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
cpu_map_alloc(union bpf_attr * attr)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
get_cpu_map_entry(struct bpf_cpu_map_entry * rcpu)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 */
cpu_map_kthread_stop(struct work_struct * work)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
cpu_map_build_skb(struct bpf_cpu_map_entry * rcpu,struct xdp_frame * xdpf,struct sk_buff * skb)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
__cpu_map_ring_cleanup(struct ptr_ring * ring)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
put_cpu_map_entry(struct bpf_cpu_map_entry * rcpu)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
cpu_map_kthread_run(void * data)249 static int cpu_map_kthread_run(void *data)
250 {
251 struct bpf_cpu_map_entry *rcpu = data;
252 unsigned long last_qs = jiffies;
253
254 set_current_state(TASK_INTERRUPTIBLE);
255
256 /* When kthread gives stop order, then rcpu have been disconnected
257 * from map, thus no new packets can enter. Remaining in-flight
258 * per CPU stored packets are flushed to this queue. Wait honoring
259 * kthread_stop signal until queue is empty.
260 */
261 while (!kthread_should_stop() || !__ptr_ring_empty(rcpu->queue)) {
262 unsigned int drops = 0, sched = 0;
263 void *frames[CPUMAP_BATCH];
264 void *skbs[CPUMAP_BATCH];
265 gfp_t gfp = __GFP_ZERO | GFP_ATOMIC;
266 int i, n, m;
267
268 /* Release CPU reschedule checks */
269 if (__ptr_ring_empty(rcpu->queue)) {
270 set_current_state(TASK_INTERRUPTIBLE);
271 /* Recheck to avoid lost wake-up */
272 if (__ptr_ring_empty(rcpu->queue)) {
273 schedule();
274 sched = 1;
275 last_qs = jiffies;
276 } else {
277 __set_current_state(TASK_RUNNING);
278 }
279 } else {
280 rcu_softirq_qs_periodic(last_qs);
281 sched = cond_resched();
282 }
283
284 /*
285 * The bpf_cpu_map_entry is single consumer, with this
286 * kthread CPU pinned. Lockless access to ptr_ring
287 * consume side valid as no-resize allowed of queue.
288 */
289 n = ptr_ring_consume_batched(rcpu->queue, frames, CPUMAP_BATCH);
290
291 for (i = 0; i < n; i++) {
292 void *f = frames[i];
293 struct page *page = virt_to_page(f);
294
295 /* Bring struct page memory area to curr CPU. Read by
296 * build_skb_around via page_is_pfmemalloc(), and when
297 * freed written by page_frag_free call.
298 */
299 prefetchw(page);
300 }
301
302 m = kmem_cache_alloc_bulk(skbuff_head_cache, gfp, n, skbs);
303 if (unlikely(m == 0)) {
304 for (i = 0; i < n; i++)
305 skbs[i] = NULL; /* effect: xdp_return_frame */
306 drops = n;
307 }
308
309 local_bh_disable();
310 for (i = 0; i < n; i++) {
311 struct xdp_frame *xdpf = frames[i];
312 struct sk_buff *skb = skbs[i];
313 int ret;
314
315 skb = cpu_map_build_skb(rcpu, xdpf, skb);
316 if (!skb) {
317 xdp_return_frame(xdpf);
318 continue;
319 }
320
321 /* Inject into network stack */
322 ret = netif_receive_skb_core(skb);
323 if (ret == NET_RX_DROP)
324 drops++;
325 }
326 /* Feedback loop via tracepoint */
327 trace_xdp_cpumap_kthread(rcpu->map_id, n, drops, sched);
328
329 local_bh_enable(); /* resched point, may call do_softirq() */
330 }
331 __set_current_state(TASK_RUNNING);
332
333 put_cpu_map_entry(rcpu);
334 return 0;
335 }
336
__cpu_map_entry_alloc(u32 qsize,u32 cpu,int map_id)337 static struct bpf_cpu_map_entry *__cpu_map_entry_alloc(u32 qsize, u32 cpu,
338 int map_id)
339 {
340 gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
341 struct bpf_cpu_map_entry *rcpu;
342 struct xdp_bulk_queue *bq;
343 int numa, err, i;
344
345 /* Have map->numa_node, but choose node of redirect target CPU */
346 numa = cpu_to_node(cpu);
347
348 rcpu = kzalloc_node(sizeof(*rcpu), gfp, numa);
349 if (!rcpu)
350 return NULL;
351
352 /* Alloc percpu bulkq */
353 rcpu->bulkq = __alloc_percpu_gfp(sizeof(*rcpu->bulkq),
354 sizeof(void *), gfp);
355 if (!rcpu->bulkq)
356 goto free_rcu;
357
358 for_each_possible_cpu(i) {
359 bq = per_cpu_ptr(rcpu->bulkq, i);
360 bq->obj = rcpu;
361 }
362
363 /* Alloc queue */
364 rcpu->queue = kzalloc_node(sizeof(*rcpu->queue), gfp, numa);
365 if (!rcpu->queue)
366 goto free_bulkq;
367
368 err = ptr_ring_init(rcpu->queue, qsize, gfp);
369 if (err)
370 goto free_queue;
371
372 rcpu->cpu = cpu;
373 rcpu->map_id = map_id;
374 rcpu->qsize = qsize;
375
376 /* Setup kthread */
377 rcpu->kthread = kthread_create_on_node(cpu_map_kthread_run, rcpu, numa,
378 "cpumap/%d/map:%d", cpu, map_id);
379 if (IS_ERR(rcpu->kthread))
380 goto free_ptr_ring;
381
382 get_cpu_map_entry(rcpu); /* 1-refcnt for being in cmap->cpu_map[] */
383 get_cpu_map_entry(rcpu); /* 1-refcnt for kthread */
384
385 /* Make sure kthread runs on a single CPU */
386 kthread_bind(rcpu->kthread, cpu);
387 wake_up_process(rcpu->kthread);
388
389 return rcpu;
390
391 free_ptr_ring:
392 ptr_ring_cleanup(rcpu->queue, NULL);
393 free_queue:
394 kfree(rcpu->queue);
395 free_bulkq:
396 free_percpu(rcpu->bulkq);
397 free_rcu:
398 kfree(rcpu);
399 return NULL;
400 }
401
__cpu_map_entry_free(struct rcu_head * rcu)402 static void __cpu_map_entry_free(struct rcu_head *rcu)
403 {
404 struct bpf_cpu_map_entry *rcpu;
405 int cpu;
406
407 /* This cpu_map_entry have been disconnected from map and one
408 * RCU graze-period have elapsed. Thus, XDP cannot queue any
409 * new packets and cannot change/set flush_needed that can
410 * find this entry.
411 */
412 rcpu = container_of(rcu, struct bpf_cpu_map_entry, rcu);
413
414 /* Flush remaining packets in percpu bulkq */
415 for_each_online_cpu(cpu) {
416 struct xdp_bulk_queue *bq = per_cpu_ptr(rcpu->bulkq, cpu);
417
418 /* No concurrent bq_enqueue can run at this point */
419 bq_flush_to_queue(bq, false);
420 }
421 free_percpu(rcpu->bulkq);
422 /* Cannot kthread_stop() here, last put free rcpu resources */
423 put_cpu_map_entry(rcpu);
424 }
425
426 /* After xchg pointer to bpf_cpu_map_entry, use the call_rcu() to
427 * ensure any driver rcu critical sections have completed, but this
428 * does not guarantee a flush has happened yet. Because driver side
429 * rcu_read_lock/unlock only protects the running XDP program. The
430 * atomic xchg and NULL-ptr check in __cpu_map_flush() makes sure a
431 * pending flush op doesn't fail.
432 *
433 * The bpf_cpu_map_entry is still used by the kthread, and there can
434 * still be pending packets (in queue and percpu bulkq). A refcnt
435 * makes sure to last user (kthread_stop vs. call_rcu) free memory
436 * resources.
437 *
438 * The rcu callback __cpu_map_entry_free flush remaining packets in
439 * percpu bulkq to queue. Due to caller map_delete_elem() disable
440 * preemption, cannot call kthread_stop() to make sure queue is empty.
441 * Instead a work_queue is started for stopping kthread,
442 * cpu_map_kthread_stop, which waits for an RCU graze period before
443 * stopping kthread, emptying the queue.
444 */
__cpu_map_entry_replace(struct bpf_cpu_map * cmap,u32 key_cpu,struct bpf_cpu_map_entry * rcpu)445 static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
446 u32 key_cpu, struct bpf_cpu_map_entry *rcpu)
447 {
448 struct bpf_cpu_map_entry *old_rcpu;
449
450 old_rcpu = xchg(&cmap->cpu_map[key_cpu], rcpu);
451 if (old_rcpu) {
452 call_rcu(&old_rcpu->rcu, __cpu_map_entry_free);
453 INIT_WORK(&old_rcpu->kthread_stop_wq, cpu_map_kthread_stop);
454 schedule_work(&old_rcpu->kthread_stop_wq);
455 }
456 }
457
cpu_map_delete_elem(struct bpf_map * map,void * key)458 static int cpu_map_delete_elem(struct bpf_map *map, void *key)
459 {
460 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
461 u32 key_cpu = *(u32 *)key;
462
463 if (key_cpu >= map->max_entries)
464 return -EINVAL;
465
466 /* notice caller map_delete_elem() use preempt_disable() */
467 __cpu_map_entry_replace(cmap, key_cpu, NULL);
468 return 0;
469 }
470
cpu_map_update_elem(struct bpf_map * map,void * key,void * value,u64 map_flags)471 static int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
472 u64 map_flags)
473 {
474 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
475 struct bpf_cpu_map_entry *rcpu;
476
477 /* Array index key correspond to CPU number */
478 u32 key_cpu = *(u32 *)key;
479 /* Value is the queue size */
480 u32 qsize = *(u32 *)value;
481
482 if (unlikely(map_flags > BPF_EXIST))
483 return -EINVAL;
484 if (unlikely(key_cpu >= cmap->map.max_entries))
485 return -E2BIG;
486 if (unlikely(map_flags == BPF_NOEXIST))
487 return -EEXIST;
488 if (unlikely(qsize > 16384)) /* sanity limit on qsize */
489 return -EOVERFLOW;
490
491 /* Make sure CPU is a valid possible cpu */
492 if (key_cpu >= nr_cpumask_bits || !cpu_possible(key_cpu))
493 return -ENODEV;
494
495 if (qsize == 0) {
496 rcpu = NULL; /* Same as deleting */
497 } else {
498 /* Updating qsize cause re-allocation of bpf_cpu_map_entry */
499 rcpu = __cpu_map_entry_alloc(qsize, key_cpu, map->id);
500 if (!rcpu)
501 return -ENOMEM;
502 rcpu->cmap = cmap;
503 }
504 rcu_read_lock();
505 __cpu_map_entry_replace(cmap, key_cpu, rcpu);
506 rcu_read_unlock();
507 return 0;
508 }
509
cpu_map_free(struct bpf_map * map)510 static void cpu_map_free(struct bpf_map *map)
511 {
512 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
513 int cpu;
514 u32 i;
515
516 /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
517 * so the bpf programs (can be more than one that used this map) were
518 * disconnected from events. Wait for outstanding critical sections in
519 * these programs to complete. The rcu critical section only guarantees
520 * no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
521 * It does __not__ ensure pending flush operations (if any) are
522 * complete.
523 */
524
525 bpf_clear_redirect_map(map);
526 synchronize_rcu();
527
528 /* To ensure all pending flush operations have completed wait for flush
529 * list be empty on _all_ cpus. Because the above synchronize_rcu()
530 * ensures the map is disconnected from the program we can assume no new
531 * items will be added to the list.
532 */
533 for_each_online_cpu(cpu) {
534 struct list_head *flush_list = per_cpu_ptr(cmap->flush_list, cpu);
535
536 while (!list_empty(flush_list))
537 cond_resched();
538 }
539
540 /* For cpu_map the remote CPUs can still be using the entries
541 * (struct bpf_cpu_map_entry).
542 */
543 for (i = 0; i < cmap->map.max_entries; i++) {
544 struct bpf_cpu_map_entry *rcpu;
545
546 rcpu = READ_ONCE(cmap->cpu_map[i]);
547 if (!rcpu)
548 continue;
549
550 /* bq flush and cleanup happens after RCU graze-period */
551 __cpu_map_entry_replace(cmap, i, NULL); /* call_rcu */
552 }
553 free_percpu(cmap->flush_list);
554 bpf_map_area_free(cmap->cpu_map);
555 kfree(cmap);
556 }
557
__cpu_map_lookup_elem(struct bpf_map * map,u32 key)558 struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
559 {
560 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
561 struct bpf_cpu_map_entry *rcpu;
562
563 if (key >= map->max_entries)
564 return NULL;
565
566 rcpu = READ_ONCE(cmap->cpu_map[key]);
567 return rcpu;
568 }
569
cpu_map_lookup_elem(struct bpf_map * map,void * key)570 static void *cpu_map_lookup_elem(struct bpf_map *map, void *key)
571 {
572 struct bpf_cpu_map_entry *rcpu =
573 __cpu_map_lookup_elem(map, *(u32 *)key);
574
575 return rcpu ? &rcpu->qsize : NULL;
576 }
577
cpu_map_get_next_key(struct bpf_map * map,void * key,void * next_key)578 static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
579 {
580 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
581 u32 index = key ? *(u32 *)key : U32_MAX;
582 u32 *next = next_key;
583
584 if (index >= cmap->map.max_entries) {
585 *next = 0;
586 return 0;
587 }
588
589 if (index == cmap->map.max_entries - 1)
590 return -ENOENT;
591 *next = index + 1;
592 return 0;
593 }
594
595 const struct bpf_map_ops cpu_map_ops = {
596 .map_alloc = cpu_map_alloc,
597 .map_free = cpu_map_free,
598 .map_delete_elem = cpu_map_delete_elem,
599 .map_update_elem = cpu_map_update_elem,
600 .map_lookup_elem = cpu_map_lookup_elem,
601 .map_get_next_key = cpu_map_get_next_key,
602 .map_check_btf = map_check_no_btf,
603 };
604
bq_flush_to_queue(struct xdp_bulk_queue * bq,bool in_napi_ctx)605 static int bq_flush_to_queue(struct xdp_bulk_queue *bq, bool in_napi_ctx)
606 {
607 struct bpf_cpu_map_entry *rcpu = bq->obj;
608 unsigned int processed = 0, drops = 0;
609 const int to_cpu = rcpu->cpu;
610 struct ptr_ring *q;
611 int i;
612
613 if (unlikely(!bq->count))
614 return 0;
615
616 q = rcpu->queue;
617 spin_lock(&q->producer_lock);
618
619 for (i = 0; i < bq->count; i++) {
620 struct xdp_frame *xdpf = bq->q[i];
621 int err;
622
623 err = __ptr_ring_produce(q, xdpf);
624 if (err) {
625 drops++;
626 if (likely(in_napi_ctx))
627 xdp_return_frame_rx_napi(xdpf);
628 else
629 xdp_return_frame(xdpf);
630 }
631 processed++;
632 }
633 bq->count = 0;
634 spin_unlock(&q->producer_lock);
635
636 __list_del_clearprev(&bq->flush_node);
637
638 /* Feedback loop via tracepoints */
639 trace_xdp_cpumap_enqueue(rcpu->map_id, processed, drops, to_cpu);
640 return 0;
641 }
642
643 /* Runs under RCU-read-side, plus in softirq under NAPI protection.
644 * Thus, safe percpu variable access.
645 */
bq_enqueue(struct bpf_cpu_map_entry * rcpu,struct xdp_frame * xdpf)646 static int bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
647 {
648 struct list_head *flush_list = this_cpu_ptr(rcpu->cmap->flush_list);
649 struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
650
651 if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
652 bq_flush_to_queue(bq, true);
653
654 /* Notice, xdp_buff/page MUST be queued here, long enough for
655 * driver to code invoking us to finished, due to driver
656 * (e.g. ixgbe) recycle tricks based on page-refcnt.
657 *
658 * Thus, incoming xdp_frame is always queued here (else we race
659 * with another CPU on page-refcnt and remaining driver code).
660 * Queue time is very short, as driver will invoke flush
661 * operation, when completing napi->poll call.
662 */
663 bq->q[bq->count++] = xdpf;
664
665 if (!bq->flush_node.prev)
666 list_add(&bq->flush_node, flush_list);
667
668 return 0;
669 }
670
cpu_map_enqueue(struct bpf_cpu_map_entry * rcpu,struct xdp_buff * xdp,struct net_device * dev_rx)671 int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp,
672 struct net_device *dev_rx)
673 {
674 struct xdp_frame *xdpf;
675
676 xdpf = convert_to_xdp_frame(xdp);
677 if (unlikely(!xdpf))
678 return -EOVERFLOW;
679
680 /* Info needed when constructing SKB on remote CPU */
681 xdpf->dev_rx = dev_rx;
682
683 bq_enqueue(rcpu, xdpf);
684 return 0;
685 }
686
__cpu_map_flush(struct bpf_map * map)687 void __cpu_map_flush(struct bpf_map *map)
688 {
689 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
690 struct list_head *flush_list = this_cpu_ptr(cmap->flush_list);
691 struct xdp_bulk_queue *bq, *tmp;
692
693 list_for_each_entry_safe(bq, tmp, flush_list, flush_node) {
694 bq_flush_to_queue(bq, true);
695
696 /* If already running, costs spin_lock_irqsave + smb_mb */
697 wake_up_process(bq->obj->kthread);
698 }
699 }
700