"IRQ problem dom0 xen4.5-amd64"
i have mothrboard geforce 6100pm-m2(v3.0) latest bios and athtlon 64 x2 5000+ cpu
Mothrboard based on nforce 430 chipset
if in bios enabled apic mode. Xen boot stops on trying to load dom0 kernel (gentoo kernel v4.5 or ubuntu kernel v 4.2)  and just showing black screen, but kernel without xen loads normally.

if in bios disable apic mode Xen boot dom0 but not see any disk (of cource scsi libata and nforce deivers enabled in kernel by "Y") and keyboard does not work.
logs on screen that i can see:
genirq: flags mismatch irq12 00000080 (i8042) vs 00000000 (mce)
genirq: flags mismatch irq1 00000080 (i8042) vs 0002cc00 (spinlock0)
genirq: flags mismatch irq1 00000080 (rtc0) vs 0002cc00 (xen-pcpu)
genirq: flags mismatch irq5 00000080 (sata_nv) vs 0002cc00 (callfunction0)