                 pvcalls_exit();
 180                 return IRQ_HANDLED;
 181         }
 182
 183 again:
 184         while (RING_HAS_UNCONSUMED_RESPONSES(&bedata->ring)) {
 185                 rsp = RING_GET_RESPONSE(&bedata->ring, bedata->ring.rsp_cons);
 186
 187                 req_id = rsp->req_id;
 188                 if (rsp->cmd == PVCALLS_POLL) {
 189                         struct sock_mapping *map = (struct sock_mapping *)(uintptr_t)
 190                                                    rsp->u.poll.id;
 191
 192                         clear_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 193                                   (void *)&map->passive.flags);
 194                         /*
 195                          * clear INFLIGHT, then set RET. It pairs with
 196                          * the checks at the beginning of
 197                          * pvcalls_front_poll_passive.
 198                          */
 199                         smp_wmb();
 200                         set_bit(PVCALLS_FLAG_POLL_RET,
 201                                 (void *)&map->passive.flags);
 202                 } else {
 203                         dst = (uint8_t *)&bedata->rsp[req_id] +
 204                               sizeof(rsp->req_id);
 205                         src = (uint8_t *)rsp + sizeof(rsp->req_id);
 206                         memcpy(dst, src, sizeof(*rsp) - sizeof(rsp->req_id));
 207                         /*
 208                          * First copy the rest of the data, then req_id. It is
 209                          * paired with the barrier when accessing bedata->rsp.
 210                          */
 211                         smp_wmb();
 212                         bedata->rsp[req_id].req_id = req_id;
 213                 }
 214
 215                 done = 1;
 216                 bedata->ring.rsp_cons++;
 217         }
 218
 219         RING_FINAL_CHECK_FOR_RESPONSES(&bedata->ring, more);
 220         if (more)
 221                 goto again;
 222         if (done)
 223                 wake_up(&bedata->inflight_req);
 224         pvcalls_exit();
 225         return IRQ_HANDLED;
 226 }
 227
 228 static void free_active_ring(struct sock_mapping *map);
 229
 230 static void pvcalls_front_destroy_active(struct pvcalls_bedata *bedata,
 231                                          struct sock_mapping *map)
 232 {
 233         int i;
 234
 235         unbind_from_irqhandler(map->active.irq, map);
 236
 237         if (bedata) {
 238                 spin_lock(&bedata->socket_lock);
 239                 if (!list_empty(&map->list))
 240                         list_del_init(&map->list);
 241                 spin_unlock(&bedata->socket_lock);
 242         }
 243
 244         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 245                 gnttab_end_foreign_access(map->active.ring->ref[i], NULL);
 246         gnttab_end_foreign_access(map->active.ref, NULL);
 247         free_active_ring(map);
 248 }
 249
 250 static void pvcalls_front_free_map(struct pvcalls_bedata *bedata,
 251                                    struct sock_mapping *map)
 252 {
 253         pvcalls_front_destroy_active(bedata, map);
 254
 255         kfree(map);
 256 }
 257
 258 static irqreturn_t pvcalls_front_conn_handler(int irq, void *sock_map)
 259 {
 260         struct sock_mapping *map = sock_map;
 261
 262         if (map == NULL)
 263                 return IRQ_HANDLED;
 264
 265         wake_up_interruptible(&map->active.inflight_conn_req);
 266
 267         return IRQ_HANDLED;
 268 }
 269
 270 int pvcalls_front_socket(struct socket *sock)
 271 {
 272         struct pvcalls_bedata *bedata;
 273         struct sock_mapping *map = NULL;
 274         struct xen_pvcalls_request *req;
 275         int notify, req_id, ret;
 276
 277         /*
 278          * PVCalls only supports domain AF_INET,
 279          * type SOCK_STREAM and protocol 0 sockets for now.
 280          *
 281          * Check socket type here, AF_INET and protocol checks are done
 282          * by the caller.
 283          */
 284         if (sock->type != SOCK_STREAM)
 285                 return -EOPNOTSUPP;
 286
 287         pvcalls_enter();
 288         if (!pvcalls_front_dev) {
 289                 pvcalls_exit();
 290                 return -EACCES;
 291         }
 292         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 293
 294         map = kzalloc(sizeof(*map), GFP_KERNEL);
 295         if (map == NULL) {
 296                 pvcalls_exit();
 297                 return -ENOMEM;
 298         }
 299
 300         spin_lock(&bedata->socket_lock);
 301
 302         ret = get_request(bedata, &req_id);
 303         if (ret < 0) {
 304                 kfree(map);
 305                 spin_unlock(&bedata->socket_lock);
 306                 pvcalls_exit();
 307                 return ret;
 308         }
 309
 310         /*
 311          * sock->sk->sk_send_head is not used for ip sockets: reuse the
 312          * field to store a pointer to the struct sock_mapping
 313          * corresponding to the socket. This way, we can easily get the
 314          * struct sock_mapping from the struct socket.
 315          */
 316         sock->sk->sk_send_head = (void *)map;
 317         list_add_tail(&map->list, &bedata->socket_mappings);
 318
 319         req = RING_GET_REQUEST(&bedata->ring, req_id);
 320         req->req_id = req_id;
 321         req->cmd = PVCALLS_SOCKET;
 322         req->u.socket.id = (uintptr_t) map;
 323         req->u.socket.domain = AF_INET;
 324         req->u.socket.type = SOCK_STREAM;
 325         req->u.socket.protocol = IPPROTO_IP;
 326
 327         bedata->ring.req_prod_pvt++;
 328         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 329         spin_unlock(&bedata->socket_lock);
 330         if (notify)
 331                 notify_remote_via_irq(bedata->irq);
 332
 333         wait_event(bedata->inflight_req,
 334                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 335
 336         /* read req_id, then the content */
 337         smp_rmb();
 338         ret = bedata->rsp[req_id].ret;
 339         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 340
 341         pvcalls_exit();
 342         return ret;
 343 }
 344
 345 static void free_active_ring(struct sock_mapping *map)
 346 {
 347         if (!map->active.ring)
 348                 return;
 349
 350         free_pages_exact(map->active.data.in,
 351                          PAGE_SIZE << map->active.ring->ring_order);
 352         free_page((unsigned long)map->active.ring);
 353 }
 354
 355 static int alloc_active_ring(struct sock_mapping *map)
 356 {
 357         void *bytes;
 358
 359         map->active.ring = (struct pvcalls_data_intf *)
 360                 get_zeroed_page(GFP_KERNEL);
 361         if (!map->active.ring)
 362                 goto out;
 363
 364         map->active.ring->ring_order = PVCALLS_RING_ORDER;
 365         bytes = alloc_pages_exact(PAGE_SIZE << PVCALLS_RING_ORDER,
 366                                   GFP_KERNEL | __GFP_ZERO);
 367         if (!bytes)
 368                 goto out;
 369
 370         map->active.data.in = bytes;
 371         map->active.data.out = bytes +
 372                 XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 373
 374         return 0;
 375
 376 out:
 377         free_active_ring(map);
 378         return -ENOMEM;
 379 }
 380
 381 static int create_active(struct sock_mapping *map, evtchn_port_t *evtchn)
 382 {
 383         void *bytes;
 384         int ret, irq = -1, i;
 385
 386         *evtchn = 0;
 387         init_waitqueue_head(&map->active.inflight_conn_req);
 388
 389         bytes = map->active.data.in;
 390         for (i = 0; i < (1 << PVCALLS_RING_ORDER); i++)
 391                 map->active.ring->ref[i] = gnttab_grant_foreign_access(
 392                         pvcalls_front_dev->otherend_id,
 393                         pfn_to_gfn(virt_to_pfn(bytes) + i), 0);
 394
 395         map->active.ref = gnttab_grant_foreign_access(
 396                 pvcalls_front_dev->otherend_id,
 397                 pfn_to_gfn(virt_to_pfn((void *)map->active.ring)), 0);
 398
 399         ret = xenbus_alloc_evtchn(pvcalls_front_dev, evtchn);
 400         if (ret)
 401                 goto out_error;
 402         irq = bind_evtchn_to_irqhandler(*evtchn, pvcalls_front_conn_handler,
 403                                         0, "pvcalls-frontend", map);
 404         if (irq < 0) {
 405                 ret = irq;
 406                 goto out_error;
 407         }
 408
 409         map->active.irq = irq;
 410         map->active_socket = true;
 411         mutex_init(&map->active.in_mutex);
 412         mutex_init(&map->active.out_mutex);
 413
 414         return 0;
 415
 416 out_error:
 417         if (*evtchn > 0)
 418                 xenbus_free_evtchn(pvcalls_front_dev, *evtchn);
 419         return ret;
 420 }
 421
 422 int pvcalls_front_connect(struct socket *sock, struct sockaddr *addr,
 423                                 int addr_len, int flags)
 424 {
 425         struct pvcalls_bedata *bedata;
 426         struct sock_mapping *map = NULL;
 427         struct xen_pvcalls_request *req;
 428         int notify, req_id, ret;
 429         evtchn_port_t evtchn;
 430
 431         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 432                 return -EOPNOTSUPP;
 433
 434         map = pvcalls_enter_sock(sock);
 435         if (IS_ERR(map))
 436                 return PTR_ERR(map);
 437
 438         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 439         ret = alloc_active_ring(map);
 440         if (ret < 0) {
 441                 pvcalls_exit_sock(sock);
 442                 return ret;
 443         }
 444         ret = create_active(map, &evtchn);
 445         if (ret < 0) {
 446                 free_active_ring(map);
 447                 pvcalls_exit_sock(sock);
 448                 return ret;
 449         }
 450
 451         spin_lock(&bedata->socket_lock);
 452         ret = get_request(bedata, &req_id);
 453         if (ret < 0) {
 454                 spin_unlock(&bedata->socket_lock);
 455                 pvcalls_front_destroy_active(NULL, map);
 456                 pvcalls_exit_sock(sock);
 457                 return ret;
 458         }
 459
 460         req = RING_GET_REQUEST(&bedata->ring, req_id);
 461         req->req_id = req_id;
 462         req->cmd = PVCALLS_CONNECT;
 463         req->u.connect.id = (uintptr_t)map;
 464         req->u.connect.len = addr_len;
 465         req->u.connect.flags = flags;
 466         req->u.connect.ref = map->active.ref;
 467         req->u.connect.evtchn = evtchn;
 468         memcpy(req->u.connect.addr, addr, sizeof(*addr));
 469
 470         map->sock = sock;
 471
 472         bedata->ring.req_prod_pvt++;
 473         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 474         spin_unlock(&bedata->socket_lock);
 475
 476         if (notify)
 477                 notify_remote_via_irq(bedata->irq);
 478
 479         wait_event(bedata->inflight_req,
 480                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 481
 482         /* read req_id, then the content */
 483         smp_rmb();
 484         ret = bedata->rsp[req_id].ret;
 485         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 486         pvcalls_exit_sock(sock);
 487         return ret;
 488 }
 489
 490 static int __write_ring(struct pvcalls_data_intf *intf,
 491                         struct pvcalls_data *data,
 492                         struct iov_iter *msg_iter,
 493                         int len)
 494 {
 495         RING_IDX cons, prod, size, masked_prod, masked_cons;
 496         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 497         int32_t error;
 498
 499         error = intf->out_error;
 500         if (error < 0)
 501                 return error;
 502         cons = intf->out_cons;
 503         prod = intf->out_prod;
 504         /* read indexes before continuing */
 505         virt_mb();
 506
 507         size = pvcalls_queued(prod, cons, array_size);
 508         if (size > array_size)
 509                 return -EINVAL;
 510         if (size == array_size)
 511                 return 0;
 512         if (len > array_size - size)
 513                 len = array_size - size;
 514
 515         masked_prod = pvcalls_mask(prod, array_size);
 516         masked_cons = pvcalls_mask(cons, array_size);
 517
 518         if (masked_prod < masked_cons) {
 519                 len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 520         } else {
 521                 if (len > array_size - masked_prod) {
 522                         int ret = copy_from_iter(data->out + masked_prod,
 523                                        array_size - masked_prod, msg_iter);
 524                         if (ret != array_size - masked_prod) {
 525                                 len = ret;
 526                                 goto out;
 527                         }
 528                         len = ret + copy_from_iter(data->out, len - ret, msg_iter);
 529                 } else {
 530                         len = copy_from_iter(data->out + masked_prod, len, msg_iter);
 531                 }
 532         }
 533 out:
 534         /* write to ring before updating pointer */
 535         virt_wmb();
 536         intf->out_prod += len;
 537
 538         return len;
 539 }
 540
 541 int pvcalls_front_sendmsg(struct socket *sock, struct msghdr *msg,
 542                           size_t len)
 543 {
 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
 556         mutex_lock(&map->active.out_mutex);
 557         if ((flags & MSG_DONTWAIT) && !pvcalls_front_write_todo(map)) {
 558                 mutex_unlock(&map->active.out_mutex);
 559                 pvcalls_exit_sock(sock);
 560                 return -EAGAIN;
 561         }
 562         if (len > INT_MAX)
 563                 len = INT_MAX;
 564
 565 again:
 566         count++;
 567         sent = __write_ring(map->active.ring,
 568                             &map->active.data, &msg->msg_iter,
 569                             len);
 570         if (sent > 0) {
 571                 len -= sent;
 572                 tot_sent += sent;
 573                 notify_remote_via_irq(map->active.irq);
 574         }
 575         if (sent >= 0 && len > 0 && count < PVCALLS_FRONT_MAX_SPIN)
 576                 goto again;
 577         if (sent < 0)
 578                 tot_sent = sent;
 579
 580         mutex_unlock(&map->active.out_mutex);
 581         pvcalls_exit_sock(sock);
 582         return tot_sent;
 583 }
 584
 585 static int __read_ring(struct pvcalls_data_intf *intf,
 586                        struct pvcalls_data *data,
 587                        struct iov_iter *msg_iter,
 588                        size_t len, int flags)
 589 {
 590         RING_IDX cons, prod, size, masked_prod, masked_cons;
 591         RING_IDX array_size = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 592         int32_t error;
 593
 594         cons = intf->in_cons;
 595         prod = intf->in_prod;
 596         error = intf->in_error;
 597         /* get pointers before reading from the ring */
 598         virt_rmb();
 599
 600         size = pvcalls_queued(prod, cons, array_size);
 601         masked_prod = pvcalls_mask(prod, array_size);
 602         masked_cons = pvcalls_mask(cons, array_size);
 603
 604         if (size == 0)
 605                 return error ?: size;
 606
 607         if (len > size)
 608                 len = size;
 609
 610         if (masked_prod > masked_cons) {
 611                 len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 612         } else {
 613                 if (len > (array_size - masked_cons)) {
 614                         int ret = copy_to_iter(data->in + masked_cons,
 615                                      array_size - masked_cons, msg_iter);
 616                         if (ret != array_size - masked_cons) {
 617                                 len = ret;
 618                                 goto out;
 619                         }
 620                         len = ret + copy_to_iter(data->in, len - ret, msg_iter);
 621                 } else {
 622                         len = copy_to_iter(data->in + masked_cons, len, msg_iter);
 623                 }
 624         }
 625 out:
 626         /* read data from the ring before increasing the index */
 627         virt_mb();
 628         if (!(flags & MSG_PEEK))
 629                 intf->in_cons += len;
 630
 631         return len;
 632 }
 633
 634 int pvcalls_front_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
 635                      int flags)
 636 {
 637         int ret;
 638         struct sock_mapping *map;
 639
 640         if (flags & (MSG_CMSG_CLOEXEC|MSG_ERRQUEUE|MSG_OOB|MSG_TRUNC))
 641                 return -EOPNOTSUPP;
 642
 643         map = pvcalls_enter_sock(sock);
 644         if (IS_ERR(map))
 645                 return PTR_ERR(map);
 646
 647         mutex_lock(&map->active.in_mutex);
 648         if (len > XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER))
 649                 len = XEN_FLEX_RING_SIZE(PVCALLS_RING_ORDER);
 650
 651         while (!(flags & MSG_DONTWAIT) && !pvcalls_front_read_todo(map)) {
 652                 wait_event_interruptible(map->active.inflight_conn_req,
 653                                          pvcalls_front_read_todo(map));
 654         }
 655         ret = __read_ring(map->active.ring, &map->active.data,
 656                           &msg->msg_iter, len, flags);
 657
 658         if (ret > 0)
 659                 notify_remote_via_irq(map->active.irq);
 660         if (ret == 0)
 661                 ret = (flags & MSG_DONTWAIT) ? -EAGAIN : 0;
 662         if (ret == -ENOTCONN)
 663                 ret = 0;
 664
 665         mutex_unlock(&map->active.in_mutex);
 666         pvcalls_exit_sock(sock);
 667         return ret;
 668 }
 669
 670 int pvcalls_front_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
 671 {
 672         struct pvcalls_bedata *bedata;
 673         struct sock_mapping *map = NULL;
 674         struct xen_pvcalls_request *req;
 675         int notify, req_id, ret;
 676
 677         if (addr->sa_family != AF_INET || sock->type != SOCK_STREAM)
 678                 return -EOPNOTSUPP;
 679
 680         map = pvcalls_enter_sock(sock);
 681         if (IS_ERR(map))
 682                 return PTR_ERR(map);
 683         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 684
 685         spin_lock(&bedata->socket_lock);
 686         ret = get_request(bedata, &req_id);
 687         if (ret < 0) {
 688                 spin_unlock(&bedata->socket_lock);
 689                 pvcalls_exit_sock(sock);
 690                 return ret;
 691         }
 692         req = RING_GET_REQUEST(&bedata->ring, req_id);
 693         req->req_id = req_id;
 694         map->sock = sock;
 695         req->cmd = PVCALLS_BIND;
 696         req->u.bind.id = (uintptr_t)map;
 697         memcpy(req->u.bind.addr, addr, sizeof(*addr));
 698         req->u.bind.len = addr_len;
 699
 700         init_waitqueue_head(&map->passive.inflight_accept_req);
 701
 702         map->active_socket = false;
 703
 704         bedata->ring.req_prod_pvt++;
 705         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 706         spin_unlock(&bedata->socket_lock);
 707         if (notify)
 708                 notify_remote_via_irq(bedata->irq);
 709
 710         wait_event(bedata->inflight_req,
 711                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 712
 713         /* read req_id, then the content */
 714         smp_rmb();
 715         ret = bedata->rsp[req_id].ret;
 716         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 717
 718         map->passive.status = PVCALLS_STATUS_BIND;
 719         pvcalls_exit_sock(sock);
 720         return 0;
 721 }
 722
 723 int pvcalls_front_listen(struct socket *sock, int backlog)
 724 {
 725         struct pvcalls_bedata *bedata;
 726         struct sock_mapping *map;
 727         struct xen_pvcalls_request *req;
 728         int notify, req_id, ret;
 729
 730         map = pvcalls_enter_sock(sock);
 731         if (IS_ERR(map))
 732                 return PTR_ERR(map);
 733         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 734
 735         if (map->passive.status != PVCALLS_STATUS_BIND) {
 736                 pvcalls_exit_sock(sock);
 737                 return -EOPNOTSUPP;
 738         }
 739
 740         spin_lock(&bedata->socket_lock);
 741         ret = get_request(bedata, &req_id);
 742         if (ret < 0) {
 743                 spin_unlock(&bedata->socket_lock);
 744                 pvcalls_exit_sock(sock);
 745                 return ret;
 746         }
 747         req = RING_GET_REQUEST(&bedata->ring, req_id);
 748         req->req_id = req_id;
 749         req->cmd = PVCALLS_LISTEN;
 750         req->u.listen.id = (uintptr_t) map;
 751         req->u.listen.backlog = backlog;
 752
 753         bedata->ring.req_prod_pvt++;
 754         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 755         spin_unlock(&bedata->socket_lock);
 756         if (notify)
 757                 notify_remote_via_irq(bedata->irq);
 758
 759         wait_event(bedata->inflight_req,
 760                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
 761
 762         /* read req_id, then the content */
 763         smp_rmb();
 764         ret = bedata->rsp[req_id].ret;
 765         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 766
 767         map->passive.status = PVCALLS_STATUS_LISTEN;
 768         pvcalls_exit_sock(sock);
 769         return ret;
 770 }
 771
 772 int pvcalls_front_accept(struct socket *sock, struct socket *newsock, int flags)
 773 {
 774         struct pvcalls_bedata *bedata;
 775         struct sock_mapping *map;
 776         struct sock_mapping *map2 = NULL;
 777         struct xen_pvcalls_request *req;
 778         int notify, req_id, ret, nonblock;
 779         evtchn_port_t evtchn;
 780
 781         map = pvcalls_enter_sock(sock);
 782         if (IS_ERR(map))
 783                 return PTR_ERR(map);
 784         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 785
 786         if (map->passive.status != PVCALLS_STATUS_LISTEN) {
 787                 pvcalls_exit_sock(sock);
 788                 return -EINVAL;
 789         }
 790
 791         nonblock = flags & SOCK_NONBLOCK;
 792         /*
 793          * Backend only supports 1 inflight accept request, will return
 794          * errors for the others
 795          */
 796         if (test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 797                              (void *)&map->passive.flags)) {
 798                 req_id = READ_ONCE(map->passive.inflight_req_id);
 799                 if (req_id != PVCALLS_INVALID_ID &&
 800                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id) {
 801                         map2 = map->passive.accept_map;
 802                         goto received;
 803                 }
 804                 if (nonblock) {
 805                         pvcalls_exit_sock(sock);
 806                         return -EAGAIN;
 807                 }
 808                 if (wait_event_interruptible(map->passive.inflight_accept_req,
 809                         !test_and_set_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 810                                           (void *)&map->passive.flags))) {
 811                         pvcalls_exit_sock(sock);
 812                         return -EINTR;
 813                 }
 814         }
 815
 816         map2 = kzalloc(sizeof(*map2), GFP_KERNEL);
 817         if (map2 == NULL) {
 818                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 819                           (void *)&map->passive.flags);
 820                 pvcalls_exit_sock(sock);
 821                 return -ENOMEM;
 822         }
 823         ret = alloc_active_ring(map2);
 824         if (ret < 0) {
 825                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 826                                 (void *)&map->passive.flags);
 827                 kfree(map2);
 828                 pvcalls_exit_sock(sock);
 829                 return ret;
 830         }
 831         ret = create_active(map2, &evtchn);
 832         if (ret < 0) {
 833                 free_active_ring(map2);
 834                 kfree(map2);
 835                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 836                           (void *)&map->passive.flags);
 837                 pvcalls_exit_sock(sock);
 838                 return ret;
 839         }
 840
 841         spin_lock(&bedata->socket_lock);
 842         ret = get_request(bedata, &req_id);
 843         if (ret < 0) {
 844                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 845                           (void *)&map->passive.flags);
 846                 spin_unlock(&bedata->socket_lock);
 847                 pvcalls_front_free_map(bedata, map2);
 848                 pvcalls_exit_sock(sock);
 849                 return ret;
 850         }
 851
 852         list_add_tail(&map2->list, &bedata->socket_mappings);
 853
 854         req = RING_GET_REQUEST(&bedata->ring, req_id);
 855         req->req_id = req_id;
 856         req->cmd = PVCALLS_ACCEPT;
 857         req->u.accept.id = (uintptr_t) map;
 858         req->u.accept.ref = map2->active.ref;
 859         req->u.accept.id_new = (uintptr_t) map2;
 860         req->u.accept.evtchn = evtchn;
 861         map->passive.accept_map = map2;
 862
 863         bedata->ring.req_prod_pvt++;
 864         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 865         spin_unlock(&bedata->socket_lock);
 866         if (notify)
 867                 notify_remote_via_irq(bedata->irq);
 868         /* We could check if we have received a response before returning. */
 869         if (nonblock) {
 870                 WRITE_ONCE(map->passive.inflight_req_id, req_id);
 871                 pvcalls_exit_sock(sock);
 872                 return -EAGAIN;
 873         }
 874
 875         if (wait_event_interruptible(bedata->inflight_req,
 876                 READ_ONCE(bedata->rsp[req_id].req_id) == req_id)) {
 877                 pvcalls_exit_sock(sock);
 878                 return -EINTR;
 879         }
 880         /* read req_id, then the content */
 881         smp_rmb();
 882
 883 received:
 884         map2->sock = newsock;
 885         newsock->sk = sk_alloc(sock_net(sock->sk), PF_INET, GFP_KERNEL, &pvcalls_proto, false);
 886         if (!newsock->sk) {
 887                 bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 888                 map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 889                 clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 890                           (void *)&map->passive.flags);
 891                 pvcalls_front_free_map(bedata, map2);
 892                 pvcalls_exit_sock(sock);
 893                 return -ENOMEM;
 894         }
 895         newsock->sk->sk_send_head = (void *)map2;
 896
 897         ret = bedata->rsp[req_id].ret;
 898         bedata->rsp[req_id].req_id = PVCALLS_INVALID_ID;
 899         map->passive.inflight_req_id = PVCALLS_INVALID_ID;
 900
 901         clear_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT, (void *)&map->passive.flags);
 902         wake_up(&map->passive.inflight_accept_req);
 903
 904         pvcalls_exit_sock(sock);
 905         return ret;
 906 }
 907
 908 static __poll_t pvcalls_front_poll_passive(struct file *file,
 909                                                struct pvcalls_bedata *bedata,
 910                                                struct sock_mapping *map,
 911                                                poll_table *wait)
 912 {
 913         int notify, req_id, ret;
 914         struct xen_pvcalls_request *req;
 915
 916         if (test_bit(PVCALLS_FLAG_ACCEPT_INFLIGHT,
 917                      (void *)&map->passive.flags)) {
 918                 uint32_t req_id = READ_ONCE(map->passive.inflight_req_id);
 919
 920                 if (req_id != PVCALLS_INVALID_ID &&
 921                     READ_ONCE(bedata->rsp[req_id].req_id) == req_id)
 922                         return EPOLLIN | EPOLLRDNORM;
 923
 924                 poll_wait(file, &map->passive.inflight_accept_req, wait);
 925                 return 0;
 926         }
 927
 928         if (test_and_clear_bit(PVCALLS_FLAG_POLL_RET,
 929                                (void *)&map->passive.flags))
 930                 return EPOLLIN | EPOLLRDNORM;
 931
 932         /*
 933          * First check RET, then INFLIGHT. No barriers necessary to
 934          * ensure execution ordering because of the conditional
 935          * instructions creating control dependencies.
 936          */
 937
 938         if (test_and_set_bit(PVCALLS_FLAG_POLL_INFLIGHT,
 939                              (void *)&map->passive.flags)) {
 940                 poll_wait(file, &bedata->inflight_req, wait);
 941                 return 0;
 942         }
 943
 944         spin_lock(&bedata->socket_lock);
 945         ret = get_request(bedata, &req_id);
 946         if (ret < 0) {
 947                 spin_unlock(&bedata->socket_lock);
 948                 return ret;
 949         }
 950         req = RING_GET_REQUEST(&bedata->ring, req_id);
 951         req->req_id = req_id;
 952         req->cmd = PVCALLS_POLL;
 953         req->u.poll.id = (uintptr_t) map;
 954
 955         bedata->ring.req_prod_pvt++;
 956         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
 957         spin_unlock(&bedata->socket_lock);
 958         if (notify)
 959                 notify_remote_via_irq(bedata->irq);
 960
 961         poll_wait(file, &bedata->inflight_req, wait);
 962         return 0;
 963 }
 964
 965 static __poll_t pvcalls_front_poll_active(struct file *file,
 966                                               struct pvcalls_bedata *bedata,
 967                                               struct sock_mapping *map,
 968                                               poll_table *wait)
 969 {
 970         __poll_t mask = 0;
 971         int32_t in_error, out_error;
 972         struct pvcalls_data_intf *intf = map->active.ring;
 973
 974         out_error = intf->out_error;
 975         in_error = intf->in_error;
 976
 977         poll_wait(file, &map->active.inflight_conn_req, wait);
 978         if (pvcalls_front_write_todo(map))
 979                 mask |= EPOLLOUT | EPOLLWRNORM;
 980         if (pvcalls_front_read_todo(map))
 981                 mask |= EPOLLIN | EPOLLRDNORM;
 982         if (in_error != 0 || out_error != 0)
 983                 mask |= EPOLLERR;
 984
 985         return mask;
 986 }
 987
 988 __poll_t pvcalls_front_poll(struct file *file, struct socket *sock,
 989                                poll_table *wait)
 990 {
 991         struct pvcalls_bedata *bedata;
 992         struct sock_mapping *map;
 993         __poll_t ret;
 994
 995         map = pvcalls_enter_sock(sock);
 996         if (IS_ERR(map))
 997                 return EPOLLNVAL;
 998         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
 999
1000         if (map->active_socket)
1001                 ret = pvcalls_front_poll_active(file, bedata, map, wait);
1002         else
1003                 ret = pvcalls_front_poll_passive(file, bedata, map, wait);
1004         pvcalls_exit_sock(sock);
1005         return ret;
1006 }
1007
1008 int pvcalls_front_release(struct socket *sock)
1009 {
1010         struct pvcalls_bedata *bedata;
1011         struct sock_mapping *map;
1012         int req_id, notify, ret;
1013         struct xen_pvcalls_request *req;
1014
1015         if (sock->sk == NULL)
1016                 return 0;
1017
1018         map = pvcalls_enter_sock(sock);
1019         if (IS_ERR(map)) {
1020                 if (PTR_ERR(map) == -ENOTCONN)
1021                         return -EIO;
1022                 else
1023                         return 0;
1024         }
1025         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1026
1027         spin_lock(&bedata->socket_lock);
1028         ret = get_request(bedata, &req_id);
1029         if (ret < 0) {
1030                 spin_unlock(&bedata->socket_lock);
1031                 pvcalls_exit_sock(sock);
1032                 return ret;
1033         }
1034         sock->sk->sk_send_head = NULL;
1035
1036         req = RING_GET_REQUEST(&bedata->ring, req_id);
1037         req->req_id = req_id;
1038         req->cmd = PVCALLS_RELEASE;
1039         req->u.release.id = (uintptr_t)map;
1040
1041         bedata->ring.req_prod_pvt++;
1042         RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&bedata->ring, notify);
1043         spin_unlock(&bedata->socket_lock);
1044         if (notify)
1045                 notify_remote_via_irq(bedata->irq);
1046
1047         wait_event(bedata->inflight_req,
1048                    READ_ONCE(bedata->rsp[req_id].req_id) == req_id);
1049
1050         if (map->active_socket) {
1051                 /*
1052                  * Set in_error and wake up inflight_conn_req to force
1053                  * recvmsg waiters to exit.
1054                  */
1055                 map->active.ring->in_error = -EBADF;
1056                 wake_up_interruptible(&map->active.inflight_conn_req);
1057
1058                 /*
1059                  * We need to make sure that sendmsg/recvmsg on this socket have
1060                  * not started before we've cleared sk_send_head here. The
1061                  * easiest way to guarantee this is to see that no pvcalls
1062                  * (other than us) is in progress on this socket.
1063                  */
1064                 while (atomic_read(&map->refcount) > 1)
1065                         cpu_relax();
1066
1067                 pvcalls_front_free_map(bedata, map);
1068         } else {
1069                 wake_up(&bedata->inflight_req);
1070                 wake_up(&map->passive.inflight_accept_req);
1071
1072                 while (atomic_read(&map->refcount) > 1)
1073                         cpu_relax();
1074
1075                 spin_lock(&bedata->socket_lock);
1076                 list_del(&map->list);
1077                 spin_unlock(&bedata->socket_lock);
1078                 if (READ_ONCE(map->passive.inflight_req_id) != PVCALLS_INVALID_ID &&
1079                         READ_ONCE(map->passive.inflight_req_id) != 0) {
1080                         pvcalls_front_free_map(bedata,
1081                                                map->passive.accept_map);
1082                 }
1083                 kfree(map);
1084         }
1085         WRITE_ONCE(bedata->rsp[req_id].req_id, PVCALLS_INVALID_ID);
1086
1087         pvcalls_exit();
1088         return 0;
1089 }
1090
1091 static const struct xenbus_device_id pvcalls_front_ids[] = {
1092         { "pvcalls" },
1093         { "" }
1094 };
1095
1096 static void pvcalls_front_remove(struct xenbus_device *dev)
1097 {
1098         struct pvcalls_bedata *bedata;
1099         struct sock_mapping *map = NULL, *n;
1100
1101         bedata = dev_get_drvdata(&pvcalls_front_dev->dev);
1102         dev_set_drvdata(&dev->dev, NULL);
1103         pvcalls_front_dev = NULL;
1104         if (bedata->irq >= 0)
1105                 unbind_from_irqhandler(bedata->irq, dev);
1106
1107         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1108                 map->sock->sk->sk_send_head = NULL;
1109                 if (map->active_socket) {
1110                         map->active.ring->in_error = -EBADF;
1111                         wake_up_interruptible(&map->active.inflight_conn_req);
1112                 }
1113         }
1114
1115         smp_mb();
1116         while (atomic_read(&pvcalls_refcount) > 0)
1117                 cpu_relax();
1118         list_for_each_entry_safe(map, n, &bedata->socket_mappings, list) {
1119                 if (map->active_socket) {
1120                         /* No need to lock, refcount is 0 */
1121                         pvcalls_front_free_map(bedata, map);
1122                 } else {
1123                         list_del(&map->list);
1124                         kfree(map);
1125                 }
1126         }
1127         if (bedata->ref != -1)
1128                 gnttab_end_foreign_access(bedata->ref, NULL);
1129         kfree(bedata->ring.sring);
1130         kfree(bedata);
1131         xenbus_switch_state(dev, XenbusStateClosed);
1132 }
1133
1134 static int pvcalls_front_probe(struct xenbus_device *dev,
1135                           const struct xenbus_device_id *id)
1136 {
1137         int ret = -ENOMEM, i;
1138         evtchn_port_t evtchn;
1139         unsigned int max_page_order, function_calls, len;
1140         char *versions;
1141         grant_ref_t gref_head = 0;
1142         struct xenbus_transaction xbt;
1143         struct pvcalls_bedata *bedata = NULL;
1144         struct xen_pvcalls_sring *sring;
1145
1146         if (pvcalls_front_dev != NULL) {
1147                 dev_err(&dev->dev, "only one PV Calls connection supported\n");
1148                 return -EINVAL;
1149         }
1150
1151         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
1152         if (IS_ERR(versions))
1153                 return PTR_ERR(versions);
1154         if (!len)
1155                 return -EINVAL;
1156         if (strcmp(versions, "1")) {
1157                 kfree(versions);
1158                 return -EINVAL;
1159         }
1160         kfree(versions);
1161         max_page_order = xenbus_read_unsigned(dev->otherend,
1162                                               "max-page-order", 0);
1163         if (max_page_order < PVCALLS_RING_ORDER)
1164                 return -ENODEV;
1165         function_calls = xenbus_read_unsigned(dev->otherend,
1166                                               "function-calls", 0);
1167         /* See XENBUS_FUNCTIONS_CALLS in pvcalls.h */
1168         if (function_calls != 1)
1169                 return -ENODEV;
1170         pr_info("%s max-page-order is %u\n", __func__, max_page_order);
1171
1172         bedata = kzalloc(sizeof(struct pvcalls_bedata), GFP_KERNEL);
1173         if (!bedata)
1174                 return -ENOMEM;
1175
1176         dev_set_drvdata(&dev->dev, bedata);
1177         pvcalls_front_dev = dev;
1178         init_waitqueue_head(&bedata->inflight_req);
1179         INIT_LIST_HEAD(&bedata->socket_mappings);
1180         spin_lock_init(&bedata->socket_lock);
1181         bedata->irq = -1;
1182         bedata->ref = -1;
1183
1184         for (i = 0; i < PVCALLS_NR_RSP_PER_RING; i++)
1185                 bedata->rsp[i].req_id = PVCALLS_INVALID_ID;
1186
1187         sring = (struct xen_pvcalls_sring *) __get_free_page(GFP_KERNEL |
1188                                                              __GFP_ZERO);
1189         if (!sring)
1190                 goto error;
1191         SHARED_RING_INIT(sring);
1192         FRONT_RING_INIT(&bedata->ring, sring, XEN_PAGE_SIZE);
1193
1194         ret = xenbus_alloc_evtchn(dev, &evtchn);
1195         if (ret)
1196                 goto error;
1197
1198         bedata->irq = bind_evtchn_to_irqhandler(evtchn,
1199                                                 pvcalls_front_event_handler,
1200                                                 0, "pvcalls-frontend", dev);
1201         if (bedata->irq < 0) {
1202                 ret = bedata->irq;
1203                 goto error;
1204         }
1205
1206         ret = gnttab_alloc_grant_references(1, &gref_head);
1207         if (ret < 0)
1208                 goto error;
1209         ret = gnttab_claim_grant_reference(&gref_head);
1210         if (ret < 0)
1211                 goto error;
1212         bedata->ref = ret;
1213         gnttab_grant_foreign_access_ref(bedata->ref, dev->otherend_id,
1214                                         virt_to_gfn((void *)sring), 0);
1215
1216  again:
1217         ret = xenbus_transaction_start(&xbt);
1218         if (ret) {
1219                 xenbus_dev_fatal(dev, ret, "starting transaction");
1220                 goto error;
1221         }
1222         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
1223         if (ret)
1224                 goto error_xenbus;
1225         ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", bedata->ref);
1226         if (ret)
1227                 goto error_xenbus;
1228         ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
1229                             evtchn);
1230         if (ret)
1231                 goto error_xenbus;
1232         ret = xenbus_transaction_end(xbt, 0);
1233         if (ret) {
1234                 if (ret == -EAGAIN)
1235                         goto again;
1236                 xenbus_dev_fatal(dev, ret, "completing transaction");
1237                 goto error;
1238         }
1239         xenbus_switch_state(dev, XenbusStateInitialised);
1240
1241         return 0;
1242
1243  error_xenbus:
1244         xenbus_transaction_end(xbt, 1);
1245         xenbus_dev_fatal(dev, ret, "writing xenstore");
1246  error:
1247         pvcalls_front_remove(dev);
1248         return ret;
1249 }
1250
1251 static void pvcalls_front_changed(struct xenbus_device *dev,
1252                             enum xenbus_state backend_state)
1253 {
1254         switch (backend_state) {
1255         case XenbusStateReconfiguring:
1256         case XenbusStateReconfigured:
1257         case XenbusStateInitialising:
1258         case XenbusStateInitialised:
1259         case XenbusStateUnknown:
1260                 break;
1261
1262         case XenbusStateInitWait:
1263                 break;
1264
1265         case XenbusStateConnected:
1266                 xenbus_switch_state(dev, XenbusStateConnected);
1267                 break;
1268
1269         case XenbusStateClosed:
1270                 if (dev->state == XenbusStateClosed)
1271                         break;
1272                 /* Missed the backend's CLOSING state */
1273                 fallthrough;
1274         case XenbusStateClosing:
1275                 xenbus_frontend_closed(dev);
1276                 break;
1277         }
1278 }
1279
1280 static struct xenbus_driver pvcalls_front_driver = {
1281         .ids = pvcalls_front_ids,
1282         .probe = pvcalls_front_probe,
1283         .remove = pvcalls_front_remove,
1284         .otherend_changed = pvcalls_front_changed,
1285         .not_essential = true,
1286 };
1287
1288 static int __init pvcalls_frontend_init(void)
1289 {
1290         if (!xen_domain())
1291                 return -ENODEV;
1292
1293         pr_info("Initialising Xen pvcalls frontend driver\n");
1294
1295         return xenbus_register_frontend(&pvcalls_front_driver);
1296 }
1297
1298 module_init(pvcalls_frontend_init);
1299
1300 MODULE_DESCRIPTION("Xen PV Calls frontend driver");
1301 MODULE_AUTHOR("Stefano Stabellini <sstabellini@kernel.org>");
1302 MODULE_LICENSE("GPL");