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1 /*
2 * linux/fs/9p/trans_xen
3 *
4 * Xen transport layer.
5 *
6 * Copyright (C) 2017 by Stefano Stabellini <stefano@aporeto.com>
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License version 2
10 * as published by the Free Software Foundation; or, when distributed
11 * separately from the Linux kernel or incorporated into other
12 * software packages, subject to the following license:
13 *
14 * Permission is hereby granted, free of charge, to any person obtaining a copy
15 * of this source file (the "Software"), to deal in the Software without
16 * restriction, including without limitation the rights to use, copy, modify,
17 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
18 * and to permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
20 *
21 * The above copyright notice and this permission notice shall be included in
22 * all copies or substantial portions of the Software.
23 *
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
25 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
26 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
27 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
28 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
29 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
30 * IN THE SOFTWARE.
31 */
32
33 #include <xen/events.h>
34 #include <xen/grant_table.h>
35 #include <xen/xen.h>
36 #include <xen/xenbus.h>
37 #include <xen/interface/io/9pfs.h>
38
39 #include <linux/module.h>
40 #include <linux/spinlock.h>
41 #include <linux/rwlock.h>
42 #include <net/9p/9p.h>
43 #include <net/9p/client.h>
44 #include <net/9p/transport.h>
45
46 #define XEN_9PFS_NUM_RINGS 2
47 #define XEN_9PFS_RING_ORDER 6
48 #define XEN_9PFS_RING_SIZE XEN_FLEX_RING_SIZE(XEN_9PFS_RING_ORDER)
49
50 struct xen_9pfs_header {
51 uint32_t size;
52 uint8_t id;
53 uint16_t tag;
54
55 /* uint8_t sdata[]; */
56 } __attribute__((packed));
57
58 /* One per ring, more than one per 9pfs share */
59 struct xen_9pfs_dataring {
60 struct xen_9pfs_front_priv *priv;
61
62 struct xen_9pfs_data_intf *intf;
63 grant_ref_t ref;
64 int evtchn;
65 int irq;
66 /* protect a ring from concurrent accesses */
67 spinlock_t lock;
68
69 struct xen_9pfs_data data;
70 wait_queue_head_t wq;
71 struct work_struct work;
72 };
73
74 /* One per 9pfs share */
75 struct xen_9pfs_front_priv {
76 struct list_head list;
77 struct xenbus_device *dev;
78 char *tag;
79 struct p9_client *client;
80
81 int num_rings;
82 struct xen_9pfs_dataring *rings;
83 };
84
85 static LIST_HEAD(xen_9pfs_devs);
86 static DEFINE_RWLOCK(xen_9pfs_lock);
87
88 /* We don't currently allow canceling of requests */
89 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
90 {
91 return 1;
92 }
93
94 static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
95 {
96 struct xen_9pfs_front_priv *priv;
97
98 read_lock(&xen_9pfs_lock);
99 list_for_each_entry(priv, &xen_9pfs_devs, list) {
100 if (!strcmp(priv->tag, addr)) {
101 priv->client = client;
102 read_unlock(&xen_9pfs_lock);
103 return 0;
104 }
105 }
106 read_unlock(&xen_9pfs_lock);
107 return -EINVAL;
108 }
109
110 static void p9_xen_close(struct p9_client *client)
111 {
112 struct xen_9pfs_front_priv *priv;
113
114 read_lock(&xen_9pfs_lock);
115 list_for_each_entry(priv, &xen_9pfs_devs, list) {
116 if (priv->client == client) {
117 priv->client = NULL;
118 read_unlock(&xen_9pfs_lock);
119 return;
120 }
121 }
122 read_unlock(&xen_9pfs_lock);
123 }
124
125 static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
126 {
127 RING_IDX cons, prod;
128
129 cons = ring->intf->out_cons;
130 prod = ring->intf->out_prod;
131 virt_mb();
132
133 return XEN_9PFS_RING_SIZE -
134 xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) >= size;
135 }
136
137 static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
138 {
139 struct xen_9pfs_front_priv *priv = NULL;
140 RING_IDX cons, prod, masked_cons, masked_prod;
141 unsigned long flags;
142 u32 size = p9_req->tc->size;
143 struct xen_9pfs_dataring *ring;
144 int num;
145
146 read_lock(&xen_9pfs_lock);
147 list_for_each_entry(priv, &xen_9pfs_devs, list) {
148 if (priv->client == client)
149 break;
150 }
151 read_unlock(&xen_9pfs_lock);
152 if (!priv || priv->client != client)
153 return -EINVAL;
154
155 num = p9_req->tc->tag % priv->num_rings;
156 ring = &priv->rings[num];
157
158 again:
159 while (wait_event_interruptible(ring->wq,
160 p9_xen_write_todo(ring, size)) != 0)
161 ;
162
163 spin_lock_irqsave(&ring->lock, flags);
164 cons = ring->intf->out_cons;
165 prod = ring->intf->out_prod;
166 virt_mb();
167
168 if (XEN_9PFS_RING_SIZE - xen_9pfs_queued(prod, cons,
169 XEN_9PFS_RING_SIZE) < size) {
170 spin_unlock_irqrestore(&ring->lock, flags);
171 goto again;
172 }
173
174 masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
175 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
176
177 xen_9pfs_write_packet(ring->data.out, p9_req->tc->sdata, size,
178 &masked_prod, masked_cons, XEN_9PFS_RING_SIZE);
179
180 p9_req->status = REQ_STATUS_SENT;
181 virt_wmb(); /* write ring before updating pointer */
182 prod += size;
183 ring->intf->out_prod = prod;
184 spin_unlock_irqrestore(&ring->lock, flags);
185 notify_remote_via_irq(ring->irq);
186
187 return 0;
188 }
189
190 static void p9_xen_response(struct work_struct *work)
191 {
192 struct xen_9pfs_front_priv *priv;
193 struct xen_9pfs_dataring *ring;
194 RING_IDX cons, prod, masked_cons, masked_prod;
195 struct xen_9pfs_header h;
196 struct p9_req_t *req;
197 int status;
198
199 ring = container_of(work, struct xen_9pfs_dataring, work);
200 priv = ring->priv;
201
202 while (1) {
203 cons = ring->intf->in_cons;
204 prod = ring->intf->in_prod;
205 virt_rmb();
206
207 if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE) <
208 sizeof(h)) {
209 notify_remote_via_irq(ring->irq);
210 return;
211 }
212
213 masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE);
214 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
215
216 /* First, read just the header */
217 xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
218 masked_prod, &masked_cons,
219 XEN_9PFS_RING_SIZE);
220
221 req = p9_tag_lookup(priv->client, h.tag);
222 if (!req || req->status != REQ_STATUS_SENT) {
223 dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
224 cons += h.size;
225 virt_mb();
226 ring->intf->in_cons = cons;
227 continue;
228 }
229
230 memcpy(req->rc, &h, sizeof(h));
231 req->rc->offset = 0;
232
233 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE);
234 /* Then, read the whole packet (including the header) */
235 xen_9pfs_read_packet(req->rc->sdata, ring->data.in, h.size,
236 masked_prod, &masked_cons,
237 XEN_9PFS_RING_SIZE);
238
239 virt_mb();
240 cons += h.size;
241 ring->intf->in_cons = cons;
242
243 status = (req->status != REQ_STATUS_ERROR) ?
244 REQ_STATUS_RCVD : REQ_STATUS_ERROR;
245
246 p9_client_cb(priv->client, req, status);
247 }
248 }
249
250 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
251 {
252 struct xen_9pfs_dataring *ring = r;
253
254 if (!ring || !ring->priv->client) {
255 /* ignore spurious interrupt */
256 return IRQ_HANDLED;
257 }
258
259 wake_up_interruptible(&ring->wq);
260 schedule_work(&ring->work);
261
262 return IRQ_HANDLED;
263 }
264
265 static struct p9_trans_module p9_xen_trans = {
266 .name = "xen",
267 .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT),
268 .def = 1,
269 .create = p9_xen_create,
270 .close = p9_xen_close,
271 .request = p9_xen_request,
272 .cancel = p9_xen_cancel,
273 .owner = THIS_MODULE,
274 };
275
276 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
277 { "9pfs" },
278 { "" }
279 };
280
281 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
282 {
283 int i, j;
284
285 write_lock(&xen_9pfs_lock);
286 list_del(&priv->list);
287 write_unlock(&xen_9pfs_lock);
288
289 for (i = 0; i < priv->num_rings; i++) {
290 if (!priv->rings[i].intf)
291 break;
292 if (priv->rings[i].irq > 0)
293 unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
294 if (priv->rings[i].data.in) {
295 for (j = 0; j < (1 << XEN_9PFS_RING_ORDER); j++) {
296 grant_ref_t ref;
297
298 ref = priv->rings[i].intf->ref[j];
299 gnttab_end_foreign_access(ref, 0, 0);
300 }
301 free_pages((unsigned long)priv->rings[i].data.in,
302 XEN_9PFS_RING_ORDER -
303 (PAGE_SHIFT - XEN_PAGE_SHIFT));
304 }
305 gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
306 free_page((unsigned long)priv->rings[i].intf);
307 }
308 kfree(priv->rings);
309 kfree(priv->tag);
310 kfree(priv);
311 }
312
313 static int xen_9pfs_front_remove(struct xenbus_device *dev)
314 {
315 struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
316
317 dev_set_drvdata(&dev->dev, NULL);
318 xen_9pfs_front_free(priv);
319 return 0;
320 }
321
322 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
323 struct xen_9pfs_dataring *ring)
324 {
325 int i = 0;
326 int ret = -ENOMEM;
327 void *bytes = NULL;
328
329 init_waitqueue_head(&ring->wq);
330 spin_lock_init(&ring->lock);
331 INIT_WORK(&ring->work, p9_xen_response);
332
333 ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
334 if (!ring->intf)
335 return ret;
336 ret = gnttab_grant_foreign_access(dev->otherend_id,
337 virt_to_gfn(ring->intf), 0);
338 if (ret < 0)
339 goto out;
340 ring->ref = ret;
341 bytes = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
342 XEN_9PFS_RING_ORDER - (PAGE_SHIFT - XEN_PAGE_SHIFT));
343 if (!bytes) {
344 ret = -ENOMEM;
345 goto out;
346 }
347 for (; i < (1 << XEN_9PFS_RING_ORDER); i++) {
348 ret = gnttab_grant_foreign_access(
349 dev->otherend_id, virt_to_gfn(bytes) + i, 0);
350 if (ret < 0)
351 goto out;
352 ring->intf->ref[i] = ret;
353 }
354 ring->intf->ring_order = XEN_9PFS_RING_ORDER;
355 ring->data.in = bytes;
356 ring->data.out = bytes + XEN_9PFS_RING_SIZE;
357
358 ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
359 if (ret)
360 goto out;
361 ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
362 xen_9pfs_front_event_handler,
363 0, "xen_9pfs-frontend", ring);
364 if (ring->irq >= 0)
365 return 0;
366
367 xenbus_free_evtchn(dev, ring->evtchn);
368 ret = ring->irq;
369 out:
370 if (bytes) {
371 for (i--; i >= 0; i--)
372 gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
373 free_pages((unsigned long)bytes,
374 XEN_9PFS_RING_ORDER -
375 (PAGE_SHIFT - XEN_PAGE_SHIFT));
376 }
377 gnttab_end_foreign_access(ring->ref, 0, 0);
378 free_page((unsigned long)ring->intf);
379 return ret;
380 }
381
382 static int xen_9pfs_front_probe(struct xenbus_device *dev,
383 const struct xenbus_device_id *id)
384 {
385 int ret, i;
386 struct xenbus_transaction xbt;
387 struct xen_9pfs_front_priv *priv = NULL;
388 char *versions;
389 unsigned int max_rings, max_ring_order, len = 0;
390
391 versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
392 if (!len)
393 return -EINVAL;
394 if (strcmp(versions, "1")) {
395 kfree(versions);
396 return -EINVAL;
397 }
398 kfree(versions);
399 max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
400 if (max_rings < XEN_9PFS_NUM_RINGS)
401 return -EINVAL;
402 max_ring_order = xenbus_read_unsigned(dev->otherend,
403 "max-ring-page-order", 0);
404 if (max_ring_order < XEN_9PFS_RING_ORDER)
405 return -EINVAL;
406
407 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
408 if (!priv)
409 return -ENOMEM;
410
411 priv->dev = dev;
412 priv->num_rings = XEN_9PFS_NUM_RINGS;
413 priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
414 GFP_KERNEL);
415 if (!priv->rings) {
416 kfree(priv);
417 return -ENOMEM;
418 }
419
420 for (i = 0; i < priv->num_rings; i++) {
421 priv->rings[i].priv = priv;
422 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i]);
423 if (ret < 0)
424 goto error;
425 }
426
427 again:
428 ret = xenbus_transaction_start(&xbt);
429 if (ret) {
430 xenbus_dev_fatal(dev, ret, "starting transaction");
431 goto error;
432 }
433 ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
434 if (ret)
435 goto error_xenbus;
436 ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
437 priv->num_rings);
438 if (ret)
439 goto error_xenbus;
440 for (i = 0; i < priv->num_rings; i++) {
441 char str[16];
442
443 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
444 sprintf(str, "ring-ref%u", i);
445 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
446 priv->rings[i].ref);
447 if (ret)
448 goto error_xenbus;
449
450 sprintf(str, "event-channel-%u", i);
451 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
452 priv->rings[i].evtchn);
453 if (ret)
454 goto error_xenbus;
455 }
456 priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
457 if (!priv->tag) {
458 ret = -EINVAL;
459 goto error_xenbus;
460 }
461 ret = xenbus_transaction_end(xbt, 0);
462 if (ret) {
463 if (ret == -EAGAIN)
464 goto again;
465 xenbus_dev_fatal(dev, ret, "completing transaction");
466 goto error;
467 }
468
469 write_lock(&xen_9pfs_lock);
470 list_add_tail(&priv->list, &xen_9pfs_devs);
471 write_unlock(&xen_9pfs_lock);
472 dev_set_drvdata(&dev->dev, priv);
473 xenbus_switch_state(dev, XenbusStateInitialised);
474
475 return 0;
476
477 error_xenbus:
478 xenbus_transaction_end(xbt, 1);
479 xenbus_dev_fatal(dev, ret, "writing xenstore");
480 error:
481 dev_set_drvdata(&dev->dev, NULL);
482 xen_9pfs_front_free(priv);
483 return ret;
484 }
485
486 static int xen_9pfs_front_resume(struct xenbus_device *dev)
487 {
488 dev_warn(&dev->dev, "suspsend/resume unsupported\n");
489 return 0;
490 }
491
492 static void xen_9pfs_front_changed(struct xenbus_device *dev,
493 enum xenbus_state backend_state)
494 {
495 switch (backend_state) {
496 case XenbusStateReconfiguring:
497 case XenbusStateReconfigured:
498 case XenbusStateInitialising:
499 case XenbusStateInitialised:
500 case XenbusStateUnknown:
501 break;
502
503 case XenbusStateInitWait:
504 break;
505
506 case XenbusStateConnected:
507 xenbus_switch_state(dev, XenbusStateConnected);
508 break;
509
510 case XenbusStateClosed:
511 if (dev->state == XenbusStateClosed)
512 break;
513 /* Missed the backend's CLOSING state -- fallthrough */
514 case XenbusStateClosing:
515 xenbus_frontend_closed(dev);
516 break;
517 }
518 }
519
520 static struct xenbus_driver xen_9pfs_front_driver = {
521 .ids = xen_9pfs_front_ids,
522 .probe = xen_9pfs_front_probe,
523 .remove = xen_9pfs_front_remove,
524 .resume = xen_9pfs_front_resume,
525 .otherend_changed = xen_9pfs_front_changed,
526 };
527
528 int p9_trans_xen_init(void)
529 {
530 if (!xen_domain())
531 return -ENODEV;
532
533 pr_info("Initialising Xen transport for 9pfs\n");
534
535 v9fs_register_trans(&p9_xen_trans);
536 return xenbus_register_frontend(&xen_9pfs_front_driver);
537 }
538 module_init(p9_trans_xen_init);
539
540 void p9_trans_xen_exit(void)
541 {
542 v9fs_unregister_trans(&p9_xen_trans);
543 return xenbus_unregister_driver(&xen_9pfs_front_driver);
544 }
545 module_exit(p9_trans_xen_exit);