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 } 465