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From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <42aa8736-bc23-d66d-27de-dbaf83ea2f99@redhat.com>
Date: Thu, 19 Oct 2017 17:43:18 +0200
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Subject: Re: [Qemu-devel] [PATCH v4 1/4] vhost-user: add new vhost user
 messages to support virtio config space
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To: "Michael S. Tsirkin" <mst@redhat.com>, Changpeng Liu <changpeng.liu@intel.com>
Cc: qemu-devel@nongnu.org, stefanha@gmail.com, marcandre.lureau@redhat.com, felipe@nutanix.com, james.r.harris@intel.com

On 19/10/2017 17:39, Michael S. Tsirkin wrote:
>> Add VHOST_USER_GET_CONFIG/VHOST_USER_SET_CONFIG messages which can be
>> used for live migration of vhost user devices, also vhost user devices
>> can benefit from the messages to get/set virtio config space from/to the
>> I/O target. For the purpose to support virtio config space change,
>> VHOST_USER_SET_CONFIG_FD message is added as the event notifier
>> in case virtio config space change in the I/O target.
>>
>> Signed-off-by: Changpeng Liu <changpeng.liu@intel.com>
> I don't much like it that config is getting passed through.
> 
> IMO this makes managing things harder not easier.
> 
> How about specific messages about specific parts of
> config space that you want to get from the backend?

In the case of virtio-blk that would be all of it.  Do you have a case
in mind where some part of the configuration space is owned by QEMU?

Paolo