dataplane: remove EventPoll in favor of AioContext

During the review of the dataplane code, the EventPoll API morphed itself
(not concidentially) into something very very similar to an AioContext.
Thus, it is trivial to convert virtio-blk-dataplane to use AioContext,
and a first baby step towards letting dataplane talk directly to the
QEMU block layer.

The only interesting note is the value-copy of EventNotifiers.  At least
in my opinion this is part of the EventNotifier API and is even portable
to Windows.  Of course, in this case you should not close the notifier's
underlying file descriptors or handle with event_notifier_cleanup.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 28 insertions, 20 deletions

diff --git a/hw/dataplane/virtio-blk.c b/hw/dataplane/virtio-blk.c
index 3f2da22669..aa9b04078b 100644
--- a/hw/dataplane/virtio-blk.c
+++ b/hw/dataplane/virtio-blk.c
@@ -14,13 +14,13 @@
 
 #include "trace.h"
 #include "qemu/iov.h"
-#include "event-poll.h"
 #include "qemu/thread.h"
 #include "vring.h"
 #include "ioq.h"
 #include "migration/migration.h"
 #include "hw/virtio-blk.h"
 #include "hw/dataplane/virtio-blk.h"
+#include "block/aio.h"
 
 enum {
     SEG_MAX = 126,                  /* maximum number of I/O segments */
@@ -51,9 +51,14 @@ struct VirtIOBlockDataPlane {
     Vring vring;                    /* virtqueue vring */
     EventNotifier *guest_notifier;  /* irq */
 
-    EventPoll event_poll;           /* event poller */
-    EventHandler io_handler;        /* Linux AIO completion handler */
-    EventHandler notify_handler;    /* virtqueue notify handler */
+    /* Note that these EventNotifiers are assigned by value.  This is
+     * fine as long as you do not call event_notifier_cleanup on them
+     * (because you don't own the file descriptor or handle; you just
+     * use it).
+     */
+    AioContext *ctx;
+    EventNotifier io_notifier;      /* Linux AIO completion */
+    EventNotifier host_notifier;    /* doorbell */
 
     IOQueue ioqueue;                /* Linux AIO queue (should really be per
                                        dataplane thread) */
@@ -256,10 +261,10 @@ static int process_request(IOQueue *ioq, struct iovec iov[],
     }
 }
 
-static void handle_notify(EventHandler *handler)
+static void handle_notify(EventNotifier *e)
 {
-    VirtIOBlockDataPlane *s = container_of(handler, VirtIOBlockDataPlane,
-                                           notify_handler);
+    VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane,
+                                           host_notifier);
 
     /* There is one array of iovecs into which all new requests are extracted
      * from the vring.  Requests are read from the vring and the translated
@@ -286,6 +291,7 @@ static void handle_notify(EventHandler *handler)
     unsigned int out_num = 0, in_num = 0;
     unsigned int num_queued;
 
+    event_notifier_test_and_clear(&s->host_notifier);
     for (;;) {
         /* Disable guest->host notifies to avoid unnecessary vmexits */
         vring_disable_notification(s->vdev, &s->vring);
@@ -334,11 +340,12 @@ static void handle_notify(EventHandler *handler)
     }
 }
 
-static void handle_io(EventHandler *handler)
+static void handle_io(EventNotifier *e)
 {
-    VirtIOBlockDataPlane *s = container_of(handler, VirtIOBlockDataPlane,
-                                           io_handler);
+    VirtIOBlockDataPlane *s = container_of(e, VirtIOBlockDataPlane,
+                                           io_notifier);
 
+    event_notifier_test_and_clear(&s->io_notifier);
     if (ioq_run_completion(&s->ioqueue, complete_request, s) > 0) {
         notify_guest(s);
     }
@@ -348,7 +355,7 @@ static void handle_io(EventHandler *handler)
      * requests.
      */
     if (unlikely(vring_more_avail(&s->vring))) {
-        handle_notify(&s->notify_handler);
+        handle_notify(&s->host_notifier);
     }
 }
 
@@ -357,7 +364,7 @@ static void *data_plane_thread(void *opaque)
     VirtIOBlockDataPlane *s = opaque;
 
     do {
-        event_poll(&s->event_poll);
+        aio_poll(s->ctx, true);
     } while (!s->stopping || s->num_reqs > 0);
     return NULL;
 }
@@ -445,7 +452,7 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
         return;
     }
 
-    event_poll_init(&s->event_poll);
+    s->ctx = aio_context_new();
 
     /* Set up guest notifier (irq) */
     if (s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, 1,
@@ -462,17 +469,16 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
         fprintf(stderr, "virtio-blk failed to set host notifier\n");
         exit(1);
     }
-    event_poll_add(&s->event_poll, &s->notify_handler,
-                   virtio_queue_get_host_notifier(vq),
-                   handle_notify);
+    s->host_notifier = *virtio_queue_get_host_notifier(vq);
+    aio_set_event_notifier(s->ctx, &s->host_notifier, handle_notify, NULL);
 
     /* Set up ioqueue */
     ioq_init(&s->ioqueue, s->fd, REQ_MAX);
     for (i = 0; i < ARRAY_SIZE(s->requests); i++) {
         ioq_put_iocb(&s->ioqueue, &s->requests[i].iocb);
     }
-    event_poll_add(&s->event_poll, &s->io_handler,
-                   ioq_get_notifier(&s->ioqueue), handle_io);
+    s->io_notifier = *ioq_get_notifier(&s->ioqueue);
+    aio_set_event_notifier(s->ctx, &s->io_notifier, handle_io, NULL);
 
     s->started = true;
     trace_virtio_blk_data_plane_start(s);
@@ -498,15 +504,17 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
         qemu_bh_delete(s->start_bh);
         s->start_bh = NULL;
     } else {
-        event_poll_notify(&s->event_poll);
+        aio_notify(s->ctx);
         qemu_thread_join(&s->thread);
     }
 
+    aio_set_event_notifier(s->ctx, &s->io_notifier, NULL, NULL);
     ioq_cleanup(&s->ioqueue);
 
+    aio_set_event_notifier(s->ctx, &s->host_notifier, NULL, NULL);
     s->vdev->binding->set_host_notifier(s->vdev->binding_opaque, 0, false);
 
-    event_poll_cleanup(&s->event_poll);
+    aio_context_unref(s->ctx);
 
     /* Clean up guest notifier (irq) */
     s->vdev->binding->set_guest_notifiers(s->vdev->binding_opaque, 1, false);