OvmfPkg/AmdSevDxe: Shim Reboot workaround (RHEL only)

Oliver Steffenrequested to merge
osteffen/edk2:sev-vtpm-workaround-c9s into c9s

Merge Request Required Information

Summary of Changes

Add a workaround in the AmdSev firmware for a boot loop of SEV confidential guests using shim, in case a vTPM device is present. Setting the FB_NO_REBOOT efi variable under the shim guid at the end of the Dxe phase. The presence of this variable causes shim to boot onward instead of issuing a reboot.

Approved Development Ticket

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2218196

Edited by Miroslav Rezanina

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