input_server relies on domain_read_is_pv_domain function to handle or not a guest to use the vkbd backend.
This might be a legacy debt from before PV-on-HVM support and certainly was implemented before PVH(v2) support.
Some conflict with the emulated inputs may have motivated that decision, in a effort to go step by step, enabling PVH(v2) guests to be handled as PV guests by input_server is required to let PVH guests receive input events and does not affect existing HVM configurations.
PVH guests receive inputs on creation
Connection is established between vkbd-frontend and input_server