Is there a post explaining the BIOS settings for Qubes, other than UEFI is not preferred, (and bios should support virtualization features mentioned in the hardware requirements page)?
I had a Qubes installation working good, running from USB drive. I had played with UEFI Bios options for it to work: enable the two Intel hardware virtualization features, no secure boot, no raid, no hyper-threading.
I reset the bios configuration to defaults, and USB drive is no longer recognized as an option in the boot menu.
The EFI entries are stored in NVRAM and after you reset your BIOS they were removed as well.
So you’ll have to restore your EFI entry by booting from another system and running this command, assuming that /dev/sda is your Qubes drive and 1 is your EFI System partition number:
efibootmgr -v -c -u -L QubesOS -l /EFI/qubes/grubx64.efi -d /dev/sda -p 1
But is there a way to find out which options are needed, and just set them in bios?
I can of course access bios and play with options. I just don’t what combination worked last time.
Anything other than those options that I mentioned?
If you’re asking which BIOS options do you have to set to be able to boot from your Qubes USB drive then the answer is none (almost certainly). Missing Qubes boot option in your BIOS has nothing to do with you BIOS options being misconfigured, you need to restore your EFI entry.