virtio-serial: Don't copy guest buf to host, flow control

Hello,

This series is now separated from the chardev flow control series. The virtio-serial code now does not copy over data from the guest to the host. It instead keeps track of how far we are in consuming the data and maintains this state.

For flow control, when a user of the virtio-serial port signals it has consumed less data than given, port throttling is enabled. The consumer can then later disable throttling and we can re-start sending the data from where we left off.

Finally, new fields introduced are added to the save/restore section to preserve state across live migrations.

Please apply.

Amit Shah (7):
virtio-console: Factor out common init between console and generic
ports
virtio-console: Remove unnecessary braces
virtio-serial-bus: separate out discard logic in a separate function
virtio-serial: Don't copy over guest buffer to host
virtio-serial: Let virtio-serial-bus know if all data was consumed
virtio-serial: Add support for flow control
virtio-serial: save/restore new fields in port struct

 hw/virtio-console.c    |   38 +++++++--------
 hw/virtio-serial-bus.c |  123 +++++++++++++++++++++++++++++++++++++++---------
 hw/virtio-serial.h     |   24 ++++++++-
 3 files changed, 139 insertions(+), 46 deletions(-)

1.7.3.4