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

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Message-ID: <ae48fad0-d40e-4142-87d0-8205abdf42d6@nvidia.com>
Date: Wed, 1 Oct 2025 15:38:59 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Zhi Wang <zhiw@...dia.com>, Danilo Krummrich <dakr@...nel.org>,
 Alistair Popple <apopple@...dia.com>
Cc: Alexandre Courbot <acourbot@...dia.com>,
 Joel Fernandes <joelagnelf@...dia.com>, Timur Tabi <ttabi@...dia.com>,
 Surath Mitra <smitra@...dia.com>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Bjorn Helgaas <bhelgaas@...gle.com>,
 Krzysztof Wilczyński <kwilczynski@...nel.org>,
 Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
 "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
 "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
 "rust-for-linux@...r.kernel.org" <rust-for-linux@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>, Jason Gunthorpe <jgg@...dia.com>,
 Alex Williamson <alex.williamson@...hat.com>
Subject: Re: [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@...dia.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