Re: [PATCH 0/2] rust: pci: expose is_virtfn() and reject VFs in nova-core

["Danilo Krummrich" <dakr@kernel.org>]

On Thu Oct 2, 2025 at 1:51 AM CEST, John Hubbard wrote:
> On 10/1/25 4:47 PM, Joel Fernandes wrote:
>>> On Oct 1, 2025, at 7:00 PM, John Hubbard <jhubbard@nvidia.com> wrote:
>>> On 10/1/25 3:52 PM, Danilo Krummrich wrote:
>>>>> On Thu Oct 2, 2025 at 12:38 AM CEST, John Hubbard wrote:
>>>>> On 10/1/25 6:52 AM, Zhi Wang wrote:
>>>>>> On 1.10.2025 13.32, Danilo Krummrich wrote:
>>>>>>> On Wed Oct 1, 2025 at 3:22 AM CEST, John Hubbard wrote:
>>>>>>>> On 9/30/25 5:29 PM, Alistair Popple wrote:
>>>>>>>>> On 2025-10-01 at 08:07 +1000, John Hubbard <jhubbard@nvidia.com> wrote...
>>>>> ...
>> Here is my opinion and correct me if I missed something:
>> 
>> It feels premature to remove the option of nova-core binding to a VF, since other options to disable auto probing do exist as Jason pointed out.
>> 
>> Taking a parallel with VFIO pass through for instance, the user already has to do some diligence like preventing drivers from binding and then making vfio-pci bind to the device IDs. This case is similar though slightly different, but VFIO setup requires some configuration anyway so will it really improve anything?
>> 
>> I quietly suggest holding on till there is a real need or we are sure nova cannot bind to, or operate on a VF. This 
>
> I'm confident that nova-core cannot properly handle a VF with *today's* code.
> There is no expectation at all for a VF to show up--yet.
>
> Which is why I think it's appropriate to skip it right now.

I agree with John.

If a driver does not support a certain device, it is not the user's
responsibility to prevent probing. Currently nova-core does not support VFs, so
it should never get probed for them in the first place.