trans_xen.c

  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 <linux/fs_context.h>
 19#include <net/9p/9p.h>
 20#include <net/9p/client.h>
 21#include <net/9p/transport.h>
 22
 23#define XEN_9PFS_NUM_RINGS 2
 24#define XEN_9PFS_RING_ORDER 9
 25#define XEN_9PFS_RING_SIZE(ring)  XEN_FLEX_RING_SIZE(ring->intf->ring_order)
 26
 27struct xen_9pfs_header {
 28	uint32_t size;
 29	uint8_t id;
 30	uint16_t tag;
 31
 32	/* uint8_t sdata[]; */
 33} __attribute__((packed));
 34
 35/* One per ring, more than one per 9pfs share */
 36struct xen_9pfs_dataring {
 37	struct xen_9pfs_front_priv *priv;
 38
 39	struct xen_9pfs_data_intf *intf;
 40	grant_ref_t ref;
 41	int evtchn;
 42	int irq;
 43	/* protect a ring from concurrent accesses */
 44	spinlock_t lock;
 45
 46	struct xen_9pfs_data data;
 47	wait_queue_head_t wq;
 48	struct work_struct work;
 49};
 50
 51/* One per 9pfs share */
 52struct xen_9pfs_front_priv {
 53	struct list_head list;
 54	struct xenbus_device *dev;
 55	char *tag;
 56	struct p9_client *client;
 57
 58	struct xen_9pfs_dataring *rings;
 59};
 60
 61static LIST_HEAD(xen_9pfs_devs);
 62static DEFINE_RWLOCK(xen_9pfs_lock);
 63
 64/* We don't currently allow canceling of requests */
 65static int p9_xen_cancel(struct p9_client *client, struct p9_req_t *req)
 66{
 67	return 1;
 68}
 69
 70static int p9_xen_create(struct p9_client *client, struct fs_context *fc)
 71{
 72	const char *addr = fc->source;
 73	struct xen_9pfs_front_priv *priv;
 74
 75	if (addr == NULL)
 76		return -EINVAL;
 77
 78	read_lock(&xen_9pfs_lock);
 79	list_for_each_entry(priv, &xen_9pfs_devs, list) {
 80		if (!strcmp(priv->tag, addr)) {
 81			priv->client = client;
 82			read_unlock(&xen_9pfs_lock);
 83			return 0;
 84		}
 85	}
 86	read_unlock(&xen_9pfs_lock);
 87	return -EINVAL;
 88}
 89
 90static void p9_xen_close(struct p9_client *client)
 91{
 92	struct xen_9pfs_front_priv *priv;
 93
 94	read_lock(&xen_9pfs_lock);
 95	list_for_each_entry(priv, &xen_9pfs_devs, list) {
 96		if (priv->client == client) {
 97			priv->client = NULL;
 98			read_unlock(&xen_9pfs_lock);
 99			return;
100		}
101	}
102	read_unlock(&xen_9pfs_lock);
103}
104
105static bool p9_xen_write_todo(struct xen_9pfs_dataring *ring, RING_IDX size)
106{
107	RING_IDX cons, prod;
108
109	cons = ring->intf->out_cons;
110	prod = ring->intf->out_prod;
111	virt_mb();
112
113	return XEN_9PFS_RING_SIZE(ring) -
114		xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) >= size;
115}
116
117static int p9_xen_request(struct p9_client *client, struct p9_req_t *p9_req)
118{
119	struct xen_9pfs_front_priv *priv;
120	RING_IDX cons, prod, masked_cons, masked_prod;
121	unsigned long flags;
122	u32 size = p9_req->tc.size;
123	struct xen_9pfs_dataring *ring;
124	int num;
125
126	read_lock(&xen_9pfs_lock);
127	list_for_each_entry(priv, &xen_9pfs_devs, list) {
128		if (priv->client == client)
129			break;
130	}
131	read_unlock(&xen_9pfs_lock);
132	if (list_entry_is_head(priv, &xen_9pfs_devs, list))
133		return -EINVAL;
134
135	num = p9_req->tc.tag % XEN_9PFS_NUM_RINGS;
136	ring = &priv->rings[num];
137
138again:
139	while (wait_event_killable(ring->wq,
140				   p9_xen_write_todo(ring, size)) != 0)
141		;
142
143	spin_lock_irqsave(&ring->lock, flags);
144	cons = ring->intf->out_cons;
145	prod = ring->intf->out_prod;
146	virt_mb();
147
148	if (XEN_9PFS_RING_SIZE(ring) -
149	    xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) < size) {
150		spin_unlock_irqrestore(&ring->lock, flags);
151		goto again;
152	}
153
154	masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
155	masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
156
157	xen_9pfs_write_packet(ring->data.out, p9_req->tc.sdata, size,
158			      &masked_prod, masked_cons,
159			      XEN_9PFS_RING_SIZE(ring));
160
161	WRITE_ONCE(p9_req->status, REQ_STATUS_SENT);
162	virt_wmb();			/* write ring before updating pointer */
163	prod += size;
164	ring->intf->out_prod = prod;
165	spin_unlock_irqrestore(&ring->lock, flags);
166	notify_remote_via_irq(ring->irq);
167	p9_req_put(client, p9_req);
168
169	return 0;
170}
171
172static void p9_xen_response(struct work_struct *work)
173{
174	struct xen_9pfs_front_priv *priv;
175	struct xen_9pfs_dataring *ring;
176	RING_IDX cons, prod, masked_cons, masked_prod;
177	struct xen_9pfs_header h;
178	struct p9_req_t *req;
179	int status;
180
181	ring = container_of(work, struct xen_9pfs_dataring, work);
182	priv = ring->priv;
183
184	while (1) {
185		cons = ring->intf->in_cons;
186		prod = ring->intf->in_prod;
187		virt_rmb();
188
189		if (xen_9pfs_queued(prod, cons, XEN_9PFS_RING_SIZE(ring)) <
190		    sizeof(h)) {
191			notify_remote_via_irq(ring->irq);
192			return;
193		}
194
195		masked_prod = xen_9pfs_mask(prod, XEN_9PFS_RING_SIZE(ring));
196		masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
197
198		/* First, read just the header */
199		xen_9pfs_read_packet(&h, ring->data.in, sizeof(h),
200				     masked_prod, &masked_cons,
201				     XEN_9PFS_RING_SIZE(ring));
202
203		req = p9_tag_lookup(priv->client, h.tag);
204		if (!req || req->status != REQ_STATUS_SENT) {
205			dev_warn(&priv->dev->dev, "Wrong req tag=%x\n", h.tag);
206			cons += h.size;
207			virt_mb();
208			ring->intf->in_cons = cons;
209			continue;
210		}
211
212		if (h.size > req->rc.capacity) {
213			dev_warn(&priv->dev->dev,
214				 "requested packet size too big: %d for tag %d with capacity %zd\n",
215				 h.size, h.tag, req->rc.capacity);
216			WRITE_ONCE(req->status, REQ_STATUS_ERROR);
217			goto recv_error;
218		}
219
220		req->rc.size = h.size;
221		req->rc.id = h.id;
222		req->rc.tag = h.tag;
223		req->rc.offset = 0;
224
225		masked_cons = xen_9pfs_mask(cons, XEN_9PFS_RING_SIZE(ring));
226		/* Then, read the whole packet (including the header) */
227		xen_9pfs_read_packet(req->rc.sdata, ring->data.in, h.size,
228				     masked_prod, &masked_cons,
229				     XEN_9PFS_RING_SIZE(ring));
230
231recv_error:
232		virt_mb();
233		cons += h.size;
234		ring->intf->in_cons = cons;
235
236		status = (req->status != REQ_STATUS_ERROR) ?
237			REQ_STATUS_RCVD : REQ_STATUS_ERROR;
238
239		p9_client_cb(priv->client, req, status);
240	}
241}
242
243static irqreturn_t xen_9pfs_front_event_handler(int irq, void *r)
244{
245	struct xen_9pfs_dataring *ring = r;
246
247	if (!ring || !ring->priv->client) {
248		/* ignore spurious interrupt */
249		return IRQ_HANDLED;
250	}
251
252	wake_up_interruptible(&ring->wq);
253	schedule_work(&ring->work);
254
255	return IRQ_HANDLED;
256}
257
258static struct p9_trans_module p9_xen_trans = {
259	.name = "xen",
260	.maxsize = 1 << (XEN_9PFS_RING_ORDER + XEN_PAGE_SHIFT - 2),
261	.pooled_rbuffers = false,
262	.def = true,
263	.supports_vmalloc = false,
264	.create = p9_xen_create,
265	.close = p9_xen_close,
266	.request = p9_xen_request,
267	.cancel = p9_xen_cancel,
268	.owner = THIS_MODULE,
269};
270
271static const struct xenbus_device_id xen_9pfs_front_ids[] = {
272	{ "9pfs" },
273	{ "" }
274};
275
276static void xen_9pfs_front_free(struct xen_9pfs_front_priv *priv)
277{
278	int i, j;
279
280	if (priv->rings) {
281		for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
282			struct xen_9pfs_dataring *ring = &priv->rings[i];
283
284			cancel_work_sync(&ring->work);
285
286			if (!priv->rings[i].intf)
287				break;
288			if (priv->rings[i].irq > 0)
289				unbind_from_irqhandler(priv->rings[i].irq, ring);
290			if (priv->rings[i].data.in) {
291				for (j = 0;
292				     j < (1 << priv->rings[i].intf->ring_order);
293				     j++) {
294					grant_ref_t ref;
295
296					ref = priv->rings[i].intf->ref[j];
297					gnttab_end_foreign_access(ref, NULL);
298				}
299				free_pages_exact(priv->rings[i].data.in,
300				   1UL << (priv->rings[i].intf->ring_order +
301					   XEN_PAGE_SHIFT));
302			}
303			gnttab_end_foreign_access(priv->rings[i].ref, NULL);
304			free_page((unsigned long)priv->rings[i].intf);
305		}
306		kfree(priv->rings);
307	}
308	kfree(priv->tag);
309	kfree(priv);
310}
311
312static void xen_9pfs_front_remove(struct xenbus_device *dev)
313{
314	struct xen_9pfs_front_priv *priv;
315
316	write_lock(&xen_9pfs_lock);
317	priv = dev_get_drvdata(&dev->dev);
318	if (priv == NULL) {
319		write_unlock(&xen_9pfs_lock);
320		return;
321	}
322	dev_set_drvdata(&dev->dev, NULL);
323	list_del(&priv->list);
324	write_unlock(&xen_9pfs_lock);
325
326	xen_9pfs_front_free(priv);
327}
328
329static int xen_9pfs_front_alloc_dataring(struct xenbus_device *dev,
330					 struct xen_9pfs_dataring *ring,
331					 unsigned int order)
332{
333	int i = 0;
334	int ret = -ENOMEM;
335	void *bytes = NULL;
336
337	init_waitqueue_head(&ring->wq);
338	spin_lock_init(&ring->lock);
339	INIT_WORK(&ring->work, p9_xen_response);
340
341	ring->intf = (struct xen_9pfs_data_intf *)get_zeroed_page(GFP_KERNEL);
342	if (!ring->intf)
343		return ret;
344	ret = gnttab_grant_foreign_access(dev->otherend_id,
345					  virt_to_gfn(ring->intf), 0);
346	if (ret < 0)
347		goto out;
348	ring->ref = ret;
349	bytes = alloc_pages_exact(1UL << (order + XEN_PAGE_SHIFT),
350				  GFP_KERNEL | __GFP_ZERO);
351	if (!bytes) {
352		ret = -ENOMEM;
353		goto out;
354	}
355	for (; i < (1 << order); i++) {
356		ret = gnttab_grant_foreign_access(
357				dev->otherend_id, virt_to_gfn(bytes) + i, 0);
358		if (ret < 0)
359			goto out;
360		ring->intf->ref[i] = ret;
361	}
362	ring->intf->ring_order = order;
363	ring->data.in = bytes;
364	ring->data.out = bytes + XEN_FLEX_RING_SIZE(order);
365
366	ret = xenbus_alloc_evtchn(dev, &ring->evtchn);
367	if (ret)
368		goto out;
369	ring->irq = bind_evtchn_to_irqhandler(ring->evtchn,
370					      xen_9pfs_front_event_handler,
371					      0, "xen_9pfs-frontend", ring);
372	if (ring->irq >= 0)
373		return 0;
374
375	xenbus_free_evtchn(dev, ring->evtchn);
376	ret = ring->irq;
377out:
378	if (bytes) {
379		for (i--; i >= 0; i--)
380			gnttab_end_foreign_access(ring->intf->ref[i], NULL);
381		free_pages_exact(bytes, 1UL << (order + XEN_PAGE_SHIFT));
382	}
383	gnttab_end_foreign_access(ring->ref, NULL);
384	free_page((unsigned long)ring->intf);
385	return ret;
386}
387
388static int xen_9pfs_front_init(struct xenbus_device *dev)
389{
390	int ret, i;
391	struct xenbus_transaction xbt;
392	struct xen_9pfs_front_priv *priv;
393	char *versions, *v;
394	unsigned int max_rings, max_ring_order, len = 0;
395
396	versions = xenbus_read(XBT_NIL, dev->otherend, "versions", &len);
397	if (IS_ERR(versions))
398		return PTR_ERR(versions);
399	for (v = versions; *v; v++) {
400		if (simple_strtoul(v, &v, 10) == 1) {
401			v = NULL;
402			break;
403		}
404	}
405	if (v) {
406		kfree(versions);
407		return -EINVAL;
408	}
409	kfree(versions);
410	max_rings = xenbus_read_unsigned(dev->otherend, "max-rings", 0);
411	if (max_rings < XEN_9PFS_NUM_RINGS)
412		return -EINVAL;
413	max_ring_order = xenbus_read_unsigned(dev->otherend,
414					      "max-ring-page-order", 0);
415	if (max_ring_order > XEN_9PFS_RING_ORDER)
416		max_ring_order = XEN_9PFS_RING_ORDER;
417	if (p9_xen_trans.maxsize > XEN_FLEX_RING_SIZE(max_ring_order))
418		p9_xen_trans.maxsize = XEN_FLEX_RING_SIZE(max_ring_order) / 2;
419
420	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
421	if (!priv)
422		return -ENOMEM;
423	priv->dev = dev;
424	priv->rings = kcalloc(XEN_9PFS_NUM_RINGS, sizeof(*priv->rings),
425			      GFP_KERNEL);
426	if (!priv->rings) {
427		kfree(priv);
428		return -ENOMEM;
429	}
430
431	for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
432		priv->rings[i].priv = priv;
433		ret = xen_9pfs_front_alloc_dataring(dev, &priv->rings[i],
434						    max_ring_order);
435		if (ret < 0)
436			goto error;
437	}
438
439 again:
440	ret = xenbus_transaction_start(&xbt);
441	if (ret) {
442		xenbus_dev_fatal(dev, ret, "starting transaction");
443		goto error;
444	}
445	ret = xenbus_printf(xbt, dev->nodename, "version", "%u", 1);
446	if (ret)
447		goto error_xenbus;
448	ret = xenbus_printf(xbt, dev->nodename, "num-rings", "%u",
449			    XEN_9PFS_NUM_RINGS);
450	if (ret)
451		goto error_xenbus;
452
453	for (i = 0; i < XEN_9PFS_NUM_RINGS; i++) {
454		char str[16];
455
456		BUILD_BUG_ON(XEN_9PFS_NUM_RINGS > 9);
457		sprintf(str, "ring-ref%d", i);
458		ret = xenbus_printf(xbt, dev->nodename, str, "%d",
459				    priv->rings[i].ref);
460		if (ret)
461			goto error_xenbus;
462
463		sprintf(str, "event-channel-%d", i);
464		ret = xenbus_printf(xbt, dev->nodename, str, "%u",
465				    priv->rings[i].evtchn);
466		if (ret)
467			goto error_xenbus;
468	}
469	priv->tag = xenbus_read(xbt, dev->nodename, "tag", NULL);
470	if (IS_ERR(priv->tag)) {
471		ret = PTR_ERR(priv->tag);
472		goto error_xenbus;
473	}
474	ret = xenbus_transaction_end(xbt, 0);
475	if (ret) {
476		if (ret == -EAGAIN)
477			goto again;
478		xenbus_dev_fatal(dev, ret, "completing transaction");
479		goto error;
480	}
481
482	write_lock(&xen_9pfs_lock);
483	dev_set_drvdata(&dev->dev, priv);
484	list_add_tail(&priv->list, &xen_9pfs_devs);
485	write_unlock(&xen_9pfs_lock);
486
487	xenbus_switch_state(dev, XenbusStateInitialised);
488	return 0;
489
490 error_xenbus:
491	xenbus_transaction_end(xbt, 1);
492	xenbus_dev_fatal(dev, ret, "writing xenstore");
493 error:
494	xen_9pfs_front_free(priv);
495	return ret;
496}
497
498static int xen_9pfs_front_probe(struct xenbus_device *dev,
499				const struct xenbus_device_id *id)
500{
501	return 0;
502}
503
504static int xen_9pfs_front_resume(struct xenbus_device *dev)
505{
506	dev_warn(&dev->dev, "suspend/resume unsupported\n");
507	return 0;
508}
509
510static void xen_9pfs_front_changed(struct xenbus_device *dev,
511				   enum xenbus_state backend_state)
512{
513	switch (backend_state) {
514	case XenbusStateReconfiguring:
515	case XenbusStateReconfigured:
516	case XenbusStateInitialising:
517	case XenbusStateInitialised:
518	case XenbusStateUnknown:
519		break;
520
521	case XenbusStateInitWait:
522		if (dev->state != XenbusStateInitialising)
523			break;
524
525		xen_9pfs_front_init(dev);
526		break;
527
528	case XenbusStateConnected:
529		xenbus_switch_state(dev, XenbusStateConnected);
530		break;
531
532	case XenbusStateClosed:
533		if (dev->state == XenbusStateClosed)
534			break;
535		fallthrough;	/* Missed the backend's CLOSING state */
536	case XenbusStateClosing:
537		xenbus_frontend_closed(dev);
538		break;
539	}
540}
541
542static struct xenbus_driver xen_9pfs_front_driver = {
543	.ids = xen_9pfs_front_ids,
544	.probe = xen_9pfs_front_probe,
545	.remove = xen_9pfs_front_remove,
546	.resume = xen_9pfs_front_resume,
547	.otherend_changed = xen_9pfs_front_changed,
548};
549
550static int __init p9_trans_xen_init(void)
551{
552	int rc;
553
554	if (!xen_domain())
555		return -ENODEV;
556
557	pr_info("Initialising Xen transport for 9pfs\n");
558
559	v9fs_register_trans(&p9_xen_trans);
560	rc = xenbus_register_frontend(&xen_9pfs_front_driver);
561	if (rc)
562		v9fs_unregister_trans(&p9_xen_trans);
563
564	return rc;
565}
566module_init(p9_trans_xen_init);
567MODULE_ALIAS_9P("xen");
568
569static void __exit p9_trans_xen_exit(void)
570{
571	v9fs_unregister_trans(&p9_xen_trans);
572	return xenbus_unregister_driver(&xen_9pfs_front_driver);
573}
574module_exit(p9_trans_xen_exit);
575
576MODULE_ALIAS("xen:9pfs");
577MODULE_AUTHOR("Stefano Stabellini <stefano@aporeto.com>");
578MODULE_DESCRIPTION("Xen Transport for 9P");
579MODULE_LICENSE("GPL");