xref: /openbmc/linux/kernel/bpf/cpumap.c (revision dc6a81c3)
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 };
76 
77 static DEFINE_PER_CPU(struct list_head, cpu_map_flush_list);
78 
79 static int bq_flush_to_queue(struct xdp_bulk_queue *bq);
80 
81 static struct bpf_map *cpu_map_alloc(union bpf_attr *attr)
82 {
83 	struct bpf_cpu_map *cmap;
84 	int err = -ENOMEM;
85 	u64 cost;
86 	int ret;
87 
88 	if (!capable(CAP_SYS_ADMIN))
89 		return ERR_PTR(-EPERM);
90 
91 	/* check sanity of attributes */
92 	if (attr->max_entries == 0 || attr->key_size != 4 ||
93 	    attr->value_size != 4 || attr->map_flags & ~BPF_F_NUMA_NODE)
94 		return ERR_PTR(-EINVAL);
95 
96 	cmap = kzalloc(sizeof(*cmap), GFP_USER);
97 	if (!cmap)
98 		return ERR_PTR(-ENOMEM);
99 
100 	bpf_map_init_from_attr(&cmap->map, attr);
101 
102 	/* Pre-limit array size based on NR_CPUS, not final CPU check */
103 	if (cmap->map.max_entries > NR_CPUS) {
104 		err = -E2BIG;
105 		goto free_cmap;
106 	}
107 
108 	/* make sure page count doesn't overflow */
109 	cost = (u64) cmap->map.max_entries * sizeof(struct bpf_cpu_map_entry *);
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 	/* Alloc array for possible remote "destination" CPUs */
119 	cmap->cpu_map = bpf_map_area_alloc(cmap->map.max_entries *
120 					   sizeof(struct bpf_cpu_map_entry *),
121 					   cmap->map.numa_node);
122 	if (!cmap->cpu_map)
123 		goto free_charge;
124 
125 	return &cmap->map;
126 free_charge:
127 	bpf_map_charge_finish(&cmap->map.memory);
128 free_cmap:
129 	kfree(cmap);
130 	return ERR_PTR(err);
131 }
132 
133 static void get_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
134 {
135 	atomic_inc(&rcpu->refcnt);
136 }
137 
138 /* called from workqueue, to workaround syscall using preempt_disable */
139 static void cpu_map_kthread_stop(struct work_struct *work)
140 {
141 	struct bpf_cpu_map_entry *rcpu;
142 
143 	rcpu = container_of(work, struct bpf_cpu_map_entry, kthread_stop_wq);
144 
145 	/* Wait for flush in __cpu_map_entry_free(), via full RCU barrier,
146 	 * as it waits until all in-flight call_rcu() callbacks complete.
147 	 */
148 	rcu_barrier();
149 
150 	/* kthread_stop will wake_up_process and wait for it to complete */
151 	kthread_stop(rcpu->kthread);
152 }
153 
154 static struct sk_buff *cpu_map_build_skb(struct bpf_cpu_map_entry *rcpu,
155 					 struct xdp_frame *xdpf,
156 					 struct sk_buff *skb)
157 {
158 	unsigned int hard_start_headroom;
159 	unsigned int frame_size;
160 	void *pkt_data_start;
161 
162 	/* Part of headroom was reserved to xdpf */
163 	hard_start_headroom = sizeof(struct xdp_frame) +  xdpf->headroom;
164 
165 	/* build_skb need to place skb_shared_info after SKB end, and
166 	 * also want to know the memory "truesize".  Thus, need to
167 	 * know the memory frame size backing xdp_buff.
168 	 *
169 	 * XDP was designed to have PAGE_SIZE frames, but this
170 	 * assumption is not longer true with ixgbe and i40e.  It
171 	 * would be preferred to set frame_size to 2048 or 4096
172 	 * depending on the driver.
173 	 *   frame_size = 2048;
174 	 *   frame_len  = frame_size - sizeof(*xdp_frame);
175 	 *
176 	 * Instead, with info avail, skb_shared_info in placed after
177 	 * packet len.  This, unfortunately fakes the truesize.
178 	 * Another disadvantage of this approach, the skb_shared_info
179 	 * is not at a fixed memory location, with mixed length
180 	 * packets, which is bad for cache-line hotness.
181 	 */
182 	frame_size = SKB_DATA_ALIGN(xdpf->len + hard_start_headroom) +
183 		SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
184 
185 	pkt_data_start = xdpf->data - hard_start_headroom;
186 	skb = build_skb_around(skb, pkt_data_start, frame_size);
187 	if (unlikely(!skb))
188 		return NULL;
189 
190 	skb_reserve(skb, hard_start_headroom);
191 	__skb_put(skb, xdpf->len);
192 	if (xdpf->metasize)
193 		skb_metadata_set(skb, xdpf->metasize);
194 
195 	/* Essential SKB info: protocol and skb->dev */
196 	skb->protocol = eth_type_trans(skb, xdpf->dev_rx);
197 
198 	/* Optional SKB info, currently missing:
199 	 * - HW checksum info		(skb->ip_summed)
200 	 * - HW RX hash			(skb_set_hash)
201 	 * - RX ring dev queue index	(skb_record_rx_queue)
202 	 */
203 
204 	/* Until page_pool get SKB return path, release DMA here */
205 	xdp_release_frame(xdpf);
206 
207 	/* Allow SKB to reuse area used by xdp_frame */
208 	xdp_scrub_frame(xdpf);
209 
210 	return skb;
211 }
212 
213 static void __cpu_map_ring_cleanup(struct ptr_ring *ring)
214 {
215 	/* The tear-down procedure should have made sure that queue is
216 	 * empty.  See __cpu_map_entry_replace() and work-queue
217 	 * invoked cpu_map_kthread_stop(). Catch any broken behaviour
218 	 * gracefully and warn once.
219 	 */
220 	struct xdp_frame *xdpf;
221 
222 	while ((xdpf = ptr_ring_consume(ring)))
223 		if (WARN_ON_ONCE(xdpf))
224 			xdp_return_frame(xdpf);
225 }
226 
227 static void put_cpu_map_entry(struct bpf_cpu_map_entry *rcpu)
228 {
229 	if (atomic_dec_and_test(&rcpu->refcnt)) {
230 		/* The queue should be empty at this point */
231 		__cpu_map_ring_cleanup(rcpu->queue);
232 		ptr_ring_cleanup(rcpu->queue, NULL);
233 		kfree(rcpu->queue);
234 		kfree(rcpu);
235 	}
236 }
237 
238 #define CPUMAP_BATCH 8
239 
240 static int cpu_map_kthread_run(void *data)
241 {
242 	struct bpf_cpu_map_entry *rcpu = data;
243 
244 	set_current_state(TASK_INTERRUPTIBLE);
245 
246 	/* When kthread gives stop order, then rcpu have been disconnected
247 	 * from map, thus no new packets can enter. Remaining in-flight
248 	 * per CPU stored packets are flushed to this queue.  Wait honoring
249 	 * kthread_stop signal until queue is empty.
250 	 */
251 	while (!kthread_should_stop() || !__ptr_ring_empty(rcpu->queue)) {
252 		unsigned int drops = 0, sched = 0;
253 		void *frames[CPUMAP_BATCH];
254 		void *skbs[CPUMAP_BATCH];
255 		gfp_t gfp = __GFP_ZERO | GFP_ATOMIC;
256 		int i, n, m;
257 
258 		/* Release CPU reschedule checks */
259 		if (__ptr_ring_empty(rcpu->queue)) {
260 			set_current_state(TASK_INTERRUPTIBLE);
261 			/* Recheck to avoid lost wake-up */
262 			if (__ptr_ring_empty(rcpu->queue)) {
263 				schedule();
264 				sched = 1;
265 			} else {
266 				__set_current_state(TASK_RUNNING);
267 			}
268 		} else {
269 			sched = cond_resched();
270 		}
271 
272 		/*
273 		 * The bpf_cpu_map_entry is single consumer, with this
274 		 * kthread CPU pinned. Lockless access to ptr_ring
275 		 * consume side valid as no-resize allowed of queue.
276 		 */
277 		n = ptr_ring_consume_batched(rcpu->queue, frames, CPUMAP_BATCH);
278 
279 		for (i = 0; i < n; i++) {
280 			void *f = frames[i];
281 			struct page *page = virt_to_page(f);
282 
283 			/* Bring struct page memory area to curr CPU. Read by
284 			 * build_skb_around via page_is_pfmemalloc(), and when
285 			 * freed written by page_frag_free call.
286 			 */
287 			prefetchw(page);
288 		}
289 
290 		m = kmem_cache_alloc_bulk(skbuff_head_cache, gfp, n, skbs);
291 		if (unlikely(m == 0)) {
292 			for (i = 0; i < n; i++)
293 				skbs[i] = NULL; /* effect: xdp_return_frame */
294 			drops = n;
295 		}
296 
297 		local_bh_disable();
298 		for (i = 0; i < n; i++) {
299 			struct xdp_frame *xdpf = frames[i];
300 			struct sk_buff *skb = skbs[i];
301 			int ret;
302 
303 			skb = cpu_map_build_skb(rcpu, xdpf, skb);
304 			if (!skb) {
305 				xdp_return_frame(xdpf);
306 				continue;
307 			}
308 
309 			/* Inject into network stack */
310 			ret = netif_receive_skb_core(skb);
311 			if (ret == NET_RX_DROP)
312 				drops++;
313 		}
314 		/* Feedback loop via tracepoint */
315 		trace_xdp_cpumap_kthread(rcpu->map_id, n, drops, sched);
316 
317 		local_bh_enable(); /* resched point, may call do_softirq() */
318 	}
319 	__set_current_state(TASK_RUNNING);
320 
321 	put_cpu_map_entry(rcpu);
322 	return 0;
323 }
324 
325 static struct bpf_cpu_map_entry *__cpu_map_entry_alloc(u32 qsize, u32 cpu,
326 						       int map_id)
327 {
328 	gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
329 	struct bpf_cpu_map_entry *rcpu;
330 	struct xdp_bulk_queue *bq;
331 	int numa, err, i;
332 
333 	/* Have map->numa_node, but choose node of redirect target CPU */
334 	numa = cpu_to_node(cpu);
335 
336 	rcpu = kzalloc_node(sizeof(*rcpu), gfp, numa);
337 	if (!rcpu)
338 		return NULL;
339 
340 	/* Alloc percpu bulkq */
341 	rcpu->bulkq = __alloc_percpu_gfp(sizeof(*rcpu->bulkq),
342 					 sizeof(void *), gfp);
343 	if (!rcpu->bulkq)
344 		goto free_rcu;
345 
346 	for_each_possible_cpu(i) {
347 		bq = per_cpu_ptr(rcpu->bulkq, i);
348 		bq->obj = rcpu;
349 	}
350 
351 	/* Alloc queue */
352 	rcpu->queue = kzalloc_node(sizeof(*rcpu->queue), gfp, numa);
353 	if (!rcpu->queue)
354 		goto free_bulkq;
355 
356 	err = ptr_ring_init(rcpu->queue, qsize, gfp);
357 	if (err)
358 		goto free_queue;
359 
360 	rcpu->cpu    = cpu;
361 	rcpu->map_id = map_id;
362 	rcpu->qsize  = qsize;
363 
364 	/* Setup kthread */
365 	rcpu->kthread = kthread_create_on_node(cpu_map_kthread_run, rcpu, numa,
366 					       "cpumap/%d/map:%d", cpu, map_id);
367 	if (IS_ERR(rcpu->kthread))
368 		goto free_ptr_ring;
369 
370 	get_cpu_map_entry(rcpu); /* 1-refcnt for being in cmap->cpu_map[] */
371 	get_cpu_map_entry(rcpu); /* 1-refcnt for kthread */
372 
373 	/* Make sure kthread runs on a single CPU */
374 	kthread_bind(rcpu->kthread, cpu);
375 	wake_up_process(rcpu->kthread);
376 
377 	return rcpu;
378 
379 free_ptr_ring:
380 	ptr_ring_cleanup(rcpu->queue, NULL);
381 free_queue:
382 	kfree(rcpu->queue);
383 free_bulkq:
384 	free_percpu(rcpu->bulkq);
385 free_rcu:
386 	kfree(rcpu);
387 	return NULL;
388 }
389 
390 static void __cpu_map_entry_free(struct rcu_head *rcu)
391 {
392 	struct bpf_cpu_map_entry *rcpu;
393 
394 	/* This cpu_map_entry have been disconnected from map and one
395 	 * RCU grace-period have elapsed.  Thus, XDP cannot queue any
396 	 * new packets and cannot change/set flush_needed that can
397 	 * find this entry.
398 	 */
399 	rcpu = container_of(rcu, struct bpf_cpu_map_entry, rcu);
400 
401 	free_percpu(rcpu->bulkq);
402 	/* Cannot kthread_stop() here, last put free rcpu resources */
403 	put_cpu_map_entry(rcpu);
404 }
405 
406 /* After xchg pointer to bpf_cpu_map_entry, use the call_rcu() to
407  * ensure any driver rcu critical sections have completed, but this
408  * does not guarantee a flush has happened yet. Because driver side
409  * rcu_read_lock/unlock only protects the running XDP program.  The
410  * atomic xchg and NULL-ptr check in __cpu_map_flush() makes sure a
411  * pending flush op doesn't fail.
412  *
413  * The bpf_cpu_map_entry is still used by the kthread, and there can
414  * still be pending packets (in queue and percpu bulkq).  A refcnt
415  * makes sure to last user (kthread_stop vs. call_rcu) free memory
416  * resources.
417  *
418  * The rcu callback __cpu_map_entry_free flush remaining packets in
419  * percpu bulkq to queue.  Due to caller map_delete_elem() disable
420  * preemption, cannot call kthread_stop() to make sure queue is empty.
421  * Instead a work_queue is started for stopping kthread,
422  * cpu_map_kthread_stop, which waits for an RCU grace period before
423  * stopping kthread, emptying the queue.
424  */
425 static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
426 				    u32 key_cpu, struct bpf_cpu_map_entry *rcpu)
427 {
428 	struct bpf_cpu_map_entry *old_rcpu;
429 
430 	old_rcpu = xchg(&cmap->cpu_map[key_cpu], rcpu);
431 	if (old_rcpu) {
432 		call_rcu(&old_rcpu->rcu, __cpu_map_entry_free);
433 		INIT_WORK(&old_rcpu->kthread_stop_wq, cpu_map_kthread_stop);
434 		schedule_work(&old_rcpu->kthread_stop_wq);
435 	}
436 }
437 
438 static int cpu_map_delete_elem(struct bpf_map *map, void *key)
439 {
440 	struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
441 	u32 key_cpu = *(u32 *)key;
442 
443 	if (key_cpu >= map->max_entries)
444 		return -EINVAL;
445 
446 	/* notice caller map_delete_elem() use preempt_disable() */
447 	__cpu_map_entry_replace(cmap, key_cpu, NULL);
448 	return 0;
449 }
450 
451 static int cpu_map_update_elem(struct bpf_map *map, void *key, void *value,
452 			       u64 map_flags)
453 {
454 	struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
455 	struct bpf_cpu_map_entry *rcpu;
456 
457 	/* Array index key correspond to CPU number */
458 	u32 key_cpu = *(u32 *)key;
459 	/* Value is the queue size */
460 	u32 qsize = *(u32 *)value;
461 
462 	if (unlikely(map_flags > BPF_EXIST))
463 		return -EINVAL;
464 	if (unlikely(key_cpu >= cmap->map.max_entries))
465 		return -E2BIG;
466 	if (unlikely(map_flags == BPF_NOEXIST))
467 		return -EEXIST;
468 	if (unlikely(qsize > 16384)) /* sanity limit on qsize */
469 		return -EOVERFLOW;
470 
471 	/* Make sure CPU is a valid possible cpu */
472 	if (!cpu_possible(key_cpu))
473 		return -ENODEV;
474 
475 	if (qsize == 0) {
476 		rcpu = NULL; /* Same as deleting */
477 	} else {
478 		/* Updating qsize cause re-allocation of bpf_cpu_map_entry */
479 		rcpu = __cpu_map_entry_alloc(qsize, key_cpu, map->id);
480 		if (!rcpu)
481 			return -ENOMEM;
482 		rcpu->cmap = cmap;
483 	}
484 	rcu_read_lock();
485 	__cpu_map_entry_replace(cmap, key_cpu, rcpu);
486 	rcu_read_unlock();
487 	return 0;
488 }
489 
490 static void cpu_map_free(struct bpf_map *map)
491 {
492 	struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
493 	u32 i;
494 
495 	/* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
496 	 * so the bpf programs (can be more than one that used this map) were
497 	 * disconnected from events. Wait for outstanding critical sections in
498 	 * these programs to complete. The rcu critical section only guarantees
499 	 * no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
500 	 * It does __not__ ensure pending flush operations (if any) are
501 	 * complete.
502 	 */
503 
504 	bpf_clear_redirect_map(map);
505 	synchronize_rcu();
506 
507 	/* For cpu_map the remote CPUs can still be using the entries
508 	 * (struct bpf_cpu_map_entry).
509 	 */
510 	for (i = 0; i < cmap->map.max_entries; i++) {
511 		struct bpf_cpu_map_entry *rcpu;
512 
513 		rcpu = READ_ONCE(cmap->cpu_map[i]);
514 		if (!rcpu)
515 			continue;
516 
517 		/* bq flush and cleanup happens after RCU grace-period */
518 		__cpu_map_entry_replace(cmap, i, NULL); /* call_rcu */
519 	}
520 	bpf_map_area_free(cmap->cpu_map);
521 	kfree(cmap);
522 }
523 
524 struct bpf_cpu_map_entry *__cpu_map_lookup_elem(struct bpf_map *map, u32 key)
525 {
526 	struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
527 	struct bpf_cpu_map_entry *rcpu;
528 
529 	if (key >= map->max_entries)
530 		return NULL;
531 
532 	rcpu = READ_ONCE(cmap->cpu_map[key]);
533 	return rcpu;
534 }
535 
536 static void *cpu_map_lookup_elem(struct bpf_map *map, void *key)
537 {
538 	struct bpf_cpu_map_entry *rcpu =
539 		__cpu_map_lookup_elem(map, *(u32 *)key);
540 
541 	return rcpu ? &rcpu->qsize : NULL;
542 }
543 
544 static int cpu_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
545 {
546 	struct bpf_cpu_map *cmap = container_of(map, struct bpf_cpu_map, map);
547 	u32 index = key ? *(u32 *)key : U32_MAX;
548 	u32 *next = next_key;
549 
550 	if (index >= cmap->map.max_entries) {
551 		*next = 0;
552 		return 0;
553 	}
554 
555 	if (index == cmap->map.max_entries - 1)
556 		return -ENOENT;
557 	*next = index + 1;
558 	return 0;
559 }
560 
561 const struct bpf_map_ops cpu_map_ops = {
562 	.map_alloc		= cpu_map_alloc,
563 	.map_free		= cpu_map_free,
564 	.map_delete_elem	= cpu_map_delete_elem,
565 	.map_update_elem	= cpu_map_update_elem,
566 	.map_lookup_elem	= cpu_map_lookup_elem,
567 	.map_get_next_key	= cpu_map_get_next_key,
568 	.map_check_btf		= map_check_no_btf,
569 };
570 
571 static int bq_flush_to_queue(struct xdp_bulk_queue *bq)
572 {
573 	struct bpf_cpu_map_entry *rcpu = bq->obj;
574 	unsigned int processed = 0, drops = 0;
575 	const int to_cpu = rcpu->cpu;
576 	struct ptr_ring *q;
577 	int i;
578 
579 	if (unlikely(!bq->count))
580 		return 0;
581 
582 	q = rcpu->queue;
583 	spin_lock(&q->producer_lock);
584 
585 	for (i = 0; i < bq->count; i++) {
586 		struct xdp_frame *xdpf = bq->q[i];
587 		int err;
588 
589 		err = __ptr_ring_produce(q, xdpf);
590 		if (err) {
591 			drops++;
592 			xdp_return_frame_rx_napi(xdpf);
593 		}
594 		processed++;
595 	}
596 	bq->count = 0;
597 	spin_unlock(&q->producer_lock);
598 
599 	__list_del_clearprev(&bq->flush_node);
600 
601 	/* Feedback loop via tracepoints */
602 	trace_xdp_cpumap_enqueue(rcpu->map_id, processed, drops, to_cpu);
603 	return 0;
604 }
605 
606 /* Runs under RCU-read-side, plus in softirq under NAPI protection.
607  * Thus, safe percpu variable access.
608  */
609 static int bq_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_frame *xdpf)
610 {
611 	struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
612 	struct xdp_bulk_queue *bq = this_cpu_ptr(rcpu->bulkq);
613 
614 	if (unlikely(bq->count == CPU_MAP_BULK_SIZE))
615 		bq_flush_to_queue(bq);
616 
617 	/* Notice, xdp_buff/page MUST be queued here, long enough for
618 	 * driver to code invoking us to finished, due to driver
619 	 * (e.g. ixgbe) recycle tricks based on page-refcnt.
620 	 *
621 	 * Thus, incoming xdp_frame is always queued here (else we race
622 	 * with another CPU on page-refcnt and remaining driver code).
623 	 * Queue time is very short, as driver will invoke flush
624 	 * operation, when completing napi->poll call.
625 	 */
626 	bq->q[bq->count++] = xdpf;
627 
628 	if (!bq->flush_node.prev)
629 		list_add(&bq->flush_node, flush_list);
630 
631 	return 0;
632 }
633 
634 int cpu_map_enqueue(struct bpf_cpu_map_entry *rcpu, struct xdp_buff *xdp,
635 		    struct net_device *dev_rx)
636 {
637 	struct xdp_frame *xdpf;
638 
639 	xdpf = convert_to_xdp_frame(xdp);
640 	if (unlikely(!xdpf))
641 		return -EOVERFLOW;
642 
643 	/* Info needed when constructing SKB on remote CPU */
644 	xdpf->dev_rx = dev_rx;
645 
646 	bq_enqueue(rcpu, xdpf);
647 	return 0;
648 }
649 
650 void __cpu_map_flush(void)
651 {
652 	struct list_head *flush_list = this_cpu_ptr(&cpu_map_flush_list);
653 	struct xdp_bulk_queue *bq, *tmp;
654 
655 	list_for_each_entry_safe(bq, tmp, flush_list, flush_node) {
656 		bq_flush_to_queue(bq);
657 
658 		/* If already running, costs spin_lock_irqsave + smb_mb */
659 		wake_up_process(bq->obj->kthread);
660 	}
661 }
662 
663 static int __init cpu_map_init(void)
664 {
665 	int cpu;
666 
667 	for_each_possible_cpu(cpu)
668 		INIT_LIST_HEAD(&per_cpu(cpu_map_flush_list, cpu));
669 	return 0;
670 }
671 
672 subsys_initcall(cpu_map_init);
673