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/barrier.h>
  45 #include <asm/sync_bitops.h>
  46 #include <asm/xen/hypercall.h>
  47 #include <asm/xen/hypervisor.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 #include <xen/page.h>
  55
  56 #include "events_internal.h"
  57
  58 #define EVENT_WORDS_PER_PAGE (XEN_PAGE_SIZE / sizeof(event_word_t))
  59 #define MAX_EVENT_ARRAY_PAGES (EVTCHN_FIFO_NR_CHANNELS / EVENT_WORDS_PER_PAGE)
  60
  61 struct evtchn_fifo_queue {
  62         uint32_t head[EVTCHN_FIFO_MAX_QUEUES];
  63 };
  64
  65 static DEFINE_PER_CPU(struct evtchn_fifo_control_block *, cpu_control_block);
  66 static DEFINE_PER_CPU(struct evtchn_fifo_queue, cpu_queue);
  67 static event_word_t *event_array[MAX_EVENT_ARRAY_PAGES] __read_mostly;
  68 static unsigned event_array_pages __read_mostly;
  69
  70 /*
  71  * sync_set_bit() and friends must be unsigned long aligned.
  72  */
  73 #if 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 int init_control_block(int cpu,
 104                               struct evtchn_fifo_control_block *control_block)
 105 {
 106         struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
 107         struct evtchn_init_control init_control;
 108         unsigned int i;
 109
 110         /* Reset the control block and the local HEADs. */
 111         clear_page(control_block);
 112         for (i = 0; i < EVTCHN_FIFO_MAX_QUEUES; i++)
 113                 q->head[i] = 0;
 114
 115         init_control.control_gfn = virt_to_gfn(control_block);
 116         init_control.offset      = 0;
 117         init_control.vcpu        = cpu;
 118
 119         return HYPERVISOR_event_channel_op(EVTCHNOP_init_control, &init_control);
 120 }
 121
 122 static void free_unused_array_pages(void)
 123 {
 124         unsigned i;
 125
 126         for (i = event_array_pages; i < MAX_EVENT_ARRAY_PAGES; i++) {
 127                 if (!event_array[i])
 128                         break;
 129                 free_page((unsigned long)event_array[i]);
 130                 event_array[i] = NULL;
 131         }
 132 }
 133
 134 static void init_array_page(event_word_t *array_page)
 135 {
 136         unsigned i;
 137
 138         for (i = 0; i < EVENT_WORDS_PER_PAGE; i++)
 139                 array_page[i] = 1 << EVTCHN_FIFO_MASKED;
 140 }
 141
 142 static int evtchn_fifo_setup(struct irq_info *info)
 143 {
 144         unsigned port = info->evtchn;
 145         unsigned new_array_pages;
 146         int ret;
 147
 148         new_array_pages = port / EVENT_WORDS_PER_PAGE + 1;
 149
 150         if (new_array_pages > MAX_EVENT_ARRAY_PAGES)
 151                 return -EINVAL;
 152
 153         while (event_array_pages < new_array_pages) {
 154                 void *array_page;
 155                 struct evtchn_expand_array expand_array;
 156
 157                 /* Might already have a page if we've resumed. */
 158                 array_page = event_array[event_array_pages];
 159                 if (!array_page) {
 160                         array_page = (void *)__get_free_page(GFP_KERNEL);
 161                         if (array_page == NULL) {
 162                                 ret = -ENOMEM;
 163                                 goto error;
 164                         }
 165                         event_array[event_array_pages] = array_page;
 166                 }
 167
 168                 /* Mask all events in this page before adding it. */
 169                 init_array_page(array_page);
 170
 171                 expand_array.array_gfn = virt_to_gfn(array_page);
 172
 173                 ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array);
 174                 if (ret < 0)
 175                         goto error;
 176
 177                 event_array_pages++;
 178         }
 179         return 0;
 180
 181   error:
 182         if (event_array_pages == 0)
 183                 panic("xen: unable to expand event array with initial page (%d)\n", ret);
 184         else
 185                 pr_err("unable to expand event array (%d)\n", ret);
 186         free_unused_array_pages();
 187         return ret;
 188 }
 189
 190 static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu)
 191 {
 192         /* no-op */
 193 }
 194
 195 static void evtchn_fifo_clear_pending(unsigned port)
 196 {
 197         event_word_t *word = event_word_from_port(port);
 198         sync_clear_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
 199 }
 200
 201 static void evtchn_fifo_set_pending(unsigned port)
 202 {
 203         event_word_t *word = event_word_from_port(port);
 204         sync_set_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
 205 }
 206
 207 static bool evtchn_fifo_is_pending(unsigned port)
 208 {
 209         event_word_t *word = event_word_from_port(port);
 210         return sync_test_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word));
 211 }
 212
 213 static bool evtchn_fifo_test_and_set_mask(unsigned port)
 214 {
 215         event_word_t *word = event_word_from_port(port);
 216         return sync_test_and_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
 217 }
 218
 219 static void evtchn_fifo_mask(unsigned port)
 220 {
 221         event_word_t *word = event_word_from_port(port);
 222         sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
 223 }
 224
 225 static bool evtchn_fifo_is_masked(unsigned port)
 226 {
 227         event_word_t *word = event_word_from_port(port);
 228         return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));
 229 }
 230 /*
 231  * Clear MASKED, spinning if BUSY is set.
 232  */
 233 static void clear_masked(volatile event_word_t *word)
 234 {
 235         event_word_t new, old, w;
 236
 237         w = *word;
 238
 239         do {
 240                 old = w & ~(1 << EVTCHN_FIFO_BUSY);
 241                 new = old & ~(1 << EVTCHN_FIFO_MASKED);
 242                 w = sync_cmpxchg(word, old, new);
 243         } while (w != old);
 244 }
 245
 246 static void evtchn_fifo_unmask(unsigned port)
 247 {
 248         event_word_t *word = event_word_from_port(port);
 249
 250         BUG_ON(!irqs_disabled());
 251
 252         clear_masked(word);
 253         if (evtchn_fifo_is_pending(port)) {
 254                 struct evtchn_unmask unmask = { .port = port };
 255                 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);
 256         }
 257 }
 258
 259 static uint32_t clear_linked(volatile event_word_t *word)
 260 {
 261         event_word_t new, old, w;
 262
 263         w = *word;
 264
 265         do {
 266                 old = w;
 267                 new = (w & ~((1 << EVTCHN_FIFO_LINKED)
 268                              | EVTCHN_FIFO_LINK_MASK));
 269         } while ((w = sync_cmpxchg(word, old, new)) != old);
 270
 271         return w & EVTCHN_FIFO_LINK_MASK;
 272 }
 273
 274 static void handle_irq_for_port(unsigned port)
 275 {
 276         int irq;
 277
 278         irq = get_evtchn_to_irq(port);
 279         if (irq != -1)
 280                 generic_handle_irq(irq);
 281 }
 282
 283 static void consume_one_event(unsigned cpu,
 284                               struct evtchn_fifo_control_block *control_block,
 285                               unsigned priority, unsigned long *ready,
 286                               bool drop)
 287 {
 288         struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);
 289         uint32_t head;
 290         unsigned port;
 291         event_word_t *word;
 292
 293         head = q->head[priority];
 294
 295         /*
 296          * Reached the tail last time?  Read the new HEAD from the
 297          * control block.
 298          */
 299         if (head == 0) {
 300                 virt_rmb(); /* Ensure word is up-to-date before reading head. */
 301                 head = control_block->head[priority];
 302         }
 303
 304         port = head;
 305         word = event_word_from_port(port);
 306         head = clear_linked(word);
 307
 308         /*
 309          * If the link is non-zero, there are more events in the
 310          * queue, otherwise the queue is empty.
 311          *
 312          * If the queue is empty, clear this priority from our local
 313          * copy of the ready word.
 314          */
 315         if (head == 0)
 316                 clear_bit(priority, ready);
 317
 318         if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port)) {
 319                 if (unlikely(drop))
 320                         pr_warn("Dropping pending event for port %u\n", port);
 321                 else
 322                         handle_irq_for_port(port);
 323         }
 324
 325         q->head[priority] = head;
 326 }
 327
 328 static void __evtchn_fifo_handle_events(unsigned cpu, bool drop)
 329 {
 330         struct evtchn_fifo_control_block *control_block;
 331         unsigned long ready;
 332         unsigned q;
 333
 334         control_block = per_cpu(cpu_control_block, cpu);
 335
 336         ready = xchg(&control_block->ready, 0);
 337
 338         while (ready) {
 339                 q = find_first_bit(&ready, EVTCHN_FIFO_MAX_QUEUES);
 340                 consume_one_event(cpu, control_block, q, &ready, drop);
 341                 ready |= xchg(&control_block->ready, 0);
 342         }
 343 }
 344
 345 static void evtchn_fifo_handle_events(unsigned cpu)
 346 {
 347         __evtchn_fifo_handle_events(cpu, false);
 348 }
 349
 350 static void evtchn_fifo_resume(void)
 351 {
 352         unsigned cpu;
 353
 354         for_each_possible_cpu(cpu) {
 355                 void *control_block = per_cpu(cpu_control_block, cpu);
 356                 int ret;
 357
 358                 if (!control_block)
 359                         continue;
 360
 361                 /*
 362                  * If this CPU is offline, take the opportunity to
 363                  * free the control block while it is not being
 364                  * used.
 365                  */
 366                 if (!cpu_online(cpu)) {
 367                         free_page((unsigned long)control_block);
 368                         per_cpu(cpu_control_block, cpu) = NULL;
 369                         continue;
 370                 }
 371
 372                 ret = init_control_block(cpu, control_block);
 373                 if (ret < 0)
 374                         BUG();
 375         }
 376
 377         /*
 378          * The event array starts out as empty again and is extended
 379          * as normal when events are bound.  The existing pages will
 380          * be reused.
 381          */
 382         event_array_pages = 0;
 383 }
 384
 385 static const struct evtchn_ops evtchn_ops_fifo = {
 386         .max_channels      = evtchn_fifo_max_channels,
 387         .nr_channels       = evtchn_fifo_nr_channels,
 388         .setup             = evtchn_fifo_setup,
 389         .bind_to_cpu       = evtchn_fifo_bind_to_cpu,
 390         .clear_pending     = evtchn_fifo_clear_pending,
 391         .set_pending       = evtchn_fifo_set_pending,
 392         .is_pending        = evtchn_fifo_is_pending,
 393         .test_and_set_mask = evtchn_fifo_test_and_set_mask,
 394         .mask              = evtchn_fifo_mask,
 395         .unmask            = evtchn_fifo_unmask,
 396         .handle_events     = evtchn_fifo_handle_events,
 397         .resume            = evtchn_fifo_resume,
 398 };
 399
 400 static int evtchn_fifo_alloc_control_block(unsigned cpu)
 401 {
 402         void *control_block = NULL;
 403         int ret = -ENOMEM;
 404
 405         control_block = (void *)__get_free_page(GFP_KERNEL);
 406         if (control_block == NULL)
 407                 goto error;
 408
 409         ret = init_control_block(cpu, control_block);
 410         if (ret < 0)
 411                 goto error;
 412
 413         per_cpu(cpu_control_block, cpu) = control_block;
 414
 415         return 0;
 416
 417   error:
 418         free_page((unsigned long)control_block);
 419         return ret;
 420 }
 421
 422 static int evtchn_fifo_cpu_notification(struct notifier_block *self,
 423                                                   unsigned long action,
 424                                                   void *hcpu)
 425 {
 426         int cpu = (long)hcpu;
 427         int ret = 0;
 428
 429         switch (action) {
 430         case CPU_UP_PREPARE:
 431                 if (!per_cpu(cpu_control_block, cpu))
 432                         ret = evtchn_fifo_alloc_control_block(cpu);
 433                 break;
 434         case CPU_DEAD:
 435                 __evtchn_fifo_handle_events(cpu, true);
 436                 break;
 437         default:
 438                 break;
 439         }
 440         return ret < 0 ? NOTIFY_BAD : NOTIFY_OK;
 441 }
 442
 443 static struct notifier_block evtchn_fifo_cpu_notifier = {
 444         .notifier_call  = evtchn_fifo_cpu_notification,
 445 };
 446
 447 int __init xen_evtchn_fifo_init(void)
 448 {
 449         int cpu = get_cpu();
 450         int ret;
 451
 452         ret = evtchn_fifo_alloc_control_block(cpu);
 453         if (ret < 0)
 454                 goto out;
 455
 456         pr_info("Using FIFO-based ABI\n");
 457
 458         evtchn_ops = &evtchn_ops_fifo;
 459
 460         register_cpu_notifier(&evtchn_fifo_cpu_notifier);
 461 out:
 462         put_cpu();
 463         return ret;
 464 }