Comment 7 for bug 1960758

Test Results:
---

OVMF_CODE.fd boots "everywhere", on q35/pc with SMM on/off.

OVMF_CODE.secboot.fd boots _only_ on q35 _and_ with SMM on.

Tests:
---

for SMM in on off; do
    for MACH in q35 pc; do
        for FW in OVMF_CODE.fd OVMF_CODE.secboot.fd; do

          echo
          echo "- SMM $SMM / $MACH / $FW"

          cp /usr/share/OVMF/OVMF_VARS.fd .
          timeout 5 \
          qemu-system-x86_64 \
              -M $MACH,smm=$SMM,accel=kvm \
              -drive if=pflash,format=raw,unit=0,file=/usr/share/OVMF/$FW,readonly=on \
              -drive if=pflash,format=raw,unit=1,file=OVMF_VARS.fd \
              -global ICH9-LPC.disable_s3=1 \
              -nodefaults -nographic -no-user-config \
              -serial stdio 2>&1 \
          | grep 'UEFI.*EDK'

        done
    done
done

- SMM on / q35 / OVMF_CODE.fd
UEFI v2.70 (EDK II, 0x00010000)
Terminated

- SMM on / q35 / OVMF_CODE.secboot.fd
UEFI v2.70 (EDK II, 0x00010000)
Terminated

- SMM on / pc / OVMF_CODE.fd
UEFI v2.70 (EDK II, 0x00010000)
Terminated

- SMM on / pc / OVMF_CODE.secboot.fd
Terminated

- SMM off / q35 / OVMF_CODE.fd
UEFI v2.70 (EDK II, 0x00010000)
Terminated

- SMM off / q35 / OVMF_CODE.secboot.fd
Terminated

- SMM off / pc / OVMF_CODE.fd
UEFI v2.70 (EDK II, 0x00010000)
Terminated

- SMM off / pc / OVMF_CODE.secboot.fd
Terminated