qemu VM with OVMF_VARS.fd doesn't run, OVMF_VARS.fd differs from OVMF_VARS_4M.qcow2

[djasa]

I need to use customized nvram with qemu, which is better based on the raw image. However the raw OVMF_VARS.fd image as shipped in Fedora packages is different from the OVMF_VARS_4M.qcow2 qcow2 image used by qemu by default and the VM doesn't boot, gets stuck with only this message after qemu cmdline in the domain log:

char device redirected to /dev/pts/9 (label charserial0)

The spice display shows just Display output is not active message and no booting progress. The qcow2 image converted to raw however boots fine but it has some bytes different from the shipped raw image.

The same story goes for the secure boot images: OVMF_VARS_4M.secboot.qcow2 converted to raw is OK, use of OVMF_VARS.secboot.fd makes booting stuck the same way.

edk2 version tested:

• edk2-ovmf-20250523 builds for Fedora 42 and 43
• an old version for reference: edk2-ovmf-20221207gitfff6d81270b5-9.el9_2.8.noarch. This version lacks *_4M*qcow2 files and raw files work OK here (but this nvram lacks the option of dbx updates)

Test system: Fedora 42 with qemu-kvm-9.2.4-1.fc42.x86_64

hexdump of the image in OVMF_VARS_4M.qcow2 converted to raw:

0000000 0000 0000 0000 0000 0000 0000 0000 0000
0000010 2b8d fff1 7696 4c8b 85a9 4727 5b07 504f
0000020 4000 0008 0000 0000 465f 4856 feff 0004
0000030 0048 b8af 0000 0200 0084 0000 1000 0000
0000040 0000 0000 0000 0000 2c78 aaf3 947b 439a
0000050 80a1 142e c34e 9277 ffb8 0003 fe5a 0000
0000060 0000 0000 ffff ffff ffff ffff ffff ffff
0000070 ffff ffff ffff ffff ffff ffff ffff ffff
*
0041000 292b 9e58 7c68 497d cea0 0065 9ffd 951b
0041010 af2c 642c fffe ffff 0fe0 0000 0000 0000
0041020 ffff ffff ffff ffff ffff ffff ffff ffff
*
0084000

hexdump of the /usr/share/edk2/ovmf/OVMF_VARS.fd image:

0000000 0000 0000 0000 0000 0000 0000 0000 0000
0000010 2b8d fff1 7696 4c8b 85a9 4727 5b07 504f
0000020 0000 0002 0000 0000 465f 4856 feff 0004
0000030 0048 f919 0000 0200 0020 0000 1000 0000
0000040 0000 0000 0000 0000 2c78 aaf3 947b 439a
0000050 80a1 142e c34e 9277 dfb8 0000 fe5a 0000
0000060 0000 0000 ffff ffff ffff ffff ffff ffff
0000070 ffff ffff ffff ffff ffff ffff ffff ffff
*
000f000 292b 9e58 7c68 497d cea0 0065 9ffd 951b
000f010 af2c 642c fffe ffff 0fe0 0000 0000 0000
000f020 ffff ffff ffff ffff ffff ffff ffff ffff
*
0020000