netdev - Re: [Xen-devel] compound skb frag pages appearing in start

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Date:	Wed, 10 Oct 2012 16:49:49 +0200
From:	Sander Eikelenboom <linux@...elenboom.it>
To:	Ian Campbell <Ian.Campbell@...rix.com>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	xen-devel <xen-devel@...ts.xen.org>,
	"Konrad Rzeszutek Wilk" <konrad@...nel.org>
Subject: Re: [Xen-devel] compound skb frag pages appearing in start_xmit


Wednesday, October 10, 2012, 3:09:58 PM, you wrote:

> On Wed, 2012-10-10 at 11:13 +0100, Ian Campbell wrote:
>> I haven't tackled netfront yet. 

> I seem to be totally unable to reproduce the equivalent issue on the
> netfront xmit side, even though it seems like the loop in
> xennet_make_frags ought to be obviously susceptible to it.

> Konrad, Sander, are either of you able to repro, e.g. with:


Hmrrrmm i don't see any traces, only strange behaviour ..

- i can connect to guests by ssh, but it's sluggish, and sometimes stops working
- The guest seem to keep trying to connect to netback:

[  658.276719] xen_bridge: port 2(vif40.0) entered forwarding state
[  658.282258] xen_bridge: port 2(vif40.0) entered forwarding state
[  663.945964] xen_bridge: port 7(vif39.0) entered forwarding state
[  669.674277] xen_bridge: port 2(vif40.0) entered disabled state
[  669.680290] device vif40.0 left promiscuous mode
[  669.685464] xen_bridge: port 2(vif40.0) entered disabled state
[  672.857222] device vif41.0 entered promiscuous mode
[  673.166254] xen-blkback:ring-ref 8, event-channel 9, protocol 1 (x86_64-abi)
[  673.176368] xen_bridge: port 2(vif41.0) entered forwarding state
[  673.182042] xen_bridge: port 2(vif41.0) entered forwarding state
[  674.439725] xen_bridge: port 7(vif39.0) entered disabled state
[  674.445708] device vif39.0 left promiscuous mode
[  674.450955] xen_bridge: port 7(vif39.0) entered disabled state
[  677.726040] device vif42.0 entered promiscuous mode
[  678.053381] xen-blkback:ring-ref 8, event-channel 9, protocol 1 (x86_64-abi)
[  678.062804] xen_bridge: port 7(vif42.0) entered forwarding state
[  678.068433] xen_bridge: port 7(vif42.0) entered forwarding state
[  688.224736] xen_bridge: port 2(vif41.0) entered forwarding state
[  693.080557] xen_bridge: port 7(vif42.0) entered forwarding state
[  700.786276] xen_bridge: port 7(vif42.0) entered disabled state
[  700.792484] device vif42.0 left promiscuous mode
[  700.802409] xen_bridge: port 7(vif42.0) entered disabled state
[  704.133606] device vif43.0 entered promiscuous mode
[  704.460160] xen-blkback:ring-ref 8, event-channel 9, protocol 1 (x86_64-abi)
[  704.469800] xen_bridge: port 7(vif43.0) entered forwarding state
[  704.475303] xen_bridge: port 7(vif43.0) entered forwarding state
[  719.493788] xen_bridge: port 7(vif43.0) entered forwarding state
[  726.302456] xen_bridge: port 7(vif43.0) entered disabled state
[  726.308898] device vif43.0 left promiscuous mode
[  726.314029] xen_bridge: port 7(vif43.0) entered disabled state

All the guests are already up, but this keeps on going and going and going ....



> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index b06ef81..8a3f770 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -462,6 +462,8 @@ static void xennet_make_frags(struct sk_buff *skb, struct net_device *dev,
>                 ref = gnttab_claim_grant_reference(&np->gref_tx_head);
>                 BUG_ON((signed short)ref < 0);
>  
> +               BUG_ON(PageCompound(skb_frag_page(frag)));
> +
>                 mfn = pfn_to_mfn(page_to_pfn(skb_frag_page(frag)));
>                 gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,
>                                                 mfn, GNTMAP_readonly);

> My repro for netback was just to netcat a wodge of data from dom0->domU
> but going the other way doesn't seem to trigger.



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