Implementation of the FW CFG DMA interface.
When running a Linux guest on top of QEMU, using the -kernel options, this is the timing improvement for x86:
QEMU commit 2be4f242b50a8 and SeaBIOS commit 908a58c1d5ff QEMU startup time: .078 BIOS startup time: .060 Kernel setup time: .578 Total time: .716
QEMU with this patch series and SeaBIOS with this patch series QEMU startup time: .080 BIOS startup time: .039 Kernel setup time: .002 Total time: .121
QEMU startup time is the time between the start and the first kvm_entry. BIOS startup time is the time between the first kvm_entry and the start of function do_boot, in SeaBIOS. Kernel setup time is the time between the start of the function do_boot in SeaBIOS and the jump to the Linux kernel.
As you can see, both the BIOS (because of ACPI tables and other configurations) and the Linux kernel boot (because of the copy to memory) are greatly improved with this new interface.
Also, this new interface is an addon to the old interface. Both interfaces are compatible and interchangeable.