[Qemu-devel] Re: [PATCH 00/17] v4: virtio-serial fixes, new abi for port discovery

[Juan Quintela]

Amit Shah <address@hidden> wrote:
> Hello,
>
> These patches rework the way ports are announced to the guests. A
> control message is used to let the guest know a new port is
> added. Initial port discovery and port hot-plug work via this way now.
>
> This was done to have the host and guest port numbering in sync to
> avoid surprises after several hotplug/unplug operations and
> migrations.
>
> The ability to assign a particular port number to ports is also added
> so that management software can control the placement of ports.
>
> Differences from v3:
> - Removed the QMP events (will ride on top of new infrastructure by
>   Luiz)
>
> - Add flow control: ports can signal to the virtio-serial code to stop
>   sending data till it's ready to accept more.
>
> - A fix for not abusing the virtqueue_push() api: we should signal to
>   the guest the number of bytes written for guest to consume. We were
>   using the number to signify the bytes consumed by hosts.
>
> - Juan's comment about re-using control queue buffers
>
> Overall:
> - Users can set the port id they wish to instantiate ports at by using
>   the ,nr= parameter to 'virtserialport' and 'virtconsole' devices
>
> - Migration fixes: refuse migration when:
>   - number of active ports is different between the src and destination
>   - max_nr_ports a device can support on the src is more
>
> - If a qemu chardev connection to a port is closed on the dest while
>   it was open on the src, inform the guest about this. (Also do the
>   same for port closed on src but open on dest.)
>
> - Use control messages for relaying new port information instead of
>   config space (changes abi)
>
> - Propagate error message from guest in instantiating a port or a
>   device to the user.
>
> - Handle scatter/gather for control output and data output from the
>   guest
>
> - Fix abuse of virtio api in the virtqueue_push() function
>
> - Add an API for the ports for flow control: ports can signal when
>   they're ready to accept data / stop sending data.

Reviewed-by: Juan Quintela <address@hidden>

Later, Juan.