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(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 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(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 else 183 pr_err("unable to expand event array (%d)\n", ret); 184 free_unused_array_pages(); 185 return ret; 186 } 187 188 static void evtchn_fifo_bind_to_cpu(evtchn_port_t evtchn, unsigned int cpu, 189 unsigned int old_cpu) 190 { 191 /* no-op */ 192 } 193 194 static 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 } 199 200 static 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 } 205 206 static 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 } 211 212 static 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 } 217 218 static 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 */ 227 static 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 } 246 247 static 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 } 258 259 static 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 } 272 273 static 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 the 286 * 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 the 299 * queue, otherwise the queue is empty. 300 * 301 * If the queue is empty, clear this priority from our local 302 * 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 else 311 handle_irq_for_port(port, ctrl); 312 } 313 314 q->head[priority] = head; 315 } 316 317 static 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 } 334 335 static void evtchn_fifo_handle_events(unsigned cpu, 336 struct evtchn_loop_ctrl *ctrl) 337 { 338 __evtchn_fifo_handle_events(cpu, ctrl); 339 } 340 341 static 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 to 354 * free the control block while it is not being 355 * 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 extended 369 * as normal when events are bound. The existing pages will 370 * be reused. 371 */ 372 event_array_pages = 0; 373 } 374 375 static 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 } 396 397 static 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 } 403 404 static int evtchn_fifo_percpu_deinit(unsigned int cpu) 405 { 406 __evtchn_fifo_handle_events(cpu, NULL); 407 return 0; 408 } 409 410 static 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 }; 425 426 int __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