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(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 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
xen_9pfs_front_event_handler(int irq,void * r)231 static 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
246 static 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
257 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
258 { "9pfs" },
259 { "" }
260 };
261
xen_9pfs_front_free(struct xen_9pfs_front_priv * priv)262 static 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, 0, 0);
283 }
284 free_pages((unsigned long)priv->rings[i].data.in,
285 priv->rings[i].intf->ring_order -
286 (PAGE_SHIFT - XEN_PAGE_SHIFT));
287 }
288 gnttab_end_foreign_access(priv->rings[i].ref, 0, 0);
289 free_page((unsigned long)priv->rings[i].intf);
290 }
291 kfree(priv->rings);
292 kfree(priv->tag);
293 kfree(priv);
294 }
295
xen_9pfs_front_remove(struct xenbus_device * dev)296 static 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
xen_9pfs_front_alloc_dataring(struct xenbus_device * dev,struct xen_9pfs_dataring * ring,unsigned int order)305 static 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 = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
326 order - (PAGE_SHIFT - XEN_PAGE_SHIFT));
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;
353 out:
354 if (bytes) {
355 for (i--; i >= 0; i--)
356 gnttab_end_foreign_access(ring->intf->ref[i], 0, 0);
357 free_pages((unsigned long)bytes,
358 ring->intf->ring_order -
359 (PAGE_SHIFT - XEN_PAGE_SHIFT));
360 }
361 gnttab_end_foreign_access(ring->ref, 0, 0);
362 free_page((unsigned long)ring->intf);
363 return ret;
364 }
365
xen_9pfs_front_probe(struct xenbus_device * dev,const struct xenbus_device_id * id)366 static int xen_9pfs_front_probe(struct xenbus_device *dev,
367 const struct xenbus_device_id *id)
368 {
369 int ret, i;
370 struct xenbus_transaction xbt;
371 struct xen_9pfs_front_priv *priv = NULL;
372 char *versions;
373 unsigned int max_rings, max_ring_order, len = 0;
374
375 versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
376 if (IS_ERR(versions))
377 return PTR_ERR(versions);
378 if (strcmp(versions, "1")) {
379 kfree(versions);
380 return -EINVAL;
381 }
382 kfree(versions);
383 max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
384 if (max_rings < XEN_9PFS_NUM_RINGS)
385 return -EINVAL;
386 max_ring_order = xenbus_read_unsigned(dev->otherend,
387 "max-ring-page-order", 0);
388 if (max_ring_order > XEN_9PFS_RING_ORDER)
389 max_ring_order = XEN_9PFS_RING_ORDER;
390 if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
391 p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
392
393 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
394 if (!priv)
395 return -ENOMEM;
396
397 priv->dev = dev;
398 priv->num_rings = XEN_9PFS_NUM_RINGS;
399 priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
400 GFP_KERNEL);
401 if (!priv->rings) {
402 kfree(priv);
403 return -ENOMEM;
404 }
405
406 for (i = 0; i < priv->num_rings; i++) {
407 priv->rings[i].priv = priv;
408 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
409 max_ring_order);
410 if (ret < 0)
411 goto error;
412 }
413
414 again:
415 ret = xenbus_transaction_start(&xbt);
416 if (ret) {
417 xenbus_dev_fatal(dev, ret, "starting transaction");
418 goto error;
419 }
420 ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
421 if (ret)
422 goto error_xenbus;
423 ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
424 priv->num_rings);
425 if (ret)
426 goto error_xenbus;
427 for (i = 0; i < priv->num_rings; i++) {
428 char str[16];
429
430 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
431 sprintf(str, "ring-ref%d", i);
432 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
433 priv->rings[i].ref);
434 if (ret)
435 goto error_xenbus;
436
437 sprintf(str, "event-channel-%d", i);
438 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
439 priv->rings[i].evtchn);
440 if (ret)
441 goto error_xenbus;
442 }
443 priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
444 if (IS_ERR(priv->tag)) {
445 ret = PTR_ERR(priv->tag);
446 goto error_xenbus;
447 }
448 ret = xenbus_transaction_end(xbt, 0);
449 if (ret) {
450 if (ret == -EAGAIN)
451 goto again;
452 xenbus_dev_fatal(dev, ret, "completing transaction");
453 goto error;
454 }
455
456 write_lock(&xen_9pfs_lock);
457 list_add_tail(&priv->list, &xen_9pfs_devs);
458 write_unlock(&xen_9pfs_lock);
459 dev_set_drvdata(&dev->dev, priv);
460 xenbus_switch_state(dev, XenbusStateInitialised);
461
462 return 0;
463
464 error_xenbus:
465 xenbus_transaction_end(xbt, 1);
466 xenbus_dev_fatal(dev, ret, "writing xenstore");
467 error:
468 dev_set_drvdata(&dev->dev, NULL);
469 xen_9pfs_front_free(priv);
470 return ret;
471 }
472
xen_9pfs_front_resume(struct xenbus_device * dev)473 static int xen_9pfs_front_resume(struct xenbus_device *dev)
474 {
475 dev_warn(&dev->dev, "suspend/resume unsupported\n");
476 return 0;
477 }
478
xen_9pfs_front_changed(struct xenbus_device * dev,enum xenbus_state backend_state)479 static void xen_9pfs_front_changed(struct xenbus_device *dev,
480 enum xenbus_state backend_state)
481 {
482 switch (backend_state) {
483 case XenbusStateReconfiguring:
484 case XenbusStateReconfigured:
485 case XenbusStateInitialising:
486 case XenbusStateInitialised:
487 case XenbusStateUnknown:
488 break;
489
490 case XenbusStateInitWait:
491 break;
492
493 case XenbusStateConnected:
494 xenbus_switch_state(dev, XenbusStateConnected);
495 break;
496
497 case XenbusStateClosed:
498 if (dev->state == XenbusStateClosed)
499 break;
500 fallthrough; /* Missed the backend's CLOSING state */
501 case XenbusStateClosing:
502 xenbus_frontend_closed(dev);
503 break;
504 }
505 }
506
507 static struct xenbus_driver xen_9pfs_front_driver = {
508 .ids = xen_9pfs_front_ids,
509 .probe = xen_9pfs_front_probe,
510 .remove = xen_9pfs_front_remove,
511 .resume = xen_9pfs_front_resume,
512 .otherend_changed = xen_9pfs_front_changed,
513 };
514
p9_trans_xen_init(void)515 static int p9_trans_xen_init(void)
516 {
517 int rc;
518
519 if (!xen_domain())
520 return -ENODEV;
521
522 pr_info("Initialising Xen transport for 9pfs\n");
523
524 v9fs_register_trans(&p9_xen_trans);
525 rc = xenbus_register_frontend(&xen_9pfs_front_driver);
526 if (rc)
527 v9fs_unregister_trans(&p9_xen_trans);
528
529 return rc;
530 }
531 module_init(p9_trans_xen_init);
532 MODULE_ALIAS_9P("xen");
533
p9_trans_xen_exit(void)534 static void p9_trans_xen_exit(void)
535 {
536 v9fs_unregister_trans(&p9_xen_trans);
537 return xenbus_unregister_driver(&xen_9pfs_front_driver);
538 }
539 module_exit(p9_trans_xen_exit);
540
541 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
542 MODULE_DESCRIPTION("Xen Transport for 9P");
543 MODULE_LICENSE("GPL");
544