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

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...
>> ...
>> As I mentioned in the other fork of this thread, I do think this is
>> a good start. So unless someone disagrees, I'd like to go with this
>> series (perhaps with better wording in the commit messages, and maybe
>> a better comment above the probe() failure return) for now.
> 
> Indicating whether the driver supports VFs through a boolean in struct
> pci_driver is about the same effort (well, maybe slightly more), but solves
the
> problem in a cleaner way since it avoids probe() being called in the first
> place. Other existing drivers benefit from that as well.
Yes, that is cleaner, and like you say, nearly as easy.
> 
> Forget about the SR-IOV RFC I was talking about; I really just intended to
offer
> to take care of that. :)
I can send out a v2 with that "PCI driver bool: supports VFs"
approach,
glad to do that.


thanks,
-- 
John Hubbard

> 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...
>>> ...
>>> As I mentioned in the other fork of this thread, I do think this is
>>> a good start. So unless someone disagrees, I'd like to go with
this
>>> series (perhaps with better wording in the commit messages, and
maybe
>>> a better comment above the probe() failure return) for now.
>> 
>> Indicating whether the driver supports VFs through a boolean in struct
>> pci_driver is about the same effort (well, maybe slightly more), but
solves the
>> problem in a cleaner way since it avoids probe() being called in the
first
>> place. Other existing drivers benefit from that as well.
> 
> Yes, that is cleaner, and like you say, nearly as easy.
> 
>> 
>> Forget about the SR-IOV RFC I was talking about; I really just intended
to offer
>> to take care of that. :)
> 
> I can send out a v2 with that "PCI driver bool: supports VFs"
approach,
> glad to do that.
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 might also close the door to say any
future testing we may do by binding to a VF for instance (yes we can delete a
statement but..).

Just my suggestion, but I do not strongly oppose either.

thanks,

- Joel
> 
> 
> thanks,
> --
> John Hubbard
>

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...
>>>> ...
> 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.

thanks,
-- 
John Hubbard