Merge tag 'for-linus-4.10-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git...
[sfrench/cifs-2.6.git] / drivers / xen / events / events_fifo.c
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/smp.h>
40 #include <linux/percpu.h>
41 #include <linux/cpu.h>
42
43 #include <asm/barrier.h>
44 #include <asm/sync_bitops.h>
45 #include <asm/xen/hypercall.h>
46 #include <asm/xen/hypervisor.h>
47
48 #include <xen/xen.h>
49 #include <xen/xen-ops.h>
50 #include <xen/events.h>
51 #include <xen/interface/xen.h>
52 #include <xen/interface/event_channel.h>
53 #include <xen/page.h>
54
55 #include "events_internal.h"
56
57 #define EVENT_WORDS_PER_PAGE (XEN_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.
71  */
72 #if BITS_PER_LONG > 32
73
74 #define BM(w) (unsigned long *)((unsigned long)w & ~0x7UL)
75 #define EVTCHN_FIFO_BIT(b, w) \
76     (((unsigned long)w & 0x4UL) ? (EVTCHN_FIFO_ ##b + 32) : EVTCHN_FIFO_ ##b)
77
78 #else
79
80 #define BM(w) ((unsigned long *)(w))
81 #define EVTCHN_FIFO_BIT(b, w) EVTCHN_FIFO_ ##b
82
83 #endif
84
85 static inline event_word_t *event_word_from_port(unsigned port)
86 {
87         unsigned i = port / EVENT_WORDS_PER_PAGE;
88
89         return event_array[i] + port % EVENT_WORDS_PER_PAGE;
90 }
91
92 static unsigned evtchn_fifo_max_channels(void)
93 {
94         return EVTCHN_FIFO_NR_CHANNELS;
95 }
96
97 static unsigned evtchn_fifo_nr_channels(void)
98 {
99         return event_array_pages * EVENT_WORDS_PER_PAGE;
100 }
101
102 static int init_control_block(int cpu,
103                               struct evtchn_fifo_control_block *control_block)
104 {
105         struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
106         struct evtchn_init_control init_control;
107         unsigned int i;
108
109         /* Reset the control block and the local HEADs. */
110         clear_page(control_block);
111         for (i = 0; i < EVTCHN_FIFO_MAX_QUEUES; i++)
112                 q->head[i] = 0;
113
114         init_control.control_gfn = virt_to_gfn(control_block);
115         init_control.offset      = 0;
116         init_control.vcpu        = xen_vcpu_nr(cpu);
117
118         return HYPERVISOR_event_channel_op(EVTCHNOP_init_control, &init_control);
119 }
120
121 static void free_unused_array_pages(void)
122 {
123         unsigned i;
124
125         for (i = event_array_pages; i < MAX_EVENT_ARRAY_PAGES; i++) {
126                 if (!event_array[i])
127                         break;
128                 free_page((unsigned long)event_array[i]);
129                 event_array[i] = NULL;
130         }
131 }
132
133 static void init_array_page(event_word_t *array_page)
134 {
135         unsigned i;
136
137         for (i = 0; i < EVENT_WORDS_PER_PAGE; i++)
138                 array_page[i] = 1 << EVTCHN_FIFO_MASKED;
139 }
140
141 static int evtchn_fifo_setup(struct irq_info *info)
142 {
143         unsigned port = info->evtchn;
144         unsigned new_array_pages;
145         int ret;
146
147         new_array_pages = port / EVENT_WORDS_PER_PAGE + 1;
148
149         if (new_array_pages > MAX_EVENT_ARRAY_PAGES)
150                 return -EINVAL;
151
152         while (event_array_pages < new_array_pages) {
153                 void *array_page;
154                 struct evtchn_expand_array expand_array;
155
156                 /* Might already have a page if we've resumed. */
157                 array_page = event_array[event_array_pages];
158                 if (!array_page) {
159                         array_page = (void *)__get_free_page(GFP_KERNEL);
160                         if (array_page == NULL) {
161                                 ret = -ENOMEM;
162                                 goto error;
163                         }
164                         event_array[event_array_pages] = array_page;
165                 }
166
167                 /* Mask all events in this page before adding it. */
168                 init_array_page(array_page);
169
170                 expand_array.array_gfn = virt_to_gfn(array_page);
171
172                 ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array);
173                 if (ret < 0)
174                         goto error;
175
176                 event_array_pages++;
177         }
178         return 0;
179
180   error:
181         if (event_array_pages == 0)
182                 panic("xen: unable to expand event array with initial page (%d)\n", ret);
183         else
184                 pr_err("unable to expand event array (%d)\n", ret);
185         free_unused_array_pages();
186         return ret;
187 }
188
189 static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu)
190 {
191         /* no-op */
192 }
193
194 static void evtchn_fifo_clear_pending(unsigned port)
195 {
196         event_word_t *word = event_word_from_port(port);
197         sync_clear_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
198 }
199
200 static void evtchn_fifo_set_pending(unsigned port)
201 {
202         event_word_t *word = event_word_from_port(port);
203         sync_set_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
204 }
205
206 static bool evtchn_fifo_is_pending(unsigned port)
207 {
208         event_word_t *word = event_word_from_port(port);
209         return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
210 }
211
212 static bool evtchn_fifo_test_and_set_mask(unsigned port)
213 {
214         event_word_t *word = event_word_from_port(port);
215         return sync_test_and_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
216 }
217
218 static void evtchn_fifo_mask(unsigned port)
219 {
220         event_word_t *word = event_word_from_port(port);
221         sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
222 }
223
224 static bool evtchn_fifo_is_masked(unsigned port)
225 {
226         event_word_t *word = event_word_from_port(port);
227         return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
228 }
229 /*
230  * Clear MASKED, spinning if BUSY is set.
231  */
232 static void clear_masked(volatile event_word_t *word)
233 {
234         event_word_t new, old, w;
235
236         w = *word;
237
238         do {
239                 old = w & ~(1 << EVTCHN_FIFO_BUSY);
240                 new = old & ~(1 << EVTCHN_FIFO_MASKED);
241                 w = sync_cmpxchg(word, old, new);
242         } while (w != old);
243 }
244
245 static void evtchn_fifo_unmask(unsigned port)
246 {
247         event_word_t *word = event_word_from_port(port);
248
249         BUG_ON(!irqs_disabled());
250
251         clear_masked(word);
252         if (evtchn_fifo_is_pending(port)) {
253                 struct evtchn_unmask unmask = { .port = port };
254                 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
255         }
256 }
257
258 static uint32_t clear_linked(volatile event_word_t *word)
259 {
260         event_word_t new, old, w;
261
262         w = *word;
263
264         do {
265                 old = w;
266                 new = (w & ~((1 << EVTCHN_FIFO_LINKED)
267                              | EVTCHN_FIFO_LINK_MASK));
268         } while ((w = sync_cmpxchg(word, old, new)) != old);
269
270         return w & EVTCHN_FIFO_LINK_MASK;
271 }
272
273 static void handle_irq_for_port(unsigned port)
274 {
275         int irq;
276
277         irq = get_evtchn_to_irq(port);
278         if (irq != -1)
279                 generic_handle_irq(irq);
280 }
281
282 static void consume_one_event(unsigned cpu,
283                               struct evtchn_fifo_control_block *control_block,
284                               unsigned priority, unsigned long *ready,
285                               bool drop)
286 {
287         struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
288         uint32_t head;
289         unsigned port;
290         event_word_t *word;
291
292         head = q->head[priority];
293
294         /*
295          * Reached the tail last time?  Read the new HEAD from the
296          * control block.
297          */
298         if (head == 0) {
299                 virt_rmb(); /* Ensure word is up-to-date before reading head. */
300                 head = control_block->head[priority];
301         }
302
303         port = head;
304         word = event_word_from_port(port);
305         head = clear_linked(word);
306
307         /*
308          * If the link is non-zero, there are more events in the
309          * queue, otherwise the queue is empty.
310          *
311          * If the queue is empty, clear this priority from our local
312          * copy of the ready word.
313          */
314         if (head == 0)
315                 clear_bit(priority, ready);
316
317         if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port)) {
318                 if (unlikely(drop))
319                         pr_warn("Dropping pending event for port %u\n", port);
320                 else
321                         handle_irq_for_port(port);
322         }
323
324         q->head[priority] = head;
325 }
326
327 static void __evtchn_fifo_handle_events(unsigned cpu, bool drop)
328 {
329         struct evtchn_fifo_control_block *control_block;
330         unsigned long ready;
331         unsigned q;
332
333         control_block = per_cpu(cpu_control_block, cpu);
334
335         ready = xchg(&control_block->ready, 0);
336
337         while (ready) {
338                 q = find_first_bit(&ready, EVTCHN_FIFO_MAX_QUEUES);
339                 consume_one_event(cpu, control_block, q, &ready, drop);
340                 ready |= xchg(&control_block->ready, 0);
341         }
342 }
343
344 static void evtchn_fifo_handle_events(unsigned cpu)
345 {
346         __evtchn_fifo_handle_events(cpu, false);
347 }
348
349 static void evtchn_fifo_resume(void)
350 {
351         unsigned cpu;
352
353         for_each_possible_cpu(cpu) {
354                 void *control_block = per_cpu(cpu_control_block, cpu);
355                 int ret;
356
357                 if (!control_block)
358                         continue;
359
360                 /*
361                  * If this CPU is offline, take the opportunity to
362                  * free the control block while it is not being
363                  * used.
364                  */
365                 if (!cpu_online(cpu)) {
366                         free_page((unsigned long)control_block);
367                         per_cpu(cpu_control_block, cpu) = NULL;
368                         continue;
369                 }
370
371                 ret = init_control_block(cpu, control_block);
372                 BUG_ON(ret < 0);
373         }
374
375         /*
376          * The event array starts out as empty again and is extended
377          * as normal when events are bound.  The existing pages will
378          * be reused.
379          */
380         event_array_pages = 0;
381 }
382
383 static const struct evtchn_ops evtchn_ops_fifo = {
384         .max_channels      = evtchn_fifo_max_channels,
385         .nr_channels       = evtchn_fifo_nr_channels,
386         .setup             = evtchn_fifo_setup,
387         .bind_to_cpu       = evtchn_fifo_bind_to_cpu,
388         .clear_pending     = evtchn_fifo_clear_pending,
389         .set_pending       = evtchn_fifo_set_pending,
390         .is_pending        = evtchn_fifo_is_pending,
391         .test_and_set_mask = evtchn_fifo_test_and_set_mask,
392         .mask              = evtchn_fifo_mask,
393         .unmask            = evtchn_fifo_unmask,
394         .handle_events     = evtchn_fifo_handle_events,
395         .resume            = evtchn_fifo_resume,
396 };
397
398 static int evtchn_fifo_alloc_control_block(unsigned cpu)
399 {
400         void *control_block = NULL;
401         int ret = -ENOMEM;
402
403         control_block = (void *)__get_free_page(GFP_KERNEL);
404         if (control_block == NULL)
405                 goto error;
406
407         ret = init_control_block(cpu, control_block);
408         if (ret < 0)
409                 goto error;
410
411         per_cpu(cpu_control_block, cpu) = control_block;
412
413         return 0;
414
415   error:
416         free_page((unsigned long)control_block);
417         return ret;
418 }
419
420 static int xen_evtchn_cpu_prepare(unsigned int cpu)
421 {
422         if (!per_cpu(cpu_control_block, cpu))
423                 return evtchn_fifo_alloc_control_block(cpu);
424         return 0;
425 }
426
427 static int xen_evtchn_cpu_dead(unsigned int cpu)
428 {
429         __evtchn_fifo_handle_events(cpu, true);
430         return 0;
431 }
432
433 int __init xen_evtchn_fifo_init(void)
434 {
435         int cpu = get_cpu();
436         int ret;
437
438         ret = evtchn_fifo_alloc_control_block(cpu);
439         if (ret < 0)
440                 goto out;
441
442         pr_info("Using FIFO-based ABI\n");
443
444         evtchn_ops = &evtchn_ops_fifo;
445
446         cpuhp_setup_state_nocalls(CPUHP_XEN_EVTCHN_PREPARE,
447                                   "xen/evtchn:prepare",
448                                   xen_evtchn_cpu_prepare, xen_evtchn_cpu_dead);
449 out:
450         put_cpu();
451         return ret;
452 }