Merge remote-tracking branch 'bonzini/threadpool' into staging

* bonzini/threadpool: (39 commits)
  raw-win32: implement native asynchronous I/O
  raw-posix: move linux-aio.c to block/
  raw-win32: add emulated AIO support
  raw-posix: rename raw-posix-aio.h, hide unavailable prototypes
  raw: merge posix-aio-compat.c into block/raw-posix.c
  block: switch posix-aio-compat to threadpool
  threadpool: do not take lock in event_notifier_ready
  aio: add generic thread-pool facility
  qemu-thread: add QemuSemaphore
  linux-aio: use event notifiers
  aio: clean up now-unused functions
  main-loop: use aio_notify for qemu_notify_event
  main-loop: use GSource to poll AIO file descriptors
  aio: call aio_notify after setting I/O handlers
  aio: add aio_notify
  aio: make AioContexts GSources
  aio: add Win32 implementation
  aio: prepare for introducing GSource-based dispatch
  aio: add non-blocking variant of aio_wait
  aio: test node->deleted before calling io_flush
  ...

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

49 files changed, 2429 insertions, 1489 deletions

diff --git a/Makefile b/Makefile
index b522b10195..2ba981c8a5 100644
--- a/Makefile
+++ b/Makefile
@@ -171,8 +171,7 @@ endif
 qemu-img.o: qemu-img-cmds.h
 
 tools-obj-y = $(oslib-obj-y) $(trace-obj-y) qemu-tool.o qemu-timer.o \
-	qemu-timer-common.o main-loop.o notify.o \
-	iohandler.o cutils.o iov.o async.o error.o
+	main-loop.o iohandler.o error.o
 tools-obj-$(CONFIG_POSIX) += compatfd.o
 
 qemu-img$(EXESUF): qemu-img.o $(tools-obj-y) $(block-obj-y)
@@ -181,7 +180,7 @@ qemu-io$(EXESUF): qemu-io.o cmd.o $(tools-obj-y) $(block-obj-y)
 
 qemu-bridge-helper$(EXESUF): qemu-bridge-helper.o
 
-vscclient$(EXESUF): $(libcacard-y) $(oslib-obj-y) $(trace-obj-y) $(tools-obj-y) qemu-timer-common.o libcacard/vscclient.o
+vscclient$(EXESUF): $(libcacard-y) $(oslib-obj-y) $(trace-obj-y) libcacard/vscclient.o
 	$(call quiet-command,$(CC) $(LDFLAGS) -o $@ $^ $(libcacard_libs) $(LIBS),"  LINK  $@")
 
 fsdev/virtfs-proxy-helper$(EXESUF): fsdev/virtfs-proxy-helper.o fsdev/virtio-9p-marshal.o oslib-posix.o $(trace-obj-y)
@@ -224,7 +223,7 @@ $(SRC_PATH)/qapi-schema.json $(SRC_PATH)/scripts/qapi-commands.py $(qapi-py)
 QGALIB_GEN=$(addprefix qga/qapi-generated/, qga-qapi-types.h qga-qapi-visit.h qga-qmp-commands.h)
 $(qga-obj-y) qemu-ga.o: $(QGALIB_GEN)
 
-qemu-ga$(EXESUF): qemu-ga.o $(qga-obj-y) $(tools-obj-y) $(qapi-obj-y) $(qobject-obj-y) $(version-obj-y)
+qemu-ga$(EXESUF): qemu-ga.o $(qga-obj-y) $(oslib-obj-y) $(trace-obj-y) $(qapi-obj-y) $(qobject-obj-y) $(version-obj-y)
 
 QEMULIBS=libuser libdis libdis-user
 
diff --git a/Makefile.objs b/Makefile.objs
index 9eca179903..2b5427ee5f 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -19,7 +19,7 @@ universal-obj-y += $(qom-obj-y)
 
 #######################################################################
 # oslib-obj-y is code depending on the OS (win32 vs posix)
-oslib-obj-y = osdep.o
+oslib-obj-y = osdep.o cutils.o qemu-timer-common.o
 oslib-obj-$(CONFIG_WIN32) += oslib-win32.o qemu-thread-win32.o
 oslib-obj-$(CONFIG_POSIX) += oslib-posix.o qemu-thread-posix.o
 
@@ -41,12 +41,12 @@ coroutine-obj-$(CONFIG_WIN32) += coroutine-win32.o
 #######################################################################
 # block-obj-y is code used by both qemu system emulation and qemu-img
 
-block-obj-y = cutils.o iov.o cache-utils.o qemu-option.o module.o async.o
-block-obj-y += nbd.o block.o blockjob.o aio.o aes.o qemu-config.o
-block-obj-y += qemu-progress.o qemu-sockets.o uri.o notify.o
+block-obj-y = iov.o cache-utils.o qemu-option.o module.o async.o
+block-obj-y += nbd.o block.o blockjob.o aes.o qemu-config.o
+block-obj-y += thread-pool.o qemu-progress.o qemu-sockets.o uri.o notify.o
 block-obj-y += $(coroutine-obj-y) $(qobject-obj-y) $(version-obj-y)
-block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
-block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
+block-obj-$(CONFIG_POSIX) += event_notifier-posix.o aio-posix.o
+block-obj-$(CONFIG_WIN32) += event_notifier-win32.o aio-win32.o
 block-obj-y += block/
 block-obj-y += $(qapi-obj-y) qapi-types.o qapi-visit.o
 
@@ -92,9 +92,8 @@ common-obj-y += ui/
 common-obj-y += bt-host.o bt-vhci.o
 
 common-obj-y += dma-helpers.o
-common-obj-y += iov.o acl.o
+common-obj-y += acl.o
 common-obj-$(CONFIG_POSIX) += compatfd.o
-common-obj-y += event_notifier.o
 common-obj-y += qemu-timer.o qemu-timer-common.o
 common-obj-y += qtest.o
 common-obj-y += vl.o
@@ -113,7 +112,7 @@ endif
 user-obj-y =
 user-obj-y += envlist.o path.o
 user-obj-y += tcg-runtime.o host-utils.o
-user-obj-y += cutils.o iov.o cache-utils.o
+user-obj-y += cache-utils.o
 user-obj-y += module.o
 user-obj-y += qemu-user.o
 user-obj-y += $(trace-obj-y)
@@ -228,9 +227,8 @@ universal-obj-y += $(qapi-obj-y)
 ######################################################################
 # guest agent
 
-qga-obj-y = qga/ qemu-ga.o module.o
-qga-obj-$(CONFIG_WIN32) += oslib-win32.o
-qga-obj-$(CONFIG_POSIX) += oslib-posix.o qemu-sockets.o qemu-option.o
+qga-obj-y = qga/ qemu-ga.o module.o qemu-tool.o
+qga-obj-$(CONFIG_POSIX) += qemu-sockets.o qemu-option.o
 
 vl.o: QEMU_CFLAGS+=$(GPROF_CFLAGS)
 
diff --git a/aio-posix.c b/aio-posix.c
new file mode 100644
index 0000000000..05cc84e121
--- /dev/null
+++ b/aio-posix.c
@@ -0,0 +1,268 @@
+/*
+ * QEMU aio implementation
+ *
+ * Copyright IBM, Corp. 2008
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Contributions after 2012-01-13 are licensed under the terms of the
+ * GNU GPL, version 2 or (at your option) any later version.
+ */
+
+#include "qemu-common.h"
+#include "block.h"
+#include "qemu-queue.h"
+#include "qemu_socket.h"
+
+struct AioHandler
+{
+    GPollFD pfd;
+    IOHandler *io_read;
+    IOHandler *io_write;
+    AioFlushHandler *io_flush;
+    int deleted;
+    void *opaque;
+    QLIST_ENTRY(AioHandler) node;
+};
+
+static AioHandler *find_aio_handler(AioContext *ctx, int fd)
+{
+    AioHandler *node;
+
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+        if (node->pfd.fd == fd)
+            if (!node->deleted)
+                return node;
+    }
+
+    return NULL;
+}
+
+void aio_set_fd_handler(AioContext *ctx,
+                        int fd,
+                        IOHandler *io_read,
+                        IOHandler *io_write,
+                        AioFlushHandler *io_flush,
+                        void *opaque)
+{
+    AioHandler *node;
+
+    node = find_aio_handler(ctx, fd);
+
+    /* Are we deleting the fd handler? */
+    if (!io_read && !io_write) {
+        if (node) {
+            g_source_remove_poll(&ctx->source, &node->pfd);
+
+            /* If the lock is held, just mark the node as deleted */
+            if (ctx->walking_handlers) {
+                node->deleted = 1;
+                node->pfd.revents = 0;
+            } else {
+                /* Otherwise, delete it for real.  We can't just mark it as
+                 * deleted because deleted nodes are only cleaned up after
+                 * releasing the walking_handlers lock.
+                 */
+                QLIST_REMOVE(node, node);
+                g_free(node);
+            }
+        }
+    } else {
+        if (node == NULL) {
+            /* Alloc and insert if it's not already there */
+            node = g_malloc0(sizeof(AioHandler));
+            node->pfd.fd = fd;
+            QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node);
+
+            g_source_add_poll(&ctx->source, &node->pfd);
+        }
+        /* Update handler with latest information */
+        node->io_read = io_read;
+        node->io_write = io_write;
+        node->io_flush = io_flush;
+        node->opaque = opaque;
+
+        node->pfd.events = (io_read ? G_IO_IN | G_IO_HUP : 0);
+        node->pfd.events |= (io_write ? G_IO_OUT : 0);
+    }
+
+    aio_notify(ctx);
+}
+
+void aio_set_event_notifier(AioContext *ctx,
+                            EventNotifier *notifier,
+                            EventNotifierHandler *io_read,
+                            AioFlushEventNotifierHandler *io_flush)
+{
+    aio_set_fd_handler(ctx, event_notifier_get_fd(notifier),
+                       (IOHandler *)io_read, NULL,
+                       (AioFlushHandler *)io_flush, notifier);
+}
+
+bool aio_pending(AioContext *ctx)
+{
+    AioHandler *node;
+
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+        int revents;
+
+        /*
+         * FIXME: right now we cannot get G_IO_HUP and G_IO_ERR because
+         * main-loop.c is still select based (due to the slirp legacy).
+         * If main-loop.c ever switches to poll, G_IO_ERR should be
+         * tested too.  Dispatching G_IO_ERR to both handlers should be
+         * okay, since handlers need to be ready for spurious wakeups.
+         */
+        revents = node->pfd.revents & node->pfd.events;
+        if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read) {
+            return true;
+        }
+        if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+bool aio_poll(AioContext *ctx, bool blocking)
+{
+    static struct timeval tv0;
+    AioHandler *node;
+    fd_set rdfds, wrfds;
+    int max_fd = -1;
+    int ret;
+    bool busy, progress;
+
+    progress = false;
+
+    /*
+     * If there are callbacks left that have been queued, we need to call then.
+     * Do not call select in this case, because it is possible that the caller
+     * does not need a complete flush (as is the case for qemu_aio_wait loops).
+     */
+    if (aio_bh_poll(ctx)) {
+        blocking = false;
+        progress = true;
+    }
+
+    /*
+     * Then dispatch any pending callbacks from the GSource.
+     *
+     * We have to walk very carefully in case qemu_aio_set_fd_handler is
+     * called while we're walking.
+     */
+    node = QLIST_FIRST(&ctx->aio_handlers);
+    while (node) {
+        AioHandler *tmp;
+        int revents;
+
+        ctx->walking_handlers++;
+
+        revents = node->pfd.revents & node->pfd.events;
+        node->pfd.revents = 0;
+
+        /* See comment in aio_pending.  */
+        if (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR) && node->io_read) {
+            node->io_read(node->opaque);
+            progress = true;
+        }
+        if (revents & (G_IO_OUT | G_IO_ERR) && node->io_write) {
+            node->io_write(node->opaque);
+            progress = true;
+        }
+
+        tmp = node;
+        node = QLIST_NEXT(node, node);
+
+        ctx->walking_handlers--;
+
+        if (!ctx->walking_handlers && tmp->deleted) {
+            QLIST_REMOVE(tmp, node);
+            g_free(tmp);
+        }
+    }
+
+    if (progress && !blocking) {
+        return true;
+    }
+
+    ctx->walking_handlers++;
+
+    FD_ZERO(&rdfds);
+    FD_ZERO(&wrfds);
+
+    /* fill fd sets */
+    busy = false;
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+        /* If there aren't pending AIO operations, don't invoke callbacks.
+         * Otherwise, if there are no AIO requests, qemu_aio_wait() would
+         * wait indefinitely.
+         */
+        if (!node->deleted && node->io_flush) {
+            if (node->io_flush(node->opaque) == 0) {
+                continue;
+            }
+            busy = true;
+        }
+        if (!node->deleted && node->io_read) {
+            FD_SET(node->pfd.fd, &rdfds);
+            max_fd = MAX(max_fd, node->pfd.fd + 1);
+        }
+        if (!node->deleted && node->io_write) {
+            FD_SET(node->pfd.fd, &wrfds);
+            max_fd = MAX(max_fd, node->pfd.fd + 1);
+        }
+    }
+
+    ctx->walking_handlers--;
+
+    /* No AIO operations?  Get us out of here */
+    if (!busy) {
+        return progress;
+    }
+
+    /* wait until next event */
+    ret = select(max_fd, &rdfds, &wrfds, NULL, blocking ? NULL : &tv0);
+
+    /* if we have any readable fds, dispatch event */
+    if (ret > 0) {
+        /* we have to walk very carefully in case
+         * qemu_aio_set_fd_handler is called while we're walking */
+        node = QLIST_FIRST(&ctx->aio_handlers);
+        while (node) {
+            AioHandler *tmp;
+
+            ctx->walking_handlers++;
+
+            if (!node->deleted &&
+                FD_ISSET(node->pfd.fd, &rdfds) &&
+                node->io_read) {
+                node->io_read(node->opaque);
+                progress = true;
+            }
+            if (!node->deleted &&
+                FD_ISSET(node->pfd.fd, &wrfds) &&
+                node->io_write) {
+                node->io_write(node->opaque);
+                progress = true;
+            }
+
+            tmp = node;
+            node = QLIST_NEXT(node, node);
+
+            ctx->walking_handlers--;
+
+            if (!ctx->walking_handlers && tmp->deleted) {
+                QLIST_REMOVE(tmp, node);
+                g_free(tmp);
+            }
+        }
+    }
+
+    return progress;
+}
diff --git a/aio-win32.c b/aio-win32.c
new file mode 100644
index 0000000000..a84eb71246
--- /dev/null
+++ b/aio-win32.c
@@ -0,0 +1,215 @@
+/*
+ * QEMU aio implementation
+ *
+ * Copyright IBM Corp., 2008
+ * Copyright Red Hat Inc., 2012
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Paolo Bonzini     <pbonzini@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Contributions after 2012-01-13 are licensed under the terms of the
+ * GNU GPL, version 2 or (at your option) any later version.
+ */
+
+#include "qemu-common.h"
+#include "block.h"
+#include "qemu-queue.h"
+#include "qemu_socket.h"
+
+struct AioHandler {
+    EventNotifier *e;
+    EventNotifierHandler *io_notify;
+    AioFlushEventNotifierHandler *io_flush;
+    GPollFD pfd;
+    int deleted;
+    QLIST_ENTRY(AioHandler) node;
+};
+
+void aio_set_event_notifier(AioContext *ctx,
+                            EventNotifier *e,
+                            EventNotifierHandler *io_notify,
+                            AioFlushEventNotifierHandler *io_flush)
+{
+    AioHandler *node;
+
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+        if (node->e == e && !node->deleted) {
+            break;
+        }
+    }
+
+    /* Are we deleting the fd handler? */
+    if (!io_notify) {
+        if (node) {
+            g_source_remove_poll(&ctx->source, &node->pfd);
+
+            /* If the lock is held, just mark the node as deleted */
+            if (ctx->walking_handlers) {
+                node->deleted = 1;
+                node->pfd.revents = 0;
+            } else {
+                /* Otherwise, delete it for real.  We can't just mark it as
+                 * deleted because deleted nodes are only cleaned up after
+                 * releasing the walking_handlers lock.
+                 */
+                QLIST_REMOVE(node, node);
+                g_free(node);
+            }
+        }
+    } else {
+        if (node == NULL) {
+            /* Alloc and insert if it's not already there */
+            node = g_malloc0(sizeof(AioHandler));
+            node->e = e;
+            node->pfd.fd = (uintptr_t)event_notifier_get_handle(e);
+            node->pfd.events = G_IO_IN;
+            QLIST_INSERT_HEAD(&ctx->aio_handlers, node, node);
+
+            g_source_add_poll(&ctx->source, &node->pfd);
+        }
+        /* Update handler with latest information */
+        node->io_notify = io_notify;
+        node->io_flush = io_flush;
+    }
+
+    aio_notify(ctx);
+}
+
+bool aio_pending(AioContext *ctx)
+{
+    AioHandler *node;
+
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+        if (node->pfd.revents && node->io_notify) {
+            return true;
+        }
+    }
+
+    return false;
+}
+
+bool aio_poll(AioContext *ctx, bool blocking)
+{
+    AioHandler *node;
+    HANDLE events[MAXIMUM_WAIT_OBJECTS + 1];
+    bool busy, progress;
+    int count;
+
+    progress = false;
+
+    /*
+     * If there are callbacks left that have been queued, we need to call then.
+     * Do not call select in this case, because it is possible that the caller
+     * does not need a complete flush (as is the case for qemu_aio_wait loops).
+     */
+    if (aio_bh_poll(ctx)) {
+        blocking = false;
+        progress = true;
+    }
+
+    /*
+     * Then dispatch any pending callbacks from the GSource.
+     *
+     * We have to walk very carefully in case qemu_aio_set_fd_handler is
+     * called while we're walking.
+     */
+    node = QLIST_FIRST(&ctx->aio_handlers);
+    while (node) {
+        AioHandler *tmp;
+
+        ctx->walking_handlers++;
+
+        if (node->pfd.revents && node->io_notify) {
+            node->pfd.revents = 0;
+            node->io_notify(node->e);
+            progress = true;
+        }
+
+        tmp = node;
+        node = QLIST_NEXT(node, node);
+
+        ctx->walking_handlers--;
+
+        if (!ctx->walking_handlers && tmp->deleted) {
+            QLIST_REMOVE(tmp, node);
+            g_free(tmp);
+        }
+    }
+
+    if (progress && !blocking) {
+        return true;
+    }
+
+    ctx->walking_handlers++;
+
+    /* fill fd sets */
+    busy = false;
+    count = 0;
+    QLIST_FOREACH(node, &ctx->aio_handlers, node) {
+        /* If there aren't pending AIO operations, don't invoke callbacks.
+         * Otherwise, if there are no AIO requests, qemu_aio_wait() would
+         * wait indefinitely.
+         */
+        if (!node->deleted && node->io_flush) {
+            if (node->io_flush(node->e) == 0) {
+                continue;
+            }
+            busy = true;
+        }
+        if (!node->deleted && node->io_notify) {
+            events[count++] = event_notifier_get_handle(node->e);
+        }
+    }
+
+    ctx->walking_handlers--;
+
+    /* No AIO operations?  Get us out of here */
+    if (!busy) {
+        return progress;
+    }
+
+    /* wait until next event */
+    for (;;) {
+        int timeout = blocking ? INFINITE : 0;
+        int ret = WaitForMultipleObjects(count, events, FALSE, timeout);
+
+        /* if we have any signaled events, dispatch event */
+        if ((DWORD) (ret - WAIT_OBJECT_0) >= count) {
+            break;
+        }
+
+        blocking = false;
+
+        /* we have to walk very carefully in case
+         * qemu_aio_set_fd_handler is called while we're walking */
+        node = QLIST_FIRST(&ctx->aio_handlers);
+        while (node) {
+            AioHandler *tmp;
+
+            ctx->walking_handlers++;
+
+            if (!node->deleted &&
+                event_notifier_get_handle(node->e) == events[ret - WAIT_OBJECT_0] &&
+                node->io_notify) {
+                node->io_notify(node->e);
+                progress = true;
+            }
+
+            tmp = node;
+            node = QLIST_NEXT(node, node);
+
+            ctx->walking_handlers--;
+
+            if (!ctx->walking_handlers && tmp->deleted) {
+                QLIST_REMOVE(tmp, node);
+                g_free(tmp);
+            }
+        }
+    }
+
+    return progress;
+}
diff --git a/aio.c b/aio.c
deleted file mode 100644
index c738a4e15d..0000000000
--- a/aio.c
+++ /dev/null
@@ -1,194 +0,0 @@
-/*
- * QEMU aio implementation
- *
- * Copyright IBM, Corp. 2008
- *
- * Authors:
- *  Anthony Liguori   <aliguori@us.ibm.com>
- *
- * This work is licensed under the terms of the GNU GPL, version 2.  See
- * the COPYING file in the top-level directory.
- *
- * Contributions after 2012-01-13 are licensed under the terms of the
- * GNU GPL, version 2 or (at your option) any later version.
- */
-
-#include "qemu-common.h"
-#include "block.h"
-#include "qemu-queue.h"
-#include "qemu_socket.h"
-
-typedef struct AioHandler AioHandler;
-
-/* The list of registered AIO handlers */
-static QLIST_HEAD(, AioHandler) aio_handlers;
-
-/* This is a simple lock used to protect the aio_handlers list.  Specifically,
- * it's used to ensure that no callbacks are removed while we're walking and
- * dispatching callbacks.
- */
-static int walking_handlers;
-
-struct AioHandler
-{
-    int fd;
-    IOHandler *io_read;
-    IOHandler *io_write;
-    AioFlushHandler *io_flush;
-    int deleted;
-    void *opaque;
-    QLIST_ENTRY(AioHandler) node;
-};
-
-static AioHandler *find_aio_handler(int fd)
-{
-    AioHandler *node;
-
-    QLIST_FOREACH(node, &aio_handlers, node) {
-        if (node->fd == fd)
-            if (!node->deleted)
-                return node;
-    }
-
-    return NULL;
-}
-
-int qemu_aio_set_fd_handler(int fd,
-                            IOHandler *io_read,
-                            IOHandler *io_write,
-                            AioFlushHandler *io_flush,
-                            void *opaque)
-{
-    AioHandler *node;
-
-    node = find_aio_handler(fd);
-
-    /* Are we deleting the fd handler? */
-    if (!io_read && !io_write) {
-        if (node) {
-            /* If the lock is held, just mark the node as deleted */
-            if (walking_handlers)
-                node->deleted = 1;
-            else {
-                /* Otherwise, delete it for real.  We can't just mark it as
-                 * deleted because deleted nodes are only cleaned up after
-                 * releasing the walking_handlers lock.
-                 */
-                QLIST_REMOVE(node, node);
-                g_free(node);
-            }
-        }
-    } else {
-        if (node == NULL) {
-            /* Alloc and insert if it's not already there */
-            node = g_malloc0(sizeof(AioHandler));
-            node->fd = fd;
-            QLIST_INSERT_HEAD(&aio_handlers, node, node);
-        }
-        /* Update handler with latest information */
-        node->io_read = io_read;
-        node->io_write = io_write;
-        node->io_flush = io_flush;
-        node->opaque = opaque;
-    }
-
-    qemu_set_fd_handler2(fd, NULL, io_read, io_write, opaque);
-
-    return 0;
-}
-
-void qemu_aio_flush(void)
-{
-    while (qemu_aio_wait());
-}
-
-bool qemu_aio_wait(void)
-{
-    AioHandler *node;
-    fd_set rdfds, wrfds;
-    int max_fd = -1;
-    int ret;
-    bool busy;
-
-    /*
-     * If there are callbacks left that have been queued, we need to call then.
-     * Do not call select in this case, because it is possible that the caller
-     * does not need a complete flush (as is the case for qemu_aio_wait loops).
-     */
-    if (qemu_bh_poll()) {
-        return true;
-    }
-
-    walking_handlers++;
-
-    FD_ZERO(&rdfds);
-    FD_ZERO(&wrfds);
-
-    /* fill fd sets */
-    busy = false;
-    QLIST_FOREACH(node, &aio_handlers, node) {
-        /* If there aren't pending AIO operations, don't invoke callbacks.
-         * Otherwise, if there are no AIO requests, qemu_aio_wait() would
-         * wait indefinitely.
-         */
-        if (node->io_flush) {
-            if (node->io_flush(node->opaque) == 0) {
-                continue;
-            }
-            busy = true;
-        }
-        if (!node->deleted && node->io_read) {
-            FD_SET(node->fd, &rdfds);
-            max_fd = MAX(max_fd, node->fd + 1);
-        }
-        if (!node->deleted && node->io_write) {
-            FD_SET(node->fd, &wrfds);
-            max_fd = MAX(max_fd, node->fd + 1);
-        }
-    }
-
-    walking_handlers--;
-
-    /* No AIO operations?  Get us out of here */
-    if (!busy) {
-        return false;
-    }
-
-    /* wait until next event */
-    ret = select(max_fd, &rdfds, &wrfds, NULL, NULL);
-
-    /* if we have any readable fds, dispatch event */
-    if (ret > 0) {
-        /* we have to walk very carefully in case
-         * qemu_aio_set_fd_handler is called while we're walking */
-        node = QLIST_FIRST(&aio_handlers);
-        while (node) {
-            AioHandler *tmp;
-
-            walking_handlers++;
-
-            if (!node->deleted &&
-                FD_ISSET(node->fd, &rdfds) &&
-                node->io_read) {
-                node->io_read(node->opaque);
-            }
-            if (!node->deleted &&
-                FD_ISSET(node->fd, &wrfds) &&
-                node->io_write) {
-                node->io_write(node->opaque);
-            }
-
-            tmp = node;
-            node = QLIST_NEXT(node, node);
-
-            walking_handlers--;
-
-            if (!walking_handlers && tmp->deleted) {
-                QLIST_REMOVE(tmp, node);
-                g_free(tmp);
-            }
-        }
-    }
-
-    return true;
-}
diff --git a/arch_init.h b/arch_init.h
index d9c572aee8..5fc780c63d 100644
--- a/arch_init.h
+++ b/arch_init.h
@@ -34,6 +34,6 @@ int tcg_available(void);
 int kvm_available(void);
 int xen_available(void);
 
-CpuDefinitionInfoList GCC_WEAK_DECL *arch_query_cpu_definitions(Error **errp);
+CpuDefinitionInfoList *arch_query_cpu_definitions(Error **errp);
 
 #endif
diff --git a/async.c b/async.c
index 85cc6410c5..04f9dcbb4d 100644
--- a/async.c
+++ b/async.c
@@ -26,13 +26,11 @@
 #include "qemu-aio.h"
 #include "main-loop.h"
 
-/* Anchor of the list of Bottom Halves belonging to the context */
-static struct QEMUBH *first_bh;
-
 /***********************************************************/
 /* bottom halves (can be seen as timers which expire ASAP) */
 
 struct QEMUBH {
+    AioContext *ctx;
     QEMUBHFunc *cb;
     void *opaque;
     QEMUBH *next;
@@ -41,27 +39,27 @@ struct QEMUBH {
     bool deleted;
 };
 
-QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque)
+QEMUBH *aio_bh_new(AioContext *ctx, QEMUBHFunc *cb, void *opaque)
 {
     QEMUBH *bh;
     bh = g_malloc0(sizeof(QEMUBH));
+    bh->ctx = ctx;
     bh->cb = cb;
     bh->opaque = opaque;
-    bh->next = first_bh;
-    first_bh = bh;
+    bh->next = ctx->first_bh;
+    ctx->first_bh = bh;
     return bh;
 }
 
-int qemu_bh_poll(void)
+int aio_bh_poll(AioContext *ctx)
 {
     QEMUBH *bh, **bhp, *next;
     int ret;
-    static int nesting = 0;
 
-    nesting++;
+    ctx->walking_bh++;
 
     ret = 0;
-    for (bh = first_bh; bh; bh = next) {
+    for (bh = ctx->first_bh; bh; bh = next) {
         next = bh->next;
         if (!bh->deleted && bh->scheduled) {
             bh->scheduled = 0;
@@ -72,11 +70,11 @@ int qemu_bh_poll(void)
         }
     }
 
-    nesting--;
+    ctx->walking_bh--;
 
     /* remove deleted bhs */
-    if (!nesting) {
-        bhp = &first_bh;
+    if (!ctx->walking_bh) {
+        bhp = &ctx->first_bh;
         while (*bhp) {
             bh = *bhp;
             if (bh->deleted) {
@@ -105,8 +103,7 @@ void qemu_bh_schedule(QEMUBH *bh)
         return;
     bh->scheduled = 1;
     bh->idle = 0;
-    /* stop the currently executing CPU to execute the BH ASAP */
-    qemu_notify_event();
+    aio_notify(bh->ctx);
 }
 
 void qemu_bh_cancel(QEMUBH *bh)
@@ -120,16 +117,20 @@ void qemu_bh_delete(QEMUBH *bh)
     bh->deleted = 1;
 }
 
-void qemu_bh_update_timeout(uint32_t *timeout)
+static gboolean
+aio_ctx_prepare(GSource *source, gint    *timeout)
 {
+    AioContext *ctx = (AioContext *) source;
     QEMUBH *bh;
+    bool scheduled = false;
 
-    for (bh = first_bh; bh; bh = bh->next) {
+    for (bh = ctx->first_bh; bh; bh = bh->next) {
         if (!bh->deleted && bh->scheduled) {
+            scheduled = true;
             if (bh->idle) {
                 /* idle bottom halves will be polled at least
                  * every 10ms */
-                *timeout = MIN(10, *timeout);
+                *timeout = 10;
             } else {
                 /* non-idle bottom halves will be executed
                  * immediately */
@@ -138,5 +139,86 @@ void qemu_bh_update_timeout(uint32_t *timeout)
             }
         }
     }
+
+    return scheduled;
+}
+
+static gboolean
+aio_ctx_check(GSource *source)
+{
+    AioContext *ctx = (AioContext *) source;
+    QEMUBH *bh;
+
+    for (bh = ctx->first_bh; bh; bh = bh->next) {
+        if (!bh->deleted && bh->scheduled) {
+            return true;
+	}
+    }
+    return aio_pending(ctx);
+}
+
+static gboolean
+aio_ctx_dispatch(GSource     *source,
+                 GSourceFunc  callback,
+                 gpointer     user_data)
+{
+    AioContext *ctx = (AioContext *) source;
+
+    assert(callback == NULL);
+    aio_poll(ctx, false);
+    return true;
+}
+
+static void
+aio_ctx_finalize(GSource     *source)
+{
+    AioContext *ctx = (AioContext *) source;
+
+    aio_set_event_notifier(ctx, &ctx->notifier, NULL, NULL);
+    event_notifier_cleanup(&ctx->notifier);
+}
+
+static GSourceFuncs aio_source_funcs = {
+    aio_ctx_prepare,
+    aio_ctx_check,
+    aio_ctx_dispatch,
+    aio_ctx_finalize
+};
+
+GSource *aio_get_g_source(AioContext *ctx)
+{
+    g_source_ref(&ctx->source);
+    return &ctx->source;
+}
+
+void aio_notify(AioContext *ctx)
+{
+    event_notifier_set(&ctx->notifier);
+}
+
+AioContext *aio_context_new(void)
+{
+    AioContext *ctx;
+    ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
+    event_notifier_init(&ctx->notifier, false);
+    aio_set_event_notifier(ctx, &ctx->notifier, 
+                           (EventNotifierHandler *)
+                           event_notifier_test_and_clear, NULL);
+
+    return ctx;
 }
 
+void aio_context_ref(AioContext *ctx)
+{
+    g_source_ref(&ctx->source);
+}
+
+void aio_context_unref(AioContext *ctx)
+{
+    g_source_unref(&ctx->source);
+}
+
+void aio_flush(AioContext *ctx)
+{
+    while (aio_poll(ctx, true));
+}
diff --git a/block/Makefile.objs b/block/Makefile.objs
index 806e526eb4..7f015105b1 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -2,13 +2,18 @@ block-obj-y += raw.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o vpc.o vvfat
 block-obj-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o qcow2-cache.o
 block-obj-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
 block-obj-y += qed-check.o
-block-obj-y += parallels.o nbd.o blkdebug.o sheepdog.o blkverify.o
-block-obj-$(CONFIG_WIN32) += raw-win32.o
+block-obj-y += parallels.o blkdebug.o blkverify.o
+block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
 block-obj-$(CONFIG_POSIX) += raw-posix.o
+block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
+
+ifeq ($(CONFIG_POSIX),y)
+block-obj-y += nbd.o sheepdog.o
 block-obj-$(CONFIG_LIBISCSI) += iscsi.o
 block-obj-$(CONFIG_CURL) += curl.o
 block-obj-$(CONFIG_RBD) += rbd.o
 block-obj-$(CONFIG_GLUSTERFS) += gluster.o
+endif
 
 common-obj-y += stream.o
 common-obj-y += commit.o
diff --git a/linux-aio.c b/block/linux-aio.c
index ce9b5d4be8..6ca984dbe8 100644
--- a/linux-aio.c
+++ b/block/linux-aio.c
@@ -9,9 +9,10 @@
  */
 #include "qemu-common.h"
 #include "qemu-aio.h"
-#include "block/raw-posix-aio.h"
+#include "qemu-queue.h"
+#include "block/raw-aio.h"
+#include "event_notifier.h"
 
-#include <sys/eventfd.h>
 #include <libaio.h>
 
 /*
@@ -37,7 +38,7 @@ struct qemu_laiocb {
 
 struct qemu_laio_state {
     io_context_t ctx;
-    int efd;
+    EventNotifier e;
     int count;
 };
 
@@ -76,29 +77,17 @@ static void qemu_laio_process_completion(struct qemu_laio_state *s,
     qemu_aio_release(laiocb);
 }
 
-static void qemu_laio_completion_cb(void *opaque)
+static void qemu_laio_completion_cb(EventNotifier *e)
 {
-    struct qemu_laio_state *s = opaque;
+    struct qemu_laio_state *s = container_of(e, struct qemu_laio_state, e);
 
-    while (1) {
+    while (event_notifier_test_and_clear(&s->e)) {
         struct io_event events[MAX_EVENTS];
-        uint64_t val;
-        ssize_t ret;
         struct timespec ts = { 0 };
         int nevents, i;
 
         do {
-            ret = read(s->efd, &val, sizeof(val));
-        } while (ret == -1 && errno == EINTR);
-
-        if (ret == -1 && errno == EAGAIN)
-            break;
-
-        if (ret != 8)
-            break;
-
-        do {
-            nevents = io_getevents(s->ctx, val, MAX_EVENTS, events, &ts);
+            nevents = io_getevents(s->ctx, MAX_EVENTS, MAX_EVENTS, events, &ts);
         } while (nevents == -EINTR);
 
         for (i = 0; i < nevents; i++) {
@@ -112,9 +101,9 @@ static void qemu_laio_completion_cb(void *opaque)
     }
 }
 
-static int qemu_laio_flush_cb(void *opaque)
+static int qemu_laio_flush_cb(EventNotifier *e)
 {
-    struct qemu_laio_state *s = opaque;
+    struct qemu_laio_state *s = container_of(e, struct qemu_laio_state, e);
 
     return (s->count > 0) ? 1 : 0;
 }
@@ -146,8 +135,9 @@ static void laio_cancel(BlockDriverAIOCB *blockacb)
      * We might be able to do this slightly more optimal by removing the
      * O_NONBLOCK flag.
      */
-    while (laiocb->ret == -EINPROGRESS)
-        qemu_laio_completion_cb(laiocb->ctx);
+    while (laiocb->ret == -EINPROGRESS) {
+        qemu_laio_completion_cb(&laiocb->ctx->e);
+    }
 }
 
 static AIOPool laio_pool = {
@@ -186,7 +176,7 @@ BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
                         __func__, type);
         goto out_free_aiocb;
     }
-    io_set_eventfd(&laiocb->iocb, s->efd);
+    io_set_eventfd(&laiocb->iocb, event_notifier_get_fd(&s->e));
     s->count++;
 
     if (io_submit(s->ctx, 1, &iocbs) < 0)
@@ -205,21 +195,21 @@ void *laio_init(void)
     struct qemu_laio_state *s;
 
     s = g_malloc0(sizeof(*s));
-    s->efd = eventfd(0, 0);
-    if (s->efd == -1)
+    if (event_notifier_init(&s->e, false) < 0) {
         goto out_free_state;
-    fcntl(s->efd, F_SETFL, O_NONBLOCK);
+    }
 
-    if (io_setup(MAX_EVENTS, &s->ctx) != 0)
+    if (io_setup(MAX_EVENTS, &s->ctx) != 0) {
         goto out_close_efd;
+    }
 
-    qemu_aio_set_fd_handler(s->efd, qemu_laio_completion_cb, NULL,
-        qemu_laio_flush_cb, s);
+    qemu_aio_set_event_notifier(&s->e, qemu_laio_completion_cb,
+                                qemu_laio_flush_cb);
 
     return s;
 
 out_close_efd:
-    close(s->efd);
+    event_notifier_cleanup(&s->e);
 out_free_state:
     g_free(s);
     return NULL;
diff --git a/block/raw-posix-aio.h b/block/raw-aio.h
index ba118f616b..e77f361148 100644
--- a/block/raw-posix-aio.h
+++ b/block/raw-aio.h
@@ -1,5 +1,5 @@
 /*
- * QEMU Posix block I/O backend AIO support
+ * Declarations for AIO in the raw protocol
  *
  * Copyright IBM, Corp. 2008
  *
@@ -12,8 +12,8 @@
  * Contributions after 2012-01-13 are licensed under the terms of the
  * GNU GPL, version 2 or (at your option) any later version.
  */
-#ifndef QEMU_RAW_POSIX_AIO_H
-#define QEMU_RAW_POSIX_AIO_H
+#ifndef QEMU_RAW_AIO_H
+#define QEMU_RAW_AIO_H
 
 /* AIO request types */
 #define QEMU_AIO_READ         0x0001
@@ -27,19 +27,22 @@
 #define QEMU_AIO_MISALIGNED   0x1000
 
 
-/* posix-aio-compat.c - thread pool based implementation */
-int paio_init(void);
-BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
-        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
-        BlockDriverCompletionFunc *cb, void *opaque, int type);
-BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
-        unsigned long int req, void *buf,
-        BlockDriverCompletionFunc *cb, void *opaque);
-
 /* linux-aio.c - Linux native implementation */
+#ifdef CONFIG_LINUX_AIO
 void *laio_init(void);
 BlockDriverAIOCB *laio_submit(BlockDriverState *bs, void *aio_ctx, int fd,
         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
         BlockDriverCompletionFunc *cb, void *opaque, int type);
+#endif
+
+#ifdef _WIN32
+typedef struct QEMUWin32AIOState QEMUWin32AIOState;
+QEMUWin32AIOState *win32_aio_init(void);
+int win32_aio_attach(QEMUWin32AIOState *aio, HANDLE hfile);
+BlockDriverAIOCB *win32_aio_submit(BlockDriverState *bs,
+        QEMUWin32AIOState *aio, HANDLE hfile,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockDriverCompletionFunc *cb, void *opaque, int type);
+#endif
 
-#endif /* QEMU_RAW_POSIX_AIO_H */
+#endif /* QEMU_RAW_AIO_H */
diff --git a/block/raw-posix.c b/block/raw-posix.c
index 28d439fa81..f2f0404f6f 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -27,7 +27,10 @@
 #include "qemu-log.h"
 #include "block_int.h"
 #include "module.h"
-#include "block/raw-posix-aio.h"
+#include "trace.h"
+#include "thread-pool.h"
+#include "iov.h"
+#include "raw-aio.h"
 
 #if defined(__APPLE__) && (__MACH__)
 #include <paths.h>
@@ -149,6 +152,20 @@ typedef struct BDRVRawReopenState {
 static int fd_open(BlockDriverState *bs);
 static int64_t raw_getlength(BlockDriverState *bs);
 
+typedef struct RawPosixAIOData {
+    BlockDriverState *bs;
+    int aio_fildes;
+    union {
+        struct iovec *aio_iov;
+        void *aio_ioctl_buf;
+    };
+    int aio_niov;
+    size_t aio_nbytes;
+#define aio_ioctl_cmd   aio_nbytes /* for QEMU_AIO_IOCTL */
+    off_t aio_offset;
+    int aio_type;
+} RawPosixAIOData;
+
 #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
 static int cdrom_reopen(BlockDriverState *bs);
 #endif
@@ -266,14 +283,10 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
     }
     s->fd = fd;
 
-    /* We're falling back to POSIX AIO in some cases so init always */
-    if (paio_init() < 0) {
-        goto out_close;
-    }
-
 #ifdef CONFIG_LINUX_AIO
     if (raw_set_aio(&s->aio_ctx, &s->use_aio, bdrv_flags)) {
-        goto out_close;
+        qemu_close(fd);
+        return -errno;
     }
 #endif
 
@@ -284,10 +297,6 @@ static int raw_open_common(BlockDriverState *bs, const char *filename,
 #endif
 
     return 0;
-
-out_close:
-    qemu_close(fd);
-    return -errno;
 }
 
 static int raw_open(BlockDriverState *bs, const char *filename, int flags)
@@ -434,6 +443,283 @@ static int qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov)
     return 1;
 }
 
+static ssize_t handle_aiocb_ioctl(RawPosixAIOData *aiocb)
+{
+    int ret;
+
+    ret = ioctl(aiocb->aio_fildes, aiocb->aio_ioctl_cmd, aiocb->aio_ioctl_buf);
+    if (ret == -1) {
+        return -errno;
+    }
+
+    /*
+     * This looks weird, but the aio code only considers a request
+     * successful if it has written the full number of bytes.
+     *
+     * Now we overload aio_nbytes as aio_ioctl_cmd for the ioctl command,
+     * so in fact we return the ioctl command here to make posix_aio_read()
+     * happy..
+     */
+    return aiocb->aio_nbytes;
+}
+
+static ssize_t handle_aiocb_flush(RawPosixAIOData *aiocb)
+{
+    int ret;
+
+    ret = qemu_fdatasync(aiocb->aio_fildes);
+    if (ret == -1) {
+        return -errno;
+    }
+    return 0;
+}
+
+#ifdef CONFIG_PREADV
+
+static bool preadv_present = true;
+
+static ssize_t
+qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)
+{
+    return preadv(fd, iov, nr_iov, offset);
+}
+
+static ssize_t
+qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)
+{
+    return pwritev(fd, iov, nr_iov, offset);
+}
+
+#else
+
+static bool preadv_present = false;
+
+static ssize_t
+qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)
+{
+    return -ENOSYS;
+}
+
+static ssize_t
+qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)
+{
+    return -ENOSYS;
+}
+
+#endif
+
+static ssize_t handle_aiocb_rw_vector(RawPosixAIOData *aiocb)
+{
+    ssize_t len;
+
+    do {
+        if (aiocb->aio_type & QEMU_AIO_WRITE)
+            len = qemu_pwritev(aiocb->aio_fildes,
+                               aiocb->aio_iov,
+                               aiocb->aio_niov,
+                               aiocb->aio_offset);
+         else
+            len = qemu_preadv(aiocb->aio_fildes,
+                              aiocb->aio_iov,
+                              aiocb->aio_niov,
+                              aiocb->aio_offset);
+    } while (len == -1 && errno == EINTR);
+
+    if (len == -1) {
+        return -errno;
+    }
+    return len;
+}
+
+/*
+ * Read/writes the data to/from a given linear buffer.
+ *
+ * Returns the number of bytes handles or -errno in case of an error. Short
+ * reads are only returned if the end of the file is reached.
+ */
+static ssize_t handle_aiocb_rw_linear(RawPosixAIOData *aiocb, char *buf)
+{
+    ssize_t offset = 0;
+    ssize_t len;
+
+    while (offset < aiocb->aio_nbytes) {
+        if (aiocb->aio_type & QEMU_AIO_WRITE) {
+            len = pwrite(aiocb->aio_fildes,
+                         (const char *)buf + offset,
+                         aiocb->aio_nbytes - offset,
+                         aiocb->aio_offset + offset);
+        } else {
+            len = pread(aiocb->aio_fildes,
+                        buf + offset,
+                        aiocb->aio_nbytes - offset,
+                        aiocb->aio_offset + offset);
+        }
+        if (len == -1 && errno == EINTR) {
+            continue;
+        } else if (len == -1) {
+            offset = -errno;
+            break;
+        } else if (len == 0) {
+            break;
+        }
+        offset += len;
+    }
+
+    return offset;
+}
+
+static ssize_t handle_aiocb_rw(RawPosixAIOData *aiocb)
+{
+    ssize_t nbytes;
+    char *buf;
+
+    if (!(aiocb->aio_type & QEMU_AIO_MISALIGNED)) {
+        /*
+         * If there is just a single buffer, and it is properly aligned
+         * we can just use plain pread/pwrite without any problems.
+         */
+        if (aiocb->aio_niov == 1) {
+             return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base);
+        }
+        /*
+         * We have more than one iovec, and all are properly aligned.
+         *
+         * Try preadv/pwritev first and fall back to linearizing the
+         * buffer if it's not supported.
+         */
+        if (preadv_present) {
+            nbytes = handle_aiocb_rw_vector(aiocb);
+            if (nbytes == aiocb->aio_nbytes ||
+                (nbytes < 0 && nbytes != -ENOSYS)) {
+                return nbytes;
+            }
+            preadv_present = false;
+        }
+
+        /*
+         * XXX(hch): short read/write.  no easy way to handle the reminder
+         * using these interfaces.  For now retry using plain
+         * pread/pwrite?
+         */
+    }
+
+    /*
+     * Ok, we have to do it the hard way, copy all segments into
+     * a single aligned buffer.
+     */
+    buf = qemu_blockalign(aiocb->bs, aiocb->aio_nbytes);
+    if (aiocb->aio_type & QEMU_AIO_WRITE) {
+        char *p = buf;
+        int i;
+
+        for (i = 0; i < aiocb->aio_niov; ++i) {
+            memcpy(p, aiocb->aio_iov[i].iov_base, aiocb->aio_iov[i].iov_len);
+            p += aiocb->aio_iov[i].iov_len;
+        }
+    }
+
+    nbytes = handle_aiocb_rw_linear(aiocb, buf);
+    if (!(aiocb->aio_type & QEMU_AIO_WRITE)) {
+        char *p = buf;
+        size_t count = aiocb->aio_nbytes, copy;
+        int i;
+
+        for (i = 0; i < aiocb->aio_niov && count; ++i) {
+            copy = count;
+            if (copy > aiocb->aio_iov[i].iov_len) {
+                copy = aiocb->aio_iov[i].iov_len;
+            }
+            memcpy(aiocb->aio_iov[i].iov_base, p, copy);
+            p     += copy;
+            count -= copy;
+        }
+    }
+    qemu_vfree(buf);
+
+    return nbytes;
+}
+
+static int aio_worker(void *arg)
+{
+    RawPosixAIOData *aiocb = arg;
+    ssize_t ret = 0;
+
+    switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
+    case QEMU_AIO_READ:
+        ret = handle_aiocb_rw(aiocb);
+        if (ret >= 0 && ret < aiocb->aio_nbytes && aiocb->bs->growable) {
+            iov_memset(aiocb->aio_iov, aiocb->aio_niov, ret,
+                      0, aiocb->aio_nbytes - ret);
+
+            ret = aiocb->aio_nbytes;
+        }
+        if (ret == aiocb->aio_nbytes) {
+            ret = 0;
+        } else if (ret >= 0 && ret < aiocb->aio_nbytes) {
+            ret = -EINVAL;
+        }
+        break;
+    case QEMU_AIO_WRITE:
+        ret = handle_aiocb_rw(aiocb);
+        if (ret == aiocb->aio_nbytes) {
+            ret = 0;
+        } else if (ret >= 0 && ret < aiocb->aio_nbytes) {
+            ret = -EINVAL;
+        }
+        break;
+    case QEMU_AIO_FLUSH:
+        ret = handle_aiocb_flush(aiocb);
+        break;
+    case QEMU_AIO_IOCTL:
+        ret = handle_aiocb_ioctl(aiocb);
+        break;
+    default:
+        fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
+        ret = -EINVAL;
+        break;
+    }
+
+    g_slice_free(RawPosixAIOData, aiocb);
+    return ret;
+}
+
+static BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockDriverCompletionFunc *cb, void *opaque, int type)
+{
+    RawPosixAIOData *acb = g_slice_new(RawPosixAIOData);
+
+    acb->bs = bs;
+    acb->aio_type = type;
+    acb->aio_fildes = fd;
+
+    if (qiov) {
+        acb->aio_iov = qiov->iov;
+        acb->aio_niov = qiov->niov;
+    }
+    acb->aio_nbytes = nb_sectors * 512;
+    acb->aio_offset = sector_num * 512;
+
+    trace_paio_submit(acb, opaque, sector_num, nb_sectors, type);
+    return thread_pool_submit_aio(aio_worker, acb, cb, opaque);
+}
+
+static BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
+        unsigned long int req, void *buf,
+        BlockDriverCompletionFunc *cb, void *opaque)
+{
+    RawPosixAIOData *acb = g_slice_new(RawPosixAIOData);
+
+    acb->bs = bs;
+    acb->aio_type = QEMU_AIO_IOCTL;
+    acb->aio_fildes = fd;
+    acb->aio_offset = 0;
+    acb->aio_ioctl_buf = buf;
+    acb->aio_ioctl_cmd = req;
+
+    return thread_pool_submit_aio(aio_worker, acb, cb, opaque);
+}
+
 static BlockDriverAIOCB *raw_aio_submit(BlockDriverState *bs,
         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
         BlockDriverCompletionFunc *cb, void *opaque, int type)
diff --git a/block/raw-win32.c b/block/raw-win32.c
index 78c830648b..0c05c58c5a 100644
--- a/block/raw-win32.c
+++ b/block/raw-win32.c
@@ -25,6 +25,10 @@
 #include "qemu-timer.h"
 #include "block_int.h"
 #include "module.h"
+#include "raw-aio.h"
+#include "trace.h"
+#include "thread-pool.h"
+#include "iov.h"
 #include <windows.h>
 #include <winioctl.h>
 
@@ -32,12 +36,130 @@
 #define FTYPE_CD     1
 #define FTYPE_HARDDISK 2
 
+static QEMUWin32AIOState *aio;
+
+typedef struct RawWin32AIOData {
+    BlockDriverState *bs;
+    HANDLE hfile;
+    struct iovec *aio_iov;
+    int aio_niov;
+    size_t aio_nbytes;
+    off64_t aio_offset;
+    int aio_type;
+} RawWin32AIOData;
+
 typedef struct BDRVRawState {
     HANDLE hfile;
     int type;
     char drive_path[16]; /* format: "d:\" */
+    QEMUWin32AIOState *aio;
 } BDRVRawState;
 
+/*
+ * Read/writes the data to/from a given linear buffer.
+ *
+ * Returns the number of bytes handles or -errno in case of an error. Short
+ * reads are only returned if the end of the file is reached.
+ */
+static size_t handle_aiocb_rw(RawWin32AIOData *aiocb)
+{
+    size_t offset = 0;
+    int i;
+
+    for (i = 0; i < aiocb->aio_niov; i++) {
+        OVERLAPPED ov;
+        DWORD ret, ret_count, len;
+
+        memset(&ov, 0, sizeof(ov));
+        ov.Offset = (aiocb->aio_offset + offset);
+        ov.OffsetHigh = (aiocb->aio_offset + offset) >> 32;
+        len = aiocb->aio_iov[i].iov_len;
+        if (aiocb->aio_type & QEMU_AIO_WRITE) {
+            ret = WriteFile(aiocb->hfile, aiocb->aio_iov[i].iov_base,
+                            len, &ret_count, &ov);
+        } else {
+            ret = ReadFile(aiocb->hfile, aiocb->aio_iov[i].iov_base,
+                           len, &ret_count, &ov);
+        }
+        if (!ret) {
+            ret_count = 0;
+        }
+        if (ret_count != len) {
+            break;
+        }
+        offset += len;
+    }
+
+    return offset;
+}
+
+static int aio_worker(void *arg)
+{
+    RawWin32AIOData *aiocb = arg;
+    ssize_t ret = 0;
+    size_t count;
+
+    switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
+    case QEMU_AIO_READ:
+        count = handle_aiocb_rw(aiocb);
+        if (count < aiocb->aio_nbytes && aiocb->bs->growable) {
+            /* A short read means that we have reached EOF. Pad the buffer
+             * with zeros for bytes after EOF. */
+            iov_memset(aiocb->aio_iov, aiocb->aio_niov, count,
+                      0, aiocb->aio_nbytes - count);
+
+            count = aiocb->aio_nbytes;
+        }
+        if (count == aiocb->aio_nbytes) {
+            ret = 0;
+        } else {
+            ret = -EINVAL;
+        }
+        break;
+    case QEMU_AIO_WRITE:
+        count = handle_aiocb_rw(aiocb);
+        if (count == aiocb->aio_nbytes) {
+            count = 0;
+        } else {
+            count = -EINVAL;
+        }
+        break;
+    case QEMU_AIO_FLUSH:
+        if (!FlushFileBuffers(aiocb->hfile)) {
+            return -EIO;
+        }
+        break;
+    default:
+        fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
+        ret = -EINVAL;
+        break;
+    }
+
+    g_slice_free(RawWin32AIOData, aiocb);
+    return ret;
+}
+
+static BlockDriverAIOCB *paio_submit(BlockDriverState *bs, HANDLE hfile,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockDriverCompletionFunc *cb, void *opaque, int type)
+{
+    RawWin32AIOData *acb = g_slice_new(RawWin32AIOData);
+
+    acb->bs = bs;
+    acb->hfile = hfile;
+    acb->aio_type = type;
+
+    if (qiov) {
+        acb->aio_iov = qiov->iov;
+        acb->aio_niov = qiov->niov;
+    }
+    acb->aio_nbytes = nb_sectors * 512;
+    acb->aio_offset = sector_num * 512;
+
+    trace_paio_submit(acb, opaque, sector_num, nb_sectors, type);
+    return thread_pool_submit_aio(aio_worker, acb, cb, opaque);
+}
+
 int qemu_ftruncate64(int fd, int64_t length)
 {
     LARGE_INTEGER li;
@@ -89,6 +211,9 @@ static void raw_parse_flags(int flags, int *access_flags, DWORD *overlapped)
     }
 
     *overlapped = FILE_ATTRIBUTE_NORMAL;
+    if (flags & BDRV_O_NATIVE_AIO) {
+        *overlapped |= FILE_FLAG_OVERLAPPED;
+    }
     if (flags & BDRV_O_NOCACHE) {
         *overlapped |= FILE_FLAG_NO_BUFFERING;
     }
@@ -103,6 +228,13 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags)
     s->type = FTYPE_FILE;
 
     raw_parse_flags(flags, &access_flags, &overlapped);
+    
+    if ((flags & BDRV_O_NATIVE_AIO) && aio == NULL) {
+        aio = win32_aio_init();
+        if (aio == NULL) {
+            return -EINVAL;
+        }
+    }
 
     s->hfile = CreateFile(filename, access_flags,
                           FILE_SHARE_READ, NULL,
@@ -112,64 +244,53 @@ static int raw_open(BlockDriverState *bs, const char *filename, int flags)
 
         if (err == ERROR_ACCESS_DENIED)
             return -EACCES;
-        return -1;
+        return -EINVAL;
+    }
+
+    if (flags & BDRV_O_NATIVE_AIO) {
+        int ret = win32_aio_attach(aio, s->hfile);
+        if (ret < 0) {
+            CloseHandle(s->hfile);
+            return ret;
+        }
+        s->aio = aio;
     }
     return 0;
 }
 
-static int raw_read(BlockDriverState *bs, int64_t sector_num,
-                    uint8_t *buf, int nb_sectors)
+static BlockDriverAIOCB *raw_aio_readv(BlockDriverState *bs,
+                         int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+                         BlockDriverCompletionFunc *cb, void *opaque)
 {
     BDRVRawState *s = bs->opaque;
-    OVERLAPPED ov;
-    DWORD ret_count;
-    int ret;
-    int64_t offset = sector_num * 512;
-    int count = nb_sectors * 512;
-
-    memset(&ov, 0, sizeof(ov));
-    ov.Offset = offset;
-    ov.OffsetHigh = offset >> 32;
-    ret = ReadFile(s->hfile, buf, count, &ret_count, &ov);
-    if (!ret)
-        return ret_count;
-    if (ret_count == count)
-        ret_count = 0;
-    return ret_count;
+    if (s->aio) {
+        return win32_aio_submit(bs, s->aio, s->hfile, sector_num, qiov,
+                                nb_sectors, cb, opaque, QEMU_AIO_READ); 
+    } else {
+        return paio_submit(bs, s->hfile, sector_num, qiov, nb_sectors,
+                           cb, opaque, QEMU_AIO_READ);
+    }
 }
 
-static int raw_write(BlockDriverState *bs, int64_t sector_num,
-                     const uint8_t *buf, int nb_sectors)
+static BlockDriverAIOCB *raw_aio_writev(BlockDriverState *bs,
+                          int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+                          BlockDriverCompletionFunc *cb, void *opaque)
 {
     BDRVRawState *s = bs->opaque;
-    OVERLAPPED ov;
-    DWORD ret_count;
-    int ret;
-    int64_t offset = sector_num * 512;
-    int count = nb_sectors * 512;
-
-    memset(&ov, 0, sizeof(ov));
-    ov.Offset = offset;
-    ov.OffsetHigh = offset >> 32;
-    ret = WriteFile(s->hfile, buf, count, &ret_count, &ov);
-    if (!ret)
-        return ret_count;
-    if (ret_count == count)
-        ret_count = 0;
-    return ret_count;
+    if (s->aio) {
+        return win32_aio_submit(bs, s->aio, s->hfile, sector_num, qiov,
+                                nb_sectors, cb, opaque, QEMU_AIO_WRITE); 
+    } else {
+        return paio_submit(bs, s->hfile, sector_num, qiov, nb_sectors,
+                           cb, opaque, QEMU_AIO_WRITE);
+    }
 }
 
-static int raw_flush(BlockDriverState *bs)
+static BlockDriverAIOCB *raw_aio_flush(BlockDriverState *bs,
+                         BlockDriverCompletionFunc *cb, void *opaque)
 {
     BDRVRawState *s = bs->opaque;
-    int ret;
-
-    ret = FlushFileBuffers(s->hfile);
-    if (ret == 0) {
-        return -EIO;
-    }
-
-    return 0;
+    return paio_submit(bs, s->hfile, 0, NULL, 0, cb, opaque, QEMU_AIO_FLUSH);
 }
 
 static void raw_close(BlockDriverState *bs)
@@ -290,9 +411,9 @@ static BlockDriver bdrv_file = {
     .bdrv_close		= raw_close,
     .bdrv_create	= raw_create,
 
-    .bdrv_read              = raw_read,
-    .bdrv_write             = raw_write,
-    .bdrv_co_flush_to_disk  = raw_flush,
+    .bdrv_aio_readv     = raw_aio_readv,
+    .bdrv_aio_writev    = raw_aio_writev,
+    .bdrv_aio_flush     = raw_aio_flush,
 
     .bdrv_truncate	= raw_truncate,
     .bdrv_getlength	= raw_getlength,
@@ -413,9 +534,9 @@ static BlockDriver bdrv_host_device = {
     .bdrv_close		= raw_close,
     .bdrv_has_zero_init = hdev_has_zero_init,
 
-    .bdrv_read              = raw_read,
-    .bdrv_write             = raw_write,
-    .bdrv_co_flush_to_disk  = raw_flush,
+    .bdrv_aio_readv     = raw_aio_readv,
+    .bdrv_aio_writev    = raw_aio_writev,
+    .bdrv_aio_flush     = raw_aio_flush,
 
     .bdrv_getlength	= raw_getlength,
     .bdrv_get_allocated_file_size
diff --git a/block/win32-aio.c b/block/win32-aio.c
new file mode 100644
index 0000000000..c34dc73b6c
--- /dev/null
+++ b/block/win32-aio.c
@@ -0,0 +1,226 @@
+/*
+ * Block driver for RAW files (win32)
+ *
+ * Copyright (c) 2006 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-common.h"
+#include "qemu-timer.h"
+#include "block_int.h"
+#include "module.h"
+#include "qemu-common.h"
+#include "qemu-aio.h"
+#include "raw-aio.h"
+#include "event_notifier.h"
+#include <windows.h>
+#include <winioctl.h>
+
+#define FTYPE_FILE 0
+#define FTYPE_CD     1
+#define FTYPE_HARDDISK 2
+
+struct QEMUWin32AIOState {
+    HANDLE hIOCP;
+    EventNotifier e;
+    int count;
+};
+
+typedef struct QEMUWin32AIOCB {
+    BlockDriverAIOCB common;
+    struct QEMUWin32AIOState *ctx;
+    int nbytes;
+    OVERLAPPED ov;
+    QEMUIOVector *qiov;
+    void *buf;
+    bool is_read;
+    bool is_linear;
+} QEMUWin32AIOCB;
+
+/*
+ * Completes an AIO request (calls the callback and frees the ACB).
+ */
+static void win32_aio_process_completion(QEMUWin32AIOState *s,
+    QEMUWin32AIOCB *waiocb, DWORD count)
+{
+    int ret;
+    s->count--;
+
+    if (waiocb->ov.Internal != 0) {
+        ret = -EIO;
+    } else {
+        ret = 0;
+        if (count < waiocb->nbytes) {
+            /* Short reads mean EOF, pad with zeros. */
+            if (waiocb->is_read) {
+                qemu_iovec_memset(waiocb->qiov, count, 0,
+                    waiocb->qiov->size - count);
+            } else {
+                ret = -EINVAL;
+            }
+       }
+    }
+
+    if (!waiocb->is_linear) {
+        if (ret == 0 && waiocb->is_read) {
+            QEMUIOVector *qiov = waiocb->qiov;
+            char *p = waiocb->buf;
+            int i;
+
+            for (i = 0; i < qiov->niov; ++i) {
+                memcpy(p, qiov->iov[i].iov_base, qiov->iov[i].iov_len);
+                p += qiov->iov[i].iov_len;
+            }
+            g_free(waiocb->buf);
+        }
+    }
+
+
+    waiocb->common.cb(waiocb->common.opaque, ret);
+    qemu_aio_release(waiocb);
+}
+
+static void win32_aio_completion_cb(EventNotifier *e)
+{
+    QEMUWin32AIOState *s = container_of(e, QEMUWin32AIOState, e);
+    DWORD count;
+    ULONG_PTR key;
+    OVERLAPPED *ov;
+
+    event_notifier_test_and_clear(&s->e);
+    while (GetQueuedCompletionStatus(s->hIOCP, &count, &key, &ov, 0)) {
+        QEMUWin32AIOCB *waiocb = container_of(ov, QEMUWin32AIOCB, ov);
+
+        win32_aio_process_completion(s, waiocb, count);
+    }
+}
+
+static int win32_aio_flush_cb(EventNotifier *e)
+{
+    QEMUWin32AIOState *s = container_of(e, QEMUWin32AIOState, e);
+
+    return (s->count > 0) ? 1 : 0;
+}
+
+static void win32_aio_cancel(BlockDriverAIOCB *blockacb)
+{
+    QEMUWin32AIOCB *waiocb = (QEMUWin32AIOCB *)blockacb;
+
+    /*
+     * CancelIoEx is only supported in Vista and newer.  For now, just
+     * wait for completion.
+     */
+    while (!HasOverlappedIoCompleted(&waiocb->ov)) {
+        qemu_aio_wait();
+    }
+}
+
+static AIOPool win32_aio_pool = {
+    .aiocb_size         = sizeof(QEMUWin32AIOCB),
+    .cancel             = win32_aio_cancel,
+};
+
+BlockDriverAIOCB *win32_aio_submit(BlockDriverState *bs,
+        QEMUWin32AIOState *aio, HANDLE hfile,
+        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
+        BlockDriverCompletionFunc *cb, void *opaque, int type)
+{
+    struct QEMUWin32AIOCB *waiocb;
+    uint64_t offset = sector_num * 512;
+    DWORD rc;
+
+    waiocb = qemu_aio_get(&win32_aio_pool, bs, cb, opaque);
+    waiocb->nbytes = nb_sectors * 512;
+    waiocb->qiov = qiov;
+    waiocb->is_read = (type == QEMU_AIO_READ);
+
+    if (qiov->niov > 1) {
+        waiocb->buf = qemu_blockalign(bs, qiov->size);
+        if (type & QEMU_AIO_WRITE) {
+            char *p = waiocb->buf;
+            int i;
+
+            for (i = 0; i < qiov->niov; ++i) {
+                memcpy(p, qiov->iov[i].iov_base, qiov->iov[i].iov_len);
+                p += qiov->iov[i].iov_len;
+            }
+        }
+        waiocb->is_linear = false;
+    } else {
+        waiocb->buf = qiov->iov[0].iov_base;
+        waiocb->is_linear = true;
+    }
+
+    waiocb->ov = (OVERLAPPED) {
+        .Offset = (DWORD) offset,
+        .OffsetHigh = (DWORD) (offset >> 32),
+        .hEvent = event_notifier_get_handle(&aio->e)
+    };
+    aio->count++;
+
+    if (type & QEMU_AIO_READ) {
+        rc = ReadFile(hfile, waiocb->buf, waiocb->nbytes, NULL, &waiocb->ov);
+    } else {
+        rc = WriteFile(hfile, waiocb->buf, waiocb->nbytes, NULL, &waiocb->ov);
+    }
+    if(rc == 0 && GetLastError() != ERROR_IO_PENDING) {
+        goto out_dec_count;
+    }
+    return &waiocb->common;
+
+out_dec_count:
+    aio->count--;
+    qemu_aio_release(waiocb);
+    return NULL;
+}
+
+int win32_aio_attach(QEMUWin32AIOState *aio, HANDLE hfile)
+{
+    if (CreateIoCompletionPort(hfile, aio->hIOCP, (ULONG_PTR) 0, 0) == NULL) {
+        return -EINVAL;
+    } else {
+        return 0;
+    }
+}
+
+QEMUWin32AIOState *win32_aio_init(void)
+{
+    QEMUWin32AIOState *s;
+
+    s = g_malloc0(sizeof(*s));
+    if (event_notifier_init(&s->e, false) < 0) {
+        goto out_free_state;
+    }
+
+    s->hIOCP = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0);
+    if (s->hIOCP == NULL) {
+        goto out_close_efd;
+    }
+
+    qemu_aio_set_event_notifier(&s->e, win32_aio_completion_cb,
+                                win32_aio_flush_cb);
+
+    return s;
+
+out_close_efd:
+    event_notifier_cleanup(&s->e);
+out_free_state:
+    g_free(s);
+    return NULL;
+}
diff --git a/compiler.h b/compiler.h
index c734a71c67..58865d65e8 100644
--- a/compiler.h
+++ b/compiler.h
@@ -50,16 +50,13 @@
 #   define __printf__ __gnu_printf__
 #  endif
 # endif
-#if defined(_WIN32)
-#define GCC_WEAK __attribute__((weak))
-#define GCC_WEAK_DECL GCC_WEAK
-#else
-#define GCC_WEAK __attribute__((weak))
-#define GCC_WEAK_DECL
-#endif
+# define QEMU_WEAK_ALIAS(newname, oldname) \
+        typeof(oldname) newname __attribute__((weak, alias (#oldname)))
 #else
 #define GCC_ATTR /**/
 #define GCC_FMT_ATTR(n, m)
+#define QEMU_WEAK_ALIAS(newname, oldname) \
+        _Pragma("weak " #newname "=" #oldname)
 #endif
 
 #endif /* COMPILER_H */
diff --git a/cutils.c b/cutils.c
index 8edd8fa13c..4f0692f78e 100644
--- a/cutils.c
+++ b/cutils.c
@@ -142,109 +142,6 @@ int qemu_fdatasync(int fd)
 #endif
 }
 
-/* io vectors */
-
-void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
-{
-    qiov->iov = g_malloc(alloc_hint * sizeof(struct iovec));
-    qiov->niov = 0;
-    qiov->nalloc = alloc_hint;
-    qiov->size = 0;
-}
-
-void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
-{
-    int i;
-
-    qiov->iov = iov;
-    qiov->niov = niov;
-    qiov->nalloc = -1;
-    qiov->size = 0;
-    for (i = 0; i < niov; i++)
-        qiov->size += iov[i].iov_len;
-}
-
-void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
-{
-    assert(qiov->nalloc != -1);
-
-    if (qiov->niov == qiov->nalloc) {
-        qiov->nalloc = 2 * qiov->nalloc + 1;
-        qiov->iov = g_realloc(qiov->iov, qiov->nalloc * sizeof(struct iovec));
-    }
-    qiov->iov[qiov->niov].iov_base = base;
-    qiov->iov[qiov->niov].iov_len = len;
-    qiov->size += len;
-    ++qiov->niov;
-}
-
-/*
- * Concatenates (partial) iovecs from src to the end of dst.
- * It starts copying after skipping `soffset' bytes at the
- * beginning of src and adds individual vectors from src to
- * dst copies up to `sbytes' bytes total, or up to the end
- * of src if it comes first.  This way, it is okay to specify
- * very large value for `sbytes' to indicate "up to the end
- * of src".
- * Only vector pointers are processed, not the actual data buffers.
- */
-void qemu_iovec_concat(QEMUIOVector *dst,
-                       QEMUIOVector *src, size_t soffset, size_t sbytes)
-{
-    int i;
-    size_t done;
-    struct iovec *siov = src->iov;
-    assert(dst->nalloc != -1);
-    assert(src->size >= soffset);
-    for (i = 0, done = 0; done < sbytes && i < src->niov; i++) {
-        if (soffset < siov[i].iov_len) {
-            size_t len = MIN(siov[i].iov_len - soffset, sbytes - done);
-            qemu_iovec_add(dst, siov[i].iov_base + soffset, len);
-            done += len;
-            soffset = 0;
-        } else {
-            soffset -= siov[i].iov_len;
-        }
-    }
-    /* return done; */
-}
-
-void qemu_iovec_destroy(QEMUIOVector *qiov)
-{
-    assert(qiov->nalloc != -1);
-
-    qemu_iovec_reset(qiov);
-    g_free(qiov->iov);
-    qiov->nalloc = 0;
-    qiov->iov = NULL;
-}
-
-void qemu_iovec_reset(QEMUIOVector *qiov)
-{
-    assert(qiov->nalloc != -1);
-
-    qiov->niov = 0;
-    qiov->size = 0;
-}
-
-size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
-                         void *buf, size_t bytes)
-{
-    return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
-}
-
-size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
-                           const void *buf, size_t bytes)
-{
-    return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
-}
-
-size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
-                         int fillc, size_t bytes)
-{
-    return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
-}
-
 /*
  * Checks if a buffer is all zeroes
  *
@@ -383,11 +280,6 @@ int qemu_parse_fd(const char *param)
     return fd;
 }
 
-int qemu_parse_fdset(const char *param)
-{
-    return qemu_parse_fd(param);
-}
-
 /* round down to the nearest power of 2*/
 int64_t pow2floor(int64_t value)
 {
diff --git a/event_notifier-posix.c b/event_notifier-posix.c
new file mode 100644
index 0000000000..6f3239a3fc
--- /dev/null
+++ b/event_notifier-posix.c
@@ -0,0 +1,120 @@
+/*
+ * event notifier support
+ *
+ * Copyright Red Hat, Inc. 2010
+ *
+ * Authors:
+ *  Michael S. Tsirkin <mst@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu-common.h"
+#include "event_notifier.h"
+#include "qemu-char.h"
+
+#ifdef CONFIG_EVENTFD
+#include <sys/eventfd.h>
+#endif
+
+void event_notifier_init_fd(EventNotifier *e, int fd)
+{
+    e->rfd = fd;
+    e->wfd = fd;
+}
+
+int event_notifier_init(EventNotifier *e, int active)
+{
+    int fds[2];
+    int ret;
+
+#ifdef CONFIG_EVENTFD
+    ret = eventfd(0, EFD_NONBLOCK | EFD_CLOEXEC);
+#else
+    ret = -1;
+    errno = ENOSYS;
+#endif
+    if (ret >= 0) {
+        e->rfd = e->wfd = ret;
+    } else {
+        if (errno != ENOSYS) {
+            return -errno;
+        }
+        if (qemu_pipe(fds) < 0) {
+            return -errno;
+        }
+        ret = fcntl_setfl(fds[0], O_NONBLOCK);
+        if (ret < 0) {
+            ret = -errno;
+            goto fail;
+        }
+        ret = fcntl_setfl(fds[1], O_NONBLOCK);
+        if (ret < 0) {
+            ret = -errno;
+            goto fail;
+        }
+        e->rfd = fds[0];
+        e->wfd = fds[1];
+    }
+    if (active) {
+        event_notifier_set(e);
+    }
+    return 0;
+
+fail:
+    close(fds[0]);
+    close(fds[1]);
+    return ret;
+}
+
+void event_notifier_cleanup(EventNotifier *e)
+{
+    if (e->rfd != e->wfd) {
+        close(e->rfd);
+    }
+    close(e->wfd);
+}
+
+int event_notifier_get_fd(EventNotifier *e)
+{
+    return e->rfd;
+}
+
+int event_notifier_set_handler(EventNotifier *e,
+                               EventNotifierHandler *handler)
+{
+    return qemu_set_fd_handler(e->rfd, (IOHandler *)handler, NULL, e);
+}
+
+int event_notifier_set(EventNotifier *e)
+{
+    static const uint64_t value = 1;
+    ssize_t ret;
+
+    do {
+        ret = write(e->wfd, &value, sizeof(value));
+    } while (ret < 0 && errno == EINTR);
+
+    /* EAGAIN is fine, a read must be pending.  */
+    if (ret < 0 && errno != EAGAIN) {
+        return -errno;
+    }
+    return 0;
+}
+
+int event_notifier_test_and_clear(EventNotifier *e)
+{
+    int value;
+    ssize_t len;
+    char buffer[512];
+
+    /* Drain the notify pipe.  For eventfd, only 8 bytes will be read.  */
+    value = 0;
+    do {
+        len = read(e->rfd, buffer, sizeof(buffer));
+        value |= (len > 0);
+    } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
+
+    return value;
+}
diff --git a/event_notifier-win32.c b/event_notifier-win32.c
new file mode 100644
index 0000000000..c723dadf31
--- /dev/null
+++ b/event_notifier-win32.c
@@ -0,0 +1,59 @@
+/*
+ * event notifier support
+ *
+ * Copyright Red Hat, Inc. 2010
+ *
+ * Authors:
+ *  Michael S. Tsirkin <mst@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu-common.h"
+#include "event_notifier.h"
+#include "main-loop.h"
+
+int event_notifier_init(EventNotifier *e, int active)
+{
+    e->event = CreateEvent(NULL, FALSE, FALSE, NULL);
+    assert(e->event);
+    return 0;
+}
+
+void event_notifier_cleanup(EventNotifier *e)
+{
+    CloseHandle(e->event);
+}
+
+HANDLE event_notifier_get_handle(EventNotifier *e)
+{
+    return e->event;
+}
+
+int event_notifier_set_handler(EventNotifier *e,
+                               EventNotifierHandler *handler)
+{
+    if (handler) {
+        return qemu_add_wait_object(e->event, (IOHandler *)handler, e);
+    } else {
+        qemu_del_wait_object(e->event, (IOHandler *)handler, e);
+        return 0;
+    }
+}
+
+int event_notifier_set(EventNotifier *e)
+{
+    SetEvent(e->event);
+    return 0;
+}
+
+int event_notifier_test_and_clear(EventNotifier *e)
+{
+    int ret = WaitForSingleObject(e->event, 0);
+    if (ret == WAIT_OBJECT_0) {
+        ResetEvent(e->event);
+        return true;
+    }
+    return false;
+}
diff --git a/event_notifier.c b/event_notifier.c
deleted file mode 100644
index 2c207e1399..0000000000
--- a/event_notifier.c
+++ /dev/null
@@ -1,67 +0,0 @@
-/*
- * event notifier support
- *
- * Copyright Red Hat, Inc. 2010
- *
- * Authors:
- *  Michael S. Tsirkin <mst@redhat.com>
- *
- * This work is licensed under the terms of the GNU GPL, version 2 or later.
- * See the COPYING file in the top-level directory.
- */
-
-#include "qemu-common.h"
-#include "event_notifier.h"
-#include "qemu-char.h"
-
-#ifdef CONFIG_EVENTFD
-#include <sys/eventfd.h>
-#endif
-
-void event_notifier_init_fd(EventNotifier *e, int fd)
-{
-    e->fd = fd;
-}
-
-int event_notifier_init(EventNotifier *e, int active)
-{
-#ifdef CONFIG_EVENTFD
-    int fd = eventfd(!!active, EFD_NONBLOCK | EFD_CLOEXEC);
-    if (fd < 0)
-        return -errno;
-    e->fd = fd;
-    return 0;
-#else
-    return -ENOSYS;
-#endif
-}
-
-void event_notifier_cleanup(EventNotifier *e)
-{
-    close(e->fd);
-}
-
-int event_notifier_get_fd(EventNotifier *e)
-{
-    return e->fd;
-}
-
-int event_notifier_set_handler(EventNotifier *e,
-                               EventNotifierHandler *handler)
-{
-    return qemu_set_fd_handler(e->fd, (IOHandler *)handler, NULL, e);
-}
-
-int event_notifier_set(EventNotifier *e)
-{
-    uint64_t value = 1;
-    int r = write(e->fd, &value, sizeof(value));
-    return r == sizeof(value);
-}
-
-int event_notifier_test_and_clear(EventNotifier *e)
-{
-    uint64_t value;
-    int r = read(e->fd, &value, sizeof(value));
-    return r == sizeof(value);
-}
diff --git a/event_notifier.h b/event_notifier.h
index f0ec2f2171..88b57af7ce 100644
--- a/event_notifier.h
+++ b/event_notifier.h
@@ -15,18 +15,32 @@
 
 #include "qemu-common.h"
 
+#ifdef _WIN32
+#include <windows.h>
+#endif
+
 struct EventNotifier {
-    int fd;
+#ifdef _WIN32
+    HANDLE event;
+#else
+    int rfd;
+    int wfd;
+#endif
 };
 
 typedef void EventNotifierHandler(EventNotifier *);
 
-void event_notifier_init_fd(EventNotifier *, int fd);
 int event_notifier_init(EventNotifier *, int active);
 void event_notifier_cleanup(EventNotifier *);
-int event_notifier_get_fd(EventNotifier *);
 int event_notifier_set(EventNotifier *);
 int event_notifier_test_and_clear(EventNotifier *);
 int event_notifier_set_handler(EventNotifier *, EventNotifierHandler *);
 
+#ifdef CONFIG_POSIX
+void event_notifier_init_fd(EventNotifier *, int fd);
+int event_notifier_get_fd(EventNotifier *);
+#else
+HANDLE event_notifier_get_handle(EventNotifier *);
+#endif
+
 #endif
diff --git a/hw/hw.h b/hw/hw.h
index b337ee3042..f530f6f41a 100644
--- a/hw/hw.h
+++ b/hw/hw.h
@@ -10,6 +10,7 @@
 
 #include "ioport.h"
 #include "irq.h"
+#include "qemu-aio.h"
 #include "qemu-file.h"
 #include "vmstate.h"
 #include "qemu-log.h"
diff --git a/iohandler.c b/iohandler.c
index a2d871bb91..60460a6f88 100644
--- a/iohandler.c
+++ b/iohandler.c
@@ -26,6 +26,7 @@
 #include "qemu-common.h"
 #include "qemu-char.h"
 #include "qemu-queue.h"
+#include "qemu-aio.h"
 #include "main-loop.h"
 
 #ifndef _WIN32
diff --git a/iov.c b/iov.c
index b7378bf7ce..a81eedcedb 100644
--- a/iov.c
+++ b/iov.c
@@ -251,3 +251,106 @@ unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt,
     assert(offset == 0);
     return j;
 }
+
+/* io vectors */
+
+void qemu_iovec_init(QEMUIOVector *qiov, int alloc_hint)
+{
+    qiov->iov = g_malloc(alloc_hint * sizeof(struct iovec));
+    qiov->niov = 0;
+    qiov->nalloc = alloc_hint;
+    qiov->size = 0;
+}
+
+void qemu_iovec_init_external(QEMUIOVector *qiov, struct iovec *iov, int niov)
+{
+    int i;
+
+    qiov->iov = iov;
+    qiov->niov = niov;
+    qiov->nalloc = -1;
+    qiov->size = 0;
+    for (i = 0; i < niov; i++)
+        qiov->size += iov[i].iov_len;
+}
+
+void qemu_iovec_add(QEMUIOVector *qiov, void *base, size_t len)
+{
+    assert(qiov->nalloc != -1);
+
+    if (qiov->niov == qiov->nalloc) {
+        qiov->nalloc = 2 * qiov->nalloc + 1;
+        qiov->iov = g_realloc(qiov->iov, qiov->nalloc * sizeof(struct iovec));
+    }
+    qiov->iov[qiov->niov].iov_base = base;
+    qiov->iov[qiov->niov].iov_len = len;
+    qiov->size += len;
+    ++qiov->niov;
+}
+
+/*
+ * Concatenates (partial) iovecs from src to the end of dst.
+ * It starts copying after skipping `soffset' bytes at the
+ * beginning of src and adds individual vectors from src to
+ * dst copies up to `sbytes' bytes total, or up to the end
+ * of src if it comes first.  This way, it is okay to specify
+ * very large value for `sbytes' to indicate "up to the end
+ * of src".
+ * Only vector pointers are processed, not the actual data buffers.
+ */
+void qemu_iovec_concat(QEMUIOVector *dst,
+                       QEMUIOVector *src, size_t soffset, size_t sbytes)
+{
+    int i;
+    size_t done;
+    struct iovec *siov = src->iov;
+    assert(dst->nalloc != -1);
+    assert(src->size >= soffset);
+    for (i = 0, done = 0; done < sbytes && i < src->niov; i++) {
+        if (soffset < siov[i].iov_len) {
+            size_t len = MIN(siov[i].iov_len - soffset, sbytes - done);
+            qemu_iovec_add(dst, siov[i].iov_base + soffset, len);
+            done += len;
+            soffset = 0;
+        } else {
+            soffset -= siov[i].iov_len;
+        }
+    }
+    /* return done; */
+}
+
+void qemu_iovec_destroy(QEMUIOVector *qiov)
+{
+    assert(qiov->nalloc != -1);
+
+    qemu_iovec_reset(qiov);
+    g_free(qiov->iov);
+    qiov->nalloc = 0;
+    qiov->iov = NULL;
+}
+
+void qemu_iovec_reset(QEMUIOVector *qiov)
+{
+    assert(qiov->nalloc != -1);
+
+    qiov->niov = 0;
+    qiov->size = 0;
+}
+
+size_t qemu_iovec_to_buf(QEMUIOVector *qiov, size_t offset,
+                         void *buf, size_t bytes)
+{
+    return iov_to_buf(qiov->iov, qiov->niov, offset, buf, bytes);
+}
+
+size_t qemu_iovec_from_buf(QEMUIOVector *qiov, size_t offset,
+                           const void *buf, size_t bytes)
+{
+    return iov_from_buf(qiov->iov, qiov->niov, offset, buf, bytes);
+}
+
+size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset,
+                         int fillc, size_t bytes)
+{
+    return iov_memset(qiov->iov, qiov->niov, offset, fillc, bytes);
+}
diff --git a/main-loop.c b/main-loop.c
index eb3b6e6253..e43c7c8e8d 100644
--- a/main-loop.c
+++ b/main-loop.c
@@ -26,75 +26,12 @@
 #include "qemu-timer.h"
 #include "slirp/slirp.h"
 #include "main-loop.h"
+#include "qemu-aio.h"
 
 #ifndef _WIN32
 
 #include "compatfd.h"
 
-static int io_thread_fd = -1;
-
-void qemu_notify_event(void)
-{
-    /* Write 8 bytes to be compatible with eventfd.  */
-    static const uint64_t val = 1;
-    ssize_t ret;
-
-    if (io_thread_fd == -1) {
-        return;
-    }
-    do {
-        ret = write(io_thread_fd, &val, sizeof(val));
-    } while (ret < 0 && errno == EINTR);
-
-    /* EAGAIN is fine, a read must be pending.  */
-    if (ret < 0 && errno != EAGAIN) {
-        fprintf(stderr, "qemu_notify_event: write() failed: %s\n",
-                strerror(errno));
-        exit(1);
-    }
-}
-
-static void qemu_event_read(void *opaque)
-{
-    int fd = (intptr_t)opaque;
-    ssize_t len;
-    char buffer[512];
-
-    /* Drain the notify pipe.  For eventfd, only 8 bytes will be read.  */
-    do {
-        len = read(fd, buffer, sizeof(buffer));
-    } while ((len == -1 && errno == EINTR) || len == sizeof(buffer));
-}
-
-static int qemu_event_init(void)
-{
-    int err;
-    int fds[2];
-
-    err = qemu_eventfd(fds);
-    if (err == -1) {
-        return -errno;
-    }
-    err = fcntl_setfl(fds[0], O_NONBLOCK);
-    if (err < 0) {
-        goto fail;
-    }
-    err = fcntl_setfl(fds[1], O_NONBLOCK);
-    if (err < 0) {
-        goto fail;
-    }
-    qemu_set_fd_handler2(fds[0], NULL, qemu_event_read, NULL,
-                         (void *)(intptr_t)fds[0]);
-
-    io_thread_fd = fds[1];
-    return 0;
-
-fail:
-    close(fds[0]);
-    close(fds[1]);
-    return err;
-}
-
 /* 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.
@@ -164,44 +101,29 @@ static int qemu_signal_init(void)
 
 #else /* _WIN32 */
 
-static HANDLE qemu_event_handle = NULL;
-
-static void dummy_event_handler(void *opaque)
-{
-}
-
-static int qemu_event_init(void)
+static int qemu_signal_init(void)
 {
-    qemu_event_handle = CreateEvent(NULL, FALSE, FALSE, NULL);
-    if (!qemu_event_handle) {
-        fprintf(stderr, "Failed CreateEvent: %ld\n", GetLastError());
-        return -1;
-    }
-    qemu_add_wait_object(qemu_event_handle, dummy_event_handler, NULL);
     return 0;
 }
+#endif
+
+static AioContext *qemu_aio_context;
 
 void qemu_notify_event(void)
 {
-    if (!qemu_event_handle) {
+    if (!qemu_aio_context) {
         return;
     }
-    if (!SetEvent(qemu_event_handle)) {
-        fprintf(stderr, "qemu_notify_event: SetEvent failed: %ld\n",
-                GetLastError());
-        exit(1);
-    }
-}
-
-static int qemu_signal_init(void)
-{
-    return 0;
+    aio_notify(qemu_aio_context);
 }
-#endif
 
-int main_loop_init(void)
+int qemu_init_main_loop(void)
 {
     int ret;
+    GSource *src;
+
+    init_clocks();
+    init_timer_alarm();
 
     qemu_mutex_lock_iothread();
     ret = qemu_signal_init();
@@ -209,12 +131,10 @@ int main_loop_init(void)
         return ret;
     }
 
-    /* Note eventfd must be drained before signalfd handlers run */
-    ret = qemu_event_init();
-    if (ret) {
-        return ret;
-    }
-
+    qemu_aio_context = aio_context_new();
+    src = aio_get_g_source(qemu_aio_context);
+    g_source_attach(src, NULL);
+    g_source_unref(src);
     return 0;
 }
 
@@ -400,7 +320,8 @@ void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque)
 
 void qemu_fd_register(int fd)
 {
-    WSAEventSelect(fd, qemu_event_handle, FD_READ | FD_ACCEPT | FD_CLOSE |
+    WSAEventSelect(fd, event_notifier_get_handle(&qemu_aio_context->notifier),
+                   FD_READ | FD_ACCEPT | FD_CLOSE |
                    FD_CONNECT | FD_WRITE | FD_OOB);
 }
 
@@ -477,8 +398,6 @@ int main_loop_wait(int nonblocking)
 
     if (nonblocking) {
         timeout = 0;
-    } else {
-        qemu_bh_update_timeout(&timeout);
     }
 
     /* poll any events */
@@ -501,9 +420,41 @@ int main_loop_wait(int nonblocking)
 
     qemu_run_all_timers();
 
-    /* Check bottom-halves last in case any of the earlier events triggered
-       them.  */
-    qemu_bh_poll();
-
     return ret;
 }
+
+/* Functions to operate on the main QEMU AioContext.  */
+
+QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque)
+{
+    return aio_bh_new(qemu_aio_context, cb, opaque);
+}
+
+void qemu_aio_flush(void)
+{
+    aio_flush(qemu_aio_context);
+}
+
+bool qemu_aio_wait(void)
+{
+    return aio_poll(qemu_aio_context, true);
+}
+
+#ifdef CONFIG_POSIX
+void qemu_aio_set_fd_handler(int fd,
+                             IOHandler *io_read,
+                             IOHandler *io_write,
+                             AioFlushHandler *io_flush,
+                             void *opaque)
+{
+    aio_set_fd_handler(qemu_aio_context, fd, io_read, io_write, io_flush,
+                       opaque);
+}
+#endif
+
+void qemu_aio_set_event_notifier(EventNotifier *notifier,
+                                 EventNotifierHandler *io_read,
+                                 AioFlushEventNotifierHandler *io_flush)
+{
+    aio_set_event_notifier(qemu_aio_context, notifier, io_read, io_flush);
+}
diff --git a/main-loop.h b/main-loop.h
index dce1cd9d7c..326c74269c 100644
--- a/main-loop.h
+++ b/main-loop.h
@@ -25,6 +25,8 @@
 #ifndef QEMU_MAIN_LOOP_H
 #define QEMU_MAIN_LOOP_H 1
 
+#include "qemu-aio.h"
+
 #define SIG_IPI SIGUSR1
 
 /**
@@ -43,16 +45,6 @@
 int qemu_init_main_loop(void);
 
 /**
- * main_loop_init: Initializes main loop
- *
- * Internal (but shared for compatibility reasons) initialization routine
- * for the main loop. This should not be used by applications directly,
- * use qemu_init_main_loop() instead.
- *
- */
-int main_loop_init(void);
-
-/**
  * main_loop_wait: Run one iteration of the main loop.
  *
  * If @nonblocking is true, poll for events, otherwise suspend until
@@ -173,7 +165,6 @@ void qemu_del_wait_object(HANDLE handle, WaitObjectFunc *func, void *opaque);
 
 typedef void IOReadHandler(void *opaque, const uint8_t *buf, int size);
 typedef int IOCanReadHandler(void *opaque);
-typedef void IOHandler(void *opaque);
 
 /**
  * qemu_set_fd_handler2: Register a file descriptor with the main loop
@@ -254,56 +245,6 @@ int qemu_set_fd_handler(int fd,
                         IOHandler *fd_write,
                         void *opaque);
 
-typedef struct QEMUBH QEMUBH;
-typedef void QEMUBHFunc(void *opaque);
-
-/**
- * qemu_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 *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
-
-/**
- * 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.
- *
- * @bh: The bottom half to be deleted.
- */
-void qemu_bh_delete(QEMUBH *bh);
-
 #ifdef CONFIG_POSIX
 /**
  * qemu_add_child_watch: Register a child process for reaping.
@@ -359,8 +300,7 @@ void qemu_fd_register(int fd);
 void qemu_iohandler_fill(int *pnfds, fd_set *readfds, fd_set *writefds, fd_set *xfds);
 void qemu_iohandler_poll(fd_set *readfds, fd_set *writefds, fd_set *xfds, int rc);
 
+QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
 void qemu_bh_schedule_idle(QEMUBH *bh);
-int qemu_bh_poll(void);
-void qemu_bh_update_timeout(uint32_t *timeout);
 
 #endif
diff --git a/osdep.c b/osdep.c
index c822a01c04..a87d4a453d 100644
--- a/osdep.c
+++ b/osdep.c
@@ -134,6 +134,11 @@ fail:
     errno = serrno;
     return -1;
 }
+
+static int qemu_parse_fdset(const char *param)
+{
+    return qemu_parse_fd(param);
+}
 #endif
 
 /*
@@ -394,3 +399,28 @@ bool fips_get_state(void)
 {
     return fips_enabled;
 }
+
+
+static int default_fdset_get_fd(int64_t fdset_id, int flags)
+{
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_fdset_get_fd, default_fdset_get_fd);
+
+static int default_fdset_dup_fd_add(int64_t fdset_id, int dup_fd)
+{
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_fdset_dup_fd_add, default_fdset_dup_fd_add);
+
+static int default_fdset_dup_fd_remove(int dup_fd)
+{
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_fdset_dup_fd_remove, default_fdset_dup_fd_remove);
+
+static int default_fdset_dup_fd_find(int dup_fd)
+{
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_fdset_dup_fd_find, default_fdset_dup_fd_find);
diff --git a/oslib-posix.c b/oslib-posix.c
index dbeb6272b8..9db9c3d8af 100644
--- a/oslib-posix.c
+++ b/oslib-posix.c
@@ -61,9 +61,6 @@ static int running_on_valgrind = -1;
 #ifdef CONFIG_LINUX
 #include <sys/syscall.h>
 #endif
-#ifdef CONFIG_EVENTFD
-#include <sys/eventfd.h>
-#endif
 
 int qemu_get_thread_id(void)
 {
@@ -183,34 +180,6 @@ int qemu_pipe(int pipefd[2])
     return ret;
 }
 
-/*
- * Creates an eventfd that looks like a pipe and has EFD_CLOEXEC set.
- */
-int qemu_eventfd(int fds[2])
-{
-#ifdef CONFIG_EVENTFD
-    int ret;
-
-    ret = eventfd(0, 0);
-    if (ret >= 0) {
-        fds[0] = ret;
-        fds[1] = dup(ret);
-        if (fds[1] == -1) {
-            close(ret);
-            return -1;
-        }
-        qemu_set_cloexec(ret);
-        qemu_set_cloexec(fds[1]);
-        return 0;
-    }
-    if (errno != ENOSYS) {
-        return -1;
-    }
-#endif
-
-    return qemu_pipe(fds);
-}
-
 int qemu_utimens(const char *path, const struct timespec *times)
 {
     struct timeval tv[2], tv_now;
diff --git a/oslib-win32.c b/oslib-win32.c
index 51b33e8b20..9ca83df011 100644
--- a/oslib-win32.c
+++ b/oslib-win32.c
@@ -150,3 +150,8 @@ int qemu_get_thread_id(void)
 {
     return GetCurrentThreadId();
 }
+
+static void default_qemu_fd_register(int fd)
+{
+}
+QEMU_WEAK_ALIAS(qemu_fd_register, default_qemu_fd_register);
diff --git a/posix-aio-compat.c b/posix-aio-compat.c
deleted file mode 100644
index 96e4daf505..0000000000
--- a/posix-aio-compat.c
+++ /dev/null
@@ -1,679 +0,0 @@
-/*
- * QEMU posix-aio emulation
- *
- * Copyright IBM, Corp. 2008
- *
- * Authors:
- *  Anthony Liguori   <aliguori@us.ibm.com>
- *
- * This work is licensed under the terms of the GNU GPL, version 2.  See
- * the COPYING file in the top-level directory.
- *
- * Contributions after 2012-01-13 are licensed under the terms of the
- * GNU GPL, version 2 or (at your option) any later version.
- */
-
-#include <sys/ioctl.h>
-#include <sys/types.h>
-#include <pthread.h>
-#include <unistd.h>
-#include <errno.h>
-#include <time.h>
-#include <string.h>
-#include <stdlib.h>
-#include <stdio.h>
-
-#include "qemu-queue.h"
-#include "osdep.h"
-#include "sysemu.h"
-#include "qemu-common.h"
-#include "trace.h"
-#include "block_int.h"
-#include "iov.h"
-
-#include "block/raw-posix-aio.h"
-
-static void do_spawn_thread(void);
-
-struct qemu_paiocb {
-    BlockDriverAIOCB common;
-    int aio_fildes;
-    union {
-        struct iovec *aio_iov;
-        void *aio_ioctl_buf;
-    };
-    int aio_niov;
-    size_t aio_nbytes;
-#define aio_ioctl_cmd   aio_nbytes /* for QEMU_AIO_IOCTL */
-    off_t aio_offset;
-
-    QTAILQ_ENTRY(qemu_paiocb) node;
-    int aio_type;
-    ssize_t ret;
-    int active;
-    struct qemu_paiocb *next;
-};
-
-typedef struct PosixAioState {
-    int rfd, wfd;
-    struct qemu_paiocb *first_aio;
-} PosixAioState;
-
-
-static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
-static pthread_t thread_id;
-static pthread_attr_t attr;
-static int max_threads = 64;
-static int cur_threads = 0;
-static int idle_threads = 0;
-static int new_threads = 0;     /* backlog of threads we need to create */
-static int pending_threads = 0; /* threads created but not running yet */
-static QEMUBH *new_thread_bh;
-static QTAILQ_HEAD(, qemu_paiocb) request_list;
-
-#ifdef CONFIG_PREADV
-static int preadv_present = 1;
-#else
-static int preadv_present = 0;
-#endif
-
-static void die2(int err, const char *what)
-{
-    fprintf(stderr, "%s failed: %s\n", what, strerror(err));
-    abort();
-}
-
-static void die(const char *what)
-{
-    die2(errno, what);
-}
-
-static void mutex_lock(pthread_mutex_t *mutex)
-{
-    int ret = pthread_mutex_lock(mutex);
-    if (ret) die2(ret, "pthread_mutex_lock");
-}
-
-static void mutex_unlock(pthread_mutex_t *mutex)
-{
-    int ret = pthread_mutex_unlock(mutex);
-    if (ret) die2(ret, "pthread_mutex_unlock");
-}
-
-static int cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
-                           struct timespec *ts)
-{
-    int ret = pthread_cond_timedwait(cond, mutex, ts);
-    if (ret && ret != ETIMEDOUT) die2(ret, "pthread_cond_timedwait");
-    return ret;
-}
-
-static void cond_signal(pthread_cond_t *cond)
-{
-    int ret = pthread_cond_signal(cond);
-    if (ret) die2(ret, "pthread_cond_signal");
-}
-
-static void thread_create(pthread_t *thread, pthread_attr_t *attr,
-                          void *(*start_routine)(void*), void *arg)
-{
-    int ret = pthread_create(thread, attr, start_routine, arg);
-    if (ret) die2(ret, "pthread_create");
-}
-
-static ssize_t handle_aiocb_ioctl(struct qemu_paiocb *aiocb)
-{
-    int ret;
-
-    ret = ioctl(aiocb->aio_fildes, aiocb->aio_ioctl_cmd, aiocb->aio_ioctl_buf);
-    if (ret == -1)
-        return -errno;
-
-    /*
-     * This looks weird, but the aio code only considers a request
-     * successful if it has written the full number of bytes.
-     *
-     * Now we overload aio_nbytes as aio_ioctl_cmd for the ioctl command,
-     * so in fact we return the ioctl command here to make posix_aio_read()
-     * happy..
-     */
-    return aiocb->aio_nbytes;
-}
-
-static ssize_t handle_aiocb_flush(struct qemu_paiocb *aiocb)
-{
-    int ret;
-
-    ret = qemu_fdatasync(aiocb->aio_fildes);
-    if (ret == -1)
-        return -errno;
-    return 0;
-}
-
-#ifdef CONFIG_PREADV
-
-static ssize_t
-qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)
-{
-    return preadv(fd, iov, nr_iov, offset);
-}
-
-static ssize_t
-qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)
-{
-    return pwritev(fd, iov, nr_iov, offset);
-}
-
-#else
-
-static ssize_t
-qemu_preadv(int fd, const struct iovec *iov, int nr_iov, off_t offset)
-{
-    return -ENOSYS;
-}
-
-static ssize_t
-qemu_pwritev(int fd, const struct iovec *iov, int nr_iov, off_t offset)
-{
-    return -ENOSYS;
-}
-
-#endif
-
-static ssize_t handle_aiocb_rw_vector(struct qemu_paiocb *aiocb)
-{
-    ssize_t len;
-
-    do {
-        if (aiocb->aio_type & QEMU_AIO_WRITE)
-            len = qemu_pwritev(aiocb->aio_fildes,
-                               aiocb->aio_iov,
-                               aiocb->aio_niov,
-                               aiocb->aio_offset);
-         else
-            len = qemu_preadv(aiocb->aio_fildes,
-                              aiocb->aio_iov,
-                              aiocb->aio_niov,
-                              aiocb->aio_offset);
-    } while (len == -1 && errno == EINTR);
-
-    if (len == -1)
-        return -errno;
-    return len;
-}
-
-/*
- * Read/writes the data to/from a given linear buffer.
- *
- * Returns the number of bytes handles or -errno in case of an error. Short
- * reads are only returned if the end of the file is reached.
- */
-static ssize_t handle_aiocb_rw_linear(struct qemu_paiocb *aiocb, char *buf)
-{
-    ssize_t offset = 0;
-    ssize_t len;
-
-    while (offset < aiocb->aio_nbytes) {
-         if (aiocb->aio_type & QEMU_AIO_WRITE)
-             len = pwrite(aiocb->aio_fildes,
-                          (const char *)buf + offset,
-                          aiocb->aio_nbytes - offset,
-                          aiocb->aio_offset + offset);
-         else
-             len = pread(aiocb->aio_fildes,
-                         buf + offset,
-                         aiocb->aio_nbytes - offset,
-                         aiocb->aio_offset + offset);
-
-         if (len == -1 && errno == EINTR)
-             continue;
-         else if (len == -1) {
-             offset = -errno;
-             break;
-         } else if (len == 0)
-             break;
-
-         offset += len;
-    }
-
-    return offset;
-}
-
-static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
-{
-    ssize_t nbytes;
-    char *buf;
-
-    if (!(aiocb->aio_type & QEMU_AIO_MISALIGNED)) {
-        /*
-         * If there is just a single buffer, and it is properly aligned
-         * we can just use plain pread/pwrite without any problems.
-         */
-        if (aiocb->aio_niov == 1)
-             return handle_aiocb_rw_linear(aiocb, aiocb->aio_iov->iov_base);
-
-        /*
-         * We have more than one iovec, and all are properly aligned.
-         *
-         * Try preadv/pwritev first and fall back to linearizing the
-         * buffer if it's not supported.
-         */
-        if (preadv_present) {
-            nbytes = handle_aiocb_rw_vector(aiocb);
-            if (nbytes == aiocb->aio_nbytes)
-                return nbytes;
-            if (nbytes < 0 && nbytes != -ENOSYS)
-                return nbytes;
-            preadv_present = 0;
-        }
-
-        /*
-         * XXX(hch): short read/write.  no easy way to handle the reminder
-         * using these interfaces.  For now retry using plain
-         * pread/pwrite?
-         */
-    }
-
-    /*
-     * Ok, we have to do it the hard way, copy all segments into
-     * a single aligned buffer.
-     */
-    buf = qemu_blockalign(aiocb->common.bs, aiocb->aio_nbytes);
-    if (aiocb->aio_type & QEMU_AIO_WRITE) {
-        char *p = buf;
-        int i;
-
-        for (i = 0; i < aiocb->aio_niov; ++i) {
-            memcpy(p, aiocb->aio_iov[i].iov_base, aiocb->aio_iov[i].iov_len);
-            p += aiocb->aio_iov[i].iov_len;
-        }
-    }
-
-    nbytes = handle_aiocb_rw_linear(aiocb, buf);
-    if (!(aiocb->aio_type & QEMU_AIO_WRITE)) {
-        char *p = buf;
-        size_t count = aiocb->aio_nbytes, copy;
-        int i;
-
-        for (i = 0; i < aiocb->aio_niov && count; ++i) {
-            copy = count;
-            if (copy > aiocb->aio_iov[i].iov_len)
-                copy = aiocb->aio_iov[i].iov_len;
-            memcpy(aiocb->aio_iov[i].iov_base, p, copy);
-            p     += copy;
-            count -= copy;
-        }
-    }
-    qemu_vfree(buf);
-
-    return nbytes;
-}
-
-static void posix_aio_notify_event(void);
-
-static void *aio_thread(void *unused)
-{
-    mutex_lock(&lock);
-    pending_threads--;
-    mutex_unlock(&lock);
-    do_spawn_thread();
-
-    while (1) {
-        struct qemu_paiocb *aiocb;
-        ssize_t ret = 0;
-        qemu_timeval tv;
-        struct timespec ts;
-
-        qemu_gettimeofday(&tv);
-        ts.tv_sec = tv.tv_sec + 10;
-        ts.tv_nsec = 0;
-
-        mutex_lock(&lock);
-
-        while (QTAILQ_EMPTY(&request_list) &&
-               !(ret == ETIMEDOUT)) {
-            idle_threads++;
-            ret = cond_timedwait(&cond, &lock, &ts);
-            idle_threads--;
-        }
-
-        if (QTAILQ_EMPTY(&request_list))
-            break;
-
-        aiocb = QTAILQ_FIRST(&request_list);
-        QTAILQ_REMOVE(&request_list, aiocb, node);
-        aiocb->active = 1;
-        mutex_unlock(&lock);
-
-        switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
-        case QEMU_AIO_READ:
-            ret = handle_aiocb_rw(aiocb);
-            if (ret >= 0 && ret < aiocb->aio_nbytes && aiocb->common.bs->growable) {
-                /* A short read means that we have reached EOF. Pad the buffer
-                 * with zeros for bytes after EOF. */
-                iov_memset(aiocb->aio_iov, aiocb->aio_niov, ret,
-                           0, aiocb->aio_nbytes - ret);
-
-                ret = aiocb->aio_nbytes;
-            }
-            break;
-        case QEMU_AIO_WRITE:
-            ret = handle_aiocb_rw(aiocb);
-            break;
-        case QEMU_AIO_FLUSH:
-            ret = handle_aiocb_flush(aiocb);
-            break;
-        case QEMU_AIO_IOCTL:
-            ret = handle_aiocb_ioctl(aiocb);
-            break;
-        default:
-            fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
-            ret = -EINVAL;
-            break;
-        }
-
-        mutex_lock(&lock);
-        aiocb->ret = ret;
-        mutex_unlock(&lock);
-
-        posix_aio_notify_event();
-    }
-
-    cur_threads--;
-    mutex_unlock(&lock);
-
-    return NULL;
-}
-
-static void do_spawn_thread(void)
-{
-    sigset_t set, oldset;
-
-    mutex_lock(&lock);
-    if (!new_threads) {
-        mutex_unlock(&lock);
-        return;
-    }
-
-    new_threads--;
-    pending_threads++;
-
-    mutex_unlock(&lock);
-
-    /* block all signals */
-    if (sigfillset(&set)) die("sigfillset");
-    if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
-
-    thread_create(&thread_id, &attr, aio_thread, NULL);
-
-    if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
-}
-
-static void spawn_thread_bh_fn(void *opaque)
-{
-    do_spawn_thread();
-}
-
-static void spawn_thread(void)
-{
-    cur_threads++;
-    new_threads++;
-    /* If there are threads being created, they will spawn new workers, so
-     * we don't spend time creating many threads in a loop holding a mutex or
-     * starving the current vcpu.
-     *
-     * If there are no idle threads, ask the main thread to create one, so we
-     * inherit the correct affinity instead of the vcpu affinity.
-     */
-    if (!pending_threads) {
-        qemu_bh_schedule(new_thread_bh);
-    }
-}
-
-static void qemu_paio_submit(struct qemu_paiocb *aiocb)
-{
-    aiocb->ret = -EINPROGRESS;
-    aiocb->active = 0;
-    mutex_lock(&lock);
-    if (idle_threads == 0 && cur_threads < max_threads)
-        spawn_thread();
-    QTAILQ_INSERT_TAIL(&request_list, aiocb, node);
-    mutex_unlock(&lock);
-    cond_signal(&cond);
-}
-
-static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
-{
-    ssize_t ret;
-
-    mutex_lock(&lock);
-    ret = aiocb->ret;
-    mutex_unlock(&lock);
-
-    return ret;
-}
-
-static int qemu_paio_error(struct qemu_paiocb *aiocb)
-{
-    ssize_t ret = qemu_paio_return(aiocb);
-
-    if (ret < 0)
-        ret = -ret;
-    else
-        ret = 0;
-
-    return ret;
-}
-
-static void posix_aio_read(void *opaque)
-{
-    PosixAioState *s = opaque;
-    struct qemu_paiocb *acb, **pacb;
-    int ret;
-    ssize_t len;
-
-    /* read all bytes from signal pipe */
-    for (;;) {
-        char bytes[16];
-
-        len = read(s->rfd, bytes, sizeof(bytes));
-        if (len == -1 && errno == EINTR)
-            continue; /* try again */
-        if (len == sizeof(bytes))
-            continue; /* more to read */
-        break;
-    }
-
-    for(;;) {
-        pacb = &s->first_aio;
-        for(;;) {
-            acb = *pacb;
-            if (!acb)
-                return;
-
-            ret = qemu_paio_error(acb);
-            if (ret == ECANCELED) {
-                /* remove the request */
-                *pacb = acb->next;
-                qemu_aio_release(acb);
-            } else if (ret != EINPROGRESS) {
-                /* end of aio */
-                if (ret == 0) {
-                    ret = qemu_paio_return(acb);
-                    if (ret == acb->aio_nbytes)
-                        ret = 0;
-                    else
-                        ret = -EINVAL;
-                } else {
-                    ret = -ret;
-                }
-
-                trace_paio_complete(acb, acb->common.opaque, ret);
-
-                /* remove the request */
-                *pacb = acb->next;
-                /* call the callback */
-                acb->common.cb(acb->common.opaque, ret);
-                qemu_aio_release(acb);
-                break;
-            } else {
-                pacb = &acb->next;
-            }
-        }
-    }
-}
-
-static int posix_aio_flush(void *opaque)
-{
-    PosixAioState *s = opaque;
-    return !!s->first_aio;
-}
-
-static PosixAioState *posix_aio_state;
-
-static void posix_aio_notify_event(void)
-{
-    char byte = 0;
-    ssize_t ret;
-
-    ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
-    if (ret < 0 && errno != EAGAIN)
-        die("write()");
-}
-
-static void paio_remove(struct qemu_paiocb *acb)
-{
-    struct qemu_paiocb **pacb;
-
-    /* remove the callback from the queue */
-    pacb = &posix_aio_state->first_aio;
-    for(;;) {
-        if (*pacb == NULL) {
-            fprintf(stderr, "paio_remove: aio request not found!\n");
-            break;
-        } else if (*pacb == acb) {
-            *pacb = acb->next;
-            qemu_aio_release(acb);
-            break;
-        }
-        pacb = &(*pacb)->next;
-    }
-}
-
-static void paio_cancel(BlockDriverAIOCB *blockacb)
-{
-    struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
-    int active = 0;
-
-    trace_paio_cancel(acb, acb->common.opaque);
-
-    mutex_lock(&lock);
-    if (!acb->active) {
-        QTAILQ_REMOVE(&request_list, acb, node);
-        acb->ret = -ECANCELED;
-    } else if (acb->ret == -EINPROGRESS) {
-        active = 1;
-    }
-    mutex_unlock(&lock);
-
-    if (active) {
-        /* fail safe: if the aio could not be canceled, we wait for
-           it */
-        while (qemu_paio_error(acb) == EINPROGRESS)
-            ;
-    }
-
-    paio_remove(acb);
-}
-
-static AIOPool raw_aio_pool = {
-    .aiocb_size         = sizeof(struct qemu_paiocb),
-    .cancel             = paio_cancel,
-};
-
-BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
-        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,
-        BlockDriverCompletionFunc *cb, void *opaque, int type)
-{
-    struct qemu_paiocb *acb;
-
-    acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);
-    acb->aio_type = type;
-    acb->aio_fildes = fd;
-
-    if (qiov) {
-        acb->aio_iov = qiov->iov;
-        acb->aio_niov = qiov->niov;
-    }
-    acb->aio_nbytes = nb_sectors * 512;
-    acb->aio_offset = sector_num * 512;
-
-    acb->next = posix_aio_state->first_aio;
-    posix_aio_state->first_aio = acb;
-
-    trace_paio_submit(acb, opaque, sector_num, nb_sectors, type);
-    qemu_paio_submit(acb);
-    return &acb->common;
-}
-
-BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
-        unsigned long int req, void *buf,
-        BlockDriverCompletionFunc *cb, void *opaque)
-{
-    struct qemu_paiocb *acb;
-
-    acb = qemu_aio_get(&raw_aio_pool, bs, cb, opaque);
-    acb->aio_type = QEMU_AIO_IOCTL;
-    acb->aio_fildes = fd;
-    acb->aio_offset = 0;
-    acb->aio_ioctl_buf = buf;
-    acb->aio_ioctl_cmd = req;
-
-    acb->next = posix_aio_state->first_aio;
-    posix_aio_state->first_aio = acb;
-
-    qemu_paio_submit(acb);
-    return &acb->common;
-}
-
-int paio_init(void)
-{
-    PosixAioState *s;
-    int fds[2];
-    int ret;
-
-    if (posix_aio_state)
-        return 0;
-
-    s = g_malloc(sizeof(PosixAioState));
-
-    s->first_aio = NULL;
-    if (qemu_pipe(fds) == -1) {
-        fprintf(stderr, "failed to create pipe\n");
-        g_free(s);
-        return -1;
-    }
-
-    s->rfd = fds[0];
-    s->wfd = fds[1];
-
-    fcntl(s->rfd, F_SETFL, O_NONBLOCK);
-    fcntl(s->wfd, F_SETFL, O_NONBLOCK);
-
-    qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush, s);
-
-    ret = pthread_attr_init(&attr);
-    if (ret)
-        die2(ret, "pthread_attr_init");
-
-    ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-    if (ret)
-        die2(ret, "pthread_attr_setdetachstate");
-
-    QTAILQ_INIT(&request_list);
-    new_thread_bh = qemu_bh_new(spawn_thread_bh_fn, NULL);
-
-    posix_aio_state = s;
-    return 0;
-}
diff --git a/qapi/Makefile.objs b/qapi/Makefile.objs
index 5f5846e767..f9bd3b9910 100644
--- a/qapi/Makefile.objs
+++ b/qapi/Makefile.objs
@@ -1,3 +1,5 @@
 qapi-obj-y = qapi-visit-core.o qapi-dealloc-visitor.o qmp-input-visitor.o
 qapi-obj-y += qmp-output-visitor.o qmp-registry.o qmp-dispatch.o
-qapi-obj-y += string-input-visitor.o string-output-visitor.o opts-visitor.o
+qapi-obj-y += string-input-visitor.o string-output-visitor.o
+
+common-obj-y += opts-visitor.o
diff --git a/qemu-aio.h b/qemu-aio.h
index bfdd35f02c..1b7eb6ef5b 100644
--- a/qemu-aio.h
+++ b/qemu-aio.h
@@ -15,7 +15,8 @@
 #define QEMU_AIO_H
 
 #include "qemu-common.h"
-#include "qemu-char.h"
+#include "qemu-queue.h"
+#include "event_notifier.h"
 
 typedef struct BlockDriverAIOCB BlockDriverAIOCB;
 typedef void BlockDriverCompletionFunc(void *opaque, int ret);
@@ -38,20 +39,162 @@ void *qemu_aio_get(AIOPool *pool, BlockDriverState *bs,
                    BlockDriverCompletionFunc *cb, void *opaque);
 void qemu_aio_release(void *p);
 
+typedef struct AioHandler AioHandler;
+typedef void QEMUBHFunc(void *opaque);
+typedef void IOHandler(void *opaque);
+
+typedef struct AioContext {
+    GSource source;
+
+    /* The list of registered AIO handlers */
+    QLIST_HEAD(, AioHandler) aio_handlers;
+
+    /* This is a simple lock used to protect the aio_handlers list.
+     * Specifically, it's used to ensure that no callbacks are removed while
+     * we're walking and dispatching callbacks.
+     */
+    int walking_handlers;
+
+    /* Anchor of the list of Bottom Halves belonging to the context */
+    struct QEMUBH *first_bh;
+
+    /* A simple lock used to protect the first_bh list, and ensure that
+     * no callbacks are removed while we're walking and dispatching callbacks.
+     */
+    int walking_bh;
+
+    /* Used for aio_notify.  */
+    EventNotifier notifier;
+} AioContext;
+
 /* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
-typedef int (AioFlushHandler)(void *opaque);
+typedef int (AioFlushEventNotifierHandler)(EventNotifier *e);
+
+/**
+ * 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(void);
+
+/**
+ * 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);
+
+/**
+ * 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_wait to exit, so that the next call will re-examine pending events.
+ * The caller of aio_notify will usually call aio_wait 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_bh_poll: Poll bottom halves for an AioContext.
+ *
+ * These are internal functions used by the QEMU main loop.
+ */
+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.
+ *
+ * @bh: The bottom half to be deleted.
+ */
+void qemu_bh_delete(QEMUBH *bh);
 
 /* Flush any pending AIO operation. This function will block until all
  * outstanding AIO operations have been completed or cancelled. */
-void qemu_aio_flush(void);
+void aio_flush(AioContext *ctx);
 
-/* Wait for a single AIO completion to occur.  This function will wait
- * until a single AIO event has completed and it will ensure something
- * has moved before returning. This can issue new pending aio as
- * result of executing I/O completion or bh callbacks.
+/* Return whether there are any pending callbacks from the GSource
+ * attached to the AioContext.
  *
- * Return whether there is still any pending AIO operation.  */
-bool qemu_aio_wait(void);
+ * This is used internally in the implementation of the GSource.
+ */
+bool aio_pending(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.
+ *
+ * If there is no pending AIO operation or completion (bottom half),
+ * return false.  If there are pending bottom halves, return true.
+ *
+ * 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.
+ *
+ * If @blocking is false, this function will also return false if the
+ * function cannot make any progress without blocking.
+ */
+bool aio_poll(AioContext *ctx, bool blocking);
+
+#ifdef CONFIG_POSIX
+/* Returns 1 if there are still outstanding AIO requests; 0 otherwise */
+typedef int (AioFlushHandler)(void *opaque);
 
 /* Register a file descriptor and associated callbacks.  Behaves very similarly
  * to qemu_set_fd_handler2.  Unlike qemu_set_fd_handler2, these callbacks will
@@ -60,10 +203,45 @@ bool qemu_aio_wait(void);
  * Code that invokes AIO completion functions should rely on this function
  * instead of qemu_set_fd_handler[2].
  */
-int qemu_aio_set_fd_handler(int fd,
-                            IOHandler *io_read,
-                            IOHandler *io_write,
-                            AioFlushHandler *io_flush,
-                            void *opaque);
+void aio_set_fd_handler(AioContext *ctx,
+                        int fd,
+                        IOHandler *io_read,
+                        IOHandler *io_write,
+                        AioFlushHandler *io_flush,
+                        void *opaque);
+#endif
+
+/* 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 either qemu_aio_wait() or qemu_aio_flush().
+ *
+ * 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,
+                            EventNotifierHandler *io_read,
+                            AioFlushEventNotifierHandler *io_flush);
+
+/* Return a GSource that lets the main loop poll the file descriptors attached
+ * to this AioContext.
+ */
+GSource *aio_get_g_source(AioContext *ctx);
+
+/* Functions to operate on the main QEMU AioContext.  */
+
+void qemu_aio_flush(void);
+bool qemu_aio_wait(void);
+void qemu_aio_set_event_notifier(EventNotifier *notifier,
+                                 EventNotifierHandler *io_read,
+                                 AioFlushEventNotifierHandler *io_flush);
+
+#ifdef CONFIG_POSIX
+void qemu_aio_set_fd_handler(int fd,
+                             IOHandler *io_read,
+                             IOHandler *io_write,
+                             AioFlushHandler *io_flush,
+                             void *opaque);
+#endif
 
 #endif
diff --git a/qemu-char.h b/qemu-char.h
index 297dd98342..a121e04cdc 100644
--- a/qemu-char.h
+++ b/qemu-char.h
@@ -5,6 +5,7 @@
 #include "qemu-queue.h"
 #include "qemu-option.h"
 #include "qemu-config.h"
+#include "qemu-aio.h"
 #include "qobject.h"
 #include "qstring.h"
 #include "main-loop.h"
diff --git a/qemu-common.h b/qemu-common.h
index 2011c00fe2..bef58262f3 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -14,6 +14,7 @@
 
 typedef struct QEMUTimer QEMUTimer;
 typedef struct QEMUFile QEMUFile;
+typedef struct QEMUBH QEMUBH;
 typedef struct DeviceState DeviceState;
 
 struct Monitor;
@@ -167,7 +168,6 @@ int qemu_fls(int i);
 int qemu_fdatasync(int fd);
 int fcntl_setfl(int fd, int flag);
 int qemu_parse_fd(const char *param);
-int qemu_parse_fdset(const char *param);
 
 /*
  * strtosz() suffixes used to specify the default treatment of an
@@ -218,7 +218,6 @@ ssize_t qemu_recv_full(int fd, void *buf, size_t count, int flags)
     QEMU_WARN_UNUSED_RESULT;
 
 #ifndef _WIN32
-int qemu_eventfd(int pipefd[2]);
 int qemu_pipe(int pipefd[2]);
 #endif
 
diff --git a/qemu-coroutine-lock.c b/qemu-coroutine-lock.c
index 26ad76bf50..9dda3f86c9 100644
--- a/qemu-coroutine-lock.c
+++ b/qemu-coroutine-lock.c
@@ -26,7 +26,7 @@
 #include "qemu-coroutine.h"
 #include "qemu-coroutine-int.h"
 #include "qemu-queue.h"
-#include "main-loop.h"
+#include "qemu-aio.h"
 #include "trace.h"
 
 static QTAILQ_HEAD(, Coroutine) unlock_bh_queue =
diff --git a/qemu-os-win32.h b/qemu-os-win32.h
index 8ba466dbfb..d0e9234d24 100644
--- a/qemu-os-win32.h
+++ b/qemu-os-win32.h
@@ -28,7 +28,6 @@
 
 #include <windows.h>
 #include <winsock2.h>
-#include "main-loop.h"
 
 /* Workaround for older versions of MinGW. */
 #ifndef ECONNREFUSED
diff --git a/qemu-sockets.c b/qemu-sockets.c
index cfed9c5a5b..f2a637165b 100644
--- a/qemu-sockets.c
+++ b/qemu-sockets.c
@@ -967,3 +967,21 @@ int socket_init(void)
 #endif
     return 0;
 }
+
+static int default_monitor_get_fd(Monitor *mon, const char *name, Error **errp)
+{
+    error_setg(errp, "only QEMU supports file descriptor passing");
+    return -1;
+}
+QEMU_WEAK_ALIAS(monitor_get_fd, default_monitor_get_fd);
+
+static int default_qemu_set_fd_handler2(int fd,
+                                        IOCanReadHandler *fd_read_poll,
+                                        IOHandler *fd_read,
+                                        IOHandler *fd_write,
+                                        void *opaque)
+
+{
+    abort();
+}
+QEMU_WEAK_ALIAS(qemu_set_fd_handler2, default_qemu_set_fd_handler2);
diff --git a/qemu-thread-posix.c b/qemu-thread-posix.c
index 8fbabdac36..6a3d3a12a8 100644
--- a/qemu-thread-posix.c
+++ b/qemu-thread-posix.c
@@ -17,6 +17,9 @@
 #include <signal.h>
 #include <stdint.h>
 #include <string.h>
+#include <limits.h>
+#include <unistd.h>
+#include <sys/time.h>
 #include "qemu-thread.h"
 
 static void error_exit(int err, const char *msg)
@@ -115,6 +118,83 @@ void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
         error_exit(err, __func__);
 }
 
+void qemu_sem_init(QemuSemaphore *sem, int init)
+{
+    int rc;
+
+    rc = sem_init(&sem->sem, 0, init);
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+}
+
+void qemu_sem_destroy(QemuSemaphore *sem)
+{
+    int rc;
+
+    rc = sem_destroy(&sem->sem);
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+}
+
+void qemu_sem_post(QemuSemaphore *sem)
+{
+    int rc;
+
+    rc = sem_post(&sem->sem);
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+}
+
+int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
+{
+    int rc;
+
+    if (ms <= 0) {
+        /* This is cheaper than sem_timedwait.  */
+        do {
+            rc = sem_trywait(&sem->sem);
+        } while (rc == -1 && errno == EINTR);
+        if (rc == -1 && errno == EAGAIN) {
+            return -1;
+        }
+    } else {
+        struct timeval tv;
+        struct timespec ts;
+        gettimeofday(&tv, NULL);
+        ts.tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000;
+        ts.tv_sec = tv.tv_sec + ms / 1000;
+        if (ts.tv_nsec >= 1000000000) {
+            ts.tv_sec++;
+            ts.tv_nsec -= 1000000000;
+        }
+        do {
+            rc = sem_timedwait(&sem->sem, &ts);
+        } while (rc == -1 && errno == EINTR);
+        if (rc == -1 && errno == ETIMEDOUT) {
+            return -1;
+        }
+    }
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+    return 0;
+}
+
+void qemu_sem_wait(QemuSemaphore *sem)
+{
+    int rc;
+
+    do {
+        rc = sem_wait(&sem->sem);
+    } while (rc == -1 && errno == EINTR);
+    if (rc < 0) {
+        error_exit(errno, __func__);
+    }
+}
+
 void qemu_thread_create(QemuThread *thread,
                        void *(*start_routine)(void*),
                        void *arg, int mode)
diff --git a/qemu-thread-posix.h b/qemu-thread-posix.h
index ee4618e620..2542c15200 100644
--- a/qemu-thread-posix.h
+++ b/qemu-thread-posix.h
@@ -1,6 +1,7 @@
 #ifndef __QEMU_THREAD_POSIX_H
 #define __QEMU_THREAD_POSIX_H 1
 #include "pthread.h"
+#include <semaphore.h>
 
 struct QemuMutex {
     pthread_mutex_t lock;
@@ -10,6 +11,10 @@ struct QemuCond {
     pthread_cond_t cond;
 };
 
+struct QemuSemaphore {
+    sem_t sem;
+};
+
 struct QemuThread {
     pthread_t thread;
 };
diff --git a/qemu-thread-win32.c b/qemu-thread-win32.c
index 177b398cc4..4b3db60f5c 100644
--- a/qemu-thread-win32.c
+++ b/qemu-thread-win32.c
@@ -192,6 +192,41 @@ void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
     qemu_mutex_lock(mutex);
 }
 
+void qemu_sem_init(QemuSemaphore *sem, int init)
+{
+    /* Manual reset.  */
+    sem->sema = CreateSemaphore(NULL, init, LONG_MAX, NULL);
+}
+
+void qemu_sem_destroy(QemuSemaphore *sem)
+{
+    CloseHandle(sem->sema);
+}
+
+void qemu_sem_post(QemuSemaphore *sem)
+{
+    ReleaseSemaphore(sem->sema, 1, NULL);
+}
+
+int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
+{
+    int rc = WaitForSingleObject(sem->sema, ms);
+    if (rc == WAIT_OBJECT_0) {
+        return 0;
+    }
+    if (rc != WAIT_TIMEOUT) {
+        error_exit(GetLastError(), __func__);
+    }
+    return -1;
+}
+
+void qemu_sem_wait(QemuSemaphore *sem)
+{
+    if (WaitForSingleObject(sem->sema, INFINITE) != WAIT_OBJECT_0) {
+        error_exit(GetLastError(), __func__);
+    }
+}
+
 struct QemuThreadData {
     /* Passed to win32_start_routine.  */
     void             *(*start_routine)(void *);
diff --git a/qemu-thread-win32.h b/qemu-thread-win32.h
index b9d1be8478..13adb958f0 100644
--- a/qemu-thread-win32.h
+++ b/qemu-thread-win32.h
@@ -13,6 +13,10 @@ struct QemuCond {
     HANDLE continue_event;
 };
 
+struct QemuSemaphore {
+    HANDLE sema;
+};
+
 typedef struct QemuThreadData QemuThreadData;
 struct QemuThread {
     QemuThreadData *data;
diff --git a/qemu-thread.h b/qemu-thread.h
index 05fdaaf50e..3ee2f6b1f9 100644
--- a/qemu-thread.h
+++ b/qemu-thread.h
@@ -6,6 +6,7 @@
 
 typedef struct QemuMutex QemuMutex;
 typedef struct QemuCond QemuCond;
+typedef struct QemuSemaphore QemuSemaphore;
 typedef struct QemuThread QemuThread;
 
 #ifdef _WIN32
@@ -38,6 +39,12 @@ void qemu_cond_signal(QemuCond *cond);
 void qemu_cond_broadcast(QemuCond *cond);
 void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex);
 
+void qemu_sem_init(QemuSemaphore *sem, int init);
+void qemu_sem_post(QemuSemaphore *sem);
+void qemu_sem_wait(QemuSemaphore *sem);
+int qemu_sem_timedwait(QemuSemaphore *sem, int ms);
+void qemu_sem_destroy(QemuSemaphore *sem);
+
 void qemu_thread_create(QemuThread *thread,
                         void *(*start_routine)(void *),
                         void *arg, int mode);
diff --git a/qemu-timer.c b/qemu-timer.c
index ede84ffd56..f3426c9937 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -430,9 +430,11 @@ void qemu_unregister_clock_reset_notifier(QEMUClock *clock, Notifier *notifier)
 
 void init_clocks(void)
 {
-    rt_clock = qemu_new_clock(QEMU_CLOCK_REALTIME);
-    vm_clock = qemu_new_clock(QEMU_CLOCK_VIRTUAL);
-    host_clock = qemu_new_clock(QEMU_CLOCK_HOST);
+    if (!rt_clock) {
+        rt_clock = qemu_new_clock(QEMU_CLOCK_REALTIME);
+        vm_clock = qemu_new_clock(QEMU_CLOCK_VIRTUAL);
+        host_clock = qemu_new_clock(QEMU_CLOCK_HOST);
+    }
 }
 
 uint64_t qemu_timer_expire_time_ns(QEMUTimer *ts)
@@ -745,6 +747,10 @@ int init_timer_alarm(void)
     struct qemu_alarm_timer *t = NULL;
     int i, err = -1;
 
+    if (alarm_timer) {
+        return 0;
+    }
+
     for (i = 0; alarm_timers[i].name; i++) {
         t = &alarm_timers[i];
 
diff --git a/qemu-tool.c b/qemu-tool.c
index da4c05aaf7..b46631e422 100644
--- a/qemu-tool.c
+++ b/qemu-tool.c
@@ -38,12 +38,6 @@ const char *qemu_get_vm_name(void)
 
 Monitor *cur_mon;
 
-int monitor_get_fd(Monitor *mon, const char *name, Error **errp)
-{
-    error_setg(errp, "only QEMU supports file descriptor passing");
-    return -1;
-}
-
 void vm_stop(RunState state)
 {
     abort();
@@ -74,29 +68,9 @@ void monitor_protocol_event(MonitorEvent event, QObject *data)
 {
 }
 
-int monitor_fdset_get_fd(int64_t fdset_id, int flags)
-{
-    return -1;
-}
-
-int monitor_fdset_dup_fd_add(int64_t fdset_id, int dup_fd)
-{
-    return -1;
-}
-
-int monitor_fdset_dup_fd_remove(int dup_fd)
-{
-    return -1;
-}
-
-int monitor_fdset_dup_fd_find(int dup_fd)
-{
-    return -1;
-}
-
 int64_t cpu_get_clock(void)
 {
-    return qemu_get_clock_ns(rt_clock);
+    return get_clock_realtime();
 }
 
 int64_t cpu_get_icount(void)
@@ -118,13 +92,6 @@ void qemu_clock_warp(QEMUClock *clock)
 {
 }
 
-int qemu_init_main_loop(void)
-{
-    init_clocks();
-    init_timer_alarm();
-    return main_loop_init();
-}
-
 void slirp_update_timeout(uint32_t *timeout)
 {
 }
diff --git a/qemu-user.c b/qemu-user.c
index 13fb9ae77b..08ccb0fe8e 100644
--- a/qemu-user.c
+++ b/qemu-user.c
@@ -35,23 +35,3 @@ void monitor_vprintf(Monitor *mon, const char *fmt, va_list ap)
 void monitor_set_error(Monitor *mon, QError *qerror)
 {
 }
-
-int monitor_fdset_get_fd(int64_t fdset_id, int flags)
-{
-    return -1;
-}
-
-int monitor_fdset_dup_fd_add(int64_t fdset_id, int dup_fd)
-{
-    return -1;
-}
-
-int monitor_fdset_dup_fd_remove(int dup_fd)
-{
-    return -1;
-}
-
-int monitor_fdset_dup_fd_find(int dup_fd)
-{
-    return -1;
-}
diff --git a/qmp.c b/qmp.c
index d8a3c00b97..638888a64e 100644
--- a/qmp.c
+++ b/qmp.c
@@ -471,11 +471,12 @@ DevicePropertyInfoList *qmp_device_list_properties(const char *typename,
     return prop_list;
 }
 
-CpuDefinitionInfoList GCC_WEAK *arch_query_cpu_definitions(Error **errp)
+static CpuDefinitionInfoList *default_arch_query_cpu_definitions(Error **errp)
 {
     error_set(errp, QERR_NOT_SUPPORTED);
     return NULL;
 }
+QEMU_WEAK_ALIAS(arch_query_cpu_definitions, default_arch_query_cpu_definitions);
 
 CpuDefinitionInfoList *qmp_query_cpu_definitions(Error **errp)
 {
diff --git a/tests/Makefile b/tests/Makefile
index 86c9b79ebe..9bf0765de3 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -36,7 +36,7 @@ test-obj-y = tests/check-qint.o tests/check-qstring.o tests/check-qdict.o \
 	tests/test-qmp-input-visitor.o tests/test-qmp-input-strict.o \
 	tests/test-qmp-commands.o tests/test-visitor-serialization.o
 
-test-qapi-obj-y =  $(qobject-obj-y) $(qapi-obj-y) $(tools-obj-y)
+test-qapi-obj-y =  $(qobject-obj-y) $(qapi-obj-y) qemu-tool.o
 test-qapi-obj-y += tests/test-qapi-visit.o tests/test-qapi-types.o
 test-qapi-obj-y += module.o
 
@@ -47,8 +47,8 @@ tests/check-qstring$(EXESUF): tests/check-qstring.o qstring.o
 tests/check-qdict$(EXESUF): tests/check-qdict.o qdict.o qfloat.o qint.o qstring.o qbool.o qlist.o
 tests/check-qlist$(EXESUF): tests/check-qlist.o qlist.o qint.o
 tests/check-qfloat$(EXESUF): tests/check-qfloat.o qfloat.o
-tests/check-qjson$(EXESUF): tests/check-qjson.o $(qobject-obj-y) $(tools-obj-y)
-tests/test-coroutine$(EXESUF): tests/test-coroutine.o $(coroutine-obj-y) $(tools-obj-y)
+tests/check-qjson$(EXESUF): tests/check-qjson.o $(qobject-obj-y) qemu-tool.o
+tests/test-coroutine$(EXESUF): tests/test-coroutine.o $(coroutine-obj-y) $(tools-obj-y) $(block-obj-y) iov.o
 tests/test-iov$(EXESUF): tests/test-iov.o iov.o
 
 tests/test-qapi-types.c tests/test-qapi-types.h :\
@@ -81,7 +81,7 @@ TARGETS=$(patsubst %-softmmu,%, $(filter %-softmmu,$(TARGET_DIRS)))
 QTEST_TARGETS=$(foreach TARGET,$(TARGETS), $(if $(check-qtest-$(TARGET)-y), $(TARGET),))
 check-qtest-$(CONFIG_POSIX)=$(foreach TARGET,$(TARGETS), $(check-qtest-$(TARGET)-y))
 
-qtest-obj-y = tests/libqtest.o $(oslib-obj-y) $(tools-obj-y)
+qtest-obj-y = tests/libqtest.o $(oslib-obj-y)
 $(check-qtest-y): $(qtest-obj-y)
 
 .PHONY: check-help
diff --git a/thread-pool.c b/thread-pool.c
new file mode 100644
index 0000000000..651b32419b
--- /dev/null
+++ b/thread-pool.c
@@ -0,0 +1,289 @@
+/*
+ * QEMU block layer thread pool
+ *
+ * Copyright IBM, Corp. 2008
+ * Copyright Red Hat, Inc. 2012
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Paolo Bonzini     <pbonzini@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Contributions after 2012-01-13 are licensed under the terms of the
+ * GNU GPL, version 2 or (at your option) any later version.
+ */
+#include "qemu-common.h"
+#include "qemu-queue.h"
+#include "qemu-thread.h"
+#include "osdep.h"
+#include "qemu-coroutine.h"
+#include "trace.h"
+#include "block_int.h"
+#include "event_notifier.h"
+#include "thread-pool.h"
+
+static void do_spawn_thread(void);
+
+typedef struct ThreadPoolElement ThreadPoolElement;
+
+enum ThreadState {
+    THREAD_QUEUED,
+    THREAD_ACTIVE,
+    THREAD_DONE,
+    THREAD_CANCELED,
+};
+
+struct ThreadPoolElement {
+    BlockDriverAIOCB common;
+    ThreadPoolFunc *func;
+    void *arg;
+
+    /* Moving state out of THREAD_QUEUED is protected by lock.  After
+     * that, only the worker thread can write to it.  Reads and writes
+     * of state and ret are ordered with memory barriers.
+     */
+    enum ThreadState state;
+    int ret;
+
+    /* Access to this list is protected by lock.  */
+    QTAILQ_ENTRY(ThreadPoolElement) reqs;
+
+    /* Access to this list is protected by the global mutex.  */
+    QLIST_ENTRY(ThreadPoolElement) all;
+};
+
+static EventNotifier notifier;
+static QemuMutex lock;
+static QemuCond check_cancel;
+static QemuSemaphore sem;
+static int max_threads = 64;
+static QEMUBH *new_thread_bh;
+
+/* The following variables are protected by the global mutex.  */
+static QLIST_HEAD(, ThreadPoolElement) head;
+
+/* The following variables are protected by lock.  */
+static QTAILQ_HEAD(, ThreadPoolElement) request_list;
+static int cur_threads;
+static int idle_threads;
+static int new_threads;     /* backlog of threads we need to create */
+static int pending_threads; /* threads created but not running yet */
+static int pending_cancellations; /* whether we need a cond_broadcast */
+
+static void *worker_thread(void *unused)
+{
+    qemu_mutex_lock(&lock);
+    pending_threads--;
+    do_spawn_thread();
+
+    while (1) {
+        ThreadPoolElement *req;
+        int ret;
+
+        do {
+            idle_threads++;
+            qemu_mutex_unlock(&lock);
+            ret = qemu_sem_timedwait(&sem, 10000);
+            qemu_mutex_lock(&lock);
+            idle_threads--;
+        } while (ret == -1 && !QTAILQ_EMPTY(&request_list));
+        if (ret == -1) {
+            break;
+        }
+
+        req = QTAILQ_FIRST(&request_list);
+        QTAILQ_REMOVE(&request_list, req, reqs);
+        req->state = THREAD_ACTIVE;
+        qemu_mutex_unlock(&lock);
+
+        ret = req->func(req->arg);
+
+        req->ret = ret;
+        /* Write ret before state.  */
+        smp_wmb();
+        req->state = THREAD_DONE;
+
+        qemu_mutex_lock(&lock);
+        if (pending_cancellations) {
+            qemu_cond_broadcast(&check_cancel);
+        }
+
+        event_notifier_set(&notifier);
+    }
+
+    cur_threads--;
+    qemu_mutex_unlock(&lock);
+    return NULL;
+}
+
+static void do_spawn_thread(void)
+{
+    QemuThread t;
+
+    /* Runs with lock taken.  */
+    if (!new_threads) {
+        return;
+    }
+
+    new_threads--;
+    pending_threads++;
+
+    qemu_thread_create(&t, worker_thread, NULL, QEMU_THREAD_DETACHED);
+}
+
+static void spawn_thread_bh_fn(void *opaque)
+{
+    qemu_mutex_lock(&lock);
+    do_spawn_thread();
+    qemu_mutex_unlock(&lock);
+}
+
+static void spawn_thread(void)
+{
+    cur_threads++;
+    new_threads++;
+    /* If there are threads being created, they will spawn new workers, so
+     * we don't spend time creating many threads in a loop holding a mutex or
+     * starving the current vcpu.
+     *
+     * If there are no idle threads, ask the main thread to create one, so we
+     * inherit the correct affinity instead of the vcpu affinity.
+     */
+    if (!pending_threads) {
+        qemu_bh_schedule(new_thread_bh);
+    }
+}
+
+static void event_notifier_ready(EventNotifier *notifier)
+{
+    ThreadPoolElement *elem, *next;
+
+    event_notifier_test_and_clear(notifier);
+restart:
+    QLIST_FOREACH_SAFE(elem, &head, all, next) {
+        if (elem->state != THREAD_CANCELED && elem->state != THREAD_DONE) {
+            continue;
+        }
+        if (elem->state == THREAD_DONE) {
+            trace_thread_pool_complete(elem, elem->common.opaque, elem->ret);
+        }
+        if (elem->state == THREAD_DONE && elem->common.cb) {
+            QLIST_REMOVE(elem, all);
+            /* Read state before ret.  */
+            smp_rmb();
+            elem->common.cb(elem->common.opaque, elem->ret);
+            qemu_aio_release(elem);
+            goto restart;
+        } else {
+            /* remove the request */
+            QLIST_REMOVE(elem, all);
+            qemu_aio_release(elem);
+        }
+    }
+}
+
+static int thread_pool_active(EventNotifier *notifier)
+{
+    return !QLIST_EMPTY(&head);
+}
+
+static void thread_pool_cancel(BlockDriverAIOCB *acb)
+{
+    ThreadPoolElement *elem = (ThreadPoolElement *)acb;
+
+    trace_thread_pool_cancel(elem, elem->common.opaque);
+
+    qemu_mutex_lock(&lock);
+    if (elem->state == THREAD_QUEUED &&
+        /* No thread has yet started working on elem. we can try to "steal"
+         * the item from the worker if we can get a signal from the
+         * semaphore.  Because this is non-blocking, we can do it with
+         * the lock taken and ensure that elem will remain THREAD_QUEUED.
+         */
+        qemu_sem_timedwait(&sem, 0) == 0) {
+        QTAILQ_REMOVE(&request_list, elem, reqs);
+        elem->state = THREAD_CANCELED;
+        event_notifier_set(&notifier);
+    } else {
+        pending_cancellations++;
+        while (elem->state != THREAD_CANCELED && elem->state != THREAD_DONE) {
+            qemu_cond_wait(&check_cancel, &lock);
+        }
+        pending_cancellations--;
+    }
+    qemu_mutex_unlock(&lock);
+}
+
+static AIOPool thread_pool_cb_pool = {
+    .aiocb_size         = sizeof(ThreadPoolElement),
+    .cancel             = thread_pool_cancel,
+};
+
+BlockDriverAIOCB *thread_pool_submit_aio(ThreadPoolFunc *func, void *arg,
+        BlockDriverCompletionFunc *cb, void *opaque)
+{
+    ThreadPoolElement *req;
+
+    req = qemu_aio_get(&thread_pool_cb_pool, NULL, cb, opaque);
+    req->func = func;
+    req->arg = arg;
+    req->state = THREAD_QUEUED;
+
+    QLIST_INSERT_HEAD(&head, req, all);
+
+    trace_thread_pool_submit(req, arg);
+
+    qemu_mutex_lock(&lock);
+    if (idle_threads == 0 && cur_threads < max_threads) {
+        spawn_thread();
+    }
+    QTAILQ_INSERT_TAIL(&request_list, req, reqs);
+    qemu_mutex_unlock(&lock);
+    qemu_sem_post(&sem);
+    return &req->common;
+}
+
+typedef struct ThreadPoolCo {
+    Coroutine *co;
+    int ret;
+} ThreadPoolCo;
+
+static void thread_pool_co_cb(void *opaque, int ret)
+{
+    ThreadPoolCo *co = opaque;
+
+    co->ret = ret;
+    qemu_coroutine_enter(co->co, NULL);
+}
+
+int coroutine_fn thread_pool_submit_co(ThreadPoolFunc *func, void *arg)
+{
+    ThreadPoolCo tpc = { .co = qemu_coroutine_self(), .ret = -EINPROGRESS };
+    assert(qemu_in_coroutine());
+    thread_pool_submit_aio(func, arg, thread_pool_co_cb, &tpc);
+    qemu_coroutine_yield();
+    return tpc.ret;
+}
+
+void thread_pool_submit(ThreadPoolFunc *func, void *arg)
+{
+    thread_pool_submit_aio(func, arg, NULL, NULL);
+}
+
+static void thread_pool_init(void)
+{
+    QLIST_INIT(&head);
+    event_notifier_init(&notifier, false);
+    qemu_mutex_init(&lock);
+    qemu_cond_init(&check_cancel);
+    qemu_sem_init(&sem, 0);
+    qemu_aio_set_event_notifier(&notifier, event_notifier_ready,
+                                thread_pool_active);
+
+    QTAILQ_INIT(&request_list);
+    new_thread_bh = qemu_bh_new(spawn_thread_bh_fn, NULL);
+}
+
+block_init(thread_pool_init)
diff --git a/thread-pool.h b/thread-pool.h
new file mode 100644
index 0000000000..378a4ac9f9
--- /dev/null
+++ b/thread-pool.h
@@ -0,0 +1,34 @@
+/*
+ * QEMU block layer thread pool
+ *
+ * Copyright IBM, Corp. 2008
+ * Copyright Red Hat, Inc. 2012
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Paolo Bonzini     <pbonzini@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ * Contributions after 2012-01-13 are licensed under the terms of the
+ * GNU GPL, version 2 or (at your option) any later version.
+ */
+
+#ifndef QEMU_THREAD_POOL_H
+#define QEMU_THREAD_POOL_H 1
+
+#include "qemu-common.h"
+#include "qemu-queue.h"
+#include "qemu-thread.h"
+#include "qemu-coroutine.h"
+#include "block_int.h"
+
+typedef int ThreadPoolFunc(void *opaque);
+
+BlockDriverAIOCB *thread_pool_submit_aio(ThreadPoolFunc *func, void *arg,
+     BlockDriverCompletionFunc *cb, void *opaque);
+int coroutine_fn thread_pool_submit_co(ThreadPoolFunc *func, void *arg);
+void thread_pool_submit(ThreadPoolFunc *func, void *arg);
+
+#endif
diff --git a/trace-events b/trace-events
index 7ee21e58ea..066cdaf15e 100644
--- a/trace-events
+++ b/trace-events
@@ -98,6 +98,11 @@ virtio_blk_rw_complete(void *req, int ret) "req %p ret %d"
 virtio_blk_handle_write(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
 virtio_blk_handle_read(void *req, uint64_t sector, size_t nsectors) "req %p sector %"PRIu64" nsectors %zu"
 
+# thread-pool.c
+thread_pool_submit(void *req, void *opaque) "req %p opaque %p"
+thread_pool_complete(void *req, void *opaque, int ret) "req %p opaque %p ret %d"
+thread_pool_cancel(void *req, void *opaque) "req %p opaque %p"
+
 # posix-aio-compat.c
 paio_submit(void *acb, void *opaque, int64_t sector_num, int nb_sectors, int type) "acb %p opaque %p sector_num %"PRId64" nb_sectors %d type %d"
 paio_complete(void *acb, void *opaque, int ret) "acb %p opaque %p ret %d"
diff --git a/vl.c b/vl.c
index 9ef217363f..8d04f614b3 100644
--- a/vl.c
+++ b/vl.c
@@ -2441,11 +2441,6 @@ static void free_and_trace(gpointer mem)
     free(mem);
 }
 
-int qemu_init_main_loop(void)
-{
-    return main_loop_init();
-}
-
 int main(int argc, char **argv, char **envp)
 {
     int i;
@@ -3451,6 +3446,12 @@ int main(int argc, char **argv, char **envp)
     }
     loc_set_none();
 
+    qemu_init_cpu_loop();
+    if (qemu_init_main_loop()) {
+        fprintf(stderr, "qemu_init_main_loop failed\n");
+        exit(1);
+    }
+
     if (qemu_opts_foreach(qemu_find_opts("sandbox"), parse_sandbox, NULL, 0)) {
         exit(1);
     }
@@ -3618,12 +3619,6 @@ int main(int argc, char **argv, char **envp)
 
     configure_accelerator();
 
-    qemu_init_cpu_loop();
-    if (qemu_init_main_loop()) {
-        fprintf(stderr, "qemu_init_main_loop failed\n");
-        exit(1);
-    }
-
     machine_opts = qemu_opts_find(qemu_find_opts("machine"), 0);
     if (machine_opts) {
         kernel_filename = qemu_opt_get(machine_opts, "kernel");