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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_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 */
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 int bq_flush_to_queue(struct xdp_bulk_queue *bq);
83
84static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
85{
86 u32 value_size = attr->value_size;
87 struct bpf_cpu_map *cmap;
88 int err = -ENOMEM;
89 u64 cost;
90 int ret;
91
92 if (!bpf_capable())
93 return ERR_PTR(-EPERM);
94
95 /* check sanity of attributes */
96 if (attr->max_entries == 0 || attr->key_size != 4 ||
97 (value_size != offsetofend(struct bpf_cpumap_val, qsize) &&
98 value_size != offsetofend(struct bpf_cpumap_val, bpf_prog.fd)) ||
99 attr->map_flags & ~BPF_F_NUMA_NODE)
100 return ERR_PTR(-EINVAL);
101
102 cmap = kzalloc(sizeof(*cmap), GFP_USER);
103 if (!cmap)
104 return ERR_PTR(-ENOMEM);
105
106 bpf_map_init_from_attr(&cmap->map, attr);
107
108 /* Pre-limit array size based on NR_CPUS, not final CPU check */
109 if (cmap->map.max_entries > NR_CPUS) {
110 err = -E2BIG;
111 goto free_cmap;
112 }
113
114 /* make sure page count doesn't overflow */
115 cost = (u64) cmap->map.max_entries * sizeof(struct bpf_cpu_map_entry *);
116
117 /* Notice returns -EPERM on if map size is larger than memlock limit */
118 ret = bpf_map_charge_init(&cmap->map.memory, cost);
119 if (ret) {
120 err = ret;
121 goto free_cmap;
122 }
123
124 /* Alloc array for possible remote "destination" CPUs */
125 cmap->cpu_map = bpf_map_area_alloc(cmap->map.max_entries *
126 sizeof(struct bpf_cpu_map_entry *),
127 cmap->map.numa_node);
128 if (!cmap->cpu_map)
129 goto free_charge;
130
131 return &cmap->map;
132free_charge:
133 bpf_map_charge_finish(&cmap->map.memory);
134free_cmap:
135 kfree(cmap);
136 return ERR_PTR(err);
137}
138
139static void get_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
140{
141 atomic_inc(&rcpu->refcnt);
142}
143
144/* called from workqueue, to workaround syscall using preempt_disable */
145static void cpu_map_kthread_stop(struct work_struct *work)
146{
147 struct bpf_cpu_map_entry *rcpu;
148
149 rcpu = container_of(work, struct bpf_cpu_map_entry, kthread_stop_wq);
150
151 /* Wait for flush in __cpu_map_entry_free(), via full RCU barrier,
152 * as it waits until all in-flight call_rcu() callbacks complete.
153 */
154 rcu_barrier();
155
156 /* kthread_stop will wake_up_process and wait for it to complete */
157 kthread_stop(rcpu->kthread);
158}
159
160static struct sk_buff *cpu_map_build_skb(struct bpf_cpu_map_entry *rcpu,
161 struct xdp_frame *xdpf,
162 struct sk_buff *skb)
163{
164 unsigned int hard_start_headroom;
165 unsigned int frame_size;
166 void *pkt_data_start;
167
168 /* Part of headroom was reserved to xdpf */
169 hard_start_headroom = sizeof(struct xdp_frame) + xdpf->headroom;
170
171 /* Memory size backing xdp_frame data already have reserved
172 * room for build_skb to place skb_shared_info in tailroom.
173 */
174 frame_size = xdpf->frame_sz;
175
176 pkt_data_start = xdpf->data - hard_start_headroom;
177 skb = build_skb_around(skb, pkt_data_start, frame_size);
178 if (unlikely(!skb))
179 return NULL;
180
181 skb_reserve(skb, hard_start_headroom);
182 __skb_put(skb, xdpf->len);
183 if (xdpf->metasize)
184 skb_metadata_set(skb, xdpf->metasize);
185
186 /* Essential SKB info: protocol and skb->dev */
187 skb->protocol = eth_type_trans(skb, xdpf->dev_rx);
188
189 /* Optional SKB info, currently missing:
190 * - HW checksum info (skb->ip_summed)
191 * - HW RX hash (skb_set_hash)
192 * - RX ring dev queue index (skb_record_rx_queue)
193 */
194
195 /* Until page_pool get SKB return path, release DMA here */
196 xdp_release_frame(xdpf);
197
198 /* Allow SKB to reuse area used by xdp_frame */
199 xdp_scrub_frame(xdpf);
200
201 return skb;
202}
203
204static void __cpu_map_ring_cleanup(struct ptr_ring *ring)
205{
206 /* The tear-down procedure should have made sure that queue is
207 * empty. See __cpu_map_entry_replace() and work-queue
208 * invoked cpu_map_kthread_stop(). Catch any broken behaviour
209 * gracefully and warn once.
210 */
211 struct xdp_frame *xdpf;
212
213 while ((xdpf = ptr_ring_consume(ring)))
214 if (WARN_ON_ONCE(xdpf))
215 xdp_return_frame(xdpf);
216}
217
218static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
219{
220 if (atomic_dec_and_test(&rcpu->refcnt)) {
221 if (rcpu->prog)
222 bpf_prog_put(rcpu->prog);
223 /* The queue should be empty at this point */
224 __cpu_map_ring_cleanup(rcpu->queue);
225 ptr_ring_cleanup(rcpu->queue, NULL);
226 kfree(rcpu->queue);
227 kfree(rcpu);
228 }
229}
230
231static int cpu_map_bpf_prog_run_xdp(struct bpf_cpu_map_entry *rcpu,
232 void **frames, int n,
233 struct xdp_cpumap_stats *stats)
234{
235 struct xdp_rxq_info rxq;
236 struct xdp_buff xdp;
237 int i, nframes = 0;
238
239 if (!rcpu->prog)
240 return n;
241
242 rcu_read_lock_bh();
243
244 xdp_set_return_frame_no_direct();
245 xdp.rxq = &rxq;
246
247 for (i = 0; i < n; i++) {
248 struct xdp_frame *xdpf = frames[i];
249 u32 act;
250 int err;
251
252 rxq.dev = xdpf->dev_rx;
253 rxq.mem = xdpf->mem;
254 /* TODO: report queue_index to xdp_rxq_info */
255
256 xdp_convert_frame_to_buff(xdpf, &xdp);
257
258 act = bpf_prog_run_xdp(rcpu->prog, &xdp);
259 switch (act) {
260 case XDP_PASS:
261 err = xdp_update_frame_from_buff(&xdp, xdpf);
262 if (err < 0) {
263 xdp_return_frame(xdpf);
264 stats->drop++;
265 } else {
266 frames[nframes++] = xdpf;
267 stats->pass++;
268 }
269 break;
270 case XDP_REDIRECT:
271 err = xdp_do_redirect(xdpf->dev_rx, &xdp,
272 rcpu->prog);
273 if (unlikely(err)) {
274 xdp_return_frame(xdpf);
275 stats->drop++;
276 } else {
277 stats->redirect++;
278 }
279 break;
280 default:
281 bpf_warn_invalid_xdp_action(act);
282 fallthrough;
283 case XDP_DROP:
284 xdp_return_frame(xdpf);
285 stats->drop++;
286 break;
287 }
288 }
289
290 if (stats->redirect)
291 xdp_do_flush_map();
292
293 xdp_clear_return_frame_no_direct();
294
295 rcu_read_unlock_bh(); /* resched point, may call do_softirq() */
296
297 return nframes;
298}
299
300#define CPUMAP_BATCH 8
301
302static int cpu_map_kthread_run(void *data)
303{
304 struct bpf_cpu_map_entry *rcpu = data;
305
306 set_current_state(TASK_INTERRUPTIBLE);
307
308 /* When kthread gives stop order, then rcpu have been disconnected
309 * from map, thus no new packets can enter. Remaining in-flight
310 * per CPU stored packets are flushed to this queue. Wait honoring
311 * kthread_stop signal until queue is empty.
312 */
313 while (!kthread_should_stop() || !__ptr_ring_empty(rcpu->queue)) {
314 struct xdp_cpumap_stats stats = {}; /* zero stats */
315 gfp_t gfp = __GFP_ZERO | GFP_ATOMIC;
316 unsigned int drops = 0, sched = 0;
317 void *frames[CPUMAP_BATCH];
318 void *skbs[CPUMAP_BATCH];
319 int i, n, m, nframes;
320
321 /* Release CPU reschedule checks */
322 if (__ptr_ring_empty(rcpu->queue)) {
323 set_current_state(TASK_INTERRUPTIBLE);
324 /* Recheck to avoid lost wake-up */
325 if (__ptr_ring_empty(rcpu->queue)) {
326 schedule();
327 sched = 1;
328 } else {
329 __set_current_state(TASK_RUNNING);
330 }
331 } else {
332 sched = cond_resched();
333 }
334
335 /*
336 * The bpf_cpu_map_entry is single consumer, with this
337 * kthread CPU pinned. Lockless access to ptr_ring
338 * consume side valid as no-resize allowed of queue.
339 */
340 n = __ptr_ring_consume_batched(rcpu->queue, frames,
341 CPUMAP_BATCH);
342 for (i = 0; i < n; i++) {
343 void *f = frames[i];
344 struct page *page = virt_to_page(f);
345
346 /* Bring struct page memory area to curr CPU. Read by
347 * build_skb_around via page_is_pfmemalloc(), and when
348 * freed written by page_frag_free call.
349 */
350 prefetchw(page);
351 }
352
353 /* Support running another XDP prog on this CPU */
354 nframes = cpu_map_bpf_prog_run_xdp(rcpu, frames, n, &stats);
355 if (nframes) {
356 m = kmem_cache_alloc_bulk(skbuff_head_cache, gfp, nframes, skbs);
357 if (unlikely(m == 0)) {
358 for (i = 0; i < nframes; i++)
359 skbs[i] = NULL; /* effect: xdp_return_frame */
360 drops += nframes;
361 }
362 }
363
364 local_bh_disable();
365 for (i = 0; i < nframes; i++) {
366 struct xdp_frame *xdpf = frames[i];
367 struct sk_buff *skb = skbs[i];
368 int ret;
369
370 skb = cpu_map_build_skb(rcpu, xdpf, skb);
371 if (!skb) {
372 xdp_return_frame(xdpf);
373 continue;
374 }
375
376 /* Inject into network stack */
377 ret = netif_receive_skb_core(skb);
378 if (ret == NET_RX_DROP)
379 drops++;
380 }
381 /* Feedback loop via tracepoint */
382 trace_xdp_cpumap_kthread(rcpu->map_id, n, drops, sched, &stats);
383
384 local_bh_enable(); /* resched point, may call do_softirq() */
385 }
386 __set_current_state(TASK_RUNNING);
387
388 put_cpu_map_entry(rcpu);
389 return 0;
390}
391
392bool cpu_map_prog_allowed(struct bpf_map *map)
393{
394 return map->map_type == BPF_MAP_TYPE_CPUMAP &&
395 map->value_size != offsetofend(struct bpf_cpumap_val, qsize);
396}
397
398static int __cpu_map_load_bpf_program(struct bpf_cpu_map_entry *rcpu, int fd)
399{
400 struct bpf_prog *prog;
401
402 prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_XDP);
403 if (IS_ERR(prog))
404 return PTR_ERR(prog);
405
406 if (prog->expected_attach_type != BPF_XDP_CPUMAP) {
407 bpf_prog_put(prog);
408 return -EINVAL;
409 }
410
411 rcpu->value.bpf_prog.id = prog->aux->id;
412 rcpu->prog = prog;
413
414 return 0;
415}
416
417static struct bpf_cpu_map_entry *
418__cpu_map_entry_alloc(struct bpf_cpumap_val *value, u32 cpu, int map_id)
419{
420 int numa, err, i, fd = value->bpf_prog.fd;
421 gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
422 struct bpf_cpu_map_entry *rcpu;
423 struct xdp_bulk_queue *bq;
424
425 /* Have map->numa_node, but choose node of redirect target CPU */
426 numa = cpu_to_node(cpu);
427
428 rcpu = kzalloc_node(sizeof(*rcpu), gfp, numa);
429 if (!rcpu)
430 return NULL;
431
432 /* Alloc percpu bulkq */
433 rcpu->bulkq = __alloc_percpu_gfp(sizeof(*rcpu->bulkq),
434 sizeof(void *), gfp);
435 if (!rcpu->bulkq)
436 goto free_rcu;
437
438 for_each_possible_cpu(i) {
439 bq = per_cpu_ptr(rcpu->bulkq, i);
440 bq->obj = rcpu;
441 }
442
443 /* Alloc queue */
444 rcpu->queue = kzalloc_node(sizeof(*rcpu->queue), gfp, numa);
445 if (!rcpu->queue)
446 goto free_bulkq;
447
448 err = ptr_ring_init(rcpu->queue, value->qsize, gfp);
449 if (err)
450 goto free_queue;
451
452 rcpu->cpu = cpu;
453 rcpu->map_id = map_id;
454 rcpu->value.qsize = value->qsize;
455
456 if (fd > 0 && __cpu_map_load_bpf_program(rcpu, fd))
457 goto free_ptr_ring;
458
459 /* Setup kthread */
460 rcpu->kthread = kthread_create_on_node(cpu_map_kthread_run, rcpu, numa,
461 "cpumap/%d/map:%d", cpu, map_id);
462 if (IS_ERR(rcpu->kthread))
463 goto free_prog;
464
465 get_cpu_map_entry(rcpu); /* 1-refcnt for being in cmap->cpu_map[] */
466 get_cpu_map_entry(rcpu); /* 1-refcnt for kthread */
467
468 /* Make sure kthread runs on a single CPU */
469 kthread_bind(rcpu->kthread, cpu);
470 wake_up_process(rcpu->kthread);
471
472 return rcpu;
473
474free_prog:
475 if (rcpu->prog)
476 bpf_prog_put(rcpu->prog);
477free_ptr_ring:
478 ptr_ring_cleanup(rcpu->queue, NULL);
479free_queue:
480 kfree(rcpu->queue);
481free_bulkq:
482 free_percpu(rcpu->bulkq);
483free_rcu:
484 kfree(rcpu);
485 return NULL;
486}
487
488static void __cpu_map_entry_free(struct rcu_head *rcu)
489{
490 struct bpf_cpu_map_entry *rcpu;
491
492 /* This cpu_map_entry have been disconnected from map and one
493 * RCU grace-period have elapsed. Thus, XDP cannot queue any
494 * new packets and cannot change/set flush_needed that can
495 * find this entry.
496 */
497 rcpu = container_of(rcu, struct bpf_cpu_map_entry, rcu);
498
499 free_percpu(rcpu->bulkq);
500 /* Cannot kthread_stop() here, last put free rcpu resources */
501 put_cpu_map_entry(rcpu);
502}
503
504/* After xchg pointer to bpf_cpu_map_entry, use the call_rcu() to
505 * ensure any driver rcu critical sections have completed, but this
506 * does not guarantee a flush has happened yet. Because driver side
507 * rcu_read_lock/unlock only protects the running XDP program. The
508 * atomic xchg and NULL-ptr check in __cpu_map_flush() makes sure a
509 * pending flush op doesn't fail.
510 *
511 * The bpf_cpu_map_entry is still used by the kthread, and there can
512 * still be pending packets (in queue and percpu bulkq). A refcnt
513 * makes sure to last user (kthread_stop vs. call_rcu) free memory
514 * resources.
515 *
516 * The rcu callback __cpu_map_entry_free flush remaining packets in
517 * percpu bulkq to queue. Due to caller map_delete_elem() disable
518 * preemption, cannot call kthread_stop() to make sure queue is empty.
519 * Instead a work_queue is started for stopping kthread,
520 * cpu_map_kthread_stop, which waits for an RCU grace period before
521 * stopping kthread, emptying the queue.
522 */
523static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
524 u32 key_cpu, struct bpf_cpu_map_entry *rcpu)
525{
526 struct bpf_cpu_map_entry *old_rcpu;
527
528 old_rcpu = xchg(&cmap->cpu_map[key_cpu], rcpu);
529 if (old_rcpu) {
530 call_rcu(&old_rcpu->rcu, __cpu_map_entry_free);
531 INIT_WORK(&old_rcpu->kthread_stop_wq, cpu_map_kthread_stop);
532 schedule_work(&old_rcpu->kthread_stop_wq);
533 }
534}
535
536static int cpu_map_delete_elem(struct bpf_map *map, void *key)
537{
538 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
539 u32 key_cpu = *(u32 *)key;
540
541 if (key_cpu >= map->max_entries)
542 return -EINVAL;
543
544 /* notice caller map_delete_elem() use preempt_disable() */
545 __cpu_map_entry_replace(cmap, key_cpu, NULL);
546 return 0;
547}
548
549static int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
550 u64 map_flags)
551{
552 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
553 struct bpf_cpumap_val cpumap_value = {};
554 struct bpf_cpu_map_entry *rcpu;
555 /* Array index key correspond to CPU number */
556 u32 key_cpu = *(u32 *)key;
557
558 memcpy(&cpumap_value, value, map->value_size);
559
560 if (unlikely(map_flags > BPF_EXIST))
561 return -EINVAL;
562 if (unlikely(key_cpu >= cmap->map.max_entries))
563 return -E2BIG;
564 if (unlikely(map_flags == BPF_NOEXIST))
565 return -EEXIST;
566 if (unlikely(cpumap_value.qsize > 16384)) /* sanity limit on qsize */
567 return -EOVERFLOW;
568
569 /* Make sure CPU is a valid possible cpu */
570 if (key_cpu >= nr_cpumask_bits || !cpu_possible(key_cpu))
571 return -ENODEV;
572
573 if (cpumap_value.qsize == 0) {
574 rcpu = NULL; /* Same as deleting */
575 } else {
576 /* Updating qsize cause re-allocation of bpf_cpu_map_entry */
577 rcpu = __cpu_map_entry_alloc(&cpumap_value, key_cpu, map->id);
578 if (!rcpu)
579 return -ENOMEM;
580 rcpu->cmap = cmap;
581 }
582 rcu_read_lock();
583 __cpu_map_entry_replace(cmap, key_cpu, rcpu);
584 rcu_read_unlock();
585 return 0;
586}
587
588static void cpu_map_free(struct bpf_map *map)
589{
590 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
591 u32 i;
592
593 /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
594 * so the bpf programs (can be more than one that used this map) were
595 * disconnected from events. Wait for outstanding critical sections in
596 * these programs to complete. The rcu critical section only guarantees
597 * no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
598 * It does __not__ ensure pending flush operations (if any) are
599 * complete.
600 */
601
602 bpf_clear_redirect_map(map);
603 synchronize_rcu();
604
605 /* For cpu_map the remote CPUs can still be using the entries
606 * (struct bpf_cpu_map_entry).
607 */
608 for (i = 0; i < cmap->map.max_entries; i++) {
609 struct bpf_cpu_map_entry *rcpu;
610
611 rcpu = READ_ONCE(cmap->cpu_map[i]);
612 if (!rcpu)
613 continue;
614
615 /* bq flush and cleanup happens after RCU grace-period */
616 __cpu_map_entry_replace(cmap, i, NULL); /* call_rcu */
617 }
618 bpf_map_area_free(cmap->cpu_map);
619 kfree(cmap);
620}
621
622struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
623{
624 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
625 struct bpf_cpu_map_entry *rcpu;
626
627 if (key >= map->max_entries)
628 return NULL;
629
630 rcpu = READ_ONCE(cmap->cpu_map[key]);
631 return rcpu;
632}
633
634static void *cpu_map_lookup_elem(struct bpf_map *map, void *key)
635{
636 struct bpf_cpu_map_entry *rcpu =
637 __cpu_map_lookup_elem(map, *(u32 *)key);
638
639 return rcpu ? &rcpu->value : NULL;
640}
641
642static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
643{
644 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
645 u32 index = key ? *(u32 *)key : U32_MAX;
646 u32 *next = next_key;
647
648 if (index >= cmap->map.max_entries) {
649 *next = 0;
650 return 0;
651 }
652
653 if (index == cmap->map.max_entries - 1)
654 return -ENOENT;
655 *next = index + 1;
656 return 0;
657}
658
659static int cpu_map_btf_id;
660const struct bpf_map_ops cpu_map_ops = {
661 .map_alloc = cpu_map_alloc,
662 .map_free = cpu_map_free,
663 .map_delete_elem = cpu_map_delete_elem,
664 .map_update_elem = cpu_map_update_elem,
665 .map_lookup_elem = cpu_map_lookup_elem,
666 .map_get_next_key = cpu_map_get_next_key,
667 .map_check_btf = map_check_no_btf,
668 .map_btf_name = "bpf_cpu_map",
669 .map_btf_id = &cpu_map_btf_id,
670};
671
672static int bq_flush_to_queue(struct xdp_bulk_queue *bq)
673{
674 struct bpf_cpu_map_entry *rcpu = bq->obj;
675 unsigned int processed = 0, drops = 0;
676 const int to_cpu = rcpu->cpu;
677 struct ptr_ring *q;
678 int i;
679
680 if (unlikely(!bq->count))
681 return 0;
682
683 q = rcpu->queue;
684 spin_lock(&q->producer_lock);
685
686 for (i = 0; i < bq->count; i++) {
687 struct xdp_frame *xdpf = bq->q[i];
688 int err;
689
690 err = __ptr_ring_produce(q, xdpf);
691 if (err) {
692 drops++;
693 xdp_return_frame_rx_napi(xdpf);
694 }
695 processed++;
696 }
697 bq->count = 0;
698 spin_unlock(&q->producer_lock);
699
700 __list_del_clearprev(&bq->flush_node);
701
702 /* Feedback loop via tracepoints */
703 trace_xdp_cpumap_enqueue(rcpu->map_id, processed, drops, to_cpu);
704 return 0;
705}
706
707/* Runs under RCU-read-side, plus in softirq under NAPI protection.
708 * Thus, safe percpu variable access.
709 */
710static int bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
711{
712 struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
713 struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
714
715 if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
716 bq_flush_to_queue(bq);
717
718 /* Notice, xdp_buff/page MUST be queued here, long enough for
719 * driver to code invoking us to finished, due to driver
720 * (e.g. ixgbe) recycle tricks based on page-refcnt.
721 *
722 * Thus, incoming xdp_frame is always queued here (else we race
723 * with another CPU on page-refcnt and remaining driver code).
724 * Queue time is very short, as driver will invoke flush
725 * operation, when completing napi->poll call.
726 */
727 bq->q[bq->count++] = xdpf;
728
729 if (!bq->flush_node.prev)
730 list_add(&bq->flush_node, flush_list);
731
732 return 0;
733}
734
735int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp,
736 struct net_device *dev_rx)
737{
738 struct xdp_frame *xdpf;
739
740 xdpf = xdp_convert_buff_to_frame(xdp);
741 if (unlikely(!xdpf))
742 return -EOVERFLOW;
743
744 /* Info needed when constructing SKB on remote CPU */
745 xdpf->dev_rx = dev_rx;
746
747 bq_enqueue(rcpu, xdpf);
748 return 0;
749}
750
751void __cpu_map_flush(void)
752{
753 struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
754 struct xdp_bulk_queue *bq, *tmp;
755
756 list_for_each_entry_safe(bq, tmp, flush_list, flush_node) {
757 bq_flush_to_queue(bq);
758
759 /* If already running, costs spin_lock_irqsave + smb_mb */
760 wake_up_process(bq->obj->kthread);
761 }
762}
763
764static int __init cpu_map_init(void)
765{
766 int cpu;
767
768 for_each_possible_cpu(cpu)
769 INIT_LIST_HEAD(&per_cpu(cpu_map_flush_list, cpu));
770 return 0;
771}
772
773subsys_initcall(cpu_map_init);
1/* bpf/cpumap.c
2 *
3 * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
4 * Released under terms in GPL version 2. See COPYING.
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
23#include <linux/sched.h>
24#include <linux/workqueue.h>
25#include <linux/kthread.h>
26#include <linux/capability.h>
27#include <trace/events/xdp.h>
28
29#include <linux/netdevice.h> /* netif_receive_skb_core */
30#include <linux/etherdevice.h> /* eth_type_trans */
31
32/* General idea: XDP packets getting XDP redirected to another CPU,
33 * will maximum be stored/queued for one driver ->poll() call. It is
34 * guaranteed that setting flush bit and flush operation happen on
35 * same CPU. Thus, cpu_map_flush operation can deduct via this_cpu_ptr()
36 * which queue in bpf_cpu_map_entry contains packets.
37 */
38
39#define CPU_MAP_BULK_SIZE 8 /* 8 == one cacheline on 64-bit archs */
40struct xdp_bulk_queue {
41 void *q[CPU_MAP_BULK_SIZE];
42 unsigned int count;
43};
44
45/* Struct for every remote "destination" CPU in map */
46struct bpf_cpu_map_entry {
47 u32 cpu; /* kthread CPU and map index */
48 int map_id; /* Back reference to map */
49 u32 qsize; /* Queue size placeholder for map lookup */
50
51 /* XDP can run multiple RX-ring queues, need __percpu enqueue store */
52 struct xdp_bulk_queue __percpu *bulkq;
53
54 /* Queue with potential multi-producers, and single-consumer kthread */
55 struct ptr_ring *queue;
56 struct task_struct *kthread;
57 struct work_struct kthread_stop_wq;
58
59 atomic_t refcnt; /* Control when this struct can be free'ed */
60 struct rcu_head rcu;
61};
62
63struct bpf_cpu_map {
64 struct bpf_map map;
65 /* Below members specific for map type */
66 struct bpf_cpu_map_entry **cpu_map;
67 unsigned long __percpu *flush_needed;
68};
69
70static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
71 struct xdp_bulk_queue *bq);
72
73static u64 cpu_map_bitmap_size(const union bpf_attr *attr)
74{
75 return BITS_TO_LONGS(attr->max_entries) * sizeof(unsigned long);
76}
77
78static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
79{
80 struct bpf_cpu_map *cmap;
81 int err = -ENOMEM;
82 u64 cost;
83 int ret;
84
85 if (!capable(CAP_SYS_ADMIN))
86 return ERR_PTR(-EPERM);
87
88 /* check sanity of attributes */
89 if (attr->max_entries == 0 || attr->key_size != 4 ||
90 attr->value_size != 4 || attr->map_flags & ~BPF_F_NUMA_NODE)
91 return ERR_PTR(-EINVAL);
92
93 cmap = kzalloc(sizeof(*cmap), GFP_USER);
94 if (!cmap)
95 return ERR_PTR(-ENOMEM);
96
97 bpf_map_init_from_attr(&cmap->map, attr);
98
99 /* Pre-limit array size based on NR_CPUS, not final CPU check */
100 if (cmap->map.max_entries > NR_CPUS) {
101 err = -E2BIG;
102 goto free_cmap;
103 }
104
105 /* make sure page count doesn't overflow */
106 cost = (u64) cmap->map.max_entries * sizeof(struct bpf_cpu_map_entry *);
107 cost += cpu_map_bitmap_size(attr) * num_possible_cpus();
108 if (cost >= U32_MAX - PAGE_SIZE)
109 goto free_cmap;
110 cmap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;
111
112 /* Notice returns -EPERM on if map size is larger than memlock limit */
113 ret = bpf_map_precharge_memlock(cmap->map.pages);
114 if (ret) {
115 err = ret;
116 goto free_cmap;
117 }
118
119 /* A per cpu bitfield with a bit per possible CPU in map */
120 cmap->flush_needed = __alloc_percpu(cpu_map_bitmap_size(attr),
121 __alignof__(unsigned long));
122 if (!cmap->flush_needed)
123 goto free_cmap;
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;
133free_percpu:
134 free_percpu(cmap->flush_needed);
135free_cmap:
136 kfree(cmap);
137 return ERR_PTR(err);
138}
139
140static void __cpu_map_queue_destructor(void *ptr)
141{
142 /* The tear-down procedure should have made sure that queue is
143 * empty. See __cpu_map_entry_replace() and work-queue
144 * invoked cpu_map_kthread_stop(). Catch any broken behaviour
145 * gracefully and warn once.
146 */
147 if (WARN_ON_ONCE(ptr))
148 page_frag_free(ptr);
149}
150
151static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
152{
153 if (atomic_dec_and_test(&rcpu->refcnt)) {
154 /* The queue should be empty at this point */
155 ptr_ring_cleanup(rcpu->queue, __cpu_map_queue_destructor);
156 kfree(rcpu->queue);
157 kfree(rcpu);
158 }
159}
160
161static void get_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
162{
163 atomic_inc(&rcpu->refcnt);
164}
165
166/* called from workqueue, to workaround syscall using preempt_disable */
167static void cpu_map_kthread_stop(struct work_struct *work)
168{
169 struct bpf_cpu_map_entry *rcpu;
170
171 rcpu = container_of(work, struct bpf_cpu_map_entry, kthread_stop_wq);
172
173 /* Wait for flush in __cpu_map_entry_free(), via full RCU barrier,
174 * as it waits until all in-flight call_rcu() callbacks complete.
175 */
176 rcu_barrier();
177
178 /* kthread_stop will wake_up_process and wait for it to complete */
179 kthread_stop(rcpu->kthread);
180}
181
182/* For now, xdp_pkt is a cpumap internal data structure, with info
183 * carried between enqueue to dequeue. It is mapped into the top
184 * headroom of the packet, to avoid allocating separate mem.
185 */
186struct xdp_pkt {
187 void *data;
188 u16 len;
189 u16 headroom;
190 u16 metasize;
191 struct net_device *dev_rx;
192};
193
194/* Convert xdp_buff to xdp_pkt */
195static struct xdp_pkt *convert_to_xdp_pkt(struct xdp_buff *xdp)
196{
197 struct xdp_pkt *xdp_pkt;
198 int metasize;
199 int headroom;
200
201 /* Assure headroom is available for storing info */
202 headroom = xdp->data - xdp->data_hard_start;
203 metasize = xdp->data - xdp->data_meta;
204 metasize = metasize > 0 ? metasize : 0;
205 if (unlikely((headroom - metasize) < sizeof(*xdp_pkt)))
206 return NULL;
207
208 /* Store info in top of packet */
209 xdp_pkt = xdp->data_hard_start;
210
211 xdp_pkt->data = xdp->data;
212 xdp_pkt->len = xdp->data_end - xdp->data;
213 xdp_pkt->headroom = headroom - sizeof(*xdp_pkt);
214 xdp_pkt->metasize = metasize;
215
216 return xdp_pkt;
217}
218
219static struct sk_buff *cpu_map_build_skb(struct bpf_cpu_map_entry *rcpu,
220 struct xdp_pkt *xdp_pkt)
221{
222 unsigned int frame_size;
223 void *pkt_data_start;
224 struct sk_buff *skb;
225
226 /* build_skb need to place skb_shared_info after SKB end, and
227 * also want to know the memory "truesize". Thus, need to
228 * know the memory frame size backing xdp_buff.
229 *
230 * XDP was designed to have PAGE_SIZE frames, but this
231 * assumption is not longer true with ixgbe and i40e. It
232 * would be preferred to set frame_size to 2048 or 4096
233 * depending on the driver.
234 * frame_size = 2048;
235 * frame_len = frame_size - sizeof(*xdp_pkt);
236 *
237 * Instead, with info avail, skb_shared_info in placed after
238 * packet len. This, unfortunately fakes the truesize.
239 * Another disadvantage of this approach, the skb_shared_info
240 * is not at a fixed memory location, with mixed length
241 * packets, which is bad for cache-line hotness.
242 */
243 frame_size = SKB_DATA_ALIGN(xdp_pkt->len) + xdp_pkt->headroom +
244 SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
245
246 pkt_data_start = xdp_pkt->data - xdp_pkt->headroom;
247 skb = build_skb(pkt_data_start, frame_size);
248 if (!skb)
249 return NULL;
250
251 skb_reserve(skb, xdp_pkt->headroom);
252 __skb_put(skb, xdp_pkt->len);
253 if (xdp_pkt->metasize)
254 skb_metadata_set(skb, xdp_pkt->metasize);
255
256 /* Essential SKB info: protocol and skb->dev */
257 skb->protocol = eth_type_trans(skb, xdp_pkt->dev_rx);
258
259 /* Optional SKB info, currently missing:
260 * - HW checksum info (skb->ip_summed)
261 * - HW RX hash (skb_set_hash)
262 * - RX ring dev queue index (skb_record_rx_queue)
263 */
264
265 return skb;
266}
267
268static int cpu_map_kthread_run(void *data)
269{
270 struct bpf_cpu_map_entry *rcpu = data;
271
272 set_current_state(TASK_INTERRUPTIBLE);
273
274 /* When kthread gives stop order, then rcpu have been disconnected
275 * from map, thus no new packets can enter. Remaining in-flight
276 * per CPU stored packets are flushed to this queue. Wait honoring
277 * kthread_stop signal until queue is empty.
278 */
279 while (!kthread_should_stop() || !__ptr_ring_empty(rcpu->queue)) {
280 unsigned int processed = 0, drops = 0, sched = 0;
281 struct xdp_pkt *xdp_pkt;
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 /* Process packets in rcpu->queue */
298 local_bh_disable();
299 /*
300 * The bpf_cpu_map_entry is single consumer, with this
301 * kthread CPU pinned. Lockless access to ptr_ring
302 * consume side valid as no-resize allowed of queue.
303 */
304 while ((xdp_pkt = __ptr_ring_consume(rcpu->queue))) {
305 struct sk_buff *skb;
306 int ret;
307
308 skb = cpu_map_build_skb(rcpu, xdp_pkt);
309 if (!skb) {
310 page_frag_free(xdp_pkt);
311 continue;
312 }
313
314 /* Inject into network stack */
315 ret = netif_receive_skb_core(skb);
316 if (ret == NET_RX_DROP)
317 drops++;
318
319 /* Limit BH-disable period */
320 if (++processed == 8)
321 break;
322 }
323 /* Feedback loop via tracepoint */
324 trace_xdp_cpumap_kthread(rcpu->map_id, processed, 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
334static 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 int numa, err;
340
341 /* Have map->numa_node, but choose node of redirect target CPU */
342 numa = cpu_to_node(cpu);
343
344 rcpu = kzalloc_node(sizeof(*rcpu), gfp, numa);
345 if (!rcpu)
346 return NULL;
347
348 /* Alloc percpu bulkq */
349 rcpu->bulkq = __alloc_percpu_gfp(sizeof(*rcpu->bulkq),
350 sizeof(void *), gfp);
351 if (!rcpu->bulkq)
352 goto free_rcu;
353
354 /* Alloc queue */
355 rcpu->queue = kzalloc_node(sizeof(*rcpu->queue), gfp, numa);
356 if (!rcpu->queue)
357 goto free_bulkq;
358
359 err = ptr_ring_init(rcpu->queue, qsize, gfp);
360 if (err)
361 goto free_queue;
362
363 rcpu->cpu = cpu;
364 rcpu->map_id = map_id;
365 rcpu->qsize = qsize;
366
367 /* Setup kthread */
368 rcpu->kthread = kthread_create_on_node(cpu_map_kthread_run, rcpu, numa,
369 "cpumap/%d/map:%d", cpu, map_id);
370 if (IS_ERR(rcpu->kthread))
371 goto free_ptr_ring;
372
373 get_cpu_map_entry(rcpu); /* 1-refcnt for being in cmap->cpu_map[] */
374 get_cpu_map_entry(rcpu); /* 1-refcnt for kthread */
375
376 /* Make sure kthread runs on a single CPU */
377 kthread_bind(rcpu->kthread, cpu);
378 wake_up_process(rcpu->kthread);
379
380 return rcpu;
381
382free_ptr_ring:
383 ptr_ring_cleanup(rcpu->queue, NULL);
384free_queue:
385 kfree(rcpu->queue);
386free_bulkq:
387 free_percpu(rcpu->bulkq);
388free_rcu:
389 kfree(rcpu);
390 return NULL;
391}
392
393static void __cpu_map_entry_free(struct rcu_head *rcu)
394{
395 struct bpf_cpu_map_entry *rcpu;
396 int cpu;
397
398 /* This cpu_map_entry have been disconnected from map and one
399 * RCU graze-period have elapsed. Thus, XDP cannot queue any
400 * new packets and cannot change/set flush_needed that can
401 * find this entry.
402 */
403 rcpu = container_of(rcu, struct bpf_cpu_map_entry, rcu);
404
405 /* Flush remaining packets in percpu bulkq */
406 for_each_online_cpu(cpu) {
407 struct xdp_bulk_queue *bq = per_cpu_ptr(rcpu->bulkq, cpu);
408
409 /* No concurrent bq_enqueue can run at this point */
410 bq_flush_to_queue(rcpu, bq);
411 }
412 free_percpu(rcpu->bulkq);
413 /* Cannot kthread_stop() here, last put free rcpu resources */
414 put_cpu_map_entry(rcpu);
415}
416
417/* After xchg pointer to bpf_cpu_map_entry, use the call_rcu() to
418 * ensure any driver rcu critical sections have completed, but this
419 * does not guarantee a flush has happened yet. Because driver side
420 * rcu_read_lock/unlock only protects the running XDP program. The
421 * atomic xchg and NULL-ptr check in __cpu_map_flush() makes sure a
422 * pending flush op doesn't fail.
423 *
424 * The bpf_cpu_map_entry is still used by the kthread, and there can
425 * still be pending packets (in queue and percpu bulkq). A refcnt
426 * makes sure to last user (kthread_stop vs. call_rcu) free memory
427 * resources.
428 *
429 * The rcu callback __cpu_map_entry_free flush remaining packets in
430 * percpu bulkq to queue. Due to caller map_delete_elem() disable
431 * preemption, cannot call kthread_stop() to make sure queue is empty.
432 * Instead a work_queue is started for stopping kthread,
433 * cpu_map_kthread_stop, which waits for an RCU graze period before
434 * stopping kthread, emptying the queue.
435 */
436static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
437 u32 key_cpu, struct bpf_cpu_map_entry *rcpu)
438{
439 struct bpf_cpu_map_entry *old_rcpu;
440
441 old_rcpu = xchg(&cmap->cpu_map[key_cpu], rcpu);
442 if (old_rcpu) {
443 call_rcu(&old_rcpu->rcu, __cpu_map_entry_free);
444 INIT_WORK(&old_rcpu->kthread_stop_wq, cpu_map_kthread_stop);
445 schedule_work(&old_rcpu->kthread_stop_wq);
446 }
447}
448
449static int cpu_map_delete_elem(struct bpf_map *map, void *key)
450{
451 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
452 u32 key_cpu = *(u32 *)key;
453
454 if (key_cpu >= map->max_entries)
455 return -EINVAL;
456
457 /* notice caller map_delete_elem() use preempt_disable() */
458 __cpu_map_entry_replace(cmap, key_cpu, NULL);
459 return 0;
460}
461
462static int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
463 u64 map_flags)
464{
465 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
466 struct bpf_cpu_map_entry *rcpu;
467
468 /* Array index key correspond to CPU number */
469 u32 key_cpu = *(u32 *)key;
470 /* Value is the queue size */
471 u32 qsize = *(u32 *)value;
472
473 if (unlikely(map_flags > BPF_EXIST))
474 return -EINVAL;
475 if (unlikely(key_cpu >= cmap->map.max_entries))
476 return -E2BIG;
477 if (unlikely(map_flags == BPF_NOEXIST))
478 return -EEXIST;
479 if (unlikely(qsize > 16384)) /* sanity limit on qsize */
480 return -EOVERFLOW;
481
482 /* Make sure CPU is a valid possible cpu */
483 if (!cpu_possible(key_cpu))
484 return -ENODEV;
485
486 if (qsize == 0) {
487 rcpu = NULL; /* Same as deleting */
488 } else {
489 /* Updating qsize cause re-allocation of bpf_cpu_map_entry */
490 rcpu = __cpu_map_entry_alloc(qsize, key_cpu, map->id);
491 if (!rcpu)
492 return -ENOMEM;
493 }
494 rcu_read_lock();
495 __cpu_map_entry_replace(cmap, key_cpu, rcpu);
496 rcu_read_unlock();
497 return 0;
498}
499
500static void cpu_map_free(struct bpf_map *map)
501{
502 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
503 int cpu;
504 u32 i;
505
506 /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
507 * so the bpf programs (can be more than one that used this map) were
508 * disconnected from events. Wait for outstanding critical sections in
509 * these programs to complete. The rcu critical section only guarantees
510 * no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
511 * It does __not__ ensure pending flush operations (if any) are
512 * complete.
513 */
514 synchronize_rcu();
515
516 /* To ensure all pending flush operations have completed wait for flush
517 * bitmap to indicate all flush_needed bits to be zero on _all_ cpus.
518 * Because the above synchronize_rcu() ensures the map is disconnected
519 * from the program we can assume no new bits will be set.
520 */
521 for_each_online_cpu(cpu) {
522 unsigned long *bitmap = per_cpu_ptr(cmap->flush_needed, cpu);
523
524 while (!bitmap_empty(bitmap, cmap->map.max_entries))
525 cond_resched();
526 }
527
528 /* For cpu_map the remote CPUs can still be using the entries
529 * (struct bpf_cpu_map_entry).
530 */
531 for (i = 0; i < cmap->map.max_entries; i++) {
532 struct bpf_cpu_map_entry *rcpu;
533
534 rcpu = READ_ONCE(cmap->cpu_map[i]);
535 if (!rcpu)
536 continue;
537
538 /* bq flush and cleanup happens after RCU graze-period */
539 __cpu_map_entry_replace(cmap, i, NULL); /* call_rcu */
540 }
541 free_percpu(cmap->flush_needed);
542 bpf_map_area_free(cmap->cpu_map);
543 kfree(cmap);
544}
545
546struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
547{
548 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
549 struct bpf_cpu_map_entry *rcpu;
550
551 if (key >= map->max_entries)
552 return NULL;
553
554 rcpu = READ_ONCE(cmap->cpu_map[key]);
555 return rcpu;
556}
557
558static void *cpu_map_lookup_elem(struct bpf_map *map, void *key)
559{
560 struct bpf_cpu_map_entry *rcpu =
561 __cpu_map_lookup_elem(map, *(u32 *)key);
562
563 return rcpu ? &rcpu->qsize : NULL;
564}
565
566static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
567{
568 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
569 u32 index = key ? *(u32 *)key : U32_MAX;
570 u32 *next = next_key;
571
572 if (index >= cmap->map.max_entries) {
573 *next = 0;
574 return 0;
575 }
576
577 if (index == cmap->map.max_entries - 1)
578 return -ENOENT;
579 *next = index + 1;
580 return 0;
581}
582
583const struct bpf_map_ops cpu_map_ops = {
584 .map_alloc = cpu_map_alloc,
585 .map_free = cpu_map_free,
586 .map_delete_elem = cpu_map_delete_elem,
587 .map_update_elem = cpu_map_update_elem,
588 .map_lookup_elem = cpu_map_lookup_elem,
589 .map_get_next_key = cpu_map_get_next_key,
590};
591
592static int bq_flush_to_queue(struct bpf_cpu_map_entry *rcpu,
593 struct xdp_bulk_queue *bq)
594{
595 unsigned int processed = 0, drops = 0;
596 const int to_cpu = rcpu->cpu;
597 struct ptr_ring *q;
598 int i;
599
600 if (unlikely(!bq->count))
601 return 0;
602
603 q = rcpu->queue;
604 spin_lock(&q->producer_lock);
605
606 for (i = 0; i < bq->count; i++) {
607 void *xdp_pkt = bq->q[i];
608 int err;
609
610 err = __ptr_ring_produce(q, xdp_pkt);
611 if (err) {
612 drops++;
613 page_frag_free(xdp_pkt); /* Free xdp_pkt */
614 }
615 processed++;
616 }
617 bq->count = 0;
618 spin_unlock(&q->producer_lock);
619
620 /* Feedback loop via tracepoints */
621 trace_xdp_cpumap_enqueue(rcpu->map_id, processed, drops, to_cpu);
622 return 0;
623}
624
625/* Runs under RCU-read-side, plus in softirq under NAPI protection.
626 * Thus, safe percpu variable access.
627 */
628static int bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_pkt *xdp_pkt)
629{
630 struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
631
632 if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
633 bq_flush_to_queue(rcpu, bq);
634
635 /* Notice, xdp_buff/page MUST be queued here, long enough for
636 * driver to code invoking us to finished, due to driver
637 * (e.g. ixgbe) recycle tricks based on page-refcnt.
638 *
639 * Thus, incoming xdp_pkt is always queued here (else we race
640 * with another CPU on page-refcnt and remaining driver code).
641 * Queue time is very short, as driver will invoke flush
642 * operation, when completing napi->poll call.
643 */
644 bq->q[bq->count++] = xdp_pkt;
645 return 0;
646}
647
648int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp,
649 struct net_device *dev_rx)
650{
651 struct xdp_pkt *xdp_pkt;
652
653 xdp_pkt = convert_to_xdp_pkt(xdp);
654 if (unlikely(!xdp_pkt))
655 return -EOVERFLOW;
656
657 /* Info needed when constructing SKB on remote CPU */
658 xdp_pkt->dev_rx = dev_rx;
659
660 bq_enqueue(rcpu, xdp_pkt);
661 return 0;
662}
663
664void __cpu_map_insert_ctx(struct bpf_map *map, u32 bit)
665{
666 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
667 unsigned long *bitmap = this_cpu_ptr(cmap->flush_needed);
668
669 __set_bit(bit, bitmap);
670}
671
672void __cpu_map_flush(struct bpf_map *map)
673{
674 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
675 unsigned long *bitmap = this_cpu_ptr(cmap->flush_needed);
676 u32 bit;
677
678 /* The napi->poll softirq makes sure __cpu_map_insert_ctx()
679 * and __cpu_map_flush() happen on same CPU. Thus, the percpu
680 * bitmap indicate which percpu bulkq have packets.
681 */
682 for_each_set_bit(bit, bitmap, map->max_entries) {
683 struct bpf_cpu_map_entry *rcpu = READ_ONCE(cmap->cpu_map[bit]);
684 struct xdp_bulk_queue *bq;
685
686 /* This is possible if entry is removed by user space
687 * between xdp redirect and flush op.
688 */
689 if (unlikely(!rcpu))
690 continue;
691
692 __clear_bit(bit, bitmap);
693
694 /* Flush all frames in bulkq to real queue */
695 bq = this_cpu_ptr(rcpu->bulkq);
696 bq_flush_to_queue(rcpu, bq);
697
698 /* If already running, costs spin_lock_irqsave + smb_mb */
699 wake_up_process(rcpu->kthread);
700 }
701}