1// SPDX-License-Identifier: GPL-2.0-only
2/* bpf/cpumap.c
3 *
4 * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
5 */
6
7/**
8 * DOC: cpu map
9 * The 'cpumap' is primarily used as a backend map for XDP BPF helper
10 * call bpf_redirect_map() and XDP_REDIRECT action, like 'devmap'.
11 *
12 * Unlike devmap which redirects XDP frames out to another NIC device,
13 * this map type redirects raw XDP frames to another CPU. The remote
14 * CPU will do SKB-allocation and call the normal network stack.
15 */
16/*
17 * This is a scalability and isolation mechanism, that allow
18 * separating the early driver network XDP layer, from the rest of the
19 * netstack, and assigning dedicated CPUs for this stage. This
20 * basically allows for 10G wirespeed pre-filtering via bpf.
21 */
22#include <linux/bitops.h>
23#include <linux/bpf.h>
24#include <linux/filter.h>
25#include <linux/ptr_ring.h>
26#include <net/xdp.h>
27#include <net/hotdata.h>
28
29#include <linux/sched.h>
30#include <linux/workqueue.h>
31#include <linux/kthread.h>
32#include <linux/completion.h>
33#include <trace/events/xdp.h>
34#include <linux/btf_ids.h>
35
36#include <linux/netdevice.h> /* netif_receive_skb_list */
37#include <linux/etherdevice.h> /* eth_type_trans */
38
39/* General idea: XDP packets getting XDP redirected to another CPU,
40 * will maximum be stored/queued for one driver ->poll() call. It is
41 * guaranteed that queueing the frame and the flush operation happen on
42 * same CPU. Thus, cpu_map_flush operation can deduct via this_cpu_ptr()
43 * which queue in bpf_cpu_map_entry contains packets.
44 */
45
46#define CPU_MAP_BULK_SIZE 8 /* 8 == one cacheline on 64-bit archs */
47struct bpf_cpu_map_entry;
48struct bpf_cpu_map;
49
50struct xdp_bulk_queue {
51 void *q[CPU_MAP_BULK_SIZE];
52 struct list_head flush_node;
53 struct bpf_cpu_map_entry *obj;
54 unsigned int count;
55};
56
57/* Struct for every remote "destination" CPU in map */
58struct bpf_cpu_map_entry {
59 u32 cpu; /* kthread CPU and map index */
60 int map_id; /* Back reference to map */
61
62 /* XDP can run multiple RX-ring queues, need __percpu enqueue store */
63 struct xdp_bulk_queue __percpu *bulkq;
64
65 /* Queue with potential multi-producers, and single-consumer kthread */
66 struct ptr_ring *queue;
67 struct task_struct *kthread;
68
69 struct bpf_cpumap_val value;
70 struct bpf_prog *prog;
71
72 struct completion kthread_running;
73 struct rcu_work free_work;
74};
75
76struct bpf_cpu_map {
77 struct bpf_map map;
78 /* Below members specific for map type */
79 struct bpf_cpu_map_entry __rcu **cpu_map;
80};
81
82static DEFINE_PER_CPU(struct list_head, cpu_map_flush_list);
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
89 /* check sanity of attributes */
90 if (attr->max_entries == 0 || attr->key_size != 4 ||
91 (value_size != offsetofend(struct bpf_cpumap_val, qsize) &&
92 value_size != offsetofend(struct bpf_cpumap_val, bpf_prog.fd)) ||
93 attr->map_flags & ~BPF_F_NUMA_NODE)
94 return ERR_PTR(error: -EINVAL);
95
96 /* Pre-limit array size based on NR_CPUS, not final CPU check */
97 if (attr->max_entries > NR_CPUS)
98 return ERR_PTR(error: -E2BIG);
99
100 cmap = bpf_map_area_alloc(size: sizeof(*cmap), NUMA_NO_NODE);
101 if (!cmap)
102 return ERR_PTR(error: -ENOMEM);
103
104 bpf_map_init_from_attr(map: &cmap->map, attr);
105
106 /* Alloc array for possible remote "destination" CPUs */
107 cmap->cpu_map = bpf_map_area_alloc(size: cmap->map.max_entries *
108 sizeof(struct bpf_cpu_map_entry *),
109 numa_node: cmap->map.numa_node);
110 if (!cmap->cpu_map) {
111 bpf_map_area_free(base: cmap);
112 return ERR_PTR(error: -ENOMEM);
113 }
114
115 return &cmap->map;
116}
117
118static void __cpu_map_ring_cleanup(struct ptr_ring *ring)
119{
120 /* The tear-down procedure should have made sure that queue is
121 * empty. See __cpu_map_entry_replace() and work-queue
122 * invoked cpu_map_kthread_stop(). Catch any broken behaviour
123 * gracefully and warn once.
124 */
125 void *ptr;
126
127 while ((ptr = ptr_ring_consume(r: ring))) {
128 WARN_ON_ONCE(1);
129 if (unlikely(__ptr_test_bit(0, &ptr))) {
130 __ptr_clear_bit(0, &ptr);
131 kfree_skb(skb: ptr);
132 continue;
133 }
134 xdp_return_frame(xdpf: ptr);
135 }
136}
137
138static void cpu_map_bpf_prog_run_skb(struct bpf_cpu_map_entry *rcpu,
139 struct list_head *listp,
140 struct xdp_cpumap_stats *stats)
141{
142 struct sk_buff *skb, *tmp;
143 struct xdp_buff xdp;
144 u32 act;
145 int err;
146
147 list_for_each_entry_safe(skb, tmp, listp, list) {
148 act = bpf_prog_run_generic_xdp(skb, xdp: &xdp, xdp_prog: rcpu->prog);
149 switch (act) {
150 case XDP_PASS:
151 break;
152 case XDP_REDIRECT:
153 skb_list_del_init(skb);
154 err = xdp_do_generic_redirect(dev: skb->dev, skb, xdp: &xdp,
155 prog: rcpu->prog);
156 if (unlikely(err)) {
157 kfree_skb(skb);
158 stats->drop++;
159 } else {
160 stats->redirect++;
161 }
162 return;
163 default:
164 bpf_warn_invalid_xdp_action(NULL, prog: rcpu->prog, act);
165 fallthrough;
166 case XDP_ABORTED:
167 trace_xdp_exception(dev: skb->dev, xdp: rcpu->prog, act);
168 fallthrough;
169 case XDP_DROP:
170 skb_list_del_init(skb);
171 kfree_skb(skb);
172 stats->drop++;
173 return;
174 }
175 }
176}
177
178static int cpu_map_bpf_prog_run_xdp(struct bpf_cpu_map_entry *rcpu,
179 void **frames, int n,
180 struct xdp_cpumap_stats *stats)
181{
182 struct xdp_rxq_info rxq = {};
183 struct xdp_buff xdp;
184 int i, nframes = 0;
185
186 xdp_set_return_frame_no_direct();
187 xdp.rxq = &rxq;
188
189 for (i = 0; i < n; i++) {
190 struct xdp_frame *xdpf = frames[i];
191 u32 act;
192 int err;
193
194 rxq.dev = xdpf->dev_rx;
195 rxq.mem = xdpf->mem;
196 /* TODO: report queue_index to xdp_rxq_info */
197
198 xdp_convert_frame_to_buff(frame: xdpf, xdp: &xdp);
199
200 act = bpf_prog_run_xdp(prog: rcpu->prog, xdp: &xdp);
201 switch (act) {
202 case XDP_PASS:
203 err = xdp_update_frame_from_buff(xdp: &xdp, xdp_frame: xdpf);
204 if (err < 0) {
205 xdp_return_frame(xdpf);
206 stats->drop++;
207 } else {
208 frames[nframes++] = xdpf;
209 stats->pass++;
210 }
211 break;
212 case XDP_REDIRECT:
213 err = xdp_do_redirect(dev: xdpf->dev_rx, xdp: &xdp,
214 prog: rcpu->prog);
215 if (unlikely(err)) {
216 xdp_return_frame(xdpf);
217 stats->drop++;
218 } else {
219 stats->redirect++;
220 }
221 break;
222 default:
223 bpf_warn_invalid_xdp_action(NULL, prog: rcpu->prog, act);
224 fallthrough;
225 case XDP_DROP:
226 xdp_return_frame(xdpf);
227 stats->drop++;
228 break;
229 }
230 }
231
232 xdp_clear_return_frame_no_direct();
233
234 return nframes;
235}
236
237#define CPUMAP_BATCH 8
238
239static int cpu_map_bpf_prog_run(struct bpf_cpu_map_entry *rcpu, void **frames,
240 int xdp_n, struct xdp_cpumap_stats *stats,
241 struct list_head *list)
242{
243 int nframes;
244
245 if (!rcpu->prog)
246 return xdp_n;
247
248 rcu_read_lock_bh();
249
250 nframes = cpu_map_bpf_prog_run_xdp(rcpu, frames, n: xdp_n, stats);
251
252 if (stats->redirect)
253 xdp_do_flush();
254
255 if (unlikely(!list_empty(list)))
256 cpu_map_bpf_prog_run_skb(rcpu, listp: list, stats);
257
258 rcu_read_unlock_bh(); /* resched point, may call do_softirq() */
259
260 return nframes;
261}
262
263static int cpu_map_kthread_run(void *data)
264{
265 struct bpf_cpu_map_entry *rcpu = data;
266 unsigned long last_qs = jiffies;
267
268 complete(&rcpu->kthread_running);
269 set_current_state(TASK_INTERRUPTIBLE);
270
271 /* When kthread gives stop order, then rcpu have been disconnected
272 * from map, thus no new packets can enter. Remaining in-flight
273 * per CPU stored packets are flushed to this queue. Wait honoring
274 * kthread_stop signal until queue is empty.
275 */
276 while (!kthread_should_stop() || !__ptr_ring_empty(r: rcpu->queue)) {
277 struct xdp_cpumap_stats stats = {}; /* zero stats */
278 unsigned int kmem_alloc_drops = 0, sched = 0;
279 gfp_t gfp = __GFP_ZERO | GFP_ATOMIC;
280 int i, n, m, nframes, xdp_n;
281 void *frames[CPUMAP_BATCH];
282 void *skbs[CPUMAP_BATCH];
283 LIST_HEAD(list);
284
285 /* Release CPU reschedule checks */
286 if (__ptr_ring_empty(r: rcpu->queue)) {
287 set_current_state(TASK_INTERRUPTIBLE);
288 /* Recheck to avoid lost wake-up */
289 if (__ptr_ring_empty(r: rcpu->queue)) {
290 schedule();
291 sched = 1;
292 last_qs = jiffies;
293 } else {
294 __set_current_state(TASK_RUNNING);
295 }
296 } else {
297 rcu_softirq_qs_periodic(last_qs);
298 sched = cond_resched();
299 }
300
301 /*
302 * The bpf_cpu_map_entry is single consumer, with this
303 * kthread CPU pinned. Lockless access to ptr_ring
304 * consume side valid as no-resize allowed of queue.
305 */
306 n = __ptr_ring_consume_batched(r: rcpu->queue, array: frames,
307 CPUMAP_BATCH);
308 for (i = 0, xdp_n = 0; i < n; i++) {
309 void *f = frames[i];
310 struct page *page;
311
312 if (unlikely(__ptr_test_bit(0, &f))) {
313 struct sk_buff *skb = f;
314
315 __ptr_clear_bit(0, &skb);
316 list_add_tail(new: &skb->list, head: &list);
317 continue;
318 }
319
320 frames[xdp_n++] = f;
321 page = virt_to_page(f);
322
323 /* Bring struct page memory area to curr CPU. Read by
324 * build_skb_around via page_is_pfmemalloc(), and when
325 * freed written by page_frag_free call.
326 */
327 prefetchw(x: page);
328 }
329
330 /* Support running another XDP prog on this CPU */
331 nframes = cpu_map_bpf_prog_run(rcpu, frames, xdp_n, stats: &stats, list: &list);
332 if (nframes) {
333 m = kmem_cache_alloc_bulk(s: net_hotdata.skbuff_cache,
334 flags: gfp, size: nframes, p: skbs);
335 if (unlikely(m == 0)) {
336 for (i = 0; i < nframes; i++)
337 skbs[i] = NULL; /* effect: xdp_return_frame */
338 kmem_alloc_drops += nframes;
339 }
340 }
341
342 local_bh_disable();
343 for (i = 0; i < nframes; i++) {
344 struct xdp_frame *xdpf = frames[i];
345 struct sk_buff *skb = skbs[i];
346
347 skb = __xdp_build_skb_from_frame(xdpf, skb,
348 dev: xdpf->dev_rx);
349 if (!skb) {
350 xdp_return_frame(xdpf);
351 continue;
352 }
353
354 list_add_tail(new: &skb->list, head: &list);
355 }
356 netif_receive_skb_list(head: &list);
357
358 /* Feedback loop via tracepoint */
359 trace_xdp_cpumap_kthread(map_id: rcpu->map_id, processed: n, drops: kmem_alloc_drops,
360 sched, xdp_stats: &stats);
361
362 local_bh_enable(); /* resched point, may call do_softirq() */
363 }
364 __set_current_state(TASK_RUNNING);
365
366 return 0;
367}
368
369static int __cpu_map_load_bpf_program(struct bpf_cpu_map_entry *rcpu,
370 struct bpf_map *map, int fd)
371{
372 struct bpf_prog *prog;
373
374 prog = bpf_prog_get_type(ufd: fd, type: BPF_PROG_TYPE_XDP);
375 if (IS_ERR(ptr: prog))
376 return PTR_ERR(ptr: prog);
377
378 if (prog->expected_attach_type != BPF_XDP_CPUMAP ||
379 !bpf_prog_map_compatible(map, fp: prog)) {
380 bpf_prog_put(prog);
381 return -EINVAL;
382 }
383
384 rcpu->value.bpf_prog.id = prog->aux->id;
385 rcpu->prog = prog;
386
387 return 0;
388}
389
390static struct bpf_cpu_map_entry *
391__cpu_map_entry_alloc(struct bpf_map *map, struct bpf_cpumap_val *value,
392 u32 cpu)
393{
394 int numa, err, i, fd = value->bpf_prog.fd;
395 gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
396 struct bpf_cpu_map_entry *rcpu;
397 struct xdp_bulk_queue *bq;
398
399 /* Have map->numa_node, but choose node of redirect target CPU */
400 numa = cpu_to_node(cpu);
401
402 rcpu = bpf_map_kmalloc_node(map, size: sizeof(*rcpu), flags: gfp | __GFP_ZERO, node: numa);
403 if (!rcpu)
404 return NULL;
405
406 /* Alloc percpu bulkq */
407 rcpu->bulkq = bpf_map_alloc_percpu(map, size: sizeof(*rcpu->bulkq),
408 align: sizeof(void *), flags: gfp);
409 if (!rcpu->bulkq)
410 goto free_rcu;
411
412 for_each_possible_cpu(i) {
413 bq = per_cpu_ptr(rcpu->bulkq, i);
414 bq->obj = rcpu;
415 }
416
417 /* Alloc queue */
418 rcpu->queue = bpf_map_kmalloc_node(map, size: sizeof(*rcpu->queue), flags: gfp,
419 node: numa);
420 if (!rcpu->queue)
421 goto free_bulkq;
422
423 err = ptr_ring_init(r: rcpu->queue, size: value->qsize, gfp);
424 if (err)
425 goto free_queue;
426
427 rcpu->cpu = cpu;
428 rcpu->map_id = map->id;
429 rcpu->value.qsize = value->qsize;
430
431 if (fd > 0 && __cpu_map_load_bpf_program(rcpu, map, fd))
432 goto free_ptr_ring;
433
434 /* Setup kthread */
435 init_completion(x: &rcpu->kthread_running);
436 rcpu->kthread = kthread_create_on_node(threadfn: cpu_map_kthread_run, data: rcpu, node: numa,
437 namefmt: "cpumap/%d/map:%d", cpu,
438 map->id);
439 if (IS_ERR(ptr: rcpu->kthread))
440 goto free_prog;
441
442 /* Make sure kthread runs on a single CPU */
443 kthread_bind(k: rcpu->kthread, cpu);
444 wake_up_process(tsk: rcpu->kthread);
445
446 /* Make sure kthread has been running, so kthread_stop() will not
447 * stop the kthread prematurely and all pending frames or skbs
448 * will be handled by the kthread before kthread_stop() returns.
449 */
450 wait_for_completion(&rcpu->kthread_running);
451
452 return rcpu;
453
454free_prog:
455 if (rcpu->prog)
456 bpf_prog_put(prog: rcpu->prog);
457free_ptr_ring:
458 ptr_ring_cleanup(r: rcpu->queue, NULL);
459free_queue:
460 kfree(objp: rcpu->queue);
461free_bulkq:
462 free_percpu(pdata: rcpu->bulkq);
463free_rcu:
464 kfree(objp: rcpu);
465 return NULL;
466}
467
468static void __cpu_map_entry_free(struct work_struct *work)
469{
470 struct bpf_cpu_map_entry *rcpu;
471
472 /* This cpu_map_entry have been disconnected from map and one
473 * RCU grace-period have elapsed. Thus, XDP cannot queue any
474 * new packets and cannot change/set flush_needed that can
475 * find this entry.
476 */
477 rcpu = container_of(to_rcu_work(work), struct bpf_cpu_map_entry, free_work);
478
479 /* kthread_stop will wake_up_process and wait for it to complete.
480 * cpu_map_kthread_run() makes sure the pointer ring is empty
481 * before exiting.
482 */
483 kthread_stop(k: rcpu->kthread);
484
485 if (rcpu->prog)
486 bpf_prog_put(prog: rcpu->prog);
487 /* The queue should be empty at this point */
488 __cpu_map_ring_cleanup(ring: rcpu->queue);
489 ptr_ring_cleanup(r: rcpu->queue, NULL);
490 kfree(objp: rcpu->queue);
491 free_percpu(pdata: rcpu->bulkq);
492 kfree(objp: rcpu);
493}
494
495/* After the xchg of the bpf_cpu_map_entry pointer, we need to make sure the old
496 * entry is no longer in use before freeing. We use queue_rcu_work() to call
497 * __cpu_map_entry_free() in a separate workqueue after waiting for an RCU grace
498 * period. This means that (a) all pending enqueue and flush operations have
499 * completed (because of the RCU callback), and (b) we are in a workqueue
500 * context where we can stop the kthread and wait for it to exit before freeing
501 * everything.
502 */
503static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
504 u32 key_cpu, struct bpf_cpu_map_entry *rcpu)
505{
506 struct bpf_cpu_map_entry *old_rcpu;
507
508 old_rcpu = unrcu_pointer(xchg(&cmap->cpu_map[key_cpu], RCU_INITIALIZER(rcpu)));
509 if (old_rcpu) {
510 INIT_RCU_WORK(&old_rcpu->free_work, __cpu_map_entry_free);
511 queue_rcu_work(wq: system_wq, rwork: &old_rcpu->free_work);
512 }
513}
514
515static long cpu_map_delete_elem(struct bpf_map *map, void *key)
516{
517 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
518 u32 key_cpu = *(u32 *)key;
519
520 if (key_cpu >= map->max_entries)
521 return -EINVAL;
522
523 /* notice caller map_delete_elem() uses rcu_read_lock() */
524 __cpu_map_entry_replace(cmap, key_cpu, NULL);
525 return 0;
526}
527
528static long cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
529 u64 map_flags)
530{
531 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
532 struct bpf_cpumap_val cpumap_value = {};
533 struct bpf_cpu_map_entry *rcpu;
534 /* Array index key correspond to CPU number */
535 u32 key_cpu = *(u32 *)key;
536
537 memcpy(&cpumap_value, value, map->value_size);
538
539 if (unlikely(map_flags > BPF_EXIST))
540 return -EINVAL;
541 if (unlikely(key_cpu >= cmap->map.max_entries))
542 return -E2BIG;
543 if (unlikely(map_flags == BPF_NOEXIST))
544 return -EEXIST;
545 if (unlikely(cpumap_value.qsize > 16384)) /* sanity limit on qsize */
546 return -EOVERFLOW;
547
548 /* Make sure CPU is a valid possible cpu */
549 if (key_cpu >= nr_cpumask_bits || !cpu_possible(cpu: key_cpu))
550 return -ENODEV;
551
552 if (cpumap_value.qsize == 0) {
553 rcpu = NULL; /* Same as deleting */
554 } else {
555 /* Updating qsize cause re-allocation of bpf_cpu_map_entry */
556 rcpu = __cpu_map_entry_alloc(map, value: &cpumap_value, cpu: key_cpu);
557 if (!rcpu)
558 return -ENOMEM;
559 }
560 rcu_read_lock();
561 __cpu_map_entry_replace(cmap, key_cpu, rcpu);
562 rcu_read_unlock();
563 return 0;
564}
565
566static void cpu_map_free(struct bpf_map *map)
567{
568 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
569 u32 i;
570
571 /* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
572 * so the bpf programs (can be more than one that used this map) were
573 * disconnected from events. Wait for outstanding critical sections in
574 * these programs to complete. synchronize_rcu() below not only
575 * guarantees no further "XDP/bpf-side" reads against
576 * bpf_cpu_map->cpu_map, but also ensure pending flush operations
577 * (if any) are completed.
578 */
579 synchronize_rcu();
580
581 /* The only possible user of bpf_cpu_map_entry is
582 * cpu_map_kthread_run().
583 */
584 for (i = 0; i < cmap->map.max_entries; i++) {
585 struct bpf_cpu_map_entry *rcpu;
586
587 rcpu = rcu_dereference_raw(cmap->cpu_map[i]);
588 if (!rcpu)
589 continue;
590
591 /* Stop kthread and cleanup entry directly */
592 __cpu_map_entry_free(work: &rcpu->free_work.work);
593 }
594 bpf_map_area_free(base: cmap->cpu_map);
595 bpf_map_area_free(base: cmap);
596}
597
598/* Elements are kept alive by RCU; either by rcu_read_lock() (from syscall) or
599 * by local_bh_disable() (from XDP calls inside NAPI). The
600 * rcu_read_lock_bh_held() below makes lockdep accept both.
601 */
602static void *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
603{
604 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
605 struct bpf_cpu_map_entry *rcpu;
606
607 if (key >= map->max_entries)
608 return NULL;
609
610 rcpu = rcu_dereference_check(cmap->cpu_map[key],
611 rcu_read_lock_bh_held());
612 return rcpu;
613}
614
615static void *cpu_map_lookup_elem(struct bpf_map *map, void *key)
616{
617 struct bpf_cpu_map_entry *rcpu =
618 __cpu_map_lookup_elem(map, key: *(u32 *)key);
619
620 return rcpu ? &rcpu->value : NULL;
621}
622
623static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
624{
625 struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
626 u32 index = key ? *(u32 *)key : U32_MAX;
627 u32 *next = next_key;
628
629 if (index >= cmap->map.max_entries) {
630 *next = 0;
631 return 0;
632 }
633
634 if (index == cmap->map.max_entries - 1)
635 return -ENOENT;
636 *next = index + 1;
637 return 0;
638}
639
640static long cpu_map_redirect(struct bpf_map *map, u64 index, u64 flags)
641{
642 return __bpf_xdp_redirect_map(map, index, flags, flag_mask: 0,
643 lookup_elem: __cpu_map_lookup_elem);
644}
645
646static u64 cpu_map_mem_usage(const struct bpf_map *map)
647{
648 u64 usage = sizeof(struct bpf_cpu_map);
649
650 /* Currently the dynamically allocated elements are not counted */
651 usage += (u64)map->max_entries * sizeof(struct bpf_cpu_map_entry *);
652 return usage;
653}
654
655BTF_ID_LIST_SINGLE(cpu_map_btf_ids, struct, bpf_cpu_map)
656const struct bpf_map_ops cpu_map_ops = {
657 .map_meta_equal = bpf_map_meta_equal,
658 .map_alloc = cpu_map_alloc,
659 .map_free = cpu_map_free,
660 .map_delete_elem = cpu_map_delete_elem,
661 .map_update_elem = cpu_map_update_elem,
662 .map_lookup_elem = cpu_map_lookup_elem,
663 .map_get_next_key = cpu_map_get_next_key,
664 .map_check_btf = map_check_no_btf,
665 .map_mem_usage = cpu_map_mem_usage,
666 .map_btf_id = &cpu_map_btf_ids[0],
667 .map_redirect = cpu_map_redirect,
668};
669
670static void bq_flush_to_queue(struct xdp_bulk_queue *bq)
671{
672 struct bpf_cpu_map_entry *rcpu = bq->obj;
673 unsigned int processed = 0, drops = 0;
674 const int to_cpu = rcpu->cpu;
675 struct ptr_ring *q;
676 int i;
677
678 if (unlikely(!bq->count))
679 return;
680
681 q = rcpu->queue;
682 spin_lock(lock: &q->producer_lock);
683
684 for (i = 0; i < bq->count; i++) {
685 struct xdp_frame *xdpf = bq->q[i];
686 int err;
687
688 err = __ptr_ring_produce(r: q, ptr: xdpf);
689 if (err) {
690 drops++;
691 xdp_return_frame_rx_napi(xdpf);
692 }
693 processed++;
694 }
695 bq->count = 0;
696 spin_unlock(lock: &q->producer_lock);
697
698 __list_del_clearprev(entry: &bq->flush_node);
699
700 /* Feedback loop via tracepoints */
701 trace_xdp_cpumap_enqueue(map_id: rcpu->map_id, processed, drops, to_cpu);
702}
703
704/* Runs under RCU-read-side, plus in softirq under NAPI protection.
705 * Thus, safe percpu variable access.
706 */
707static void bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
708{
709 struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
710 struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
711
712 if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
713 bq_flush_to_queue(bq);
714
715 /* Notice, xdp_buff/page MUST be queued here, long enough for
716 * driver to code invoking us to finished, due to driver
717 * (e.g. ixgbe) recycle tricks based on page-refcnt.
718 *
719 * Thus, incoming xdp_frame is always queued here (else we race
720 * with another CPU on page-refcnt and remaining driver code).
721 * Queue time is very short, as driver will invoke flush
722 * operation, when completing napi->poll call.
723 */
724 bq->q[bq->count++] = xdpf;
725
726 if (!bq->flush_node.prev)
727 list_add(new: &bq->flush_node, head: flush_list);
728}
729
730int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf,
731 struct net_device *dev_rx)
732{
733 /* Info needed when constructing SKB on remote CPU */
734 xdpf->dev_rx = dev_rx;
735
736 bq_enqueue(rcpu, xdpf);
737 return 0;
738}
739
740int cpu_map_generic_redirect(struct bpf_cpu_map_entry *rcpu,
741 struct sk_buff *skb)
742{
743 int ret;
744
745 __skb_pull(skb, len: skb->mac_len);
746 skb_set_redirected(skb, from_ingress: false);
747 __ptr_set_bit(0, &skb);
748
749 ret = ptr_ring_produce(r: rcpu->queue, ptr: skb);
750 if (ret < 0)
751 goto trace;
752
753 wake_up_process(tsk: rcpu->kthread);
754trace:
755 trace_xdp_cpumap_enqueue(map_id: rcpu->map_id, processed: !ret, drops: !!ret, to_cpu: rcpu->cpu);
756 return ret;
757}
758
759void __cpu_map_flush(void)
760{
761 struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
762 struct xdp_bulk_queue *bq, *tmp;
763
764 list_for_each_entry_safe(bq, tmp, flush_list, flush_node) {
765 bq_flush_to_queue(bq);
766
767 /* If already running, costs spin_lock_irqsave + smb_mb */
768 wake_up_process(tsk: bq->obj->kthread);
769 }
770}
771
772#ifdef CONFIG_DEBUG_NET
773bool cpu_map_check_flush(void)
774{
775 if (list_empty(this_cpu_ptr(&cpu_map_flush_list)))
776 return false;
777 __cpu_map_flush();
778 return true;
779}
780#endif
781
782static int __init cpu_map_init(void)
783{
784 int cpu;
785
786 for_each_possible_cpu(cpu)
787 INIT_LIST_HEAD(list: &per_cpu(cpu_map_flush_list, cpu));
788 return 0;
789}
790
791subsys_initcall(cpu_map_init);
792

source code of linux/kernel/bpf/cpumap.c