netdev - Re: [net-next-2.6 PATCH 0/3 RFC] macvlan: MAC Address filtering support for passthru mode

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Message-ID: <20110911093832.GD27096@redhat.com>
Date:	Sun, 11 Sep 2011 12:38:32 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Roopa Prabhu <roprabhu@...co.com>
Cc:	netdev@...r.kernel.org, dragos.tatulea@...il.com, arnd@...db.de,
	dwang2@...co.com, benve@...co.com, kaber@...sh.net, sri@...ibm.com,
	davem@...emloft.net, eric.dumazet@...il.com, mchan@...adcom.com,
	kvm@...r.kernel.org
Subject: Re: [net-next-2.6 PATCH 0/3 RFC] macvlan: MAC Address filtering
 support for passthru mode

On Fri, Sep 09, 2011 at 09:33:33AM -0700, Roopa Prabhu wrote:
> 
> 
> 
> On 9/8/11 10:55 PM, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> 
> > On Thu, Sep 08, 2011 at 07:53:11PM -0700, Roopa Prabhu wrote:
> >>>> Phase 1: Goal: Enable hardware filtering for all macvlan modes
> >>>>     - In macvlan passthru mode the single guest virtio-nic connected will
> >>>>       receive traffic that he requested for
> >>>>     - In macvlan non-passthru mode all guest virtio-nics sharing the
> >>>>       physical nic will see all other guest traffic
> >>>>       but the filtering at guest virtio-nic
> >>> 
> >>> I don't think guests currently filter anything.
> >>> 
> >> I was referring to Qemu-kvm virtio-net in
> >> virtion_net_receive->receive_filter. I think It only passes pkts that the
> >> guest OS is interested. It uses the filter table that I am passing to
> >> macvtap in this patch.
> > 
> > This happens after userspace thread gets woken up and data
> > is copied there. So relying on filtering at that level is
> > going to be very inefficient on a system with
> > multiple active guests. Further, and for that reason, vhost-net
> > doesn't do filtering at all, relying on the backends
> > to pass it correct packets.
> 
> Ok thanks for the info. So in which case, phase 1 is best for PASSTHRU mode
> and for non-PASSTHRU when there is a single guest connected to a VF.
> For non-PASSTHRU multi guest sharing the same VF, Phase 1 is definitely
> better than putting the VF in promiscuous mode.
> But to address the concern you mention above, in phase 2 when we have more
> than one guest sharing the VF,

It's probably more interesting for a card without SRIOV support.

> we will have to add filter lookup in macvlan
> to filter pkts for each guest.

Any chance to enable hardware filters for that?

> This will need some performance tests too.
> 
> Will start investigating the netlink interface comments for phase 1 first.
> 
> Thanks!
> -Roopa
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