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/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 #define BM(w) ((unsigned long *)(w))
  70
  71 static inline event_word_t *event_word_from_port(unsigned port)
  72 {
  73         unsigned i = port / EVENT_WORDS_PER_PAGE;
  74
  75         return event_array[i] + port % EVENT_WORDS_PER_PAGE;
  76 }
  77
  78 static unsigned evtchn_fifo_max_channels(void)
  79 {
  80         return EVTCHN_FIFO_NR_CHANNELS;
  81 }
  82
  83 static unsigned evtchn_fifo_nr_channels(void)
  84 {
  85         return event_array_pages * EVENT_WORDS_PER_PAGE;
  86 }
  87
  88 static void free_unused_array_pages(void)
  89 {
  90         unsigned i;
  91
  92         for (i = event_array_pages; i < MAX_EVENT_ARRAY_PAGES; i++) {
  93                 if (!event_array[i])
  94                         break;
  95                 free_page((unsigned long)event_array[i]);
  96                 event_array[i] = NULL;
  97         }
  98 }
  99
 100 static void init_array_page(event_word_t *array_page)
 101 {
 102         unsigned i;
 103
 104         for (i = 0; i < EVENT_WORDS_PER_PAGE; i++)
 105                 array_page[i] = 1 << EVTCHN_FIFO_MASKED;
 106 }
 107
 108 static int evtchn_fifo_setup(struct irq_info *info)
 109 {
 110         unsigned port = info->evtchn;
 111         unsigned new_array_pages;
 112         int ret;
 113
 114         new_array_pages = port / EVENT_WORDS_PER_PAGE + 1;
 115
 116         if (new_array_pages > MAX_EVENT_ARRAY_PAGES)
 117                 return -EINVAL;
 118
 119         while (event_array_pages < new_array_pages) {
 120                 void *array_page;
 121                 struct evtchn_expand_array expand_array;
 122
 123                 /* Might already have a page if we've resumed. */
 124                 array_page = event_array[event_array_pages];
 125                 if (!array_page) {
 126                         array_page = (void *)__get_free_page(GFP_KERNEL);
 127                         if (array_page == NULL) {
 128                                 ret = -ENOMEM;
 129                                 goto error;
 130                         }
 131                         event_array[event_array_pages] = array_page;
 132                 }
 133
 134                 /* Mask all events in this page before adding it. */
 135                 init_array_page(array_page);
 136
 137                 expand_array.array_gfn = virt_to_mfn(array_page);
 138
 139                 ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array);
 140                 if (ret < 0)
 141                         goto error;
 142
 143                 event_array_pages++;
 144         }
 145         return 0;
 146
 147   error:
 148         if (event_array_pages == 0)
 149                 panic("xen: unable to expand event array with initial page (%d)\n", ret);
 150         else
 151                 pr_err("unable to expand event array (%d)\n", ret);
 152         free_unused_array_pages();
 153         return ret;
 154 }
 155
 156 static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu)
 157 {
 158         /* no-op */
 159 }
 160
 161 static void evtchn_fifo_clear_pending(unsigned port)
 162 {
 163         event_word_t *word = event_word_from_port(port);
 164         sync_clear_bit(EVTCHN_FIFO_PENDING, BM(word));
 165 }
 166
 167 static void evtchn_fifo_set_pending(unsigned port)
 168 {
 169         event_word_t *word = event_word_from_port(port);
 170         sync_set_bit(EVTCHN_FIFO_PENDING, BM(word));
 171 }
 172
 173 static bool evtchn_fifo_is_pending(unsigned port)
 174 {
 175         event_word_t *word = event_word_from_port(port);
 176         return sync_test_bit(EVTCHN_FIFO_PENDING, BM(word));
 177 }
 178
 179 static bool evtchn_fifo_test_and_set_mask(unsigned port)
 180 {
 181         event_word_t *word = event_word_from_port(port);
 182         return sync_test_and_set_bit(EVTCHN_FIFO_MASKED, BM(word));
 183 }
 184
 185 static void evtchn_fifo_mask(unsigned port)
 186 {
 187         event_word_t *word = event_word_from_port(port);
 188         sync_set_bit(EVTCHN_FIFO_MASKED, BM(word));
 189 }
 190
 191 /*
 192  * Clear MASKED, spinning if BUSY is set.
 193  */
 194 static void clear_masked(volatile event_word_t *word)
 195 {
 196         event_word_t new, old, w;
 197
 198         w = *word;
 199
 200         do {
 201                 old = w & ~(1 << EVTCHN_FIFO_BUSY);
 202                 new = old & ~(1 << EVTCHN_FIFO_MASKED);
 203                 w = sync_cmpxchg(word, old, new);
 204         } while (w != old);
 205 }
 206
 207 static void evtchn_fifo_unmask(unsigned port)
 208 {
 209         event_word_t *word = event_word_from_port(port);
 210
 211         BUG_ON(!irqs_disabled());
 212
 213         clear_masked(word);
 214         if (sync_test_bit(EVTCHN_FIFO_PENDING, BM(word))) {
 215                 struct evtchn_unmask unmask = { .port = port };
 216                 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
 217         }
 218 }
 219
 220 static uint32_t clear_linked(volatile event_word_t *word)
 221 {
 222         event_word_t new, old, w;
 223
 224         w = *word;
 225
 226         do {
 227                 old = w;
 228                 new = (w & ~((1 << EVTCHN_FIFO_LINKED)
 229                              | EVTCHN_FIFO_LINK_MASK));
 230         } while ((w = sync_cmpxchg(word, old, new)) != old);
 231
 232         return w & EVTCHN_FIFO_LINK_MASK;
 233 }
 234
 235 static void handle_irq_for_port(unsigned port)
 236 {
 237         int irq;
 238
 239         irq = get_evtchn_to_irq(port);
 240         if (irq != -1)
 241                 generic_handle_irq(irq);
 242 }
 243
 244 static void consume_one_event(unsigned cpu,
 245                               struct evtchn_fifo_control_block *control_block,
 246                               unsigned priority, uint32_t *ready)
 247 {
 248         struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
 249         uint32_t head;
 250         unsigned port;
 251         event_word_t *word;
 252
 253         head = q->head[priority];
 254
 255         /*
 256          * Reached the tail last time?  Read the new HEAD from the
 257          * control block.
 258          */
 259         if (head == 0) {
 260                 rmb(); /* Ensure word is up-to-date before reading head. */
 261                 head = control_block->head[priority];
 262         }
 263
 264         port = head;
 265         word = event_word_from_port(port);
 266         head = clear_linked(word);
 267
 268         /*
 269          * If the link is non-zero, there are more events in the
 270          * queue, otherwise the queue is empty.
 271          *
 272          * If the queue is empty, clear this priority from our local
 273          * copy of the ready word.
 274          */
 275         if (head == 0)
 276                 clear_bit(priority, BM(ready));
 277
 278         if (sync_test_bit(EVTCHN_FIFO_PENDING, BM(word))
 279             && !sync_test_bit(EVTCHN_FIFO_MASKED, BM(word)))
 280                 handle_irq_for_port(port);
 281
 282         q->head[priority] = head;
 283 }
 284
 285 static void evtchn_fifo_handle_events(unsigned cpu)
 286 {
 287         struct evtchn_fifo_control_block *control_block;
 288         uint32_t ready;
 289         unsigned q;
 290
 291         control_block = per_cpu(cpu_control_block, cpu);
 292
 293         ready = xchg(&control_block->ready, 0);
 294
 295         while (ready) {
 296                 q = find_first_bit(BM(&ready), EVTCHN_FIFO_MAX_QUEUES);
 297                 consume_one_event(cpu, control_block, q, &ready);
 298                 ready |= xchg(&control_block->ready, 0);
 299         }
 300 }
 301
 302 static void evtchn_fifo_resume(void)
 303 {
 304         unsigned cpu;
 305
 306         for_each_possible_cpu(cpu) {
 307                 void *control_block = per_cpu(cpu_control_block, cpu);
 308                 struct evtchn_init_control init_control;
 309                 int ret;
 310
 311                 if (!control_block)
 312                         continue;
 313
 314                 /*
 315                  * If this CPU is offline, take the opportunity to
 316                  * free the control block while it is not being
 317                  * used.
 318                  */
 319                 if (!cpu_online(cpu)) {
 320                         free_page((unsigned long)control_block);
 321                         per_cpu(cpu_control_block, cpu) = NULL;
 322                         continue;
 323                 }
 324
 325                 init_control.control_gfn = virt_to_mfn(control_block);
 326                 init_control.offset = 0;
 327                 init_control.vcpu = cpu;
 328
 329                 ret = HYPERVISOR_event_channel_op(EVTCHNOP_init_control,
 330                                                   &init_control);
 331                 if (ret < 0)
 332                         BUG();
 333         }
 334
 335         /*
 336          * The event array starts out as empty again and is extended
 337          * as normal when events are bound.  The existing pages will
 338          * be reused.
 339          */
 340         event_array_pages = 0;
 341 }
 342
 343 static const struct evtchn_ops evtchn_ops_fifo = {
 344         .max_channels      = evtchn_fifo_max_channels,
 345         .nr_channels       = evtchn_fifo_nr_channels,
 346         .setup             = evtchn_fifo_setup,
 347         .bind_to_cpu       = evtchn_fifo_bind_to_cpu,
 348         .clear_pending     = evtchn_fifo_clear_pending,
 349         .set_pending       = evtchn_fifo_set_pending,
 350         .is_pending        = evtchn_fifo_is_pending,
 351         .test_and_set_mask = evtchn_fifo_test_and_set_mask,
 352         .mask              = evtchn_fifo_mask,
 353         .unmask            = evtchn_fifo_unmask,
 354         .handle_events     = evtchn_fifo_handle_events,
 355         .resume            = evtchn_fifo_resume,
 356 };
 357
 358 static int evtchn_fifo_init_control_block(unsigned cpu)
 359 {
 360         struct page *control_block = NULL;
 361         struct evtchn_init_control init_control;
 362         int ret = -ENOMEM;
 363
 364         control_block = alloc_page(GFP_KERNEL|__GFP_ZERO);
 365         if (control_block == NULL)
 366                 goto error;
 367
 368         init_control.control_gfn = virt_to_mfn(page_address(control_block));
 369         init_control.offset      = 0;
 370         init_control.vcpu        = cpu;
 371
 372         ret = HYPERVISOR_event_channel_op(EVTCHNOP_init_control, &init_control);
 373         if (ret < 0)
 374                 goto error;
 375
 376         per_cpu(cpu_control_block, cpu) = page_address(control_block);
 377
 378         return 0;
 379
 380   error:
 381         __free_page(control_block);
 382         return ret;
 383 }
 384
 385 static int evtchn_fifo_cpu_notification(struct notifier_block *self,
 386                                                   unsigned long action,
 387                                                   void *hcpu)
 388 {
 389         int cpu = (long)hcpu;
 390         int ret = 0;
 391
 392         switch (action) {
 393         case CPU_UP_PREPARE:
 394                 if (!per_cpu(cpu_control_block, cpu))
 395                         ret = evtchn_fifo_init_control_block(cpu);
 396                 break;
 397         default:
 398                 break;
 399         }
 400         return ret < 0 ? NOTIFY_BAD : NOTIFY_OK;
 401 }
 402
 403 static struct notifier_block evtchn_fifo_cpu_notifier = {
 404         .notifier_call  = evtchn_fifo_cpu_notification,
 405 };
 406
 407 int __init xen_evtchn_fifo_init(void)
 408 {
 409         int cpu = get_cpu();
 410         int ret;
 411
 412         ret = evtchn_fifo_init_control_block(cpu);
 413         if (ret < 0)
 414                 goto out;
 415
 416         pr_info("Using FIFO-based ABI\n");
 417
 418         evtchn_ops = &evtchn_ops_fifo;
 419
 420         register_cpu_notifier(&evtchn_fifo_cpu_notifier);
 421 out:
 422         put_cpu();
 423         return ret;
 424 }