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Date: Thu, 30 Apr 2009 19:57:51 +0300
Message-ID: <f43fc5580904300957w38c795as24ddfb89b78aaea0@mail.gmail.com>
Subject: Re: [Qemu-devel] Re: [PATCH 9/9] Introduce VLANClientState::cleanup()
From: Blue Swirl <blauwirbel@gmail.com>
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To: Anthony Liguori <aliguori@us.ibm.com>
Cc: Mark McLoughlin <markmc@redhat.com>, Marcelo Tosatti <mtosatti@redhat.com>, Markus Armbruster <armbru@redhat.com>, qemu-devel@nongnu.org, Avi Kivity <avi@redhat.com>, Paul Brook <paul@codesourcery.com>

On 4/30/09, Anthony Liguori <aliguori@us.ibm.com> wrote:
> Paul Brook wrote:
>
> >
> > > Sure, you can short-ciruit the case where you have a pair of devices,
> > > but then you need to revoke posted receive descriptors.
> > >
> > >
> >
> > Isn't the same true with a point-point API? When you add a third device to
> the vlan you're going to have to break the tap-guest link, and insert a
> proxy in the middle.
> >
> >
>
>  The difference is that if you assume vlan, then you have to handle
> renegotiation of features which is not actually possible.  With virtio-net,
> once you enable guest GSO, you cannot disable it.  You would have to
> implement GSO emulation within QEMU if you wanted to disable it on the tap
> device.
>
>  If you don't assume vlan, then you can choose the least amount of features
> when in a vlan.  Then you never have to deal with this problem.
>
>  And yes, that means that if you wanted to support the existing syntax, you
> would need a flag like:
>
>  -net tap,i-will-never-add-more-devices-to-this-vlan=on
> -net nic,model=virtio
>

-net pointopoint,tap,nic,model=virtio ?