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 <net/9p/9p.h>
42 #include <net/9p/client.h>
43 #include <net/9p/transport.h>
44
45 #define XEN_9PFS_NUM_RINGS 2
46 #define XEN_9PFS_RING_ORDER 9
47 #define XEN_9PFS_RING_SIZE(ring) XEN_FLEX_RING_SIZE(ring->intf->ring_order)
48
49 struct xen_9pfs_header {
50 uint32_t size;
51 uint8_t id;
52 uint16_t tag;
53
54 /* uint8_t sdata[]; */
55 } __attribute__((packed));
56
57 /* One per ring, more than one per 9pfs share */
58 struct xen_9pfs_dataring {
59 struct xen_9pfs_front_priv *priv;
60
61 struct xen_9pfs_data_intf *intf;
62 grant_ref_t ref;
63 int evtchn;
64 int irq;
65 /* protect a ring from concurrent accesses */
66 spinlock_t lock;
67
68 struct xen_9pfs_data data;
69 wait_queue_head_t wq;
70 struct work_struct work;
71 };
72
73 /* One per 9pfs share */
74 struct xen_9pfs_front_priv {
75 struct list_head list;
76 struct xenbus_device *dev;
77 char *tag;
78 struct p9_client *client;
79
80 int num_rings;
81 struct xen_9pfs_dataring *rings;
82 };
83
84 static LIST_HEAD(xen_9pfs_devs);
85 static DEFINE_RWLOCK(xen_9pfs_lock);
86
87 /* We don't currently allow canceling of requests */
p9_xen_cancel(struct p9_client * client,struct p9_req_t * req)88 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
89 {
90 return 1;
91 }
92
p9_xen_create(struct p9_client * client,const char * addr,char * args)93 static int p9_xen_create(struct p9_client *client, const char *addr, char *args)
94 {
95 struct xen_9pfs_front_priv *priv;
96
97 if (addr == NULL)
98 return -EINVAL;
99
100 read_lock(&xen_9pfs_lock);
101 list_for_each_entry(priv, &xen_9pfs_devs, list) {
102 if (!strcmp(priv->tag, addr)) {
103 priv->client = client;
104 read_unlock(&xen_9pfs_lock);
105 return 0;
106 }
107 }
108 read_unlock(&xen_9pfs_lock);
109 return -EINVAL;
110 }
111
p9_xen_close(struct p9_client * client)112 static void p9_xen_close(struct p9_client *client)
113 {
114 struct xen_9pfs_front_priv *priv;
115
116 read_lock(&xen_9pfs_lock);
117 list_for_each_entry(priv, &xen_9pfs_devs, list) {
118 if (priv->client == client) {
119 priv->client = NULL;
120 read_unlock(&xen_9pfs_lock);
121 return;
122 }
123 }
124 read_unlock(&xen_9pfs_lock);
125 }
126
p9_xen_write_todo(struct xen_9pfs_dataring * ring,RING_IDX size)127 static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
128 {
129 RING_IDX cons, prod;
130
131 cons = ring->intf->out_cons;
132 prod = ring->intf->out_prod;
133 virt_mb();
134
135 return XEN_9PFS_RING_SIZE(ring) -
136 xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) >= size;
137 }
138
p9_xen_request(struct p9_client * client,struct p9_req_t * p9_req)139 static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
140 {
141 struct xen_9pfs_front_priv *priv;
142 RING_IDX cons, prod, masked_cons, masked_prod;
143 unsigned long flags;
144 u32 size = p9_req->tc.size;
145 struct xen_9pfs_dataring *ring;
146 int num;
147
148 read_lock(&xen_9pfs_lock);
149 list_for_each_entry(priv, &xen_9pfs_devs, list) {
150 if (priv->client == client)
151 break;
152 }
153 read_unlock(&xen_9pfs_lock);
154 if (list_entry_is_head(priv, &xen_9pfs_devs, list))
155 return -EINVAL;
156
157 num = p9_req->tc.tag % priv->num_rings;
158 ring = &priv->rings[num];
159
160 again:
161 while (wait_event_killable(ring->wq,
162 p9_xen_write_todo(ring, size)) != 0)
163 ;
164
165 spin_lock_irqsave(&ring->lock, flags);
166 cons = ring->intf->out_cons;
167 prod = ring->intf->out_prod;
168 virt_mb();
169
170 if (XEN_9PFS_RING_SIZE(ring) -
171 xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) < size) {
172 spin_unlock_irqrestore(&ring->lock, flags);
173 goto again;
174 }
175
176 masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
177 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
178
179 xen_9pfs_write_packet(ring->data.out, p9_req->tc.sdata, size,
180 &masked_prod, masked_cons,
181 XEN_9PFS_RING_SIZE(ring));
182
183 p9_req->status = REQ_STATUS_SENT;
184 virt_wmb(); /* write ring before updating pointer */
185 prod += size;
186 ring->intf->out_prod = prod;
187 spin_unlock_irqrestore(&ring->lock, flags);
188 notify_remote_via_irq(ring->irq);
189 p9_req_put(p9_req);
190
191 return 0;
192 }
193
p9_xen_response(struct work_struct * work)194 static void p9_xen_response(struct work_struct *work)
195 {
196 struct xen_9pfs_front_priv *priv;
197 struct xen_9pfs_dataring *ring;
198 RING_IDX cons, prod, masked_cons, masked_prod;
199 struct xen_9pfs_header h;
200 struct p9_req_t *req;
201 int status;
202
203 ring = container_of(work, struct xen_9pfs_dataring, work);
204 priv = ring->priv;
205
206 while (1) {
207 cons = ring->intf->in_cons;
208 prod = ring->intf->in_prod;
209 virt_rmb();
210
211 if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) <
212 sizeof(h)) {
213 notify_remote_via_irq(ring->irq);
214 return;
215 }
216
217 masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
218 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
219
220 /* First, read just the header */
221 xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
222 masked_prod, &masked_cons,
223 XEN_9PFS_RING_SIZE(ring));
224
225 req = p9_tag_lookup(priv->client, h.tag);
226 if (!req || req->status != REQ_STATUS_SENT) {
227 dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
228 cons += h.size;
229 virt_mb();
230 ring->intf->in_cons = cons;
231 continue;
232 }
233
234 if (h.size > req->rc.capacity) {
235 dev_warn(&priv->dev->dev,
236 "requested packet size too big: %d for tag %d with capacity %zd\n",
237 h.size, h.tag, req->rc.capacity);
238 req->status = REQ_STATUS_ERROR;
239 goto recv_error;
240 }
241
242 memcpy(&req->rc, &h, sizeof(h));
243 req->rc.offset = 0;
244
245 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
246 /* Then, read the whole packet (including the header) */
247 xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
248 masked_prod, &masked_cons,
249 XEN_9PFS_RING_SIZE(ring));
250
251 recv_error:
252 virt_mb();
253 cons += h.size;
254 ring->intf->in_cons = cons;
255
256 status = (req->status != REQ_STATUS_ERROR) ?
257 REQ_STATUS_RCVD : REQ_STATUS_ERROR;
258
259 p9_client_cb(priv->client, req, status);
260 }
261 }
262
xen_9pfs_front_event_handler(int irq,void * r)263 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
264 {
265 struct xen_9pfs_dataring *ring = r;
266
267 if (!ring || !ring->priv->client) {
268 /* ignore spurious interrupt */
269 return IRQ_HANDLED;
270 }
271
272 wake_up_interruptible(&ring->wq);
273 schedule_work(&ring->work);
274
275 return IRQ_HANDLED;
276 }
277
278 static struct p9_trans_module p9_xen_trans = {
279 .name = "xen",
280 .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
281 .def = 1,
282 .create = p9_xen_create,
283 .close = p9_xen_close,
284 .request = p9_xen_request,
285 .cancel = p9_xen_cancel,
286 .owner = THIS_MODULE,
287 };
288
289 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
290 { "9pfs" },
291 { "" }
292 };
293
xen_9pfs_front_free(struct xen_9pfs_front_priv * priv)294 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
295 {
296 int i, j;
297
298 write_lock(&xen_9pfs_lock);
299 list_del(&priv->list);
300 write_unlock(&xen_9pfs_lock);
301
302 for (i = 0; i < priv->num_rings; i++) {
303 struct xen_9pfs_dataring *ring = &priv->rings[i];
304
305 cancel_work_sync(&ring->work);
306
307 if (!priv->rings[i].intf)
308 break;
309 if (priv->rings[i].irq > 0)
310 unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
311 if (priv->rings[i].data.in) {
312 for (j = 0;
313 j < (1 << priv->rings[i].intf->ring_order);
314 j++) {
315 grant_ref_t ref;
316
317 ref = priv->rings[i].intf->ref[j];
318 gnttab_end_foreign_access(ref, 0, 0);
319 }
320 free_pages_exact(priv->rings[i].data.in,
321 1UL << (priv->rings[i].intf->ring_order +
322 XEN_PAGE_SHIFT));
323 }
324 gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
325 free_page((unsigned long)priv->rings[i].intf);
326 }
327 kfree(priv->rings);
328 kfree(priv->tag);
329 kfree(priv);
330 }
331
xen_9pfs_front_remove(struct xenbus_device * dev)332 static int xen_9pfs_front_remove(struct xenbus_device *dev)
333 {
334 struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
335
336 dev_set_drvdata(&dev->dev, NULL);
337 xen_9pfs_front_free(priv);
338 return 0;
339 }
340
xen_9pfs_front_alloc_dataring(struct xenbus_device * dev,struct xen_9pfs_dataring * ring,unsigned int order)341 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
342 struct xen_9pfs_dataring *ring,
343 unsigned int order)
344 {
345 int i = 0;
346 int ret = -ENOMEM;
347 void *bytes = NULL;
348
349 init_waitqueue_head(&ring->wq);
350 spin_lock_init(&ring->lock);
351 INIT_WORK(&ring->work, p9_xen_response);
352
353 ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
354 if (!ring->intf)
355 return ret;
356 ret = gnttab_grant_foreign_access(dev->otherend_id,
357 virt_to_gfn(ring->intf), 0);
358 if (ret < 0)
359 goto out;
360 ring->ref = ret;
361 bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT),
362 GFP_KERNEL | __GFP_ZERO);
363 if (!bytes) {
364 ret = -ENOMEM;
365 goto out;
366 }
367 for (; i < (1 << order); i++) {
368 ret = gnttab_grant_foreign_access(
369 dev->otherend_id, virt_to_gfn(bytes) + i, 0);
370 if (ret < 0)
371 goto out;
372 ring->intf->ref[i] = ret;
373 }
374 ring->intf->ring_order = order;
375 ring->data.in = bytes;
376 ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
377
378 ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
379 if (ret)
380 goto out;
381 ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
382 xen_9pfs_front_event_handler,
383 0, "xen_9pfs-frontend", ring);
384 if (ring->irq >= 0)
385 return 0;
386
387 xenbus_free_evtchn(dev, ring->evtchn);
388 ret = ring->irq;
389 out:
390 if (bytes) {
391 for (i--; i >= 0; i--)
392 gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
393 free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
394 }
395 gnttab_end_foreign_access(ring->ref, 0, 0);
396 free_page((unsigned long)ring->intf);
397 return ret;
398 }
399
xen_9pfs_front_probe(struct xenbus_device * dev,const struct xenbus_device_id * id)400 static int xen_9pfs_front_probe(struct xenbus_device *dev,
401 const struct xenbus_device_id *id)
402 {
403 int ret, i;
404 struct xenbus_transaction xbt;
405 struct xen_9pfs_front_priv *priv = NULL;
406 char *versions;
407 unsigned int max_rings, max_ring_order, len = 0;
408
409 versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
410 if (IS_ERR(versions))
411 return PTR_ERR(versions);
412 if (strcmp(versions, "1")) {
413 kfree(versions);
414 return -EINVAL;
415 }
416 kfree(versions);
417 max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
418 if (max_rings < XEN_9PFS_NUM_RINGS)
419 return -EINVAL;
420 max_ring_order = xenbus_read_unsigned(dev->otherend,
421 "max-ring-page-order", 0);
422 if (max_ring_order > XEN_9PFS_RING_ORDER)
423 max_ring_order = XEN_9PFS_RING_ORDER;
424 if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
425 p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
426
427 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
428 if (!priv)
429 return -ENOMEM;
430
431 priv->dev = dev;
432 priv->num_rings = XEN_9PFS_NUM_RINGS;
433 priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
434 GFP_KERNEL);
435 if (!priv->rings) {
436 kfree(priv);
437 return -ENOMEM;
438 }
439
440 for (i = 0; i < priv->num_rings; i++) {
441 priv->rings[i].priv = priv;
442 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
443 max_ring_order);
444 if (ret < 0)
445 goto error;
446 }
447
448 again:
449 ret = xenbus_transaction_start(&xbt);
450 if (ret) {
451 xenbus_dev_fatal(dev, ret, "starting transaction");
452 goto error;
453 }
454 ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
455 if (ret)
456 goto error_xenbus;
457 ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
458 priv->num_rings);
459 if (ret)
460 goto error_xenbus;
461 for (i = 0; i < priv->num_rings; i++) {
462 char str[16];
463
464 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
465 sprintf(str, "ring-ref%d", i);
466 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
467 priv->rings[i].ref);
468 if (ret)
469 goto error_xenbus;
470
471 sprintf(str, "event-channel-%d", i);
472 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
473 priv->rings[i].evtchn);
474 if (ret)
475 goto error_xenbus;
476 }
477 priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
478 if (IS_ERR(priv->tag)) {
479 ret = PTR_ERR(priv->tag);
480 goto error_xenbus;
481 }
482 ret = xenbus_transaction_end(xbt, 0);
483 if (ret) {
484 if (ret == -EAGAIN)
485 goto again;
486 xenbus_dev_fatal(dev, ret, "completing transaction");
487 goto error;
488 }
489
490 write_lock(&xen_9pfs_lock);
491 list_add_tail(&priv->list, &xen_9pfs_devs);
492 write_unlock(&xen_9pfs_lock);
493 dev_set_drvdata(&dev->dev, priv);
494 xenbus_switch_state(dev, XenbusStateInitialised);
495
496 return 0;
497
498 error_xenbus:
499 xenbus_transaction_end(xbt, 1);
500 xenbus_dev_fatal(dev, ret, "writing xenstore");
501 error:
502 dev_set_drvdata(&dev->dev, NULL);
503 xen_9pfs_front_free(priv);
504 return ret;
505 }
506
xen_9pfs_front_resume(struct xenbus_device * dev)507 static int xen_9pfs_front_resume(struct xenbus_device *dev)
508 {
509 dev_warn(&dev->dev, "suspend/resume unsupported\n");
510 return 0;
511 }
512
xen_9pfs_front_changed(struct xenbus_device * dev,enum xenbus_state backend_state)513 static void xen_9pfs_front_changed(struct xenbus_device *dev,
514 enum xenbus_state backend_state)
515 {
516 switch (backend_state) {
517 case XenbusStateReconfiguring:
518 case XenbusStateReconfigured:
519 case XenbusStateInitialising:
520 case XenbusStateInitialised:
521 case XenbusStateUnknown:
522 break;
523
524 case XenbusStateInitWait:
525 break;
526
527 case XenbusStateConnected:
528 xenbus_switch_state(dev, XenbusStateConnected);
529 break;
530
531 case XenbusStateClosed:
532 if (dev->state == XenbusStateClosed)
533 break;
534 fallthrough; /* Missed the backend's CLOSING state */
535 case XenbusStateClosing:
536 xenbus_frontend_closed(dev);
537 break;
538 }
539 }
540
541 static struct xenbus_driver xen_9pfs_front_driver = {
542 .ids = xen_9pfs_front_ids,
543 .probe = xen_9pfs_front_probe,
544 .remove = xen_9pfs_front_remove,
545 .resume = xen_9pfs_front_resume,
546 .otherend_changed = xen_9pfs_front_changed,
547 };
548
p9_trans_xen_init(void)549 static int p9_trans_xen_init(void)
550 {
551 int rc;
552
553 if (!xen_domain())
554 return -ENODEV;
555
556 pr_info("Initialising Xen transport for 9pfs\n");
557
558 v9fs_register_trans(&p9_xen_trans);
559 rc = xenbus_register_frontend(&xen_9pfs_front_driver);
560 if (rc)
561 v9fs_unregister_trans(&p9_xen_trans);
562
563 return rc;
564 }
565 module_init(p9_trans_xen_init);
566
p9_trans_xen_exit(void)567 static void p9_trans_xen_exit(void)
568 {
569 v9fs_unregister_trans(&p9_xen_trans);
570 return xenbus_unregister_driver(&xen_9pfs_front_driver);
571 }
572 module_exit(p9_trans_xen_exit);
573
574 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
575 MODULE_DESCRIPTION("Xen Transport for 9P");
576 MODULE_LICENSE("GPL");
577