Re: [Qemu-devel] [PATCH v2 1/2] virtio: Add function to check whether backend supports VIRTIO_1

[Marcel Apfelbaum <marcel@redhat.com>]

On 09/09/2016 04:10 PM, Maxime Coquelin wrote:
> This patch adds virtio_test_backend_virtio_1() function to
> check whether backend supports VIRTIO_F_VERSION_1 before the
> negociation takes place.
>
> Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
> Cc: Marcel Apfelbaum <marcel@redhat.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>
> Cc: qemu-stable@nongnu.org
> Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> ---
>  hw/virtio/virtio.c         | 13 +++++++++++++
>  include/hw/virtio/virtio.h |  1 +
>  2 files changed, 14 insertions(+)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 74c085c..8b30b69 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -1481,6 +1481,19 @@ void virtio_vmstate_save(QEMUFile *f, void *opaque, size_t size)
>      virtio_save(VIRTIO_DEVICE(opaque), f);
>  }
>
> +bool virtio_test_backend_virtio_1(VirtIODevice *vdev, Error **errp)
> +{
> +    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> +    uint64_t feature;
> +

I would set "feature = 0" even if doesn't really matter.
Anyway:

Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>

Thanks,
Marcel

> +    virtio_add_feature(&feature, VIRTIO_F_VERSION_1);
> +
> +    assert(k->get_features != NULL);
> +    feature = k->get_features(vdev, feature, errp);
> +
> +    return virtio_has_feature(feature, VIRTIO_F_VERSION_1);
> +}
> +
>  static int virtio_set_features_nocheck(VirtIODevice *vdev, uint64_t val)
>  {
>      VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index d2490c1..3a31754 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -235,6 +235,7 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val);
>  void virtio_reset(void *opaque);
>  void virtio_update_irq(VirtIODevice *vdev);
>  int virtio_set_features(VirtIODevice *vdev, uint64_t val);
> +bool virtio_test_backend_virtio_1(VirtIODevice *vdev, Error **errp);
>
>  /* Base devices.  */
>  typedef struct VirtIOBlkConf VirtIOBlkConf;
>