Date: Wed, 3 Dec 2014 15:27:27 +0100
From: Cornelia Huck <cornelia.huck@de.ibm.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
        virtualization@lists.linux-foundation.org
Subject: Re: [PATCH RFC 1/2] virtio_balloon: convert to virtio 1.0
 endian-ness
Message-ID: <20141203152727.5b4d3e34.cornelia.huck@de.ibm.com>
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On Wed, 3 Dec 2014 16:02:28 +0200
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Tue, Dec 02, 2014 at 07:39:30PM +0100, Cornelia Huck wrote:
> > On Tue, 2 Dec 2014 13:44:06 +0200
> > "Michael S. Tsirkin" <mst@redhat.com> wrote:
> > 
> > > balloon device is not part of virtio 1.0 spec.  Still, it's easy enough
> > > to make it handle endian-ness exactly as other virtio 1.0 devices: what
> > > we gain from this, is that there's no need to special-case it in virtio
> > > core.
> > 
> > Well, the balloon is weird in a number of ways, including its always
> > little-endian config space.
> 
> Hmm yes, I forgot about that.
> 
> > But I'm not quite sure the spec covers this?
> 
> The spec does not cover balloon.  It merely includes a reference section
> about legacy balloon device.  What to do when that device sets VERSION_1
> is really up to us.
> 
> Patchset v8 simply makes balloon tell core it's legacy_only.
> This is I guess fine as far as it goes.
> I was still looking for the best way that involves minimal noise
> in core. This looked like the best way: change 4 lines,
> and drop all special casing in core, but given the config space
> endian-ness mess, I'm not sure anymore.
> I guess we'll just stick to what v8 does for now.

I don't think the legacy_only approach is so bad, let's keep it for now.

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