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

[Zhi Wang <zhiw@nvidia.com>]

On 1.10.2025 3.26, Alexandre Courbot wrote:
> On Wed Oct 1, 2025 at 7:07 AM JST, John Hubbard wrote:
>> Post-Kangrejos, the approach for NovaCore + VFIO has changed a bit: the
>> idea now is that VFIO drivers, for NVIDIA GPUs that are supported by
>> NovaCore, should bind directly to the GPU's VFs. (An earlier idea was to
>> let NovaCore bind to the VFs, and then have NovaCore call into the upper
>> (VFIO) module via Aux Bus, but this turns out to be awkward and is no
>> longer in favor.) So, in order to support that:
>>
>> Nova-core must only bind to Physical Functions (PFs) and regular PCI
>> devices, not to Virtual Functions (VFs) created through SR-IOV.
> 
> Naive question: will guests also see the passed-through VF as a VF? If
> so, wouldn't this change also prevents guests from using Nova?

In the entire software stack (firmware and interface, host/guest 
driver,and management stack), the entire design assumes that a VF is
tied to a VM.

NVIDIA GPU already provides good enough mechanisms to enforce
those between containers on PF. Moreover, VF on baremetal is not the
only way to support *container* environments. Surely, there are also
other approaches, for example, PF driver with DRM cgroup.

Like what I mentioned, it is really device/use-case specific. The device
vendor chooses the best approaches based on their device characteristic
and schedule/resource isolation capabilities for supporting containers
on bare metal.

Z.