util/main-loop.c - qemu - Git at Google

 /*
  * QEMU System Emulator
  *
  * Copyright (c) 2003-2008 Fabrice Bellard
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */

 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "qemu/cutils.h"
 #include "qemu/timer.h"
 #include "sysemu/cpu-timers.h"
 #include "sysemu/replay.h"
 #include "qemu/main-loop.h"
 #include "block/aio.h"
 #include "block/thread-pool.h"
 #include "qemu/error-report.h"
 #include "qemu/queue.h"
 #include "qom/object.h"

 #ifndef _WIN32
 #include <sys/wait.h>
 #endif

 #ifndef _WIN32

 /* If we have signalfd, we mask out the signals we want to handle and then
  * use signalfd to listen for them.  We rely on whatever the current signal
  * handler is to dispatch the signals when we receive them.
  */
 /*
  * Disable CFI checks.
  * We are going to call a signal handler directly. Such handler may or may not
  * have been defined in our binary, so there's no guarantee that the pointer
  * used to set the handler is a cfi-valid pointer. Since the handlers are
  * stored in kernel memory, changing the handler to an attacker-defined
  * function requires being able to call a sigaction() syscall,
  * which is not as easy as overwriting a pointer in memory.
  */
 QEMU_DISABLE_CFI
 static void sigfd_handler(void *opaque)
 {
     int fd = (intptr_t)opaque;
     struct qemu_signalfd_siginfo info;
     struct sigaction action;
     ssize_t len;

     while (1) {
         len = RETRY_ON_EINTR(read(fd, &info, sizeof(info)));

         if (len == -1 && errno == EAGAIN) {
             break;
         }

         if (len != sizeof(info)) {
             error_report("read from sigfd returned %zd: %s", len,
                          g_strerror(errno));
             return;
         }

         sigaction(info.ssi_signo, NULL, &action);
         if ((action.sa_flags & SA_SIGINFO) && action.sa_sigaction) {
             sigaction_invoke(&action, &info);
         } else if (action.sa_handler) {
             action.sa_handler(info.ssi_signo);
         }
     }
 }

 static int qemu_signal_init(Error **errp)
 {
     int sigfd;
     sigset_t set;

     /*
      * SIG_IPI must be blocked in the main thread and must not be caught
      * by sigwait() in the signal thread. Otherwise, the cpu thread will
      * not catch it reliably.
      */
     sigemptyset(&set);
     sigaddset(&set, SIG_IPI);
     sigaddset(&set, SIGIO);
     sigaddset(&set, SIGALRM);
     sigaddset(&set, SIGBUS);
     /* SIGINT cannot be handled via signalfd, so that ^C can be used
      * to interrupt QEMU when it is being run under gdb.  SIGHUP and
      * SIGTERM are also handled asynchronously, even though it is not
      * strictly necessary, because they use the same handler as SIGINT.
      */
     pthread_sigmask(SIG_BLOCK, &set, NULL);

     sigdelset(&set, SIG_IPI);
     sigfd = qemu_signalfd(&set);
     if (sigfd == -1) {
         error_setg_errno(errp, errno, "failed to create signalfd");
         return -errno;
     }

     g_unix_set_fd_nonblocking(sigfd, true, NULL);

     qemu_set_fd_handler(sigfd, sigfd_handler, NULL, (void *)(intptr_t)sigfd);

     return 0;
 }

 #else /* _WIN32 */

 static int qemu_signal_init(Error **errp)
 {
     return 0;
 }
 #endif

 static AioContext *qemu_aio_context;
 static QEMUBH *qemu_notify_bh;

 static void notify_event_cb(void *opaque)
 {
     /* No need to do anything; this bottom half is only used to
      * kick the kernel out of ppoll/poll/WaitForMultipleObjects.
      */
 }

 AioContext *qemu_get_aio_context(void)
 {
     return qemu_aio_context;
 }

 void qemu_notify_event(void)
 {
     if (!qemu_aio_context) {
         return;
     }
     qemu_bh_schedule(qemu_notify_bh);
 }

 static GArray *gpollfds;

 int qemu_init_main_loop(Error **errp)
 {
     int ret;
     GSource *src;

     init_clocks(qemu_timer_notify_cb);

     ret = qemu_signal_init(errp);
     if (ret) {
         return ret;
     }

     qemu_aio_context = aio_context_new(errp);
     if (!qemu_aio_context) {
         return -EMFILE;
     }
     qemu_set_current_aio_context(qemu_aio_context);
     qemu_notify_bh = qemu_bh_new(notify_event_cb, NULL);
     gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
     src = aio_get_g_source(qemu_aio_context);
     g_source_set_name(src, "aio-context");
     g_source_attach(src, NULL);
     g_source_unref(src);
     src = iohandler_get_g_source();
     g_source_set_name(src, "io-handler");
     g_source_attach(src, NULL);
     g_source_unref(src);
     return 0;
 }

 static void main_loop_update_params(EventLoopBase *base, Error **errp)
 {
     ERRP_GUARD();

     if (!qemu_aio_context) {
         error_setg(errp, "qemu aio context not ready");
         return;
     }

     aio_context_set_aio_params(qemu_aio_context, base->aio_max_batch);

     aio_context_set_thread_pool_params(qemu_aio_context, base->thread_pool_min,
                                        base->thread_pool_max, errp);
 }

 MainLoop *mloop;

 static void main_loop_init(EventLoopBase *base, Error **errp)
 {
     MainLoop *m = MAIN_LOOP(base);

     if (mloop) {
         error_setg(errp, "only one main-loop instance allowed");
         return;
     }

     main_loop_update_params(base, errp);

     mloop = m;
     return;
 }

 static bool main_loop_can_be_deleted(EventLoopBase *base)
 {
     return false;
 }

 static void main_loop_class_init(ObjectClass *oc, void *class_data)
 {
     EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(oc);

     bc->init = main_loop_init;
     bc->update_params = main_loop_update_params;
     bc->can_be_deleted = main_loop_can_be_deleted;
 }

 static const TypeInfo main_loop_info = {
     .name = TYPE_MAIN_LOOP,
     .parent = TYPE_EVENT_LOOP_BASE,
     .class_init = main_loop_class_init,
     .instance_size = sizeof(MainLoop),
 };

 static void main_loop_register_types(void)
 {
     type_register_static(&main_loop_info);
 }

 type_init(main_loop_register_types)

 static int max_priority;

 #ifndef _WIN32
 static int glib_pollfds_idx;
 static int glib_n_poll_fds;

 static void glib_pollfds_fill(int64_t *cur_timeout)
 {
     GMainContext *context = g_main_context_default();
     int timeout = 0;
     int64_t timeout_ns;
     int n;

     g_main_context_prepare(context, &max_priority);

     glib_pollfds_idx = gpollfds->len;
     n = glib_n_poll_fds;
     do {
         GPollFD *pfds;
         glib_n_poll_fds = n;
         g_array_set_size(gpollfds, glib_pollfds_idx + glib_n_poll_fds);
         pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);
         n = g_main_context_query(context, max_priority, &timeout, pfds,
                                  glib_n_poll_fds);
     } while (n != glib_n_poll_fds);

     if (timeout < 0) {
         timeout_ns = -1;
     } else {
         timeout_ns = (int64_t)timeout * (int64_t)SCALE_MS;
     }

     *cur_timeout = qemu_soonest_timeout(timeout_ns, *cur_timeout);
 }

 static void glib_pollfds_poll(void)
 {
     GMainContext *context = g_main_context_default();
     GPollFD *pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);

     if (g_main_context_check(context, max_priority, pfds, glib_n_poll_fds)) {
         g_main_context_dispatch(context);
     }
 }

 #define MAX_MAIN_LOOP_SPIN (1000)

 static int os_host_main_loop_wait(int64_t timeout)
 {
     GMainContext *context = g_main_context_default();
     int ret;

     g_main_context_acquire(context);

     glib_pollfds_fill(&timeout);

     bql_unlock();
     replay_mutex_unlock();

     ret = qemu_poll_ns((GPollFD *)gpollfds->data, gpollfds->len, timeout);

     replay_mutex_lock();
     bql_lock();

     glib_pollfds_poll();

     g_main_context_release(context);

     return ret;
 }
 #else
 /***********************************************************/
 /* Polling handling */

 typedef struct PollingEntry {
     PollingFunc *func;
     void *opaque;
     struct PollingEntry *next;
 } PollingEntry;

 static PollingEntry *first_polling_entry;

 int qemu_add_polling_cb(PollingFunc *func, void *opaque)
 {
     PollingEntry **ppe, *pe;
     pe = g_new0(PollingEntry, 1);
     pe->func = func;
     pe->opaque = opaque;
     for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next);
     *ppe = pe;
     return 0;
 }

 void qemu_del_polling_cb(PollingFunc *func, void *opaque)
 {
     PollingEntry **ppe, *pe;
     for(ppe = &first_polling_entry; *ppe != NULL; ppe = &(*ppe)->next) {
         pe = *ppe;
         if (pe->func == func && pe->opaque == opaque) {
             *ppe = pe->next;
             g_free(pe);
             break;
         }
     }
 }

 /***********************************************************/
 /* Wait objects support */
 typedef struct WaitObjects {
     int num;
     int revents[MAXIMUM_WAIT_OBJECTS];
     HANDLE events[MAXIMUM_WAIT_OBJECTS];
     WaitObjectFunc *func[MAXIMUM_WAIT_OBJECTS];
     void *opaque[MAXIMUM_WAIT_OBJECTS];
 } WaitObjects;

 static WaitObjects wait_objects = {0};

 int qemu_add_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
 {
     int i;
     WaitObjects *w = &wait_objects;

     if (w->num >= MAXIMUM_WAIT_OBJECTS) {
         return -1;
     }

     for (i = 0; i < w->num; i++) {
         /* check if the same handle is added twice */
         if (w->events[i] == handle) {
             return -1;
         }
     }

     w->events[w->num] = handle;
     w->func[w->num] = func;
     w->opaque[w->num] = opaque;
     w->revents[w->num] = 0;
     w->num++;
     return 0;
 }

 void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
 {
     int i, found;
     WaitObjects *w = &wait_objects;

     found = 0;
     for (i = 0; i < w->num; i++) {
         if (w->events[i] == handle) {
             found = 1;
         }
         if (found && i < (MAXIMUM_WAIT_OBJECTS - 1)) {
             w->events[i] = w->events[i + 1];
             w->func[i] = w->func[i + 1];
             w->opaque[i] = w->opaque[i + 1];
             w->revents[i] = w->revents[i + 1];
         }
     }
     if (found) {
         w->num--;
     }
 }

 static int pollfds_fill(GArray *pollfds, fd_set *rfds, fd_set *wfds,
                         fd_set *xfds)
 {
     int nfds = -1;
     int i;

     for (i = 0; i < pollfds->len; i++) {
         GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
         int fd = pfd->fd;
         int events = pfd->events;
         if (events & G_IO_IN) {
             FD_SET(fd, rfds);
             nfds = MAX(nfds, fd);
         }
         if (events & G_IO_OUT) {
             FD_SET(fd, wfds);
             nfds = MAX(nfds, fd);
         }
         if (events & G_IO_PRI) {
             FD_SET(fd, xfds);
             nfds = MAX(nfds, fd);
         }
     }
     return nfds;
 }

 static void pollfds_poll(GArray *pollfds, int nfds, fd_set *rfds,
                          fd_set *wfds, fd_set *xfds)
 {
     int i;

     for (i = 0; i < pollfds->len; i++) {
         GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
         int fd = pfd->fd;
         int revents = 0;

         if (FD_ISSET(fd, rfds)) {
             revents |= G_IO_IN;
         }
         if (FD_ISSET(fd, wfds)) {
             revents |= G_IO_OUT;
         }
         if (FD_ISSET(fd, xfds)) {
             revents |= G_IO_PRI;
         }
         pfd->revents = revents & pfd->events;
     }
 }

 static int os_host_main_loop_wait(int64_t timeout)
 {
     GMainContext *context = g_main_context_default();
     GPollFD poll_fds[1024 * 2]; /* this is probably overkill */
     int select_ret = 0;
     int g_poll_ret, ret, i, n_poll_fds;
     PollingEntry *pe;
     WaitObjects *w = &wait_objects;
     gint poll_timeout;
     int64_t poll_timeout_ns;
     static struct timeval tv0;
     fd_set rfds, wfds, xfds;
     int nfds;

     g_main_context_acquire(context);

     /* XXX: need to suppress polling by better using win32 events */
     ret = 0;
     for (pe = first_polling_entry; pe != NULL; pe = pe->next) {
         ret |= pe->func(pe->opaque);
     }
     if (ret != 0) {
         g_main_context_release(context);
         return ret;
     }

     FD_ZERO(&rfds);
     FD_ZERO(&wfds);
     FD_ZERO(&xfds);
     nfds = pollfds_fill(gpollfds, &rfds, &wfds, &xfds);
     if (nfds >= 0) {
         select_ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv0);
         if (select_ret != 0) {
             timeout = 0;
         }
         if (select_ret > 0) {
             pollfds_poll(gpollfds, nfds, &rfds, &wfds, &xfds);
         }
     }

     g_main_context_prepare(context, &max_priority);
     n_poll_fds = g_main_context_query(context, max_priority, &poll_timeout,
                                       poll_fds, ARRAY_SIZE(poll_fds));
     g_assert(n_poll_fds + w->num <= ARRAY_SIZE(poll_fds));

     for (i = 0; i < w->num; i++) {
         poll_fds[n_poll_fds + i].fd = (DWORD_PTR)w->events[i];
         poll_fds[n_poll_fds + i].events = G_IO_IN;
     }

     if (poll_timeout < 0) {
         poll_timeout_ns = -1;
     } else {
         poll_timeout_ns = (int64_t)poll_timeout * (int64_t)SCALE_MS;
     }

     poll_timeout_ns = qemu_soonest_timeout(poll_timeout_ns, timeout);

     bql_unlock();

     replay_mutex_unlock();

     g_poll_ret = qemu_poll_ns(poll_fds, n_poll_fds + w->num, poll_timeout_ns);

     replay_mutex_lock();

     bql_lock();
     if (g_poll_ret > 0) {
         for (i = 0; i < w->num; i++) {
             w->revents[i] = poll_fds[n_poll_fds + i].revents;
         }
         for (i = 0; i < w->num; i++) {
             if (w->revents[i] && w->func[i]) {
                 w->func[i](w->opaque[i]);
             }
         }
     }

     if (g_main_context_check(context, max_priority, poll_fds, n_poll_fds)) {
         g_main_context_dispatch(context);
     }

     g_main_context_release(context);

     return select_ret || g_poll_ret;
 }
 #endif

 static NotifierList main_loop_poll_notifiers =
     NOTIFIER_LIST_INITIALIZER(main_loop_poll_notifiers);

 void main_loop_poll_add_notifier(Notifier *notify)
 {
     notifier_list_add(&main_loop_poll_notifiers, notify);
 }

 void main_loop_poll_remove_notifier(Notifier *notify)
 {
     notifier_remove(notify);
 }

 void main_loop_wait(int nonblocking)
 {
     MainLoopPoll mlpoll = {
         .state = MAIN_LOOP_POLL_FILL,
         .timeout = UINT32_MAX,
         .pollfds = gpollfds,
     };
     int ret;
     int64_t timeout_ns;

     if (nonblocking) {
         mlpoll.timeout = 0;
     }

     /* poll any events */
     g_array_set_size(gpollfds, 0); /* reset for new iteration */
     /* XXX: separate device handlers from system ones */
     notifier_list_notify(&main_loop_poll_notifiers, &mlpoll);

     if (mlpoll.timeout == UINT32_MAX) {
         timeout_ns = -1;
     } else {
         timeout_ns = (uint64_t)mlpoll.timeout * (int64_t)(SCALE_MS);
     }

     timeout_ns = qemu_soonest_timeout(timeout_ns,
                                       timerlistgroup_deadline_ns(
                                           &main_loop_tlg));

     ret = os_host_main_loop_wait(timeout_ns);
     mlpoll.state = ret < 0 ? MAIN_LOOP_POLL_ERR : MAIN_LOOP_POLL_OK;
     notifier_list_notify(&main_loop_poll_notifiers, &mlpoll);

     if (icount_enabled()) {
         /*
          * CPU thread can infinitely wait for event after
          * missing the warp
          */
         icount_start_warp_timer();
     }
     qemu_clock_run_all_timers();
 }

 /* Functions to operate on the main QEMU AioContext.  */

 QEMUBH *qemu_bh_new_full(QEMUBHFunc *cb, void *opaque, const char *name,
                          MemReentrancyGuard *reentrancy_guard)
 {
     return aio_bh_new_full(qemu_aio_context, cb, opaque, name,
                            reentrancy_guard);
 }

 /*
  * Functions to operate on the I/O handler AioContext.
  * This context runs on top of main loop. We can't reuse qemu_aio_context
  * because iohandlers mustn't be polled by aio_poll(qemu_aio_context).
  */
 static AioContext *iohandler_ctx;

 static void iohandler_init(void)
 {
     if (!iohandler_ctx) {
         iohandler_ctx = aio_context_new(&error_abort);
     }
 }

 AioContext *iohandler_get_aio_context(void)
 {
     iohandler_init();
     return iohandler_ctx;
 }

 GSource *iohandler_get_g_source(void)
 {
     iohandler_init();
     return aio_get_g_source(iohandler_ctx);
 }

 void qemu_set_fd_handler(int fd,
                          IOHandler *fd_read,
                          IOHandler *fd_write,
                          void *opaque)
 {
     iohandler_init();
     aio_set_fd_handler(iohandler_ctx, fd, fd_read, fd_write, NULL, NULL,
                        opaque);
 }

 void event_notifier_set_handler(EventNotifier *e,
                                 EventNotifierHandler *handler)
 {
     iohandler_init();
     aio_set_event_notifier(iohandler_ctx, e, handler, NULL, NULL);
 }
	/*
	* QEMU System Emulator
	*
	* Copyright (c) 2003-2008 Fabrice Bellard
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/

	#include "qemu/osdep.h"
	#include "qapi/error.h"
	#include "qemu/cutils.h"
	#include "qemu/timer.h"
	#include "sysemu/cpu-timers.h"
	#include "sysemu/replay.h"
	#include "qemu/main-loop.h"
	#include "block/aio.h"
	#include "block/thread-pool.h"
	#include "qemu/error-report.h"
	#include "qemu/queue.h"
	#include "qom/object.h"

	#ifndef _WIN32
	#include <sys/wait.h>
	#endif

	#ifndef _WIN32

	/* If we have signalfd, we mask out the signals we want to handle and then
	* use signalfd to listen for them. We rely on whatever the current signal
	* handler is to dispatch the signals when we receive them.
	*/
	/*
	* Disable CFI checks.
	* We are going to call a signal handler directly. Such handler may or may not
	* have been defined in our binary, so there's no guarantee that the pointer
	* used to set the handler is a cfi-valid pointer. Since the handlers are
	* stored in kernel memory, changing the handler to an attacker-defined
	* function requires being able to call a sigaction() syscall,
	* which is not as easy as overwriting a pointer in memory.
	*/
	QEMU_DISABLE_CFI
	static void sigfd_handler(void *opaque)
	{
	int fd = (intptr_t)opaque;
	struct qemu_signalfd_siginfo info;
	struct sigaction action;
	ssize_t len;

	while (1) {
	len = RETRY_ON_EINTR(read(fd, &info, sizeof(info)));

	if (len == -1 && errno == EAGAIN) {
	break;
	}

	if (len != sizeof(info)) {
	error_report("read from sigfd returned %zd: %s", len,
	g_strerror(errno));
	return;
	}

	sigaction(info.ssi_signo, NULL, &action);
	if ((action.sa_flags & SA_SIGINFO) && action.sa_sigaction) {
	sigaction_invoke(&action, &info);
	} else if (action.sa_handler) {
	action.sa_handler(info.ssi_signo);
	}
	}
	}

	static int qemu_signal_init(Error **errp)
	{
	int sigfd;
	sigset_t set;

	/*
	* SIG_IPI must be blocked in the main thread and must not be caught
	* by sigwait() in the signal thread. Otherwise, the cpu thread will
	* not catch it reliably.
	*/
	sigemptyset(&set);
	sigaddset(&set, SIG_IPI);
	sigaddset(&set, SIGIO);
	sigaddset(&set, SIGALRM);
	sigaddset(&set, SIGBUS);
	/* SIGINT cannot be handled via signalfd, so that ^C can be used
	* to interrupt QEMU when it is being run under gdb. SIGHUP and
	* SIGTERM are also handled asynchronously, even though it is not
	* strictly necessary, because they use the same handler as SIGINT.
	*/
	pthread_sigmask(SIG_BLOCK, &set, NULL);

	sigdelset(&set, SIG_IPI);
	sigfd = qemu_signalfd(&set);
	if (sigfd == -1) {
	error_setg_errno(errp, errno, "failed to create signalfd");
	return -errno;
	}

	g_unix_set_fd_nonblocking(sigfd, true, NULL);

	qemu_set_fd_handler(sigfd, sigfd_handler, NULL, (void *)(intptr_t)sigfd);

	return 0;
	}

	#else /* _WIN32 */

	static int qemu_signal_init(Error **errp)
	{
	return 0;
	}
	#endif

	static AioContext *qemu_aio_context;
	static QEMUBH *qemu_notify_bh;

	static void notify_event_cb(void *opaque)
	{
	/* No need to do anything; this bottom half is only used to
	* kick the kernel out of ppoll/poll/WaitForMultipleObjects.
	*/
	}

	AioContext *qemu_get_aio_context(void)
	{
	return qemu_aio_context;
	}

	void qemu_notify_event(void)
	{
	if (!qemu_aio_context) {
	return;
	}
	qemu_bh_schedule(qemu_notify_bh);
	}

	static GArray *gpollfds;

	int qemu_init_main_loop(Error **errp)
	{
	int ret;
	GSource *src;

	init_clocks(qemu_timer_notify_cb);

	ret = qemu_signal_init(errp);
	if (ret) {
	return ret;
	}

	qemu_aio_context = aio_context_new(errp);
	if (!qemu_aio_context) {
	return -EMFILE;
	}
	qemu_set_current_aio_context(qemu_aio_context);
	qemu_notify_bh = qemu_bh_new(notify_event_cb, NULL);
	gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
	src = aio_get_g_source(qemu_aio_context);
	g_source_set_name(src, "aio-context");
	g_source_attach(src, NULL);
	g_source_unref(src);
	src = iohandler_get_g_source();
	g_source_set_name(src, "io-handler");
	g_source_attach(src, NULL);
	g_source_unref(src);
	return 0;
	}

	static void main_loop_update_params(EventLoopBase base, Error *errp)
	{
	ERRP_GUARD();

	if (!qemu_aio_context) {
	error_setg(errp, "qemu aio context not ready");
	return;
	}

	aio_context_set_aio_params(qemu_aio_context, base->aio_max_batch);

	aio_context_set_thread_pool_params(qemu_aio_context, base->thread_pool_min,
	base->thread_pool_max, errp);
	}

	MainLoop *mloop;

	static void main_loop_init(EventLoopBase base, Error *errp)
	{
	MainLoop *m = MAIN_LOOP(base);

	if (mloop) {
	error_setg(errp, "only one main-loop instance allowed");
	return;
	}

	main_loop_update_params(base, errp);

	mloop = m;
	return;
	}

	static bool main_loop_can_be_deleted(EventLoopBase *base)
	{
	return false;
	}

	static void main_loop_class_init(ObjectClass oc, void class_data)
	{
	EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(oc);

	bc->init = main_loop_init;
	bc->update_params = main_loop_update_params;
	bc->can_be_deleted = main_loop_can_be_deleted;
	}

	static const TypeInfo main_loop_info = {
	.name = TYPE_MAIN_LOOP,
	.parent = TYPE_EVENT_LOOP_BASE,
	.class_init = main_loop_class_init,
	.instance_size = sizeof(MainLoop),
	};

	static void main_loop_register_types(void)
	{
	type_register_static(&main_loop_info);
	}

	type_init(main_loop_register_types)

	static int max_priority;

	#ifndef _WIN32
	static int glib_pollfds_idx;
	static int glib_n_poll_fds;

	static void glib_pollfds_fill(int64_t *cur_timeout)
	{
	GMainContext *context = g_main_context_default();
	int timeout = 0;
	int64_t timeout_ns;
	int n;

	g_main_context_prepare(context, &max_priority);

	glib_pollfds_idx = gpollfds->len;
	n = glib_n_poll_fds;
	do {
	GPollFD *pfds;
	glib_n_poll_fds = n;
	g_array_set_size(gpollfds, glib_pollfds_idx + glib_n_poll_fds);
	pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);
	n = g_main_context_query(context, max_priority, &timeout, pfds,
	glib_n_poll_fds);
	} while (n != glib_n_poll_fds);

	if (timeout < 0) {
	timeout_ns = -1;
	} else {
	timeout_ns = (int64_t)timeout * (int64_t)SCALE_MS;
	}

	cur_timeout = qemu_soonest_timeout(timeout_ns, cur_timeout);
	}

	static void glib_pollfds_poll(void)
	{
	GMainContext *context = g_main_context_default();
	GPollFD *pfds = &g_array_index(gpollfds, GPollFD, glib_pollfds_idx);

	if (g_main_context_check(context, max_priority, pfds, glib_n_poll_fds)) {
	g_main_context_dispatch(context);
	}
	}

	#define MAX_MAIN_LOOP_SPIN (1000)

	static int os_host_main_loop_wait(int64_t timeout)
	{
	GMainContext *context = g_main_context_default();
	int ret;

	g_main_context_acquire(context);

	glib_pollfds_fill(&timeout);

	bql_unlock();
	replay_mutex_unlock();

	ret = qemu_poll_ns((GPollFD *)gpollfds->data, gpollfds->len, timeout);

	replay_mutex_lock();
	bql_lock();

	glib_pollfds_poll();

	g_main_context_release(context);

	return ret;
	}
	#else
	/***********************************************************/
	/* Polling handling */

	typedef struct PollingEntry {
	PollingFunc *func;
	void *opaque;
	struct PollingEntry *next;
	} PollingEntry;

	static PollingEntry *first_polling_entry;

	int qemu_add_polling_cb(PollingFunc func, void opaque)
	{
	PollingEntry *ppe, pe;
	pe = g_new0(PollingEntry, 1);
	pe->func = func;
	pe->opaque = opaque;
	for(ppe = &first_polling_entry; ppe != NULL; ppe = &(ppe)->next);
	*ppe = pe;
	return 0;
	}

	void qemu_del_polling_cb(PollingFunc func, void opaque)
	{
	PollingEntry *ppe, pe;
	for(ppe = &first_polling_entry; ppe != NULL; ppe = &(ppe)->next) {
	pe = *ppe;
	if (pe->func == func && pe->opaque == opaque) {
	*ppe = pe->next;
	g_free(pe);
	break;
	}
	}
	}

	/***********************************************************/
	/* Wait objects support */
	typedef struct WaitObjects {
	int num;
	int revents[MAXIMUM_WAIT_OBJECTS];
	HANDLE events[MAXIMUM_WAIT_OBJECTS];
	WaitObjectFunc *func[MAXIMUM_WAIT_OBJECTS];
	void *opaque[MAXIMUM_WAIT_OBJECTS];
	} WaitObjects;

	static WaitObjects wait_objects = {0};

	int qemu_add_wait_object(HANDLE handle, WaitObjectFunc func, void opaque)
	{
	int i;
	WaitObjects *w = &wait_objects;

	if (w->num >= MAXIMUM_WAIT_OBJECTS) {
	return -1;
	}

	for (i = 0; i < w->num; i++) {
	/* check if the same handle is added twice */
	if (w->events[i] == handle) {
	return -1;
	}
	}

	w->events[w->num] = handle;
	w->func[w->num] = func;
	w->opaque[w->num] = opaque;
	w->revents[w->num] = 0;
	w->num++;
	return 0;
	}

	void qemu_del_wait_object(HANDLE handle, WaitObjectFunc func, void opaque)
	{
	int i, found;
	WaitObjects *w = &wait_objects;

	found = 0;
	for (i = 0; i < w->num; i++) {
	if (w->events[i] == handle) {
	found = 1;
	}
	if (found && i < (MAXIMUM_WAIT_OBJECTS - 1)) {
	w->events[i] = w->events[i + 1];
	w->func[i] = w->func[i + 1];
	w->opaque[i] = w->opaque[i + 1];
	w->revents[i] = w->revents[i + 1];
	}
	}
	if (found) {
	w->num--;
	}
	}

	static int pollfds_fill(GArray pollfds, fd_set rfds, fd_set *wfds,
	fd_set *xfds)
	{
	int nfds = -1;
	int i;

	for (i = 0; i < pollfds->len; i++) {
	GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
	int fd = pfd->fd;
	int events = pfd->events;
	if (events & G_IO_IN) {
	FD_SET(fd, rfds);
	nfds = MAX(nfds, fd);
	}
	if (events & G_IO_OUT) {
	FD_SET(fd, wfds);
	nfds = MAX(nfds, fd);
	}
	if (events & G_IO_PRI) {
	FD_SET(fd, xfds);
	nfds = MAX(nfds, fd);
	}
	}
	return nfds;
	}

	static void pollfds_poll(GArray pollfds, int nfds, fd_set rfds,
	fd_set wfds, fd_set xfds)
	{
	int i;

	for (i = 0; i < pollfds->len; i++) {
	GPollFD *pfd = &g_array_index(pollfds, GPollFD, i);
	int fd = pfd->fd;
	int revents = 0;

	if (FD_ISSET(fd, rfds)) {
	revents \|= G_IO_IN;
	}
	if (FD_ISSET(fd, wfds)) {
	revents \|= G_IO_OUT;
	}
	if (FD_ISSET(fd, xfds)) {
	revents \|= G_IO_PRI;
	}
	pfd->revents = revents & pfd->events;
	}
	}

	static int os_host_main_loop_wait(int64_t timeout)
	{
	GMainContext *context = g_main_context_default();
	GPollFD poll_fds[1024 * 2]; /* this is probably overkill */
	int select_ret = 0;
	int g_poll_ret, ret, i, n_poll_fds;
	PollingEntry *pe;
	WaitObjects *w = &wait_objects;
	gint poll_timeout;
	int64_t poll_timeout_ns;
	static struct timeval tv0;
	fd_set rfds, wfds, xfds;
	int nfds;

	g_main_context_acquire(context);

	/* XXX: need to suppress polling by better using win32 events */
	ret = 0;
	for (pe = first_polling_entry; pe != NULL; pe = pe->next) {
	ret \|= pe->func(pe->opaque);
	}
	if (ret != 0) {
	g_main_context_release(context);
	return ret;
	}

	FD_ZERO(&rfds);
	FD_ZERO(&wfds);
	FD_ZERO(&xfds);
	nfds = pollfds_fill(gpollfds, &rfds, &wfds, &xfds);
	if (nfds >= 0) {
	select_ret = select(nfds + 1, &rfds, &wfds, &xfds, &tv0);
	if (select_ret != 0) {
	timeout = 0;
	}
	if (select_ret > 0) {
	pollfds_poll(gpollfds, nfds, &rfds, &wfds, &xfds);
	}
	}

	g_main_context_prepare(context, &max_priority);
	n_poll_fds = g_main_context_query(context, max_priority, &poll_timeout,
	poll_fds, ARRAY_SIZE(poll_fds));
	g_assert(n_poll_fds + w->num <= ARRAY_SIZE(poll_fds));

	for (i = 0; i < w->num; i++) {
	poll_fds[n_poll_fds + i].fd = (DWORD_PTR)w->events[i];
	poll_fds[n_poll_fds + i].events = G_IO_IN;
	}

	if (poll_timeout < 0) {
	poll_timeout_ns = -1;
	} else {
	poll_timeout_ns = (int64_t)poll_timeout * (int64_t)SCALE_MS;
	}

	poll_timeout_ns = qemu_soonest_timeout(poll_timeout_ns, timeout);

	bql_unlock();

	replay_mutex_unlock();

	g_poll_ret = qemu_poll_ns(poll_fds, n_poll_fds + w->num, poll_timeout_ns);

	replay_mutex_lock();

	bql_lock();
	if (g_poll_ret > 0) {
	for (i = 0; i < w->num; i++) {
	w->revents[i] = poll_fds[n_poll_fds + i].revents;
	}
	for (i = 0; i < w->num; i++) {
	if (w->revents[i] && w->func[i]) {
	w->func[i](w->opaque[i]);
	}
	}
	}

	if (g_main_context_check(context, max_priority, poll_fds, n_poll_fds)) {
	g_main_context_dispatch(context);
	}

	g_main_context_release(context);

	return select_ret \|\| g_poll_ret;
	}
	#endif

	static NotifierList main_loop_poll_notifiers =
	NOTIFIER_LIST_INITIALIZER(main_loop_poll_notifiers);

	void main_loop_poll_add_notifier(Notifier *notify)
	{
	notifier_list_add(&main_loop_poll_notifiers, notify);
	}

	void main_loop_poll_remove_notifier(Notifier *notify)
	{
	notifier_remove(notify);
	}

	void main_loop_wait(int nonblocking)
	{
	MainLoopPoll mlpoll = {
	.state = MAIN_LOOP_POLL_FILL,
	.timeout = UINT32_MAX,
	.pollfds = gpollfds,
	};
	int ret;
	int64_t timeout_ns;

	if (nonblocking) {
	mlpoll.timeout = 0;
	}

	/* poll any events */
	g_array_set_size(gpollfds, 0); /* reset for new iteration */
	/* XXX: separate device handlers from system ones */
	notifier_list_notify(&main_loop_poll_notifiers, &mlpoll);

	if (mlpoll.timeout == UINT32_MAX) {
	timeout_ns = -1;
	} else {
	timeout_ns = (uint64_t)mlpoll.timeout * (int64_t)(SCALE_MS);
	}

	timeout_ns = qemu_soonest_timeout(timeout_ns,
	timerlistgroup_deadline_ns(
	&main_loop_tlg));

	ret = os_host_main_loop_wait(timeout_ns);
	mlpoll.state = ret < 0 ? MAIN_LOOP_POLL_ERR : MAIN_LOOP_POLL_OK;
	notifier_list_notify(&main_loop_poll_notifiers, &mlpoll);

	if (icount_enabled()) {
	/*
	* CPU thread can infinitely wait for event after
	* missing the warp
	*/
	icount_start_warp_timer();
	}
	qemu_clock_run_all_timers();
	}

	/* Functions to operate on the main QEMU AioContext. */

	QEMUBH qemu_bh_new_full(QEMUBHFunc cb, void opaque, const char name,
	MemReentrancyGuard *reentrancy_guard)
	{
	return aio_bh_new_full(qemu_aio_context, cb, opaque, name,
	reentrancy_guard);
	}

	/*
	* Functions to operate on the I/O handler AioContext.
	* This context runs on top of main loop. We can't reuse qemu_aio_context
	* because iohandlers mustn't be polled by aio_poll(qemu_aio_context).
	*/
	static AioContext *iohandler_ctx;

	static void iohandler_init(void)
	{
	if (!iohandler_ctx) {
	iohandler_ctx = aio_context_new(&error_abort);
	}
	}

	AioContext *iohandler_get_aio_context(void)
	{
	iohandler_init();
	return iohandler_ctx;
	}

	GSource *iohandler_get_g_source(void)
	{
	iohandler_init();
	return aio_get_g_source(iohandler_ctx);
	}

	void qemu_set_fd_handler(int fd,
	IOHandler *fd_read,
	IOHandler *fd_write,
	void *opaque)
	{
	iohandler_init();
	aio_set_fd_handler(iohandler_ctx, fd, fd_read, fd_write, NULL, NULL,
	opaque);
	}

	void event_notifier_set_handler(EventNotifier *e,
	EventNotifierHandler *handler)
	{
	iohandler_init();
	aio_set_event_notifier(iohandler_ctx, e, handler, NULL, NULL);
	}