INTRng can leak resources when INTx interrupts are re-routed, which is
typically harmless but can be fatal when devices are (repeatedly) hot
plugged into PCI buses on INTRng systems. Re-routing INTx interrupts
is nonetheless still necessary on some systems, and identifying whether
the re-routing should be enabled or disabled seems to be nontrivial.
Add a hw.pci.intx_reroute sysctl/tunable so systems which don't want
legacy PCI interrupt re-routing can turn it off. This is probably not
the best fix but it's something which can be safely included in FreeBSD
14.3.
Co-Authored-by: jhb
Reviewed by: bz, jhb
MFC after: 3 days
Sponsored by: Amazon
Differential Revision: https://reviews.freebsd.org/D49849
(cherry picked from commit 2187ec93ada1c7399f2f3537920f6277bec4a0ef)
b0bbefc465