Re: [PATCH RFC 2/3] virtio_ccw: legacy: don't negotiate rev 1/features

From: Cornelia Huck
Date: Thu Dec 04 2014 - 12:56:22 EST


On Thu, 4 Dec 2014 19:26:45 +0200
"Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:

> Legacy balloon device doesn't pretend to support revision 1 or 64 bit
> features.
>
> But just in case someone implements a broken one that does, let's not
> even try to drive legacy only devices using revision 1, and let's not
> give them a chance to say they support VIRTIO_F_VERSION_1 by not reading
> high feature bits.
>
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> drivers/s390/kvm/virtio_ccw.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
> index 4a3e6e5..088bdf1 100644
> --- a/drivers/s390/kvm/virtio_ccw.c
> +++ b/drivers/s390/kvm/virtio_ccw.c
> @@ -733,6 +733,9 @@ static u64 virtio_ccw_get_features(struct virtio_device *vdev)
>
> rc = le32_to_cpu(features->features);
>
> + if (vcdev->revision == 0)
> + goto out_free;
> +
> /* Read second half of the feature bits from the host. */
> features->index = 1;
> ccw->cmd_code = CCW_CMD_READ_FEAT;
> @@ -1182,9 +1185,13 @@ static int virtio_ccw_online(struct ccw_device *cdev)
> vcdev->vdev.id.vendor = cdev->id.cu_type;
> vcdev->vdev.id.device = cdev->id.cu_model;
>
> - ret = virtio_ccw_set_transport_rev(vcdev);
> - if (ret)
> - goto out_free;
> + if (virtio_device_is_legacy_only(vcdev->vdev.id)) {

Inverted logic?

> + ret = virtio_ccw_set_transport_rev(vcdev);
> + if (ret)
> + goto out_free;
> + } else {
> + vcdev->revision = 0;
> + }
>
> ret = register_virtio_device(&vcdev->vdev);
> if (ret) {

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