I booted again, and IRQ9 has 10x the interrupts as any other source. I guess that means it's not a shared one?
Hmm and MPtable has no entries for this IRQ? So it must be something else. It makes me wonder what changes trigger the irq9 storm. Perhaps kernel would complain even when there is none handler at all.
Any ideas what it could be? maybe booting irqroute=pic or smth like this could force the old way of pci routing... but leaving IRQ9 for acpi. Should be interesting test.
Maybe you have smth wrong in FADT? Dont know
Won't I have to add IRQ 9 to the mptable? Will it find it otherwise?
If Irq 9 is not used then it must be something else. Is old coreboot having MPtable entries >15? Or write simple kernel driver just requesting IRQ9 and returing IRQ_NONE with old coreboot. See if IRQ is busy too.
Rudolf