xref: /openbmc/linux/drivers/tty/hvc/hvc_xen.c (revision 9a29f5fc) 
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 	XENCONS_RING_IDX out_cons;
41 	unsigned int out_cons_same;
42 	struct hvc_struct *hvc;
43 	int irq;
44 	int vtermno;
45 	grant_ref_t gntref;
46 };
47 
48 static LIST_HEAD(xenconsoles);
49 static DEFINE_SPINLOCK(xencons_lock);
50 
51 /* ------------------------------------------------------------------ */
52 
53 static struct xencons_info *vtermno_to_xencons(int vtermno)
54 {
55 	struct xencons_info *entry, *n, *ret = NULL;
56 
57 	if (list_empty(&xenconsoles))
58 			return NULL;
59 
60 	list_for_each_entry_safe(entry, n, &xenconsoles, list) {
61 		if (entry->vtermno == vtermno) {
62 			ret  = entry;
63 			break;
64 		}
65 	}
66 
67 	return ret;
68 }
69 
70 static inline int xenbus_devid_to_vtermno(int devid)
71 {
72 	return devid + HVC_COOKIE;
73 }
74 
75 static inline void notify_daemon(struct xencons_info *cons)
76 {
77 	/* Use evtchn: this is called early, before irq is set up. */
78 	notify_remote_via_evtchn(cons->evtchn);
79 }
80 
81 static int __write_console(struct xencons_info *xencons,
82 		const char *data, int len)
83 {
84 	XENCONS_RING_IDX cons, prod;
85 	struct xencons_interface *intf = xencons->intf;
86 	int sent = 0;
87 
88 	cons = intf->out_cons;
89 	prod = intf->out_prod;
90 	mb();			/* update queue values before going on */
91 
92 	if ((prod - cons) > sizeof(intf->out)) {
93 		pr_err_once("xencons: Illegal ring page indices");
94 		return -EINVAL;
95 	}
96 
97 	while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
98 		intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];
99 
100 	wmb();			/* write ring before updating pointer */
101 	intf->out_prod = prod;
102 
103 	if (sent)
104 		notify_daemon(xencons);
105 	return sent;
106 }
107 
108 static int domU_write_console(uint32_t vtermno, const char *data, int len)
109 {
110 	int ret = len;
111 	struct xencons_info *cons = vtermno_to_xencons(vtermno);
112 	if (cons == NULL)
113 		return -EINVAL;
114 
115 	/*
116 	 * Make sure the whole buffer is emitted, polling if
117 	 * necessary.  We don't ever want to rely on the hvc daemon
118 	 * because the most interesting console output is when the
119 	 * kernel is crippled.
120 	 */
121 	while (len) {
122 		int sent = __write_console(cons, data, len);
123 
124 		if (sent < 0)
125 			return sent;
126 
127 		data += sent;
128 		len -= sent;
129 
130 		if (unlikely(len))
131 			HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
132 	}
133 
134 	return ret;
135 }
136 
137 static int domU_read_console(uint32_t vtermno, char *buf, int len)
138 {
139 	struct xencons_interface *intf;
140 	XENCONS_RING_IDX cons, prod;
141 	int recv = 0;
142 	struct xencons_info *xencons = vtermno_to_xencons(vtermno);
143 	unsigned int eoiflag = 0;
144 
145 	if (xencons == NULL)
146 		return -EINVAL;
147 	intf = xencons->intf;
148 
149 	cons = intf->in_cons;
150 	prod = intf->in_prod;
151 	mb();			/* get pointers before reading ring */
152 
153 	if ((prod - cons) > sizeof(intf->in)) {
154 		pr_err_once("xencons: Illegal ring page indices");
155 		return -EINVAL;
156 	}
157 
158 	while (cons != prod && recv < len)
159 		buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
160 
161 	mb();			/* read ring before consuming */
162 	intf->in_cons = cons;
163 
164 	/*
165 	 * When to mark interrupt having been spurious:
166 	 * - there was no new data to be read, and
167 	 * - the backend did not consume some output bytes, and
168 	 * - the previous round with no read data didn't see consumed bytes
169 	 *   (we might have a race with an interrupt being in flight while
170 	 *   updating xencons->out_cons, so account for that by allowing one
171 	 *   round without any visible reason)
172 	 */
173 	if (intf->out_cons != xencons->out_cons) {
174 		xencons->out_cons = intf->out_cons;
175 		xencons->out_cons_same = 0;
176 	}
177 	if (recv) {
178 		notify_daemon(xencons);
179 	} else if (xencons->out_cons_same++ > 1) {
180 		eoiflag = XEN_EOI_FLAG_SPURIOUS;
181 	}
182 
183 	xen_irq_lateeoi(xencons->irq, eoiflag);
184 
185 	return recv;
186 }
187 
188 static const struct hv_ops domU_hvc_ops = {
189 	.get_chars = domU_read_console,
190 	.put_chars = domU_write_console,
191 	.notifier_add = notifier_add_irq,
192 	.notifier_del = notifier_del_irq,
193 	.notifier_hangup = notifier_hangup_irq,
194 };
195 
196 static int dom0_read_console(uint32_t vtermno, char *buf, int len)
197 {
198 	return HYPERVISOR_console_io(CONSOLEIO_read, len, buf);
199 }
200 
201 /*
202  * Either for a dom0 to write to the system console, or a domU with a
203  * debug version of Xen
204  */
205 static int dom0_write_console(uint32_t vtermno, const char *str, int len)
206 {
207 	int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (char *)str);
208 	if (rc < 0)
209 		return rc;
210 
211 	return len;
212 }
213 
214 static const struct hv_ops dom0_hvc_ops = {
215 	.get_chars = dom0_read_console,
216 	.put_chars = dom0_write_console,
217 	.notifier_add = notifier_add_irq,
218 	.notifier_del = notifier_del_irq,
219 	.notifier_hangup = notifier_hangup_irq,
220 };
221 
222 static int xen_hvm_console_init(void)
223 {
224 	int r;
225 	uint64_t v = 0;
226 	unsigned long gfn;
227 	struct xencons_info *info;
228 
229 	if (!xen_hvm_domain())
230 		return -ENODEV;
231 
232 	info = vtermno_to_xencons(HVC_COOKIE);
233 	if (!info) {
234 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
235 		if (!info)
236 			return -ENOMEM;
237 	} else if (info->intf != NULL) {
238 		/* already configured */
239 		return 0;
240 	}
241 	/*
242 	 * If the toolstack (or the hypervisor) hasn't set these values, the
243 	 * default value is 0. Even though gfn = 0 and evtchn = 0 are
244 	 * theoretically correct values, in practice they never are and they
245 	 * mean that a legacy toolstack hasn't initialized the pv console correctly.
246 	 */
247 	r = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
248 	if (r < 0 || v == 0)
249 		goto err;
250 	info->evtchn = v;
251 	v = 0;
252 	r = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
253 	if (r < 0 || v == 0)
254 		goto err;
255 	gfn = v;
256 	info->intf = memremap(gfn << XEN_PAGE_SHIFT, XEN_PAGE_SIZE, MEMREMAP_WB);
257 	if (info->intf == NULL)
258 		goto err;
259 	info->vtermno = HVC_COOKIE;
260 
261 	spin_lock(&xencons_lock);
262 	list_add_tail(&info->list, &xenconsoles);
263 	spin_unlock(&xencons_lock);
264 
265 	return 0;
266 err:
267 	kfree(info);
268 	return -ENODEV;
269 }
270 
271 static int xencons_info_pv_init(struct xencons_info *info, int vtermno)
272 {
273 	info->evtchn = xen_start_info->console.domU.evtchn;
274 	/* GFN == MFN for PV guest */
275 	info->intf = gfn_to_virt(xen_start_info->console.domU.mfn);
276 	info->vtermno = vtermno;
277 
278 	list_add_tail(&info->list, &xenconsoles);
279 
280 	return 0;
281 }
282 
283 static int xen_pv_console_init(void)
284 {
285 	struct xencons_info *info;
286 
287 	if (!xen_pv_domain())
288 		return -ENODEV;
289 
290 	if (!xen_start_info->console.domU.evtchn)
291 		return -ENODEV;
292 
293 	info = vtermno_to_xencons(HVC_COOKIE);
294 	if (!info) {
295 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
296 		if (!info)
297 			return -ENOMEM;
298 	} else if (info->intf != NULL) {
299 		/* already configured */
300 		return 0;
301 	}
302 	spin_lock(&xencons_lock);
303 	xencons_info_pv_init(info, HVC_COOKIE);
304 	spin_unlock(&xencons_lock);
305 
306 	return 0;
307 }
308 
309 static int xen_initial_domain_console_init(void)
310 {
311 	struct xencons_info *info;
312 
313 	if (!xen_initial_domain())
314 		return -ENODEV;
315 
316 	info = vtermno_to_xencons(HVC_COOKIE);
317 	if (!info) {
318 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
319 		if (!info)
320 			return -ENOMEM;
321 	}
322 
323 	info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0, false);
324 	info->vtermno = HVC_COOKIE;
325 
326 	spin_lock(&xencons_lock);
327 	list_add_tail(&info->list, &xenconsoles);
328 	spin_unlock(&xencons_lock);
329 
330 	return 0;
331 }
332 
333 static void xen_console_update_evtchn(struct xencons_info *info)
334 {
335 	if (xen_hvm_domain()) {
336 		uint64_t v = 0;
337 		int err;
338 
339 		err = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
340 		if (!err && v)
341 			info->evtchn = v;
342 	} else
343 		info->evtchn = xen_start_info->console.domU.evtchn;
344 }
345 
346 void xen_console_resume(void)
347 {
348 	struct xencons_info *info = vtermno_to_xencons(HVC_COOKIE);
349 	if (info != NULL && info->irq) {
350 		if (!xen_initial_domain())
351 			xen_console_update_evtchn(info);
352 		rebind_evtchn_irq(info->evtchn, info->irq);
353 	}
354 }
355 
356 #ifdef CONFIG_HVC_XEN_FRONTEND
357 static void xencons_disconnect_backend(struct xencons_info *info)
358 {
359 	if (info->irq > 0)
360 		unbind_from_irqhandler(info->irq, NULL);
361 	info->irq = 0;
362 	if (info->evtchn > 0)
363 		xenbus_free_evtchn(info->xbdev, info->evtchn);
364 	info->evtchn = 0;
365 	if (info->gntref > 0)
366 		gnttab_free_grant_references(info->gntref);
367 	info->gntref = 0;
368 	if (info->hvc != NULL)
369 		hvc_remove(info->hvc);
370 	info->hvc = NULL;
371 }
372 
373 static void xencons_free(struct xencons_info *info)
374 {
375 	free_page((unsigned long)info->intf);
376 	info->intf = NULL;
377 	info->vtermno = 0;
378 	kfree(info);
379 }
380 
381 static int xen_console_remove(struct xencons_info *info)
382 {
383 	xencons_disconnect_backend(info);
384 	spin_lock(&xencons_lock);
385 	list_del(&info->list);
386 	spin_unlock(&xencons_lock);
387 	if (info->xbdev != NULL)
388 		xencons_free(info);
389 	else {
390 		if (xen_hvm_domain())
391 			iounmap(info->intf);
392 		kfree(info);
393 	}
394 	return 0;
395 }
396 
397 static int xencons_remove(struct xenbus_device *dev)
398 {
399 	return xen_console_remove(dev_get_drvdata(&dev->dev));
400 }
401 
402 static int xencons_connect_backend(struct xenbus_device *dev,
403 				  struct xencons_info *info)
404 {
405 	int ret, evtchn, devid, ref, irq;
406 	struct xenbus_transaction xbt;
407 	grant_ref_t gref_head;
408 
409 	ret = xenbus_alloc_evtchn(dev, &evtchn);
410 	if (ret)
411 		return ret;
412 	info->evtchn = evtchn;
413 	irq = bind_interdomain_evtchn_to_irq_lateeoi(dev, evtchn);
414 	if (irq < 0)
415 		return irq;
416 	info->irq = irq;
417 	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
418 	info->hvc = hvc_alloc(xenbus_devid_to_vtermno(devid),
419 			irq, &domU_hvc_ops, 256);
420 	if (IS_ERR(info->hvc))
421 		return PTR_ERR(info->hvc);
422 	ret = gnttab_alloc_grant_references(1, &gref_head);
423 	if (ret < 0)
424 		return ret;
425 	info->gntref = gref_head;
426 	ref = gnttab_claim_grant_reference(&gref_head);
427 	if (ref < 0)
428 		return ref;
429 	gnttab_grant_foreign_access_ref(ref, info->xbdev->otherend_id,
430 					virt_to_gfn(info->intf), 0);
431 
432  again:
433 	ret = xenbus_transaction_start(&xbt);
434 	if (ret) {
435 		xenbus_dev_fatal(dev, ret, "starting transaction");
436 		return ret;
437 	}
438 	ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", ref);
439 	if (ret)
440 		goto error_xenbus;
441 	ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
442 			    evtchn);
443 	if (ret)
444 		goto error_xenbus;
445 	ret = xenbus_transaction_end(xbt, 0);
446 	if (ret) {
447 		if (ret == -EAGAIN)
448 			goto again;
449 		xenbus_dev_fatal(dev, ret, "completing transaction");
450 		return ret;
451 	}
452 
453 	xenbus_switch_state(dev, XenbusStateInitialised);
454 	return 0;
455 
456  error_xenbus:
457 	xenbus_transaction_end(xbt, 1);
458 	xenbus_dev_fatal(dev, ret, "writing xenstore");
459 	return ret;
460 }
461 
462 static int xencons_probe(struct xenbus_device *dev,
463 				  const struct xenbus_device_id *id)
464 {
465 	int ret, devid;
466 	struct xencons_info *info;
467 
468 	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
469 	if (devid == 0)
470 		return -ENODEV;
471 
472 	info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
473 	if (!info)
474 		return -ENOMEM;
475 	dev_set_drvdata(&dev->dev, info);
476 	info->xbdev = dev;
477 	info->vtermno = xenbus_devid_to_vtermno(devid);
478 	info->intf = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
479 	if (!info->intf)
480 		goto error_nomem;
481 
482 	ret = xencons_connect_backend(dev, info);
483 	if (ret < 0)
484 		goto error;
485 	spin_lock(&xencons_lock);
486 	list_add_tail(&info->list, &xenconsoles);
487 	spin_unlock(&xencons_lock);
488 
489 	return 0;
490 
491  error_nomem:
492 	ret = -ENOMEM;
493 	xenbus_dev_fatal(dev, ret, "allocating device memory");
494  error:
495 	xencons_disconnect_backend(info);
496 	xencons_free(info);
497 	return ret;
498 }
499 
500 static int xencons_resume(struct xenbus_device *dev)
501 {
502 	struct xencons_info *info = dev_get_drvdata(&dev->dev);
503 
504 	xencons_disconnect_backend(info);
505 	memset(info->intf, 0, XEN_PAGE_SIZE);
506 	return xencons_connect_backend(dev, info);
507 }
508 
509 static void xencons_backend_changed(struct xenbus_device *dev,
510 				   enum xenbus_state backend_state)
511 {
512 	switch (backend_state) {
513 	case XenbusStateReconfiguring:
514 	case XenbusStateReconfigured:
515 	case XenbusStateInitialising:
516 	case XenbusStateInitialised:
517 	case XenbusStateUnknown:
518 		break;
519 
520 	case XenbusStateInitWait:
521 		break;
522 
523 	case XenbusStateConnected:
524 		xenbus_switch_state(dev, XenbusStateConnected);
525 		break;
526 
527 	case XenbusStateClosed:
528 		if (dev->state == XenbusStateClosed)
529 			break;
530 		fallthrough;	/* Missed the backend's CLOSING state */
531 	case XenbusStateClosing:
532 		xenbus_frontend_closed(dev);
533 		break;
534 	}
535 }
536 
537 static const struct xenbus_device_id xencons_ids[] = {
538 	{ "console" },
539 	{ "" }
540 };
541 
542 static struct xenbus_driver xencons_driver = {
543 	.name = "xenconsole",
544 	.ids = xencons_ids,
545 	.probe = xencons_probe,
546 	.remove = xencons_remove,
547 	.resume = xencons_resume,
548 	.otherend_changed = xencons_backend_changed,
549 	.not_essential = true,
550 };
551 #endif /* CONFIG_HVC_XEN_FRONTEND */
552 
553 static int __init xen_hvc_init(void)
554 {
555 	int r;
556 	struct xencons_info *info;
557 	const struct hv_ops *ops;
558 
559 	if (!xen_domain())
560 		return -ENODEV;
561 
562 	if (xen_initial_domain()) {
563 		ops = &dom0_hvc_ops;
564 		r = xen_initial_domain_console_init();
565 		if (r < 0)
566 			return r;
567 		info = vtermno_to_xencons(HVC_COOKIE);
568 	} else {
569 		ops = &domU_hvc_ops;
570 		if (xen_hvm_domain())
571 			r = xen_hvm_console_init();
572 		else
573 			r = xen_pv_console_init();
574 		if (r < 0)
575 			return r;
576 
577 		info = vtermno_to_xencons(HVC_COOKIE);
578 		info->irq = bind_evtchn_to_irq_lateeoi(info->evtchn);
579 	}
580 	if (info->irq < 0)
581 		info->irq = 0; /* NO_IRQ */
582 	else
583 		irq_set_noprobe(info->irq);
584 
585 	info->hvc = hvc_alloc(HVC_COOKIE, info->irq, ops, 256);
586 	if (IS_ERR(info->hvc)) {
587 		r = PTR_ERR(info->hvc);
588 		spin_lock(&xencons_lock);
589 		list_del(&info->list);
590 		spin_unlock(&xencons_lock);
591 		if (info->irq)
592 			unbind_from_irqhandler(info->irq, NULL);
593 		kfree(info);
594 		return r;
595 	}
596 
597 	r = 0;
598 #ifdef CONFIG_HVC_XEN_FRONTEND
599 	r = xenbus_register_frontend(&xencons_driver);
600 #endif
601 	return r;
602 }
603 device_initcall(xen_hvc_init);
604 
605 static int xen_cons_init(void)
606 {
607 	const struct hv_ops *ops;
608 
609 	if (!xen_domain())
610 		return 0;
611 
612 	if (xen_initial_domain())
613 		ops = &dom0_hvc_ops;
614 	else {
615 		int r;
616 		ops = &domU_hvc_ops;
617 
618 		if (xen_hvm_domain())
619 			r = xen_hvm_console_init();
620 		else
621 			r = xen_pv_console_init();
622 		if (r < 0)
623 			return r;
624 	}
625 
626 	hvc_instantiate(HVC_COOKIE, 0, ops);
627 	return 0;
628 }
629 console_initcall(xen_cons_init);
630 
631 #ifdef CONFIG_X86
632 static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len)
633 {
634 	if (xen_cpuid_base())
635 		outsb(0xe9, str, len);
636 }
637 #else
638 static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len) { }
639 #endif
640 
641 #ifdef CONFIG_EARLY_PRINTK
642 static int __init xenboot_console_setup(struct console *console, char *string)
643 {
644 	static struct xencons_info xenboot;
645 
646 	if (xen_initial_domain() || !xen_pv_domain())
647 		return 0;
648 
649 	return xencons_info_pv_init(&xenboot, 0);
650 }
651 
652 static void xenboot_write_console(struct console *console, const char *string,
653 				  unsigned len)
654 {
655 	unsigned int linelen, off = 0;
656 	const char *pos;
657 
658 	if (dom0_write_console(0, string, len) >= 0)
659 		return;
660 
661 	if (!xen_pv_domain()) {
662 		xen_hvm_early_write(0, string, len);
663 		return;
664 	}
665 
666 	if (domU_write_console(0, "(early) ", 8) < 0)
667 		return;
668 	while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
669 		linelen = pos-string+off;
670 		if (off + linelen > len)
671 			break;
672 		domU_write_console(0, string+off, linelen);
673 		domU_write_console(0, "\r\n", 2);
674 		off += linelen + 1;
675 	}
676 	if (off < len)
677 		domU_write_console(0, string+off, len-off);
678 }
679 
680 struct console xenboot_console = {
681 	.name		= "xenboot",
682 	.write		= xenboot_write_console,
683 	.setup		= xenboot_console_setup,
684 	.flags		= CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME,
685 	.index		= -1,
686 };
687 #endif	/* CONFIG_EARLY_PRINTK */
688 
689 void xen_raw_console_write(const char *str)
690 {
691 	ssize_t len = strlen(str);
692 	int rc = 0;
693 
694 	if (xen_domain()) {
695 		rc = dom0_write_console(0, str, len);
696 		if (rc != -ENOSYS || !xen_hvm_domain())
697 			return;
698 	}
699 	xen_hvm_early_write(0, str, len);
700 }
701 
702 void xen_raw_printk(const char *fmt, ...)
703 {
704 	static char buf[512];
705 	va_list ap;
706 
707 	va_start(ap, fmt);
708 	vsnprintf(buf, sizeof(buf), fmt, ap);
709 	va_end(ap);
710 
711 	xen_raw_console_write(buf);
712 }
713 
714 static void xenboot_earlycon_write(struct console *console,
715 				  const char *string,
716 				  unsigned len)
717 {
718 	dom0_write_console(0, string, len);
719 }
720 
721 static int __init xenboot_earlycon_setup(struct earlycon_device *device,
722 					    const char *opt)
723 {
724 	device->con->write = xenboot_earlycon_write;
725 	return 0;
726 }
727 EARLYCON_DECLARE(xenboot, xenboot_earlycon_setup);
728