xref: /linux/drivers/xen/events/events_fifo.c (revision 988b0c541ed8b1c633c4d4df7169010635942e18)
1 /*
2  * Xen event channels (FIFO-based ABI)
3  *
4  * Copyright (C) 2013 Citrix Systems R&D ltd.
5  *
6  * This source code is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License as
8  * published by the Free Software Foundation; either version 2 of the
9  * License, or (at your option) any later version.
10  *
11  * Or, when distributed separately from the Linux kernel or
12  * incorporated into other software packages, subject to the following
13  * license:
14  *
15  * Permission is hereby granted, free of charge, to any person obtaining a copy
16  * of this source file (the "Software"), to deal in the Software without
17  * restriction, including without limitation the rights to use, copy, modify,
18  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
19  * and to permit persons to whom the Software is furnished to do so, subject to
20  * the following conditions:
21  *
22  * The above copyright notice and this permission notice shall be included in
23  * all copies or substantial portions of the Software.
24  *
25  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
26  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
27  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
28  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
29  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
30  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
31  * IN THE SOFTWARE.
32  */
33 
34 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
35 
36 #include <linux/linkage.h>
37 #include <linux/interrupt.h>
38 #include <linux/irq.h>
39 #include <linux/module.h>
40 #include <linux/smp.h>
41 #include <linux/percpu.h>
42 #include <linux/cpu.h>
43 
44 #include <asm/sync_bitops.h>
45 #include <asm/xen/hypercall.h>
46 #include <asm/xen/hypervisor.h>
47 #include <asm/xen/page.h>
48 
49 #include <xen/xen.h>
50 #include <xen/xen-ops.h>
51 #include <xen/events.h>
52 #include <xen/interface/xen.h>
53 #include <xen/interface/event_channel.h>
54 
55 #include "events_internal.h"
56 
57 #define EVENT_WORDS_PER_PAGE (PAGE_SIZE / sizeof(event_word_t))
58 #define MAX_EVENT_ARRAY_PAGES (EVTCHN_FIFO_NR_CHANNELS / EVENT_WORDS_PER_PAGE)
59 
60 struct evtchn_fifo_queue {
61 	uint32_t head[EVTCHN_FIFO_MAX_QUEUES];
62 };
63 
64 static DEFINE_PER_CPU(struct evtchn_fifo_control_block *, cpu_control_block);
65 static DEFINE_PER_CPU(struct evtchn_fifo_queue, cpu_queue);
66 static event_word_t *event_array[MAX_EVENT_ARRAY_PAGES] __read_mostly;
67 static unsigned event_array_pages __read_mostly;
68 
69 /*
70  * sync_set_bit() and friends must be unsigned long aligned on non-x86
71  * platforms.
72  */
73 #if !defined(CONFIG_X86) && BITS_PER_LONG > 32
74 
75 #define BM(w) (unsigned long *)((unsigned long)w & ~0x7UL)
76 #define EVTCHN_FIFO_BIT(b, w) \
77     (((unsigned long)w & 0x4UL) ? (EVTCHN_FIFO_ ##b + 32) : EVTCHN_FIFO_ ##b)
78 
79 #else
80 
81 #define BM(w) ((unsigned long *)(w))
82 #define EVTCHN_FIFO_BIT(b, w) EVTCHN_FIFO_ ##b
83 
84 #endif
85 
86 static inline event_word_t *event_word_from_port(unsigned port)
87 {
88 	unsigned i = port / EVENT_WORDS_PER_PAGE;
89 
90 	return event_array[i] + port % EVENT_WORDS_PER_PAGE;
91 }
92 
93 static unsigned evtchn_fifo_max_channels(void)
94 {
95 	return EVTCHN_FIFO_NR_CHANNELS;
96 }
97 
98 static unsigned evtchn_fifo_nr_channels(void)
99 {
100 	return event_array_pages * EVENT_WORDS_PER_PAGE;
101 }
102 
103 static void free_unused_array_pages(void)
104 {
105 	unsigned i;
106 
107 	for (i = event_array_pages; i < MAX_EVENT_ARRAY_PAGES; i++) {
108 		if (!event_array[i])
109 			break;
110 		free_page((unsigned long)event_array[i]);
111 		event_array[i] = NULL;
112 	}
113 }
114 
115 static void init_array_page(event_word_t *array_page)
116 {
117 	unsigned i;
118 
119 	for (i = 0; i < EVENT_WORDS_PER_PAGE; i++)
120 		array_page[i] = 1 << EVTCHN_FIFO_MASKED;
121 }
122 
123 static int evtchn_fifo_setup(struct irq_info *info)
124 {
125 	unsigned port = info->evtchn;
126 	unsigned new_array_pages;
127 	int ret;
128 
129 	new_array_pages = port / EVENT_WORDS_PER_PAGE + 1;
130 
131 	if (new_array_pages > MAX_EVENT_ARRAY_PAGES)
132 		return -EINVAL;
133 
134 	while (event_array_pages < new_array_pages) {
135 		void *array_page;
136 		struct evtchn_expand_array expand_array;
137 
138 		/* Might already have a page if we've resumed. */
139 		array_page = event_array[event_array_pages];
140 		if (!array_page) {
141 			array_page = (void *)__get_free_page(GFP_KERNEL);
142 			if (array_page == NULL) {
143 				ret = -ENOMEM;
144 				goto error;
145 			}
146 			event_array[event_array_pages] = array_page;
147 		}
148 
149 		/* Mask all events in this page before adding it. */
150 		init_array_page(array_page);
151 
152 		expand_array.array_gfn = virt_to_mfn(array_page);
153 
154 		ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array);
155 		if (ret < 0)
156 			goto error;
157 
158 		event_array_pages++;
159 	}
160 	return 0;
161 
162   error:
163 	if (event_array_pages == 0)
164 		panic("xen: unable to expand event array with initial page (%d)\n", ret);
165 	else
166 		pr_err("unable to expand event array (%d)\n", ret);
167 	free_unused_array_pages();
168 	return ret;
169 }
170 
171 static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu)
172 {
173 	/* no-op */
174 }
175 
176 static void evtchn_fifo_clear_pending(unsigned port)
177 {
178 	event_word_t *word = event_word_from_port(port);
179 	sync_clear_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
180 }
181 
182 static void evtchn_fifo_set_pending(unsigned port)
183 {
184 	event_word_t *word = event_word_from_port(port);
185 	sync_set_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
186 }
187 
188 static bool evtchn_fifo_is_pending(unsigned port)
189 {
190 	event_word_t *word = event_word_from_port(port);
191 	return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
192 }
193 
194 static bool evtchn_fifo_test_and_set_mask(unsigned port)
195 {
196 	event_word_t *word = event_word_from_port(port);
197 	return sync_test_and_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
198 }
199 
200 static void evtchn_fifo_mask(unsigned port)
201 {
202 	event_word_t *word = event_word_from_port(port);
203 	sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
204 }
205 
206 static bool evtchn_fifo_is_masked(unsigned port)
207 {
208 	event_word_t *word = event_word_from_port(port);
209 	return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
210 }
211 /*
212  * Clear MASKED, spinning if BUSY is set.
213  */
214 static void clear_masked(volatile event_word_t *word)
215 {
216 	event_word_t new, old, w;
217 
218 	w = *word;
219 
220 	do {
221 		old = w & ~(1 << EVTCHN_FIFO_BUSY);
222 		new = old & ~(1 << EVTCHN_FIFO_MASKED);
223 		w = sync_cmpxchg(word, old, new);
224 	} while (w != old);
225 }
226 
227 static void evtchn_fifo_unmask(unsigned port)
228 {
229 	event_word_t *word = event_word_from_port(port);
230 
231 	BUG_ON(!irqs_disabled());
232 
233 	clear_masked(word);
234 	if (evtchn_fifo_is_pending(port)) {
235 		struct evtchn_unmask unmask = { .port = port };
236 		(void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
237 	}
238 }
239 
240 static uint32_t clear_linked(volatile event_word_t *word)
241 {
242 	event_word_t new, old, w;
243 
244 	w = *word;
245 
246 	do {
247 		old = w;
248 		new = (w & ~((1 << EVTCHN_FIFO_LINKED)
249 			     | EVTCHN_FIFO_LINK_MASK));
250 	} while ((w = sync_cmpxchg(word, old, new)) != old);
251 
252 	return w & EVTCHN_FIFO_LINK_MASK;
253 }
254 
255 static void handle_irq_for_port(unsigned port)
256 {
257 	int irq;
258 
259 	irq = get_evtchn_to_irq(port);
260 	if (irq != -1)
261 		generic_handle_irq(irq);
262 }
263 
264 static void consume_one_event(unsigned cpu,
265 			      struct evtchn_fifo_control_block *control_block,
266 			      unsigned priority, unsigned long *ready)
267 {
268 	struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
269 	uint32_t head;
270 	unsigned port;
271 	event_word_t *word;
272 
273 	head = q->head[priority];
274 
275 	/*
276 	 * Reached the tail last time?  Read the new HEAD from the
277 	 * control block.
278 	 */
279 	if (head == 0) {
280 		rmb(); /* Ensure word is up-to-date before reading head. */
281 		head = control_block->head[priority];
282 	}
283 
284 	port = head;
285 	word = event_word_from_port(port);
286 	head = clear_linked(word);
287 
288 	/*
289 	 * If the link is non-zero, there are more events in the
290 	 * queue, otherwise the queue is empty.
291 	 *
292 	 * If the queue is empty, clear this priority from our local
293 	 * copy of the ready word.
294 	 */
295 	if (head == 0)
296 		clear_bit(priority, ready);
297 
298 	if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port))
299 		handle_irq_for_port(port);
300 
301 	q->head[priority] = head;
302 }
303 
304 static void evtchn_fifo_handle_events(unsigned cpu)
305 {
306 	struct evtchn_fifo_control_block *control_block;
307 	unsigned long ready;
308 	unsigned q;
309 
310 	control_block = per_cpu(cpu_control_block, cpu);
311 
312 	ready = xchg(&control_block->ready, 0);
313 
314 	while (ready) {
315 		q = find_first_bit(BM(&ready), EVTCHN_FIFO_MAX_QUEUES);
316 		consume_one_event(cpu, control_block, q, &ready);
317 		ready |= xchg(&control_block->ready, 0);
318 	}
319 }
320 
321 static void evtchn_fifo_resume(void)
322 {
323 	unsigned cpu;
324 
325 	for_each_possible_cpu(cpu) {
326 		void *control_block = per_cpu(cpu_control_block, cpu);
327 		struct evtchn_init_control init_control;
328 		int ret;
329 
330 		if (!control_block)
331 			continue;
332 
333 		/*
334 		 * If this CPU is offline, take the opportunity to
335 		 * free the control block while it is not being
336 		 * used.
337 		 */
338 		if (!cpu_online(cpu)) {
339 			free_page((unsigned long)control_block);
340 			per_cpu(cpu_control_block, cpu) = NULL;
341 			continue;
342 		}
343 
344 		init_control.control_gfn = virt_to_mfn(control_block);
345 		init_control.offset = 0;
346 		init_control.vcpu = cpu;
347 
348 		ret = HYPERVISOR_event_channel_op(EVTCHNOP_init_control,
349 						  &init_control);
350 		if (ret < 0)
351 			BUG();
352 	}
353 
354 	/*
355 	 * The event array starts out as empty again and is extended
356 	 * as normal when events are bound.  The existing pages will
357 	 * be reused.
358 	 */
359 	event_array_pages = 0;
360 }
361 
362 static const struct evtchn_ops evtchn_ops_fifo = {
363 	.max_channels      = evtchn_fifo_max_channels,
364 	.nr_channels       = evtchn_fifo_nr_channels,
365 	.setup             = evtchn_fifo_setup,
366 	.bind_to_cpu       = evtchn_fifo_bind_to_cpu,
367 	.clear_pending     = evtchn_fifo_clear_pending,
368 	.set_pending       = evtchn_fifo_set_pending,
369 	.is_pending        = evtchn_fifo_is_pending,
370 	.test_and_set_mask = evtchn_fifo_test_and_set_mask,
371 	.mask              = evtchn_fifo_mask,
372 	.unmask            = evtchn_fifo_unmask,
373 	.handle_events     = evtchn_fifo_handle_events,
374 	.resume            = evtchn_fifo_resume,
375 };
376 
377 static int evtchn_fifo_init_control_block(unsigned cpu)
378 {
379 	struct page *control_block = NULL;
380 	struct evtchn_init_control init_control;
381 	int ret = -ENOMEM;
382 
383 	control_block = alloc_page(GFP_KERNEL|__GFP_ZERO);
384 	if (control_block == NULL)
385 		goto error;
386 
387 	init_control.control_gfn = virt_to_mfn(page_address(control_block));
388 	init_control.offset      = 0;
389 	init_control.vcpu        = cpu;
390 
391 	ret = HYPERVISOR_event_channel_op(EVTCHNOP_init_control, &init_control);
392 	if (ret < 0)
393 		goto error;
394 
395 	per_cpu(cpu_control_block, cpu) = page_address(control_block);
396 
397 	return 0;
398 
399   error:
400 	__free_page(control_block);
401 	return ret;
402 }
403 
404 static int evtchn_fifo_cpu_notification(struct notifier_block *self,
405 						  unsigned long action,
406 						  void *hcpu)
407 {
408 	int cpu = (long)hcpu;
409 	int ret = 0;
410 
411 	switch (action) {
412 	case CPU_UP_PREPARE:
413 		if (!per_cpu(cpu_control_block, cpu))
414 			ret = evtchn_fifo_init_control_block(cpu);
415 		break;
416 	default:
417 		break;
418 	}
419 	return ret < 0 ? NOTIFY_BAD : NOTIFY_OK;
420 }
421 
422 static struct notifier_block evtchn_fifo_cpu_notifier = {
423 	.notifier_call	= evtchn_fifo_cpu_notification,
424 };
425 
426 int __init xen_evtchn_fifo_init(void)
427 {
428 	int cpu = get_cpu();
429 	int ret;
430 
431 	ret = evtchn_fifo_init_control_block(cpu);
432 	if (ret < 0)
433 		goto out;
434 
435 	pr_info("Using FIFO-based ABI\n");
436 
437 	evtchn_ops = &evtchn_ops_fifo;
438 
439 	register_cpu_notifier(&evtchn_fifo_cpu_notifier);
440 out:
441 	put_cpu();
442 	return ret;
443 }
444