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