Mellanox PCIe passthru - manually fix IRQ conflict?

[sadpanda]

Probably skating uphill here but I was attempting to pass entire Connectx-2 card, VM fails to load with this error:

kvm: -device vfio-pci,host=0000:01:00.0,id=hostpci0,bus=ich9-pcie-port-1,addr=0x0,rombar=0: vfio 0000:01:00.0: Failed to set up TRIGGER eventfd signaling for interrupt INTX-0: VFIO_DEVICE_SET_IRQS failure: Device or resource busy
TASK ERROR: start failed: QEMU exited with code 1

Older HP mini tower with 1 pcie2.0(16) and 3 pcie2.0(1x) so no opportunity to simply change slots; pcie(16) IOMMU was shared with chipset bridge so I added pcie_acs_override=downstream (guide) and that does seem to have split out the card to its on IOMMU but no joy so I added options vfio_iommu_type1 allow_unsafe_interrupts=1 which results in genirq: Flags mismatch IRQ 16.

Looking at lspci-v, it appears despite the different IOMMUs, the NIC, chipset bridge and a whole host of subsequent devices uses IRQ 16.

Is there anyway to manually change IRQ and revet the 'unsafe interrupts'?

Only thing I have really found is this but there is not much explanation.

Thanks

 

[Capoeira]

@sadpanda did you solved your IRQ conflict?
I have also IRQ conflict, and I have described in this topic, but I don't know how to fix it:
PCI Passthrough - IRQ