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Date: Mon, 14 Dec 2015 20:26:35 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 6/6] vmw_pvscsi: Introduce
 'x-disable-pcie' backword compatability property
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Dmitry Fleytman <dmitry@daynix.com>, Marcel Apfelbaum <marcel@redhat.com>, idan brown <idan.brown@ravellosystems.com>, Shmulik Ladkani <shmulik.ladkani@ravellosystems.com>, qemu-devel@nongnu.org

On Mon, Dec 14, 2015 at 07:04:33PM +0100, Paolo Bonzini wrote:
> 
> 
> On 14/12/2015 18:35, Michael S. Tsirkin wrote:
> > > What distinguishes an internal from an external property?  Everything
> > > except links to backends would be "internal".
> > 
> > How do you mean? We have a ton of properties e.g.
> > to control which offloads are allowed for virtio net.
> 
> Why would users set them?
> 
> > It's set internally by machine types to avoid breaking
> > migration.  I don't see any reason for users to set it.
> 
> But they do set it :) albeit only through machine types.  I don't think
> it's different from offloads, just much more specialized.
> 
> Or do you mean that it could go away if we decide to remove very old
> machine types?  I think we would remove compat properties connected to
> those machine types as well, even without "x-".
> 
> Paolo

Then we'll break users who set them directly for some reason.
So x- means "not part of stable ABI".
No?