xref: /linux/net/9p/trans_xen.c (revision 2da68a77) 
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 
26 struct 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 */
35 struct 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 */
51 struct 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 
61 static LIST_HEAD(xen_9pfs_devs);
62 static DEFINE_RWLOCK(xen_9pfs_lock);
63 
64 /* We don't currently allow canceling of requests */
65 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
66 {
67 	return 1;
68 }
69 
70 static 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 
89 static 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 
104 static 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 
116 static 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 
137 again:
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 
171 static 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 		if (h.size > req->rc.capacity) {
212 			dev_warn(&priv->dev->dev,
213 				 "requested packet size too big: %d for tag %d with capacity %zd\n",
214 				 h.size, h.tag, req->rc.capacity);
215 			req->status = REQ_STATUS_ERROR;
216 			goto recv_error;
217 		}
218 
219 		memcpy(&req->rc, &h, sizeof(h));
220 		req->rc.offset = 0;
221 
222 		masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
223 		/* Then, read the whole packet (including the header) */
224 		xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
225 				     masked_prod, &masked_cons,
226 				     XEN_9PFS_RING_SIZE(ring));
227 
228 recv_error:
229 		virt_mb();
230 		cons += h.size;
231 		ring->intf->in_cons = cons;
232 
233 		status = (req->status != REQ_STATUS_ERROR) ?
234 			REQ_STATUS_RCVD : REQ_STATUS_ERROR;
235 
236 		p9_client_cb(priv->client, req, status);
237 	}
238 }
239 
240 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
241 {
242 	struct xen_9pfs_dataring *ring = r;
243 
244 	if (!ring || !ring->priv->client) {
245 		/* ignore spurious interrupt */
246 		return IRQ_HANDLED;
247 	}
248 
249 	wake_up_interruptible(&ring->wq);
250 	schedule_work(&ring->work);
251 
252 	return IRQ_HANDLED;
253 }
254 
255 static struct p9_trans_module p9_xen_trans = {
256 	.name = "xen",
257 	.maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
258 	.pooled_rbuffers = false,
259 	.def = 1,
260 	.create = p9_xen_create,
261 	.close = p9_xen_close,
262 	.request = p9_xen_request,
263 	.cancel = p9_xen_cancel,
264 	.owner = THIS_MODULE,
265 };
266 
267 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
268 	{ "9pfs" },
269 	{ "" }
270 };
271 
272 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
273 {
274 	int i, j;
275 
276 	write_lock(&xen_9pfs_lock);
277 	list_del(&priv->list);
278 	write_unlock(&xen_9pfs_lock);
279 
280 	for (i = 0; i < priv->num_rings; i++) {
281 		if (!priv->rings[i].intf)
282 			break;
283 		if (priv->rings[i].irq > 0)
284 			unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
285 		if (priv->rings[i].data.in) {
286 			for (j = 0;
287 			     j < (1 << priv->rings[i].intf->ring_order);
288 			     j++) {
289 				grant_ref_t ref;
290 
291 				ref = priv->rings[i].intf->ref[j];
292 				gnttab_end_foreign_access(ref, NULL);
293 			}
294 			free_pages_exact(priv->rings[i].data.in,
295 				   1UL << (priv->rings[i].intf->ring_order +
296 					   XEN_PAGE_SHIFT));
297 		}
298 		gnttab_end_foreign_access(priv->rings[i].ref, NULL);
299 		free_page((unsigned long)priv->rings[i].intf);
300 	}
301 	kfree(priv->rings);
302 	kfree(priv->tag);
303 	kfree(priv);
304 }
305 
306 static int xen_9pfs_front_remove(struct xenbus_device *dev)
307 {
308 	struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
309 
310 	dev_set_drvdata(&dev->dev, NULL);
311 	xen_9pfs_front_free(priv);
312 	return 0;
313 }
314 
315 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
316 					 struct xen_9pfs_dataring *ring,
317 					 unsigned int order)
318 {
319 	int i = 0;
320 	int ret = -ENOMEM;
321 	void *bytes = NULL;
322 
323 	init_waitqueue_head(&ring->wq);
324 	spin_lock_init(&ring->lock);
325 	INIT_WORK(&ring->work, p9_xen_response);
326 
327 	ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
328 	if (!ring->intf)
329 		return ret;
330 	ret = gnttab_grant_foreign_access(dev->otherend_id,
331 					  virt_to_gfn(ring->intf), 0);
332 	if (ret < 0)
333 		goto out;
334 	ring->ref = ret;
335 	bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT),
336 				  GFP_KERNEL | __GFP_ZERO);
337 	if (!bytes) {
338 		ret = -ENOMEM;
339 		goto out;
340 	}
341 	for (; i < (1 << order); i++) {
342 		ret = gnttab_grant_foreign_access(
343 				dev->otherend_id, virt_to_gfn(bytes) + i, 0);
344 		if (ret < 0)
345 			goto out;
346 		ring->intf->ref[i] = ret;
347 	}
348 	ring->intf->ring_order = order;
349 	ring->data.in = bytes;
350 	ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
351 
352 	ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
353 	if (ret)
354 		goto out;
355 	ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
356 					      xen_9pfs_front_event_handler,
357 					      0, "xen_9pfs-frontend", ring);
358 	if (ring->irq >= 0)
359 		return 0;
360 
361 	xenbus_free_evtchn(dev, ring->evtchn);
362 	ret = ring->irq;
363 out:
364 	if (bytes) {
365 		for (i--; i >= 0; i--)
366 			gnttab_end_foreign_access(ring->intf->ref[i], NULL);
367 		free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
368 	}
369 	gnttab_end_foreign_access(ring->ref, NULL);
370 	free_page((unsigned long)ring->intf);
371 	return ret;
372 }
373 
374 static int xen_9pfs_front_probe(struct xenbus_device *dev,
375 				const struct xenbus_device_id *id)
376 {
377 	int ret, i;
378 	struct xenbus_transaction xbt;
379 	struct xen_9pfs_front_priv *priv = NULL;
380 	char *versions;
381 	unsigned int max_rings, max_ring_order, len = 0;
382 
383 	versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
384 	if (IS_ERR(versions))
385 		return PTR_ERR(versions);
386 	if (strcmp(versions, "1")) {
387 		kfree(versions);
388 		return -EINVAL;
389 	}
390 	kfree(versions);
391 	max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
392 	if (max_rings < XEN_9PFS_NUM_RINGS)
393 		return -EINVAL;
394 	max_ring_order = xenbus_read_unsigned(dev->otherend,
395 					      "max-ring-page-order", 0);
396 	if (max_ring_order > XEN_9PFS_RING_ORDER)
397 		max_ring_order = XEN_9PFS_RING_ORDER;
398 	if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
399 		p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
400 
401 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
402 	if (!priv)
403 		return -ENOMEM;
404 
405 	priv->dev = dev;
406 	priv->num_rings = XEN_9PFS_NUM_RINGS;
407 	priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
408 			      GFP_KERNEL);
409 	if (!priv->rings) {
410 		kfree(priv);
411 		return -ENOMEM;
412 	}
413 
414 	for (i = 0; i < priv->num_rings; i++) {
415 		priv->rings[i].priv = priv;
416 		ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
417 						    max_ring_order);
418 		if (ret < 0)
419 			goto error;
420 	}
421 
422  again:
423 	ret = xenbus_transaction_start(&xbt);
424 	if (ret) {
425 		xenbus_dev_fatal(dev, ret, "starting transaction");
426 		goto error;
427 	}
428 	ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
429 	if (ret)
430 		goto error_xenbus;
431 	ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
432 			    priv->num_rings);
433 	if (ret)
434 		goto error_xenbus;
435 	for (i = 0; i < priv->num_rings; i++) {
436 		char str[16];
437 
438 		BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
439 		sprintf(str, "ring-ref%d", i);
440 		ret = xenbus_printf(xbt, dev->nodename, str, "%d",
441 				    priv->rings[i].ref);
442 		if (ret)
443 			goto error_xenbus;
444 
445 		sprintf(str, "event-channel-%d", i);
446 		ret = xenbus_printf(xbt, dev->nodename, str, "%u",
447 				    priv->rings[i].evtchn);
448 		if (ret)
449 			goto error_xenbus;
450 	}
451 	priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
452 	if (IS_ERR(priv->tag)) {
453 		ret = PTR_ERR(priv->tag);
454 		goto error_xenbus;
455 	}
456 	ret = xenbus_transaction_end(xbt, 0);
457 	if (ret) {
458 		if (ret == -EAGAIN)
459 			goto again;
460 		xenbus_dev_fatal(dev, ret, "completing transaction");
461 		goto error;
462 	}
463 
464 	write_lock(&xen_9pfs_lock);
465 	list_add_tail(&priv->list, &xen_9pfs_devs);
466 	write_unlock(&xen_9pfs_lock);
467 	dev_set_drvdata(&dev->dev, priv);
468 	xenbus_switch_state(dev, XenbusStateInitialised);
469 
470 	return 0;
471 
472  error_xenbus:
473 	xenbus_transaction_end(xbt, 1);
474 	xenbus_dev_fatal(dev, ret, "writing xenstore");
475  error:
476 	dev_set_drvdata(&dev->dev, NULL);
477 	xen_9pfs_front_free(priv);
478 	return ret;
479 }
480 
481 static int xen_9pfs_front_resume(struct xenbus_device *dev)
482 {
483 	dev_warn(&dev->dev, "suspend/resume unsupported\n");
484 	return 0;
485 }
486 
487 static void xen_9pfs_front_changed(struct xenbus_device *dev,
488 				   enum xenbus_state backend_state)
489 {
490 	switch (backend_state) {
491 	case XenbusStateReconfiguring:
492 	case XenbusStateReconfigured:
493 	case XenbusStateInitialising:
494 	case XenbusStateInitialised:
495 	case XenbusStateUnknown:
496 		break;
497 
498 	case XenbusStateInitWait:
499 		break;
500 
501 	case XenbusStateConnected:
502 		xenbus_switch_state(dev, XenbusStateConnected);
503 		break;
504 
505 	case XenbusStateClosed:
506 		if (dev->state == XenbusStateClosed)
507 			break;
508 		fallthrough;	/* Missed the backend's CLOSING state */
509 	case XenbusStateClosing:
510 		xenbus_frontend_closed(dev);
511 		break;
512 	}
513 }
514 
515 static struct xenbus_driver xen_9pfs_front_driver = {
516 	.ids = xen_9pfs_front_ids,
517 	.probe = xen_9pfs_front_probe,
518 	.remove = xen_9pfs_front_remove,
519 	.resume = xen_9pfs_front_resume,
520 	.otherend_changed = xen_9pfs_front_changed,
521 };
522 
523 static int __init p9_trans_xen_init(void)
524 {
525 	int rc;
526 
527 	if (!xen_domain())
528 		return -ENODEV;
529 
530 	pr_info("Initialising Xen transport for 9pfs\n");
531 
532 	v9fs_register_trans(&p9_xen_trans);
533 	rc = xenbus_register_frontend(&xen_9pfs_front_driver);
534 	if (rc)
535 		v9fs_unregister_trans(&p9_xen_trans);
536 
537 	return rc;
538 }
539 module_init(p9_trans_xen_init);
540 MODULE_ALIAS_9P("xen");
541 
542 static void __exit p9_trans_xen_exit(void)
543 {
544 	v9fs_unregister_trans(&p9_xen_trans);
545 	return xenbus_unregister_driver(&xen_9pfs_front_driver);
546 }
547 module_exit(p9_trans_xen_exit);
548 
549 MODULE_ALIAS("xen:9pfs");
550 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
551 MODULE_DESCRIPTION("Xen Transport for 9P");
552 MODULE_LICENSE("GPL");
553