Google Engineers Get Windows Booting When Kexec'ed Under Linux

An interesting summer internship at Google has led to an experimental effort to get Microsoft Windows running via Kexec from Linux. The engineers involved have been implementing enough of the EFI Boot Services to be able to kexec Windows from Linux.

Kexec has traditionally just been used for loading and booting alternative Linux kernels from a running kernel using this system call in order to minimize system downtime. Kexec is also used by the likes of Raptor's POWER9 systems for booting the system from Petitboot.

Up to now we've only heard of Kexec on Linux being used for booting different Linux kernels, but Google engineers with some EFI tinkering has managed to get it booting Windows.

Windows is UP AND RUNNING, kexec'd from Linux!

We got serial console access at the moment. Graphics are next.@ofir1942 says he's never been so impressed by the output of ipconfig in his life! https://t.co/gEUs1hCQhk pic.twitter.com/7o1F9AUCFi

— chris (@hugelgupf) August 5, 2019

While Windows is "up and running" at the moment it's only accessible via a serial console but there is hope it could be easy getting graphics output working via the UEFI Graphics Protocol. It will be interesting to see where this leads and ultimately allowing Windows to handle the likes of LinuxBoot with the Google folks involved working on their firmware/security efforts.