The loading time of a VM is quite significant when its virtio devices uses a large amount of virt-queues (e.g. a virtio-serial device with max_ports=511). Most of the time is spend in the creation of all the required event notifiers (ioeventfd and memory regions).
This patch pack all the changes to the memory regions in a single memory transaction. Reported-by: Sitong Liu <si...@redhat.com> Reported-by: Xiaoling Gao <xia...@redhat.com> Signed-off-by: Gal Hammer <gham...@redhat.com> --- hw/virtio/virtio.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index ad564b0..8d8d93d 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -2574,6 +2574,7 @@ static int virtio_device_start_ioeventfd_impl(VirtIODevice *vdev) VirtioBusState *qbus = VIRTIO_BUS(qdev_get_parent_bus(DEVICE(vdev))); int n, r, err; + memory_region_transaction_begin(); for (n = 0; n < VIRTIO_QUEUE_MAX; n++) { VirtQueue *vq = &vdev->vq[n]; if (!virtio_queue_get_num(vdev, n)) { @@ -2596,6 +2597,7 @@ static int virtio_device_start_ioeventfd_impl(VirtIODevice *vdev) } event_notifier_set(&vq->host_notifier); } + memory_region_transaction_commit(); return 0; assign_error: @@ -2609,6 +2611,7 @@ assign_error: r = virtio_bus_set_host_notifier(qbus, n, false); assert(r >= 0); } + memory_region_transaction_commit(); return err; } @@ -2625,6 +2628,7 @@ static void virtio_device_stop_ioeventfd_impl(VirtIODevice *vdev) VirtioBusState *qbus = VIRTIO_BUS(qdev_get_parent_bus(DEVICE(vdev))); int n, r; + memory_region_transaction_begin(); for (n = 0; n < VIRTIO_QUEUE_MAX; n++) { VirtQueue *vq = &vdev->vq[n]; @@ -2632,6 +2636,13 @@ static void virtio_device_stop_ioeventfd_impl(VirtIODevice *vdev) continue; } event_notifier_set_handler(&vq->host_notifier, NULL); + } + memory_region_transaction_commit(); + + for (n = 0; n < VIRTIO_QUEUE_MAX; n++) { + if (!virtio_queue_get_num(vdev, n)) { + continue; + } r = virtio_bus_set_host_notifier(qbus, n, false); assert(r >= 0); } -- 2.7.5