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

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...
...
>> So, this patch series does not do anything uncommon.
>>
>>>> I'm guessing the proposal is to fail the probe() function
in nova-core for
>>>> the VFs - I'm not sure but does the driver core continue to
try probing other
>>>> drivers if one fails probe()? It seems like this would be
something best
>>>> filtered on in the device id table, although I understand
that's not possible
>>>> today.
>>
>> Yes, the driver core keeps going until it finds a driver that succeeds
probing
>> or no driver is left to probe. (This behavior is also the reason for
the name
>> probe() in the first place.)
>>
>> However, nowadays we ideally know whether a driver fits a device before
probe()
>> is called, but there are still exceptions; with PCI virtual functions
we've just
>> hit one of those.
>>
>> Theoretically, we could also indicate whether a driver handles virtual
functions
>> through a boolean in struct pci_driver, which would be a bit more
elegant.
>>
>> If you want I can also pick this up with my SR-IOV RFC which will
probably touch
>> the driver structure as well; I plan to send something in a few days.
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.

And then we can add SRIOV support into nova-core when we are ready.

Let me know--especially Jason--if that sounds reasonable, and if
so I'll draft more accurate wording. 

thanks,
-- 
John Hubbard

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...
> ...
>>> So, this patch series does not do anything uncommon.
>>>
>>>>> I'm guessing the proposal is to fail the probe()
function in nova-core for
>>>>> the VFs - I'm not sure but does the driver core
continue to try probing other
>>>>> drivers if one fails probe()? It seems like this would be
something best
>>>>> filtered on in the device id table, although I understand
that's not possible
>>>>> today.
>>>
>>> Yes, the driver core keeps going until it finds a driver that
succeeds probing
>>> or no driver is left to probe. (This behavior is also the reason
for the name
>>> probe() in the first place.)
>>>
>>> However, nowadays we ideally know whether a driver fits a device
before probe()
>>> is called, but there are still exceptions; with PCI virtual
functions we've just
>>> hit one of those.
>>>
>>> Theoretically, we could also indicate whether a driver handles
virtual functions
>>> through a boolean in struct pci_driver, which would be a bit more
elegant.
>>>
>>> If you want I can also pick this up with my SR-IOV RFC which will
probably touch
>>> the driver structure as well; I plan to send something in a few
days.
>
> 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.

Forget about the SR-IOV RFC I was talking about; I really just intended to offer
to take care of that. :)