[gpvos]

> And in general, would kernel emulation be a performant approach for running userspace of any OS in any other OS?

It can come close to the host OS, but that requires a lot of work.

[quietplatypus]

Would this include stuff like printing to stderr being slower on Windows? If they get to write kernel drivers, there could be a chance that they could replicate the file handling behaviors of Linux.

[gpvos]

I don't really know anything about this, but if stderr is really slower on Windows, I would suppose that's a userland library thing. I would not know why that would be slower at kernel level. So that problem might not even arise under the Linux emulation.