Nouveau - Oct 2025 - [PATCH 0/2] rust: pci: expose is_virtfn() and reject VFs in nova-core

On 10/1/25 5:48 PM, Joel Fernandes wrote:
>> On Oct 1, 2025, at 7:56?PM, Danilo Krummrich <dakr at kernel.org>
wrote:
>> ?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 at
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 at nvidia.com> wrote...
>>>>>>> ...
>> 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.
> 
> That works for me. If we are doing this, I would also suggest adding a
detailed comment preceding the if statement,
The nova-core piece that decides this is not an if statement. It's
a const. It really is cleaner. :)

 saying the reason for this is because the VFs share the same device IDs when in
reality we have 2 different drivers that handle the different
functions.
> 
I've got it passing tests already, I'll add appropriate comments and
post it
shortly, and let's see what you think.

thanks,
-- 
John Hubbard

On Wed, Oct 01, 2025 at 05:54:45PM -0700, John Hubbard wrote:
>  saying the reason for this is because the VFs share the same device
>  IDs when in reality we have 2 different drivers that handle the
>  different functions.
That's the fundamental problem here. Presenting the same device ID
when the device actually has a very different programming model is
against how PCI is supposed to operate.

For examplem mlx5 devices give unique IDs to their VFs - though they
don't have different programming models.

If novacore doesn't work on VFs at all, even in VMs, then use the
register based detection that was said earlier.

Jason