I have been trying to get Kali to boot from a USB drive on my Surface Pro 2 w/ Win 8.1, but can not seem to get it to work. I can take the USB and put it in my desktop computer and it boots into Kali no problem. I have created the /efi/boot directory on the USB drive and put bootx64.efi and grub.cfg in it. I also disabled "Secure Boot Control". I have tried going to PC Setting/Update and recovery/Recovery/Advanced setup and selecting to boot from USB. Does anyone have any suggestion or tell me what am I missing? Thank you.