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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/or7 * modify it under the terms of the GNU General Public License as8 * published by the Free Software Foundation; either version 2 of the9 * License, or (at your option) any later version.10 *11 * Or, when distributed separately from the Linux kernel or12 * incorporated into other software packages, subject to the following13 * license:14 *15 * Permission is hereby granted, free of charge, to any person obtaining a copy16 * of this source file (the "Software"), to deal in the Software without17 * 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 to20 * the following conditions:21 *22 * The above copyright notice and this permission notice shall be included in23 * all copies or substantial portions of the Software.24 *25 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR26 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,27 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE28 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER29 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING30 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS31 * IN THE SOFTWARE.32 */33 34#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt35 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 60struct evtchn_fifo_queue {61 uint32_t head[EVTCHN_FIFO_MAX_QUEUES];62};63 64static DEFINE_PER_CPU(struct evtchn_fifo_control_block *, cpu_control_block);65static DEFINE_PER_CPU(struct evtchn_fifo_queue, cpu_queue);66static event_word_t *event_array[MAX_EVENT_ARRAY_PAGES] __read_mostly;67static 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 > 3273 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#else79 80#define BM(w) ((unsigned long *)(w))81#define EVTCHN_FIFO_BIT(b, w) EVTCHN_FIFO_ ##b82 83#endif84 85static inline event_word_t *event_word_from_port(evtchn_port_t port)86{87 unsigned i = port / EVENT_WORDS_PER_PAGE;88 89 return event_array[i] + port % EVENT_WORDS_PER_PAGE;90}91 92static unsigned evtchn_fifo_max_channels(void)93{94 return EVTCHN_FIFO_NR_CHANNELS;95}96 97static unsigned evtchn_fifo_nr_channels(void)98{99 return event_array_pages * EVENT_WORDS_PER_PAGE;100}101 102static 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 121static 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 133static 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 141static int evtchn_fifo_setup(evtchn_port_t port)142{143 unsigned new_array_pages;144 int ret;145 146 new_array_pages = port / EVENT_WORDS_PER_PAGE + 1;147 148 if (new_array_pages > MAX_EVENT_ARRAY_PAGES)149 return -EINVAL;150 151 while (event_array_pages < new_array_pages) {152 void *array_page;153 struct evtchn_expand_array expand_array;154 155 /* Might already have a page if we've resumed. */156 array_page = event_array[event_array_pages];157 if (!array_page) {158 array_page = (void *)__get_free_page(GFP_KERNEL);159 if (array_page == NULL) {160 ret = -ENOMEM;161 goto error;162 }163 event_array[event_array_pages] = array_page;164 }165 166 /* Mask all events in this page before adding it. */167 init_array_page(array_page);168 169 expand_array.array_gfn = virt_to_gfn(array_page);170 171 ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array);172 if (ret < 0)173 goto error;174 175 event_array_pages++;176 }177 return 0;178 179 error:180 if (event_array_pages == 0)181 panic("xen: unable to expand event array with initial page (%d)\n", ret);182 else183 pr_err("unable to expand event array (%d)\n", ret);184 free_unused_array_pages();185 return ret;186}187 188static void evtchn_fifo_bind_to_cpu(evtchn_port_t evtchn, unsigned int cpu, 189 unsigned int old_cpu)190{191 /* no-op */192}193 194static void evtchn_fifo_clear_pending(evtchn_port_t 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 200static void evtchn_fifo_set_pending(evtchn_port_t 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 206static bool evtchn_fifo_is_pending(evtchn_port_t 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 212static void evtchn_fifo_mask(evtchn_port_t port)213{214 event_word_t *word = event_word_from_port(port);215 sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));216}217 218static bool evtchn_fifo_is_masked(evtchn_port_t port)219{220 event_word_t *word = event_word_from_port(port);221 return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word));222}223/*224 * Clear MASKED if not PENDING, spinning if BUSY is set.225 * Return true if mask was cleared.226 */227static bool clear_masked_cond(volatile event_word_t *word)228{229 event_word_t new, old;230 231 old = *word;232 233 do {234 if (!(old & (1 << EVTCHN_FIFO_MASKED)))235 return true;236 237 if (old & (1 << EVTCHN_FIFO_PENDING))238 return false;239 240 old = old & ~(1 << EVTCHN_FIFO_BUSY);241 new = old & ~(1 << EVTCHN_FIFO_MASKED);242 } while (!sync_try_cmpxchg(word, &old, new));243 244 return true;245}246 247static void evtchn_fifo_unmask(evtchn_port_t port)248{249 event_word_t *word = event_word_from_port(port);250 251 BUG_ON(!irqs_disabled());252 253 if (!clear_masked_cond(word)) {254 struct evtchn_unmask unmask = { .port = port };255 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask);256 }257}258 259static uint32_t clear_linked(volatile event_word_t *word)260{261 event_word_t new, old;262 263 old = *word;264 265 do {266 new = (old & ~((1 << EVTCHN_FIFO_LINKED)267 | EVTCHN_FIFO_LINK_MASK));268 } while (!sync_try_cmpxchg(word, &old, new));269 270 return old & EVTCHN_FIFO_LINK_MASK;271}272 273static void consume_one_event(unsigned cpu, struct evtchn_loop_ctrl *ctrl,274 struct evtchn_fifo_control_block *control_block,275 unsigned priority, unsigned long *ready)276{277 struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu);278 uint32_t head;279 evtchn_port_t port;280 event_word_t *word;281 282 head = q->head[priority];283 284 /*285 * Reached the tail last time? Read the new HEAD from the286 * control block.287 */288 if (head == 0) {289 virt_rmb(); /* Ensure word is up-to-date before reading head. */290 head = control_block->head[priority];291 }292 293 port = head;294 word = event_word_from_port(port);295 head = clear_linked(word);296 297 /*298 * If the link is non-zero, there are more events in the299 * queue, otherwise the queue is empty.300 *301 * If the queue is empty, clear this priority from our local302 * copy of the ready word.303 */304 if (head == 0)305 clear_bit(priority, ready);306 307 if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port)) {308 if (unlikely(!ctrl))309 pr_warn("Dropping pending event for port %u\n", port);310 else311 handle_irq_for_port(port, ctrl);312 }313 314 q->head[priority] = head;315}316 317static void __evtchn_fifo_handle_events(unsigned cpu,318 struct evtchn_loop_ctrl *ctrl)319{320 struct evtchn_fifo_control_block *control_block;321 unsigned long ready;322 unsigned q;323 324 control_block = per_cpu(cpu_control_block, cpu);325 326 ready = xchg(&control_block->ready, 0);327 328 while (ready) {329 q = find_first_bit(&ready, EVTCHN_FIFO_MAX_QUEUES);330 consume_one_event(cpu, ctrl, control_block, q, &ready);331 ready |= xchg(&control_block->ready, 0);332 }333}334 335static void evtchn_fifo_handle_events(unsigned cpu,336 struct evtchn_loop_ctrl *ctrl)337{338 __evtchn_fifo_handle_events(cpu, ctrl);339}340 341static void evtchn_fifo_resume(void)342{343 unsigned cpu;344 345 for_each_possible_cpu(cpu) {346 void *control_block = per_cpu(cpu_control_block, cpu);347 int ret;348 349 if (!control_block)350 continue;351 352 /*353 * If this CPU is offline, take the opportunity to354 * free the control block while it is not being355 * used.356 */357 if (!cpu_online(cpu)) {358 free_page((unsigned long)control_block);359 per_cpu(cpu_control_block, cpu) = NULL;360 continue;361 }362 363 ret = init_control_block(cpu, control_block);364 BUG_ON(ret < 0);365 }366 367 /*368 * The event array starts out as empty again and is extended369 * as normal when events are bound. The existing pages will370 * be reused.371 */372 event_array_pages = 0;373}374 375static int evtchn_fifo_alloc_control_block(unsigned cpu)376{377 void *control_block = NULL;378 int ret = -ENOMEM;379 380 control_block = (void *)__get_free_page(GFP_KERNEL);381 if (control_block == NULL)382 goto error;383 384 ret = init_control_block(cpu, control_block);385 if (ret < 0)386 goto error;387 388 per_cpu(cpu_control_block, cpu) = control_block;389 390 return 0;391 392 error:393 free_page((unsigned long)control_block);394 return ret;395}396 397static int evtchn_fifo_percpu_init(unsigned int cpu)398{399 if (!per_cpu(cpu_control_block, cpu))400 return evtchn_fifo_alloc_control_block(cpu);401 return 0;402}403 404static int evtchn_fifo_percpu_deinit(unsigned int cpu)405{406 __evtchn_fifo_handle_events(cpu, NULL);407 return 0;408}409 410static const struct evtchn_ops evtchn_ops_fifo = {411 .max_channels = evtchn_fifo_max_channels,412 .nr_channels = evtchn_fifo_nr_channels,413 .setup = evtchn_fifo_setup,414 .bind_to_cpu = evtchn_fifo_bind_to_cpu,415 .clear_pending = evtchn_fifo_clear_pending,416 .set_pending = evtchn_fifo_set_pending,417 .is_pending = evtchn_fifo_is_pending,418 .mask = evtchn_fifo_mask,419 .unmask = evtchn_fifo_unmask,420 .handle_events = evtchn_fifo_handle_events,421 .resume = evtchn_fifo_resume,422 .percpu_init = evtchn_fifo_percpu_init,423 .percpu_deinit = evtchn_fifo_percpu_deinit,424};425 426int __init xen_evtchn_fifo_init(void)427{428 int cpu = smp_processor_id();429 int ret;430 431 ret = evtchn_fifo_alloc_control_block(cpu);432 if (ret < 0)433 return ret;434 435 pr_info("Using FIFO-based ABI\n");436 437 evtchn_ops = &evtchn_ops_fifo;438 439 return ret;440}441