4.2 misses:
the three known "moved between HW and PC compat
"migration" "send-configuration" "off", user_provided = false, used = true
"migration" "send-section-footer" "off", user_provided = false, used = true
"migration" "store-global-state" "off", user_provided = false, used = true

4.2 has "too much"
Those are probably all or mostly due to using hw_compat_2.3 instead of hw_compat_2.4+the-three-above
"virtio-blk-pci" "any_layout" "off", used = false, optional = false
"virtio-balloon-pci" "any_layout" "off", used = false, optional = false
"virtio-serial-pci" "any_layout" "off", used = false, optional = false
"virtio-9p-pci" "any_layout" "off", used = false, optional = false
"virtio-rng-pci" "any_layout" "off", used = false, optional = false
"pci-device" "x-pcie-lnksta-dllla" "off", used = false, optional = false
^^ the above are missing
"migration" "send-configuration" "off", used = false, optional = false
"migration" "send-section-footer" "off", used = false, optional = false
"migration" "store-global-state" "off", used = false, optional = false
^^ those three it got from hw_compat_2_3 but need to get on top of hw_compat_2_3 instead

vv those cpu attributes below are from pc_compat_2_3 and should be pc_compat_2_4
"qemu32-x86_64-cpu" "model-id" "QEMU Virtual CPU version 2.3.0", used = false, optional = false
"qemu64-x86_64-cpu" "model-id" "QEMU Virtual CPU version 2.3.0", used = false, optional = false
"athlon-x86_64-cpu" "model-id" "QEMU Virtual CPU version 2.3.0", used = false, optional = false
"x86_64-cpu" "arat" "off", used = false, optional = false
"qemu64-x86_64-cpu" "min-level" "4", used = false, optional = false
"kvm64-x86_64-cpu" "min-level" "5", used = false, optional = false
"pentium3-x86_64-cpu" "min-level" "2", used = false, optional = false
"n270-x86_64-cpu" "min-level" "5", used = false, optional = false
"Conroe-x86_64-cpu" "min-level" "4", used = false, optional = false
"Penryn-x86_64-cpu" "min-level" "4", used = false, optional = false
"Nehalem-x86_64-cpu" "min-level" "4", used = false, optional = false
"n270-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"Penryn-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"Conroe-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"Nehalem-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"Westmere-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"SandyBridge-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"IvyBridge-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"Haswell-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"Haswell-noTSX-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"Broadwell-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"Broadwell-noTSX-x86_64-cpu" "min-xlevel" "0x8000000a", used = false, optional = false
"x86_64-cpu" "kvm-no-smi-migration" "on", used = false, optional = false


TODO:
- create hw_compat_2.4+the-three-migration-attribs
- wily to use hw_compat_2.4+the-three-migration-attribs
- wily to use pc_compat_2.4

Once patched and built for Focal re-test the above and re-compare attributes in gdb.