virtio-pci in qemu-system-arm is broken in 8.2

[Michael Tokarev]

It looks like virtio-pci is entirely broke in qemu-system-arm, at least in tcg
mode running on x86.  The guest (current linux system) just does not detect
any virtio-pci devices at all.

When 8.1 is booting, the following messages are displayed (debian initramfs):

Loading, please wait...
Starting systemd-udevd version 255-1
[    6.455941] virtio-pci 0000:00:01.0: enabling device (0100 -> 0103)
[    6.929155] virtio-pci 0000:00:02.0: enabling device (0100 -> 0103)
[    7.764652] virtio_blk virtio1: 2/0/0 default/read/poll queues
[    7.783216] virtio_blk virtio1: [vda] 2097026 512-byte logical blocks (1.07 
GB/1024 MiB)
[    8.636453] virtio_net virtio0 enp0s1: renamed from eth0

But when 8.2 is booting, it ends up at:

Loading, please wait...
Starting systemd-udevd version 255-1
..and nothing.  here it waits for the root fs to appear, and drops into the 
shell

git bisect points at this commit:

commit b8f7959f28c4f36496bc0a694fa28bf5078152c5
Author: Peter Maydell <peter.maydell@linaro.org>
Date:   Mon Jul 24 18:43:33 2023 +0100

    target/arm: Do all "ARM_FEATURE_X implies Y" checks in post_init

Reverting this commit on top of 8.2.0 (or current qemu master)
makes things works again.

It's interesting how we missed this out entirely, as it's been applied
at the beginning of 8.2 development cycle, it's 228th commit after
8.1.0.

It looks like we've quite a bit more regressions like this in 8.2.0.. :(

/mjt