[…]In this PR OpenXT is extended to allow booting under UEFI while maintaining current security properties.,Changes to Measured Launch,,Booting OpenXT under UEFI introduces significant changes to the Measured Launch system of OpenXT by switching to the use of SRTM PCRs. Performing DRTM with TXT when booting under UEFI is not supported but can be implemented at a later date. OpenXT under UEFI relies on the shim EFI application to perform necessary measurements of critical boot components of OpenXT. OpenXT’s static PCR list is extended to include PCR4, PCR5, PCR7 and PCR8. Specific to OpenXT’s context, PCR4 holds the measurements of the shim, Xen and the dom0 kernel while PCR8 holds the measurements of openxt.cfg, the dom0 initrd image and the XSM policy. Any change in these components, selecting a boot entry other then the one used when Sealing took place and/or booting any application before the shim will result in the Measured Launch system tripping.[…]
https://github.com/OpenXT/xenclient-oe/pull/828
Firmware Security 