aboutsummaryrefslogtreecommitdiff
path: root/drivers/scsi/virtio_scsi.c
blob: 74ab67a169ec2b170cd9c92137852cfdb56e6fea (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
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
/*
 * Virtio SCSI HBA driver
 *
 * Copyright IBM Corp. 2010
 * Copyright Red Hat, Inc. 2011
 *
 * Authors:
 *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
 *  Paolo Bonzini   <pbonzini@redhat.com>
 *
 * This work is licensed under the terms of the GNU GPL, version 2 or later.
 * See the COPYING file in the top-level directory.
 *
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/mempool.h>
#include <linux/virtio.h>
#include <linux/virtio_ids.h>
#include <linux/virtio_config.h>
#include <linux/virtio_scsi.h>
#include <scsi/scsi_host.h>
#include <scsi/scsi_device.h>
#include <scsi/scsi_cmnd.h>

#define VIRTIO_SCSI_MEMPOOL_SZ 64
#define VIRTIO_SCSI_EVENT_LEN 8

/* Command queue element */
struct virtio_scsi_cmd {
	struct scsi_cmnd *sc;
	struct completion *comp;
	union {
		struct virtio_scsi_cmd_req       cmd;
		struct virtio_scsi_ctrl_tmf_req  tmf;
		struct virtio_scsi_ctrl_an_req   an;
	} req;
	union {
		struct virtio_scsi_cmd_resp      cmd;
		struct virtio_scsi_ctrl_tmf_resp tmf;
		struct virtio_scsi_ctrl_an_resp  an;
		struct virtio_scsi_event         evt;
	} resp;
} ____cacheline_aligned_in_smp;

struct virtio_scsi_event_node {
	struct virtio_scsi *vscsi;
	struct virtio_scsi_event event;
	struct work_struct work;
};

struct virtio_scsi_vq {
	/* Protects vq */
	spinlock_t vq_lock;

	struct virtqueue *vq;
};

/* Per-target queue state */
struct virtio_scsi_target_state {
	/* Protects sg.  Lock hierarchy is tgt_lock -> vq_lock.  */
	spinlock_t tgt_lock;

	/* For sglist construction when adding commands to the virtqueue.  */
	struct scatterlist sg[];
};

/* Driver instance state */
struct virtio_scsi {
	struct virtio_device *vdev;

	struct virtio_scsi_vq ctrl_vq;
	struct virtio_scsi_vq event_vq;
	struct virtio_scsi_vq req_vq;

	/* Get some buffers ready for event vq */
	struct virtio_scsi_event_node event_list[VIRTIO_SCSI_EVENT_LEN];

	struct virtio_scsi_target_state *tgt[];
};

static struct kmem_cache *virtscsi_cmd_cache;
static mempool_t *virtscsi_cmd_pool;

static inline struct Scsi_Host *virtio_scsi_host(struct virtio_device *vdev)
{
	return vdev->priv;
}

static void virtscsi_compute_resid(struct scsi_cmnd *sc, u32 resid)
{
	if (!resid)
		return;

	if (!scsi_bidi_cmnd(sc)) {
		scsi_set_resid(sc, resid);
		return;
	}

	scsi_in(sc)->resid = min(resid, scsi_in(sc)->length);
	scsi_out(sc)->resid = resid - scsi_in(sc)->resid;
}

/**
 * virtscsi_complete_cmd - finish a scsi_cmd and invoke scsi_done
 *
 * Called with vq_lock held.
 */
static void virtscsi_complete_cmd(void *buf)
{
	struct virtio_scsi_cmd *cmd = buf;
	struct scsi_cmnd *sc = cmd->sc;
	struct virtio_scsi_cmd_resp *resp = &cmd->resp.cmd;

	dev_dbg(&sc->device->sdev_gendev,
		"cmd %p response %u status %#02x sense_len %u\n",
		sc, resp->response, resp->status, resp->sense_len);

	sc->result = resp->status;
	virtscsi_compute_resid(sc, resp->resid);
	switch (resp->response) {
	case VIRTIO_SCSI_S_OK:
		set_host_byte(sc, DID_OK);
		break;
	case VIRTIO_SCSI_S_OVERRUN:
		set_host_byte(sc, DID_ERROR);
		break;
	case VIRTIO_SCSI_S_ABORTED:
		set_host_byte(sc, DID_ABORT);
		break;
	case VIRTIO_SCSI_S_BAD_TARGET:
		set_host_byte(sc, DID_BAD_TARGET);
		break;
	case VIRTIO_SCSI_S_RESET:
		set_host_byte(sc, DID_RESET);
		break;
	case VIRTIO_SCSI_S_BUSY:
		set_host_byte(sc, DID_BUS_BUSY);
		break;
	case VIRTIO_SCSI_S_TRANSPORT_FAILURE:
		set_host_byte(sc, DID_TRANSPORT_DISRUPTED);
		break;
	case VIRTIO_SCSI_S_TARGET_FAILURE:
		set_host_byte(sc, DID_TARGET_FAILURE);
		break;
	case VIRTIO_SCSI_S_NEXUS_FAILURE:
		set_host_byte(sc, DID_NEXUS_FAILURE);
		break;
	default:
		scmd_printk(KERN_WARNING, sc, "Unknown response %d",
			    resp->response);
		/* fall through */
	case VIRTIO_SCSI_S_FAILURE:
		set_host_byte(sc, DID_ERROR);
		break;
	}

	WARN_ON(resp->sense_len > VIRTIO_SCSI_SENSE_SIZE);
	if (sc->sense_buffer) {
		memcpy(sc->sense_buffer, resp->sense,
		       min_t(u32, resp->sense_len, VIRTIO_SCSI_SENSE_SIZE));
		if (resp->sense_len)
			set_driver_byte(sc, DRIVER_SENSE);
	}

	mempool_free(cmd, virtscsi_cmd_pool);
	sc->scsi_done(sc);
}

static void virtscsi_vq_done(struct virtqueue *vq, void (*fn)(void *buf))
{
	void *buf;
	unsigned int len;

	do {
		virtqueue_disable_cb(vq);
		while ((buf = virtqueue_get_buf(vq, &len)) != NULL)
			fn(buf);
	} while (!virtqueue_enable_cb(vq));
}

static void virtscsi_req_done(struct virtqueue *vq)
{
	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
	struct virtio_scsi *vscsi = shost_priv(sh);
	unsigned long flags;

	spin_lock_irqsave(&vscsi->req_vq.vq_lock, flags);
	virtscsi_vq_done(vq, virtscsi_complete_cmd);
	spin_unlock_irqrestore(&vscsi->req_vq.vq_lock, flags);
};

static void virtscsi_complete_free(void *buf)
{
	struct virtio_scsi_cmd *cmd = buf;

	if (cmd->comp)
		complete_all(cmd->comp);
	else
		mempool_free(cmd, virtscsi_cmd_pool);
}

static void virtscsi_ctrl_done(struct virtqueue *vq)
{
	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
	struct virtio_scsi *vscsi = shost_priv(sh);
	unsigned long flags;

	spin_lock_irqsave(&vscsi->ctrl_vq.vq_lock, flags);
	virtscsi_vq_done(vq, virtscsi_complete_free);
	spin_unlock_irqrestore(&vscsi->ctrl_vq.vq_lock, flags);
};

static int virtscsi_kick_event(struct virtio_scsi *vscsi,
			       struct virtio_scsi_event_node *event_node)
{
	int err;
	struct scatterlist sg;
	unsigned long flags;

	sg_init_one(&sg, &event_node->event, sizeof(struct virtio_scsi_event));

	spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);

	err = virtqueue_add_buf(vscsi->event_vq.vq, &sg, 0, 1, event_node,
				GFP_ATOMIC);
	if (!err)
		virtqueue_kick(vscsi->event_vq.vq);

	spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);

	return err;
}

static int virtscsi_kick_event_all(struct virtio_scsi *vscsi)
{
	int i;

	for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++) {
		vscsi->event_list[i].vscsi = vscsi;
		virtscsi_kick_event(vscsi, &vscsi->event_list[i]);
	}

	return 0;
}

static void virtscsi_cancel_event_work(struct virtio_scsi *vscsi)
{
	int i;

	for (i = 0; i < VIRTIO_SCSI_EVENT_LEN; i++)
		cancel_work_sync(&vscsi->event_list[i].work);
}

static void virtscsi_handle_transport_reset(struct virtio_scsi *vscsi,
						struct virtio_scsi_event *event)
{
	struct scsi_device *sdev;
	struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
	unsigned int target = event->lun[1];
	unsigned int lun = (event->lun[2] << 8) | event->lun[3];

	switch (event->reason) {
	case VIRTIO_SCSI_EVT_RESET_RESCAN:
		scsi_add_device(shost, 0, target, lun);
		break;
	case VIRTIO_SCSI_EVT_RESET_REMOVED:
		sdev = scsi_device_lookup(shost, 0, target, lun);
		if (sdev) {
			scsi_remove_device(sdev);
			scsi_device_put(sdev);
		} else {
			pr_err("SCSI device %d 0 %d %d not found\n",
				shost->host_no, target, lun);
		}
		break;
	default:
		pr_info("Unsupport virtio scsi event reason %x\n", event->reason);
	}
}

static void virtscsi_handle_param_change(struct virtio_scsi *vscsi,
					 struct virtio_scsi_event *event)
{
	struct scsi_device *sdev;
	struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
	unsigned int target = event->lun[1];
	unsigned int lun = (event->lun[2] << 8) | event->lun[3];
	u8 asc = event->reason & 255;
	u8 ascq = event->reason >> 8;

	sdev = scsi_device_lookup(shost, 0, target, lun);
	if (!sdev) {
		pr_err("SCSI device %d 0 %d %d not found\n",
			shost->host_no, target, lun);
		return;
	}

	/* Handle "Parameters changed", "Mode parameters changed", and
	   "Capacity data has changed".  */
	if (asc == 0x2a && (ascq == 0x00 || ascq == 0x01 || ascq == 0x09))
		scsi_rescan_device(&sdev->sdev_gendev);

	scsi_device_put(sdev);
}

static void virtscsi_handle_event(struct work_struct *work)
{
	struct virtio_scsi_event_node *event_node =
		container_of(work, struct virtio_scsi_event_node, work);
	struct virtio_scsi *vscsi = event_node->vscsi;
	struct virtio_scsi_event *event = &event_node->event;

	if (event->event & VIRTIO_SCSI_T_EVENTS_MISSED) {
		event->event &= ~VIRTIO_SCSI_T_EVENTS_MISSED;
		scsi_scan_host(virtio_scsi_host(vscsi->vdev));
	}

	switch (event->event) {
	case VIRTIO_SCSI_T_NO_EVENT:
		break;
	case VIRTIO_SCSI_T_TRANSPORT_RESET:
		virtscsi_handle_transport_reset(vscsi, event);
		break;
	case VIRTIO_SCSI_T_PARAM_CHANGE:
		virtscsi_handle_param_change(vscsi, event);
		break;
	default:
		pr_err("Unsupport virtio scsi event %x\n", event->event);
	}
	virtscsi_kick_event(vscsi, event_node);
}

static void virtscsi_complete_event(void *buf)
{
	struct virtio_scsi_event_node *event_node = buf;

	INIT_WORK(&event_node->work, virtscsi_handle_event);
	schedule_work(&event_node->work);
}

static void virtscsi_event_done(struct virtqueue *vq)
{
	struct Scsi_Host *sh = virtio_scsi_host(vq->vdev);
	struct virtio_scsi *vscsi = shost_priv(sh);
	unsigned long flags;

	spin_lock_irqsave(&vscsi->event_vq.vq_lock, flags);
	virtscsi_vq_done(vq, virtscsi_complete_event);
	spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
};

static void virtscsi_map_sgl(struct scatterlist *sg, unsigned int *p_idx,
			     struct scsi_data_buffer *sdb)
{
	struct sg_table *table = &sdb->table;
	struct scatterlist *sg_elem;
	unsigned int idx = *p_idx;
	int i;

	for_each_sg(table->sgl, sg_elem, table->nents, i)
		sg[idx++] = *sg_elem;

	*p_idx = idx;
}

/**
 * virtscsi_map_cmd - map a scsi_cmd to a virtqueue scatterlist
 * @vscsi	: virtio_scsi state
 * @cmd		: command structure
 * @out_num	: number of read-only elements
 * @in_num	: number of write-only elements
 * @req_size	: size of the request buffer
 * @resp_size	: size of the response buffer
 *
 * Called with tgt_lock held.
 */
static void virtscsi_map_cmd(struct virtio_scsi_target_state *tgt,
			     struct virtio_scsi_cmd *cmd,
			     unsigned *out_num, unsigned *in_num,
			     size_t req_size, size_t resp_size)
{
	struct scsi_cmnd *sc = cmd->sc;
	struct scatterlist *sg = tgt->sg;
	unsigned int idx = 0;

	/* Request header.  */
	sg_set_buf(&sg[idx++], &cmd->req, req_size);

	/* Data-out buffer.  */
	if (sc && sc->sc_data_direction != DMA_FROM_DEVICE)
		virtscsi_map_sgl(sg, &idx, scsi_out(sc));

	*out_num = idx;

	/* Response header.  */
	sg_set_buf(&sg[idx++], &cmd->resp, resp_size);

	/* Data-in buffer */
	if (sc && sc->sc_data_direction != DMA_TO_DEVICE)
		virtscsi_map_sgl(sg, &idx, scsi_in(sc));

	*in_num = idx - *out_num;
}

static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt,
			     struct virtio_scsi_vq *vq,
			     struct virtio_scsi_cmd *cmd,
			     size_t req_size, size_t resp_size, gfp_t gfp)
{
	unsigned int out_num, in_num;
	unsigned long flags;
	int err;
	bool needs_kick = false;

	spin_lock_irqsave(&tgt->tgt_lock, flags);
	virtscsi_map_cmd(tgt, cmd, &out_num, &in_num, req_size, resp_size);

	spin_lock(&vq->vq_lock);
	err = virtqueue_add_buf(vq->vq, tgt->sg, out_num, in_num, cmd, gfp);
	spin_unlock(&tgt->tgt_lock);
	if (!err)
		needs_kick = virtqueue_kick_prepare(vq->vq);

	spin_unlock_irqrestore(&vq->vq_lock, flags);

	if (needs_kick)
		virtqueue_notify(vq->vq);
	return err;
}

static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc)
{
	struct virtio_scsi *vscsi = shost_priv(sh);
	struct virtio_scsi_target_state *tgt = vscsi->tgt[sc->device->id];
	struct virtio_scsi_cmd *cmd;
	int ret;

	struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
	BUG_ON(scsi_sg_count(sc) > shost->sg_tablesize);

	/* TODO: check feature bit and fail if unsupported?  */
	BUG_ON(sc->sc_data_direction == DMA_BIDIRECTIONAL);

	dev_dbg(&sc->device->sdev_gendev,
		"cmd %p CDB: %#02x\n", sc, sc->cmnd[0]);

	ret = SCSI_MLQUEUE_HOST_BUSY;
	cmd = mempool_alloc(virtscsi_cmd_pool, GFP_ATOMIC);
	if (!cmd)
		goto out;

	memset(cmd, 0, sizeof(*cmd));
	cmd->sc = sc;
	cmd->req.cmd = (struct virtio_scsi_cmd_req){
		.lun[0] = 1,
		.lun[1] = sc->device->id,
		.lun[2] = (sc->device->lun >> 8) | 0x40,
		.lun[3] = sc->device->lun & 0xff,
		.tag = (unsigned long)sc,
		.task_attr = VIRTIO_SCSI_S_SIMPLE,
		.prio = 0,
		.crn = 0,
	};

	BUG_ON(sc->cmd_len > VIRTIO_SCSI_CDB_SIZE);
	memcpy(cmd->req.cmd.cdb, sc->cmnd, sc->cmd_len);

	if (virtscsi_kick_cmd(tgt, &vscsi->req_vq, cmd,
			      sizeof cmd->req.cmd, sizeof cmd->resp.cmd,
			      GFP_ATOMIC) == 0)
		ret = 0;
	else
		mempool_free(cmd, virtscsi_cmd_pool);

out:
	return ret;
}

static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
{
	DECLARE_COMPLETION_ONSTACK(comp);
	struct virtio_scsi_target_state *tgt = vscsi->tgt[cmd->sc->device->id];
	int ret = FAILED;

	cmd->comp = &comp;
	if (virtscsi_kick_cmd(tgt, &vscsi->ctrl_vq, cmd,
			      sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
			      GFP_NOIO) < 0)
		goto out;

	wait_for_completion(&comp);
	if (cmd->resp.tmf.response == VIRTIO_SCSI_S_OK ||
	    cmd->resp.tmf.response == VIRTIO_SCSI_S_FUNCTION_SUCCEEDED)
		ret = SUCCESS;

out:
	mempool_free(cmd, virtscsi_cmd_pool);
	return ret;
}

static int virtscsi_device_reset(struct scsi_cmnd *sc)
{
	struct virtio_scsi *vscsi = shost_priv(sc->device->host);
	struct virtio_scsi_cmd *cmd;

	sdev_printk(KERN_INFO, sc->device, "device reset\n");
	cmd = mempool_alloc(virtscsi_cmd_pool, GFP_NOIO);
	if (!cmd)
		return FAILED;

	memset(cmd, 0, sizeof(*cmd));
	cmd->sc = sc;
	cmd->req.tmf = (struct virtio_scsi_ctrl_tmf_req){
		.type = VIRTIO_SCSI_T_TMF,
		.subtype = VIRTIO_SCSI_T_TMF_LOGICAL_UNIT_RESET,
		.lun[0] = 1,
		.lun[1] = sc->device->id,
		.lun[2] = (sc->device->lun >> 8) | 0x40,
		.lun[3] = sc->device->lun & 0xff,
	};
	return virtscsi_tmf(vscsi, cmd);
}

static int virtscsi_abort(struct scsi_cmnd *sc)
{
	struct virtio_scsi *vscsi = shost_priv(sc->device->host);
	struct virtio_scsi_cmd *cmd;

	scmd_printk(KERN_INFO, sc, "abort\n");
	cmd = mempool_alloc(virtscsi_cmd_pool, GFP_NOIO);
	if (!cmd)
		return FAILED;

	memset(cmd, 0, sizeof(*cmd));
	cmd->sc = sc;
	cmd->req.tmf = (struct virtio_scsi_ctrl_tmf_req){
		.type = VIRTIO_SCSI_T_TMF,
		.subtype = VIRTIO_SCSI_T_TMF_ABORT_TASK,
		.lun[0] = 1,
		.lun[1] = sc->device->id,
		.lun[2] = (sc->device->lun >> 8) | 0x40,
		.lun[3] = sc->device->lun & 0xff,
		.tag = (unsigned long)sc,
	};
	return virtscsi_tmf(vscsi, cmd);
}

static struct scsi_host_template virtscsi_host_template = {
	.module = THIS_MODULE,
	.name = "Virtio SCSI HBA",
	.proc_name = "virtio_scsi",
	.queuecommand = virtscsi_queuecommand,
	.this_id = -1,
	.eh_abort_handler = virtscsi_abort,
	.eh_device_reset_handler = virtscsi_device_reset,

	.can_queue = 1024,
	.dma_boundary = UINT_MAX,
	.use_clustering = ENABLE_CLUSTERING,
};

#define virtscsi_config_get(vdev, fld) \
	({ \
		typeof(((struct virtio_scsi_config *)0)->fld) __val; \
		vdev->config->get(vdev, \
				  offsetof(struct virtio_scsi_config, fld), \
				  &__val, sizeof(__val)); \
		__val; \
	})

#define virtscsi_config_set(vdev, fld, val) \
	(void)({ \
		typeof(((struct virtio_scsi_config *)0)->fld) __val = (val); \
		vdev->config->set(vdev, \
				  offsetof(struct virtio_scsi_config, fld), \
				  &__val, sizeof(__val)); \
	})

static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
			     struct virtqueue *vq)
{
	spin_lock_init(&virtscsi_vq->vq_lock);
	virtscsi_vq->vq = vq;
}

static struct virtio_scsi_target_state *virtscsi_alloc_tgt(
	struct virtio_device *vdev, int sg_elems)
{
	struct virtio_scsi_target_state *tgt;
	gfp_t gfp_mask = GFP_KERNEL;

	/* We need extra sg elements at head and tail.  */
	tgt = kmalloc(sizeof(*tgt) + sizeof(tgt->sg[0]) * (sg_elems + 2),
		      gfp_mask);

	if (!tgt)
		return NULL;

	spin_lock_init(&tgt->tgt_lock);
	sg_init_table(tgt->sg, sg_elems + 2);
	return tgt;
}

static void virtscsi_scan(struct virtio_device *vdev)
{
	struct Scsi_Host *shost = (struct Scsi_Host *)vdev->priv;

	scsi_scan_host(shost);
}

static void virtscsi_remove_vqs(struct virtio_device *vdev)
{
	struct Scsi_Host *sh = virtio_scsi_host(vdev);
	struct virtio_scsi *vscsi = shost_priv(sh);
	u32 i, num_targets;

	/* Stop all the virtqueues. */
	vdev->config->reset(vdev);

	num_targets = sh->max_id;
	for (i = 0; i < num_targets; i++) {
		kfree(vscsi->tgt[i]);
		vscsi->tgt[i] = NULL;
	}

	vdev->config->del_vqs(vdev);
}

static int virtscsi_init(struct virtio_device *vdev,
			 struct virtio_scsi *vscsi, int num_targets)
{
	int err;
	struct virtqueue *vqs[3];
	u32 i, sg_elems;

	vq_callback_t *callbacks[] = {
		virtscsi_ctrl_done,
		virtscsi_event_done,
		virtscsi_req_done
	};
	const char *names[] = {
		"control",
		"event",
		"request"
	};

	/* Discover virtqueues and write information to configuration.  */
	err = vdev->config->find_vqs(vdev, 3, vqs, callbacks, names);
	if (err)
		return err;

	virtscsi_init_vq(&vscsi->ctrl_vq, vqs[0]);
	virtscsi_init_vq(&vscsi->event_vq, vqs[1]);
	virtscsi_init_vq(&vscsi->req_vq, vqs[2]);

	virtscsi_config_set(vdev, cdb_size, VIRTIO_SCSI_CDB_SIZE);
	virtscsi_config_set(vdev, sense_size, VIRTIO_SCSI_SENSE_SIZE);

	if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
		virtscsi_kick_event_all(vscsi);

	/* We need to know how many segments before we allocate.  */
	sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;

	for (i = 0; i < num_targets; i++) {
		vscsi->tgt[i] = virtscsi_alloc_tgt(vdev, sg_elems);
		if (!vscsi->tgt[i]) {
			err = -ENOMEM;
			goto out;
		}
	}
	err = 0;

out:
	if (err)
		virtscsi_remove_vqs(vdev);
	return err;
}

static int __devinit virtscsi_probe(struct virtio_device *vdev)
{
	struct Scsi_Host *shost;
	struct virtio_scsi *vscsi;
	int err;
	u32 sg_elems, num_targets;
	u32 cmd_per_lun;

	/* Allocate memory and link the structs together.  */
	num_targets = virtscsi_config_get(vdev, max_target) + 1;
	shost = scsi_host_alloc(&virtscsi_host_template,
		sizeof(*vscsi)
		+ num_targets * sizeof(struct virtio_scsi_target_state));

	if (!shost)
		return -ENOMEM;

	sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;
	shost->sg_tablesize = sg_elems;
	vscsi = shost_priv(shost);
	vscsi->vdev = vdev;
	vdev->priv = shost;

	err = virtscsi_init(vdev, vscsi, num_targets);
	if (err)
		goto virtscsi_init_failed;

	cmd_per_lun = virtscsi_config_get(vdev, cmd_per_lun) ?: 1;
	shost->cmd_per_lun = min_t(u32, cmd_per_lun, shost->can_queue);
	shost->max_sectors = virtscsi_config_get(vdev, max_sectors) ?: 0xFFFF;

	/* LUNs > 256 are reported with format 1, so they go in the range
	 * 16640-32767.
	 */
	shost->max_lun = virtscsi_config_get(vdev, max_lun) + 1 + 0x4000;
	shost->max_id = num_targets;
	shost->max_channel = 0;
	shost->max_cmd_len = VIRTIO_SCSI_CDB_SIZE;
	err = scsi_add_host(shost, &vdev->dev);
	if (err)
		goto scsi_add_host_failed;
	/*
	 * scsi_scan_host() happens in virtscsi_scan() via virtio_driver->scan()
	 * after VIRTIO_CONFIG_S_DRIVER_OK has been set..
	 */
	return 0;

scsi_add_host_failed:
	vdev->config->del_vqs(vdev);
virtscsi_init_failed:
	scsi_host_put(shost);
	return err;
}

static void __devexit virtscsi_remove(struct virtio_device *vdev)
{
	struct Scsi_Host *shost = virtio_scsi_host(vdev);
	struct virtio_scsi *vscsi = shost_priv(shost);

	if (virtio_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG))
		virtscsi_cancel_event_work(vscsi);

	scsi_remove_host(shost);

	virtscsi_remove_vqs(vdev);
	scsi_host_put(shost);
}

#ifdef CONFIG_PM
static int virtscsi_freeze(struct virtio_device *vdev)
{
	virtscsi_remove_vqs(vdev);
	return 0;
}

static int virtscsi_restore(struct virtio_device *vdev)
{
	struct Scsi_Host *sh = virtio_scsi_host(vdev);
	struct virtio_scsi *vscsi = shost_priv(sh);

	return virtscsi_init(vdev, vscsi, sh->max_id);
}
#endif

static struct virtio_device_id id_table[] = {
	{ VIRTIO_ID_SCSI, VIRTIO_DEV_ANY_ID },
	{ 0 },
};

static unsigned int features[] = {
	VIRTIO_SCSI_F_HOTPLUG,
	VIRTIO_SCSI_F_CHANGE,
};

static struct virtio_driver virtio_scsi_driver = {
	.feature_table = features,
	.feature_table_size = ARRAY_SIZE(features),
	.driver.name = KBUILD_MODNAME,
	.driver.owner = THIS_MODULE,
	.id_table = id_table,
	.probe = virtscsi_probe,
	.scan = virtscsi_scan,
#ifdef CONFIG_PM
	.freeze = virtscsi_freeze,
	.restore = virtscsi_restore,
#endif
	.remove = __devexit_p(virtscsi_remove),
};

static int __init init(void)
{
	int ret = -ENOMEM;

	virtscsi_cmd_cache = KMEM_CACHE(virtio_scsi_cmd, 0);
	if (!virtscsi_cmd_cache) {
		printk(KERN_ERR "kmem_cache_create() for "
				"virtscsi_cmd_cache failed\n");
		goto error;
	}


	virtscsi_cmd_pool =
		mempool_create_slab_pool(VIRTIO_SCSI_MEMPOOL_SZ,
					 virtscsi_cmd_cache);
	if (!virtscsi_cmd_pool) {
		printk(KERN_ERR "mempool_create() for"
				"virtscsi_cmd_pool failed\n");
		goto error;
	}
	ret = register_virtio_driver(&virtio_scsi_driver);
	if (ret < 0)
		goto error;

	return 0;

error:
	if (virtscsi_cmd_pool) {
		mempool_destroy(virtscsi_cmd_pool);
		virtscsi_cmd_pool = NULL;
	}
	if (virtscsi_cmd_cache) {
		kmem_cache_destroy(virtscsi_cmd_cache);
		virtscsi_cmd_cache = NULL;
	}
	return ret;
}

static void __exit fini(void)
{
	unregister_virtio_driver(&virtio_scsi_driver);
	mempool_destroy(virtscsi_cmd_pool);
	kmem_cache_destroy(virtscsi_cmd_cache);
}
module_init(init);
module_exit(fini);

MODULE_DEVICE_TABLE(virtio, id_table);
MODULE_DESCRIPTION("Virtio SCSI HBA driver");
MODULE_LICENSE("GPL");