patch review: MPTABLE_LINUX_BUG_COMPAT

[Emile `iMil' Heitor <imil%home.imil.net@localhost>]

Hi,

Prior to MMIO-over-command-line integration, the following patch
is needed. The Firecracker VMM doesn't have ACPI, either, it relies on
MP tables. This patch allows IOAPIC to be detected by introducing a
Linux-specific behavior expected by, at least, the Firecracker VMM.
This issue was found by Colin Percival and described here:
https://www.usenix.org/publications/loginonline/freebsd-firecracker
The patch is mostly a port of Colin's work which can be seen here:
https://lists.freebsd.org/archives/dev-commits-src-main/2022-October/010275.html

The patch: https://imil.net/NetBSD/mptable.patch

Thanks,

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Emile `iMil' Heitor <imil@{home.imil.net,NetBSD.org}> | https://imil.net