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 WRITE_ONCE(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 WRITE_ONCE(req->status, REQ_STATUS_ERROR);
216 goto recv_error;
217 }
218
219 req->rc.size = h.size;
220 req->rc.id = h.id;
221 req->rc.tag = h.tag;
222 req->rc.offset = 0;
223
224 masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
225 /* Then, read the whole packet (including the header) */
226 xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
227 masked_prod, &masked_cons,
228 XEN_9PFS_RING_SIZE(ring));
229
230 recv_error:
231 virt_mb();
232 cons += h.size;
233 ring->intf->in_cons = cons;
234
235 status = (req->status != REQ_STATUS_ERROR) ?
236 REQ_STATUS_RCVD : REQ_STATUS_ERROR;
237
238 p9_client_cb(priv->client, req, status);
239 }
240 }
241
xen_9pfs_front_event_handler(int irq,void * r)242 static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
243 {
244 struct xen_9pfs_dataring *ring = r;
245
246 if (!ring || !ring->priv->client) {
247 /* ignore spurious interrupt */
248 return IRQ_HANDLED;
249 }
250
251 wake_up_interruptible(&ring->wq);
252 schedule_work(&ring->work);
253
254 return IRQ_HANDLED;
255 }
256
257 static struct p9_trans_module p9_xen_trans = {
258 .name = "xen",
259 .maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
260 .pooled_rbuffers = false,
261 .def = 1,
262 .create = p9_xen_create,
263 .close = p9_xen_close,
264 .request = p9_xen_request,
265 .cancel = p9_xen_cancel,
266 .owner = THIS_MODULE,
267 };
268
269 static const struct xenbus_device_id xen_9pfs_front_ids[] = {
270 { "9pfs" },
271 { "" }
272 };
273
xen_9pfs_front_free(struct xen_9pfs_front_priv * priv)274 static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
275 {
276 int i, j;
277
278 write_lock(&xen_9pfs_lock);
279 list_del(&priv->list);
280 write_unlock(&xen_9pfs_lock);
281
282 for (i = 0; i < priv->num_rings; i++) {
283 if (!priv->rings[i].intf)
284 break;
285 if (priv->rings[i].irq > 0)
286 unbind_from_irqhandler(priv->rings[i].irq, priv->dev);
287 if (priv->rings[i].data.in) {
288 for (j = 0;
289 j < (1 << priv->rings[i].intf->ring_order);
290 j++) {
291 grant_ref_t ref;
292
293 ref = priv->rings[i].intf->ref[j];
294 gnttab_end_foreign_access(ref, NULL);
295 }
296 free_pages_exact(priv->rings[i].data.in,
297 1UL << (priv->rings[i].intf->ring_order +
298 XEN_PAGE_SHIFT));
299 }
300 gnttab_end_foreign_access(priv->rings[i].ref, NULL);
301 free_page((unsigned long)priv->rings[i].intf);
302 }
303 kfree(priv->rings);
304 kfree(priv->tag);
305 kfree(priv);
306 }
307
xen_9pfs_front_remove(struct xenbus_device * dev)308 static void xen_9pfs_front_remove(struct xenbus_device *dev)
309 {
310 struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
311
312 dev_set_drvdata(&dev->dev, NULL);
313 xen_9pfs_front_free(priv);
314 }
315
xen_9pfs_front_alloc_dataring(struct xenbus_device * dev,struct xen_9pfs_dataring * ring,unsigned int order)316 static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
317 struct xen_9pfs_dataring *ring,
318 unsigned int order)
319 {
320 int i = 0;
321 int ret = -ENOMEM;
322 void *bytes = NULL;
323
324 init_waitqueue_head(&ring->wq);
325 spin_lock_init(&ring->lock);
326 INIT_WORK(&ring->work, p9_xen_response);
327
328 ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
329 if (!ring->intf)
330 return ret;
331 ret = gnttab_grant_foreign_access(dev->otherend_id,
332 virt_to_gfn(ring->intf), 0);
333 if (ret < 0)
334 goto out;
335 ring->ref = ret;
336 bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT),
337 GFP_KERNEL | __GFP_ZERO);
338 if (!bytes) {
339 ret = -ENOMEM;
340 goto out;
341 }
342 for (; i < (1 << order); i++) {
343 ret = gnttab_grant_foreign_access(
344 dev->otherend_id, virt_to_gfn(bytes) + i, 0);
345 if (ret < 0)
346 goto out;
347 ring->intf->ref[i] = ret;
348 }
349 ring->intf->ring_order = order;
350 ring->data.in = bytes;
351 ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
352
353 ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
354 if (ret)
355 goto out;
356 ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
357 xen_9pfs_front_event_handler,
358 0, "xen_9pfs-frontend", ring);
359 if (ring->irq >= 0)
360 return 0;
361
362 xenbus_free_evtchn(dev, ring->evtchn);
363 ret = ring->irq;
364 out:
365 if (bytes) {
366 for (i--; i >= 0; i--)
367 gnttab_end_foreign_access(ring->intf->ref[i], NULL);
368 free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
369 }
370 gnttab_end_foreign_access(ring->ref, NULL);
371 free_page((unsigned long)ring->intf);
372 return ret;
373 }
374
xen_9pfs_front_init(struct xenbus_device * dev)375 static int xen_9pfs_front_init(struct xenbus_device *dev)
376 {
377 int ret, i;
378 struct xenbus_transaction xbt;
379 struct xen_9pfs_front_priv *priv = dev_get_drvdata(&dev->dev);
380 char *versions, *v;
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 for (v = versions; *v; v++) {
387 if (simple_strtoul(v, &v, 10) == 1) {
388 v = NULL;
389 break;
390 }
391 }
392 if (v) {
393 kfree(versions);
394 return -EINVAL;
395 }
396 kfree(versions);
397 max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
398 if (max_rings < XEN_9PFS_NUM_RINGS)
399 return -EINVAL;
400 max_ring_order = xenbus_read_unsigned(dev->otherend,
401 "max-ring-page-order", 0);
402 if (max_ring_order > XEN_9PFS_RING_ORDER)
403 max_ring_order = XEN_9PFS_RING_ORDER;
404 if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
405 p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
406
407 priv->num_rings = XEN_9PFS_NUM_RINGS;
408 priv->rings = kcalloc(priv->num_rings, sizeof(*priv->rings),
409 GFP_KERNEL);
410 if (!priv->rings) {
411 kfree(priv);
412 return -ENOMEM;
413 }
414
415 for (i = 0; i < priv->num_rings; i++) {
416 priv->rings[i].priv = priv;
417 ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
418 max_ring_order);
419 if (ret < 0)
420 goto error;
421 }
422
423 again:
424 ret = xenbus_transaction_start(&xbt);
425 if (ret) {
426 xenbus_dev_fatal(dev, ret, "starting transaction");
427 goto error;
428 }
429 ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
430 if (ret)
431 goto error_xenbus;
432 ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
433 priv->num_rings);
434 if (ret)
435 goto error_xenbus;
436 for (i = 0; i < priv->num_rings; i++) {
437 char str[16];
438
439 BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
440 sprintf(str, "ring-ref%d", i);
441 ret = xenbus_printf(xbt, dev->nodename, str, "%d",
442 priv->rings[i].ref);
443 if (ret)
444 goto error_xenbus;
445
446 sprintf(str, "event-channel-%d", i);
447 ret = xenbus_printf(xbt, dev->nodename, str, "%u",
448 priv->rings[i].evtchn);
449 if (ret)
450 goto error_xenbus;
451 }
452 priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
453 if (IS_ERR(priv->tag)) {
454 ret = PTR_ERR(priv->tag);
455 goto error_xenbus;
456 }
457 ret = xenbus_transaction_end(xbt, 0);
458 if (ret) {
459 if (ret == -EAGAIN)
460 goto again;
461 xenbus_dev_fatal(dev, ret, "completing transaction");
462 goto error;
463 }
464
465 return 0;
466
467 error_xenbus:
468 xenbus_transaction_end(xbt, 1);
469 xenbus_dev_fatal(dev, ret, "writing xenstore");
470 error:
471 xen_9pfs_front_free(priv);
472 return ret;
473 }
474
xen_9pfs_front_probe(struct xenbus_device * dev,const struct xenbus_device_id * id)475 static int xen_9pfs_front_probe(struct xenbus_device *dev,
476 const struct xenbus_device_id *id)
477 {
478 struct xen_9pfs_front_priv *priv = NULL;
479
480 priv = kzalloc(sizeof(*priv), GFP_KERNEL);
481 if (!priv)
482 return -ENOMEM;
483
484 priv->dev = dev;
485 dev_set_drvdata(&dev->dev, priv);
486
487 write_lock(&xen_9pfs_lock);
488 list_add_tail(&priv->list, &xen_9pfs_devs);
489 write_unlock(&xen_9pfs_lock);
490
491 return 0;
492 }
493
xen_9pfs_front_resume(struct xenbus_device * dev)494 static int xen_9pfs_front_resume(struct xenbus_device *dev)
495 {
496 dev_warn(&dev->dev, "suspend/resume unsupported\n");
497 return 0;
498 }
499
xen_9pfs_front_changed(struct xenbus_device * dev,enum xenbus_state backend_state)500 static void xen_9pfs_front_changed(struct xenbus_device *dev,
501 enum xenbus_state backend_state)
502 {
503 switch (backend_state) {
504 case XenbusStateReconfiguring:
505 case XenbusStateReconfigured:
506 case XenbusStateInitialising:
507 case XenbusStateInitialised:
508 case XenbusStateUnknown:
509 break;
510
511 case XenbusStateInitWait:
512 if (!xen_9pfs_front_init(dev))
513 xenbus_switch_state(dev, XenbusStateInitialised);
514 break;
515
516 case XenbusStateConnected:
517 xenbus_switch_state(dev, XenbusStateConnected);
518 break;
519
520 case XenbusStateClosed:
521 if (dev->state == XenbusStateClosed)
522 break;
523 fallthrough; /* Missed the backend's CLOSING state */
524 case XenbusStateClosing:
525 xenbus_frontend_closed(dev);
526 break;
527 }
528 }
529
530 static struct xenbus_driver xen_9pfs_front_driver = {
531 .ids = xen_9pfs_front_ids,
532 .probe = xen_9pfs_front_probe,
533 .remove = xen_9pfs_front_remove,
534 .resume = xen_9pfs_front_resume,
535 .otherend_changed = xen_9pfs_front_changed,
536 };
537
p9_trans_xen_init(void)538 static int __init p9_trans_xen_init(void)
539 {
540 int rc;
541
542 if (!xen_domain())
543 return -ENODEV;
544
545 pr_info("Initialising Xen transport for 9pfs\n");
546
547 v9fs_register_trans(&p9_xen_trans);
548 rc = xenbus_register_frontend(&xen_9pfs_front_driver);
549 if (rc)
550 v9fs_unregister_trans(&p9_xen_trans);
551
552 return rc;
553 }
554 module_init(p9_trans_xen_init);
555 MODULE_ALIAS_9P("xen");
556
p9_trans_xen_exit(void)557 static void __exit p9_trans_xen_exit(void)
558 {
559 v9fs_unregister_trans(&p9_xen_trans);
560 return xenbus_unregister_driver(&xen_9pfs_front_driver);
561 }
562 module_exit(p9_trans_xen_exit);
563
564 MODULE_ALIAS("xen:9pfs");
565 MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
566 MODULE_DESCRIPTION("Xen Transport for 9P");
567 MODULE_LICENSE("GPL");
568