summaryrefslogtreecommitdiff
path: root/drivers/net/ethernet/google/gve/gve_tx.c
blob: 6938f3a939d64654ef9982865d34b18d4005e6fa (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
// SPDX-License-Identifier: (GPL-2.0 OR MIT)
/* Google virtual Ethernet (gve) driver
 *
 * Copyright (C) 2015-2019 Google, Inc.
 */

#include "gve.h"
#include "gve_adminq.h"
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/vmalloc.h>
#include <linux/skbuff.h>

static inline void gve_tx_put_doorbell(struct gve_priv *priv,
				       struct gve_queue_resources *q_resources,
				       u32 val)
{
	iowrite32be(val, &priv->db_bar2[be32_to_cpu(q_resources->db_index)]);
}

/* gvnic can only transmit from a Registered Segment.
 * We copy skb payloads into the registered segment before writing Tx
 * descriptors and ringing the Tx doorbell.
 *
 * gve_tx_fifo_* manages the Registered Segment as a FIFO - clients must
 * free allocations in the order they were allocated.
 */

static int gve_tx_fifo_init(struct gve_priv *priv, struct gve_tx_fifo *fifo)
{
	fifo->base = vmap(fifo->qpl->pages, fifo->qpl->num_entries, VM_MAP,
			  PAGE_KERNEL);
	if (unlikely(!fifo->base)) {
		netif_err(priv, drv, priv->dev, "Failed to vmap fifo, qpl_id = %d\n",
			  fifo->qpl->id);
		return -ENOMEM;
	}

	fifo->size = fifo->qpl->num_entries * PAGE_SIZE;
	atomic_set(&fifo->available, fifo->size);
	fifo->head = 0;
	return 0;
}

static void gve_tx_fifo_release(struct gve_priv *priv, struct gve_tx_fifo *fifo)
{
	WARN(atomic_read(&fifo->available) != fifo->size,
	     "Releasing non-empty fifo");

	vunmap(fifo->base);
}

static int gve_tx_fifo_pad_alloc_one_frag(struct gve_tx_fifo *fifo,
					  size_t bytes)
{
	return (fifo->head + bytes < fifo->size) ? 0 : fifo->size - fifo->head;
}

static bool gve_tx_fifo_can_alloc(struct gve_tx_fifo *fifo, size_t bytes)
{
	return (atomic_read(&fifo->available) <= bytes) ? false : true;
}

/* gve_tx_alloc_fifo - Allocate fragment(s) from Tx FIFO
 * @fifo: FIFO to allocate from
 * @bytes: Allocation size
 * @iov: Scatter-gather elements to fill with allocation fragment base/len
 *
 * Returns number of valid elements in iov[] or negative on error.
 *
 * Allocations from a given FIFO must be externally synchronized but concurrent
 * allocation and frees are allowed.
 */
static int gve_tx_alloc_fifo(struct gve_tx_fifo *fifo, size_t bytes,
			     struct gve_tx_iovec iov[2])
{
	size_t overflow, padding;
	u32 aligned_head;
	int nfrags = 0;

	if (!bytes)
		return 0;

	/* This check happens before we know how much padding is needed to
	 * align to a cacheline boundary for the payload, but that is fine,
	 * because the FIFO head always start aligned, and the FIFO's boundaries
	 * are aligned, so if there is space for the data, there is space for
	 * the padding to the next alignment.
	 */
	WARN(!gve_tx_fifo_can_alloc(fifo, bytes),
	     "Reached %s when there's not enough space in the fifo", __func__);

	nfrags++;

	iov[0].iov_offset = fifo->head;
	iov[0].iov_len = bytes;
	fifo->head += bytes;

	if (fifo->head > fifo->size) {
		/* If the allocation did not fit in the tail fragment of the
		 * FIFO, also use the head fragment.
		 */
		nfrags++;
		overflow = fifo->head - fifo->size;
		iov[0].iov_len -= overflow;
		iov[1].iov_offset = 0;	/* Start of fifo*/
		iov[1].iov_len = overflow;

		fifo->head = overflow;
	}

	/* Re-align to a cacheline boundary */
	aligned_head = L1_CACHE_ALIGN(fifo->head);
	padding = aligned_head - fifo->head;
	iov[nfrags - 1].iov_padding = padding;
	atomic_sub(bytes + padding, &fifo->available);
	fifo->head = aligned_head;

	if (fifo->head == fifo->size)
		fifo->head = 0;

	return nfrags;
}

/* gve_tx_free_fifo - Return space to Tx FIFO
 * @fifo: FIFO to return fragments to
 * @bytes: Bytes to free
 */
static void gve_tx_free_fifo(struct gve_tx_fifo *fifo, size_t bytes)
{
	atomic_add(bytes, &fifo->available);
}

static void gve_tx_remove_from_block(struct gve_priv *priv, int queue_idx)
{
	struct gve_notify_block *block =
			&priv->ntfy_blocks[gve_tx_idx_to_ntfy(priv, queue_idx)];

	block->tx = NULL;
}

static int gve_clean_tx_done(struct gve_priv *priv, struct gve_tx_ring *tx,
			     u32 to_do, bool try_to_wake);

static void gve_tx_free_ring(struct gve_priv *priv, int idx)
{
	struct gve_tx_ring *tx = &priv->tx[idx];
	struct device *hdev = &priv->pdev->dev;
	size_t bytes;
	u32 slots;

	gve_tx_remove_from_block(priv, idx);
	slots = tx->mask + 1;
	gve_clean_tx_done(priv, tx, tx->req, false);
	netdev_tx_reset_queue(tx->netdev_txq);

	dma_free_coherent(hdev, sizeof(*tx->q_resources),
			  tx->q_resources, tx->q_resources_bus);
	tx->q_resources = NULL;

	if (!tx->raw_addressing) {
		gve_tx_fifo_release(priv, &tx->tx_fifo);
		gve_unassign_qpl(priv, tx->tx_fifo.qpl->id);
		tx->tx_fifo.qpl = NULL;
	}

	bytes = sizeof(*tx->desc) * slots;
	dma_free_coherent(hdev, bytes, tx->desc, tx->bus);
	tx->desc = NULL;

	vfree(tx->info);
	tx->info = NULL;

	netif_dbg(priv, drv, priv->dev, "freed tx queue %d\n", idx);
}

static void gve_tx_add_to_block(struct gve_priv *priv, int queue_idx)
{
	int ntfy_idx = gve_tx_idx_to_ntfy(priv, queue_idx);
	struct gve_notify_block *block = &priv->ntfy_blocks[ntfy_idx];
	struct gve_tx_ring *tx = &priv->tx[queue_idx];

	block->tx = tx;
	tx->ntfy_id = ntfy_idx;
}

static int gve_tx_alloc_ring(struct gve_priv *priv, int idx)
{
	struct gve_tx_ring *tx = &priv->tx[idx];
	struct device *hdev = &priv->pdev->dev;
	u32 slots = priv->tx_desc_cnt;
	size_t bytes;

	/* Make sure everything is zeroed to start */
	memset(tx, 0, sizeof(*tx));
	tx->q_num = idx;

	tx->mask = slots - 1;

	/* alloc metadata */
	tx->info = vzalloc(sizeof(*tx->info) * slots);
	if (!tx->info)
		return -ENOMEM;

	/* alloc tx queue */
	bytes = sizeof(*tx->desc) * slots;
	tx->desc = dma_alloc_coherent(hdev, bytes, &tx->bus, GFP_KERNEL);
	if (!tx->desc)
		goto abort_with_info;

	tx->raw_addressing = priv->raw_addressing;
	tx->dev = &priv->pdev->dev;
	if (!tx->raw_addressing) {
		tx->tx_fifo.qpl = gve_assign_tx_qpl(priv);

		/* map Tx FIFO */
		if (gve_tx_fifo_init(priv, &tx->tx_fifo))
			goto abort_with_desc;
	}

	tx->q_resources =
		dma_alloc_coherent(hdev,
				   sizeof(*tx->q_resources),
				   &tx->q_resources_bus,
				   GFP_KERNEL);
	if (!tx->q_resources)
		goto abort_with_fifo;

	netif_dbg(priv, drv, priv->dev, "tx[%d]->bus=%lx\n", idx,
		  (unsigned long)tx->bus);
	tx->netdev_txq = netdev_get_tx_queue(priv->dev, idx);
	gve_tx_add_to_block(priv, idx);

	return 0;

abort_with_fifo:
	if (!tx->raw_addressing)
		gve_tx_fifo_release(priv, &tx->tx_fifo);
abort_with_desc:
	dma_free_coherent(hdev, bytes, tx->desc, tx->bus);
	tx->desc = NULL;
abort_with_info:
	vfree(tx->info);
	tx->info = NULL;
	return -ENOMEM;
}

int gve_tx_alloc_rings(struct gve_priv *priv)
{
	int err = 0;
	int i;

	for (i = 0; i < priv->tx_cfg.num_queues; i++) {
		err = gve_tx_alloc_ring(priv, i);
		if (err) {
			netif_err(priv, drv, priv->dev,
				  "Failed to alloc tx ring=%d: err=%d\n",
				  i, err);
			break;
		}
	}
	/* Unallocate if there was an error */
	if (err) {
		int j;

		for (j = 0; j < i; j++)
			gve_tx_free_ring(priv, j);
	}
	return err;
}

void gve_tx_free_rings(struct gve_priv *priv)
{
	int i;

	for (i = 0; i < priv->tx_cfg.num_queues; i++)
		gve_tx_free_ring(priv, i);
}

/* gve_tx_avail - Calculates the number of slots available in the ring
 * @tx: tx ring to check
 *
 * Returns the number of slots available
 *
 * The capacity of the queue is mask + 1. We don't need to reserve an entry.
 **/
static inline u32 gve_tx_avail(struct gve_tx_ring *tx)
{
	return tx->mask + 1 - (tx->req - tx->done);
}

static inline int gve_skb_fifo_bytes_required(struct gve_tx_ring *tx,
					      struct sk_buff *skb)
{
	int pad_bytes, align_hdr_pad;
	int bytes;
	int hlen;

	hlen = skb_is_gso(skb) ? skb_checksum_start_offset(skb) +
				 tcp_hdrlen(skb) : skb_headlen(skb);

	pad_bytes = gve_tx_fifo_pad_alloc_one_frag(&tx->tx_fifo,
						   hlen);
	/* We need to take into account the header alignment padding. */
	align_hdr_pad = L1_CACHE_ALIGN(hlen) - hlen;
	bytes = align_hdr_pad + pad_bytes + skb->len;

	return bytes;
}

/* The most descriptors we could need is MAX_SKB_FRAGS + 3 : 1 for each skb frag,
 * +1 for the skb linear portion, +1 for when tcp hdr needs to be in separate descriptor,
 * and +1 if the payload wraps to the beginning of the FIFO.
 */
#define MAX_TX_DESC_NEEDED	(MAX_SKB_FRAGS + 3)
static void gve_tx_unmap_buf(struct device *dev, struct gve_tx_buffer_state *info)
{
	if (info->skb) {
		dma_unmap_single(dev, dma_unmap_addr(&info->buf, dma),
				 dma_unmap_len(&info->buf, len),
				 DMA_TO_DEVICE);
		dma_unmap_len_set(&info->buf, len, 0);
	} else {
		dma_unmap_page(dev, dma_unmap_addr(&info->buf, dma),
			       dma_unmap_len(&info->buf, len),
			       DMA_TO_DEVICE);
		dma_unmap_len_set(&info->buf, len, 0);
	}
}

/* Check if sufficient resources (descriptor ring space, FIFO space) are
 * available to transmit the given number of bytes.
 */
static inline bool gve_can_tx(struct gve_tx_ring *tx, int bytes_required)
{
	bool can_alloc = true;

	if (!tx->raw_addressing)
		can_alloc = gve_tx_fifo_can_alloc(&tx->tx_fifo, bytes_required);

	return (gve_tx_avail(tx) >= MAX_TX_DESC_NEEDED && can_alloc);
}

/* Stops the queue if the skb cannot be transmitted. */
static int gve_maybe_stop_tx(struct gve_tx_ring *tx, struct sk_buff *skb)
{
	int bytes_required = 0;

	if (!tx->raw_addressing)
		bytes_required = gve_skb_fifo_bytes_required(tx, skb);

	if (likely(gve_can_tx(tx, bytes_required)))
		return 0;

	/* No space, so stop the queue */
	tx->stop_queue++;
	netif_tx_stop_queue(tx->netdev_txq);
	smp_mb();	/* sync with restarting queue in gve_clean_tx_done() */

	/* Now check for resources again, in case gve_clean_tx_done() freed
	 * resources after we checked and we stopped the queue after
	 * gve_clean_tx_done() checked.
	 *
	 * gve_maybe_stop_tx()			gve_clean_tx_done()
	 *   nsegs/can_alloc test failed
	 *					  gve_tx_free_fifo()
	 *					  if (tx queue stopped)
	 *					    netif_tx_queue_wake()
	 *   netif_tx_stop_queue()
	 *   Need to check again for space here!
	 */
	if (likely(!gve_can_tx(tx, bytes_required)))
		return -EBUSY;

	netif_tx_start_queue(tx->netdev_txq);
	tx->wake_queue++;
	return 0;
}

static void gve_tx_fill_pkt_desc(union gve_tx_desc *pkt_desc,
				 struct sk_buff *skb, bool is_gso,
				 int l4_hdr_offset, u32 desc_cnt,
				 u16 hlen, u64 addr)
{
	/* l4_hdr_offset and csum_offset are in units of 16-bit words */
	if (is_gso) {
		pkt_desc->pkt.type_flags = GVE_TXD_TSO | GVE_TXF_L4CSUM;
		pkt_desc->pkt.l4_csum_offset = skb->csum_offset >> 1;
		pkt_desc->pkt.l4_hdr_offset = l4_hdr_offset >> 1;
	} else if (likely(skb->ip_summed == CHECKSUM_PARTIAL)) {
		pkt_desc->pkt.type_flags = GVE_TXD_STD | GVE_TXF_L4CSUM;
		pkt_desc->pkt.l4_csum_offset = skb->csum_offset >> 1;
		pkt_desc->pkt.l4_hdr_offset = l4_hdr_offset >> 1;
	} else {
		pkt_desc->pkt.type_flags = GVE_TXD_STD;
		pkt_desc->pkt.l4_csum_offset = 0;
		pkt_desc->pkt.l4_hdr_offset = 0;
	}
	pkt_desc->pkt.desc_cnt = desc_cnt;
	pkt_desc->pkt.len = cpu_to_be16(skb->len);
	pkt_desc->pkt.seg_len = cpu_to_be16(hlen);
	pkt_desc->pkt.seg_addr = cpu_to_be64(addr);
}

static void gve_tx_fill_seg_desc(union gve_tx_desc *seg_desc,
				 struct sk_buff *skb, bool is_gso,
				 u16 len, u64 addr)
{
	seg_desc->seg.type_flags = GVE_TXD_SEG;
	if (is_gso) {
		if (skb_is_gso_v6(skb))
			seg_desc->seg.type_flags |= GVE_TXSF_IPV6;
		seg_desc->seg.l3_offset = skb_network_offset(skb) >> 1;
		seg_desc->seg.mss = cpu_to_be16(skb_shinfo(skb)->gso_size);
	}
	seg_desc->seg.seg_len = cpu_to_be16(len);
	seg_desc->seg.seg_addr = cpu_to_be64(addr);
}

static void gve_dma_sync_for_device(struct device *dev, dma_addr_t *page_buses,
				    u64 iov_offset, u64 iov_len)
{
	u64 last_page = (iov_offset + iov_len - 1) / PAGE_SIZE;
	u64 first_page = iov_offset / PAGE_SIZE;
	u64 page;

	for (page = first_page; page <= last_page; page++)
		dma_sync_single_for_device(dev, page_buses[page], PAGE_SIZE, DMA_TO_DEVICE);
}

static int gve_tx_add_skb_copy(struct gve_priv *priv, struct gve_tx_ring *tx, struct sk_buff *skb)
{
	int pad_bytes, hlen, hdr_nfrags, payload_nfrags, l4_hdr_offset;
	union gve_tx_desc *pkt_desc, *seg_desc;
	struct gve_tx_buffer_state *info;
	bool is_gso = skb_is_gso(skb);
	u32 idx = tx->req & tx->mask;
	int payload_iov = 2;
	int copy_offset;
	u32 next_idx;
	int i;

	info = &tx->info[idx];
	pkt_desc = &tx->desc[idx];

	l4_hdr_offset = skb_checksum_start_offset(skb);
	/* If the skb is gso, then we want the tcp header in the first segment
	 * otherwise we want the linear portion of the skb (which will contain
	 * the checksum because skb->csum_start and skb->csum_offset are given
	 * relative to skb->head) in the first segment.
	 */
	hlen = is_gso ? l4_hdr_offset + tcp_hdrlen(skb) :
			skb_headlen(skb);

	info->skb =  skb;
	/* We don't want to split the header, so if necessary, pad to the end
	 * of the fifo and then put the header at the beginning of the fifo.
	 */
	pad_bytes = gve_tx_fifo_pad_alloc_one_frag(&tx->tx_fifo, hlen);
	hdr_nfrags = gve_tx_alloc_fifo(&tx->tx_fifo, hlen + pad_bytes,
				       &info->iov[0]);
	WARN(!hdr_nfrags, "hdr_nfrags should never be 0!");
	payload_nfrags = gve_tx_alloc_fifo(&tx->tx_fifo, skb->len - hlen,
					   &info->iov[payload_iov]);

	gve_tx_fill_pkt_desc(pkt_desc, skb, is_gso, l4_hdr_offset,
			     1 + payload_nfrags, hlen,
			     info->iov[hdr_nfrags - 1].iov_offset);

	skb_copy_bits(skb, 0,
		      tx->tx_fifo.base + info->iov[hdr_nfrags - 1].iov_offset,
		      hlen);
	gve_dma_sync_for_device(&priv->pdev->dev, tx->tx_fifo.qpl->page_buses,
				info->iov[hdr_nfrags - 1].iov_offset,
				info->iov[hdr_nfrags - 1].iov_len);
	copy_offset = hlen;

	for (i = payload_iov; i < payload_nfrags + payload_iov; i++) {
		next_idx = (tx->req + 1 + i - payload_iov) & tx->mask;
		seg_desc = &tx->desc[next_idx];

		gve_tx_fill_seg_desc(seg_desc, skb, is_gso,
				     info->iov[i].iov_len,
				     info->iov[i].iov_offset);

		skb_copy_bits(skb, copy_offset,
			      tx->tx_fifo.base + info->iov[i].iov_offset,
			      info->iov[i].iov_len);
		gve_dma_sync_for_device(&priv->pdev->dev, tx->tx_fifo.qpl->page_buses,
					info->iov[i].iov_offset,
					info->iov[i].iov_len);
		copy_offset += info->iov[i].iov_len;
	}

	return 1 + payload_nfrags;
}

static int gve_tx_add_skb_no_copy(struct gve_priv *priv, struct gve_tx_ring *tx,
				  struct sk_buff *skb)
{
	const struct skb_shared_info *shinfo = skb_shinfo(skb);
	int hlen, payload_nfrags, l4_hdr_offset;
	union gve_tx_desc *pkt_desc, *seg_desc;
	struct gve_tx_buffer_state *info;
	bool is_gso = skb_is_gso(skb);
	u32 idx = tx->req & tx->mask;
	struct gve_tx_dma_buf *buf;
	u64 addr;
	u32 len;
	int i;

	info = &tx->info[idx];
	pkt_desc = &tx->desc[idx];

	l4_hdr_offset = skb_checksum_start_offset(skb);
	/* If the skb is gso, then we want only up to the tcp header in the first segment
	 * to efficiently replicate on each segment otherwise we want the linear portion
	 * of the skb (which will contain the checksum because skb->csum_start and
	 * skb->csum_offset are given relative to skb->head) in the first segment.
	 */
	hlen = is_gso ? l4_hdr_offset + tcp_hdrlen(skb) : skb_headlen(skb);
	len = skb_headlen(skb);

	info->skb =  skb;

	addr = dma_map_single(tx->dev, skb->data, len, DMA_TO_DEVICE);
	if (unlikely(dma_mapping_error(tx->dev, addr))) {
		tx->dma_mapping_error++;
		goto drop;
	}
	buf = &info->buf;
	dma_unmap_len_set(buf, len, len);
	dma_unmap_addr_set(buf, dma, addr);

	payload_nfrags = shinfo->nr_frags;
	if (hlen < len) {
		/* For gso the rest of the linear portion of the skb needs to
		 * be in its own descriptor.
		 */
		payload_nfrags++;
		gve_tx_fill_pkt_desc(pkt_desc, skb, is_gso, l4_hdr_offset,
				     1 + payload_nfrags, hlen, addr);

		len -= hlen;
		addr += hlen;
		idx = (tx->req + 1) & tx->mask;
		seg_desc = &tx->desc[idx];
		gve_tx_fill_seg_desc(seg_desc, skb, is_gso, len, addr);
	} else {
		gve_tx_fill_pkt_desc(pkt_desc, skb, is_gso, l4_hdr_offset,
				     1 + payload_nfrags, hlen, addr);
	}

	for (i = 0; i < shinfo->nr_frags; i++) {
		const skb_frag_t *frag = &shinfo->frags[i];

		idx = (idx + 1) & tx->mask;
		seg_desc = &tx->desc[idx];
		len = skb_frag_size(frag);
		addr = skb_frag_dma_map(tx->dev, frag, 0, len, DMA_TO_DEVICE);
		if (unlikely(dma_mapping_error(tx->dev, addr))) {
			tx->dma_mapping_error++;
			goto unmap_drop;
		}
		buf = &tx->info[idx].buf;
		tx->info[idx].skb = NULL;
		dma_unmap_len_set(buf, len, len);
		dma_unmap_addr_set(buf, dma, addr);

		gve_tx_fill_seg_desc(seg_desc, skb, is_gso, len, addr);
	}

	return 1 + payload_nfrags;

unmap_drop:
	i += (payload_nfrags == shinfo->nr_frags ? 1 : 2);
	while (i--) {
		idx--;
		gve_tx_unmap_buf(tx->dev, &tx->info[idx & tx->mask]);
	}
drop:
	tx->dropped_pkt++;
	return 0;
}

netdev_tx_t gve_tx(struct sk_buff *skb, struct net_device *dev)
{
	struct gve_priv *priv = netdev_priv(dev);
	struct gve_tx_ring *tx;
	int nsegs;

	WARN(skb_get_queue_mapping(skb) > priv->tx_cfg.num_queues,
	     "skb queue index out of range");
	tx = &priv->tx[skb_get_queue_mapping(skb)];
	if (unlikely(gve_maybe_stop_tx(tx, skb))) {
		/* We need to ring the txq doorbell -- we have stopped the Tx
		 * queue for want of resources, but prior calls to gve_tx()
		 * may have added descriptors without ringing the doorbell.
		 */

		gve_tx_put_doorbell(priv, tx->q_resources, tx->req);
		return NETDEV_TX_BUSY;
	}
	if (tx->raw_addressing)
		nsegs = gve_tx_add_skb_no_copy(priv, tx, skb);
	else
		nsegs = gve_tx_add_skb_copy(priv, tx, skb);

	/* If the packet is getting sent, we need to update the skb */
	if (nsegs) {
		netdev_tx_sent_queue(tx->netdev_txq, skb->len);
		skb_tx_timestamp(skb);
		tx->req += nsegs;
	} else {
		dev_kfree_skb_any(skb);
	}

	if (!netif_xmit_stopped(tx->netdev_txq) && netdev_xmit_more())
		return NETDEV_TX_OK;

	/* Give packets to NIC. Even if this packet failed to send the doorbell
	 * might need to be rung because of xmit_more.
	 */
	gve_tx_put_doorbell(priv, tx->q_resources, tx->req);
	return NETDEV_TX_OK;
}

#define GVE_TX_START_THRESH	PAGE_SIZE

static int gve_clean_tx_done(struct gve_priv *priv, struct gve_tx_ring *tx,
			     u32 to_do, bool try_to_wake)
{
	struct gve_tx_buffer_state *info;
	u64 pkts = 0, bytes = 0;
	size_t space_freed = 0;
	struct sk_buff *skb;
	int i, j;
	u32 idx;

	for (j = 0; j < to_do; j++) {
		idx = tx->done & tx->mask;
		netif_info(priv, tx_done, priv->dev,
			   "[%d] %s: idx=%d (req=%u done=%u)\n",
			   tx->q_num, __func__, idx, tx->req, tx->done);
		info = &tx->info[idx];
		skb = info->skb;

		/* Unmap the buffer */
		if (tx->raw_addressing)
			gve_tx_unmap_buf(tx->dev, info);
		tx->done++;
		/* Mark as free */
		if (skb) {
			info->skb = NULL;
			bytes += skb->len;
			pkts++;
			dev_consume_skb_any(skb);
			if (tx->raw_addressing)
				continue;
			/* FIFO free */
			for (i = 0; i < ARRAY_SIZE(info->iov); i++) {
				space_freed += info->iov[i].iov_len + info->iov[i].iov_padding;
				info->iov[i].iov_len = 0;
				info->iov[i].iov_padding = 0;
			}
		}
	}

	if (!tx->raw_addressing)
		gve_tx_free_fifo(&tx->tx_fifo, space_freed);
	u64_stats_update_begin(&tx->statss);
	tx->bytes_done += bytes;
	tx->pkt_done += pkts;
	u64_stats_update_end(&tx->statss);
	netdev_tx_completed_queue(tx->netdev_txq, pkts, bytes);

	/* start the queue if we've stopped it */
#ifndef CONFIG_BQL
	/* Make sure that the doorbells are synced */
	smp_mb();
#endif
	if (try_to_wake && netif_tx_queue_stopped(tx->netdev_txq) &&
	    likely(gve_can_tx(tx, GVE_TX_START_THRESH))) {
		tx->wake_queue++;
		netif_tx_wake_queue(tx->netdev_txq);
	}

	return pkts;
}

__be32 gve_tx_load_event_counter(struct gve_priv *priv,
				 struct gve_tx_ring *tx)
{
	u32 counter_index = be32_to_cpu((tx->q_resources->counter_index));

	return READ_ONCE(priv->counter_array[counter_index]);
}

bool gve_tx_poll(struct gve_notify_block *block, int budget)
{
	struct gve_priv *priv = block->priv;
	struct gve_tx_ring *tx = block->tx;
	bool repoll = false;
	u32 nic_done;
	u32 to_do;

	/* If budget is 0, do all the work */
	if (budget == 0)
		budget = INT_MAX;

	/* Find out how much work there is to be done */
	tx->last_nic_done = gve_tx_load_event_counter(priv, tx);
	nic_done = be32_to_cpu(tx->last_nic_done);
	if (budget > 0) {
		/* Do as much work as we have that the budget will
		 * allow
		 */
		to_do = min_t(u32, (nic_done - tx->done), budget);
		gve_clean_tx_done(priv, tx, to_do, true);
	}
	/* If we still have work we want to repoll */
	repoll |= (nic_done != tx->done);
	return repoll;
}