That PR doesn't actually say anything about running Windows. You can't just port the app. A VM on an ARM system is still ARM inside, and given that the PR specifically mentions "support of x64 applications in Windows on ARM", this is clearly for ARM VMs. You'd need actual Intel emulation in order to run the normal version of Windows.
> You'd need actual Intel emulation in order to run the normal version of Windows.
Microsoft is working on enabling x64 emulation on ARM, it should roll out in preview this month[1]. I can see Windows 10 ARM-edition working inside Parallels with its own x64 emulation inside. The issue right now is that MS does not sell Win 10 ARM, it is available for OEMs only.
x86 emulation on Windows 10 ARM was already done few years ago, when MS shipped their Surface ARM notebook.
That actually seems more logical than the alternatives.
One of the big hopes for Rosetta2 is the possibility of intercepting library calls and passing them to the native library where possible. So a well-behaved app using OS libraries for everything it can, and really only driving the business logic itself, would be running mostly-native with the business logic emulated/translated.
(This is hopes/dreams/speculation with no insider knowledge.)
If Windows could do the same, then letting windows-arm do the translation of windows-x86/64 binaries would allow it to leverage windows-arm libraries - so an app could be running in mostly-virt with some-emu. If we let parallels/qemu/etc do the emu, it can only ever be 100% emu.
You can emulate anything on anything (pretty much), but the real question is can you emulate it at a speed that’s sufficient. That takes host-system-specific optimizations.
