xref: /kernel/linux/linux-6.6/drivers/tty/hvc/hvc_xen.c (revision 62306a36) 
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
35struct 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	spinlock_t ring_lock;
47};
48
49static LIST_HEAD(xenconsoles);
50static DEFINE_SPINLOCK(xencons_lock);
51
52/* ------------------------------------------------------------------ */
53
54static struct xencons_info *vtermno_to_xencons(int vtermno)
55{
56	struct xencons_info *entry, *ret = NULL;
57	unsigned long flags;
58
59	spin_lock_irqsave(&xencons_lock, flags);
60	if (list_empty(&xenconsoles)) {
61		spin_unlock_irqrestore(&xencons_lock, flags);
62		return NULL;
63	}
64
65	list_for_each_entry(entry, &xenconsoles, list) {
66		if (entry->vtermno == vtermno) {
67			ret  = entry;
68			break;
69		}
70	}
71	spin_unlock_irqrestore(&xencons_lock, flags);
72
73	return ret;
74}
75
76static inline int xenbus_devid_to_vtermno(int devid)
77{
78	return devid + HVC_COOKIE;
79}
80
81static inline void notify_daemon(struct xencons_info *cons)
82{
83	/* Use evtchn: this is called early, before irq is set up. */
84	notify_remote_via_evtchn(cons->evtchn);
85}
86
87static int __write_console(struct xencons_info *xencons,
88		const char *data, int len)
89{
90	XENCONS_RING_IDX cons, prod;
91	struct xencons_interface *intf = xencons->intf;
92	int sent = 0;
93	unsigned long flags;
94
95	spin_lock_irqsave(&xencons->ring_lock, flags);
96	cons = intf->out_cons;
97	prod = intf->out_prod;
98	mb();			/* update queue values before going on */
99
100	if ((prod - cons) > sizeof(intf->out)) {
101		spin_unlock_irqrestore(&xencons->ring_lock, flags);
102		pr_err_once("xencons: Illegal ring page indices");
103		return -EINVAL;
104	}
105
106	while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
107		intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];
108
109	wmb();			/* write ring before updating pointer */
110	intf->out_prod = prod;
111	spin_unlock_irqrestore(&xencons->ring_lock, flags);
112
113	if (sent)
114		notify_daemon(xencons);
115	return sent;
116}
117
118static int domU_write_console(uint32_t vtermno, const char *data, int len)
119{
120	int ret = len;
121	struct xencons_info *cons = vtermno_to_xencons(vtermno);
122	if (cons == NULL)
123		return -EINVAL;
124
125	/*
126	 * Make sure the whole buffer is emitted, polling if
127	 * necessary.  We don't ever want to rely on the hvc daemon
128	 * because the most interesting console output is when the
129	 * kernel is crippled.
130	 */
131	while (len) {
132		int sent = __write_console(cons, data, len);
133
134		if (sent < 0)
135			return sent;
136
137		data += sent;
138		len -= sent;
139
140		if (unlikely(len))
141			HYPERVISOR_sched_op(SCHEDOP_yield, NULL);
142	}
143
144	return ret;
145}
146
147static int domU_read_console(uint32_t vtermno, char *buf, int len)
148{
149	struct xencons_interface *intf;
150	XENCONS_RING_IDX cons, prod;
151	int recv = 0;
152	struct xencons_info *xencons = vtermno_to_xencons(vtermno);
153	unsigned int eoiflag = 0;
154	unsigned long flags;
155
156	if (xencons == NULL)
157		return -EINVAL;
158	intf = xencons->intf;
159
160	spin_lock_irqsave(&xencons->ring_lock, flags);
161	cons = intf->in_cons;
162	prod = intf->in_prod;
163	mb();			/* get pointers before reading ring */
164
165	if ((prod - cons) > sizeof(intf->in)) {
166		spin_unlock_irqrestore(&xencons->ring_lock, flags);
167		pr_err_once("xencons: Illegal ring page indices");
168		return -EINVAL;
169	}
170
171	while (cons != prod && recv < len)
172		buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
173
174	mb();			/* read ring before consuming */
175	intf->in_cons = cons;
176
177	/*
178	 * When to mark interrupt having been spurious:
179	 * - there was no new data to be read, and
180	 * - the backend did not consume some output bytes, and
181	 * - the previous round with no read data didn't see consumed bytes
182	 *   (we might have a race with an interrupt being in flight while
183	 *   updating xencons->out_cons, so account for that by allowing one
184	 *   round without any visible reason)
185	 */
186	if (intf->out_cons != xencons->out_cons) {
187		xencons->out_cons = intf->out_cons;
188		xencons->out_cons_same = 0;
189	}
190	if (!recv && xencons->out_cons_same++ > 1) {
191		eoiflag = XEN_EOI_FLAG_SPURIOUS;
192	}
193	spin_unlock_irqrestore(&xencons->ring_lock, flags);
194
195	if (recv) {
196		notify_daemon(xencons);
197	}
198
199	xen_irq_lateeoi(xencons->irq, eoiflag);
200
201	return recv;
202}
203
204static const struct hv_ops domU_hvc_ops = {
205	.get_chars = domU_read_console,
206	.put_chars = domU_write_console,
207	.notifier_add = notifier_add_irq,
208	.notifier_del = notifier_del_irq,
209	.notifier_hangup = notifier_hangup_irq,
210};
211
212static int dom0_read_console(uint32_t vtermno, char *buf, int len)
213{
214	return HYPERVISOR_console_io(CONSOLEIO_read, len, buf);
215}
216
217/*
218 * Either for a dom0 to write to the system console, or a domU with a
219 * debug version of Xen
220 */
221static int dom0_write_console(uint32_t vtermno, const char *str, int len)
222{
223	int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (char *)str);
224	if (rc < 0)
225		return rc;
226
227	return len;
228}
229
230static const struct hv_ops dom0_hvc_ops = {
231	.get_chars = dom0_read_console,
232	.put_chars = dom0_write_console,
233	.notifier_add = notifier_add_irq,
234	.notifier_del = notifier_del_irq,
235	.notifier_hangup = notifier_hangup_irq,
236};
237
238static int xen_hvm_console_init(void)
239{
240	int r;
241	uint64_t v = 0;
242	unsigned long gfn, flags;
243	struct xencons_info *info;
244
245	if (!xen_hvm_domain())
246		return -ENODEV;
247
248	info = vtermno_to_xencons(HVC_COOKIE);
249	if (!info) {
250		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
251		if (!info)
252			return -ENOMEM;
253		spin_lock_init(&info->ring_lock);
254	} else if (info->intf != NULL) {
255		/* already configured */
256		return 0;
257	}
258	/*
259	 * If the toolstack (or the hypervisor) hasn't set these values, the
260	 * default value is 0. Even though gfn = 0 and evtchn = 0 are
261	 * theoretically correct values, in practice they never are and they
262	 * mean that a legacy toolstack hasn't initialized the pv console correctly.
263	 */
264	r = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
265	if (r < 0 || v == 0)
266		goto err;
267	info->evtchn = v;
268	v = 0;
269	r = hvm_get_parameter(HVM_PARAM_CONSOLE_PFN, &v);
270	if (r < 0 || v == 0)
271		goto err;
272	gfn = v;
273	info->intf = memremap(gfn << XEN_PAGE_SHIFT, XEN_PAGE_SIZE, MEMREMAP_WB);
274	if (info->intf == NULL)
275		goto err;
276	info->vtermno = HVC_COOKIE;
277
278	spin_lock_irqsave(&xencons_lock, flags);
279	list_add_tail(&info->list, &xenconsoles);
280	spin_unlock_irqrestore(&xencons_lock, flags);
281
282	return 0;
283err:
284	kfree(info);
285	return -ENODEV;
286}
287
288static int xencons_info_pv_init(struct xencons_info *info, int vtermno)
289{
290	spin_lock_init(&info->ring_lock);
291	info->evtchn = xen_start_info->console.domU.evtchn;
292	/* GFN == MFN for PV guest */
293	info->intf = gfn_to_virt(xen_start_info->console.domU.mfn);
294	info->vtermno = vtermno;
295
296	list_add_tail(&info->list, &xenconsoles);
297
298	return 0;
299}
300
301static int xen_pv_console_init(void)
302{
303	struct xencons_info *info;
304	unsigned long flags;
305
306	if (!xen_pv_domain())
307		return -ENODEV;
308
309	if (!xen_start_info->console.domU.evtchn)
310		return -ENODEV;
311
312	info = vtermno_to_xencons(HVC_COOKIE);
313	if (!info) {
314		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
315		if (!info)
316			return -ENOMEM;
317	} else if (info->intf != NULL) {
318		/* already configured */
319		return 0;
320	}
321	spin_lock_irqsave(&xencons_lock, flags);
322	xencons_info_pv_init(info, HVC_COOKIE);
323	spin_unlock_irqrestore(&xencons_lock, flags);
324
325	return 0;
326}
327
328static int xen_initial_domain_console_init(void)
329{
330	struct xencons_info *info;
331	unsigned long flags;
332
333	if (!xen_initial_domain())
334		return -ENODEV;
335
336	info = vtermno_to_xencons(HVC_COOKIE);
337	if (!info) {
338		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
339		if (!info)
340			return -ENOMEM;
341		spin_lock_init(&info->ring_lock);
342	}
343
344	info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0, false);
345	info->vtermno = HVC_COOKIE;
346
347	spin_lock_irqsave(&xencons_lock, flags);
348	list_add_tail(&info->list, &xenconsoles);
349	spin_unlock_irqrestore(&xencons_lock, flags);
350
351	return 0;
352}
353
354static void xen_console_update_evtchn(struct xencons_info *info)
355{
356	if (xen_hvm_domain()) {
357		uint64_t v = 0;
358		int err;
359
360		err = hvm_get_parameter(HVM_PARAM_CONSOLE_EVTCHN, &v);
361		if (!err && v)
362			info->evtchn = v;
363	} else
364		info->evtchn = xen_start_info->console.domU.evtchn;
365}
366
367void xen_console_resume(void)
368{
369	struct xencons_info *info = vtermno_to_xencons(HVC_COOKIE);
370	if (info != NULL && info->irq) {
371		if (!xen_initial_domain())
372			xen_console_update_evtchn(info);
373		rebind_evtchn_irq(info->evtchn, info->irq);
374	}
375}
376
377#ifdef CONFIG_HVC_XEN_FRONTEND
378static void xencons_disconnect_backend(struct xencons_info *info)
379{
380	if (info->hvc != NULL)
381		hvc_remove(info->hvc);
382	info->hvc = NULL;
383	if (info->irq > 0) {
384		evtchn_put(info->evtchn);
385		info->irq = 0;
386		info->evtchn = 0;
387	}
388	/* evtchn_put() will also close it so this is only an error path */
389	if (info->evtchn > 0)
390		xenbus_free_evtchn(info->xbdev, info->evtchn);
391	info->evtchn = 0;
392	if (info->gntref > 0)
393		gnttab_free_grant_references(info->gntref);
394	info->gntref = 0;
395}
396
397static void xencons_free(struct xencons_info *info)
398{
399	free_page((unsigned long)info->intf);
400	info->intf = NULL;
401	info->vtermno = 0;
402	kfree(info);
403}
404
405static int xen_console_remove(struct xencons_info *info)
406{
407	unsigned long flags;
408
409	xencons_disconnect_backend(info);
410	spin_lock_irqsave(&xencons_lock, flags);
411	list_del(&info->list);
412	spin_unlock_irqrestore(&xencons_lock, flags);
413	if (info->xbdev != NULL)
414		xencons_free(info);
415	else {
416		if (xen_hvm_domain())
417			iounmap(info->intf);
418		kfree(info);
419	}
420	return 0;
421}
422
423static void xencons_remove(struct xenbus_device *dev)
424{
425	xen_console_remove(dev_get_drvdata(&dev->dev));
426}
427
428static int xencons_connect_backend(struct xenbus_device *dev,
429				  struct xencons_info *info)
430{
431	int ret, evtchn, devid, ref, irq;
432	struct xenbus_transaction xbt;
433	grant_ref_t gref_head;
434
435	ret = xenbus_alloc_evtchn(dev, &evtchn);
436	if (ret)
437		return ret;
438	info->evtchn = evtchn;
439	irq = bind_evtchn_to_irq_lateeoi(evtchn);
440	if (irq < 0)
441		return irq;
442	info->irq = irq;
443	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
444	info->hvc = hvc_alloc(xenbus_devid_to_vtermno(devid),
445			irq, &domU_hvc_ops, 256);
446	if (IS_ERR(info->hvc))
447		return PTR_ERR(info->hvc);
448	ret = gnttab_alloc_grant_references(1, &gref_head);
449	if (ret < 0)
450		return ret;
451	info->gntref = gref_head;
452	ref = gnttab_claim_grant_reference(&gref_head);
453	if (ref < 0)
454		return ref;
455	gnttab_grant_foreign_access_ref(ref, info->xbdev->otherend_id,
456					virt_to_gfn(info->intf), 0);
457
458 again:
459	ret = xenbus_transaction_start(&xbt);
460	if (ret) {
461		xenbus_dev_fatal(dev, ret, "starting transaction");
462		return ret;
463	}
464	ret = xenbus_printf(xbt, dev->nodename, "ring-ref", "%d", ref);
465	if (ret)
466		goto error_xenbus;
467	ret = xenbus_printf(xbt, dev->nodename, "port", "%u",
468			    evtchn);
469	if (ret)
470		goto error_xenbus;
471	ret = xenbus_transaction_end(xbt, 0);
472	if (ret) {
473		if (ret == -EAGAIN)
474			goto again;
475		xenbus_dev_fatal(dev, ret, "completing transaction");
476		return ret;
477	}
478
479	xenbus_switch_state(dev, XenbusStateInitialised);
480	return 0;
481
482 error_xenbus:
483	xenbus_transaction_end(xbt, 1);
484	xenbus_dev_fatal(dev, ret, "writing xenstore");
485	return ret;
486}
487
488static int xencons_probe(struct xenbus_device *dev,
489				  const struct xenbus_device_id *id)
490{
491	int ret, devid;
492	struct xencons_info *info;
493	unsigned long flags;
494
495	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
496	if (devid == 0)
497		return -ENODEV;
498
499	info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
500	if (!info)
501		return -ENOMEM;
502	spin_lock_init(&info->ring_lock);
503	dev_set_drvdata(&dev->dev, info);
504	info->xbdev = dev;
505	info->vtermno = xenbus_devid_to_vtermno(devid);
506	info->intf = (void *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
507	if (!info->intf)
508		goto error_nomem;
509
510	ret = xencons_connect_backend(dev, info);
511	if (ret < 0)
512		goto error;
513	spin_lock_irqsave(&xencons_lock, flags);
514	list_add_tail(&info->list, &xenconsoles);
515	spin_unlock_irqrestore(&xencons_lock, flags);
516
517	return 0;
518
519 error_nomem:
520	ret = -ENOMEM;
521	xenbus_dev_fatal(dev, ret, "allocating device memory");
522 error:
523	xencons_disconnect_backend(info);
524	xencons_free(info);
525	return ret;
526}
527
528static int xencons_resume(struct xenbus_device *dev)
529{
530	struct xencons_info *info = dev_get_drvdata(&dev->dev);
531
532	xencons_disconnect_backend(info);
533	memset(info->intf, 0, XEN_PAGE_SIZE);
534	return xencons_connect_backend(dev, info);
535}
536
537static void xencons_backend_changed(struct xenbus_device *dev,
538				   enum xenbus_state backend_state)
539{
540	switch (backend_state) {
541	case XenbusStateReconfiguring:
542	case XenbusStateReconfigured:
543	case XenbusStateInitialising:
544	case XenbusStateInitialised:
545	case XenbusStateUnknown:
546		break;
547
548	case XenbusStateInitWait:
549		break;
550
551	case XenbusStateConnected:
552		xenbus_switch_state(dev, XenbusStateConnected);
553		break;
554
555	case XenbusStateClosed:
556		if (dev->state == XenbusStateClosed)
557			break;
558		fallthrough;	/* Missed the backend's CLOSING state */
559	case XenbusStateClosing: {
560		struct xencons_info *info = dev_get_drvdata(&dev->dev);;
561
562		/*
563		 * Don't tear down the evtchn and grant ref before the other
564		 * end has disconnected, but do stop userspace from trying
565		 * to use the device before we allow the backend to close.
566		 */
567		if (info->hvc) {
568			hvc_remove(info->hvc);
569			info->hvc = NULL;
570		}
571
572		xenbus_frontend_closed(dev);
573		break;
574	}
575	}
576}
577
578static const struct xenbus_device_id xencons_ids[] = {
579	{ "console" },
580	{ "" }
581};
582
583static struct xenbus_driver xencons_driver = {
584	.name = "xenconsole",
585	.ids = xencons_ids,
586	.probe = xencons_probe,
587	.remove = xencons_remove,
588	.resume = xencons_resume,
589	.otherend_changed = xencons_backend_changed,
590	.not_essential = true,
591};
592#endif /* CONFIG_HVC_XEN_FRONTEND */
593
594static int __init xen_hvc_init(void)
595{
596	int r;
597	struct xencons_info *info;
598	const struct hv_ops *ops;
599
600	if (!xen_domain())
601		return -ENODEV;
602
603	if (xen_initial_domain()) {
604		ops = &dom0_hvc_ops;
605		r = xen_initial_domain_console_init();
606		if (r < 0)
607			goto register_fe;
608		info = vtermno_to_xencons(HVC_COOKIE);
609	} else {
610		ops = &domU_hvc_ops;
611		if (xen_hvm_domain())
612			r = xen_hvm_console_init();
613		else
614			r = xen_pv_console_init();
615		if (r < 0)
616			goto register_fe;
617
618		info = vtermno_to_xencons(HVC_COOKIE);
619		info->irq = bind_evtchn_to_irq_lateeoi(info->evtchn);
620	}
621	if (info->irq < 0)
622		info->irq = 0; /* NO_IRQ */
623	else
624		irq_set_noprobe(info->irq);
625
626	info->hvc = hvc_alloc(HVC_COOKIE, info->irq, ops, 256);
627	if (IS_ERR(info->hvc)) {
628		unsigned long flags;
629
630		r = PTR_ERR(info->hvc);
631		spin_lock_irqsave(&xencons_lock, flags);
632		list_del(&info->list);
633		spin_unlock_irqrestore(&xencons_lock, flags);
634		if (info->irq)
635			evtchn_put(info->evtchn);
636		kfree(info);
637		return r;
638	}
639
640	r = 0;
641 register_fe:
642#ifdef CONFIG_HVC_XEN_FRONTEND
643	r = xenbus_register_frontend(&xencons_driver);
644#endif
645	return r;
646}
647device_initcall(xen_hvc_init);
648
649static int xen_cons_init(void)
650{
651	const struct hv_ops *ops;
652
653	if (!xen_domain())
654		return 0;
655
656	if (xen_initial_domain())
657		ops = &dom0_hvc_ops;
658	else {
659		int r;
660		ops = &domU_hvc_ops;
661
662		if (xen_hvm_domain())
663			r = xen_hvm_console_init();
664		else
665			r = xen_pv_console_init();
666		if (r < 0)
667			return r;
668	}
669
670	hvc_instantiate(HVC_COOKIE, 0, ops);
671	return 0;
672}
673console_initcall(xen_cons_init);
674
675#ifdef CONFIG_X86
676static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len)
677{
678	if (xen_cpuid_base())
679		outsb(0xe9, str, len);
680}
681#else
682static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len) { }
683#endif
684
685#ifdef CONFIG_EARLY_PRINTK
686static int __init xenboot_console_setup(struct console *console, char *string)
687{
688	static struct xencons_info xenboot;
689
690	if (xen_initial_domain() || !xen_pv_domain())
691		return 0;
692
693	return xencons_info_pv_init(&xenboot, 0);
694}
695
696static void xenboot_write_console(struct console *console, const char *string,
697				  unsigned len)
698{
699	unsigned int linelen, off = 0;
700	const char *pos;
701
702	if (dom0_write_console(0, string, len) >= 0)
703		return;
704
705	if (!xen_pv_domain()) {
706		xen_hvm_early_write(0, string, len);
707		return;
708	}
709
710	if (domU_write_console(0, "(early) ", 8) < 0)
711		return;
712	while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
713		linelen = pos-string+off;
714		if (off + linelen > len)
715			break;
716		domU_write_console(0, string+off, linelen);
717		domU_write_console(0, "\r\n", 2);
718		off += linelen + 1;
719	}
720	if (off < len)
721		domU_write_console(0, string+off, len-off);
722}
723
724struct console xenboot_console = {
725	.name		= "xenboot",
726	.write		= xenboot_write_console,
727	.setup		= xenboot_console_setup,
728	.flags		= CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME,
729	.index		= -1,
730};
731#endif	/* CONFIG_EARLY_PRINTK */
732
733void xen_raw_console_write(const char *str)
734{
735	ssize_t len = strlen(str);
736	int rc = 0;
737
738	if (xen_domain()) {
739		rc = dom0_write_console(0, str, len);
740		if (rc != -ENOSYS || !xen_hvm_domain())
741			return;
742	}
743	xen_hvm_early_write(0, str, len);
744}
745
746void xen_raw_printk(const char *fmt, ...)
747{
748	static char buf[512];
749	va_list ap;
750
751	va_start(ap, fmt);
752	vsnprintf(buf, sizeof(buf), fmt, ap);
753	va_end(ap);
754
755	xen_raw_console_write(buf);
756}
757
758static void xenboot_earlycon_write(struct console *console,
759				  const char *string,
760				  unsigned len)
761{
762	dom0_write_console(0, string, len);
763}
764
765static int __init xenboot_earlycon_setup(struct earlycon_device *device,
766					    const char *opt)
767{
768	device->con->write = xenboot_earlycon_write;
769	return 0;
770}
771EARLYCON_DECLARE(xenboot, xenboot_earlycon_setup);
772