In qemu v2.11-rc1, Windows 10 version 1709 (build 16299) for "ARM64", as Microsoft calls it, can now install and boot using this UEFI firmware image: https://github.com/Googulator/edk2/releases/tag/AHCI

Extract the contents of the ISO into a 5GB VHDX or other qemu-compatible image format, create a 2nd, empty VHDX of about 50GB, then run qemu like this (change "-smp 8" if you don't want to emulate that many cores): qemu-system-aarch64 -M virt -m 8192 -cpu cortex-a57 -smp 8 -bios QEMU_EFI.fd -device VGA -device nec-usb-xhci -device usb-kbd -device usb-tablet -drive file=50gb.vhdx,id=install,if=none -netdev user,id=network -device virtio-net,netdev=network -device ahci,id=ahci -device ide-hd,drive=install,bus=ahci.0 -drive file=5gb.vhdx,id=dvd,if=none -device ahci,id=ahci2 -device ide-hd,drive=dvd,bus=ahci2.0

Walk through setup as you would on an x86 system.

Probably won't work under KVM on real ARM hardware, as it depends on the emulated VGA framebuffer, which is fundamentally incompatible with KVM. Unfortunately, virtio-gpu can't be used as an alternative because Windows requires runtime graphics capability through UEFI GOP after ExitBootServices(), which means it can't run on PixelBltOnly screens like the one provided by virtio-gpu.

EDIT: 2.11-rc1 is required, earlier versions have some bug related to memory management(?) that cause Windows to blackscreen early during boot.