[Qemu-devel] [PATCH 8/9] virtio-blk: dataplane multiqueue support

[Stefan Hajnoczi <stefanha@redhat.com>]

Monitor ioeventfds for all virtqueues in the device's AioContext.  This
is not true multiqueue because requests from all virtqueues are
processed in a single IOThread.  In the future it will be possible to
use multiple IOThreads when the QEMU block layer supports multiqueue.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 hw/block/dataplane/virtio-blk.c | 50 ++++++++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 16 deletions(-)

diff --git a/hw/block/dataplane/virtio-blk.c b/hw/block/dataplane/virtio-blk.c
index 592aa95..48c0bb7 100644
--- a/hw/block/dataplane/virtio-blk.c
+++ b/hw/block/dataplane/virtio-blk.c
@@ -31,9 +31,7 @@ struct VirtIOBlockDataPlane {
     bool stopping;
 
     VirtIOBlkConf *conf;
-
     VirtIODevice *vdev;
-    VirtQueue *vq;                  /* virtqueue vring */
 
     Notifier insert_notifier, remove_notifier;
 
@@ -190,6 +188,8 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s->vdev)));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
+    unsigned i;
+    unsigned nvqs = s->conf->num_queues;
     int r;
 
     if (vblk->dataplane_started || s->starting) {
@@ -197,10 +197,9 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
     }
 
     s->starting = true;
-    s->vq = virtio_get_queue(s->vdev, 0);
 
     /* Set up guest notifier (irq) */
-    r = k->set_guest_notifiers(qbus->parent, 1, true);
+    r = k->set_guest_notifiers(qbus->parent, nvqs, true);
     if (r != 0) {
         fprintf(stderr, "virtio-blk failed to set guest notifier (%d), "
                 "ensure -enable-kvm is set\n", r);
@@ -208,10 +207,15 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
     }
 
     /* Set up virtqueue notify */
-    r = k->set_host_notifier(qbus->parent, 0, true);
-    if (r != 0) {
-        fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
-        goto fail_host_notifier;
+    for (i = 0; i < nvqs; i++) {
+        r = k->set_host_notifier(qbus->parent, i, true);
+        if (r != 0) {
+            fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
+            while (i--) {
+                k->set_host_notifier(qbus->parent, i, false);
+            }
+            goto fail_guest_notifiers;
+        }
     }
 
     s->starting = false;
@@ -221,17 +225,23 @@ void virtio_blk_data_plane_start(VirtIOBlockDataPlane *s)
     blk_set_aio_context(s->conf->conf.blk, s->ctx);
 
     /* Kick right away to begin processing requests already in vring */
-    event_notifier_set(virtio_queue_get_host_notifier(s->vq));
+    for (i = 0; i < nvqs; i++) {
+        VirtQueue *vq = virtio_get_queue(s->vdev, i);
+
+        event_notifier_set(virtio_queue_get_host_notifier(vq));
+    }
 
     /* Get this show started by hooking up our callbacks */
     aio_context_acquire(s->ctx);
-    virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx,
-                                               virtio_blk_data_plane_handle_output);
+    for (i = 0; i < nvqs; i++) {
+        VirtQueue *vq = virtio_get_queue(s->vdev, i);
+
+        virtio_queue_aio_set_host_notifier_handler(vq, s->ctx,
+                virtio_blk_data_plane_handle_output);
+    }
     aio_context_release(s->ctx);
     return;
 
-  fail_host_notifier:
-    k->set_guest_notifiers(qbus->parent, 1, false);
   fail_guest_notifiers:
     vblk->dataplane_disabled = true;
     s->starting = false;
@@ -244,6 +254,8 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(s->vdev)));
     VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
     VirtIOBlock *vblk = VIRTIO_BLK(s->vdev);
+    unsigned i;
+    unsigned nvqs = s->conf->num_queues;
 
     if (!vblk->dataplane_started || s->stopping) {
         return;
@@ -261,17 +273,23 @@ void virtio_blk_data_plane_stop(VirtIOBlockDataPlane *s)
     aio_context_acquire(s->ctx);
 
     /* Stop notifications for new requests from guest */
-    virtio_queue_aio_set_host_notifier_handler(s->vq, s->ctx, NULL);
+    for (i = 0; i < nvqs; i++) {
+        VirtQueue *vq = virtio_get_queue(s->vdev, i);
+
+        virtio_queue_aio_set_host_notifier_handler(vq, s->ctx, NULL);
+    }
 
     /* Drain and switch bs back to the QEMU main loop */
     blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());
 
     aio_context_release(s->ctx);
 
-    k->set_host_notifier(qbus->parent, 0, false);
+    for (i = 0; i < nvqs; i++) {
+        k->set_host_notifier(qbus->parent, i, false);
+    }
 
     /* Clean up guest notifier (irq) */
-    k->set_guest_notifiers(qbus->parent, 1, false);
+    k->set_guest_notifiers(qbus->parent, nvqs, false);
 
     vblk->dataplane_started = false;
     s->stopping = false;
-- 
2.5.5