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/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 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. 71 */ 72 #if BITS_PER_LONG > 32 73 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 #else 79 80 #define BM(w) ((unsigned long *)(w)) 81 #define EVTCHN_FIFO_BIT(b, w) EVTCHN_FIFO_ ##b 82 83 #endif 84 85 static inline event_word_t *event_word_from_port(unsigned port) 86 { 87 unsigned i = port / EVENT_WORDS_PER_PAGE; 88 89 return event_array[i] + port % EVENT_WORDS_PER_PAGE; 90 } 91 92 static unsigned evtchn_fifo_max_channels(void) 93 { 94 return EVTCHN_FIFO_NR_CHANNELS; 95 } 96 97 static unsigned evtchn_fifo_nr_channels(void) 98 { 99 return event_array_pages * EVENT_WORDS_PER_PAGE; 100 } 101 102 static 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 } 120 121 static 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 } 132 133 static 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 } 140 141 static int evtchn_fifo_setup(struct irq_info *info) 142 { 143 unsigned port = info->evtchn; 144 unsigned new_array_pages; 145 int ret; 146 147 new_array_pages = port / EVENT_WORDS_PER_PAGE + 1; 148 149 if (new_array_pages > MAX_EVENT_ARRAY_PAGES) 150 return -EINVAL; 151 152 while (event_array_pages < new_array_pages) { 153 void *array_page; 154 struct evtchn_expand_array expand_array; 155 156 /* Might already have a page if we've resumed. */ 157 array_page = event_array[event_array_pages]; 158 if (!array_page) { 159 array_page = (void *)__get_free_page(GFP_KERNEL); 160 if (array_page == NULL) { 161 ret = -ENOMEM; 162 goto error; 163 } 164 event_array[event_array_pages] = array_page; 165 } 166 167 /* Mask all events in this page before adding it. */ 168 init_array_page(array_page); 169 170 expand_array.array_gfn = virt_to_gfn(array_page); 171 172 ret = HYPERVISOR_event_channel_op(EVTCHNOP_expand_array, &expand_array); 173 if (ret < 0) 174 goto error; 175 176 event_array_pages++; 177 } 178 return 0; 179 180 error: 181 if (event_array_pages == 0) 182 panic("xen: unable to expand event array with initial page (%d)\n", ret); 183 else 184 pr_err("unable to expand event array (%d)\n", ret); 185 free_unused_array_pages(); 186 return ret; 187 } 188 189 static void evtchn_fifo_bind_to_cpu(struct irq_info *info, unsigned cpu) 190 { 191 /* no-op */ 192 } 193 194 static void evtchn_fifo_clear_pending(unsigned port) 195 { 196 event_word_t *word = event_word_from_port(port); 197 sync_clear_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word)); 198 } 199 200 static void evtchn_fifo_set_pending(unsigned port) 201 { 202 event_word_t *word = event_word_from_port(port); 203 sync_set_bit(EVTCHN_FIFO_BIT(PENDING, word), BM(word)); 204 } 205 206 static bool evtchn_fifo_is_pending(unsigned 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 } 211 212 static bool evtchn_fifo_test_and_set_mask(unsigned port) 213 { 214 event_word_t *word = event_word_from_port(port); 215 return sync_test_and_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word)); 216 } 217 218 static void evtchn_fifo_mask(unsigned port) 219 { 220 event_word_t *word = event_word_from_port(port); 221 sync_set_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word)); 222 } 223 224 static bool evtchn_fifo_is_masked(unsigned port) 225 { 226 event_word_t *word = event_word_from_port(port); 227 return sync_test_bit(EVTCHN_FIFO_BIT(MASKED, word), BM(word)); 228 } 229 /* 230 * Clear MASKED, spinning if BUSY is set. 231 */ 232 static void clear_masked(volatile event_word_t *word) 233 { 234 event_word_t new, old, w; 235 236 w = *word; 237 238 do { 239 old = w & ~(1 << EVTCHN_FIFO_BUSY); 240 new = old & ~(1 << EVTCHN_FIFO_MASKED); 241 w = sync_cmpxchg(word, old, new); 242 } while (w != old); 243 } 244 245 static void evtchn_fifo_unmask(unsigned port) 246 { 247 event_word_t *word = event_word_from_port(port); 248 249 BUG_ON(!irqs_disabled()); 250 251 clear_masked(word); 252 if (evtchn_fifo_is_pending(port)) { 253 struct evtchn_unmask unmask = { .port = port }; 254 (void)HYPERVISOR_event_channel_op(EVTCHNOP_unmask, &unmask); 255 } 256 } 257 258 static uint32_t clear_linked(volatile event_word_t *word) 259 { 260 event_word_t new, old, w; 261 262 w = *word; 263 264 do { 265 old = w; 266 new = (w & ~((1 << EVTCHN_FIFO_LINKED) 267 | EVTCHN_FIFO_LINK_MASK)); 268 } while ((w = sync_cmpxchg(word, old, new)) != old); 269 270 return w & EVTCHN_FIFO_LINK_MASK; 271 } 272 273 static void handle_irq_for_port(unsigned port) 274 { 275 int irq; 276 277 irq = get_evtchn_to_irq(port); 278 if (irq != -1) 279 generic_handle_irq(irq); 280 } 281 282 static void consume_one_event(unsigned cpu, 283 struct evtchn_fifo_control_block *control_block, 284 unsigned priority, unsigned long *ready, 285 bool drop) 286 { 287 struct evtchn_fifo_queue *q = &per_cpu(cpu_queue, cpu); 288 uint32_t head; 289 unsigned port; 290 event_word_t *word; 291 292 head = q->head[priority]; 293 294 /* 295 * Reached the tail last time? Read the new HEAD from the 296 * control block. 297 */ 298 if (head == 0) { 299 virt_rmb(); /* Ensure word is up-to-date before reading head. */ 300 head = control_block->head[priority]; 301 } 302 303 port = head; 304 word = event_word_from_port(port); 305 head = clear_linked(word); 306 307 /* 308 * If the link is non-zero, there are more events in the 309 * queue, otherwise the queue is empty. 310 * 311 * If the queue is empty, clear this priority from our local 312 * copy of the ready word. 313 */ 314 if (head == 0) 315 clear_bit(priority, ready); 316 317 if (evtchn_fifo_is_pending(port) && !evtchn_fifo_is_masked(port)) { 318 if (unlikely(drop)) 319 pr_warn("Dropping pending event for port %u\n", port); 320 else 321 handle_irq_for_port(port); 322 } 323 324 q->head[priority] = head; 325 } 326 327 static void __evtchn_fifo_handle_events(unsigned cpu, bool drop) 328 { 329 struct evtchn_fifo_control_block *control_block; 330 unsigned long ready; 331 unsigned q; 332 333 control_block = per_cpu(cpu_control_block, cpu); 334 335 ready = xchg(&control_block->ready, 0); 336 337 while (ready) { 338 q = find_first_bit(&ready, EVTCHN_FIFO_MAX_QUEUES); 339 consume_one_event(cpu, control_block, q, &ready, drop); 340 ready |= xchg(&control_block->ready, 0); 341 } 342 } 343 344 static void evtchn_fifo_handle_events(unsigned cpu) 345 { 346 __evtchn_fifo_handle_events(cpu, false); 347 } 348 349 static void evtchn_fifo_resume(void) 350 { 351 unsigned cpu; 352 353 for_each_possible_cpu(cpu) { 354 void *control_block = per_cpu(cpu_control_block, cpu); 355 int ret; 356 357 if (!control_block) 358 continue; 359 360 /* 361 * If this CPU is offline, take the opportunity to 362 * free the control block while it is not being 363 * used. 364 */ 365 if (!cpu_online(cpu)) { 366 free_page((unsigned long)control_block); 367 per_cpu(cpu_control_block, cpu) = NULL; 368 continue; 369 } 370 371 ret = init_control_block(cpu, control_block); 372 BUG_ON(ret < 0); 373 } 374 375 /* 376 * The event array starts out as empty again and is extended 377 * as normal when events are bound. The existing pages will 378 * be reused. 379 */ 380 event_array_pages = 0; 381 } 382 383 static const struct evtchn_ops evtchn_ops_fifo = { 384 .max_channels = evtchn_fifo_max_channels, 385 .nr_channels = evtchn_fifo_nr_channels, 386 .setup = evtchn_fifo_setup, 387 .bind_to_cpu = evtchn_fifo_bind_to_cpu, 388 .clear_pending = evtchn_fifo_clear_pending, 389 .set_pending = evtchn_fifo_set_pending, 390 .is_pending = evtchn_fifo_is_pending, 391 .test_and_set_mask = evtchn_fifo_test_and_set_mask, 392 .mask = evtchn_fifo_mask, 393 .unmask = evtchn_fifo_unmask, 394 .handle_events = evtchn_fifo_handle_events, 395 .resume = evtchn_fifo_resume, 396 }; 397 398 static int evtchn_fifo_alloc_control_block(unsigned cpu) 399 { 400 void *control_block = NULL; 401 int ret = -ENOMEM; 402 403 control_block = (void *)__get_free_page(GFP_KERNEL); 404 if (control_block == NULL) 405 goto error; 406 407 ret = init_control_block(cpu, control_block); 408 if (ret < 0) 409 goto error; 410 411 per_cpu(cpu_control_block, cpu) = control_block; 412 413 return 0; 414 415 error: 416 free_page((unsigned long)control_block); 417 return ret; 418 } 419 420 static int xen_evtchn_cpu_prepare(unsigned int cpu) 421 { 422 if (!per_cpu(cpu_control_block, cpu)) 423 return evtchn_fifo_alloc_control_block(cpu); 424 return 0; 425 } 426 427 static int xen_evtchn_cpu_dead(unsigned int cpu) 428 { 429 __evtchn_fifo_handle_events(cpu, true); 430 return 0; 431 } 432 433 int __init xen_evtchn_fifo_init(void) 434 { 435 int cpu = get_cpu(); 436 int ret; 437 438 ret = evtchn_fifo_alloc_control_block(cpu); 439 if (ret < 0) 440 goto out; 441 442 pr_info("Using FIFO-based ABI\n"); 443 444 evtchn_ops = &evtchn_ops_fifo; 445 446 cpuhp_setup_state_nocalls(CPUHP_XEN_EVTCHN_PREPARE, 447 "xen/evtchn:prepare", 448 xen_evtchn_cpu_prepare, xen_evtchn_cpu_dead); 449 out: 450 put_cpu(); 451 return ret; 452 } 453