xref: /openbmc/qemu/util/main-loop.c (revision 195801d7)
1 /*
2  * QEMU System Emulator
3  *
4  * Copyright (c) 2003-2008 Fabrice Bellard
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining a copy
7  * of this software and associated documentation files (the "Software"), to deal
8  * in the Software without restriction, including without limitation the rights
9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10  * copies of the Software, and to permit persons to whom the Software is
11  * furnished to do so, subject to the following conditions:
12  *
13  * The above copyright notice and this permission notice shall be included in
14  * all copies or substantial portions of the Software.
15  *
16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22  * THE SOFTWARE.
23  */
24 
25 #include "qemu/osdep.h"
26 #include "qapi/error.h"
27 #include "qemu/cutils.h"
28 #include "qemu/timer.h"
29 #include "sysemu/cpu-timers.h"
30 #include "sysemu/replay.h"
31 #include "qemu/main-loop.h"
32 #include "block/aio.h"
33 #include "block/thread-pool.h"
34 #include "qemu/error-report.h"
35 #include "qemu/queue.h"
36 #include "qom/object.h"
37 
38 #ifndef _WIN32
39 #include <sys/wait.h>
40 #endif
41 
42 #ifndef _WIN32
43 
44 /* If we have signalfd, we mask out the signals we want to handle and then
45  * use signalfd to listen for them.  We rely on whatever the current signal
46  * handler is to dispatch the signals when we receive them.
47  */
48 /*
49  * Disable CFI checks.
50  * We are going to call a signal handler directly. Such handler may or may not
51  * have been defined in our binary, so there's no guarantee that the pointer
52  * used to set the handler is a cfi-valid pointer. Since the handlers are
53  * stored in kernel memory, changing the handler to an attacker-defined
54  * function requires being able to call a sigaction() syscall,
55  * which is not as easy as overwriting a pointer in memory.
56  */
57 QEMU_DISABLE_CFI
sigfd_handler(void * opaque)58 static void sigfd_handler(void *opaque)
59 {
60     int fd = (intptr_t)opaque;
61     struct qemu_signalfd_siginfo info;
62     struct sigaction action;
63     ssize_t len;
64 
65     while (1) {
66         len = RETRY_ON_EINTR(read(fd, &info, sizeof(info)));
67 
68         if (len == -1 && errno == EAGAIN) {
69             break;
70         }
71 
72         if (len != sizeof(info)) {
73             error_report("read from sigfd returned %zd: %s", len,
74                          g_strerror(errno));
75             return;
76         }
77 
78         sigaction(info.ssi_signo, NULL, &action);
79         if ((action.sa_flags & SA_SIGINFO) && action.sa_sigaction) {
80             sigaction_invoke(&action, &info);
81         } else if (action.sa_handler) {
82             action.sa_handler(info.ssi_signo);
83         }
84     }
85 }
86 
qemu_signal_init(Error ** errp)87 static int qemu_signal_init(Error **errp)
88 {
89     int sigfd;
90     sigset_t set;
91 
92     /*
93      * SIG_IPI must be blocked in the main thread and must not be caught
94      * by sigwait() in the signal thread. Otherwise, the cpu thread will
95      * not catch it reliably.
96      */
97     sigemptyset(&set);
98     sigaddset(&set, SIG_IPI);
99     sigaddset(&set, SIGIO);
100     sigaddset(&set, SIGALRM);
101     sigaddset(&set, SIGBUS);
102     /* SIGINT cannot be handled via signalfd, so that ^C can be used
103      * to interrupt QEMU when it is being run under gdb.  SIGHUP and
104      * SIGTERM are also handled asynchronously, even though it is not
105      * strictly necessary, because they use the same handler as SIGINT.
106      */
107     pthread_sigmask(SIG_BLOCK, &set, NULL);
108 
109     sigdelset(&set, SIG_IPI);
110     sigfd = qemu_signalfd(&set);
111     if (sigfd == -1) {
112         error_setg_errno(errp, errno, "failed to create signalfd");
113         return -errno;
114     }
115 
116     g_unix_set_fd_nonblocking(sigfd, true, NULL);
117 
118     qemu_set_fd_handler(sigfd, sigfd_handler, NULL, (void *)(intptr_t)sigfd);
119 
120     return 0;
121 }
122 
123 #else /* _WIN32 */
124 
qemu_signal_init(Error ** errp)125 static int qemu_signal_init(Error **errp)
126 {
127     return 0;
128 }
129 #endif
130 
131 static AioContext *qemu_aio_context;
132 static QEMUBH *qemu_notify_bh;
133 
notify_event_cb(void * opaque)134 static void notify_event_cb(void *opaque)
135 {
136     /* No need to do anything; this bottom half is only used to
137      * kick the kernel out of ppoll/poll/WaitForMultipleObjects.
138      */
139 }
140 
qemu_get_aio_context(void)141 AioContext *qemu_get_aio_context(void)
142 {
143     return qemu_aio_context;
144 }
145 
qemu_notify_event(void)146 void qemu_notify_event(void)
147 {
148     if (!qemu_aio_context) {
149         return;
150     }
151     qemu_bh_schedule(qemu_notify_bh);
152 }
153 
154 static GArray *gpollfds;
155 
qemu_init_main_loop(Error ** errp)156 int qemu_init_main_loop(Error **errp)
157 {
158     int ret;
159     GSource *src;
160 
161     init_clocks(qemu_timer_notify_cb);
162 
163     ret = qemu_signal_init(errp);
164     if (ret) {
165         return ret;
166     }
167 
168     qemu_aio_context = aio_context_new(errp);
169     if (!qemu_aio_context) {
170         return -EMFILE;
171     }
172     qemu_set_current_aio_context(qemu_aio_context);
173     qemu_notify_bh = qemu_bh_new(notify_event_cb, NULL);
174     gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
175     src = aio_get_g_source(qemu_aio_context);
176     g_source_set_name(src, "aio-context");
177     g_source_attach(src, NULL);
178     g_source_unref(src);
179     src = iohandler_get_g_source();
180     g_source_set_name(src, "io-handler");
181     g_source_attach(src, NULL);
182     g_source_unref(src);
183     return 0;
184 }
185 
main_loop_update_params(EventLoopBase * base,Error ** errp)186 static void main_loop_update_params(EventLoopBase *base, Error **errp)
187 {
188     ERRP_GUARD();
189 
190     if (!qemu_aio_context) {
191         error_setg(errp, "qemu aio context not ready");
192         return;
193     }
194 
195     aio_context_set_aio_params(qemu_aio_context, base->aio_max_batch);
196 
197     aio_context_set_thread_pool_params(qemu_aio_context, base->thread_pool_min,
198                                        base->thread_pool_max, errp);
199 }
200 
201 MainLoop *mloop;
202 
main_loop_init(EventLoopBase * base,Error ** errp)203 static void main_loop_init(EventLoopBase *base, Error **errp)
204 {
205     MainLoop *m = MAIN_LOOP(base);
206 
207     if (mloop) {
208         error_setg(errp, "only one main-loop instance allowed");
209         return;
210     }
211 
212     main_loop_update_params(base, errp);
213 
214     mloop = m;
215     return;
216 }
217 
main_loop_can_be_deleted(EventLoopBase * base)218 static bool main_loop_can_be_deleted(EventLoopBase *base)
219 {
220     return false;
221 }
222 
main_loop_class_init(ObjectClass * oc,void * class_data)223 static void main_loop_class_init(ObjectClass *oc, void *class_data)
224 {
225     EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(oc);
226 
227     bc->init = main_loop_init;
228     bc->update_params = main_loop_update_params;
229     bc->can_be_deleted = main_loop_can_be_deleted;
230 }
231 
232 static const TypeInfo main_loop_info = {
233     .name = TYPE_MAIN_LOOP,
234     .parent = TYPE_EVENT_LOOP_BASE,
235     .class_init = main_loop_class_init,
236     .instance_size = sizeof(MainLoop),
237 };
238 
main_loop_register_types(void)239 static void main_loop_register_types(void)
240 {
241     type_register_static(&main_loop_info);
242 }
243 
244 type_init(main_loop_register_types)
245 
246 static int max_priority;
247 
248 #ifndef _WIN32
249 static int glib_pollfds_idx;
250 static int glib_n_poll_fds;
251 
glib_pollfds_fill(int64_t * cur_timeout)252 static void glib_pollfds_fill(int64_t *cur_timeout)
253 {
254     GMainContext *context = g_main_context_default();
255     int timeout = 0;
256     int64_t timeout_ns;
257     int n;
258 
259     g_main_context_prepare(context, &max_priority);
260 
261     glib_pollfds_idx = gpollfds->len;
262     n = glib_n_poll_fds;
263     do {
264         GPollFD *pfds;
265         glib_n_poll_fds = n;
266         g_array_set_size(gpollfds, glib_pollfds_idx + glib_n_poll_fds);
267         pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);
268         n = g_main_context_query(context, max_priority, &timeout, pfds,
269                                  glib_n_poll_fds);
270     } while (n != glib_n_poll_fds);
271 
272     if (timeout < 0) {
273         timeout_ns = -1;
274     } else {
275         timeout_ns = (int64_t)timeout * (int64_t)SCALE_MS;
276     }
277 
278     *cur_timeout = qemu_soonest_timeout(timeout_ns, *cur_timeout);
279 }
280 
glib_pollfds_poll(void)281 static void glib_pollfds_poll(void)
282 {
283     GMainContext *context = g_main_context_default();
284     GPollFD *pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);
285 
286     if (g_main_context_check(context, max_priority, pfds, glib_n_poll_fds)) {
287         g_main_context_dispatch(context);
288     }
289 }
290 
291 #define MAX_MAIN_LOOP_SPIN (1000)
292 
os_host_main_loop_wait(int64_t timeout)293 static int os_host_main_loop_wait(int64_t timeout)
294 {
295     GMainContext *context = g_main_context_default();
296     int ret;
297 
298     g_main_context_acquire(context);
299 
300     glib_pollfds_fill(&timeout);
301 
302     bql_unlock();
303     replay_mutex_unlock();
304 
305     ret = qemu_poll_ns((GPollFD *)gpollfds->data, gpollfds->len, timeout);
306 
307     replay_mutex_lock();
308     bql_lock();
309 
310     glib_pollfds_poll();
311 
312     g_main_context_release(context);
313 
314     return ret;
315 }
316 #else
317 /***********************************************************/
318 /* Polling handling */
319 
320 typedef struct PollingEntry {
321     PollingFunc *func;
322     void *opaque;
323     struct PollingEntry *next;
324 } PollingEntry;
325 
326 static PollingEntry *first_polling_entry;
327 
328 int qemu_add_polling_cb(PollingFunc *func, void *opaque)
329 {
330     PollingEntry **ppe, *pe;
331     pe = g_new0(PollingEntry, 1);
332     pe->func = func;
333     pe->opaque = opaque;
334     for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next);
335     *ppe = pe;
336     return 0;
337 }
338 
339 void qemu_del_polling_cb(PollingFunc *func, void *opaque)
340 {
341     PollingEntry **ppe, *pe;
342     for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next) {
343         pe = *ppe;
344         if (pe->func == func && pe->opaque == opaque) {
345             *ppe = pe->next;
346             g_free(pe);
347             break;
348         }
349     }
350 }
351 
352 /***********************************************************/
353 /* Wait objects support */
354 typedef struct WaitObjects {
355     int num;
356     int revents[MAXIMUM_WAIT_OBJECTS];
357     HANDLE events[MAXIMUM_WAIT_OBJECTS];
358     WaitObjectFunc *func[MAXIMUM_WAIT_OBJECTS];
359     void *opaque[MAXIMUM_WAIT_OBJECTS];
360 } WaitObjects;
361 
362 static WaitObjects wait_objects = {0};
363 
364 int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
365 {
366     int i;
367     WaitObjects *w = &wait_objects;
368 
369     if (w->num >= MAXIMUM_WAIT_OBJECTS) {
370         return -1;
371     }
372 
373     for (i = 0; i < w->num; i++) {
374         /* check if the same handle is added twice */
375         if (w->events[i] == handle) {
376             return -1;
377         }
378     }
379 
380     w->events[w->num] = handle;
381     w->func[w->num] = func;
382     w->opaque[w->num] = opaque;
383     w->revents[w->num] = 0;
384     w->num++;
385     return 0;
386 }
387 
388 void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
389 {
390     int i, found;
391     WaitObjects *w = &wait_objects;
392 
393     found = 0;
394     for (i = 0; i < w->num; i++) {
395         if (w->events[i] == handle) {
396             found = 1;
397         }
398         if (found && i < (MAXIMUM_WAIT_OBJECTS - 1)) {
399             w->events[i] = w->events[i + 1];
400             w->func[i] = w->func[i + 1];
401             w->opaque[i] = w->opaque[i + 1];
402             w->revents[i] = w->revents[i + 1];
403         }
404     }
405     if (found) {
406         w->num--;
407     }
408 }
409 
410 static int pollfds_fill(GArray *pollfds, fd_set *rfds, fd_set *wfds,
411                         fd_set *xfds)
412 {
413     int nfds = -1;
414     int i;
415 
416     for (i = 0; i < pollfds->len; i++) {
417         GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
418         int fd = pfd->fd;
419         int events = pfd->events;
420         if (events & G_IO_IN) {
421             FD_SET(fd, rfds);
422             nfds = MAX(nfds, fd);
423         }
424         if (events & G_IO_OUT) {
425             FD_SET(fd, wfds);
426             nfds = MAX(nfds, fd);
427         }
428         if (events & G_IO_PRI) {
429             FD_SET(fd, xfds);
430             nfds = MAX(nfds, fd);
431         }
432     }
433     return nfds;
434 }
435 
436 static void pollfds_poll(GArray *pollfds, int nfds, fd_set *rfds,
437                          fd_set *wfds, fd_set *xfds)
438 {
439     int i;
440 
441     for (i = 0; i < pollfds->len; i++) {
442         GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
443         int fd = pfd->fd;
444         int revents = 0;
445 
446         if (FD_ISSET(fd, rfds)) {
447             revents |= G_IO_IN;
448         }
449         if (FD_ISSET(fd, wfds)) {
450             revents |= G_IO_OUT;
451         }
452         if (FD_ISSET(fd, xfds)) {
453             revents |= G_IO_PRI;
454         }
455         pfd->revents = revents & pfd->events;
456     }
457 }
458 
459 static int os_host_main_loop_wait(int64_t timeout)
460 {
461     GMainContext *context = g_main_context_default();
462     GPollFD poll_fds[1024 * 2]; /* this is probably overkill */
463     int select_ret = 0;
464     int g_poll_ret, ret, i, n_poll_fds;
465     PollingEntry *pe;
466     WaitObjects *w = &wait_objects;
467     gint poll_timeout;
468     int64_t poll_timeout_ns;
469     static struct timeval tv0;
470     fd_set rfds, wfds, xfds;
471     int nfds;
472 
473     g_main_context_acquire(context);
474 
475     /* XXX: need to suppress polling by better using win32 events */
476     ret = 0;
477     for (pe = first_polling_entry; pe != NULL; pe = pe->next) {
478         ret |= pe->func(pe->opaque);
479     }
480     if (ret != 0) {
481         g_main_context_release(context);
482         return ret;
483     }
484 
485     FD_ZERO(&rfds);
486     FD_ZERO(&wfds);
487     FD_ZERO(&xfds);
488     nfds = pollfds_fill(gpollfds, &rfds, &wfds, &xfds);
489     if (nfds >= 0) {
490         select_ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv0);
491         if (select_ret != 0) {
492             timeout = 0;
493         }
494         if (select_ret > 0) {
495             pollfds_poll(gpollfds, nfds, &rfds, &wfds, &xfds);
496         }
497     }
498 
499     g_main_context_prepare(context, &max_priority);
500     n_poll_fds = g_main_context_query(context, max_priority, &poll_timeout,
501                                       poll_fds, ARRAY_SIZE(poll_fds));
502     g_assert(n_poll_fds + w->num <= ARRAY_SIZE(poll_fds));
503 
504     for (i = 0; i < w->num; i++) {
505         poll_fds[n_poll_fds + i].fd = (DWORD_PTR)w->events[i];
506         poll_fds[n_poll_fds + i].events = G_IO_IN;
507     }
508 
509     if (poll_timeout < 0) {
510         poll_timeout_ns = -1;
511     } else {
512         poll_timeout_ns = (int64_t)poll_timeout * (int64_t)SCALE_MS;
513     }
514 
515     poll_timeout_ns = qemu_soonest_timeout(poll_timeout_ns, timeout);
516 
517     bql_unlock();
518 
519     replay_mutex_unlock();
520 
521     g_poll_ret = qemu_poll_ns(poll_fds, n_poll_fds + w->num, poll_timeout_ns);
522 
523     replay_mutex_lock();
524 
525     bql_lock();
526     if (g_poll_ret > 0) {
527         for (i = 0; i < w->num; i++) {
528             w->revents[i] = poll_fds[n_poll_fds + i].revents;
529         }
530         for (i = 0; i < w->num; i++) {
531             if (w->revents[i] && w->func[i]) {
532                 w->func[i](w->opaque[i]);
533             }
534         }
535     }
536 
537     if (g_main_context_check(context, max_priority, poll_fds, n_poll_fds)) {
538         g_main_context_dispatch(context);
539     }
540 
541     g_main_context_release(context);
542 
543     return select_ret || g_poll_ret;
544 }
545 #endif
546 
547 static NotifierList main_loop_poll_notifiers =
548     NOTIFIER_LIST_INITIALIZER(main_loop_poll_notifiers);
549 
main_loop_poll_add_notifier(Notifier * notify)550 void main_loop_poll_add_notifier(Notifier *notify)
551 {
552     notifier_list_add(&main_loop_poll_notifiers, notify);
553 }
554 
main_loop_poll_remove_notifier(Notifier * notify)555 void main_loop_poll_remove_notifier(Notifier *notify)
556 {
557     notifier_remove(notify);
558 }
559 
main_loop_wait(int nonblocking)560 void main_loop_wait(int nonblocking)
561 {
562     MainLoopPoll mlpoll = {
563         .state = MAIN_LOOP_POLL_FILL,
564         .timeout = UINT32_MAX,
565         .pollfds = gpollfds,
566     };
567     int ret;
568     int64_t timeout_ns;
569 
570     if (nonblocking) {
571         mlpoll.timeout = 0;
572     }
573 
574     /* poll any events */
575     g_array_set_size(gpollfds, 0); /* reset for new iteration */
576     /* XXX: separate device handlers from system ones */
577     notifier_list_notify(&main_loop_poll_notifiers, &mlpoll);
578 
579     if (mlpoll.timeout == UINT32_MAX) {
580         timeout_ns = -1;
581     } else {
582         timeout_ns = (uint64_t)mlpoll.timeout * (int64_t)(SCALE_MS);
583     }
584 
585     timeout_ns = qemu_soonest_timeout(timeout_ns,
586                                       timerlistgroup_deadline_ns(
587                                           &main_loop_tlg));
588 
589     ret = os_host_main_loop_wait(timeout_ns);
590     mlpoll.state = ret < 0 ? MAIN_LOOP_POLL_ERR : MAIN_LOOP_POLL_OK;
591     notifier_list_notify(&main_loop_poll_notifiers, &mlpoll);
592 
593     if (icount_enabled()) {
594         /*
595          * CPU thread can infinitely wait for event after
596          * missing the warp
597          */
598         icount_start_warp_timer();
599     }
600     qemu_clock_run_all_timers();
601 }
602 
603 /* Functions to operate on the main QEMU AioContext.  */
604 
qemu_bh_new_full(QEMUBHFunc * cb,void * opaque,const char * name,MemReentrancyGuard * reentrancy_guard)605 QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name,
606                          MemReentrancyGuard *reentrancy_guard)
607 {
608     return aio_bh_new_full(qemu_aio_context, cb, opaque, name,
609                            reentrancy_guard);
610 }
611 
612 /*
613  * Functions to operate on the I/O handler AioContext.
614  * This context runs on top of main loop. We can't reuse qemu_aio_context
615  * because iohandlers mustn't be polled by aio_poll(qemu_aio_context).
616  */
617 static AioContext *iohandler_ctx;
618 
iohandler_init(void)619 static void iohandler_init(void)
620 {
621     if (!iohandler_ctx) {
622         iohandler_ctx = aio_context_new(&error_abort);
623     }
624 }
625 
iohandler_get_aio_context(void)626 AioContext *iohandler_get_aio_context(void)
627 {
628     iohandler_init();
629     return iohandler_ctx;
630 }
631 
iohandler_get_g_source(void)632 GSource *iohandler_get_g_source(void)
633 {
634     iohandler_init();
635     return aio_get_g_source(iohandler_ctx);
636 }
637 
qemu_set_fd_handler(int fd,IOHandler * fd_read,IOHandler * fd_write,void * opaque)638 void qemu_set_fd_handler(int fd,
639                          IOHandler *fd_read,
640                          IOHandler *fd_write,
641                          void *opaque)
642 {
643     iohandler_init();
644     aio_set_fd_handler(iohandler_ctx, fd, fd_read, fd_write, NULL, NULL,
645                        opaque);
646 }
647 
event_notifier_set_handler(EventNotifier * e,EventNotifierHandler * handler)648 void event_notifier_set_handler(EventNotifier *e,
649                                 EventNotifierHandler *handler)
650 {
651     iohandler_init();
652     aio_set_event_notifier(iohandler_ctx, e, handler, NULL, NULL);
653 }
654