jcs.org
qemu with hax to log dma reads & writes
jcs.org/2018/11/12/vfio
1/*
2 * QEMU aio implementation
3 *
4 * Copyright IBM, Corp. 2008
5 *
6 * Authors:
7 * Anthony Liguori <aliguori@us.ibm.com>
8 *
9 * This work is licensed under the terms of the GNU GPL, version 2. See
10 * the COPYING file in the top-level directory.
11 *
12 */
13
14#ifndef QEMU_AIO_H
15#define QEMU_AIO_H
16
17#ifdef CONFIG_LINUX_IO_URING
18#include <liburing.h>
19#endif
20#include "qemu/queue.h"
21#include "qemu/event_notifier.h"
22#include "qemu/thread.h"
23#include "qemu/timer.h"
24
25typedef struct BlockAIOCB BlockAIOCB;
26typedef void BlockCompletionFunc(void *opaque, int ret);
27
28typedef struct AIOCBInfo {
29 void (*cancel_async)(BlockAIOCB *acb);
30 AioContext *(*get_aio_context)(BlockAIOCB *acb);
31 size_t aiocb_size;
32} AIOCBInfo;
33
34struct BlockAIOCB {
35 const AIOCBInfo *aiocb_info;
36 BlockDriverState *bs;
37 BlockCompletionFunc *cb;
38 void *opaque;
39 int refcnt;
40};
41
42void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
43 BlockCompletionFunc *cb, void *opaque);
44void qemu_aio_unref(void *p);
45void qemu_aio_ref(void *p);
46
47typedef struct AioHandler AioHandler;
48typedef QLIST_HEAD(, AioHandler) AioHandlerList;
49typedef void QEMUBHFunc(void *opaque);
50typedef bool AioPollFn(void *opaque);
51typedef void IOHandler(void *opaque);
52
53struct Coroutine;
54struct ThreadPool;
55struct LinuxAioState;
56struct LuringState;
57
58/* Is polling disabled? */
59bool aio_poll_disabled(AioContext *ctx);
60
61/* Callbacks for file descriptor monitoring implementations */
62typedef struct {
63 /*
64 * update:
65 * @ctx: the AioContext
66 * @old_node: the existing handler or NULL if this file descriptor is being
67 * monitored for the first time
68 * @new_node: the new handler or NULL if this file descriptor is being
69 * removed
70 *
71 * Add/remove/modify a monitored file descriptor.
72 *
73 * Called with ctx->list_lock acquired.
74 */
75 void (*update)(AioContext *ctx, AioHandler *old_node, AioHandler *new_node);
76
77 /*
78 * wait:
79 * @ctx: the AioContext
80 * @ready_list: list for handlers that become ready
81 * @timeout: maximum duration to wait, in nanoseconds
82 *
83 * Wait for file descriptors to become ready and place them on ready_list.
84 *
85 * Called with ctx->list_lock incremented but not locked.
86 *
87 * Returns: number of ready file descriptors.
88 */
89 int (*wait)(AioContext *ctx, AioHandlerList *ready_list, int64_t timeout);
90
91 /*
92 * need_wait:
93 * @ctx: the AioContext
94 *
95 * Tell aio_poll() when to stop userspace polling early because ->wait()
96 * has fds ready.
97 *
98 * File descriptor monitoring implementations that cannot poll fd readiness
99 * from userspace should use aio_poll_disabled() here. This ensures that
100 * file descriptors are not starved by handlers that frequently make
101 * progress via userspace polling.
102 *
103 * Returns: true if ->wait() should be called, false otherwise.
104 */
105 bool (*need_wait)(AioContext *ctx);
106} FDMonOps;
107
108/*
109 * Each aio_bh_poll() call carves off a slice of the BH list, so that newly
110 * scheduled BHs are not processed until the next aio_bh_poll() call. All
111 * active aio_bh_poll() calls chain their slices together in a list, so that
112 * nested aio_bh_poll() calls process all scheduled bottom halves.
113 */
114typedef QSLIST_HEAD(, QEMUBH) BHList;
115typedef struct BHListSlice BHListSlice;
116struct BHListSlice {
117 BHList bh_list;
118 QSIMPLEQ_ENTRY(BHListSlice) next;
119};
120
121typedef QSLIST_HEAD(, AioHandler) AioHandlerSList;
122
123struct AioContext {
124 GSource source;
125
126 /* Used by AioContext users to protect from multi-threaded access. */
127 QemuRecMutex lock;
128
129 /* The list of registered AIO handlers. Protected by ctx->list_lock. */
130 AioHandlerList aio_handlers;
131
132 /* The list of AIO handlers to be deleted. Protected by ctx->list_lock. */
133 AioHandlerList deleted_aio_handlers;
134
135 /* Used to avoid unnecessary event_notifier_set calls in aio_notify;
136 * only written from the AioContext home thread, or under the BQL in
137 * the case of the main AioContext. However, it is read from any
138 * thread so it is still accessed with atomic primitives.
139 *
140 * If this field is 0, everything (file descriptors, bottom halves,
141 * timers) will be re-evaluated before the next blocking poll() or
142 * io_uring wait; therefore, the event_notifier_set call can be
143 * skipped. If it is non-zero, you may need to wake up a concurrent
144 * aio_poll or the glib main event loop, making event_notifier_set
145 * necessary.
146 *
147 * Bit 0 is reserved for GSource usage of the AioContext, and is 1
148 * between a call to aio_ctx_prepare and the next call to aio_ctx_check.
149 * Bits 1-31 simply count the number of active calls to aio_poll
150 * that are in the prepare or poll phase.
151 *
152 * The GSource and aio_poll must use a different mechanism because
153 * there is no certainty that a call to GSource's prepare callback
154 * (via g_main_context_prepare) is indeed followed by check and
155 * dispatch. It's not clear whether this would be a bug, but let's
156 * play safe and allow it---it will just cause extra calls to
157 * event_notifier_set until the next call to dispatch.
158 *
159 * Instead, the aio_poll calls include both the prepare and the
160 * dispatch phase, hence a simple counter is enough for them.
161 */
162 uint32_t notify_me;
163
164 /* A lock to protect between QEMUBH and AioHandler adders and deleter,
165 * and to ensure that no callbacks are removed while we're walking and
166 * dispatching them.
167 */
168 QemuLockCnt list_lock;
169
170 /* Bottom Halves pending aio_bh_poll() processing */
171 BHList bh_list;
172
173 /* Chained BH list slices for each nested aio_bh_poll() call */
174 QSIMPLEQ_HEAD(, BHListSlice) bh_slice_list;
175
176 /* Used by aio_notify.
177 *
178 * "notified" is used to avoid expensive event_notifier_test_and_clear
179 * calls. When it is clear, the EventNotifier is clear, or one thread
180 * is going to clear "notified" before processing more events. False
181 * positives are possible, i.e. "notified" could be set even though the
182 * EventNotifier is clear.
183 *
184 * Note that event_notifier_set *cannot* be optimized the same way. For
185 * more information on the problem that would result, see "#ifdef BUG2"
186 * in the docs/aio_notify_accept.promela formal model.
187 */
188 bool notified;
189 EventNotifier notifier;
190
191 QSLIST_HEAD(, Coroutine) scheduled_coroutines;
192 QEMUBH *co_schedule_bh;
193
194 /* Thread pool for performing work and receiving completion callbacks.
195 * Has its own locking.
196 */
197 struct ThreadPool *thread_pool;
198
199#ifdef CONFIG_LINUX_AIO
200 /*
201 * State for native Linux AIO. Uses aio_context_acquire/release for
202 * locking.
203 */
204 struct LinuxAioState *linux_aio;
205#endif
206#ifdef CONFIG_LINUX_IO_URING
207 /*
208 * State for Linux io_uring. Uses aio_context_acquire/release for
209 * locking.
210 */
211 struct LuringState *linux_io_uring;
212
213 /* State for file descriptor monitoring using Linux io_uring */
214 struct io_uring fdmon_io_uring;
215 AioHandlerSList submit_list;
216#endif
217
218 /* TimerLists for calling timers - one per clock type. Has its own
219 * locking.
220 */
221 QEMUTimerListGroup tlg;
222
223 int external_disable_cnt;
224
225 /* Number of AioHandlers without .io_poll() */
226 int poll_disable_cnt;
227
228 /* Polling mode parameters */
229 int64_t poll_ns; /* current polling time in nanoseconds */
230 int64_t poll_max_ns; /* maximum polling time in nanoseconds */
231 int64_t poll_grow; /* polling time growth factor */
232 int64_t poll_shrink; /* polling time shrink factor */
233
234 /*
235 * List of handlers participating in userspace polling. Protected by
236 * ctx->list_lock. Iterated and modified mostly by the event loop thread
237 * from aio_poll() with ctx->list_lock incremented. aio_set_fd_handler()
238 * only touches the list to delete nodes if ctx->list_lock's count is zero.
239 */
240 AioHandlerList poll_aio_handlers;
241
242 /* Are we in polling mode or monitoring file descriptors? */
243 bool poll_started;
244
245 /* epoll(7) state used when built with CONFIG_EPOLL */
246 int epollfd;
247
248 const FDMonOps *fdmon_ops;
249};
250
251/**
252 * aio_context_new: Allocate a new AioContext.
253 *
254 * AioContext provide a mini event-loop that can be waited on synchronously.
255 * They also provide bottom halves, a service to execute a piece of code
256 * as soon as possible.
257 */
258AioContext *aio_context_new(Error **errp);
259
260/**
261 * aio_context_ref:
262 * @ctx: The AioContext to operate on.
263 *
264 * Add a reference to an AioContext.
265 */
266void aio_context_ref(AioContext *ctx);
267
268/**
269 * aio_context_unref:
270 * @ctx: The AioContext to operate on.
271 *
272 * Drop a reference to an AioContext.
273 */
274void aio_context_unref(AioContext *ctx);
275
276/* Take ownership of the AioContext. If the AioContext will be shared between
277 * threads, and a thread does not want to be interrupted, it will have to
278 * take ownership around calls to aio_poll(). Otherwise, aio_poll()
279 * automatically takes care of calling aio_context_acquire and
280 * aio_context_release.
281 *
282 * Note that this is separate from bdrv_drained_begin/bdrv_drained_end. A
283 * thread still has to call those to avoid being interrupted by the guest.
284 *
285 * Bottom halves, timers and callbacks can be created or removed without
286 * acquiring the AioContext.
287 */
288void aio_context_acquire(AioContext *ctx);
289
290/* Relinquish ownership of the AioContext. */
291void aio_context_release(AioContext *ctx);
292
293/**
294 * aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run
295 * only once and as soon as possible.
296 */
297void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
298
299/**
300 * aio_bh_new: Allocate a new bottom half structure.
301 *
302 * Bottom halves are lightweight callbacks whose invocation is guaranteed
303 * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
304 * is opaque and must be allocated prior to its use.
305 */
306QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
307
308/**
309 * aio_notify: Force processing of pending events.
310 *
311 * Similar to signaling a condition variable, aio_notify forces
312 * aio_poll to exit, so that the next call will re-examine pending events.
313 * The caller of aio_notify will usually call aio_poll again very soon,
314 * or go through another iteration of the GLib main loop. Hence, aio_notify
315 * also has the side effect of recalculating the sets of file descriptors
316 * that the main loop waits for.
317 *
318 * Calling aio_notify is rarely necessary, because for example scheduling
319 * a bottom half calls it already.
320 */
321void aio_notify(AioContext *ctx);
322
323/**
324 * aio_notify_accept: Acknowledge receiving an aio_notify.
325 *
326 * aio_notify() uses an EventNotifier in order to wake up a sleeping
327 * aio_poll() or g_main_context_iteration(). Calls to aio_notify() are
328 * usually rare, but the AioContext has to clear the EventNotifier on
329 * every aio_poll() or g_main_context_iteration() in order to avoid
330 * busy waiting. This event_notifier_test_and_clear() cannot be done
331 * using the usual aio_context_set_event_notifier(), because it must
332 * be done before processing all events (file descriptors, bottom halves,
333 * timers).
334 *
335 * aio_notify_accept() is an optimized event_notifier_test_and_clear()
336 * that is specific to an AioContext's notifier; it is used internally
337 * to clear the EventNotifier only if aio_notify() had been called.
338 */
339void aio_notify_accept(AioContext *ctx);
340
341/**
342 * aio_bh_call: Executes callback function of the specified BH.
343 */
344void aio_bh_call(QEMUBH *bh);
345
346/**
347 * aio_bh_poll: Poll bottom halves for an AioContext.
348 *
349 * These are internal functions used by the QEMU main loop.
350 * And notice that multiple occurrences of aio_bh_poll cannot
351 * be called concurrently
352 */
353int aio_bh_poll(AioContext *ctx);
354
355/**
356 * qemu_bh_schedule: Schedule a bottom half.
357 *
358 * Scheduling a bottom half interrupts the main loop and causes the
359 * execution of the callback that was passed to qemu_bh_new.
360 *
361 * Bottom halves that are scheduled from a bottom half handler are instantly
362 * invoked. This can create an infinite loop if a bottom half handler
363 * schedules itself.
364 *
365 * @bh: The bottom half to be scheduled.
366 */
367void qemu_bh_schedule(QEMUBH *bh);
368
369/**
370 * qemu_bh_cancel: Cancel execution of a bottom half.
371 *
372 * Canceling execution of a bottom half undoes the effect of calls to
373 * qemu_bh_schedule without freeing its resources yet. While cancellation
374 * itself is also wait-free and thread-safe, it can of course race with the
375 * loop that executes bottom halves unless you are holding the iothread
376 * mutex. This makes it mostly useless if you are not holding the mutex.
377 *
378 * @bh: The bottom half to be canceled.
379 */
380void qemu_bh_cancel(QEMUBH *bh);
381
382/**
383 *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
384 *
385 * Deleting a bottom half frees the memory that was allocated for it by
386 * qemu_bh_new. It also implies canceling the bottom half if it was
387 * scheduled.
388 * This func is async. The bottom half will do the delete action at the finial
389 * end.
390 *
391 * @bh: The bottom half to be deleted.
392 */
393void qemu_bh_delete(QEMUBH *bh);
394
395/* Return whether there are any pending callbacks from the GSource
396 * attached to the AioContext, before g_poll is invoked.
397 *
398 * This is used internally in the implementation of the GSource.
399 */
400bool aio_prepare(AioContext *ctx);
401
402/* Return whether there are any pending callbacks from the GSource
403 * attached to the AioContext, after g_poll is invoked.
404 *
405 * This is used internally in the implementation of the GSource.
406 */
407bool aio_pending(AioContext *ctx);
408
409/* Dispatch any pending callbacks from the GSource attached to the AioContext.
410 *
411 * This is used internally in the implementation of the GSource.
412 */
413void aio_dispatch(AioContext *ctx);
414
415/* Progress in completing AIO work to occur. This can issue new pending
416 * aio as a result of executing I/O completion or bh callbacks.
417 *
418 * Return whether any progress was made by executing AIO or bottom half
419 * handlers. If @blocking == true, this should always be true except
420 * if someone called aio_notify.
421 *
422 * If there are no pending bottom halves, but there are pending AIO
423 * operations, it may not be possible to make any progress without
424 * blocking. If @blocking is true, this function will wait until one
425 * or more AIO events have completed, to ensure something has moved
426 * before returning.
427 */
428bool aio_poll(AioContext *ctx, bool blocking);
429
430/* Register a file descriptor and associated callbacks. Behaves very similarly
431 * to qemu_set_fd_handler. Unlike qemu_set_fd_handler, these callbacks will
432 * be invoked when using aio_poll().
433 *
434 * Code that invokes AIO completion functions should rely on this function
435 * instead of qemu_set_fd_handler[2].
436 */
437void aio_set_fd_handler(AioContext *ctx,
438 int fd,
439 bool is_external,
440 IOHandler *io_read,
441 IOHandler *io_write,
442 AioPollFn *io_poll,
443 void *opaque);
444
445/* Set polling begin/end callbacks for a file descriptor that has already been
446 * registered with aio_set_fd_handler. Do nothing if the file descriptor is
447 * not registered.
448 */
449void aio_set_fd_poll(AioContext *ctx, int fd,
450 IOHandler *io_poll_begin,
451 IOHandler *io_poll_end);
452
453/* Register an event notifier and associated callbacks. Behaves very similarly
454 * to event_notifier_set_handler. Unlike event_notifier_set_handler, these callbacks
455 * will be invoked when using aio_poll().
456 *
457 * Code that invokes AIO completion functions should rely on this function
458 * instead of event_notifier_set_handler.
459 */
460void aio_set_event_notifier(AioContext *ctx,
461 EventNotifier *notifier,
462 bool is_external,
463 EventNotifierHandler *io_read,
464 AioPollFn *io_poll);
465
466/* Set polling begin/end callbacks for an event notifier that has already been
467 * registered with aio_set_event_notifier. Do nothing if the event notifier is
468 * not registered.
469 */
470void aio_set_event_notifier_poll(AioContext *ctx,
471 EventNotifier *notifier,
472 EventNotifierHandler *io_poll_begin,
473 EventNotifierHandler *io_poll_end);
474
475/* Return a GSource that lets the main loop poll the file descriptors attached
476 * to this AioContext.
477 */
478GSource *aio_get_g_source(AioContext *ctx);
479
480/* Return the ThreadPool bound to this AioContext */
481struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
482
483/* Setup the LinuxAioState bound to this AioContext */
484struct LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp);
485
486/* Return the LinuxAioState bound to this AioContext */
487struct LinuxAioState *aio_get_linux_aio(AioContext *ctx);
488
489/* Setup the LuringState bound to this AioContext */
490struct LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp);
491
492/* Return the LuringState bound to this AioContext */
493struct LuringState *aio_get_linux_io_uring(AioContext *ctx);
494/**
495 * aio_timer_new_with_attrs:
496 * @ctx: the aio context
497 * @type: the clock type
498 * @scale: the scale
499 * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values
500 * to assign
501 * @cb: the callback to call on timer expiry
502 * @opaque: the opaque pointer to pass to the callback
503 *
504 * Allocate a new timer (with attributes) attached to the context @ctx.
505 * The function is responsible for memory allocation.
506 *
507 * The preferred interface is aio_timer_init or aio_timer_init_with_attrs.
508 * Use that unless you really need dynamic memory allocation.
509 *
510 * Returns: a pointer to the new timer
511 */
512static inline QEMUTimer *aio_timer_new_with_attrs(AioContext *ctx,
513 QEMUClockType type,
514 int scale, int attributes,
515 QEMUTimerCB *cb, void *opaque)
516{
517 return timer_new_full(&ctx->tlg, type, scale, attributes, cb, opaque);
518}
519
520/**
521 * aio_timer_new:
522 * @ctx: the aio context
523 * @type: the clock type
524 * @scale: the scale
525 * @cb: the callback to call on timer expiry
526 * @opaque: the opaque pointer to pass to the callback
527 *
528 * Allocate a new timer attached to the context @ctx.
529 * See aio_timer_new_with_attrs for details.
530 *
531 * Returns: a pointer to the new timer
532 */
533static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type,
534 int scale,
535 QEMUTimerCB *cb, void *opaque)
536{
537 return timer_new_full(&ctx->tlg, type, scale, 0, cb, opaque);
538}
539
540/**
541 * aio_timer_init_with_attrs:
542 * @ctx: the aio context
543 * @ts: the timer
544 * @type: the clock type
545 * @scale: the scale
546 * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values
547 * to assign
548 * @cb: the callback to call on timer expiry
549 * @opaque: the opaque pointer to pass to the callback
550 *
551 * Initialise a new timer (with attributes) attached to the context @ctx.
552 * The caller is responsible for memory allocation.
553 */
554static inline void aio_timer_init_with_attrs(AioContext *ctx,
555 QEMUTimer *ts, QEMUClockType type,
556 int scale, int attributes,
557 QEMUTimerCB *cb, void *opaque)
558{
559 timer_init_full(ts, &ctx->tlg, type, scale, attributes, cb, opaque);
560}
561
562/**
563 * aio_timer_init:
564 * @ctx: the aio context
565 * @ts: the timer
566 * @type: the clock type
567 * @scale: the scale
568 * @cb: the callback to call on timer expiry
569 * @opaque: the opaque pointer to pass to the callback
570 *
571 * Initialise a new timer attached to the context @ctx.
572 * See aio_timer_init_with_attrs for details.
573 */
574static inline void aio_timer_init(AioContext *ctx,
575 QEMUTimer *ts, QEMUClockType type,
576 int scale,
577 QEMUTimerCB *cb, void *opaque)
578{
579 timer_init_full(ts, &ctx->tlg, type, scale, 0, cb, opaque);
580}
581
582/**
583 * aio_compute_timeout:
584 * @ctx: the aio context
585 *
586 * Compute the timeout that a blocking aio_poll should use.
587 */
588int64_t aio_compute_timeout(AioContext *ctx);
589
590/**
591 * aio_disable_external:
592 * @ctx: the aio context
593 *
594 * Disable the further processing of external clients.
595 */
596static inline void aio_disable_external(AioContext *ctx)
597{
598 atomic_inc(&ctx->external_disable_cnt);
599}
600
601/**
602 * aio_enable_external:
603 * @ctx: the aio context
604 *
605 * Enable the processing of external clients.
606 */
607static inline void aio_enable_external(AioContext *ctx)
608{
609 int old;
610
611 old = atomic_fetch_dec(&ctx->external_disable_cnt);
612 assert(old > 0);
613 if (old == 1) {
614 /* Kick event loop so it re-arms file descriptors */
615 aio_notify(ctx);
616 }
617}
618
619/**
620 * aio_external_disabled:
621 * @ctx: the aio context
622 *
623 * Return true if the external clients are disabled.
624 */
625static inline bool aio_external_disabled(AioContext *ctx)
626{
627 return atomic_read(&ctx->external_disable_cnt);
628}
629
630/**
631 * aio_node_check:
632 * @ctx: the aio context
633 * @is_external: Whether or not the checked node is an external event source.
634 *
635 * Check if the node's is_external flag is okay to be polled by the ctx at this
636 * moment. True means green light.
637 */
638static inline bool aio_node_check(AioContext *ctx, bool is_external)
639{
640 return !is_external || !atomic_read(&ctx->external_disable_cnt);
641}
642
643/**
644 * aio_co_schedule:
645 * @ctx: the aio context
646 * @co: the coroutine
647 *
648 * Start a coroutine on a remote AioContext.
649 *
650 * The coroutine must not be entered by anyone else while aio_co_schedule()
651 * is active. In addition the coroutine must have yielded unless ctx
652 * is the context in which the coroutine is running (i.e. the value of
653 * qemu_get_current_aio_context() from the coroutine itself).
654 */
655void aio_co_schedule(AioContext *ctx, struct Coroutine *co);
656
657/**
658 * aio_co_wake:
659 * @co: the coroutine
660 *
661 * Restart a coroutine on the AioContext where it was running last, thus
662 * preventing coroutines from jumping from one context to another when they
663 * go to sleep.
664 *
665 * aio_co_wake may be executed either in coroutine or non-coroutine
666 * context. The coroutine must not be entered by anyone else while
667 * aio_co_wake() is active.
668 */
669void aio_co_wake(struct Coroutine *co);
670
671/**
672 * aio_co_enter:
673 * @ctx: the context to run the coroutine
674 * @co: the coroutine to run
675 *
676 * Enter a coroutine in the specified AioContext.
677 */
678void aio_co_enter(AioContext *ctx, struct Coroutine *co);
679
680/**
681 * Return the AioContext whose event loop runs in the current thread.
682 *
683 * If called from an IOThread this will be the IOThread's AioContext. If
684 * called from another thread it will be the main loop AioContext.
685 */
686AioContext *qemu_get_current_aio_context(void);
687
688/**
689 * aio_context_setup:
690 * @ctx: the aio context
691 *
692 * Initialize the aio context.
693 */
694void aio_context_setup(AioContext *ctx);
695
696/**
697 * aio_context_destroy:
698 * @ctx: the aio context
699 *
700 * Destroy the aio context.
701 */
702void aio_context_destroy(AioContext *ctx);
703
704/* Used internally, do not call outside AioContext code */
705void aio_context_use_g_source(AioContext *ctx);
706
707/**
708 * aio_context_set_poll_params:
709 * @ctx: the aio context
710 * @max_ns: how long to busy poll for, in nanoseconds
711 * @grow: polling time growth factor
712 * @shrink: polling time shrink factor
713 *
714 * Poll mode can be disabled by setting poll_max_ns to 0.
715 */
716void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
717 int64_t grow, int64_t shrink,
718 Error **errp);
719
720#endif