netdev - Re: [PATCH 0/3] macvlan: support for guest vm direct rx/tx

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Message-ID: <20091127213824.53c5a23a@nehalam>
Date:	Fri, 27 Nov 2009 21:38:24 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	David Miller <davem@...emloft.net>
Cc:	arnd@...db.de, pmullaney@...ell.com, kaber@...sh.net,
	netdev@...r.kernel.org, alacrityvm-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, bridge@...ts.linux-foundation.org
Subject: Re: [PATCH 0/3] macvlan: support for guest vm direct rx/tx

On Fri, 27 Nov 2009 16:19:57 -0800 (PST)
David Miller <davem@...emloft.net> wrote:

> From: Arnd Bergmann <arnd@...db.de>
> Date: Sat, 28 Nov 2009 00:43:58 +0100
> 
> > On Friday 13 November 2009, Stephen Hemminger wrote:
> >> Also, macvlan should really being calling netif_receive_skb()
> >> not going through another queue/softirq cycle.
> > 
> > I've added a patch for this in my experimental queue now.
> > When I last tried this, I saw a kernel stack overflow
> > but it seems fine now.
> 
> I think it is unwise for any virtual device layer to use netif_receive_skb().
> Just like tunnels they should always use netif_rx().
> 
> Otherwise stack overflow is a very real concern.

Maybe we should figure out a way for protocols to return new skb in netif_receive_skb
to avoid extra softirq, but avoid stack overflow?

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