1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21 /*
22 * Copyright 2009 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
24 */
25 /*
26 * Copyright (c) 2010, Intel Corporation.
27 * All rights reserved.
28 * Copyright 2018 Joyent, Inc.
29 */
30
31 #include <sys/types.h>
32 #include <sys/param.h>
33 #include <sys/t_lock.h>
34 #include <sys/thread.h>
35 #include <sys/cpuvar.h>
36 #include <sys/x_call.h>
37 #include <sys/xc_levels.h>
38 #include <sys/cpu.h>
39 #include <sys/psw.h>
40 #include <sys/sunddi.h>
41 #include <sys/debug.h>
42 #include <sys/systm.h>
43 #include <sys/archsystm.h>
44 #include <sys/machsystm.h>
45 #include <sys/mutex_impl.h>
46 #include <sys/stack.h>
47 #include <sys/promif.h>
48 #include <sys/x86_archext.h>
49
50 /*
51 * Implementation for cross-processor calls via interprocessor interrupts
52 *
53 * This implementation uses a message passing architecture to allow multiple
54 * concurrent cross calls to be in flight at any given time. We use the cmpxchg
55 * instruction, aka atomic_cas_ptr(), to implement simple efficient work
56 * queues for message passing between CPUs with almost no need for regular
57 * locking. See xc_extract() and xc_insert() below.
58 *
59 * The general idea is that initiating a cross call means putting a message
60 * on a target(s) CPU's work queue. Any synchronization is handled by passing
61 * the message back and forth between initiator and target(s).
62 *
63 * Every CPU has xc_work_cnt, which indicates it has messages to process.
64 * This value is incremented as message traffic is initiated and decremented
65 * with every message that finishes all processing.
66 *
67 * The code needs no mfence or other membar_*() calls. The uses of
68 * atomic_cas_ptr(), atomic_cas_32() and atomic_dec_32() for the message
69 * passing are implemented with LOCK prefix instructions which are
70 * equivalent to mfence.
71 *
72 * One interesting aspect of this implmentation is that it allows 2 or more
73 * CPUs to initiate cross calls to intersecting sets of CPUs at the same time.
74 * The cross call processing by the CPUs will happen in any order with only
75 * a guarantee, for xc_call() and xc_sync(), that an initiator won't return
76 * from cross calls before all slaves have invoked the function.
77 *
78 * The reason for this asynchronous approach is to allow for fast global
79 * TLB shootdowns. If all CPUs, say N, tried to do a global TLB invalidation
80 * on a different Virtual Address at the same time. The old code required
81 * N squared IPIs. With this method, depending on timing, it could happen
82 * with just N IPIs.
83 *
84 * Here are the normal transitions for XC_MSG_* values in ->xc_command. A
85 * transition of "->" happens in the slave cpu and "=>" happens in the master
86 * cpu as the messages are passed back and forth.
87 *
88 * FREE => ASYNC -> DONE => FREE
89 * FREE => CALL -> DONE => FREE
90 * FREE => SYNC -> WAITING => RELEASED -> DONE => FREE
91 *
92 * The interesting one above is ASYNC. You might ask, why not go directly
93 * to FREE, instead of DONE? If it did that, it might be possible to exhaust
94 * the master's xc_free list if a master can generate ASYNC messages faster
95 * then the slave can process them. That could be handled with more complicated
96 * handling. However since nothing important uses ASYNC, I've not bothered.
97 */
98
99 /*
100 * The default is to not enable collecting counts of IPI information, since
101 * the updating of shared cachelines could cause excess bus traffic.
102 */
103 uint_t xc_collect_enable = 0;
104 uint64_t xc_total_cnt = 0; /* total #IPIs sent for cross calls */
105 uint64_t xc_multi_cnt = 0; /* # times we piggy backed on another IPI */
106
107 /*
108 * We allow for one high priority message at a time to happen in the system.
109 * This is used for panic, kmdb, etc., so no locking is done.
110 */
111 static volatile cpuset_t xc_priority_set_store;
112 static volatile ulong_t *xc_priority_set = CPUSET2BV(xc_priority_set_store);
113 static xc_data_t xc_priority_data;
114
115 /*
116 * Decrement a CPU's work count
117 */
118 static void
119 xc_decrement(struct machcpu *mcpu)
120 {
121 atomic_dec_32(&mcpu->xc_work_cnt);
122 }
123
124 /*
125 * Increment a CPU's work count and return the old value
126 */
127 static int
128 xc_increment(struct machcpu *mcpu)
129 {
130 int old;
131 do {
132 old = mcpu->xc_work_cnt;
133 } while (atomic_cas_32(&mcpu->xc_work_cnt, old, old + 1) != old);
134 return (old);
135 }
136
137 /*
138 * Put a message into a queue. The insertion is atomic no matter
139 * how many different inserts/extracts to the same queue happen.
140 */
141 static void
142 xc_insert(void *queue, xc_msg_t *msg)
143 {
144 xc_msg_t *old_head;
145
146 /*
147 * FREE messages should only ever be getting inserted into
148 * the xc_master CPUs xc_free queue.
149 */
150 ASSERT(msg->xc_command != XC_MSG_FREE ||
151 cpu[msg->xc_master] == NULL || /* possible only during init */
152 queue == &cpu[msg->xc_master]->cpu_m.xc_free);
153
154 do {
155 old_head = (xc_msg_t *)*(volatile xc_msg_t **)queue;
156 msg->xc_next = old_head;
157 } while (atomic_cas_ptr(queue, old_head, msg) != old_head);
158 }
159
160 /*
161 * Extract a message from a queue. The extraction is atomic only
162 * when just one thread does extractions from the queue.
163 * If the queue is empty, NULL is returned.
164 */
165 static xc_msg_t *
166 xc_extract(xc_msg_t **queue)
167 {
168 xc_msg_t *old_head;
169
170 do {
171 old_head = (xc_msg_t *)*(volatile xc_msg_t **)queue;
172 if (old_head == NULL)
173 return (old_head);
174 } while (atomic_cas_ptr(queue, old_head, old_head->xc_next) !=
175 old_head);
176 old_head->xc_next = NULL;
177 return (old_head);
178 }
179
180 /*
181 * Extract the next message from the CPU's queue, and place the message in
182 * .xc_curmsg. The latter is solely to make debugging (and ::xcall) more
183 * useful.
184 */
185 static xc_msg_t *
186 xc_get(void)
187 {
188 struct machcpu *mcpup = &CPU->cpu_m;
189 xc_msg_t *msg = xc_extract(&mcpup->xc_msgbox);
190 mcpup->xc_curmsg = msg;
191 return (msg);
192 }
193
194 /*
195 * Initialize the machcpu fields used for cross calls
196 */
197 static uint_t xc_initialized = 0;
198
199 void
200 xc_init_cpu(struct cpu *cpup)
201 {
202 xc_msg_t *msg;
203 int c;
204
205 /*
206 * Allocate message buffers for the new CPU.
207 */
208 for (c = 0; c < max_ncpus; ++c) {
209 if (plat_dr_support_cpu()) {
210 /*
211 * Allocate a message buffer for every CPU possible
212 * in system, including our own, and add them to our xc
213 * message queue.
214 */
215 msg = kmem_zalloc(sizeof (*msg), KM_SLEEP);
216 msg->xc_command = XC_MSG_FREE;
217 msg->xc_master = cpup->cpu_id;
218 xc_insert(&cpup->cpu_m.xc_free, msg);
219 } else if (cpu[c] != NULL && cpu[c] != cpup) {
220 /*
221 * Add a new message buffer to each existing CPU's free
222 * list, as well as one for my list for each of them.
223 * Note: cpu0 is statically inserted into cpu[] array,
224 * so need to check cpu[c] isn't cpup itself to avoid
225 * allocating extra message buffers for cpu0.
226 */
227 msg = kmem_zalloc(sizeof (*msg), KM_SLEEP);
228 msg->xc_command = XC_MSG_FREE;
229 msg->xc_master = c;
230 xc_insert(&cpu[c]->cpu_m.xc_free, msg);
231
232 msg = kmem_zalloc(sizeof (*msg), KM_SLEEP);
233 msg->xc_command = XC_MSG_FREE;
234 msg->xc_master = cpup->cpu_id;
235 xc_insert(&cpup->cpu_m.xc_free, msg);
236 }
237 }
238
239 if (!plat_dr_support_cpu()) {
240 /*
241 * Add one for self messages if CPU hotplug is disabled.
242 */
243 msg = kmem_zalloc(sizeof (*msg), KM_SLEEP);
244 msg->xc_command = XC_MSG_FREE;
245 msg->xc_master = cpup->cpu_id;
246 xc_insert(&cpup->cpu_m.xc_free, msg);
247 }
248
249 if (!xc_initialized)
250 xc_initialized = 1;
251 }
252
253 void
254 xc_fini_cpu(struct cpu *cpup)
255 {
256 xc_msg_t *msg;
257
258 ASSERT((cpup->cpu_flags & CPU_READY) == 0);
259 ASSERT(cpup->cpu_m.xc_msgbox == NULL);
260 ASSERT(cpup->cpu_m.xc_work_cnt == 0);
261
262 while ((msg = xc_extract(&cpup->cpu_m.xc_free)) != NULL) {
263 kmem_free(msg, sizeof (*msg));
264 }
265 }
266
267 #define XC_FLUSH_MAX_WAITS 1000
268
269 /* Flush inflight message buffers. */
270 int
271 xc_flush_cpu(struct cpu *cpup)
272 {
273 int i;
274
275 ASSERT((cpup->cpu_flags & CPU_READY) == 0);
276
277 /*
278 * Pause all working CPUs, which ensures that there's no CPU in
279 * function xc_common().
280 * This is used to work around a race condition window in xc_common()
281 * between checking CPU_READY flag and increasing working item count.
282 */
283 pause_cpus(cpup, NULL);
284 start_cpus();
285
286 for (i = 0; i < XC_FLUSH_MAX_WAITS; i++) {
287 if (cpup->cpu_m.xc_work_cnt == 0) {
288 break;
289 }
290 DELAY(1);
291 }
292 for (; i < XC_FLUSH_MAX_WAITS; i++) {
293 if (!BT_TEST(xc_priority_set, cpup->cpu_id)) {
294 break;
295 }
296 DELAY(1);
297 }
298
299 return (i >= XC_FLUSH_MAX_WAITS ? ETIME : 0);
300 }
301
302 /*
303 * X-call message processing routine. Note that this is used by both
304 * senders and recipients of messages.
305 *
306 * We're protected against changing CPUs by either being in a high-priority
307 * interrupt, having preemption disabled or by having a raised SPL.
308 */
309 /*ARGSUSED*/
310 uint_t
311 xc_serv(caddr_t arg1, caddr_t arg2)
312 {
313 struct machcpu *mcpup = &(CPU->cpu_m);
314 xc_msg_t *msg;
315 xc_data_t *data;
316 xc_msg_t *xc_waiters = NULL;
317 uint32_t num_waiting = 0;
318 xc_func_t func;
319 xc_arg_t a1;
320 xc_arg_t a2;
321 xc_arg_t a3;
322 uint_t rc = DDI_INTR_UNCLAIMED;
323
324 while (mcpup->xc_work_cnt != 0) {
325 rc = DDI_INTR_CLAIMED;
326
327 /*
328 * We may have to wait for a message to arrive.
329 */
330 for (msg = NULL; msg == NULL; msg = xc_get()) {
331
332 /*
333 * Alway check for and handle a priority message.
334 */
335 if (BT_TEST(xc_priority_set, CPU->cpu_id)) {
336 func = xc_priority_data.xc_func;
337 a1 = xc_priority_data.xc_a1;
338 a2 = xc_priority_data.xc_a2;
339 a3 = xc_priority_data.xc_a3;
340 BT_ATOMIC_CLEAR(xc_priority_set, CPU->cpu_id);
341 xc_decrement(mcpup);
342 func(a1, a2, a3);
343 if (mcpup->xc_work_cnt == 0)
344 return (rc);
345 }
346
347 /*
348 * wait for a message to arrive
349 */
350 SMT_PAUSE();
351 }
352
353
354 /*
355 * process the message
356 */
357 switch (msg->xc_command) {
358
359 /*
360 * ASYNC gives back the message immediately, then we do the
361 * function and return with no more waiting.
362 */
363 case XC_MSG_ASYNC:
364 data = &cpu[msg->xc_master]->cpu_m.xc_data;
365 func = data->xc_func;
366 a1 = data->xc_a1;
367 a2 = data->xc_a2;
368 a3 = data->xc_a3;
369 msg->xc_command = XC_MSG_DONE;
370 xc_insert(&cpu[msg->xc_master]->cpu_m.xc_msgbox, msg);
371 if (func != NULL)
372 (void) (*func)(a1, a2, a3);
373 xc_decrement(mcpup);
374 break;
375
376 /*
377 * SYNC messages do the call, then send it back to the master
378 * in WAITING mode
379 */
380 case XC_MSG_SYNC:
381 data = &cpu[msg->xc_master]->cpu_m.xc_data;
382 if (data->xc_func != NULL)
383 (void) (*data->xc_func)(data->xc_a1,
384 data->xc_a2, data->xc_a3);
385 msg->xc_command = XC_MSG_WAITING;
386 xc_insert(&cpu[msg->xc_master]->cpu_m.xc_msgbox, msg);
387 break;
388
389 /*
390 * WAITING messsages are collected by the master until all
391 * have arrived. Once all arrive, we release them back to
392 * the slaves
393 */
394 case XC_MSG_WAITING:
395 xc_insert(&xc_waiters, msg);
396 if (++num_waiting < mcpup->xc_wait_cnt)
397 break;
398 while ((msg = xc_extract(&xc_waiters)) != NULL) {
399 msg->xc_command = XC_MSG_RELEASED;
400 xc_insert(&cpu[msg->xc_slave]->cpu_m.xc_msgbox,
401 msg);
402 --num_waiting;
403 }
404 if (num_waiting != 0)
405 panic("wrong number waiting");
406 mcpup->xc_wait_cnt = 0;
407 break;
408
409 /*
410 * CALL messages do the function and then, like RELEASE,
411 * send the message is back to master as DONE.
412 */
413 case XC_MSG_CALL:
414 data = &cpu[msg->xc_master]->cpu_m.xc_data;
415 if (data->xc_func != NULL)
416 (void) (*data->xc_func)(data->xc_a1,
417 data->xc_a2, data->xc_a3);
418 /*FALLTHROUGH*/
419 case XC_MSG_RELEASED:
420 msg->xc_command = XC_MSG_DONE;
421 xc_insert(&cpu[msg->xc_master]->cpu_m.xc_msgbox, msg);
422 xc_decrement(mcpup);
423 break;
424
425 /*
426 * DONE means a slave has completely finished up.
427 * Once we collect all the DONE messages, we'll exit
428 * processing too.
429 */
430 case XC_MSG_DONE:
431 msg->xc_command = XC_MSG_FREE;
432 xc_insert(&mcpup->xc_free, msg);
433 xc_decrement(mcpup);
434 break;
435
436 case XC_MSG_FREE:
437 panic("free message 0x%p in msgbox", (void *)msg);
438 break;
439
440 default:
441 panic("bad message 0x%p in msgbox", (void *)msg);
442 break;
443 }
444
445 CPU->cpu_m.xc_curmsg = NULL;
446 }
447 return (rc);
448 }
449
450 /*
451 * Initiate cross call processing.
452 */
453 static void
454 xc_common(
455 xc_func_t func,
456 xc_arg_t arg1,
457 xc_arg_t arg2,
458 xc_arg_t arg3,
459 ulong_t *set,
460 uint_t command)
461 {
462 int c;
463 struct cpu *cpup;
464 xc_msg_t *msg;
465 xc_data_t *data;
466 int cnt;
467 int save_spl;
468
469 if (!xc_initialized) {
470 if (BT_TEST(set, CPU->cpu_id) && (CPU->cpu_flags & CPU_READY) &&
471 func != NULL)
472 (void) (*func)(arg1, arg2, arg3);
473 return;
474 }
475
476 save_spl = splr(ipltospl(XC_HI_PIL));
477
478 /*
479 * fill in cross call data
480 */
481 data = &CPU->cpu_m.xc_data;
482 data->xc_func = func;
483 data->xc_a1 = arg1;
484 data->xc_a2 = arg2;
485 data->xc_a3 = arg3;
486
487 /*
488 * Post messages to all CPUs involved that are CPU_READY
489 */
490 CPU->cpu_m.xc_wait_cnt = 0;
491 for (c = 0; c < max_ncpus; ++c) {
492 if (!BT_TEST(set, c))
493 continue;
494 cpup = cpu[c];
495 if (cpup == NULL || !(cpup->cpu_flags & CPU_READY))
496 continue;
497
498 /*
499 * Fill out a new message.
500 */
501 msg = xc_extract(&CPU->cpu_m.xc_free);
502 if (msg == NULL)
503 panic("Ran out of free xc_msg_t's");
504 msg->xc_command = command;
505 if (msg->xc_master != CPU->cpu_id)
506 panic("msg %p has wrong xc_master", (void *)msg);
507 msg->xc_slave = c;
508
509 /*
510 * Increment my work count for all messages that I'll
511 * transition from DONE to FREE.
512 * Also remember how many XC_MSG_WAITINGs to look for
513 */
514 (void) xc_increment(&CPU->cpu_m);
515 if (command == XC_MSG_SYNC)
516 ++CPU->cpu_m.xc_wait_cnt;
517
518 /*
519 * Increment the target CPU work count then insert the message
520 * in the target msgbox. If I post the first bit of work
521 * for the target to do, send an IPI to the target CPU.
522 */
523 cnt = xc_increment(&cpup->cpu_m);
524 xc_insert(&cpup->cpu_m.xc_msgbox, msg);
525 if (cpup != CPU) {
526 if (cnt == 0) {
527 CPU_STATS_ADDQ(CPU, sys, xcalls, 1);
528 send_dirint(c, XC_HI_PIL);
529 if (xc_collect_enable)
530 ++xc_total_cnt;
531 } else if (xc_collect_enable) {
532 ++xc_multi_cnt;
533 }
534 }
535 }
536
537 /*
538 * Now drop into the message handler until all work is done
539 */
540 (void) xc_serv(NULL, NULL);
541 splx(save_spl);
542 }
543
544 /*
545 * Push out a priority cross call.
546 */
547 static void
548 xc_priority_common(
549 xc_func_t func,
550 xc_arg_t arg1,
551 xc_arg_t arg2,
552 xc_arg_t arg3,
553 ulong_t *set)
554 {
555 int i;
556 int c;
557 struct cpu *cpup;
558
559 /*
560 * Wait briefly for any previous xc_priority to have finished.
561 */
562 for (c = 0; c < max_ncpus; ++c) {
563 cpup = cpu[c];
564 if (cpup == NULL || !(cpup->cpu_flags & CPU_READY))
565 continue;
566
567 /*
568 * The value of 40000 here is from old kernel code. It
569 * really should be changed to some time based value, since
570 * under a hypervisor, there's no guarantee a remote CPU
571 * is even scheduled.
572 */
573 for (i = 0; BT_TEST(xc_priority_set, c) && i < 40000; ++i)
574 SMT_PAUSE();
575
576 /*
577 * Some CPU did not respond to a previous priority request. It's
578 * probably deadlocked with interrupts blocked or some such
579 * problem. We'll just erase the previous request - which was
580 * most likely a kmdb_enter that has already expired - and plow
581 * ahead.
582 */
583 if (BT_TEST(xc_priority_set, c)) {
584 BT_ATOMIC_CLEAR(xc_priority_set, c);
585 if (cpup->cpu_m.xc_work_cnt > 0)
586 xc_decrement(&cpup->cpu_m);
587 }
588 }
589
590 /*
591 * fill in cross call data
592 */
593 xc_priority_data.xc_func = func;
594 xc_priority_data.xc_a1 = arg1;
595 xc_priority_data.xc_a2 = arg2;
596 xc_priority_data.xc_a3 = arg3;
597
598 /*
599 * Post messages to all CPUs involved that are CPU_READY
600 * We'll always IPI, plus bang on the xc_msgbox for i86_mwait()
601 */
602 for (c = 0; c < max_ncpus; ++c) {
603 if (!BT_TEST(set, c))
604 continue;
605 cpup = cpu[c];
606 if (cpup == NULL || !(cpup->cpu_flags & CPU_READY) ||
607 cpup == CPU)
608 continue;
609 (void) xc_increment(&cpup->cpu_m);
610 BT_ATOMIC_SET(xc_priority_set, c);
611 send_dirint(c, XC_HI_PIL);
612 for (i = 0; i < 10; ++i) {
613 (void) atomic_cas_ptr(&cpup->cpu_m.xc_msgbox,
614 cpup->cpu_m.xc_msgbox, cpup->cpu_m.xc_msgbox);
615 }
616 }
617 }
618
619 /*
620 * Do cross call to all other CPUs with absolutely no waiting or handshaking.
621 * This should only be used for extraordinary operations, like panic(), which
622 * need to work, in some fashion, in a not completely functional system.
623 * All other uses that want minimal waiting should use xc_call_nowait().
624 */
625 void
626 xc_priority(
627 xc_arg_t arg1,
628 xc_arg_t arg2,
629 xc_arg_t arg3,
630 ulong_t *set,
631 xc_func_t func)
632 {
633 extern int IGNORE_KERNEL_PREEMPTION;
634 int save_spl = splr(ipltospl(XC_HI_PIL));
635 int save_kernel_preemption = IGNORE_KERNEL_PREEMPTION;
636
637 IGNORE_KERNEL_PREEMPTION = 1;
638 xc_priority_common((xc_func_t)func, arg1, arg2, arg3, set);
639 IGNORE_KERNEL_PREEMPTION = save_kernel_preemption;
640 splx(save_spl);
641 }
642
643 /*
644 * Wrapper for kmdb to capture other CPUs, causing them to enter the debugger.
645 */
646 void
647 kdi_xc_others(int this_cpu, void (*func)(void))
648 {
649 extern int IGNORE_KERNEL_PREEMPTION;
650 int save_kernel_preemption;
651 cpuset_t set;
652
653 if (!xc_initialized)
654 return;
655
656 save_kernel_preemption = IGNORE_KERNEL_PREEMPTION;
657 IGNORE_KERNEL_PREEMPTION = 1;
658 CPUSET_ALL_BUT(set, this_cpu);
659 xc_priority_common((xc_func_t)func, 0, 0, 0, CPUSET2BV(set));
660 IGNORE_KERNEL_PREEMPTION = save_kernel_preemption;
661 }
662
663
664
665 /*
666 * Invoke function on specified processors. Remotes may continue after
667 * service with no waiting. xc_call_nowait() may return immediately too.
668 */
669 void
670 xc_call_nowait(
671 xc_arg_t arg1,
672 xc_arg_t arg2,
673 xc_arg_t arg3,
674 ulong_t *set,
675 xc_func_t func)
676 {
677 xc_common(func, arg1, arg2, arg3, set, XC_MSG_ASYNC);
678 }
679
680 /*
681 * Invoke function on specified processors. Remotes may continue after
682 * service with no waiting. xc_call() returns only after remotes have finished.
683 */
684 void
685 xc_call(
686 xc_arg_t arg1,
687 xc_arg_t arg2,
688 xc_arg_t arg3,
689 ulong_t *set,
690 xc_func_t func)
691 {
692 xc_common(func, arg1, arg2, arg3, set, XC_MSG_CALL);
693 }
694
695 /*
696 * Invoke function on specified processors. Remotes wait until all have
697 * finished. xc_sync() also waits until all remotes have finished.
698 */
699 void
700 xc_sync(
701 xc_arg_t arg1,
702 xc_arg_t arg2,
703 xc_arg_t arg3,
704 ulong_t *set,
705 xc_func_t func)
706 {
707 xc_common(func, arg1, arg2, arg3, set, XC_MSG_SYNC);
708 }