net/9p/trans_xen.c

   1 /*
   2  * linux/fs/9p/trans_xen
   3  *
   4  * Xen transport layer.
   5  *
   6  * Copyright (C) 2017 by Stefano Stabellini <stefano@aporeto.com>
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License version 2
  10  * as published by the Free Software Foundation; or, when distributed
  11  * separately from the Linux kernel or incorporated into other
  12  * software packages, subject to the following license:
  13  *
  14  * Permission is hereby granted, free of charge, to any person obtaining a copy
  15  * of this source file (the "Software"), to deal in the Software without
  16  * restriction, including without limitation the rights to use, copy, modify,
  17  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  18  * and to permit persons to whom the Software is furnished to do so, subject to
  19  * the following conditions:
  20  *
  21  * The above copyright notice and this permission notice shall be included in
  22  * all copies or substantial portions of the Software.
  23  *
  24  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  25  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  26  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  27  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  28  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  29  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  30  * IN THE SOFTWARE.
  31  */
  32
  33 #include <xen/events.h>
  34 #include <xen/grant_table.h>
  35 #include <xen/xen.h>
  36 #include <xen/xenbus.h>
  37 #include <xen/interface/io/9pfs.h>
  38
  39 #include <linux/module.h>
  40 #include <linux/spinlock.h>
  41 #include <linux/rwlock.h>
  42 #include <net/9p/9p.h>
  43 #include <net/9p/client.h>
  44 #include <net/9p/transport.h>
  45
  46 #define XEN_9PFS_NUM_RINGS 2
  47 #define XEN_9PFS_RING_ORDER 6
  48 #define XEN_9PFS_RING_SIZE  XEN_FLEX_RING_SIZE(XEN_9PFS_RING_ORDER)
  49
  50 struct xen_9pfs_header {
  51         uint32_t size;
  52         uint8_t id;
  53         uint16_t tag;
  54
  55         /* uint8_t sdata[]; */
  56 } __attribute__((packed));
  57
  58 /* One per ring, more than one per 9pfs share */
  59 struct xen_9pfs_dataring {
  60         struct xen_9pfs_front_priv *priv;
  61
  62         struct xen_9pfs_data_intf *intf;
  63         grant_ref_t ref;
  64         int evtchn;
  65         int irq;
  66         /* protect a ring from concurrent accesses */
  67         spinlock_t lock;
  68
  69         struct xen_9pfs_data data;
  70         wait_queue_head_t wq;
  71         struct work_struct work;
  72 };
  73
  74 /* One per 9pfs share */
  75 struct xen_9pfs_front_priv {
  76         struct list_head list;
  77         struct xenbus_device *dev;
  78         char *tag;
  79         struct p9_client *client;
  80
  81         int num_rings;
  82         struct xen_9pfs_dataring *rings;
  83 };
  84
  85 static LIST_HEAD(xen_9pfs_devs);
  86 static DEFINE_RWLOCK(xen_9pfs_lock);
  87
  88 /* We don't currently allow canceling of requests */
  89 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
  90 {
  91         return 1;
  92 }
  93
  94 static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
  95 {
  96         struct xen_9pfs_front_priv *priv;
  97
  98         read_lock(&xen_9pfs_lock);
  99         list_for_each_entry(priv, &xen_9pfs_devs, list) {
 100                 if (!strcmp(priv->tag, addr)) {
 101                         priv->client = client;
 102                         read_unlock(&xen_9pfs_lock);
 103                         return 0;
 104                 }
 105         }
 106         read_unlock(&xen_9pfs_lock);
 107         return -EINVAL;
 108 }
 109
 110 static void p9_xen_close(struct p9_client *client)
 111 {
 112         struct xen_9pfs_front_priv *priv;
 113
 114         read_lock(&xen_9pfs_lock);
 115         list_for_each_entry(priv, &xen_9pfs_devs, list) {
 116                 if (priv->client == client) {
 117                         priv->client = NULL;
 118                         read_unlock(&xen_9pfs_lock);
 119                         return;
 120                 }
 121         }
 122         read_unlock(&xen_9pfs_lock);
 123 }
 124
 125 static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
 126 {
 127         RING_IDX cons, prod;
 128
 129         cons = ring->intf->out_cons;
 130         prod = ring->intf->out_prod;
 131         virt_mb();
 132
 133         return XEN_9PFS_RING_SIZE -
 134                 xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) >= size;
 135 }
 136
 137 static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
 138 {
 139         struct xen_9pfs_front_priv *priv = NULL;
 140         RING_IDX cons, prod, masked_cons, masked_prod;
 141         unsigned long flags;
 142         u32 size = p9_req->tc->size;
 143         struct xen_9pfs_dataring *ring;
 144         int num;
 145
 146         read_lock(&xen_9pfs_lock);
 147         list_for_each_entry(priv, &xen_9pfs_devs, list) {
 148                 if (priv->client == client)
 149                         break;
 150         }
 151         read_unlock(&xen_9pfs_lock);
 152         if (!priv || priv->client != client)
 153                 return -EINVAL;
 154
 155         num = p9_req->tc->tag % priv->num_rings;
 156         ring = &priv->rings[num];
 157
 158 again:
 159         while (wait_event_interruptible(ring->wq,
 160                                         p9_xen_write_todo(ring, size)) != 0)
 161                 ;
 162
 163         spin_lock_irqsave(&ring->lock, flags);
 164         cons = ring->intf->out_cons;
 165         prod = ring->intf->out_prod;
 166         virt_mb();
 167
 168         if (XEN_9PFS_RING_SIZE - xen_9pfs_queued(prod, cons,
 169                                                  XEN_9PFS_RING_SIZE) < size) {
 170                 spin_unlock_irqrestore(&ring->lock, flags);
 171                 goto again;
 172         }
 173
 174         masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
 175         masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
 176
 177         xen_9pfs_write_packet(ring->data.out, p9_req->tc->sdata, size,
 178                               &masked_prod, masked_cons, XEN_9PFS_RING_SIZE);
 179
 180         p9_req->status = REQ_STATUS_SENT;
 181         virt_wmb();                     /* write ring before updating pointer */
 182         prod += size;
 183         ring->intf->out_prod = prod;
 184         spin_unlock_irqrestore(&ring->lock, flags);
 185         notify_remote_via_irq(ring->irq);
 186
 187         return 0;
 188 }
 189
 190 static void p9_xen_response(struct work_struct *work)
 191 {
 192 }
 193
 194 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
 195 {
 196         struct xen_9pfs_dataring *ring = r;
 197
 198         if (!ring || !ring->priv->client) {
 199                 /* ignore spurious interrupt */
 200                 return IRQ_HANDLED;
 201         }
 202
 203         wake_up_interruptible(&ring->wq);
 204         schedule_work(&ring->work);
 205
 206         return IRQ_HANDLED;
 207 }
 208
 209 static struct p9_trans_module p9_xen_trans = {
 210         .name = "xen",
 211         .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT),
 212         .def = 1,
 213         .create = p9_xen_create,
 214         .close = p9_xen_close,
 215         .request = p9_xen_request,
 216         .cancel = p9_xen_cancel,
 217         .owner = THIS_MODULE,
 218 };
 219
 220 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
 221         { "9pfs" },
 222         { "" }
 223 };
 224
 225 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
 226 {
 227         int i, j;
 228
 229         write_lock(&xen_9pfs_lock);
 230         list_del(&priv->list);
 231         write_unlock(&xen_9pfs_lock);
 232
 233         for (i = 0; i < priv->num_rings; i++) {
 234                 if (!priv->rings[i].intf)
 235                         break;
 236                 if (priv->rings[i].irq > 0)
 237                         unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
 238                 if (priv->rings[i].data.in) {
 239                         for (j = 0; j < (1 << XEN_9PFS_RING_ORDER); j++) {
 240                                 grant_ref_t ref;
 241
 242                                 ref = priv->rings[i].intf->ref[j];
 243                                 gnttab_end_foreign_access(ref, 0, 0);
 244                         }
 245                         free_pages((unsigned long)priv->rings[i].data.in,
 246                                    XEN_9PFS_RING_ORDER -
 247                                    (PAGE_SHIFT - XEN_PAGE_SHIFT));
 248                 }
 249                 gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
 250                 free_page((unsigned long)priv->rings[i].intf);
 251         }
 252         kfree(priv->rings);
 253         kfree(priv->tag);
 254         kfree(priv);
 255 }
 256
 257 static int xen_9pfs_front_remove(struct xenbus_device *dev)
 258 {
 259         struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
 260
 261         dev_set_drvdata(&dev->dev, NULL);
 262         xen_9pfs_front_free(priv);
 263         return 0;
 264 }
 265
 266 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
 267                                          struct xen_9pfs_dataring *ring)
 268 {
 269         int i = 0;
 270         int ret = -ENOMEM;
 271         void *bytes = NULL;
 272
 273         init_waitqueue_head(&ring->wq);
 274         spin_lock_init(&ring->lock);
 275         INIT_WORK(&ring->work, p9_xen_response);
 276
 277         ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
 278         if (!ring->intf)
 279                 return ret;
 280         ret = gnttab_grant_foreign_access(dev->otherend_id,
 281                                           virt_to_gfn(ring->intf), 0);
 282         if (ret < 0)
 283                 goto out;
 284         ring->ref = ret;
 285         bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
 286                         XEN_9PFS_RING_ORDER - (PAGE_SHIFT - XEN_PAGE_SHIFT));
 287         if (!bytes) {
 288                 ret = -ENOMEM;
 289                 goto out;
 290         }
 291         for (; i < (1 << XEN_9PFS_RING_ORDER); i++) {
 292                 ret = gnttab_grant_foreign_access(
 293                                 dev->otherend_id, virt_to_gfn(bytes) + i, 0);
 294                 if (ret < 0)
 295                         goto out;
 296                 ring->intf->ref[i] = ret;
 297         }
 298         ring->intf->ring_order = XEN_9PFS_RING_ORDER;
 299         ring->data.in = bytes;
 300         ring->data.out = bytes + XEN_9PFS_RING_SIZE;
 301
 302         ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
 303         if (ret)
 304                 goto out;
 305         ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
 306                                               xen_9pfs_front_event_handler,
 307                                               0, "xen_9pfs-frontend", ring);
 308         if (ring->irq >= 0)
 309                 return 0;
 310
 311         xenbus_free_evtchn(dev, ring->evtchn);
 312         ret = ring->irq;
 313 out:
 314         if (bytes) {
 315                 for (i--; i >= 0; i--)
 316                         gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
 317                 free_pages((unsigned long)bytes,
 318                            XEN_9PFS_RING_ORDER -
 319                            (PAGE_SHIFT - XEN_PAGE_SHIFT));
 320         }
 321         gnttab_end_foreign_access(ring->ref, 0, 0);
 322         free_page((unsigned long)ring->intf);
 323         return ret;
 324 }
 325
 326 static int xen_9pfs_front_probe(struct xenbus_device *dev,
 327                                 const struct xenbus_device_id *id)
 328 {
 329         int ret, i;
 330         struct xenbus_transaction xbt;
 331         struct xen_9pfs_front_priv *priv = NULL;
 332         char *versions;
 333         unsigned int max_rings, max_ring_order, len;
 334
 335         versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
 336         if (!len)
 337                 return -EINVAL;
 338         if (strcmp(versions, "1")) {
 339                 kfree(versions);
 340                 return -EINVAL;
 341         }
 342         kfree(versions);
 343         max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
 344         if (max_rings < XEN_9PFS_NUM_RINGS)
 345                 return -EINVAL;
 346         max_ring_order = xenbus_read_unsigned(dev->otherend,
 347                                               "max-ring-page-order", 0);
 348         if (max_ring_order < XEN_9PFS_RING_ORDER)
 349                 return -EINVAL;
 350
 351         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 352         if (!priv)
 353                 return -ENOMEM;
 354
 355         priv->dev = dev;
 356         priv->num_rings = XEN_9PFS_NUM_RINGS;
 357         priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
 358                               GFP_KERNEL);
 359         if (!priv->rings) {
 360                 kfree(priv);
 361                 return -ENOMEM;
 362         }
 363
 364         for (i = 0; i < priv->num_rings; i++) {
 365                 priv->rings[i].priv = priv;
 366                 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i]);
 367                 if (ret < 0)
 368                         goto error;
 369         }
 370
 371  again:
 372         ret = xenbus_transaction_start(&xbt);
 373         if (ret) {
 374                 xenbus_dev_fatal(dev, ret, "starting transaction");
 375                 goto error;
 376         }
 377         ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
 378         if (ret)
 379                 goto error_xenbus;
 380         ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
 381                             priv->num_rings);
 382         if (ret)
 383                 goto error_xenbus;
 384         for (i = 0; i < priv->num_rings; i++) {
 385                 char str[16];
 386
 387                 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
 388                 sprintf(str, "ring-ref%u", i);
 389                 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
 390                                     priv->rings[i].ref);
 391                 if (ret)
 392                         goto error_xenbus;
 393
 394                 sprintf(str, "event-channel-%u", i);
 395                 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
 396                                     priv->rings[i].evtchn);
 397                 if (ret)
 398                         goto error_xenbus;
 399         }
 400         priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
 401         if (!priv->tag) {
 402                 ret = -EINVAL;
 403                 goto error_xenbus;
 404         }
 405         ret = xenbus_transaction_end(xbt, 0);
 406         if (ret) {
 407                 if (ret == -EAGAIN)
 408                         goto again;
 409                 xenbus_dev_fatal(dev, ret, "completing transaction");
 410                 goto error;
 411         }
 412
 413         write_lock(&xen_9pfs_lock);
 414         list_add_tail(&priv->list, &xen_9pfs_devs);
 415         write_unlock(&xen_9pfs_lock);
 416         dev_set_drvdata(&dev->dev, priv);
 417         xenbus_switch_state(dev, XenbusStateInitialised);
 418
 419         return 0;
 420
 421  error_xenbus:
 422         xenbus_transaction_end(xbt, 1);
 423         xenbus_dev_fatal(dev, ret, "writing xenstore");
 424  error:
 425         dev_set_drvdata(&dev->dev, NULL);
 426         xen_9pfs_front_free(priv);
 427         return ret;
 428 }
 429
 430 static int xen_9pfs_front_resume(struct xenbus_device *dev)
 431 {
 432         dev_warn(&dev->dev, "suspsend/resume unsupported\n");
 433         return 0;
 434 }
 435
 436 static void xen_9pfs_front_changed(struct xenbus_device *dev,
 437                                    enum xenbus_state backend_state)
 438 {
 439         switch (backend_state) {
 440         case XenbusStateReconfiguring:
 441         case XenbusStateReconfigured:
 442         case XenbusStateInitialising:
 443         case XenbusStateInitialised:
 444         case XenbusStateUnknown:
 445                 break;
 446
 447         case XenbusStateInitWait:
 448                 break;
 449
 450         case XenbusStateConnected:
 451                 xenbus_switch_state(dev, XenbusStateConnected);
 452                 break;
 453
 454         case XenbusStateClosed:
 455                 if (dev->state == XenbusStateClosed)
 456                         break;
 457                 /* Missed the backend's CLOSING state -- fallthrough */
 458         case XenbusStateClosing:
 459                 xenbus_frontend_closed(dev);
 460                 break;
 461         }
 462 }
 463
 464 static struct xenbus_driver xen_9pfs_front_driver = {
 465         .ids = xen_9pfs_front_ids,
 466         .probe = xen_9pfs_front_probe,
 467         .remove = xen_9pfs_front_remove,
 468         .resume = xen_9pfs_front_resume,
 469         .otherend_changed = xen_9pfs_front_changed,
 470 };
 471
 472 int p9_trans_xen_init(void)
 473 {
 474         if (!xen_domain())
 475                 return -ENODEV;
 476
 477         pr_info("Initialising Xen transport for 9pfs\n");
 478
 479         v9fs_register_trans(&p9_xen_trans);
 480         return xenbus_register_frontend(&xen_9pfs_front_driver);
 481 }
 482 module_init(p9_trans_xen_init);
 483
 484 void p9_trans_xen_exit(void)
 485 {
 486         v9fs_unregister_trans(&p9_xen_trans);
 487         return xenbus_unregister_driver(&xen_9pfs_front_driver);
 488 }
 489 module_exit(p9_trans_xen_exit);