Pileus Git - ~andy/linux/blob - drivers/misc/vmw_vmci/vmci_doorbell.c

   1 /*
   2  * VMware VMCI Driver
   3  *
   4  * Copyright (C) 2012 VMware, Inc. All rights reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation version 2 and no later version.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  12  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * for more details.
  14  */
  15
  16 #include <linux/vmw_vmci_defs.h>
  17 #include <linux/vmw_vmci_api.h>
  18 #include <linux/completion.h>
  19 #include <linux/hash.h>
  20 #include <linux/kernel.h>
  21 #include <linux/list.h>
  22 #include <linux/module.h>
  23 #include <linux/sched.h>
  24 #include <linux/slab.h>
  25
  26 #include "vmci_datagram.h"
  27 #include "vmci_doorbell.h"
  28 #include "vmci_resource.h"
  29 #include "vmci_driver.h"
  30 #include "vmci_route.h"
  31
  32
  33 #define VMCI_DOORBELL_INDEX_BITS        6
  34 #define VMCI_DOORBELL_INDEX_TABLE_SIZE  (1 << VMCI_DOORBELL_INDEX_BITS)
  35 #define VMCI_DOORBELL_HASH(_idx)        hash_32(_idx, VMCI_DOORBELL_INDEX_BITS)
  36
  37 /*
  38  * DoorbellEntry describes the a doorbell notification handle allocated by the
  39  * host.
  40  */
  41 struct dbell_entry {
  42         struct vmci_resource resource;
  43         struct hlist_node node;
  44         struct work_struct work;
  45         vmci_callback notify_cb;
  46         void *client_data;
  47         u32 idx;
  48         u32 priv_flags;
  49         bool run_delayed;
  50         atomic_t active;        /* Only used by guest personality */
  51 };
  52
  53 /* The VMCI index table keeps track of currently registered doorbells. */
  54 struct dbell_index_table {
  55         spinlock_t lock;        /* Index table lock */
  56         struct hlist_head entries[VMCI_DOORBELL_INDEX_TABLE_SIZE];
  57 };
  58
  59 static struct dbell_index_table vmci_doorbell_it = {
  60         .lock = __SPIN_LOCK_UNLOCKED(vmci_doorbell_it.lock),
  61 };
  62
  63 /*
  64  * The max_notify_idx is one larger than the currently known bitmap index in
  65  * use, and is used to determine how much of the bitmap needs to be scanned.
  66  */
  67 static u32 max_notify_idx;
  68
  69 /*
  70  * The notify_idx_count is used for determining whether there are free entries
  71  * within the bitmap (if notify_idx_count + 1 < max_notify_idx).
  72  */
  73 static u32 notify_idx_count;
  74
  75 /*
  76  * The last_notify_idx_reserved is used to track the last index handed out - in
  77  * the case where multiple handles share a notification index, we hand out
  78  * indexes round robin based on last_notify_idx_reserved.
  79  */
  80 static u32 last_notify_idx_reserved;
  81
  82 /* This is a one entry cache used to by the index allocation. */
  83 static u32 last_notify_idx_released = PAGE_SIZE;
  84
  85
  86 /*
  87  * Utility function that retrieves the privilege flags associated
  88  * with a given doorbell handle. For guest endpoints, the
  89  * privileges are determined by the context ID, but for host
  90  * endpoints privileges are associated with the complete
  91  * handle. Hypervisor endpoints are not yet supported.
  92  */
  93 int vmci_dbell_get_priv_flags(struct vmci_handle handle, u32 *priv_flags)
  94 {
  95         if (priv_flags == NULL || handle.context == VMCI_INVALID_ID)
  96                 return VMCI_ERROR_INVALID_ARGS;
  97
  98         if (handle.context == VMCI_HOST_CONTEXT_ID) {
  99                 struct dbell_entry *entry;
 100                 struct vmci_resource *resource;
 101
 102                 resource = vmci_resource_by_handle(handle,
 103                                                    VMCI_RESOURCE_TYPE_DOORBELL);
 104                 if (!resource)
 105                         return VMCI_ERROR_NOT_FOUND;
 106
 107                 entry = container_of(resource, struct dbell_entry, resource);
 108                 *priv_flags = entry->priv_flags;
 109                 vmci_resource_put(resource);
 110         } else if (handle.context == VMCI_HYPERVISOR_CONTEXT_ID) {
 111                 /*
 112                  * Hypervisor endpoints for notifications are not
 113                  * supported (yet).
 114                  */
 115                 return VMCI_ERROR_INVALID_ARGS;
 116         } else {
 117                 *priv_flags = vmci_context_get_priv_flags(handle.context);
 118         }
 119
 120         return VMCI_SUCCESS;
 121 }
 122
 123 /*
 124  * Find doorbell entry by bitmap index.
 125  */
 126 static struct dbell_entry *dbell_index_table_find(u32 idx)
 127 {
 128         u32 bucket = VMCI_DOORBELL_HASH(idx);
 129         struct dbell_entry *dbell;
 130         struct hlist_node *node;
 131
 132         hlist_for_each_entry(dbell, node, &vmci_doorbell_it.entries[bucket],
 133                              node) {
 134                 if (idx == dbell->idx)
 135                         return dbell;
 136         }
 137
 138         return NULL;
 139 }
 140
 141 /*
 142  * Add the given entry to the index table.  This willi take a reference to the
 143  * entry's resource so that the entry is not deleted before it is removed from
 144  * the * table.
 145  */
 146 static void dbell_index_table_add(struct dbell_entry *entry)
 147 {
 148         u32 bucket;
 149         u32 new_notify_idx;
 150
 151         vmci_resource_get(&entry->resource);
 152
 153         spin_lock_bh(&vmci_doorbell_it.lock);
 154
 155         /*
 156          * Below we try to allocate an index in the notification
 157          * bitmap with "not too much" sharing between resources. If we
 158          * use less that the full bitmap, we either add to the end if
 159          * there are no unused flags within the currently used area,
 160          * or we search for unused ones. If we use the full bitmap, we
 161          * allocate the index round robin.
 162          */
 163         if (max_notify_idx < PAGE_SIZE || notify_idx_count < PAGE_SIZE) {
 164                 if (last_notify_idx_released < max_notify_idx &&
 165                     !dbell_index_table_find(last_notify_idx_released)) {
 166                         new_notify_idx = last_notify_idx_released;
 167                         last_notify_idx_released = PAGE_SIZE;
 168                 } else {
 169                         bool reused = false;
 170                         new_notify_idx = last_notify_idx_reserved;
 171                         if (notify_idx_count + 1 < max_notify_idx) {
 172                                 do {
 173                                         if (!dbell_index_table_find
 174                                             (new_notify_idx)) {
 175                                                 reused = true;
 176                                                 break;
 177                                         }
 178                                         new_notify_idx = (new_notify_idx + 1) %
 179                                             max_notify_idx;
 180                                 } while (new_notify_idx !=
 181                                          last_notify_idx_released);
 182                         }
 183                         if (!reused) {
 184                                 new_notify_idx = max_notify_idx;
 185                                 max_notify_idx++;
 186                         }
 187                 }
 188         } else {
 189                 new_notify_idx = (last_notify_idx_reserved + 1) % PAGE_SIZE;
 190         }
 191
 192         last_notify_idx_reserved = new_notify_idx;
 193         notify_idx_count++;
 194
 195         entry->idx = new_notify_idx;
 196         bucket = VMCI_DOORBELL_HASH(entry->idx);
 197         hlist_add_head(&entry->node, &vmci_doorbell_it.entries[bucket]);
 198
 199         spin_unlock_bh(&vmci_doorbell_it.lock);
 200 }
 201
 202 /*
 203  * Remove the given entry from the index table.  This will release() the
 204  * entry's resource.
 205  */
 206 static void dbell_index_table_remove(struct dbell_entry *entry)
 207 {
 208         spin_lock_bh(&vmci_doorbell_it.lock);
 209
 210         hlist_del_init(&entry->node);
 211
 212         notify_idx_count--;
 213         if (entry->idx == max_notify_idx - 1) {
 214                 /*
 215                  * If we delete an entry with the maximum known
 216                  * notification index, we take the opportunity to
 217                  * prune the current max. As there might be other
 218                  * unused indices immediately below, we lower the
 219                  * maximum until we hit an index in use.
 220                  */
 221                 while (max_notify_idx > 0 &&
 222                        !dbell_index_table_find(max_notify_idx - 1))
 223                         max_notify_idx--;
 224         }
 225
 226         last_notify_idx_released = entry->idx;
 227
 228         spin_unlock_bh(&vmci_doorbell_it.lock);
 229
 230         vmci_resource_put(&entry->resource);
 231 }
 232
 233 /*
 234  * Creates a link between the given doorbell handle and the given
 235  * index in the bitmap in the device backend. A notification state
 236  * is created in hypervisor.
 237  */
 238 static int dbell_link(struct vmci_handle handle, u32 notify_idx)
 239 {
 240         struct vmci_doorbell_link_msg link_msg;
 241
 242         link_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
 243                                             VMCI_DOORBELL_LINK);
 244         link_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
 245         link_msg.hdr.payload_size = sizeof(link_msg) - VMCI_DG_HEADERSIZE;
 246         link_msg.handle = handle;
 247         link_msg.notify_idx = notify_idx;
 248
 249         return vmci_send_datagram(&link_msg.hdr);
 250 }
 251
 252 /*
 253  * Unlinks the given doorbell handle from an index in the bitmap in
 254  * the device backend. The notification state is destroyed in hypervisor.
 255  */
 256 static int dbell_unlink(struct vmci_handle handle)
 257 {
 258         struct vmci_doorbell_unlink_msg unlink_msg;
 259
 260         unlink_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
 261                                               VMCI_DOORBELL_UNLINK);
 262         unlink_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
 263         unlink_msg.hdr.payload_size = sizeof(unlink_msg) - VMCI_DG_HEADERSIZE;
 264         unlink_msg.handle = handle;
 265
 266         return vmci_send_datagram(&unlink_msg.hdr);
 267 }
 268
 269 /*
 270  * Notify another guest or the host.  We send a datagram down to the
 271  * host via the hypervisor with the notification info.
 272  */
 273 static int dbell_notify_as_guest(struct vmci_handle handle, u32 priv_flags)
 274 {
 275         struct vmci_doorbell_notify_msg notify_msg;
 276
 277         notify_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
 278                                               VMCI_DOORBELL_NOTIFY);
 279         notify_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
 280         notify_msg.hdr.payload_size = sizeof(notify_msg) - VMCI_DG_HEADERSIZE;
 281         notify_msg.handle = handle;
 282
 283         return vmci_send_datagram(&notify_msg.hdr);
 284 }
 285
 286 /*
 287  * Calls the specified callback in a delayed context.
 288  */
 289 static void dbell_delayed_dispatch(struct work_struct *work)
 290 {
 291         struct dbell_entry *entry = container_of(work,
 292                                                  struct dbell_entry, work);
 293
 294         entry->notify_cb(entry->client_data);
 295         vmci_resource_put(&entry->resource);
 296 }
 297
 298 /*
 299  * Dispatches a doorbell notification to the host context.
 300  */
 301 int vmci_dbell_host_context_notify(u32 src_cid, struct vmci_handle handle)
 302 {
 303         struct dbell_entry *entry;
 304         struct vmci_resource *resource;
 305
 306         if (vmci_handle_is_invalid(handle)) {
 307                 pr_devel("Notifying an invalid doorbell (handle=0x%x:0x%x)\n",
 308                          handle.context, handle.resource);
 309                 return VMCI_ERROR_INVALID_ARGS;
 310         }
 311
 312         resource = vmci_resource_by_handle(handle,
 313                                            VMCI_RESOURCE_TYPE_DOORBELL);
 314         if (!resource) {
 315                 pr_devel("Notifying an unknown doorbell (handle=0x%x:0x%x)\n",
 316                          handle.context, handle.resource);
 317                 return VMCI_ERROR_NOT_FOUND;
 318         }
 319
 320         entry = container_of(resource, struct dbell_entry, resource);
 321         if (entry->run_delayed) {
 322                 schedule_work(&entry->work);
 323         } else {
 324                 entry->notify_cb(entry->client_data);
 325                 vmci_resource_put(resource);
 326         }
 327
 328         return VMCI_SUCCESS;
 329 }
 330
 331 /*
 332  * Register the notification bitmap with the host.
 333  */
 334 bool vmci_dbell_register_notification_bitmap(u32 bitmap_ppn)
 335 {
 336         int result;
 337         struct vmci_notify_bm_set_msg bitmap_set_msg;
 338
 339         bitmap_set_msg.hdr.dst = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
 340                                                   VMCI_SET_NOTIFY_BITMAP);
 341         bitmap_set_msg.hdr.src = VMCI_ANON_SRC_HANDLE;
 342         bitmap_set_msg.hdr.payload_size = sizeof(bitmap_set_msg) -
 343             VMCI_DG_HEADERSIZE;
 344         bitmap_set_msg.bitmap_ppn = bitmap_ppn;
 345
 346         result = vmci_send_datagram(&bitmap_set_msg.hdr);
 347         if (result != VMCI_SUCCESS) {
 348                 pr_devel("Failed to register (PPN=%u) as notification bitmap (error=%d)\n",
 349                          bitmap_ppn, result);
 350                 return false;
 351         }
 352         return true;
 353 }
 354
 355 /*
 356  * Executes or schedules the handlers for a given notify index.
 357  */
 358 static void dbell_fire_entries(u32 notify_idx)
 359 {
 360         u32 bucket = VMCI_DOORBELL_HASH(notify_idx);
 361         struct dbell_entry *dbell;
 362         struct hlist_node *node;
 363
 364         spin_lock_bh(&vmci_doorbell_it.lock);
 365
 366         hlist_for_each_entry(dbell, node,
 367                              &vmci_doorbell_it.entries[bucket], node) {
 368                 if (dbell->idx == notify_idx &&
 369                     atomic_read(&dbell->active) == 1) {
 370                         if (dbell->run_delayed) {
 371                                 vmci_resource_get(&dbell->resource);
 372                                 schedule_work(&dbell->work);
 373                         } else {
 374                                 dbell->notify_cb(dbell->client_data);
 375                         }
 376                 }
 377         }
 378
 379         spin_unlock_bh(&vmci_doorbell_it.lock);
 380 }
 381
 382 /*
 383  * Scans the notification bitmap, collects pending notifications,
 384  * resets the bitmap and invokes appropriate callbacks.
 385  */
 386 void vmci_dbell_scan_notification_entries(u8 *bitmap)
 387 {
 388         u32 idx;
 389
 390         for (idx = 0; idx < max_notify_idx; idx++) {
 391                 if (bitmap[idx] & 0x1) {
 392                         bitmap[idx] &= ~1;
 393                         dbell_fire_entries(idx);
 394                 }
 395         }
 396 }
 397
 398 /*
 399  * vmci_doorbell_create() - Creates a doorbell
 400  * @handle:     A handle used to track the resource.  Can be invalid.
 401  * @flags:      Flag that determines context of callback.
 402  * @priv_flags: Privileges flags.
 403  * @notify_cb:  The callback to be ivoked when the doorbell fires.
 404  * @client_data:        A parameter to be passed to the callback.
 405  *
 406  * Creates a doorbell with the given callback. If the handle is
 407  * VMCI_INVALID_HANDLE, a free handle will be assigned, if
 408  * possible. The callback can be run immediately (potentially with
 409  * locks held - the default) or delayed (in a kernel thread) by
 410  * specifying the flag VMCI_FLAG_DELAYED_CB. If delayed execution
 411  * is selected, a given callback may not be run if the kernel is
 412  * unable to allocate memory for the delayed execution (highly
 413  * unlikely).
 414  */
 415 int vmci_doorbell_create(struct vmci_handle *handle,
 416                          u32 flags,
 417                          u32 priv_flags,
 418                          vmci_callback notify_cb, void *client_data)
 419 {
 420         struct dbell_entry *entry;
 421         struct vmci_handle new_handle;
 422         int result;
 423
 424         if (!handle || !notify_cb || flags & ~VMCI_FLAG_DELAYED_CB ||
 425             priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS)
 426                 return VMCI_ERROR_INVALID_ARGS;
 427
 428         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 429         if (entry == NULL) {
 430                 pr_warn("Failed allocating memory for datagram entry\n");
 431                 return VMCI_ERROR_NO_MEM;
 432         }
 433
 434         if (vmci_handle_is_invalid(*handle)) {
 435                 u32 context_id = vmci_get_context_id();
 436
 437                 /* Let resource code allocate a free ID for us */
 438                 new_handle = vmci_make_handle(context_id, VMCI_INVALID_ID);
 439         } else {
 440                 bool valid_context = false;
 441
 442                 /*
 443                  * Validate the handle.  We must do both of the checks below
 444                  * because we can be acting as both a host and a guest at the
 445                  * same time. We always allow the host context ID, since the
 446                  * host functionality is in practice always there with the
 447                  * unified driver.
 448                  */
 449                 if (handle->context == VMCI_HOST_CONTEXT_ID ||
 450                     (vmci_guest_code_active() &&
 451                      vmci_get_context_id() == handle->context)) {
 452                         valid_context = true;
 453                 }
 454
 455                 if (!valid_context || handle->resource == VMCI_INVALID_ID) {
 456                         pr_devel("Invalid argument (handle=0x%x:0x%x)\n",
 457                                  handle->context, handle->resource);
 458                         result = VMCI_ERROR_INVALID_ARGS;
 459                         goto free_mem;
 460                 }
 461
 462                 new_handle = *handle;
 463         }
 464
 465         entry->idx = 0;
 466         INIT_HLIST_NODE(&entry->node);
 467         entry->priv_flags = priv_flags;
 468         INIT_WORK(&entry->work, dbell_delayed_dispatch);
 469         entry->run_delayed = flags & VMCI_FLAG_DELAYED_CB;
 470         entry->notify_cb = notify_cb;
 471         entry->client_data = client_data;
 472         atomic_set(&entry->active, 0);
 473
 474         result = vmci_resource_add(&entry->resource,
 475                                    VMCI_RESOURCE_TYPE_DOORBELL,
 476                                    new_handle);
 477         if (result != VMCI_SUCCESS) {
 478                 pr_warn("Failed to add new resource (handle=0x%x:0x%x), error: %d\n",
 479                         new_handle.context, new_handle.resource, result);
 480                 goto free_mem;
 481         }
 482
 483         new_handle = vmci_resource_handle(&entry->resource);
 484         if (vmci_guest_code_active()) {
 485                 dbell_index_table_add(entry);
 486                 result = dbell_link(new_handle, entry->idx);
 487                 if (VMCI_SUCCESS != result)
 488                         goto destroy_resource;
 489
 490                 atomic_set(&entry->active, 1);
 491         }
 492
 493         *handle = new_handle;
 494
 495         return result;
 496
 497  destroy_resource:
 498         dbell_index_table_remove(entry);
 499         vmci_resource_remove(&entry->resource);
 500  free_mem:
 501         kfree(entry);
 502         return result;
 503 }
 504 EXPORT_SYMBOL_GPL(vmci_doorbell_create);
 505
 506 /*
 507  * vmci_doorbell_destroy() - Destroy a doorbell.
 508  * @handle:     The handle tracking the resource.
 509  *
 510  * Destroys a doorbell previously created with vmcii_doorbell_create. This
 511  * operation may block waiting for a callback to finish.
 512  */
 513 int vmci_doorbell_destroy(struct vmci_handle handle)
 514 {
 515         struct dbell_entry *entry;
 516         struct vmci_resource *resource;
 517
 518         if (vmci_handle_is_invalid(handle))
 519                 return VMCI_ERROR_INVALID_ARGS;
 520
 521         resource = vmci_resource_by_handle(handle,
 522                                            VMCI_RESOURCE_TYPE_DOORBELL);
 523         if (!resource) {
 524                 pr_devel("Failed to destroy doorbell (handle=0x%x:0x%x)\n",
 525                          handle.context, handle.resource);
 526                 return VMCI_ERROR_NOT_FOUND;
 527         }
 528
 529         entry = container_of(resource, struct dbell_entry, resource);
 530
 531         if (vmci_guest_code_active()) {
 532                 int result;
 533
 534                 dbell_index_table_remove(entry);
 535
 536                 result = dbell_unlink(handle);
 537                 if (VMCI_SUCCESS != result) {
 538
 539                         /*
 540                          * The only reason this should fail would be
 541                          * an inconsistency between guest and
 542                          * hypervisor state, where the guest believes
 543                          * it has an active registration whereas the
 544                          * hypervisor doesn't. One case where this may
 545                          * happen is if a doorbell is unregistered
 546                          * following a hibernation at a time where the
 547                          * doorbell state hasn't been restored on the
 548                          * hypervisor side yet. Since the handle has
 549                          * now been removed in the guest, we just
 550                          * print a warning and return success.
 551                          */
 552                         pr_devel("Unlink of doorbell (handle=0x%x:0x%x) unknown by hypervisor (error=%d)\n",
 553                                  handle.context, handle.resource, result);
 554                 }
 555         }
 556
 557         /*
 558          * Now remove the resource from the table.  It might still be in use
 559          * after this, in a callback or still on the delayed work queue.
 560          */
 561         vmci_resource_put(&entry->resource);
 562         vmci_resource_remove(&entry->resource);
 563
 564         kfree(entry);
 565
 566         return VMCI_SUCCESS;
 567 }
 568 EXPORT_SYMBOL_GPL(vmci_doorbell_destroy);
 569
 570 /*
 571  * vmci_doorbell_notify() - Ring the doorbell (and hide in the bushes).
 572  * @dst:        The handlle identifying the doorbell resource
 573  * @priv_flags: Priviledge flags.
 574  *
 575  * Generates a notification on the doorbell identified by the
 576  * handle. For host side generation of notifications, the caller
 577  * can specify what the privilege of the calling side is.
 578  */
 579 int vmci_doorbell_notify(struct vmci_handle dst, u32 priv_flags)
 580 {
 581         int retval;
 582         enum vmci_route route;
 583         struct vmci_handle src;
 584
 585         if (vmci_handle_is_invalid(dst) ||
 586             (priv_flags & ~VMCI_PRIVILEGE_ALL_FLAGS))
 587                 return VMCI_ERROR_INVALID_ARGS;
 588
 589         src = VMCI_INVALID_HANDLE;
 590         retval = vmci_route(&src, &dst, false, &route);
 591         if (retval < VMCI_SUCCESS)
 592                 return retval;
 593
 594         if (VMCI_ROUTE_AS_HOST == route)
 595                 return vmci_ctx_notify_dbell(VMCI_HOST_CONTEXT_ID,
 596                                              dst, priv_flags);
 597
 598         if (VMCI_ROUTE_AS_GUEST == route)
 599                 return dbell_notify_as_guest(dst, priv_flags);
 600
 601         pr_warn("Unknown route (%d) for doorbell\n", route);
 602         return VMCI_ERROR_DST_UNREACHABLE;
 603 }
 604 EXPORT_SYMBOL_GPL(vmci_doorbell_notify);