Re: [Qemu-devel] [PATCH 6/9] virtio-blk: use aio handler for data plane

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Wed, 30 Mar 2016 14:48:05 +0200
Paolo Bonzini <pbonzini@redhat.com> wrote:

> From: "Michael S. Tsirkin" <mst@redhat.com>
> 
> In addition to handling IO in vcpu thread and in io thread, dataplane
> introduces yet another mode: handling it by aio.
> 
> This reuses the same handler as previous modes, which triggers races as
> these were not designed to be reentrant.
> 
> Use a separate handler just for aio, and disable regular handlers when
> dataplane is active.
> 
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  hw/block/dataplane/virtio-blk.c | 13 +++++++++++++
>  hw/block/virtio-blk.c           | 27 +++++++++++++++++----------
>  include/hw/virtio/virtio-blk.h  |  2 ++
>  3 files changed, 32 insertions(+), 10 deletions(-)
> 

> diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> index 77221c1..47ad9ed 100644
> --- a/hw/block/virtio-blk.c
> +++ b/hw/block/virtio-blk.c
> @@ -577,20 +577,11 @@ void virtio_blk_handle_request(VirtIOBlockReq *req, MultiReqBuffer *mrb)
>      }
>  }
> 
> -static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
> +void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
>  {
> -    VirtIOBlock *s = VIRTIO_BLK(vdev);
>      VirtIOBlockReq *req;
>      MultiReqBuffer mrb = {};
> 
> -    /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
> -     * dataplane here instead of waiting for .set_status().
> -     */
> -    if (s->dataplane && !s->dataplane_started) {
> -        virtio_blk_data_plane_start(s->dataplane);
> -        return;
> -    }
> -
>      assert(atomic_fetch_inc(&s->reentrancy_test) == 0);

Hm, based on wrong branch?

>      blk_io_plug(s->blk);
>