xref: /linux/drivers/tty/hvc/hvc_xen.c (revision 762f99f4f3cb41a775b5157dd761217beba65873) 
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * xen console driver interface to hvc_console.c
4  *
5  * (c) 2007 Gerd Hoffmann <kraxel@suse.de>
6  */
7 
8 #include <linux/console.h>
9 #include <linux/delay.h>
10 #include <linux/err.h>
11 #include <linux/irq.h>
12 #include <linux/init.h>
13 #include <linux/types.h>
14 #include <linux/list.h>
15 #include <linux/serial_core.h>
16 
17 #include <asm/io.h>
18 #include <asm/xen/hypervisor.h>
19 
20 #include <xen/xen.h>
21 #include <xen/interface/xen.h>
22 #include <xen/hvm.h>
23 #include <xen/grant_table.h>
24 #include <xen/page.h>
25 #include <xen/events.h>
26 #include <xen/interface/io/console.h>
27 #include <xen/interface/sched.h>
28 #include <xen/hvc-console.h>
29 #include <xen/xenbus.h>
30 
31 #include "hvc_console.h"
32 
33 #define HVC_COOKIE   0x58656e /* "Xen" in hex */
34 
35 struct xencons_info {
36 	struct list_head list;
37 	struct xenbus_device *xbdev;
38 	struct xencons_interface *intf;
39 	unsigned int evtchn;
40 	struct hvc_struct *hvc;
41 	int irq;
42 	int vtermno;
43 	grant_ref_t gntref;
44 };
45 
46 static LIST_HEAD(xenconsoles);
47 static DEFINE_SPINLOCK(xencons_lock);
48 
49 /* ------------------------------------------------------------------ */
50 
51 static struct xencons_info *vtermno_to_xencons(int vtermno)
52 {
53 	struct xencons_info *entry, *n, *ret = NULL;
54 
55 	if (list_empty(&xenconsoles))
56 			return NULL;
57 
58 	list_for_each_entry_safe(entry, n, &xenconsoles, list) {
59 		if (entry->vtermno == vtermno) {
60 			ret  = entry;
61 			break;
62 		}
63 	}
64 
65 	return ret;
66 }
67 
68 static inline int xenbus_devid_to_vtermno(int devid)
69 {
70 	return devid + HVC_COOKIE;
71 }
72 
73 static inline void notify_daemon(struct xencons_info *cons)
74 {
75 	/* Use evtchn: this is called early, before irq is set up. */
76 	notify_remote_via_evtchn(cons->evtchn);
77 }
78 
79 static int __write_console(struct xencons_info *xencons,
80 		const char *data, int len)
81 {
82 	XENCONS_RING_IDX cons, prod;
83 	struct xencons_interface *intf = xencons->intf;
84 	int sent = 0;
85 
86 	cons = intf->out_cons;
87 	prod = intf->out_prod;
88 	mb();			/* update queue values before going on */
89 
90 	if ((prod - cons) > sizeof(intf->out)) {
91 		pr_err_once("xencons: Illegal ring page indices");
92 		return -EINVAL;
93 	}
94 
95 	while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
96 		intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];
97 
98 	wmb();			/* write ring before updating pointer */
99 	intf->out_prod = prod;
100 
101 	if (sent)
102 		notify_daemon(xencons);
103 	return sent;
104 }
105 
106 static int domU_write_console(uint32_t vtermno, const char *data, int len)
107 {
108 	int ret = len;
109 	struct xencons_info *cons = vtermno_to_xencons(vtermno);
110 	if (cons == NULL)
111 		return -EINVAL;
112 
113 	/*
114 	 * Make sure the whole buffer is emitted, polling if
115 	 * necessary.  We don't ever want to rely on the hvc daemon
116 	 * because the most interesting console output is when the
117 	 * kernel is crippled.
118 	 */
119 	while (len) {
120 		int sent = __write_console(cons, data, len);
121 
122 		if (sent < 0)
123 			return sent;
124 
125 		data += sent;
126 		len -= sent;
127 
128 		if (unlikely(len))
129 			HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
130 	}
131 
132 	return ret;
133 }
134 
135 static int domU_read_console(uint32_t vtermno, char *buf, int len)
136 {
137 	struct xencons_interface *intf;
138 	XENCONS_RING_IDX cons, prod;
139 	int recv = 0;
140 	struct xencons_info *xencons = vtermno_to_xencons(vtermno);
141 	if (xencons == NULL)
142 		return -EINVAL;
143 	intf = xencons->intf;
144 
145 	cons = intf->in_cons;
146 	prod = intf->in_prod;
147 	mb();			/* get pointers before reading ring */
148 
149 	if ((prod - cons) > sizeof(intf->in)) {
150 		pr_err_once("xencons: Illegal ring page indices");
151 		return -EINVAL;
152 	}
153 
154 	while (cons != prod && recv < len)
155 		buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
156 
157 	mb();			/* read ring before consuming */
158 	intf->in_cons = cons;
159 
160 	notify_daemon(xencons);
161 	return recv;
162 }
163 
164 static const struct hv_ops domU_hvc_ops = {
165 	.get_chars = domU_read_console,
166 	.put_chars = domU_write_console,
167 	.notifier_add = notifier_add_irq,
168 	.notifier_del = notifier_del_irq,
169 	.notifier_hangup = notifier_hangup_irq,
170 };
171 
172 static int dom0_read_console(uint32_t vtermno, char *buf, int len)
173 {
174 	return HYPERVISOR_console_io(CONSOLEIO_read, len, buf);
175 }
176 
177 /*
178  * Either for a dom0 to write to the system console, or a domU with a
179  * debug version of Xen
180  */
181 static int dom0_write_console(uint32_t vtermno, const char *str, int len)
182 {
183 	int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (char *)str);
184 	if (rc < 0)
185 		return rc;
186 
187 	return len;
188 }
189 
190 static const struct hv_ops dom0_hvc_ops = {
191 	.get_chars = dom0_read_console,
192 	.put_chars = dom0_write_console,
193 	.notifier_add = notifier_add_irq,
194 	.notifier_del = notifier_del_irq,
195 	.notifier_hangup = notifier_hangup_irq,
196 };
197 
198 static int xen_hvm_console_init(void)
199 {
200 	int r;
201 	uint64_t v = 0;
202 	unsigned long gfn;
203 	struct xencons_info *info;
204 
205 	if (!xen_hvm_domain())
206 		return -ENODEV;
207 
208 	info = vtermno_to_xencons(HVC_COOKIE);
209 	if (!info) {
210 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
211 		if (!info)
212 			return -ENOMEM;
213 	} else if (info->intf != NULL) {
214 		/* already configured */
215 		return 0;
216 	}
217 	/*
218 	 * If the toolstack (or the hypervisor) hasn't set these values, the
219 	 * default value is 0. Even though gfn = 0 and evtchn = 0 are
220 	 * theoretically correct values, in practice they never are and they
221 	 * mean that a legacy toolstack hasn't initialized the pv console correctly.
222 	 */
223 	r = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
224 	if (r < 0 || v == 0)
225 		goto err;
226 	info->evtchn = v;
227 	v = 0;
228 	r = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
229 	if (r < 0 || v == 0)
230 		goto err;
231 	gfn = v;
232 	info->intf = xen_remap(gfn << XEN_PAGE_SHIFT, XEN_PAGE_SIZE);
233 	if (info->intf == NULL)
234 		goto err;
235 	info->vtermno = HVC_COOKIE;
236 
237 	spin_lock(&xencons_lock);
238 	list_add_tail(&info->list, &xenconsoles);
239 	spin_unlock(&xencons_lock);
240 
241 	return 0;
242 err:
243 	kfree(info);
244 	return -ENODEV;
245 }
246 
247 static int xencons_info_pv_init(struct xencons_info *info, int vtermno)
248 {
249 	info->evtchn = xen_start_info->console.domU.evtchn;
250 	/* GFN == MFN for PV guest */
251 	info->intf = gfn_to_virt(xen_start_info->console.domU.mfn);
252 	info->vtermno = vtermno;
253 
254 	list_add_tail(&info->list, &xenconsoles);
255 
256 	return 0;
257 }
258 
259 static int xen_pv_console_init(void)
260 {
261 	struct xencons_info *info;
262 
263 	if (!xen_pv_domain())
264 		return -ENODEV;
265 
266 	if (!xen_start_info->console.domU.evtchn)
267 		return -ENODEV;
268 
269 	info = vtermno_to_xencons(HVC_COOKIE);
270 	if (!info) {
271 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
272 		if (!info)
273 			return -ENOMEM;
274 	} else if (info->intf != NULL) {
275 		/* already configured */
276 		return 0;
277 	}
278 	spin_lock(&xencons_lock);
279 	xencons_info_pv_init(info, HVC_COOKIE);
280 	spin_unlock(&xencons_lock);
281 
282 	return 0;
283 }
284 
285 static int xen_initial_domain_console_init(void)
286 {
287 	struct xencons_info *info;
288 
289 	if (!xen_initial_domain())
290 		return -ENODEV;
291 
292 	info = vtermno_to_xencons(HVC_COOKIE);
293 	if (!info) {
294 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
295 		if (!info)
296 			return -ENOMEM;
297 	}
298 
299 	info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0, false);
300 	info->vtermno = HVC_COOKIE;
301 
302 	spin_lock(&xencons_lock);
303 	list_add_tail(&info->list, &xenconsoles);
304 	spin_unlock(&xencons_lock);
305 
306 	return 0;
307 }
308 
309 static void xen_console_update_evtchn(struct xencons_info *info)
310 {
311 	if (xen_hvm_domain()) {
312 		uint64_t v = 0;
313 		int err;
314 
315 		err = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
316 		if (!err && v)
317 			info->evtchn = v;
318 	} else
319 		info->evtchn = xen_start_info->console.domU.evtchn;
320 }
321 
322 void xen_console_resume(void)
323 {
324 	struct xencons_info *info = vtermno_to_xencons(HVC_COOKIE);
325 	if (info != NULL && info->irq) {
326 		if (!xen_initial_domain())
327 			xen_console_update_evtchn(info);
328 		rebind_evtchn_irq(info->evtchn, info->irq);
329 	}
330 }
331 
332 #ifdef CONFIG_HVC_XEN_FRONTEND
333 static void xencons_disconnect_backend(struct xencons_info *info)
334 {
335 	if (info->irq > 0)
336 		unbind_from_irqhandler(info->irq, NULL);
337 	info->irq = 0;
338 	if (info->evtchn > 0)
339 		xenbus_free_evtchn(info->xbdev, info->evtchn);
340 	info->evtchn = 0;
341 	if (info->gntref > 0)
342 		gnttab_free_grant_references(info->gntref);
343 	info->gntref = 0;
344 	if (info->hvc != NULL)
345 		hvc_remove(info->hvc);
346 	info->hvc = NULL;
347 }
348 
349 static void xencons_free(struct xencons_info *info)
350 {
351 	free_page((unsigned long)info->intf);
352 	info->intf = NULL;
353 	info->vtermno = 0;
354 	kfree(info);
355 }
356 
357 static int xen_console_remove(struct xencons_info *info)
358 {
359 	xencons_disconnect_backend(info);
360 	spin_lock(&xencons_lock);
361 	list_del(&info->list);
362 	spin_unlock(&xencons_lock);
363 	if (info->xbdev != NULL)
364 		xencons_free(info);
365 	else {
366 		if (xen_hvm_domain())
367 			iounmap(info->intf);
368 		kfree(info);
369 	}
370 	return 0;
371 }
372 
373 static int xencons_remove(struct xenbus_device *dev)
374 {
375 	return xen_console_remove(dev_get_drvdata(&dev->dev));
376 }
377 
378 static int xencons_connect_backend(struct xenbus_device *dev,
379 				  struct xencons_info *info)
380 {
381 	int ret, evtchn, devid, ref, irq;
382 	struct xenbus_transaction xbt;
383 	grant_ref_t gref_head;
384 
385 	ret = xenbus_alloc_evtchn(dev, &evtchn);
386 	if (ret)
387 		return ret;
388 	info->evtchn = evtchn;
389 	irq = bind_evtchn_to_irq(evtchn);
390 	if (irq < 0)
391 		return irq;
392 	info->irq = irq;
393 	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
394 	info->hvc = hvc_alloc(xenbus_devid_to_vtermno(devid),
395 			irq, &domU_hvc_ops, 256);
396 	if (IS_ERR(info->hvc))
397 		return PTR_ERR(info->hvc);
398 	ret = gnttab_alloc_grant_references(1, &gref_head);
399 	if (ret < 0)
400 		return ret;
401 	info->gntref = gref_head;
402 	ref = gnttab_claim_grant_reference(&gref_head);
403 	if (ref < 0)
404 		return ref;
405 	gnttab_grant_foreign_access_ref(ref, info->xbdev->otherend_id,
406 					virt_to_gfn(info->intf), 0);
407 
408  again:
409 	ret = xenbus_transaction_start(&xbt);
410 	if (ret) {
411 		xenbus_dev_fatal(dev, ret, "starting transaction");
412 		return ret;
413 	}
414 	ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", ref);
415 	if (ret)
416 		goto error_xenbus;
417 	ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
418 			    evtchn);
419 	if (ret)
420 		goto error_xenbus;
421 	ret = xenbus_transaction_end(xbt, 0);
422 	if (ret) {
423 		if (ret == -EAGAIN)
424 			goto again;
425 		xenbus_dev_fatal(dev, ret, "completing transaction");
426 		return ret;
427 	}
428 
429 	xenbus_switch_state(dev, XenbusStateInitialised);
430 	return 0;
431 
432  error_xenbus:
433 	xenbus_transaction_end(xbt, 1);
434 	xenbus_dev_fatal(dev, ret, "writing xenstore");
435 	return ret;
436 }
437 
438 static int xencons_probe(struct xenbus_device *dev,
439 				  const struct xenbus_device_id *id)
440 {
441 	int ret, devid;
442 	struct xencons_info *info;
443 
444 	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
445 	if (devid == 0)
446 		return -ENODEV;
447 
448 	info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
449 	if (!info)
450 		return -ENOMEM;
451 	dev_set_drvdata(&dev->dev, info);
452 	info->xbdev = dev;
453 	info->vtermno = xenbus_devid_to_vtermno(devid);
454 	info->intf = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
455 	if (!info->intf)
456 		goto error_nomem;
457 
458 	ret = xencons_connect_backend(dev, info);
459 	if (ret < 0)
460 		goto error;
461 	spin_lock(&xencons_lock);
462 	list_add_tail(&info->list, &xenconsoles);
463 	spin_unlock(&xencons_lock);
464 
465 	return 0;
466 
467  error_nomem:
468 	ret = -ENOMEM;
469 	xenbus_dev_fatal(dev, ret, "allocating device memory");
470  error:
471 	xencons_disconnect_backend(info);
472 	xencons_free(info);
473 	return ret;
474 }
475 
476 static int xencons_resume(struct xenbus_device *dev)
477 {
478 	struct xencons_info *info = dev_get_drvdata(&dev->dev);
479 
480 	xencons_disconnect_backend(info);
481 	memset(info->intf, 0, XEN_PAGE_SIZE);
482 	return xencons_connect_backend(dev, info);
483 }
484 
485 static void xencons_backend_changed(struct xenbus_device *dev,
486 				   enum xenbus_state backend_state)
487 {
488 	switch (backend_state) {
489 	case XenbusStateReconfiguring:
490 	case XenbusStateReconfigured:
491 	case XenbusStateInitialising:
492 	case XenbusStateInitialised:
493 	case XenbusStateUnknown:
494 		break;
495 
496 	case XenbusStateInitWait:
497 		break;
498 
499 	case XenbusStateConnected:
500 		xenbus_switch_state(dev, XenbusStateConnected);
501 		break;
502 
503 	case XenbusStateClosed:
504 		if (dev->state == XenbusStateClosed)
505 			break;
506 		fallthrough;	/* Missed the backend's CLOSING state */
507 	case XenbusStateClosing:
508 		xenbus_frontend_closed(dev);
509 		break;
510 	}
511 }
512 
513 static const struct xenbus_device_id xencons_ids[] = {
514 	{ "console" },
515 	{ "" }
516 };
517 
518 static struct xenbus_driver xencons_driver = {
519 	.name = "xenconsole",
520 	.ids = xencons_ids,
521 	.probe = xencons_probe,
522 	.remove = xencons_remove,
523 	.resume = xencons_resume,
524 	.otherend_changed = xencons_backend_changed,
525 };
526 #endif /* CONFIG_HVC_XEN_FRONTEND */
527 
528 static int __init xen_hvc_init(void)
529 {
530 	int r;
531 	struct xencons_info *info;
532 	const struct hv_ops *ops;
533 
534 	if (!xen_domain())
535 		return -ENODEV;
536 
537 	if (xen_initial_domain()) {
538 		ops = &dom0_hvc_ops;
539 		r = xen_initial_domain_console_init();
540 		if (r < 0)
541 			return r;
542 		info = vtermno_to_xencons(HVC_COOKIE);
543 	} else {
544 		ops = &domU_hvc_ops;
545 		if (xen_hvm_domain())
546 			r = xen_hvm_console_init();
547 		else
548 			r = xen_pv_console_init();
549 		if (r < 0)
550 			return r;
551 
552 		info = vtermno_to_xencons(HVC_COOKIE);
553 		info->irq = bind_evtchn_to_irq(info->evtchn);
554 	}
555 	if (info->irq < 0)
556 		info->irq = 0; /* NO_IRQ */
557 	else
558 		irq_set_noprobe(info->irq);
559 
560 	info->hvc = hvc_alloc(HVC_COOKIE, info->irq, ops, 256);
561 	if (IS_ERR(info->hvc)) {
562 		r = PTR_ERR(info->hvc);
563 		spin_lock(&xencons_lock);
564 		list_del(&info->list);
565 		spin_unlock(&xencons_lock);
566 		if (info->irq)
567 			unbind_from_irqhandler(info->irq, NULL);
568 		kfree(info);
569 		return r;
570 	}
571 
572 	r = 0;
573 #ifdef CONFIG_HVC_XEN_FRONTEND
574 	r = xenbus_register_frontend(&xencons_driver);
575 #endif
576 	return r;
577 }
578 device_initcall(xen_hvc_init);
579 
580 static int xen_cons_init(void)
581 {
582 	const struct hv_ops *ops;
583 
584 	if (!xen_domain())
585 		return 0;
586 
587 	if (xen_initial_domain())
588 		ops = &dom0_hvc_ops;
589 	else {
590 		int r;
591 		ops = &domU_hvc_ops;
592 
593 		if (xen_hvm_domain())
594 			r = xen_hvm_console_init();
595 		else
596 			r = xen_pv_console_init();
597 		if (r < 0)
598 			return r;
599 	}
600 
601 	hvc_instantiate(HVC_COOKIE, 0, ops);
602 	return 0;
603 }
604 console_initcall(xen_cons_init);
605 
606 #ifdef CONFIG_X86
607 static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len)
608 {
609 	if (xen_cpuid_base())
610 		outsb(0xe9, str, len);
611 }
612 #else
613 static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len) { }
614 #endif
615 
616 #ifdef CONFIG_EARLY_PRINTK
617 static int __init xenboot_console_setup(struct console *console, char *string)
618 {
619 	static struct xencons_info xenboot;
620 
621 	if (xen_initial_domain() || !xen_pv_domain())
622 		return 0;
623 
624 	return xencons_info_pv_init(&xenboot, 0);
625 }
626 
627 static void xenboot_write_console(struct console *console, const char *string,
628 				  unsigned len)
629 {
630 	unsigned int linelen, off = 0;
631 	const char *pos;
632 
633 	if (dom0_write_console(0, string, len) >= 0)
634 		return;
635 
636 	if (!xen_pv_domain()) {
637 		xen_hvm_early_write(0, string, len);
638 		return;
639 	}
640 
641 	if (domU_write_console(0, "(early) ", 8) < 0)
642 		return;
643 	while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
644 		linelen = pos-string+off;
645 		if (off + linelen > len)
646 			break;
647 		domU_write_console(0, string+off, linelen);
648 		domU_write_console(0, "\r\n", 2);
649 		off += linelen + 1;
650 	}
651 	if (off < len)
652 		domU_write_console(0, string+off, len-off);
653 }
654 
655 struct console xenboot_console = {
656 	.name		= "xenboot",
657 	.write		= xenboot_write_console,
658 	.setup		= xenboot_console_setup,
659 	.flags		= CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME,
660 	.index		= -1,
661 };
662 #endif	/* CONFIG_EARLY_PRINTK */
663 
664 void xen_raw_console_write(const char *str)
665 {
666 	ssize_t len = strlen(str);
667 	int rc = 0;
668 
669 	if (xen_domain()) {
670 		rc = dom0_write_console(0, str, len);
671 		if (rc != -ENOSYS || !xen_hvm_domain())
672 			return;
673 	}
674 	xen_hvm_early_write(0, str, len);
675 }
676 
677 void xen_raw_printk(const char *fmt, ...)
678 {
679 	static char buf[512];
680 	va_list ap;
681 
682 	va_start(ap, fmt);
683 	vsnprintf(buf, sizeof(buf), fmt, ap);
684 	va_end(ap);
685 
686 	xen_raw_console_write(buf);
687 }
688 
689 static void xenboot_earlycon_write(struct console *console,
690 				  const char *string,
691 				  unsigned len)
692 {
693 	dom0_write_console(0, string, len);
694 }
695 
696 static int __init xenboot_earlycon_setup(struct earlycon_device *device,
697 					    const char *opt)
698 {
699 	device->con->write = xenboot_earlycon_write;
700 	return 0;
701 }
702 EARLYCON_DECLARE(xenboot, xenboot_earlycon_setup);
703