virtio-serial: add plumbing for virtio console emergency write support
Add the infrastructure required for the virtio 1.0 "emergency write"
(VIRTIO_CONSOLE_F_EMERG_WRITE) feature. Because we don't touch the
size of the configuration area, guests will not be able to actually
make use of this without further patches.
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>