1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/fs/9p/trans_xen
4 *
5 * Xen transport layer.
6 *
7 * Copyright (C) 2017 by Stefano Stabellini <stefano@aporeto.com>
8 */
9
10#include <xen/events.h>
11#include <xen/grant_table.h>
12#include <xen/xen.h>
13#include <xen/xenbus.h>
14#include <xen/interface/io/9pfs.h>
15
16#include <linux/module.h>
17#include <linux/spinlock.h>
18#include <net/9p/9p.h>
19#include <net/9p/client.h>
20#include <net/9p/transport.h>
21
22#define XEN_9PFS_NUM_RINGS 2
23#define XEN_9PFS_RING_ORDER 9
24#define XEN_9PFS_RING_SIZE(ring)  XEN_FLEX_RING_SIZE(ring->intf->ring_order)
25
26struct xen_9pfs_header {
27	uint32_t size;
28	uint8_t id;
29	uint16_t tag;
30
31	/* uint8_t sdata[]; */
32} __attribute__((packed));
33
34/* One per ring, more than one per 9pfs share */
35struct xen_9pfs_dataring {
36	struct xen_9pfs_front_priv *priv;
37
38	struct xen_9pfs_data_intf *intf;
39	grant_ref_t ref;
40	int evtchn;
41	int irq;
42	/* protect a ring from concurrent accesses */
43	spinlock_t lock;
44
45	struct xen_9pfs_data data;
46	wait_queue_head_t wq;
47	struct work_struct work;
48};
49
50/* One per 9pfs share */
51struct xen_9pfs_front_priv {
52	struct list_head list;
53	struct xenbus_device *dev;
54	char *tag;
55	struct p9_client *client;
56
57	int num_rings;
58	struct xen_9pfs_dataring *rings;
59};
60
61static LIST_HEAD(xen_9pfs_devs);
62static DEFINE_RWLOCK(xen_9pfs_lock);
63
64/* We don't currently allow canceling of requests */
65static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
66{
67	return 1;
68}
69
70static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
71{
72	struct xen_9pfs_front_priv *priv;
73
74	if (addr == NULL)
75		return -EINVAL;
76
77	read_lock(&xen_9pfs_lock);
78	list_for_each_entry(priv, &xen_9pfs_devs, list) {
79		if (!strcmp(priv->tag, addr)) {
80			priv->client = client;
81			read_unlock(&xen_9pfs_lock);
82			return 0;
83		}
84	}
85	read_unlock(&xen_9pfs_lock);
86	return -EINVAL;
87}
88
89static void p9_xen_close(struct p9_client *client)
90{
91	struct xen_9pfs_front_priv *priv;
92
93	read_lock(&xen_9pfs_lock);
94	list_for_each_entry(priv, &xen_9pfs_devs, list) {
95		if (priv->client == client) {
96			priv->client = NULL;
97			read_unlock(&xen_9pfs_lock);
98			return;
99		}
100	}
101	read_unlock(&xen_9pfs_lock);
102}
103
104static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
105{
106	RING_IDX cons, prod;
107
108	cons = ring->intf->out_cons;
109	prod = ring->intf->out_prod;
110	virt_mb();
111
112	return XEN_9PFS_RING_SIZE(ring) -
113		xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) >= size;
114}
115
116static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
117{
118	struct xen_9pfs_front_priv *priv;
119	RING_IDX cons, prod, masked_cons, masked_prod;
120	unsigned long flags;
121	u32 size = p9_req->tc.size;
122	struct xen_9pfs_dataring *ring;
123	int num;
124
125	read_lock(&xen_9pfs_lock);
126	list_for_each_entry(priv, &xen_9pfs_devs, list) {
127		if (priv->client == client)
128			break;
129	}
130	read_unlock(&xen_9pfs_lock);
131	if (list_entry_is_head(priv, &xen_9pfs_devs, list))
132		return -EINVAL;
133
134	num = p9_req->tc.tag % priv->num_rings;
135	ring = &priv->rings[num];
136
137again:
138	while (wait_event_killable(ring->wq,
139				   p9_xen_write_todo(ring, size)) != 0)
140		;
141
142	spin_lock_irqsave(&ring->lock, flags);
143	cons = ring->intf->out_cons;
144	prod = ring->intf->out_prod;
145	virt_mb();
146
147	if (XEN_9PFS_RING_SIZE(ring) -
148	    xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) < size) {
149		spin_unlock_irqrestore(&ring->lock, flags);
150		goto again;
151	}
152
153	masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
154	masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
155
156	xen_9pfs_write_packet(ring->data.out, p9_req->tc.sdata, size,
157			      &masked_prod, masked_cons,
158			      XEN_9PFS_RING_SIZE(ring));
159
160	p9_req->status = REQ_STATUS_SENT;
161	virt_wmb();			/* write ring before updating pointer */
162	prod += size;
163	ring->intf->out_prod = prod;
164	spin_unlock_irqrestore(&ring->lock, flags);
165	notify_remote_via_irq(ring->irq);
166	p9_req_put(client, p9_req);
167
168	return 0;
169}
170
171static void p9_xen_response(struct work_struct *work)
172{
173	struct xen_9pfs_front_priv *priv;
174	struct xen_9pfs_dataring *ring;
175	RING_IDX cons, prod, masked_cons, masked_prod;
176	struct xen_9pfs_header h;
177	struct p9_req_t *req;
178	int status;
179
180	ring = container_of(work, struct xen_9pfs_dataring, work);
181	priv = ring->priv;
182
183	while (1) {
184		cons = ring->intf->in_cons;
185		prod = ring->intf->in_prod;
186		virt_rmb();
187
188		if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) <
189		    sizeof(h)) {
190			notify_remote_via_irq(ring->irq);
191			return;
192		}
193
194		masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
195		masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
196
197		/* First, read just the header */
198		xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
199				     masked_prod, &masked_cons,
200				     XEN_9PFS_RING_SIZE(ring));
201
202		req = p9_tag_lookup(priv->client, h.tag);
203		if (!req || req->status != REQ_STATUS_SENT) {
204			dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
205			cons += h.size;
206			virt_mb();
207			ring->intf->in_cons = cons;
208			continue;
209		}
210
211		memcpy(&req->rc, &h, sizeof(h));
212		req->rc.offset = 0;
213
214		masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
215		/* Then, read the whole packet (including the header) */
216		xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
217				     masked_prod, &masked_cons,
218				     XEN_9PFS_RING_SIZE(ring));
219
220		virt_mb();
221		cons += h.size;
222		ring->intf->in_cons = cons;
223
224		status = (req->status != REQ_STATUS_ERROR) ?
225			REQ_STATUS_RCVD : REQ_STATUS_ERROR;
226
227		p9_client_cb(priv->client, req, status);
228	}
229}
230
231static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
232{
233	struct xen_9pfs_dataring *ring = r;
234
235	if (!ring || !ring->priv->client) {
236		/* ignore spurious interrupt */
237		return IRQ_HANDLED;
238	}
239
240	wake_up_interruptible(&ring->wq);
241	schedule_work(&ring->work);
242
243	return IRQ_HANDLED;
244}
245
246static struct p9_trans_module p9_xen_trans = {
247	.name = "xen",
248	.maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
249	.def = 1,
250	.create = p9_xen_create,
251	.close = p9_xen_close,
252	.request = p9_xen_request,
253	.cancel = p9_xen_cancel,
254	.owner = THIS_MODULE,
255};
256
257static const struct xenbus_device_id xen_9pfs_front_ids[] = {
258	{ "9pfs" },
259	{ "" }
260};
261
262static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
263{
264	int i, j;
265
266	write_lock(&xen_9pfs_lock);
267	list_del(&priv->list);
268	write_unlock(&xen_9pfs_lock);
269
270	for (i = 0; i < priv->num_rings; i++) {
271		if (!priv->rings[i].intf)
272			break;
273		if (priv->rings[i].irq > 0)
274			unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
275		if (priv->rings[i].data.in) {
276			for (j = 0;
277			     j < (1 << priv->rings[i].intf->ring_order);
278			     j++) {
279				grant_ref_t ref;
280
281				ref = priv->rings[i].intf->ref[j];
282				gnttab_end_foreign_access(ref, NULL);
283			}
284			free_pages_exact(priv->rings[i].data.in,
285				   1UL << (priv->rings[i].intf->ring_order +
286					   XEN_PAGE_SHIFT));
287		}
288		gnttab_end_foreign_access(priv->rings[i].ref, NULL);
289		free_page((unsigned long)priv->rings[i].intf);
290	}
291	kfree(priv->rings);
292	kfree(priv->tag);
293	kfree(priv);
294}
295
296static int xen_9pfs_front_remove(struct xenbus_device *dev)
297{
298	struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
299
300	dev_set_drvdata(&dev->dev, NULL);
301	xen_9pfs_front_free(priv);
302	return 0;
303}
304
305static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
306					 struct xen_9pfs_dataring *ring,
307					 unsigned int order)
308{
309	int i = 0;
310	int ret = -ENOMEM;
311	void *bytes = NULL;
312
313	init_waitqueue_head(&ring->wq);
314	spin_lock_init(&ring->lock);
315	INIT_WORK(&ring->work, p9_xen_response);
316
317	ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
318	if (!ring->intf)
319		return ret;
320	ret = gnttab_grant_foreign_access(dev->otherend_id,
321					  virt_to_gfn(ring->intf), 0);
322	if (ret < 0)
323		goto out;
324	ring->ref = ret;
325	bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT),
326				  GFP_KERNEL | __GFP_ZERO);
327	if (!bytes) {
328		ret = -ENOMEM;
329		goto out;
330	}
331	for (; i < (1 << order); i++) {
332		ret = gnttab_grant_foreign_access(
333				dev->otherend_id, virt_to_gfn(bytes) + i, 0);
334		if (ret < 0)
335			goto out;
336		ring->intf->ref[i] = ret;
337	}
338	ring->intf->ring_order = order;
339	ring->data.in = bytes;
340	ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
341
342	ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
343	if (ret)
344		goto out;
345	ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
346					      xen_9pfs_front_event_handler,
347					      0, "xen_9pfs-frontend", ring);
348	if (ring->irq >= 0)
349		return 0;
350
351	xenbus_free_evtchn(dev, ring->evtchn);
352	ret = ring->irq;
353out:
354	if (bytes) {
355		for (i--; i >= 0; i--)
356			gnttab_end_foreign_access(ring->intf->ref[i], NULL);
357		free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
358	}
359	gnttab_end_foreign_access(ring->ref, NULL);
360	free_page((unsigned long)ring->intf);
361	return ret;
362}
363
364static int xen_9pfs_front_probe(struct xenbus_device *dev,
365				const struct xenbus_device_id *id)
366{
367	int ret, i;
368	struct xenbus_transaction xbt;
369	struct xen_9pfs_front_priv *priv = NULL;
370	char *versions;
371	unsigned int max_rings, max_ring_order, len = 0;
372
373	versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
374	if (IS_ERR(versions))
375		return PTR_ERR(versions);
376	if (strcmp(versions, "1")) {
377		kfree(versions);
378		return -EINVAL;
379	}
380	kfree(versions);
381	max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
382	if (max_rings < XEN_9PFS_NUM_RINGS)
383		return -EINVAL;
384	max_ring_order = xenbus_read_unsigned(dev->otherend,
385					      "max-ring-page-order", 0);
386	if (max_ring_order > XEN_9PFS_RING_ORDER)
387		max_ring_order = XEN_9PFS_RING_ORDER;
388	if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
389		p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
390
391	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
392	if (!priv)
393		return -ENOMEM;
394
395	priv->dev = dev;
396	priv->num_rings = XEN_9PFS_NUM_RINGS;
397	priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
398			      GFP_KERNEL);
399	if (!priv->rings) {
400		kfree(priv);
401		return -ENOMEM;
402	}
403
404	for (i = 0; i < priv->num_rings; i++) {
405		priv->rings[i].priv = priv;
406		ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
407						    max_ring_order);
408		if (ret < 0)
409			goto error;
410	}
411
412 again:
413	ret = xenbus_transaction_start(&xbt);
414	if (ret) {
415		xenbus_dev_fatal(dev, ret, "starting transaction");
416		goto error;
417	}
418	ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
419	if (ret)
420		goto error_xenbus;
421	ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
422			    priv->num_rings);
423	if (ret)
424		goto error_xenbus;
425	for (i = 0; i < priv->num_rings; i++) {
426		char str[16];
427
428		BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
429		sprintf(str, "ring-ref%d", i);
430		ret = xenbus_printf(xbt, dev->nodename, str, "%d",
431				    priv->rings[i].ref);
432		if (ret)
433			goto error_xenbus;
434
435		sprintf(str, "event-channel-%d", i);
436		ret = xenbus_printf(xbt, dev->nodename, str, "%u",
437				    priv->rings[i].evtchn);
438		if (ret)
439			goto error_xenbus;
440	}
441	priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
442	if (IS_ERR(priv->tag)) {
443		ret = PTR_ERR(priv->tag);
444		goto error_xenbus;
445	}
446	ret = xenbus_transaction_end(xbt, 0);
447	if (ret) {
448		if (ret == -EAGAIN)
449			goto again;
450		xenbus_dev_fatal(dev, ret, "completing transaction");
451		goto error;
452	}
453
454	write_lock(&xen_9pfs_lock);
455	list_add_tail(&priv->list, &xen_9pfs_devs);
456	write_unlock(&xen_9pfs_lock);
457	dev_set_drvdata(&dev->dev, priv);
458	xenbus_switch_state(dev, XenbusStateInitialised);
459
460	return 0;
461
462 error_xenbus:
463	xenbus_transaction_end(xbt, 1);
464	xenbus_dev_fatal(dev, ret, "writing xenstore");
465 error:
466	dev_set_drvdata(&dev->dev, NULL);
467	xen_9pfs_front_free(priv);
468	return ret;
469}
470
471static int xen_9pfs_front_resume(struct xenbus_device *dev)
472{
473	dev_warn(&dev->dev, "suspend/resume unsupported\n");
474	return 0;
475}
476
477static void xen_9pfs_front_changed(struct xenbus_device *dev,
478				   enum xenbus_state backend_state)
479{
480	switch (backend_state) {
481	case XenbusStateReconfiguring:
482	case XenbusStateReconfigured:
483	case XenbusStateInitialising:
484	case XenbusStateInitialised:
485	case XenbusStateUnknown:
486		break;
487
488	case XenbusStateInitWait:
489		break;
490
491	case XenbusStateConnected:
492		xenbus_switch_state(dev, XenbusStateConnected);
493		break;
494
495	case XenbusStateClosed:
496		if (dev->state == XenbusStateClosed)
497			break;
498		fallthrough;	/* Missed the backend's CLOSING state */
499	case XenbusStateClosing:
500		xenbus_frontend_closed(dev);
501		break;
502	}
503}
504
505static struct xenbus_driver xen_9pfs_front_driver = {
506	.ids = xen_9pfs_front_ids,
507	.probe = xen_9pfs_front_probe,
508	.remove = xen_9pfs_front_remove,
509	.resume = xen_9pfs_front_resume,
510	.otherend_changed = xen_9pfs_front_changed,
511};
512
513static int p9_trans_xen_init(void)
514{
515	int rc;
516
517	if (!xen_domain())
518		return -ENODEV;
519
520	pr_info("Initialising Xen transport for 9pfs\n");
521
522	v9fs_register_trans(&p9_xen_trans);
523	rc = xenbus_register_frontend(&xen_9pfs_front_driver);
524	if (rc)
525		v9fs_unregister_trans(&p9_xen_trans);
526
527	return rc;
528}
529module_init(p9_trans_xen_init);
530MODULE_ALIAS_9P("xen");
531
532static void p9_trans_xen_exit(void)
533{
534	v9fs_unregister_trans(&p9_xen_trans);
535	return xenbus_unregister_driver(&xen_9pfs_front_driver);
536}
537module_exit(p9_trans_xen_exit);
538
539MODULE_ALIAS("xen:9pfs");
540MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
541MODULE_DESCRIPTION("Xen Transport for 9P");
542MODULE_LICENSE("GPL");
543