Sorry for the confusing description of the background in this proposal. To be clear, we here divide the implementation of trap-and-emulated I/O devices into full emulated I/O devices and paravirtual I/O devices. This proposal only focuses on improving the performance of full emulated I/O devices implemented in userspace, such as UART. Besides, we believe that other mmio emulation devices which require Guest OS to trap and exit to userspace, such as rtc, can also benefit from our proposal.
Paravirtual I/O devices, which require the GuestOS to trap and send in-kernel interrupts to interact with VirtIO backend, i.e., vHost you mentioned, are not considered in this proposal.
