cachepc-qemu

Fork of AMDESE/qemu with changes for cachepc side-channel attack
git clone https://git.sinitax.com/sinitax/cachepc-qemu
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aio-wait.h (5892B)

      1/*
      2 * AioContext wait support
      3 *
      4 * Copyright (C) 2018 Red Hat, Inc.
      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#ifndef QEMU_AIO_WAIT_H
     26#define QEMU_AIO_WAIT_H
     27
     28#include "block/aio.h"
     29#include "qemu/main-loop.h"
     30
     31/**
     32 * AioWait:
     33 *
     34 * An object that facilitates synchronous waiting on a condition. A single
     35 * global AioWait object (global_aio_wait) is used internally.
     36 *
     37 * The main loop can wait on an operation running in an IOThread as follows:
     38 *
     39 *   AioContext *ctx = ...;
     40 *   MyWork work = { .done = false };
     41 *   schedule_my_work_in_iothread(ctx, &work);
     42 *   AIO_WAIT_WHILE(ctx, !work.done);
     43 *
     44 * The IOThread must call aio_wait_kick() to notify the main loop when
     45 * work.done changes:
     46 *
     47 *   static void do_work(...)
     48 *   {
     49 *       ...
     50 *       work.done = true;
     51 *       aio_wait_kick();
     52 *   }
     53 */
     54typedef struct {
     55    /* Number of waiting AIO_WAIT_WHILE() callers. Accessed with atomic ops. */
     56    unsigned num_waiters;
     57} AioWait;
     58
     59extern AioWait global_aio_wait;
     60
     61/**
     62 * AIO_WAIT_WHILE:
     63 * @ctx: the aio context, or NULL if multiple aio contexts (for which the
     64 *       caller does not hold a lock) are involved in the polling condition.
     65 * @cond: wait while this conditional expression is true
     66 *
     67 * Wait while a condition is true.  Use this to implement synchronous
     68 * operations that require event loop activity.
     69 *
     70 * The caller must be sure that something calls aio_wait_kick() when the value
     71 * of @cond might have changed.
     72 *
     73 * The caller's thread must be the IOThread that owns @ctx or the main loop
     74 * thread (with @ctx acquired exactly once).  This function cannot be used to
     75 * wait on conditions between two IOThreads since that could lead to deadlock,
     76 * go via the main loop instead.
     77 */
     78#define AIO_WAIT_WHILE(ctx, cond) ({                               \
     79    bool waited_ = false;                                          \
     80    AioWait *wait_ = &global_aio_wait;                             \
     81    AioContext *ctx_ = (ctx);                                      \
     82    /* Increment wait_->num_waiters before evaluating cond. */     \
     83    qatomic_inc(&wait_->num_waiters);                              \
     84    if (ctx_ && in_aio_context_home_thread(ctx_)) {                \
     85        while ((cond)) {                                           \
     86            aio_poll(ctx_, true);                                  \
     87            waited_ = true;                                        \
     88        }                                                          \
     89    } else {                                                       \
     90        assert(qemu_get_current_aio_context() ==                   \
     91               qemu_get_aio_context());                            \
     92        while ((cond)) {                                           \
     93            if (ctx_) {                                            \
     94                aio_context_release(ctx_);                         \
     95            }                                                      \
     96            aio_poll(qemu_get_aio_context(), true);                \
     97            if (ctx_) {                                            \
     98                aio_context_acquire(ctx_);                         \
     99            }                                                      \
    100            waited_ = true;                                        \
    101        }                                                          \
    102    }                                                              \
    103    qatomic_dec(&wait_->num_waiters);                              \
    104    waited_; })
    105
    106/**
    107 * aio_wait_kick:
    108 * Wake up the main thread if it is waiting on AIO_WAIT_WHILE().  During
    109 * synchronous operations performed in an IOThread, the main thread lets the
    110 * IOThread's event loop run, waiting for the operation to complete.  A
    111 * aio_wait_kick() call will wake up the main thread.
    112 */
    113void aio_wait_kick(void);
    114
    115/**
    116 * aio_wait_bh_oneshot:
    117 * @ctx: the aio context
    118 * @cb: the BH callback function
    119 * @opaque: user data for the BH callback function
    120 *
    121 * Run a BH in @ctx and wait for it to complete.
    122 *
    123 * Must be called from the main loop thread with @ctx acquired exactly once.
    124 * Note that main loop event processing may occur.
    125 */
    126void aio_wait_bh_oneshot(AioContext *ctx, QEMUBHFunc *cb, void *opaque);
    127
    128/**
    129 * in_aio_context_home_thread:
    130 * @ctx: the aio context
    131 *
    132 * Return whether we are running in the thread that normally runs @ctx.  Note
    133 * that acquiring/releasing ctx does not affect the outcome, each AioContext
    134 * still only has one home thread that is responsible for running it.
    135 */
    136static inline bool in_aio_context_home_thread(AioContext *ctx)
    137{
    138    if (ctx == qemu_get_current_aio_context()) {
    139        return true;
    140    }
    141
    142    if (ctx == qemu_get_aio_context()) {
    143        return qemu_mutex_iothread_locked();
    144    } else {
    145        return false;
    146    }
    147}
    148
    149#endif /* QEMU_AIO_WAIT_H */