root/kernel/bpf/cpumap.c

DEFINITIONS

1. cpu_map_alloc
2. get_cpu_map_entry
3. cpu_map_kthread_stop
4. cpu_map_build_skb
5. __cpu_map_ring_cleanup
6. put_cpu_map_entry
7. cpu_map_kthread_run
8. __cpu_map_entry_alloc
9. __cpu_map_entry_free
10. __cpu_map_entry_replace
11. cpu_map_delete_elem
12. cpu_map_update_elem
13. cpu_map_free
14. __cpu_map_lookup_elem
15. cpu_map_lookup_elem
16. cpu_map_get_next_key
17. bq_flush_to_queue
18. bq_enqueue
19. cpu_map_enqueue
20. __cpu_map_flush

   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_core */
  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 */
  41 struct bpf_cpu_map_entry;
  42 struct bpf_cpu_map;
  43 
  44 struct 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 */
  52 struct bpf_cpu_map_entry {
  53         u32 cpu;    /* kthread CPU and map index */
  54         int map_id; /* Back reference to map */
  55         u32 qsize;  /* Queue size placeholder for map lookup */
  56 
  57         /* XDP can run multiple RX-ring queues, need __percpu enqueue store */
  58         struct xdp_bulk_queue __percpu *bulkq;
  59 
  60         struct bpf_cpu_map *cmap;
  61 
  62         /* Queue with potential multi-producers, and single-consumer kthread */
  63         struct ptr_ring *queue;
  64         struct task_struct *kthread;
  65         struct work_struct kthread_stop_wq;
  66 
  67         atomic_t refcnt; /* Control when this struct can be free'ed */
  68         struct rcu_head rcu;
  69 };
  70 
  71 struct bpf_cpu_map {
  72         struct bpf_map map;
  73         /* Below members specific for map type */
  74         struct bpf_cpu_map_entry **cpu_map;
  75         struct list_head __percpu *flush_list;
  76 };
  77 
  78 static int bq_flush_to_queue(struct xdp_bulk_queue *bq, bool in_napi_ctx);
  79 
  80 static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
  81 {
  82         struct bpf_cpu_map *cmap;
  83         int err = -ENOMEM;
  84         int ret, cpu;
  85         u64 cost;
  86 
  87         if (!capable(CAP_SYS_ADMIN))
  88                 return ERR_PTR(-EPERM);
  89 
  90         /* check sanity of attributes */
  91         if (attr->max_entries == 0 || attr->key_size != 4 ||
  92             attr->value_size != 4 || attr->map_flags & ~BPF_F_NUMA_NODE)
  93                 return ERR_PTR(-EINVAL);
  94 
  95         cmap = kzalloc(sizeof(*cmap), GFP_USER);
  96         if (!cmap)
  97                 return ERR_PTR(-ENOMEM);
  98 
  99         bpf_map_init_from_attr(&cmap->map, attr);
 100 
 101         /* Pre-limit array size based on NR_CPUS, not final CPU check */
 102         if (cmap->map.max_entries > NR_CPUS) {
 103                 err = -E2BIG;
 104                 goto free_cmap;
 105         }
 106 
 107         /* make sure page count doesn't overflow */
 108         cost = (u64) cmap->map.max_entries * sizeof(struct bpf_cpu_map_entry *);
 109         cost += sizeof(struct list_head) * num_possible_cpus();
 110 
 111         /* Notice returns -EPERM on if map size is larger than memlock limit */
 112         ret = bpf_map_charge_init(&cmap->map.memory, cost);
 113         if (ret) {
 114                 err = ret;
 115                 goto free_cmap;
 116         }
 117 
 118         cmap->flush_list = alloc_percpu(struct list_head);
 119         if (!cmap->flush_list)
 120                 goto free_charge;
 121 
 122         for_each_possible_cpu(cpu)
 123                 INIT_LIST_HEAD(per_cpu_ptr(cmap->flush_list, cpu));
 124 
 125         /* Alloc array for possible remote "destination" CPUs */
 126         cmap->cpu_map = bpf_map_area_alloc(cmap->map.max_entries *
 127                                            sizeof(struct bpf_cpu_map_entry *),
 128                                            cmap->map.numa_node);
 129         if (!cmap->cpu_map)
 130                 goto free_percpu;
 131 
 132         return &cmap->map;
 133 free_percpu:
 134         free_percpu(cmap->flush_list);
 135 free_charge:
 136         bpf_map_charge_finish(&cmap->map.memory);
 137 free_cmap:
 138         kfree(cmap);
 139         return ERR_PTR(err);
 140 }
 141 
 142 static void get_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
 143 {
 144         atomic_inc(&rcpu->refcnt);
 145 }
 146 
 147 /* called from workqueue, to workaround syscall using preempt_disable */
 148 static void cpu_map_kthread_stop(struct work_struct *work)
 149 {
 150         struct bpf_cpu_map_entry *rcpu;
 151 
 152         rcpu = container_of(work, struct bpf_cpu_map_entry, kthread_stop_wq);
 153 
 154         /* Wait for flush in __cpu_map_entry_free(), via full RCU barrier,
 155          * as it waits until all in-flight call_rcu() callbacks complete.
 156          */
 157         rcu_barrier();
 158 
 159         /* kthread_stop will wake_up_process and wait for it to complete */
 160         kthread_stop(rcpu->kthread);
 161 }
 162 
 163 static struct sk_buff *cpu_map_build_skb(struct bpf_cpu_map_entry *rcpu,
 164                                          struct xdp_frame *xdpf,
 165                                          struct sk_buff *skb)
 166 {
 167         unsigned int hard_start_headroom;
 168         unsigned int frame_size;
 169         void *pkt_data_start;
 170 
 171         /* Part of headroom was reserved to xdpf */
 172         hard_start_headroom = sizeof(struct xdp_frame) +  xdpf->headroom;
 173 
 174         /* build_skb need to place skb_shared_info after SKB end, and
 175          * also want to know the memory "truesize".  Thus, need to
 176          * know the memory frame size backing xdp_buff.
 177          *
 178          * XDP was designed to have PAGE_SIZE frames, but this
 179          * assumption is not longer true with ixgbe and i40e.  It
 180          * would be preferred to set frame_size to 2048 or 4096
 181          * depending on the driver.
 182          *   frame_size = 2048;
 183          *   frame_len  = frame_size - sizeof(*xdp_frame);
 184          *
 185          * Instead, with info avail, skb_shared_info in placed after
 186          * packet len.  This, unfortunately fakes the truesize.
 187          * Another disadvantage of this approach, the skb_shared_info
 188          * is not at a fixed memory location, with mixed length
 189          * packets, which is bad for cache-line hotness.
 190          */
 191         frame_size = SKB_DATA_ALIGN(xdpf->len + hard_start_headroom) +
 192                 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
 193 
 194         pkt_data_start = xdpf->data - hard_start_headroom;
 195         skb = build_skb_around(skb, pkt_data_start, frame_size);
 196         if (unlikely(!skb))
 197                 return NULL;
 198 
 199         skb_reserve(skb, hard_start_headroom);
 200         __skb_put(skb, xdpf->len);
 201         if (xdpf->metasize)
 202                 skb_metadata_set(skb, xdpf->metasize);
 203 
 204         /* Essential SKB info: protocol and skb->dev */
 205         skb->protocol = eth_type_trans(skb, xdpf->dev_rx);
 206 
 207         /* Optional SKB info, currently missing:
 208          * - HW checksum info           (skb->ip_summed)
 209          * - HW RX hash                 (skb_set_hash)
 210          * - RX ring dev queue index    (skb_record_rx_queue)
 211          */
 212 
 213         /* Until page_pool get SKB return path, release DMA here */
 214         xdp_release_frame(xdpf);
 215 
 216         /* Allow SKB to reuse area used by xdp_frame */
 217         xdp_scrub_frame(xdpf);
 218 
 219         return skb;
 220 }
 221 
 222 static void __cpu_map_ring_cleanup(struct ptr_ring *ring)
 223 {
 224         /* The tear-down procedure should have made sure that queue is
 225          * empty.  See __cpu_map_entry_replace() and work-queue
 226          * invoked cpu_map_kthread_stop(). Catch any broken behaviour
 227          * gracefully and warn once.
 228          */
 229         struct xdp_frame *xdpf;
 230 
 231         while ((xdpf = ptr_ring_consume(ring)))
 232                 if (WARN_ON_ONCE(xdpf))
 233                         xdp_return_frame(xdpf);
 234 }
 235 
 236 static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
 237 {
 238         if (atomic_dec_and_test(&rcpu->refcnt)) {
 239                 /* The queue should be empty at this point */
 240                 __cpu_map_ring_cleanup(rcpu->queue);
 241                 ptr_ring_cleanup(rcpu->queue, NULL);
 242                 kfree(rcpu->queue);
 243                 kfree(rcpu);
 244         }
 245 }
 246 
 247 #define CPUMAP_BATCH 8
 248 
 249 static int cpu_map_kthread_run(void *data)
 250 {
 251         struct bpf_cpu_map_entry *rcpu = data;
 252 
 253         set_current_state(TASK_INTERRUPTIBLE);
 254 
 255         /* When kthread gives stop order, then rcpu have been disconnected
 256          * from map, thus no new packets can enter. Remaining in-flight
 257          * per CPU stored packets are flushed to this queue.  Wait honoring
 258          * kthread_stop signal until queue is empty.
 259          */
 260         while (!kthread_should_stop() || !__ptr_ring_empty(rcpu->queue)) {
 261                 unsigned int drops = 0, sched = 0;
 262                 void *frames[CPUMAP_BATCH];
 263                 void *skbs[CPUMAP_BATCH];
 264                 gfp_t gfp = __GFP_ZERO | GFP_ATOMIC;
 265                 int i, n, m;
 266 
 267                 /* Release CPU reschedule checks */
 268                 if (__ptr_ring_empty(rcpu->queue)) {
 269                         set_current_state(TASK_INTERRUPTIBLE);
 270                         /* Recheck to avoid lost wake-up */
 271                         if (__ptr_ring_empty(rcpu->queue)) {
 272                                 schedule();
 273                                 sched = 1;
 274                         } else {
 275                                 __set_current_state(TASK_RUNNING);
 276                         }
 277                 } else {
 278                         sched = cond_resched();
 279                 }
 280 
 281                 /*
 282                  * The bpf_cpu_map_entry is single consumer, with this
 283                  * kthread CPU pinned. Lockless access to ptr_ring
 284                  * consume side valid as no-resize allowed of queue.
 285                  */
 286                 n = ptr_ring_consume_batched(rcpu->queue, frames, CPUMAP_BATCH);
 287 
 288                 for (i = 0; i < n; i++) {
 289                         void *f = frames[i];
 290                         struct page *page = virt_to_page(f);
 291 
 292                         /* Bring struct page memory area to curr CPU. Read by
 293                          * build_skb_around via page_is_pfmemalloc(), and when
 294                          * freed written by page_frag_free call.
 295                          */
 296                         prefetchw(page);
 297                 }
 298 
 299                 m = kmem_cache_alloc_bulk(skbuff_head_cache, gfp, n, skbs);
 300                 if (unlikely(m == 0)) {
 301                         for (i = 0; i < n; i++)
 302                                 skbs[i] = NULL; /* effect: xdp_return_frame */
 303                         drops = n;
 304                 }
 305 
 306                 local_bh_disable();
 307                 for (i = 0; i < n; i++) {
 308                         struct xdp_frame *xdpf = frames[i];
 309                         struct sk_buff *skb = skbs[i];
 310                         int ret;
 311 
 312                         skb = cpu_map_build_skb(rcpu, xdpf, skb);
 313                         if (!skb) {
 314                                 xdp_return_frame(xdpf);
 315                                 continue;
 316                         }
 317 
 318                         /* Inject into network stack */
 319                         ret = netif_receive_skb_core(skb);
 320                         if (ret == NET_RX_DROP)
 321                                 drops++;
 322                 }
 323                 /* Feedback loop via tracepoint */
 324                 trace_xdp_cpumap_kthread(rcpu->map_id, n, drops, sched);
 325 
 326                 local_bh_enable(); /* resched point, may call do_softirq() */
 327         }
 328         __set_current_state(TASK_RUNNING);
 329 
 330         put_cpu_map_entry(rcpu);
 331         return 0;
 332 }
 333 
 334 static struct bpf_cpu_map_entry *__cpu_map_entry_alloc(u32 qsize, u32 cpu,
 335                                                        int map_id)
 336 {
 337         gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
 338         struct bpf_cpu_map_entry *rcpu;
 339         struct xdp_bulk_queue *bq;
 340         int numa, err, i;
 341 
 342         /* Have map->numa_node, but choose node of redirect target CPU */
 343         numa = cpu_to_node(cpu);
 344 
 345         rcpu = kzalloc_node(sizeof(*rcpu), gfp, numa);
 346         if (!rcpu)
 347                 return NULL;
 348 
 349         /* Alloc percpu bulkq */
 350         rcpu->bulkq = __alloc_percpu_gfp(sizeof(*rcpu->bulkq),
 351                                          sizeof(void *), gfp);
 352         if (!rcpu->bulkq)
 353                 goto free_rcu;
 354 
 355         for_each_possible_cpu(i) {
 356                 bq = per_cpu_ptr(rcpu->bulkq, i);
 357                 bq->obj = rcpu;
 358         }
 359 
 360         /* Alloc queue */
 361         rcpu->queue = kzalloc_node(sizeof(*rcpu->queue), gfp, numa);
 362         if (!rcpu->queue)
 363                 goto free_bulkq;
 364 
 365         err = ptr_ring_init(rcpu->queue, qsize, gfp);
 366         if (err)
 367                 goto free_queue;
 368 
 369         rcpu->cpu    = cpu;
 370         rcpu->map_id = map_id;
 371         rcpu->qsize  = qsize;
 372 
 373         /* Setup kthread */
 374         rcpu->kthread = kthread_create_on_node(cpu_map_kthread_run, rcpu, numa,
 375                                                "cpumap/%d/map:%d", cpu, map_id);
 376         if (IS_ERR(rcpu->kthread))
 377                 goto free_ptr_ring;
 378 
 379         get_cpu_map_entry(rcpu); /* 1-refcnt for being in cmap->cpu_map[] */
 380         get_cpu_map_entry(rcpu); /* 1-refcnt for kthread */
 381 
 382         /* Make sure kthread runs on a single CPU */
 383         kthread_bind(rcpu->kthread, cpu);
 384         wake_up_process(rcpu->kthread);
 385 
 386         return rcpu;
 387 
 388 free_ptr_ring:
 389         ptr_ring_cleanup(rcpu->queue, NULL);
 390 free_queue:
 391         kfree(rcpu->queue);
 392 free_bulkq:
 393         free_percpu(rcpu->bulkq);
 394 free_rcu:
 395         kfree(rcpu);
 396         return NULL;
 397 }
 398 
 399 static void __cpu_map_entry_free(struct rcu_head *rcu)
 400 {
 401         struct bpf_cpu_map_entry *rcpu;
 402         int cpu;
 403 
 404         /* This cpu_map_entry have been disconnected from map and one
 405          * RCU graze-period have elapsed.  Thus, XDP cannot queue any
 406          * new packets and cannot change/set flush_needed that can
 407          * find this entry.
 408          */
 409         rcpu = container_of(rcu, struct bpf_cpu_map_entry, rcu);
 410 
 411         /* Flush remaining packets in percpu bulkq */
 412         for_each_online_cpu(cpu) {
 413                 struct xdp_bulk_queue *bq = per_cpu_ptr(rcpu->bulkq, cpu);
 414 
 415                 /* No concurrent bq_enqueue can run at this point */
 416                 bq_flush_to_queue(bq, false);
 417         }
 418         free_percpu(rcpu->bulkq);
 419         /* Cannot kthread_stop() here, last put free rcpu resources */
 420         put_cpu_map_entry(rcpu);
 421 }
 422 
 423 /* After xchg pointer to bpf_cpu_map_entry, use the call_rcu() to
 424  * ensure any driver rcu critical sections have completed, but this
 425  * does not guarantee a flush has happened yet. Because driver side
 426  * rcu_read_lock/unlock only protects the running XDP program.  The
 427  * atomic xchg and NULL-ptr check in __cpu_map_flush() makes sure a
 428  * pending flush op doesn't fail.
 429  *
 430  * The bpf_cpu_map_entry is still used by the kthread, and there can
 431  * still be pending packets (in queue and percpu bulkq).  A refcnt
 432  * makes sure to last user (kthread_stop vs. call_rcu) free memory
 433  * resources.
 434  *
 435  * The rcu callback __cpu_map_entry_free flush remaining packets in
 436  * percpu bulkq to queue.  Due to caller map_delete_elem() disable
 437  * preemption, cannot call kthread_stop() to make sure queue is empty.
 438  * Instead a work_queue is started for stopping kthread,
 439  * cpu_map_kthread_stop, which waits for an RCU graze period before
 440  * stopping kthread, emptying the queue.
 441  */
 442 static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
 443                                     u32 key_cpu, struct bpf_cpu_map_entry *rcpu)
 444 {
 445         struct bpf_cpu_map_entry *old_rcpu;
 446 
 447         old_rcpu = xchg(&cmap->cpu_map[key_cpu], rcpu);
 448         if (old_rcpu) {
 449                 call_rcu(&old_rcpu->rcu, __cpu_map_entry_free);
 450                 INIT_WORK(&old_rcpu->kthread_stop_wq, cpu_map_kthread_stop);
 451                 schedule_work(&old_rcpu->kthread_stop_wq);
 452         }
 453 }
 454 
 455 static int cpu_map_delete_elem(struct bpf_map *map, void *key)
 456 {
 457         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 458         u32 key_cpu = *(u32 *)key;
 459 
 460         if (key_cpu >= map->max_entries)
 461                 return -EINVAL;
 462 
 463         /* notice caller map_delete_elem() use preempt_disable() */
 464         __cpu_map_entry_replace(cmap, key_cpu, NULL);
 465         return 0;
 466 }
 467 
 468 static int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
 469                                u64 map_flags)
 470 {
 471         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 472         struct bpf_cpu_map_entry *rcpu;
 473 
 474         /* Array index key correspond to CPU number */
 475         u32 key_cpu = *(u32 *)key;
 476         /* Value is the queue size */
 477         u32 qsize = *(u32 *)value;
 478 
 479         if (unlikely(map_flags > BPF_EXIST))
 480                 return -EINVAL;
 481         if (unlikely(key_cpu >= cmap->map.max_entries))
 482                 return -E2BIG;
 483         if (unlikely(map_flags == BPF_NOEXIST))
 484                 return -EEXIST;
 485         if (unlikely(qsize > 16384)) /* sanity limit on qsize */
 486                 return -EOVERFLOW;
 487 
 488         /* Make sure CPU is a valid possible cpu */
 489         if (key_cpu >= nr_cpumask_bits || !cpu_possible(key_cpu))
 490                 return -ENODEV;
 491 
 492         if (qsize == 0) {
 493                 rcpu = NULL; /* Same as deleting */
 494         } else {
 495                 /* Updating qsize cause re-allocation of bpf_cpu_map_entry */
 496                 rcpu = __cpu_map_entry_alloc(qsize, key_cpu, map->id);
 497                 if (!rcpu)
 498                         return -ENOMEM;
 499                 rcpu->cmap = cmap;
 500         }
 501         rcu_read_lock();
 502         __cpu_map_entry_replace(cmap, key_cpu, rcpu);
 503         rcu_read_unlock();
 504         return 0;
 505 }
 506 
 507 static void cpu_map_free(struct bpf_map *map)
 508 {
 509         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 510         int cpu;
 511         u32 i;
 512 
 513         /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
 514          * so the bpf programs (can be more than one that used this map) were
 515          * disconnected from events. Wait for outstanding critical sections in
 516          * these programs to complete. The rcu critical section only guarantees
 517          * no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
 518          * It does __not__ ensure pending flush operations (if any) are
 519          * complete.
 520          */
 521 
 522         bpf_clear_redirect_map(map);
 523         synchronize_rcu();
 524 
 525         /* To ensure all pending flush operations have completed wait for flush
 526          * list be empty on _all_ cpus. Because the above synchronize_rcu()
 527          * ensures the map is disconnected from the program we can assume no new
 528          * items will be added to the list.
 529          */
 530         for_each_online_cpu(cpu) {
 531                 struct list_head *flush_list = per_cpu_ptr(cmap->flush_list, cpu);
 532 
 533                 while (!list_empty(flush_list))
 534                         cond_resched();
 535         }
 536 
 537         /* For cpu_map the remote CPUs can still be using the entries
 538          * (struct bpf_cpu_map_entry).
 539          */
 540         for (i = 0; i < cmap->map.max_entries; i++) {
 541                 struct bpf_cpu_map_entry *rcpu;
 542 
 543                 rcpu = READ_ONCE(cmap->cpu_map[i]);
 544                 if (!rcpu)
 545                         continue;
 546 
 547                 /* bq flush and cleanup happens after RCU graze-period */
 548                 __cpu_map_entry_replace(cmap, i, NULL); /* call_rcu */
 549         }
 550         free_percpu(cmap->flush_list);
 551         bpf_map_area_free(cmap->cpu_map);
 552         kfree(cmap);
 553 }
 554 
 555 struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
 556 {
 557         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 558         struct bpf_cpu_map_entry *rcpu;
 559 
 560         if (key >= map->max_entries)
 561                 return NULL;
 562 
 563         rcpu = READ_ONCE(cmap->cpu_map[key]);
 564         return rcpu;
 565 }
 566 
 567 static void *cpu_map_lookup_elem(struct bpf_map *map, void *key)
 568 {
 569         struct bpf_cpu_map_entry *rcpu =
 570                 __cpu_map_lookup_elem(map, *(u32 *)key);
 571 
 572         return rcpu ? &rcpu->qsize : NULL;
 573 }
 574 
 575 static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
 576 {
 577         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 578         u32 index = key ? *(u32 *)key : U32_MAX;
 579         u32 *next = next_key;
 580 
 581         if (index >= cmap->map.max_entries) {
 582                 *next = 0;
 583                 return 0;
 584         }
 585 
 586         if (index == cmap->map.max_entries - 1)
 587                 return -ENOENT;
 588         *next = index + 1;
 589         return 0;
 590 }
 591 
 592 const struct bpf_map_ops cpu_map_ops = {
 593         .map_alloc              = cpu_map_alloc,
 594         .map_free               = cpu_map_free,
 595         .map_delete_elem        = cpu_map_delete_elem,
 596         .map_update_elem        = cpu_map_update_elem,
 597         .map_lookup_elem        = cpu_map_lookup_elem,
 598         .map_get_next_key       = cpu_map_get_next_key,
 599         .map_check_btf          = map_check_no_btf,
 600 };
 601 
 602 static int bq_flush_to_queue(struct xdp_bulk_queue *bq, bool in_napi_ctx)
 603 {
 604         struct bpf_cpu_map_entry *rcpu = bq->obj;
 605         unsigned int processed = 0, drops = 0;
 606         const int to_cpu = rcpu->cpu;
 607         struct ptr_ring *q;
 608         int i;
 609 
 610         if (unlikely(!bq->count))
 611                 return 0;
 612 
 613         q = rcpu->queue;
 614         spin_lock(&q->producer_lock);
 615 
 616         for (i = 0; i < bq->count; i++) {
 617                 struct xdp_frame *xdpf = bq->q[i];
 618                 int err;
 619 
 620                 err = __ptr_ring_produce(q, xdpf);
 621                 if (err) {
 622                         drops++;
 623                         if (likely(in_napi_ctx))
 624                                 xdp_return_frame_rx_napi(xdpf);
 625                         else
 626                                 xdp_return_frame(xdpf);
 627                 }
 628                 processed++;
 629         }
 630         bq->count = 0;
 631         spin_unlock(&q->producer_lock);
 632 
 633         __list_del_clearprev(&bq->flush_node);
 634 
 635         /* Feedback loop via tracepoints */
 636         trace_xdp_cpumap_enqueue(rcpu->map_id, processed, drops, to_cpu);
 637         return 0;
 638 }
 639 
 640 /* Runs under RCU-read-side, plus in softirq under NAPI protection.
 641  * Thus, safe percpu variable access.
 642  */
 643 static int bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
 644 {
 645         struct list_head *flush_list = this_cpu_ptr(rcpu->cmap->flush_list);
 646         struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
 647 
 648         if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
 649                 bq_flush_to_queue(bq, true);
 650 
 651         /* Notice, xdp_buff/page MUST be queued here, long enough for
 652          * driver to code invoking us to finished, due to driver
 653          * (e.g. ixgbe) recycle tricks based on page-refcnt.
 654          *
 655          * Thus, incoming xdp_frame is always queued here (else we race
 656          * with another CPU on page-refcnt and remaining driver code).
 657          * Queue time is very short, as driver will invoke flush
 658          * operation, when completing napi->poll call.
 659          */
 660         bq->q[bq->count++] = xdpf;
 661 
 662         if (!bq->flush_node.prev)
 663                 list_add(&bq->flush_node, flush_list);
 664 
 665         return 0;
 666 }
 667 
 668 int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp,
 669                     struct net_device *dev_rx)
 670 {
 671         struct xdp_frame *xdpf;
 672 
 673         xdpf = convert_to_xdp_frame(xdp);
 674         if (unlikely(!xdpf))
 675                 return -EOVERFLOW;
 676 
 677         /* Info needed when constructing SKB on remote CPU */
 678         xdpf->dev_rx = dev_rx;
 679 
 680         bq_enqueue(rcpu, xdpf);
 681         return 0;
 682 }
 683 
 684 void __cpu_map_flush(struct bpf_map *map)
 685 {
 686         struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
 687         struct list_head *flush_list = this_cpu_ptr(cmap->flush_list);
 688         struct xdp_bulk_queue *bq, *tmp;
 689 
 690         list_for_each_entry_safe(bq, tmp, flush_list, flush_node) {
 691                 bq_flush_to_queue(bq, true);
 692 
 693                 /* If already running, costs spin_lock_irqsave + smb_mb */
 694                 wake_up_process(bq->obj->kthread);
 695         }
 696 }