Re: [Qemu-devel] [PATCH v4 1/4] vhost-user: add new vhost user messages to support virtio config space

[Paolo Bonzini]

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 <address@hidden>
> 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