Re: [PATCH] openvswitch: Orphan frags before sending to userspace via Netlink to avoid guest stall

Zoltan Kiss
2014-03-06T17:09:20Z

Do you have any feedback on this? I'm also adding KVM list as they might
be interested in this.

Zoli

On 28/02/14 19:16, Zoltan Kiss wrote:
> The kernel datapath now switched to zerocopy Netlink messages, but that also
> means that the pages on frags array are sent straight to userspace. If those
> pages came outside the kernel, we have to swap them out with local copies.
>
> Signed-off-by: Zoltan Kiss <zoltan.kiss@citrix.com>
> ---
> net/openvswitch/datapath.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
> index 36f8872..ffb563c 100644
> --- a/net/openvswitch/datapath.c
> +++ b/net/openvswitch/datapath.c
> @@ -464,6 +464,12 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
> }
> nla->nla_len = nla_attr_size(skb->len);
>
> + if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC))) {
> + err = -ENOMEM;
> + skb_tx_error(skb);
> + goto out;
> + }
> +
> skb_zerocopy(user_skb, skb, skb->len, hlen);
>
> /* Pad OVS_PACKET_ATTR_PACKET if linear copy was performed */
>