VFIO support on hyperv (vfio_pci_core_ioctl())

[Mukesh R <mrathor@linux.microsoft.com>]

Hi Alex et al:

I've been looking at making pci passthru irq setup/remap work on hyperv
for the latest (6.19) version using vfio core. Unfortunately, it's just
not fitting well because in case of hyperv the irq remap is done by
the hypervisor. Specifically, for a robust and proper solution, we need
to override vfio_pci_set_msi_trigger(). As such, for the best way forward
I am trying to figure how much flexibility there is to modify
vfio_pci_intrs.c with "if (running_on_hyperv())" branches (putting hyperv
code in separate file).

If none, then the alternative would be to create vfio-hyperv.c with
vfio_device_ops.ioctl = hyperv_vfio_pci_core_ioctl(). But, then I'd
be replicating code for other sub ioctls like vfio_pci_ioctl_get_info(),
vfio_pci_ioctl_get_irq_info(), etc. Would it be acceptable to make them
non static in this case?

Please let me know your thoughts or if you have other suggestions.

Thanks,
-Mukesh