Re: [Qemu-devel] [PATCH] virtio-net: count VIRTIO_NET_F_MAC when calculating config_len

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Apr 25, 2013 at 02:21:29PM +0800, Jason Wang wrote:
> Commit 14f9b664 (hw/virtio-net.c: set config size using host features) tries to
> calculate config size based on the host features. But it forgets the
> VIRTIO_NET_F_MAC were always set for qemu later. This will lead a zero config
> len for virtio-net device when both VIRTIO_NET_F_STATUS and VIRTIO_NET_F_MQ were
> disabled form command line. Then qemu will crash when user tries to read the
> config of virtio-net.
> 
> Fix this by counting VIRTIO_NET_F_MAC and make sure the config at least contains
> the mac address.
> 
> Cc: Jesse Larrew <jlarrew@linux.vnet.ibm.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---
>  hw/net/virtio-net.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index 70c8fce..33a70ef 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -1264,7 +1264,8 @@ static void virtio_net_guest_notifier_mask(VirtIODevice *vdev, int idx,
>  
>  void virtio_net_set_config_size(VirtIONet *n, uint32_t host_features)
>  {
> -    int i, config_size = 0;
> +    /* VIRTIO_NET_F_MAC can't be disabled from qemu side */
> +    int i, config_size = feature_sizes[0].end;

This would be cleaner:
	host_features |= (1 << VIRTIO_NET_F_MAC);

no need for a comment then.

>      for (i = 0; feature_sizes[i].flags != 0; i++) {
>          if (host_features & feature_sizes[i].flags) {
>              config_size = MAX(feature_sizes[i].end, config_size);
> -- 
> 1.7.1