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Date: Tue, 16 Sep 2014 18:57:31 +0300
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20140916155731.GA2350@redhat.com>
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Subject: Re: [Qemu-devel] [PULL 12/12] vhost-user: fix
	VIRTIO_NET_F_MRG_RXBUF negotiation
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To: qemu-devel@nongnu.org
Cc: Peter Maydell <peter.maydell@linaro.org>, Damjan Marion <damarion@cisco.com>, Anthony Liguori <aliguori@amazon.com>, qemu-stable@nongnu.org

On Sun, Sep 14, 2014 at 09:41:56PM +0300, Michael S. Tsirkin wrote:
> From: Damjan Marion <damarion@cisco.com>
> 
> Header length check should happen only if backend is kernel. For user
> backend there is no reason to reset this bit.
> 
> vhost-user code does not define .has_vnet_hdr_len so
> VIRTIO_NET_F_MRG_RXBUF cannot be negotiated even if both sides
> support it.
> 
> Signed-off-by: Damjan Marion <damarion@cisco.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Cc: qemu-stable@nongnu.org

> ---
>  hw/net/vhost_net.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index b21e7a4..77bb93e 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -163,11 +163,11 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
>      if (r < 0) {
>          goto fail;
>      }
> -    if (!qemu_has_vnet_hdr_len(options->net_backend,
> -                               sizeof(struct virtio_net_hdr_mrg_rxbuf))) {
> -        net->dev.features &= ~(1 << VIRTIO_NET_F_MRG_RXBUF);
> -    }
>      if (backend_kernel) {
> +        if (!qemu_has_vnet_hdr_len(options->net_backend,
> +                               sizeof(struct virtio_net_hdr_mrg_rxbuf))) {
> +            net->dev.features &= ~(1 << VIRTIO_NET_F_MRG_RXBUF);
> +        }
>          if (~net->dev.features & net->dev.backend_features) {
>              fprintf(stderr, "vhost lacks feature mask %" PRIu64
>                     " for backend\n",
> -- 
> MST
>