Re: VFIO support on hyperv (vfio_pci_core_ioctl())

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

On 2/27/26 11:29, Alex Williamson wrote:
> On Wed, 25 Feb 2026 14:04:49 -0800
> Mukesh R <mrathor@linux.microsoft.com> wrote:
> 
>> 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.
> 
> Hi Mukesh,
> 
> In general, littering the code with running_on_hyperv() tests is not
> acceptable, but the presented alternative isn't really accurate either.
> If you want to substitute in your own ioctl callback, you can still
> call vfio_pci_core_ioctl() for all the unhandled ioctls, without extra

Yes, I realized that after looking at how other callers were using it.

> exports.  We can also look at whether vfio_pci_device_ops could have a
> callback specifically addressing an alternative set_msi_trigger
> handler.  Thanks,

Sounds good. thanks as always,
-Mukesh


> Alex