On 19/10/2017 19:43, Michael S. Tsirkin wrote: > On Thu, Oct 19, 2017 at 05:43:18PM +0200, Paolo Bonzini wrote: >> 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....@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 > > Yes. seg_max
The seg_max limit is established by whoever reads buffers from the vring and passes them down to the lower layer. For vhost-blk that's the device server, not QEMU. Paolo
