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From: Juergen Gross <jgross@suse.com>
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Date: Mon, 4 Apr 2016 11:30:54 +0200
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Subject: Re: [Qemu-devel] [Xen-devel] [PATCH] xen: write information about
 supported backends
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To: David Vrabel <david.vrabel@citrix.com>, qemu-devel@nongnu.org, xen-devel@lists.xensource.com
Cc: kraxel@redhat.com, stefano.stabellini@eu.citrix.com

On 04/04/16 11:18, David Vrabel wrote:
> On 30/03/16 15:10, Juergen Gross wrote:
>> Add a Xenstore directory for each supported pv backend. This will allow
>> Xen tools to decide which backend type to use in case there are
>> multiple possibilities.
>>
>> The information is added under
>> /local/domain/<backend-domid>/device-model/<domid>/backends
>> before the "running" state is written to Xenstore. Using a directory
>> for each directory enables us to add parameters for specific backends
>> in the future.
> 
> "Using a directory for each backend..."?

Yes. As I've written: this enables us to enhance the interface later
without the need to modify it first.

>> In order to reuse the Xenstore directory creation already present in
>> hw/xen/xen_devconfig.c move the related functions to
>> hw/xen/xen_backend.c where they fit better.
> 
> Why Xenstore and not QMP?

We need to communicate with qemu only once instead of each time a
device is added to the domain. Doing the communication via Xenstore
is much simpler.

Juergen