Performance degradation for WinXP boot time after b55f54bc

Duplicating launchpad ticket: https://bugs.launchpad.net/bugs/1896754

Qemu 5.1 loads Windows XP in TCG mode 5-6 times slower (~2 minutes) than 4.2 (25 seconds), I git bisected it, and it appears that commit b55f54bc causes this issue. Probably similar to an older fixed bug https://bugs.launchpad.net/qemu/+bug/1672383

Command line is trivial: qemu-system-x86_64 -nodefaults -vga std -m 4096M -hda WinXP.qcow2 -monitor stdio -snapshot

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