Re: [Qemu-devel] [PATCH 2/2] virtio-net: mark VIRTIO_NET_F_GSO as legacy

[Cornelia Huck]

On Fri, 4 Nov 2016 13:01:40 +0200
"Michael S. Tsirkin" <address@hidden> wrote:

> virtio 1.0 spec says this is a legacy feature bit,
> hide it from guests in legacy mode.
> 
> Note: for cross-version migration compatibility,
> we keep the bit set in host_features.
> The result will be that a guest migrating cross-version
> will see host features change under it.
> As guests only seem to read it once, this should
> not be an issue. Meanwhile, will work to fix guests to
> ignore this bit in virtio1 mode, too.

This also means that guest may see a different feature set if it is
e.g. rebooted after migration. But I agree that this should not be an
issue.

> 
> Cc: address@hidden

You also need to cc: the previous patch to stable.

> Signed-off-by: Michael S. Tsirkin <address@hidden>
> ---
>  hw/net/virtio-net.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 20aa63e..b68c69d 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1942,6 +1942,7 @@ static void virtio_net_class_init(ObjectClass *klass, 
> void *data)
>      vdc->guest_notifier_pending = virtio_net_guest_notifier_pending;
>      vdc->load = virtio_net_load_device;
>      vdc->save = virtio_net_save_device;
> +    vdc->legacy_features |= (0x1 << VIRTIO_NET_F_GSO);
>  }
> 
>  static const TypeInfo virtio_net_info = {

Reviewed-by: Cornelia Huck <address@hidden>