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

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Message-ID: <5318ABC0.4040307@citrix.com>
Date:	Thu, 6 Mar 2014 17:09:20 +0000
From:	Zoltan Kiss <zoltan.kiss@...rix.com>
To:	Jesse Gross <jesse@...ira.com>, <pshelar@...ira.com>,
	<tgraf@...hat.com>, <dev@...nvswitch.org>
CC:	<xen-devel@...ts.xenproject.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>
Subject: Re: [PATCH] openvswitch: Orphan frags before sending to userspace
 via Netlink to avoid guest stall

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@...rix.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 */
>

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