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 /*
  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 }