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Date: Mon, 14 Dec 2009 23:14:16 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCH RFC] virtio: add features qdev property
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To: Gerd Hoffmann <kraxel@redhat.com>
Cc: Markus Armbruster <armbru@redhat.com>, qemu-devel@nongnu.org

On Mon, Dec 14, 2009 at 10:12:14PM +0100, Gerd Hoffmann wrote:
> On 12/14/09 21:43, Michael S. Tsirkin wrote:
>> What do we put in e.g. 0.11 compat? Any features we enable
>> there might not be supported by host.
>
> compat properties as usual?
>
> Sorry, I still fail to see your problem.
>
> You'll have a 'disable' bitmap.  Fill it via 'features=<bitmap-prop>'.  
> Or using separate properties for each feature.
> qemu goes figure host_features.  When done it masks out the features  
> disabled via properties.  The result is used as final feature bitmap.
>
> -M pc-0.11 will disable hw_checksum
> management software can do it too via -device virtio-net-pci,... if some  
> machines in the pool don't support it.  And of course qemu will disable  
> it on its own in case the host kernel doesn't support it.
>
> cheers,
>   Gerd

management is always behind :).  Imagine a new and improved qemu. I run
old management.  I expect to see old properties, but old management can
not disable new ones :)


-- 
MST