MEASURED_BOOT

VMAware reads the TBS TCG log for event EV_EFI_PLATFORM_FIRMWARE_BLOB (event 0x80000008, PCR 0) and compares it against OVMF's known firmware-volume bounds. The check is an exact match on the base address and length pair (vmaware.hpp, measured_boot()):

if ((base_addr == 0x830000 && blob_len == 0xD0000) ||   /* PEIFV */
    (base_addr == 0x900000 && blob_len == 0xE80000)) {  /* DXEFV */
    return true;
}

Both branches test the base address only, so moving either volume defeats the match.

Fix

patches/EDK2/AMD-edk2-stable202605.patch moves MEMFD_BASE_ADDRESS from 0x800000 to 0x820000 in OvmfPkg/Include/Fdf/OvmfPkgDefines.fdf.inc. Every volume inside MEMFD sits at a fixed offset from that base (OvmfPkg/Include/Fdf/MemFd.fdf.inc: PEIFV at +0x030000, DXEFV at +0x100000), so one define moves both.

PCD	Value	VMAware expects
PcdOvmfPeiMemFvBase	0x850000	0x830000 — no match
PcdOvmfPeiMemFvSize	0x0D0000	0x0D0000
PcdOvmfDxeMemFvBase	0x920000	0x900000 — no match
PcdOvmfDxeMemFvSize	0xE80000	0xE80000

Only OVMF_CODE.fd changes. OVMF_VARS.fd (the variable store) does not depend on MEMFD_BASE_ADDRESS, so a rebuild produces a byte-identical variable store and any enrolled Secure Boot keys or per-domain NVRAM stay valid.

Rollback

The pre-change firmware is kept at /opt/vmw/firmware/OVMF_CODE.fd.pre-memfd.bak:

cp /opt/vmw/firmware/OVMF_CODE.fd.pre-memfd.bak \
   /opt/vmw/firmware/OVMF_CODE.fd

Applying a firmware change

pflash images load at domain start. A reboot from inside the guest keeps the old firmware; the domain must be stopped and started for a firmware change to take effect. Confirm the running QEMU process has picked up the new image by checking its open file handles:

ls -l /proc/<pid>/fd | grep OVMF_CODE

If a firmware change trips a BitLocker recovery prompt, suspend protection for one boot from inside the guest first:

manage-bde -status C:
manage-bde -protectors -disable C: -RebootCount 1