[coreboot] Any live usb for recovery flash coreboot?

[Dalao]

Hi, I was using Seabios but recently switched to Tianocore. However, the tianocore can't boot my Manjaro linux distribution which was installed using the non-uefi method. So I want to flash back.

I only have a Manjaro live usb at hand. The tianecore can boot it. However this live usb is not set with iomem=relaxed, so I can't read or write the bios using flashrom.

I don't know how to set the live usb's grub settings because when it boots, it's already running commands. When using this tianocore with vgabios I can't see the grub screen when booting.

So how to set the live usb with iomem=relaxed?
Is there any live usb that already have the iomem=relaxed set?
Could anyone help me build a usb image dedicated for automatically recover flashing?