1/* SPDX-License-Identifier: GPL-2.0 */
2/* XDP user-space ring structure
3 * Copyright(c) 2018 Intel Corporation.
4 */
5
6#ifndef _LINUX_XSK_QUEUE_H
7#define _LINUX_XSK_QUEUE_H
8
9#include <linux/types.h>
10#include <linux/if_xdp.h>
11#include <net/xdp_sock.h>
12#include <net/xsk_buff_pool.h>
13
14#include "xsk.h"
15
16struct xdp_ring {
17 u32 producer ____cacheline_aligned_in_smp;
18 /* Hinder the adjacent cache prefetcher to prefetch the consumer
19 * pointer if the producer pointer is touched and vice versa.
20 */
21 u32 pad1 ____cacheline_aligned_in_smp;
22 u32 consumer ____cacheline_aligned_in_smp;
23 u32 pad2 ____cacheline_aligned_in_smp;
24 u32 flags;
25 u32 pad3 ____cacheline_aligned_in_smp;
26};
27
28/* Used for the RX and TX queues for packets */
29struct xdp_rxtx_ring {
30 struct xdp_ring ptrs;
31 struct xdp_desc desc[] ____cacheline_aligned_in_smp;
32};
33
34/* Used for the fill and completion queues for buffers */
35struct xdp_umem_ring {
36 struct xdp_ring ptrs;
37 u64 desc[] ____cacheline_aligned_in_smp;
38};
39
40struct xsk_queue {
41 u32 ring_mask;
42 u32 nentries;
43 u32 cached_prod;
44 u32 cached_cons;
45 struct xdp_ring *ring;
46 u64 invalid_descs;
47 u64 queue_empty_descs;
48 size_t ring_vmalloc_size;
49};
50
51struct parsed_desc {
52 u32 mb;
53 u32 valid;
54};
55
56/* The structure of the shared state of the rings are a simple
57 * circular buffer, as outlined in
58 * Documentation/core-api/circular-buffers.rst. For the Rx and
59 * completion ring, the kernel is the producer and user space is the
60 * consumer. For the Tx and fill rings, the kernel is the consumer and
61 * user space is the producer.
62 *
63 * producer consumer
64 *
65 * if (LOAD ->consumer) { (A) LOAD.acq ->producer (C)
66 * STORE $data LOAD $data
67 * STORE.rel ->producer (B) STORE.rel ->consumer (D)
68 * }
69 *
70 * (A) pairs with (D), and (B) pairs with (C).
71 *
72 * Starting with (B), it protects the data from being written after
73 * the producer pointer. If this barrier was missing, the consumer
74 * could observe the producer pointer being set and thus load the data
75 * before the producer has written the new data. The consumer would in
76 * this case load the old data.
77 *
78 * (C) protects the consumer from speculatively loading the data before
79 * the producer pointer actually has been read. If we do not have this
80 * barrier, some architectures could load old data as speculative loads
81 * are not discarded as the CPU does not know there is a dependency
82 * between ->producer and data.
83 *
84 * (A) is a control dependency that separates the load of ->consumer
85 * from the stores of $data. In case ->consumer indicates there is no
86 * room in the buffer to store $data we do not. The dependency will
87 * order both of the stores after the loads. So no barrier is needed.
88 *
89 * (D) protects the load of the data to be observed to happen after the
90 * store of the consumer pointer. If we did not have this memory
91 * barrier, the producer could observe the consumer pointer being set
92 * and overwrite the data with a new value before the consumer got the
93 * chance to read the old value. The consumer would thus miss reading
94 * the old entry and very likely read the new entry twice, once right
95 * now and again after circling through the ring.
96 */
97
98/* The operations on the rings are the following:
99 *
100 * producer consumer
101 *
102 * RESERVE entries PEEK in the ring for entries
103 * WRITE data into the ring READ data from the ring
104 * SUBMIT entries RELEASE entries
105 *
106 * The producer reserves one or more entries in the ring. It can then
107 * fill in these entries and finally submit them so that they can be
108 * seen and read by the consumer.
109 *
110 * The consumer peeks into the ring to see if the producer has written
111 * any new entries. If so, the consumer can then read these entries
112 * and when it is done reading them release them back to the producer
113 * so that the producer can use these slots to fill in new entries.
114 *
115 * The function names below reflect these operations.
116 */
117
118/* Functions that read and validate content from consumer rings. */
119
120static inline void __xskq_cons_read_addr_unchecked(struct xsk_queue *q, u32 cached_cons, u64 *addr)
121{
122 struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
123 u32 idx = cached_cons & q->ring_mask;
124
125 *addr = ring->desc[idx];
126}
127
128static inline bool xskq_cons_read_addr_unchecked(struct xsk_queue *q, u64 *addr)
129{
130 if (q->cached_cons != q->cached_prod) {
131 __xskq_cons_read_addr_unchecked(q, cached_cons: q->cached_cons, addr);
132 return true;
133 }
134
135 return false;
136}
137
138static inline bool xp_unused_options_set(u32 options)
139{
140 return options & ~XDP_PKT_CONTD;
141}
142
143static inline bool xp_aligned_validate_desc(struct xsk_buff_pool *pool,
144 struct xdp_desc *desc)
145{
146 u64 offset = desc->addr & (pool->chunk_size - 1);
147
148 if (!desc->len)
149 return false;
150
151 if (offset + desc->len > pool->chunk_size)
152 return false;
153
154 if (desc->addr >= pool->addrs_cnt)
155 return false;
156
157 if (xp_unused_options_set(options: desc->options))
158 return false;
159 return true;
160}
161
162static inline bool xp_unaligned_validate_desc(struct xsk_buff_pool *pool,
163 struct xdp_desc *desc)
164{
165 u64 addr = xp_unaligned_add_offset_to_addr(addr: desc->addr);
166
167 if (!desc->len)
168 return false;
169
170 if (desc->len > pool->chunk_size)
171 return false;
172
173 if (addr >= pool->addrs_cnt || addr + desc->len > pool->addrs_cnt ||
174 xp_desc_crosses_non_contig_pg(pool, addr, len: desc->len))
175 return false;
176
177 if (xp_unused_options_set(options: desc->options))
178 return false;
179 return true;
180}
181
182static inline bool xp_validate_desc(struct xsk_buff_pool *pool,
183 struct xdp_desc *desc)
184{
185 return pool->unaligned ? xp_unaligned_validate_desc(pool, desc) :
186 xp_aligned_validate_desc(pool, desc);
187}
188
189static inline bool xskq_has_descs(struct xsk_queue *q)
190{
191 return q->cached_cons != q->cached_prod;
192}
193
194static inline bool xskq_cons_is_valid_desc(struct xsk_queue *q,
195 struct xdp_desc *d,
196 struct xsk_buff_pool *pool)
197{
198 if (!xp_validate_desc(pool, desc: d)) {
199 q->invalid_descs++;
200 return false;
201 }
202 return true;
203}
204
205static inline bool xskq_cons_read_desc(struct xsk_queue *q,
206 struct xdp_desc *desc,
207 struct xsk_buff_pool *pool)
208{
209 if (q->cached_cons != q->cached_prod) {
210 struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
211 u32 idx = q->cached_cons & q->ring_mask;
212
213 *desc = ring->desc[idx];
214 return xskq_cons_is_valid_desc(q, d: desc, pool);
215 }
216
217 q->queue_empty_descs++;
218 return false;
219}
220
221static inline void xskq_cons_release_n(struct xsk_queue *q, u32 cnt)
222{
223 q->cached_cons += cnt;
224}
225
226static inline void parse_desc(struct xsk_queue *q, struct xsk_buff_pool *pool,
227 struct xdp_desc *desc, struct parsed_desc *parsed)
228{
229 parsed->valid = xskq_cons_is_valid_desc(q, d: desc, pool);
230 parsed->mb = xp_mb_desc(desc);
231}
232
233static inline
234u32 xskq_cons_read_desc_batch(struct xsk_queue *q, struct xsk_buff_pool *pool,
235 u32 max)
236{
237 u32 cached_cons = q->cached_cons, nb_entries = 0;
238 struct xdp_desc *descs = pool->tx_descs;
239 u32 total_descs = 0, nr_frags = 0;
240
241 /* track first entry, if stumble upon *any* invalid descriptor, rewind
242 * current packet that consists of frags and stop the processing
243 */
244 while (cached_cons != q->cached_prod && nb_entries < max) {
245 struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
246 u32 idx = cached_cons & q->ring_mask;
247 struct parsed_desc parsed;
248
249 descs[nb_entries] = ring->desc[idx];
250 cached_cons++;
251 parse_desc(q, pool, desc: &descs[nb_entries], parsed: &parsed);
252 if (unlikely(!parsed.valid))
253 break;
254
255 if (likely(!parsed.mb)) {
256 total_descs += (nr_frags + 1);
257 nr_frags = 0;
258 } else {
259 nr_frags++;
260 if (nr_frags == pool->netdev->xdp_zc_max_segs) {
261 nr_frags = 0;
262 break;
263 }
264 }
265 nb_entries++;
266 }
267
268 cached_cons -= nr_frags;
269 /* Release valid plus any invalid entries */
270 xskq_cons_release_n(q, cnt: cached_cons - q->cached_cons);
271 return total_descs;
272}
273
274/* Functions for consumers */
275
276static inline void __xskq_cons_release(struct xsk_queue *q)
277{
278 smp_store_release(&q->ring->consumer, q->cached_cons); /* D, matchees A */
279}
280
281static inline void __xskq_cons_peek(struct xsk_queue *q)
282{
283 /* Refresh the local pointer */
284 q->cached_prod = smp_load_acquire(&q->ring->producer); /* C, matches B */
285}
286
287static inline void xskq_cons_get_entries(struct xsk_queue *q)
288{
289 __xskq_cons_release(q);
290 __xskq_cons_peek(q);
291}
292
293static inline u32 xskq_cons_nb_entries(struct xsk_queue *q, u32 max)
294{
295 u32 entries = q->cached_prod - q->cached_cons;
296
297 if (entries >= max)
298 return max;
299
300 __xskq_cons_peek(q);
301 entries = q->cached_prod - q->cached_cons;
302
303 return entries >= max ? max : entries;
304}
305
306static inline bool xskq_cons_has_entries(struct xsk_queue *q, u32 cnt)
307{
308 return xskq_cons_nb_entries(q, max: cnt) >= cnt;
309}
310
311static inline bool xskq_cons_peek_addr_unchecked(struct xsk_queue *q, u64 *addr)
312{
313 if (q->cached_prod == q->cached_cons)
314 xskq_cons_get_entries(q);
315 return xskq_cons_read_addr_unchecked(q, addr);
316}
317
318static inline bool xskq_cons_peek_desc(struct xsk_queue *q,
319 struct xdp_desc *desc,
320 struct xsk_buff_pool *pool)
321{
322 if (q->cached_prod == q->cached_cons)
323 xskq_cons_get_entries(q);
324 return xskq_cons_read_desc(q, desc, pool);
325}
326
327/* To improve performance in the xskq_cons_release functions, only update local state here.
328 * Reflect this to global state when we get new entries from the ring in
329 * xskq_cons_get_entries() and whenever Rx or Tx processing are completed in the NAPI loop.
330 */
331static inline void xskq_cons_release(struct xsk_queue *q)
332{
333 q->cached_cons++;
334}
335
336static inline void xskq_cons_cancel_n(struct xsk_queue *q, u32 cnt)
337{
338 q->cached_cons -= cnt;
339}
340
341static inline u32 xskq_cons_present_entries(struct xsk_queue *q)
342{
343 /* No barriers needed since data is not accessed */
344 return READ_ONCE(q->ring->producer) - READ_ONCE(q->ring->consumer);
345}
346
347/* Functions for producers */
348
349static inline u32 xskq_prod_nb_free(struct xsk_queue *q, u32 max)
350{
351 u32 free_entries = q->nentries - (q->cached_prod - q->cached_cons);
352
353 if (free_entries >= max)
354 return max;
355
356 /* Refresh the local tail pointer */
357 q->cached_cons = READ_ONCE(q->ring->consumer);
358 free_entries = q->nentries - (q->cached_prod - q->cached_cons);
359
360 return free_entries >= max ? max : free_entries;
361}
362
363static inline bool xskq_prod_is_full(struct xsk_queue *q)
364{
365 return xskq_prod_nb_free(q, max: 1) ? false : true;
366}
367
368static inline void xskq_prod_cancel_n(struct xsk_queue *q, u32 cnt)
369{
370 q->cached_prod -= cnt;
371}
372
373static inline int xskq_prod_reserve(struct xsk_queue *q)
374{
375 if (xskq_prod_is_full(q))
376 return -ENOSPC;
377
378 /* A, matches D */
379 q->cached_prod++;
380 return 0;
381}
382
383static inline int xskq_prod_reserve_addr(struct xsk_queue *q, u64 addr)
384{
385 struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
386
387 if (xskq_prod_is_full(q))
388 return -ENOSPC;
389
390 /* A, matches D */
391 ring->desc[q->cached_prod++ & q->ring_mask] = addr;
392 return 0;
393}
394
395static inline void xskq_prod_write_addr_batch(struct xsk_queue *q, struct xdp_desc *descs,
396 u32 nb_entries)
397{
398 struct xdp_umem_ring *ring = (struct xdp_umem_ring *)q->ring;
399 u32 i, cached_prod;
400
401 /* A, matches D */
402 cached_prod = q->cached_prod;
403 for (i = 0; i < nb_entries; i++)
404 ring->desc[cached_prod++ & q->ring_mask] = descs[i].addr;
405 q->cached_prod = cached_prod;
406}
407
408static inline int xskq_prod_reserve_desc(struct xsk_queue *q,
409 u64 addr, u32 len, u32 flags)
410{
411 struct xdp_rxtx_ring *ring = (struct xdp_rxtx_ring *)q->ring;
412 u32 idx;
413
414 if (xskq_prod_is_full(q))
415 return -ENOBUFS;
416
417 /* A, matches D */
418 idx = q->cached_prod++ & q->ring_mask;
419 ring->desc[idx].addr = addr;
420 ring->desc[idx].len = len;
421 ring->desc[idx].options = flags;
422
423 return 0;
424}
425
426static inline void __xskq_prod_submit(struct xsk_queue *q, u32 idx)
427{
428 smp_store_release(&q->ring->producer, idx); /* B, matches C */
429}
430
431static inline void xskq_prod_submit(struct xsk_queue *q)
432{
433 __xskq_prod_submit(q, idx: q->cached_prod);
434}
435
436static inline void xskq_prod_submit_n(struct xsk_queue *q, u32 nb_entries)
437{
438 __xskq_prod_submit(q, idx: q->ring->producer + nb_entries);
439}
440
441static inline bool xskq_prod_is_empty(struct xsk_queue *q)
442{
443 /* No barriers needed since data is not accessed */
444 return READ_ONCE(q->ring->consumer) == READ_ONCE(q->ring->producer);
445}
446
447/* For both producers and consumers */
448
449static inline u64 xskq_nb_invalid_descs(struct xsk_queue *q)
450{
451 return q ? q->invalid_descs : 0;
452}
453
454static inline u64 xskq_nb_queue_empty_descs(struct xsk_queue *q)
455{
456 return q ? q->queue_empty_descs : 0;
457}
458
459struct xsk_queue *xskq_create(u32 nentries, bool umem_queue);
460void xskq_destroy(struct xsk_queue *q_ops);
461
462#endif /* _LINUX_XSK_QUEUE_H */
463

source code of linux/net/xdp/xsk_queue.h