1 /* $NetBSD: subr_ipi.c,v 1.11 2023/02/24 11:02:27 riastradh Exp $ */ 2 3 /*- 4 * Copyright (c) 2014 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Mindaugas Rasiukevicius. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 /* 33 * Inter-processor interrupt (IPI) interface: asynchronous IPIs to 34 * invoke functions with a constant argument and synchronous IPIs 35 * with the cross-call support. 36 */ 37 38 #include <sys/cdefs.h> 39 __KERNEL_RCSID(0, "$NetBSD: subr_ipi.c,v 1.11 2023/02/24 11:02:27 riastradh Exp $"); 40 41 #include <sys/param.h> 42 #include <sys/types.h> 43 44 #include <sys/atomic.h> 45 #include <sys/evcnt.h> 46 #include <sys/cpu.h> 47 #include <sys/ipi.h> 48 #include <sys/intr.h> 49 #include <sys/kcpuset.h> 50 #include <sys/kmem.h> 51 #include <sys/lock.h> 52 #include <sys/mutex.h> 53 54 /* 55 * An array of the IPI handlers used for asynchronous invocation. 56 * The lock protects the slot allocation. 57 */ 58 59 typedef struct { 60 ipi_func_t func; 61 void * arg; 62 } ipi_intr_t; 63 64 static kmutex_t ipi_mngmt_lock; 65 static ipi_intr_t ipi_intrs[IPI_MAXREG] __cacheline_aligned; 66 67 /* 68 * Per-CPU mailbox for IPI messages: it is a single cache line storing 69 * up to IPI_MSG_MAX messages. This interface is built on top of the 70 * synchronous IPIs. 71 */ 72 73 #define IPI_MSG_SLOTS (CACHE_LINE_SIZE / sizeof(ipi_msg_t *)) 74 #define IPI_MSG_MAX IPI_MSG_SLOTS 75 76 typedef struct { 77 ipi_msg_t * msg[IPI_MSG_SLOTS]; 78 } ipi_mbox_t; 79 80 81 /* Mailboxes for the synchronous IPIs. */ 82 static ipi_mbox_t * ipi_mboxes __read_mostly; 83 static struct evcnt ipi_mboxfull_ev __cacheline_aligned; 84 static void ipi_msg_cpu_handler(void *); 85 86 /* Handler for the synchronous IPIs - it must be zero. */ 87 #define IPI_SYNCH_ID 0 88 89 #ifndef MULTIPROCESSOR 90 #define cpu_ipi(ci) KASSERT(ci == NULL) 91 #endif 92 93 void 94 ipi_sysinit(void) 95 { 96 97 mutex_init(&ipi_mngmt_lock, MUTEX_DEFAULT, IPL_NONE); 98 memset(ipi_intrs, 0, sizeof(ipi_intrs)); 99 100 /* 101 * Register the handler for synchronous IPIs. This mechanism 102 * is built on top of the asynchronous interface. Slot zero is 103 * reserved permanently; it is also handy to use zero as a failure 104 * for other registers (as it is potentially less error-prone). 105 */ 106 ipi_intrs[IPI_SYNCH_ID].func = ipi_msg_cpu_handler; 107 108 evcnt_attach_dynamic(&ipi_mboxfull_ev, EVCNT_TYPE_MISC, NULL, 109 "ipi", "full"); 110 } 111 112 void 113 ipi_percpu_init(void) 114 { 115 const size_t len = ncpu * sizeof(ipi_mbox_t); 116 117 /* Initialise the per-CPU bit fields. */ 118 for (u_int i = 0; i < ncpu; i++) { 119 struct cpu_info *ci = cpu_lookup(i); 120 memset(&ci->ci_ipipend, 0, sizeof(ci->ci_ipipend)); 121 } 122 123 /* Allocate per-CPU IPI mailboxes. */ 124 ipi_mboxes = kmem_zalloc(len, KM_SLEEP); 125 KASSERT(ipi_mboxes != NULL); 126 } 127 128 /* 129 * ipi_register: register an asynchronous IPI handler. 130 * 131 * => Returns IPI ID which is greater than zero; on failure - zero. 132 */ 133 u_int 134 ipi_register(ipi_func_t func, void *arg) 135 { 136 mutex_enter(&ipi_mngmt_lock); 137 for (u_int i = 0; i < IPI_MAXREG; i++) { 138 if (ipi_intrs[i].func == NULL) { 139 /* Register the function. */ 140 ipi_intrs[i].func = func; 141 ipi_intrs[i].arg = arg; 142 mutex_exit(&ipi_mngmt_lock); 143 144 KASSERT(i != IPI_SYNCH_ID); 145 return i; 146 } 147 } 148 mutex_exit(&ipi_mngmt_lock); 149 printf("WARNING: ipi_register: table full, increase IPI_MAXREG\n"); 150 return 0; 151 } 152 153 /* 154 * ipi_unregister: release the IPI handler given the ID. 155 */ 156 void 157 ipi_unregister(u_int ipi_id) 158 { 159 ipi_msg_t ipimsg = { .func = __FPTRCAST(ipi_func_t, nullop) }; 160 161 KASSERT(ipi_id != IPI_SYNCH_ID); 162 KASSERT(ipi_id < IPI_MAXREG); 163 164 /* Release the slot. */ 165 mutex_enter(&ipi_mngmt_lock); 166 KASSERT(ipi_intrs[ipi_id].func != NULL); 167 ipi_intrs[ipi_id].func = NULL; 168 169 /* Ensure that there are no IPIs in flight. */ 170 kpreempt_disable(); 171 ipi_broadcast(&ipimsg, false); 172 ipi_wait(&ipimsg); 173 kpreempt_enable(); 174 mutex_exit(&ipi_mngmt_lock); 175 } 176 177 /* 178 * ipi_mark_pending: internal routine to mark an IPI pending on the 179 * specified CPU (which might be curcpu()). 180 */ 181 static bool 182 ipi_mark_pending(u_int ipi_id, struct cpu_info *ci) 183 { 184 const u_int i = ipi_id >> IPI_BITW_SHIFT; 185 const uint32_t bitm = 1U << (ipi_id & IPI_BITW_MASK); 186 187 KASSERT(ipi_id < IPI_MAXREG); 188 KASSERT(kpreempt_disabled()); 189 190 /* Mark as pending and return true if not previously marked. */ 191 if ((atomic_load_acquire(&ci->ci_ipipend[i]) & bitm) == 0) { 192 membar_release(); 193 atomic_or_32(&ci->ci_ipipend[i], bitm); 194 return true; 195 } 196 return false; 197 } 198 199 /* 200 * ipi_trigger: asynchronously send an IPI to the specified CPU. 201 */ 202 void 203 ipi_trigger(u_int ipi_id, struct cpu_info *ci) 204 { 205 206 KASSERT(curcpu() != ci); 207 if (ipi_mark_pending(ipi_id, ci)) { 208 cpu_ipi(ci); 209 } 210 } 211 212 /* 213 * ipi_trigger_multi_internal: the guts of ipi_trigger_multi() and 214 * ipi_trigger_broadcast(). 215 */ 216 static void 217 ipi_trigger_multi_internal(u_int ipi_id, const kcpuset_t *target, 218 bool skip_self) 219 { 220 const cpuid_t selfid = cpu_index(curcpu()); 221 CPU_INFO_ITERATOR cii; 222 struct cpu_info *ci; 223 224 KASSERT(kpreempt_disabled()); 225 KASSERT(target != NULL); 226 227 for (CPU_INFO_FOREACH(cii, ci)) { 228 const cpuid_t cpuid = cpu_index(ci); 229 230 if (!kcpuset_isset(target, cpuid) || cpuid == selfid) { 231 continue; 232 } 233 ipi_trigger(ipi_id, ci); 234 } 235 if (!skip_self && kcpuset_isset(target, selfid)) { 236 ipi_mark_pending(ipi_id, curcpu()); 237 int s = splhigh(); 238 ipi_cpu_handler(); 239 splx(s); 240 } 241 } 242 243 /* 244 * ipi_trigger_multi: same as ipi_trigger() but sends to the multiple 245 * CPUs given the target CPU set. 246 */ 247 void 248 ipi_trigger_multi(u_int ipi_id, const kcpuset_t *target) 249 { 250 ipi_trigger_multi_internal(ipi_id, target, false); 251 } 252 253 /* 254 * ipi_trigger_broadcast: same as ipi_trigger_multi() to kcpuset_attached, 255 * optionally skipping the sending CPU. 256 */ 257 void 258 ipi_trigger_broadcast(u_int ipi_id, bool skip_self) 259 { 260 ipi_trigger_multi_internal(ipi_id, kcpuset_attached, skip_self); 261 } 262 263 /* 264 * put_msg: insert message into the mailbox. 265 * 266 * Caller is responsible for issuing membar_release first. 267 */ 268 static inline void 269 put_msg(ipi_mbox_t *mbox, ipi_msg_t *msg) 270 { 271 int count = SPINLOCK_BACKOFF_MIN; 272 again: 273 for (u_int i = 0; i < IPI_MSG_MAX; i++) { 274 if (atomic_cas_ptr(&mbox->msg[i], NULL, msg) == NULL) { 275 return; 276 } 277 } 278 279 /* All slots are full: we have to spin-wait. */ 280 ipi_mboxfull_ev.ev_count++; 281 SPINLOCK_BACKOFF(count); 282 goto again; 283 } 284 285 /* 286 * ipi_cpu_handler: the IPI handler. 287 */ 288 void 289 ipi_cpu_handler(void) 290 { 291 struct cpu_info * const ci = curcpu(); 292 293 /* 294 * Handle asynchronous IPIs: inspect per-CPU bit field, extract 295 * IPI ID numbers and execute functions in those slots. 296 */ 297 for (u_int i = 0; i < IPI_BITWORDS; i++) { 298 uint32_t pending, bit; 299 300 if (atomic_load_relaxed(&ci->ci_ipipend[i]) == 0) { 301 continue; 302 } 303 pending = atomic_swap_32(&ci->ci_ipipend[i], 0); 304 membar_acquire(); 305 while ((bit = ffs(pending)) != 0) { 306 const u_int ipi_id = (i << IPI_BITW_SHIFT) | --bit; 307 ipi_intr_t *ipi_hdl = &ipi_intrs[ipi_id]; 308 309 pending &= ~(1U << bit); 310 KASSERT(ipi_hdl->func != NULL); 311 ipi_hdl->func(ipi_hdl->arg); 312 } 313 } 314 } 315 316 /* 317 * ipi_msg_cpu_handler: handle synchronous IPIs - iterate mailbox, 318 * execute the passed functions and acknowledge the messages. 319 */ 320 static void 321 ipi_msg_cpu_handler(void *arg __unused) 322 { 323 const struct cpu_info * const ci = curcpu(); 324 ipi_mbox_t *mbox = &ipi_mboxes[cpu_index(ci)]; 325 326 for (u_int i = 0; i < IPI_MSG_MAX; i++) { 327 ipi_msg_t *msg; 328 329 /* Get the message. */ 330 if ((msg = atomic_load_acquire(&mbox->msg[i])) == NULL) { 331 continue; 332 } 333 atomic_store_relaxed(&mbox->msg[i], NULL); 334 335 /* Execute the handler. */ 336 KASSERT(msg->func); 337 msg->func(msg->arg); 338 339 /* Ack the request. */ 340 membar_release(); 341 atomic_dec_uint(&msg->_pending); 342 } 343 } 344 345 /* 346 * ipi_unicast: send an IPI to a single CPU. 347 * 348 * => The CPU must be remote; must not be local. 349 * => The caller must ipi_wait() on the message for completion. 350 */ 351 void 352 ipi_unicast(ipi_msg_t *msg, struct cpu_info *ci) 353 { 354 const cpuid_t id = cpu_index(ci); 355 356 KASSERT(msg->func != NULL); 357 KASSERT(kpreempt_disabled()); 358 KASSERT(curcpu() != ci); 359 360 msg->_pending = 1; 361 membar_release(); 362 363 put_msg(&ipi_mboxes[id], msg); 364 ipi_trigger(IPI_SYNCH_ID, ci); 365 } 366 367 /* 368 * ipi_multicast: send an IPI to each CPU in the specified set. 369 * 370 * => The caller must ipi_wait() on the message for completion. 371 */ 372 void 373 ipi_multicast(ipi_msg_t *msg, const kcpuset_t *target) 374 { 375 const struct cpu_info * const self = curcpu(); 376 CPU_INFO_ITERATOR cii; 377 struct cpu_info *ci; 378 u_int local; 379 380 KASSERT(msg->func != NULL); 381 KASSERT(kpreempt_disabled()); 382 383 local = !!kcpuset_isset(target, cpu_index(self)); 384 msg->_pending = kcpuset_countset(target) - local; 385 membar_release(); 386 387 for (CPU_INFO_FOREACH(cii, ci)) { 388 cpuid_t id; 389 390 if (__predict_false(ci == self)) { 391 continue; 392 } 393 id = cpu_index(ci); 394 if (!kcpuset_isset(target, id)) { 395 continue; 396 } 397 put_msg(&ipi_mboxes[id], msg); 398 ipi_trigger(IPI_SYNCH_ID, ci); 399 } 400 if (local) { 401 msg->func(msg->arg); 402 } 403 } 404 405 /* 406 * ipi_broadcast: send an IPI to all CPUs. 407 * 408 * => The caller must ipi_wait() on the message for completion. 409 */ 410 void 411 ipi_broadcast(ipi_msg_t *msg, bool skip_self) 412 { 413 const struct cpu_info * const self = curcpu(); 414 CPU_INFO_ITERATOR cii; 415 struct cpu_info *ci; 416 417 KASSERT(msg->func != NULL); 418 KASSERT(kpreempt_disabled()); 419 420 msg->_pending = ncpu - 1; 421 membar_release(); 422 423 /* Broadcast IPIs for remote CPUs. */ 424 for (CPU_INFO_FOREACH(cii, ci)) { 425 cpuid_t id; 426 427 if (__predict_false(ci == self)) { 428 continue; 429 } 430 id = cpu_index(ci); 431 put_msg(&ipi_mboxes[id], msg); 432 ipi_trigger(IPI_SYNCH_ID, ci); 433 } 434 435 if (!skip_self) { 436 /* Finally, execute locally. */ 437 msg->func(msg->arg); 438 } 439 } 440 441 /* 442 * ipi_wait: spin-wait until the message is processed. 443 */ 444 void 445 ipi_wait(ipi_msg_t *msg) 446 { 447 int count = SPINLOCK_BACKOFF_MIN; 448 449 while (atomic_load_acquire(&msg->_pending)) { 450 KASSERT(atomic_load_relaxed(&msg->_pending) < ncpu); 451 SPINLOCK_BACKOFF(count); 452 } 453 } 454