On 12/05/20 19:14, Alex Williamson wrote: > But why not assign the individual platform devices via vfio-platform > rather than assign the i2c controller via vfio-pci and then assembling > the interrupts from those sub-devices with this ad-hoc interface? An > emulated i2c controller in the guest could provide the same discovery > mechanism as is available in the host. I agree. I read the whole discussion, but I still don't understand why this is not using vfio-platform. Alternatively, if you assign the i2c controller, I don't understand why the guest doesn't discover interrupts on its own. Of course you need to tell the guest about the devices in the ACPI tables, but why is this new concept necessary? (Finally, in the past we were doing device assignment tasks within KVM and it was a bad idea. Anything you want to do within KVM with respect to device assignment, someone else will want to do it from bare metal. virt/lib/irqbypass.c is a special case because it's an IOMMU feature that is designed to work in concert with VMX posted interrupts and SVM AVIC, so in guest mode only). Paolo
