/* * QEMU aio implementation * * Copyright IBM, Corp. 2008 * * Authors: * Anthony Liguori * * This work is licensed under the terms of the GNU GPL, version 2. See * the COPYING file in the top-level directory. * */ #ifndef QEMU_AIO_H #define QEMU_AIO_H #ifdef CONFIG_LINUX_IO_URING #include #endif #include "qemu/coroutine.h" #include "qemu/queue.h" #include "qemu/event_notifier.h" #include "qemu/thread.h" #include "qemu/timer.h" typedef struct BlockAIOCB BlockAIOCB; typedef void BlockCompletionFunc(void *opaque, int ret); typedef struct AIOCBInfo { void (*cancel_async)(BlockAIOCB *acb); AioContext *(*get_aio_context)(BlockAIOCB *acb); size_t aiocb_size; } AIOCBInfo; struct BlockAIOCB { const AIOCBInfo *aiocb_info; BlockDriverState *bs; BlockCompletionFunc *cb; void *opaque; int refcnt; }; void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs, BlockCompletionFunc *cb, void *opaque); void qemu_aio_unref(void *p); void qemu_aio_ref(void *p); typedef struct AioHandler AioHandler; typedef QLIST_HEAD(, AioHandler) AioHandlerList; typedef void QEMUBHFunc(void *opaque); typedef bool AioPollFn(void *opaque); typedef void IOHandler(void *opaque); struct Coroutine; struct ThreadPool; struct LinuxAioState; struct LuringState; /* Is polling disabled? */ bool aio_poll_disabled(AioContext *ctx); /* Callbacks for file descriptor monitoring implementations */ typedef struct { /* * update: * @ctx: the AioContext * @old_node: the existing handler or NULL if this file descriptor is being * monitored for the first time * @new_node: the new handler or NULL if this file descriptor is being * removed * * Add/remove/modify a monitored file descriptor. * * Called with ctx->list_lock acquired. */ void (*update)(AioContext *ctx, AioHandler *old_node, AioHandler *new_node); /* * wait: * @ctx: the AioContext * @ready_list: list for handlers that become ready * @timeout: maximum duration to wait, in nanoseconds * * Wait for file descriptors to become ready and place them on ready_list. * * Called with ctx->list_lock incremented but not locked. * * Returns: number of ready file descriptors. */ int (*wait)(AioContext *ctx, AioHandlerList *ready_list, int64_t timeout); /* * need_wait: * @ctx: the AioContext * * Tell aio_poll() when to stop userspace polling early because ->wait() * has fds ready. * * File descriptor monitoring implementations that cannot poll fd readiness * from userspace should use aio_poll_disabled() here. This ensures that * file descriptors are not starved by handlers that frequently make * progress via userspace polling. * * Returns: true if ->wait() should be called, false otherwise. */ bool (*need_wait)(AioContext *ctx); } FDMonOps; /* * Each aio_bh_poll() call carves off a slice of the BH list, so that newly * scheduled BHs are not processed until the next aio_bh_poll() call. All * active aio_bh_poll() calls chain their slices together in a list, so that * nested aio_bh_poll() calls process all scheduled bottom halves. */ typedef QSLIST_HEAD(, QEMUBH) BHList; typedef struct BHListSlice BHListSlice; struct BHListSlice { BHList bh_list; QSIMPLEQ_ENTRY(BHListSlice) next; }; typedef QSLIST_HEAD(, AioHandler) AioHandlerSList; struct AioContext { GSource source; /* Used by AioContext users to protect from multi-threaded access. */ QemuRecMutex lock; /* The list of registered AIO handlers. Protected by ctx->list_lock. */ AioHandlerList aio_handlers; /* The list of AIO handlers to be deleted. Protected by ctx->list_lock. */ AioHandlerList deleted_aio_handlers; /* Used to avoid unnecessary event_notifier_set calls in aio_notify; * only written from the AioContext home thread, or under the BQL in * the case of the main AioContext. However, it is read from any * thread so it is still accessed with atomic primitives. * * If this field is 0, everything (file descriptors, bottom halves, * timers) will be re-evaluated before the next blocking poll() or * io_uring wait; therefore, the event_notifier_set call can be * skipped. If it is non-zero, you may need to wake up a concurrent * aio_poll or the glib main event loop, making event_notifier_set * necessary. * * Bit 0 is reserved for GSource usage of the AioContext, and is 1 * between a call to aio_ctx_prepare and the next call to aio_ctx_check. * Bits 1-31 simply count the number of active calls to aio_poll * that are in the prepare or poll phase. * * The GSource and aio_poll must use a different mechanism because * there is no certainty that a call to GSource's prepare callback * (via g_main_context_prepare) is indeed followed by check and * dispatch. It's not clear whether this would be a bug, but let's * play safe and allow it---it will just cause extra calls to * event_notifier_set until the next call to dispatch. * * Instead, the aio_poll calls include both the prepare and the * dispatch phase, hence a simple counter is enough for them. */ uint32_t notify_me; /* A lock to protect between QEMUBH and AioHandler adders and deleter, * and to ensure that no callbacks are removed while we're walking and * dispatching them. */ QemuLockCnt list_lock; /* Bottom Halves pending aio_bh_poll() processing */ BHList bh_list; /* Chained BH list slices for each nested aio_bh_poll() call */ QSIMPLEQ_HEAD(, BHListSlice) bh_slice_list; /* Used by aio_notify. * * "notified" is used to avoid expensive event_notifier_test_and_clear * calls. When it is clear, the EventNotifier is clear, or one thread * is going to clear "notified" before processing more events. False * positives are possible, i.e. "notified" could be set even though the * EventNotifier is clear. * * Note that event_notifier_set *cannot* be optimized the same way. For * more information on the problem that would result, see "#ifdef BUG2" * in the docs/aio_notify_accept.promela formal model. */ bool notified; EventNotifier notifier; QSLIST_HEAD(, Coroutine) scheduled_coroutines; QEMUBH *co_schedule_bh; /* Thread pool for performing work and receiving completion callbacks. * Has its own locking. */ struct ThreadPool *thread_pool; #ifdef CONFIG_LINUX_AIO /* * State for native Linux AIO. Uses aio_context_acquire/release for * locking. */ struct LinuxAioState *linux_aio; #endif #ifdef CONFIG_LINUX_IO_URING /* * State for Linux io_uring. Uses aio_context_acquire/release for * locking. */ struct LuringState *linux_io_uring; /* State for file descriptor monitoring using Linux io_uring */ struct io_uring fdmon_io_uring; AioHandlerSList submit_list; #endif /* TimerLists for calling timers - one per clock type. Has its own * locking. */ QEMUTimerListGroup tlg; int external_disable_cnt; /* Number of AioHandlers without .io_poll() */ int poll_disable_cnt; /* Polling mode parameters */ int64_t poll_ns; /* current polling time in nanoseconds */ int64_t poll_max_ns; /* maximum polling time in nanoseconds */ int64_t poll_grow; /* polling time growth factor */ int64_t poll_shrink; /* polling time shrink factor */ /* * List of handlers participating in userspace polling. Protected by * ctx->list_lock. Iterated and modified mostly by the event loop thread * from aio_poll() with ctx->list_lock incremented. aio_set_fd_handler() * only touches the list to delete nodes if ctx->list_lock's count is zero. */ AioHandlerList poll_aio_handlers; /* Are we in polling mode or monitoring file descriptors? */ bool poll_started; /* epoll(7) state used when built with CONFIG_EPOLL */ int epollfd; const FDMonOps *fdmon_ops; }; /** * aio_context_new: Allocate a new AioContext. * * AioContext provide a mini event-loop that can be waited on synchronously. * They also provide bottom halves, a service to execute a piece of code * as soon as possible. */ AioContext *aio_context_new(Error **errp); /** * aio_context_ref: * @ctx: The AioContext to operate on. * * Add a reference to an AioContext. */ void aio_context_ref(AioContext *ctx); /** * aio_context_unref: * @ctx: The AioContext to operate on. * * Drop a reference to an AioContext. */ void aio_context_unref(AioContext *ctx); /* Take ownership of the AioContext. If the AioContext will be shared between * threads, and a thread does not want to be interrupted, it will have to * take ownership around calls to aio_poll(). Otherwise, aio_poll() * automatically takes care of calling aio_context_acquire and * aio_context_release. * * Note that this is separate from bdrv_drained_begin/bdrv_drained_end. A * thread still has to call those to avoid being interrupted by the guest. * * Bottom halves, timers and callbacks can be created or removed without * acquiring the AioContext. */ void aio_context_acquire(AioContext *ctx); /* Relinquish ownership of the AioContext. */ void aio_context_release(AioContext *ctx); /** * aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run * only once and as soon as possible. */ void aio_bh_schedule_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque); /** * aio_bh_new: Allocate a new bottom half structure. * * Bottom halves are lightweight callbacks whose invocation is guaranteed * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure * is opaque and must be allocated prior to its use. */ QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque); /** * aio_notify: Force processing of pending events. * * Similar to signaling a condition variable, aio_notify forces * aio_poll to exit, so that the next call will re-examine pending events. * The caller of aio_notify will usually call aio_poll again very soon, * or go through another iteration of the GLib main loop. Hence, aio_notify * also has the side effect of recalculating the sets of file descriptors * that the main loop waits for. * * Calling aio_notify is rarely necessary, because for example scheduling * a bottom half calls it already. */ void aio_notify(AioContext *ctx); /** * aio_notify_accept: Acknowledge receiving an aio_notify. * * aio_notify() uses an EventNotifier in order to wake up a sleeping * aio_poll() or g_main_context_iteration(). Calls to aio_notify() are * usually rare, but the AioContext has to clear the EventNotifier on * every aio_poll() or g_main_context_iteration() in order to avoid * busy waiting. This event_notifier_test_and_clear() cannot be done * using the usual aio_context_set_event_notifier(), because it must * be done before processing all events (file descriptors, bottom halves, * timers). * * aio_notify_accept() is an optimized event_notifier_test_and_clear() * that is specific to an AioContext's notifier; it is used internally * to clear the EventNotifier only if aio_notify() had been called. */ void aio_notify_accept(AioContext *ctx); /** * aio_bh_call: Executes callback function of the specified BH. */ void aio_bh_call(QEMUBH *bh); /** * aio_bh_poll: Poll bottom halves for an AioContext. * * These are internal functions used by the QEMU main loop. * And notice that multiple occurrences of aio_bh_poll cannot * be called concurrently */ int aio_bh_poll(AioContext *ctx); /** * qemu_bh_schedule: Schedule a bottom half. * * Scheduling a bottom half interrupts the main loop and causes the * execution of the callback that was passed to qemu_bh_new. * * Bottom halves that are scheduled from a bottom half handler are instantly * invoked. This can create an infinite loop if a bottom half handler * schedules itself. * * @bh: The bottom half to be scheduled. */ void qemu_bh_schedule(QEMUBH *bh); /** * qemu_bh_cancel: Cancel execution of a bottom half. * * Canceling execution of a bottom half undoes the effect of calls to * qemu_bh_schedule without freeing its resources yet. While cancellation * itself is also wait-free and thread-safe, it can of course race with the * loop that executes bottom halves unless you are holding the iothread * mutex. This makes it mostly useless if you are not holding the mutex. * * @bh: The bottom half to be canceled. */ void qemu_bh_cancel(QEMUBH *bh); /** *qemu_bh_delete: Cancel execution of a bottom half and free its resources. * * Deleting a bottom half frees the memory that was allocated for it by * qemu_bh_new. It also implies canceling the bottom half if it was * scheduled. * This func is async. The bottom half will do the delete action at the finial * end. * * @bh: The bottom half to be deleted. */ void qemu_bh_delete(QEMUBH *bh); /* Return whether there are any pending callbacks from the GSource * attached to the AioContext, before g_poll is invoked. * * This is used internally in the implementation of the GSource. */ bool aio_prepare(AioContext *ctx); /* Return whether there are any pending callbacks from the GSource * attached to the AioContext, after g_poll is invoked. * * This is used internally in the implementation of the GSource. */ bool aio_pending(AioContext *ctx); /* Dispatch any pending callbacks from the GSource attached to the AioContext. * * This is used internally in the implementation of the GSource. */ void aio_dispatch(AioContext *ctx); /* Progress in completing AIO work to occur. This can issue new pending * aio as a result of executing I/O completion or bh callbacks. * * Return whether any progress was made by executing AIO or bottom half * handlers. If @blocking == true, this should always be true except * if someone called aio_notify. * * If there are no pending bottom halves, but there are pending AIO * operations, it may not be possible to make any progress without * blocking. If @blocking is true, this function will wait until one * or more AIO events have completed, to ensure something has moved * before returning. */ bool aio_poll(AioContext *ctx, bool blocking); /* Register a file descriptor and associated callbacks. Behaves very similarly * to qemu_set_fd_handler. Unlike qemu_set_fd_handler, these callbacks will * be invoked when using aio_poll(). * * Code that invokes AIO completion functions should rely on this function * instead of qemu_set_fd_handler[2]. */ void aio_set_fd_handler(AioContext *ctx, int fd, bool is_external, IOHandler *io_read, IOHandler *io_write, AioPollFn *io_poll, void *opaque); /* Set polling begin/end callbacks for a file descriptor that has already been * registered with aio_set_fd_handler. Do nothing if the file descriptor is * not registered. */ void aio_set_fd_poll(AioContext *ctx, int fd, IOHandler *io_poll_begin, IOHandler *io_poll_end); /* Register an event notifier and associated callbacks. Behaves very similarly * to event_notifier_set_handler. Unlike event_notifier_set_handler, these callbacks * will be invoked when using aio_poll(). * * Code that invokes AIO completion functions should rely on this function * instead of event_notifier_set_handler. */ void aio_set_event_notifier(AioContext *ctx, EventNotifier *notifier, bool is_external, EventNotifierHandler *io_read, AioPollFn *io_poll); /* Set polling begin/end callbacks for an event notifier that has already been * registered with aio_set_event_notifier. Do nothing if the event notifier is * not registered. */ void aio_set_event_notifier_poll(AioContext *ctx, EventNotifier *notifier, EventNotifierHandler *io_poll_begin, EventNotifierHandler *io_poll_end); /* Return a GSource that lets the main loop poll the file descriptors attached * to this AioContext. */ GSource *aio_get_g_source(AioContext *ctx); /* Return the ThreadPool bound to this AioContext */ struct ThreadPool *aio_get_thread_pool(AioContext *ctx); /* Setup the LinuxAioState bound to this AioContext */ struct LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp); /* Return the LinuxAioState bound to this AioContext */ struct LinuxAioState *aio_get_linux_aio(AioContext *ctx); /* Setup the LuringState bound to this AioContext */ struct LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp); /* Return the LuringState bound to this AioContext */ struct LuringState *aio_get_linux_io_uring(AioContext *ctx); /** * aio_timer_new_with_attrs: * @ctx: the aio context * @type: the clock type * @scale: the scale * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_ values * to assign * @cb: the callback to call on timer expiry * @opaque: the opaque pointer to pass to the callback * * Allocate a new timer (with attributes) attached to the context @ctx. * The function is responsible for memory allocation. * * The preferred interface is aio_timer_init or aio_timer_init_with_attrs. * Use that unless you really need dynamic memory allocation. * * Returns: a pointer to the new timer */ static inline QEMUTimer *aio_timer_new_with_attrs(AioContext *ctx, QEMUClockType type, int scale, int attributes, QEMUTimerCB *cb, void *opaque) { return timer_new_full(&ctx->tlg, type, scale, attributes, cb, opaque); } /** * aio_timer_new: * @ctx: the aio context * @type: the clock type * @scale: the scale * @cb: the callback to call on timer expiry * @opaque: the opaque pointer to pass to the callback * * Allocate a new timer attached to the context @ctx. * See aio_timer_new_with_attrs for details. * * Returns: a pointer to the new timer */ static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type, int scale, QEMUTimerCB *cb, void *opaque) { return timer_new_full(&ctx->tlg, type, scale, 0, cb, opaque); } /** * aio_timer_init_with_attrs: * @ctx: the aio context * @ts: the timer * @type: the clock type * @scale: the scale * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_ values * to assign * @cb: the callback to call on timer expiry * @opaque: the opaque pointer to pass to the callback * * Initialise a new timer (with attributes) attached to the context @ctx. * The caller is responsible for memory allocation. */ static inline void aio_timer_init_with_attrs(AioContext *ctx, QEMUTimer *ts, QEMUClockType type, int scale, int attributes, QEMUTimerCB *cb, void *opaque) { timer_init_full(ts, &ctx->tlg, type, scale, attributes, cb, opaque); } /** * aio_timer_init: * @ctx: the aio context * @ts: the timer * @type: the clock type * @scale: the scale * @cb: the callback to call on timer expiry * @opaque: the opaque pointer to pass to the callback * * Initialise a new timer attached to the context @ctx. * See aio_timer_init_with_attrs for details. */ static inline void aio_timer_init(AioContext *ctx, QEMUTimer *ts, QEMUClockType type, int scale, QEMUTimerCB *cb, void *opaque) { timer_init_full(ts, &ctx->tlg, type, scale, 0, cb, opaque); } /** * aio_compute_timeout: * @ctx: the aio context * * Compute the timeout that a blocking aio_poll should use. */ int64_t aio_compute_timeout(AioContext *ctx); /** * aio_disable_external: * @ctx: the aio context * * Disable the further processing of external clients. */ static inline void aio_disable_external(AioContext *ctx) { qatomic_inc(&ctx->external_disable_cnt); } /** * aio_enable_external: * @ctx: the aio context * * Enable the processing of external clients. */ static inline void aio_enable_external(AioContext *ctx) { int old; old = qatomic_fetch_dec(&ctx->external_disable_cnt); assert(old > 0); if (old == 1) { /* Kick event loop so it re-arms file descriptors */ aio_notify(ctx); } } /** * aio_external_disabled: * @ctx: the aio context * * Return true if the external clients are disabled. */ static inline bool aio_external_disabled(AioContext *ctx) { return qatomic_read(&ctx->external_disable_cnt); } /** * aio_node_check: * @ctx: the aio context * @is_external: Whether or not the checked node is an external event source. * * Check if the node's is_external flag is okay to be polled by the ctx at this * moment. True means green light. */ static inline bool aio_node_check(AioContext *ctx, bool is_external) { return !is_external || !qatomic_read(&ctx->external_disable_cnt); } /** * aio_co_schedule: * @ctx: the aio context * @co: the coroutine * * Start a coroutine on a remote AioContext. * * The coroutine must not be entered by anyone else while aio_co_schedule() * is active. In addition the coroutine must have yielded unless ctx * is the context in which the coroutine is running (i.e. the value of * qemu_get_current_aio_context() from the coroutine itself). */ void aio_co_schedule(AioContext *ctx, struct Coroutine *co); /** * aio_co_reschedule_self: * @new_ctx: the new context * * Move the currently running coroutine to new_ctx. If the coroutine is already * running in new_ctx, do nothing. */ void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx); /** * aio_co_wake: * @co: the coroutine * * Restart a coroutine on the AioContext where it was running last, thus * preventing coroutines from jumping from one context to another when they * go to sleep. * * aio_co_wake may be executed either in coroutine or non-coroutine * context. The coroutine must not be entered by anyone else while * aio_co_wake() is active. */ void aio_co_wake(struct Coroutine *co); /** * aio_co_enter: * @ctx: the context to run the coroutine * @co: the coroutine to run * * Enter a coroutine in the specified AioContext. */ void aio_co_enter(AioContext *ctx, struct Coroutine *co); /** * Return the AioContext whose event loop runs in the current thread. * * If called from an IOThread this will be the IOThread's AioContext. If * called from the main thread or with the "big QEMU lock" taken it * will be the main loop AioContext. */ AioContext *qemu_get_current_aio_context(void); void qemu_set_current_aio_context(AioContext *ctx); /** * aio_context_setup: * @ctx: the aio context * * Initialize the aio context. */ void aio_context_setup(AioContext *ctx); /** * aio_context_destroy: * @ctx: the aio context * * Destroy the aio context. */ void aio_context_destroy(AioContext *ctx); /* Used internally, do not call outside AioContext code */ void aio_context_use_g_source(AioContext *ctx); /** * aio_context_set_poll_params: * @ctx: the aio context * @max_ns: how long to busy poll for, in nanoseconds * @grow: polling time growth factor * @shrink: polling time shrink factor * * Poll mode can be disabled by setting poll_max_ns to 0. */ void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns, int64_t grow, int64_t shrink, Error **errp); #endif