kernel/bpf/cpumap.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* bpf/cpumap.c
   3  *
   4  * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
   5  */
   6
   7 /**
   8  * DOC: cpu map
   9  * The 'cpumap' is primarily used as a backend map for XDP BPF helper
  10  * call bpf_redirect_map() and XDP_REDIRECT action, like 'devmap'.
  11  *
  12  * Unlike devmap which redirects XDP frames out to another NIC device,
  13  * this map type redirects raw XDP frames to another CPU.  The remote
  14  * CPU will do SKB-allocation and call the normal network stack.
  15  */
  16 /*
  17  * This is a scalability and isolation mechanism, that allow
  18  * separating the early driver network XDP layer, from the rest of the
  19  * netstack, and assigning dedicated CPUs for this stage.  This
  20  * basically allows for 10G wirespeed pre-filtering via bpf.
  21  */
  22 #include <linux/bitops.h>
  23 #include <linux/bpf.h>
  24 #include <linux/filter.h>
  25 #include <linux/ptr_ring.h>
  26 #include <net/xdp.h>
  27
  28 #include <linux/sched.h>
  29 #include <linux/workqueue.h>
  30 #include <linux/kthread.h>
  31 #include <linux/completion.h>
  32 #include <trace/events/xdp.h>
  33 #include <linux/btf_ids.h>
  34
  35 #include <linux/netdevice.h>   /* netif_receive_skb_list */
  36 #include <linux/etherdevice.h> /* eth_type_trans */
  37
  38 /* General idea: XDP packets getting XDP redirected to another CPU,
  39  * will maximum be stored/queued for one driver ->poll() call.  It is
  40  * guaranteed that queueing the frame and the flush operation happen on
  41  * same CPU.  Thus, cpu_map_flush operation can deduct via this_cpu_ptr()
  42  * which queue in bpf_cpu_map_entry contains packets.
  43  */
  44
  45 #define CPU_MAP_BULK_SIZE 8  /* 8 == one cacheline on 64-bit archs */
  46 struct bpf_cpu_map_entry;
  47 struct bpf_cpu_map;
  48
  49 struct xdp_bulk_queue {
  50         void *q[CPU_MAP_BULK_SIZE];
  51         struct list_head flush_node;
  52         struct bpf_cpu_map_entry *obj;
  53         unsigned int count;
  54 };
  55
  56 /* Struct for every remote "destination" CPU in map */
  57 struct bpf_cpu_map_entry {
  58         u32 cpu;    /* kthread CPU and map index */
  59         int map_id; /* Back reference to map */
  60
  61         /* XDP can run multiple RX-ring queues, need __percpu enqueue store */
  62         struct xdp_bulk_queue __percpu *bulkq;
  63
  64         /* Queue with potential multi-producers, and single-consumer kthread */
  65         struct ptr_ring *queue;
  66         struct task_struct *kthread;
  67
  68         struct bpf_cpumap_val value;
  69         struct bpf_prog *prog;
  70
  71         struct completion kthread_running;
  72         struct rcu_work free_work;
  73 };
  74
  75 struct bpf_cpu_map {
  76         struct bpf_map map;
  77         /* Below members specific for map type */
  78         struct bpf_cpu_map_entry __rcu **cpu_map;
  79 };
  80
  81 static DEFINE_PER_CPU(struct list_head, cpu_map_flush_list);
  82
  83 static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
  84 {
  85         u32 value_size = attr->value_size;
  86         struct bpf_cpu_map *cmap;
  87
  88         /* check sanity of attributes */
  89         if (attr->max_entries == 0 || attr->key_size != 4 ||
  90             (value_size != offsetofend(struct bpf_cpumap_val, qsize) &&
  91              value_size != offsetofend(struct bpf_cpumap_val, bpf_prog.fd)) ||
  92             attr->map_flags & ~BPF_F_NUMA_NODE)
  93                 return ERR_PTR(-EINVAL);
  94
  95         /* Pre-limit array size based on NR_CPUS, not final CPU check */
  96         if (attr->max_entries > NR_CPUS)
  97                 return ERR_PTR(-E2BIG);
  98
  99         cmap = bpf_map_area_alloc(sizeof(*cmap), NUMA_NO_NODE);
 100         if (!cmap)
 101                 return ERR_PTR(-ENOMEM);
 102
 103         bpf_map_init_from_attr(&cmap->map, attr);
 104
 105         /* Alloc array for possible remote "destination" CPUs */
 106         cmap->cpu_map = bpf_map_area_alloc(cmap->map.max_entries *
 107                                            sizeof(struct bpf_cpu_map_entry *),
 108                                            cmap->map.numa_node);
 109         if (!cmap->cpu_map) {
 110                 bpf_map_area_free(cmap);
 111                 return ERR_PTR(-ENOMEM);
 112         }
 113
 114         return &cmap->map;
 115 }
 116
 117 static void __cpu_map_ring_cleanup(struct ptr_ring *ring)
 118 {
 119         /* The tear-down procedure should have made sure that queue is
 120          * empty.  See __cpu_map_entry_replace() and work-queue
 121          * invoked cpu_map_kthread_stop(). Catch any broken behaviour
 122          * gracefully and warn once.
 123          */
 124         void *ptr;
 125
 126         while ((ptr = ptr_ring_consume(ring))) {
 127                 WARN_ON_ONCE(1);
 128                 if (unlikely(__ptr_test_bit(0, &ptr))) {
 129                         __ptr_clear_bit(0, &ptr);
 130                         kfree_skb(ptr);
 131                         continue;
 132                 }
 133                 xdp_return_frame(ptr);
 134         }
 135 }
 136
 137 static void cpu_map_bpf_prog_run_skb(struct bpf_cpu_map_entry *rcpu,
 138                                      struct list_head *listp,
 139                                      struct xdp_cpumap_stats *stats)
 140 {
 141         struct sk_buff *skb, *tmp;
 142         struct xdp_buff xdp;
 143         u32 act;
 144         int err;
 145
 146         list_for_each_entry_safe(skb, tmp, listp, list) {
 147                 act = bpf_prog_run_generic_xdp(skb, &xdp, rcpu->prog);
 148                 switch (act) {
 149                 case XDP_PASS:
 150                         break;
 151                 case XDP_REDIRECT:
 152                         skb_list_del_init(skb);
 153                         err = xdp_do_generic_redirect(skb->dev, skb, &xdp,
 154                                                       rcpu->prog);
 155                         if (unlikely(err)) {
 156                                 kfree_skb(skb);
 157                                 stats->drop++;
 158                         } else {
 159                                 stats->redirect++;
 160                         }
 161                         return;
 162                 default:
 163                         bpf_warn_invalid_xdp_action(NULL, rcpu->prog, act);
 164                         fallthrough;
 165                 case XDP_ABORTED:
 166                         trace_xdp_exception(skb->dev, rcpu->prog, act);
 167                         fallthrough;
 168                 case XDP_DROP:
 169                         skb_list_del_init(skb);
 170                         kfree_skb(skb);
 171                         stats->drop++;
 172                         return;
 173                 }
 174         }
 175 }
 176
 177 static int cpu_map_bpf_prog_run_xdp(struct bpf_cpu_map_entry *rcpu,
 178                                     void **frames, int n,
 179                                     struct xdp_cpumap_stats *stats)
 180 {
 181         struct xdp_rxq_info rxq;
 182         struct xdp_buff xdp;
 183         int i, nframes = 0;
 184
 185         xdp_set_return_frame_no_direct();
 186         xdp.rxq = &rxq;
 187
 188         for (i = 0; i < n; i++) {
 189                 struct xdp_frame *xdpf = frames[i];
 190                 u32 act;
 191                 int err;
 192
 193                 rxq.dev = xdpf->dev_rx;
 194                 rxq.mem = xdpf->mem;
 195                 /* TODO: report queue_index to xdp_rxq_info */
 196
 197                 xdp_convert_frame_to_buff(xdpf, &xdp);
 198
 199                 act = bpf_prog_run_xdp(rcpu->prog, &xdp);
 200                 switch (act) {
 201                 case XDP_PASS:
 202                         err = xdp_update_frame_from_buff(&xdp, xdpf);
 203                         if (err < 0) {
 204                                 xdp_return_frame(xdpf);
 205                                 stats->drop++;
 206                         } else {
 207                                 frames[nframes++] = xdpf;
 208                                 stats->pass++;
 209                         }
 210                         break;
 211                 case XDP_REDIRECT:
 212                         err = xdp_do_redirect(xdpf->dev_rx, &xdp,
 213                                               rcpu->prog);
 214                         if (unlikely(err)) {
 215                                 xdp_return_frame(xdpf);
 216                                 stats->drop++;
 217                         } else {
 218                                 stats->redirect++;
 219                         }
 220                         break;
 221                 default:
 222                         bpf_warn_invalid_xdp_action(NULL, rcpu->prog, act);
 223                         fallthrough;
 224                 case XDP_DROP:
 225                         xdp_return_frame(xdpf);
 226                         stats->drop++;
 227                         break;
 228                 }
 229         }
 230
 231         xdp_clear_return_frame_no_direct();
 232
 233         return nframes;
 234 }
 235
 236 #define CPUMAP_BATCH 8
 237
 238 static int cpu_map_bpf_prog_run(struct bpf_cpu_map_entry *rcpu, void **frames,
 239                                 int xdp_n, struct xdp_cpumap_stats *stats,
 240                                 struct list_head *list)
 241 {
 242         int nframes;
 243
 244         if (!rcpu->prog)
 245                 return xdp_n;
 246
 247         rcu_read_lock_bh();
 248
 249         nframes = cpu_map_bpf_prog_run_xdp(rcpu, frames, xdp_n, stats);
 250
 251         if (stats->redirect)
 252                 xdp_do_flush();
 253
 254         if (unlikely(!list_empty(list)))
 255                 cpu_map_bpf_prog_run_skb(rcpu, list, stats);
 256
 257         rcu_read_unlock_bh(); /* resched point, may call do_softirq() */
 258
 259         return nframes;
 260 }
 261
 262 static int cpu_map_kthread_run(void *data)
 263 {
 264         struct bpf_cpu_map_entry *rcpu = data;
 265
 266         complete(&rcpu->kthread_running);
 267         set_current_state(TASK_INTERRUPTIBLE);
 268
 269         /* When kthread gives stop order, then rcpu have been disconnected
 270          * from map, thus no new packets can enter. Remaining in-flight
 271          * per CPU stored packets are flushed to this queue.  Wait honoring
 272          * kthread_stop signal until queue is empty.
 273          */
 274         while (!kthread_should_stop() || !__ptr_ring_empty(rcpu->queue)) {
 275                 struct xdp_cpumap_stats stats = {}; /* zero stats */
 276                 unsigned int kmem_alloc_drops = 0, sched = 0;
 277                 gfp_t gfp = __GFP_ZERO | GFP_ATOMIC;
 278                 int i, n, m, nframes, xdp_n;
 279                 void *frames[CPUMAP_BATCH];
 280                 void *skbs[CPUMAP_BATCH];
 281                 LIST_HEAD(list);
 282
 283                 /* Release CPU reschedule checks */
 284                 if (__ptr_ring_empty(rcpu->queue)) {
 285                         set_current_state(TASK_INTERRUPTIBLE);
 286                         /* Recheck to avoid lost wake-up */
 287                         if (__ptr_ring_empty(rcpu->queue)) {
 288                                 schedule();
 289                                 sched = 1;
 290                         } else {
 291                                 __set_current_state(TASK_RUNNING);
 292                         }
 293                 } else {
 294                         sched = cond_resched();
 295                 }
 296
 297                 /*
 298                  * The bpf_cpu_map_entry is single consumer, with this
 299                  * kthread CPU pinned. Lockless access to ptr_ring
 300                  * consume side valid as no-resize allowed of queue.
 301                  */
 302                 n = __ptr_ring_consume_batched(rcpu->queue, frames,
 303                                                CPUMAP_BATCH);
 304                 for (i = 0, xdp_n = 0; i < n; i++) {
 305                         void *f = frames[i];
 306                         struct page *page;
 307
 308                         if (unlikely(__ptr_test_bit(0, &f))) {
 309                                 struct sk_buff *skb = f;
 310
 311                                 __ptr_clear_bit(0, &skb);
 312                                 list_add_tail(&skb->list, &list);
 313                                 continue;
 314                         }
 315
 316                         frames[xdp_n++] = f;
 317                         page = virt_to_page(f);
 318
 319                         /* Bring struct page memory area to curr CPU. Read by
 320                          * build_skb_around via page_is_pfmemalloc(), and when
 321                          * freed written by page_frag_free call.
 322                          */
 323                         prefetchw(page);
 324                 }
 325
 326                 /* Support running another XDP prog on this CPU */
 327                 nframes = cpu_map_bpf_prog_run(rcpu, frames, xdp_n, &stats, &list);
 328                 if (nframes) {
 329                         m = kmem_cache_alloc_bulk(skbuff_cache, gfp, nframes, skbs);
 330                         if (unlikely(m == 0)) {
 331                                 for (i = 0; i < nframes; i++)
 332                                         skbs[i] = NULL; /* effect: xdp_return_frame */
 333                                 kmem_alloc_drops += nframes;
 334                         }
 335                 }
 336
 337                 local_bh_disable();
 338                 for (i = 0; i < nframes; i++) {
 339                         struct xdp_frame *xdpf = frames[i];
 340                         struct sk_buff *skb = skbs[i];
 341
 342                         skb = __xdp_build_skb_from_frame(xdpf, skb,
 343                                                          xdpf->dev_rx);
 344                         if (!skb) {
 345                                 xdp_return_frame(xdpf);
 346                                 continue;
 347                         }
 348
 349                         list_add_tail(&skb->list, &list);
 350                 }
 351                 netif_receive_skb_list(&list);
 352
 353                 /* Feedback loop via tracepoint */
 354                 trace_xdp_cpumap_kthread(rcpu->map_id, n, kmem_alloc_drops,
 355                                          sched, &stats);
 356
 357                 local_bh_enable(); /* resched point, may call do_softirq() */
 358         }
 359         __set_current_state(TASK_RUNNING);
 360
 361         return 0;
 362 }
 363
 364 static int __cpu_map_load_bpf_program(struct bpf_cpu_map_entry *rcpu,
 365                                       struct bpf_map *map, int fd)
 366 {
 367         struct bpf_prog *prog;
 368
 369         prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_XDP);
 370         if (IS_ERR(prog))
 371                 return PTR_ERR(prog);
 372
 373         if (prog->expected_attach_type != BPF_XDP_CPUMAP ||
 374             !bpf_prog_map_compatible(map, prog)) {
 375                 bpf_prog_put(prog);
 376                 return -EINVAL;
 377         }
 378
 379         rcpu->value.bpf_prog.id = prog->aux->id;
 380         rcpu->prog = prog;
 381
 382         return 0;
 383 }
 384
 385 static struct bpf_cpu_map_entry *
 386 __cpu_map_entry_alloc(struct bpf_map *map, struct bpf_cpumap_val *value,
 387                       u32 cpu)
 388 {
 389         int numa, err, i, fd = value->bpf_prog.fd;
 390         gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
 391         struct bpf_cpu_map_entry *rcpu;
 392         struct xdp_bulk_queue *bq;
 393
 394         /* Have map->numa_node, but choose node of redirect target CPU */
 395         numa = cpu_to_node(cpu);
 396
 397         rcpu = bpf_map_kmalloc_node(map, sizeof(*rcpu), gfp | __GFP_ZERO, numa);
 398         if (!rcpu)
 399                 return NULL;
 400
 401         /* Alloc percpu bulkq */
 402         rcpu->bulkq = bpf_map_alloc_percpu(map, sizeof(*rcpu->bulkq),
 403                                            sizeof(void *), gfp);
 404         if (!rcpu->bulkq)
 405                 goto free_rcu;
 406
 407         for_each_possible_cpu(i) {
 408                 bq = per_cpu_ptr(rcpu->bulkq, i);
 409                 bq->obj = rcpu;
 410         }
 411
 412         /* Alloc queue */
 413         rcpu->queue = bpf_map_kmalloc_node(map, sizeof(*rcpu->queue), gfp,
 414                                            numa);
 415         if (!rcpu->queue)
 416                 goto free_bulkq;
 417
 418         err = ptr_ring_init(rcpu->queue, value->qsize, gfp);
 419         if (err)
 420                 goto free_queue;
 421
 422         rcpu->cpu    = cpu;
 423         rcpu->map_id = map->id;
 424         rcpu->value.qsize  = value->qsize;
 425
 426         if (fd > 0 && __cpu_map_load_bpf_program(rcpu, map, fd))
 427                 goto free_ptr_ring;
 428
 429         /* Setup kthread */
 430         init_completion(&rcpu->kthread_running);
 431         rcpu->kthread = kthread_create_on_node(cpu_map_kthread_run, rcpu, numa,
 432                                                "cpumap/%d/map:%d", cpu,
 433                                                map->id);
 434         if (IS_ERR(rcpu->kthread))
 435                 goto free_prog;
 436
 437         /* Make sure kthread runs on a single CPU */
 438         kthread_bind(rcpu->kthread, cpu);
 439         wake_up_process(rcpu->kthread);
 440
 441         /* Make sure kthread has been running, so kthread_stop() will not
 442          * stop the kthread prematurely and all pending frames or skbs
 443          * will be handled by the kthread before kthread_stop() returns.
 444          */
 445         wait_for_completion(&rcpu->kthread_running);
 446
 447         return rcpu;
 448
 449 free_prog:
 450         if (rcpu->prog)
 451                 bpf_prog_put(rcpu->prog);
 452 free_ptr_ring:
 453         ptr_ring_cleanup(rcpu->queue, NULL);
 454 free_queue:
 455         kfree(rcpu->queue);
 456 free_bulkq:
 457         free_percpu(rcpu->bulkq);
 458 free_rcu:
 459         kfree(rcpu);
 460         return NULL;
 461 }
 462
 463 static void __cpu_map_entry_free(struct work_struct *work)
 464 {
 465         struct bpf_cpu_map_entry *rcpu;
 466
 467         /* This cpu_map_entry have been disconnected from map and one
 468          * RCU grace-period have elapsed. Thus, XDP cannot queue any
 469          * new packets and cannot change/set flush_needed that can
 470          * find this entry.
 471          */
 472         rcpu = container_of(to_rcu_work(work), struct bpf_cpu_map_entry, free_work);
 473
 474         /* kthread_stop will wake_up_process and wait for it to complete.
 475          * cpu_map_kthread_run() makes sure the pointer ring is empty
 476          * before exiting.
 477          */
 478         kthread_stop(rcpu->kthread);
 479
 480         if (rcpu->prog)
 481                 bpf_prog_put(rcpu->prog);
 482         /* The queue should be empty at this point */
 483         __cpu_map_ring_cleanup(rcpu->queue);
 484         ptr_ring_cleanup(rcpu->queue, NULL);
 485         kfree(rcpu->queue);
 486         free_percpu(rcpu->bulkq);
 487         kfree(rcpu);
 488 }
 489
 490 /* After the xchg of the bpf_cpu_map_entry pointer, we need to make sure the old
 491  * entry is no longer in use before freeing. We use queue_rcu_work() to call
 492  * __cpu_map_entry_free() in a separate workqueue after waiting for an RCU grace
 493  * period. This means that (a) all pending enqueue and flush operations have
 494  * completed (because of the RCU callback), and (b) we are in a workqueue
 495  * context where we can stop the kthread and wait for it to exit before freeing
 496  * everything.
 497  */
 498 static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
 499                                     u32 key_cpu, struct bpf_cpu_map_entry *rcpu)
 500 {
 501         struct bpf_cpu_map_entry *old_rcpu;
 502
 503         old_rcpu = unrcu_pointer(xchg(&cmap->cpu_map[key_cpu], RCU_INITIALIZER(rcpu)));
 504         if (old_rcpu) {
 505                 INIT_RCU_WORK(&old_rcpu->free_work, __cpu_map_entry_free);
 506                 queue_rcu_work(system_wq, &old_rcpu->free_work);
 507         }
 508 }
 509
 510 static long cpu_map_delete_elem(struct bpf_map *map, void *key)
 511 {
 512         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 513         u32 key_cpu = *(u32 *)key;
 514
 515         if (key_cpu >= map->max_entries)
 516                 return -EINVAL;
 517
 518         /* notice caller map_delete_elem() uses rcu_read_lock() */
 519         __cpu_map_entry_replace(cmap, key_cpu, NULL);
 520         return 0;
 521 }
 522
 523 static long cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
 524                                 u64 map_flags)
 525 {
 526         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 527         struct bpf_cpumap_val cpumap_value = {};
 528         struct bpf_cpu_map_entry *rcpu;
 529         /* Array index key correspond to CPU number */
 530         u32 key_cpu = *(u32 *)key;
 531
 532         memcpy(&cpumap_value, value, map->value_size);
 533
 534         if (unlikely(map_flags > BPF_EXIST))
 535                 return -EINVAL;
 536         if (unlikely(key_cpu >= cmap->map.max_entries))
 537                 return -E2BIG;
 538         if (unlikely(map_flags == BPF_NOEXIST))
 539                 return -EEXIST;
 540         if (unlikely(cpumap_value.qsize > 16384)) /* sanity limit on qsize */
 541                 return -EOVERFLOW;
 542
 543         /* Make sure CPU is a valid possible cpu */
 544         if (key_cpu >= nr_cpumask_bits || !cpu_possible(key_cpu))
 545                 return -ENODEV;
 546
 547         if (cpumap_value.qsize == 0) {
 548                 rcpu = NULL; /* Same as deleting */
 549         } else {
 550                 /* Updating qsize cause re-allocation of bpf_cpu_map_entry */
 551                 rcpu = __cpu_map_entry_alloc(map, &cpumap_value, key_cpu);
 552                 if (!rcpu)
 553                         return -ENOMEM;
 554         }
 555         rcu_read_lock();
 556         __cpu_map_entry_replace(cmap, key_cpu, rcpu);
 557         rcu_read_unlock();
 558         return 0;
 559 }
 560
 561 static void cpu_map_free(struct bpf_map *map)
 562 {
 563         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 564         u32 i;
 565
 566         /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
 567          * so the bpf programs (can be more than one that used this map) were
 568          * disconnected from events. Wait for outstanding critical sections in
 569          * these programs to complete. synchronize_rcu() below not only
 570          * guarantees no further "XDP/bpf-side" reads against
 571          * bpf_cpu_map->cpu_map, but also ensure pending flush operations
 572          * (if any) are completed.
 573          */
 574         synchronize_rcu();
 575
 576         /* The only possible user of bpf_cpu_map_entry is
 577          * cpu_map_kthread_run().
 578          */
 579         for (i = 0; i < cmap->map.max_entries; i++) {
 580                 struct bpf_cpu_map_entry *rcpu;
 581
 582                 rcpu = rcu_dereference_raw(cmap->cpu_map[i]);
 583                 if (!rcpu)
 584                         continue;
 585
 586                 /* Stop kthread and cleanup entry directly */
 587                 __cpu_map_entry_free(&rcpu->free_work.work);
 588         }
 589         bpf_map_area_free(cmap->cpu_map);
 590         bpf_map_area_free(cmap);
 591 }
 592
 593 /* Elements are kept alive by RCU; either by rcu_read_lock() (from syscall) or
 594  * by local_bh_disable() (from XDP calls inside NAPI). The
 595  * rcu_read_lock_bh_held() below makes lockdep accept both.
 596  */
 597 static void *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
 598 {
 599         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 600         struct bpf_cpu_map_entry *rcpu;
 601
 602         if (key >= map->max_entries)
 603                 return NULL;
 604
 605         rcpu = rcu_dereference_check(cmap->cpu_map[key],
 606                                      rcu_read_lock_bh_held());
 607         return rcpu;
 608 }
 609
 610 static void *cpu_map_lookup_elem(struct bpf_map *map, void *key)
 611 {
 612         struct bpf_cpu_map_entry *rcpu =
 613                 __cpu_map_lookup_elem(map, *(u32 *)key);
 614
 615         return rcpu ? &rcpu->value : NULL;
 616 }
 617
 618 static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 619 {
 620         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 621         u32 index = key ? *(u32 *)key : U32_MAX;
 622         u32 *next = next_key;
 623
 624         if (index >= cmap->map.max_entries) {
 625                 *next = 0;
 626                 return 0;
 627         }
 628
 629         if (index == cmap->map.max_entries - 1)
 630                 return -ENOENT;
 631         *next = index + 1;
 632         return 0;
 633 }
 634
 635 static long cpu_map_redirect(struct bpf_map *map, u64 index, u64 flags)
 636 {
 637         return __bpf_xdp_redirect_map(map, index, flags, 0,
 638                                       __cpu_map_lookup_elem);
 639 }
 640
 641 static u64 cpu_map_mem_usage(const struct bpf_map *map)
 642 {
 643         u64 usage = sizeof(struct bpf_cpu_map);
 644
 645         /* Currently the dynamically allocated elements are not counted */
 646         usage += (u64)map->max_entries * sizeof(struct bpf_cpu_map_entry *);
 647         return usage;
 648 }
 649
 650 BTF_ID_LIST_SINGLE(cpu_map_btf_ids, struct, bpf_cpu_map)
 651 const struct bpf_map_ops cpu_map_ops = {
 652         .map_meta_equal         = bpf_map_meta_equal,
 653         .map_alloc              = cpu_map_alloc,
 654         .map_free               = cpu_map_free,
 655         .map_delete_elem        = cpu_map_delete_elem,
 656         .map_update_elem        = cpu_map_update_elem,
 657         .map_lookup_elem        = cpu_map_lookup_elem,
 658         .map_get_next_key       = cpu_map_get_next_key,
 659         .map_check_btf          = map_check_no_btf,
 660         .map_mem_usage          = cpu_map_mem_usage,
 661         .map_btf_id             = &cpu_map_btf_ids[0],
 662         .map_redirect           = cpu_map_redirect,
 663 };
 664
 665 static void bq_flush_to_queue(struct xdp_bulk_queue *bq)
 666 {
 667         struct bpf_cpu_map_entry *rcpu = bq->obj;
 668         unsigned int processed = 0, drops = 0;
 669         const int to_cpu = rcpu->cpu;
 670         struct ptr_ring *q;
 671         int i;
 672
 673         if (unlikely(!bq->count))
 674                 return;
 675
 676         q = rcpu->queue;
 677         spin_lock(&q->producer_lock);
 678
 679         for (i = 0; i < bq->count; i++) {
 680                 struct xdp_frame *xdpf = bq->q[i];
 681                 int err;
 682
 683                 err = __ptr_ring_produce(q, xdpf);
 684                 if (err) {
 685                         drops++;
 686                         xdp_return_frame_rx_napi(xdpf);
 687                 }
 688                 processed++;
 689         }
 690         bq->count = 0;
 691         spin_unlock(&q->producer_lock);
 692
 693         __list_del_clearprev(&bq->flush_node);
 694
 695         /* Feedback loop via tracepoints */
 696         trace_xdp_cpumap_enqueue(rcpu->map_id, processed, drops, to_cpu);
 697 }
 698
 699 /* Runs under RCU-read-side, plus in softirq under NAPI protection.
 700  * Thus, safe percpu variable access.
 701  */
 702 static void bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
 703 {
 704         struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
 705         struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
 706
 707         if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
 708                 bq_flush_to_queue(bq);
 709
 710         /* Notice, xdp_buff/page MUST be queued here, long enough for
 711          * driver to code invoking us to finished, due to driver
 712          * (e.g. ixgbe) recycle tricks based on page-refcnt.
 713          *
 714          * Thus, incoming xdp_frame is always queued here (else we race
 715          * with another CPU on page-refcnt and remaining driver code).
 716          * Queue time is very short, as driver will invoke flush
 717          * operation, when completing napi->poll call.
 718          */
 719         bq->q[bq->count++] = xdpf;
 720
 721         if (!bq->flush_node.prev)
 722                 list_add(&bq->flush_node, flush_list);
 723 }
 724
 725 int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf,
 726                     struct net_device *dev_rx)
 727 {
 728         /* Info needed when constructing SKB on remote CPU */
 729         xdpf->dev_rx = dev_rx;
 730
 731         bq_enqueue(rcpu, xdpf);
 732         return 0;
 733 }
 734
 735 int cpu_map_generic_redirect(struct bpf_cpu_map_entry *rcpu,
 736                              struct sk_buff *skb)
 737 {
 738         int ret;
 739
 740         __skb_pull(skb, skb->mac_len);
 741         skb_set_redirected(skb, false);
 742         __ptr_set_bit(0, &skb);
 743
 744         ret = ptr_ring_produce(rcpu->queue, skb);
 745         if (ret < 0)
 746                 goto trace;
 747
 748         wake_up_process(rcpu->kthread);
 749 trace:
 750         trace_xdp_cpumap_enqueue(rcpu->map_id, !ret, !!ret, rcpu->cpu);
 751         return ret;
 752 }
 753
 754 void __cpu_map_flush(void)
 755 {
 756         struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
 757         struct xdp_bulk_queue *bq, *tmp;
 758
 759         list_for_each_entry_safe(bq, tmp, flush_list, flush_node) {
 760                 bq_flush_to_queue(bq);
 761
 762                 /* If already running, costs spin_lock_irqsave + smb_mb */
 763                 wake_up_process(bq->obj->kthread);
 764         }
 765 }
 766
 767 static int __init cpu_map_init(void)
 768 {
 769         int cpu;
 770
 771         for_each_possible_cpu(cpu)
 772                 INIT_LIST_HEAD(&per_cpu(cpu_map_flush_list, cpu));
 773         return 0;
 774 }
 775
 776 subsys_initcall(cpu_map_init);