linux-kernel - Re: [PATCH 2/2] gpu: nova-core: reject binding to SR-IOV Virtual Functions

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Message-ID: <6cbc2df0-00e6-4d56-adbb-6695575d1563@nvidia.com>
Date: Tue, 30 Sep 2025 18:26:54 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Alistair Popple <apopple@...dia.com>
Cc: Danilo Krummrich <dakr@...nel.org>,
 Alexandre Courbot <acourbot@...dia.com>,
 Joel Fernandes <joelagnelf@...dia.com>, Timur Tabi <ttabi@...dia.com>,
 Zhi Wang <zhiw@...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, linux-pci@...r.kernel.org,
 rust-for-linux@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] gpu: nova-core: reject binding to SR-IOV Virtual
 Functions

On 9/30/25 5:33 PM, Alistair Popple wrote:
> On 2025-10-01 at 08:07 +1000, John Hubbard <jhubbard@...dia.com> wrote...
>> Nova-core must only bind to Physical Functions (PFs) and regular PCI
>> devices, not to Virtual Functions (VFs) created through SR-IOV.
>>
>> Detect VFs using the newly added is_virtfn() method, and leave them
>> unclaimed. This allows a VFIO kernel module to claim the VFs instead.
> 
> See my comments on the cover letter, but does the kernel driver core continue
> trying to probe other drivers if this one failed? Or does it just give up? If it
> just gives up I'm not sure this really helps much, although I suppose if
> NovaCore can't use the VFs for anything useful anyway then it probably should
> fail.

It keeps going. :)

thanks,
John Hubbard

> 
>> Signed-off-by: John Hubbard <jhubbard@...dia.com>
>> ---
>>  drivers/gpu/nova-core/driver.rs | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
>> index 5d23a91f51dd..004c15763694 100644
>> --- a/drivers/gpu/nova-core/driver.rs
>> +++ b/drivers/gpu/nova-core/driver.rs
>> @@ -54,6 +54,11 @@ impl pci::Driver for NovaCore {
>>      fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
>>          dev_dbg!(pdev.as_ref(), "Probe Nova Core GPU driver.\n");
>>  
>> +        // NovaCore must only bind to Physical Functions (PFs), not Virtual Functions (VFs)
>> +        if pdev.is_virtfn() {
>> +            return Err(ENODEV);
>> +        }
>> +
>>          pdev.enable_device_mem()?;
>>          pdev.set_master();
>>  
>> -- 
>> 2.51.0
>>