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 */
p9_xen_cancel(struct p9_client * client,struct p9_req_t * req)65 static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
66 {
67 return 1;
68 }
69
p9_xen_create(struct p9_client * client,const char * addr,char * args)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
p9_xen_close(struct p9_client * client)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
p9_xen_write_todo(struct xen_9pfs_dataring * ring,RING_IDX size)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
p9_xen_request(struct p9_client * client,struct p9_req_t * p9_req)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
p9_xen_response(struct work_struct * work)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
xen_9pfs_front_event_handler(int irq,void * r)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
xen_9pfs_front_free(struct xen_9pfs_front_priv * priv)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
xen_9pfs_front_remove(struct xenbus_device * dev)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
xen_9pfs_front_alloc_dataring(struct xenbus_device * dev,struct xen_9pfs_dataring * ring,unsigned int order)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
xen_9pfs_front_probe(struct xenbus_device * dev,const struct xenbus_device_id * id)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
xen_9pfs_front_resume(struct xenbus_device * dev)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
xen_9pfs_front_changed(struct xenbus_device * dev,enum xenbus_state backend_state)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
p9_trans_xen_init(void)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
p9_trans_xen_exit(void)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
